Degradatie van per- en polyfluoralkylstoffen (PFAS) in afvalwater door geavanceerde reductieprocessen

Per- and polyfluoroalkyl substances (PFAS) are highly persistent aquatic contaminants due to the strength of the carbon-fluorine (C-F) bond, rendering conventional treatment methods ineffective for their degradation and defluorination. Advanced reduction processes (ARPs) based on hydrated electrons (eaq⁻) have emerged as a promising alternative, as they can directly cleave C-F bonds. However, their practical application remains limited by insufficient understanding of eaq⁻ generation, stability, and delivery mechanisms. This study establishes a mechanistic framework for hydrated electron-driven ARPs through systematic investigation of two homogeneous and two heterogeneous systems targeting perfluorooctanoic acid (PFOA). In homogeneous systems, the UV/sulfite/iodide process revealed that eaq⁻ availability is strongly influenced by solution chemistry and dosing strategy. Continuous sulfite dosing significantly enhanced PFOA degradation (98%) and defluorination (34.0% within 30 min), highlighting the importance of sustaining eaq⁻ concentrations. Furthermore, wavelength-dependent radical speciation in dithionite-activated ARPs demonstrated that UV254 favors SO₂•⁻ formation, whereas vacuum UV (VUV) selectively generates eaq⁻, achieving complete PFOA degradation. This establishes wavelength control as a molecular switch for directing reductive pathways. To improve applicability, heterogeneous systems were developed to couple interfacial enrichment with in situ eaq⁻ generation. Hydrogen-terminated nanodiamond enabled simultaneous adsorption and photocatalytic degradation, achieving complete PFOA removal and 61% defluorination within 120 min. A VUV-assisted boron-doped diamond photoelectrochemical system further enhanced performance via electro-photochemical synergy, achieving 100% removal and 65% defluorination within 8 h. Overall, PFAS degradation efficiency is governed by three interconnected factors: eaq⁻ generation, preservation against scavenging, and targeted delivery at reactive interfaces. This work establishes hydrated electron-based ARPs as a unified and scalable platform for PFAS remediation, providing mechanistic insights and engineering strategies for next-generation reductive water treatment technologies.