Adsorption of a hard sphere fluid in disordered microporous quenched matrix of short chain molecules, integral equations and grand canonical Monte Carlo simulations

A model of hard spheres adsorbed in a disordered quenched matrix of chain m olecules is studied by using the replica Ornstein-Zernike equations and gra nd canonical Monte Carlo simulations. The pair distribution functions and t he adsorption isotherms are obtained and discussed. The theory agrees well with simulation data. The Percus-Yevick and the hypernetted chain approxima tions are almost equally adequate for the description of the structure and thermodynamics of adsorbed hard sphere fluid. It is shown that the excluded volume effects of chain matrix, prepared by chemical association mechanism and then quenched, have predominant influence on the adsorption of a hard sphere fluid at fixed matrix packing fraction in matrices of chains with 4, 8, and 16 hard sphere beads. The partitioning coefficient is weakly depend ent on the fluid chemical potential at fixed matrix packing. It, however, s ubstantially decreases with decreasing microporosity of the matrix. (C) 199 9 Academic Press.