Effect of iron ions on the extraction of copper by cyclone electrowinning

Copper-containing wastewater and acidic leachates of copper-bearing solid wastes are often contaminated with significant amounts of iron ions as impurities. In conventional copper electrodeposition processes, a high concentration of copper ions is required, while impurity ions must be maintained at low levels. Cyclone electrowinning technology has been demonstrated to enable efficient selective recovery of target metal ions from low-concentration solutions under mild reaction conditions, with significantly improved metal recovery rates and purity. In this study, the effects of Fe³⁺ concentration and cyclone rotational speed on copper electrodeposition in acidic solutions with low-concentration copper ion are investigated using cyclic voltammetry and chronoamperometry. The results reveal that the reducibility of copper during cyclone electrowinning is influenced by Fe³⁺ concentration. At Fe³⁺ concentrations below 0.50 g/L, a certain cathodic depolarization effect is observed, promoting copper electrodeposition. However, further increases in Fe³⁺ concentration are found to inhibit copper reduction. When the Fe³⁺ concentration ranged in 0.20-2.00 g/L, the current efficiency is significantly enhanced with increasing cyclone speed. The highest current efficiency of 80% is achieved at an Fe³⁺ concentration of 0.40 g/L and a cyclone speed of 500 L/h. Moreover, the microstructure of the electrodeposited copper is observed to transition from elongated blocks with adhered particles to a mixed morphology of hexagonal/polygonal flakes and elongated blocks as the cyclone speed is increased. This study provides theoretical and practical insights into the recovery and purification of copper from low-concentration acidic copper-containing wastewater or solid waste leachates by analyzing the influence of iron ions on cyclone electrowinning in acidic solutions.