Recovery of nickel and iron from ferronickel powder and high nickel matte via the atmospheric leaching-hematite precipitation process

This study introduces a novel synergistic leaching process for ferronickel powder and high nickel matte, enabling the atmospheric leaching and the hematite precipitation process to mitigate carbon emissions associated with the treatment of Ni laterite. The results indicated that following seven cycles of synergistic leaching, the Ni2+ concentration in the solution exceeded 80 g/L, compared with the 15 cycles required for non-synergistic leaching. Optimal leaching conditions included a temperature range of 80°C−95°C, a stirring speed of 300 rpm, an initial H2SO4 concentration of 100 g/L, and a reaction time of 8 h, maintaining a final pH of 3.5−4.5, and an excess of ferronickel powder. Leaching successfully extracted Ni and Fe from ferronickel powder, with Cu2+ in the solution being reduced and enriched in the leaching residue. For the hematite precipitation process, optimal conditions involved a temperature of 200°C, a stirring speed of 500 rpm, a reaction time of 3 h, and an addition of 20 g/L of high Ni matte. The Fe removal efficiency exceeded 86%, resulting in hematite products that contained 61.15% Fe, 0.60% Ni and 1.48% S. These products can be commercially utilised, either sold to cement plants or utilized as raw materials for ironmaking.