DESCRIPTION OF DIFFERENT SOLID ADSORBENT SURFACES ADSORPTION MECHANISMS BASED ON A SEQUENTIAL DECOMPOSITION OF ISOTHERMS

Pablo D. Humpola (), Hector S. Odetti, Ethel S. E. Flores () and Jose Luis Vicente ()
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Pablo D. Humpola: Catedra de Quimica Inorganica, Facultad de Bioquimica y Ciencias Biologicas, Universidad del Litoral, Santa Fe, 3000/CC 242, Argentine
Hector S. Odetti: Catedra de Quimica Inorganica, Facultad de Bioquimica y Ciencias Biologicas, Universidad del Litoral, Santa Fe, 3000/CC 242, Argentine
Ethel S. E. Flores: INFTA, Universidad Nacional de La Plata, 64 y diag. 113, La Plata, 1900/CC 16, Argentine
Jose Luis Vicente: INFTA, Universidad Nacional de La Plata, 64 y diag. 113, La Plata, 1900/CC 16, Argentine

Surface Review and Letters (SRL), 2013, vol. 20, issue 02, 1-12

Abstract: In order to analyze the adsorption capacities of different solid substrates, we present a multi-step method to separately study the isotherm at different pressure ranges (steps). The method is based on simple gas isotherm measurements (nitrogen, methane, carbon dioxide, argon, and oxygen) and is tested to describe the adsorption process and characterize a graphitized surface (GCB) and two different granular activated carbons (GAC). The GCB isotherms are described as a sum of Fowler-Guggenheim-Langmuir shifted curves; isotherm behaviors are quite similar at different temperatures, but change below a certain threshold. In GAC the first steps show the same adsorption characteristics at low pressures (Dubinin's description), but this behavior changes at higher pressure regimes, which allows one to elucidate how heterogeneous the surfaces are or how strong the interactions between adsorbed molecules are for this marginal adsorption to occur. We tested different approaches (from BET multilayer to Aranovich) and found quite different features. We finally conclude that if the description of the adsorption on complex substrates, such as those presented here, is carried using only one model, e. g. Dubinin in case of GACs, the resulting characteristics of the adsorbent would be very biased.

Keywords: Surface characterization; adsorption steps; isotherm decomposition; graphite; activated carbon; micro mesopore; nitrogen; methane (search for similar items in EconPapers)
Date: 2013
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DOI: 10.1142/S0218625X13500224

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