To Örebro University

Short-chain (C4-C6) per- and polyfluoroalkyl substances (PFAS) have become the dominant PFAS fraction in the environment following the phase-out of long-chain analogues. Their exceptional chemical stability, amphiphilic character and resistance to degradation have led to ubiquitous occurrence of short-chain PFAS across the global hydrological cycle. At the same time, their enhanced aqueous solubility, mobility and persistence resulted in poor removal by conventional water treatment leading to widespread detection in drinking water. By first providing the general classification of PFAS, this Review summarises the physicochemical properties of short-chain PFAS and their interactions to elucidate their removal challenges. While heterogeneous photocatalysis has long been the vanguard technology for the abatement of aqueous-phase micropollutants, it now finds itself in uncharted territory. Previously, photocatalysts that efficiently generate hydroxyl radicals generally exhibit strong activity toward hydrocarbon-based micropollutants; however, in the absence (or lacking) of C-H bonds in PFAS, this paradigm may no longer apply. Hence, this Review presents an up-to-date understanding of short-chain PFAS and their abatement through heterogeneous photocatalysis. As the field remains in its infancy, critical knowledge gaps must be addressed before the rational design of PFAS-targeted photocatalysts and treatment processes can be realized.