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1、THEADSORPTIONOFFLUORIDEIONFROMAQUEOUSSOLUTIONBYACTIVATEDALUMINAYOUNGKU∗andHWEI-MEICHIOUDepartmentofChemicalEngineering,NationalTaiwanUniversityofScienceandTechnology,Taiwan107,Taipei,TaiwanR.O.C.(∗authorforcorrespondence,e-mail:ku@ch.ntust.edu.tw;fax:886-2-2
2、3485535)(Received8February2000;accepted19January2001)Abstract.Theadsorptionoffluorideioninaqueoussolutionbyusingaluminawasstudiedinthisresearch.TheexperimentalresultsindicatedthattheremovalefficiencywasinfluencedsignificantlybysolutionpHandtheoptimumoperatingpHw
3、asfoundtobeintherangeof5to7.Forneutralandacidicsolutions,theadsorptioncapacitiesoffluoridebyaluminawasinterferedbythepresenceofsulfate.TheLangmuirandFreundlichisothermscanwelldescribetheequilibriumbehaviorsoftheadsorptionprocesses.Theexperimentallydeterminedl
4、owvaluesofactivationenergyindicatenonspecificadsorptionisthepredominantmechanism.Thesurfacereaction-limitingbatchkineticmodelcanadequatelydescribetheremovalbehaviorsoffluorideionbyaluminaadsorptioninthebatchsystem.Keywords:adsorption,alumina,fluoride1.Introduct
5、ionEventhoughfluorideisoneoftheessentialelementsforhumanhealth,fluorideionspresentinaqueousenvironmentsarestillofconcernbecauseoftheirpossibleaccumulationanddamagetohumantissues(Chaturvedietal.,1990).TheWorldHealthOrganizationsuggestedalimitingvalueof1.5mgl−1f
6、orfluoridepresentindrinkingwater(Popatetal.,1994).Themajorsourcesforfluoridecontaminationinwatersincludethecontactofwaterwithnaturallypresentfluorine-containingcompounds(forexample,fluospar)andthedischargeofindustrialwastewatersfromthemanufacturingofsemiconducto
7、rs,glass,etc.intowaterbodies.Therefore,severaltechnologieshavebeendevelopedforreducingtheamountoffluoridetolowerlevelsfromwatersandwastewatersincludingprecipitation,ionexchange,membraneseparation,andadsorption(Tokunagaetal.,1995;Popatetal.,1994;Haronetal.,199
8、5).Theprecipitationtechniquesaremostwidelyappliedandusu-allycarriedoutbyaddingcalciumcompoundsintofluoride-containingwaterstoformcalciumfluorideprecipitatesfollowedbycoagulation/flocculationforsoli
