The influence of fluoride ions on the equilibrium between titanium ions and titanium metal in fused alkali chloride melts

• Published in: Faraday discussions Vol. 19; pp. 421 - 432
• Main Authors: Song, Jianxun, Wang, Qiuyu, Wu, Jinyu, Jiao, Shuqiang, Zhu, Hongmin
• Format: Journal Article
• Language: English
• Published: England 2016
• Subjects: Chemical equilibrium; Chlorides; Coordination compounds; Disproportionation; Fluorides; Formations; Melts; Titanium
• ISSN: 1359-6640; 1364-5498
• DOI: 10.1039/c6fd00007j

KF is employed as a source of fluoride ions added to the melt to disclose the influence of fluoride on the disproportionation reactions of titanium ions, 3Ti 2+ = 2Ti 3+ + Ti, and 4Ti 3+ = 3Ti 4+ + Ti. The results reveal that the equilibrium transferred to the right direction for the first reaction and the apparent equilibrium constant increased sharply, mainly because of the formation of coordination compounds: TiF i 3− i . The accurate values of the equilibrium constants referring to the formation reactions of Ti 3+ + i F − = TiF i 3− i ( i = 1-6) in NaCl-KCl melt at 1023 K were evaluated with a best fit least squares method. It is also revealed that the stable states of the coordination compounds are TiF 2+ , TiF 2 + , TiF 4 − and TiF 6 3− . Moreover, the Gibbs free energies for complex formation were estimated. Ti 2+ was undetectable when the concentration of fluoride ion was high enough. The equilibrium constant for the formation reaction, Ti 4− + 6F − = TiF 6 2− , was evaluated. The equilibrium constant, K c2 , for the disproportionation reaction 4Ti 3+ = 3Ti 4+ + Ti, in chloride melt was determined as 0.015.