Institute of High-temperature Electrochemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

Yu. P. Zaykov, Director, e-mail: dir@ihte.uran.ru

V. P. Batukhtin, Senior Researcher

A. V. Suzdaltsev, Researcher

Nowadays, pure Ca is produced from the Cu – Ca alloy, which is electrolytically obtained in CaCl₂ – KCl melt or by metallothermal way with following vacuum distillation. Both methods require high energy consumption due to multistage. Therefore, improvement of existing technologies and development of new methods of pure Ca production are urgent. This work is devoted to definition of optimal electrorefining parameters of Cu – Ca alloy in molten CaCl₂. It is also aimed at the development of new process of pure Ca production in a single electrolyzer without the use of additional stage of vacuum distillation. The influence of conditions of electrolysis (copper content in Cu – Ca alloy anode, anode and cathode current density, temperature) on the values of cathode and anode current efficiency and cathode Ca purity was investigated in laboratory electrolyzer at the amperage of 20–80 A. It is shown that anode current efficiency is decreased during the decreasing of Ca content in Cu – Ca anode alloy. At the same time, cathode current efficiency is decreased during the increasing of the process temperature and anode current density. Maximum values of cathode current efficiency were obtained at the cathode current density of 4–8 A/cm₂ at 58–6 9% (wt.) of Ca in anode alloy. Primary and side reactions are described during the electrorefining of Cu – Ca alloy in molten CaCl₂. There is shown an influence of Ca – CaCl₂ solutions on the presence of side electrode or chemical reactions. The optimal parameters of Cu – Ca alloy electrorefining were obtained. Obtained and analyzed results can be used for development of new ecologically pure technologies of obtaining of metals (particularly, Ca) and alloys during the electrolysis of CaCl₂-based melts.

This work was carried out with the support of the Ministry of Education and Science of Russian Federation, agreement 2012-1.5-14-000-2025-007.

1. Kulifeev V. K., Kropachev A. N., Miklushevskiy V. V., Vatulin I. I. Tsvetnye Metally — Non-ferrous metals. 2004. No. 10. pp. 58–61.
2. Doronin N. A. Kaltsiy (Calcium). Moscow : Gosatomizdat, 1962. 191 p.
3. Rodyakin V. V. Kaltsiy, ego soedineniya i splavy (Calcium, its compounds and alloys). Moscow : Metallurgiya, 1967. 186 p.
4. Zaykov Yu. P., Shurov N. I., Suzdaltsev A. V. Vysokotemperaturnaya elektrokhimiya kaltsiya (High-temperature electrochemistry of calcium). Ekaterinburg : Editorship-Publishing Department of Ural Branch of Russian Academy of Sciences, 2013. 200 р.
5. Vostryakov A. A., Bykov A. S., Lepinskikh B. M. Zashchita metallov — Protection of Metals. 1981. No. 4. pp. 463–465.
6. Bredig M. A. Mixtures of metals with molten salts. Molten Salt Chemistry. Editor : M. Blender. New York : Interscience Publishers, 1964. pp. 367–425.
7. Richter D., Emons H.-H. Auflosung der Erdalkalimetalle in ihren geschmolzenen Halogeniden. Zeitschricht fur Chemie. 1966. Bd. 6. pp. 407–416.
8. Sharma R. A. The solubilities of calcium in liquid calcium chloride in equilibrium with calcium-copper alloys. Journal of Physical Chemistry. 1970. Vol. 74. pp. 3896–3900.
9. Dworkin A. S., Bronstein H. R., Bredig M. A. The electrical conductivity of solutions of metals in their molten halides. Journal of Physical Chemistry. 1966. Vol. 70. pp. 2384–2388.
10. Zaykov Yu. P., Kozhevnikov V. G., Ivanovskiy L. E. Rasplavy — Melts. 1989. No. 3. pp. 92–94.
11. Sychev A. G., Nikulin N. A., Zaykov Yu. P., Ivanovskiy L. E. Rasplavy — Melts. 1992. No. 6. pp. 32–37.
12. Kapusta A. B., Shamota V. P. Magnitnaya gidrodinamika — Magnetohydrodynamics. 1990. No. 4. pp. 131–134.