Molecular theory of physical adsorption on heterogeneous surfaces: Temperature dependence of henry constant

Abstract

Abstract The atomic structure of a heterogeneous surface of highly dispersed oxide was simulated as a dense random packing of hard balls (oxygen ions) by the Bernal model. For this model adsorbent, the Henry constants were calculated for Ar and Xe in a broad range of temperatures on the basis of the atom-ion approximation and the general formula that is valid for heterogeneous as well as for homogeneous surfaces. The Henry constants of the same atoms on a homogeneous surface with a regular dense packing of oxygen ions were calculated for comparison. The logarithm of the Henry constant depends linearly on the reciprocal of temperature for homogeneous surfaces; for heterogeneous surfaces, the dependence is nonlinear, but asymptotically approaches the two intersecting straight lines at high and low temperatures. Diagrams of the Henry constant density distribution over the surface show that at high temperatures adsorption on a heterogeneous surface occurs as on a homogeneous one. At low temperatures the Henry constant is determined by the strongest adsorption sites.