Adsorption of Isolated and Hydrated Linear Per‐ and Polyfluoroalkyl Substances on Clay Surfaces: A Periodic Density Functional Theory Study

The spread of per- and polyfluoroalkyl substances (PFAS) in global waterways has become a subject of significant concern. Modeling the interaction of PFAS with the major constituents of natural and artificial waterways will advance our understanding of the spread of PFAS and aid in the development of adsorption and remediation methods. In this work, it considers the adsorption of linear perfluoroalkyl acids on two model clay hydrophobic surfaces: montmorillonite and kaolinite. This investigates the absorption affinities and preferential adsorption of acidic linear PFAS on model clay surfaces with varying fluorocarbon tail lengths. It also consideres the binding affinity when these PFAS are hydrated. Both carboxylic and sulfonic acid head groups are considered. The computed results indicate that there is an increased binding energy of the target PFAS on the clay surfaces with increasing chain length, and that perfluoroalkyl sulfonic acids have greater binding energy than perfluorocarboxylic acids with the same tail length.