Title: Kinetics of the oxidation of chromium(III) ions by trimanganese tetroxide and by manganese(III) oxide
Abstract: The kinetics of the oxidation of chromium(III) ions in solution by Mn2O3 were studied at three temperatures. The initial reaction followed first-order kinetics with an activation energy of 79 kJ mol−1. Mn3O4 showed stronger oxidation of chromium(III) than Mn2O3 at the same pH and temperature. X-ray diffraction patterns of Mn2O3 and Mn3O4 before and after chromium(III) oxidation were recorded. For the reduced Mn2O3, the pattern showed less intense lines; moreover, the disappearance of some line was noticed. A few new lines appeared in the reduced Mn3O4 pattern; these may indicate the formation of the lower oxide MnO or could be due to a mixed MnCr oxide. The leaching of Mn3+ ions in Mn3O4 by pyrophosphate solution takes place more readily than in Mn2O3, which is in agreement with exchange between manganese ions in these solids and some cations in solution. The rate of chromium(III) oxidation in solution may depend on the availability of free Mn3+ ions in the oxidant solid.
Publication Year: 1982
Publication Date: 1982-07-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 17
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