Solvent extraction of europium(III) from technogenic solutions with the use of surfactants

Objectives. The extraction and separation of rare-earth metals is a complicated process that requires a multidisciplinary and detailed investigation. Liquid-liquid extraction with the use of surfactant, along with the thermodynamic analysis of the parameters is considered a promising approach. The extraction and separation of rare-earth metals from low-concentration solutions represents an attractive research opportunity. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates has been experimentally studied. This work focuses on the study of fundamental and alternative sources of rare-earth metals and their extraction and separation.

Methods. The extraction was performed on a top drive ES-8300 D equipment for 30 min at about 700 rpm. Infrared spectroscopy (Nicolet 6700 spectrometer) was used to determine the type of salts extracted into the organic phase. Extraction was studied in solutions with single cations and with a combination of the target element and interfering cations. For the latter, the concentrations of extracted elements in the aqueous phase were determined by optical emission spectroscopy with inductively coupled plasma on an ICPE-9000 (Shimadzu) spectrometer. The spectrometer was calibrated using standard samples for ICP CertiPUR (Merck).

Results. The dependence of the distribution and separation coefficients of rare-earth metals during extraction on the pH value of the aqueous phase at equilibrium was investigated. Moreover, the form in which the elements are extracted was analyzed based on thermodynamic parameters. The minimum concentration of the target component in the aqueous phase was observed at pH 4.0. In general, the dependence of the distribution coefficient on the pH value of the medium is poorly expressed over the entire range of the pH range of the water phase. Based on the spectra of spent and pure isooctyl alcohol, it was concluded that europium dodecyl sulfates are extracted into the organic phase as Eu(C₁₂H₂₅OSO₃)₃ solvates.

Conclusions. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates was demonstrated. The advantages of the proposed method are the possibility of selective extraction of the target component from dilute solutions and the use of an easily available surfactant (sodium dodecyl sulfate). The efficiency of extraction of europium dodecyl sulfates was maximal in the pH range from 2.0 to 7.5, which reflects a weak dependence on the acidity of the aqueous phase. In addition, in the highly alkaline pH region, the extraction efficiency is reduced.

1. Sharaf M., Yoshida W., Kubota F., Goto M. Selective Extraction of Scandium by a Long Alkyl Chain Carboxylic Acid/Organophosphonic Ester Binary Extractant. Solvent Extr. Ion Exc. 2018;36(7):647-657. https://doi.org/10.1080/07366299.2018.1532139

2. Kostikova G.V., Zhilov V.I., Tsivadze A.Y., Sal’nikova E.V. Use of carboxylic acids in the extractive conversion of rare earth chlorides into nitrates. Russ. J. Inorg. Chem. 2017;62(7):1003-1006. https://doi.org/10.1134/S0036023617070105

3. Wang Y., Wang Y., Su X., Zhou H., Sun X. Complete separation of aluminium from rare earths using two-stage solvent extraction. Hydrometallurgy. 2018;179:181-187. https://doi.org/10.1016/j.hydromet.2018.06.004

4. Roy S., Basu S. Synergistic extraction of cerium(III)- oxinates in presence of tributyl phosphine oxide. J. Indian Chem. Soc. 2015;92(8):1199-1206.

5. Pyartman A.K., Kopyrin D.A., Zhikharev A.A. Extraction of Lanthanide(III) and Yttrium(III) Nitrates with a Toluene Solution of Trialkylbenzylammonium Naphthenate. Russ. J. Appl. Chem. 2003;76(1):55-59. https://doi.org/10.1023/A:1023335615099

6. Pyartman A.K., Lishchuk V.V., Keskinov V.A. Extraction of thorium(IV), lantanum(III), and yttrium(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylamine. Russ. J. Appl. Chem. 2006;79(8):1266-1270. https://doi.org/10.1134/S107042720608009X

7. Wang Y., Ge J., Zhuo W., Guo S., Zhang J. Electrochemical extraction of lanthanum in molten fluoride salts assisted by KF or NaF. Electrochem. Commun. 2019;104:106468. https://doi.org/10.1016/j.elecom.2019.05.017

8. Cánovas C.R., Chapron S., Arrachart G., PelletRostaing S. Leaching of rare earth elements (REEs) and impurities from phosphogypsum: A preliminary insight for further recovery of critical raw materials. J. Clean. Prod. 2019;219:225-235. https://doi.org/10.1016/j.jclepro.2019.02.104

9. Kabangu M.J., Lubbe S.J., Crouse P.L. Extraction and Separation of Zirconium Using 1-Octanol. Mining, Metallurgy & Exploration. 2020;37(1):93-100. https://doi.org/10.1007/s42461-019-0089-z

10. Lemlich R. Adsorptive bubble separation techniques. N-Y., London: Academic Press; 1972. 244 р.

11. Chirkst D.E., Lobacheva O.L., Dzhevaga N.V. Thermodynamic properties of lanthanum(III) and holmium(III) hydroxo compounds. Russ. J. Phys. Chem. A. 2011;85(11):1872-1875. https://doi.org/10.1134/S0036024411110057

12. Chirkst D.E., Lobacheva O.L., Berlinskii I.V. The thermodynamic properties of hydroxo compounds and the mechanism of ion flotation for cerium, europium, and yttrium. Russ. J. Phys. Chem. A. 2009;83(12):2022-2027. https://doi.org/10.1134/S0036024409120036

13. Ksenofontov B.S. Simulation of wastewater treatment in flotation machine. In: AIP Conference Proceedings. 2019;2195(1):020070. https://doi.org/10.1063/1.5140170

14. Kubota F., Goto M. Application of ionic liquids for rare-earth recovery from waste electric materials. In book: Waste Electrical and Electronic Equipment Recycling: Aqueous Recovery Methods. 2018. P. 333-356. https://doi.org/10.1016/B978-0-08-102057-9.00012-3

15. Ivanenko V.I., Korneikov R.I., Lokshin,E.P., Petrov A.M. Ion-exchange processes in deactivated liquid radioactive waste. Ekologia i promyshlennost Rossii = Ecology and Industry of Russia. 2018;22(1):20-25 (in Russ.). https://doi.org/10.18412/1816-0395-2018-1-20-25

16. Kumari A., Singh S., Parmar K., Pathak D.D., Jha M.K. Treatment of monazite processed effluent to recover rare earth metals (REMs). J. Ind. Eng. Chem. 2020;83:421-429. https://doi.org/10.1016/j.jiec.2019.12.015

17. Bugrieva E.P., Dyakin V.I., Selivanovskiy А.K., Trubakov Y.M. Understanding the possibility of extracting easily recoverable rare metals from niobium/rare earth ores of the Tomtor deposit. Tsvetnye Metally. 2020;(2):50-56. https://doi.org/10.17580/tsm.2020.02.06

18. Smirnova E., Lutskiy D. Improving the efficiency of purification in the technological cycles of limestone processing. ARPN Journal of Engineering and Applied Sciences (ARPNJEAS). 2019;14(12):2306-2309.