On the Pore Size Distributions and Fractal Dimensions of Activated Carbons Evaluated on the Basis of the Analysis of Nitrogen, Argon and Benzene Vapour Adsorption Data

Abstract

The Dubinin-Stoeckli equation and the Horvath-Kawazoe equation have been used for the determination of the pore size distribution (PSD) for three fractions of activated carbon separated by elutriation due to their different degrees of activation (bum-off). A comparison of the PSD functions on the basis of nitrogen. argon and benzene adsorption isotherms has been undertaken. The general form of the Dubinin-Stoeckli equation has been developed for nitrogen and argon as an adsorbate. For all adsorbates studied, correctionfactors including adsorptionin mesopores were introduced. New formulaefor this correctionfactor have been proposedfor nitrogen and argon. Quantitative evaluations of PSD functions for these three different adsorbates lead to the conclusion that it is possible to use the benzene isotherm as well as the nitrogen or argon isotherms to characterise the microporous structure of the adsorbent. Comparison of the porous structure parameters was extended by a fractal analysis.

A Modified Pore-Filling Isotherm for Liquid-Phase Adsorption in Activated Carbon

“…Several methods of analysis have been developed and applied for characterizing the pore structure of activated carbon, among which gas adsorption measurements are most commonly used. One of the most widely used isotherm equations in the characterization of pore structure and description of the micropore filling process in microporous adsorbents is the Dubinin−Radushkevich equation. − The Dubinin−Radushkevich (DR) equation has a uniform general form that is useful for most adsorbates and follows the expression where θ is fractional adsorption, q is the amount adsorbed, q max is the maximum capacity in the pore, whereas β and E o are an affinity coefficient and characteristic energy, respectively. The adsorption potential, A , is usually expressed as here p o and p are the saturation pressure and equilibrium pressure, respectively.…”

Molecular Simulation of Benzene Adsorption in Graphitic and Amorphous Carbon Slit Pores

“…Note that we consider only the adsorption branches of the isotherms, because the experimental adsorption isotherms of benzene vapor on microporous carbons are often reversible or show very small hysteresis loops − of Type H4, according to the IUPAC classification . It is unlikely that desorption isotherms obtained by GCMC could reproduce the experimental hysteresis loops.…”