PreparationofPolyethersulfoneUltrafiltrationTuburM

:86-22-2452-8226E-mail:[e-mail]nviaimmersionprecipitationwasemployedforPEStubularmembranepreparationandusingN,N-dimethylacetamide(DMAc)assolvent,PEG-400asmainconstantadditive.ThroughtheexperimentalstudyweobtainapreparationprocessofPEStubularmembranewithsuperiorproperties.Ethanolcausedanincrementinthefluxatlowcoagulationbathtemperaturerelativetothenon-ethanol.Andthelowtemperatureofcoagulationbathalsoimprovemembrane’srejectionanditsinfluencewasmostimportant.Otherconditionsincludedthatthecastingsolutiontemperaturemustnotbetoohigh(15℃wasbest)andthemembranedon’tbeexposedtoatmosphereinlongtime.Thepreparedmembraneunderthisconditionshowsexcellentperformanceonfluxandretention.Testresultsshowthatthefluxcanbeupto160L·m-2h-1andtherejectioncanreachmorethan97%(forovalbvmin)underthiscondition.Thefluxwasincreasedclearlycomparetonon-ethanolandhightemperature.Keywords:Membrane,Polyethersulfone,Ultrafiltartio,AdditivesIntroductionGenerally,polysulfone(PSF)andpolyethersulfone(PES)arewidelyusedforthepreparationofmicrofiltration(MF),ultrafiltration(UF)andgasseparationmembranes.Besides,theyareprincipallytothefavorablecharacteristicsofwidetemperaturelimits,widepHtolerances,fairlygoodchlorineresistance,easytofabricatemembranesinawidevarietyofconfigurationsandmodules,widerangeofporesizesavailableforUFandMFapplicationsrangingfrom10Åto0.2umandgoodchemicalresistancetoaliphatichydrocarbons,alcoholsandacids.Thecommontechniqueforthepreparationofasymmetricultrafiltrationmembranesisthephaseinversionmethod.Membraneformationoccursinaveryshorttimeandinvolvesagreatnumberofelementarysteps.However,morelikelyinsomesystems,afeworonemechanismisimportant,soitisworthwhiletolookforsomeconsistencorrelationbetweenasingleparameterandtheobtainedmembranestructure.Severalresearcheshavereportedtheeflfectofadditivessuchaspolyvinylpyrolidone(PVP)ontheperformanceofanultrafiltrationmembrane.ThisexperimentwasconductedtostudytheeffectofadditivessuchasPEG-400andethanolontheperformanceofmembrane.ExperimentalMaterialsPolyethersulfone(UltrasonE6020P,Mw=58000g/mol)providedbyBASFCo(Germany).N,N-dimethylacetamide(DMAc)waspurchasedfromMerck(Hohenbrunn,Germany).PEGwaspurchasedfromTiaJjinChemicalReagentCo.ThemolecularweightMwofPEGwas400g/mo1.Distilledwaterwasusedthroughtheexperiments.EthanolwaspurchasedfromTianJinChemicalReagentCo.UltravioletspectrophotometerwaspurchasedfromSHIMADZUCo.PreparationofMembranesHomogeneoussolutionsofthepolymerdissolvedinDMAcwerepreparedusingPEGadditivesbystirringandheatingat70℃untilthesolutioniscompletelydissolvedandhomogeneous.Theresultantpolymersolutionwaskeptinaglassbottleandairbubblesinthecastingsolutionswerereducedbyultrasonificationprocessforseveralhours.Thesolutionwascastonsupporttubebymachineatroomtemperature.Inordertoguaranteeacompletephaseseparation,themembranewasstoredinthecoagulationbathfor24h.Thisallowsthewatersolublecomponentsinthemembranetobeleachedout.FluxandRejectionTheperformancesofthepreparedmembraneswerecharacterizedbyusingacrossflowsystem.Al1filtrationexperimentswerecarriedoutinacrossflowcel1.Theretentatewascirculatedbyacentrifugalpump.ThedetailoftheexperimentalsetupisshowninFig.1.Eggalbuminwasusedasthefeedforallvails.Theretentionofproteinwasinvestigatedforpreparedmembranesbymeasuringtheamountofproteininthepermeate.The℃.Theperformanceofthepreparedmembraneswerecharacterizedbyusingacrossflowsystem.ThedetailoftheexperimentalsetupisshowninFig.1.ResultsandDiscussionsFig.1showspurewaterpermeationofpreparedmembranescastfrom28wt%PES,51wt%DMAcand10wt%,14wt%,18wt%and22wt%PEG.Thefluxesofeachmembraneweredeterminedat10minwithatransmembranepressureof0.1MPa.UFexperimentaldataaresummarizedinFig.1.UsingPEGasadditive,fluxesofeachmembraneincreasesfrom47to167l/m2h-1withanincreaseofethanolconcentrationinthedopesolution.thetuburmembraneswiththedopesolutioncontaining0–25wt.%ethanolconcentrationhaveadenseexternalsurfaceanddifferentporesizesininternalsurface.Withthecoagulationbathtemperaturedecrease,thefluxdeclineobviously.Andinthecoagulationbathtemperature30~40℃thefluxchangegreatly.Butunder20℃thefluxdeclineslowing.Thecoagulationbathtemperatureplayanimportantroleinallthefactorsoffilmforming.FromFig.2,itisobservedthattheinfluenceofdifferentsmallmoleculeadditiveonmembranefluxissignificant.Inthethreeadditives,byadding3%ethanolthefluxobviouslyisthebiggest,andtheeffectofaddingacetoneandlithiumchlorideisweak,whichisfarlessobviouscomparetoaddingethanol.Coagulationbathatdifferenttemperaturesshowthesamerules.TheFig.2showthataddingethanolinthecastingsolutioncanincreasethemembraneflux.Thepict