Solubility of Some Transition Metal Oxides in Cryolite-Alumina Melts: Part II. Solubility of TiO_2

摘要

The solubility of TiO_2 in cryolite-alumina melts at 1020 deg C was measured; it decreased with increasing alumina concentration up to approx 3.5 wt pct total oxide and then increased at higher alumina concentrations. The solubility was found to be 3.1 wt pct Ti in cryolite, and 2.7 wt pct Ti in an alumina-saturated melt. Modeling indicated that the most probable titanium species are TiOF_2 and Na_2TiO_3, which coexist in the solution; the former dominates at low alumina concentrations and the latter at high alumina concentrations. Additional unknown amounts of fluoride may also be associated with these species. Determination of the solubility of TiO_2 in alumina-saturated melts as a function of temperature showed that the solubility increased from 1.9 wt pct Ti at 975 deg C to 2.8 wt pet Ti at 1035 deg C, the apparent partial molar enthalpy of dissolution of TiO_2 being 88 +- 4 kJ mol~(-1).