Electrolysis of TiO2 or TiCl2 Using Bi Liquid Cathode in Molten CaCl2

A new continuous smelting process of Ti using Bi-Ti liquid alloys is examined. In this process, titanium ore (TiO2) are reduced on the Bi liquid cathode to form Bi-Ti liquid alloys and, subsequently, electrorefining or vacuum distillation is performed to get pure Ti metal. Bi was used as a solvent to dissolve Ti since it has a large solubility of Ti and a relatively low vapor pressure suitable for the proposed process. Electrochemical reduction of TiO2 in molten CaCl2 produced the Bi-Ti alloys containing 0.6-2.2 at% of Ti and 17.9-34.9 at% of Ca. Calcium contamination in the alloys is attributed to its small activity coefficient in Bi. However, in case of electrolysis of TiCl2, Ti concentration in the alloy reached 29.0 at% and Ca contamination was suppressed. Thermodynamic consideration using E-pO(2-) diagram for the Ti-Ca-O-Cl system indicates that it is important to keep high pO(2-), in other words, low O2- concentration in the electrolyte to obtain the Bi-Ti alloys to keep low level of Ca contamination. (C) 2013 The Electrochemical Society. All rights reserved.