Polyelectrolyte and Silver Nanoparticle Modification of Microfiltration Membranes To Mitigate Organic and Bacterial Fouling

Membrane fouling remains one of the most problematic issues surrounding membrane use in water and wastewater treatment applications. Organic and biological fouling contribute to irreversible fouling and flux decline in these processes. The aim of this study was to reduce both organic and biological fouling by modifying the surface of commercially available poly(ether sulfone) (PES) membranes using the polyelectrolyte multilayer modification method with poly(styrenesulfonate) (PSS), poly(diallyldimethylammonium chloride) (PDADMAC), and silver nanoparticles (nanoAg) integrated onto the surface as stable, thin (15 nm) films. PSS increases the hydrophilicity of the membrane and increases the negative surface charge, while integration of nanoAg into the top PSS layer imparts biocidal characteristics to the modified surface. Fouling was simulated by filtering aqueous solutions of humic acid (5 and 20 mg L–1), a suspension of Escherichia coli (106 colony-forming units (CFU) mL–1), and a mixture of both foulants through unmodified and modified PES membranes under batch conditions. Filtration and cleaning studies confirmed that the modification significantly reduced organic and biological fouling.