PREDICTION OF MULTICOMPONENT ION-EXCHANGE EQUILIBRIA

A model has been developed for the prediction of multicomponent ion ex change equilibria which uses equilibrium data from binary systems to p redict behaviour in multicomponent systems. Non-idealities in the solu tion phase are considered by applying Pitzer's model for electrolyte b ehaviour while the resin phase activity coefficients are calculated by applying Wilson's model. In addition the equilibrium constants are ob tained from the Gaines and Thomas approach and are independent of the resin phase activity coefficients. The model also considers the non-av ailability of some ions for exchange due to the formation of ion pairs in the solution phase. When applied to cation exchange in the binary and ternary systems involving H+, Na+, K+ and Ca2+ ions, the model pre dicts well the equilibrium behaviour. 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 parti cular non-exchanging anionic species present in the solution.