A universal study of liquid metal cathodes for direct extraction of titanium within a closed loop

Abstract

Due to the environmental pollution, long process, and high cost of the current titanium recycling technologies, hundred million tons of titanium containing blast furnace slag generated in the iron making process are abandoned, which calls for urgent and effective utilization. Herein, we report a universal study of a series of high titanium affinitive liquid metal cathodes coupled with graphite anode for direct titanium extraction from titanium containing slag in a molten oxide electrolysis method. Two cost free slags, titanium containing blast furnace slag and electroslag remelting slag, serve as the electrolytes, and a series of liquid cathode metals are tuned to reveal the depolarization effect. Through thermodynamic and experimental analyses and kinetic calculations, we find binding energy, work function, and activities of titanium in liquid metal cathodes can synergistically affect the preferential deposition of titanium. After galvanostatic electrolysis, titanium–rich alloy cathodes are obtained, which can be directly used as industrial products or further distillated in vacuum to separate pure titanium and recyclable cathode metals, forming a closed loop throughout its life cycle. An ultrahigh cathodic current efficiency (∼64%) with short process and low energy consumption is achieved in this work. The outcomes reveal this environmentally friendly strategy can achieve efficient utilization of titanium resources, significantly reduce the loss of energy in the extraction process and lower the industrial production costs, and the breakthrough of directly extracting titanium from titanium containing oxides in this work is of great importance to titanium industry.