Effect of iron chloride salts on the leaching kinetics of cobalt, manganese, and nickel from spent lithium-ion batteries in acidic chloride media: a comparative study

Spent lithium batteries have become a strategic secondary resource for cobalt, nickel, manganese, and lithium due to the growth of the electronics industry. This paper investigates the effect of iron chloride salts on the dissolution rate of Co, Ni, and Mn in acidic chloride media. The study compares the leaching performance of these metals under oxidative and reductive conditions. Analytical-grade reagents, including ferric chloride (FeCl3), ferrous chloride tetrahydrate (FeCl2 · 4H2O), and hydrochloric acid (HCl), supply ferric ions (Fe3+), ferrous ions (Fe2+), and acidic chloride media (Cl-), respectively. The effects of solid/liquid ratio (2-6 g/L), agitation speed (50-300 rpm), temperature (30-60 °C), and concentrations of ferric chloride (0.05-0.3 M), ferrous chloride tetrahydrate (0.05-0.3 M), and HCl were studied.The removal of carbon affected the samples, as shown by XRD and SEM/EDX analysis, which revealed differences between non-calcined and calcined samples. Increasing ferric chloride concentration enhanced the leaching efficiency of Co, Ni, and Mn, with recoveries exceeding 95.0%. Ferrous chloride tetrahydrate was more effective in leaching Mn than Co and Ni. Consequently, oxidative leaching exhibited non-selectivity compared to reductive leaching. The leaching rate generally increased with higher temperature, agitation speed, acid concentration, and ferric or ferrous chloride levels. Since this work is industrial in scale, replicate tests demonstrated low variability and good reproducibility. A mixed-controlled shrinking core model best described the reactions and controlled both oxidative and reductive leaching rates. The activation energies were found to be 62.57 kJ/mol, 40.05 kJ/mol, and 58.08 kJ/mol for Co, Ni, and Mn in oxidative leaching, respectively. In reductive leaching, these values were 78.63 kJ/mol, 55.76 kJ/mol, and 87.00 kJ/mol.