Auto-cleaning functionalization of the polyvinylidene fluoride membrane by the biocidal oxine/TiO2 nanocomposite for anti-biofouling properties

Abstract

Membrane biofouling is a critical challenge in the application of membrane bioreactor (MBR) technology in wastewater treatment. Gram-negative bacteria isolated from MBRs were used to study the antibacterial and antibiofilm properties of oxine and TiO₂. The commercial polyvinylidene fluoride (PVDF) polymer was modified with TiO₂ nanoparticle-doped oxine to develop an auto-cleaning functionalized hybrid membrane with a long lasting antibiofilm effect. Scanning electron microscopy (SEM), contact angle measurements, as well as antibiofouling and antibacterial tests were performed for modified membranes. The results showed that the addition of oxine and TiO₂ increases the porosity (80%) and pore size (61 nm) of the pristine PVDF membranes. The antifouling performance of the oxine-modified membranes showed a high water flux of 207.14 L m⁻² h⁻¹, a flux recovery ratio (FRR) of 80.6% and a low irreversible fouling (R_ir) of 19.3% compared to the pristine membrane. The membranes modified by oxine and TiO₂ nanoparticle surface functionalization exhibited a higher zone of inhibition (ZOI) of 38 mm. SEM showed that the existence of oxine in combination with TiO₂ nanoparticles on the membrane surfaces prevents >90% initial attachment of the bacteria that cause biofouling. Conversely, surface modification of the membranes did not have any effect on the water flux or mechanical performance. These results suggest that oxine functionalization of membrane surfaces can be an alternative strategy for the development of antibiofouling MBRs.