Investigation of Pulse Reverse Copper Electrowinning, Eliminating Solvent Extraction for High Iron contents

Iron in copper electrolyte during electrowinning reduces efficiency and increases power consumption by participating in redox reactions, leading to energy wastage and decreased process efficiency. This study explores the use of pulse reverse current in experiments to enhance copper recovery efficiency and reduce energy consumption, particularly in the presence of high iron levels. The aim is to optimize copper retrieval and potentially eliminate the need for solvent extraction in small-scale production setups. Continuous experiments in two cells, with and without a separator, were conducted to assess the impact of parameters, while keeping certain factors constant like forward-to-reverse current ratio (40:1 second) and iron concentration (20 g.l⁻¹) at ambient temperature. The study established optimal conditions for copper recovery: copper and sulfuric acid concentrations of 22.5 g.l⁻¹, and 10 g.l⁻¹, forward and reverse current densities of 250 and 300 A.m⁻², respectively, using response surface methodology. Results closely matched software predictions, showing 85.2 pct current efficiency and 2.67 kWh energy consumption per kilogram of copper, with modest deviations from conventional electrowinning, but requiring less capital, process complexity and equipment. Cathode analysis revealed a minimum purity of 99.9 pct. Bench-scale runs validated the findings. Scanning electron microscopy confirmed copper nucleation and growth, highlighting enhanced crack formations due to the reverse current application, explaining minute impurity levels. Preliminary investigations indicated the positive impact of a temperature increase up to 40 °C on efficiency and power consumption, while iron concentrations had detrimental effects on both metrics.