ADSORPTION IN PORES WITH HETEROGENEOUS SURFACES

Adsorption in porous sorbents is described by a lattice-gas model considering lateral interactions between adsorbed molecules and using a quasichemical approximation. Chemical and structural imperfections of pore walls are taken into account. Surface composition and the occurrence of different adsorption centers are included by introducing certain distribution functions. Homogeneous, stepped, and rough walls of pores are considered. The self-consistent description of equilibrium (the local occupations of the different adsorption centers, isotherms, and isosteric heats of adsorption) and kinetic characteristics (the diffusion coefficients of the adsorbed molecules) can be performed with the present model. Isotherms as well as a dependence of the isosteric heat of adsorption and the diffusion coefficient on concentration are investigated, and a relation between these generated theoretical curves and the corresponding experimental data is briefly discussed. In addition, qualitative description of SF6 isotherms on controlled-pore glasses is presented.