New Synthetic Membranes for Reverse Osmosis Desalination

摘要

Several polymeric substrates were studied, from the standpoint of their ability to form reverse osmosis membranes with improved performance. The aim in each case was to control inherent water uptake, either through cross-linking, or through copolymerization, and to develop products with water contents in the range 10-20%. Several systems were found to be successful in rejecting salt initially, but in most cases structure, and hence properties, was impaired after relatively short times of operation. One exception was the copolymer system based on galactose methacrylate and methyl methcrylate. Several samples have been prepared with water contents ranging from 7 - 20%. Sodium chloride rejection is effectively 100% for the lower water content copolymers, and begins to decrease at water contents between 10 and 15%. Magnesium sulphate rejection, however, is maintained at approximately 100%. The resistance of these films to pressure in the homogeneous state, is better than for cellulose acetate, and alkali resistance is similarly improved. A series of experiments was carried out in an attempt to produce high throughput asymmetric membranes based on these copolymers. One most favourable feature of some products is their ability to reject divalent ion salt even when sodium chloride rejection is quite low. Thus one membrane which rejects only 35% sodium chloride, rejects 99% magnesium sulphate. (Author)