Development of Molten Salt Electrolysis of MgO Using a Metal Cathode and Vacuum Distillation to Produce Ultra-High Purity Mg Metal

Abstract

© 2022, The Minerals, Metals & Materials Society.To resolve the drawbacks of the current Mg production process, direct use of MgO as feedstock via an electrolytic method has been attempted. In this study, molten salt electrolysis of MgO using a metallic cathode such as Sn, Cu, or Ag and a graphite anode followed by vacuum distillation was developed to produce ultra-high purity Mg metal. During the electrolysis of MgO in MgF2–LiF molten salt at 1053 K, Mg alloy is produced at the bottom of the electrolysis cell owing to the high density of the cathode. Afterward, 99.999% Mg metal is produced through vacuum distillation of the Mg alloy at 1200–1300 K. In addition, the use of secondary resources containing MgO as feedstock, the stability of the structural materials that are used, and scale-up of the process were also investigated in order to establish a cost-effective and environmentally friendly Mg production process.