Zeolite cation selectivity

A proposal that cation selectivity of zeolites is mainly a function of anionic site separation distances was tested with high and low silica-to-alumina ratios of the same zeolite crystal structure (faujasite and Type A). Anionic site separation distances of the high silica zeolites were assumed to be relatively greater than the low silica zeolites. The high silica zeolites were considerably more cesium-selective from a sodium-cesium system than the lower silica zeolites, as expected. Strontium selectivity from a sodium-strontium system was generally greater with the low silica zeolites, but was complicated by anionic site separation distance heterogeneity.