Bioinspired superhydrophobic and superlipophilic nanofiber membrane with pine needle-like structure for efficient gravity-driven oil/water separation

The challenge of effectively separating oily wastewater discharge in the industry has inspired researchers to explore advanced oil/water separation materials. In this work, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber (PNF) membranes were prepared by solution blow spinning, which is a novel type of spinning technology with advantages of high fiber yield, high safety and low energy consumption. Then, pine needle-like titanium dioxide (TiO2) nanorods (TNs) were grown on PNF by hydrothermal method. This pine needle-like hierarchical micro-nano structure greatly increased the roughness of the membrane surface. Then, further fluorination treatment made the prepared PNF@TNs-1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) membrane exhibited superhydrophobicity and superlipophilicity which water contact angle was 155.0 degrees and oil contact angle was 0 degrees. The PNF@TNs-PFDS membrane could effectively separate a variety of oil/water mixtures (such as dichloromethane, n-hexane, kerosene and toluene) by gravity. The separation efficiency (toluene/water) of the membrane reached up to 99.99% and the oil (dichloromethane)/water separation flux reached up to 9845 L m(-2) h(-1). Moreover, the membrane exhibited excellent self-cleaning performance and cycle performance. The toner on the membrane could be washed away with water flow and the membrane still maintained high separation efficiency after being recycled for 10 times. In addition, the PNF@TNs-PFDS membrane could also degrade organic pollutants when treating industrial oily wastewater, indicating its potential application in water purification treatment.

Automated summary

This study successfully prepared PVDF-HFP nanofiber membranes with superhydrophobicity and superlipophilicity, achieving efficient separation of various oil/water mixtures with a separation efficiency of up to 99.99%. The membrane demonstrated excellent self-cleaning and cycle performance, and was capable of degrading organic pollutants when treating industrial oily wastewater.