Electrifying PFAS Cleanup: Remediation of per- and Polyfluoroalkyl Substances (PFAS) from Water Using Electrosorption and Electrooxidation Techniques

Per- and polyfluoroalkyl substances (PFAS) are a class of man-made chemicals extensively utilized in various industrial applications, including the production of waterproof coatings, non-stick surfaces, surfactants, and firefighting agents. The pervasive use of PFAS has led to their widespread dissemination into the environment, where they are commonly detected in soil, groundwater, drinking water sources, and even remote regions such as Antarctic snow. Recent toxicological investigations have elucidated the propensity of PFAS to bioaccumulate within biological systems, thereby posing significant health risks to both humans and wildlife. Despite advancements in water treatment methodologies, the elimination of PFAS remains a formidable challenge due to their resistance to chemical and biological degradation conferred by their strong carbon-fluorine (C-F) bonds, which render traditional degradation approaches energy-intensive (~108 kWh/g). Thus, effective remediation of PFAS from aqueous matrices is a pressing challenge which requires thoughtful design of materials and scalable systems. Electrochemically driven techniques offer promising avenues for modular and energy efficient PFAS capture and destruction. In this study, we investigated the electrosorption of PFAS using functionalized redox-active copolymer electrodes with 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) groups. Our investigation demonstrated the feasibility of employing oxidizing or reducing potentials to effectuate the capture or release of PFAS via a switch-like mechanism. By tailoring the structural properties of the copolymers to optimize electrostatic and affinity interactions, a notable enhancement in separation efficiency towards hydrophilic short-chain PFAS was achieved. Specifically, the introduction of selective fluorophilic interactions within the redox copolymer structure facilitated the enhanced capture of short-chain PFAS, while the inherent hydrophobicity of the TEMPO copolymer sufficed to drive long-chain PFAS capture via electrostatic interactions. Notably, our research showcases the potential for PFAS capture under environmentally relevant conditions without using additional chemical agents for sorbent regeneration. This was achieved through electro-assisted regeneration upon reduction of the electrode, with a regeneration efficiency of at least 80% observed. Furthermore, we explored the synergistic integration of electrosorption with electrooxidation as a viable strategy for in-situ PFAS eradication from wastewater post-capture.