Synthesis of Magnetite-Graphite Oxide Diatomite as an ......siloxane (-Si-O-Si) and silanol (-Si-OH)...

Philippine Journal of Science145 (1): 79-88, March 2016ISSN 0031 - 7683Date Received: ?? Feb 20??

Key words: adsorption, diatomite, graphite oxide, heavy metal, magnetite, silica

Synthesis of Magnetite-Graphite Oxide Diatomite as an Alternative Adsorbent for Heavy Metal Ions

Chemistry Department, Xavier University,Corrales Avenue, Cagayan de Oro City, Philippines, 9000

*Corresponding author: [email protected]

Juliet Q. Dalagan* and Romelisa A. Ibale

In this recent work, magnetite-graphite oxide-diatomite (Mag-GO-diatomite) composite was produced and was used to remove heavy metal ions, Cr3+, Cu2+ and Pb2+, in aqueous solution. GO was prepared by modified Hummer’s method and characterized by Fourier Transform Infrared (FTIR) and Scanning Electron microscopy (SEM). Mag-GO-diatomite was synthesized using a facile method and characterized by FTIR and SEM-energy dispersive Xray (EDX). Results of IR analysis revealed presence of Fe-O at 750 cm-1 which indicates strong interaction between iron oxide particles of magnetite with the ester O of GO. This was confirmed by EDX analysis which showed strong signals for Fe and O. SEM images corroborated with the IR and EDX analyses with the occurrence of a rough textural surface indicating the presence of magnetite. Adsorption of the heavy metal ions Cr3+, Cu2+, and Pb2+ on GO-diatomite revealed a greater amount of heavy metals adsorbed on the adsorbent with magnetite than the one without magnetite. Furthermore, the adsorption of the 3 metal ions on Mag-GO-diatomite in the presence of each other was investigated and results showed that there is no significant competitive adsorption between Cu2+ and Pb2+. However, Cr3+ manifested a competitive adsorption behavior with the divalent cations.

INTRODUCTIONWater contamination by hazardous metal ions is a worldwide concern. Recent studies have been conducted to eliminate organic and inorganic pollutants. Some commonly used techniques for reducing level of contamination include chemical precipitation by controlling pH (Ito et al. 2000), chemical oxidation, chemical reduction, ion exchange (Mier et al. 2001), membrane filtration using coagulants, electrochemical treatment, evaporation, constructed wetland, and adsorption (Tchobanoglous et al. 2003; Mouflih et al. 2005). Among these methods, the use of novel adsorbents has been widely studied due to its fast adsorption rate, large adsorption capacity, and high adsorption selectivity

for hazardous metal ions. Numerous adsorbents such as activated carbon (Sekar et al. 2004), synthetic resin (Demirbas et al. 2005), mesoporous silica (Feng et al. 1997), carbon nanotubes (Li et al. 2005; Wang et al. 2007), natural and synthetic zeolite (Wang et al. 2008; Wingenfelder et al. 2005), clay minerals (Sari et al. 2007), natural and modified diatomite (Zhang et al. 2008; Osmanlioglu 2007) and biomass (Khraisheh et al. 2004) have been tested for their potential application to remove hazardous metal ions from wastewater.

GO modified with diatomite silica was known to attract cationic biomolecules due to the negative surface charge developed on GO-silica. However, stacking of the graphite sheets must be addressed to further enhance its application as an adsorbent. Thus, the introduction of magnetite to act

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as a spacer between GO sheets and open its surface for adsorbing molecules or ions was explored. Magnetite-GO-diatomite is an alternative adsorbent which could increase the amount of heavy metals adsorbed. This is worth investigating since the use of magnetite-GO-diatomite composite as adsorbent for heavy metals has not been reported yet.

MATERIALS AND METHODS

Preparation of Graphite Oxide (GO) from GraphiteGO was prepared by modified Hummer’s method. In brief, about 5 grams of graphite was placed in a flask and added with concentrated H2SO4. The mixture was heated in an oil bath at 80°C for 4.5 hours and cooled. The dispersion was left overnight and filtered under vacuum. The pre-oxidized graphite with concentrated H2SO4 was placed in an ice bath and about 30 g KMnO4 was added. The mixture was stirred for 2 hours. Distilled H2O was slowly added and stirring was continued for another 2 hours. Twenty (20) mL of hydrogen peroxide was added to the mixture followed with 700 mL of distilled H2O.

To ensure that oxygen functionalities were introduced into the graphite lattice, instrumental characterizations were done on both graphite and GO. Fourier Transform-Infrared (FTIR) Spectroscopy using Perkin Elmer Spectrum 100 was used to identify the functional groups present in GO and graphite. The morphology was examined by scanning electron microscopy (SEM).

Preparation of Diatomite by Pseudomorphic synthesisAbout 2 g of cetyltriammonium bromide (CTAB-Ajax FineChem) was dissolved in 24 ml of a 0.7 M solution of NaOH. Four (4) g of diatomites (Kieselguhr, LabChem) was then added and the suspension was stirred at room temperature for 30 min. After this time, the reaction mixture was incubated in an oven (Binder) at 100 ˚C for 3 days. The product was filtered and washed with distilled water, then dried for 24 h at room temperature. Calcination was performed by heating the solid to a temperature of 540 ˚C for 5 hours using the Thermolyne 1400 Furnace (Fowler et al. 2004).

Synthesis of GO-diatomite composite (solvothermal method)

The GO-diatomite composite was prepared using the method reported by Dalagan et al. (2010). About 0.5 g of GO and 0.5 g of diatomite were combined in a round bottom flask. Twenty mL of distilled water was used to dissolve the solid. Ten (10) mL of concentrated H2SO4

was added to the mixture and it was refluxed for 24 hours at 90˚C. The GO-diatomite was filtered and washed with distilled water and dried room temperature.

Synthesis of Magnetite (coprecipitation method) supported on GO-diatomite composite (Mag-GO-diatomite)Graphite oxide (0.5 g) was first dispersed in 150 mL deionized (DI) water. An aqueous solution of FeCl3.6H2O was prepared by dissolving about 1.5 g in 50 mL of DI water. The solution was added slowly to GO solution at room temperature (RT). NH4OH (15 M) was added to make the solution pH equal to 10. The temperature was raised to 90˚C and was continuously stirred for 4 hours. It was cooled to room temperature after heating. The black solution was filtered, washed with water, and dried at room temperature. The Mag-GO-diatomite powder obtained was characterized by IR spectroscopy, SEM, and Energy Dispersive Xray (EDX) analysis (Chandra et al. 2010).

Adsorption of Cr, Pb and Cu on Mag-GO-diatomite and on GO-diatomiteIn this experiment, the pH was monitored to be less than or equal to 7 to prevent heavy metal precipitation. Ten (10) mL of 10 ppm Cr3+ solution and about 15 mg of the Mag-GO-diatomite adsorbent were equilibrated by shaking using a Mechanical Shaker at 180 rpm for 24 hrs. It was filtered and the filtrate was analyzed for metal content using the Atomic Absorption Spectroscopy (AAS). Two other metals, Pb and Cu, were also subjected to the same procedure as above. For comparison purposes, GO-diatomite was also used as adsorbent for the 3 metals. To investigate the effect competing heavy metal ions on the adsorption behavior, 10 mL of 10 ppm mixture of Cu, Pb and Cr, 10 ppm of Cr and Pb, 10 ppm of Cr and Cu, 10 ppm of Pb and Cu were equilibrated with a known amount of Mag-GO-diatomite. The same procedure as above was followed to determine the concentration of the metal ions.

RESULTS AND DISCUSSION

Preparation of GO from graphiteOxidation of graphite becomes an important chemical route to manipulate the properties of graphitic materials. GO was synthesized from graphite through oxidation. The IR spectra overlay of GO and graphite is shown in Figure 1. The IR spectrum of graphite showed no IR active groups. Graphite does not have polar groups and is symmetrical since pi electrons are delocalized. The IR spectrum of GO illustrated a broad peak at 3270 cm-1,

Dalagan & Ibale: Magnetite-Graphite Oxide Diatomite: An Alternative Adsorbent for Heavy Metal Ions

Philippine Journal of ScienceVol. 145 No. 1, March 2016

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Figure 1. IR overlay of graphite and GO showing the oxygen functionalities that are present in GO and are absent in graphite.

sharp peak at 1629 cm-1, and weak bands at 1489 cm-1, 1227 cm-1, and 1096 cm-1 which indicate O-H stretching, C=O stretching, O-H deformation of C-OH groups, C-OH stretching and C-O-C stretching, respectively. The presence of oxygen functional groups means graphite has been oxidized to GO (Zhu et al. 2010).

Scanning electron micrographs in Figure 2 revealed the difference in the morphology of graphite and GO. Graphite appeared as flat and smooth thick sheets (as shown by the blue arrow) while GO looked soft (as indicated by the red arrow). GO does not have surfaces as smooth as graphite due to the oxygen functionalities. The thickness of graphite is due to the stacked graphite layers (Dalagan et al. 2013).

Synthesis of Mag-GO-DiatomiteGraphene oxide (GO) as discussed previously contains oxygen functionalities which could interact with the siloxane (-Si-O-Si) and silanol (-Si-OH) groups of diatomite. With the 3-D structure of diatomites, GO has expanded its application. In this recent work, GO-diatomite was decorated with iron oxide or magnetite. Figure 3 shows the FTIR spectra of GO-diatomite and Mag-GO-diatomite powders. Both spectra were in good agreement with the reported work of Shen et al. 2010. For Mag-GO-Diatomite, the appearance of a vibrational

band at around 1400 cm-1 can be assigned to the formation of either a monodentate complex or a bidentate complex between the carboxyl group and Fe on the surface of the magnetic particles. This confirms that the iron oxide articles are covalently bonded to GO. The peak at 750 cm-1 can be attributed to the lattice absorption of iron oxide which indicates the strong interaction of the iron oxide particles with the ester O. These results corroborated with the SEM-EDX analysis for Mag-GO-diatomite in Figure 7. For GO-Diatomite, the bands were consistent with other reported work. The intense peaks at 3300-3400 and 1200 cm-1 are attributed to stretching of the O-H band of CO-H. The band at 1650-1700 cm-1 is associated with stretching of the C=O bond of carboxyl groups. Presence of siloxane, Si-O-Si, is represented by the peak at 1100 cm-1 (Erena et al. 2009).

Figure 4 shows the SEM analysis of diatomite and Mag-GO-Diatomite. The image revealed a clean diatom shell with clear porous structure. On the other hand, Mag-GO-diatomite revealed a rough textural image which could be attributed to the presence of Fe. Energy dispersive X-ray spectroscopy (EDX) analysis corroborates with these results. Figure 5 illustrates a typical EDX pattern for GO-diatomite (A) which includes prominent peaks for Si, C, and O. On the other hand, Mag-GO-diatomite (B) EDX pattern revealed strong signals for Fe, Si, and O.



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Figure 2. SEM images of graphite oxide (A) and graphite (B) that show the thick layers of graphite sheets and the softer morphology of GO compared to graphite.

Figure 3. FTIR spectra of Mag-GO-diatomite and GO-diatomite showing the unique peaks for magnetite for Mag-GO-diatomite.



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The emergence of the Fe signal proves that magnetite was successfully embedded in the GO-diatomite composite. Similar EDX patterns were reported by Shen et al. (2010) for the synthesis of GO-magnetic nanoparticles.

Adsorption of heavy metals on GO-diatomite and Mag-GO-diatomite To investigate the adsorption of metal ions on Mag-GO-diatomite, SEM, EDX, and FTIR analyses were conducted. FTIR spectra shown in Figure 6 revealed vibrational bands that indicate metal-functional group interaction. The disappearance of the broad and strong band of OH- at 3400 cm-1 and the weakening of the C=O band at 1650 cm-1 can be attributed to surface complexation of the metal ions with the adsorbent (Yang

Figure 4. SEM images of Diatomite (A) and Mag-GO-Diatomite (B) which show the rough textural image for GO-diatomite with magnetite and a smooth morphology for diatomite.

Figure 5. Energy Dispersive Xray Spectroscopy (EDX) analysis of (a) GO-Diatomite and (b) Mag-GO-Diatomite composites that reveal peaks for Fe which is prominently present in magnetite.

et al. 2014). The appearance of the 640 cm-1 (Tsuge et al. 1990) and 750 cm-1 (Fuks et al. 2010) peaks could be due to Cu2+ and Cr-O vibrational bands, respectively. The remarkable change in the intensity of the 1050 cm-1 band could also mean surface interaction of the metal ions with Mag-GO-diatomite. Presumably, the formation of new absorption bands, the change in absorption intensity, and the disappearance or weakening of absorption intensity of functional groups could be attributed to complexation between metal ions and binding sites of the adsorbent (Yusoff et al. 2014).

The SEM images on Figure 7 also corroborate with the IR results. Morphology of the Mag-GO-diatomite becomes foamy-like and there were folds, creases, and defects that were introduced on the surface. There was



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Figure 6. FTIR spectra of heavy metal ions adsorbed on Mag-GO-diatomite (A) wide view, (B) zoomed view of the spectra show peaks that confirm presence of heavy metals that are adsorbed.

also some lump kind structure that could be seen in the SEM images (Lagashetty et al. 2002). This could be due to the strong interaction between the metal ions and Mag-GO-diatomite. EDX analysis on Appendix F (A-D) showed that only Cu was detected which could mean that the amount of Cr and Pb adsorbed was not significant.

For comparison purposes, the metals were also allowed to be equilibrated on GO-diatomite (without magnetite). Experimental results showed that a larger amount of metals were adsorbed on Mag-GO-diatomite (Figure 8). Possible explanation for this is the difference in electrostatic attraction between the heavy metals and the adsorbent and the different tendencies of the metals to complex with the adsorbent (Giraldo et al. 2013). Surface adsorption of magnetite operates through Fe-OH groups at the surface of Fe oxides. These groups attain negative or positive charge by dissociation (≡FeOH ≡FeO- + H+ ) or association (≡FeOH + H+ FeOH2 + ) of protons. As magnetite becomes more basic, the surface attains a negative charge leading to the adsorption of the metal species. This is called electrostatic interaction or bonds between the metal ions and the oxide surfaces. Another route for adsorption of heavy metals by magnetite is through the exchange of heavy metals Mn+ with protons at the surface hydroxyl groups - MOH and this is called surface complexation (Petrova et al. 2011). GO-diatomite utilizes the OH, C=O and Si-O-Si functional groups in the adsorption of heavy metals. Both GO-diatomite and Mag-GO-diatomite have a negative surface charge at a higher pH so they can adsorb heavy metals through electrostatic interaction. However, GO-diatomite has a tendency to restack into GO sheets thus reducing exposure of the adsorption sites. It is possible that magnetite functions as a “spacer” as shown in Figure 9 thus preventing restacking of GO-diatomite sheets. This increases the distance between sheets and enhances accessibility of the possible sites for adsorption (Wang et al. 2014).

Adsorption of 10 ppm mixture of heavy metals (Pb2+, Cu2+ and Cr3+) on Mag-GO-diatomiteThe adsorption behavior when mixtures of metal ions are allowed to adsorb on Mag-GO-diatomite is illustrated on Figure 10. The ions tend to compete with each other in accessing the adsorption sites. Trivalent Cr has the highest adsorption in the absence of the 2 other metals. This could be due to chromium’s small ionic radius (Cr3+

, 62 pm<Cu2+, 73 pm<Pb2+,119 pm) which makes it adhere strongly and closely to the adsorption sites. However, Cr3+ showed the lowest adsorption when it was adsorbed in the presence of Pb2+ and Cu2+. This could be attributed to the difference in their hydrated ionic radii in which Cr 3+ has the highest value. Similar trend in adsorption were reported by Chen et al. (2010) when Cd2+, Cu2+ and Pb2+ were adsorbed on nano-hydroxyapatite.

Possible precipitation of the metal hydroxides, Cu(OH)2, Pb(OH)2 and Cr(OH)3 can also affect the amount of metal ions adsorbed as shown in this equation:

M2+(aq) + 2OH-(aq) -> M(OH)2 (s)

The solubility product constants, Ksp, at 25ᵒC, for Cu(OH)2, Pb(OH)2 and Cr(OH)3, are 5.0 x 10-20, 1.2 x 10-15 and 1.0 x 10-30, respectively (Peng et al. 2005; Wu et al. 2008) . The hydroxide of chromium has a tendency to precipitate first in the presence of the other 2 metal hydroxides thus decreasing its capacity to adsorbed in the Mag-GO diatomite. Heavy precipitation can reduce the amount of metal ions adsorbed thus controlled pH should be observed in the experiment. The effect of solution pH on the adsorption of Pb2+ on diatomite and manganese oxide was studied by Al-degs et al (2001). The pH used in the investigation was kept at 4.0. This was based on the calculated pH when Pb(OH)2 would start to precipitate which is at pH of 8.0. Another study of Al-degs et al (2006) was on the adsorption of Pb2+, Zn2+, and Co2+

using natural sorbents. Similarly, pH was considered as an



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Figure 8. Plot representing % of heavy metals adsorb by Mag-GO-diatomite and GO-diatomite which exemplifies a higher adsorption by the adsorbent with magnetite than the one without magnetite.

Figure 7. SEM images of Mag-GO-diatomite with heavy metals adsorbed (A) bare Mag-GO-diatomite, (B) with Cr, (C) with Pb, (D) with Cu. Images show the morphological changes that occur when heavy metals are adsorbed.



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important factor in the adsorption of the heavy metal ions. The pH of the solution was maintained at a pH less than the precipitation pH for each of the metal (Al-degs 2006).

The concentration used was 10 mg/L, so the pH in which precipitation can possibly occur was 6.24, 6.34, and 5.36, for Cu(OH)2, Pb(OH)2 and Cr(OH)3, respectively. Within the pH range used (a neutral to acidic pH), possible precipitation could have been possible but was not observed by the researchers throughout the duration of the equilibration experiment. A possible reason for the non-occurrence of the metal hydroxide precipitate was the high room temperature in the lab which could prevent precipitation since Ksp values increase with increasing temperature. Albrecht et al. (2011) reported similar results when metal hydroxide was formed at

temperatures between 5 °C and 20 °C. Thus, the removal of the metal ions was mainly due to adsorption not on surface precipitation.

Sorption Capacity of the Mag-GO-DiatomiteThe relative adsorption capacity of Mag-GO-diatomite was predicted using the Langmuir and Freundlich isotherm models. Results revealed that the capacity of the adsorbent to adsorb Cu2+, Pb2+, and Cr3+ are 0.0226 mg/g, 113.5 mg/g, and 1.02 mg/g, respectively. Other adsorbents such as activated carbon of palm oil empty fruit bunch and graphene-zinc oxide composite showed a higher adsorption capacity than Mag-GO-diatomite. This could be due to the difference in surface properties of the adsorbent and surface interactions.

Figure 10. Data showing the adsorption and competitive behavior of heavy metals in the presence of each other. The concentration of the mixture of heavy metals used was 10 ppm.

Figure 9. Illustration showing the role of magnetite as “spacer” between GO sheets which could contribute to a higher adsorption of Mag-GO-diatomite.



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CONCLUSIONGO-diatomite was prepared and modified with magnetite. This composite was used to adsorb heavy metal ions, Cr3+, Pb2+, and Cu2+. The presence of the magnetite particle made it possible to increase the adsorption sites by acting as a spacer between GO sheets. Thus, this led to a higher amount of adsorbed cations. It was also revealed that Cr3+ competed with the divalent ions during the adsorption. These results are beneficial when the adsorbent, Mag-GO-diatomite, is used to remove heavy metals in sea water samples.

ACKNOWLEDGEMENTThe authors would like to thank Kinaadman Research Center (KRC) of Xavier University (XU) for funding this research and the Chemistry Department of Xavier University for the use of the facilities.

REFERENCESALBRECHT TWJ, ADDAI-MENSAH J, FORNASIERO

D. 2011. Effect of pH, concentration and temperature on copper and zinc hydroxide formation/precipitation in solution [online]. In: Chemeca 2011: Engineering a Better World; 2011 September 18-21; Sydney Hilton Hotel, NSW, Australia: Barton, A.C.T.: Engineers Australia. p.2100-2110.

AL-DEGS Y, KHRAISHEH M, TUTUNJI M. 2001. Sorption of lead ions on diatomite and manganese-oxides modified diatomite. Water Research 34:3724-3728.

AL-DEGS Y, EL-BARGHOUTHI M, ISSA A, KHRAISHEH M, WALKER G. 2006. Sorption of Zn(II), Pb(II), and Co(II) using natural sorbents: equilibrium and kinetic studies. Water Research 40: 2645-2658.

CHANDRA V, PARK J, CHUN Y, LEE JW, HWANG I, KIM KS. 2010. Water-dispersible magnetite-reduced graphene oxide composites for arsenic removal. ACS Nano. 4:3979–3986.

CHEN, SB, MA YB, CHEN L, XIAN K. 2010. Adsorption of aqueous Cd2+, Pb2+, Cu2+ ions by nano-Hydroxyapatite: single and multimetal competitive adsorption study. Geochemical Journal 44:233-239.

DALAGAN J, ENRIQUEZ, EP, LI LJ. 2013. Simultaneous functionalization and reduction of

graphene oxide with diatom silica. J of Mat Science J Mater Sci 48:3415–3421.

DEMIRBAS A, PEHLIVAN E, GODE F, ALTUN T, ARSLAN G. 2005. Adsorption of Cu(II), Zn(II), Ni(II), Pb(II), and Cd(II) from Aqueous Solution on Amberlite IR-120 Synthetic Resin. J Colloid Interface Sci 282:20–25.

ERENA E, AFSIN B, ONAL Y. 2009. Removal of lead ions by acid activated and manganese oxide-coated bentonite. Journal of Hazardous Materials 161: 677–685.

FENG X, FRYXELL GE, WANG LQ, KIM AY, LIU J, KEMNER KM. 1997. Functionalized monolayers on ordered mesoporous supports. science. 276:923–926.

FOWLER CE, HOOG Y, VIDAL L, LEBEAU B. 2004. Mesoporosity in diatoms via surfactant-induced silica rearrangement. Chemical Physics Letters 398:414–417.

FUKS H, KACZMAREK SM, BOSACKA M. 2010. EPR and IR investigations of some chromium (III) phosphate (V) compounds, Rev Adv Mater Sci 23: 57-63.

GIRALDO L, ERTO A, MORENO-PIRAJÁN JC. 2013. Magnetite nanoparticles for removal of heavy metals from aqueous solutions: Synthesis and Characterization. Adsorption 19:465-474.

ITO A, UMITA T, AIZAWA J, TAKACHI T, MORINAGA K. 2000. Removal of heavy metals from anaerobically digested sewage sludge by a new chemical method using ferric sulfate. Water Res 34:751–758.

KHRAISHEH MAM, AL-DEGS YS, MCMINN WAM. 2004. Remediation of wastewater containing heavy metals using raw and modified diatomite. Chem Eng J 99:177–184.

L A G A S H E T T Y A , M A L L I K A R J U N A N N , VENTAKATARAMAN A. 2003. Adsorption studies of lead ions on Fe2O3-thiourea complex composite. Indian Journal of Chemical Technology 10:63-66

LI YH, DI ZC, DING J, WU DH, LUAN ZK, ZHU YQ. 2005. Adsorption thermodynamic, kinetic and desorption studies of Pb2+ on carbon nanotubes. Water Res 39:605–609.

MIER MV, CALLEJAS RL, GEHR R, CISNEROS BEJ, ALVAREZ PJJ. 2001. Heavy metal removal with mexican clinoptilolite:: multi-component ionic exchange. Water Res 35:373–378.

MOUFLIH M, AKLIL AS, SEBTIB J. 2005. Removal of lead from aqueous solutions by activated phosphate. Journal of Hazardous Materials 119(1-3):183–188.



87

OSMANLIOGLU AE. 2007. Natural diatomite process for removal of radioactivity from liquid waste. Appl Radiat Isot 65:17–20.

PENG X, LUAN Z, DI Z, ZHANG Z, ZHU C. 2005. Carbon nanotubes-iron oxides magnetic composites as adsorbent for removal of Pb(II) and Cu(II) from water. Carbon 43:855-894

PETROVA T M, FACHIKOV L, HRISTOV J. 2011. The Magnetite as Adsorbent for Some Hazardous Species from Aqueous Solutions: A Review. International Review of Chemical Engineering (I.RE.CH.E.). 3(2): 121-134.

SARI A, TUZEN M, SOYLAK M. 2007. Adsorption of Pb(II) and Cr(III) from aqueous solution on celtek clay. J Hazard Mater 144:41–46.

SEKAR M, SAKTHI V, RENGARAJ S. 2004. Kinetics and equilibrium adsorption study of Lead(II) on activated carbon prepared from coconut shell. J Colloid Interface Sci 279:307–313.

SHEN J, HU Y, SHI M, LI N, MA H, YE M. 2010. One step synthesis of graphene oxide-magnetic nanoparticle composite. J Phys Chem C 114:1498-1503.

TCHOBANOGLOUS G, BURTON FL, STENSEL HD. 2003. Wastewater Engineering: Treatment and Reuse. New York, USA: The McGraw-Hill Inc. 25p.

TSUGE A, UWAMINO Y, ISHIZUKA T. 1990. Determination of Copper (I) and Copper (II) oxides on a copper powder surface by diffuse reflectance infrared fourier transform spectroscopy. Analytical Sciences 6:819-822

WANG SB, TERDKIATBURANA T, TADÉ MO. 2008. Adsorption of Cu(II), Pb(II) and humic acid on natural zeolite tuff in single and binary systems. Sep Purif Technol 2:64–70.

WANG HJ, ZHOU AL, PENG YU FH, CHEN LF. 2007. Adsorption characteristic of acidified carbon nanotubes for heavy metal Pb(II) in aqueous solution. Mater Sci Eng 466: 201–206.

WANG Y, HE Q, QU H, ZHANG X, GUO J, ZHU J, ZHAO G, COLORADO HA, YU J, SUN L, BHANA S, KHAN MA, HUANG X, YOUNG DP, WANG H, WANG X, WEI S, GUO Z. 2014. Magnetic graphene oxide nanocomposites: nanoparticles growth mechanism and property analysis. J Mater Chem C 2:9478-9488.

WINGENFELDER U, HANSEN C, FURRER G, SCHULIN R. Removal of heavy metals from mine waters by natural zeolites. 2005. Environ Sci Technol 39:4606–4613.

WU D, SUI Y, HE S, WANG X, LI C, KONG H. 2008. Removal of trivalent chromium from aqueous solution by zeolite synthesized from coal fly ash. Journal of Hazardous Materials 155(3):415-423.

YANG X, YANG L, WEN Z. 2014. Adsorption of Pb (II) from solution using peanut shell as biosorbent in the presence of amino acid and sodium chloride. BioResources 9(2): 2446-2458.

YUSOFF S, KAMARI A, PUTRA W, ISHAK C, MOHAMED A, ASHIM N, ISA I. 2014. Removal of Cu(II), Pb(II) and Zn(II) Ions from aqueous solutions using selected agricultural wastes: Adsorption and Characterisation Studies. Journal of Environmental Protection 5:289-300.

ZHANG SQ, HOU WG. 2008. Adsorption behavior of Pb(II) on montmorillonite, colloids surf. A: Physicochem Eng Aspects 20:92-97.

ZHU Y, MURALI S, CAI W, LI X, SUK JW, POTTS JR, RUOFF RS. 2010. Graphene and graphene oxide: Synthesis, Properties, and Applications. Adv Mater 22(46): 1-19.



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Synthesis of Magnetite-Graphite Oxide Diatomite as an ......siloxane (-Si-O-Si) and silanol (-Si-OH)...

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