Thermodynamically Consistent Enthalpies of Adsorption of Mixtures from Classical Density Functional Theory
Year: 2026
Type: article
Abstract: Classical density functional theory (cDFT) has been established as an efficient and robust framework for predicting adsorption isotherms. Moreover, the mathematical form of cDFT─an optimization instead of the more widely used molecular simulations─opens up additional opportunities based on calculating noise-free derivatives of interfacial properties. One of these opportunities is the rapid, consistent calculation of thermodynamic properties, such as the enthalpy of adsorption. This work showcases cDFT as a thermodynamically fully consistent model for fluids that describes all homogeneous and adsorbed phases with a single model, providing access to phase equilibria, density profiles, enthalpies, and more. Because the enthalpy of adsorption of a mixture is difficult to measure experimentally and is rarely discussed in modeling approaches, we first revisit its definition from an energy balance perspective and in the context of the Clausius-Clapeyron relation, independent of specific model assumptions. We follow this up by deriving expressions for the enthalpy of adsorption suitable for cDFT. The resulting framework is demonstrated using the PC-SAFT Helmholtz energy model for the adsorption of real gases in a model slit pore for a pure fluid, a binary mixture, and a multicomponent system.
Author: Philipp Rehner
Institution: ETH Zurich
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7136133317