(7d) The Use of Green Nanoparticles As a Biofouling-Resistant Agent in Membrane Separations

With the rapid growth and development of countries around the world, and the inherent need of clean water, it is imperative to treat brackish- and sea-water sources. The two leading desalination technologies are thermal and membrane technologies, specifically reverse osmosis (RO). While nanofiltration (NF) is used for the removal of other substances from water source, it is also commonly used for the desalination of water. While both RO and NF can produce potable water, RO removes a large majority of solutes, which leaves the permeate water void of any essential nutrients (calcium, magnesium ions, etc.), placing the nutrient levels below that of the required World Health Organization standards. This means nutrients must be added back (i.e. reminerailization) to bring the water back to the standard levels for drinking water. NF methods, on the other hand, remove fewer solutes, and thus may avoid the need to remineralize the water. Thus, it is a more desirable technology for developing nations.

This project seeks to address a major technical challenge in membrane technology, mitigation of membrane biofouling, due to rejected chemicals and microbes, by impregnating the solutions with cost effective nanoparticles. Most of the research and development in the area of biofouling prevention has focused on pretreatment of the feed water, improved cleaning solutions and cleaning procedures. In this project, biofouling-resistant (BRN) nanocomposite membranes, loaded with green silver nanoparticles were studied from synthesis to macro-scale production. 

Filtration experiments were performed with synthetic brackish water containing biofoulant Pseudomonas fluorescens Migula to test regular cellulose acetate (CA) membranes and CA membranes loaded with silver nanoparticles (CA-AgNP).  CA-AgNP membranes resulted in lower flux declines when compared to CA membranes. CA membranes showed a flux decline of approximately 26% as compared to 20% for CA-AgNP membranes during 7 hours of filtration. Though the differences are small in the decline of flux, the flux recovered after backwashing was higher for the CA-AgNP membranes (93%) than for the CA membrane (84%). Therefore, filtration experiments using p. fluorscens showed that CA-AgNP membranes were more effective at mitigating biofouling formation.