Green Capture of Silver by Bismuth from Decoppered Anode Slime with Low Energy Consumption

Abstract

As a consequence of lead pollution, low efficiency, and high energy consumption in the current pyrometallurgical processing of copper anode slime, a novel metallurgical recycling technology for processing copper anode slime was developed in this research. The new process uses bismuth instead of lead to realize high-efficiency enrichment of silver with lower energy consumption and higher capture efficiency. In this study, to determine the mechanism of silver capture by bismuth and confirm the possibility of low-temperature silver capture, the effects of coke powder, Na2CO3, SiO2, Bi2O3, and temperature on the silver content in slag during bismuth capture of precious metals were investigated. The results show that the silver content remaining in slag is only 0.157% with a Bi2O3 addition of 25% and a Na2O/SiO2 ratio of 0.417 at 950 °C for 8 h. The silver content in slag obtained from the proposed process was significantly lower than the allowable residue standard of China (silver content in slag <1%). The obtained bismuth–silver alloy can facilitate the recycling of bismuth through the blowing process. Considering that bismuth is a green metal, the pollution of lead in the silver recovery process is avoided, and the capture temperature of silver is only 950 °C, which is significantly lower than that of lead capture (1100–1200 °C). The energy consumption is significantly reduced, so the proposed process can accomplish the clean recovery of rare and precious metals in copper anode slime and promote the green development of the copper metallurgy industry.