Mechanism of water transport through reverse osmotic membranes
Cellulose acetate membranes show a higher permeability to water than to salt and are being used for desalination of salt water by reverse osmosis. Use of highly acetylated cellulose membranes give a higher salt rejection but also decrease flow rate of the water. The addition of very-short-chain subs...
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| Format: | Others |
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BYU ScholarsArchive
1969
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| Online Access: | https://scholarsarchive.byu.edu/etd/8312 https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=9312&context=etd |
| Summary: | Cellulose acetate membranes show a higher permeability to water than to salt and are being used for desalination of salt water by reverse osmosis. Use of highly acetylated cellulose membranes give a higher salt rejection but also decrease flow rate of the water. The addition of very-short-chain substances or alkyl groups larger than one carbon atom to the cellulose membrane also decreases water flux. A proposed mechanism of transport through the membrane is that the water molecule is passed along the chain by hydrogen bonding with the acetyl groups, The NMR shows a change in the chemical shift of water with an increasing concentration of an acetylated saccharide or with decreasing temperature which indicates hydrogen bonding. The ring oxygen of Tetrahydropyran is a poor hydrogen bonding site according to NMR data. Also from NMR data, Cellulose Triacetate ties up at least 18 water molecules. The osmometer data indicates that α-D Glucose Penta-acetate has two hydrogen bonding sites per molecule with Phenol. |
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