A critical review of the estimation of the thermodynamic parameters on adsorption equilibria. Wrong use of equilibrium constant in the Van't Hoof equation for calculation of thermodynamic parameters of adsorption

• Published in: Journal of molecular liquids Vol. 273; pp. 425 - 434
• Main Authors: Lima, Eder C., Hosseini-Bandegharaei, Ahmad, Moreno-Piraján, Juan Carlos, Anastopoulos, Ioannis
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2019
• Subjects: Equilibrium constant; Isotherm models; Thermodynamic parameters of adsorption; Van't Hoof equation; Thermodynamic parameters of adsorption; Equilibrium constant; Isotherm models; Van't Hoof equation
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2018.10.048

In the adsorption literature, the Van't Hoff equation is used in different manners without any criteria about the concepts of physical-chemistry of equilibrium for calculation of thermodynamic parameters of adsorption. Indeed, the equilibrium constant (K) should be dimensionless for being used in the Van't Hoff equation. However, this is not a simple adjustment of units, as being spread in the literature, to become K dimensionless. In this paper, it will be calculated the equilibrium constants using numeric examples and show the flaws of the thermodynamics calculations, when the value of K is wrongly calculated, and what are the expected results of the changes in enthalpy (ΔH°) and changes in the entropy (ΔS°) that are spread in the literature. •Determination of thermodynamic parameters by using Van't Hoof equation.•The correct equilibrium constant for determination of thermodynamic parameters of adsorption.•Use of nonlinear equilibrium isotherms at several temperatures to obtain the K.