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

A. S. Medvedev, Professor of a Chair of Non-Ferrous Metals and Gold
R. T. Khayrullina, Assistant Professor of a Chair of Non-Ferrous Metals and Gold
S. S. Kirov, Assistant Professor of a Chair of Non-Ferrous Metals and Gold, e-mail: kirovs13@yandex.ru

LLC “RUSAL Engineering-Technical Center”, Saint-Petersburg, Russia:
A. G. Suss, Director of Technological Department of Engineering-Technological Directorate of Clayey Prodiuction

The possibility of production of scandium-containing compounds as the main target products made of industrial alumina production wastes (red mud) is of considerable interest. A suggested option is based on concentration of solution obtained by direct sulphuric acid leaching of red mud, or by carbonatebicarbonate leaching followed by the scandium hydroxide precipitation out of sodium solution and its dissolution in sulfuric acid. Precipitation of scandium as hydroxide allows the scandium separation from alkaline and alkaline-earth metals. Scandium extraction from scandiumcontaining solutions is carried out by the same methods (precipitation of slow-soluble compounds, extraction or sorption), independently of the solution obtaining method: sulphuric acid leaching or carbonate leaching of red mud. The ability of scandium extraction from the obtained solutions by precipitation, extraction and ion exchange depends on its concentration and impurity content. The process of the commercial purity scandium oxide extraction from evaporated sulphuric-acid solutions with concentration of scandium of more than 26 mg/l was investigated. Received solutions are directed to the scandium liquid-phase extraction with di-(2-ethylhexyl)phosphoric acid (DEHPA) and tributyl phosphate addition. The influence of the DEHPA concentration on scandium and ferrous behavior was shown, and the optimal extraction conditions were determined. Scandium fluoride is produced due to re-extraction. Its following dissolution in alkali and other operations result in producing of 95%-content scandium hydroxide. There is offered a flow diagram of the production of commercial purity scandium oxide based on the sodium carbonate technology for processing of Urals Aluminum Smelter red muds produced by the Bayer process.
This article was written within the implementation of the Agreement for subsidies No. 14.578.21.0014 of June 5, 2014. (Unique identifier of the Agreement: RFMEFI57814X0014) between National University of Science and Technology “MISiS” and the Ministry of Education and Science of Russian Federation within the realization of the Federal Target Program “Investigations and developments of priority ways of development of scientific-technological complex of Russia for 2014–2020”, approved by the Decree of the Government of Russian Federation of November 28, 2013, No. 1096.

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