Transformation of 6:2 fluorotelomer sulfonic acid in laccase-mediator systems

6:2 Fluorotelomer sulfonic acid (FTS) has been used as an alternative to perfluorooctane sulfonate (PFOS) as chrome mist suppressant in electroplating, emulsion aid in fluoropolymer processing, etc. Its biotic degradation is slow and incomplete, generating short chain perfluoroalkyl acids (PFAAs) and it is frequently detected in the environment. This proof-of-concept study reports possible transformation of 6:2 FTS by enzyme-catalyzed oxidative humification reactions (ECOHRs) in laccase-mediator systems (LMS) using crude or purified laccases, either mediated by a synthetic chemical (1-hydroxybenzotriazole) or a natural organic material (soybean meal extract; SBMe). The LMS with crude laccase, SBMe and 10 mM CuSO 4 exhibited a 23.8% reduction in concentration (mean of three technical replicates) relative to its control. A 34.8% reduction in adsorbable organic fluorine provided a supporting observation for transformation and potentially degradation. High-resolution mass spectrometry (HRMS) analysis unveiled a suite of tentative transformation products ranging from C8 to C3, including C 3 F 7 O 3 S, a previously unreported candidate formula for 6:2 FTS transformation products and potentially consistent with perfluoropropanesulfonate (PFPrS). Additionally, the calculated bond dissociation energies (BDEs) of the C-C bonds and the C-S bond in the 6:2 FTS were higher than those of PFOS, which could potentially explain the variable degradation observed in different studies. These findings underscore the potential of ECOHRs to transform per-and polyfluoroalkyl substances (PFAS) precursors. Future investigations into the transformation of PFAS mixtures in complex soil systems could provide actionable insights into ECOHRs as a potentially cost-effective remediation technique for vast crop lands, and pastures.