Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals that have been used in a wide range of applications. Recent studies have revealed that PFAS are persistent and accumulative both in the environment and the human body. The technologies that are currently in use for PFAS removal from water rely on physisorption. While it is effective for removing PFAS with a longer fluoroalkyl chain (e.g., (CH2)7 or longer), its efficacy for those with a shorter chain (e.g., (CH2)6 or shorter) is an issue. Electric-field aided sorption (i.e., electrosorption) has been explored as an alternative to overcome such limitations. Herein, we demonstrate electrosorption of PFAS with varied fluoroalkyl chains by utilizing an inexpensive carbonaceous electrode (graphite). Upon application of electric field across the electrodes, anionic PFAS is attracted and adsorbed to the anode surface while proton is adsorbed to the cathode. The results show that our device can exhibit very high adsorption capacity for both long and short fluoroalkyl chain PFAS (Perfluorooctanoic acid and Perfluoropentanoic acid, respectively). This can be attributed to an additional electrostatic interaction between the electrode and the anionic PFAS by electrical double layer whereas conventional physisorption primarily relies solely on hydrophobic interaction. We also demonstrate that anionic PFAS can be spontaneously released to water upon reversing the electric field which makes it reusable. Finally, we develop a mathematical model that can describe electric field-driven PFAS sorption by utilizing a pseudo-first-order kinetics model.

Electric field-aided reversible adsorption-desorption of PFAS via inexpensive carbonaceous electrode in a portable device

ACS Fall 2021

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