Near-complete destruction of PFAS in aqueous film-forming foam by integrated photo-electrochemical processes

Per- and polyfluoroalkyl substances (PFAS) are highly recalcitrant pollutants in the water environment worldwide. Aqueous film-forming foam (AFFF) used for firefighting is a major source of PFAS pollution. However, complete defluorination (that is, cleaving all C–F bonds into F⁻ ions) of PFAS by non-thermal technology is rare. The destruction of the PFAS mixture in the complex organic matrix of AFFF is even more challenging. Here we designed and demonstrated an ultraviolet/sulfite–electrochemical oxidation (UV/S–EO) process. The tandem UV/S–EO leverages the complementary advantages of UV/S and EO modules in the PFAS transformation mechanism and the engineering process design (for example, foaming control, chemical dosage and energy consumption). At ambient temperature and pressure, the UV/S–EO realized near-complete defluorination and mineralization of most PFAS and organics in AFFF (50–5,000 times diluted, containing up to 200 mg l⁻¹ organic fluorine and 3,764 mg l⁻¹ organic carbon). This work highlights the integration of molecular-level insight and engineering design towards solving the major challenges of AFFF water pollution.