Selective Volatilization and Recovery of Valuable Metals by Vacuum Carbothermal Reduction of Copper Anode Slime

Copper anode slime produced by electrorefining copper has a high recovery value due to the valuable metals and platinum group metals present. Neither traditional cupellation processes nor hydrometallurgical leaching processes can solve the problem of arsenic enrichment in the system. According to thermodynamic analysis, vacuum carbothermal reduction is feasible, but the saturation vapor pressure varies greatly among the reduction products. Therefore, separation of arsenic oxide, lead-bismuth compounds and precious metal components can be achieved via vacuum carbothermal reduction with selective volatilization. At the vacuum carbothermal reduction stage (823 K), the arsenic content in the residue was reduced from 9.35% to 0.48%, indicating a 94.89% arsenic removal efficiency. The vacuum distillation stage (1173 K) exhibited 94.21% Pb and 98.19% Bi removal efficiencies, and the recovery efficiencies for silver and gold were 97.49% and 99.99%, respectively.