Tailoring PVDF membrane antifouling properties via tannic acid blending and chitosan surface coating

Polyvinylidene Polyvinylidene fluoride (PVDF) membranes are widely applied in water treatment but their inherent hydrophobicity leads to severe organic fouling and microbial contamination. In this study, a dual-modification strategy combining tannic acid and chitosan was employed to enhance the hydrophilicity and biofouling resistance of PVDF membranes. The membranes were fabricated via non-solvent induced phase separation, followed by tannic acid incorporation and chitosan surface coating at different concentrations and immersion times. Comprehensive characterization was performed, including water contact angle, scanning electron microscopy, FTIR spectroscopy, pure water flux, humic acid rejection, flux recovery ratio, and Escherichia coli inactivation. Among the prepared samples, the membrane containing 3 % tannic acid and coated with 1 % chitosan for 30 min (M4) exhibited the best overall performance, achieving a reduced water contact angle of 72.92°, a flux recovery ratio of 121.33 %, humic acid rejection of 98.47 %, and E. coli reduction exceeding 95 %. Elemental analysis confirmed the successful incorporation of hydrophilic and antimicrobial functional groups. These enhancements are attributed to the combined effects of the biopolymer additives, which improved permeability and resistance to fouling. The findings highlight that membrane M5 demonstrated the optimal balance of hydrophilicity, antifouling, and biofouling resistance. This research presents a sustainable approach to membrane surface engineering using natural materials, offering a viable alternative for advanced water treatment.