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 calcium is produced from the copper-calcium 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 calcium production are urgent. This work is devoted to definition of optimal electrorefining parameters of copper-calcium alloy in molten CaCl₂. It is also aimed at the development of new process of pure calcium production in a single electrolyzer without the use of additional stage of vacuum distillation. The influence of conditions of electrolysis (copper content in copper-calcium alloy anode, anode and cathode current density, temperature) on the values of cathode and anode current efficiency and cathode calcium 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 calcium content in copper-calcium 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·cm^–2 at 58–69% (wt) of calcium in anode alloy. Primary and side reactions, during the electrorefining of coppercalcium alloy in molten CaCl₂, are described. There is shown an influence of Ca–CaCl₂ solutions on the presence of side electrode or chemical reactions. The optimal parameters of copper-calcium alloy electrorefining were obtained. Obtained and analyzed results can be used for development of new ecologically pure technologies of obtaining of metals (particularly, calcium) and alloys during the electrolysis of CaCl₂-based melts.

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