The nature of salt effect in enhancing the extraction of rare earths by non-functional ionic liquids: Synergism of salt anion complexation and Hofmeister bias

Pan Sun, Kun Huang, Huizhou Liu

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

Separation and recycling of rare-earths using ionic liquids as extractant are becoming a promising approach to replace traditional volatile organic solvents in recent years. Generally, the addition of some special salts could improve the extraction efficiency of rare-earths by numerous non-functional ionic liquids. However, knowledge behind the nature of the salt effect is limited. Here, we found that the enhancement in the extraction of rare-earth ions, Pr3+ ions, using non-functional ionic liquid, [A336][NO3] (Tricaprylmethylammonium nitrate) was driven by the synergism of Hofmeister bias and complexation behaviors of salt anions with Pr3+ ions. Molecular dynamic simulations offered a new insight into the interaction mechanism of the ionic liquid with Pr3+ ions at liquid/liquid interface. It was revealed that salt anions could perform as a bridge to connect Pr3+ ions and the ionic liquid, so that promoted the extraction of Pr3+ ions. Therefore, the strong complexation ability of salt anions with Pr3+ ions and poor hydration of salt anions faciliated the transport of Pr3+ ions across liquid/liquid interface.

Original languageEnglish
Pages (from-to)214-222
Number of pages9
JournalJournal of Colloid and Interface Science
Volume539
DOIs
StatePublished - Mar 15 2019
Externally publishedYes

Funding

This work was financially supported by the National Natural Science Foundation of China (Nos. 51574213 , 51074150 ), the Key Project of Chinese National Programs for Fundamental Research and Development (973 Program no. 2013CB632602 ). We thank the Supercomputing Centre of Chinese Academy of Sciences for allowing us to use the ScGrid for theoretical calculations.

Keywords

  • Ionic liquids
  • Rare earths
  • Salt anion complexation
  • Salt effect
  • Solvent extraction

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