A New Molecular Probe Method To Study Surface Topography of Carbonaceous Solid Surfaces

Abstract

Adsorption on a heterogeneous surface of flexible molecules composed of a number of mers, like n-alkanes for instance, is strongly affected by topography of surface adsorption sites. Therefore, fitting to experimental adsorption isotherms, theoretical expressions developed for multisite-occupancy adsorption on heterogeneous surfaces characterized by random and patchwise topography should make it possible to distinguish whether a studied solid surface is characterized by random or by patchwise topography. For certain fundamental but also practical reasons, we took into consideration carbonaceous adsorbents. Following the general approach to multisite-occupancy adsorption published recently by Rudziński and Everett, we have developed here a generalized form of the Dubinin−Astakhov isotherm equation, taking into account surface topography and the interactions between the adsorbed molecules. The developed isotherm equation has been used successfully by us to study the nature of surface topography of a number of carbonaceous adsorbents.

Heterogeneity of multiwalled carbon nanotubes based on adsorption of simple aromatic compounds from aqueous solutions

“…It is known that the heat of adsorption profile reveals both the energy heterogeneity of the system and the strength of the interactions between the neighboring molecules in the adsorbed phase (Rudziński et al 1996;Nieszporek et al 2009;Podkościelny and Nieszporek 2011).…”

“…Conversely, an increase of the heat curves is characteristic of homogeneous surfaces and cooperative interactions between the admolecules. Finally, if the heat of adsorption is independent of the amount adsorbed, this indicates a balance between the strength of the adsorbate -adsorbate interactions and the degree of heterogeneity of the adsorbent -adsorbate system (Podkościelny and Nieszporek 2011;Rudziński et al 1996;Nieszporek et al 2009). …”

Statistical Thermodynamics of Lattice Gas Models of Multisite Adsorption

“…The assumption of one-center adsorption becomes even more inadequate at the description of adsorption of linear and quasilinear molecules such as the simple saturated and unsaturated hydrocarbons [7,8]. In the paper complete review of the experimental results on the adsorption of simple hydrocarbons on the surface of metal monocrystals (Pt, Pd) was given and, particularly, the adsorption of such molecules was shown to occur parallel to the solid surface in connection with which multicenter nature of the adsorption becomes apparent.…”

“…The necessity of describing of the n-alkane adsorption in the framework of the models with multisite adsorption is also supported by the fact that at the interpretation of experimental adsorption isotherms by using the known multisite Langmuir model and other analytical models there exists good correlation between the model parameter k (the number of active sites occupied by adsorbate molecule) and the real number of segments in the molecule of the adsorbate [7,8,[10][11][12]. It should be noted that the above analytical models of multisite adsorption are used to determine the specific surface of porous solids and its topography (in the case of energetically heterogeneous surfaces).…”

Low-pressure argon adsorption assessment of micropore connectivities in activated carbons

“…A high-resolution gas adsorption technique at very low partial pressure has been successfully developed to characterize surface heterogeneity of minerals [1] using argon or nitrogen. Some papers discuss the potentialities of the techniques to describe the gas/solid interaction of carbonmineral matrix [2,3], but very few are available for the characterization of pure carbonaceous adsorbents [4,5].…”