二级出水典型污染物超滤膜污染行为的分子动力学模拟研究.docx

二级出水典型污染物超滤膜污染行为的分子动力学模拟研究
摘要
本文通过分子动力学模拟方法探究了超滤膜在二级出水典型污染物的污染行为。通过对单一污染物和多种污染物的模拟，得出了超滤膜中多孔结构对污染物扩散和分离过程的影响，以及不同污染物在超滤膜中的吸附和排斥特性。研究表明，超滤膜中的孔隙形态和大小对污染物的扩散和分离有一定影响，同时，污染物间存在竞争作用，较强的亲水性和亲油性污染物对超滤膜的影响更容易受到孔隙结构的影响。对于研究污染物在超滤膜中的污染行为具有一定的指导意义。
关键词：超滤膜；二级出水；污染物；分子动力学模拟
Introduction
Overthepastfewdecades,membranefiltrationtechnologyhasbecomeawidelyacceptedprocessforthetreatmentofwastewater.Amongvariousmembranefiltrationprocesses,ultrafiltration(UF)hasbeenextensivelyusedfortheseparationandremovalofpollutantsinthesecondarywastewatertreatmentprocess.However,membranefouling,whichreferstotheaccumulationandretentionofparticles,colloids,andmacromoleculesonthemembranesurfaceorwithinthemembranepores,leadstoperformancereductionandincreasedoperatingcosts.Therefore,anunderstandingofUFmembranefoulingmechanismsisessentialfortheefficientoperationofwastewatertreatmentprocesses.Moleculardynamic(MD)simulationhasbeenusedtogaininsightintomembranefoulingmechanismsinrecentyearsduetoitsabilitytoprovidemolecularlevelinformationaboutthecomplexdynamicprocessesinvolvedinthefoulingmechanisms.
Methods
Inthisresearch,theMDsimulationwasusedtoinvestigatethefoulingbehavioroftypicalpollutantsinaUFmembrane.Themembranewasmodeledwithfourlayersofpolyethersulfone(PES)polymerchains,andeachlayercontaining25chains.Thewatermoleculesandpollutants,includinghumicacidandsodiumdodecylsulfate(SDS),weremodeledusingaforcefieldwithcenterruleparameters.Theunitcellwasbuilt,andthesimulationwascarriedoutfor10nsat298Kwithaconstantpressureof1atm.
Results
TheresultsshowedthattheporesizeandmorphologyoftheUFmembranehavesignificantimpactsonthepollutantdiffusionandseparationprocess.Thelargertheporesize,theeasieritisforthepollutantmoleculestopenetratethroughthemembrane.Forinstance,theHumicacidmoleculeiseasiertopenetratethroughalargerporesizethanSDS,whichisbecauseofitssmallersize.Moreover,thesmallertheaverageporesize,theeasieritisforthepollutantmoleculestoaccumulateinthemembrane,astheyexperiencemoreinteractionswiththepolymerstructure.Sim