Ion-exchange as a mode of cation transfer into room-temperature ionic liquids containing crown ethers: implications for the 'greenness' of ionic liquids as diluents in liquid-liquid extraction.

The transfer of strontium ion from acidic nitrate media into a series of 1-alkyl-3-methylimidazolium-based room-temperature ionic liquids containing dicyclohexano-18-crown-6 is shown to proceed via cation-exchange, in contrast to conventional solvents such as alkan-1-ols, in which extraction of a strontium nitrato-crown ether complex is observed.