Reaction Characteristics of Calcium Carbonates with Manganese Ions

概要

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Reaction characteristics of calcium carbonates (calcite, aragonite and vaterite) with Mn2+ ions in aqueous solutions containing various counter-anions (CL-, NO3- and CH3COO-) have been investigated using a normal batch method at 25°C. The reaction characteristics are independent of the kind of counter-anions, and the order of the reaction rates was found to be as follows; vaterite > aragonite >> calcite. About 80% of Ca2+ions were released from aragonite and vaterite during long time reactions. Although Mn2+ ions were fixed as Ca-substituted manganese carbonates by aragonite and vaterite, the ions scarcely reacted with calcite. The amount of Ca in Ca-substituted manganese carbonates, whose morphologies were different from those of starting materials, increased with increasing reaction time. From the curious results, it was concluded that the immobilization of Mn2+ ions in aqueous solution using aragonite and vaterite proceeds by a complexed ion-exchange mechanism with a reverse ion-exchange reaction of Mn2+ ions in manganese carbonate for Ca2+ in aqueous solution.
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