The physico-chemical properties of the copper electrolyte significantly affect the energy consumption of the electrorefining process and the quality of the cathode product. Favorable conditions for electrorefining processes are typically achieved by keeping both the electrolyte conductivity and diffusion coefficient of Cu(II) high, while ensuring low electrolyte viscosity. In this work the conductivity of the copper electrorefining electrolyte was investigated as a function of temperature (50–70 °C) and concentrations of copper (Cu(II), 40–60 g/L), nickel (Ni(II), 0–20 g/L), arsenic (As(III), 0–30 g/L) and sulfuric acid (160–220 g/L). In total 165 different combinations of these factors were studied. The results were treated using factorial analysis, and as a result, four electrolyte conductivity models were built up. Models were constructed both with and without arsenic as the presence of As(III) appeared to cause non-linearity in some factor effects and thus impacted the conductivity in more complex ways than previously detailed in literature. In all models the combined effect of factors was shown to be minor when compared to the effect of single factors. Conductivity was shown to increase when copper, nickel and arsenic concentrations were decreased and increase with increased temperature and acidity. Moreover, the arsenic concentration was shown to decrease the level of conductivity more than previously suggested in the literature.

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.