Efficient lithium recovery from electrolytic aluminum slag via an environmentally friendly process: Leaching behavior and mechanism

The electrolytic aluminum industry generates a large amount lithium (Li)-containing electrolytic aluminum slag (EAS) annually, and this can result in severe environmental pollution and wasting of Li resources. This paper proposes a method for recovering Li from the slag using AlCl3 as the leaching agent. The effects of the leaching temperature, AlCl3 concentration, pH, and solid-to-liquid ratio (S/L) on the leaching efficiency of Li+ were systematically examined. The structural transformation during the Li leaching process was revealed by SEM, XRD, 27Al NMR, and XPS analyses. The results indicate that up to 88.3% of Li + can be leached out using 0.85 M of AlCl3 with an S/L of 1:3 at a leaching temperature of 95 °C and pH of 0.5. The addition of AlCl3 played an essential role in the decomposition of cryolite/cryolithionite, ultimately resulting in Al–F fracture and Li+ release in the leaching solution. Moreover, Al3+ enters the interior of the slag to participate in the reconstruction of the chiolite with a low NaF/AlF3 ratio, and reacts with OH− ionized from H2O to form hydroxyl aluminum fluoride species. Fluorine ions were solidified in the leaching residues for subsequent cryolite regeneration. This study not only provides an environmentally friendly process for resource utilization from EAS but also reduces the environmental threat caused by the storage of the hazardous waste.