Some mistakes and misinterpretations in the analysis of thermodynamic adsorption data

• Published in: Journal of molecular liquids 2022-04, Vol.352, p.118762, Article 118762
• Main Authors: Salvestrini, Stefano, Ambrosone, Luigi, Kopinke, Frank-Dieter
• Format: Article
• Language: English
• Subjects: Adsorption spontaneity; Dimensional consistency of equations; Isosteric heat of adsorption; Standard Gibbs adsorption energy; Temkin isotherm; van’t Hoff equation
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2022.118762

•The assumptions underlying the Temkin isotherm model are reviewed.•Calculated parameters should be always accompanied by their errors of estimate.•The classical linear van’t Hoff plot may lead to erroneous prediction of thermodynamic parameters.•Misleading interpretation of the spontaneity of adsorption processes are discussed.•The selected isotherm model must be consistent with the isosteric heat of adsorption trend. In this work, we discuss some results and statements recently published in the scientific adsorption literature. In particular, we focus on the thermodynamic aspects of the adsorption process, including dimensional inconsistency of fitted parameters, Temkin isotherm assumptions, inaccurate calculation of ΔH° and ΔS°, parameter determination without providing the errors of estimate, mismatch between selected isotherm models and isosteric heat of adsorption, misleading interpretation of the spontaneity of a process, and interchangeability of ΔG and ΔG°. A graphical method is proposed for assessing data reliability and applicability of the van’t Hoff equation.