Preparation of hydrophilic and antibacterial nanofiltration membrane by post-grafting N-(3-Aminopropyl)-imidazole

In this research, we introduce a novel and efficient approach for enhancing both the antibacterial efficacy and resistance to protein fouling of nanofiltration (NF) membranes, marking the first report of a method capable of concurrently addressing these critical membrane performance parameters. After traditional interface polymerization (IP), NF membranes were post-treated by the antibacterial N-(3-Aminopropyl)-imidazole (ANPI) which can be grafted on the membrane by its amino group reacting with rest acyl chloride in IP on the surface. After parameter optimization of the ANPI concentration, the modified membrane NF-12 demonstrated up to 99% antibacterial activity against two representative pathogens, Escherichia coli and Staphylococcus aureus . Except for this, due to the zwitterionic effect, the modified membrane achieved a remarkable 68.7% enhancement in water flux and the recovery rate of BSA cyclic pollution reached 97.5%. From mechanism analysis, it can be proposed that the post-grafted ANPI brought antibacterial properties to the NF membrane, which was able to kill bacteria attached to the membrane surfaces. Also, the imidazole protonation introduced positive charges to the NF membrane surface, mixing with negative charges produced by acyl chloride hydration, which produced the zwitterionic effect and facilitated the formation of a robust hydrophilic hydration layer, thereby significantly diminishing the adhesion of contaminants.