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

Abstract

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 Ti^[3+] and O^[2−] was not confirmed in the molten salt by absorption spectroscopy. The result of XRD for the solidified sample containing Ti^[3+] and O^[2−] implies that O2− reacts with Ti^[3+] and Cl^− to form TiOCl(s). The concentration quotient of the equilibrium between titanium ions (Ti^[2+], Ti^[3+]) and metallic Ti, Kc, was revaluated at 740℃ as follows:3Ti^[2+]⇄2Ti^[3+]+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℃ was determined using the results of absorption spectra, Ksp=1.2×10^[−2] mol^2 L−2=5.1×10^[−3] mol^2 kg^[−2].