A general approach based on morphological thermodynamics for a fluid confined in various porous media

We propose a general approach based on morphological thermodynamics for determining adsorption isotherms, i.e., the chemical potential of a confined fluid as a function of its density. The validity of this approach and its versatility are established by its remarkable accuracy compared to Monte-Carlo simulation results and its capability of accounting for a quite large variety of porous media, ranging from a simple slit pore to a random sponge matrix. It is also revealed that the contribution of the curvature terms to the chemical potential of the confined fluid is negligibly small when the interface curvature is not too large. This finding is of a particular importance for simplifying the treatment of experimental results of adsorption isotherms since no experimental technique is currently available for determining the curvatures of the pore surface inside a porous material.