Transforming PA RO membrane with [3-(2-aminoethyl) aminopropyl] triethoxysilane (AEAPTES) for superior antifouling and water purification

Abstract

Aromatic polyamide (PA) reverse osmosis (RO) membrane has gained widespread usage in desalination and water production. Nevertheless, their surfaces are prone to fouling during practical applications stemming from their inherent physicochemical properties. Therefore, conducting research on enhancing the antifouling properties of PA membranes through surface modification is of significant importance. In this work, high-flux and superior antifouling RO membranes were fabricated via surface grafting and self-crossing of [3-(2-aminoethyl) aminopropyl] triethoxysilane (AEAPTES) on the pristine PA membrane surface. Benefiting from solvent activation by n-hexane/n-decane and the strong hydrophilicity of AEAPTES, the modified membranes showed a significant enhancement in water permeance by approximately 73 % (reaching up to 4.10 LMH/bar) compared to unmodified PA membrane, while maintaining NaCl rejection above 98.67 %. Additionally, the modified membrane exhibited outstanding stability. Dynamic fouling experiments with charged model foulants of varying molecular sizes, supported by molecular dynamics simulation analysis, demonstrated that the surface charge plays a crucial role in resisting small-molecule foulants, while hydrophilicity is more effective against macromolecule foulants. Although AEAPTES incorporation did not improve the antifouling performance to negatively charged sodium dodecyl sulfate (SDS), it significantly improved resistance to positively charged dodecyl trimethyl ammonium bromide (DTAB) and charged protein model foulants, including lysozyme (LYZ) and bovine serum albumin (BSA). These improvements are attributed to the creation of a thick hydration layer, as well as the electrostatic interactions and steric hindrance effects provided by the AEAPTES modified layer. This research offers new perspectives on the antifouling mechanisms of PA membranes modified by organoalkoxysilane molecules.