High-efficiency separation of Ni from Cu-Ni alloy by electrorefining in choline chloride-ethylene glycol deep eutectic solvent

Abstract High-purity Cu powders (99.967%) can be obtained by the electrorefining of Cu-Ni alloy (Ni ≤ 5%) in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES) at near room temperature. The electrochemical separation behaviors of Cu and Ni have been investigated by linear sweep voltammetry in 0.1 M CuCl + ChCl-EG DES. The results show that the oxidation potential of Cu is more positive than that of Ni, which implies Cu and Ni can be separated by electrochemistry. And the increasing of temperature is beneficial to the decontamination of Ni from Cu-Ni alloy. Besides, the effects of current density (2–10 mA·cm−2) and reaction temperature (323–363 K) on the current efficiency and specific energy consumption during the electrorefining process are also analyzed, respectively. The highest current efficiency (99.89%) and the corresponding specific energy consumption (281.492 kW·h·t−1) can be achieved at 10 mA·cm−2 and 363 K. The morphologies of Cu powders change from cauliflower-like to wheat ear-like with the increasing of current density. This finding provides a theoretical guidance for the separation of Ni from Cu-Ni alloy by an eco-friendly and facile electrorefining in ChCl-EG DES.