Thermodynamics of water and ethanol adsorption on four starches as model biomass separation systems.

Adsorption of water and ethanol on four starches has been studied in the temperature range of 50-90 degrees C. The results show that adsorption of water on starch-based materials is enhanced when the amount of amylopectin is highest. Adsorption of ethanol is not significantly affected by the kind of starch used. Heats of adsorption calculated from retention data are in the range from -9.3 to -13.7 kcal/g mol for water and -5.6 to -6.76 kcal/g mol for ethanol. Calculated free energies of adsorption suggest that adsorption is most spontaneous at lower temperatures as expected.