JSC “Giredmet”, Moscow, Russia:

A. A. Gasanov, Head of Department of Highly Purified Materials, Rare and Rare-Earth Metals, e-mail: A.A.Gasanov@giredmet.ru
O. V. Yurasova, Head of Laboratory
T. A. Kharlamova, Leading Researcher
A. F. Alaferdov, Senior Researcher

In industrial practice, cerium is often isolated on the first stages of processing of rare-earth metals in connection with its prevail content in rare-earth raw materials. Separation methods, based on its capability for oxidation to Ce (IV), are widely used for these purposes. Processes of Ce (III) oxidation with its following separation are widely used in industry. Electrochemical method is one of well-known and practically applied Се (III) oxidation methods. Electrochemically oxidized Ce (IV) is very stable, in contrast to the similar one, obtained by chemical method (particularly, oxidized by H₂O₂, mostly reduced for rather short time). This article shows the analysis of the given electrolyzer designs. There were defined the benefits of diaphragm electrolyzers, offered for Ce (III) oxidation process. Modern Russian model of diaphragm electrolyzer, chosen for researches of cerium electrochemical oxidation process, is detaily described. Information about the materials of electrodes, diaphragm and their configurations is given. Researches, carried out on standard test solutions, have shown the operational stability of unit and high Ce (III) oxidation current efficiency in nitrate solutions. For the four months of unit exploitation, there was defined the stable operation of electrochemical reactor in the given mode with Се (III) oxidation level in nitrate solutions to 98–99% with quantitative current efficiency. Electrical power consumption in optimal conditions is ~0.6 kW/h per 1 kg of Се (IV) oxide.
This work was carried out with co-financing of Ministry of Education and Science of Russian Federation within the agreement No.14.579.21.0049 of August 26, 2014 (unique identifier of application research studies (project) is RFMEFI57914X0049).

1. Lokshin E. P., Sedneva T. A., Kalinnikov V. T. Sposob polucheniya dioksida tseriya (Cerium dioxide obtaining method). Patent RF, No. 2341459, IPC C 01 F 17/00. Applier and patent-holder: I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials (Kola Science Center of Russian Academy of Sciences). Applied: May 02, 2004. Published: December 20, 2008. Bulletin No. 35.
2. Rudnev V. S., Yarovaya T. P., Nedozorov P. M. Sposob polucheniya smeshannykh oksidov tseriya i tsirkoniya (Method of obtaining of mixed cerium and zirconium oxides). Patent No. 2367519, IPC B 01 J 21/06. Applied: May 19, 2008. Published: September 20, 2009. Bulletin No. 26.
3. Chung Y. H., Park S.-M. Destruction of aniline by mediated electrochemical oxidation with Ce (IV) and Co (III) as mediators. Journal of Applied Electrochemistry. 2000. Vol. 30. pp. 685–691.
4. Korovin S. S., Zimina G. V., Reznik A. M., Bukin V. I. et al. Redkie i rasseyannye elementy. Khimiya i tekhnologiya (Rare and scattered elements. Chemistry and technology). Moscow : MISiS, 1996. Vol. 1. pp. 259–278.
5. Khimiya i tekhnologiya redkikh i rasseyannykh elementov. Chast 2 (Chemistry and technology of rare and scattered elements. Part 2). Under the editorship of K. A. Bolshakov. Moscow : Vysshaya shkola, 1976. 360 p.
6. Mikhaylichenko A. I., Mikhlin E. B., Patrikeev Yu. B. Redkozemelnye metally (Rare-earth metals). Moscow : Metallurgiya, 1987. 233 p.
7. Baulin A. A. Ekstraktsionnoe razdelenie redkozemelnykh elementov zhidkimi membranami v nestatsionarnykh usloviyakh : dissertatsiya … kandidata khimicheskikh nauk (Extraction separation of rare-earth elements by fluid membranes in unsteady conditions : dissertation … of Candidate of Chemical Sciences). Saint Petersburg : Saint Petersburg State Technological Institute, 2005. 126 p.
8. Sedneva T. A., Tikhomirova I. A. Okislenie tseriya v membrannom elektrolizere (Cerium oxidation in membrane electrolyzer). Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials (Kola Science Center of Russian Academy of Sciences). Apatity, 2002. Deposited in All-Russian Institute for Scientific and Technical Information (VINITI), August 12, 2002, No. 1475-V2002.
9. Gray J., Schneider A., Cormak A., Ayers A. Apparatus for electrolytic oxidation or reduction, concentration, and separation of elements in solution. Patent US, No. 3770612. Published : June 11, 1973.
10. Pozdeev S. S., Kondrateva E. S., Gubin A. F., Kolesnikov V. A. Elektrookislenie ionov tseriya (III) v elektrolizere membrannogo tipa (Electrical oxidation of cerium (III) ions in membrane-type electrolyzer). Uspekhi v khimii i khimicheskoy tekhnologii = Journal Adnvances in Chemistry and Chemical Technology. 2014. Vol. XVIII, No. 5. p. 98.
11. Strunnikov S. G. Izyskanie vozmozhnosti okisleniya tseriya na dvuokisnosvintsovykh anodakh (Search of possibilities of cerium oxidation on dioxidelead anodes). Publishing house Education and Science s.r.o. Available at: http://www.rusnauka.com/14_APSN_2008/Chimia/32608.doc.htm.
12. Bakhir V. M. Elektrokhimicheskaya modulnaya yacheyka dlya obrabotki rastvorov elektrolita (Electrochemical modular cabinet for processing of electrolyte solutions). Patent RF, No. 2516226, IPC C 25 B 9/00. Applied: February 21, 2012. Published : August 27, 2013. Bulletin No. 24.