Song Jianxun, Wang Qiuyu, Wu Jinyu, Jiao Shuqiang, Zhu Hongmin
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing, 100083, China.
Faraday Discuss. 2016 Aug 15;190:421-32. 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: TiFi(3-i). The accurate values of the equilibrium constants referring to the formation reactions of Ti(3+) + iF(-) = TiFi(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+), TiF2(+), TiF4(-) and TiF6(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(-) = TiF6(2-), was evaluated. The equilibrium constant, Kc2, for the disproportionation reaction 4Ti(3+) = 3Ti(4+) + Ti, in chloride melt was determined as 0.015.
KF用作添加到熔体中的氟离子源，以揭示氟对钛离子歧化反应3Ti(2+) = 2Ti(3+) + Ti和4Ti(3+) = 3Ti(4+) + Ti的影响。结果表明，第一个反应的平衡向正方向移动，表观平衡常数急剧增加，主要是由于形成了配位化合物：TiFi(3-i)。采用最佳拟合最小二乘法评估了1023K下NaCl-KCl熔体中Ti(3+) + iF(-) = TiFi(3-i)（i = 1-6）形成反应的平衡常数准确值。还表明配位化合物的稳定状态为TiF(2+)、TiF2(+)、TiF4(-)和TiF6(3-)。此外，估算了络合物形成的吉布斯自由能。当氟离子浓度足够高时，Ti(2+)无法检测到。评估了形成反应Ti(4-) + 6F(-) = TiF6(2-)的平衡常数。确定了氯化物熔体中歧化反应4Ti(3+) = 3Ti(4+) + Ti的平衡常数Kc2为0.015。
