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Role of ionic liquids in the efficient transfer of lithium by Cyanex 923 in solvent extraction system

Authors
  • Cui, Li
  • Jiang, Kun
  • Wang, Junfeng
  • Dong, Kun
  • Zhang, Xiangping
  • Cheng, Fangqin
Publication Date
Aug 01, 2019
Source
Institutional Repository of Institute of Process Engineering, CAS (IPE-IR)
Keywords
License
Unknown
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Abstract

The solvent extraction of Li+ by Cyanex 923 was investigated upon the addition of different imidazolium-based ionic liquids (ILs). The results showed 1-hydroxylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HOEmim][NTf2]) can improve the extraction of Li+ most effectively. The fundamental mechanism is that [HOEmim][NTf2] can remarkably enhance the coordination ability of Cyanex 923 to Li+ to form more stable and hydrophobic ion-pair species [Li(Cyanex 923)(n)][NTf2] (n(max) = 3) resulting from the electrostatic interaction and typical hydrogen bonding of IL, and thus facilitating the transfer of Li+ into organic phase. This work has revealed the transfer mechanism of Li+ in a solvent extraction system comprising of IL and neural ligand. The knowledge of the coordination environment of Li+ in the presence of IL also gives us a new insight into the separation of Li-6/Li-7. The disadvantage of this process is the loss of IL. However, this study provides guidance for the design of better IL-based systems for the separation of metal ions.

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