Effect of the Composition of the Zeolite Framework of Natural Clinoptilolites on the Exchange of Cations Na⁺ On Ca²⁺

The effect of the zeolite framework composition on the selectivity and thermodynamic parameters of ion exchange is studied for the exchange reaction of Ca2+ cations on Na-forms of clinoptilolites from nine deposits of Central and Southeast Europe, Northeast Asia, and North America. An increase in the thermodynamic affinity of Na-forms towards Ca(2+ )cations is shown with a decrease in the Si/Al ratio in their zeolite framework.