Lithium recovery from spent lithium-ion battery wastewater: Application study of H_1.6Mn_1.6O₄ adsorbents

Direct recycling, a process in spent lithium-ion battery (SLIB) recycling, separates the anode and cathode active materials from water-dispersed black mass (BM) to recover valuable metals. However, the wastewater generated from this process contains significant amounts of lithium, which is a valuable material, but little research has been conducted on its recovery, leading to its loss. In this study, SLIB wastewater was regarded as a water-based lithium resource and utilized as a novel source for lithium recovery. Chemical composition analysis revealed lithium concentrations of 121.4–664 mg/L, depending on the pyrolysis pretreatment temperature of the BM, with low competing ion concentrations and a highly alkaline environment (pH > 11) serving as favorable factors for lithium adsorption. For lithium recovery and adsorption, a direct lithium extraction (DLE) technique was adopted, followed by the use of H_1.6Mn_1.6O₄ adsorbents to systematically validate the recovery feasibility. The adsorbents were synthesized from the Li_1.6Mn_1.6O₄ precursor in powder and granular forms and utilized in lithium adsorption experiments. Optimal adsorption conditions (24 h contact time, solid-to-liquid ratio of 3 g/L) were determined and applied to actual SLIB wastewater (pretreated at 400 °C and 500 °C) through three adsorption cycles, achieving maximum lithium recovery efficiencies of 53.7 % and 78.8 %, respectively. These findings demonstrate the potential of SLIB wastewater as a water-based lithium resource and the applicability of H_1.6Mn_1.6O₄ adsorbents, suggesting the need for further recycling processes targeting SLIB wastewater.