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 150g of copper slag and 60g of 85% sulfuric acid was granulated and then roasted in the temperature range of 473-643K (200-370 degrees C) followed by sulfuric acid leaching. Once the roasting temperature and duration are, respectively, 643K (370 degrees C) and 150min, the recovery% values of metals to water-soluble form reaches, accordingly: Fe80.6, Zn88.7, Cu81.8. The resulting calcine was subjected to sulfuric acid leaching; after solid: liquid separation, a filtrate was obtained with the following composition, g/L: Fe(2+)0.60; Zn(2+)3.58; Cu(2+)1.03. On adding ammonia water into the filtrate, 98% of iron was selectively precipitated, thereby separating from zinc and copper.