Aspects of the Application of Electrochemistry to the Extraction of Titanium and Its Applications

Abstract

For over ve decades the main route for the extraction of titanium has been the Kroll process. It is regarded as being expensive, labour intensive, reliant on a high quality feedstock, and environmentally unfriendly, but it has thus far not been possible to replace it. As a result the usage of titanium is still restricted to a few high end applications. During the past twenty years several new molten salt based electrochemical approaches for the reduction of titanium oxide have been introduced to meet these challenges, and these may, eventually, lead to novel extraction processes for titanium and other reactive metals. This paper summarises the many interesting concepts that underlie these electrochemical methods, of which some have already advanced to the stage of substantial pilot plants whilst others are still being developed at the laboratory level. The paper also reviews the development of new materials for use as the anode in these processes. Finally, it touches upon the development of processes for the regeneration of oxidised titanium and for the welding of titanium under cathodic protection in cases where protective gas shielding is not possible.

Development of the Fray-Farthing-Chen Cambridge Process: Towards the Sustainable Production of Titanium and Its Alloys

“…R5) and carbon dioxides (CO 2 ) can react with O 2À ions in the molten salt to form carbonate ions (CO 3 2À ) which can then transfer to, and be reduced to carbon at the cathode. 22,54,72 These parasitic reactions lower the current efficiency and cause contamination to the cathodic products via, e.g., carbide formation. 22 When evolving gases, the carbon anode may also release carbon debris that float on the molten salt surface and potentially short circuit the cell, further impairing the current efficiency.…”

“…22,54,72 These parasitic reactions lower the current efficiency and cause contamination to the cathodic products via, e.g., carbide formation. 22 When evolving gases, the carbon anode may also release carbon debris that float on the molten salt surface and potentially short circuit the cell, further impairing the current efficiency. 59 Thus, by replacing carbon with an inert material, pure oxygen can evolve as the only anodic off-gas (cf.…”

“…74 However, an insulating layer of calcium stannate (CaSnO 3 ) formed on the anode surface after 24 h electrolysis, which ultimately terminated the operation. 22,73,74 CaRuO 3 was tested as the inert anode material to evolve pure oxygen during electro-reduction of TiO 2 and proven highly stable in chloride melts (see supplementary Fig. S4a and S4b).…”

“…50 kWh/kg Ti 6 ), environmentally unfriendly (> 2 kg CO 2 per kg Ti) and a semi-batch process. Thus, there have been continuous research and industrial efforts to improve or replace the Kroll process [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] as summarised in the supplementary Table S1.…”

Influence of bath composition on Ti metal deposition in molten CaCl2 containing calcium titanate

“…A new Ti production process replacing the Kroll process is desired. Many researchers have been studying the innovative smelting process, [1][2][3][4][5][6][7] but those processes are still under development. In our laboratory, the direct electrowinning of liquid Ti has been studied in molten fluoride, and it was shown that Ti metal was obtained.…”