Liquid–liquid extraction of neodymium ions from aqueous solutions of NdCl3 by phosphonium-based ionic liquids

Mrutyunjay Panigrahi*, Mariusz Grzegorz Grabda, Dmytro Kozak, Arunkumar Dorai, Etsuro Shibata, Junichi Kawamura, Takashi Nakamura

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Citations (Scopus)


A protocol for the recovery of rare earth elements based on the dissolution of an aqueous solution of a rare earth metal chloride in an ionic liquid (IL) followed by stripping of the dissolved metal ions into an aqueous phase is proposed. The use of ILs is a departure from the traditional strategies employed for extraction. Liquid–liquid extraction of neodymium (Nd) ions from an aqueous solution of NdCl3 with and without hydrochloric acid (HCl) was carried out using phosphonium-based ILs, namely trihexyl(tetradecyl)phosphonium benzoate [T66614][BA] and trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide [T66614][TFSA]. The extraction was also conducted using a mixture of the aforementioned ILs and toluene. The efficiency of the extraction decreased with increasing concentrations of Nd in the aqueous solution. Furthermore, increasing the concentration of HCl in the aqueous phase decreased the percentage of extracted Nd ions. It indicates that the extraction followed a neutral or ion-pair extraction type of mechanism. Stripping of Nd ions from the metal-loaded organic phase using different acids revealed that HCl and HNO3 were the most effective stripping agents for complete re-extraction of the metal ions. Trihexyl(tetradecyl)phosphonium-based IL with a benzoate counter anion was more effective for Nd extraction than the congener with the bis(trifluoromethylsulfonyl)imide anion.

Original languageEnglish
Pages (from-to)263-269
Number of pages7
JournalSeparation and Purification Technology
Publication statusPublished - 2016 Oct 17
Externally publishedYes


  • IL
  • Liquid–liquid extraction
  • NdCl
  • Stripping

ASJC Scopus subject areas

  • Analytical Chemistry
  • Filtration and Separation


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