Membrane distillation for dilute ethanol - Separation from aqueous streams

Air-gap membrane distillation was examined as a possible technique for ethanol-water separation using PVDF membranes. The composition and flux of the permeate were monitored as feed concentration, feed temperature, feed flow rate, cooling temperature and cooling flow rate were varied. The effect of salt addition to the feed mixture was also examined. The upper feed concentration tested was 10 wt.% ethanol. Within the feed temperature range of 40-70 degrees C, ethanol selectivity of 2-3.5 was achieved. Two versions of a general mathematical model were solved numerically for the ethanol-water system; one did not include temperature and concentration polarization effects while the other did. Good agreement between experimental and predicted values was obtained with the latter version of the model. (C) 1999 Elsevier Science B.V. All rights reserved.