Can ultraviolet-assisted advanced reduction processes effectively destroy per- and polyfluoroalkyl substances in real water matrices?

The societal concerns about the widespread occurrence of toxic per- and polyfluoroalkyl substances (PFAS) in different compartments of the environment have been increasing. Many remediation techniques are being investigated to lower PFAS levels in the aquatic environment. Among these various methods, ultraviolet-assisted advanced reduction processes (UV-ARPs) that use highly reducing hydrated electrons (e_aq^–) to convert PFAS into nonfluorinated small organics and fluoride (F^–) ions have received significant attention in recent years. This mini-review provides a mechanistic understanding of the degradation of PFAS using UV coupled with reductants — sulfite and iodide (i.e. UV-sulfite and UV-iodide systems). The potential advantages and difficulties of scaling up UV-ARP technology for real-time PFAS degradation are discussed. Emphasis is laid on the effectivity of UV-ARP under anoxic conditions in water. Yet, in the presence of dissolved oxygen and dissolved organic matter (DOM), PFAS degradation efficacy decreases mainly due to the rapid reactions of O₂ with reductive species (e.g. hydrated electron (e_aq^–) and atomic hydrogen (H^•)) and UV absorption by DOM. This review aims to draw the researcher's attention to pretreatment to remove DOM and anoxic conditions needed to realize the effectiveness of UV-ARPs in degrading PFAS in complex environmental water samples.