Recovery of Metals from Solid Wastes in Copper Smelter

Kaixi Jiang, Haibei Wang, Yufang Wang, Xiaoping Zou

In copper smelters some solid wastes containing arsenic like flue dust, arsenic cake, black copper mud and lead cake were produced. They all contain high arsenic and also some valuable metals like copper, lead, zinc, antimony, bismuth and precious metals. BGRIMM carried out series of research and engineering works in recent years. Some technologies were developed to treat arsenic and recovering the metals. Pressure leaching process was developed to treat arsenic sulfide cake. At 105 – 110 C arsenic sulfide was oxidized into elemental sulfur with oxygen partial pressure 500 kPa. More than 95 % of arsenic was dissolved into solution as H2AsO4-. At the same time more than 95 % and 98 % of copper and rhenium were also leached into solution. The leaching residue was sent back to the smelting furnace. The leaching solution was firstly reduced by SO2 and then was crystallized by cooling to produce As2O3. Rhenium was recovered by solvent extraction with N235. Finally copper solution or copper sulfate by crystallization went back to copper electrolysis. In 2008 BGRIMM cooperated with Jiangxi Copper and built a pressure leaching plant in Guixi smelter. The capacity is 25000 t/a arsenic sulfide treated and with the output of 2500 t/a As2O3. Atmospheric leaching process was developed to treat flue dust and black copper mud. At 85 C more than 90 % of copper, zinc and arsenic were leached into solution by blowing air. Leaching residue will go to double side blowing furnace to extract lead, antimony, bismuth and precious metals. Leaching solution was firstly precipitated arsenic into FeAsO4 at 85 C and pH value 1.5. Then SX-EW process was used to extract copper from solution. The raffinate was removed arsenic again by precipitation with FeSO4. Finally zinc sulfate or ZnO can produce from the solution. Double side blowing furnace was developed to treat above leaching residue and other wastes containing lead, antimony, bismuth and precious metals. In furnace lead, bismuth and precious metals will convert into alloy. Most of antimony will go to off gas to produce antimony oxide by dust collection. The alloy went to electrolysis to produce lead metal. The anode slime went to recover bismuth and precious metals by pyro-metallurgical process.