SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS XXXVI. SYNTHESIS OF CRYPTOMELANE-TYPE HYDROUS MANGANESE DIOXIDE AS AN ION-EXCHANGE MATERIAL AND THEIR ION-EXCHANGE SELECTIVITIES TOWARDS ALKALI AND ALKALINE EARTH METAL IONS

Abstract Hydrous manganese dioxide in a cryptomelane-type showed an excellent ion-exchange selectivity for K+, Rb+and Ba2+ ions having the effective ionic radii of about 1.4 Å. Log-log plots of distribution coefficients for alkali and alkaline earth metal ions vs. [HNO3] yielded a straight line with a slope of −1 and −2, respectively, indicating the “ideal” ion-exchange mechanism. The stoichiometry of ion-exchange reactions was also established for the uptake of macro-amounts of alkali metal ions in nitrate media.