Surface Reaction Route To Increase the Loading of Antimicrobial Ag Nanoparticles in Forward Osmosis Membranes

Biofilm formation from bacterial growth and colonization is a known cause for membrane performance deterioration in water treatment. A broad-spectrum biocide such as silver nanoparticles (Ag NPs) is generally added to the membrane to impart biofilm resistance. Because biofilm formation begins with the membrane surface in contact with the feedwater, a high loading of uniformly dispersed Ag nanoparticles (Ag NPs) on the membrane exterior surface is desirable for a good antimicrobial performance. This was accomplished in this work by a short alkaline treatment of a hydrolyzable membrane (polyacrylonitrile, PAN) to introduce negative charge to the surface. A subsequent exposure to a Ag precursor solution followed by reduction under mild reducing condition (CO) limited the Ag NP deposition to within a narrow region of the membrane surface. The Ag content on the resultant membrane exterior surface in this study was also the highest in the literature. Different from previously reported methods, this method of Ag NP incorporation can be applied to thin film composite (TFC) membranes without any adverse effect on the water flux. The TFC membranes modified as such have shown good antibacterial resistance for 14 days under laboratory conditions optimized for the growth of Escherichia coli