1_1型单组分盐溶液中荷电膜膜电位的研究

2009年第67卷化学学报Vol.67,2009第9期,969～973ACTACHIMICASINICANo.9,969～973*E-mail:xl-wang@tsinghua.edu.cn;Tel.:010-62794741ReceivedJune24,2008;revisedSeptember25,2008;acceptedDecember29,2008.国家973计划(No.2009CB623404)资助项目.·研究论文·1-1型单组分盐溶液中荷电膜膜电位的研究尚伟娟王弘历涂丛慧丁宁王晓琳*(清华大学化工系北京100084)摘要摘要根据固定电荷模型和非线性最小二乘法,研究膜体积电荷密度为定值和其大小随电解质主体溶液浓度呈指数变化的两种初始条件下,五种纳滤膜(NTR7450,ESNA1,ESNA1-LF,LES90和UTC60)在不同浓度的氯化钠和氯化钾溶液中的膜电位,获得膜体积电荷密度与电解质主体溶液浓度的关系.结果表明,当体积电荷密度随浓度呈指数变化时,拟合的膜电位与实验结果更接近,得到的固定电荷密度更精确.膜电位的大小与膜两侧电解质溶液浓度的比值相关.在较高浓度时,膜电位的值还与扩散系数相关;其中阴阳离子的扩散系数之比大于1.0是膜电位反号的标志.在中间浓度时,膜电位随电解质主体溶液浓度近似呈线性变化.关键词关键词固定电荷模型;非线性最小二乘法;荷电膜;膜电位;固定电荷密度MembranePotentialofChargedPorousMembranesinSingle1-1ElectrolyteSolutionsShang,WeijuanWang,HongliTu,ConghuiDing,NingWang,Xiaolin*(DepartmentofChemicalEngineering,TsinghuaUniversity,Beijing100084)AbstractAccordingtotheTeorellMeyerSievers(TMS)modelandthenonlinearleastsquaresprocedure,volumetricchargedensitiesoffivecommercialnanofiltrationmembranes(NTR7450,ESNA1,ESNA1-LF,LES90andUTC60)canbeobtainedbymeasuringthemembranepotentials(MP)ofNaClandKClsolutionsacrossthesemembranes.Thesimulationwascalculatedundertwokindsofinitialconditions:auniformandanexponentialvariationofvolumetricchargedensitywiththebulkelectrolyteconcentration.Theresultssuggestedthattheexponentialvariationofvolumetricchargedensitywiththebulkelectrolyteconcentrationismorefavorabletodescribethemembranepotentialandtoevaluatetheinducedfixedchargedensity.MPwasdependentontheconcentrationratioofelectrolytesolutionsofeachside.Inthehighcon-centrationregion,MPalsoreliedonionicdiffusioncoefficient,anditsvaluewouldbereversedifthediffu-sioncoefficientratioofco-iontocounter-ionwaslargerthan1.0.Whileintheintermediateconcentrationregion,MPasafunctionofelectrolyteconcentrationwasalmostlinear.KeywordsTeorellMeyerSieversmodel;nonlinearleastsquaresprocedure;chargedmembrane;mem-branepotential;volumetricchargedensity当荷电膜与溶液接触时,膜活性层内的表界面基团发生解离或吸附而成为离子基团,这使得膜的活性层带有“电荷”.在静电作用下与膜面电荷同号的离子被排斥,异号的离子则被吸引,从而影响膜内离子的传递过程.由于电荷排斥作用,荷电膜在透过通量、抗污染以及选择性方面