Attachment of silver nanoparticles (AgNPs) onto thin-film composite (TFC) membranes through covalent bonding to reduce membrane biofouling

Membrane biofouling has a negative impact on the membrane treatment performance. Silver nanoparticles (AgNPs) are well-known antimicrobial agent. Herein, AgNPs with approximately 15 nm in diameter were effectively attached to the surface of polyamide (PA) thin-film composite (TFC) membrane via covalent bonding, with cysteamine as a bridging agent. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and cross-sectional transmission electron microscopy (TEM) studies all showed the immobilization of AgNPs. Compared with the pristine TFC membrane, thiol-terminated membrane (TFC-SH) and AgNPs grafted membrane (TFC-S-AgNPs) both showed a higher water flux with slightly lower salt rejection. At a constant transmenbrane pressure of 300 psi, the water permeability of TFC-SH, TFC-S-AgNPs, and control TFC membranes was 70.6±0.5, 69.4±0.3, and 49.8±1.7 L/m2h, respectively, while NaCl rejection was 93.4±0.1%, 93.6±0.2%, and 95.9±0.6%, respectively. TFC-S-AgNPs had an improved antibacterial ability to inhibit E. coli growth. The silver leaching from the TFC-S-AgNPs membrane surfaces was minimal, as tested by both batch and flow-through methods. The results successfully demonstrated that AgNPs could be grafted onto TFC via chemical bonding, leading towards the development of an advanced functional TFC membrane with anti-biofouling properties.