Revaluation of equilibrium quotient between titanium ions and metallic titanium in NaCl–KCl equimolar molten salt

In this study, the effect of oxide ion on the equilibrium between titanium ions and metallic titanium was investigated in NaCl–KCl equimolar molten salt. The soluble species containing Ti3+ and O2− was not confirmed in the molten salt by absorption spectroscopy. The result of XRD for the solidified sample containing Ti3+ and O2− implies that O2− reacts with Ti3+ and Cl− to form TiOCl(s). The concentration quotient of the equilibrium between titanium ions (Ti2+, Ti3+) and metallic Ti, Kc, was revaluated at 740 °C as follows:3Ti2+⇄2Ti3++Ti,Kc=8.0×10−2 mol L−1=1.2×10−1 mol kg−1.In addition, the solubility product of TiOCl(s) in NaCl–KCl equimolar molten salt, Ksp, at 700 °C was determined using the results of absorption spectra,Ksp=1.2×10−2 mol2 L−2=5.1×10−3 mol2 kg−2.Ksp=1.2×10−2 mol2 L−2=5.1×10−3 mol2 kg−2.

► In this study, the effect of O2− on the equilibrium between Ti2+, Ti3+ and Ti was investigated. ► We measured the concentration of O2− in NaCl–KCl equimolar molten salt. ► The solubility product of TiOCl(s) in the molten salt is 1.2 × 10−3 mol L−2 at 700 °C. ► The concentration quotient of the equilibrium is Kc=(CTi3+)2/(CTi2+)3=8.0×10−2 mol L−1Kc=(CTi3+)2/(CTi2+)3=8.0×10−2 mol L−1 at 740 °C.