Molecular dynamics simulation of the distribution of potassium perfluorooctanesulfonate in water

We used the molecular dynamics method to simulate the behavior of potassium perfluorohexanesulfonate (KPFOS) in water/gas system. The results indicate that PFOS− can spontaneously migrate to the water/gas interface and form a layered structure with hydrophobic tail chains facing the gas phase and hydrophilic sulfonic acid groups immersed in the water phase, while some PFOS− molecules within the solution formed spherical micelles. Both the number density and charge density distributions confirm that PFOS− and K+ are mainly distributed at the water/gas interface, and a small amount of PFOS− and K+ are distributed in the bulk solution. Based on the results of radial distribution function, the probability of K+ appearing near oxygen atoms in PFOS− is very high due to electrostatic attraction. Based on the IGMH analysis, the oxygen atoms in PFOS− can form multiple hydrogen bonds with adjacent water molecules, while there is only weak van der Waals interaction between K+ and water molecules.