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SynthesisofNa-AandfaujasiticzeolitesfromhighsiliconflyashF.Fotovata,H.Kazemianb,c,M.Kazemeinia,*aDepartmentofChemicalandPetroleumEngineering,SharifUniversityofTechnology,AzadiAvenue,P.O.Box11365-9465,Tehran,IranbR&DLab.OfSPAGCo.,Technologyincubator,Sci.&Technol.ParkofTehranUniversity,Tehran,IrancNSTRI,P.O.Box11365-3486,Tehran,Iran1.IntroductionFlyashisaninorganicresidueobtainedfromthefluegasesofpowerplantsfurnaces.Generally,twomainsourcesareintroducedforflyashincluding:apulverizedcoalpowerplantandmunicipalwasteincinerationplant.Manyinvestigationsdoneoncoalflyashtoexploititasacheapandeffectivematerial.Thecoalflyashiswidelyutilizedincementmanufacturing.Aboutonebarrelofoilsavedif1tonofflyashreplaces1tonofcement[1].Oneofthepromisingapplicationsofcoalflyashisitsapplicationasaprecursorinzeolitesynthesizing.Zeolitesareporousaluminosilicatecompoundshavingnumerousproperties,suchas,molecularsieving,highthermalstability,ionexchangecapability,andshapeselectivecatalyticbehaviorbecauseoftheirspecialstructure.Zeolitescategorizedintonaturalandsynthesizedgroups.Usually,synthesizedzeolitesarepreferredovernaturalonesduetothepossibilityofadjustingtheirporesizethroughdifferentsynthesizingtechniques.About24typesofdifferentzeolitessynthesizedfromcoalflyashamongstwhichzeolitesA[2,3],X[4]andY[5]aremorevaluablebecauseoftheirextensivecatalyticapplicationsindetergent,petroleumrefiningandpetrochemicalindustries.FirsttimeShigemotoetal.[6]performedsynthesisofthesematerialsbyaddinganalkalinefusionstagebeforeconventionalflyashzeolitization.Themajorcrystalinephasesfoundintheflyasharequartz,mulliteandaluminosilicateglass.Ontheotherhand,alargeamountofsodiumsilicateexistsinthefusedflyash,whichimpliesthatfusioniseffectiveinextractionofsiliconfromquartz[7].ThehighionexchangepotentialofzeolitesAandXresultedfromtheirlowSi/Alratioindicatesthattheymightbesignificantagentsinwastewaterdecontaminationtechnology.Nevertheless,thepossibleexistenceofpotentiallyhazardousleachableelements(suchasMo,As,CrandV)intheresidualflyashparticlesisaprominentlimitationfortheapplicationofthezeoliticmaterialinordertouptakecationsfromwastewaters.Thisrestriction,mightbeeliminatedifpurezeoliticmaterialsynthesizedfromSiflyashextractsisutilized[1].Itdemonstratedthatthecompositionofusedflyashisadeterminingparameterinconvertingitintozeolites[8].Allofthestudiesaboutzeolitesynthesizingfromflyashareaboutthecoalwithnormalchemicalcomposition.Despitetheproductionofveryhighvolumesofflyasheswithhighsiliconcontentallovertheworldasaby-productofdifferentindustries,thereisnoknownwideandprominentsolutionfortheeffectiveuseofthismaterial.Thiskindofflyashenumeratedasanenvironmentalproblemintermsofalandfill.Veryhighsiliconflyashhasachemicalcompositionsimilartosilicafumebuttheirphysicalspecificationsaredifferent.ThispaperaimsatinvestigatingsynthesisandunderstandingcharacterizationofzeolitesAandXfromhighsiliconflyash(HSFA)asasourceofsiliconwiththepurposeofutilizingresultingzeolitesascatalystsfortheFischer–TropshsynthesisinGastoLiquids(GTL)MaterialsResearchBulletin44(2009)913–917ARTICLEINFOArticlehistory:Received10March2008Receivedinrevisedform6August2008Accepted6August2008Availableonline14August2008Keywords:A.AmorphousmaterialsA.InorganiccompoundsC.X-raydiffractionC.ElectronmicroscopyD.CrystalstructureABSTRACTHighsiliconflyash(HSFA)utilizedasasourceofsiliconinsynthesizingofNa-A,-Xand-Yzeolitesthroughalkalifusionfollowedbyhydrothermaltreatmentat1008Cfor12h.VarioustypesofzeoliteswithdifferentdegreesofpuritywerepreparedbychangingSi/Alratioofthereactionmixturefrom1.6to3.0.Inaddition,exactboundariesofthisratioforsynthesisofeachzeolitetypeweredetermined.Furthermore,theeffectofNaOHamountutilizedinalkalinefusionsteponcrystalinityofsamplesinvestigated.Thesynthesizedzeoliteswerecharacterizedusingvarioustechniquesincluding;XRD,TGA,FTIR,SEMandBET.Theion-exchangebehaviorsofzeoliticsamplestestedwithCo2+.TheobtainedNa-Xzeolitewascrystaline,hadaveryhighcation-exchangecapabilityof4.9mequiv.g1andpossessedrelativelyhighspecificsurfaceareaofabout434m2g1.2008ElsevierLtd.Allrightsreserved.*Correspondingauthor.Tel.:+982166165425;fax:+982166022853.E-mailaddress:kazemini@sharif.edu(M.Kazemeini).ContentslistsavailableatScienceDirectMaterialsResearchBulletinjournalhomepage:–seefrontmatter2008ElsevierLtd.Allrightsreserved.doi:10.1016/j.materresbull.2008.08.008processes.Moreover,inordertoconsiderthecatalyticactivityofthesynthesizedzeolites,theirionexchangebehaviortowardcobaltspeciesisstudied.2.Experimental2.1.MaterialsHighsiliconflyashsuppliedbyIranFerrosiliceCompany.BecauseofverylowamountofAl2O3andveryhighcontentofSiO2,theuseofanaluminumsaltwasessentialinordertoconvertthisHSFAtozeolite.Assuch,NaAlO2asasourceofaluminumandNaOHforalkalinefusionofHSFAobtainedfromtheMerckChemicalCo.Also13XandNa-Yzeolites(AldrichChemicalCo.)employedasstandardsamples.2.2.ZeolitesynthesisandevaluationHSFAmixedwithaNaOHpowderinratiosof1:1.2and1:2.Themixturethenfusedat6008Cfor1.5h.TheeffectofheatpretreatmentontheutilizedHSFAinvest