Activated-carbon

Activatedcarbonfromcharobtainedfromvacuumpyrolysisofteaksawdust:porestructuredevelopmentandcharacterizationS.Ismadji*,Y.Sudaryanto,S.B.Hartono,L.E.K.Setiawan,A.AyucitraDepartmentofChemicalEngineering,WidyaMandalaCatholicUniversity,Kalijudan37,Surabaya60114,IndonesiaReceived15June2004;receivedinrevisedform13November2004;accepted14November2004Availableonline1January2005AbstractThepreparationofactivatedcarbonfromvacuumpyrolysischarofteaksawdustwasstudiedandtheresultsarepresentedinthispaper.Theeffectsofprocessvariablessuchastemperatureandactivationtimeontheporestructureofactivatedcarbonswerestud-ied.Theactivatedcarbonpreparedfromcharobtainedbyvacuumpyrolysishashighersurfaceareaandporevolumethanthatfromatmosphericpyrolysischar.TheBETsurfaceareaandporevolumeofactivatedcarbonpreparedfromvacuumpyrolysischarwere1150m2/gand0.43cm3/g,respectively.
2004ElsevierLtd.Allrightsreserved.Keywords:Activatedcarbon;Char;Vacuumpyrolysis;Porestructure1.IntroductionActivatedcarbonisoneofthemostimportantmicro-porousadsorbentsfromanindustrialviewofpoint.Ithasaverycomplexstructure,withporesizesrangingfrommicropores(20A˚slitwidth)tomacropores(500A˚slitwidth),andhasavarietyofsurfacegroups,impurities,andirregularities.Activatedcarboncanbeproducedfromanumberofprecursormaterialssuchascoal,peat,coconutshellandanyotherinexpensivematerialswithhighcarboncontent(Laineetal.,1989;AhmadpourandDo,1996;DiPanfiloandEgiebor,1996;Usmanietal.,1996;Tolesetal.,1996;Tsayetal.,1998;Kailappanetal.,2000;Lafi,2001;Tsaietal.,2001;Diaoetal.,2002).Themanufactureofacti-vatedcarbongenerallycarriedoutintwomainsteps:thecarbonizationofrawmaterialsinaninertatmosphereandtheactivationoftheresultingcharinthepresenceofsuitableoxidizingagents.Inchemicalactivationpro-cess,thesetwostepsareconductedsimultaneouslyusingchemicalactivatingagentsasdehydratingagentsandoxidants(Bansaletal.,1988).Theadsorptioncapacityofactivatedcarbondependsnotonlyonitssurfacearea,butalsoonitsinternalporestructure,surfacecharacteristicandthepresenceoffunctionalgrouponporesurface.Sincethesurfacechar-acteristicandinternalporestructureoftheactivatedcarbonplayanimportantroleinadsorptionprocessesanddependbothontheprecursorusedandthemethodofpreparation,therefore,characterizationofthesearecrucialtotheadsorptionandseparationprocesses.Sev-eralmethodsofanalysishavebeendevelopedandap-pliedforcharacterizingtheporestructureofactivatedcarbon,amongwhichgasadsorptionmeasurementsarethemostcommonlyused(Diazetal.,1999;DaviesandSeaton,1999;NguyenandDo,2000).Althoughtherearemanystudiesintheliteraturerelatingtothepreparationandcharacterizationofacti-vatedcarbonfromagriculturalwastesasmentionedbefore,however,thereisnoinformationfortheprepa-rationoftheactivatedcarbonusingteaksawdustastheprecursor.Inthepresentstudy,teaksawdust0960-8524/$-seefrontmatter
2004ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2004.11.007*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](S.Ismadji).BioresourceTechnology96(2005)1364–1369obtainedfromlocaltimberindustrieshasbeenchosenastheprecursorofactivatedcarbon.Themainobjectivesofthisworkaretostudytheinfluenceofpyrolysismeth-odsandtheactivationoftheresultingcharonthedevel-opmentofporestructureoftheactivatedcarbon.2.Experimental2.1.MaterialsTheproximateandultimateanalysisoftheteaksaw-dustusedinthisstudy,aregiveninTable1.ThecontentsofC,H,N,OandSelementsintheultimateanalysisweredeterminedbyanelementalanalyzer(Heraeus,CHN-O-RAPID).TheanalyticalresultsshowninTable1revealthatteaksawdusthashighcarbonandlowashcontentindicatingthatthisprecursorissuitablefortheprepara-tionofactivatedcarbon.Priortotheuse,theteaksawdustwasrepeatedlywashedwithdistilledwaterinordertore-movedustandotherinorganicimpurities,thenoven-driedfor24hat120Ctoreducethemoisturecontent.2.2.CarbonizationandactivationTeaksawdustusedinthisstudywasobtainedfromlocaltimberindustries.Approximately150gofthismaterialwasplacedinthepyrolysisreactorwithvac-uumcondition(totalpressurearound20kPa)thenheatedtoatemperatureof600Cwiththeheatingrateof20C/minandheldatthistemperaturefor1h.Thentheresultingcharwasallowedtocoolunderthesamevacuumcondition.Thesteamactivationoftheresultingcharwascarriedoutatthetemperaturerangingfrom750to900Cinaverticaltubereactor.Around30gofcharwasplacedinareactor,andthenthisreactorwaspurgedwith150ml/minofnitrogenforatleast1h.Underthesamenitrogenflow,thischarwasheatedtoadesiredactivationtem-perature.Whenthetemperaturewasreached,thenitro-genflowwasswitchedtosteam(100%H2O,0.02g/min)andheldfor2–10h.Afterthisprocesscompleted,theactivatedcarbonwasallowedtocoolinanitrogenflowwiththesameflowratedescribedabove.Here,theactivatedcarbonwasalsopreparedfromcharobtainedfrompyrolysisattheatmosphericcondi-tion.Theatmosphericcarbonizationofthesameprecur-sorwasperformedat600Cwithaheatingrateof20C/minunderanitrogenflowof150ml/min.Thesteamactivationwascarriedoutatthesameconditionasdescribedabove.2.3.CharacterizationoftheporestructureTheporestructurecharacteristicsoftheresultingcharandactivatedcarbonsweredete