Advancements in water purification: A defective MPN-based light-responsive self-cleaning membrane for superior bacteria and resistance gene removal, biofouling mitigation, and mechanistic insights

To address the significant challenge of biofouling in ultrafiltration (UF) membranes, primarily caused by bacteria during water purification, we have developed an innovative light-responsive active self-cleaning membrane (TA@Fe-TiO2/PVDF). This membrane is produced by coating polyvinylidene fluoride (PVDF) with a metal-polyphenol-based complex (TA@Fe-TiO2 MPN). Compared to traditional photocatalytic membranes, such as TiO2/PVDF, the TA@Fe-TiO2/PVDF self-cleaning membrane demonstrates superior anti-biofouling and self-cleaning properties, achieving nearly complete flux recovery (∼100%) and bactericidal efficiency (close to 100%) in the treatment of municipal secondary effluent without the need for chemical additives. This effectiveness is attributed to the generation of hydroxyl radicals (·OH) and singlet oxygen (1O2) when the membrane is exposed to light, enhanced by the significant photothermal performance of TA@Fe. Notably, the TA@Fe-TiO2/PVDF membrane also excels in removing antibiotic resistance genes (ARGs), such as tetracycline and sulfadiazine, from wastewater. The removal of bacteria and ARGs is facilitated by a self-cleaning mechanism that combines partial mineralization and oxidation, as evidenced by increased hydrophilicity, active oxygen sites, and electron transfer. The membrane's efficient light-responsive excitation, self-cleaning capability, and stability herald new avenues for the sustainable application of membrane technology in water purification, characterized by reduced energy demands.