Lotus leaf-like SiO2 nanofiber coating on polyvinylidene fluoride nanofiber membrane for water-in-oil emulsion separation and antifouling enhancement

Separation of water-in-oil emulsions is necessary to recycle valuable resources in practical industries, as well as to protect the natural environment from damage. However, the formation of a filter cake layer by tiny water droplets, which commonly sticks to the membrane surface and is difficult to remove, limits the efficiency of the separation process. Therefore, an enhancement in the antifouling property is required to relieve the impact of the high cost and energy consumption caused by fouling. The construction of a hierarchical surface is a promising strategy, but extant coating methods have shortcomings that inhibit their widespread application and scalability. We report a sprayable premodified SiO2 nanofiber coating, which has a lotus leaf-like hierarchical surface, interconnected porous network, and superwetting properties, on a polyvinylidene fluoride nanofiber membrane to mitigate the fouling. The resultant membrane with the biomimetic coating exhibited a completely recovered flux in the recycling test while the pristine membrane exhibited an irreversible flux. Owing to this favorable reusability, this biomimetic coating membrane is a promising platform for an industrial water-in-oil emulsion separation.