Determination of total oxidizable precursors in foam surfactants and foam contaminated water based on UV-activated persulfate oxidation

Abstract

In this study, ultraviolet (UV)-activated persulfate under alkaline condition was developed as an alternative Total Oxidizable Precursor (TOP) assay to convert per- and polyfluoroalkyl substances (PFASs) precursors into detectable perfluoroalkyl acids (PFAAs). The conventional heat-based TOP assay takes 6 h at 85 °C, which is time consuming and may lose the volatile PFASs. Shorter time treatment would be beneficial to promote the analysis efficiency of the samples. We here report the UV-based TOP method as faster replacement of conventional heat-based TOP assay. The 6:2 fluorotelomer sulfonate (FTS), 8:2 FTS, and perfluorooctanesulfonamide (FOSA) achieved nearly complete conversion (with the molar yield of PFAAs of 97.2%–109.9%) at 60 min. This new UV-based TOP assay was then applied to 23 industry samples, and the results are comparable with the heat-based TOP assay. The perfluoroalkyl carboxylic acids (PFCAs) concentrations of 23 samples before and after normal TOP assay were 0–4290 mg L−1 and 438–77,420 mg L−1, respectively. The PFCAs after 60 min UV-based TOP assay was 310–81,881 mg L−1. The QuotientMol of 21 samples were 0.71–1.28, the QuotientMol of other two samples were 1.45 and 1.68, this probably due to the loss of volatile precursors during heat-based TOP assay. The UV-based TOP assay is an efficient, reliable and faster alternative to the conventional heat-based TOP assay.