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

Abstract: 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 ۲۰ to ۶۰ °C and decreasing ore particle size from −۱۶+۲۰ to −۶۰+۱۰۰ mesh considerably enhance both the dissolution rate and efficiency. Molar ratios of Fe۲+/MnO۲ and H۲SO۴/MnO۲ in excess to the stoichiometric amounts were needed for successful manganese dissolution. Under the optimum condition (ore particle size of −۶۰+۱۰۰ mesh, Fe۲+/MnO۲ molar ratio of ۳.۰, H۲SO۴/MnO۲ molar ratio of ۲.۰) manganese could be extracted with over ۹۵% efficiency by ۲۰ 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 ۲۸.۱ kJ/mole for the proposed mechanism.

Keywords:

Leaching , Manganese ore , Pyrolusite , Ferrous ion , Reduced-time plot , Diffusioncontrolled