Compensation Effect for the Kinetics of Adsorption/Desorption of Gases/Vapors on Microporous Carbon Materials

Abstract

Preliminary studies of adsorption kinetics on activated carbon provided some tentative evidence for a possible compensation effect where the activation energies and ln(preexponential factors) obtained from the Arrhenius equation obey a linear correlation. However, a detailed analysis was not carried out. The adsorption characteristics of a series of n-alcohol vapors on the activated carbon BAX950 were investigated over the relative pressure range p/p o ) 0-0.97, for temperatures in the range 288-318 K. These data, in combination with our previous results for water, n-octane, and n-nonane adsorption provide a comprehensive adsorption kinetic study on an active carbon covering a full range of adsorptives with varying hydrophilic/ hydrophobic character to establish the general validity, applicability, and mechanism of the compensation effect. The results are discussed with reference to the pore structure and the adsorption mechanism. Detailed comparisons show that the compensation effect is a general phenomenon for adsorption and desorption on microporous carbons and may extend further to other porous systems.

Enthalpy–entropy compensation for isosteric state adsorption at near ambient temperatures

“…Studies have shown that EEC also occurs during the adsorption of low molecular weight gases on active surfaces (Burevski et al 1991;Fletcher and Thomas 2000;Garrone et al 2008;Korolev et al 2011;Hercigonja and Rakić 2013;Pera-Titus 2016;Zukal et al 2009;Kelut et al 2014), wherein the dependence isn't necessarily linear, as Eq. (1) in unequivocal manner (Fletcher and Thomas 2000;Garrone et al 2008).…”

On the equilibrium and dynamic behavior of alcohol vapors in activated carbon

“…Activated carbon has hydrophobic sites acting as primary adsorption sites for hydrocarbons mostly in micropores and hydrophilic functional groups as primary sites for water vapor adsorption (Fletcher and Thomas, 2000). During the course of the activation process (particularly chemical activation) the polar functional groups are commonly formed at the edges of graphite planes (Segarra and Glandt, 1994).…”

Comparison of the kinetics of methanol adsorption in static and continuous flow conditions on activated carbons with different burn-off degree

“…. ) covers a wide range of behaviour [16]. In our case, it seems that the evolution of the rate constant at very low relative pressure (<0.02) is different because this is not a peak, only a decrease of the rate constant is observed.…”