Physical Adsorption on Non-Uniform Surfaces

Abstract

Analysis of adsorption on a uniform surface using the quasi-chemical theory of interaction shows that the hypotheses of the BET theory lead to substantially no adsorption beyond the first layer if E2 = EL, and stepwise isotherms if E1>E2>E3>···>EL. For the monolayer adsorption of gases on silver, platinum, and steel, the heterogeneous nature of the adsorbing surface is clearly indicated. Cooperative adsorption on the non-uniform surface is treated, and the cooperative analog of the Freundlich equation derived. The typical multi-layer isotherm is shown to be composed of three regions: non-cooperative adsorption on a strongly heterogeneous surface; cooperative adsorption on a still heterogeneous surface; and cooperative multi-layer adsorption induced by small van der Waals perturbations some distance from the surface. The isotherm p/p0=exp{—a/θr} is derived and shown to be a good representation of adsorption data that conform to the BET Type I, II, or III shapes.

Understanding the adsorption mechanism of chitosan onto poly(lactide-co-glycolide) particles

“…The Halsey model describes multilayer condensation at relatively large distances from a non-uniform surface. According to Halsey model [25], the typical multilayer isotherm is composed of 3 regions: noncooperative adsorption on a strongly heterogeneous surface; cooperative adsorption on a still heterogeneous surface; and cooperative multilayer adsorption induced by small van der Waals perturbations at some distance from the surface [48]. The Henderson model is a semi-empirical model derived on thermodynamic procedures.…”

Equilibrium, kinetic and thermodynamic studies on the removal of U(VI) by low cost agricultural waste

“…Halsey [30] proposed an expression for condensation of a multilayer process at a relatively large distance from the surface:…”

High-temperature and high-concentration SCR of NO with NH3: Application in a CCS process for removal of carbon dioxide

“…Pore volume analysis was performed using the BJH method [19]. The Halsey formula [20] was used for calculation of the thickness of the adsorbed layer (t value). The desorption isotherm was use for the analysis.…”