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Open AccessArticle

Functionalized Cellulose Nanocrystal Nanocomposite Membranes with Controlled Interfacial Transport for Improved Reverse Osmosis Performance

1
Department of Chemical Engineering, Virginia Tech, Blacksburg, VA 24060, USA
2
Macromolecules Innovation Institute, Virginia Tech, Blacksburg, VA 24060, USA
3
Department of Materials Science and Engineering, Virginia Tech, Blacksburg, VA 24060, USA
4
National Center for Earth and Environmental Nanotechnology Infrastructure, Virginia Tech, Blacksburg, VA 24060, USA
*
Author to whom correspondence should be addressed.
Nanomaterials 2019, 9(1), 125; https://doi.org/10.3390/nano9010125
Received: 15 December 2018 / Revised: 12 January 2019 / Accepted: 17 January 2019 / Published: 20 January 2019
(This article belongs to the Special Issue Cellulose Nanomaterials)
Thin-film nanocomposite membranes (TFNs) are a recent class of materials that use nanoparticles to provide improvements over traditional thin-film composite (TFC) reverse osmosis membranes by addressing various design challenges, e.g., low flux for brackish water sources, biofouling, etc. In this study, TFNs were produced using as-received cellulose nanocrystals (CNCs) and 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TOCNs) as nanoparticle additives. Cellulose nanocrystals are broadly interesting due to their high aspect ratios, low cost, sustainability, and potential for surface modification. Two methods of membrane fabrication were used in order to study the effects of nanoparticle dispersion on membrane flux and salt rejection: a vacuum filtration method and a monomer dispersion method. In both cases, various quantities of CNCs and TOCNs were incorporated into a polyamide TFC membrane via in-situ interfacial polymerization. The flux and rejection performance of the resulting membranes was evaluated, and the membranes were characterized via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The vacuum filtration method resulted in inconsistent TFN formation with poor nanocrystal dispersion in the polymer. In contrast, the dispersion method resulted in more consistent TFN formation with improvements in both water flux and salt rejection observed. The best improvement was obtained via the monomer dispersion method at 0.5 wt% TOCN loading resulting in a 260% increase in water flux and an increase in salt rejection to 98.98 ± 0.41% compared to 97.53 ± 0.31% for the plain polyamide membrane. The increased flux is attributed to the formation of nanochannels at the interface between the high aspect ratio nanocrystals and the polyamide matrix. These nanochannels serve as rapid transport pathways through the membrane, and can be used to tune selectivity via control of particle/polymer interactions. View Full-Text
Keywords: reverse osmosis; thin-film composite; cellulose; nanocomposite; nanocrystal reverse osmosis; thin-film composite; cellulose; nanocomposite; nanocrystal
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MDPI and ACS Style

Smith, E.D.; Hendren, K.D.; Haag, J.V., IV; Foster, E.J.; Martin, S.M. Functionalized Cellulose Nanocrystal Nanocomposite Membranes with Controlled Interfacial Transport for Improved Reverse Osmosis Performance. Nanomaterials 2019, 9, 125.

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