Review ArticleQualitative and Quantitative Analysis of Graphene-BasedAdsorbents in Wastewater Treatment
P Jayakaran 1 G S Nirmala2 and L Govindarajan3
1Research Scholar Department of Chemical Engineering VIT University Vellore India2Associate Professor Department of Chemical Engineering VIT University Vellore India3Associate Professor Department of Chemical Eng College of Applied Sciences Sohar Oman
Correspondence should be addressed to P Jayakaran jayakaranresearchgmailcom
Received 14 November 2018 Revised 9 March 2019 Accepted 16 April 2019 Published 4 July 2019
Academic Editor Eric Guibal
Copyright copy 2019 P Jayakaran et al +is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Nowadays water bodies across the world are heavily polluted due to uncontrollable contamination of heavy metal particles toxicdyes and other harmful wastes discharged by emerging industries other than normal domestic wastages +is contaminationneeds sufficient control to protect the natural water bodies+ere are various methodologies to be followed to perform wastewatertreatment in which the adsorption method of filtration is found to be efficient +e adsorption method is a high priority andpreferable filtration method compared to other waste water treatment methods due to its peculiar characteristics Considering theadsorption method there are multiple options available in selecting material and methodology for the filtration process Inselecting the filtering material there is much attraction towards graphene and its oxides which have widespread range ofdifferential applications in commercial industries because of their eco-friendly characteristic features +e importance of variousgraphene composites and their chemical properties is found to be significant in various fields Analyzing the adsorbing propertiesof graphene widely this article deeply reviews about the improvements and the technologies identified for using graphene and(GO) graphene oxide in wastewater treatment taken into discussion elaborately+erefore in this hard review the advantages anddemerits of using graphene for wastewater treatment as well as improving its properties to make it more suitable for wastewatertreatment are detailed
1 Introduction
Water in a suitable form is required for various purposes onEarth from survival to essential utilization In olden days thewidespread natural water available on Earth was sufficientfor usage and the environmental cycle was tolerable tohandle the water management But considering recentscenarios overcrowding of industries and man-made arti-ficial things against natural environment introduces morecontamination in water bodies +is uncontrollable in-trusion of water contamination needs to be controlled else itwill affect the entire biodiversity leading to destruction ofliving and nonliving things on Earth To control pollutionthe major contaminating sources need to be narrowed downto avoid more effluence Such identified water contami-nating sources should take required measures to processtheir outputs by removing toxic and hazardous wastes from
their sludge before it is discharged into the water bodies+ismakes the water more suitable for household purposesnatural usages groundwater recycling and many otherpurposes
+e water treatment process involves removing or re-ducing the water contaminants so that it is suitable fornatural uses All water treatment methodologies involve theremoval of solid materials harmful microorganisms andorganic as well as inorganic compounds present in thewastewaters A wastewater treatment usually has three levelsa primary level which is mechanical involves in removingsolids from raw sewage through filtration as well as co-agulation +is level itself would be capable of removingaround half of the solids present in it +en in the conse-quent second level beginning of biological treatment takesplace During this second level removal of microorganismsescaping from the primary treatment is done Here a wide
HindawiInternational Journal of Chemical EngineeringVolume 2019 Article ID 9872502 17 pageshttpsdoiorg10115520199872502
range of bacteria fungi and algae convert the sludge intocarbon dioxide (CO2) and water (H2O) During this levelsome amount of energy in terms of biogas production isgenerated During the last treatment level any impuritiesthat are left out from the above two processes are removedproducing the water fit for environment and generalpurposes
As water is very much important for all the living or-ganisms and due to limited availability as well as high de-mand the research community intends to bring novelmethodologies that can ensure the sustainability of waterresources Some of the few novel methodologies establishedby the research community are listed below
(1) +ere is a much attraction towards the use ofnanomaterials on wastewater treatment It has nu-merous potential merits which includes high effi-cient treatment due to wide surface area and betterchemical properties In addition to that less costhigh reusability and availability of effective recoveryof nanomaterials after their use made them morelucrativeToday numerous researches aimed inexploiting the potential of nanomaterials [1] by usingit in different forms such as nanotubes nano-adsorbents catalysts in Nano-sized semi permeablemembrane made from Nano fibers Nanomaterialswith magnetic properties Nano flakes and Nanogranules etc and recently reviewed the role of Nanoscience and nanotechnology on the treatment ofwastewaters
(2) Another research area in which much attentionfocused in recent years is membrane-based waste-water treatment Today researchers tested the effi-cacy of multiple ranges of membrane technologieswhich include microfiltration ultrafiltration nano-filtration and reverse osmosis Microfiltration usesthe membrane of pore size 004 to 01 microns whilein ultrafiltration process the membrane with poresize 001 to 002 microns is used for water purifi-cation processes Microfiltration is also used inwastewater treatment but with larger pore sized (02to 04 microns) membrane However microfiltrationas well as ultrafiltration allows the flow of dissolvedsolids present in water +is can be eliminated withnanofiltration and reverse osmosis +us micro-filtration can be generously used as pretreatment toRO and nanofiltration +us the membrane-basedwastewater technologies are found to be more ef-fective on eliminating suspended as well as dissolvedsolids in addition to removal of pathogens Howeverthey have a big limitation corresponding to costincurred as they require very large amount of energyin comparison with conventional treatmentmethodologies
Earlier wastewater was considered as troublesome andmore problematic but today wastewater is recycled andconsidered as renewable source of energy +e wastewatercontains more than 4 times of energy required for treatmentand abundance of energy is present in wastewater in terms of
chemical thermal and hydraulic energy Among thesethermal energy stands first with about 80 chemical energyavailability attributes to about 20 and hydraulic energyavailability attributes to a negligible amount (lt1) +usimplementation of effective treatment methodology not onlydegrades the wastewater but can also produce energythrough biogas production
Wide ranges of eco-friendly and high-cost nano-materials are tested by the research community in thetreatment of wastewaters +ese materials are developedwith certain unique functional and surface characteristicsfor the purification of surface water and groundwater Inaddition these nanomaterials were also used in degrada-tion of industrial effluents [2] In recent decades nano-particles have been studied for their capacity as adsorbents+e size of the nanoparticles is considered as an importantfactor in deciding the chemical activities such as adsorption[3 4]
+e inorganic nanoparticle oxides produced frommetalsas well as nonmetals are considered as most promisingnanoadsorbents +ese oxide-based nanoadsorbents areemployed for removing the hazardous pollutants present inwastewaters Some of these nanoadsorbents reported in thepast decade includes titanium oxides [5] titanium oxidesand dendrimer composites [6 7] manganese oxides [8]ferric oxides [9] zinc oxides [10] and magnesium oxides[11]+e successful use of nanoadsorbents on degradation ofpollutants attributed to several reasons that include highsurface area less impact on environment easy availabilityand nongeneration of secondary pollutants [12] that requiresfurther treatment and thus these inorganic nanoadsorbentsare considered as one among the best adsorbents
Graphene is a type of carbon having layered structuredwith special features that tends to several environmentalapplications [13] Graphene oxide (GO) which is an ex-tension of carbon material that has two-dimensionalstructure is produced by oxidation of graphite layer bymeans of chemical method Surprisingly graphene is in-credibly flexible even though its strength is more than 200times higher than steel In addition it is ultralight in weightbut highly tough in nature It is possibly one of the extremelythinnest materials in the world with highly transparentnature In the year 1962 graphene was observed through theelectron microscope for the first time Later in 2004 AndreGeim and Konstantin rediscovered and characterized thegraphene nanoparticles for which they received Nobel prizefor physics in the year 2010 Graphene is considered as oneamong the materials having wide surface area ie it has asurface area about 2630m2g (theoretical) while the carbonnanotubes have a surface area of 1000m2g
Hummersrsquo method was considered as one of the efficientas well as faster methods for the preparation of GO in whichpure carbon graphene combines to react with molecularoxygen Another advantage behind this method is producingGO with relatively high carbon-oxygen ratio GO has twomain characteristic features when compared to othernanomaterials like carbon nanotubes (CNTs) In the firststep of preparation synthesis of single layer of GOwhich hasmaximum heavy metal ion adsorption is done In the second
2 International Journal of Chemical Engineering
step chemical exfoliation of raw graphite without the ad-dition of any metallic catalyst is carried out which does notneed the help of any complex instruments
+e contamination of heavy metal ions in water causesundesirable consequences [14] To overcome the effect ofcontamination various methods such as filtration ad-sorption precipitation coagulation ion exchange oxidationprocesses etc [15] were carried out to remove the haz-ardous contaminants from wastewaters Among the variousmethods adsorption was sorted to be more efficient It isfamiliarly employed in industries because of its less costsimple design less sensitivity and easy operation towardsthe toxic pollutants In this broad review the structureproperties and preparation methodologies of grapheneoxide are elaborated Subsequently its applications onwastewater treatment as well as other major areas werereviewed along with the negative impacts of GO
2 Structure of GO
Figure 1 describes the structure of graphene graphene oxideand reduced graphene oxide +e chemical and physicalstructure of GO has been the major subject of considerablediscussion due to its complex nature characteristics and var-iability in sample to sample Graphene oxide is nothing but theoxidative form of graphene as graphene is highly expensive anddifficult to produce [16] Rather GO can be produced easily atless cost Graphene oxide contains oxygen functionalization ofabout 20 to 30 in the basal plane Several models werepostulated to predict the structure of GO Among these pos-tulations highly accepted model called Lerf-Klinowski modelshows that basically GO contains carbon basal plane with theepoxy and hydroxyl functional groups with the edges of thesheet terminated by carboxylic acid +e highly ordered sp2regions are present in long range interrupted by disordered sp3regions especially in carbon basal plane [17] Furthermoreamorphous materials as well as defects present in small patcheson the long range and presence of amorphous materials mightbe due to surface contamination
3 Properties of GO
Since oxygen functional groups are present in its structuregraphene oxide dispersed rapidly in different solvents whichinclude organic solvents and water +e mechanical andelectrical properties of graphene oxide composite are en-hanced by combining the GOwith matrices made of ceramicor polymers [18] Graphene oxide when there is a change insp2 bonding can be widely used as an excellent insulator inrelative terms of electrical flow Furthermore the tensilestrength elasticity conductivity and many more propertiescan be improvised by mixing GO with different polymersand other materials [19] +e reduced graphene oxide (re-ferred as rGO) is produced due to the removal of the ionicoxygen groups present it rGO has some properties differedfrom GO as it is highly difficult to disperse as it gets ag-gregated +e desired qualities of graphene oxide are ob-tained bymodifying the functional groups involved in it+efullerene-functionalized secondary amines as well as
porphyrin-functionalized primary amines could be linkedwith platelets of GO in order to improvise the nonlinearoptical behavior of GO +e fragments of GO can be at-tached with each other to produce stable and thin stablestructures which can easily be stretched and folded +esestructures are having wide range applications in storage ofhydrogen ion conductors and in the production ofmembranes meant for nanofiltrations
Graphene is a single layer of carbon atoms tightly boundin a hexagonal honeycomb lattice+e speciality of grapheneis its sp2 hybridization and very low atomic thickness whichallows it to dissolve in various solvents Hence it is per-formed through the structure of π-π noncovalent conver-sion which is carried out using surfactants such aswrapping for example the interaction observed between 1-pyrenebutanoic acid succinimidyl ester (PyBS) and thepotassium salt of coronene tetra-carboxylic acid Grapheneoxide (GO) and reduced graphene oxide (rGO) have beenexploited for the fabrication of graphene-based nano-composites More interest is towards the development of agraphene adsorbent since it has a lot of novel grapheneproperties and a lot of applications [20] +is paper concisethe properties of graphene namely electrical optical mag-netic chemical and mechanical characteristics
4 Mechanical Properties
Van lier et al [21] Reddy et al [22] and Kudin et al [23]described the mechanical properties of monolayer grapheneincluding Youngrsquos modulus and fracture strength in-vestigated by numerical simulations such as molecular dy-namics Ranjibartoreh in 2011 describes the defect-freegraphene as the stiffest material with 10 TPa Youngrsquosmodulus which is usually described in nature and has highintrinsic strength of about 130GPa Terrones et al [24] havedescribed the high fracture strength and average youngsmodulus of 120 MPa and 22 GPa in graphene sheet func-tionalization Park et al [26] and Ruoff [27] have studied thestrength and elastic properties of monolayer graphenethrough nanoindentation by using AFM where they showedthat the GO paper mechanical properties can be improvedby the introduction of cross-linking of individual platelets bydivalent ions +e processed graphene papers have beeninvestigated for its various mechanical properties such astensile indentation bending and superior hardness
41 Tensile Test +e amount of stress and the stress-baseddimensions can be explained by the following equation
εx Ux
σx F
A
εx 1lowastσx minus vσy1113872 1113873
E
(1)
where E is Youngrsquos modulus F the tensile force A the crosssection area ] Poissonrsquos ratio Ux and εx the displacement
International Journal of Chemical Engineering 3
and the strain in x direction and σx and σy the stresses in xand y directions
Dikin et al [29] described the graphene paperrsquos stress-strain curve and addition of graphene octadecylamine (G-ODA) as shown in Figure 2 which illustrates the directbehavior
Stishyness (S) is the amount of an object that resists de-formation (A) as response for an applied force (F)
S F
A (2)
Relationship between Youngrsquos modulus and stishyness isdetermined as follows
F AE
L (3)
where L is the length of stripFigure 3 shows that GP has greater Youngrsquos modulus and
ultimate strength but G-ODA sheets exhibit higher stishynessBucky papers can be prepared with consideration of
dishyerent properties such as Youngrsquos modulus (08ndash24 GPa)ultimate tensile strength (10ndash74 MPa) and strain (15ndash56) Berhan et al [30] states that the maximum Youngrsquosmodulus and ultimate tensile strength in the samples of GPare 3169GPa and 78294MPa Youngrsquos modulus of 20ndash40GPa ultimate tensile strength of 70ndash80MPa and ultimate
tensile strain of 03-04 were stated as mechanicalproperties of GP and graphene oxide papers
42 Indentation Test e radius of a spherical indenter is100 μm which is the most appropriate indenter for
Figure 1 Graphene and graphene composite structures
00023 31058 00059 52729
00056 7025700040 78294
G-ODA(1)G-ODA(2)
G(1)G(2)
0
10
20
30
40
50
60
70
80
Stre
ss (M
Pa)
0001 0002 0003 0004 0005 00060000Strain
Figure 2 Stress-strain curves for the strip GP and G-ODA [28]
4 International Journal of Chemical Engineering
measuring GP and G-ODA elastic modulus hardnessyielding strength and Poissonrsquos ratio e indentation testsare measured using Ultra Micro Indentation System (UMIS)and is repetitive for various GP points whereas the heattreated one for GP and G-ODA varies with the thickness of 3μm and 7 μm Hence the results of dimension test andtensile test for GP and G-ODA strips are illustrated inTables 1 and 2 [24]
en follow the equation
1E( )lowast
1minus ϑ2( )E
+1minus ϑ2( )Eprime
E Ph2a
(4)
Hardness is calculated as
Hy P
πa2 (5)
Hardness and yielding strength of the materials havebeen appraised above
43 Bending Test e GP and G-ODA sheetsrsquo bending ri-gidity and modulus of elasticity have been determinedthrough the bending test e intensively loaded circularplate with deiexclection equation is given below
W F
1propD2r(2)l
r
r0+ r0
2 minus r2( )[ ]
D Eh3
1 1minus ϑ2( )
(6)
where R0 ring inner radius r radial distance of intensiveloaded for the sheet center D bending rigidity F force
concentrated Emodulus of elasticity h sheet deiexclectionand w sheet deiexclection
e inner radius of two iexclat rings is 3 mm Here the sheetthickness of GP and G-ODA are 3 μmand 7 μm respectivelywhich are rigidly centxed with the help of glue on the ringrsquos iexclatsurfaces e modulus of elasticity for GP bending is3044 TPa and in the case of G-ODA is 07647 TPa
5 Optical Properties
In graphene optical properties the most familiar property isabout the performance of sturdy quencher to severalnanoparticles and luminescent dyes that are authorized astwo probable competitive processes namely photo-inducedelectron transfer and intramolecular energy transfer that areexpedited using a mechanism of through-bond because ofluminophore covalent binding e transparency of gra-phene is more centrmly associated with the eshyect of quantumrather than properties of natural material [31]
e unit cell consists of carbon atoms represented by Aand B and a1 and a2 are the lattice vectors [32] Graphenehas a honeycomb crystal lattice network of carbon atomswith sp2 hybridization whereas this lattice of honeycombhas been considered as saturation of triangular lattice alongwith two atoms per unit cell labeled as A and B e viewfrom point B is rotated by 180 degrees as compared to theview from point A e Bravais lattice is a triangle thatconsists of two atoms per unit cell represented in Figure 4and corresponding Brillouin zone showing the high-symmetry points in Figure 5
e graphene centne structure constant is utilized in thestructure of zero gap Dirac band and it is expressed in termsof the subsequent equation
a e2
h (7)
Hence the graphene dynamic conductivity (G) is con-stant as (e24h) e graphene reiexclectance (R) and trans-parency (T) can be estimated using the following equation
T asymp 1minus πa
R π2a2T2
4
(8)
e incident light of constant transmittance as Tasymp 977has been experimentally recognized in the range of visibleinfrared at 300ndash2500 nm and linear transmittance has beenreduced with the number of graphene layers
e carriers with relativistic nature of graphene are acore of interpretation that the optical transmission providedusing π times of centne structure is constant Signicentcantly
0169 6207
0120 9743
0130 169920071 18211
G-ODA(1)G-ODA(2)
G(1)G(2)
0
2
4
6
8
10
12
14
16
18
20
22
Stiff
ness
(Nm
m)
005 010 015000Stretch (mm)
Figure 3 Stishyness vs stretch of GP and G-ODA strips [24]
modulate the graphene electronic properties with latticestrain e graphene optical response with polarizationdependence consists of lattice strain induced in the grapheneband structure which can be monitored directly in thetransmission experiment Graphene and its bilayer areshown in Figure 6 and optical image of graphene is shown inFigure 7
Figure 7 expresses graphene optical image iexclakes with thelayer of 1 2 3 and 4 layers on a 285 nm thickness of SiO2-on-Si substrate [33 34]
In graphene the magnetism has occurrence which is atopic of considerable interest whereas the magnetismpresent in the graphene can be persuaded using the defect ofvacancy or by hydrogen chemisorption Bhowmick andShenoy [35] and several researchers have proposed that anessential graphene magnetic property is zigzag edges ereare some convinced magnetic features involved in thegraphene which are behavior of spin-glass para magnetismand phenomenon of magnetic switching like antiferro-magnetic or ferromagnetic
At room temperature the graphene with ferromag-netic behaviour has limited saturation and magnetizationvalue of about 0004 to 0020 emugminus1 after the
diamagnetic background deduction e graphene sam-ples with magnetic properties created from EG nano-diamond (DG) conversion and graphite arc evaporationover hydrogen (HG) are represented e magnetizationwith temperature dependence present in the HG and EGmeasured sample is shown in Figure 8 as 500 Oe whereasthe sample of graphene in room temperature withmagnetic hysteresis is shown in Figure 9 Hence thetemperature increases as the MS value is increased but
Table 2 Tensile test results of GP and G-ODA strips
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
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[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
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[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
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[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
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[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
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[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
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[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
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[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
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16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
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[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
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range of bacteria fungi and algae convert the sludge intocarbon dioxide (CO2) and water (H2O) During this levelsome amount of energy in terms of biogas production isgenerated During the last treatment level any impuritiesthat are left out from the above two processes are removedproducing the water fit for environment and generalpurposes
As water is very much important for all the living or-ganisms and due to limited availability as well as high de-mand the research community intends to bring novelmethodologies that can ensure the sustainability of waterresources Some of the few novel methodologies establishedby the research community are listed below
(1) +ere is a much attraction towards the use ofnanomaterials on wastewater treatment It has nu-merous potential merits which includes high effi-cient treatment due to wide surface area and betterchemical properties In addition to that less costhigh reusability and availability of effective recoveryof nanomaterials after their use made them morelucrativeToday numerous researches aimed inexploiting the potential of nanomaterials [1] by usingit in different forms such as nanotubes nano-adsorbents catalysts in Nano-sized semi permeablemembrane made from Nano fibers Nanomaterialswith magnetic properties Nano flakes and Nanogranules etc and recently reviewed the role of Nanoscience and nanotechnology on the treatment ofwastewaters
(2) Another research area in which much attentionfocused in recent years is membrane-based waste-water treatment Today researchers tested the effi-cacy of multiple ranges of membrane technologieswhich include microfiltration ultrafiltration nano-filtration and reverse osmosis Microfiltration usesthe membrane of pore size 004 to 01 microns whilein ultrafiltration process the membrane with poresize 001 to 002 microns is used for water purifi-cation processes Microfiltration is also used inwastewater treatment but with larger pore sized (02to 04 microns) membrane However microfiltrationas well as ultrafiltration allows the flow of dissolvedsolids present in water +is can be eliminated withnanofiltration and reverse osmosis +us micro-filtration can be generously used as pretreatment toRO and nanofiltration +us the membrane-basedwastewater technologies are found to be more ef-fective on eliminating suspended as well as dissolvedsolids in addition to removal of pathogens Howeverthey have a big limitation corresponding to costincurred as they require very large amount of energyin comparison with conventional treatmentmethodologies
Earlier wastewater was considered as troublesome andmore problematic but today wastewater is recycled andconsidered as renewable source of energy +e wastewatercontains more than 4 times of energy required for treatmentand abundance of energy is present in wastewater in terms of
chemical thermal and hydraulic energy Among thesethermal energy stands first with about 80 chemical energyavailability attributes to about 20 and hydraulic energyavailability attributes to a negligible amount (lt1) +usimplementation of effective treatment methodology not onlydegrades the wastewater but can also produce energythrough biogas production
Wide ranges of eco-friendly and high-cost nano-materials are tested by the research community in thetreatment of wastewaters +ese materials are developedwith certain unique functional and surface characteristicsfor the purification of surface water and groundwater Inaddition these nanomaterials were also used in degrada-tion of industrial effluents [2] In recent decades nano-particles have been studied for their capacity as adsorbents+e size of the nanoparticles is considered as an importantfactor in deciding the chemical activities such as adsorption[3 4]
+e inorganic nanoparticle oxides produced frommetalsas well as nonmetals are considered as most promisingnanoadsorbents +ese oxide-based nanoadsorbents areemployed for removing the hazardous pollutants present inwastewaters Some of these nanoadsorbents reported in thepast decade includes titanium oxides [5] titanium oxidesand dendrimer composites [6 7] manganese oxides [8]ferric oxides [9] zinc oxides [10] and magnesium oxides[11]+e successful use of nanoadsorbents on degradation ofpollutants attributed to several reasons that include highsurface area less impact on environment easy availabilityand nongeneration of secondary pollutants [12] that requiresfurther treatment and thus these inorganic nanoadsorbentsare considered as one among the best adsorbents
Graphene is a type of carbon having layered structuredwith special features that tends to several environmentalapplications [13] Graphene oxide (GO) which is an ex-tension of carbon material that has two-dimensionalstructure is produced by oxidation of graphite layer bymeans of chemical method Surprisingly graphene is in-credibly flexible even though its strength is more than 200times higher than steel In addition it is ultralight in weightbut highly tough in nature It is possibly one of the extremelythinnest materials in the world with highly transparentnature In the year 1962 graphene was observed through theelectron microscope for the first time Later in 2004 AndreGeim and Konstantin rediscovered and characterized thegraphene nanoparticles for which they received Nobel prizefor physics in the year 2010 Graphene is considered as oneamong the materials having wide surface area ie it has asurface area about 2630m2g (theoretical) while the carbonnanotubes have a surface area of 1000m2g
Hummersrsquo method was considered as one of the efficientas well as faster methods for the preparation of GO in whichpure carbon graphene combines to react with molecularoxygen Another advantage behind this method is producingGO with relatively high carbon-oxygen ratio GO has twomain characteristic features when compared to othernanomaterials like carbon nanotubes (CNTs) In the firststep of preparation synthesis of single layer of GOwhich hasmaximum heavy metal ion adsorption is done In the second
2 International Journal of Chemical Engineering
step chemical exfoliation of raw graphite without the ad-dition of any metallic catalyst is carried out which does notneed the help of any complex instruments
+e contamination of heavy metal ions in water causesundesirable consequences [14] To overcome the effect ofcontamination various methods such as filtration ad-sorption precipitation coagulation ion exchange oxidationprocesses etc [15] were carried out to remove the haz-ardous contaminants from wastewaters Among the variousmethods adsorption was sorted to be more efficient It isfamiliarly employed in industries because of its less costsimple design less sensitivity and easy operation towardsthe toxic pollutants In this broad review the structureproperties and preparation methodologies of grapheneoxide are elaborated Subsequently its applications onwastewater treatment as well as other major areas werereviewed along with the negative impacts of GO
2 Structure of GO
Figure 1 describes the structure of graphene graphene oxideand reduced graphene oxide +e chemical and physicalstructure of GO has been the major subject of considerablediscussion due to its complex nature characteristics and var-iability in sample to sample Graphene oxide is nothing but theoxidative form of graphene as graphene is highly expensive anddifficult to produce [16] Rather GO can be produced easily atless cost Graphene oxide contains oxygen functionalization ofabout 20 to 30 in the basal plane Several models werepostulated to predict the structure of GO Among these pos-tulations highly accepted model called Lerf-Klinowski modelshows that basically GO contains carbon basal plane with theepoxy and hydroxyl functional groups with the edges of thesheet terminated by carboxylic acid +e highly ordered sp2regions are present in long range interrupted by disordered sp3regions especially in carbon basal plane [17] Furthermoreamorphous materials as well as defects present in small patcheson the long range and presence of amorphous materials mightbe due to surface contamination
3 Properties of GO
Since oxygen functional groups are present in its structuregraphene oxide dispersed rapidly in different solvents whichinclude organic solvents and water +e mechanical andelectrical properties of graphene oxide composite are en-hanced by combining the GOwith matrices made of ceramicor polymers [18] Graphene oxide when there is a change insp2 bonding can be widely used as an excellent insulator inrelative terms of electrical flow Furthermore the tensilestrength elasticity conductivity and many more propertiescan be improvised by mixing GO with different polymersand other materials [19] +e reduced graphene oxide (re-ferred as rGO) is produced due to the removal of the ionicoxygen groups present it rGO has some properties differedfrom GO as it is highly difficult to disperse as it gets ag-gregated +e desired qualities of graphene oxide are ob-tained bymodifying the functional groups involved in it+efullerene-functionalized secondary amines as well as
porphyrin-functionalized primary amines could be linkedwith platelets of GO in order to improvise the nonlinearoptical behavior of GO +e fragments of GO can be at-tached with each other to produce stable and thin stablestructures which can easily be stretched and folded +esestructures are having wide range applications in storage ofhydrogen ion conductors and in the production ofmembranes meant for nanofiltrations
Graphene is a single layer of carbon atoms tightly boundin a hexagonal honeycomb lattice+e speciality of grapheneis its sp2 hybridization and very low atomic thickness whichallows it to dissolve in various solvents Hence it is per-formed through the structure of π-π noncovalent conver-sion which is carried out using surfactants such aswrapping for example the interaction observed between 1-pyrenebutanoic acid succinimidyl ester (PyBS) and thepotassium salt of coronene tetra-carboxylic acid Grapheneoxide (GO) and reduced graphene oxide (rGO) have beenexploited for the fabrication of graphene-based nano-composites More interest is towards the development of agraphene adsorbent since it has a lot of novel grapheneproperties and a lot of applications [20] +is paper concisethe properties of graphene namely electrical optical mag-netic chemical and mechanical characteristics
4 Mechanical Properties
Van lier et al [21] Reddy et al [22] and Kudin et al [23]described the mechanical properties of monolayer grapheneincluding Youngrsquos modulus and fracture strength in-vestigated by numerical simulations such as molecular dy-namics Ranjibartoreh in 2011 describes the defect-freegraphene as the stiffest material with 10 TPa Youngrsquosmodulus which is usually described in nature and has highintrinsic strength of about 130GPa Terrones et al [24] havedescribed the high fracture strength and average youngsmodulus of 120 MPa and 22 GPa in graphene sheet func-tionalization Park et al [26] and Ruoff [27] have studied thestrength and elastic properties of monolayer graphenethrough nanoindentation by using AFM where they showedthat the GO paper mechanical properties can be improvedby the introduction of cross-linking of individual platelets bydivalent ions +e processed graphene papers have beeninvestigated for its various mechanical properties such astensile indentation bending and superior hardness
41 Tensile Test +e amount of stress and the stress-baseddimensions can be explained by the following equation
εx Ux
σx F
A
εx 1lowastσx minus vσy1113872 1113873
E
(1)
where E is Youngrsquos modulus F the tensile force A the crosssection area ] Poissonrsquos ratio Ux and εx the displacement
International Journal of Chemical Engineering 3
and the strain in x direction and σx and σy the stresses in xand y directions
Dikin et al [29] described the graphene paperrsquos stress-strain curve and addition of graphene octadecylamine (G-ODA) as shown in Figure 2 which illustrates the directbehavior
Stishyness (S) is the amount of an object that resists de-formation (A) as response for an applied force (F)
S F
A (2)
Relationship between Youngrsquos modulus and stishyness isdetermined as follows
F AE
L (3)
where L is the length of stripFigure 3 shows that GP has greater Youngrsquos modulus and
ultimate strength but G-ODA sheets exhibit higher stishynessBucky papers can be prepared with consideration of
dishyerent properties such as Youngrsquos modulus (08ndash24 GPa)ultimate tensile strength (10ndash74 MPa) and strain (15ndash56) Berhan et al [30] states that the maximum Youngrsquosmodulus and ultimate tensile strength in the samples of GPare 3169GPa and 78294MPa Youngrsquos modulus of 20ndash40GPa ultimate tensile strength of 70ndash80MPa and ultimate
tensile strain of 03-04 were stated as mechanicalproperties of GP and graphene oxide papers
42 Indentation Test e radius of a spherical indenter is100 μm which is the most appropriate indenter for
Figure 1 Graphene and graphene composite structures
00023 31058 00059 52729
00056 7025700040 78294
G-ODA(1)G-ODA(2)
G(1)G(2)
0
10
20
30
40
50
60
70
80
Stre
ss (M
Pa)
0001 0002 0003 0004 0005 00060000Strain
Figure 2 Stress-strain curves for the strip GP and G-ODA [28]
4 International Journal of Chemical Engineering
measuring GP and G-ODA elastic modulus hardnessyielding strength and Poissonrsquos ratio e indentation testsare measured using Ultra Micro Indentation System (UMIS)and is repetitive for various GP points whereas the heattreated one for GP and G-ODA varies with the thickness of 3μm and 7 μm Hence the results of dimension test andtensile test for GP and G-ODA strips are illustrated inTables 1 and 2 [24]
en follow the equation
1E( )lowast
1minus ϑ2( )E
+1minus ϑ2( )Eprime
E Ph2a
(4)
Hardness is calculated as
Hy P
πa2 (5)
Hardness and yielding strength of the materials havebeen appraised above
43 Bending Test e GP and G-ODA sheetsrsquo bending ri-gidity and modulus of elasticity have been determinedthrough the bending test e intensively loaded circularplate with deiexclection equation is given below
W F
1propD2r(2)l
r
r0+ r0
2 minus r2( )[ ]
D Eh3
1 1minus ϑ2( )
(6)
where R0 ring inner radius r radial distance of intensiveloaded for the sheet center D bending rigidity F force
concentrated Emodulus of elasticity h sheet deiexclectionand w sheet deiexclection
e inner radius of two iexclat rings is 3 mm Here the sheetthickness of GP and G-ODA are 3 μmand 7 μm respectivelywhich are rigidly centxed with the help of glue on the ringrsquos iexclatsurfaces e modulus of elasticity for GP bending is3044 TPa and in the case of G-ODA is 07647 TPa
5 Optical Properties
In graphene optical properties the most familiar property isabout the performance of sturdy quencher to severalnanoparticles and luminescent dyes that are authorized astwo probable competitive processes namely photo-inducedelectron transfer and intramolecular energy transfer that areexpedited using a mechanism of through-bond because ofluminophore covalent binding e transparency of gra-phene is more centrmly associated with the eshyect of quantumrather than properties of natural material [31]
e unit cell consists of carbon atoms represented by Aand B and a1 and a2 are the lattice vectors [32] Graphenehas a honeycomb crystal lattice network of carbon atomswith sp2 hybridization whereas this lattice of honeycombhas been considered as saturation of triangular lattice alongwith two atoms per unit cell labeled as A and B e viewfrom point B is rotated by 180 degrees as compared to theview from point A e Bravais lattice is a triangle thatconsists of two atoms per unit cell represented in Figure 4and corresponding Brillouin zone showing the high-symmetry points in Figure 5
e graphene centne structure constant is utilized in thestructure of zero gap Dirac band and it is expressed in termsof the subsequent equation
a e2
h (7)
Hence the graphene dynamic conductivity (G) is con-stant as (e24h) e graphene reiexclectance (R) and trans-parency (T) can be estimated using the following equation
T asymp 1minus πa
R π2a2T2
4
(8)
e incident light of constant transmittance as Tasymp 977has been experimentally recognized in the range of visibleinfrared at 300ndash2500 nm and linear transmittance has beenreduced with the number of graphene layers
e carriers with relativistic nature of graphene are acore of interpretation that the optical transmission providedusing π times of centne structure is constant Signicentcantly
0169 6207
0120 9743
0130 169920071 18211
G-ODA(1)G-ODA(2)
G(1)G(2)
0
2
4
6
8
10
12
14
16
18
20
22
Stiff
ness
(Nm
m)
005 010 015000Stretch (mm)
Figure 3 Stishyness vs stretch of GP and G-ODA strips [24]
modulate the graphene electronic properties with latticestrain e graphene optical response with polarizationdependence consists of lattice strain induced in the grapheneband structure which can be monitored directly in thetransmission experiment Graphene and its bilayer areshown in Figure 6 and optical image of graphene is shown inFigure 7
Figure 7 expresses graphene optical image iexclakes with thelayer of 1 2 3 and 4 layers on a 285 nm thickness of SiO2-on-Si substrate [33 34]
In graphene the magnetism has occurrence which is atopic of considerable interest whereas the magnetismpresent in the graphene can be persuaded using the defect ofvacancy or by hydrogen chemisorption Bhowmick andShenoy [35] and several researchers have proposed that anessential graphene magnetic property is zigzag edges ereare some convinced magnetic features involved in thegraphene which are behavior of spin-glass para magnetismand phenomenon of magnetic switching like antiferro-magnetic or ferromagnetic
At room temperature the graphene with ferromag-netic behaviour has limited saturation and magnetizationvalue of about 0004 to 0020 emugminus1 after the
diamagnetic background deduction e graphene sam-ples with magnetic properties created from EG nano-diamond (DG) conversion and graphite arc evaporationover hydrogen (HG) are represented e magnetizationwith temperature dependence present in the HG and EGmeasured sample is shown in Figure 8 as 500 Oe whereasthe sample of graphene in room temperature withmagnetic hysteresis is shown in Figure 9 Hence thetemperature increases as the MS value is increased but
Table 2 Tensile test results of GP and G-ODA strips
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
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[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
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[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
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[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
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[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
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[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
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[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
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[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
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[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
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[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
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[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
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[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
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[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
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[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
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[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
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[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
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step chemical exfoliation of raw graphite without the ad-dition of any metallic catalyst is carried out which does notneed the help of any complex instruments
+e contamination of heavy metal ions in water causesundesirable consequences [14] To overcome the effect ofcontamination various methods such as filtration ad-sorption precipitation coagulation ion exchange oxidationprocesses etc [15] were carried out to remove the haz-ardous contaminants from wastewaters Among the variousmethods adsorption was sorted to be more efficient It isfamiliarly employed in industries because of its less costsimple design less sensitivity and easy operation towardsthe toxic pollutants In this broad review the structureproperties and preparation methodologies of grapheneoxide are elaborated Subsequently its applications onwastewater treatment as well as other major areas werereviewed along with the negative impacts of GO
2 Structure of GO
Figure 1 describes the structure of graphene graphene oxideand reduced graphene oxide +e chemical and physicalstructure of GO has been the major subject of considerablediscussion due to its complex nature characteristics and var-iability in sample to sample Graphene oxide is nothing but theoxidative form of graphene as graphene is highly expensive anddifficult to produce [16] Rather GO can be produced easily atless cost Graphene oxide contains oxygen functionalization ofabout 20 to 30 in the basal plane Several models werepostulated to predict the structure of GO Among these pos-tulations highly accepted model called Lerf-Klinowski modelshows that basically GO contains carbon basal plane with theepoxy and hydroxyl functional groups with the edges of thesheet terminated by carboxylic acid +e highly ordered sp2regions are present in long range interrupted by disordered sp3regions especially in carbon basal plane [17] Furthermoreamorphous materials as well as defects present in small patcheson the long range and presence of amorphous materials mightbe due to surface contamination
3 Properties of GO
Since oxygen functional groups are present in its structuregraphene oxide dispersed rapidly in different solvents whichinclude organic solvents and water +e mechanical andelectrical properties of graphene oxide composite are en-hanced by combining the GOwith matrices made of ceramicor polymers [18] Graphene oxide when there is a change insp2 bonding can be widely used as an excellent insulator inrelative terms of electrical flow Furthermore the tensilestrength elasticity conductivity and many more propertiescan be improvised by mixing GO with different polymersand other materials [19] +e reduced graphene oxide (re-ferred as rGO) is produced due to the removal of the ionicoxygen groups present it rGO has some properties differedfrom GO as it is highly difficult to disperse as it gets ag-gregated +e desired qualities of graphene oxide are ob-tained bymodifying the functional groups involved in it+efullerene-functionalized secondary amines as well as
porphyrin-functionalized primary amines could be linkedwith platelets of GO in order to improvise the nonlinearoptical behavior of GO +e fragments of GO can be at-tached with each other to produce stable and thin stablestructures which can easily be stretched and folded +esestructures are having wide range applications in storage ofhydrogen ion conductors and in the production ofmembranes meant for nanofiltrations
Graphene is a single layer of carbon atoms tightly boundin a hexagonal honeycomb lattice+e speciality of grapheneis its sp2 hybridization and very low atomic thickness whichallows it to dissolve in various solvents Hence it is per-formed through the structure of π-π noncovalent conver-sion which is carried out using surfactants such aswrapping for example the interaction observed between 1-pyrenebutanoic acid succinimidyl ester (PyBS) and thepotassium salt of coronene tetra-carboxylic acid Grapheneoxide (GO) and reduced graphene oxide (rGO) have beenexploited for the fabrication of graphene-based nano-composites More interest is towards the development of agraphene adsorbent since it has a lot of novel grapheneproperties and a lot of applications [20] +is paper concisethe properties of graphene namely electrical optical mag-netic chemical and mechanical characteristics
4 Mechanical Properties
Van lier et al [21] Reddy et al [22] and Kudin et al [23]described the mechanical properties of monolayer grapheneincluding Youngrsquos modulus and fracture strength in-vestigated by numerical simulations such as molecular dy-namics Ranjibartoreh in 2011 describes the defect-freegraphene as the stiffest material with 10 TPa Youngrsquosmodulus which is usually described in nature and has highintrinsic strength of about 130GPa Terrones et al [24] havedescribed the high fracture strength and average youngsmodulus of 120 MPa and 22 GPa in graphene sheet func-tionalization Park et al [26] and Ruoff [27] have studied thestrength and elastic properties of monolayer graphenethrough nanoindentation by using AFM where they showedthat the GO paper mechanical properties can be improvedby the introduction of cross-linking of individual platelets bydivalent ions +e processed graphene papers have beeninvestigated for its various mechanical properties such astensile indentation bending and superior hardness
41 Tensile Test +e amount of stress and the stress-baseddimensions can be explained by the following equation
εx Ux
σx F
A
εx 1lowastσx minus vσy1113872 1113873
E
(1)
where E is Youngrsquos modulus F the tensile force A the crosssection area ] Poissonrsquos ratio Ux and εx the displacement
International Journal of Chemical Engineering 3
and the strain in x direction and σx and σy the stresses in xand y directions
Dikin et al [29] described the graphene paperrsquos stress-strain curve and addition of graphene octadecylamine (G-ODA) as shown in Figure 2 which illustrates the directbehavior
Stishyness (S) is the amount of an object that resists de-formation (A) as response for an applied force (F)
S F
A (2)
Relationship between Youngrsquos modulus and stishyness isdetermined as follows
F AE
L (3)
where L is the length of stripFigure 3 shows that GP has greater Youngrsquos modulus and
ultimate strength but G-ODA sheets exhibit higher stishynessBucky papers can be prepared with consideration of
dishyerent properties such as Youngrsquos modulus (08ndash24 GPa)ultimate tensile strength (10ndash74 MPa) and strain (15ndash56) Berhan et al [30] states that the maximum Youngrsquosmodulus and ultimate tensile strength in the samples of GPare 3169GPa and 78294MPa Youngrsquos modulus of 20ndash40GPa ultimate tensile strength of 70ndash80MPa and ultimate
tensile strain of 03-04 were stated as mechanicalproperties of GP and graphene oxide papers
42 Indentation Test e radius of a spherical indenter is100 μm which is the most appropriate indenter for
Figure 1 Graphene and graphene composite structures
00023 31058 00059 52729
00056 7025700040 78294
G-ODA(1)G-ODA(2)
G(1)G(2)
0
10
20
30
40
50
60
70
80
Stre
ss (M
Pa)
0001 0002 0003 0004 0005 00060000Strain
Figure 2 Stress-strain curves for the strip GP and G-ODA [28]
4 International Journal of Chemical Engineering
measuring GP and G-ODA elastic modulus hardnessyielding strength and Poissonrsquos ratio e indentation testsare measured using Ultra Micro Indentation System (UMIS)and is repetitive for various GP points whereas the heattreated one for GP and G-ODA varies with the thickness of 3μm and 7 μm Hence the results of dimension test andtensile test for GP and G-ODA strips are illustrated inTables 1 and 2 [24]
en follow the equation
1E( )lowast
1minus ϑ2( )E
+1minus ϑ2( )Eprime
E Ph2a
(4)
Hardness is calculated as
Hy P
πa2 (5)
Hardness and yielding strength of the materials havebeen appraised above
43 Bending Test e GP and G-ODA sheetsrsquo bending ri-gidity and modulus of elasticity have been determinedthrough the bending test e intensively loaded circularplate with deiexclection equation is given below
W F
1propD2r(2)l
r
r0+ r0
2 minus r2( )[ ]
D Eh3
1 1minus ϑ2( )
(6)
where R0 ring inner radius r radial distance of intensiveloaded for the sheet center D bending rigidity F force
concentrated Emodulus of elasticity h sheet deiexclectionand w sheet deiexclection
e inner radius of two iexclat rings is 3 mm Here the sheetthickness of GP and G-ODA are 3 μmand 7 μm respectivelywhich are rigidly centxed with the help of glue on the ringrsquos iexclatsurfaces e modulus of elasticity for GP bending is3044 TPa and in the case of G-ODA is 07647 TPa
5 Optical Properties
In graphene optical properties the most familiar property isabout the performance of sturdy quencher to severalnanoparticles and luminescent dyes that are authorized astwo probable competitive processes namely photo-inducedelectron transfer and intramolecular energy transfer that areexpedited using a mechanism of through-bond because ofluminophore covalent binding e transparency of gra-phene is more centrmly associated with the eshyect of quantumrather than properties of natural material [31]
e unit cell consists of carbon atoms represented by Aand B and a1 and a2 are the lattice vectors [32] Graphenehas a honeycomb crystal lattice network of carbon atomswith sp2 hybridization whereas this lattice of honeycombhas been considered as saturation of triangular lattice alongwith two atoms per unit cell labeled as A and B e viewfrom point B is rotated by 180 degrees as compared to theview from point A e Bravais lattice is a triangle thatconsists of two atoms per unit cell represented in Figure 4and corresponding Brillouin zone showing the high-symmetry points in Figure 5
e graphene centne structure constant is utilized in thestructure of zero gap Dirac band and it is expressed in termsof the subsequent equation
a e2
h (7)
Hence the graphene dynamic conductivity (G) is con-stant as (e24h) e graphene reiexclectance (R) and trans-parency (T) can be estimated using the following equation
T asymp 1minus πa
R π2a2T2
4
(8)
e incident light of constant transmittance as Tasymp 977has been experimentally recognized in the range of visibleinfrared at 300ndash2500 nm and linear transmittance has beenreduced with the number of graphene layers
e carriers with relativistic nature of graphene are acore of interpretation that the optical transmission providedusing π times of centne structure is constant Signicentcantly
0169 6207
0120 9743
0130 169920071 18211
G-ODA(1)G-ODA(2)
G(1)G(2)
0
2
4
6
8
10
12
14
16
18
20
22
Stiff
ness
(Nm
m)
005 010 015000Stretch (mm)
Figure 3 Stishyness vs stretch of GP and G-ODA strips [24]
modulate the graphene electronic properties with latticestrain e graphene optical response with polarizationdependence consists of lattice strain induced in the grapheneband structure which can be monitored directly in thetransmission experiment Graphene and its bilayer areshown in Figure 6 and optical image of graphene is shown inFigure 7
Figure 7 expresses graphene optical image iexclakes with thelayer of 1 2 3 and 4 layers on a 285 nm thickness of SiO2-on-Si substrate [33 34]
In graphene the magnetism has occurrence which is atopic of considerable interest whereas the magnetismpresent in the graphene can be persuaded using the defect ofvacancy or by hydrogen chemisorption Bhowmick andShenoy [35] and several researchers have proposed that anessential graphene magnetic property is zigzag edges ereare some convinced magnetic features involved in thegraphene which are behavior of spin-glass para magnetismand phenomenon of magnetic switching like antiferro-magnetic or ferromagnetic
At room temperature the graphene with ferromag-netic behaviour has limited saturation and magnetizationvalue of about 0004 to 0020 emugminus1 after the
diamagnetic background deduction e graphene sam-ples with magnetic properties created from EG nano-diamond (DG) conversion and graphite arc evaporationover hydrogen (HG) are represented e magnetizationwith temperature dependence present in the HG and EGmeasured sample is shown in Figure 8 as 500 Oe whereasthe sample of graphene in room temperature withmagnetic hysteresis is shown in Figure 9 Hence thetemperature increases as the MS value is increased but
Table 2 Tensile test results of GP and G-ODA strips
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
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and the strain in x direction and σx and σy the stresses in xand y directions
Dikin et al [29] described the graphene paperrsquos stress-strain curve and addition of graphene octadecylamine (G-ODA) as shown in Figure 2 which illustrates the directbehavior
Stishyness (S) is the amount of an object that resists de-formation (A) as response for an applied force (F)
S F
A (2)
Relationship between Youngrsquos modulus and stishyness isdetermined as follows
F AE
L (3)
where L is the length of stripFigure 3 shows that GP has greater Youngrsquos modulus and
ultimate strength but G-ODA sheets exhibit higher stishynessBucky papers can be prepared with consideration of
dishyerent properties such as Youngrsquos modulus (08ndash24 GPa)ultimate tensile strength (10ndash74 MPa) and strain (15ndash56) Berhan et al [30] states that the maximum Youngrsquosmodulus and ultimate tensile strength in the samples of GPare 3169GPa and 78294MPa Youngrsquos modulus of 20ndash40GPa ultimate tensile strength of 70ndash80MPa and ultimate
tensile strain of 03-04 were stated as mechanicalproperties of GP and graphene oxide papers
42 Indentation Test e radius of a spherical indenter is100 μm which is the most appropriate indenter for
Figure 1 Graphene and graphene composite structures
00023 31058 00059 52729
00056 7025700040 78294
G-ODA(1)G-ODA(2)
G(1)G(2)
0
10
20
30
40
50
60
70
80
Stre
ss (M
Pa)
0001 0002 0003 0004 0005 00060000Strain
Figure 2 Stress-strain curves for the strip GP and G-ODA [28]
4 International Journal of Chemical Engineering
measuring GP and G-ODA elastic modulus hardnessyielding strength and Poissonrsquos ratio e indentation testsare measured using Ultra Micro Indentation System (UMIS)and is repetitive for various GP points whereas the heattreated one for GP and G-ODA varies with the thickness of 3μm and 7 μm Hence the results of dimension test andtensile test for GP and G-ODA strips are illustrated inTables 1 and 2 [24]
en follow the equation
1E( )lowast
1minus ϑ2( )E
+1minus ϑ2( )Eprime
E Ph2a
(4)
Hardness is calculated as
Hy P
πa2 (5)
Hardness and yielding strength of the materials havebeen appraised above
43 Bending Test e GP and G-ODA sheetsrsquo bending ri-gidity and modulus of elasticity have been determinedthrough the bending test e intensively loaded circularplate with deiexclection equation is given below
W F
1propD2r(2)l
r
r0+ r0
2 minus r2( )[ ]
D Eh3
1 1minus ϑ2( )
(6)
where R0 ring inner radius r radial distance of intensiveloaded for the sheet center D bending rigidity F force
concentrated Emodulus of elasticity h sheet deiexclectionand w sheet deiexclection
e inner radius of two iexclat rings is 3 mm Here the sheetthickness of GP and G-ODA are 3 μmand 7 μm respectivelywhich are rigidly centxed with the help of glue on the ringrsquos iexclatsurfaces e modulus of elasticity for GP bending is3044 TPa and in the case of G-ODA is 07647 TPa
5 Optical Properties
In graphene optical properties the most familiar property isabout the performance of sturdy quencher to severalnanoparticles and luminescent dyes that are authorized astwo probable competitive processes namely photo-inducedelectron transfer and intramolecular energy transfer that areexpedited using a mechanism of through-bond because ofluminophore covalent binding e transparency of gra-phene is more centrmly associated with the eshyect of quantumrather than properties of natural material [31]
e unit cell consists of carbon atoms represented by Aand B and a1 and a2 are the lattice vectors [32] Graphenehas a honeycomb crystal lattice network of carbon atomswith sp2 hybridization whereas this lattice of honeycombhas been considered as saturation of triangular lattice alongwith two atoms per unit cell labeled as A and B e viewfrom point B is rotated by 180 degrees as compared to theview from point A e Bravais lattice is a triangle thatconsists of two atoms per unit cell represented in Figure 4and corresponding Brillouin zone showing the high-symmetry points in Figure 5
e graphene centne structure constant is utilized in thestructure of zero gap Dirac band and it is expressed in termsof the subsequent equation
a e2
h (7)
Hence the graphene dynamic conductivity (G) is con-stant as (e24h) e graphene reiexclectance (R) and trans-parency (T) can be estimated using the following equation
T asymp 1minus πa
R π2a2T2
4
(8)
e incident light of constant transmittance as Tasymp 977has been experimentally recognized in the range of visibleinfrared at 300ndash2500 nm and linear transmittance has beenreduced with the number of graphene layers
e carriers with relativistic nature of graphene are acore of interpretation that the optical transmission providedusing π times of centne structure is constant Signicentcantly
0169 6207
0120 9743
0130 169920071 18211
G-ODA(1)G-ODA(2)
G(1)G(2)
0
2
4
6
8
10
12
14
16
18
20
22
Stiff
ness
(Nm
m)
005 010 015000Stretch (mm)
Figure 3 Stishyness vs stretch of GP and G-ODA strips [24]
modulate the graphene electronic properties with latticestrain e graphene optical response with polarizationdependence consists of lattice strain induced in the grapheneband structure which can be monitored directly in thetransmission experiment Graphene and its bilayer areshown in Figure 6 and optical image of graphene is shown inFigure 7
Figure 7 expresses graphene optical image iexclakes with thelayer of 1 2 3 and 4 layers on a 285 nm thickness of SiO2-on-Si substrate [33 34]
In graphene the magnetism has occurrence which is atopic of considerable interest whereas the magnetismpresent in the graphene can be persuaded using the defect ofvacancy or by hydrogen chemisorption Bhowmick andShenoy [35] and several researchers have proposed that anessential graphene magnetic property is zigzag edges ereare some convinced magnetic features involved in thegraphene which are behavior of spin-glass para magnetismand phenomenon of magnetic switching like antiferro-magnetic or ferromagnetic
At room temperature the graphene with ferromag-netic behaviour has limited saturation and magnetizationvalue of about 0004 to 0020 emugminus1 after the
diamagnetic background deduction e graphene sam-ples with magnetic properties created from EG nano-diamond (DG) conversion and graphite arc evaporationover hydrogen (HG) are represented e magnetizationwith temperature dependence present in the HG and EGmeasured sample is shown in Figure 8 as 500 Oe whereasthe sample of graphene in room temperature withmagnetic hysteresis is shown in Figure 9 Hence thetemperature increases as the MS value is increased but
Table 2 Tensile test results of GP and G-ODA strips
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
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Hindawiwwwhindawicom Volume 2018
Navigation and Observation
International Journal of
Hindawi
wwwhindawicom Volume 2018
Advances in
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Submit your manuscripts atwwwhindawicom
measuring GP and G-ODA elastic modulus hardnessyielding strength and Poissonrsquos ratio e indentation testsare measured using Ultra Micro Indentation System (UMIS)and is repetitive for various GP points whereas the heattreated one for GP and G-ODA varies with the thickness of 3μm and 7 μm Hence the results of dimension test andtensile test for GP and G-ODA strips are illustrated inTables 1 and 2 [24]
en follow the equation
1E( )lowast
1minus ϑ2( )E
+1minus ϑ2( )Eprime
E Ph2a
(4)
Hardness is calculated as
Hy P
πa2 (5)
Hardness and yielding strength of the materials havebeen appraised above
43 Bending Test e GP and G-ODA sheetsrsquo bending ri-gidity and modulus of elasticity have been determinedthrough the bending test e intensively loaded circularplate with deiexclection equation is given below
W F
1propD2r(2)l
r
r0+ r0
2 minus r2( )[ ]
D Eh3
1 1minus ϑ2( )
(6)
where R0 ring inner radius r radial distance of intensiveloaded for the sheet center D bending rigidity F force
concentrated Emodulus of elasticity h sheet deiexclectionand w sheet deiexclection
e inner radius of two iexclat rings is 3 mm Here the sheetthickness of GP and G-ODA are 3 μmand 7 μm respectivelywhich are rigidly centxed with the help of glue on the ringrsquos iexclatsurfaces e modulus of elasticity for GP bending is3044 TPa and in the case of G-ODA is 07647 TPa
5 Optical Properties
In graphene optical properties the most familiar property isabout the performance of sturdy quencher to severalnanoparticles and luminescent dyes that are authorized astwo probable competitive processes namely photo-inducedelectron transfer and intramolecular energy transfer that areexpedited using a mechanism of through-bond because ofluminophore covalent binding e transparency of gra-phene is more centrmly associated with the eshyect of quantumrather than properties of natural material [31]
e unit cell consists of carbon atoms represented by Aand B and a1 and a2 are the lattice vectors [32] Graphenehas a honeycomb crystal lattice network of carbon atomswith sp2 hybridization whereas this lattice of honeycombhas been considered as saturation of triangular lattice alongwith two atoms per unit cell labeled as A and B e viewfrom point B is rotated by 180 degrees as compared to theview from point A e Bravais lattice is a triangle thatconsists of two atoms per unit cell represented in Figure 4and corresponding Brillouin zone showing the high-symmetry points in Figure 5
e graphene centne structure constant is utilized in thestructure of zero gap Dirac band and it is expressed in termsof the subsequent equation
a e2
h (7)
Hence the graphene dynamic conductivity (G) is con-stant as (e24h) e graphene reiexclectance (R) and trans-parency (T) can be estimated using the following equation
T asymp 1minus πa
R π2a2T2
4
(8)
e incident light of constant transmittance as Tasymp 977has been experimentally recognized in the range of visibleinfrared at 300ndash2500 nm and linear transmittance has beenreduced with the number of graphene layers
e carriers with relativistic nature of graphene are acore of interpretation that the optical transmission providedusing π times of centne structure is constant Signicentcantly
0169 6207
0120 9743
0130 169920071 18211
G-ODA(1)G-ODA(2)
G(1)G(2)
0
2
4
6
8
10
12
14
16
18
20
22
Stiff
ness
(Nm
m)
005 010 015000Stretch (mm)
Figure 3 Stishyness vs stretch of GP and G-ODA strips [24]
modulate the graphene electronic properties with latticestrain e graphene optical response with polarizationdependence consists of lattice strain induced in the grapheneband structure which can be monitored directly in thetransmission experiment Graphene and its bilayer areshown in Figure 6 and optical image of graphene is shown inFigure 7
Figure 7 expresses graphene optical image iexclakes with thelayer of 1 2 3 and 4 layers on a 285 nm thickness of SiO2-on-Si substrate [33 34]
In graphene the magnetism has occurrence which is atopic of considerable interest whereas the magnetismpresent in the graphene can be persuaded using the defect ofvacancy or by hydrogen chemisorption Bhowmick andShenoy [35] and several researchers have proposed that anessential graphene magnetic property is zigzag edges ereare some convinced magnetic features involved in thegraphene which are behavior of spin-glass para magnetismand phenomenon of magnetic switching like antiferro-magnetic or ferromagnetic
At room temperature the graphene with ferromag-netic behaviour has limited saturation and magnetizationvalue of about 0004 to 0020 emugminus1 after the
diamagnetic background deduction e graphene sam-ples with magnetic properties created from EG nano-diamond (DG) conversion and graphite arc evaporationover hydrogen (HG) are represented e magnetizationwith temperature dependence present in the HG and EGmeasured sample is shown in Figure 8 as 500 Oe whereasthe sample of graphene in room temperature withmagnetic hysteresis is shown in Figure 9 Hence thetemperature increases as the MS value is increased but
Table 2 Tensile test results of GP and G-ODA strips
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
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[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
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[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
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[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
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[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
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[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
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[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
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[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
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[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
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[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Navigation and Observation
International Journal of
Hindawi
wwwhindawicom Volume 2018
Advances in
Multimedia
Submit your manuscripts atwwwhindawicom
modulate the graphene electronic properties with latticestrain e graphene optical response with polarizationdependence consists of lattice strain induced in the grapheneband structure which can be monitored directly in thetransmission experiment Graphene and its bilayer areshown in Figure 6 and optical image of graphene is shown inFigure 7
Figure 7 expresses graphene optical image iexclakes with thelayer of 1 2 3 and 4 layers on a 285 nm thickness of SiO2-on-Si substrate [33 34]
In graphene the magnetism has occurrence which is atopic of considerable interest whereas the magnetismpresent in the graphene can be persuaded using the defect ofvacancy or by hydrogen chemisorption Bhowmick andShenoy [35] and several researchers have proposed that anessential graphene magnetic property is zigzag edges ereare some convinced magnetic features involved in thegraphene which are behavior of spin-glass para magnetismand phenomenon of magnetic switching like antiferro-magnetic or ferromagnetic
At room temperature the graphene with ferromag-netic behaviour has limited saturation and magnetizationvalue of about 0004 to 0020 emugminus1 after the
diamagnetic background deduction e graphene sam-ples with magnetic properties created from EG nano-diamond (DG) conversion and graphite arc evaporationover hydrogen (HG) are represented e magnetizationwith temperature dependence present in the HG and EGmeasured sample is shown in Figure 8 as 500 Oe whereasthe sample of graphene in room temperature withmagnetic hysteresis is shown in Figure 9 Hence thetemperature increases as the MS value is increased but
Table 2 Tensile test results of GP and G-ODA strips
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Navigation and Observation
International Journal of
Hindawi
wwwhindawicom Volume 2018
Advances in
Multimedia
Submit your manuscripts atwwwhindawicom
shown HG is the best feature of hysteretic in saturationWhen the DG presented with saturation magnetizationMS is to low in comparison with HG
+e graphene modification with the magnetic nano-particles is generally obtained using in situ reduction of ironcobalt or nickel salt precursors or assembly of the pre-synthesized magnetic nanoparticles on the surface ofgraphene-based frameworks
6 Chemical Properties
Chemical doping is one of the most widely used tech-niques to tailor the surface and electronic structure ofgraphene However the relatively inert nature of gra-phene is the biggest challenge for chemical functionali-zation or doping of graphene to a high level Recentlyphotochemical reactions been explored for addressingthis issue [36] A variety of photosources includingsunlight UV light and exciter laser radiation have beenapplied to reduce the energy barriers of graphene re-actions It produces highly reactive chemical species
under irradiation mainly the free radicals Photo-induced free radicals usually can overcome the highreaction barriers of graphene addition reactions Underirradiation the functional groups of CMG provide re-active sites for photochemical modifications such asphoto reduction and photo patterning [37]
61 Free Radical-Based Photochemical Reactions Chlorine(Cl) radicals can be produced from Cl2 by irradiation In-spired by the addition reaction of chlorine and benzene toproduce a well-known insecticide hexa chloro cyclohexane(C6Cl6) Liu et al [38] developed a photochemical approachto chlorinate graphene by covalently bonding chlorineradicals to the basal plane carbon atoms (Figure 10) In thiscase graphene sheets with coverage of CndashCl bonds up to 8-atom percentage were formed
Because the CQC bonds of graphene transformed fromsp2 to sp3 the resistance of graphene increased over fourorders of magnitude and a band was gap created [40]Moreover graphene sheets with desired chemical patternscan be prepared by localized photochlorination (Figure 11)offering a feasible approach to realize all graphene circuits+eoretical calculations have been used to analyze thestructural and energetic changes of chlorinated graphene inthe photochemical process as shown in Figure 12 In theinitial stage of photochemical reaction photochemicalmolecules generated with chlorine atoms have been likely toadsorb in graphene for attaining a stable Cl-graphene charge[41] +e C orbital has retained sp2 hybridization and thegraphene was p-type doped Further chlorination inducedthe formation of two adsorption states one is covalentbonding of Cl pairs to the C atoms with a structure close tosp3 hybridization [42] Successively it changed into a morestable configuration the neighboring Cl atoms bonded withcarbon atoms arranged in a hexagonal ring Another state isa nonbonding one Two adjacent chlorine atoms combinewith each other forming chlorine molecules to desorb fromthe graphene surface [43] tuning the band gap of chlori-nated graphene in the range of 0ndash13 eV by its chlorinecoverage
7 Electrical Properties
+e graphenersquos electrical properties have been determined asthe best while compared with several related materialsnamely carbon nanotubes due to its high electric conduc-tivity and more surface area whereas these propertiesprovide a potential graphene for enhancing biosensorselectronics and probable battery cells
Graphene is a two-dimensional array of sp2 carbonatoms with a hexagonal lattice structure whereas thestructure has more simple visualization as nanowire with themolecular scale Hence the graphene has more conductivityin a high surface area which creates its optimal use in theelectrochemical cells Graphene is comparatively low cost forproducing since there are various methods for synthesizingit chemically +e rGO can obtained by reducing the GOeither by quick thermal expansion or with hydrazine +e
0322
0315
0308
0018
0012
00060 50 100 150
T (K)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
200 250 300
0
0
01
01
00
04
100 200 300
45 90 135T (K)
T (K)
H = 1T
H = 1T
HG
EG
H = 500 Oe
180 225 270
Figure 8 Temperature variation of magnetization of few-layergraphene
04
02
00
ndash02
ndash04ndash4000 ndash2000 20000
T = 300 K
H (Oe)
M (e
mumiddot
gndash1)
M (e
mumiddot
gndash1)
DG04
02
00
ndash02
ndash04ndash15 ndash10 ndash05 ndash00
H (T)05 10 15
HG
DG
EG
T = 5 K
4000
Figure 9 Magnetic hysteresis
International Journal of Chemical Engineering 7
structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
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[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
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[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
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[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
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[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
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[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
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[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
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[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
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[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
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[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
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[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
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[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
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Navigation and Observation
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structure of graphene and graphene oxide is illustrated inFigures 13 and 14 respectively
In general hydrazine is an organic reducing agent due toits reaction by products which are normally water and ni-trogen gas whereas hydrazine is utilized for reducing GO inorder to produce chemically modicented grapheneismodicented chemical combination due to rGO with hydrazinedoes not eliminate all the impurities present in the material
However carbonyl carboxyl and hydroxyl groups are notextinguished from the surface of graphene completely usingreduction of hydrazineerefore Gao et al have proposed amechanism to reduce graphene using hydrazine as shown inFigure 15
Most of the experimental research studies on graphenefocus on the electronic properties e most prominentproperty in the earlier research about graphene transistors isthe capability for frequent tuning of carrier charges from holesand electrons An example of the gate dependence in singlelayer graphene is shown in Figure 16 In this thinnest samplethis eshyect is most noticeable but the weakest gate dependence isshown in the sample of multiple layers because of electric centeldscreening using the other layers
Novoselov et al [45] specicented that at low temperaturesand highmagnetic centelds the exceptionalmobility of grapheneallows for the observation of the quantum Hall eshyect for bothelectrons and holes as shown in Figure 17
e quantum Hall eshyects of graphene shown above statethe dishyerence in unique bond structure compared with thetraditional quantum Hall eshyects whereas the plateaus occurat the half integers of 4e2h instead of typical 4e2h For moreapplications that are practical one would like to utilize thestrong gate dependence of graphene for either sensing ortransistor applications whereas no band gap is available ingraphene and the respective resistant modicentcations aresmall Hence the less onoshy ratio annoys the transistor ofgraphene using its nature In addition this limitation can beovercome by carving the graphene into narrow ribbons
When the ribbon was made to shrink the charge carriermomentum present in transverse direction evolved intoquantized that made the results of band gap opening
10microm
Figure 11 Raman D band mapping for a CVD-grown graphenecentlm after a patterned photochlorination [39]
Chlorination of graphene
Covalent bonding
Charge-transfercomplex
Nonbonding
Cl2 molecule
Figure 12 Schematic diagram for the evolution of various ad-sorptions [39]
Figure 13 Chemical structure of graphene
O
O
O
OH
COOH
HO
OH
O
Figure 14 Chemical structure of graphene oxide
Chv
Cl
Photochlorination of graphene
Figure 10 Schematic illustration of graphene photochlorination[39]
8 International Journal of Chemical Engineering
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
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Navigation and Observation
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Advances in
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Submit your manuscripts atwwwhindawicom
whereas the width of ribbon is directly proportional to theband gap is noticeable eshyect present in the carbonnanotube is based on the nanotube band gap which is di-rectly proportional to its diameter Li et al [40] specify theband gap opening that is present in the graphene ribbon
8 Preparation of GO
Micromechanical cleavage epitaxial growth above SiCsubstrates chemical vapor deposition chemical reductionof GO through exfoliation exfoliation of graphite in liquidphase and unzipping the nanotubes made from carbonare some of the well-known most familiar techniquesemployed for graphene production [46]ese methods areeshyective in some terms with several merits as well as de-merits with respect to its applications and operatingconditions [47] Among these abovementioned methodsliquid phase exfoliation technique has high potential for
large-scale production of nanographene materials in costeshyective manner
In addition to the existing preparation methods severalother methods were also successfully tested It includesexfoliation technique assisted by microwave intercalationand exfoliation of graphite iexclakes by using gases and me-chanical exfoliation of graphite iexclakes using ball mill in liquidmedium or continuous attraction of solid graphite blocksagainst rotating the glass substrates in a particular solventalong with simultaneous application of ultrasound [48] eillustration of preparation is described in Figure 18
Barahuie et al [49] in 2017 had detailed about thepreparation of miniature graphene sheets in mass pro-duction using four dishyerent types of methods which helps toget sheets in economic cost suitable for introducing andusing in various applications Paredes et al [50] in 2011 have
H
HH H
H
ndashH2OndashN2H2
HO
H
HO
N N
NN
(a)
ndashH2OndashN2H2
HOO
H
H
H
H
N
N
H
H
H
N
N
(b)
Figure 15 Reaction mechanisms for the chemical reduction of graphene oxide with hydrazine
3
0ndash100 0 100
σ(mΩndash1)
B
A
Vg (V)
Vg (V)
0
2
4
6
8
ρ (k
Ω)
Figure 16 Resistivity of a single layer of graphene vs gate voltage[44]
σxy (4e2h)
n (1012middotcmndash2)ndash4
10
5
0ndash72
ndash52
ndash32
ndash12
12
32
52
72
ndash2 0
2 4n
0
14T
4K4321ndash4 ndash2
ndash1ndash2ndash3
2 4
σ xy (
4e2 h
)
ρ xx (
kΩ)
Figure 17 Single-layer graphene with quantum Hall eshyect [44]
International Journal of Chemical Engineering 9
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
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Hindawiwwwhindawicom Volume 2018
Navigation and Observation
International Journal of
Hindawi
wwwhindawicom Volume 2018
Advances in
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Submit your manuscripts atwwwhindawicom
elaborately discussed about the preparation of graphene andits nanoparticles from various waste and bioprecursors likepaper cups hemp glucose rice husk cookies cockroachlegs and grass Since there is a need for bulk graphenepreparation this is performed by using dishyerent precursorsmentioned above [51] In order to synthesis graphene and itsnanoparticles a detailed knowledge on the brief structure ofGO is highly required which was elaborated in earlier section[52]
9 Graphene-Based Water Purification
ere is a need for cleaning the waste generated duringprocess in industries and factories which pollutes air andwater erefore there is a search for a cost eshyective andhighly ecopycient adsorbent Due to its extremely wide surfacearea as well as abundance of functional groups the graphene
seems to be an ideal option to centt e research communityconsidered GO as an ecopycient and powerful choice for nextgeneration centltration membrane is is due to the fact thatthe next generation membrane should have certain potentialadvantages that include high selectivity and excellent per-meability of desired moleculesions In addition to thesemerits the membrane should be highly cost eshyective andshould have good stability in terms of mechanical chemicaland other aspects to manage wide range of applications echemical structure of graphene oxide itself enables it to act asmembrane and the GO has oxidative defects which made itdishyerent from perfectly structured graphene
Furthermore the graphene oxide is not conductive sincein graphene the holes due to the defects made it viable to actas good membrane e pores made through the channelspresent in the stack of two-dimensional GO layers and thesize of the pore is about 09 nm GO membranes are
Figure 18 Four types of methods in the synthesis of small graphene sheets by exfoliation
10 International Journal of Chemical Engineering
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
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International Journal of
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Navigation and Observation
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Submit your manuscripts atwwwhindawicom
chemically inert with numerous substances which made ithighly durable In addition GO is highly cost effective incomparison to pure graphene +us less cost and higherdurability with high selectivity and permeability madegraphene oxide membrane as a good alternative for polymermembrane Sreeprasad et al [53] have shown the possibilityof making large quantity of graphene nanomaterials in a costeffective manner in water purification
Hu and Mi [54] demonstrated the efficacy of novel ionsieves made of graphene to separate the ions present inwater In previous years several studies proposed mem-branes made of graphene that show exceptional molecularpermeability however the permeable applications wererestricted with the cutoff of around 9Adeg +is restrictionprevents these proposed membranes from separating thehydrated ions of common salts present in saline waterAnother major constraint is swelling nature of membrane inthe presence of water +e ion sieves proposed by Abrahamet al [55] were made of membrane with limited swelling inwater and the pore size ranged between 64 and 98 Adeg +isquality made the membrane more efficient on separating thehydrated ions from saline water as in their work about 97of rejection of sodium chloride was achieved
Recently Mainak Majumder from Monash Universitydeveloped a novel and revolutionary filter made of graphenewhichmight be the big solution for the water crisis across theworld+e graphene-based filter was prepared by developingthe viscous form of GO which spread to produce a thin layerusing a blade +e proposed methodology makes uniformarrangement in GO which attributes to produce the filterwith special as well as highly impressive properties +emajor advantage of this methodology includes the pro-duction of filters in a rapid manner with high effectivenessand it can filter the particles larger than 1 nm Figure 19describes about the wastewater treatment
10 Microorganism Removal by GO
Xue et al [56] successfully prepared a series of GO com-posite hydrogels using redox-active crystalline rutheniumcomplexes as considerable noncovalent crosslinkers +eadsorbed bacteria due to the hydrogels then inactivated asthe next stage It was done by introducing a high voltagecontinuous electric pulse +en they were consequentlyremoved completely from the hydrogels Because of theeffective bacteria removal rate cost effective reusability andlow production cost graphene oxide hydrogels are shown tobe the promising choice for sterilization of the medicalproducts or in the large-scale purification of drinking water
11 GO Nanomaterials inWastewater Treatment
Graphene nanomaterials comprising graphene oxide (GO)reduced graphene oxide (rGO) pristine graphene (pGr) fewlayer graphene (FLG) and multilayer graphene (MLG) havea different role in wastewater treatment Literatures clearlydepicted that the last three materials mentioned here wouldbe settled down consistently more easily than specific rGO in
the foremost primary sediment whereas GO remains insuspension although it has been generally shown that theeffective addition of a suitable coagulant can remove all thespecies from the liquid stream +ere are no clear studies onthe effect of nanomaterials in anaerobic digestive process inprimarysecondary sludge [57]
+e studies performed with aqueous solutions havedepicted that wide range of minerals can adsorb in the topsurface of graphene-family nanomaterials (GFNs) whichleads to better primary sedimentation [58]+e sunlight UVradiation in particular as well as naturally occurring ma-terials could easily reduce the GO into rGO Different ox-idative methodologies that include hydrogen peroxideozone and Fentonrsquos reaction can effectively oxidize theGFNs at rapid degradation rate In addition to that GO andRGO subject to the production of trihalomethanes abyproduct are used as a disinfectant However the specifiedlist of tests have to be performed merely in wastewaters ofprimary secondary and the final tertiary effluents for abetter understanding of the outcome of graphene nano-materials Most of the available nanomaterials in utilizationhave not been cost effective when compared to the con-ventional materials like activated carbon and thereforefuture applications should be focusing on performance ef-fective processes of nanomaterials [59]
Adsorption is one of the hopeful methods for the deg-radation of micropollutants due to several advantages suchas simple design less cost better efficiency etc +e gra-phene materials can also employed as photocatalyst ad-sorbent and disinfectants in wastewater treatment [60] Inthis work the various applications of graphene compositematerials subjected to treating pharmaceutical industrywastewater were explained Here the effective mechanism ofadsorption used in removing the micropollutants [61] hasreported a novel as well as inexpensive methodology toproduce Beta-cyclodextrin integrated graphene oxide(GOCD) that has been fabricated to attain better adsorptionof water-soluble organic dyes from aqueous solution In thisstudy a simple sonolytic methodology was employed toproduce GOCD Another form of graphene oxide is wellcharacterized for its adsorption properties by consideringadsorption of the brilliant green (BG) dye by pseudo-sec-ond-order reaction kinetics It also showed that the higherremoval rate as well as better recyclability makes it apromising choice for the purification of wastewaters as wellas recycling of water-soluble dyes in efficient manner
12 Management of OrganicPollutants by Graphene
Of all the nanoparticle-based materials developed for thereduction of organic pollutants graphene and its relatedmaterials seem to be efficient and are employed desirably toremove wide range of organic pollutants [62ndash65] +ecombination of crystalline graphene with associated nano-materials has shown to have various synergistic effects on theabatement of organic pollutants [66] It has been rigorouslyshown that graphene and its nanomaterials remove organicpollutants by two approaches namely adsorption and photo
International Journal of Chemical Engineering 11
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
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Navigation and Observation
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Submit your manuscripts atwwwhindawicom
degradation [67] For an eco-friendly atmosphere thegraphene material that is going to be used for adsorptionduring wastewater treatment should also be degraded at theearliest since the accumulation of graphene materials hadbeen shown to cause toxic eshyect
13 Heavy Metal Ion Adsorption by GO
e dishyerent heavy metal ions existing in water bodies areharmful to aquatic life human beings and surroundingenvironment [68] which has been a global concern for manyyears GO is considered to be a peculiar adsorbent for theremoval and reducing of metal ions such as zinc copperlead cadmium cobalt etc e adsorption acopynity of GO tomany metal ions seems to be strong and varies from thetypes of metal ions even though the adsorption selectivity ofGO is poor When the electronegativity of metal ions ishigher the attraction of the metal ions on the negativelyelectricented wide GO surface is stronger Better adsorption ofnano heavy metals on the surface of GO is attributed due tothe presence of hydroxyl as well as carboxyl functional groupin GO [69] Presence of higher surface area excellent me-chanical strength less weight high iexclexibility and chemicalstability made GOmore lucrative on removing heavy metalsthe presence of multibonding functional group present onGO surface also improves the adsorption process Figure 20
describes the adsorption of heavy metal ions by graphenecomposites [70]
14 Applications of Graphene Oxide
Graphene has been recently involved in the various researchcentelds which include biomedical solar cells batteries supercapacitors supporting material for metal-based catalystslow permeability components biosensors multi-functionalmaterials for the puricentcation of water etc [71] Due towidespread use of tetracycline antibiotics tremendousamount of environmental pollution has been noticed andremoval of four such antibiotics (tetracycline oxytetracy-cline chlortetracycline and doxycycline) from aqueoussolution has been attempted using graphene nanoparticles[72] Graphene has considerably high adsorption capacitythan carbon nanotubes as well as granular activated carbonbecause of its reduced amount of compact bundle structuree consequent impact of naturally available organic matteron the adsorption characteristics of synthetic organiccompounds is said to be less on graphene e consolidatedresults indicate that graphene can also serve as an eshyectivealternative adsorbent for removing organic compoundsfrom water [73]
A research group showed that the integration of amultilayered titanate nanosheet on the graphene enhances
Metal ions
(a) (b) (c)
(ndashCOOndash and ndashCOndash)
Electrostaticinteraction
Magneticgraphene
composites
Mag
net
Magneticnanoparticle
Chelatingmolecules
Modifiedgraphene
sheets
Metalcomplexation
Figure 19 Wastewater treatment electrical and magnetic approach (a) Electrostatic interaction (b) Magnetic nanocomposites (c)Conjugation with molecules
12 International Journal of Chemical Engineering
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
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Navigation and Observation
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Hindawi
wwwhindawicom Volume 2018
Advances in
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Submit your manuscripts atwwwhindawicom
the algae-killing activity highlighting the extreme benecent-ciary role of photo catalytic active titanate nanosheet [74]us the hybridization between nanographene and photocatalytically active inorganic nanosheets can help in re-moving harmful microorganisms like algal blooms in nat-ural water Heavy metal ions and ionic dyes often coexistwhich emphasizes an important as well as perilous source ofenvironmental pollution [75]e multilevel magnetic gra-phene oxide (MGO) has been used as an ecopycient adsorbentfor simultaneous removal of Cd(II)metal [76] and ioniccoloring dyes like orange G(OG) and methylene blue (MB)Liu with his colleagues in 2012 synthesized a three-dimensional (3D) graphene oxide sponge (GO sponge)from a GO material suspension It was then used to removeboth the methylene blue (MB) and methyl violet (MV) dyeswhich are the main contaminants of the present dyemanufacturing and most textile centnishing factories
Researchers produced reduced form of graphene oxides(RGOs) from GO which was synthesized by modifyingHummersrsquo method is helps to develop a new nano-composite comprising graphene oxide as a carrier as anactive anticancer agent this implies that GO could be veryecopyciently used for drug delivery for curing a dreadful diseaselike cancer e substantial aggregation of pristine graphenenanosheet has been shown to decrease its extreme powerfuladsorption capacity thereby diminishing its various prac-tical applications To overcome this weakness graphene-coated materials (GCMs) were synthesized by mixing gra-phene with silica nanoparticles (SiO2) With the inherentsupport of large sum of SiO2 the stacked interlaminatedstructures of graphene held open to express the adsorptionsites in the interlayers Here the continuous adsorption ofphenanthrene which is an aromatic pollutant loaded withgraphene nanosheets increased up to multifold comparedwith pristine graphene up to 100 times at the same absolutelevel e adsorption of GCM increases with the combiningamount of the graphene composite nanosheets and di-minished with the introduction of complex oxygen-containing groups GCM does not need a complex meth-odology for large-scale synthesis of graphene-coated ma-terials Graphene nanocoated materials using silicananoparticles react to be a peculiar framework It is found tobe cost eshyective as well as highly ecopycient in removing ar-omatic pollutants from water is can pave a way forenormous opportunities to use novel 2D nanomaterials(graphene) for environmental applications [77]
e modicentable electronic properties of GO nano-materials make them interesting choice for photovoltaicenergy conversion applications Probably applications likephotoluminescence photovoltaic and photo catalysis in-volve water splitting GO is a p-doped semiconductor be-cause electron-withdrawing oxygen functional groupsreduce electron density on graphene [14] Replacing theoxygen functionalities binding to the edge sites of GO resultsin the conversion of GO to an n-doped semiconductorAlternate mode of doping with heteroatoms (eg nitrogenand boron) as replacements for carbon atoms in the hex-agonal honeycomb lattice of graphene also generates n- or p-type conductivity e eshyectiveness of this nanomaterialdepends on the number of valence electrons associated withthe dopant [15]
Photo catalytic reduction is a novel approach to GOreduction which involves mechanisms that are dishyerentfrom those of photo thermal reduction Under light irra-diation GO semiconductors do generate electron-hole pairse photo catalytic reduction of GO involves the transfer ofphoto generated electrons to other GO sheets and photogenerated holes reacting with water which results in theformation of peroxide Sun et al [63] adopted this approachand added isopropanol as photo generated hole trappinginto the GO quantum dots suspension under UV light ir-radiation Yeh et al [78] presented a hydrothermal strategyusing ammonia solution for fabricating the amino-functionalized GOQDs from GO sheets Li et al [69]were able to produce nitrogen-doped GO quantum dots(NGOQDs) by a simple hydrothermal route using nitrogen-doped graphene as the starting material is was obtainedby annealing GO in an ammonia iniexcluenced atmosphereHan et al [79] reported an electrochemical approach forsynthesizing boron-doped GOQDs Here the developmentof three types of GOQDs was carried out at low tempera-tures with diameters in the ranges of 1ndash4 4ndash8 and 7ndash11 nmvia acidic oxidation without any reduction routes isindicates that large GOQDs have low oxidation levels [80]and these nanomaterials can be used in many applications
Several earlier studies have motivated the developmentof alternative energy sources In that solar energy isconsidered as the most valuable energy source due to itsabundance clean and eco-friendly ere are photovoltaicdevices based on the concept of electricented charge sepa-ration at the interface between two substances with dif-ferent conduction mechanisms is centeld is dominated
Heavy metal ionsAdsorbed by
graphene oxide
Figure 20 Metal ions adsorbed by graphene composite
International Journal of Chemical Engineering 13
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
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Navigation and Observation
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Submit your manuscripts atwwwhindawicom
by the solid-state junction device produced using siliconOn the other hand high-energy requirements hightemperature and high vacuum processes are needed toconstruct these conventional devices One strategy for thedevelopment of chemical-based solar energy conversionis by using semiconductor-liquid junction solar cellsGraphene-based nanomaterials have been used as a me-dium for electron transfer and transportation to enhancesolar energy conversion efficiency Different from disk-like GOQDs carbon quantum dots (CQDs) are sphericalnanoparticles consisting of graphene nanosheets with lessthan 10 nm in size [78] +ese CQDs are considered ascore structures ending with hydrogen atoms in which thegraphitic core exhibits size-dependent absorption andlarge absorption coefficient
Analogous to the sensitive surface of graphene CQDsare typically surface functionalized with oxygen-containing functional groups (ie carboxyl and hy-droxyl) during synthesis rendering them highly dis-persible molecules and stable in polar solvents Briscoeet al [81] prepared three different types of CQDs bysimple hydrothermal carbonization of glucose chitin andchitosan where the CQDs are named as G-CQDs CT-CQDs and CS-GQDs respectively GO quantum dotsshown to possess accessible triplet states due to their edgeeffect have longer lifetime and diffusion lengths In ad-dition to a high extinction coefficient modifiable bandgap and homogeneous size distribution GOQDs syn-thesized by stepwise solution processes seem to be moresuitable for solar energy conversion compared to that ofsome metal-based quantum dot sensitized solar cellsAlgothmi et al [82] have reported on the performance ofactive graphene oxide composite (Ca-Alg2GO) gel inremoval of Cu2+ ions from aqueous solution Here itshown that the encapsulated GO had more adsorbingproperty than the calcium alginate alone Resin loadedwith magnetic β-cyclodextrin and GO sheet (MCD-GO-R) was synthesized successfully [83] and suggested to bean excellent adsorbent for Hg(II) removal
Fakhri [84] investigated the use of GO as a mere al-ternative adsorbent for removing aniline from aqueoussolution Cao and Li [13] have extensively highlighted theadsorption of carbon-based graphene in the removal ofinorganic pollutants in wastewater purification Oil inwastewater can be stabilized by GO It flocculated byeither an increase or a decrease in pH conditions Gra-phene and its corresponding derivatives have been ex-amined for pollution management Poornima Parvathiet al [85] have shown that the electrical characteristicssuch as photo catalytic and chemical characteristics suchas antibacterial properties of graphene are obtained whensynthesized from sugar and combined with sand particles
Gupta et al [86] have established the synthesis ofsugar-derived graphene material supported on sand +iswork describes an eco-friendly green approach for thesynthesis of nanographene material from sugar canewhich is a common disaccharide Here a suitablemethodology was introduced to immobilize the materialalong with sand without any need of binder ending with
the synthesis of composite material referred to as GSC(graphene sand composite) Complete conversion of sugarto graphene carbon suggests a green methodology for thematerialization of an active adsorbent material Materialsof this kind are expected to contribute to purification ofdrinking water Recently researchers found that the GOcan be used as barrier and protective coating in thepackaging industry It can be achieved by modifying thestructure of GO by removing the oxygen atoms present inthe GO sheets so that a collapse in channels present insidethe GO can be induced
15 Toxic Effects of GO
Recent studies investigating the potential release ofcarbon-based nanomaterials and other nanoparticles byvarious industries have indicated that release will happendue to production consumption and reuse of thesenanomaterials Since the release of graphene into theenvironment is going to increase in coming years forwastewater treatment we should also look upon its toxiceffect in the environment Nguyena et al [87] aimed todetermine the acuteness of destroying microbial com-munity by graphene through biological treatmentprocess
16 Conclusion and Recommendations
+is work clearly illustrates the efficacy of GO onwidespread range of pollutants generated from differentindustries Due to its ideal properties the synthesis andpreparation of GO membrane offer tremendous oppor-tunities to change its physicochemical properties +enecessity for making the GO is due to its most cost-effective sustainable alternate behavior to the longtimeexisting thin-film composite membranes for water sep-aration applications In order to improve its full potentialfor its practical applications we have to resolve the mostchallenging problems by producing high quality of gra-phene via environmentally friendly processes +epresent and the latest graphene-based water purificationsystems are improved further by considering the fol-lowing aspects (1) improvement of water treatment ef-ficiency on a widespread range of pollutants (2)extension of the applicability towards different pollutantspecies (3) upgrading the recovery rate from the testedsystem and (4) enhancement and improving the effec-tiveness of the material reusability With all the abovefeatures mentioned it is very much clear that graphenecan substitute most of the nanomaterials used forwastewater treatment and can be opted as one of theleading nanomaterials for many applications
Conflicts of Interest
+e authors declare that there are no conflicts of interestregarding the publication of this paper
14 International Journal of Chemical Engineering
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
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Navigation and Observation
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Hindawi
wwwhindawicom Volume 2018
Advances in
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Submit your manuscripts atwwwhindawicom
References
[1] M Sulekha ldquoNanotechnology for wastewater treatmentrdquoInternational Journal of Chemical Studies vol 4 no 2pp 22ndash24 2016
[2] J +eron J Walker and T E Cloete ldquoNanotechnology andwater treatment applications and emerging opportunitiesrdquoCritical Reviews in Microbiology vol 34 no 1 pp 43ndash692008
[3] O M Kalfa O Yalccedilınkaya and A R Turker ldquoSynthesis ofnano B2O3TiO2 composite material as a new solid phaseextractor and its application to preconcentration and sepa-ration of cadmiumrdquo Journal of Hazardous Materials vol 166no 1 pp 455ndash461 2009
[4] S P Gubin Y A Koksharov G B Khomutov andG Y Yurkov ldquoMagnetic nanoparticles preparation structureand propertiesrdquo Russian Chemical Reviews vol 74 no 6pp 489ndash520 2005
[5] C Gao W Zhang H Li L Lang and Z Xu ldquoControllablefabrication of mesoporous MgO with various morphologiesand their absorption performance for toxic pollutants inwaterrdquoCrystal Growth ampDesign vol 8 no 10 pp 3785ndash37902008
[6] M A Barakat R I Al-Hutailah M H Hashim E Qayyumand J N Kuhn ldquoTitania-supported silver-based bimetallicnanoparticles as photocatalystsrdquo Environmental Science andPollution Research vol 20 no 6 pp 3751ndash3759 2013
[7] M A BarakatM H RamadanM A Alghamdi S S AlgarnyH L Woodcock and J N Kuhn ldquoRemediation of Cu(II)Ni(II) and Cr(III) ions from simulated wastewater bydendrimertitania compositesrdquo Journal of environmentalmanagement vol 117 no 7 pp 50ndash57 2013
[8] J Feng Y Liang H Wang et al ldquoEngineering manganeseoxidenanocarbon hybrid materials for oxygen reductionelectrocatalysisrdquo Nano Research vol 5 no 10 pp 718ndash7252012
[9] Y Xu H Bai G Lu C Li and G Shi ldquoFlexible graphene filmsvia the filtration of water-soluble noncovalent functionalizedgraphene sheetsrdquo Journal of American Chemical Societyvol 130 no 18 pp 5856-5857 2008
[10] M Tuzen and M Soylak ldquoMultiwalled carbon nanotubesfor speciation of chromium in environmental samplesrdquoJournal of Hazardous Materials vol 147 no 1-2pp 219ndash225 2007
[11] V K Gupta S Agarwal and T A Saleh ldquoSynthesis andcharacterization of alumina-coated carbon nanotubes andtheir application for lead removalrdquo Journal of HazardousMaterials vol 185 no 1 pp 17ndash23 2011
[12] V K Gupta I Tyagi H Sadegh R Shahryari GhoshekandiA S H Makhlouf and B Maazinejad ldquoNanoparticles asadsorbent a positive approach for removal of noxious metalions a reviewrdquo Science Technology and Development vol 34no 1 pp 195ndash214 2015
[13] Y Cao and X Li ldquoAdsorption of graphene for the removal ofinorganic pollutants in water purification a reviewrdquo Ad-sorption vol 20 no 5-6 pp 713ndash727 2014
[14] X Yang J Qin Y Jiang et al ldquoFabrication of P25Ag3PO4graphene oxide heterostructures for enhanced solar photo-catalytic degradation of organic pollutants and bacteriardquoApplied Catalysis B Environmental vol 166-167 pp 231ndash2402015
[15] A Reddy M Y Choi and T K Kim ldquoReduced grapheneoxide wrapped ZnSndashAg2S ternary composites synthesized viahydrothermal method applications in photo catalyst
degradation of organic pollutantsrdquo Applied Surface Sciencevol 324 no 1 pp 725ndash735 2015
[16] D R Dreyer R S Ruoff and C W Bielawski ldquoFrom con-ception to realization a historical account of graphene andsome perspectives for its futurerdquo Angewandte Chemie In-ternational Edition vol 49 no 1 pp 9336ndash9344 2010
[17] A Lerf H He M Forster and J Klinowski ldquoStructure ofgraphite oxide revisitedrdquolte Journal of Physical Chemistry Bvol 102 no 23 pp 4477ndash4482 1998
[18] A S Klinowski ldquoGraphene synthesis and band gap openingrdquoJournal of Nano science and Nanotechnology vol 11 no 1pp 6621ndash6641 2011
[19] L Y Jiao X R Wang G Diankov H L Wang and H J DaildquoFacile synthesis of high quality graphene Nano ribbonsrdquoNature Nanotechnology vol 5 no 5 pp 321ndash325 2009
[20] Y Zhu S Murali W Cai et al ldquoGraphene and grapheneoxide synthesis properties and applicationsrdquo AdvancedMaterials vol 22 no 23 pp 3906ndash3924 2010
[21] G Van Lier C Van Alsenoy V Van Doren and P GeerlingsldquoAb initio study of the elastic properties of single-walledcarbon nanotubes and graphenerdquo Chemical Physics Lettersvol 326 no 1-2 pp 181ndash185 2000
[22] C D Reddy S Rajendran and K M Liew ldquoEquilibriumconfiguration and continuum elastic properties of finite sizedgraphenerdquo Nanotechnology vol 17 no 3 pp 864ndash870 2006
[23] K N Kudin G E Scuseria and B I Yakobson ldquoTrends innanoscale mechanics mechanics of carbon nanotubes gra-phenerdquo Physical Review B vol 64 p 235406 2001
[24] M Terrones O Martın M Gonzalez et al ldquoInterphases ingraphene polymer-based nanocomposites achievements andchallengesrdquo Advanced Materials vol 23 no 44 pp 5302ndash5310 2011
[25] M Liang J wang B Luo and L Qiu ldquoEfficiency and room-temperature reduction of graphene oxide a facile green ap-proach towards flexible graphene filmsrdquo Small vol 8 no 8pp 1180ndash1184 2012
[26] J Park G Wang J Yang et al ldquoFacile synthesis and char-acterization of graphene nano sheetsrdquo Journal of PhysicalChemistry C vol 112 no 22 pp 8192ndash8195 2008
[27] S Park and R S Ruoff ldquoChemical methods for the productionof graphenesrdquo Nature Nanotechnology vol 4 no 4pp 217ndash224 2009
[28] R Ranjbartoreh B Wang X Shen and G Wang ldquoAdvancedmechanical properties of graphene paperrdquo Journal of AppliedPhysics vol 109 p 14306 2011
[29] D A Dikin S Stankovich E J Zimney et al ldquoPreparationand characterization of graphene oxide paperrdquo Naturevol 448 no 7152 pp 457ndash460 2007
[30] L Berhan Y B Yi A M Sastry E Munoz M Selvidge andR Baughman ldquoMechanical properties of nanotube sheetsalterations in joint morphology and achievable moduli inmanufacturable materialsrdquo Journal of Applied Physics vol 95no 8 pp 4335ndash4345 2004
[31] W Xiangjian Y Huang and C Yongsheng ldquoFocusing onenergy and optoelectronic applications a journey for gra-phene and graphene oxide at large scalerdquo Accounts ofChemical Research vol 45 pp 598ndash607 2012
[32] K Rana J Singh and J-H Ahn ldquoA graphene-based trans-parent electrode for use in flexible optoelectronic devicesrdquoJournal of Materials Chemistry C vol 2 no 15 pp 2646ndash2656 2014
[33] R R Nair P Blake A N Grigorenko et al ldquoFine structureconstant defines visual transparency of graphenerdquo Sciencevol 320 no 5881 p 1308 2008
International Journal of Chemical Engineering 15
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Navigation and Observation
International Journal of
Hindawi
wwwhindawicom Volume 2018
Advances in
Multimedia
Submit your manuscripts atwwwhindawicom
[34] O V Yazyev and L Helm ldquoDefect-induced magnetism ingraphenerdquo Physical Review B vol 75 no 12 article 1254082007
[35] S Bhowmick and V B Shenoy ldquoEdge state magnetism ofsingle layer graphene nanostructuresrdquo Journal of ChemicalPhysics vol 128 no 24 article 244717 2008
[36] K Singh P K Iyer and P K Giri ldquoImproved chemicalsynthesis of graphene using a thermal routerdquo InternationalJournal of Nano science vol 10 no 1 pp 1ndash4 2011
[37] E D Grayfer V G Makotchenko A S Nazarov S J Kimand V E Fedorov ldquoGraphene chemical approaches to thesynthesis and modificationrdquo Russian Chemical Reviewsvol 80 no 8 pp 751ndash770 2011
[38] F Liu S Chung G Oh and T S Seo ldquo+ree-dimensionalgraphene oxide nanostructure for fast and efficient water-soluble dye removalrdquo ACS Applied Materials amp Interfacesvol 4 no 2 pp 922ndash927 2012
[39] X Wang and G Shi ldquoAn introduction to the chemistry ofgraphenerdquo Physical Chemistry Chemical Physics vol 17no 43 pp 28484ndash28504 2015
[40] X Li X Wang L Zhang S Lee and H Dai ldquoChemicallyderived ultrasmooth graphene nanoribbon semiconductorsrdquoScience vol 319 no 5867 pp 1229ndash1232 2008
[41] S Zhang and A Hirsch ldquoChemistry with graphene andgraphene oxide-challenges for synthetic chemistsrdquo Ange-wandte Chemie International Edition vol 53 no 50pp 7720ndash7738 2014
[42] J Park and M Yan ldquoCovalent functionalization of graphenewith reactive intermediatesrdquo Accounts of Chemical Researchvol 46 no 1 pp 181ndash189 2013
[43] J E Johns and M C Hersam ldquoAtomic covalent function-alization of graphenerdquo Accounts of Chemical Research vol 46no 1 pp 77ndash86 2013
[44] J S Bunch Mechanical and Electrical Properties of GrapheneSheets Cornell University New York NY USA 2008
[45] K S Novoselov A K Geim S V Morozov et al ldquo-di-mensional gas of massless dirac fermions in graphenerdquo Na-ture vol 438 no 7065 pp 197ndash200 2005
[46] C Wonbong ldquoSynthesis of graphene and its applications areviewrdquo Critical Reviews in Solid State and Materials Sciencesvol 35 no 1 pp 52ndash71 2010
[47] J Wang M Liang Y Fang T Qiu J Zhang and L Zhi ldquoRodcoating towards large-area fabrication of uniform reducedgraphene oxide films for flexible touch screensrdquo AdvancedMaterials vol 24 no 2 pp 2874ndash2878 2012
[48] K Samba Sivudu and Y Mahajan Mass Production of HighQuality Graphene An Analysis of Worldwide PatentsNanowerk Honolulu HI USA 2012
[49] F Barahuie B Saifullah D Dorniani et al ldquoGrapheneoxide as a nanocarrier for controlled release and targeteddelivery of an anticancer active agent chlorogenic acidrdquoMaterials Science and Engineering C vol 74 no 1pp 177ndash185 2017
[50] J I Paredes S Villar-Rodil M J Fernandez-MerinoL Guardia A Martınez-Alonso and J M D Tascon ldquoEn-vironmentally friendly approaches toward the mass pro-duction of processable graphene from graphite oxiderdquo Journalof Material Chemistry vol 21 no 7 pp 298ndash306 2011
[51] W S Hummers and R E Offeman ldquoPreparation of graphiticoxiderdquo Journal of American Chemical Society vol 80 no 6p 1339 1958
[52] M A Barakat ldquoNew trends in removing heavy metals fromindustrial wastewaterrdquo Arabian Journal of Chemistry vol 4no 4 pp 361ndash377 2011
[53] T S Sreeprasad S S Gupta S MMaliyekkal and T PradeepldquoImmobilized graphene-based composite from asphalt facilesynthesis and application in water purificationrdquo Journal ofHazardousMaterials vol 246-247 no 247 pp 213ndash220 2013
[54] M Hu and B Mi ldquoEnabling graphene oxide nanosheets aswater separation membranesrdquo Environmental Science ampTechnology vol 47 no 8 pp 3715ndash3723 2013
[55] J Abraham K S Vasu C D Williams et al ldquoTunable sievingof ions using graphene oxide membranesrdquo Nature Nano-technology vol 12 no 1 pp 546ndash550 2017
[56] B Xue M Qin J Wu et al ldquoElectroresponsive supramo-lecular graphene oxide hydrogels for active bacteria adsorp-tion and removalrdquo ACS Applied Materials amp Interfaces vol 8no 24 pp 15120ndash15127 2016
[57] O Wang S Collado P Oulego and M Dıaz ldquoGraphene-family nano materials in wastewater treatment plantsrdquoChemical Engineering Journal vol 313 pp 121ndash135 2017
[58] I Chowdhury M C Duch N D Mansukhani M C Hersamand D Bouchard ldquoColloidal properties and stability of gra-phene oxide nanomaterials in the aquatic environmentrdquoEnvironmental Science amp Technology vol 47 no 12pp 6288ndash6296 2013
[59] M Bouchard R Miandad M Waqas F Gehany andM A Barakat ldquoRemediation of wastewater using variousnano-materialsrdquo Arabian Journal of Chemistry vol 10 no 4pp 1ndash23 2016
[60] A C Sophia E C Lima N Allaudeen and S Rajan ldquoAp-plication of graphene based materials for adsorption ofpharmaceutical traces from water and wastewater-reviewrdquoJournal of Desalination and Water Treatment vol 57 no 57pp 27573ndash27586 2016
[61] D Majumdar ldquoSono chemically synthesized beta- cyclo-dextrin functionalized graphene oxide and its efficient role inadsorption of water soluble brilliant green dyerdquo Journal ofEnvironment and Analytical Toxicology vol 6 no 5 pp 1ndash52016
[62] C Wang C Feng Y Gao X Ma Q Wu and Z WangldquoPreparation of a graphene-based magnetic nanocompositefor the removal of an organic dye from aqueous solutionrdquoChemical Engineering Journal vol 173 no 1 pp 92ndash97 2011
[63] H Sun S Liu G Zhou H M Ang M O Tade and S WangldquoReduced graphene oxide for catalytic oxidation of aqueousorganic pollutantsrdquo ACS Applied Material Interfaces vol 4no 10 pp 5466ndash5471 2012
[64] K Lu G Zhao and X Wang ldquoA brief review of graphene-based material synthesis and its application in environmentalpollution managementrdquo Chinese Science Bulletin vol 57no 11 pp 1223ndash1234 2012
[65] K C Kemp H Seema M Saleh et al ldquoEnvironmental ap-plications using graphene composites water remediation andgas adsorptionrdquo Nanoscale vol 5 no 8 pp 3149ndash3171 2013
[66] Q Xiang J Yu and M Jaroniec ldquoGraphene-based semi-conductor photocatalystsrdquo Chemical Society Reviews vol 41no 2 pp 782ndash796 2012
[67] V Jaroniec K-H Kim J-W Park J Hong and S KumarldquoGraphene and its nano composites as a platform for envi-ronmental applicationsrdquo Chemical Engineering Journalvol 315 no 8 pp 1ndash79 2017
[68] W Peng H Li Y Liu and S Song ldquoA review on heavy metalions adsorption from water by graphene oxide and itscompositesrdquo Journal of Molecular Liquids vol 230 no 1pp 496ndash504 2017
[69] X Li H Wang J T Robinson H Sanchez G Diankov andH Dai ldquoSimultaneous nitrogen doping and reduction of
16 International Journal of Chemical Engineering
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Navigation and Observation
International Journal of
Hindawi
wwwhindawicom Volume 2018
Advances in
Multimedia
Submit your manuscripts atwwwhindawicom
graphene oxiderdquo Journal of American Chemical Society vol 2no 3 pp 15939ndash15944 2009
[70] S Babel and T A Kurniawan ldquoLow-cost adsorbents for heavymetals uptake from contaminated water a reviewrdquo Journal ofHazardous Materials vol 97 no 1ndash3 pp 219ndash243 2003
[71] R M Frazier W L Hough N Chopra and K W HathcockldquoAdvances in graphene-related technologies synthesis de-vices and outlookrdquo Recent Patents on Nanotechnology vol 6no 2 pp 79ndash98 2012
[72] Y Lin S Xu and J Li ldquoFast and highly efficient tetracyclinesremoval from environmental waters by graphene oxidefunctionalized magnetic particlesrdquo Chemical EngineeringJournal vol 225 no 14 pp 679ndash685 2013
[73] E A D Kyzas and K A Matis ldquoGraphene oxide and itsapplication as an adsorbent for wastewater treatmentrdquoJournal of Chemical Technology amp Biotechnology vol 89 no 1pp 196ndash205 2014
[74] I Y Kim J M Lee E-H Hwang et al ldquoWater-floatingnanohybrid films of layered titanate-graphene for sanitizationof algae without secondary pollutionrdquo RSC Advances vol 6no 100 pp 98528ndash98535 2016
[75] J-H Deng X-R Zhang G-M Zeng J-L Gong Q-Y Niuand J Liang ldquoSimultaneous removal of Cd(II) and ionic dyesfrom aqueous solution using magnetic graphene oxidenanocomposite as an adsorbentrdquo Chemical EngineeringJournal vol 226 no 1 pp 189ndash200 2013
[76] J C Igwe D N Ogunewe and A A Abia ldquoCompetitiveadsorption of Zn(II) Cd(II) and Pb(II) ions from aqueous andnon-aqueous solution by maize cob and huskrdquo AfricanJournal of Biotechnology vol 4 no 10 pp 1113ndash1116 2015
[77] T Yeh C Teng L Chen S Chen and H Teng ldquoGrapheneoxide-based nanomaterials for efficient photo energy con-versionrdquo Journal of Material Chemistry A vol 4 no 6pp 2014ndash2048 2015
[78] T-F Yeh C-Y Teng L-C Chen S-J Chen and H ChenldquoGraphene oxide-based nanomaterials for efficient photo-energy conversionrdquo Journal of Materials Chemistry A vol 4no 6 pp 2014ndash2048 2016
[79] J Han L L Zhang S Lee et al ldquoGeneration of B-dopedgraphene nanoplatelets using a solution process and theirsupercapacitor applicationsrdquo ACS Nano vol 7 no 1pp 19ndash26 2013
[80] D Geng S Yang Y Zhang et al ldquoNitrogen doping effects onthe structure of graphenerdquo Applied Surface Science vol 257no 1 pp 9193ndash9198 2011
[81] J Briscoe A Marinovic M Sevilla S Dunn and M TitiricildquoBiomass-derived carbon quantum dot sensitizers for solid-state nanostructured solar cellsrdquo Angewandte Chemie In-ternational Edition vol 54 no 15 pp 4463ndash4468 2015
[82] W M Algothmi N M Bandaru Y Yu J G Shapter andA V Ellis ldquoAlginate-graphene oxide hybrid gel beads anefficient copper adsorbent materialrdquo Journal of Colloid andInterface Science vol 397 pp 32ndash38 2013
[83] L Cui Y Wang L Gao L Hu Q Wei and B Du ldquoRemovalof Hg(II) from aqueous solution by resin loaded magneticβ-cyclodextrin bead and graphene oxide sheet synthesisadsorption mechanism and separation propertiesrdquo Journal ofColloid and Interface Science vol 456 pp 42ndash49 2015
[84] A Fakhri ldquo+ermodynamic and spectroscopic studies ofalanine and phenylalanine in aqueous β-cyclodextrin solu-tionsrdquo Journal of Saudi Chemical Society vol 21 no 1pp S52ndashS142 2017
[85] V Poornima Parvathi M Umadevi and R Bhaviya RajldquoImproved waste water treatment by bio-synthesized
[86] S S Gupta T S Sreeprasad S M Maliyekkal S K Das andT Pradeep ldquoGraphene from sugar and its application in waterpurificationrdquoACS AppliedMaterials amp Interfaces vol 4 no 8pp 4156ndash4163 2012
[87] H N Nguyena S L Castrob and D F Rodrigues ldquoAcutetoxicity of graphene nano platelets on biological wastewatertreatment processrdquo Environmental Science Nano vol 1 no 1pp 1ndash12 2013
![DiestersBiolubricantBaseOil:Synthesis,Optimization ...downloads.hindawi.com/journals/ijce/2012/896598.pdfbiolubricants [2]. Synthetic biolubricant based on renewable resources are](https://static.documents.pub/doc/80x56/5fb2937c9caf334bb4463247/diestersbiolubricantbaseoilsynthesisoptimization-biolubricants-2-synthetic.jpg)
