A two-step electrochemical approach for an efficient destruction of short-chain PFAS in water

This study presents an energy-efficient, electricity-driven concentration–degradation train for perfluorobutanoic acid (PFBA), which is used as a model compound for short-chain per - and polyfluoroalkyl substances (PFAS). First, PFBA is enriched by electrosorption in an undivided electrochemical flow cell that does not require an ion-exchange membrane. The targeted electrode pair comprises a defunctionalized activated carbon felt (ACF) working electrode with high PFBA affinity and a high-surface-area, acid-functional ACF counter electrode that exhibits negligible PFBA uptake, enabling selective capture on the adsorbing electrode. Mild positive potentials enhance adsorption; switching to mild negative potentials drives release into a smaller volume of chloride-free water for the subsequent oxidation step. The low internal resistance of the cell enables efficient utilization of the electrochemical window while preventing water electrolysis at the applied bias potential of the working electrode. From sorption isotherms, a theoretical enrichment factor of 41.5 was predicted; in flow operation an enrichment factor of 14.6 was achieved at 0.174 kWh/m 3 treated water. Selective enrichment over inorganic ions present in tap water further supports robustness for realistic matrices. The PFBA-rich concentrate was then treated by electrooxidation using boron-doped diamond, achieving >99% PFBA removal with an electrical energy per order of 18.9 kWh/m 3 concentrate. Coupling electrosorption with electrooxidation reduces the energy per treated volume, generates no brine, and minimizes formation of toxic intermediates. The results demonstrate an effective route for the removal and destruction of short-chain PFAS and provide a practical basis for energy-efficient, membrane-free preconcentration integrated with advanced anodic oxidation. • Two-step electrosorption–electrooxidation enables PFBA enrichment and destruction • New undivided flow cell enables selective PFBA adsorption and desorption in chloride-free water • Electrosorption achieves enrichment factor of 14.6 at 0.17 kWh/m 3 treated water • Electrooxidation of PFBA concentrate on BDD degrades >99% with EEO of 18.9 kWh/m 3 • Sustainable trap-and-destroy approach avoids brine and toxic by-product formation