Causticizition of electrolytic aluminum slag for selective lithium recovery and fluorine fixation

Electrolytic aluminum slag (EAS) is a secondary resource containing lithium and hazardous waste with high soluble fluorine content. In this paper, a Ca(OH)₂ causticizing strategy is proposed for selective lithium recovery and fluorine leakage elimination from EAS. The impurities in EAS are causticized by Ca(OH)₂ and transformed into CaF₂, CaAl₂Si₂O₈ and Ca₃Al₂(OH)₁₂, causing the impurities in EAS to precipitate and separate from the Li dissolved in the solution. Under optimized conditions (80 °C, 60 min, Ca/E: 0.6, L/S: 10), the leaching efficiencies of Li, Al, Si and F are 99.06 %, 0.41 %, 0.80 % and 1.14 % respectively. Kinetic research shows that the leaching of Li conforms to the shrinking core model and is controlled by a mixture of solid phase diffusion and chemical reaction. Finally, Li in the solution is recovered through carbonization and precipitation, and the recovery efficiency of Li is 94.41 %. Meanwhile, F in causticizing slag shows high stability in the simulated acid rain leach agent. In summary, the causticizing of EAS proposed in this study is a hazardous waste management strategy with economic and environmental benefits.