Combined hydrometallurgical treatment of copper smelter dust and lead smelter copper dross

Abstract

At the Naoshima Smelter and Refinery, the copper smelter precipitator dust (EP dust) from the Mitsubishi process has been treated by sulfuric acid leaching for impurities bleed-off. The requirement to treat, in addition, copper dross from a lead smelter arose recently. Consequently, the behavior of copper dross during acid leaching was studied to determine whether a combined treatment was possible.Laboratory tests showed that about 80% of the copper in the dross could be extracted under the following conditions: 80°C; input sulfuric acid concentration of 200 kg/m3; 150 kg solid/m3; and 4–6 h under oxidizing conditions. In comparison, leaching of the copper smelter dust is relatively easy. Leaching can be conducted at a higher pulp density, a lower acid concentration, and a shorter retention time.Assuming a batch treatment, the combined treatment is possible by charging the dust to the dross leaching tank near the end of dross leaching. The overall plant size can be almost the same as is required just for dross leaching. The leach residue is recycled to the lead operation. Copper and cadmium are recovered from the solution by neutralization and cementation, respectively. The final solution is sent to the wastewater treatment plant. The combined treatment significantly reduces the operating costs compared to the individual treatment. The plant with a capacity to treat 300 t/month of dust and 200 t/month of dross is under construction and will start operation in 1992.