Environmental and energy gains from using molten magnesium-sodium-potassium chlorides for electro-metallisation of refractory metal oxides

The molten eutectic mixture of magnesium, sodium and potassium chlorides (MgCl2-NaCl-KCl) has inappreciable solubility for oxide ions, and can help disengage a carbon anode from the oxide ions generated at a metal oxide cathode, and effectively avoid carbon dioxide formation. This disengaging strategy was successfully demonstrated in electro-reduction of solid oxides of zirconium and tantalum. It has led to significantly higher current efficiency (93%), and lower energy consumption (1.4 kW h kg(-1)) in electrolysis of tantalum oxide to tantalum metal compared to the conventional electrolysis in molten calcium chloride (e.g. 78% and 2.4 kW h/kg-Ta). (C) 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of Chinese Materials Research Society.