Reductive leaching of manganese from low grade Sinai ore in HCl using H2O2 as reductant

Manganese leaching from a low-grade ore (8.52% Mn) from Sinai was investigated by using hydrochloric acid in the presence and absence of hydrogen peroxide as a reducing agent. Sample characterization by XRD showed the presence of a variety of manganese minerals mainly cryptomelane, chalcophanite, pyrolusite, and crednerite. The presence of iron minerals like goethite, hematite, and minor quantities of pyrite were also observed, as well as gibbsite and dolomite. Although pyrite can act as a reductant for the tetravalent manganese minerals, it was necessary to use H2O2 as an additional reductant to realize over 97% Mn leaching. Both Zn and Cu that are present in the manganese minerals chalcophanite and crednerite respectively, were simultaneously leached.The relevant leaching factors were optimized as 2 M HCl and 0.4 M H2O2 for 1 h when using a solid–liquid ratio of 1/12 at 60–95 °C. Under these conditions, the leaching efficiencies were > 97% Mn, 98% Zn together with about 81% Al and complete leaching of Cu; whilst iron dissolution did not exceed 14%.