In the past six month, the project team developed an advanced electrochemical platform that integrates membrane-based PFAS concentration with a highly selective photo-electrochemical reduction (PER) process for downstream destruction. Central to the technology is a Pd-decorated TiO₂ cathode synthesized via a scalable sol–gel coating and calcination process on titanium substrates, followed by in situ electrochemical reduction to generate metallic Pd nanoparticles embedded within an anatase TiO₂ matrix.
Mechanistic investigations combining operando spectroscopy and density functional theory revealed a previously unrecognized cathodic adsorption pathway that enables anionic PFAS, including perfluoroalkyl sulfonates, to bind strongly to TiO₂ surfaces under applied negative potentials. Cathodic polarization promotes displacement of surface-bound water and induces charge redistribution at Ti⁴⁺ sites, facilitating strong coordination with PFAS sulfonate groups in a coplanar adsorption configuration. Upon UV irradiation, Pd nanoparticles generate highly energetic electrons that drive PFAS destruction through dual pathways: direct hot-electron transfer to surface-bound perfluoroalkyl chains and indirect generation of hydrated electrons at the electrode–solution interface. This synergistic mechanism enables rapid C–S bond cleavage followed by C–F bond scission, overcoming long-standing limitations associated with cathodic PFAS reduction while avoiding formation of oxyanion byproducts.
The technology was further validated using real reverse osmosis concentrate derived from municipal wastewater reclamation, representing a highly challenging, PFAS-enriched membrane residual with elevated salinity, nitrate, chloride, and organic carbon. Without pretreatment or chemical amendment, the PER system achieved efficient removal of fluorotelomer sulfonates, PFSAs, and PFCAs within hours, accompanied by measurable fluoride release indicative of substantial defluorination. Importantly, no free chlorine, chlorate, or perchlorate formation was detected despite high chloride levels, demonstrating inherent selectivity and compatibility with membrane concentrate matrices. Energy-normalized performance metrics showed favorable specific energy consumption, underscoring the suitability of this approach as a downstream destructive treatment coupled to membrane separation for PFAS management in complex waste streams.