Ultrafast PFAS degradation using oxidant-containing microdroplets

Toxic per- and poly-fluoroalkyl substances (PFASs), known as “forever chemicals”, are harmful contaminants with huge environmental concerns. The challenge for PFAS removal is that it often requires a long time and high energy input to achieve high degradation efficiencies. This study reports a novel, ultrafast and effective method for degrading PFASs using the microdroplet technique. By forming microdroplets from PFAS solution spiked with oxidant such as sodium persulfate or Fenton’s reagent, a range of PFAS compounds including short-chain perfluorocarboxylic acids (PFCAs) such as PFPeA (C4F9COOH) were quickly degraded with degradation efficiency reaching 77-94%. The microdroplet reaction was completed in less than 1 ms under ambient conditions. In contrast, without oxidant, the microdroplet degradation efficiency was 10-17%. Also, incubating PFAS with the oxidant in bulk solution for 30 min resulted in < 8% degradation efficiency. It appears that the PFAS degradation rate can be accelerated by over 2 million times in oxidant-containing microdroplets in comparison with the bulk solution. Based on measured fluoride product concentrations, our result suggests that persulfate primarily facilitates PFAS degradation via the two-carbon degradation pathway, whereas Fenton’s reagent operates through the one-carbon degradation pathway. Overall, this study presents a new approach to PFAS degradation, offering valuable insights for developing effective PFAS removal strategies.