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.
With the imminent peak in the retirement of rechargeable lithium-ion batteries worldwide, the development of efficient methods for recycling valuable elements from LIBs has attracted considerable attention. In this work, a novel method of NH 4 HSO 4 reduction roasting-selective ammonia leaching was proposed to thoroughly separate Li and Mn from the spent LiMn 2 O 4 cathode materials . Using the TG-DSC-FTIR, XRD, SEM-EDS and ICP methods, the detailed mechanism of reduction roasting process was revealed, showing that the Mn 4+ and Mn 3+ in the spinel structure of LiMn 2 O 4 were reduced by the NH 4 + from the molten ammonium salt, and transformed into water-soluble MnSO 4 and Li 2 Mn 2 (SO 4 ) 3 . According to the water-leaching performance of the roasting products, the sulfation conversion rate of Mn reaches 98.1 %, while Li is almost completely transformed under the optimal roasting conditions (475 ℃, 60 min). Using the NH 3 ·H 2 O-air leaching-system, complete separation of Li and Mn can be achieved. It was shown that the introduction of air into the ammonia solution at a rate of 0.2 L/min under the optimal leaching condition leads to Mn precipitation in the form of nanoscale Mn 3 O 4 particles with a precipitation rate of over 99.99 %, while Li still remains completely leached. Based on the in situ detection of the oxidation reduction potential and pH during the selective leaching, the key mechanism of efficient Mn precipitation was revealed. that is, the increasing potential accelerates the oxidation of Mn(OH) 2 , and the rapid consumption of Mn(OH) 2 promotes the hydrolysis of Mn 2+ , thereby achieving a significant improvement in the separation efficiency of Li and Mn.
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