The COOL Process: A Holistic Approach Towards Lithium Recycling

Lithium is a key element in reducing mobility-induced emissions. However, processes aimed at producing lithium from hard rock mining are based on the usage of large amounts of chemicals. Additionally, only a small quantity of the mined mineral concentrates is actually valorized. In contrast, the COOL process (CO2 Leaching process) is a process that makes use of water and carbon dioxide to leach lithium from any silicate mineral, making geopolymers from the residues. On the other hand, the COOL process enables the recovery of lithium from pretreated spent lithium-ion batteries. The leaching step has been investigated concerning the selective mobilization of lithium. Further attention was brought to the mobilization of potentially disturbing ions such as fluoride, aluminum, and silicon. It was found that the CO2 leaching step is indeed suitable for the selective mobilization of lithium. Up to 65% of lithium mobilization was achieved without adding any additives and 78% by adding Na2CO3. Fluoride and silicon mobilization could be addressed by heating zinnwaldite under a wet atmosphere respectively under the addition of a carbonate. Concerning secondary resources, up to 95% of lithium could be leached from black mass, and the residue was then leached and the leach liquor separated by liquid-liquid extraction to yield the heavy metals in high recovery and selectivity. Overall, the COOL process enables the recovery of lithium from different feedstocks and valorizes the residues from the lithium leaching. This makes the COOL process a universal approach to lithium recovery.