Mathematical Modeling of the Selective Transport of Singly Charged Ions Through Multilayer Composite Ion-Exchange Membrane during Electrodialysis

Abstract

Abstract: The deposition of several alternating anion- and cation-exchange surface layers (layer-by-layer method) is a promising technique for the modification of ion-exchange membranes, which makes it possible to essentially increase their selectivity to singly charged ions. This paper presents a one-dimensional model, which is based on the Nernst–Planck–Poisson equations and describes the competitive transfer of singly and doubly charged ions through a multilayer composite ion-exchange membrane. It has been revealed for the first time that, as in the earlier studied case of a bilayer membrane, the dependence of the specific permselectivity coefficient (P1/2) of a multilayer membrane on the electrical current density passes through a maximum (Formula Presented.) It has been shown that an increase in the number of nanosized modification bilayers n leads to the growth of (Formula Presented.), but the flux of a preferably transferred ion decreases in this case. It has been established that (Formula Presented.) is attained at underlimiting current densities and relatively low potential drop. The simulated dependences (Formula Presented.)(n) qualitatively agree with the known literature experimental and theoretical results.