Reduction Leaching of Manganese Nodules with Sodium Sulfite in Ammonium Chloride Solution.

Abstract

The leaching characteristics of manganese nodules were investigated by using ammonium chloride solution with sodium sulfite as a reductant for leaching manganese, cobalt, nickel, copper and iron. Leaching behaviors of manganese, copper, cobalt and nickel depend on the amount of added sodium sulfite. The ratio of liquid and solid is an important factor in the extraction of metals during leaching. The dissolution of manganese, cobalt, nickel, copper and iron is increased with the increase in the NH4Cl concentration and in the temperature of the leachant. When the leachant pH was kept constant, the leachability increased for each of the metals. The sodium sulfite has been found to be an effective reductant for extracting more than 95.8 % of Mn, 93.5 % of Ni, 98.5 % of Cu, 89.1 % of Co, 3.1 % of Fe when leached in 5 M NH4Cl at 80 t for 2.5 h. The dissolution rates of Mn, Ni and Cu are controlled by pore diffusion, while Fe is controlled by surface chemical reactions and Co is limited by both the surface chemical reaction and pore diffusion process.