(686a) Bio-Inspired Immobilization of Casein-Coated Silver Nanoparticles on Cellulose Acetate Ultrafiltration Membranes for Biofouling Control

The focus of this project was on immobilizing Ag-NPs on ultrafiltration membranes to provide the membranes with antimicrobial properties while preventing nanoparticle leaching and membrane degradation. To this end, low-biofouling nanocomposite membranes were loaded with casein-coated silver nanoparticles (casein-Ag-NPs) using two approaches, physical blending of Ag-NPs in the dope solution (^PAg-NP/CA membranes) and chemical attachment of Ag-NPs to cast membranes (^CAg-NP/CA membranes). The functionalization of Ag-NPs onto the CA membranes was achieved via attachment with functionalized thiol groups with the use of glycidyl methacrylate (GMA) and cysteamine chemistries, which was inspired by the affinity of silver to the thiol groups of cysteine proteins in bacteria. The performance of two different membranes were characterized via structural, morphological, permeation, and biofouling studies. The ^PAg-NP/CA membranes displayed more pore channels in their cross-sections, exhibited higher average flux values, and had the highest average flux decline during short-term filtration studies. There were minor differences in pore channel morphology between CA and ^CAg-NP/CA membranes, but the latter displayed a tighter pore network compared to the other membranes due to GMA crosslinking, which contributed to its lower average flux. While the ^CAg-NP/CA membranes had a similar average flux decline compared to the CA membranes, the chemically attached Ag-NPs expressed the highest salt rejections. Lastly, ^CAg-NP/CA membranes appeared to possess better biofouling control as compared to CA membranes, based on the reduction of observable cells. There was minimum leaching of silver during cross-flow filtration of ^CAg-NP/CA membranes, and the leached water could still meet drinking water regulations.