Multicomponent ion exchange in zeolites. Part 4.—The exchange of magnesium ions in zeolites X and Y

Abstract

Equilibrium data for the exchange of magnesium into sodium and ammonium forms of X and two Y zeolites are presented. Binary and ternary exchange isotherms have been measured, and the data obtained at one solution concentration are used to predict equilibrium compositions at other concentrations using models developed previously. For Y zeolites the predictions are shown to fail badly, owing to the corrected selectivity quotients K_G varying strongly with solution concentration, an observation at variance with previous experience of zeolite exchange systems. Possible reasons for the variability of K_G are discussed, and it is concluded that while changes in the quantity and activity of imbibed water may in part explain differences between the Na/Mg-Y and NH₄/Mg-Y systems, the major cause for the failure of the prediction procedure is adsorption of chloride by the zeolites at higher solution concentrations.