Literature Review: Methods for Nickel Recovery from Spent Electrolytes in Copper Electrorefining

Spent electrolytes generated during copper electrorefining contain increasingly high concentrations of dissolved nickel, which negatively affects cathode quality, decreases current efficiency, and requires regular electrolyte purification. At the same time, nickel is a valuable strategic metal used in stainless steel production, electroplating, and energy-storage applications, making its recovery both economically and environmentally important. This review summarizes recent advances in nickel recovery technologies from spent copper electrorefining electrolytes, focusing on electrochemical, hydrometallurgical, and hybrid approaches. Electrochemical methods such as selective electrodeposition and electrowinning enable the direct recovery of metallic nickel, achieving high purity and moderate energy consumption. Emerging systems based on deep eutectic solvents offer improved selectivity and extended electrochemical windows, representing a promising alternative to traditional aqueous electrolytes. Hydrometallurgical techniques—including solvent extraction, ion exchange, and controlled precipitation—provide high separation efficiency, especially for Cu–Ni systems with complex impurity compositions. Integrated process flows combining copper removal, nickel concentration, and final purification have demonstrated superior performance compared to single-stage methods. Studies on anode slime processing further highlight the potential of pressure leaching for near-complete nickel extraction under optimized acidic and oxidizing conditions. Overall, the literature indicates that well-designed hybrid systems offer the most effective balance of selectivity, energy efficiency, and environmental sustainability for nickel recovery.