Occurrence Behaviors of As/Sb/Bi in Copper Anode Slime and Their Separation by Compound Leaching Followed by Stepwise Precipitation

Abstract

Copper anode slime is the main raw material for the extraction of rare and precious metals. However, the recovery of rare and precious metals still faces great challenges due to the variety of impurities and the complex occurrence phase. In view of this, this research focuses on the occurrence mineral phases of arsenic, antimony, and bismuth in copper anode slime, and the process consisting of chloride leaching and selective precipitation of arsenic and bismuth is proposed. The results show that in copper anode slime, As mainly exists in the form of arsenate, while Sb and Bi exist in the form of oxides. The arsenate and oxides of Sb and Bi can be effectively leached by using the compound leaching process in the chloride system. The leaching efficiencies of As, Sb, Bi, and Cu can reach 92.72, 99.98, 89.13, and 90.31%, respectively, using a H2SO4 concentration of 4 mol/L and a NaCl concentration of 120 g/L with a liquid-solid ratio of 10:1 at 70 °C for 2 h. After compound leaching, more than 98% of Sb and Bi can be separated by stepwise selective precipitation in the form of Sb4O5Cl2 and BiOCl by controlling the H+ concentration at 0.8 g/L and 0.2 g/L, respectively. After separation of Sb and Bi, the As-containing solution can be further treated by mature arsenic solidification technology. The copper-containing solution for removing arsenic, antimony, and bismuth can be returned to the electrolysis process for copper recovery. The proposed process realizes the effectively and environmentally friendly separation of As, Sb, Bi, and Cu from copper anode slime.