A novel electrolytic process using a Cu cathode for the production of Mg metal from MgO

An environmentally friendly and effective molten salt electrolysis process using a copper (Cu) cathode was developed for producing magnesium (Mg) metal from magnesium oxide (MgO). In this study, the influence of electrolysis temperature, concentration of Mg in the Mg–Cu alloy, size of the Cu pellets for the cathode, and cathodic current density on the current efficiency was investigated. In addition, the microstructure of the alumina (Al 2 O 3 ) crucible containing Mg alloy was analyzed. For the experiments, an average current of 1.42–1.63 A was applied to the electrolysis cell containing MgO in magnesium fluoride (MgF 2 )–lithium fluoride (LiF)–potassium chloride (KCl) molten salt using Cu cathode and graphite (C) anode at 1043–1173 K for 9.50–27.5 h in an argon (Ar) gas atmosphere. Under certain conditions, a current efficiency of 72.5–92.0% was obtained with the production of 9.25–14.2 mass% Mg–Cu alloys consisting of Cu (Mg) and MgCu 2 . During electrolysis, magnesium aluminum oxide was formed at the surface of the Al 2 O 3 crucible and its thickness was less than 28 µm. Therefore, the results of this study demonstrate the feasibility of the novel electrolytic process using a Cu cathode for producing Mg metal from MgO. Graphical abstract