Use of specific surface areas in inverse gas chromatography studies at zero surface coverage

• Published in: Journal of Chromatography A Vol. 1190; no. 1; pp. 271 - 277
• Main Authors: Almazán-Almazán, M.C., Pérez-Mendoza, M., Fernández-Morales, I., Domingo-García, M., López-Garzón, F.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 09-05-2008; Elsevier
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, Gas - methods; Exact sciences and technology; Gas chromatographic methods; General and physical chemistry; Inverse gas chromatography; Nitrogen and carbon dioxide surface areas; Solid-gas interface; Surface physical chemistry; Surface Properties; Thermodynamic parameters; Zero surface coverage; Zero surface coverage; Thermodynamic parameters; Inverse gas chromatography; Nitrogen and carbon dioxide surface areas; Adsorption energy; Henry constant; Carbon dioxide; Inverse gas chromatography,Zero surface coverage,Nitrogen and carbon dioxide surface areas,Thermodynamic parameters; Specific surface area; Nitrogen; Porous material; Gas solid adsorption; Gas chromatography; Microporosity; Reversed flow; Activated carbon; Surface properties; Thermodynamic properties; Physicochemical properties
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2008.02.112

Inverse gas chromatography (IGC) is frequently used to study adsorption processes at zero surface coverage on microporous activated carbons. This allows to determine the thermodynamic adsorption parameters as equilibrium constants,
V
S, standard enthalpies of adsorption,
Δ
H
A
°
, standard free energy of adsorption,
Δ
G
A
°
, and so on. Nevertheless, the surface areas of the adsorbents (microporous carbons in this case) are needed for this purpose. The experimental determination of the surface areas of microporous solids is not univocal and the results depend on the adsorbate employed in the measurements, usually N
2 or CO
2. This means that the thermodynamic parameters obtained by IGC are subjected to a degree of uncertainty depending on whether N
2 or CO
2 is used to determine the surface area values. The aim of this paper is to discuss which of the two surface area values is more appropriate to be used in IGC measurements at zero surface coverage. Experimental and theoretical considerations are supplied in a thorough discussion which supports that CO
2 surface area value is more appropriate. Thus, it is proposed that this should be used instead of the more generally extended nitrogen specific surface area obtained by the BET equation.