FabricationofaMixedMatrixMembranewithinSituSynthes

FabricationofaMixedMatrixMembranewithinSituSynthesizedQuaternizedPolyethylenimineNanoparticlesforDyePurificationandReuseJunyongZhu,†YataoZhang,*,†,‡MiaomiaoTian,†andJindunLiu*,††SchoolofChemicalEngineeringandEnergy,ZhengzhouUniversity,Zhengzhou450001,People’sRepublicofChina‡UNESCOCentreforMembraneScienceandTechnology,UniversityofNewSouthWales,Sydney,NewSouthWales2052,AustraliaABSTRACT:Afacileandnovelmethodforthefabricationofmixedmatrixmembranes(MMMs)hasbeendeveloped,i.e.,insitusynthesisofquaternizedpolyethylenimine(QPEI)softnanoparticles(SNPs)followedbyquaternizationwithbromoethaneinpoly(ethersulfone)(PES)castingsolution.Theresultingcompositemembraneswereconstructedviaphaseinversionmethod.TheinfluencesofSNPsonthemorphologyandperformanceofthehybridmembranesweresystematicallyinvestigatedbyscanningelectronmicroscopy,dynamicwatercontactangle,antifoulingmeasurement,etc.Thecompositemembranesexhibitedathintoplayerandporousfinger-likestructure,whichweregreatlyaffectedbyinsitusynthesizedSNPs.Contactangleandwateruptakemeasurementsindicatedthatthehydrophilicityofhybridmembranesmarkedlyimprovedincontrastwiththatofunfilledmembrane.Meanwhile,thewaterfluxofthemembranessignificantlyenhancedduetotheincorporationofSNPs.Theion-exchangecapacity(IEC)valuecouldachieveashighas0.72mmolg−1withaninitialPEIcontentof1.5wt%.ThesaltsrejectionofMMMsfollowedtheorder:MgCl2MgSO4Na2SO4NaCl,confirmingthatthehybridmembraneswerepositivelycharged.Meanwhile,thefoulingparametersdemonstratedthatthecompositemembranesexhibitedapreferableantifoulingproperty.Thenewlydevelopedmembranesdemonstratedanimpressiveprospectforthedyepurificationduetothehighrejectionofreactivedyeswithahighpermeationflux,aswellaslowmultivalentionsretention.ThepossibleseparationmechanismofdyesandsaltsforcompositemembranesinfluencedbysynthesizedSNPswasalsoproposedinthisstudy.KEYWORDS:Polyethylenimine,insitusynthesis,mixedmatrixmembranes,softnanoparticles,antifoulingproperty,dyespurification■INTRODUCTIONTheincreasingvolumesofdischargesofdyeeffluentstoaquaticenvironmentshavegainedgrowingconcernbecausemostofthemarenonbiodegradable,generallyquitetoxic,andevenconsumethedissolvedoxygenthatisessentialtoaquaticlife.1−4Itisestimatedthatthedyelossisabout10−15%inthedyeingprocess,specifically,200−350m3ofdyewastewaterisgeneratedtoproduce1.0tonofavailableproductinthetextileindustry.5Thus,inadequateremovalofthedyeswastewaterbeforetheirreleaseintotheenvironment,especiallytowatersystems,wouldnotonlycontaminatefreshwaterresources,thusposingarisktohumanbeings,butalsorestrainlightpermeation,havinganadverseinfluenceonaquaticlife.6−8Therefore,numerousongoingresearcheffortsattempttoachieveaneffectiveremovalofdyesfromwastewater.9−12Meanwhile,inthedyeingprocedure,inorganicsaltsincludingsodiumchloride(NaCl,∼6.0wt%)andsodiumsulfate(Na2SO4,∼5.6wt%)havebeenextensivelyusedtoenhancethedyeuptakeofthefabric.Amassofwastewatercontainingsaltsanddyesneedtobetreatedandseparatedwitheffectivemethodsfordyedesalinationandreuse.13Additionally,inthedyesynthesisprocess,someinorganicsalts(NaCl)existedinsyntheticdyesmustberemovedtoimprovedyesqualityandstability.14Theconventionalroute(salting-out)appliedindyepurificationisboundtoproduceagreatdealofwastewaterwithhighsalinityinthisprocess.15Therefore,theseparationofdyeandinorganicsalthasarousedbroadconcerninviewofdyedesalination,reuseandpurificationbothinthesyntheticanddyeingprocesses.16,17Asanalternativecandidateforwastewatertreatmenttechnology,membraneseparationisdeemedtobeenviron-mentallyfriendly,easytocontrolandoperate,aswellaslowinitialinvestmentandconsumptionenergy.18−21Hereinto,nanofiltration(NF)representsoneofthemostactiveseparationandpurificationfieldsextensivelyemployedintheapplicationsofwatersoftening,dyedesalination,pharmaceut-Received:January5,2015Revised:March4,2015Published:March10,2015ResearchArticlepubs.acs.org/journal/ascecg©2015AmericanChemicalSociety690DOI:10.1021/acssuschemeng.5b00006ACSSustainableChem.Eng.2015,3,690−701icals,wastewaterreclamation,etc.22−27Nanofiltrationisaliquid-phasepressure-drivenseparationprocess,withporesizeinthenanometerrange(0.5−2nm)andmolecularweightcutoff(MWCO,molecularweightofsolutethatis90%rejectedbythemembrane)varyingfrom100to1000Da.28−31Itsmajorseparationmechanisminvolvessterichindranceexclusion,electrostaticinteraction(Donnaneffect)andsolute-membraneaffinity.Whenappliedinthetreatmentofdyewastewater,traditionaldensenanofiltrationmembranes(NFMs)couldrejectbothorganicdyesandmultivalentsalts(SO42−)thatcouldnotonlydecreasethequalityofsyntheticdyebutalsoposeabiglossofvaluablesaltsthatcouldhavebeenrecycled.32,33Currently,positivelyornegativelychargedandhydrophilicNFMs(standsforaradicalalternativetoconventionalNFmembrane)andhaveattractedconsiderableattentionprimarilyascribedtotheimprovementofantifoulingpropertyandbetterpermeationflux.34Poly(ethersulfone)(PES)isacommerciallyavailable,structurallystablepolymerwidelyappliedinhigh-performanceapplicationsprincipallytotheexcellentcombinationofsuperiorpHandchlorinetolerance,highmechanicalstrength,andgoodthermalresistance.