Fluorinated Poly(ionic liquid)s Coated Superhydrophobic Functional Materials with Efficient Oil/Water Separation Performance

Abstract

There is an urgent need to develop new and improved oil-water separation materials with high stability and reusability for the cleanup of oily environmental pollutants. Here, fluorinated poly(ionic liquid)s were synthesized and their structure and property were characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. These fluorinated poly(ionic liquid)s were proposed as superhydrophobic coating on different metallic substrates through the combination of tethering fluorine groups in the PIL’s cation and anion exchange, and the superhydrophobic coating showed compactly stacked morphology under scanning electron microscope. The results of surface wettability experiments indicated that nearly all the fabricated materials showed a water contact angle larger than 150°, which is devoted to superhydrophobic nature. Moreover, for longer alkyl chain ILs and materials with smaller pore sizes, the water contact angle can be increased. At the same time, the fabricated superhydrophobic material exhibits a relatively high oil phase permeate flux, benefiting from the loose fibrous structure. Take the PIL@SSM300 for instance, the permeate fluxes were reached as high as 374,370 L·m−2·h−1, 337,200 L·m−2·h−1 and 302,013 L·m−2·h−1 for petroleum ether, hexane and cyclohexane, respectively. Instead, water is effectively repelled from the superhydrophobic surface. These virtues make the fabricated superhydrophobic material an effective membrane for oil/water separation under gravity. The separation efficiency and water contact angle are nearly unaffected after at least 20 cycles, confirming the excellent robustness of the coatings. These efficient poly(ionic liquid)s-based superhydrophobic materials possessed the potential to be used for oil/water separation.