Ternary ion exchange. Part 4.—Activity corrections for the solution phase

Abstract

A previously developed model for the evaluation of activity coefficient ratios in mixed dilute solution is employed with particular respect to ternary cation exchange in zeolites in the presence of up to three different coanions in solution. Potential errors arising from ignoring either completely or partially the non-ideality correction for the solution phase are evaluated and discussed. Exchanges involving counter-ions of the same valency, or involving ions of different valencies, are both considered. It is shown that when all the counter-ions have the same valency, the magnitude of the non-ideality correction is independent of the selectivity of the exchanger. When the valencies of the counter-ions are different it is essential to apply the mixed-salt activity correction for any accurate studies of ternary ion-exchange equilibria.