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Synthesis and Characterization of Electrospun Activated Carbon Nanofibers Reinforced with Cellulose Nanocrystals for Adsorption Applications
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- Author / Creator
- Awad, Rania
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Cellulose nanocrystals (CNCs) are emerging nanomaterials with desirable characteristics including biodegradability, renewable sources, high aspect ratios, high surface area, and high strength. Polyacrylonitrile (PAN) is the most commonly used polymer precursor for electrospinning due to its high melting point and large carbon yield. In this study, PAN/CNC nanofibers were electrospun from solutions of PAN and CNCs in N,N-dimethylformamide and were assessed for their adsorption performance. First, electrospinning conditions were optimized to form PAN-CNC composite nanofibers with uniform diameters and smooth morphology at CNC loadings of 0, 10, 20, and 30 % WCNC/WPAN. Second, electrospun PAN-CNC composite nanofibers were stabilized and then activated at 800°C with KOH as activating agent to produce activated carbon nanofibers (ACnFs). The ACnFs were then characterized for their morphological, thermal, mechanical, chemical properties, as well as their surface area and pore size distribution. Last, the adsorption properties of ACnFs were tested for methyl ethyl ketone (MEK) and cyclohexane. MEK and cyclohexane were selected because they are widely used organic solvents for industrial processes, and have similar boiling point, density and heats of vaporization (similar heats of adsorption).
Scanning electron microscopy images revealed that the addition of CNCs has improved fiber uniformity and decreased fiber diameter. This is attributed to the enhanced electric conductivity of electrospinning solutions in the presence of CNCs. Thermal and mechanical properties of electrospun fiber mats were studied using thermal gravimetric analysis and dynamic mechanical analysis. The addition of CNC produced minimal changes in fibers thermal behavior and resulted in significant improvement to the fibers mechanical properties. PAN-CNC composite nanofibers webs showed an increase in tensile strength compared to neat PAN nanofibers webs. The pore size distribution of analyzed samples indicated large volume of micropores and mesopores resulting in about 75 % microporosity. Among the tested samples, the maximum surface area and micropore volume are 3,497 m2/g and 1.04 cc/g for 30% WCNC/WPAN. In addition, the maximum adsorption capacity of the 30% CNC/PAN sample reached 170 % for both adsorbates. Compared to activated carbon fiber cloth and beaded activated carbon, PAN-CNC composite nanofibers depicted faster adsorption kinetics reflecting in higher mass transfer coefficients due to the small fiber diameter. These results showed that CNCs have a distinct advantage for improving the mechanical and adsorption properties of electrospun nanofibers. -
- Subjects / Keywords
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- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.