ALKALI-METAL IONS INSERTION/EXTRACTION REACTIONS WITH HOLLANDITE-TYPE MANGANESE OXIDE IN THE AQUEOUS-PHASE

H+-form hollandite-type manganese oxide (HolMO) was prepared directly by reacting LiMnO4 with Mn2+ in H2SO4 solution. The insertion/extraction reactions of alkali metal ions with HolMO were investigated by chemical, X-ray, DTA-TG analyses, FT-IR spectroscopy, pH titration, and K-d measurements. The alkali metal ions were inserted/extracted by two different mechanisms: redox-type and ion-exchange-type reactions. A model for the insertion/extraction reactions was proposed. The hollandite-type manganese oxide showed an ion-sieve property (the effective pore radius of the ion sieve is 1.41 Angstrom) for the adsorption of alkali and alkaline earth metal ions.