Dissolution of copper and nickel from nickel-rich anode slimes under oxidized pressure leaching

Anode slimes are valuable by-products in the electrolytic copper refinery process. This study aimed to investigate maximum extraction efficiency of Cu and Ni from slimes originating from the electrorefining of anodes containing high [Ni]. In addition, the extractions of Se, Te, As and Bi were determined. A factorial leaching series was conducted with T = 140–160°C, [H₂SO₄] = 12–20%, p_O2= 2–8 bars and solid/liquid ratio = 200–400 g/L. The highest Ni extraction of 99.7% was obtained with [H₂SO₄] = 20%, p_O2 = 8 bar and T = 160°C while maintaining S/L ratio of 200 g/L. The extraction of copper was found to be within 97–99% in all the leaching experiments. Increasing acidity and decreasing S/L ratio increased the efficiency of Cu extraction. Mineralogical characterizations by SEM-EDX demonstrated the presence of Ag₂Se, BaSO₄, PbSO₄ and several oxide phases in the leach residue.