Extraction of nickel and cobalt from reduced limonitic laterite using a selective chlorination–water leaching process

The selective chlorination of reduced limonitic laterite for the extraction of nickel and cobalt was investigated. Reduced ore samples were obtained from the reduction roasting of a limonitic laterite. The extraction of nickel and cobalt from the reduced ore was conducted by selective chlorination in the temperature range of 300–500 °C using aluminum chloride hexahydrate as the chlorination agent, and followed by water leaching at 80 °C. The reduced ore was partly chlorinated by hydrogen chloride generated from the thermal decomposition of AlCl3·6H2O. Then the oxydrolysis of ferrous chloride re-generated hydrogen chloride which was used to further the chlorination. In this way, iron was mostly rejected as hematite, while nickel and cobalt were selectively chlorinated and dissolved during the water leaching process. Various parameters were studied including aluminum chloride addition, chlorination temperature, chlorination time, and the degree of reduction of ore. Under the optimum experimental conditions, 91% Ni, 90% Co and < 4% Fe were extracted by water leaching.