Photocatalytic defluorination of perfluoroalkyl substances by surface-engineered ZnO nanocrystals

Abstract

Perfluoroalkyl substances (PFASs) are widely used due to their exceptional chemical stability. However, this also causes severe environmental persistence, bioaccumulation, and recycling challenges, making PFAS contamination a global issue. Conventional defluorination methods require excessive energy, limiting practical application. Therefore, developing an energy-efficient approach under ambient conditions is crucial for mitigating environmental risks and enabling fluorine material recycling. Here, we demonstrate that zinc oxide (ZnO) nanocrystals (NCs) capped with specific ligands can efficiently defluorinate perfluorooctanesulfonic acid (PFOS), which is one of the most stable PFASs, by irradiation of near UV light under ambient conditions. While NCs capped with mercaptopropionic acid achieved only 8.4% defluorination after 24 hours of 365 nm LED light irradiation, NCs capped with acetic acid exhibit 64% defluorination, reaching 92% for 24 h irradiation under optimized conditions. We further reveal that each NC can break approximately 8250 C–F bonds with high repeatability. The low toxicity, cost-effectiveness, and scalability of ZnO NCs make it a promising material for practical applications of PFAS decomposition.