Efficient lithium recovery from aluminum electrolytic slag via HCl solution: Leaching behavior and mechanism

With the continuous growth of global demand for lithium (Li) resources, developing efficient methods for recovering Li from industrial waste is of great significance. Aluminum electrolytic slag (AES) is a hazardous waste produced during the electrolytic aluminum process, containing approximately 1.0–2.7 % lithium, which has a certain value for Li extraction and environmental benefits. This study investigated the Li extraction process via direct HCl leaching with AES as the raw material. Additionally, the changes of phase, microstructure and element distribution of AES before and after leaching were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and other analytical methods. Combined with density functional theory (DFT) calculations, the reaction mechanisms during the leaching process were revealed, elucidating the key reaction steps and influencing factors. By modifying variables like AES particle size, HCl concentration, leaching temperature, and leaching time, the conditions for the Li extraction process were improved. The results show that under the optimal conditions of a particle size below 180 mesh, 6 mol/L HCl, 95 °C, 2 h, and a solid–liquid ratio (S/L) of 1:3 g/mL, the highest Li leaching efficiency reaches 95.22 %. The main phase compositions of the leaching residue are Na 2 SiF 6 , Na 5 Al 3 F 14 , Al 2 O 3 , CaF 2 , and C. This work provides an efficient approach for extracting Li from AES, which is expected to promote the sustainable utilization of Li resources and the high-value utilization of lithium-containing secondary resources.