Recovery of valuable metals from lithium-containing aluminum electrolyte slag via an NaOH leaching-aging-water leaching process

Abstract

With the continuous development of aluminum electrolysis technology, a large amount of lithium–aluminum electrolyte is stacked as waste. In this study, a “sodium hydroxide leaching-aging-water leaching” process was employed for the resource recovery of lithium, aluminum, and fluoride from this hazardous waste. The leaching efficiency of Li achieved 90.1% under the following conditions: NaOH concentration of 10 mol L⁻¹, reaction temperature of 90 °C, reaction time of 4 hours, and liquid–solid ratio of 9 : 1. An analysis of the degree of influence of reaction factors on the leaching efficiencies of valuable metals using the orthogonal design method indicated the following relationship: NaOH concentration > liquid–solid ratio > reaction temperature > reaction time. Owing to the common ion effect, fluoride was precipitated in the form of NaF, and an NaF product with a purity of 99.6% was obtained. After aging the leaching filtrate, LiAl₂(OH)₇·xH₂O was obtained, and ∼100% lithium was extracted by water leaching at 200 °C within a reaction time of 6 hours. The residue was an AlOOH product with a purity of 99.3%, and Li₂CO₃ was obtained via carbonation. This process provides a strategy for resource recycling and alleviating environmental crises.