Sustainable Recovery of Fluorine from Waste Aluminum Electrolyte by Sulfuric Acid Baking

The high-value, green and harmless purification of aluminum electrolysis comprehensive solid waste can not only reduce its harm to the environment and soil but also separate and recover the high-value rare elements. This study aims to develop a process for recovering and treating waste aluminum electrolytes by sulfuric acid roasting. The results of orthogonal experiments and single factor experiments indicate that under the premise of not decomposing sulfuric acid to produce secondary hazardous waste, the high-value element F in WAE can be effectively separated under the condition of calcination at 275 °C for 4 h and an acid to material ratio of 7, with a recovery rate of 87.31%. According to the mechanism obtained from the analysis and characterization results of SEM, XRD, and chemical analysis on the residual water leaching residue after roasting, the process of sulfuric acid roasting WAE is a multi-step separation process of fluorine: from Na 3 AlF 6 and Na 5 Al 3 F 14 to AlF 3 and Al 2 (SO 4 ) 3 . Each phase transformation process is accompanied by the precipitation of fluorine in the form of HF. Graphical Abstract