Dissolution of base-metal sulfide minerals in hydrochloric acid in the presence of manganese dioxide

An experimental investigation of the dissolution of three base-metal sulfid e minerals, namely, CuFeS2, ZnS and PbS, in hydrochloric acid medium in the presence of manganese dioxide is reported. Polarization measurements and l eaching studies were employed in the study. Dissolution occurred in the fol lowing three ways: by the cyclic action of the Fe3+/Fe2+ redox couple, by g alvanic interaction between MnO2 and the sulfide minerals, and because of c hlorine evolution from the system. The later two routes were found more eff ective at higher HCl levels. PbS appeared to be oxidized easily, whereas Cu FeS2 was the most difficult to dissolve. ZnS dissolution fell in between Pb S and CuFeS2.