Extraction Behavior of Divalent Metal Cations in Ionic Liquid Chelate Extraction Systems Using 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imides and Thenoyltrifluoroacetone

Abstract

The extraction behavior of several divalent metal cations (M 2+ ) in ionic liquid chelate extraction systems was investigated using several 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids ([Rmim][Tf2N]) as extraction solvent and thenoyltrifluoroacetone (Htta) as extractant. The behavior was compared with that using less hydrophobic 1-alkyl-3-methylimidazolium hexafluorophosphates ([Rmim][PF6]). The extracted species in the [Rmim][Tf2N] systems were neutral M(tta)2 for M = Cu and anionic M(tta)3 -for M = Mn, Co, Ni, Zn and Cd. Conversion of ionic liquid anion from PF6 -to more hydrophobic Tf2N -resulted in changing the species extracted for Ni 2+ from hydrated neutral complex to hydrophobic anionic one. Furthermore, the extractability for these metals was governed by the hydrophobicity of ionic liquid ions. Thus, in the ionic liquid chelate extraction system, selection of a suitable ionic liquid as extraction phase seems to be an important factor for enhancement of extraction selectivity.

Distribution Equilibria of Amphoteric 8-Quinolinol between 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide and Aqueous Phases and Their Effect on Ionic Liquid Chelate Extraction Behavior of Iron(III)

“…For example, several divalent transition metals 20,24 and trivalent lanthanoids 25 were extracted into ILs with 2-thenoyltrifluoroacetone (Htta) as monoanionic complexes. Moreover, the ion-exchange abilities may affect the distribution behavior of extraction reagents between the two phases.…”

Highly Selective Synergism for the Extraction of Lanthanoid(III) Ions with β-Diketones and Trioctylphosphine Oxide in an Ionic Liquid

“…[7][8][9] Because ILs can also act as liquid ion exchangers, not only neutral but also charged complexes are extractable into the IL phase by ion exchange with the cationic or anionic constituent of the ILs. [10][11][12][13] Thus, the extractability and separability of metal ions in the IL extraction system are expected to differ from those of the usual organic solvent systems. 14,15 Recently, the present authors have reported on the synergistic ionic-liquid extraction of lanthanoids(III) (Ln(III)) with 2-thenoyltrifluoroacetone (Htta) as an acidic chelating extractant and several neutral ligands in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][Tf2N]).…”

Cu(II) Extraction in Ionic Liquids and Chlorinated Solvents: Temperature Effect

“…In literature, Cu(II) extraction in ionic liquids by differrent chelating agents has been already reported [10,11]. In our previous study [12], concerning the extraction of Hg(II) ions in ionic liquids in absence of chelating agent, the key role of both working temperature and ionic liquid hydrophobicity has been pointed out.…”