(589a) Exploring Molecular-Level Interactions in the Design of Redox Copolymers for Electrochemical Remediation of per- and Polyfluoroalkyl Substances (PFAS)

Exposure to anthropogenic contaminants has been a major driver for the development of more efficient technologies for water remediation. Recent advances point to electrochemical separations as a promising approach for water purification due to their modularity, scalability and potential for net-zero emissions when coupled with renewable energy sources. Despite these advantages, the implementation of electrochemical methods is often hindered by inadequate ion rejections, which increase the overall energy consumption. Thus, tailored materials are needed to provide molecular-level selectivity and achieve energy efficient separations. We have investigated molecular-level interactions to help drive the selective capture of per- and polyfluoroalkyl substances (PFAS). PFAS have emerged as an urgent target for water remediation due to their widespread prevalence and the enactment of new regulations by governmental agencies worldwide. Despite advancements in water treatment methodologies, the elimination of PFAS remains a formidable challenge due to their stable C-F bonds which confer amphiphilic characteristics and resistance to biological degradation, thereby necessitating energy-intensive conventional degradation approaches and specialized adsorbents.

In this study, we investigated the electrosorption of per- and polyfluoroalkyl substances (PFAS) utilizing functionalized redox-active copolymer electrodes incorporating 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (HFBMA) groups. The content of redox-active functional groups (TEMPO) was carefully balanced with fluorocarbon-containing groups (HFBMA) to elucidate the intricate effects of electrostatic and fluorophilic interactions. By combining results from electrosorption experiments with molecular dynamics (MD) simulations, we gained insights into the binding behavior of short-chain PFAS with different functional groups. Our findings demonstrate that fluorophilic groups can confer selectivity towards various PFAS depending on the length of the fluorinated chain of the target species. Experimental uptake capacities of PFAS were found to be consistent with MD simulations, highlighting the significance of electrostatic interactions for short-chain PFAS binding, with the strongest influence observed on chains with carbon atoms C ≥ 6. Conversely, fluorophilic interactions were found to be favored by chains with C ≤ 5. The electrodes exhibited notable removal efficiency of short-chain PFAS in secondary wastewater effluent (>70%), underscoring their practicality to remove PFAS under environmentally relevant conditions. Furthermore, we investigated the synergistic integration of electrosorption with electrooxidation as a feasible strategy for PFAS removal and destruction in wastewater, thus delineating a comprehensive approach towards sustainable PFAS remediation.