Improvement of Polyamide Reverse Osmosis Membranes by Coating with Ag/Chitosan Nanodispersion Prepared by Gamma Radiation

This study aimed to develop new techniques to improve polyamide (PA) reverse osmosis (RO) membrane properties. This technique involves coating the membrane surface with silver/chitosan (Ag/CS) nanodispersion prepared by gamma radiation. Silver nanoparticles (Ag NPs) were applied to the surface with the objective of enhancing RO performance, improving antifouling properties, and increasing both salt rejection and water flux. The size of the Ag NPs in the prepared nanodispersion was assessed using transmission electron microscopy (TEM), revealing that the Ag NPs' size fell within the range of 8.8–16.2 nm. The modified membrane is characterized by different instruments such as FT-IR spectroscopy, contact angle measurement, and scanning electron microscope (SEM). The altered membrane exhibits greater surface hydrophilicity compared to the unmodified membrane, as evidenced by a 30.18% reduction in the contact angle. Also, the Ag-NPs enhanced the permeability of the polyamide membrane. The water flux of the modified membranes increased progressively at lower concentrations of nanoparticles in the range of 5 to 10 wt/wt%, then decreased using 20 wt/wt%. Moreover, the modified membrane showed better antibacterial ability against gram positive and gram-negative bacterial models, Staphylococcus aureus and Escherichia coli.