MODEL FOR SR-CS-CA-MG-NA ION-EXCHANGE EQUILIBRIA ON CHABAZITE

Chabazite zeolites are used at Oak Ridge National Laboratory to decont aminate wastewaters containing Sr-90 and Cs-137. Treatability studies show that chabazite can remove trace amounts of these nuclides from wa stewaters containing much higher concentrations of calcium and magnesi um. The design of ion-exchange columns for multicomponent systems requ ires a method for predicting multicomponent equilibria from binary, te rnary and quaternary experiments, since the number of experiments requ ired for an empirical equilibrium model is not generally feasible. Bin ary interaction parameters for the Wilson equation are used to predict solid-phase activity coefficients for the five-component system. The sum of squares of deviations between experimental and predicted soluti on concentrations for the data points available is calculated. The ave rage deviation per data point for the five-component system is lower t han for some of the ternary- and four-component data sets containing c alcium or magnesium.