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 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.
College and Department
Chemistry and Biochemistry
BYU ScholarsArchive Citation
Murphy, Cheryl Kay, "Mechanism of water transport through reverse osmotic membranes" (1969). Theses and Dissertations. 8312.
Water, Purification, Osmosis