It can be seen from Fig. 6 that the partitioning
ratio of C-PEG in [Bmim]PF6/water system at pH 4 increases from
3.0 to 4.5 when the temperature rises up from 15 to 40 ◦C. This may
be due to the improved hydrophobicity of PEG at high temperature
[32], which increases the partitioning ratio of functionalized PEG.
The I-PEG in [Bmim]PF6/water system at pH 6 has similar separation
efficiency as that in C-PEG system at pH 4. This phenomenon
can be explained by the result of Huddleston et al. that hydrophobic
ionic liquids phase exhibits high affinity for ionic compounds
when they are neutralized [33].