The Kaldor furnace smelting process is currently the mainstream process for treating copper anode slime, but the existence of copper, tellurium and other impurities has adverse effects on the recovery of gold and silver during the Kaldor furnace smelting stage. Therefore, it is necessary to pretreat the copper anode slime to remove these impurities before Kaldor furnace reduction smelting. However, the current pretreatment process of copper anode slime generally has the problem of low removal efficiency of copper and tellurium, and little research on the occurrence state of main metals in copper anode slime. Therefore, this study quantitatively determined the phase composition of Cu, Te, Pb, Bi, As, Sb, Se, Ag and Au, and hydrogen peroxide was introduced to enhance the leaching of impurities. The leaching behavior of each metal in copper anode slime was investigated in detail. The results demonstrate that Cu and Te in the copper anode slime mainly exist in the form of CuO and CuSO4 and Te and AuTe2, respectively. More than 99% of the Cu and 97% of the Te were leached out using 250 g/L H2SO4 and 28.8 g/L H2O2 with a leaching pressure of 0.8 MPa at 150 °C for 2 h, while the leaching of Au and Ag was both < 0.03%. The removal of Cu and Te and the enrichment of precious metals were achieved. This study provides a rich theoretical reference for the optimization of the Kaldor furnace process.

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, Na 2 CO 3 , SiO 2 , Bi 2 O 3 , 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 Bi 2 O 3 addition of 25% and a Na 2 O/SiO 2 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.

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