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Coupled Supercritical CO2 - Membrane Technology for Lipid Separations Open Access

Descriptions

Other title
Subject/Keyword
membrane
separation
lipid
supercritical
polymer
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Akin, Oguz
Supervisor and department
Temelli, Feral (Agricultural, Food and Nutritional Science)
Examining committee member and department
Diosady, Levente (Chemical Engineering and Applied Chemistry, University of Toronto)
Bressler, David (Agricultural, Food and Nutritional Science)
McCaffrey, William (Chemical and Materials Engineering)
Vasanthan, Thava (Agricultural, Food and Nutritional Science)
Department
Department of Agricultural, Food and Nutritional Science
Specialization

Date accepted
2011-10-04T18:34:00Z
Graduation date
2011-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Coupling supercritical CO2 extraction with membrane separation leads to energy savings by recycling CO2 at supercritical state while separating extract components. Commercially available polyamide-based membranes are commonly used with coupled systems due to their availability and robust structures. However, high pressure operating conditions may cause physicochemical and morphological changes in polymer membranes, which in turn can adversely affect membrane performance. Since most of the information on commercial reverse osmosis membranes is proprietary, further investigation on their structure would be beneficial for selection of the proper membranes, especially for processes involving various solvents such as supercritical CO2. Therefore, detailed characterization of four polyamide membranes was performed using advanced instrumental techniques for better understanding of their physicochemical and morphological properties. Findings suggest that AK and AG membranes had excess of intermolecular hydrogen bonds, while SG and SE had modified covalently cross-linked structure. Temperature, pressure and CO2 flux were the major processing parameters investigated to assess the interactions between the polyamide membranes and CO2. The observed interactions between the polymer and CO2 were attributed to Lewis acid and base interactions and hydrogen bonding. The change in surface hydrophobicity and drop in absorbance of particular functional groups were determined as indicator of physicochemical changes in the structure. Morphological changes were also observed upon processing with supercritical CO2 up to 24 h. Performance of the membranes was tested using pure oleic acid retention and separation of a triacylglycerol/oleic acid mixture. Covalently cross-linked membrane structures were found to be more resistant to supercritical conditions. Reorganization of the polymer network due to interactions during CO2 exposure affected the membrane performance dramatically. Investigation of performance and stability of polyamide membranes clarified the major factors responsible for adverse effects on their structures such as swelling and plasticization during processing. Results obtained in this thesis research contribute both to the fundamental understanding of polymer membrane behaviour under supercritical conditions and to the type of membrane materials needed for such novel process development without sacrificing membrane performance.
Language
English
DOI
doi:10.7939/R3QG6G
Rights
License granted by Oguz Akin (oguz@ualberta.ca) on 2011-09-30T17:08:19Z (GMT): 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 the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein 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.
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