Electrochemical extraction of titanium from carbon-doped titanium dioxide precursors by electrolysis in chloride molten salt

Abstract

In this paper, a new short process integrating carbochlorination and electrolyzation to produce metallic titanium in molten NaCl–CaCl2 electrolyte was presented. This electrochemical experiment was carried out at 1123 K using carbon-doped TiO2 precursors. The electrolysis process of intermediate produced by carbochlorination of carbon-doped TiO2 precursors was studied. The cathodic product was analyzed using X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and scanning electron microscopy (SEM) after electrolysis. The evolved gas was analyzed by a gas chromatograph equipped with a thermal conductivity detector (GC-TCD). Results showed that Ti powder of 98.7% could be obtained as the final product in the cathode by electrolysis for 5 h at 4.0 V using raw pellets with a C/TiO2 mass ratio of 0.15. Furthermore, the electrochemical process of Ti deposition was comprehensively evaluated by cyclic voltammetry and squarewave voltammetry. The electrode reaction mechanisms and particle evolution principles in molten salt during this electrolysis process were discussed. It indicated that titanium chloride in lower valence (TiCl3) with more productive advantage could exist as an intermediate, and Ti3+ ions were reduced to Ti metal by a two-step mechanism corresponding to the pathway: Ti3+ → Ti2+ → Ti.