Synergistic effects in the facilitated transfer of metal ions into room-temperature ionic liquids

Abstract

Addition of tri-n-butyl phosphate (TBP) is shown to markedly increase the extraction of strontium from acidic nitrate media into certain 1-alkyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imides by dicyclohexano-18-crown-6 (DCH18C6), the apparent result of the formation of a synergistic adduct between the strontium-DCH18C6 complex and TBP. The magnitude of the synergistic enhancement is shown to depend on the alkyl chain length of the ionic liquid (IL) cation, with the effect diminishing as the cation hydrophobicity increases. The effect also diminishes at high (>50% v/v) TBP concentrations, the likely result of changes in solvent polarity unfavorable to the extraction of metal-crown ether complexes.