Application of interfacially polymerized polyamide composite membranes to isopropanol dehydration: Effect of membrane pre-treatment and temperature

Commercial thin-film composite reverse osmosis (RO) membranes (SWC5, ESPA2 and CPAS) were dried under different membrane pre-treatments and evaluated for isopropanol dehydration at increased temperatures in pervaporation and vapor permeation systems. Water permeance was enhanced in the membranes pre-treated with ethanol-hexane and freeze drying, compared with those membranes dried by room temperature and in an oven. In particular, ethanol-hexane dried samples showed an enhanced water permeance by a factor of 1.7-3.5, depending on the structural characteristics of each membrane. The membranes exhibited stability for up to 25 operation hours in the vapor permeation system. Moreover, the operation temperature was an important factor in determining water and isopropanol permeances. With an increase in temperature, the highly permeable regions, which showed low selectivity, were plugged more rapidly. As a result, the maximum water/isopropanol separation factor was reached at 150 degrees C, alpha(water/lPA)=284, with a considerably high flux of 5.93 kg/(m(2)h) for a CPAS high-rejection RO membrane. The induced changes in the polymer morphology and separation performance data were compared to single gas permeation. The results are discussed in terms of membrane swelling, which softens the polymer and decreases the diffusion resistance to molecules in pervaporation by comparison with vapor permeation. (C) 2013 Elsevier B.V. All rights reserved.