Fabrication of a Bi2O3 Surface-Modified Polyvinylidene Fluoride Membrane via an Ultraviolet Photografting Method: Improving Hydrophilicity and Degree of Acrylic Acid Grafting

In this study, a superior hydrophilic polyvinylidene fluoride (PVDF) membrane with an enhanced monomer grafting ratio was prepared via an ultraviolet (UV) photografting polymerization method. The water contact angle (WCA) of the Bi2O3–acrylic acid (AA)-modified PVDF membrane reduces to 40.4° with the increasing of Bi2O3 content, illustrating significant enhancement of membrane hydrophilicity. Attenuated total reflection Fourier transform infrared spectra and atomic absorption spectroscopy reveal that Bi2O3–AA-modified membranes have more than five times AA grafting degree onto the surface of the hydrophobic PVDF membranes than only the AA-modified membrane. The mechanism of Bi2O3 promoting degree of AA grafting during the polymerization process is also especially explored in this research, and h+ and •O2– are proved to be primary active species in graft polymerization. Unexpectedly, the modified membrane has much better retention performance compared with the neat membrane. In addition, the Bi2O3–AA modified membrane also shows self-cleaning property for degradation dyes on the membrane surface.