Kinetics of titanium and zirconium oxides dissolution in cryolite-alumina melt

Data on kinetics of dissolution of titanium and zirconium oxides in cryolite-alumina melt were obtained. Temperature dependences of dissolution rate of titanium and zirconium oxides in pure cryolite were studied as well. The apparent activation energy of dissolution process (Esub(p)), determined according to the slope of straigh lines in lg(V/ωsup(1/2))-1/T coordinates, equals consequently 115kJ/mol for TiO2 and 144.6 kJ/mol for ZrO2. The activation energy of alumina dissolution equals 88kJ/mol. Such difference means that the process of titanium and zirconium oxide dissolution in cryolite is rather impeded, as compared to alumina. This fact can be related with the formation of fluoride and oxyfluoride complexes, which transport from dissolution zone proceeds with considerable energetic difficulties, as compared to alumina dissolution