CO2-Responsive Agents for Water Filtration
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Authors
Ellis, Sarah
Date
Type
thesis
Language
eng
Keyword
Water filtration , Forward Osmosis , Draw Agent , CO2 utilization
Alternative Title
Abstract
Water purification is essential for modern human life. Without it we could not produce clean water, process wastewater or concentrate desired products. Unfortunately, standard water purification techniques are energy intensive, especially for concentrated feeds. Forward osmosis (FO) is a promising filtration method, with the ability to process concentrated feeds at lower energy costs than conventional methods.
FO operates by placing a concentrated “draw solution” opposite the water to be filtered (the feed), separated by a semipermeable membrane. The osmotic pressure (π) difference across the membrane causes water to flow from the feed to the draw solution. After filtration is complete the draw solute is removed, leaving behind clean water. While the initial filtration requires minimal energy, removing the draw solute from the clean water after filtration can be energy intensive due to the draw solutes’ high π. The efficiency of FO hinges on the nature of the draw solute.
An ideal draw solute must possess two seemingly contradictory properties: a high π state for efficient filtration and a low π state for easy draw solute removal post-filtration. CO2-responsive materials are attractive draw solutes as they possess a high π under CO2 (πCO2) and a low π under air (πair). The most successful draw solute reported to date, trimethylamine (TMA), exerts a very high πCO2 but is also flammable, malodorous and can cross the membrane.
This work investigated new CO2-responsive materials which could be safe alternatives to TMA. Diverse CO2-responsive materials were considered, including polymers, hydrogels and magnetic particles. In each case, materials were designed and synthesized, then their performance as a draw solute was assessed by measuring their πCO2 and πair or their flux and recovery. Fluid draw agents outperformed solid draw agents due to improved mass transfer, and are easier to implement industrially.
Among all the draw solute studied, soluble poly(N,N-dimethylallylamine) (PDMAAm) showed the most promise due to its high πCO2 and low πair. The use of PDMAAm’s dual CO2- and thermo-responsive character was found to facilitate its separation from water after filtration. Future work will study the performance of PDMAAm on larger scales for industrial use.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.