Dewatering of concentrated aqueous solutions by pervaporation

The method which comprises

• passing a charge aqueous solution of ethylene glycol into contact at 40.degree. C.-120.degree. C. with, as a pervaporation membrane, (i) a perfluorinated resin membrane having the formula ##STR4## wherein M is a metal, m is a number indicating the number of (CF.sub.2 CF.sub.2) groups, and n is a number indicating the number of ##STR5## groups, said resin membrane bearing, as a counter ion, a metal of Groups IA, IB, IV B, V B, VI B, or VIII of the Periodic Table or a quaternary ammonium group R.sub.4 N wherein R is a lower alkyl, and each R group contains less than 6 carbon atoms;
• maintaining a pressure drop across said pervaporation membrane thereby forming (i) a retentate containing an increased concentration of ethylene glycol and a decreased content of water and (ii) a permeate containing a decreased concentration of ethylene glycol and an increased concentration of water;
• recovering said retentate containing increased concentration of ethylene glycol and decreased concentration of water;
• and
• recovering said permeate containing increased concentration of water and decreased concentration of ethylene glycol.