Electrochemical Behaviour of Dissolved Titanium Oxides during Aluminium Deposition from Molten Fluoride Electrolytes

A small but significant amount of dissolved titanium is always present in the molten cryolite based electrolyte used during electrowinning of aluminium. The fact that titanium can appear in several oxidation states may be a cause for reduced current efficiency for aluminium, although codepositon of titanium should be thermodynamically favoured. Voltammetric studies were carried out in molten Na3AlF6 - Al2O3 (sat) containing TiO2 at 1020℃. The results suggested that titanium was reduced in two steps from Ti (IV) to Ti (III) followed by reduction of Ti (III) to Ti metal.