2024 - Sustainable Industrial Processing Summit
SIPS 2024 Volume 16. Intl. Symp on Electrochemistry, Molten Salts, Corrosion, Recycling and Battery
| Editors: | F. Kongoli, C.A. Amatore, R. Fehrmann, G. Kipouros, I. Paspaliaris, G. Saevarsdottir, R. Singh, R. Gupta, M. Halama, D. Macdonald, F. Wang, M. Barinova, F. Ahmed, C. Gaidau, X. Guo, K. Kolomaznik, H. Ozgunay, K. Tang, N.N. Thanh, S. Yefremova, K. Aifantis, Z. Bakenov, C. Capiglia, V. Kumar, A. U. H. Qurashi, A. Tressaud, R. Yazami |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2024 |
| Pages: | 243 pages |
| ISBN: | 978-1-998384-34-1 (CD) |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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VOLATILITY OF UCl4, ThCl4, HfCl4, ZrCl4, AND TiCl4 FROM THEIR MOLTEN MIXTURES WITH ALKALI METAL CHLORIDES AND SATURATED VAPOR COMPOSITION
Alexander Salyulev1; Alexei Potapov1; Vladimir Kudyakov1;1INSTITUTE OF HIGH TEMPERATURE ELECTROCHEMISTRY, Ekaterinburg, Russian Federation;
Type of Paper: Regular
Id Paper: 172
Topic: 13
Abstract:
The changes in the saturated vapor composition and the volatility of the components of molten mixtures of uranium and some other metal tetrachlorides (ThCl4, HfCl4, ZrCl4, TiCl4) with alkali metal chlorides as functions of the temperature, concentration and cationic composition of the melts are discussed using our experimental data and those obtained by other researchers, mainly employees of the Institute of High-Temperature Electrochemistry (Ural Branch, Russian Academy of Sciences).
Like many other high-valence chemical elements, tetravalent uranium acts as a powerful complexing agent in molten alkali metal chlorides; hence, its dissolution is accompanied by substantial rearrangements of bonds of particles leading to the formation of stable complex anions: MeCl_7^(3-), MeCl_6^(2-), Me_2 Cl_10^(2-) (Me - U, Th) and MeCl_6^(2-) (Me - Hf, Zr, Ti) at the concentrations up to 50 or 33 mol % MeCl4, respectively. The complex formation is manifested as a sharp decrease in the saturated vapor pressure of the components of the molten mixtures due to which not only uranium tetrachloride but also such volatile compounds as ThCl4, HfCl4, ZrCl4, and TiCl4 are retained in solutions even at high temperatures. The strength of complex anions increases with decreasing temperature and concentration of the corresponding tetrachloride and under the counterpolarizing action of alkaline cations in the series from Li+ to Cs+ on chlorine anions in the complex chloride groups. As a result, the volatilities of UCl4, ThCl4, HfCl4, ZrCl4, andTiCl4 and the composition of vapors above the solutions in the ionic melts vary over broad ranges.
A decrease in the volatility of tetrachloride results in a decrease in its content in the saturated vapors over the melts. Hafnium, zirconium, and titanium tetrachlorides (especially TiCl4) are significantly more volatile in the individual state than UCl4 andThCl4 and have higher volatilities and contents in the saturated vapors over the solutions in molten alkali metal chlorides. The vapor over solutions in molten metal chlorides of titanium tetrachloride, which has the highest volatility among the considered tetrachlorides, almost completely consists of its molecules only.
The temperature, concentration, and composition dependences of the saturated vapor pressures and volatilities of the components of solutions of uranium, thorium, hafnium, zirconium, and titanium tetrachlorides can be used as reference material for the organization of diverse pyrometallurgical and pyrochemical (e.g. electrolytic) processes based on salt melts.