Chitosan-modified biochar enhanced PFAS degradation in UV/sulfite: impact of environmental conditions and applicability across different PFAS

The persistence of per- and polyfluoroalkyl substances (PFAS) in aquatic environments poses significant environmental and health risks, necessitating the development of effective and sustainable remediation strategies. This study evaluated the combined use of chitosan-modified biochar (Chi-BC) and ultraviolet advanced reduction processes (UV-ARP) for PFAS degradation, focusing on environmental influences and varying PFAS chemistries. Chi-BC effectively adsorbed and concentrated PFAS onto its surface, enhancing localized radical activity and enabling efficient defluorination. The Chi-BC/UV-ARP system achieved high degradation and defluorination rates, notably with long-chain PFAS, where adsorption facilitated radical access to C–F bonds. Environmental factors, including ionic strength, nitrate, and natural organic matter (NOM), impacted system efficiency by altering radical availability and PFAS interactions. Interestingly, nitrate enhanced PFAS adsorption onto Chi-BC, indirectly promoting defluorination, while NOM showed mixed effects depending on concentration. Overall, this work presented Chi-BC/UV-ARP as an energy-efficient PFAS treatment strategy, where Chi-BC's adsorption characteristics enabled the use of compact reactors and lower energy inputs, advancing practical applications for diverse water chemistries.