zeta电位对污染减轻的控制

JournalofColloidandInterfaceScience259(2003)293–300∗aDepartmentofEnvironmentalScienceandEngineering,KwangjuInstituteofScienceandTechnology(K-JIST),1Oryong-dong,Buk-gu,Gwangju500-712,SouthKoreabDepartmentofMaterialsScienceandEngineering,KwangjuInstituteofScienceandTechnology(K-JIST),1Oryong-dong,Buk-gu,Gwangju500-712,SouthKoreaReceived6May2002;accepted28October2002AbstractThefeasibilityoffoulingmitigationofanionexchangemembranes(AEMs)inthepresenceofhumatewasstudiedbyaddingthreedifferenttypesofwater-solublepolymers,i.e.,poly(acrylicacid)(PAA),poly(vinylalcohol)(PVA),andpoly(ethyleneimine)(PEI),duringelectrodialysis(ED)desalination.Measurementofzetapotentialofthehumateusedinthisstudyshowedhighlynegativepotential(about−30mV),implyingthatthehumatehadastrongfoulingpotentialontheAEMsinED.Ofthethreewater-solublepolymers,PEIshowedapositivezetapotential(about+14mV)andisabletoformaninterpolymercomplexwiththehumate.PAAandPVAhardlyformedinterpolymercomplexeswithhumateduetoelectrostaticrepulsion.ThePEI–humatemixturewithavolumeratioof1:20(PEI:humate)showedzerozetapotential,andacomplexedhumatewithzerosurfacechargewasformed,resultinginnofoulingeffectsontheAEMs.Accordingly,thedesaltingEDexperimentswithPEIshowedimprovedEDperformance.Further,blackcolloidsformedinthemixturedidnotcausethecellresistancetoincrease.2003ElsevierScience(USA).Allrightsreserved.Keywords:Foulingmitigation;Anionexchangemembrane;Humate;Water-solublepolymer;Electrodialysis;Zetapotential1.IntroductionElectrodialysis(ED)isamembraneseparationprocessinwhichanelectricalpotentialdifferenceactsasadrivingforceandchargedionsconductanelectricalcurrent[1,2].Inthisprocesselectricallychargedmembranesareemployedtoseparateionsfromaqueoussolutions.Cation(CEM)andanionexchangemembranes(AEM)areplacedinanalternat-ingpatternbetweenananodeandacathodetomakeindivid-ualcells[3,4].WhileEDhasbeenusedmainlytoproducedeionizedwaterfrombrackishwater,variousapplicationsareunderdevelopment.However,limitationsintheapplica-tionshaveoftenbeenreportedinhandlingsolutionscontain-ingfoulants[5–14].Thefoulantscausemembraneperfor-*Correspondingauthor.E-mailaddress:[e-mail](S.-H.Moon).1Currentaddress:Radiation&EnvironmentGroup,NuclearPowerLaboratory,KoreaElectricPowerResearchInstitute(KEPRI),103-16Munji-Dong,Yusung-Gu,Daejeon305-380,SouthKorea.2Currentaddress:KumhoIndustrialCo.,R&DCenter,555Sochon-dong,Gwangsan-gu,Gwangju506-711,SouthKorea.mancestodeteriorate,indicatedbyadeclineinthefluxandanincreaseintheelectricalresistance[11–15].IngeneralthefoulantspresentinnaturalstreamsarenegativelychargedandaffectAEM,whichisapolymericmembranewithfixedfunctionalgroupsofapositivechargeasstrongbasicgroups.Oneofthemostcommonfoulantsishumate,whichisapredominantcomponentofnaturalorganicmatter(NOM)andcancauseseriousfoulingofAEMsinanEDprocessduetonegativechargesofitscarboxylicandphenolicgroups[13,16,17].NegativelychargedhumatemovestowardtheAEMsunderanelectricfieldduringanEDoperation.Hu-matewithlargemolecularweightsdoesnotpassthroughandthendepositsonthemembranesurfaceduetothestericef-fectandtheelectricinteractionratherthanpenetrationintothemembranes[12–14].ThemovementanddepositionofhumatefoultheAEMs,decreasingtheEDperformance.However,ithasbeenreportedthatthecationexchangemem-brane(CEM)wasnotfouledduetoelectrostaticrepulsionbyitsnegativelychargedfunctionalgroups[13,18,19].Inearlierworksonultrafiltration[20–24],itwasreportedthatthespecificresistanceandfluxesarestronglydependent0021-9797/03/$–seefrontmatter2003ElsevierScience(USA).Allrightsreserved.doi:10.1016/S0021-9797(02)00095-4294J.-S.Parketal./JournalofColloidandInterfaceScience259(2003)293–300onthesurfacecharge(zetapotential)ofcolloidssuchassil-icasol.Leeetal.characterizedtheAEMfoulingintermsofzetapotentials,electricresistances,hydrophobicities,andexchangecapacities[25].Theyfoundthatthezetapoten-tialsoftheAEMschangedsignificantlyafterfoulingbyhu-mate.ThisbehaviorisconsistentwithapreviousstudythatfoundthatcoverageofhumatereducedcationicfunctionalityofAEMsandthendecreasedintheamountofadsorbedan-ions,thusresultinginreducedzetapotentials[26].Combeetal.[27]reportedthatthemodificationofmembranesurfacesbyoxidationincreasedthefoulingbytheincreasedadsorp-tionofhumateontothecelluloseacetatemembranes.Thesestudiessuggestthatreducingtheelectrostaticinteractionbe-tweenfoulantsandAEMsbysurfacechargecontrolmightmitigatemembranefoulinginanEDoperation.Water-solublepolymersareofgreatimportanceasfloc-culatingagentsforwastewatertreatment,concentrationandextractionofmetals,andreductionofhydrodynamicresis-tance[28–30]andhavepotentiallyversatileapplicationsduetotheircomplexingproperties.Usually,water-solublepoly-mersinteractaccordingtotheirfunctionalgroups,suchasacidic,neutral,andbasicmoieties.Thefunctionalgroupsgiverisetoanimportantutilityforthesolvationofpoly-merchainssuchassimpleinteractionofionic,polar,o