Low-Carbon and Sustainable Electrochemical Synthesis of Large-Particle Titanium from TiO2 in Mixed Molten Salts

This study develops a two-step electrolysis process using TiO2 as the raw material for large-particle titanium powder production in fluoride-chloride molten salts. TiO2 is first dissolved in NaF-K2TiF6 molten salt at 850 °C to form Ti–O–F complexes, and then titanium is electrodeposited at 1.2 A/cm2 for 4 h to produce sponge-like titanium powder. The obtained titanium powder has an average particle size of approximately 30 μm and an oxygen content of about 0.59 wt %. Due to the high oxygen content, secondary electrorefining is performed in NaCl-KCl melts, investigating the effects of TiCl4 addition, current density, and Ti2+ ion concentration. Under conditions of 0.6 A/cm2 current density and 8 wt % Ti2+ ion concentration with TiCl4 addition, the titanium powder reaches an average particle size of 220 μm, with the oxygen content significantly reduced to 0.021 wt %, and its particle size increases significantly. The oxygen content decreases. The current efficiency during the electrolysis of TiO2 is 54%, while the current efficiency during the secondary electrorefining process is 72%. COMSOL Multiphysics simulation shows good agreement with experimental results, highlighting the influence of current density and titanium ion concentration on cathodic deposition thickness. Compared with the traditional Kroll process, this method reduces energy consumption by approximately 30%, offering a more sustainable and energy-efficient alternative for titanium production. This study confirms the feasibility of using TiO2 in fluoride-based molten salt systems for continuous titanium production.