Sustainable ammonia leaching for efficient nickel and cobalt recovery from mixed hydroxide precipitate

Due to the complex process, environmental impact, and high cost of conventional solvent extraction for Ni and Co recovery from mixed hydroxide precipitate, this study introduces an ammonia leaching process to selectively extract Ni and Co. Specifically, a ball milling and water washing pretreatment removes soluble Mg 2+ , followed by (NH 4 ) 2 CO 3 leaching, which dissolves 98 % Ni and 96 % Co, leaving impurities (Mn, Mg, Fe, Al) unreactive. The leachate contains 25.68 g/L of Ni, 2.4 g/L of Co, and 0.07 g/L of Mn, with Mg, Fe, and Al levels below detection limits, demonstrating effective separation of Ni and Co. Mn is also removed through ammonia leaching and subsequent precipitation as MnCO 3 . Kinetic analysis revealed that the diffusion-controlled process allows for efficient extraction at lower temperatures, further reducing energy consumption. Moreover, the ammonia solution can be reused for five consecutive cycles, maintaining leaching efficiencies above 95 % for Ni and 92 % for Co, offering cost savings. This method simplifies the recovery process, eliminates the need for organic solvents, reduces environmental impact, and lowers operational costs, making it a more sustainable and economically viable alternative for industrial applications.