4–6 The properties of ILs, include extremely low vapor pressures, high chemical and thermal stability, and a vast array of possible cation/anion combinations, which give high affinities towards targeted compounds. In recent years, ionic liquids (ILs) as a new class of environment-friendly compounds have attracted attention for the separation of Bz/Cy mixtures. Furthermore, the requirements for aromatic content in gasoline and other fuels are becoming stricter and stricter owing to environmental considerations. Aromatic hydrocarbons are important in the chemical industry because they can be used to produce various valuable petrochemicals. The difference in the boiling temperatures of the two components is only 0.6 ☌. 1–3 A typical mixture system, such as a benzene/cyclohexane mixture, features non-polar six-membered ring compounds, which have very similar chemical and physical properties. Separation of mixtures of aromatic and aliphatic compounds is one of the most difficult processes in the chemical and petrochemical industries. These results demonstrated that the /WPU composite membranes could be effective for separation of Bz/Cy mixtures by the pervaporation method. In addition, the composite membrane exhibited excellent stability over long-term operation. The best separation factor was 8.4, and the total flux was 0.19 kg (m 2 h) −1 (50 wt% Bz/Cy mixtures at 50 ☌) at w() : w(WPU) = 10 : 100. The /WPU composite membranes enhanced the separation selectivity of Bz/Cy for an IL loading < 10 wt%. Swelling testing of the /WPU composite membranes showed that the membranes exhibited preferential adsorption of Bz, and the swelling degree of the composite membranes in Bz solvent increased from 58% to 98% and remained almost constant in cyclohexane solvent as the IL content was increased. However, at high IL loading, the IL incorporation became ineffective owing to macrophase separation, which caused an increase in the permeability, as indicated by the SEM results. This interaction inhibited a potential interaction with benzene (Bz), which initially lowered the permeability. Characterization of the change in the morphology of the membranes in response to the IL loading indicated that a preferential interaction between the IL and soft segments of WPU was induced by hydrogen bonding. We characterized the structure and properties of the /WPU composite membranes by ATR-FTIR, DSC, UV, SEM, EDX, swelling tests, and pervaporation testing. Blending an aromatic-selective ionic liquid (IL, namely 1-ethyl-3-methylimidazolium hexafluorophosphate, ) with waterborne polyurethane (WPU) enabled us to obtain -modified waterborne polyurethane composite membranes.
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