This article was downloaded by: [Universiti Sains Malaysia] On: 30 September 2013, At: 17:16 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Critical Reviews in Environmental Science and Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/best20 Oil Palm Biomass as a Precursor of Activated Carbons: A Review Mohd Rafatullah a , Tanweer Ahmad a , Arniza Ghazali a , Othman Sulaiman a , Mohammed Danish a & Rokiah Hashim a a School of Industrial Technology, Universiti Sains Malaysia, Penang, Malaysia Accepted author version posted online: 22 Mar 2012.Published online: 04 Apr 2013. To cite this article: Mohd Rafatullah , Tanweer Ahmad , Arniza Ghazali , Othman Sulaiman , Mohammed Danish & Rokiah Hashim (2013) Oil Palm Biomass as a Precursor of Activated Carbons: A Review, Critical Reviews in Environmental Science and Technology, 43:11, 1117-1161, DOI: 10.1080/10934529.2011.627039 To link to this article: http://dx.doi.org/10.1080/10934529.2011.627039 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms- and-conditions
Transcript
This article was downloaded by: [Universiti Sains Malaysia]On: 30 September 2013, At: 17:16Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Critical Reviews in EnvironmentalScience and TechnologyPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/best20
Oil Palm Biomass as a Precursor ofActivated Carbons: A ReviewMohd Rafatullah a , Tanweer Ahmad a , Arniza Ghazali a , OthmanSulaiman a , Mohammed Danish a & Rokiah Hashim aa School of Industrial Technology, Universiti Sains Malaysia, Penang,MalaysiaAccepted author version posted online: 22 Mar 2012.Publishedonline: 04 Apr 2013.
To cite this article: Mohd Rafatullah , Tanweer Ahmad , Arniza Ghazali , Othman Sulaiman ,Mohammed Danish & Rokiah Hashim (2013) Oil Palm Biomass as a Precursor of Activated Carbons:A Review, Critical Reviews in Environmental Science and Technology, 43:11, 1117-1161, DOI:10.1080/10934529.2011.627039
To link to this article: http://dx.doi.org/10.1080/10934529.2011.627039
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever orhowsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.
This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
Oil Palm Biomass as a Precursor of ActivatedCarbons: A Review
MOHD RAFATULLAH, TANWEER AHMAD, ARNIZA GHAZALI,OTHMAN SULAIMAN, MOHAMMED DANISH, and ROKIAH HASHIM
School of Industrial Technology, Universiti Sains Malaysia, Penang, Malaysia
Commercial activated carbon has been a preferred adsorbent forthe removal of various pollutants, and its widespread use is re-stricted due to its relatively high costs, which led to the researches onthe possible alternative nonconventional and low-cost adsorbents.The use of agricultural products and by-products for instance hasbeen widely investigated as a replacement for the current costlymethods of removing various pollutants. In this critical review, anextensive list of the production of activated carbon from oil palmbiomass is presented. The effects of various process parameters onthe pyrolysis stage, characteristics, and influences of physical andchemical activating conditions on the production of activated car-bons from oil palm biomass are discussed. A comparison in char-acteristics and applications of activated carbons from oil palmbiomass with commercial activated carbons is made. It is evidentfrom a literature survey of about 200 recently published articlesthat activated carbons from oil palm biomass exhibit outstandingcapabilities for removal of various pollutants.
Environmental pollution is one of the biggest problems of the society in the21st century. It is an issue that is taxing our socioeconomic well-being. Rapidindustrialization and urbanization without the awareness of sustainability in
Address correspondence to Tanweer Ahmad, School of Industrial Technology, UniversitiSains Malaysia 11800, Penang, Malaysia. E-mail: [email protected]
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mind have resulted in the generation of large quantities of aqueous efflu-ents, many of which contain high levels of toxic pollutants (Park et al., 2010;Vijayaraghavan and Yun, 2008). As a result, there is an increasingly growingpollution of air and worldwide water resources around us today. The con-tamination of the atmosphere is one of the most important environmentalproblems and among the major contributors is the emission of nitrogen ox-ides and sulfur dioxides, which result in acid rain and ground-layer ozoneformation. Owing to its high toxicity and negative impact in the environment,interest in reducing the emissions of nitrogen oxides has been increasing inthe last few years. The need to purify our waters and keep our atmosphereclean requires the development of new methods for the production of highlyefficient filtration media and effective adsorbents (Klose and Rincon, 2007;Lua et al., 2006). These and other separation concepts discovered thus far,include filtration, ultrafiltration and dialysis, ion exchange, reverse osmosis,solvent extraction, oxidation, evaporation, coagulation, adsorption, activatedsludge, aerobic and anaerobic treatment, microbial reduction, bacterial treat-ment, irradiation by nuclear radiation, and magnetic separation (Ahmad et al.,2010; Gupta et al., 2009; Rafatullah et al., 2010a). Adsorption is a well-knownequilibrium separation process and an effective method for the removal ofvarious pollutants from water and wastewater (Ahmad et al., 2007a, 2009a,2009b; Ibrahim et al., 2010; Rafatullah et al., 2009, 2010b; Sulaiman et al.,2010). Adsorption has been found to be superior to other techniques forwater re-use in terms of initial cost, flexibility and simplicity of design, easeof operation, and insensitivity to toxic pollutants. Adsorption also does notresult in the formation of harmful substances.
Activated carbon is the generic term used to describe a family of car-bonaceous adsorbents with highly crystalline forms and extensively devel-oped internal pore structures. Activated carbon has been proven to be aneffective adsorbent for the removal of a wide variety of organic and inor-ganic pollutants dissolved in aqueous media, or from gaseous environment.Apart from that, activated carbon are known as very effective adsorbentsdue to its large porous surface area, controllable pore structure, thermosta-bility and low acid/base reactivity. The said characteristics enables its useas cleansing media in pollution control, solvent recovery, food processing,chemical and pharmaceutical industries, wastewater treatment (dyes, heavymetals, detergents, herbicides, pesticides, and polyaromatic hydrocarbons),metal recovery, catalysis, and improving of odor and taste (Chingombe et al.,2005; Crini, 2006; Foo and Hameed, 2009; Li et al., 2008; Singh et al., 2008).
Despite its prolific use in adsorption processes, the biggest barrier of itsapplication by the industries is the cost-prohibitive adsorbent and difficultiesassociated with regeneration (Lata et al, 2008). In recent years, however therehas been a growing interest in the production of activated carbon from differ-ent precursors such as agricultural by-products and residual wastes. In fact,cheap material with high carbon content and low inorganic materials can be
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used as a raw material for the production of activated carbon. Agriculturalby-products have proven to be promising raw materials for the productionof activated carbons because of their availability at a low price (Zhou andHaynes, 2010). They can be used for the production of activated carbon witha high adsorption capacity, considerable mechanical strength and low ashcontent (Savova et al., 2001). Agricultural by-products such as shells, kernels,fruit stones, fruit seeds, and hulls and husks, for instance, are produced dur-ing harvesting and processing of commercial crops. Depending on the crop,some of these by-products have found uses as feedstock for animals, fillersin plasterboard, additives in paper making, and as a material resource forcombustion and cogeneration processes (Ghazali et al., 2006, 2009). Despitethese applications there is a large quantity of such by-products generatedannually that requires disposal and thus poses an environmental problem.Agricultural by-products are rich sources of cellulosic material with an aver-age composition of 40–50% cellulose, 20–30% hemi-cellulose, 20–25% lignin,and 1–5% ash making them an attractive source for activated carbon produc-tion. There have been many attempts to obtain low-cost activated carbonor adsorbent from agricultural wastes. The lists of precursor materials fromdifferent agricultural source for the production of low-cost activated carbonare presented in Table 1.
The high cost of activated carbon promotes the search for cheap materi-als mainly derived from biological origin. It has been proved that lignocellu-losic biomasses are attractive resources for the preparation of carbonaceousmaterials implemented in adsorption processes (Mohamed et al., 2010). Theeco-friendly nature of lignocellulosic biomasses, their availability, and lowcost are the main advantages of these resources, which makes them a suit-able precursor for activated carbon preparation (Parab et al., 2009). One ofthe latest types of activated carbon in the current market is biomass basedactivated carbon (Ioannidou and Zabaniotou, 2007). In Malaysia, currently,oil palm based activated carbon is gradually finding its way for a usefulutilization (Sumathi et al., 2008). Hence it can be very handful as well aseconomical to use oil palm activated carbon as an alternative to the existingcommercially available activated carbon.
The oil palm industry is one of the major contributors to thelignocellulosic-rich, solid waste materials, generated in the field and the oilmill. The main residues in the field are the pruned fronds removed duringharvesting and the trunk and fronds removed at replanting activity. The millresidues include mesocarp fiber, shell, palm kernel cake, boiler ash, emptyfruit bunches, palm oil mill effluent, and bunch ash. Except for the palmkernel cake, boiler and bunch ash, and palm oil effluent, all of the residuescontain high percentage of lignocellulose and therefore useful to be usedas a source of carbon (Hussein et al., 2001). In recent years, the recyclingof the agricultural biomass as an effective option for the provision of sus-tainable resources has received considerable increased concern all around
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TABLE 1. List of precursor materials from different agricultural source for the production oflow-cost activated carbon
Adsorbents References
Wheat Lanzetta and Di Blasi, 1998Corn straw Lanzetta and Di Blasi, 1998Olive stones Minkova et al., 2000; Minkova et al., 2001Bagasse Minkova et al., 2000; Minkova et al., 2001Birch wood Minkova et al., 2000; Minkova et al., 2001Acacia mangium wood Danish et al., 2011aMiscanthus Minkova et al., 2000; Minkova et al., 2001Sunflower shell Haykiri-Acma et al., 2005Pinecone Haykiri-Acma et al., 2005Rapeseed Haykiri-Acma et al., 2005; Predel and Kaminsky, 1998Cotton residues Haykiri-Acma et al., 2005Olive residues Haykiri-Acma et al., 2005Pinus radiata Cetin et al., 2004Eucalyptus maculata Cetin et al., 2004Sugar cane bagasse Ahmedna et al., 2000; Cetin et al., 2004Coconut husk Tan et al., 2008cAlmond shells Aygun et al., 2003; Marcilla et al., 2000; Savova et al.,
2001Peach stones Tsai et al., 1997Grape seeds Savova et al., 2001Straw Jensen et al., 2001; Minkova et al., 2000; Minkova et al.,
2001Oat hulls Fan et al., 2004; Zhang et al., 2004Corn stover Fan et al., 2004; Zhang et al., 2004Apricot stones Aygun et al., 2003; Savova et al., 2001Cotton stalk Putun et al., 2005Cherry stones Savova et al., 2001Peanut hull Girgis et al., 2002Nut shells Ahmedna et al., 2004; Ahmadroup and Do, 1997; Lua
et al., 2004; Savova et al., 2001; Yang and Lua, 2003Rice hulls Ahmedna et al., 2000Corn cob El-Hendawy et al., 2001; Tsai et al., 1997, 1998 and 2001Corn hulls Zhang et al., 2004Hazelnut shells Aygun et al., 2003Walnut Aygun et al., 2003Pecan shells Ahmedna et al., 2000Rice husks Malik, 2003; Yalcin and Sevinc, 2000Oil palm fiber Hameed et al., 2008Rose canina seed Gurses et al., 2006Fir wood Wu and Tseng, 2008Jute fiber Senthilkumaar et al., 2005Rattan sawdust Hameed et al., 2007aDurian shell Chandra et al., 2007Coir pith Kavitha and Namasivayam, 2007Bamboo sawdust Hameed et al., 2007bDate stone Danish et al., 2010, 2011b, 2011cRice straw Ahmedna et al., 2000; Oh and Park, 2002Hevea brasiliensis seed coat Hameed and Daud, 2008Sugar Legrouri et al., 2005Vetiver roots Altenor et al., 2009Vermiculata plant Bestani et al., 2008
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the globe (Yong et al., 2007). The projected growth of the cultivation of oilpalm, the supply of world oil palm biomass and its processing by productsare found to be seven times the abundance of natural timber (Basiron andChan, 2004), with the existing 184.6 million tons of biomass per year (Nathand Das, 2003). In Malaysia, an annual estimation of 73.74 million tons ofbiomass residues is expected to be contributed, in the form of palm leaves,palm fronds, palm trunks, empty fruit bunches, palm shells, palm fibers,and palm stones (Chavalparit et al., 2006; Malaysia Palm Oil Council, 2007).From each bunch of the fresh palm fruit, approximately 21% of palm oil,6–7% of palm kernels, 14–15% of palm fibers, 6–7% of palm shells, and23% of empty fruit bunches can be obtained (Dalimin, 1995). Realizing theurgency of transforming the residue into a more valuable end product, apromising option is to converting them into a prospective precursor for thepreparation of activated carbon (Chavalparit et al., 2006). Its relatively highfixed-carbon content (about 18 wt%), low ash content (less than 1.0 wt%)and the presence of inherent porous structures. This will directly solve partof the environmental problems related to by-products of oil palm industries,while increasing the output.
This review provides the literatures demonstrating the usefulness of dif-ferent parts of oil palm biomass as a precursor for the production of activatedcarbon. Effects of different pyrolysis, physical and chemical activation, con-ditions on the physical properties, and characterization of activated carbonswere discussed. In the review we attempt to summarize the developmentand potential applications of the oil palm biomass based activated carbonsas adsorbents for the removal of different types of pollutants. The presentwork is aimed at providing a concise and up-to-date picture of the presentstatus of oil palm industry in enhancing sustainability. The prospects towardthe utilization of oil palm waste as renewable sources for the preparationof activated carbons together with its comprehensive literature has beenhighlighted and outlined, to familiarize the reader with pertinent informationregarding oil palm industry.
CHEMICAL COMPOSITION OF OIL PALM BIOMASS
Oil palm is a lignocellulosic material rich in carbohydrates in the form ofstarch and sugar. Lignocellulosic substances contain three main structuralcomponents: hemicellulose, cellulose, and lignin. It also contains extrac-tives. Generally, three main components have high molecular weights andcontribute much mass, while the extractives is of small molecular size, andavailable in little quantity. The chemical compositions of different parts ofoil palm biomass are presented in Table 2 (Hashim et al., 2011).
Hemicellulose consists of different monosaccharide units. The polymerchains of hemicellulose have short branches and are amorphous. Because of
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TABLE 2. Chemical composition of different parts of oil palm biomass (Hashim et al., 2011)
Chemical composition (%)
Parts of oil palm biomass Extractives Holocellulose Cellulose Lignin
the amorphous morphology, hemicellulose is partially soluble or swellable inwater. Hemicellulose is derived mainly from chains of pentose sugars, and actas the cement material holding together the cellulose and fibers (Theander,1985). The backbone of the chains of hemicellulose can be a homopolymer(generally consisting of single sugar repeat unit) or a heteropolymer (mixtureof different sugars). Hemicellulose is largely soluble in alkali and, as such, ismore easily hydrolyzed (Demirbas, 2008; Unal and Alibas, 2007).
Cellulose is a linear polymer chain, which is formed by joining theanhydroglucose units into glucose chains (Balat, 2008a). These anhydroglu-cose units are bound together by β-(1,4)-glycosidic linkages. Owing to thislinkage, cellobiose is established as the repeat unit for cellulose chains.By forming intramolecular and intermolecular hydrogen bonds between OHgroups within the same cellulose chain and the surrounding cellulose chains,the chains tend to be arranged parallel and form a crystalline supramolecularstructure. Cellulose is insoluble in most solvents and has a low accessibil-ity to acid and enzymatic hydrolysis. Chemical modification of cellulose isa promising technique for modifying its physical and chemical propertiesto improve the adsorption property toward removal of various pollutants(Demirbas, 2009).
Lignin is the second most abundant natural raw material (Gosselinket al., 2004) and nature’s most abundant aromatic (phenolic) polymer (Loraand Glasser, 2002), whose main function is to cement the cellulose fibersin plants. Lignin is a natural polymeric product arising from an enzymeinitiated dehydrogenative polymerization of the three primary precursors(i.e., p coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol; Boeriu et al.,2004; Chakar and Ragauskas, 2004). Their functions are to provide structuralstrength, provide sealing of water conducting system that links roots withleaves, and protect plants against degradation (Glasser and Sarkanen, 1989).Lignin is a macromolecule, which consists of alkyl phenols and has a com-plex three-dimensional structure. The basic chemical phenyl propane unitsof lignin (primarily syringyl, guaiacyl, and p-hydroxy phenol) are bound
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together by a set of linkages to form a very complex matrix. This matrixcomprises a variety of functional groups, such as hydroxyl, methoxyl, andcarbonyl, which impart high polarity to the lignin macromolecule (Balat,2008b;). Cellulose and lignin structures were extensively investigated in theearlier studies (Garcia-Valls and Hatton, 2003; Mohan et al., 2006; Young,1986).
Extractives are the organic substances with low molecular weight andthat are soluble in neutral solvents. Resin (terpenes, lignans, and otheraromatics), fats, waxes, fatty acids and alcohols, terpentines, tannins, andflavonoids are categorized as extractives (Gong et al., 2008). Oil palmbiomass is now considered to be one of the most promising nonwood ligno-cellulosic raw materials as precursor for the production of activated carbonfor the removal of various pollutants.
EXPERIMENTAL CONDITIONS FOR ACTIVATED CARBONPRODUCTION FROM OIL PALM BIOMASS
Pyrolysis
Pyrolysis is a vital process in biomass combustion and gasification (Fuet al., 2009). The pyrolysis process is extremely complex and generally goesthrough a series of complex reactions (Lee and Fasina, 2009; Wang et al.,2007; Yang et al., 2004). Thus, it is very essential to understand the funda-mentals and mechanisms of agricultural residues pyrolysis. It is the thermochemical process that converts biomass into liquid (bio-oil or bio-crude),charcoal and noncondensable gases, acetic acid, acetone, and methanol byheating the biomass to about 750 K in the absence of air (Demirbas, 2001).Heating wood to a temperature slightly above 100◦C initiates some thermaldecomposition; the hemicelluloses are degraded at 200–260◦C, while the cel-lulose degrades at 240–350◦C and the lignin degrades at 280–500◦C (Sjostrom,1993). Oil palm biomass is produced in huge amount; their proximate andultimate analysis is presented in Table 3.
The first step of the activated carbon generation process is the pyrolysisof the raw material, which takes place under nitrogen atmosphere in thetemperature range of 500–600◦C. During the process primary pyrolysis gasesare produced, which separate into permanent gases and oils (tars) if theyare cooled to ambient temperatures. The residue of the pyrolysis processis the primary char, which serves as base material for the activation step.Heating rate, pyrolysis temperature, and residence time of the material inthe hot zone during pyrolysis influence the generation of initial porosity ofthe char. The chemical bond energy of the biomass is subdivided into thefractions char, tar, and gas. The chars from the pyrolysis step are treated in asecond process called activation. Here, the chars are heated to temperaturesof 800–900◦C under steam atmosphere. Some of the carbon is oxidized and
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TABLE 3. Proximate and ultimate analyses of oil palm biomass
Proximate analysis (wt%) Ultimate analysis (wt%)
Parts of oil Volatile Fixedpalm biomass Moisture matter Ash carbon C H N S O Reference
Oil palm shell 5.73 73.74 2.21 18.37 53.78 7.20 0.00 0.51 36.30 Yang et al.(2004)
Oil palm fiber 6.56 75.99 5.33 12.39 50.27 7.07 0.42 0.63 36.28 Yang et al.(2004)
Oil palm emptyfruit bunch
8.75 79.67 3.02 8.65 48.79 7.33 0.00 0.68 40.18 Yang et al.(2004)
this leads to the generation of pores. It is very important for this step to keepthe activation conditions constant. The choice of the pyrolysis and activationtemperature depends on the properties of the feedstock. Materials with ahigh content of volatile matters need a higher pyrolysis temperature to ensurethe devolatilization of the biomass. In the activation process the activationtemperature determines the reaction time of carbon oxidation and has tobe adapted to the steam flux. Both parameters influence the heterogeneouschar oxidation and lead to the loss of char mass, leading to an increase ofinner surface. Higher conversion rates (i.e., loss of char mass of more than85 wt% of the initial char mass) led to decreasing active surfaces due to thediminishing carbon content. The highest active surfaces can be achieved atconversion rates of 60–80 wt% based on the initial char mass and dependon the type of biomass (Schroder et al., 2007). Fundamentals of biomasspyrolysis have been widely investigated using fluidized-bed reactors, fixed-bed reactors, and thermogravimetric analysis.
Pyrolysis studies of extracted oil palm fibers from a palm-oil mill werecarried out to determine whether these agricultural solid wastes could bedeveloped into effective adsorbents (Lua and Guo, 1998a, 1999). Increasingthe pyrolysis temperature for a given residence time decreased the yield ofchars as increasing volatiles were evolved. Process parameters such as initial
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material size, nitrogen flow rate, pyrolysis temperature, and hold time werefound to be significant factors influencing the resultant char. Experimentalresults showed that there were significant effects of pyrolysis temperatureon densities and porosities of the chars. At a low pyrolysis temperature of450◦C, pore development was poor due to insufficient energy to release thevolatile matter. However, at a high pyrolysis temperature of 950◦C, a sinteringeffect and shrinkage of the char reduced the pore volumes and pore areas,particularly micropores.
Influence of pyrolysis conditions on pore development of oil palm shellactivated carbons were investigated (Lua et al., 2006). The pyrolysis condi-tions that yielded the activated carbon with the highest BET surface area,micropore surface area (<2 nm diameter), and micropore volume occurredat 600◦C, with hold time of 2 hr, nitrogen flow rate of 150 cm3/min, andheating rate of 10◦C/min. From this study, it can be deduced that the pyroly-sis conditions play an important role in the development of the rudimentarypore structure in the char, primarily through the release of volatiles fromthe carbon matrix. Effect of heating temperature on the properties of charsand activated carbons prepared from oil palm stones were studied by Guoand Lua (2000a). The experimental results showed that relatively high py-rolysis temperature was essential to remove volatile matters and developrudimentary pore structures. However, an extreme temperature of 900◦Cwould cause a sintering effect, resulting in a decrease in porosity. As theactivation temperature increased from 750 to 900◦C, the BET and microp-ore surface areas increased progressively. The activation process not onlyenlarged the pores created during the pyrolysis but also generated somenew pores. However, at 950◦C the surface area, especially the microporesurface area dropped dramatically due to the overreaction of carbon withcarbon dioxide. The pore size distributions also confirmed the conversionof microporosity into mesoporosity or even macroporosity at a higher acti-vation temperature. The quality of AC improved up to 900◦C but the qualitydeteriorated at 950◦C. For the surface organic functional groups, as the py-rolysis temperature increased, the ether and alcohol structures and ketonicgroups were absent due to their thermal instabilities. Oil palm shells wereconverted to activated carbons by vacuum or nitrogen pyrolysis, followed bysteam activation (Jia and Lua, 2008a). The effects of pyrolysis environment,temperature, and hold time on the physical characteristics of the activatedcarbons was studied. The optimum pyrolysis conditions for preparing ac-tivated carbons for obtaining high pore surface area are vacuum pyrolysisat a pyrolysis temperature of 675◦C and 2 hr hold time. For the pyrolysisatmosphere, it was found that significant improvement in the surface char-acteristics of the activated carbons was obtained for those pyrolyzed undervacuum. Under vacuum environment, the volatiles released from the oil palmshells during pyrolysis can be quickly removed to reduce pore blockage tosteam during the subsequent activation process. Effects of carbonization
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temperature on pore development in oil palm shell based activated carbonwere studied by Daud et al. (2000). The pore development was found to bestrongly dependent on the carbonization temperature at which the char wasprepared. High carbonization temperature would produce activated carbonwith high micropore volume. At each carbonization temperature, the abso-lute micropore volume showed a maximum value at an intermediate carbonburn-off of around 50%. A similar pattern was also observed for the varia-tion in the absolute macropore (>50 nm diameter) volume with burn-off.At all of the studied carbonization temperatures, the mesopore (2–50 nmdiameter) volume seemed rather insignificant at burn-off less than 20% butrapidly increased thereafter.Table 4 presents carbonization and activationconditions for the production of the activated carbons from different oil palmresidues.
Activation
The objective of activation is to remove organic residue from biomass thatlead to increase pore volume and widen micropores. Generally, there aretwo main techniques for activation of the chars: physical or thermal acti-vation and chemical activation. Physical activation involves the use of anoxidizing gas for activation of the chars after carbonization. Chemical ac-tivation is performed by chemical treatment of the starting material with adehydrating agent followed by heat treatment of the impregnated materialin an inert atmosphere (Mohamed et al., 2010). Table 3 presents variousactivation conditions of the oil palm biomass chars.
Physical Activation
Activated carbons have been traditionally produced by the partial gasificationof the char either with steam or CO2 or a combination of both. Usually, thephysical activation is a two-step process, which involves the carbonizationof a carbonaceous material followed by the activation of the resulting charat elevated temperature in the presence of suitable oxidizing gases suchas carbon dioxide, O2, steam, or their mixtures. The gasification reactionresults in the removal of carbon atoms and in the process simultaneouslyproduce a wide range of pores (predominantly micropores), resulting inporous activated carbon (Lim et al., 2010). The extraction of carbon from thechar may occur as follows (Marsh and Rodriguez-Reinoso, 2006):
C + H2O → CO + H2, �H = +117 kJ/mol
C + 2H2O → CO2 + 2H2, �H = +75 kJ/mol
C + CO2 → 2CO, �H = +15 9kJ/mol
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Oil
pal
msh
ell
635
m2 /
g85
0◦C
850◦
CSt
eam
—K
lose
and
Rin
con
(200
7)O
ilpal
msh
ell
596.
20m
2 /g
700◦
C/2
hr
850◦
C/2
hr
KO
H/C
O2
—Tan
etal
.(2
008)
Oil
pal
msh
ell
1014
–114
8m
2 /g
973
K(7
00◦ C
)11
73K
(900
◦ C)
KO
Han
dH
2SO
4—
Guo
etal
.(2
007)
Oil
pal
msh
ell
1014
–106
4m
2 /g
573(
300)
–973
(700
◦ C)
K/2
hr
773(
500)
–117
3(9
00◦ C
)K
/2hr
H2SO
4/C
O2
—G
uo
etal
.(2
005)
Oil
pal
msh
ell
1183
m2 /
g67
3K
(400
◦ C)
1173
K(9
00◦ C
)—
Stea
mac
tivat
ion
Lua
and
Jia
(200
7)O
ilpal
msh
ell
770
m2 /
g40
0◦C/1
hr
600◦
C/3
hr
ZnCl 2
—Pan
um
ati
etal
.(2
008)
Oil
pal
msh
ell
1366
–156
3m
2 /g
600◦
C/2
hr
500–
900◦
C/1
hK
OH
and
H2SO
4/C
O2
—Lu
aan
dG
uo
(200
1)O
ilpal
msh
ell
1408
m2 /
g60
0◦C/2
hr
800◦
C/1
hr
CO
2Im
pre
gnat
edby
10%
KO
Han
d30
%H
3PO
4
Guo
and
Lua
(200
0a)
Oil
pal
msh
ell
1408
–156
3m
2 /g
600◦
C/2
hr
800◦
C/1
hr
CO
2Im
pre
gnat
edw
ithK
OH
or
H3PO
4
Guo
and
Lua
(200
3)
Oil
pal
msh
ell
1366
m2 /
g60
0◦C/3
hr
500–
900◦
C/0
.5hr
CO
2—
Guo
and
Lua
(200
2)O
ilpal
msh
ell
1182
.76
m2 /
g67
3.15
K(4
00◦ C
)11
73.1
5K
(900
◦ C)/
1hr
Stea
mTw
o-s
tep
pro
cess
Jia
and
Lua
(200
8)O
ilpal
msh
ell
1022
–140
0m
2 /g
Char
obta
ined
from
fact
ory
800–
900◦
C/3
hr
Stea
m/N
2—
Dau
det
al.
(200
2)O
ilpal
msh
ell
988
m2 /
g67
5◦C/2
hr
900◦
C/1
hr
Stea
m/N
2—
Jia
and
Lua
(200
8)(C
onti
nu
edon
nex
tpa
ge)
1127
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TA
BLE
4.
Car
boniz
atio
nan
dac
tivat
ion
conditi
ons
ofoil
pal
mbio
mas
s(C
onti
nu
ed)
Par
tsofoil
BET
surfac
eCar
boniz
atio
nAct
ivat
ion
Chem
ical
Additi
onal
pal
mbio
mas
sar
eaco
nditi
on
conditi
on
trea
tmen
tin
form
atio
nRef
eren
ce
Oil
pal
msh
ell
—70
0◦C
850◦
CK
OH
—Tan
etal
.(2
009)
Oil
pal
msh
ell
2247
m2 /
g80
0◦C/2
hr
800◦
C/1
.5hr
CO
2/N
2Im
pre
gnat
edby
NaO
HH
amad
etal
.(2
010)
Oil
pal
msh
ell
519
m2 /
g60
0◦C/2
hr
900◦
C/0
.5hr
CO
2—
Lua
etal
.(2
006)
Oil
pal
msh
ell
1366
m2 /
g29
8(2
5)–8
73(6
00◦ C
)K
/3hr
773(
500)
–117
3(90
0◦C)
K/0
.5hr
CO
2—
Guo
and
Lua
(200
2)
Oil
pal
msh
ell
1366
m2 /
g87
3K
(600
◦ C)/
3hr
773(
500)
–117
3K
(900
◦ C)/
1hr
(10
K/m
in)
CO
2—
Lua
and
Guo
(200
1a)
Oil
pal
msh
ell
1118
m2 /
g50
0/2
hr
900/
1hr
ZnCl 2
/CO
2—
Niy
aet
al.
(201
0a)
Oil
pal
msh
ell
—50
0/4
hr
—H
3PO
4,K
3PO
4an
dK
OH
CO
2ac
tivat
ion
Kas
sim
etal
.(2
004)
Oil
pal
msh
ell
206.
9m
2 /g
750◦
C80
0◦C
KO
H,Su
lfur
Tw
o-s
tep
pro
cess
usi
ng
the
pyr
oly
sis
and
sulfur
impre
gna-
tion
Suga
war
aet
al.,
(200
7)
Oil
pal
msh
ell
260
m2 /
g85
0◦C
850◦
C(1
.33
hr)
CO
2—
Dau
dan
dA
li(2
004)
Chem
ical
lym
odifi
edoil
pal
msh
ell
—70
0◦C/2
hr
850◦
C/2
hr
KO
H—
Tan
etal
.(2
008)
Oil
pal
mem
pty
fruit
bunch
—30
0–80
0◦C/0
.5hr
300–
800◦
C/2
hr
—Phys
ical
activ
atio
n(b
oili
ng
trea
tmen
tat
150◦
C
Ala
met
al.
(200
7)
Oil
pal
mem
pty
fruit
bunch
—70
0◦C/2
hr
814◦
C/1
.9hr
KO
H/C
O2
—Tan
etal
.,(2
009)
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Oil
pal
mem
pty
fruit
bunch
1031
.5m
2 /g
450◦
C/2
hr
450◦
C/2
hr
N2
Pre
trea
ted
with
20w
t%H
3PO
4
Shaa
ranian
dH
amee
d(2
010)
Oil
pal
mem
pty
fruit
bunch
432
m2 /
g70
0◦C/1
hr
——
Pre
trea
ted
with
KO
HLi
ng
etal
.(2
005)
Oil
pal
mst
ones
1410
m2 /
g85
0◦C/2
hr
650–
950◦
C(5
to20
◦ C/m
info
r0.
5–3
hr)
CO
2O
ne-
step
activ
atio
nLu
aan
dG
uo
(200
0)O
ilpal
mst
one
825
m2 /
g40
0–90
0◦C/3
hr
750–
950◦
C/2
hr
CO
2—
Guo
and
Lua
(200
0b)
Oil
pal
mst
one
1366
m2 /
g60
0◦C/2
hr
500–
900◦
C/1
hr
CO
2—
Lua
and
Guo
(200
1b)
Oil
pal
mfr
onds
1237
.13
m2 /
g70
0◦C/2
hr
800◦
C/1
hr
KO
H/C
O2
AC
optim
ized
by
RSM
Salm
anan
dH
amee
d(2
010)
Ext
ract
ed-o
ilpal
mfiber
894.
7m
2 /g
450–
950◦
C/0
.5–4
.5hr
500–
900◦
C/0
.25–
1hr
CO
2/N
2Tw
o-s
tep
activ
atio
n,
KO
Him
-pre
gnat
ion
Lua
and
Guo
(199
8a)
Ext
ract
ed-o
ilpal
mfiber
520.
6m
2 /g
850◦
C/3
.5hr
450–
950◦
C—
—Lu
aan
dG
uo
(199
9)O
ilpal
mfiber
1354
m2 /
g70
0◦C/2
hr
850◦
C/2
hr
KO
H/C
O2
—Tan
etal
.(2
007)
Oil
pal
mfiber
1354
m2 /
g70
0◦C/2
hr
862◦
C/1
hr
KO
H/C
O2
—H
amee
det
al.,
(200
8)O
ilpal
mw
ood
1084
m2 /
g35
0–42
0◦C/4
hr
519–
806◦
C/3
.5hr
Stea
m/C
O2
—A
hm
adet
al.,
(200
7)O
ilpal
msh
ell
—50
0,80
0,an
d90
0◦C/1
hr
820◦
CN
2—
Dau
det
al.
(200
0)O
ilpal
msh
ell
1200
m2 /
g77
3(50
0)–1
173(
900◦
C)
K/1
hr
800(
527)
–900
(627
◦ C)
KK
2CO
3—
Hay
ashi
etal
.,(2
002)
Oil
pal
mfiber
521
m2 /
g85
0◦C/3
.5hr
——
—Lu
aan
dG
uo
(199
8b)
Oil
pal
msh
ell
1183
m2 /
g40
0◦C/2
hr
900◦
C/1
hr
Stea
mPhys
ical
activ
atio
nby
N2
Lua
and
Jia
(200
9)
(Con
tin
ued
onn
ext
page
)
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ber
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TA
BLE
4.
Car
boniz
atio
nan
dac
tivat
ion
conditi
ons
ofoil
pal
mbio
mas
s(C
onti
nu
ed)
Par
tsofoil
BET
surfac
eCar
boniz
atio
nAct
ivat
ion
Chem
ical
Additi
onal
pal
mbio
mas
sar
eaco
nditi
on
conditi
on
trea
tmen
tin
form
atio
nRef
eren
ce
Oil
pal
mem
pty
fruit
bunch
es34
5.1
m2 /
g10
0–12
00◦ C
900◦
C/0
.25
hr
CO
2Tw
o-s
tep
pro
cess
Ala
met
al.
(200
9)O
ilpal
msh
ell
1319
m2 /
g90
0◦C/1
hr
830◦
C/0
.5–7
hr
Stea
m—
Ahm
adet
al.
(200
8)O
ilpal
msh
ell
—60
0◦C/2
hr
——
—N
om
anbhay
and
Pal
anis
amy
(200
5)O
ilpal
msh
ell
1065
m2 /
g80
0◦C/2
hr
800◦
CN
2K
2CO
3im
-pre
gnat
edAdin
ata
etal
.,(2
007)
Oil
pal
mfles
hfiber
266
m2 /
g60
0◦C/2
hr
500–
900◦
C/1
hr
CO
2—
Guo
etal
.(2
008)
Oil
pal
msh
ell
147
m2 /
g60
0◦C/2
hr
500–
900◦
C/1
hr
CO
2—
Guo
etal
.(2
008)
Oil
pal
mst
one
318
m2 /
g80
0◦C/3
hr
—N
2—
Guo
and
Lua
(199
8)Pal
moil
mill
effluen
tsl
udge
—30
0–80
0◦C/0
.5hr
300–
800◦
C/2
hr
—Phys
ical
activ
atio
n(b
oili
ng
trea
tmen
tat
150◦
C
Ala
met
al.
(200
6)
Oil
pal
mem
pty
fruit
bunch
es—
800◦
C80
0◦C/0
.5hr
——
Ala
met
al.
(200
7)O
ilpal
mem
pty
fruit
bunch
es11
41m
2 /g
700◦
C/2
hr
814◦
C/1
.9hr
CO
2A
Coptim
ized
by
RSM
Ham
eed
etal
.(2
009)
Oil
pal
msh
ell
973
m2 /
g—
700–
1000
◦ C/0
.5–1
.5hr
CO
2A
Coptim
ized
by
RSM
Sum
athiet
al.
(201
0)O
ilpal
msh
ell
973
m2 /
g—
700–
1000
◦ C/0
.5–1
.5hr
CO
2A
Coptim
ized
by
RSM
Sum
athiet
al.
(200
9)O
ilpal
mst
one
1837
m2 /
g65
0◦C/2
hr
750◦
C/1
hr
KO
H,H
3PO
4,
ZnCl 2
/CO
2
—G
uo
and
Lua
(200
0)O
ilpal
mtrunk
1884
m2 /
g50
0◦C/3
hr
500◦
C/3
hr
CO
2Pre
trea
ted
by
H3PO
4
Huss
ein
etal
.(2
001)
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Oil
pal
msh
ell
1366
m2 /
g87
3K
(600
)or
1073
K(8
00◦ C
)/3
hr
773(
500)
–117
3K
(900
◦ C)/
0.25
–1hr
CO
2—
Guo
and
Lua
(200
1)
Oil
pal
msh
ell
1135
m2 /
g20
0–60
0◦C/2
hr
500–
900◦
C/2
hr
CO
2Im
pre
gnat
edw
ithH
3PO
4
Guo
and
Lua
(200
3)O
ilpal
mst
one
1562
m2 /
g60
0◦C/2
hr
800◦
C/1
hr
CO
2Im
pre
gnat
edw
ithH
2SO
4/K
OH
Guo
and
Lua
(199
9)O
ilpal
mst
one
1837
m2 /
g60
0◦C/2
hr
800◦
C/1
hr
CO
2Im
pre
gnat
edw
ithH
2SO
4,K
OH
and
ZnCl 2
Guo
and
Lua
(200
0)
Oil
pal
msh
ell
1612
m2 /
g—
973
K(7
00◦ C
)/2
hr
—Pre
trea
ted
with
H2SO
4,K
OH
and
ZnCl 2
Guo
and
Lua
(200
3)
Oil
pal
mem
pty
fruit
bunch
es37
9.37
m2 /
g40
0◦C/0
.5hr
700◦
C/1
hr
20%
NaO
H—
Wah
iet
al.
(200
9)O
ilpal
msh
ell
1118
,16
53,an
d12
13m
2 /g
900◦
C85
0◦C
CO
2ZnCl 2
and
H3PO
4/p
hys
ical
activ
atio
nth
erm
altrea
tmen
tat
850◦
C
Niy
aet
al.
(201
1)
Oil
pal
mem
pty
fruit
bunch
es—
700◦
C/2
hr
844◦
C/1
.8hr
KO
H/C
O2
Phys
ioch
emic
alac
tivat
ion
Tan
and
Ham
eed
(201
0)O
ilpal
msh
ell
1118
and
1652
m2 /
g45
0–50
0◦C/2
hr
850◦
C/1
–7hr
CO
2Im
pre
gnat
edw
ithH
3PO
4an
dZnCl 2
Niy
aet
al.
(201
0b)
Oil
pal
mst
one
1291
m2 /
g80
0◦C/2
hr
800◦
C/4
–5hr
CO
2Im
pre
gnat
edw
ithZnCl 2
Hu
etal
.(2
003)
Oil
pal
msh
ell
1109
m2 /
g17
0◦C/1
hr
425◦
C/0
.5hr
—Im
pre
gnat
edw
ith65
%H
3PO
4
Lim
etal
.(2
010)
Oil
pal
msh
ell
476.
8m
2 /g
900◦
C/1
hr
900◦
C/3
hr
CO
2Car
boniz
edsa
mple
wer
eim
pre
gnat
edby
NaO
H
Moham
mad
iet
al.
(201
0)O
ilpal
mse
ed12
67m
2 /g
800◦
C/2
–3hr
800◦
C/2
–3hr
CO
2Im
pre
gnat
edw
ithZnCl 2
-
Hu
and
Srin
ivas
an(2
001)
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1132 M. Rafatullah et al.
These reactions are endothermic in nature. During the activation process,steam or CO2 react with carbon to produce CO, CO2, H2, or CH4. This processis referred as burn-off. Burn-off is defined as the weight differences betweenthe char and the activated carbon divided by the weight of the original charwhich both weights are on dry basis (Reed and Williams, 2004).
Physical activation of chars with steam or CO2 causes different effectson the development of microporosity. In early stages of activation process,CO2 develops narrow micropores, while steam widens the initial microporesof the char. At high degrees of burn-off, steam generates activated chars,which exhibit larger meso- and macropore volume than those prepared byCO2. As a result, CO2 creates activated chars with larger micropore vol-ume and narrower micropore size distribution than those activated by steam(Molina-Sabio et al., 1996a). Physical activation process is widely adoptedindustrially for commercial production due to the simplicity of process anddue to the ability to produce activated carbons with well-developed mi-croporosity and desirable physical characteristics such as the good physicalstrength.
Lua and Jia (2009) prepared an activated carbon from oil palm shellsby pyrolysis under vacuum and the resulting chars were subsequently ac-tivated using steam. The activated carbon had a well-developed mesoporestructure, which accounted for 45% of the total pore volume. The BET sur-face area of the activated carbon was 1183 m2/g and the total pore volumewas 0.69 cm3/g. In their earlier attempt in 2008, however, Lua and Jia foundthat the steam activated carbon from oil palm shell pyrolyzed under vac-uum condition, the BET and nonmicropore surface areas were 988 m2/g and273 m2/g, respectively. Lua and Guo (2001b) prepared activated carbon fromoil palm shell by CO2 activation. On the basis of the experimental investi-gation, the optimum conditions for CO2 activation to derive maximum BETsurface area were found to be at an activation temperature of 1173 K and ahold time of 30 min with a heating rate of 10 K/min and CO2 flow rate of100 cm3/min. Under these conditions, the largest BET surface area for theoil palm shell activated carbon was 1366 m2/g. Guo and Lua (2002a) carriedout similar experiments except that CO2 was used as gasifying agent insteadof steam. As a result, activated carbon with maximum BET surface area of1360 m2/g and micropore volume of 0.47 cm3/g was obtained. Lua and Jia(2009) prepared activated carbon from oil palm shell by steam activation.The activated carbon had a well-developed nonmicropore structure, whichaccounted for 55% of the total pore volume. The largest BET surface area ofthe activated carbon was 1183 m2/g with a total pore volume of 0.69 cm3/g.Ahmad et al. (2008) also reported the activated carbon from palm shell bysteam activation and found maximum BET surface area and pore volume of1104 m2/g and 0.4067 cm3/g, respectively.
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Oil Palm Biomass 1133
Chemical Activation
Chemical activation is a term often used to indicate the prior impregnation ofthe precursor with a chemical agent before heat treatment. Chemical activa-tion is usually applied for the degradation of the lignocellulosic materials, andeliminating the organic residues. Various dehydrating agents such as phos-phoric acid, sulfuric acid, zinc chloride, and potassium hydroxide are appliedin chemical activation process (Hayashi et al., 2000; Mohamed et al., 2010).The impregnation of the raw material with dehydrating agent is followedby heat treatment under inert atmosphere to form the final porous structureof the activated carbon. Chemical activation does not require as high tem-peratures as physical activation (Hayashi et al., 2000; Khezami et al., 2007).Chemical activation offers several advantages, which include single step ac-tivation, low activation temperatures, low activation time, higher yields, andbetter porous structure. The dehydrating agents inhibit the formation of tarand other undesired products during the carbonization process. This is themain concept of the higher carbon yield achieved in chemical activation incomparison to physical activation process (Hayashi et al., 2000). Generally,the chemical activating agent plays two major roles during the impregnationstage. It leads to the hydrolysis of the lignocellulosic material and also causesits swelling. Besides, it occupies some volume, which inhibits the narrowingof the particle during heat treatment. As the chemical agent is washed fromthe carbonaceous material after carbonization, some porosity is formed in-side the activated char (Molina-Sabio et al., 1996b). In the chemical activationprocess, the pore size distribution and surface area are determined by theimpregnation degree, which is the ratio between the mass of the chemicalagent and the raw material.
Hussein et al. (2001) studied the chemical activation of oil palm trunkusing phosphoric acid for the production of activated carbon. The activatedcarbons prepared from oil palm trunk pretreated with phosphoric acid withthe ratio of the acid to the precursor of 0.9, followed by carbonizationand activation by carbon dioxide resulted in a high surface area of morethan 1800 m2/g with 90% content of micropore surface area. The surfacearea and the nature of the porosity of the resulting activated carbons werefound to be dependent on the amount of the activator used for a fixedquantity of the precursor. Pretreatment of the precursor at low ratio of thephosphoric acid has added advantage, due to the tremendous increase in theapparent surface area of the resulting activated carbon and at the same timeenriching its micropore nature. Now when this ratio was increased up to 7.0,there is decreased in the surface area. It was suggested that the micropores,which have high contribution to the surface area, were mainly caused bythe phosphoric acid present in the impregnated materials. This inhibits thecontraction of the material during carbonization. On the other hand, usingtoo high a ratio of phosphoric acid to the precursor did not increase the
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1134 M. Rafatullah et al.
apparent surface area very much but destroyed the micropore componentand therefore increased the mesopore fraction of the resulting activatedcarbon. This was mainly caused by the hydrolysis of the lignocellulosicmaterials and subsequent partial extraction of some of its components duringthe impregnation.
Joseph et al. (2009) investigated the preparation of activated carbonfrom oil palm shell by ZnCl2 and H3PO4 activation. Experimental resultshowed that the adsorption ability of activated carbon impregnated withZnCl2 is better than that of activated carbons impregnated with (Impreg-nation ratios ZnCl2 or H3PO4 (mol/L)/dry biomass (g) are (3.5/20, 4.0/20,4.5/20, and 5.0/20) H3PO4. Lua and Guo (1998b) prepared activated car-bon from extracted-oil palm fibers by two-step CO2 activation, one-step CO2
activation and chemical activation with KOH impregnation. For chemical ac-tivation, the effects of KOH concentration and soak time were also studied.The activated carbon with the highest BET surface area was obtained bypyrolysis at 750◦C for 2 hr and subsequent activation with CO2 at 850◦C for30 min for extracted-oil palm fibers impregnated with 0.10 M KOH for 24 hr.In another investigation, they prepared activated carbon from oil palm stoneby pretreatment with H2SO4 and KOH impregnations. The effects of impreg-nations concentration and soaking time on the textural properties, such asadsorption isotherm, porosity, surface area, and pore size distribution wereinvestigated. From adsorption tests of SO2 and NH3, it was found that theactivated carbons pretreated with KOH could adsorb more SO2 but less NH3
than those pretreated with H2SO4, even though they had almost identicalBET and micropore surface areas. This indicated that the adsorptive capacityof the activated carbon was not only determined by its textural character-istics, but also related to the surface chemistry. Chemical characterizationshowed that impregnation affected significantly the surface chemistry, i.e.,inorganic component and surface organic functional group (Guo and Lua,1999). Activated carbons with relatively high densities and well-developedporosities were prepared from oil palm stones, which were pretreated withdifferent types of impregnating agents (ZnCl2, H3PO4, or KOH). Chemicalcharacterization showed that impregnation affected significantly the surfacechemistry (i.e., surface functional group). The samples pretreated with H3PO4
presented acidic groups such as phenols and carboxylic acids, whereas thosewith KOH impregnation showed basic groups likely to be pyrones (cyclicketone) and other keto-derivatives of pyran. The sample pretreated withZnCl2 solution had pH values around 7.0 also suggesting neutral character-istic. The benefits derived from impregnation in terms of higher BET surfaceareas were generally in the following order: 20% ZnCl2 >40% H3PO4 >10%KOH. Concentrations of the impregnating solutions had significant effects onthe characteristics of the activated carbons whilst the effects of impregnationtime on the BET surface area were limited after 24 hr of impregnation. Forthe highest BET surface area obtained in this study, the optimum conditions
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Oil Palm Biomass 1135
for CO2 activation were found to be at an activation temperature of 750◦Cfor 1 hr from oil palm stones pretreated with 20% ZnCl2 for 24 hr (Guo andLua, 2000). Guo and Lua (2003b) studied the surface functional groups onthe oil palm shell adsorbents prepared by phosphoric acid and potassiumhydroxide activation were detected using Fourier transform infrared spec-troscopy(FTIR). The surface areas were increased with the increase of boththe concentration of the impregnating solution and the soaking time due toextended action of the impregnating agent. However, the BET surface areadecreased when 40% KOH solution was used due to overgasification of theprecursor, resulting in detrimental effects on pore evolution. From the ex-perimental results, it was found that surface functional groups, which weredetermined by the concentration of impregnation solution and the soak-ing time, had a significant influence on the adsorptive capacity due to theoccurrence of chemisorption.
PROPERTIES AND CHARACTERIZATION OF OIL PALM BIOMASSBASED ACTIVATED CARBONS
Surface Area
The most important property of the activated carbon is its adsorptive capac-ity, which is related to the specific surface area. Generally, the larger thesurface area of the activated carbon, the greater will its adsorptive capac-ity. The BET surface area of activated carbon is important because like otherphysicochemical characteristics, it may strongly affect the reactivity and com-bustion behavior of the activated carbon. These surface areas are generatedgradually during the activation process. The CO2 flow rate, activation tem-perature, and retention time had important influences on the BET surfacearea.
The effects of pyrolysis temperature and retention time on the BETsurface areas of the activated carbon were shown by (Guo and Lua, 1998).When the pyrolysis temperature was 400◦C, pyrolysis reactions had just com-menced, thereby producing very small BET surface areas even though theretention time was increased up to 4 hr, due to the inadequacy of heatenergy to drive away any substantial amounts of volatiles. As the tempera-ture was increased from 500 to 700◦C, greater volatile matters were releasedprogressively during pyrolysis thereby resulting in the development of somenew porosities, and hence the BET surface areas increased progressively.With further increases in temperature of 800◦C, the surface area increasedwith retention time up to a maximum value at 3 hr and thereafter decreased.This decrease in surface area was due to some of the pores being sealedoff as a result of sintering at excessive time duration. Generally, a longer re-tention time is needed to enhance porosity as well as to clear blocked poreentrances before detrimental effects set in at prolonged times. However, at
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1136 M. Rafatullah et al.
a high temperature of 900◦C, the trend was reversed. From an initial highsurface area, it deteriorated with increasing retention time. This might be dueto a sintering effect at such high temperatures, followed by shrinkage of thechar, and realignment of the char structure, which resulted in reduced pores.Similarly, the optimum conditions for pyrolysis of oil palm stones to derivemaximum BET surface areas were found to be at a pyrolysis temperature of800◦C and a retention time of 3 hr. Particle size and heating rate for variousactivation temperatures used, appeared to have no significant effects on thepore surface area of the activated carbons while CO2 flow-rate, activationtemperature and hold time had dominant effects. An activation temperatureof 850◦C and a hold time of 2 hr were used to prepare activated carbons fromoil palm stones to produce maximum BET surface area of 1410 m2/g (Luaand Guo, 2000). Furthermore, the effects of CO2 flow rate on the BET surfaceareas of the fiber and shell derived activated carbons prepared at 800◦C for30 and 50 min, respectively, were investigated by Guo et al., in 2008. It wasfound that with a low CO2 flow rate, the BET surface area was small due toan insufficient amount of CO2 reacting with the carbon to produce pores.However, with too high flow rate, the carbon-CO2 reaction was so severe thatcarbon was burned off, reducing the quality of the activated carbon. Whenthe activated carbon was prepared from palm shells with H2SO4 impreg-nation, activation temperature and acid concentration were two importantfactors in surface area development. Increasing the activation temperaturefrom 573 to 973 K or increasing the H2SO4 concentration from 5 to 30%increased the BET surface area progressively. However, use of excessiveH2SO4 (e.g., 40%) would cause overgasification of the palm-shell precursor,resulting in decreases in both BET and micropore surface areas (Guo et al.,2005). Activated carbons with relatively high densities and well-developedporosities were prepared from oil palm stones, which were pretreated withdifferent types of impregnating agents (ZnCl2, H3PO4, or KOH; Guo andLua, 2000c). The benefits derived from impregnation in terms of higher BETsurface areas were generally in the following order: 20% ZnCl2 >40% H3PO4
>10% KOH. For the highest BET surface area obtained in this study, theoptimum conditions for CO2 activation were found to be at an activationtemperature of 750◦C for 1 hr from oil palm stones pretreated with 20%ZnCl2 for 24 hr. A similar trend in the relationship between the BET surfacearea and the activation temperature was also seen for chemical activationprocess. However, a notable difference was that the pore evolution for thechemical process commenced at much lower temperatures than the thermalprocess, which resulted in a higher yield of final product since the exces-sive burn-off encountered at higher temperatures was avoided. In addition,H3PO4 formed a layer of linkage such as phosphate and polyphosphate es-ters, which could protect the internal pore structure and thus prevent theadsorbent from excessive burn-off leading to a decrease in the pore surfacearea. Increasing the acid concentration was accompanied by an increase in
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Oil Palm Biomass 1137
the BET surface area of the adsorbent. This was because the role of theimpregnating agent was to minimize the formation of tars and other liquids,which could clog up the pores and inhibit the development of pore struc-tures. In addition, impregnating agents penetrated into the precursor particleduring impregnation and occupied substantial volumes. Once they were ex-tracted by intense washing after preparation, a large amount of microporositywas created. Therefore, the internal surface area increased with enhancingthe degree of impregnation due to increasing H3PO4 concentration (Guoand Lua, 2003a). The BET surface areas of oil palm biomass based activatedcarbon by different researchers are presented in Table 4.
Pore Size and Volume
Generally, the pore size distribution is one of the characterizations of porousmaterial that represents the structural heterogeneity and represents a modelof the solid internal structure. Within the porous solid there are the com-plex void spaces constructed from an equivalent set of noninteracting andregularly shaped model pores (Ismadji and Bhatia, 2001). The pore size dis-tribution is defined as the degree of heterogeneity in the structure of theporous material and closely related to both equilibrium properties and ki-netics of these materials used in industrial applications. It is widely agreedthat the pore structure and pore size distribution of an activated carbonis largely determined by the nature of the starting material. In accordanceto the classification adopted by the International Union of Pure and Ap-plied Chemistry, pores are classified as micropores (<2 nm diameter), meso-pores (2–50 nm diameter), and macropores (>50 nm diameter; InternationalUnion of Pure and Applied Chemistry, 1982). The distinction is importantbecause most molecules of gaseous pollutants fall in the 0.4–0.9 nm diam-eter range. Therefore, gas-adsorbing carbons usually have more microporeswhile liquid-adsorbing carbons have significantly more mesopores due tothe larger size of liquid molecules. All adsorbents showed predominantlymicroporous, which pointed to potential applications of these adsorbents ingas-phase adsorption. At high temperatures (600 and 900 ºC for chemical andthermal activation processes, respectively), less micropore is present due topore enlargement and widening, arising from the conversion of microporesto meso- or macropores.
Guo et al. (2008) investigated the pore size distributions of activatedcarbons from oil palm fiber and shell prepared under different activationconditions. For the shell carbon, there was a predominance of micropores.The predominance was more marked for the carbon prepared at 800◦C for50 min, and less was apparent for the carbon prepared at 900◦C for 50 min,which had more mesopores and macropores were present because of thesevere reaction of carbon-CO2. The high microporosity in shell activated
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carbon suggests its potential application in gas-phase adsorption for air pol-lution control. However, fiber activated carbon exhibited predominance ofmesopores and macropores, which make them more suitable for liquid phaseadsorption for example wastewater treatment or drinking water purification.Guo and Lua (2000c) observed the meso- and macropore size distributionsof carbons activated at 800◦C for 1 hr from oil palm stones pretreated withdifferent impregnating solutions for 24 hours. All of them, except for thecase of 30% KOH, suggested predominance of micropores due to the sharpincrease of pore size distribution curves toward the micropore domain. Thepore size distributions also showed the degree of micro porosities in the fol-lowing order: 20% ZnCl2 > 40% H3PO4 > 10% KOH. The activated carbonspretreated with 30% KOH solution have more meso- and macropores dueto an over-gasification process of carbon with steam from KOH decompo-sition, resulting in the conversion of microporosity into meso- and macroporosities. Niya et al. (2010a) prepared activated carbon by impregnation ofoil palm shell with various solutions of ZnCl2 followed by heat treatment at500◦C under a flow of nitrogen. For this precursor, large micropore volumeof micropores with a very small volume of mesopores and macropores wasobtained with intermediate ZnCl2 mass ratio. The samples prepared withoutextra physical activation showed wider pore size distribution and averagepore width compared to the samples with further CO2 activation. After heattreatment under CO2, samples showed lower surface area and pore and mi-cropore volume, reflecting that further thermal activation causes pore shrink-age and the creation of small micropores. Daud et al. (2002) investigated theeffect of activation temperature on pore development in activated carbonproduced from palm shell. Increasing the activation temperature from 800to 900◦C did not have any marked effect on micropore volume. However,the activated carbon had a higher micropore volume at high burn-off. Forall the activation temperatures used, the maximum absolute micropore vol-umes occur at a burn-off of approximately 50%. However, an increase in theactivation temperature has no remarkable effect on mesopore and macrop-ore development.Table 5 summarizes the pore size distribution of oil palmbiomass based activated carbon by different researchers.
SURFACE CHEMISTRY OF OIL PALM BIOMASS BASEDACTIVATED CARBON
The textural structure of activated carbon is believed to consist of partiallyordered graphite layers. The spaces between the carbon layer planes andthe gaps between the stacks form an interconnected network of slit-shapedpores, which ultimately accommodate the adsorbate molecules during anadsorption process (Guo and Lua, 2000). The adsorptive capacity is not onlydetermined by the adsorbents textural or porous structure but is also strongly
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TA
BLE
5.
Char
acte
rist
ics
ofac
tivat
edca
rbons
from
oil
pal
mbio
mas
s
Par
tsofoil
Mic
ropore
Mic
ropore
Mes
opore
Tota
lpore
Poro
sity
pal
mbio
mas
ssu
rfac
ear
eavo
lum
evo
lum
evo
lum
e(%
)Ref
eren
ce
Oil
pal
msh
ell
—25
2cm
3 /g
0.13
8cm
3 /g
0.44
325
cm3 /
g—
Klo
sean
dRin
con
(200
7)O
ilpal
msh
ell
——
—0.
34cm
3 /g
—Tan
etal
.(2
008)
Oil
pal
msh
ellac
tivat
edw
ithCO
2
—0.
26cm
3 /g
——
58.4
Guo
etal
.(2
007)
Oil
pal
msh
ellac
tivat
edw
ithK
OH
—0.
25cm
3 /g
——
56.3
Guo
etal
.(2
007)
Oil
pal
msh
ellac
tivat
edw
ithH
2SO
4
—0.
28cm
3 /g
——
59.5
Guo
etal
.(2
007)
Oil
pal
msh
ellac
tivat
edw
ithCO
2
605
m2 /
g—
——
58.5
Guo
etal
.(2
005)
Oil
pal
msh
ellac
tivat
edw
ithH
2SO
4
564
m2 /
g—
——
59.5
Guo
etal
.(2
005)
Oil
pal
msh
ell
——
0.31
cm3 /
g0.
69cm
3 /g
—Lu
aan
dJia
(200
7)O
ilpal
msh
ell
958
m2 /
g—
——
66.0
Lua
and
Guo
(200
1a)
Oil
pal
msh
ellac
tivat
edw
ithK
OH
605
m2 /
g—
——
61.0
Lua
and
Guo
(200
1a)
Oil
pal
msh
ellac
tivat
edw
ithH
3PO
4
772
m2 /
g—
——
63.3
Lua
and
Guo
(200
1a)
Oil
pal
msh
ellac
tivat
edw
ithK
OH
625
m2 /
g0.
40cm
3 /g
–0.
72cm
3 /g
—G
uo
and
Lua
(200
0b)
Oil
pal
msh
ellac
tivat
edw
ithH
3PO
4
690
m2 /
g0.
43cm
3 /g
–0.
78cm
3 /g
—G
uo
and
Lua
(200
0b)
Oil
pal
msh
ell
958
m2 /
g—
——
66.0
Guo
and
Lua
(200
3c)
Oil
pal
msh
ellac
tivat
edw
ith10
%K
OH
605
m2 /
g—
——
65.7
Guo
and
Lua
(200
3c)
Oil
pal
msh
ellac
tivat
edw
ith40
%K
OH
417
m2 /
g—
——
58.5
Guo
and
Lua
(200
3c)
Oil
pal
msh
ellac
tivat
edw
ith40
%H
3PO
4
772
m2 /
g—
——
72.9
Guo
and
Lua
(200
3c)
Oil
pal
msh
ell
958
m2 /
g0.
10–0
.47
cm3 /
g—
0.21
–0.6
9cm
3 /g
23.6
–66.
0G
uo
and
Lua
(200
2a)
Oil
pal
msh
ell
——
0.38
cm3 /
g0.
69cm
3 /g
—Jia
and
Lua
(200
8b)
(Con
tin
ued
onn
ext
page
)
1139
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TA
BLE
5.
Char
acte
rist
ics
ofac
tivat
edca
rbons
from
oil
pal
mbio
mas
s(C
onti
nu
ed)
Par
tsofoil
Mic
ropore
Mic
ropore
Mes
opore
Tota
lpore
Poro
sity
pal
mbio
mas
ssu
rfac
ear
eavo
lum
evo
lum
evo
lum
e(%
)Ref
eren
ce
Oil
pal
msh
ell
——
—0.
80cm
3 /g
—H
amad
etal
.(2
010)
Oil
pal
msh
ell
457
m2 /
g0.
215
cm3 /
g—
——
Lua
etal
.(2
006)
Oil
pal
msh
ell
985
m2 /
g—
——
66.0
Guo
and
Lua
(200
2b)
Oil
pal
msh
ell
958
m2 /
g—
——
—Lu
aan
dG
uo
(200
1b)
Oil
pal
msh
ell
—0.
42cm
3 /g
—0.
51cm
3 /g
—N
iya
etal
.(2
010a
)O
ilpal
mem
pty
fruit
bunch
——
—0.
58cm
3 /g
—Sh
aara
nian
dH
amee
d(2
010)
Oil
pal
mem
pty
fruit
bunch
369.
30m
2 /g
0.19
cm3 /
g—
——
Ling
etal
.(2
005)
Oil
pal
mst
one
942
m2 /
g0.
45cm
3 /g
—0.
71cm
3 /g
57.9
Lua
and
Guo
(200
0)O
ilpal
mst
one
570
m2 /
g—
——
—G
uo
and
Lua
(200
0a)
Oil
pal
mst
one
958
m2 /
g—
——
66.0
Lua
and
Guo
(200
1c)
Oil
pal
mfr
ond
–—
—0.
667
cm3 /
g—
Salm
anan
dH
amee
d(2
010)
Ext
ract
ed-o
ilpal
mfiber
628.
2m
2 /g
——
0.67
cm3 /
g—
Lua
and
Guo
(199
8b)
Ext
ract
ed-o
ilpal
mfiber
366.
4m
2 /g
——
0.34
cm3 /
g38
.9Lu
aan
dG
uo
(199
9)O
ilpal
mfiber
——
—0.
778
cm3 /
g—
Tan
etal
.(2
007)
Oil
pal
mw
ood
931.
6m
2 /g
——
——
Ahm
adet
al.(2
007)
Oil
pal
mfiber
366
m2 /
g0.
173
cm3 /
g—
0.34
6cm
3 /g
—Lu
aan
dG
uo
(199
8a)
Oil
pal
msh
ell
——
0.38
cm3 /
g0.
69cm
3 /g
—Lu
aan
dJia
(200
9)O
ilpal
msh
ell
—0.
339
cm3 /
g–
0.72
8cm
3 /g
—Ahm
adet
al.(2
008)
Oil
pal
mem
pty
fruit
bunch
——
0.21
cm3 /
g0.
60cm
3 /g
—H
amee
det
al.(2
009)
Oil
pal
mst
one
798
m2 /
g0.
45cm
3 /g
—0.
93cm
3 /g
76.2
Guo
and
Lua
(200
0)O
ilpal
mtrunk
1698
m2 /
g0.
74cm
3 /g
——
Huss
ein
etal
.(2
001)
Oil
pal
msh
ell
958
m2 /
g—
—0.
96cm
3 /g
66.0
Guo
and
Lua
(200
1)O
ilpal
msh
ell
907
m2 /
g—
——
59.6
Guo
and
Lua
(200
3a)
Oil
pal
mst
one
718
m2 /
g0.
45cm
3 /g
—0.
75cm
3 /g
59.5
Guo
and
Lua
(199
9)O
ilpal
mst
one
798
m2 /
g—
—1.
27cm
3 /g
76.2
Guo
and
Lua
(200
0)O
ilpal
mst
one
319
m2 /
g0.
463
cm3 /
g0.
322
cm3 /
g0.
785
cm3 /
g—
Hu
etal
.(2
003)
Oil
pal
msh
ell
569.
8m
2 /g
0.31
3cm
3 /g
0.14
7cm
3 /g
0.46
0cm
3 /g
—M
oham
mad
iet
al.(2
010)
Oil
pal
mse
ed10
91m
2 /g
0.07
5cm
3 /g
1.18
8cm
3 /g
1.26
3cm
3 /g
—H
uan
dSr
iniv
san
(200
1)
1140
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influenced by the chemical structures of the surface (Ruthven, 1984). Thisis because on the adsorbent surface there might be unpaired electrons, in-completely saturated valences and/or certain functional groups, which wouldundoubtedly influence the surface attraction force and ultimately the adsorp-tive capacity, particularly when additional amounts of adsorbate are takenup onto the adsorbent via chemisorption. The surface chemistry of activatedcarbon is governed by a small amount of heteroatoms (i.e., hydrogen, oxy-gen, nitrogen, sulfur, and phosphorus), which are bounded at the edges ofaromatic sheets, or incorporated within the carbon matrix forming hetero-cyclic ring systems (Bansal et al., 1988). These heteroatoms usually exist inthe form of organic functional groups, which can be acidic, basic, or neu-tral in their chemical character (El-Sayed and Bandosz, 2004). Moreover, thetextual and chemical characteristics of the adsorbent depend on the natureof the precursor used for producing the adsorbent as well as the methodsand conditions of production.
The acidic character of activated carbon surfaces is closely related tothe oxygen containing surface groups (Ania et al., 2004; Daud et al., 2002).These groups, which are mainly present on the outer surface or edge of thebasal plane contribute toward the chemical nature of the carbon. As theseouter sites constitute the majority of the adsorption surface, the concentrationof oxygen on the surface has a great impact on the adsorption capabilitiesof the carbon (Puri, 1970; Szymanski et al., 2002). Some oxygen-containingfunctionalities detected on the carbon surface include the following: car-boxylic, lactone, phenol, carbonyl, pyrone, chromene, quinone, and ethergroups. The surface oxygen functional groups can be classified into threeclasses according to their chemical properties: acidic, basic, and neutral.Oxygen containing functionalities are created when the carbon surface isoxidized. The most commonly used activation methods to introduce oxy-gen containing acidic groups are oxidation by gases and aqueous oxidants(Ermolenko et al., 1990; Mangun et al., 1999; Puri, 1970, 1983). Oxygen,air, carbon dioxide and steam can be used in the gas phase treatment. Inthese processes, low temperature oxidations lead to formation of strongacidic groups (e.g., carboxylic) while high temperature oxidations can beused to create a considerable amount of weak acid groups (e.g., phenolic;Ermolenko et al., 1990; Mangun et al., 1999). Liquid phase oxidations canintroduce a higher amount of oxygen into the carbon surface at much lowertemperatures compared to the gas phase treatment (Mangun et al., 1999). Ithas been demonstrated that oxidation of activated carbon in the gas phaseincreases mainly the concentration of hydroxyl and carbonyl surface groupswhile oxidation in liquid phase can incorporate a higher amount of oxygenin the form of carboxylic and phenolic hydroxyl groups on to the carbonsurface at much lower temperatures compared to the gas phase oxidation(Figueiredo et al., 1999; Mangun et al., 1999).
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Basicity of activated carbon can be associated with the resonatingπ -electrons of carbon aromatic rings that attract protons, and the basic sur-face functionalities (e.g., nitrogen containing groups) that are capable ofbinding with protons (El-Sayed and Bandosz, 2002; Jia et al., 2002; Leony Leon et al., 1992; Montes-Moran et al., 2004; Pereira et al., 2003). Itwas proposed that certain oxygen containing surface functionalities such aschromene (Garten et al., 1957), ketone (Contescu et al., 1988), and pyrone(Boehm, 2002) can contribute to the carbon basicity. However, the basiccharacter of activated carbons arises primarily from delocalized π -electronsof graphene layers (Barton et al., 1997; Leon y Leon et al., 1992; Montes-Moran et al., 2004). It was pointed out that the π -electrons of these layerscould act as Lewis bases (Perez-Cadenas et al., 2003). Various characteriza-tion methods such as Boehm titration, TPD, XPS, and FT-IR are available todetect and verify the existence of surface functional groups of the activatedcarbons.
Guo and Lua (2000) investigated the effects of surface chemistry (acid-ity or basicity) on gas-phase adsorption by activated carbons prepared fromoil palm stones that were preimpregnated with various chemicals. Chemicalcharacterization showed that impregnation affected the surface functionalgroup chemistry significantly. The samples pretreated with H3PO4 presentedacidic groups such as phenols and carboxylic acids, whereas those with KOHimpregnation showed basic groups likely to be pyrones (cyclic ketone) andother keto-derivatives of pyran. Results showed that the activated carbonsprepared from oil palm stones that was impregnated with H3PO4 and KOHare suitable for adsorbing basic (NH3) and acidic (NO2) gases, respectively.In different investigation on oil palm shell based activated carbon preparedby chemical and thermal activation, (Guo and Lua, 2003a) found from FTIRspectra that the main surface functional groups present in the palm shellwere carbonyl groups (e.g., ketone and quinone), ethers and phenols. Thespectrum of the sample preimpregnated with H3PO4 showed that the surfacefunctional groups present were presumed to be phenols, carboxylic acids (orcarboxylic anhydrides if they are close together) and carbonyl groups (eitherisolated or arranged in quinone-like fashion), all of which are typical acidicfunctional groups. It is presumed that phosphoric acid changed or modifiedthe surface chemistry of adsorbent due to the formation of acidic oxygencontaining complexes by strong oxidization. These surface functional groupswould affect the performance of the adsorbents if used for acidic or basicgases. In order to further investigate their surface chemistries, FTIR spectra ofactivated carbons prepared from oil palm shell by different activation meth-ods were measured by (Guo et al., 2007). The main surface functional groupspresent on the KOH-impregnated adsorbent are presumed to be alkalinegroups of pyrones (cyclic ketone) and other keto-derivatives of pyran. Theoxygen functional groups on the H2SO4-impregnated sample are likely to bephenols, carboxylic acids (or carboxylic anhydrides if they are close together)
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and carbonyl groups (either isolated or arranged in quinone-like fashion),all of which are typical acidic functional groups. For thermally activated car-bons, only phenol and carbonyl groups were detected, while lactonic andcarbonyl groups were found on the surface of the activated carbon preparedby KOH impregnation. On the surface of the activated carbon prepared byH2SO4 impregnation, carboxyl, phenol, lactonic and carbonyl groups weredetected. After CO2 activation, the ether and ketonic groups were not founddue to their instabilities in the slightly oxidative atmosphere, and only thequinines and phenols remained. These groups are typical organic functionalgroups on the activated carbon surface. Hence, the difference between theshell activated and fiber activated carbons was insignificant (Guo et al., 2008).
APPLICATIONS OF OIL PALM BASED ACTIVATED CARBONS
Activated carbons are unique and versatile adsorbents, and they are used ex-tensively for the removal of undesirable odor, color, taste, and other organicand inorganic impurities from domestic and industrial wastewater, solventrecovery, food processing, chemical industries, and pharmaceutical prod-ucts; in air pollution control from industrial and automobile exhausts; in thepurification of many chemical, pharmaceutical, and food products; and ina variety of gas-phase applications. They are being increasingly used in thefield of hydrometallurgy for the recovery of gold, silver, and other metals, be-sides also acting as catalysts and catalyst supports. They are also well knownfor their applications in medicine for the removal of toxins and bacterialinfections in certain ailments. Activated carbons are the most widely usedbecause of their adsorptive properties arising from the highly available areapresent in their extensive internal pore structure and the ability to readilymodify their surface chemistry (El-Hendawy et al., 2001). Such high poros-ity is a function of both the precursor as well as the scheme of activation(Brennan et al., 2001). The chemical nature of activated carbons significantlyinfluences its adsorptive, electrochemical, catalytic and other properties. Theapplications of oil palm biomass based activated carbons are summarized inTable 6.
Gas-Phase Adsorption
Activated carbon is one of the adsorbents most widely used for air pollutioncontrol, as it can effectively treat industrial gas and indoor air environments(Tsai et al., 1998). They can also be used for various gas separation andpurification processes, due to its distinguished properties such as extensivepore surface area, developed internal pore structure and unique surfacechemistry (Girgis and El-Hendawy, 2002). One of the important applicationsof these porous materials in environmental protection is in the removal of
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TABLE 6. Applications of oil palm biomass based activated carbons
Parts of oilpalm biomass Applications Reference(s)
Oil palm shell Removal of NO2 Guo and Lua (2002a, 2003a, 2003b),Sumathi et al. (2010)
Oil palm shell Removal of NH3 Guo and Lua, (2002a, 2003a, 2003b), Guoet al. (2005)
Oil palm shell Removal of SO2 Guo and Lua, (2000, 2002b, 2003c), Luaand Guo (2001a, 2001b), Sumathi et al.(2009, 2010)
Oil palm shell Removal of H2S Guo et al. (2007)Oil palm shell Removal of phenol Jia and Lua (2008), Lua and Jia (2007,
2009), Panumati et al. (2008)Oil palm shell Removal of Pb(II) Aroua et al. (2008), Issabayeva et al. (2006,
2008), Kassim et al. (2004), Sugawaraet al. (2007), Yin et al. (2008b)
Oil palm shell Removal of Zn(II) Kassim et al. (2004), Sugawara et al. (2007)Oil palm shell Removal of
2,4,6-trichlorophenolTan et al. (2009a)
Oil palm shell Removal of methylene blue Tan et al. (2008a, 2008b)Oil palm shell Removal of 4-chloroguaiacol Hamad et al. (2010)Oil palm shell Removal of Cr(III) Nomanbhay and Palanisamy (2005)Oil palm shell Removal of Cr(IV) Nomanbhay and Palanisamy (2005)Oil palm shell Removal of NOx Klose and Rincon (2007), Sumathi et al.
(2010)Oil palm shell selective selection of CH4 Adinata et al. (2007), Niya et al. (2010a,
2011)Oil palm shell Removal of Rhodamine B Mohammadi et al. (2010)Oil palm shell Removal of Cu(II) Yin et al. (2008a)Oil palm shell Removal of Ni(II) Yin et al. (2008a, 2008b)Oil palm shell Removal of Fe(III) Kassim et al. (2004)Oil palm shell Removal of Endosulfan Lim et al. (2008)Oil palm shell Removal of Cd(II) Yin et al. (2008b)Oil palm empty fruit
bunchesRemoval of Phenol Alam et al. (2007a, 2009), Ling et al. (2005)
Oil palm empty fruitbunches
Removal of2,4-dichlorophenol
Alam et al. (2007b), Shaarani and Hameed(2010)
Oil palm empty fruitbunches
Removal of2,4,6-trichlorophenol
Hameed et al. (2009), Tan et al. (2009b)
Oil palm empty fruitbunches
Removal of methylene blue Tan and Hameed (2010)
Oil palm empty fruitbunches
Removal of Hg(II) Wahi et al. (2009)
Oil palm empty fruitbunches
Removal of Pb(II) Wahi et al. (2009)
Oil palm empty fruitbunches
Removal of Cu(II) Wahi et al. (2009)
Oil palm empty fruitbunches
Removal of Zn(II) Alam et al. (2008)
Oil palm stone Removal of SO2- Guo and Lua (1999), Lua and Guo (2001a)Oil palm stone Removal of NH3 Guo and Lua (1999, 2000)Oil palm stone Removal of NO2 Guo and Luo (2000), Lua and Guo (2000)Oil palm kernel shell Removal of reactive black 5 Nourouzi et al. (2009a, 2009b)Oil palm kernel shell Removal of reactive red E Nourouzi et al. (2009a, 2009b)Oil palm kernel shell Removal of remazol black 5 Zawani et al. (2009)Oil palm fronds Removal of bentazon Salman and Hameed (2010)Oil palm wood Removal of methylene blue Ahmad et al. (2007b)Oil palm fiber Removal of methylene blue Hameed et al. (2008), Tan et al. (2007)Extracted oil palm fiber Removal of nitric oxide Lua and Guo (1998)Palm oil mill effluent sludge Removal of phenol Alam et al. (2006)
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gaseous pollutants such as nitrogen oxides (NOx), hydrogen sulfide (H2S),and sulfur dioxide (SO2; Noll et al., 1992).
Guo and Lua (2000) studied the adsorption of NH3 and NO2 by activatedcarbons prepared from oil palm stones preimpregnated with H3PO4 andKOH. Experimental results showed that activated carbon prepared from oilpalm stones impregnated with H3PO4 and KOH are suitable for adsorbingbasic (NH3) and acidic (NO2) gases, respectively. In general, the activatedcarbons prepared from oil palm stones with impregnation of KOH and H2SO4
are suitable for use as gas-phase adsorbents for the removal of acidic andalkaline gases, respectively. The oil palm shell activated carbon could adsorbgaseous pollutant such as SO2 effectively, at a capacity slightly higher thanthat of the commercial product. The adsorptive capacity was found to belinearly proportional to its BET surface area or textural characteristics. Thiswas due to the neutral (or slightly acidic) surface organic functional groupsof the oil palm shell activated carbons (Lua and Guo, 2001b).
Liquid Phase Adsorption
The aqueous-phase adsorption of both organic and inorganic compoundshas been a very important application of activated carbon. In fact, it isknown that around 80% of the world production of activated carbon is usedin liquid-phase applications (Moreno-Castilla and Rivera-Utrilla, 2001). Also,the treatment of wastewater and contaminated groundwater using activatedcarbon is becoming more popular throughout the world as a result of thelimited sources of water supply (Meidl, 1997). In such treatments, activatedcarbon is normally used as a primary treatment, preceding other purificationprocesses, or as a final tertiary or advanced treatment (Dias et al., 2007).
Activated carbons are used for the removal of phenols (Jia and Lua,2008a; Lua and Jia, 2007, 2009), phenolic compounds (Alam et al., 2007b;Hameed et al., 2009; Shaarani and Hameed, 2010; Tan et al., 2009a, 2009b),heavy metals (Alam et al., 2008; Issabayeva et al., 2006, 2008; Kassim et al.,2004; Nomanbhay and Palanisamy, 2005; Sugawara et al., 2007; Wahi et al.,2009; Yin et al., 2008a, 2008b), dyes (Ahmad et al., 2007b; Hameed et al.,2008; Nourouzi et al., 2009a, 2009b; Tan et al., 2007, 2008a, 2008b; Tan andHameed, 2010; Zawani et al., 2009), and pesticides (Salman and Hameed,2010) from aqueous solutions. Phenolic derivatives belong to a group ofcommon environmental contaminants. The presence of their even low con-centrations can be an obstacle to the use (and/or) reuse of water. Phenolscause unpleasant taste and odor of drinking water and can exert negative ef-fects on different biological processes. Phenolic derivatives are widely usedas intermediates in the synthesis of plastics, colors, pesticides, and insecti-cides. Degradation of these substances means the appearance of phenol andits derivatives in the environment (Dabrowski et al., 2005). Dyes contami-nation in receiving water can lead to a variety of environmental problems.
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TABLE 7. Comparison between oil palm based activated carbons and commercial activatedcarbons
Commercial activated BET surfacecarbon area Reference(s)
Carbochem 950 m2/g Guo et al. (2008), Lua and Guo(2001c)
Microcarb 1150 m2/g Guo et al. (2008), Lua and Guo(2001b, 2001c)
Filtracarb 1150 m2/g Guo and Lua (2003c)Carbochem 1072 m2/g Lua and Guo (2000)Microcarb (Neutralization) 1195 m2/g Guo and Lua (2000)Carbochem (ZnCl2) 1380 m2/g Guo and Lua (2000)]Calgon OLC Plus 12 × 30 1113 m2/g Lua and Jia (2007)BDH from Merck 1118 m2/g Tan et al. (2007)Filtrasorb F300 957 m2/g Tan et al. (2007, 2008b)BPL from Calgon
Corporation972 m2/g Tan et al. (2007)
Commercial grade coconutshell based activatedcarbon
838.45 m2/g Tan et al. (2009b)
Commercial granular palmshell
837.8 m2/g Niya et al. (2010a)
Filtrasorb 100 937 m2/g Hu et al. (2001), Hu andSrinivasan (2001), Ling et al.(2005)
Commercial activatedcarbon
500 m2/g Wahi et al. (2009)
Several classes of dyes are considered as possible carcinogens or mutagensby European and American authorities. Methylene blue is the most importantbasic dye. It is widely used as a stain and has some biological uses (El Qadaet al., 2006).
COMPARISONS OF OIL PALM BIOMASS BASED ACTIVATEDCARBONS WITH COMMERCIAL ACTIVATED CARBON
The activated carbon devised from oil palm biomass could exhibit highsurface areas and excellent adsorption behavior comparable to commercialactivated carbon through careful control of its preparation parameters. Thisactivated carbon can compete with commercial ones, some of them present-ing even better behavior. The oil palm biomass based activated carbons areexpected to be economically viable and have the potential to compete withthe commercial ones. Some of the commercial activated carbons with theirBET surface area are summarized in Table 6.
The adsorptive capacities of two commercial activated carbons preparedfrom bituminous coal were tested for comparison with the oil palm stoneactivated carbon developed by Lua and Guo (2001). Oil palm stone acti-vated was prepared by physical activation. The resulted char was activated
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at 500–900◦C under CO2. The BET surface area of Carbochem, Microcarb, andoil palm stone activated carbon were found to be 950, 1150, and 1366 m2/g,respectively. The amounts of SO2 adsorbed for the activated carbon from oilpalm stone were obviously higher than those of commercial ones. This mustbe attributed to the higher surface area of the activated carbon prepared fromthe oil palm stone. NO2 adsorption tests showed that the adsorptive capacityof the oil palm activated carbon was better than that of the commercial one.The adsorptive capacity of the oil palm stone activated carbon was foundto be linearly proportional to its BET surface area (Lua and Guo, 2000).The methylene blue adsorption capacity of the HCl-treated activated carbonprepared from oil palm shell was relatively high compared to some otherreported commercial adsorbents reported (Tan et al., 2008b). This shows thatoil palm shell was a promising starting material for preparation of activatedcarbon for removal of methylene blue from aqueous solutions, and HCl treat-ment was able to enhance its adsorption capacity. The activated carbon pre-pared from empty fruit bunch showed relatively large 2,4,6-Trichlorophenoladsorption capacity of 500 mg/g, as compared to commercial grade coconutshell based activated carbon (Tan et al., 2009b).
CONCLUSIONS AND FUTURE DIRECTIONS
Oil palm biomass as a precursor of activated carbons have been reviewedbased on a substantial number of relevant articles published. Activated car-bons are powerful adsorbents that can efficiently remove several pollutantsfrom the aqueous and the gaseous phase. However, their large-scale appli-cation is limited by the high production costs. Several low-cost adsorbentshave been tested. However, activated carbons are known to have much bet-ter performances to treat contaminated effluents. The need for efficient andeconomic removal of pollutants, for instance, resulted in the development ofresearch on the use of waste materials as precursors for the preparation ofless costly activated carbon. The use of such materials can, therefore, be anefficient alternative for both, production of low-cost activated carbons, andadoption of effective waste management practices. Activated carbon surfaceshave a pore size that determines its adsorption capacity, a chemical structurethat influences its interaction with polar and nonpolar adsorbates, and activesites, which determine the type of chemical reactions with other molecules.
As the raw materials obtained from oil palm wastes are available freelyand abundantly, the cost for preparation of activated carbons should belower than the coal based activated carbons. Hence it can provide a poten-tially inexpensive replacement of existing commercial coal based activatedcarbons. Further research on cost feasibility for the production need tobe done. Conversion of plentiful oil palm biomass into activated carbonsthat can be used in applications such as drinking water purification, waste
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treatments, treatment of dyes and metal-ions from aqueous solution wouldadd value to agricultural commodities, help the agricultural economy withan additional market potential, offer solution to environmental problemsand help reduce the cost of waste disposal.
The results are very promising, activated carbon with high surface areasmight be obtained and adsorption behavior might be controlled by care-fully manipulating preparation parameters, attributing to the relatively highfixed carbon and volatile matters content, low ash content, and high den-sity or mechanical strengths of the precursors, associated with the inherenthighly porous structures within the carbon matrix. The findings will pro-vide a twofold advantage with respect to environmental management. First,huge volume of oil palm waste could be partly reduced, converted to useful,value-added adsorbents, and second, the low-cost adsorbent, if developed,may overcome the wastewater pollution at a reasonable cost, solving part ofthe agricultural wastes and wastewater treatment problem in Malaysia. Theproduction has a long term and far-reaching effects. These enable us to tapthe cheap raw material available in large quantities throughout the country.It can generate more income to the raw materials providers. The quality ofthe activated carbons from oil palm biomass is as good as or better thanthe activated carbon presently available in the market. In this way, it canincrease the output of the oil palm industry and turning the by-product intoa resource for another industry.
Although the amount of published work is still comparatively small, theresults so far obtained are promising and there is a need for more detailedsystematic studies at the application front. Further research is necessary to as-sess the economical feasibility and the environmental impact of the activatedcarbons produced by oil palm biomass.
ACKNOWLEDGMENTS
The authors acknowledge the research grant provided by the Universiti SainsMalaysia under the Short Term Grant Scheme (Project No. 304/PTEKIND/639062) and Research University (RU) Scheme (Project No. 1001/PTEKIND/814048).
REFERENCES
Adinata, D., Daud, W. M. A. W., and Aroua, M. K. (2007). Production of carbonmolecular sieves from palm shell based activated carbon by pore sizes modifica-tion with benzene for methane selective separation. Fuel Processing Technology,88, 599–605.
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by [
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vers
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ains
Mal
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a] a
t 17:
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0 Se
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Oil Palm Biomass 1149
Ahmad, A., Rafatullah, M., and Danish, M. (2007a). Removal of Zn(II) and Cd(II) ionsfrom aqueous solutions using treated sawdust of sissoo wood as an adsorbent.Holz als Roh- und Werkstoff, 65, 429–436.
Ahmad, A., Rafatullah, M., Sulaiman, O., Ibrahim, M. H., Chii, Y. Y., and Siddique,B. M. (2009b). Removal of Cu(II) and Pb(II) ions from aqueous solutions byadsorption on sawdust of meranti wood. Desalination, 247, 636–646.
Ahmad, A., Rafatullah, M., Sulaiman, O., Ibrahim, M. H., and Hashim, R. (2009a).Scavenging behaviour of meranti sawdust in the removal of methylene bluefrom aqueous solution. Journal of Hazardous Materials, 170, 357–365.
Ahmad, A. L., Loh, M. M., and Aziz, J. A. (2007b). Preparation and characterizationof activated carbon from oil palm wood and its evaluation on Methylene blueadsorption. Dyes and Pigments, 75, 263–272.
Ahmad, M., Daud, W. M. A. W., and Aroua, M. (2008). Adsorption kinetics of variousgases in carbon molecular sieves (CMS) produced from palm shell. Colloids andSurfaces A: Physicochemical and Engineering Aspects, 312, 131–135.
Ahmad, T., Rafatullah, M., Ghazali, A., Sulaiman, O., Hashim, R., and Ahmad, A.(2010). Removal of pesticides from water and wastewater by different adsor-bents: A review, Journal of Environmental Science and Health–Part C Environ-mental Carcinogenesis and Ecotoxicology Reviews, 28, 231–271.
Ahmadroup, A., and Do, D. D. (1997). The preparation of activated carbon fromMacadamia nutshell by chemical activation. Carbon, 35, 1723–1732.
Ahmedna, M., Marshall, W. E., Husseiny, A. A., Rao, R. M., and Goktepe, I. (2004).The use of nutshell carbons in drinking water filters for removal of trace metals.Water Resources, 38, 1062–1068.
Ahmedna, M., Marshall, W. E., and Rao, R. M. (2000). Production of granular activatedcarbons from select agricultural byproducts and evaluation of their physical,chemical and adsorption properties. Bioresource Technology, 71, 113–123.
Alam, M. Z., Ameem, E. S., Muyibi, S. A., and Kabbashi, N. A. (2009). The factorsaffecting the performance of activated carbon prepared from oil palm emptyfruit bunches for adsorption of phenol. Chemical Engineering Journal, 155,191–198.
Alam, M. Z., Muyibi, S. A., and Kamaldin, N. (2008). Production of activated carbonfrom oil palm empty fruit bunches for removal of zinc. Twelfth InternationalWater Technology Conference, IWTC12, Alexandria, Egypt.
Alam, M. Z., Muyibi, S. A., Mansor, M. F., and Wahid, R. (2006). Removal of phenolby activated carbons prepared from palm oil mill effluent sludge. Journal ofEnvironmental Sciences, 18, 446–452.
Alam, M. Z., Muyibi, S. A., Mansor, M. F., and Wahid, R. (2007a). Activated car-bons derived from oil palm empty-fruit bunches: Application to environmentalproblems. Journal of Environmental Science, 19, 103–108.
Alam, M. Z., Muyibi, S. A., and Toramae, J. (2007b). Statistical optimization of adsorp-tion processes for removal of 2, 4-dichlorophenol by activated carbon derivedfrom oil palm empty fruit bunches. Journal of Environmental Sciences, 19,674–677.
Altenor, S., Carene, B., Emmanuel, E., Lambert, J., Ehrhardt, J. J., and Gaspard, S.(2009). Adsorption studies of methylene blue and phenol onto vetiver rootsactivated carbon prepared by chemical activation. Journal of Hazardous Mate-rials, 165, 1029–1039.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
1150 M. Rafatullah et al.
Ania, C. O., Parra, J. B., and Pis, J. J. (2004). Oxygen-induced decrease in theequilibrium adsorptive capacities of activated carbons. Adsorption Science andTechnology, 22, 337–351.
Aroua, M. K., Leong, S. P. P., Teo, L. Y., Yin, C. Y., and Daud, W. M. A. W. (2008).Real-time determination of kinetics of adsorption of lead (II) onto palm shell-based activated carbon using ion selective electrode. Bioresource Technology,99, 5786–5792.
Aygun, A., Yenisoy-Karakas, S., and Duman, I. (2003). Production of granular acti-vated carbon from fruit stones and nutshells and evaluation of their physical,chemical and adsorption properties. Microporous and Mesoporous Materials, 66,189–195.
Balat, M. (2008a). Mechanisms of thermochemical biomass conversion processes.Part 1: Reactions of pyrolysis. Energy Source Part A, 30, 620–635.
Balat, M. (2008b). Mechanisms of thermochemical biomass conversion processes.Part 3: Reactions of liquefaction. Energy Source Part A, 30, 649–659.
Bansal, R. C., Donnet, J. B., and Stoeckli, F. (1988). Active carbon. New York: MarcelDekker.
Barton, S. S., Evans, M. J. B., Halliop, E., and MacDonald, J. A. F. (1997). Acidic andbasic sites on the surface of porous carbon. Carbon, 35, 1361–1366.
Basiron, Y., and Chan, K. W. (2004). The oil palm and its sustainability. Journal ofOil Palm Research, 16, 1–10.
Bestani, B., Benderdouche, N., Benstaali, B., Belhakem, M., and Addou, A. (2008).Methylene blue and iodine adsorption onto an activated desert plant. Biore-source Technology, 99, 8441–8444.
Boehm, H. P. (2002). Surface oxides on carbon and their analysis: A critical assess-ment. Carbon, 40, 145–149.
Boeriu, C. G., Bravo, D., Gosselink, R. J. A., and vanDam, J. E. G. (2004). Char-acterisation of structure-dependent functional properties of lignin with infraredspectroscopy. Industrial Crops and Products, 20, 205–218.
Brennan, J. K., Bandosz, T. J., Thomson, K. T., and Gubbins, K. E. (2001). Waterin porous carbons. Colloid and Surfaces A: Physicochemical and EngineeringAspects, 187–188, 539–568.
Cetin, E., Moghtaderi, B., Gupta, R., and Wall, T. F. (2004). Influence of pyrolysisconditions on the structure and gasification reactivity of biomass chars. Fuel,83, 2139–2150.
Chakar, F. S., and Ragauskas, A. J. (2004). Review of current and future softwoodkraft lignin process chemistry. Industrial Crops and Products, 20, 131–141.
Chandra, T. C., Mirna, M. M., Sudaryanto, Y., and Ismadji, S. (2007). Adsorp-tion of basic dye onto activated carbon prepared from durian shell: Studiesof adsorption equilibrium and kinetics. Chemical Engineering Journal, 127,121–129.
Chavalparit, O., Rulkens, W. H., Mol, A. P. J., and Khaodhair, S. (2006). Options forenvironmental sustainability of the crude palm oil industry in Thailand throughenhancement of industrial ecosystems. Environmental, Development and Sus-tainability, 8, 271–287.
Chingombe, P., Saha, B., and Wakeman, R. J. (2005). Surface modification andcharacterization of a coal-based activated carbon. Carbon, 43, 3132–3143.
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nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
Oil Palm Biomass 1151
Contescu, A., Vass, M., Contescu, C., Putyera, K., and Schwarz, J. A. (1998). Acidbuffering capacity of basic carbons revealed by their continuous pK distribution.Carbon, 36, 247–258.
Crini, G. (2006). Non-conventional low-cost adsorbents for dye removal: A review.Bioresource Technology, 97, 1061–1085.
Dabrowski, A., Podkoscielny, P., Hubicki, Z., and Barczak, M. (2005). Adsorptionof phenolic compounds by activated carbon-a critical review. Chemosphere, 58,1049–1070.
Dalimin, M. N. (1995). Renewable energy update: Malaysia. Renewable Energy, 6,435–439.
Danish, M., Sulaiman, O., Rafatullah, M., Hashim, R., and Ahmad, A. (2010). Kineticsfor the removal of paraquat dichloride from aqueous solution by activateddate (Phoenix dactylifera) stone carbon. Journal of Dispersion Science andTechnology, 31, 248–259.
Daud, W. M. A. W., and Ali, W. S. W. (2004). Comparison on pore developmentof activated carbon produced from palm shell and coconut shell. BioresourceTechnology, 93, 63–69.
Daud, W. M. A. W., Ali, W. S. W., and Sulaiman, M. Z. (2000). The effects ofcarbonization temperature on pore development in palm-shell-based activatedcarbon. Carbon, 38, 1925–1932.
Daud, W. M. A. W., Ali, W. S. W., and Sulaiman, M. Z. (2002). Effect of activationtemperature on pore development in activated carbon produced from palmshell. Journal of Chemical Technology and Biotechnology, 78, 1–5.
Demirbas, A. (2001). Biomass resource facilities and biomass conversion processingfor fuels and chemicals. Energy Conversion and Management, 42, 1357–1378.
Demirbas, A. (2008). Recent progress in biorenewable feedstocks. Energy EducationScience and Technology, 22, 69–95.
Demirbas, A. (2009). Agricultural based activated carbons for the removal of dyesfrom aqueous solutions: A review. Journal of Hazardous Materials, 167, 1–9.
Dias, J. M., Alvim-Ferraz, M. C. M., Almeida, M. F., Rivera-Utrilla, J., and Sanchez-Polo, M. (2007). Waste materials for activated carbon preparation and its usein aqueous-phase treatment: A review. Journal of Environmental Management,85, 833–846.
El Qada, E. N., Allen, S. J., and Walker, G. M. (2006). Adsorption of methyleneblue onto activated carbon produced from steam activated bituminous coal: Astudy of equilibrium adsorption isotherm. Chemical Engineering Journal, 124,103–110.
El-Hendawy, A.-N. A., Samra, S. E., and Girgis, B. S. (2001). Adsorption charac-teristics of activated carbons obtained from corncobs. Colloid and Surface A:Physicochemical Engineering Aspects, 180, 209–221.
El-Sayed, Y., and Bandosz, T. J. (2002). Acetaldehyde adsorption on nitrogen-containing activated carbons. Langmuir, 18, 3213–3218.
El-Sayed, Y., and Bandosz, T. J. (2004). Adsorption of valeric acid from aqueoussolution onto activated carbons: Role of surface basic sites. Journal of ColloidInterface Science, 273, 64–72.
Ermolenko, I. N., Lyubliner, I. P., and Gulko, N. V. (1990). Chemically modifiedcarbon fibers and their applications. New York, VCH.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
1152 M. Rafatullah et al.
Fan, M., Marshall, W., Daugaard, D., and Brown, R. C. (2004). Steam activation ofchars produced from oat hulls and corn stover. Bioresource Technology, 93,103–107.
Figueiredo, J. L., Pereira, M. F. R., Freitas, M. M. A., and Orfao, J. J. M. (1999).Modification of the surface chemistry of activated carbons. Carbon, 37, 1379–1389.
Foo, K. Y., and Hameed, B. H. (2009). Recent developments in the preparation andregeneration of activated carbons by microwaves. Advances in Colloid InterfaceScience, 149, 19–27.
Fu, P., Hu, S., Sun, L., Xiang, J., Yang, T., Zhang, A., and Zhang, J. (2009). Structuralevolution of maize stalk/char particles during pyrolysis. Bioresource Technology,100, 4877–4883.
Garcia-Valls, R., and Hatton, T. A. (2003). Metal ion complexation with lignin deriva-tives. Chemical Engineering Journal, 94, 99–105.
Garten, V. A., Weiss, D. E., and Willis, J. B. (1957). A new interpretation of theacidic and basic structures in carbons. II. The chromene-carbonium ion couplein carbon. Australian Journal of Chemistry, 10, 309–328.
Ghazali, A., Daud, W. R. W., and Law, K. N. (2006). Alkaline peroxide mechanicalpulping of oil palm lignocellulosics part 2: EFB responses to pretreatments.APPITA Journal, 59, 65–70.
Ghazali, A., Daud, W. R. W., and Law, K. N. (2009). Pre-treatment of oil palmbiomass for alkaline peroxide pulping. Cellulose Chemistry and Technology, 43,329–338.
Girgis, B. S., and El-Hendawy, A. A. (2002). Porosity development in activatedcarbons obtained from date pits under chemical activation with phosphoricacid. Microporous and Mesoporous Materials, 52, 105–117.
Girgis, B. S., Yunis, S. S., and Soliman, A. M. (2002). Characteristics of activatedcarbon from peanut hulls in relation to conditions of preparation. MaterialLetters, 57, 164–172.
Glasser, W. G., and Sarkanen, S. (Eds.). (1989). Lignin: Properties, materials.Washington, DC: American Chemical Society.
Gong, R., Liu, X., Feng, M., Liang, J., Cai, W., and Li, N. (2008). Comparative studyof methylene blue sorbed on crude and monosodium glutamate functionalizedsawdust. Journal of Health Science, 54, 623–628.
Gosselink, R. J. A., deJong, E., Guran, B., and Abacherli, A. (2004). Coordination net-work for lignin—standardisation, production and applications adapted to mar-ket requirements (EUROLIGNIN). Industrial Crops and Products, 20, 121–129.
Guo, J., Gui, B., Xiang, S.-X., Bao, X.-T., Zhang, H.-J., and Lua, A. C. (2008). Prepa-ration of activated carbons by utilizing solid wastes from palm oil processingmills. Journal of Porous Materials, 15, 535–540.
Guo, J., and Lua, A. C. (1998). Characterization of chars pyrolyzed from oil palmstones for the preparation of activated carbons. Journal of Analytical and Ap-plied Pyrolysis, 46, 113–125.
Guo, J., and Lua, A. C. (1999). Textural and chemical characterizations of activatedcarbon prepared from oil-palm stone with H2SO4 and KOH impregnation. Mi-croporous and Mesoporous Materials, 32, 111–117.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
Oil Palm Biomass 1153
Guo, J., and Lua, A. C. (2000). Effect of surface chemistry on gas-phase adsorp-tion by activated carbon prepared from oil-palm stone with pre-impregnation.Separation and Purification Technology, 18, 47–55.
Guo, J., and Lua, A. C. (2000c). Textural characterization of activated carbons pre-pared from oil-palm stones pre-treated with various impregnating agents. Jour-nal of Porous Materials, 7, 491–497.
Guo, J., and Lua, A. C. (2000a). Effect of heating temperature on the properties ofchars and activated carbons prepared from oil palm stones. Journal of ThermalAnalysis and Calorimetry, 60, 417–425.
Guo, J., and Lua, A. C. (2000b). Adsorption of sulfur dioxide onto activated carbonsprepared from oil-palm shells impregnated with potassium hydroxide. Journalof Chemical Technology and Biotechnology, 75, 971–976.
Guo, J., and Lua, A. C. (2001). Experimental and kinetic studies on pore developmentduring CO2 activation of oil-palm-shell char. Journal of Porous Materials, 8,149–157.
Guo, J., and Lua, A. C. (2002a). Characterization of adsorbent prepared from oil-palmshell by CO2 activation for removal of gaseous pollutants. Material Letters, 55,334–339.
Guo, J., and Lua, A. C. (2003a). Textural and chemical properties of adsorbentprepared from palm shell by phosphoric acid activation. Materials Chemistryand Physics, 80, 114–119.
Guo, J., and Lua, A. C. (2003b). Surface functional groups on oil-palm-shell adsor-bents prepared by H2SO4 and KOH activation and their effects on adsorptivecapacity. Trans IChemE, 81, 585–590.
Guo, J., and Lua, A. C. (2003c). Adsorption of sulphur dioxide onto activated carbonprepared from oil-palm shells with and without pre-impregnation. Separationand Purification Technology, 30, 265–273.
Guo, J., and Lua, A. C. (2002b). Microporous activated carbons prepared from palmshell by thermal activation and their application to sulfur dioxide adsorption.Journal of Colloid and Interface Science, 251, 242–247.
Guo, J., Luo, Y., Lua, A. C., Chi, R., Chen, Y.-L., Bao, X.-T., and Xiang, S.-X. (2007).Adsorption of hydrogen sulphide (H2S) by activated carbons derived from oil-palm shell. Carbon, 45, 330–336.
Guo, J., Xu, W. S., Chen, Y. L., and Lua, A. C. (2005). Adsorption of NH3 ontoactivated carbon prepared from palm shells impregnated with H2SO4. Journalof Colloid Interface Science, 281, 285–290.
Gupta, V. K., Carrott, P. J. M., Ribeiro Carrott, M. M. L., and Suhas. (2009). Low-cost adsorbents: Growing approach to wastewater treatment: A review. CriticalReviews in Environmental Science and Technology, 39, 783–842.
Gurses, A., Dogar, C., Karaca, S., Acikyildiz, M., and Bayrak, R. (2006). Produc-tion of granular activated carbon from waste Rosa canina sp. seeds and itsadsorption characteristics for dye. Journal of Hazardous Materials, B131, 254–259.
Hamad, B. K., Noor, A. M., Afida, A. R., and Asri, M. N. M. (2010). High removal of 4-chloroguaiacol by high surface area of oil palm shell-activated carbon activatedwith NaOH from aqueous solution. Desalination, 257, 1–7.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
1154 M. Rafatullah et al.
Hameed, B. H., Ahmad, A. L., and Latiff, K. N. A. (2007a). Adsorption of basic dye(methylene blue) onto activated carbon prepared from rattan sawdust. Dyesand Pigments, 75, 143–149.
Hameed, B. H., and Daud, F. B. M. (2008). Adsorption studies of basic dye onactivated carbon derived from agricultural waste: Hevea brasiliensis seed coat.Chemical Engineering Journal, 139, 48–55.
Hameed, B. H., Din, A. T. M., and Ahmad, A. L. (2007b). Adsorption of methyleneblue onto bamboo-based activated carbon: kinetics and equilibrium studies.Journal of Hazardous Materials, 141, 819–825.
Hameed, B. H., Tan, I. A.W., and Ahmad, A. L. (2008). Optimization of basic dye re-moval by oil palm fibre-based activated carbon using response surface method-ology. Journal of Hazardous Materials, 158, 324–332.
Hameed, B. H., Tan, I. A. W., and Ahmad, A. L. (2009). Preparation of oil palm emptyfruit bunch-based activated carbon for removal of 2, 4, 6-trichlorophenol: Opti-mization using response surface methodology. Journal of Hazardous Materials,164, 1316–1324.
Hashem, A., Akasha, R. A., Ghith, A., and Hussein, D. A. (2007). Adsorbent basedon agricultural wastes for heavy metal and dye removal: A review. EnergyEducation Science and Technology, 19, 69–86.
Hashim, R., Nadhari, W. N. A. W., Sulaiman, O., Kawamura, F., Hiziroglu, S., Sato,M., Sugimoto, T., Seng, T. G., and Tanaka, R. (2011). Characterization of rawmaterials and manufactured binderless particleboard from oil palm biomass.Materials and Design, 32, 246–254.
Hayashi, J., Horikawa, T., Takeda, I., Muroyama, K., and Ani, F. N. (2002). Preparingactivated carbon from various nutshells by chemical activation with K2CO3.Carbon, 40, 2381–2386.
Hayashi, J., Kazehaya, A., Muroyama, K., and Watkinson, A. (2000). Preparation ofactivated carbon from lignin by chemical activation. Carbon, 38, 1873–1878.
Haykiri-Acma, H., Yaman, S., and Kucukbayrak, S. (2005). Gasification of biomasschars in steam-nitrogen mixture. Energy Conversion and Management, 47,1004–1013.
Hu, Z., Guo, H., Srinivasan, M. P., and Yaming, N. (2003). A simple method for de-veloping mesoporosity in activated carbon. Separation and Purification Tech-nology, 31, 47–52.
Hu, Z., and Srinivasan, M. P. (2001). Mesoporous high surface area activated carbon.Microporous and Mesoporous Materials, 43, 267–275.
Hu, Z., Srinivasan, M. P., and Ni, Y. (2001). Novel activation process for preparinghighly microporous and mesoporous activated carbons. Carbon, 39, 877–886.
Hussein, M. Z. B., Rahman, M. B. B. A., Yahaya, A., Hin, T.-Y. Y., and Ahmad,N. (2001). Oil palm trunk as a raw material for activated carbon production.Journal of Porous Material, 8, 327–334.
Ibrahim, M. N. M., Ngah, W. S. W., Norliyana, M. S., Daud, W. R. W., Rafatullah,M., Sulaiman, O., and Hashim, R. (2010). A novel agricultural waste adsorbentfor the removal of lead (II) ions from aqueous solutions. Journal of HazardousMaterials, 182, 377–385.
International Union of Pure and Applied Chemistry. (1982). Manual of symbols andterminology of colloid surface. London: Butterworths.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
Oil Palm Biomass 1155
Ioannidou, O., and Zabaniotou, A. (2007). Agricultural residues as precursors for ac-tivated carbon production-a review. Renewable and Sustainable Energy Reviews,11, 1966–2005.
Ismadji, S., and Bhatia, S. K. (2001). A modified pore-filling isotherm for liquid-phaseadsorption in activated carbon. Langmuir, 17, 1488–1498.
Issabayeva, G., Aroua, M. K., and Sulaiman, N. M. N. (2006). Removal of lead fromaqueous solutions on palm shell activated carbon. Bioresource Technology, 97,2350–2355.
Issabayeva, G., Aroua, M. K., and Sulaiman, N. M. (2008). Continuous adsorptionof lead ions in a column packed with palm shell activated carbon. Journal ofHazardous Materials, 155, 109–113.
Jensen, P. A., Sander, B., and Dam-Johansen, K. (2001). Pretreatment of straw forpower production by pyrolysis and char wash. Biomass and Bioenergy, 20,431–446.
Jia, Q., and Lua, A. C. (2008a). Effects of pyrolysis conditions on the physical char-acteristics of oil-palm-shell activated carbons used in aqueous phase phenoladsorption. Journal of Analytical and Applied Pyrolysis, 83, 175–179.
Jia, Q., and Lua, A. C. (2008b). Concentration-dependent branched pore kineticmodel for aqueous phase adsorption. Chemical Engineering Journal, 136,227–235.
Jia, Y. F., Xiao, B., and Thomas, K. M. (2002). Adsorption of metal ions on nitrogensurface functional groups in activated carbons. Langmuir, 18, 470–478.
Joseph, C. G., Bono, Krishnaiah, A., D., Ling, C. Y., and Ban, N. C. (2009). Mor-phology and sorption kinetic studies of L-type activated carbons prepared fromoil palm shells by ZnCl2 and H3PO4 activation. Journal of Applied Science, 9,3131–3135.
Kassim, A., Joseph, C. G., Zainal, Z., Hussein, Mohd. Z., Haron, M. J., and Abdullah,A. H. (2004). Activated carbons prepared from oil palm shells: Application forcolumn separation of heavy metals. Journal of Indian Chemical Society, 81,946–949.
Kavitha, D., and Namasivayam, C. (2007). Experimental and kinetic studies on methy-lene blue adsorption by coir pith carbon. Bioresource Technology, 98, 14–21.
Khezami, L., Ould-Dris, A., and Capart, R. (2007). Activated carbon from thermo-compressed wood and other lignocellulosic precursors. BioResources, 2,193–209.
Klose, W., and Rincon, S. (2007). Adsorption and reaction of NO on activated carbonin the presence of oxygen and water vapour. Fuel, 86, 203–209.
Lanzetta, M., and Di Blasi, C. (1998). Pyrolysis kinetics of wheat and corn straw.Journal of Analytical and Applied Pyrolysis, 44, 181–192.
Lata, H., Garg, V. K., and Gupta, R. K. (2008). Adsorptive removal of basic dye bychemically activated Parthenium biomass: Equilibrium and kinetic modeling.Desalination, 219, 250–261.
Lee, S. B., and Fasina, O. (2009). TG-FTIR analysis of switch grass pyrolysis. Journalof Analytical and Applied Pyrolysis, 86, 39–43.
Legrouri, K., Khouyab, E., Ezzinea, M., Hannachea, H., Denoyelc, R., Pallierd, R.,and Naslaind, R. (2005). Production of activated carbon from a new precursor
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
1156 M. Rafatullah et al.
molasses by activation with sulphuric acid. Journal of Hazardous Materials,B118, 259–263.
Leon y Leon, C. A., Solar, J. M., Calemma, V., and Radovic, L. R. (1992). Evidencefor the protonation of basal plane sites on carbon. Carbon, 30, 797–811.
Li, W., Zhang, L. B., Peng, J. H., Li, N., and Zhu, X. Y. (2008). Preparation of highsurface area activated carbons from tobacco stems with K2CO3 activation usingmicrowave radiation. Industrial Crops and Products, 27, 341–347.
Lim, W. C., Srinivasakannan, C., and Balasubramanian, N. (2010). Activation of palmshells by phosphoric acid impregnation for high yielding activated carbon.Journal of Analytical and Applied Pyrolysis, 88, 181–186.
Lim, Y. N., Shaaban, M. G., and Yin, C. Y. (2008). Removal of endosulfan from waterusing oil palm shell activated carbon and rice husk ash. Journal of Oil PalmResearch, 20, 527–532.
Ling, Y. Y., Deraman, M., Jumali, M. H., Omar, R., Aziz, A. A., Abdelrahman, A. El.,Peng, T. H., Meihua, J. T., Muslimin, M., and Mohtar, M. (2005). Preparationand phenols adsorption property of porous carbon from oil palm empty fruitbunches. Solid State Science and Technology, 13, 170–178.
Lora, J. H., and Glasser, W. G. (2002). Recent industrial applications of lignin: Asustainable alternative to nonrenewable materials. Journal of Polymers Environ-ment, 10, 39–48.
Lua, A. C., and Guo, J. (1998b). Activated carbons prepared from extracted-oil palmfibers for nitric oxide reduction. Energy and Fuels, 12, 1089–1094.
Lua, A. C., and Guo, J. (2000). Activated carbon prepared from oil palm stoneby one-step CO2 activation for gaseous pollutant removal. Carbon, 38, 1089–1097.
Lua, A. C., and Guo, J. (2001a). Adsorption of sulfur dioxide on activated carbonfrom oil-palm waste. Journal of Environmental Engineering, 127, 895–901.
Lua, A. C., and Guo, J. (2001b). Microporous oil-palm-shell activated carbon preparedby physical activation for gas-phase adsorption. Langmuir, 17, 7112–7117.
Lua, A. C., and Guo, J. (2001c). Preparation and characterization of activated car-bons from Oil palm stones for gas-phase adsorption. Colloids and Surfaces A:Physicochemical and Engineering Aspects, 179, 151–162.
Lua, A. C., and Guo, J. (1998a). Preparation and characterization of chars from oilpalm waste. Carbon, 36, 1663–1670.
Lua, A. C., and Guo, J. (1999). Chars pyrolyzed from oil palm wastes for activatedcarbon preparation. Journal of Environmental Engineering, 125, 72–76.
Lua, A. C., and Jia, Q. (2007). Adsorption of phenol by oil-palm-shell activatedcarbons. Adsorption, 13, 129–137.
Lua, A. C., and Jia, Q. (2009). Adsorption of phenol by oil-palm shell activatedcarbons in a fixed bed. Chemical Engineering Journal, 150, 455–461.
Lua, A. C., Lau, F. Y., and Guo, J. (2006). Influence of pyrolysis conditions onpore development of oil-palm-shell activated carbons. Journal of Analyticaland Applied Pyrolysis, 76, 96–102.
Lua, A. C., Yang, T., and Guo, J. (2004). Effects of pyrolysis conditions on theproperties of activated carbons prepared from pistachio-nut shells. Journal ofAnalytical and Applied Pyrolysis, 72, 279–287.
Malaysia Palm Oil Council. (2007). Retrieved from http://americanpalmoil.com/publications/TreeOfLife.pdf (pp. 3–9).
Malik, P. K. (2003). Use of activated carbons prepared from sawdust and rice-huskfor adsorption of acid dyes: A case study of Acid Yellow 36. Dyes and Pigments,56, 239–249.
Mangun, C. L., Benak, K. R., Daley, M. A., and Economy, J. (1999). Oxidation ofactivated carbon fibers: Effect on pore size, surface, chemistry, and adsoprtionproperties. Chemistry of Materials, 11, 3476–3483.
Marcilla, A., Garcıa-Garcıa, S., Asensio, M., and Conesa, J. A. (2000). Influence ofthermal treatment regime on the density and reactivity of activated carbons fromalmond shells. Carbon, 38, 429–440.
Marsh, H., and Rodriguez-Reinoso, F. (2006). Activated carbon. London: Elsevier.Meidl, J. A. (1997). Responding to changing conditions: How powdered activated
carbon systems can provide the operational flexibility necessary to treat con-taminated groundwater and industrial wastes. Carbon, 35, 1207–1216.
Minkova, V., Marinov, S. P., Zanzi, R., Bjornbom, E., Budinova, T., and Stefanova,M. (2000). Thermochemical treatment of biomass in a flow of steam or in amixture of steam and carbon dioxide. Fuel Processing Technology, 62, 45–52.
Minkova, V., Razvigorova, M., Bjornbom, E., Zanzi, R., Budinova, T., and Petrov, N.(2001). Effect of water vapour and biomass nature on the yield and quality ofthe pyrolysis products from biomass. Fuel Processing Technology, 70, 53–61.
Mohamed, A. R., Mohammadi, M., and Darzi, G. N. (2010). Preparation of carbonmolecular sieve from lignocellulosic biomass: A review. Renewable and Sus-tainable Energy Reviews, 14, 1591–1599.
Mohammadi, M., Hassani, A. J., Mohamed, A. R., and Najafpour, G. D. (2010). Re-moval of rhodamine B from aqueous solution using palm shell-based activatedcarbon: Adsorption and kinetic studies. Journal of Chemical and EngineeringData, 55, 5777–5785.
Mohan, D., Pittman, C. U. Jr., and Steele, P. H. (2006). Pyrolysis of wood/biomassfor bio-oil: A critical review. Energy Fuels, 20, 848–889.
Molina-Sabio, M., Gonzalez, M., Rodriguez-Reinoso, F., and Sepulveda-Escribano, A.(1996a). Effect of steam and carbon dioxide activation in the micropore sizedistribution of activated carbon. Carbon, 34, 505–509.
Molina-Sabio, M., Rodriguez-Reinoso, F., Caturla, F., and Selles, M. (1996b). Devel-opment of porosity in combined phosphoric acid–carbon dioxide activation.Carbon, 34, 457–462.
Montes-Moran, M. A., Suarez, D., Menendez, J. A., and Fuente, E. (2004). On thenature of basic sites on carbon surfaces: An overview. Carbon, 42, 1219–1225.
Moreno-Castilla, C., and Rivera-Utrilla, J. (2001). Carbon materials as adsorbents forthe removal of pollutants from the aqueous phase. Materials Research SocietyBulletin, 26, 890–894.
Nath, K., and Das, D. (2003). Hydrogen from biomass. Current Science, 85, 265–275.Niya, A. A., Daud, W. M. A. W., and Mjalli, F. S. (2010a). Using granular activated
carbon prepared from oil palm shell by ZnCl2 and physical activation for ethaneadsorption. Journal of Analytical and Applied Pyrolysis, 89, 197–203.
Niya, A. A., Daud, W. M. A. W., and Mjalli, F. S. (2010b). Production of palm shell-based activated carbon with more homogeneous pore size distribution. Journalof Applied Science, 10, 3361–3366.
Niya, A. A., Daud, W. M. A. W., and Mjalli, F. S. (2011). Comparative study of thetextural characteristics of oil palm shell activated carbon produced by chemical
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
1158 M. Rafatullah et al.
and physical activation for methane adsorption. Chemical Engineering Researchand Design, 89, 657–664.
Noll, K. E., Gounaris, V., and Hou, W. S. (1992). Adsorption technology for air andwater pollution control. Chelsea, MI: Lewis.
Nomanbhay, S. M., and Palanisamy, K. (2005). Removal of heavy metal from in-dustrial wastewater using chitosan coated oil palm shell charcoal. ElectronicJournal of Biotechnology, 8, 43–53.
Nourouzi, M. M., Chuah, T. G., and Choong, T. S. Y. (2009a). Equilibrium andkinetic study on reactive dyes adsorption by palm kernel shell-based activatedcarbon: In single and binary systems. Journal of Environmental Engineering,135, 1393–1398.
Nourouzi, M. M., Chuah, T. G., and Choong, T. S. Y. (2009b). Adsorption of reactivedyes by palm kernel shell activated carbon: application of film surface and filmpore diffusion models. E-Journal of Chemistry, 6, 949–954.
Oh, G. H., and Park, C. R. (2002). Preparation and characteristics of rice-straw-basedporous carbons with high adsorption capacity. Fuel, 81, 327–336.
Panumati, S., Chudecha, K., Vankhaew, P., Choolert, V., Chuenchom, L., Innajitara,W., and Sirichote, O. (2008). Adsorption of phenol from diluted aqueous solu-tions by activated carbons obtained from bagasse, oil palm shell and pericarpof rubber fruit. Songklanakarin Journal of Science and Technology, 30, 185–189.
Parab, H., Sudersanan, M., Shenoy, N., Pathare, T., and Vaze, B. (2009). Use ofagro-industrial wastes for removal of basic dyes from aqueous solutions. Clean:Soil, Air, Water, 37, 963–969.
Park, D., Yun, Y. S., and Park, J. M. (2010). The past, present, and future trends ofbiosorption. Biotechnology and Bioprocess Engineering, 15, 86–102.
Pereira, M. F. R., Soares, S. F., Orfao, J. J. M., and Figueiredo, J. L. (2003). Adsorptionof dyes on activated carbons: influence of surface chemical groups. Carbon, 41,811–821.
Perez-Cadenas, A. F., Maldonado-Hodar, F. J., and Moreno-Castilla, C. (2003). Onthe nature of surface acid sites of chlorinated activated carbons. Carbon, 41,473–478.
Predel, M., and Kaminsky, W. (1998). Pyrolysis of rape-seed in a fluidized-bedreactor. Bioresource Technology, 66, 113–117.
Puri, B. R. (1970). Surface complexes on carbons. In Walker P. L. Jr. (Ed.), Chemistryand physics of carbon (pp. 191–282). New York: Marcel Dekker, New York.
Puri, B. R. (1983). Physicochemical aspects of carbon affecting adsorption from theaqueous phase. In McGuire, M. J., and Suffet, I. H. (Eds.), Advances in chemistryseries (pp. 77–93). Washington, DC: American Chemical Society.
Putun, A. E., Ozbay, N., Onal, E. P., and Putun, E. (2005). Fixed-bed pyrolysisof cotton stalk for liquid and solid products. Fuel Processing Technology, 86,1207–1219.
Rafatullah, M., Sulaiman, O., Hashim, R., and Ahmad, A. (2009). Adsorption of copper(II), chromium (III), nickel (II) and lead (II) ions from aqueous solutions bymeranti sawdust. Journal of Hazardous Materials, 170, 969–977.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
Oil Palm Biomass 1159
Rafatullah, M., Sulaiman, O., Hashim, R., and Ahmad, A. (2010a). Adsorption ofmethylene blue on low-cost adsorbents: A review. Journal of Hazardous Mate-rials, 170, 70–80.
Rafatullah, M., Sulaiman, O., Hashim, R., and Ahmad, A. (2010b). Adsorption of cop-per (II) onto different adsorbents. Journal of Dispersion Science and Technology,31, 918–930.
Reed, A. R., and Williams, P. T. (2004). Thermal processing of biomass natural fiberwastes by pyrolysis. International Journal of Energy Research, 28, 131–45.
Ruthven, D. M. (1984). Principles of Adsorption and Adsorption Processes (1st ed.).New York: Wiley.
Salman, J. M., and Hameed, B. H. (2010). Effect of preparation conditions of oil palmfronds activated carbon on adsorption of bentazon from aqueous solutions.Journal of Hazardous Materials, 175, 133–137.
Savova, D., Apak, E., Ekinci, E., Yardim, F., Petrova, N., Budinova, T., Razvigorova,M., and Minkova, V. (2001). Biomass conversion to carbon adsorbents and gas.Biomass and Bioenergy, 21, 133–142.
Schroder, E., Thomauske, K., Weber, C., Hornung, A., and Tumiatti, V. (2007).Experiments on the generation of activated carbon from biomass. Journal ofAnalytical and Applied Pyrolysis, 79, 106–111.
Senthilkumaar, S., Varadarajan, P. R., Porkodi, K., and Subbhuraam, C. V. (2005).Adsorption of methylene blue onto jute fiber carbon: Kinetics and equilibriumstudies. Journal of Colloid and Interface Science, 284, 78–82.
Shaarani, F. W., and Hameed, B. H. (2010). Batch adsorption of 2,4-dichlorophenolonto activated carbon derived from agricultural waste. Desalination, 255,159–164.
Singh, K. P., Malik, A., Sinha, S., and Ojha, P. (2008). Liquid-phase adsorptionof phenols using activated carbons derived from agricultural waste material.Journal of Hazardous Materials, 150, 626–641.
Sjostrom, E. (1993). Wood chemistry: Fundamentals and applications (2nd ed.). SanDiego: Academic Press.
Sugawara, K., Wajima, T., Kato, T., and Sugawara, T. (2007). Preparation of carbona-ceous heavy metal adsorbent from palm shell using sulfur impregnation. ArsSeparatoria Acta, 5, 88–98.
Sulaiman, O., Amini, M. H. M., Rafatullah, M., Hashim, R., and Ahmad, A. (2010).Adsorption equilibrium and thermodynamic studies of copper (II) ions fromaqueous solutions by oil palm leaves. International Journal of Chemical Reactorand Engineering, 8, A108
Sumathi, S., Bhatia, S., Lee, K. T., and Mohamed, A. R. (2009). Optimization of mi-croporous palm shell activated carbon production for flue gas desulphurization:Experimental and statistical studies. Bioresource Technology, 100, 1614–1621.
Sumathi, S., Bhatia, S., Lee, K. T., and Mohamed, A. R. (2010). Selection of bestimpregnated palm shell activated carbon (PSAC) for simultaneous removal ofSO2 and NOx. Journal of Hazardous Materials, 176, 1093–1096.
Sumathi, S., Chai, S. P., and Mohamed, A. R. (2008). Utilization of oil palm as asource of renewable energy in Malaysia. Renewable and Sustainable EnergyReviews, 12, 2404–2421.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
1160 M. Rafatullah et al.
Szymanski, G. S., Karpinski, Z., Biniak, S., and Swiatkowski, A. (2002). The effectof the gradual thermal decomposition of surface oxygen species on the chem-ical and catalytic properties of oxidized activated carbon. Carbon, 40, 2627–2639.
Tan, I. A. W., Ahmad, A. L., and Hameed, B. H. (2008a). Adsorption of basic dyeusing activated carbon prepared from oil palm shell: batch and fixed bed studies.Desalination, 225, 13–28.
Tan, I. A. W., Ahmad, A. L., and Hameed, B. H. (2008b). Enhancement of basicdye adsorption uptake from aqueous solutions using chemically modified oilpalm shell activated carbon. Colloids and Surfaces A: Physicochemical andEngineering Aspects, 318, 88–96.
Tan, I. A.W., Ahmad, A. L., and Hameed, B. H. (2008c). Adsorption of basic dyeon high-surface area activated carbon prepared from coconut husk: Equilib-rium, kinetic and thermodynamic studies. Journal of Hazardous Materials, 154,337–346.
Tan, I. A. W., Ahmad, A. L., and Hameed, B. H. (2009a). Fixed-bed adsorptionperformance of oil palm shell-based activated carbon for removal of 2,4,6-trichlorophenol. Bioresource Technology, 100, 1494–1496.
Tan, I. A. W., Ahmad, A. L., and Hameed, B. H. (2009b). Adsorption isotherms,kinetics, thermodynamics and desorption studies of 2,4,6-trichlorophenol on oilpalm empty fruit bunch-based activated carbon. Journal of Hazardous Materials,164, 473–482.
Tan, I. A. W., and Hameed, B. H. (2010). Adsorption isotherms, kinetics, thermody-namics and desorption studies of basic dye on activated carbon derived fromoil palm empty fruit bunch. Journal of Applied Science, 10, 2565–2571.
Tan, I. A. W., and Hameed, B. H., and Ahmad, A. L. (2007). Equilibrium and kineticstudies on basic dye adsorption by oil palm fibre activated carbon. ChemicalEngineering Journal, 127, 111–119.
Theander, O. (1985). Fundamentals of thermochemical biomass conversion. InOverand, R. P., Mile, T. A., and Mudge, L. K. (Eds.), Fundamentals of thermo-chemical biomass conversion (pp. 45–85). New York, Elsevier Applied Science.
Tsai, W. T., Chang, C. Y., and Lee, S. L. (1997). Preparation and characterization ofactivated carbons from corn cob. Carbon, 35, 1198–1200.
Tsai, W. T., Chang, C. Y., and Lee, S. L. (1998). A low cost adsorbent from agriculturalwaste corn cob by zinc chloride activation. Bioresource Technology, 64, 211–217.
Tsai, W. T., Chang, C. Y., Wang, S. Y., Chang, C. F., Chien, S. F., and Sun, H. F.(2001). Cleaner production of carbon adsorbents by utilizing agricultural wastecorn cob. Resources, Conservation and Recycling, 32, 43–53.
Unal, H., and Alibas, K. (2007). Agricultural residues as biomass energy. EnergySource Part B, 2, 123–140.
Vijayaraghavan, K., and Yun, Y. S. (2008). Bacterial biosorbents and biosorption.Biotechnology Advances, 26, 266–291.
Wahi, R., Ngaini, Z., and Jok, V. U. (2009). Removal of mercury, lead and copperfrom aqueous solution by activated carbon of palm oil empty fruit bunch. WorldApplied Sciences Journal, 5, 84–91.
Wang, S., Jiang, X. M., Wang, N., Yu, L. J., Li, Z., and He, P. M. (2007). Research onPyrolysis Characteristics of Seaweed. Energy Fuels, 21, 3723–3729.
Dow
nloa
ded
by [
Uni
vers
iti S
ains
Mal
aysi
a] a
t 17:
16 3
0 Se
ptem
ber
2013
Oil Palm Biomass 1161
Wu, F. C., and Tseng, R. L. (2008). High adsorption capacity NaOH-activated carbonfor dye removal from aqueous solution. Journal of Hazardous Materials, 152,1256–1267.
Yalcın, N., and Sevinc, V. (2000). Studies of the surface area and porosity of activatedcarbons prepared from rice husks. Carbon, 38, 1943–1945.
Yang, H., Yan, R., Chin, T., Liang, D. T., Chen, H., and Zheng, C. (2004). Ther-mogravimetric analysis-Fourier transform infrared analysis of palm oil wastepyrolysis. Energy Fuels, 18, 1814–1821.
Yang, T., and Lua, A. C. (2003). Characteristics of activated carbons prepared frompistachio-nut shells by physical activation. Journal of Colloid Interface Science,267, 408–417.
Yin, C. Y., Aroua, M. K., and Daud, W. M. A. W. (2008a). Polyethyleneimine im-pregnation on activated carbon: Effects of impregnation amount and molecularnumber on textural characteristics and metal adsorption capacities. Materials ofChemistry and Physics, 112, 417–422.
Yin, C. Y., Aroua, M. K., and Daud, W. M. A. W. (2008b). Enhanced adsorption ofmetal ions onto polyethyleneimine-impregnated palm shell activated carbon:Equilibrium studies. Water, Air, and Soil Pollution, 192, 337–348.
Yong, T. L. K., Lee, K. T., Mohamed, A. R., and Bhatia, S. (2007). Potential ofhydrogen from oil palm biomass as a source of renewable energy worldwide.Energy Policy, 35, 5692–5701.
Young, R. A. (1986). Structure, swelling and bonding of cellulose fibers. In Young, R.A., and Rowell, R. M. (Eds.), Cellulose: Structure, modification, and hydrolysis(pp. 131–148). New York: Wiley.
Zawani, Z., Luqman, C. A., and Choong, T. S. Y. (2009). Equilibrium, kinetics andthermodynamic studies: Adsorption of remazol black 5 on the palm kernel shellactivated carbon (PKS-AC). European Journal of Scientific Research, 37, 67–76.
Zhang, T., Walawender, W. P., Fan, L. T., Fan, M., Daugaard, D., and Brown, R.C. (2004). Preparation of activated carbon from forest and agricultural residuesthrough CO2 activation. Chemical Engineering Journal, 105, 53–59.
Zhou, H. F., and Haynes, R. J. (2010). Sorption of heavy metals by inorganic andorganic components of solid wastes: Significance to use of wastes as low-costadsorbents and immobilizing agents. Critical Reviews in Environmental Scienceand Technology, 40, 909–977.
