SEPARATION OF WATER AND ETHANOL BY THE ADSORPTION TECHNIQUE - SELECTIVE DESORPTION OF WATER FROM MICROPORES OF ACTIVE-CARBON

The hydrophobic micropores of active carbon were filled with a mixture of water and ethanol by adsorbing their mixed vapors (H2O/EtOH = 3/1) on active carbon, The desorption isotherm of each component from the micropores has been determined simultaneously at 25 degrees C by a com bination of volumetric and gravimetric methods. A more selective desor ption of water than that of ethanol was discovered from the measured i sotherms, It has been clarified from the present finding that the sepa ration of water and ethanol could be carried out by means of an adsorp tion technique using a hydrophobic active carbon adsorbent, The prefer ential desorption of water may be attributed to the weak interaction o f water with the hydrophobic micropore surface in comparison with the interaction of ethanol with the micropore surface. The adsorption ener gy of water on the micropore surface is 17-32 kJ mol(-1) at low covera ge, while that of ethanol on the micropore surface is 43-52 kJ mol(-1) , The possibility of enrichment of ethanol from its dilute aqueous sol ution made by fermentation was discussed on the basis of the present d esorption data. (C) 1996 Academic Press, Inc.