Co(II) Recovery from Hydrochloric Acid Solution Using Menthol-Based Deep Eutectic Solvents (DESs): Application to NMC Battery Recycling

Lithium-ion batteries are essential to ensure electric mobility and reduce CO₂ emissions from transportation. One of the most commonly used chemistries is nickel-cobalt-manganese (NMC) batteries, which also have applications beyond the automotive sector. The recycling of these batteries requires the development of technologies to enable the selective separation and recovery of the metals present in the battery. One of these selective technologies involves the use of deep eutectic solvents (DESs). This research study investigates the different parameters that influence the recovery of Co(II) from hydrochloric acid medium using the deep eutectic solvent 3 Aliquat 336:7 L-Menthol. Firstly, using synthetic Co(II) solutions, the parameters influencing the cobalt extraction process are examined, and then these optimal conditions are applied to the recovery of cobalt from solutions obtained by dissolving NMC 622 battery black mass in 10 M HCl. The obtained results show that the DES used is highly selective for Co(II) recovery compared to other metals present in the solution (Ni, Li and Mn), achieving recoveries of up to 90% of the cobalt initially present in solution. Stripping with H₂SO₄ 0.5 M allows the recovery of cobalt as a crystalline monohydrate salt (CoSO₄.H₂O). The optimization of the Co/Cu separation conditions is carried out, achieving the separation of Cu(II) using Aliquat 336 in kerosene.