Recovery valuable metals from lithium-containing aluminum electrolyte slag by a 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 hazard waste. The leaching efficiency of Li achieved 90.1% under the conditions of NaOH concentration of 10 mol·L-1, reaction temperature of 90 ℃, reaction time of 4 hours, and liquid-solid ratio of 9:1. An analysis of the 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. Due to the common ion effect, fluoride was precipitated in the form of NaF, and NaF product with a purity of 99.6% was obtained. LiAl2(OH)7∙xH2O was obtained after aging the leaching filtrate, and ~ 100% lithium can be extracted by water leaching at 200℃ with a reaction time of 6 hours. The residue was AlOOH product with a purity of 99.3%, and Li2CO3 can be obtained after carbonatation. This process provides a strategy for resource recycling as well as alleviating environmental crisis.