Statistical physics modeling of ethanol adsorption onto the phenol resin based adsorbents: Stereographic, energetic and thermodynamic investigations

Abstract Statistical physics treatment has been used to study the adsorption of ethanol on two types of phenol resin-based adsorbents (KOH4-PR and KOH6-PR). In this work, we have used the adsorption isotherms of the two proposed systems (ethanol/KOH4-PR and ethanol/KOH6-PR) at different temperatures, in order to interpret the evolution of physicochemical parameters involved in the proposed model. For this reason, we have applied a multilayer model with saturation which is established through the grand canonical ensemble of statistical physics. This model has been selected from others by the determination coefficient R 2 and applied to discuss the adsorption process. Five physicochemical parameters characterizing the adsorption process have been investigated namely the number of adsorbed ethanol molecules per site ( n ), the density of receptor sites ( N M ), the number of adsorbed layers ( N 2 ) and the energetic parameters ( − Δ E 1 ) and ( − Δ E 2 ). The equilibrium data were interpreted through these parameters in relation with their temperature dependence. Through this selection of the best fitting model and through fitted values of these parameters, we showed that the adsorption of ethanol molecules is not only a multilayer process but also a multimolecular process. The energetic parameters fitted values of the adsorption process showed that the adsorption process is exothermic and that the ethanol molecules are physisorbed on the phenol resin adsorbent. Van der Waals or the hydrogen interactions are implicated in the adsorption process. Thermodynamic potential functions such as the configurational entropy, Gibbs free energy and, internal energy are calculated. They indicate the macroscopic evolution of these potentials with pressure in relation with system temperature. The adsorption of ethanol onto phenol resin (KOH4-PR and KOH6-PR) is a spontaneous and globally exothermic in nature. Lastly, the adsorption isotherm of ethanol onto the types of phenol resin provides access to the pore sizes distribution (PSD), and also the adsorption energy distribution (AED).