Biocidal surfactant-assisted fabrication of thin film composite membranes with excellent and durable anti-biofouling performance

Biofouling is a critical problem for water treatment and desalination membranes because it significantly reduces process efficiency. Here, we present a new facile strategy for the fabrication of anti-biofouling polyamide (PA) thin film composite (TFC) membranes that involves the addition of the biocidal cationic surfactant, benzalkonium chloride (BAC), to an amine monomer solution during interfacial polymerization. The optimal addition of BAC effectively promotes and uniformizes amine diffusion toward the organic phase by reducing organic–aqueous interfacial tension and improving solution wettability on the support, producing a denser and more permeable PA structure. Moreover, BAC was strongly integrated into the PA matrix, presumably via strong chemical interactions between BAC and PA (i.e., electrostatic, hydrophobic, π–π stacking, and cation–π interactions), which enhanced the surface hydrophilicity and anti-bacterial activity of the membrane. Consequently, the BAC-incorporated TFC (BAC-TFC) membrane exhibited significantly enhanced reverse osmosis separation and anti-biofouling performance in comparison with the control TFC membrane. When compared with the conventional surfactant, sodium dodecyl sulfate, BAC resulted in remarkably improved biofouling resistance with comparable performance enhancement. Furthermore, the strong incorporation of BAC into PA led to the long-term durability of the BAC-TFC membrane in terms of its separation and anti-biofouling performance.