MULTILAYER ADSORPTION WITH MULTISITE OCCUPANCY

ROMÁ F.; RAMIREZ PASTOR A. J.; RICCARDO J. L.

ADSORPTION SCIENCE & TECHNOLOGY

MULTI SCIENCE PUBL CO LTD

Lugar: Brentwood, UK; Año: 2003 vol. 1 p. 645 - 649

0263-6174

Among the various theories and models that have been proposed to describe multilayeradsorption in equilibrium, the ones of Brunauer-Emmet-Teller (BET) [l] is the mostwidely used and practically applicable. The great popularity of the BET equation inexperimental studies of adsorption led some authors to extend the original theory ofmultilayer adsorption. Thus, numerous generalizations of the BET model have beenreported in the literature, including surface heterogeneity, lateral interaction between theadmolecules, differences between the adsorption energy and structure between the firstand upper layers, etc, [2,3]. These leading models, along with much recent contributions,have played a central role in the characterization of solid surfaces by means of gasadsorption [4]. One fundamental feature of BETS model is preserved in all these theories.This is the assumption that an adsorbed molecule occupies one adsorption site. In a recentwork [5], an improved solution for multilayer adsorption with multisite-occupancy onone-dimensional substrates was presented. The particular case of multilayer dimeradsorption was dealt with in detail and a new adsorption isotherm was obtained fordetermining of surface area and adsorption energy from experiments.In the present paper, the calculations have been extended to k-mers in one and twodimensionalsurfaces, based upon the Occupation Balance Approximation [6]. Thetheoretical results are compared with simulated data. The proposed model is simple, easyto apply in practice, and leads to new values of surface area and adsorption heats.Physically, these advantages are a consequence of properly considering theconfigurational entropy of the adsorbate.