Multicomponent ion exchange equilibria

© 1994 Dr. Amine MehabliaA semi-theoretical model is proposed to predict multi-component ion exchange equilibria between cations in an aqueous solution and a resin. The model uses equilibrium data from binary systems to predict behaviour in multi-component systems. Non-idealities in the soution phase are considered by applying Pitzer's model for electrolyte behaviour while the resin phase activity coefficients are calculated by applying Wilson's model. In addition the equilibrium constants are obtained from the Gaines and Thomas approach and are independent of the resin phase activity coefficients. The model also considers the non-availability of some ions for exchange due to the formation of ion pairs in the solution phase. The model is tested by applying it to the two ternary systems Na-H-K and Ca-H-Na and the quaternary Ca-H-Na-K. The predictions made by the model are significantly better than those of other models when compared to experimental data. The equilibrium constant and the two binary interaction parameters are found to be independent of the conditions of the solution phase including concentration and the particular non-exchanging anionic species present in the solution. The effect of temperature is also considered