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Modelling and Simulation in Engineering
Volume 2014, Article ID 427842, 8 pages
Research Article

Mathematical Modeling of Moisture Sorption Isotherms and Determination of Isosteric Heats of Sorption of Ziziphus Leaves

1Laboratoire d’ Energétiques en Zones Arides (ENERGARID), Equipe Gisement Solaire et ses Applications (GSA), Université de Bechar, 08000 Bechar, Algeria
2Laboratoire de Chimie Organique, Substances Naturelles et Analyses, Département de Chimie, Faculté des Sciences, Université Abou Bekr Belkaid, 13000 Tlemcen, Algeria

Received 31 January 2014; Accepted 19 March 2014; Published 27 April 2014

Academic Editor: Agostino Bruzzone

Copyright © 2014 Amel Saad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Desorption and adsorption equilibrium moisture isotherms of Ziziphus spina-christi leaves were determined using the gravimetric-static method at 30, 40, and 50°C for water activity ranging from 0.057 to 0.898. At a given , the results show that the moisture content decreases with increasing temperature. A hysteresis effect was observed. The experimental data of sorption were fitted by eight models (GAB, BET, Henderson-Thompson, modified-Chung Pfost, Halsey, Oswin, Peleg, and Adam and Shove). After evaluating the models according to several criteria, the Peleg and Oswin models were found to be the most suitable for describing the sorption curves. The net isosteric heats of desorption and adsorption of Ziziphus spina-christi leaves were calculated by applying the Clausius-Clapeyron equation to the sorption isotherms and an expression for predicting these thermodynamic properties was given.