Fabrication of pH-Sensitive Superhydrophilic/Underwater Superoleophobic Poly(vinylidene fluoride)-graft-(SiO₂ Nanoparticles and PAMAM Dendrimers) Membranes for Oil–Water Separation

The efficient treatment of oil–water emulsions under acidic condition remains a widespread concern. Poly(amidoamine) (PAMAM) dendrimer with hyperbranched structures and a large amount of primary and tertiary amino groups has exhibited advantages to solve this issue. Here, a novel poly(vinylidene fluoride)-graft-(SiO2 nanoparticles and PAMAM dendrimers) (PVDF-g-SiO2 NPs/PAMAM) membrane was fabricated using a surface-grafting strategy. SiO2 NPs were immobilized on PVDF-g-poly(acrylic acid) (PAA) membranes for improving the surface roughness, and PAMAM dendrimers were further immobilized on the membrane surface by interfacial polymerization (IP) for improving the surface energy. The obtained membrane demonstrated a water contact angle and a stable underwater–oil contact angle of 0° and >150°, respectively. These characteristics endowed the membrane with excellent water permeability [>3100 L/(m2·h) at 0.9 bar] and separation efficiency (>99%) during oil–water separation. Furthermore, the PAMAM chain will extend from a collapsed state into a fully extension state because of the protonation of amine groups under acidic condition, thus achieving a low underwater oil-adhesion property, fouling resistance, desirable stability, and recyclability (over 12 cycles) during usage. This work shows a promising prospect for the treatment of corrosive emulsions under acidic condition.