Cation-Exchange Selectivity for K⁺, Mg²⁺, and Ca²⁺ Ions on Sodium-Substituted Taeniolite

The cation-exchange selectivity for K⁺, Mg²⁺, and Ca²⁺ ions on Na-substituted taeniolite, which is one of the fluormicas with swelling property, has been investigated. The distribution coefficient for each cation was numerically estimated at infinitesimal loading based on the Kielland plots for the Na⁺ → K⁺, 2Na⁺ → Mg²⁺, and 2Na⁺ → Ca²⁺ exchanges. The separation factors for K⁺−Mg²⁺ and K⁺−Ca²⁺ pairs, which are the ratios of the distribution coefficients, were found to be 9.1 X 10⁷ and 1.4 X 10⁸, respectively. The high K⁺ ion separation effect on Na-substituted taeniolite was also supported by the experimental results made in the presence of Na⁺, Mg²⁺, and/or Ca²⁺ ions. Na-substituted taeniolite was, therefore, shown to be useful for the separation and immobilization of K⁺ ions.