ION EXCHANGE CHARACTERISTICS OP A NEW MANGANESE OXIDE : STRUCTURAL FEATURES AND ALKALI CATION EXCHANGE

Three hydrous manganese oxides were prepared by atmospheric oxidation of the hydroxide obtained by alkali addition to MnSO₄ The obtained products appear not to have been described before and their structure is a defect one resembling that of γ-Mn₂O₃ one of the samples contain some Mn(OH)2. The product obtained with ammonia, incontradistinction.to the products prepared with NaOH, has no ion exchange properties. The oxide studied in more detail and prepared with NaOH has the chemical formula N₈₄Mn₁₇O₂₇.13 H₂O. Only some of the Na in the structure could fee exchanged with other alkali ions. Besides, the oxide seems to have exchangeable H+ that can be replaced in neutral solution by K+ and to a greater extent by Cs+ but not by Li+ or Na+.Alkali ion exchanges were found to be thermodynamically irreversible, which seems to be due to differences in the defect crystalline structures of the different alkali ion forms of the oxide. A tentative picture of ion exchange mechanisms is given.