Recovery of lithium from spent aluminum electrolyte through a novel acidic complex leaching process

An acidic complex leaching process with iron-containing solution was developed to recover lithium from spent aluminum electrolyte, one of the solid wastes containing high contents of lithium, aluminum, and fluorine, from aluminum electrolysis industry. The effects of Fe³+ and H+ concentrations, liquid-to-solid ratio, leaching time, and temperature on the leaching efficiency of lithium were investigated and a maximum lithium leaching efficiency as high as 97.9% was achieved. The optimal leaching conditions were determined as an initial Fe³+ concentration of 1.5 mol/L, an initial H+ concentration of 0.1 mol/L, a liquid-to-solid ratio of 15 mL/g, a leaching time period of 2 h, and a leaching temperature of 80 °C. The lithium leaching kinetics were explored and the activation energy was determined as 37.34 kJ/mol, indicating a process mixed controlled by diffusion through the solid product layer and surface chemical reactions. Additionally, through a neutralization process, combined with a defluorination process with calcium oxide, the separation efficiency of lithium from aluminum and iron was therefore enhanced, causing a maximum lithium recovery rate as high as 97.9%. The subsequent process produced lithium carbonate with over 99% purity, efficiently recovering lithium and reducing environmental impact.