School of Non-Ferrous Metals and Material Science, Siberian Federal University, Krasnoyarsk, Russia:

I. M. Moiseenko, Master’s Student, e-mail: ilya9.97@mail.ru
A. S. Yasinskiy, Associate Professor at the Department of Non-Ferrous Metallurgy, Candidate of Technical Sciences, e-mail: ayasinskiykrsk@gmail.com
P. V. Polyakov, Professor at the Department of Non-Ferrous Metallurgy, Doctor of Chemical Sciences, e-mail: p.v.polyakov@mail.ru
D. Yu. Varyukhin, Postgraduate Student

The current three-layer aluminium refining process consumes a great amount of energy. Due to the need to save energy and because of a great interest to the recycling of off-grade aluminium scrap, the effort of developing a process for thin-layer refining of metals is of relevance today. This paper examines the kinetics of thin-layer refining in a single-capillary cell. Experiments were conducted in a cell with a capillary with the diameter of 1.5 mm and the length of 1 mm, with NaCl – KCl – AlF₃ (3 wt.%) used as electrolyte and an aluminium-coated tungsten rod – as reference electrode. Electrochemical measurements were made by means of chronopotentiometry. The design current density i limits varied between 0.70 and 1.62 A/cm² at the total voltage of ~0.2 V, whereas the mass-transfer coefficient was about 3.3·10^–5 m/s at the temperature of 890 ^oC. Based on the results of the experiments it was concluded that the capillary cell can be used to obtain reproducible polarization curves in thin layers of ion melts. This enables to broaden the range of studied salt systems and metals aimed at implementing the thin-layer refining process. The il values obtained suggest that the refining process has high performance. However, reduction of alkaline metals together with aluminium may affect the process stability and the purity of the resulting metal. The thin-layer electrolyte system offer potential. However, before it can be adopted on a commercial scale, more research is needed in order to define optimum process parameters, which include current density, dimensions of capillaries and electrolyte composition.
This research was funded by the Krasnoyarsk Krai Foundation Supporting Research and Engineering under the following project: Energy-Efficient Production of High-Purity Metals. Application Code: 2020092506647.

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