THE UNIT PROBLEM IN THE THERMODYNAMIC CALCULATION OF ADSORPTION USING THE LANGMUIR EQUATION

The equilibrium constant K in the Langmuir isotherm is usually used to calculate the standard Gibbs free energy of adsorption (ΔG°). However, in a strictly theoretical sense, this calculation method is incorrect. The reason is that the K in the Langmuir isotherm has a dimension. According to the pro...

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Bibliographic Details
Published inChemical engineering communications Vol. 201; no. 11; pp. 1459 - 1467
Main Authors Zhou, Xueyong, Zhou, Xin
Format Journal Article
LanguageEnglish
Published Philadelphia Taylor & Francis Group 01.11.2014
Taylor & Francis Ltd
Subjects
Adsorption
Langmuir equation
Molecules
Nonlinear equations
Standard equilibrium constant
Standard Gibbs free energy
Thermodynamics
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Summary:The equilibrium constant K in the Langmuir isotherm is usually used to calculate the standard Gibbs free energy of adsorption (ΔG°). However, in a strictly theoretical sense, this calculation method is incorrect. The reason is that the K in the Langmuir isotherm has a dimension. According to the provisions of the International Union of Pure and Applied Chemistry (IUPAC), the standard equilibrium constant (K°) for calculating ΔG° must be a dimensionless parameter. We examined four examples from the literature and found that the calculation of ΔG° presented in these four references was incorrect. Based on the fact that this misapplication is very common, this note reviews the related literature and gives a short comment on this problem. Two methods for calculating the thermodynamic equilibrium constant by the Langmuir equation are provided and discussed.
ISSN:0098-6445
1563-5201
DOI:10.1080/00986445.2013.818541