Adsorption characterisation of water and ethanol on wheat starch and wheat gluten using inverse gas chromatography

Adsorption of water and ethanol on wheat starch and wheat gluten has been studied in the temperature range of 60–150 °C using inverse gas chromatography (IGC). From the chromatographic retention data it is able to calculate the separation factors for the two solutes and obtain values for thermodynamic parameters such as Gibbs free energy (ΔGs) and the enthalpy (ΔHs) of adsorption of water and ethanol. The results indicate that water is adsorbed more strongly than ethanol at all temperatures, and the low temperature is found to facilitate the adsorptive separation of water from ethanol. It is also shown that the starch definitely plays a crucial role for the water and ethanol separation, despite that wheat flour includes both gluten and starch. The wheat starch is seen to have potential application in biomass water–ethanol separation to obtain fuel ethanol through the preferential adsorption of water from aqueous ethanol.