Temperature–Electrokinetic Co-Driven Perfluorooctane Sulfonic Acid (PFOS) Adsorption on Geo-Adsorbents

Abstract

Per- and polyfluoroalkyl substances (PFAS) have concerned the public due to their worldwide distribution and the threat they pose to drinking water safety and human health. Temperature and DC field-induced electroosmotic flow (EOF) are powerful tools to regulate organic contaminant adsorption and control PFOS (as a typical PFAS) transport in porous media. However, the co-driven mechanisms of temperature–electrokinetic transport of contaminants are still unclear. Here, we investigated the synergistic mechanisms of temperature–electrokinetic co-driven PFOS adsorption on zeolite and activated carbon as model geo-adsorbents. We found that DC fields increased PFOS adsorption on activated carbon by up to 19.8%, while they decreased PFOS adsorption on zeolite by up to 21.4%. Increasing the temperature decreased the adsorption of PFOS by activated carbon and zeolite. The temperature and electrokinetic synergistically drive EOF velocity to control PFOS adsorption. Synergistic mechanisms of temperature–electrokinetic regulated kinetic and temperature-regulated thermodynamic (the Gibbs free energy change ΔG) and kinetic (liquid viscosity) under various temperatures and DC field situations were analyzed with models. A kinetic approach interlinking viscosity, EOF velocity, and the kinetic adsorption constants was established to interpret the synergistic mechanisms which can be further adopted to estimate temperature–electrokinetic induced PFOS adsorption benefits to mineral and carbonaceous adsorbents. We concluded that such kinetic regulation may provide support for controlling the transmission of PFOS.