DISSOLUTION KINETICS OF MANGANESE DIOXIDE ORE IN SULFURIC ACID IN THE PRESENCE OF FERROUS ION

In this paper, kinetics of reductive leaching of manganese dioxide ore by ferrous ion in sulfuric acid media has been examined. Experimental results show that increasing temperature from 20 to 60 °C and decreasing ore particle size from ?16+20 to ?60+100 mesh considerably enhance both the dissolution rate and efficiency. Molar ratios of Fe2+/MnO2 and H2SO4/MnO2 in excess to the stoichiometric amounts were needed for successful manganese dissolution. Under the optimum condition (ore particle size of ?60+100 mesh, Fe2+/MnO2 molar ratio of 3.0, H2SO4/MnO2 molar ratio of 2.0) manganese could be extracted with over 95% efficiency by 20 minutes leaching at room temperature. A kinetic analysis based on dimensionless time method showed that shrinking core – ash diffusion control model fits the experimental results reasonably well. Value of activation energy was found to be 28.1 kJ/mole for the proposed mechanism.