Imidazole-terminal PEG (I-PEG) was separated from the aqueous phase containing penicillin to hydrophobic ionic liquid phase at basic pH, and a
weak acidic aqueous phase was then employed to recover the I-PEG from the hydrophobic ionic liquid
phase into water at pH 5.5–6. The recycle of the polymer was achieved with the aid of hydrophobic ionic
liquids.