Modeling of the Sorption Dynamics in Multicomponent Ion-Exchange Systems with Consideration of Complexation Reactions on the Basis of the Surface Complexation Theory

Abstract

The sorption dynamics in multicomponent ion-exchange systems with consideration of complexation reactions in solution is theoretically described by solving (on a computer) nonlinear material balance equations and kinetic equations of internal diffusion. Equilibria in multicomponent ion-exchange systems are characterized using the surface complexation theory. According to this theory, fixed groups of an ion exchanger and counterions form complexes located in different layers (Stern layers) at different distances from the surface. These layers constitute a circuit of series-connected capacitors. The fundamental advantage of such an approach is the fact that equilibria in multicomponent systems can be described in terms of a set of parameters obtained for binary systems. Additional account is taken of complexation reactions in the solution in the space between sorbent grains in an ion-exchange column. The H+–A–B three-component metal-ion exchange in various systems (A, B = Zn2+, Co2+, Ni2+, Cd2+, Ca2+, and Na+) is studied. Comparison is made between the results of numerical calculations of the characteristics of the H+–An+–Bn+ ion exchange in multicomponent systems containing metal ions with and without consideration of chemical reactions.