Leaching kinetics of Mn from low grade pyrolusite with SO2 in liquid phase

Leaching process of Mn from low grade pyrolusite with SO2 in liquid phase was studied. Effects of agitation speed, leaching temperature, SO2 concentration and pH on Mn extraction rate were determined. Changes of particle size and surface element content of pyrolusite were determined. The results indicated that the effect of outward diffusion can be eliminated with agitation speed at 400 r/min. Mn extraction rate increases with increasing temperature, SO2 concentration and decreasing pH. A decrease of pyrolusite particle size by 20%, a decrease of Mn by 73% and an increase of Si by 18% on pyrolusite surface were found when Mn extraction rate was 80%. The leaching kinetics showed that the leaching reaction is controlled by both chemical reaction on particle surface and diffusion across the product layer. The activation energy was found to be 36.85 kJ/mol and the reaction orders with respect to SO2 and H+ concentration was 1.5995 and 0.5884, respectively.