PERVAPORATION SEPARATION OF BINARY ORGANIC AQUEOUS LIQUID-MIXTURES USING CROSS-LINKED PVA MEMBRANES .3. ETHANOL-WATER MIXTURES

The application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process-a water-selective process-was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water-ethanol mixtures, specially 50/50 solution at 60 degrees C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75 degrees C. For water: ethanol = 50 : 50 solution, the separation factor alpha(w/e) = 260 at 75 degrees C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water-ethanol mixture showed 30 g/m(2)/h and 5800 at 75 degrees C, respectively, when a PVA/PAA = 80/20 membranes was used. (C) 1995 John Wiley & Sons, Inc.