title: Influence of Air Temperature and Humidity on Dehydration Equilibria and Kinetics of Theophylline.
abstract: The effect of hygrothermal conditions (air temperature and relative humidity) on the dehydration of theophylline monohydrate was investigated. Firstly, the equilibrium states of theophylline were investigated. The data from gravimetric analysis at constant temperature and humidity were reported as desorption isotherms. The PXRD analysis was used to identify the different polymorphic forms of theophylline: the monohydrate, the metastable anhydrate, and the stable anhydrate. Solid-solid phase diagrams for two processing times were proposed. Secondly, the dehydration kinetics were studied. The water content evolutions with time were recorded at several temperatures from 20°C to 80°C and several relative humidities from 4% to 50%. Different mathematical models were used to fit the experimental data. The spatially averaged solution of 2D Fickian transient diffusion equation best represented the water mass loss versus time experimental relationship. The dehydration rate constant was found to increase exponentially with air temperature and to decrease exponentially with air relative humidity.
authors.affiliation: Ecole Nationale d'Ingénieurs de Gabès (ENIG), Université de Gabès, rue Omar Ibn-Elkhattab, Gabès 6029, Tunisia.
authors.forename: Amira
authors.initials: A
authors.lastname: Touil
authors.affiliation: Université de Lyon, Université Lyon 1, 69622 CNRS, UMR 5007, Laboratoire d'Automatique et Génie des Procédés (LAGEP), Campus de la Doua, bât. CPE, 3 rue Victor Grignard, 69616 Villeurbanne, France.
authors.forename: Roman
authors.initials: R
authors.lastname: Peczalski
authors.affiliation: Institut Supérieur des Sciences Appliquées et de Technologie de Gabès (ISSAT), Université de Gabès, rue Omar Ibn El-Khatab, Gabès 6029, Tunisia.
authors.forename: Souad
authors.initials: S
authors.lastname: Timoumi
authors.affiliation: Institut Supérieur des Sciences et Technologies de l'Environnement (ISSTE), Université 7 Novembre de Carthage, Technopôle de Borj Cédria, Hammam-Lif 1003, Tunisia.
authors.forename: Fethi
authors.initials: F
authors.lastname: Zagrouba