Journal of Sustainable Metallurgy

, Volume 3, Issue 1, pp 73–78 | Cite as

Separation of Rare Earths by Solvent Extraction with an Undiluted Nitrate Ionic Liquid

  • Kristian Larsson
  • Koen Binnemans
Thematic Section: Green Rare Earth Elements--Innovations in Ore Processing, Hydrometallurgy, and Electrolysis


A solvent extraction system based on the ionic liquid tricaprylmethylammonium nitrate, [A336][NO3], has been investigated for separation of mixtures of rare earth elements (REE) at high total REE concentrations (up to 2 M). The chelating agent EDTA was added to the aqueous nitrate feed solution to increase the separation factors (SFs). This improvement of the SFs is based on the fact that [A336][NO3] extracts the light REE (LREE) stronger than the heavy REE (HREE), whereas a chelating agent forms more stable complexes with the HREE than with the LREE. The combination of these two effects makes that the LREE are even more efficiently extracted than in the absence of a chelating agent. The most efficient separation of the LREE La–Nd from the other REE was obtained using a total initial REE concentration of 1 M, an EDTA concentration of 0.2 M, and a total nitrate concentration of 11 M. Stripping of the extracted REE from the ionic liquid phase could be done using water.


Ionic liquids Hydrometallurgy Lanthanides Rare earths Solvent extraction 



The research leading to these results has received funding from the European Community’s Seventh Framework Programme ([FP7/2007–2013]) under Grant Agreement No. 309373 (EUARE). This publication reflects only the authors’ view, exempting the Community from any liability.


  1. 1.
    Dietz M (2006) Ionic liquids as extraction solvents: Where do we stand? Sep Sci Technol 41:2047–2063. doi: 10.1080/01496390600743144 CrossRefGoogle Scholar
  2. 2.
    Kolarik Z (2013) Ionic liquids: How far do they extend the potential of solvent extraction of f-elements? Solvent Extr Ion Exch 31:24–60. doi: 10.1080/07366299.2012.700589 CrossRefGoogle Scholar
  3. 3.
    Liu Y, Chen J, Li D (2012) Application and perspective of ionic liquids on rare earths green separation. Sep Sci Technol 47:223–232. doi: 10.1080/01496395.2011.635171 CrossRefGoogle Scholar
  4. 4.
    Earle MJ, Seddon KR (2000) Ionic liquids, green solvents for the future. Pure Appl Chem 72:1391–1398. doi: 10.1351/pac200072071391 CrossRefGoogle Scholar
  5. 5.
    Wellens S, Thijs B, Binnemans K (2012) An environmentally friendlier approach to hydrometallurgy: highly selective separation of cobalt from nickel by solvent extraction with undiluted phosphonium ionic liquids. Green Chem 14:1657–1665. doi: 10.1039/C2GC35246J CrossRefGoogle Scholar
  6. 6.
    Mikhailichenko AI, Goryacheva EG, Sokolova NP, Aksenova NM, Vdovina LV, Emelyanov AP (1984) Extraction of rare-earth elements from chloride solutions by salts of quaternary ammonium bases. Sov Radiochem 26:25–29Google Scholar
  7. 7.
    Khopkar PK, Mathur JN (1981) Extraction of trivalent actinides and lanthanides by tertiary and quaternary amines from concentrated chloride solutions. J Inorg Nucl Chem 43:1035–1040. doi: 10.1016/0022-1902(81)80170-4 CrossRefGoogle Scholar
  8. 8.
    Larsson K, Ekberg C, Ødegaard-Jensen A (2012) Using Cyanex 923 for selective extraction in a high concentration chloride medium on nickel metal hydride battery waste. Hydrometallurgy 129–130:35–42. doi: 10.1016/j.hydromet.2012.08.011 CrossRefGoogle Scholar
  9. 9.
    Černá M, Volaufová E, Rod V (1992) Extraction of light rare earth elements by amines at high inorganic nitrate concentration. Hydrometallurgy 28:339–352. doi: 10.1016/0304-386X(92)90039-3 CrossRefGoogle Scholar
  10. 10.
    Morais CA, Ciminelli VS (2007) Selection of solvent extraction reagent for the separation of europium(III) and gadolinium(III). Miner Eng 20:747–752. doi: 10.1016/j.mineng.2007.02.010 CrossRefGoogle Scholar
  11. 11.
    Lu D, Horng J, Hoh Y (1989) The separation of neodymium by quaternary amine from didymium nitrate solution. J Less Common Met 149:219–224. doi: 10.1016/0022-5088(89)90489-X CrossRefGoogle Scholar
  12. 12.
    Bauer DJ, Lindstrom RE (1971) Differential extraction of rare-earth elements in quaternary ammonium compound-chelating agent systems. Bureau of Mines Report of Investigations 7524Google Scholar
  13. 13.
    Komasawa I, Hisada K, Miyamura M (1990) Extraction and separation of rare-earth elements by tri-n-octylmethylammonium nitrate. J Chem Eng Jpn 23:308–315. doi: 10.1252/jcej.23.308 CrossRefGoogle Scholar
  14. 14.
    Preston J (1996) The recovery of rare earth oxides from a phosphoric acid by-product. Part 3. The separation of the middle and light rare earth fractions and the preparation of pure europium oxide. Hydrometallurgy 42:151–167. doi: 10.1016/0304-386X(95)00079-V CrossRefGoogle Scholar
  15. 15.
    Bauer DJ, Lindstrom RE (1967) Selective extraction and separation of lanthanides with a quaternary ammonium compound. US Patent 3,323,857Google Scholar
  16. 16.
    Gaudernack B, Hannestad G, Hundere I (1974) Process for separation of yttrium from lanthanides. US Patent 3,821,352Google Scholar
  17. 17.
    Trimble C, Strott D (1972) Yttrium purification process. US Patent 3,640,678Google Scholar
  18. 18.
    Vander Hoogerstraete T, Binnemans K (2014) Highly efficient separation of rare earths from nickel and cobalt by solvent extraction with the ionic liquid trihexyl(tetradecyl)phosphonium nitrate: process relevant to the recycling of rare earths from permanent magnets and nickel metal hydride batteries. Green Chem 16:1594–1606. doi: 10.1039/C3GC41577E CrossRefGoogle Scholar
  19. 19.
    Rout A, Binnemans K (2014) Solvent extraction of neodymium(III) by functionalized ionic liquid trioctylmethylammonium dioctyl diglycolamate in fluorine-free ionic liquid diluent. Ind Eng Chem Res 53:6500–6508. doi: 10.1021/ie404340p CrossRefGoogle Scholar
  20. 20.
    Larsson K, Binnemans K (2014) Selective extraction of metals using ionic liquids for nickel metal hydride battery recycling. Green Chem 16:4595–4603. doi: 10.1039/C3GC41930D CrossRefGoogle Scholar
  21. 21.
    Larsson K, Binnemans K (2015) Metal recovery from nickel metal hydride batteries using Cyanex 923 in tricaprylmethylammonium nitrate from chloride aqueous media. J Sustain Metall 1:161–167. doi: 10.1007/s40831-015-0017-5 CrossRefGoogle Scholar
  22. 22.
    Larsson K, Binnemans K (2015) Separation of rare earths by split-anion extraction. Hydrometallurgy 156:206–214. doi: 10.1016/j.hydromet.2015.04.020 CrossRefGoogle Scholar
  23. 23.
    Riano S, Binnemans K (2015) Extraction and separation of neodymium and dysprosium from used NdFeB magnets: an application of ionic liquids in solvent extraction towards the recycling of magnets. Green Chem 17:2931–2942. doi: 10.1039/C5GC00230C CrossRefGoogle Scholar
  24. 24.
    Larsson K, Binnemans, K (2014) Applying ionic liquid to rare earth separations. In: Proceedings of the 1st European rare earth resources conference (ERES 2014), Milos, Greece, 4–7 September 2014, p 278–290Google Scholar
  25. 25.
    ERECON (2015) Strengthening the European rare earths supply-chain: challenges and policy options. In: Kooroshy J, Ties G, Tukker A, Walton A (eds) A report by the European Rare Earths Competency Network (ERECON)Google Scholar
  26. 26.
    Reed GC (2011) NI 43-101 technical report, Norra Kärr REE—zirconium deposit. Pincock, Allen and Holt, GrännaGoogle Scholar
  27. 27.
    Sjöqvist ASL, Cornell DH, Andersen T, Erambert M, Ek M, Leijd M (2013) Three compositional varieties of rare-earth element ore: eudialyte-group minerals from the Norra Kärr alkaline complex, Southern Sweden. Minerals 3:94–120. doi: 10.3390/min3010094 CrossRefGoogle Scholar
  28. 28.
    Vander Hoogerstraete T, Jamar S, Wellens S, Binnemans K (2014) Determination of halide ions in solution by total reflection X-ray fluorescence (TXRF) spectrometry. Anal Chem 86:3931–3938. doi: 10.1021/ac403583u CrossRefGoogle Scholar

Copyright information

© The Minerals, Metals & Materials Society (TMS) 2016

Authors and Affiliations

  1. 1.Department of ChemistryKU LeuvenHeverleeBelgium

Personalised recommendations