Development of a novel electrolytic process for producing high-purity magnesium metal from magnesium oxide using a liquid tin cathode

The current electrolytic processes for magnesium(Mg)metal have several disadvantages,such as anhydrous magnesium chloride(MgCl_(2))preparation and generation of harmful chlorine(Cl_(2))gas.To overcome these drawbacks,a novel Mg production process to produce high-purity Mg metal directly from magnesium oxide(MgO)was investigated in this study.The electrolysis of MgO was conducted using a liquid tin(Sn)cathode and a carbon(C)anode in the eutectic composition of a magnesium fluoride(MgF_(2))-lithium fluoride(LiF)molten salt under an applied voltage of 2.5 V at 1053-1113 K.Under certain conditions,the Mg-Sn alloys with Mg_(2)Sn and Mg(Sn)phases were obtained with a current efficiency of 86.6%at 1053 K.To produce high-purity Mg metal from the Mg-Sn alloy,vacuum distillation was conducted at 1200-1300 K for a duration of 5-10 h.Following the vacuum distillation,the concentration of Mg in the Mg-Sn alloy feed decreased from 34.1 to 0.17 mass%,and Mg metal with a purity of 99.999%was obtained at 1200 K.Therefore,the electrolytic process developed here is feasible for the production of high-purity Mg metal from MgO using an efficient method.