Selective leaching of valuable metals from laterite nickel ore with ammonium chloride-hydrochloric acid solution

During the recent years, selective leaching from laterite ore has gained considerable interest from the scientific community because of the growing demand of valuable metals including nickel and cobalt. However, high energy consumption and serious environmental pollution have been the major drawbacks of the current leaching methods, leading to a strong desire for the development of alternative approaches. Herein, we have successfully developed a clean method to selectively leach nickel from laterite ore using chlorination hydrometallurgical technology, which has a greatly reduced environmental impact and mild reaction requirements. In this work, ammonium chloride solution was used as the chlorination agent and the process was achieved under 2 M of hydrochloric acid, 3 M of ammonium chloride and a liquid/solid ratio of 6:1 (mL/g) at 90 °C for 90 min. Notably, the process resulted in a good yield, with nickel (87.7%), cobalt (75.1%), manganese (95.6%), and iron (only 21.1%). The leaching mechanism was demonstrated by the analysis of XRD pattern of leaching residue and raw ore, suggesting that chloride ions are beneficial to the dissolution of goethite mineral in nickel laterite. When comparing with other chloride solutions which exhibit high leaching in weak acid, ammonium chloride has demonstrated a promising ability to activate hydrogen ion, as evidenced in the simulation result of OLI system. The reusability of ammonia chloride in leaching raffinate showed that this method has great potential for eco-friendly and practical industrial application toward sustainable refining of valuable metals from laterite nickel ores.