Collection of magnesium in an Mg–Pb alloy cathode placed at the bottom of the cell in MgCl2 electrolysis

The electrolytic cell features a top inserted graphite anode and a cathode, Mg–Pb alloy, placed at the bottom of the cell to reduce recombination of magnesium and chlorine in the inter-electrode region. The process involved the electrolysis of MgCl2 to form an Mg–Pb alloy that is heavier than the electrolyte and a subsequent refining of the alloy to obtain electrolytic grade magnesium. To achieve metallic magnesium production rate with the present cell, that is comparable with the conventional methods, higher current densities have to be used with the present system. The effects of current density on the cell performance have been determined in the present study.The evaluation of the results indicated that the major part of applied voltage is the theoretical decomposition potential and the IR drop. Energy consumption increased from 9.2 to 19.8 kW h kg−1 of magnesium produced during electrolysis when the current density increased from 0.48 to 1.98 A cm−2. The total energy required including the refining is 13.9 kW h kg−1 Mg at 1 A cm−2. The results obtained show that the present cell could work at comparable production rates to commercial cells with an energy consumption that is at the lower end of 13–18 kW h kg−1. Lower production rates can be used to achieve lower energy consumption.