Enhancing the Antifouling Properties of Poly(vinylidene fluoride) (PVDF) Membrane through a Novel Blending and Surface-Grafting Modification Approach

In this study, poly(vinylidene fluoride) (PVDF) membrane was modified through a novel approach by first blending an active component (poly(vinylidene fluoride-co-chlorotrifluoroethylene), P(VDF-co-CTFE)) with the PVDF base material, followed by surface grafting of the membrane on the active component to obtain a triblock copolymer functional structure. The prepared membranes were characterized by various analyses, including Fourier-transform infrared, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscope, and filtration tests. It was found that the modified membrane surface showed a much better hydrophilicity (water contact angle of 67.3°) and oleophobicity (oil contact angle of 129.7°). The modification reduced the average surface pore size (from 0.1495 to 0.1072 μm) and thus lowered the pure water flux (from 364.0 to 224.6 L m–2 h–1 at 0.10 MPa of transmembrane pressure), but significantly increased the relative flux recovery (RFR) and the retention efficiency of the modified membrane during the filtration of bovine serum albumin solution and oil/water emulsion. For example, the modified membranes showed 98.6% oil retention (at feed concentration of 0.4 g L–1), 92.7% RFR by simple water flushing after filtration, and a consistently high oil removal of 96% or above during a five-cycle-continuous filtration test, as compared to 30.4% oil retention and 51.8% RFR for unmodified PVDF/P(VDF-co-CTFE) blend membrane.