(538e) Interfacial Transport in Thin Film Nanocomposite Membranes for Water Purification

Current commercial reverse osmosis membranes are limited by the properties of the polymeric semipermeable membranes used. In the past, a variety of nanoparticles have been added in order to improve the membrane flux and selectivity. Some of these thin film nanocomposite membranes have exhibited enhanced membrane properties, allowing for improved reverse osmosis process performance. Previous work in our laboratory has demonstrated that the addition of zwitterion-functionalized carbon nanotubes (CNTs) to the selective layer of thin film composite membranes increases the overall flux of the membranes while maintaining high salt rejection.¹ The CNTs also have also shown improvements in anti-fouling behavior. There is also evidence that the improvement in flux is not necessarily due to transport inside the CNTs, but could be due to transport at the polymer matrix/nanotube interface. Due to the high cost of CNTs, other nanoparticle additives are currently being studied. Cellulose nanocrystals (CNCs) are of interest due to their lower cost and availability as well as their potential for functionalization. In the current work, polyamide/CNC based thin-film nanocomposite membranes have been fabricated on polysulfone supports via vacuum filtration and interfacial polymerization and their water flux and salt rejection have been studied for RO desalination applications. Results have shown that TEMPO-oxidized CNCs may increase the flux of the membranes by up to 40% while maintaining high salt rejection. The flux and salt rejection can be tuned via careful control of the CNC surface functionality and functional group density, and via control of polymer-surface interactions.

¹Chan, Wai-Fong, Eva Marand, and Stephen M. Martin; J. Membrane Science 509 (2016): pp. 125-137.