| abstract |
Selectively permeable, polymeric membranes for use in the reverse osmosis separation of components of aqueous mixtures and solutions, particularly saline and brackish water, are chemically treated to preserve their permeability characteristics and to protect against loss thereof during the obtention of a watertight seal with the potting compounds generally employed in permeation separation devices. The desired results are achieved by effecting a substantial replacement of membrane-associated water with an inert organic medium exhibiting a lower volatility than water. Depending on the degree of hydrophilicity and water solubility of the organic medium, replacement of the membrane-associated water is accomplished by direct contact including successive contacts of the water-wet membrane with aqueous solutions of increasing organic medium concentration and/or indirect contact including successive contacts of the membrane with organic media of decreasing hydrophilicity. Reversal of the replacement process to reintroduce water to the membrane structure restores the operability of the members and renders them effective for their intended desalination and purification functions. |