Acid and Oxidizing Leaching of Copper Refinery Anodic Slimes in Hexafluorosilicic Acid and Nitric Acid Media

Abstract

Copper refinery anodic slimes containing copper (23.8%), arsenic (2.9%), selenium 8%), tellurium (0.9%), antimony (3.2%), silver (8.3%), and gold (0.3%) were treated by acid leaching using hexafluorosilicic acid (first step) and by acid and oxidizing leaching using a mixture of hexafluorosilicic and nitric acids (second step). This treatment dissolved 99% of the Cu, Se, and Te, 97% of the As, 95% of the Sb, and 85% of the Ag. After these two leaching steps, the final solid leach residue, which represents about 28% in weight of the initial solid, is upgraded in gold (1.11% Au), containing only 0.06% Cu, 0.04% As, 0.3% Se, 0.02% Te, and 0.11% Sb, while still remaining high in silver (4.45%). The leach solutions obtained are concentrated in Cu (24.5 g/L) as the first step, and in Ag (15.3 g/L) and Se (15.5 g/L) as the second step, which is favorable for the selective extraction of metals.