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 nick-el-cobalt-manganese (NMC) batteries, which also have applications beyond the automo-tive sector. The recycling of these batteries requires the development of technologies that allow for 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 affecting the recovery of Co(II) in 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 from the dissolution of NMC 622 battery black mass in 10 M HCl. The obtained results show that the used DES 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 for the recovery of cobalt in the form of 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.