ALKALI-METAL IONS INSERTION EXTRACTION REACTIONS WITH HOLLANDITE-TYPEMANGANESE 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/extracti on reactions of alkali metal ions with HolMO were investigated by chem ical, X-ray, DTA-TG analyses, FT-IR spectroscopy, pH titration, and K- d measurements. The alkali metal ions were inserted/extracted by two d ifferent mechanisms: redox-type and ion-exchange-type reactions. A mod el 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 alkal i and alkaline earth metal ions.