Recovery of Valuable Metals from Copper Smelter Slag by Sulfation Roasting

In the present paper, recovery of valuable metals from copper smelter slag of Balkhash copper plant (Kazakhstan) was investigated. To recover Fe, Zn and Cu to water-soluble form, the mixture of 150 g of copper slag and 60 g of 85% sulfuric acid was granulated and then roasted in the temperature range of 473–643 K (200–370 °C) followed by sulfuric acid leaching. Once the roasting temperature and duration are, respectively, 643 K (370 °C) and 150 min, the recovery% values of metals to water-soluble form reaches, accordingly: Fe—80.6, Zn—88.7, Cu—81.8. The resulting calcine was subjected to sulfuric acid leaching; after solid: liquid separation, a filtrate was obtained with the following composition, g/L: Fe2+—0.60; Zn2+—3.58; Cu2+—1.03. On adding ammonia water into the filtrate, 98% of iron was selectively precipitated, thereby separating from zinc and copper.