Selective Acid Leaching of Copper and Zinc from Old Flotation Tailings

The goal of the present work was to develop hydrometallurgical method based on acid leaching, which makes it possible to perform selective extraction of non-ferrous metals from old flotation tailings. Leaching was performed with sulfuric acid solutions (from 0.5 to 10%) and distilled water. Leaching was carried out using percolators and bottle agitator. Percolators were loaded with 100 g of old tailings, and leaching was performed with 100 mL of acid solutions. Pulp density during agitation leaching (S: L) was 1: 5. Two samples of old flotation samples were studied. The first sample of flotation tailings contained 0.26% of copper, 0.22% of zinc, and 17.4% of iron; while the second sample contained 0.36% of copper, 0.23% of zinc, and 23.2% of iron. Percolation leaching made it possible to extract up to 43 and 47% of Cu and Zn from the first sample. Extraction rate was maximum during the leaching with 1 and 2.5% sulfuric acid solutions. During the agitation leaching, the maximum extraction rate was reached with a 2.5% sulfuric acid solution (52 and 54% Cu and Zn), but the leaching rate with all solutions and distilled water differed insignificantly. Percolation leaching made it possible to extract up to 54 and 37% of Cu and Zn from the second sample of tailings, while agitation leaching made it possible to extract up to 34 and 68% Cu and Zn, respectively. The rate of non-ferrous metals extraction from the second sample with water did not differ significantly from that of obtained in the experiments with sulfuric acid solutions. In all experiments, the increase in the H2SO4 concentration led to the increase in concentrations of iron ions in productive solutions, which impedes the extraction of non-ferrous metals from solutions. Thus, it was possible to reach selective leaching of non-ferrous metals and to obtain solutions with relatively low concentrations of iron ions.