Superoleophilic oil-adsorbing membranes based on porous and nonporous fluorinated polyimides for the rapid remediation of oil spills

Abstract

• Electrospun nanofibrous mats of fluorinated porous and nonporous 6FDA-based polyimides as oil sorbents. • Fine-tuning the oil-sorption performance by tuning the polymer porosity and functional groups. • The nanofibrous sorbents of fluorinated polyimides exhibited superoleophilicity. • A high crude oil-sorption capacity of 83 g g −1 was achieved by the electrospun nanofibrous mats. • Excellent sorption capacity was maintained for up to five cycles. Oil spills present significant environmental hazards that threaten the marine ecosystem and human life. To rapidly clean up oil spills and prevent ecological disasters, various oil sorbents have been developed. Here, highly effective hydrophobic nanofibrous sorbents were developed through the electrospinning of four different 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)-based polyimides with Brunauer–Emmett–Teller surface areas of 46 and 530 m 2 g −1 . Uniform nanofibers with wrinkled surfaces and mean diameters of 250–860 nm were produced. Cross-sectional images revealed the presence of pores within the fibers, attributable to the unsteady evaporation of solvent molecules from the jet. Water contact-angle (WCA) measurements demonstrated the hydrophobic nature of the nanofibers, whose WCAs were in the range of 130°–147°. Oil-sorption experiments revealed the high performance of the nanofibrous sorbents. The sorbent produced from 6FDA–3,5-diaminobenzoic acid exhibited the highest adsorption capacities for crude oil (61 g g −1 ) and diesel (109 g g −1 ). In contrast, the highest gasoline-adsorption capacity was observed for the sorbent produced from 6FDA–3,5-diamino-2,4,6-trimethylbenzene benzoic acid (6FDA–TrMCA) (41 g g −1 ). Using polymer blends, the sorption capacities of the resulting sorbents were enhanced up to 83 and 42 g g −1 for crude oil and gasoline, respectively; however, the diesel-sorption capacity decreased to 71 g g −1 . The nanofibrous sorbents could be recovered mechanically through squeezing and reused multiple times, while maintaining higher than 80% of their initial sorption capacities. These hydrophobic polyimide nanofibrous sorbents with high oil-adsorption rates and sorption capacities exhibit significant potential for application in oil-spill remediation.