E. Immelman et al., POLY(VINYL ALCOHOL) GEL SUBLAYERS FOR REVERSE-OSMOSIS MEMBRANES .1. INSOLUBILIZATION BY ACID-CATALYZED DEHYDRATION, Journal of applied polymer science, 50(6), 1993, pp. 1013-1034
Both flat-sheet and tubular composite reverse osmosis (RO) membranes w
ere prepared by depositing aqueous solutions of poly (vinyl alcohol) (
PVA) and a dehydration catalyst on asymmetric poly (arylether sulfone)
(PES) substrate membranes. The PVA coatings were insolubilized by hea
t treatment to create stable hydrophilic gel-layer membranes. The infl
uence of variables such as PVA concentration, catalyst concentration,
curing time, and curing temperature was investigated. It was shown tha
t a simple manipulation of one or two variables could lead to membrane
s with widely differing salt retention and water permeability characte
ristics. The insolubilized PVA coatings were intended to serve as hydr
ophilic gel sublayers on which ultrathin salt-retention barriers could
ultimately be formed by interfacial polycondensation. For this purpos
e, high-flux gel layers were required, whereas salt-retention capabili
ties were not regarded as important. However, the promising salt reten
tions obtained at 2 MPa (up to 85% NaCl retention and 92% MgSO4 retent
ion) showed that some of these PES-PVA composite membranes could funct
ion as medium-retention, medium-flux RO membranes, even in the absence
of an interfacially formed salt-retention barrier. (C) 1993 John Wile
y & Sons, Inc.