Recovery of pure MnSO4∙H2O by reductive leaching of manganese from pyrolusite ore by sulfuric acid and hydrogen peroxide

Manganese leaching and recovery from pyrolusite ore, was investigated by using H2SO4 as a leachant and H2O2 as a reducing agent. The effects of agitation, H2O2 concentration, H2SO4 concentration, liquid/solid mass ratio, leaching time and reaction temperature on manganese recovery were studied. The optimal leaching conditions were determined as 4.0 M H2SO4 and 0.8 M H2O2 using liquid–solid mass ratio of 5.0 for 90 min at 40 °C and ore particle size of 44–37 μm. Under these conditions, the leaching efficiency was 92.0% for Mn. It was found that the use of H2O2 as a reducing agent for the reductive leaching of manganese increased the leaching rate. Analysis of the experimental results indicted that the leaching process is fitted by a chemical reaction model in temperature range 20–40 °C, and at higher temperature, 45–70 °C, the diffusion reaction model prevails. Activation energies for these models were calculated to be 49.5 kJ∙mol− 1 and 10.6 kJ∙mol− 1, respectively. Based on the experimental results, a separation method and flow sheet were developed and tested to separate high purity MnSO4.H2O (> 99.4%). Comparison between the present results and that reported in the literature are given.

Research highlights
► Recovery of pure MnSO4. H2O.
► Reductive leaching of manganese ore.
► Kinetic study of leaching process.
► Precipitation of pure manganese sulfate from leaching solution.