The Kroll process was developed in the 1960s and remains the main commercial process for titanium production. While the production of titanium sponge in large amounts has been established, its drawbacks include high energy consumption, toxicity, high GHG emissions, and the generation of iron-contaminated titanium scrap, which remain unsolved. Therefore, many researchers have attempted to develop alternative methods for titanium production in the past decades, and electrorefining is one of these methods. The titanium electrorefining process is based on the transfer of titanium from an impure electrode (anode) to another electrode (cathode) in the electrolyte environment. The electrolyte plays a huge role in the transport of titanium, as well as in the oxidation and reduction mechanisms on the electrodes. According to past research, it is important to maintain titanium species in the form of divalent titanium (TiCl2). An increase in trivalent titanium in the electrolyte requires more electric energy and results in lowered current efficiency and lower quality of deposits. The preparation of TiCl2 is complicated by its high hygroscopic ability and the high exothermicity of the reaction, which may cause the formation of higher titanium chlorides in gaseous form. Therefore, this study is focused on the development of an in-situ synthesis method for TiCl2 electrolyte. This method is based on the preparation of a CaCl2-NaCl-CuCl solution and the addition of titanium metal powder into the solution at elevated temperatures in an argon atmosphere. As a result of the synthesis, a CaCl2-NaCl-TiCl2 solution is obtained, along with a byproduct of synthesis, copper metal, which sediments in the shape of sponge or flakes at the bottom of the crucible. Thermodynamic equilibrium evaluation revealed that the optimal temperature for TiCl2 synthesis is within the range of 600-700 °C, and the ratio of titanium addition is within the range of 1.0-1.1Ti. Additionally, the influence of temperature and the ratio of titanium addition on synthesis was studied experimentally under the same conditions. TiCl2 electrolytes were prepared and analyzed using hydrogen volumetric analysis to quantify TiCl2 concentration, titration analysis to quantify TiCl3 concentration, and ICP analysis to quantify total Ti concentration in the solution. The sedimented copper byproduct was leached from the electrolyte and analyzed by SEM/EDS to quantify the reaction yield of titanium. Experimental results showed that TiCl2 can be successfully synthesized in molten CaCl2-NaCl and that the temperature of the synthesis process and the ratio of Ti added have a strong impact on the composition of the electrolyte, Ti concentration, copper residual content in the electrolyte, and reaction yield. The optimal temperature was in good agreement with theoretical evaluation and was found to be 650 °C. A stoichiometric ratio or slight excess of Ti (1.0-1.1Ti) is recommended for the highest reaction yield of TiCl2 synthesis at 650 °C.
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