Anovelmixedmatrixmembraneallowingforflowthroughrem

Anovelmixedmatrixmembraneallowingforflow-throughremovalofboronZheWang,PanWang,JingjingCao,YufengZhang,BowenCheng,JianqiangMeng⇑StateKeyLaboratoryofSeparationMembranesandMembraneProcesses,TianjinPolytechnicUniversity,Tianjin300387,Chinahighlights
AMMMwaspreparedbyphaseinversionofpolysulfoneandaboronspecificresin.
Theresinblendingleadstoincreasedsurfaceareaandroughness.
Theresinblendingleadstoincreasedsurfacehydrophilicityandmembraneflux.
TheadsorptionshowsS-typeisothermandobeystopseudofirst-orderkineticmodel.
TheMMMhassimilarboronuptakebutmuchhigheradsorptionratethantheresin.articleinfoArticlehistory:Received18July2016Receivedinrevisedform17September2016Accepted17September2016Availableonline19September2016Keywords:Non-solventinducedphaseinversionPolysulfone(PSF)membraneMixedmatrixmembraneComplexingmembraneBoronremovalabstractInthiswork,anovelmixedmatrixmembrane(MMM)wasfabricatedbyNon-solventinducedphaseinversionoftheblendofpolysulfone(PSF)withaboronselectiveresin(BSR)andusedforboronremoval.ThemembranesurfacechemicalcompositionwascharacterizedbyATR-FTIRandXPS.ThemembranemorphologywasobservedbyFESEM,AFMandBETmeasurements.TheeffectsofBSRcontentonboronadsorptionpropertieswerestudiedindetail.AdditionofBSRleadstorougherandmorehydrophilicmembranesurfaceandhigherpermeationflux.TheboronuptakeincreasesobviouslywiththeBSRcon-tentandhasthemaximumover2.0mmol/g.ThemembraneshowsS-typeisothermandtheadsorptionkineticscanbewelldescribedbythepseudo-first-ordermodel.Comparedwiththepolymericresin,thePSF/BSRmembraneshowssimilarboronuptakebutmuchhigheradsorptionrate.Withamembraneof1.76cm2,aboronremovalefficiencyashighas97.6%canbeobtainedfor10mLof5mg/Lboronsolutionintheflow-throughexperimentatfluxrateof25L/m2h.ItisconcludedthattheMMMcancombinetheadvantageoftheresinonhighuptakeandthatofthemembraneonconvectivetransport.
2016ElsevierB.V.Allrightsreserved.1.IntroductionBoronexistsinthehydrosphereandlithosphereoftheearth.Itiswidelyfoundintheenvironmentintheformofboricacidandboratesalts[1].Asamicronutrient,boronisessentialforplantsandanimals.Itplaysacrucialroleinthegrowthofplantsinmanyways.However,boronbecomesharmfulorevenlethaltobothplantsandanimalswhenitsamountisgreaterthanrequired[2].In2011,theWorldHealthOrganization(WHO)regulatedaboroncontentstandardoflessthan2.4mg/Lfordrinkingwater[3],whiletheboroncontentofirrigationwaterislimitedto1mg/Lorless[4].Ontheotherhand,manywaterresourcesintheworldandmanywastewatereffluentsfromtheindustryhavetheboroncon-tentwellabovetheWHOregulations.Forexample,theaverageboroncontentinseawateris5mg/Lorso[5]andthatinsomeindustrialwastewaterreaches100mg/Lormore.Forexample,theboronconcentrationisabout100mg/Lingeothermalwaterandcanbeashighas1000mg/Lforeffluentfromboronreleasingmanufacturingindustries[6,7].Therefore,itisindispensabletodevelopefficientandcheaptechnologiesforboronremoval.Cur-rently,thereportedboronremovalmethodsincludeboronextrac-tion[8],adsorption[9],ionexchange[10],reverseosmosis(RO)[11],electrodialysis(ED)[12]etc.However,boronremovalstillremainsabigchallengeformostcommercialdesalinationtech-nologiesduetoitssmallmolecularsize,highdiffusionrateandnonionicnatureatnormalpHrange[11].Forexample,ROtech-nologiesaregettingtheleadingpositionforboronremoval[11]andthereisatendencyoftheROmembraneunitsreplacingthetraditionaloperationalunitsinthewatertreatmentprocess.How-ever,theboronrejectionbyROishighlydependentonthepHofsolutionwhichisrelatedtothedissociationratioofboricacid.AsinglepassROforseawaterdesalinationisusuallyonlyableto
2016ElsevierB.V.Allrightsreserved.⇑Correspondingauthor.E-mailaddresses:[e-mail],[e-mail](J.Meng).ChemicalEngineeringJournal308(2017)557–567ContentslistsavailableatScienceDirectChemicalEngineeringJournaljournalhomepage:–1.8mg/L[13].Thereasonisthatboronispredominantlyintheformofnon-ionicboricacidatthenaturalpHandhastheabilitytodiffusethroughtheROmembraneviahydrogenbonding[14].Thecomplexationofboricacidwithcompoundshavingadja-centhydroxygroups(Fig.1)hasbeendemonstratedtobeamoreeffectivesolutionforboronremovalthanothermethodsbasedonchargeandsizeexclusions[15].Variousadsorbentshavebeendevelopedusingmultihydriccompoundsasthecomplexingligands.Asanovelpolymericadsorbent[16,17],thecomplexingmembranesoffertheopportunityofflow-throughremovalofthetargetsoluteinadynamicfiltrationprocess.Comparedwithtradi-tionalpolymericresins,thecomplexingmembranescanprovidebetteradsorptionkineticsthankstothelargemesopores,asischaracterizedbyfastequilibrationofsolutesbetweenamobileliq-uidphaseandastationarysolidphaseonthemesoporewalls.Inthiscontext,wehavesynthesizedaseriesofcomplexingmem-branesviasurfacegraftingofglycopolymersontothesurfaceofmicroporousmembranes[5,16,17].Thegraftedmembranecouldadsorb2.0mmol/gboronwithin2hina300mg/Lboronsolution.Inaddition,itishardtosimultaneouslyachievehighadsorptionrateandhighuptakeforaspecificmembranematerial.Becausetheenhancementoftheuptakebyin