Electrorefining of titanium from Bi-Ti alloys in molten chlorides for a new smelting process of titanium

摘要

A new smelting process of Ti comprising magnesiothermic reduction of TiCl4 into liquid Bi and separation of Ti from Bi by electrorefining was proposed by our group. In this study, electrorefining of Ti from Bi-Ti alloys was investigated at 700 A degrees C using a Bi-Ti alloy anode and a Ni cathode in equimolar NaCl-KCl to which 1-5 mol% of TiCl2 was added. On the alloy anode, the oxidation of Ti occurred at more negative potentials than that of Bi, which allowed selective dissolution of Ti in the alloy. At the Ni cathode, metallic Ti powder was obtained without significant Bi contamination (below 180 ppm). In addition, the amount of Ti deposits decreased gradually by further electrorefining, eventually reaching an almost constant value. This phenomenon is attributed to an increase in the ratio of Ti3+ to Ti2+ in the electrolyte, and it was concluded that Ti in the alloy was oxidized mainly to Ti3+. For this reason, the current efficiency for Ti deposition was calculated to be 91-97 % assuming that Ti3+ was reduced to Ti on the cathode.