Effect of enthalpy-entropy compensation during sorption of water vapour in tropical woods: The case of Bubinga (Guibourtia tessmanii J. Léonard ; G. Pellegriniana J.L.)

The study of sorption of water vapour by a tropical wood (Bubinga) at 20°C, 38°C, 50°C and 60°C has permitted to obtain adsorption and desorption isotherms. Sigmoids have been obtained and they all show hysteresis phenomenon. From these isotherms, we were able to determine Gibbs energy, enthalpy and entropy variations. These variations were analysed and shown to be all negative for adsorption and all positive for desorption, with a great dependence to the moisture content during adsorption and desorption. Temperature had no significant effect on these parameters. Such dependence is mentioned in the scientific literature for softwood and is surely related to the availability of sorption sites. A linear relationship between enthalpy and entropy was shown to exist and the effect of enthalpy-entropy was studied for adsorption and desorption of water vapour by wood. In fact, the isokinetic temperature was determined and compared to the harmonic mean of temperatures. © 2007 Elsevier B.V. All rights reserved. (Résumé d'auteur