Antifouling Polyvinylidene Fluoride Membrane through Dopamine Self-Polymerization Enhanced Surface Segregation toward Oil-In-Water Emulsions Separation

Surface segregation method, as an in situ method for simultaneous modification of membrane external surfaces and inner pore surfaces, has been more commonly employed to fabricate antifouling membranes. In this study, dopamine (DA) with self-polymerization and bio-adhesion ability is chosen as a surface segregation agent to fabricate antifouling polyvinylidene fluoride (PVDF) membrane for oil-in-water emulsions separation through synergistically regulating phase inversion, self-polymerization of DA, and surface segregation of poly-dopamine (PDA). During the phase inversion process, DA contacts with an alkaline coagulation bath to trigger self-polymerization of DA, then the surface segregation of PDA proceeds spontaneously. The addition and self-polymerization of DA can regulate the phase inversion process to acquire membranes with high porosity, as a result, the water permeance is increased from 134 to 538 L m-2 h-1 bar-1 with the oil rejection higher than 99.8%. Because the hydrophilic PDA layer on membrane and pore surfaces leads to a robust hydration layer, the membrane exhibits super-oleophobicity underwater and excellent antifouling properties with water recovery ratio of more than 99.4%. This study may open a new route to preparing antifouling membranes by using small molecules as surface segregation agents. Dopamine is designed as a surface segregation agent to fabricate antifouling polyvinylidene fluoride (PVDF) membrane through synergistically regulating phase inversion, self-polymerization of dopamine, and surface segregation of poly-dopamine, achieving efficient separation of surfactant-stabilized oil-in-water emulsions. image