Recovery of manganese and nickel from polymetallic manganese nodule using commercial extractants

The paper describes a process for the recovery of manganese and nickel from the sulfuric acid leach liquor of Indian Ocean manganese nodules using starch as the reductant. The leach liquor contained 22.85 g/L manganese, 6.38 g/L iron, 1.01 g/L copper, 0.023 g/L zinc, 0.09 g/L cobalt and 1.44 g/L nickel. From this leach liquor, Fe was first precipitated out with Ca(OH)2 at pH 3.8 followed by the extraction of copper using LIX 84I. From the almost Fe- and Cu-free leach liquor, Zn was extracted out as an impurity with D2EHPA in kerosene, after which the extraction of Mn was carried out with NaD2EHPA. The extraction efficiency of manganese using NaD2EHPA was 99.93% in 2-stages at A:O ratio of 3:4. The co-extraction of cobalt with manganese was 43 mg/L which was subsequently removed by scrubbing in two stages with MnSO4 solution. The stripping of manganese was achieved with 4% H2SO4 in 2-stages at A:O ratio of 1:1. After extraction of Mn, Ni was extracted with NaD2EHPA. The extraction isotherm of nickel reads 2-stages at A:O ratio of 3:2. The co-extraction of cobalt with nickel was 47 mg/L for which the Ni-LO was scrubbed out with NiSO4 solution. The stripping efficiency of nickel was 99.93% with 0.5% H2SO4 in 2-stages at A:O ratio of 1:1.