Extraction and recycling of fluoride-containing phase from spent bottom sedimentation of aluminum smelting cell by leaching in Al3+ solution media

An extraction and recovery method is developed based on leaching in Al3+ solution media, neutralization for fluoride precipitation, and lithium recovery to solve the accumulation problem of spent bottom sedimentation in aluminum reduction cells. The maximum extraction efficiencies of Li, Na, K, Ca, and F were 96.6 %, 98.1 %, 95.3 %, 30.9 %, and 91.7 %, respectively, under the optimized leaching conditions initial Al3+ concentration 1.0 mol/L, liquid to solid ratio of 10:1, and leaching temperature 50 °C for 120 min. Upon analysis of the leaching residues and thermodynamics, the results demonstrated that the Al3+ solution could effectively dissolve fluoride in bottom sedimentation. After neutralization, the high recovery rate of F and acceptable purities of aluminum hydroxyfluoride hydrate product was obtained, which was used to produce aluminum fluoride. Lithium was recycled in the form of Li2CO3, which has a good purity. These results indicate that the process is a promising method for treating and utilizing spent bottom sedimentation in the aluminum reduction cell.