The thermodynamic state of a confined fluid must be described by a theory adapted to inhomogeneous systems. Among existing theories, the well-known Fundamental-Measure Theory (FMT), based upon statistical physics, have been proposed in the literature for the description of confined hard-sphere fluids [1, 2]. The aim of the present work is to propose a new description for an inhomogeneous square-well fluid from the FMT point of view, as an application of a more realistic interaction potential taking into account both repulsive and attractive interactions. This new description is then used to define a new functional of the inhomogeneous free-energy density in a formulation that is suitable with a Statistical Associating Fluid Theory (SAFT) equation of state [3] in the bulk limit.
This new functional is introduced in the Classical Density Functional Theory formalism [4] in order to study the adsorption of fluid mixtures confined in micro- and mesopores of various geometries. Density profiles in the pores are validated by comparison with Monte Carlo molecular simulations.
Otherwise, several adsorption experiments have been done with a coupled apparatus manometric/calorimetric device [5] on real samples, in order to validate the model at the macroscopic scale. To that extent, we have measured adsorption isotherms and differential heats of adsorption of carbon dioxide, alkanes and water vapor on micro- and mesoporous silica with cylindrical well-characterized pores.
[1] Rosenfeld, Y., Phys. Rev. Lett., 63, 980 (1989)
[2] Kierlik, E., Rosingerg, M. L., Phys. Rev. A, 42 (6), 3382 (1990)
[3] Gil-Villegas, A. et al., J. Chem. Phys., 106 (10), 4168 (1997)
[4] Bernet, T. et al., J. Phys. Chem. C, 121, 6184 (2017)
[5] Mouahid, A., et al., J. Therm. Anal. Calorim., 109 (2), 1077 (2012)
