An environmentally benign closed-loop process for the selective recovery of valuable metals from industrial end-of-life lithium-ion batteries

Abstract

An efficient environmentally benign hydrometallurgical process using ethylenediamine tetraacetic acid (EDTA) as the chelating agent has been developed for the recovery of valuable metals viz., cobalt (Co), lithium (Li), and copper (Cu) from the industrial end-of-life (EoL) lithium-ion batteries (LIBs). The experimental process parameters such as EDTA concentration, temperature, solid to liquid ratio (pulp density), pH, and reaction time were optimized to achieve high metal recoveries. The experimental results revealed maximum recoveries of 93.5 ± 3.1%, 96.4 ± 2.9%, and 97.1 ± 2.4% for Co, Li, and Cu respectively, under the optimized process conditions of EDTA concentration = 0.8 M, T = 90 °C, pulp density = 50 g/L, pH = 10, and reaction time = 4 h. A shrinking core model-based kinetic investigation revealed that interfacial chemical reaction is the rate-controlling step and the apparent activation energies corresponding to Co, Li, and Cu were evaluated to be 51.9, 41.0, and 42.3 kJ mol−1, respectively. Moreover, a plausible mechanism was elucidated, highlighting the synergistic effect and the role of Cu in augmenting the extraction reaction. The chelating agent, EDTA, was also recovered during the reaction and reused for cyclic repeat tests. Finally, the recovered metals were selectively separated in the downstream process via the precipitation reactions to depict a closed-loop recycling process. The envisaged approach will pave the way for a sustainable green alternative to the acid-based leaching processes used for metal extraction from EoL LIBs.