Salah Knani

Application of Statistical Physics on the Modeling of Water Vapor Desorption Isotherms

The sorption isotherms give information about the interaction of biopolymers with water vapor. These isotherms are extremely important in the modeling of the drying processes and in the prediction of the humidity changes during the product storage. An analytical expression for modeling of water vapor sorption isotherms of agricultural products was developed using the statistical physics formalism. The statistical model was further used to fit and interpret desorption isotherms of Tunisian olive leaves and some food products. In this model, five parameters in relation to the desorption process intervene, such as the number of water molecules per site n, the receptor sites density N M , the energetic parameters a 1 and a 2, and the number of multilayers N 2. The fitting results are discussed to explain the behavior of different parameters versus temperature. The statistical model was used to investigate thermodynamics functions that govern in the desorption mechanism, such as entropy, internal energy, and Gibbs free enthalpy.

Binary adsorption isotherms of two ionic liquids and ibuprofen on an activated carbon cloth: simulation and interpretations using statistical and COSMO-RS models

The adsorption equilibriums of binary mixtures of the 4-tert-butyl-1-propylpyridinium bromide (referred to IL1) and 4-tert-butyl-1-(2 carboxyethyl) pyridinium bromide (referred to IL2) ionic liquids and ibuprofen (2-(4-(2-methylpropyl) phenyl) propanoic acid: IBP) on activated carbon cloth were investigated. The binary adsorption isotherms of the studied systems (IL1/IL2, IL1/IBP and IL2/IBP) have been studied in different conditions (different temperatures ranging from 286 to 313 K and at various concentration ratios 0.5, 1 and 2). The experimental isotherms have been simulated by some new statistical physics models established from the grand canonical ensemble. According to the most appropriate model, the adsorbed ILs and IBP molecules are assumed to be parallel to the activated cloth surface. An inhibition effect has been observed between the adsorbed molecules. The determination of the monolayer adsorbed uptake at saturation has shown an endothermic adsorption process of IBP and an exothermic one of IL1 and IL2. The estimated energy values demonstrate a physical adsorption whatever the adsorbate species. The microscopic adsorption process was interpreted from the point of view of molecular stereography and interaction energy. Moreover, a conductor-like screening model for real solvents (COSMO-RS) has been applied to calculate three specific interaction energies between the adsorbate molecules and a graphene layer modeling the activated carbon surface, i.e., the electrostatic misfit energy (EMF), the hydrogen-bonding energy (EHB) and the van der Waals energy (EvdW).

Experimental and theoretical studies of adsorption of ibuprofen on raw and two chemically modified activated carbons: new physicochemical interpretations

Knowledge of the ibuprofen (IBP) adsorption isotherms is important to understand and to improve its depollution process. In this work, the double layer model with two energies was applied to simulate the adsorption isotherms of ibuprofen on raw activated and two chemically modified granular activated carbons, obtained experimentally at pH = 7 and at different temperatures (298, 313 and 323 K). The chemically modified samples were obtained by treatment at 700 °C under nitrogen flow and ultrasonic treatment in H2O2 solution of the raw granulated activated carbon. The establishment of the model is based on a statistical physics approach, particularly on the grand canonical ensemble. The double layer model with two energies for each layer was found to be the best model to describe the adsorption process of ibuprofen. Using this model, the different adsorption isotherms of ibuprofen were described sterically and energetically through these parameters. The different parameters were interpreted as a function of temperature. In addition to this, the entropy, free enthalpy and the internal energy governing the adsorption process were calculated and interpreted.