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Published on: December 20, 2016
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A specific synergistic effect in ionic liquid chelate extraction based on neutral ternary chloro-complex formation
Motoya Sakato1, Naoki Hirayama
1Department of Chemistry, Faculty of Science, Toho University.
Summary
Chloride anions enhance zinc(II) extraction into ionic liquids by forming a stable ternary complex. This synergistic effect, observed with 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 8-(p-toluenesulfonamido)quinoline, is absent in conventional solvents like chloroform.
Area of Science:
- Analytical Chemistry
- Separation Science
- Coordination Chemistry
Background:
- Ionic liquids (ILs) offer unique extraction properties compared to conventional organic solvents.
- The chelate extraction of metal ions using ligands like 8-(p-toluenesulfonamido)quinoline (Htsq) is a key separation technique.
- Understanding the influence of co-existing anions on extraction efficiency is crucial for process optimization.
Purpose of the Study:
- To investigate the effect of chloride anions on the chelate extraction of zinc(II) into an ionic liquid.
- To compare the extraction behavior in an ionic liquid versus a conventional organic solvent (chloroform).
- To elucidate the mechanism behind the observed enhancement in zinc(II) extractability.
Main Methods:
- Chelate extraction of zinc(II) using 8-(p-toluenesulfonamido)quinoline (Htsq) as the ligand.
- Utilizing 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][Tf2N]) as the ionic liquid phase.
- Varying the concentration of chloride anions in the aqueous phase.
- Analyzing the extraction efficiency and comparing results with chloroform as the organic phase.
Main Results:
- The presence of chloride anions significantly enhanced the extractability of zinc(II) into the ionic liquid [C4mim][Tf2N].
- This enhancement was attributed to the formation and extraction of a neutral ternary complex, Zn(tsq)Cl.
- No similar enhancement was observed when using chloroform as the extraction solvent, indicating a specific interaction with the ionic liquid.
- The ternary complex Zn(tsq)Cl proved to be unstable in molecular organic solvents like chloroform.
Conclusions:
- Chloride anions play a critical role in the synergistic enhancement of zinc(II) chelate extraction into specific ionic liquids.
- The formation of a stable ternary complex, Zn(tsq)Cl, is key to this enhanced extraction in ILs.
- Ionic liquids provide unique advantages over conventional solvents for specific metal extraction processes due to specific ion interactions.
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