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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ELECTRICAL CONDUCTIVITY OF MOLTEN (LiCl-KCl)eut.- HfCl4 MIXTURES
Alexander Salyulev1; Alexei Potapov1;1INSTITUTE OF HIGH TEMPERATURE ELECTROCHEMISTRY, Ekaterinburg, Russian Federation;
Type of Paper: Regular
Id Paper: 171
Topic: 13
Abstract:
Electrical conductivity is one of the most important properties required for a competent organization of electrolytic processes in molten salts media; in particular, the processes of the production and refining of metallic hafnium and its separation from zirconium. The separation of zirconium and hafnium is especially important because they have very different thermal neutron capture cross sections: Zr value is ~0.18 barn, Hf value is 115 barns. Both elements are used in nuclear engineering.
Previously, in a series of experimental works, we measured the electrical conductivity of zirconium tetrachloride solutions in various molten alkali metal chlorides [1–5]. In this work, we measured for the first time the electrical conductivity of molten HfCl4 mixtures with a low-melting solvent (LiCl-KCl)eut. A special attention was paid to the purity of the salts used. The measurements were carried out in a capillary-type quartz cell of a special design [4, 5] with a constant within the range of 95.2–91.9 cm–1. The resistance of the molten mixtures was recorded using an R-5058 AC bridge at a frequency of 10 kHz. The concentration of HfCl4 ranged from 0 to 30 mol.%, and the temperature varied from 780 to1063 K.
With increasing temperature, the values electrical conductivity of molten (LiCl-KCl)eut.-HfCl4 mixtures increased from 0.86 to 2.08 S/cm as a result of an increase in the mobility of ions (simple and complex) and a decrease in the viscosity of the melt. As the HfCl4 concentration increased, the electrical conductivity decreased.
A molecular melt of pure hafnium tetrachloride, consisting of HfCl4 and Hf2Cl8 molecules, has a high saturated vapor pressure (45-60 atm) and a very low electrical conductivity (5-7)∙10-6 S/cm [6]. When interacting with molten alkali metal chlorides, HfCl4 molecules are ionized and form strong complex anions HfCl62- that displace alkali cations into the second coordination sphere. When the HfCl4 concentration increased to 33 mol. %, the concentration of relatively weakly mobile complex groups HfCl62- increased. These groups contain 6 chlorine anions and are quite firmly bound to the four-charged metal. The concentrations of the main current carriers: Li+, K+ and especially mobile Cl- anions decreased more and more. This led to a decrease in the electrical conductivity of the melts. The previously studied molten (LiCl-KCl)-ZrCl4 mixture illustrated a smaller decrease in the electrical conductivity at the increase in the tetrachloride concentration as opposed to the hafnium-containing mixtures. This indicates a lower strength of the ZrCl62- complexes compared to HfCl62- complexes.