Analysis of multilayer adsorption of oxygen-nitrogen mixtures on anatase

A theoretical analysis of multilayer adsorption of a mixture of gases O-2 and N-2 on an amorphous surface of anatase (TiO2) was carried out. Equations of the theory are based on the lattice-gas model. Intermolecular interactions between the closest neighbors were taken into account in the mean-field approximation. The energy parameters of these interactions were determined from the data on the vapor-liquid equilibrium. The calculation of the mixed adsorption was preceded by the description of multilayer adsorption of individual gases. The model describes adequately the overall and partial isotherms of multilayer adsorption of a mixture of gases provided that (1) the roughness of the adsorbent surface is taken into account in a simplified way and (2) the relationships between the heats of adsorption of the O-2 and N-2 molecules on various sites of the heterogeneous surface of anatase are similar.