Molecular Modeling of Liquid--Liquid Extraction of Per- and Polyflouroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are a class of persistent pollutants whose strong carbon--fluorine bonds confer remarkable chemical stability but also severe environmental persistence. Understanding their molecular interactions with different solvents is key to designing effective separation and remediation strategies using liquid--liquid extraction processes. Here, we perform atomistic Molecular Dynamics simulations and free energy calculations to quantify the relative solvation of PFAS compounds in water and a diverse set of organic solvents. Trends across the PFAS series reveal that fluorocarbon chain length and headgroup functionality govern solvent affinity, with hydrophobic solvents favoring longer-chain sulfonates and carboxylates. Additional simulations incorporating explicit salts at controlled weight fractions capture ion-specific effects on PFAS solvation and partitioning. These molecular-level insights provide predictive structure--solvent relationships relevant to PFAS extraction, sorption, and transport, establishing a thermodynamic foundation for the rational design of solvent-based remediation materials.