Aqueous biphasic systems of hydrophilic ionic liquids plus sucrose for separation

In this work, we proposed a new aqueous biphasic system (ABS) composed of hydrophilic ionic liquids (ILs, namely, 1-allyl-3-methylimidazolium chloride, [Amim]Cl, 1-allyl-3-methylimidazolium bromide, [Amim]Br, and 1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim]BF4) and sucrose, forming an upper IL-rich phase and a lower sucrose-rich phase. The effects of IL structure on the phase equilibrium were investigated. It was found that the formation of ABS could be promoted by the increase of the side-chain length of ILs, but the effect was weaker than that of the anion. On the basis of phase diagrams we described, it was concluded that the chaotropicity decreased in the order [Bmim]BF4 > [Amim]Br > [Amim]Cl. This is consistent with IL + salt systems with which they were compared; however, the proposed systems are more environmentally benign for separating ILs from the aqueous phase.