Functionalization of silver nanoparticles on membranes and its influence on biofouling

The aim of this project is modifying the attachment of silver nanoparticles (Ag-NPs) on water treatment membranes, such as cellulose acetate (CA), and to observe its effect towards biofouling. Biofouling results from the accumulation of live/dead microorganisms present in water on the membrane surface and pores, and it creates several performance problems such as clogging of pores, higher operating cost, higher pressure drop, etc. Minimizing this would be ideal to lower operating cost and save expensive materials. In this project, Pseudomonas Fluorescens Migula are used because this species generates extracellular polymeric substances (EPS). EPS produced from bacteria helps create a viable structural foundation for biofilm accumulation with densely packed matrices, which in turn fouls the polymeric membranes. In this study, Ag-NPs are added to CA membranes for biofouling minimization. A concern with combining Ag-NP with membranes is the leaching of nanoparticles. If the Ag-NPs are chemically attached to the membranes, it is believed that leaching can be prevented. Different methods of introducing the Ag-NPs to the membranes studied here will include physical blending, chemically-activated blending, and chemically-crosslinked blending

Bio-inspired immobilization of casein-coated silver nanoparticles on cellulose acetate membranes for biofouling control

This study shows the results of low-biofouling nanocomposite membranes, loaded with casein-coated silver nanoparticles (casein-Ag-NPs). Membranes were cast and imbedded with 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), to determine their biofouling control properties. 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 immobilization chemistry successfully prevented leaching of silver nanoparticles during cross-flow studies. Pseudomonas fluorescens Migula in brackish water was used for dead-end filtration, where CAg-NP/CA membranes displayed lower a significant reduction in the accumulation of bacterial cells, likely due to the more dispersed nanoparticles across the surface

Desalination using low biofouling nanocomposite membranes: From batch-scale to continuous-scale membrane fabrication

This study shows the results of low-biofouling nanocomposite membranes, when using batch-scale fabrication and testing techniques, and when using continuous-scale fabrication and testing techniques. This holistic study begins with nanoparticle manufacturing and selection, then focuses on nanocomposite membrane synthesis and fabrication, and ends with testing and characterization. Nanocomposite membranes loaded with casein-coated silver nanoparticles (Casein-AgNPs) were cast using two approaches, doctor-blade extrusion (batch-scale) and slot-die casting (continuous-scale), to determine their biofouling control properties. In short-term dead-end filtration, cellulose acetate (CA) membranes showed a flux decline of approximately 26% as compared to 20% for nanocomposite (Casein-AgNPs CA) membranes, while the flux recovered after backwashing was higher for the nanocomposite membranes (93%) than for the CA membranes (84%). Cross-flow filtration experiments were conducted for 26 days. No flux decline was observed for nanocomposite membranes and SEM imaging indicated that bacterial cell damage might have occurred. Overall, filtration experiments and membrane testing following biofouling tests showed that laboratory-scale composite membranes operated for 24 h were effective in mitigating biofouling formation. Conversely, continuous-scale nanocomposite membranes operated for 26 days did not show clear improvement in biofouling control, however there was visible damage to cells accumulated on the membrane