Multicomponent Space-Charge Ion Uptake and Ion/Solvent Transport Models for Ion-Exchange Membranes

离子交换膜的多组分空间电荷离子摄取和离子/溶剂输运模型图兰大学化学工程系，LA 70118离子交换膜用于各种工业过程和电化学装置，包括电渗析分离，电化学反应器，传感器和质子交换膜燃料电池。为了更好地了解这些膜的选择性离子传输机制，新的空间电荷平衡离子摄取和离子/溶剂传输模型正在开发和测试中。这些模型考虑：(i)多价反离子/固定电荷位点离子对的形成，（ii）膜孔内浓度依赖的离子扩散率和溶剂粘度，（iii）孔流体双层内离子溶剂化的可变吉布斯能，（iv）离子与膜的固定电荷之间的静电相互作用，以及（iv）由于膜的固定电荷群产生的强电场而导致的膜孔内溶剂偶极子的取向。这些模型适用于各种系统：(i)市售的阳离子交换膜和阴离子交换膜；(2)由单价/单价阳离子和阴离子盐、单价/二价阳离子盐、碱金属/季铵盐混合物和NaCl/氨基酸（甘氨酸）混合物组成的溶液；(3)水、甲醇、甲醇/水和乙腈/水溶剂。实验测量包括多组分唐南透析和电渗析期间的离子和溶剂通量和体溶液浓度变化，以及多组分离子摄取期间的膜相反离子浓度水平。所得数据用于空间电荷膜模型的验证。开发足够详细的结构/功能模型，准确描述多种离子在离子交换膜中的吸收和传输，对于开发新膜应用和配制新聚合物膜材料的聚合物工程师和膜科学家具有重要价值。这些模型可以用于(i)模拟特定电化学装置或分离应用中给定离子交换膜的性能，以及（ii）指示具有所需离子传输速率和选择性的新膜结构。本研究项目通过扩展分子水平过程和相互作用的基础知识基础来寻求这样的模型，这些过程和相互作用控制着阴离子和阳离子交换膜中多组分盐溶液与水和非水溶剂的分离。

ABSTRACTCTS-0085679Multicomponent Space-Charge Ion Uptake and Ion/Solvent Transport Models for Ion-Exchange MembranesPeter N. PintauroDepartment of Chemical EngineeringTulane UniversityNew Orleans, LA 70118 Ion-exchange membranes are used in a variety of industrial processes and electrochemical devices, including electrodialysis separations, electrochemical reactors, sensors, and proton-exchange-membrane fuel cells. In order to understand better the mechanism of selective ion transport by these membranes, new space-charge equilibrium ion uptake and ion/solvent transport models are being developed and tested. The models consider: (i) multivalent counterion/fixed-charge-site ion-pair formation, (ii) concentration-dependent ion diffusivities and solvent viscosity within the pores of a membrane, (iii) variable Gibbs energy of ion solvation within the pore-fluid double layer, (iv) electrostatic interactions between ions and the membrane's fixed charges, and (iv) the orientation of solvent dipoles inside a membrane pore due to the strong electric field generated by the membrane's fixed-charge groups. The models are applied to a variety of systems: (i) commercially available cation-exchange and anion-exchange membranes, (2) solutions composed of monovalent/monovalent cation and anion salts, monovalent/divalent cation salts, alkali metal/quaternary ammonium salt mixtures, and NaCl/amino acid (glycine) mixtures, and (3) water, methanol, methanol/water, and acetonitrile/water solvents. Experimental measurements include ion and solvent fluxes and bulk solution concentration changes during multicomponent Donnan dialysis and electrodialysis as well as membrane-phase counterion concentration levels during multicomponent ion uptake. The data are used to test the space-charge membrane models.The development of sufficiently detailed structure/function models that describe accurately absorption and transport of multiple ionic species in ion-exchange membranes would be of great value to polymer engineers and membrane scientists who are developing new membrane applications and formulating new polymeric membrane materials. Such models could be used (i) to simulate the performance of a given ion-exchange membrane in a particular electrochemical device or separation application, and (ii) to indicate new membrane structures with desired ion-transport rates and selectivities. This research project seeks such models by expanding the fundamental knowledge-base regarding the molecular-level processes and interactions that control the separation of multicomponent salt solutions from aqueous and non-aqueous solvents in anion and cation-exchange membranes.