Kinetics of Manganese Oxides Dissolution in Sulphuric Acid Solutions Containing Oxalic Acid

The kinetics of the interaction of MnO2, Mn2O3, and Mn3O4, with sulphuric acid solutions and the effect of oxalic acid on this process are studied. As the sulphuric acid concentration is increased from 0.1 to 5 N, the dissolution rate of Mn2O3, Mn3O4 to MnO2 and Mn2+ ions decreases, whereas it increases with the concentration of Mn2+ ions. Upon the addition of H2Ox, the complete dissolution of Mn3O4 occurs more quickly. The reaction order with respect to the H+ and O x2- ions is +0.5 ± 0.1. A mechanism of MnO2 dissolution promotion by O x2- is proposed. The dissolution rate was found to depend on the concentrations of MnHOx - ions and was highest at pH 1.6 ± 0.2. A rate law and mechanism are suggested for manganese oxides dissolution.