Improving the PFAS Transport Modelling by Considering the Synergy of Adsorption of Anionic, Cationic and Zwitterionic PFAS at Fluid-Fluid Interfaces
Year: 2026
Type: conference-paper
Abstract: Per- and polyfluoroalkyl substances (PFAS) are a family of compounds listed as persistent, mobile and toxic, posing significant risks to human health and ecosystems. Some PFAS, notably those present in Aqueous Film-Forming Foam (AFFF) exhibit significant adsorption at fluid-fluid interfaces (e.g., air-water interfaces), which play a crucial role in their transport through soil and groundwater. Furthermore, AFFF formulations contain mixtures of PFAS and hydrocarbon surfactants with anionic, cationic, zwitterionic, and non-ionic species.Current thermodynamically consistent models for PFAS adsorption typically consider competitive adsorption but not the synergistic effect that occurs in presence of surfactants of different charges, thereby limiting their predictive capabilities for AFFF contamination sources.This study aims to demonstrate that incorporating the synergistic effect between PFAS and other surfactants changes the estimated quantities of PFAS adsorbed at fluid-fluid interfaces, and consequently that transport in soil is, in turn, affected.Two modelling approaches are compared. The first one, of thermodynamic chemistry, utilizes Szyszkowski parameters for each component, derived from fitting surface tension versus concentration curves for individual surfactant solutions—maintaining consistency with existing non-synergistic models. Furthermore, we provide new experimental Szyszkowski parameters for specific AFFF-derived PFAS. These values fill a gap in the current literature and can be integrated into both existing and future adsorption models. The second one, mix of thermodynamic chemistry and electrostatics, utilises the description of all the interactions occurring at the interface, based one molecular parameters and one experimental measurement of surface tension.The models are experimentally assessed for a mixture of one anionic, one cationic and one zwitterionic PFAS at different ratios and constant total concentration, by comparing the measured surface pressure to its prediction from the simulation.Finally, the impact of the synergistic effect in PFAS adsorption for PFAS transport in soil is assessed by implementing the adsorption model in a transport screening model in the unsaturated zone.
Source: HAL
Language: English
Subfield: Environmental Chemistry
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7167311892