Co-treatment of spent carbon anode and copper slag for reuse and the solidification of the constituent fluorine and heavy metals

Spent carbon anode (SCA) is a typical global hazardous solid with high risk of environmental pollution. We therefore report for the first time a novel co-treatment technology for SCA and copper slag involving clearly defined transformation paths for F, Cu, Pb and Zn. The results of the investigation showed that the F and C contents in the SCA decreased the viscosity of the slag, thereby promoting the flotation recovery of Cu, whereas the F was transformed into CaF2. The PbSiO3 and ZnO contents in the slag were reduced to Pb(g) and Zn(g), respectively. Under optimal conditions, the solidification ratio of F reached 95.71%, and 81.50% Cu, 55.84% Pb and 36.48% Zn were recovered. The residual Cu content in the tailings decreased to 0.15 wt% after flotation. Toxicity characteristic leaching procedure test revealed that the F, Cu, Pb and Zn leaching contents were 46 mg/L, 4.58 mg/L, 2.17 mg/L and 10.71 mg/L, respectively, which are below their standard limits. The tailings can be reused as high-quality building materials with minimal environmental risk. The process herein reported presents a new and effective waste disposal approach, thus contributing to the sustainability of electrolytic aluminium and copper smelting industries.