Comparison between Heterogeneous and Homogeneous MASS Action Models in the Prediction of Ternary Ion Exchange Equilibria

Abstract

In this paper two models for the prediction of multicomponent ion exchange equilibria were compared: one, a heterogeneous model, based on the mass action law in which ideal behavior for both the solution and the solid phase and the heterogeneity of ion exchange sites has been assumed, and the other a homogeneous model, based on the same mass action law in which nonideal behavior for both the solution and the solid phase has been taken into account. Considering counterions with different valences, the optimum value of the fraction of functional groups was obtained from binary systems data. It was shown that the energy distribution was practically symmetric. Likewise, a procedure for decreasing the number of adjustable parameters, based on the determination of the minimum linearly independent equilibria considering each equilibrium as a heterogeneous reaction, was developed. The adjustable parameters (namely, the equilibrium constants forced to satisfy the triangle rule) were used in the prediction of the ...