2022-Sustainable Industrial Processing Summit
SIPS2022 Volume 4 Kipouros Intl. Symp. Molten Salt, Ionic & Glass-forming Liquids & Powdered Materials
| Editors: | F. Kongoli, R. Fehrmann, V. Papangelakis, I.Paspaliaris, G. Saevarsdottir. |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2022 |
| Pages: | 100 pages |
| ISBN: | 978-1-989820-40-7(CD) |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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ELECTRICAL CONDUCTIVITY of ZrCl4 and HfCl4 SOLUTIONS in MOLTEN KCl
Alexander Salyulev1; Alexei Potapov1;1INSTITUTE OF HIGH TEMPERATURE ELECTROCHEMISTRY, Ekaterinburg, Russian Federation;
Type of Paper: Regular
Id Paper: 40
Topic: 13
Abstract:
KEYWORDS: Molten salt; Mixtures; KCl-ZrCl4; KCl-HfCl4; Electrical conductivity. To perfect the technological processes of electrodeposition and electrorefining of zirconium and hafnium, information on the electrical conductivity of ZrCl4 and HfCl4 solutions in molten alkali metal chlorides is needed. The electrical conductivity of KCl-MCl4 (M = Zr or Hf) melts, containing volatile ZrCl4 and HfCl4 up to 25–30 mol. %, was studied in the temperature range of 900-1100 K, at which the vapor pressure above the melt is less than 1 atm. Such melts are of interest for industrial use.
It was found that the electrical conductivity increases as the temperature increases and that it decreases as the MCl4 concentration increases. When interacting with molten KCl, the ZrCl4 and HfCl4 molecules ionize with the formation of strong octahedral ZrCl62- and HfCl62- anions [1]. Thus, as the concentration of MCl4 in molten alkali metal chlorides increases, the concentration of nonmobile MCl62- complexes containing six strongly bound chlorine anions increases. This leads to a decrease in the concentration of electricity carriers. The proportion of K+ and, especially, Cl- - ions decreases and, accordingly, decreases the conductivity of the melts. The specific electrical conductivity (κ, S/cm) isotherms at 1073 K of KCl-ZrCl4 and KCl-HfCl4 molten mixtures is exemplified below depending on the concentration of ZrCl4 or HfCl4 (mol. %), respectively:
k = 2.2394 - 7.7639*10-2 [ZrCl4] + 1.3656*10-3 [ZrCl4]2,
k = 2.2373 - 7.7800*10-2 [HfCl4] + 1.2902*10-3 [HfCl4]2.
The relative decrease in electrical conductivity with increasing MCl4 concentration is more pronounced in the case of HfCl4, since Hf(IV) forms stronger complex chloride anions than Zr(IV) in molten KCl.
It has been established that the values of electrical conductivity of the melts studied in this work are significantly higher (0.89–1.65 S/cm) than those of the previously studied low-melting mixtures of zirconium tetrachloride with KCl (0.23–0.33 S/cm) with the high ZrCl4 content of 65-72 mol. % [2, 3], which are also promising for industrial use.
Keywords:
Chloride; Conductivity; Moltensalt; Potassium;References:
[1] A.B. Salyulev, I.D. Zakiryanova, E.G. Vovkotrub, Rasplavy (Melts) 5 (2012) 53-61 (in Russian). [2] A.B. Salyulev, V.A. Khokhlov, A.A. Redkin, Russ. Metallurgy (Metally) 2014 (2014) 859-863. [3] A.B. Salyulev, A.M. Potapov, Z. Naturforsch. 73a (2018) 259-263.