Preparation of halloysite-based PVDF membrane for effective oil/water separation and dyes removal

The application of materials with selective superwettability to oil/water separation has attracted much attention due to frequent oil spills, large discharges of oily wastewater and many shortcomings of traditional separation methods. Herein, we successfully prepared double-defense membranes by co-precipitating dopamine hydrochloride and polyvinyl polyamine on the original commercial hydrophilic polyvinylidene fluoride (PVDF) membrane and coating the membrane with a halloysite-based hydration layer. Our membranes are highly efficient (>99.6 %) in separating oil-in-water emulsions, have outstanding recycle capacity, good anti-fouling properties (underwater oil contact angle of 156.6 ± 1.9°, low oil adhesion), and are resistant to acid, alkali, and salt. Besides, our membranes can also remove different dye solutions through simple filtration. With the advantages of double-defense design, excellent underwater oleophobic performance in various environments, oil–water emulsion separation performance, dye removal function, and low cost, our strategy might provide solutions for treating wastewater containing oil or dye, thus expanding the application range of membrane materials.