Leaching of manganese deep ocean nodules in FeSO4-H2SO4-H2O solutions

Studies have been carried out to determine maximum extraction efficiency of Co, Ni, Cu and Mn from manganese deep ocean nodules in FeSO4-H2SO4-H2O solutions and to maximise Co, Ni, Cu and Mn concentrations in the resulting leach liquors. The leaching parameters such as sulphuric acid concentration, liquid-to-solid ratio, temperature, time and grain size of nodules were varied to study their effect on metal extraction. The optimum conditions established were as follows: stoichiometric amount of FeSO4, 1.6-fold excess over stoichiometric amount of H2SO4, 90 °C, l/s of 7:1, grain size ≤1000 μm. Under these conditions, more than 85% of Co and 90% of Ni, Cu and Mn could be extracted within 30 min. The leach liquors contained approximately 146 mg Co/L, 1.63 g Ni/L, 1.69 g Cu/L and 30 g Mn/L.