National University of Science and Technology MISiS, Moscow, Russia:

A. P. Lysenko, associate professor of the Department of Non-ferrous metals and gold, e-mail address: reikis@yandex.ru
E. S. Kondrateva, post-graduate student of the Department of Non-ferrous metals and gold
S. Yu. Shilovskiy, Researcher of the Department of Non-ferrous metals and gold

The possibility of applying acid methods for the processing of kaolin clays, which are the raw material for the production of metallurgical alumina, is analyzed. Moreover, the technology of separation of aluminum and iron chlorides by the salting out method is investigated. A number of significant shortcomings were revealed. A method for electrochemical purification of the aluminum chloride solution from iron with possible regeneration of hydrochloric acid is proposed. The requirements for the electrode materials are analyzed. The electrochemical process of decomposition of an alumina chloride solution with formation of chlorine, hydrogen and iron on the corresponding electrodes is investigated. The behavior of chlorine during electrochemical decomposition of an alumina chloride solution is analyzed. Laboratory studies of the purification process of the alumina chloride solution showed that increasing the anode current density from 0.01 to 0.1 A/cm² enables to achieve a yield of 98% chlorine flow. The possibility of secondary reactions at the anode with the formation of oxychlorides of the type Al₂(OH)_nCl_{6 – n} was revealed. Technological solutions that allow controlling the anode process and eliminating the possibility of formation of Al₂(OH)_nCl_{6 – n} are proposed. Optimal regimes and parameters of the electrochemical purification process of the alumina chloride solution are presented. It was revealed that the greatest efficiency of the purification process of the alumina chloride solution occurs at the cathode current density of 0.01 to 0.15 A/cm². A schematic diagram of an apparatus for producing aluminum hydroxide by an electrochemical method is proposed. The apparatus consists of an electrolysis bath, a preparatory and a collection tank. The steel and titanium electrodes were introduced into the bath to perform the electrochemical task. The required temperature was set and maintained using a flow heater. The acidity and temperature of the solution were conti nuously monitored. The laboratory investigations of the electrochemical purification of alumina chloride solutions revealed the possibility of obtaining aluminum hydroxide with a residual iron content of less than 0.005% in the solution.
The work was carried out with the financial support of the Ministry of Education and Science of the Russian Federation within the framework of fulfilling the obligations under the Agreement on granting a subsidy from November 02, 2015 No. 14.581.21.0019 (code “Glinozem”).

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