Adsorption equilibrium modeling and solution chemistry dependence of

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1、JournalofColloidandInterfaceScience279(2004)341350www.elsevier.com/locate/jcisAdsorptionequilibriummodelingandsolutionchemistrydependenceoffluorideremovalfromwaterbytrivalent-cation-exchangedzeoliteF-9MauriceS.Onyangoa,∗,YoshihiroKojimab,OchiengAoyic,EileenC.Bernardob,HitokiMatsudabaDepartmentofCh

2、emicalEngineering,NagoyaUniversity,Nagoya464-8603,JapanbResearchCenterforAdvancedWasteandEmissionManagement,NagoyaUniversity,Nagoya464-8603,JapancDepartmentofChemicalandProcessEngineering,MoiUniversity,P.O.Box3900,Eldoret,KenyaReceived18March2004;accepted17June2004Availableonline30July2004Abstrac

3、tFluorideindrinkingwaterabovepermissiblelevelsisresponsibleforhumandentalandskeletalfluorosis.Inthisstudy,therefore,thelargeinternalsurfaceareaofzeolitewasutilizedtocreateactivesitesforfluoridesorptionbyexchangingNa+-boundzeolitewithAl3+orLa3+ions.FluorideremovalfromwaterusingAl3+-andLa3+-exchanged

4、zeoliteF-9particleswassubsequentlyinvestigatedtoevaluatethefluoridesorptioncharacteristicsofthesorbents.Equilibriumisothermssuchasthetwo-siteLangmuir(L),Freundlich(F),LangmuirFreundlich(LF),RedlichPeterson(RP),Tóth(T),andDubininRadushkevitch(DR)weresuccessfullyusedtomodeltheexperimentaldata.Modeli

5、ngresultsshowedthattheisothermparametersweaklydependedonthesolutiontemperature.FromtheDRisothermparameters,itwasconsideredthattheuptakeoffluoridebyAl3+-exchangedzeoliteproceededbyanion-exchangemechanism(E=11.32−12.13kJ/mol),whilefluorideLa3+-exchangedzeoliteinteractionproceededbyphysicaladsorption(

6、E=7.41−7.72kJ/mol).FactorsfromthesolutionchemistrythataffectedfluorideremovalfromwaterwerethesolutionpHandbicarbonatecontent.ThelatterfactorbufferedthesystempHathighervaluesandthusdiminishedtheaffinityoftheactivesitesforfluoride.NaturalgroundwatersamplesfromtwoKenyantubewellsweretestedandresultsared

7、iscussedinrelationtosolutionchemistry.Inoverall,Al3+-exchangedzeolitewasfoundtobesuperiortoLa3+-exchangedzeoliteinfluorideuptakewithinthetestedconcentrationrange.Ó2004ElsevierInc.Allrightsreserved.Keywords:Fluoride;Equi