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吸收和离子/溶剂传输模型PeterN.Pintaurod化学工程系杜兰大学新奥尔良，LA 70118离子交换膜用于各种工业过程和电化学设备，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。为了更好地理解这些膜的选择性离子传输机制，人们正在开发和测试新的空间电荷平衡离子吸收和离子/溶剂传输模型。模型考虑了：(I)多价反离子/固定电荷位离子对的形成，(Ii)膜孔内浓度相关的离子扩散系数和溶剂粘度，(Iii)孔-液双层内离子溶剂化的可变Gibbs能，(Iv)离子与膜固定电荷之间的静电相互作用，以及(Iv)由于膜固定电荷基团产生的强电场而导致的溶剂偶极子在膜孔内的取向。模型适用于各种体系：(I)市售的阳离子交换膜和阴离子交换膜，(2)由一价/一价阳离子盐和阴离子盐、一价/二价阳离子盐、碱金属/季铵盐混合物和氯化钠/氨基酸(甘氨酸)混合物组成的溶液，以及(3)水、甲醇、甲醇/水和乙腈/水的溶剂。实验测量包括多组分Donnan渗析和电渗析过程中离子和溶剂的通量和溶液浓度的变化，以及多组分离子吸收过程中膜相反离子浓度的变化。这些数据被用来检验空间电荷膜模型。发展足够详细的结构/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，对于正在开发新的膜应用和配制新的聚合物膜材料的聚合物工程师和膜科学家具有重要的价值。这些模型可用于(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)指示具有所需的离子传输速率和选择性的新的膜结构。这项研究项目通过扩展关于控制阴离子和阳离子交换膜中多组分盐溶液从水和非水溶剂中分离的分子水平过程和相互作用的基本知识库来寻求这样的模型。

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.