Membrane distillation for dilute ethanol - Separation from aqueous streams

Air-gap membrane distillation was examined as a possible technique for etha nol-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 concent ration 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 sy stem; one did not include temperature and concentration polarization effect s while the other did. Good agreement between experimental and predicted va lues was obtained with the latter version of the model. (C) 1999 Elsevier S cience B.V. All rights reserved.