Recovery of Nickel and Cobalt from a Low Grade Laterite Ore

This study focused on the development of hydrometallurgical process which allows the nickel (Ni) and cobalt (Co) recovery from a low grade laterite ore. The developed process consists of two main stages: leaching and precipitation. In the first stage, an appropriate leach liquor which contains a relatively high nickel and cobalt concentration is prepared by chemical leaching and pressure leaching followed by separation steps, respectively. The effects of sulfuric acid concentration, leaching temperature and time, internal pressure in an autoclave on the efficient leaching of Ni and Co from a laterite ore were presented. In the next stage, the Ni and Co ions present in the liquor are co-precipitated as sulfides by sulfuration with sodium hydrosulfide (pH 3.8). It was found that talc (Mg 3 Si 4 O 10 (OH) 2 ), goethite (FeOOH) and quartz (SiO 2 ) are main minerals of the laterite ore which contains 48.12% Fe, 1.8% Al, 0.95% Ni, 0.07% Co, 0.29% Cr and 0.15% Mg. The high efficiency of pressure leaching for Ni and Co from the low grade laterite ore was re vealed by comparing the chemical leaching results. The vast majority of Co (>97%) and Ni (55%) from the purified liquor resulting after neutralization with calcium carbonate (CaCO 3 ) was precipitat- ed as mixed-sulfides by adjusting the NaHS/(Co + Ni) ratio to 3 by the addition of sulfuration agent (NaHS) at the solution pH of 3.8. Based on the experimental results, the efficient recovery of cobalt (Co) and nickel (Ni) from the low grade laterite ore can be achieved using the pressure leaching and neutralization treatment followed by sulfuration.