Green Electrochemical Process Solid-Oxide Oxygen-Ion-Conducting Membrane (SOM): Direct Extraction of Ti-Fe Alloys from Natural Ilmenite

The direct electrochemical extraction of Ti-Fe alloys from natural ilmenite (FeTiO₃) in molten CaCl₂ is reported in this article. The sintered porous pellet of natural ilmenite acted as the cathode of the electrochemical system, and the carbon-saturated liquid tin contained in a solid-oxide oxygen-ion-conducting membrane (SOM) tube served as the anode of the electrolytic cell. The electrochemical process was carried out at 3.8 V, under 1223 K and 1273 K (950 °C and 1000 °C). Oxygen was ionized continuously from the cathode and discharged at the anode; solid porous Ti-Fe alloys were obtained at the cathode. The electro-deoxidation procedure of the ilmenite was characterized by analyzing partially electro-deoxidized samples taken periodically throughout the electro-deoxidation process. The findings of this study are as follows: (1) The electro-deoxidation process followed these steps: Fe₂TiO₅ → FeTiO₃ → Fe₂TiO₄ → Fe, Ti (and/or Ti-Fe alloys); and TiO₂ → CaTiO₃ → Ti; and (2) two types of particle growth pattern are observed in the experiments. The first pattern is characterized with particle fusion and second pattern is interconnection of particles to form porous structure. A microhole oxygen-ion-migration model is suggested based on the experimental evidence.