Adsorption on Heterogeneous Surfaces: Site Energy Distribution Functions from Fritz-Schlüender Isotherms

• Published in: Chemphyschem Vol. 11; no. 12; pp. 2555 - 2560
• Main Authors: Kumar, Kannuchamy Vasanth, Monteiro de Castro, Mateus Carvalho, Martinez-Escandell, Manuel, Molina-Sabio, Miguel, Rodriguez-Reinoso, Francisco
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23-08-2010; WILEY‐VCH Verlag; Wiley
• Subjects: Adsorbents; Chemistry; condensation approximation method; Exact sciences and technology; Fritz-Schlüender isotherm; General and physical chemistry; heterogeneous surfaces; site energy distribution; Surface physical chemistry; Heterogeneous surface; Energy distribution functions; Liquid solid adsorption; Adsorption isotherm; Nitrogen; Condensation; Fritz-Schlüender isotherm; Gas solid adsorption; Boron; Adsorption; Activated carbon; Distribution function; Isotherm; heterogeneous surfaces; site energy distribution; Modified material; condensation approximation method
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201000307

Different site energy distribution functions based on the condensation approximation method are proposed for the liquid‐phase or gas‐phase adsorption equilibrium data following the Fritz–Schlüender isotherm. Energy distribution functions for the four limiting cases of the Fritz–Schlüender isotherm are also discussed. The proposed models are successfully applied to the experimental equilibrium data of nitrogen molecules at 77 K on a pitch‐based activated carbon (PA) and a pitch‐based activated carbon containing boron (PBA). An energy distribution function based on FS isotherm containing five parameters suggest a unimodal distribution of binding sites for carbon PA, the binding site energies being distributed as exponential or unimodal, depending on the pressure, in the case of carbon PBA. The advantages of the proposed models are discussed.
Binding sites: A model based on the Fritz–Schlüender isotherm predicts the site energy distribution of heterogeneous surfaces on pitch‐based activated carbon with and without boron (PBA and PA, respectively, see figure). A unimodal distribution of binding sites occurs for carbon PA, the binding site energies being distributed exponentially or unimodaly (depending on the pressure) in the case of PBA.