Effect of regeneration thermal treatment of cellulosic and starchy materials on their capacity to separate water and ethanol

Inverse gas chromatography was used to study the adsorption of water and et hanol on to a starchy (wheat flour) and a cellulosic (wheat straw) substrat e, in the temperature range 50 90 degrees C, before and after their regener ation by thermal treatments at 140 and 170 degrees C, for 12 and 21 h each. From the chromatographic retention data it was possible to calculate the s eparation factor (s) of the two solutes and to obtain values for Gibb's fre e energy (Delta Gs) and enthalpy (Delta Hs) of adsorption. The results show ed that water was adsorbed more strongly than ethanol by both substrates, a t all temperatures, before and after their regeneration. In addition, it wa s found that, for both untreated and thermally treated materials, the adsor ption of both solutes was stronger at lower temperatures. Thermal treatment had no effect on the adsorption of ethanol on either substrate. In contras t, the adsorption of water was weaker for both substrates regenerated at 14 0 degrees C and even weaker for the substrates treated at 170 degrees C, ir respective of the duration of the regeneration process. Furthermore, at bot h regeneration temperatures, the decrease in water sorption was approximate ly the same for both materials, irrespective odf regeneration time. The sep aration factors followed, in general, the same trend observed for water sor ption. They had lower values for materials regenerated at 170 degrees C for 24 h. Both materials were equally affected by the regeneration process. (C ) 2000 Academic Press.