Liquid-Vapor Coexistence in the Screened Coulomb (Yukawa) Hard Sphere Binary Mixture in Disordered Porous Media: The Mean Spherical Approximation.

The thermodynamics of a two-component fluid with a hard core interaction and screened Coulomb (Yukawa) interaction between particles, similar to the primitive model of an electrolyte solution, adsorbed in a disordered matrix of hard spheres, is studied by using replica Ornstein-Zernike integral equations and the mean spherical approximation (MSA). The gas-liquid transition is localized. The coexistence curve is investigated dependent on the range of interaction between fluid species, on matrix density, and on fluid-matrix attraction. We have observed shrinking of the coexistence envelope with increasing matrix density. The critical temperature of adsorbed mixture decreases with increasing matrix density. The critical density is less affected; however, it also decreases slightly. The critical temperature is sensitive to the fluid species-matrix attraction and depends nonmonotonously on their strength. For a given matrix microporosity, it increases slightly and then decreases with augmenting strength of fluid-matrix attraction. The critical density is less affected by this attraction. However, it decreases for the model with a sufficiently long-range tail of fluid-matrix attraction. Copyright 1998 Academic Press.