PERVAPORATION OF ETHANOL-WATER MIXTURES THROUGH POLYVINYL ALCOHOL-POLYACRYLAMIDE INTERPENETRATING POLYMER NETWORK MEMBRANES UNSUPPORTED ANDSUPPORTED ON POLYETHERSULFONE ULTRAFILTRATION MEMBRANES - A COMPARISON

Polyvinyl alcohol-polyacrylamide interpenetrating polymer network (PVA -PAAM IPN) membranes, both unsupported and supported on polyethersulfo ne (PESF) ultrafiltration membranes, were prepared and investigated re garding the pervaporation of water-ethanol mixtures. Compared to the c rosslinked polyvinyl alcohol membranes, the PVA-PAAM IPN membranes exh ibit improved thermostability, mechanical properties and selectivity. The PVA-PAAM IPN membranes were synthesized by the sequential IPN tech nique. The thicknesses of the unsupported membranes were in the range 30-40 mu m, those of the supported ones were about 4 mu m, and that of the PESF membrane was 90 mu m. The selection of the compositions of t he PVA-PAAM IPN layer of the supported membranes was made by examining the pervaporation performance of the unsupported ones. Furthermore, t he effects of the feed composition, feed temperature and operating rim e on the performance of the PVA-PAAM IPN supported membrane was invest igated. Depending on the feed composition and temperature, the support ed membranes had separation factors between 30 and 28 300 and permeati on rates between 30 and 3800 g/(m(2) h). High selectivities were obtai ned at high ethanol concentrations. For the azeotropic water-ethanol m ixture (95 wt% ethanol), the supported membrane had at 60 degrees C a separation factor of 13 000 and a permeation rate of 80 g/(m(2) h). Co mpared to the unsupported membranes, the supported ones had a higher p ermeability but a somewhat lower selectivity.