Leaching of deep-sea manganese nodule and base metal sulfide minerals in hydrochloric acid

Leaching of manganese nodule in the presence of chalcopyrite. sphalerite and galena individually was studied in HCl medium. When leached together, dissolution of metal values from the nodule as well as each of the base metal sulfide minerals, was found to be more efficient compared to their leaching individually under similar conditions. Galvanic interaction between metal sulfides (MS) and MnO2 and corrosion coupling due to cyclic action of Fe3+/Fe2+ redox couple were responsible for such increase in dissolution. Chlorine gas generated in the system also dissolved the base metal sulfide minerals. This approach of combined MS-manganese nodule leaching appears to be advantageous because of more efficeint dissolution and addition of value into the final product.