Efficient and selective leaching of nickel and cobalt from nickel laterite ore by a combined atmospheric acid leaching-ferric chloride solution leaching process: optimization and mechanism

Abstract

Low-selectivity leaching of nickel and/or cobalt is a major problem for atmospheric acid leaching processes, while harsh leaching conditions make the pressurised acid leaching process costly. Thus, the development of an efficient and selective leaching process of cobalt and nickel under mild conditions is required. Here, a combined atmospheric acid leaching-ferric chloride solution leaching process was developed to leach cobalt and nickel selectively and efficiently over iron from nickeliferous laterite ores. The influences of leaching parameters on the leaching efficiency of valuable metals during the atmospheric acid and ferric chloride solution leaching processes were investigated, and the overall recovery was also calculated and analyzed. Under the optimized leaching conditions, the leaching efficiencies of Ni, Co and Mn besides Fe could reach more than 95.0% after the atmospheric acid leaching process, with the Fe³⁺ concentration varying from 62.0 g L⁻¹ to 157 g L⁻¹ in the leach liquors. After the ferric chloride solution leaching process at 180 °C for 120 min using the initial leach liquors with iron concentrations of 160 and 100 g L⁻¹, the leaching efficiencies of Ni, Mn, Co, and Mg were around 90.0%, while the precipitation efficiencies of iron were 89.0% and 90.5% for saprolite and limonite laterite ore, respectively. Efficient and selective leaching of valuable metals from limonite and saprolite laterite ore under mild conditions was thus realized using the proposed process.