Separation of cobalt and nickel from ammoniacal sulphate solution using Cyanex 272

The SO2-ammoniacal ammonium sulphate leach liquor of manganese nodule bearing iron, manganese, copper, nickel, cobalt and zinc was subjected to aeration/oxygenation to precipitate out the minor quantities of iron and manganese leaving the other metal values in tact. After extraction of copper from the Fe- and Mn-free leach liquor with LIX 84I, stripping of ammonia from the Cu-barren raffinate, precipitation of metal sulphides from the solution and leaching of the sulphide precipitates with H2SO4, the leach liquor bearing 0.58 kg/m3 Cu, 2.67 kg/m3 Zn, 2.012 kg/m3 Co, 23.747 kg/m3 Ni and 10.0 kg/m3 (NH4)2SO4 was obtained. After extraction of the remaining copper with LIX84I and zinc with D2EHPA from the leach liquor, it was left with Co, Ni and (NH4)2SO4. Extraction of cobalt from the Cu–Zn-free solution was carried out using Cyanex 272 in kerosene followed by extraction of nickel from the cobalt-free solution with NaCyanex 272 in kerosene. Extraction of both cobalt and nickel increased with increasing equilibrium pH and extractant concentration. The species extracted into the organic phase were CoA2 and NiA2·HA. The highest separation factor for cobalt and nickel was obtained with 0.1 M Cyanex 272 at pH 5.46.