Recovery of Metals from Anode Slime Containing High Sn

K. Jiang, H. Wang, Y. Wang, K. Xie

In China the quantity of spent air-conditioning, TVs, refrigerators and 3C products becomes higher and higher. After disassembling there are some materials containing copper like PCB. During secondary copper refining anode slime is produced from electrolysis. It contains Sn, Cu, Pb, Sb, Bi, Au and Ag. Beijing General Research Institute of Mining and Metallurgy (BGRIMM) carried out some research works and developed a hydrometallurgical process. The anode slime firstly was roasted at 700 – 800 C in order to oxidize Sn2+ to Sn4+. During roasting Sn, Cu and Pb are changed to oxide. Then the calcine was leached by sulfuric acid to extract copper. More than 95 % of copper went into solution with less than 0.5 % copper in the residue. The residue was leached by chloride to dissolve Pb, Sb, Bi, Au and Ag. The leaching residue is SnO2 concentrate. Au and Ag in the leaching solution were precipitated by copper powder. Then copper was precipitated by lead powder. Finally Pb was precipitated by Na2CO3 as PbCO3. In order to simplify the flow sheet the calcine was directly leached by chloride to cancel sulfuric acid leaching. Thus BGRIMM carried out solvent extraction tests to extract copper from chloride media. The results indicated that LIX984N or LIX973 could extract copper from chloride solution. The copper content in the raffinate could be less than 0.2 g/L. During pilot tests there was crud between aqueous and organic phases. It was deduced that Sn and Pb in solution had some effect on the solvent extraction.