(152bk) Biofouling Performance of Aromatic Polyamide Desalination Membranes Containing Functionalized Cellulose Nanocrystals (CNCs)

Lack of access to drinking water is an increasing problem across the world. Desalination of saline water via reverse osmosis (RO) is one of the most effective methods for producing drinking water in water-stressed regions. Fully aromatic polyamide thin film composite (TFC) membranes are the most commonly used material for desalination. One major issue with RO desalination in real world applications is membrane fouling due to biological contaminants (e.g. proteins, etc...). These biological compounds tend to accumulate on the membrane surface causing biofouling, which increases transmembrane pressure and can lead to increased concentration polarization. These combined effects result in decreased flux and salt rejection. Prior work in our lab has demonstrated that the incorporation of zwitterion functionalized carbon nanotubes into the selective TFC layer resulted in increased water flux and decreased biofouling. In this work, we have developed thin film nanocomposite membranes (TFNs) in which functionalized rod-like cellulose nanocrystals (CNCs) are incorporated in the selective layer of the membrane to decrease biofouling on the membrane surface.

The functionalized CNCs used in this study were as received CNCs, 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TOCNs) and zwitterionic functionalized cellulose nanocrystals (zCNCs). CNCs were selected for their high aspect ratio, low cost, availability, sustainability, and potential for surface modification. Our group has previously shown that the addition of as received CNCs and TOCNs to polyamide membranes increases the water flux through the membrane while maintaining high sodium rejection. Our group has also previously shown that adding carbon nanotubes containing zwitterionic functional groups has limited water flux decrease in the presence of bovine serum albumin (BSA) and sodium chloride and increased the flux recovery from washing. The membrane biofouling was studied by measuring the decrease in water flux over time using feed containing BSA and sodium chloride. The membranes were then flushed with pure water and tested a second time to determine the extent of irreversible biofouling.