Highly hydrophilic poly(vinylidene fluoride) ultrafiltration membranes modified by poly(N-acryloyl glycinamide) hydrogel based on multi-hydrogen bond self-assembly for reducing protein fouling

Abstract

Reducing protein fouling in membrane separation and purification process is still a great challenge to the widespread application of ultrafiltration (UF) membranes. In this context, polyvinylidene fluoride (PVDF) UF membranes with enhanced hydrophilicity were modified by grafting hydrophilic poly (N-acryloyl glycinamide) (PNAGA) hydrogel formed through multi-hydrogen bond self-assembly via ultraviolet (UV)-initiated radical graft polymerization. Fourier transform infrared spectra (FTIR) and X-ray photo electron spectroscopy (XPS) reveal that PNAGA gel has been grafted onto the surface of the hydrophobic PVDF membranes. Water contact angle of PNAGA modified membranes reduces from 55.2° ± 1.1 to 0° within 11 s, illustrating a superior hydrophilicity. Ultrasonic 30 min and 7 days pure water filtration tests indicate that the PNAGA hydrogel layer has good stability. The results from anti-fouling test show that, when the pH is 7.0, the flux recovery rate of modified membrane maintains at 99%, the total fouling rate is as low as 30%, and the irreversible fouling rate is only 1.2%. Furthermore, the fouling mechanism investigation shows that fouling layers are not easy to form on the anti-protein-fouling PNAGA hydrogel grafted membranes. This work provides new insights for anti-fouling membrane design and application in protein purification, bio-separation and so on.