Preparation and characterization of polyethersulfone/silver nanocomposite ultrafiltration membrane for antibacterial applications

Antimicrobial ultrafiltration membranes were prepared by coating silver nanoparticles on the surface of polyethersulfone (PES) membranes which were fabricated via phase inversion induced by the immersion precipitation technique, and their morphology and performance were compared with the antimicrobial PES membranes synthesized by adding the silver nanoparticles into the casting solution during the phase inversion process. For this purpose, stable and uniform colloidal solutions of the silver nanoparticles were prepared by chemical reduction of silver salt using fructose and dimethylformamide as a reducing agent. The silver nanoparticles were characterized by ultraviolet-visible spectroscopy, X-ray powder diffraction and dynamic light scattering analysis. The morphology and surface properties of the prepared membranes were examined by field emission scanning electron microscopy and atomic force microscopy analysis. Moreover, the separation properties, antimicrobial efficiency and amount of silver release from the PES nanocomposite membranes during the cross flow ultrafiltration were determined. The results indicated that the silver content of the coated PES membranes was greater than the membranes fabricated by the solution blending method. Also, the permeation flux of the silver-coated membranes was similar to the neat PES membranes, while the membranes prepared by the second approach had less flux. The membranes synthesized by both coating and blending methods showed high antimicrobial and bactericidal activity against gram-negative bacteria such as Escherichia coli and gram-positive bacteria such as Staphylococcus aureus. Finally, the prepared antimicrobial membranes were successfully used for the ultrafiltration of raw milk to reduce the microbial load during the concentration process. Copyright (c) 2014 John Wiley & Sons, Ltd.