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ArticleName Cost-effective separation of rare earth concentrates
DOI 10.17580/tsm.2020.02.05
ArticleAuthor Valkov A. V.

National Research Nuclear University MEPhI, Moscow, Russia:

A. V. Valkov, Professor at the Department of General Chemistry, Doctor of Engineering Sciences, e-mail:


The rare earth metals (REMs) found in apatite, loparite and the concentrates from the Tomtor deposit may lay the basis for expanding the Russian rare earths industry. The most sellable REMs with an almost unlimited demand include neodymium, praseodymium, dysprosium and terbium. They account for ~80% of the extracted individual REMs sold. It is proposed to design a processing sequence enabling to extract the above elements at minimal cost reaching maximum purity. The rest of the REMs are considered a poorly sellable product. A sequence is proposed to separate REM concentrates recovered from loparite, apatite or the concentrate from the Tomtor deposit, which involves separation of praseodymium mixed with neodymium (didymium) and terbium mixed with dysprosium (dysterbium) with the concentration of the base material being 99.95–99.99 wt%. It was decided to use the system of 100% tributyl phosphate – Ln(NO3)3 – Са(NO3)2 — to separate didymium, and the organophosphorus acid (OPA) based system: i. e. 30% OPA – Ln(NO3)3 – HNO3 -to separate dysterbium. The author examined how the centrifugal coefficient, the pure component extraction ratio and the purity of extracted elements determine the required number of stages. The process consists of four extraction cascades. Separation at the praseodymium–cerium boundary is performed without pre-separation of cerium. To separate dysterbium, they separate holmium and heavier REMs in one cascade, and gadolinium and lighter REMs – in the second cascade. The following products are obtained as a result of separation: lanthanum-cerium concentrate, didymium, dysterbium, samarium-europium-gadolinium concentrate and a concentrate of yttrium REMs from holmium to lutecium.

keywords Rare earth metals, apatite, loparite, Tomtor, didymium, dysterbium, extraction, tributyl phosphate, di-2-ethylhexyl phosphoric acid, counter-current process

1. Kosynkin V. D., Trubakov Yu. M., Sarychev G. A. The past and the future of the rare earths industry in Russia. Eurasian Scientific Association. Avai lable at: Dmitrievich.pdf.
2. Ivashchenko V. I. Raw materials base of Preсambrian rare metals in Karelia: Current conditions and development prospects. Gornyi Zhurnal. 2019. No. 3. pp. 40–44.
3. Kuleshevich L. V., Dmitrieva A. V. Rare-earth mineralization in Karelia’s alkaline and moderately alkaline complexes, associated metasomatic rocks and ores. Gornyi Zhurnal. 2019. No. 3. pp. 45–50.
4. Savelieva I. L. Russian rare earths industry: Current status, available resources. Geografiya i prirodnye resursy. 2011. No. 1. pp. 122–129.
5. Manorik P. A., Pavlyukov A. A., Bukhtiyarov V. K. High-energy permanent magnets made from neodymium-iron-boron alloys: Chemistry, materials engineering, application. Kiev : Naukova dumka, 2013. 396 p.
6. Valkov A. V., Borisov N. I., Prilipko A. I., Milevskaya N. D. The industrial technology of didymium. Khimicheskaya tekhnologiya. 2010. No. 3. pp. 159–162.
7. Igumnov S. N., Valkov V. A. Separation of rare earth elements in the system of tributyl phosphate – Ln(NO3)3 – Ca(NO3)2 in the countercurrent process. Vestnik Moskovskogo universiteta. 2017. Vol. 58, No. 3. pp. 120–125.

8. Rare earth metals. Global market. 2017. Available at:
9. TU 2435-305-05763458–01. Commercial tributyl phosphate. Specifications. Introduced: 10.07.2001.
10. Acharya S., Nayak A. Separation of D2EHPA and M2EHPA. Hydrometallurgy. 1988. Vol. 19, No. 3. pp. 309–320.
11. Mikhlin E. B., Korpusov G. V. Rare earth elements of the cerium subgroup extracted with isoamyl ether of methylphosphonic acid. Zhurnal neorganicheskoy khimii. 1965. Vol. 10, No. 12. pp. 2787–2795.
12. Mikhlin E. B., Karmannikov V. P., Evteev V. V., Kazantsev V. N., Kovalev V. V., Leonov A. P., Klimenko M. A., Berezkina V. V. Method for extracting neodymium from a rare earth metal concentrate of the cerium subgroup. Patent RF, No. 2030463. Published: 10.03.1995.
13. Korpusov G. V., Eskevich I. V., Zhirov E. P. Group separation of rare earth elements by means of counter-current extraction. Extraction. Theory, application, equipment. Issue 1. Moscow : Gosatomizdat, 1962. pp. 125–142.
14. El Nadi Y. A. Effect of diluents on the extraction of praseodymium and samarium by Cyanex 923 from acidic nitrate medium. Journal of Rare Earths. 2010. Vol. 28, No. 2. pp. 215–220. DOI: 10.1016/S1002-0721(09)60083.
15. Shengting Kuang, Zhifeng Zhang, Yanling Li, Haiqin Wei, Wuping Liao. Synergistic extraction and separation of rare earths from chloride medium by the mixture of HEHAPP and D2EHPA. Hydrometallurgy. 2017. Vol. 174. pp. 78–83. DOI: 10.1016/j.hydromet.2017.09.011.
16. Junlian Wang, Guang Chen, Shengming Xu, Linyan Li. Synthesis of novel nonsymmetric dialkylphosphinic acid extractants and studies on their extraction–separation performance for heavy rare earths. Hydrometallurgy. 2015. Vol. 154. pp. 129–136.
17. Shaohua Yin, Jiannan Pei, Jinhui Peng, Libo Zhang, Srinivasakannan C. Study on mass transfer behavior of extracting La(III) with EHEHPA (P507) using rectangular cross-section microchannel. Hydrometallurgy. 2018. Vol. 175. pp. 64–69. DOI: 10.1016/j.hydromet 2017.10.027.
18. Carvalho Gomes, Paulo Sergio, Moreira Soares. Separation of rare earths by solvent extraction using DEHPA. Rem: Revista Escola de Minas. 2015. Vol. 68, No. 4. pp. 427–434.
19. Shengting Kuang, Zhifeng Zhang, Yanling Li, Haiqin Wei, Wuping Liao. Extraction and separation of heavy rare earths from chloride medium by -aminophosphonic acid HEHAPP. Journal of Rare Earths. 2018. Vol. 36, No. 3. pp. 304–310. DOI: 10.1016/j.jre.2017.09.007.
20. Dongbei Wu, Qian Zhang, Borong Bao. Synergistic Effects in Extraction and Separation of Praseodymium(III) and Neodymium(III) with 8-Hydroxyquinoline in the Presence of 2-Ethylhexyl Phosphonic Acid Mono-2-Ethylhexyl Ester. Industrial & Engineering Chemistry Research. 2007. Vol. 46, No. 19. pp. 6320–6325. DOI: 10.1021/ie070098r.
21. Xie F., Zhang T. A., Dreisinger D., Doyle F. A critical review on solvent extraction of rare earths from aqueous solutions. Minerals Engineering. 2014. Vol. 56. pp. 10–28.
22. The chemistry and technology of rare and trace elements. Part 2. Ed. by K. A. Bolshakov. Moscow : Vysshaya shkola, 1976. p. 91.
23. Bernstrom B., Rydberg J. Studies on the Extraction of Metal Complexes. XXVIII. The Distribution of some Actinides and Fission Products between Tributyl Phosphate (TBP) and Aqueous Solutions of HNO3 and Ca(NO3)2. Acta Chemica Scandinavica. 1957. Vol. 11, No. 7. pp. 1173–1182. DOI: 10.3891/acta.chem.scand.11-1173.
24. Korpusov G. V., Eskevich I. V., Patrusheva E. N., Erchenkov V. V., Alekseeva L. R. Regularities of extraction distribution of rare earth elements in neutral solutions. Extraction. Theory, application, equipment. Issue 2. Moscow : Gosatomizdat, 1962. pp. 117–140.
25. Radhika S., Kumar B. N., Kantam M. L., Reddy B. R. Liquid–liquid extraction and separation possibilities of heavy and light rare-earths from phosphoric acid solutions with acidic organophosphorus reagents. Separation and Purification Technology. 2010. Vol. 75, No. 3. pp. 295–302. DOI: 10.1016/j.seppur.2010.08.018.
26. Rabie K. A. A group separation and purification of Sm, Eu and Gd from Egyptian beach monazite mineral using solvent extraction. Hydrometallurgy. 2007. Vol. 85, No. 2-4. pp. 81–86. DOI: 10.1016/j.hydromet. 2005.12.012.
27. Wang Z. H., Ma G. X., Lu J., Li W. P., Li D. Q. Separation of heavy rare earth elements with extraction resin containing 1-hexyl-4-ethyloctyl isopropyl-phosphonic acid. Hydrometallurgy. 2002. Vol. 66, No. 1-3. pp. 95–99. DOI: 10.1016/S0304-386X(02)00109-3.
28. Valkov A. V. Method of separating gadolinium by extraction with phosphoroorganic compounds. Patent RF, No. 2518619. Published: 10.06.2014. Bulletin No. 16.

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