Selective lithium recovery from leachates of spent NMC cathodes using deep eutectic solvent-impregnated activated carbon.

Deep eutectic solvent-impregnated activated carbon (AC-DES) is developed as a selective adsorbent for lithium recovery from complex aqueous streams relevant to spent lithium-ion battery recycling. By immobilizing a functional DES phase onto a porous carbon support, the AC-DES creates a tunable coordination environment that enables preferential Li+ binding in multicomponent systems. AC-DES (1:1 w/w) achieved up to 99% lithium removal under optimized conditions (pH 12, 75 mg, 2 h), with high selectivity over coexisting transition-metal ions. The adsorbent exhibited good stability and reusability, with negligible performance loss (≤1.5%) over four cycles, and allowed efficient lithium recovery using a mild acid solution (0.7 M HCl). Importantly, the AC-DES was successfully applied to selective lithium extraction from ethylenediaminetetraacetic acid (EDTA) leachates of spent NMC532 cathodes obtained via ultrasonic-assisted leaching, where Li+ coexists with Mn, Co, and Ni. Combined kinetic, isotherm, and pH-dependent analyses, supported by material characterization and density functional theory (DFT) calculations, reveal that lithium uptake is governed by preferential Li-DES coordination interactions. This work demonstrates a DES-functionalized solid platform for selective lithium recovery from complex leachates, offering an effective alternative to conventional solvent-based extraction systems.