Selective leaching of nickel and cobalt from limonitic laterite using phosphoric acid: An alternative for value-added processing of laterite

Abstract

Abstract Atmospheric acid leaching has advantages of low energy consumption and operating cost, compared with high pressure acid leaching of low-nickel limonitic laterites. However, it suffers low nickel recovery, low leaching selectivity of nickel/cobalt over iron and excessive waste generation. In this work, a new method was used for selective leaching of nickel and cobalt, as well as for preparing iron phosphate intermediate material by atmospheric phosphoric acid leaching of limonitic laterite. The results show that 98.7% of nickel and 89.8% of cobalt are leached from the calcined limonitic laterite under optimized leaching conditions; meanwhile, 98.3% of iron is converted into insoluble FePO4·2H2O, resulting in the selective leaching of nickel and cobalt over iron. The leaching precipitate of FePO4·2H2O has a purity of 94%, which is expected to be a high-value by-product, providing an extra economic value. This work presents an alternative for value-added processing of laterite, featured by high leaching efficiency of nickel and cobalt without generation of solid waste.