In this study, we were able to impart antimicrobial properties onto the surface of a commercial thin-film composite (TFC) reverse osmosis (RO) membrane using sustainably derived cellulose nanocrystals (CNC) extracted from elephant grass (<i>Pennisetum purpureum</i>) leaves. The CNC were characterized using Fourier Transform Infrared (FTIR) spectroscopy in attenuated total reflection (ATR) mode, zeta potential measurements, and transmission electron microscopy (TEM). CNC were chemically bound to the polyamide active layer of TFC membranes using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) mediated amide crosslinking. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and FTIR-ATR spectroscopy were conducted to investigate the presence of CNC on the membrane surface. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses were utilized to confirm the chemical attachment of CNC to the membrane surface. TFC membranes functionalized with needle-like and antimicrobial CNC showed robust toxicity to bacteria, inactivating ~89% of attached <i>Escherichia coli</i> cells under contact while demonstrating no deleterious effect on membrane performance. These findings establish that functionalization with CNC is a promising approach for mitigating biofouling on TFC membranes and substantiates the application of sustainable materials for the design of the next-generation membranes for water purification.

Sustainable cellulose nanocrystals for improved antimicrobial properties of thin film composite membranes

ACS Fall 2021

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