This presentation will report on recent results from our team applying a novel hydrothermal alkaline treatment (HALT) technology to degrade per- and polyfluoroalkyl substances (PFASs) contaminating groundwater and soil samples obtained from sites impacted by past use of aqueous film-forming foams (AFFF). Concentrations of individual PFASs during reactions at hydrothermal conditions (350 °C, 15 MPa) were tracked using high-resolution mass spectrometry (HRMS), after applying a recently reported comprehensive soil extraction method and liquid chromatography quadrupole time-of-flight mass spectrometry method capable of identifying and semi-quantifying concentrations of cationic, anionic, and zwitterionic PFASs. All detected PFASs were degraded to non-detectable levels within 2 hours when treated under HALT conditions. Among the detected PFASs, perfluoroalkyl sulfonic acids, particularly short-chain structures, were most recalcitrant and required the most severe reaction conditions. Rates of PFAS destruction in groundwater were found to be similar to measurements previously reported in laboratory synthetic solutions. Rates observed when treating PFAS-contaminated soil were lower due to base-neutralizing properties of the soil matrices. Thus, soil treatment applications need to be designed to include this consideration to ensure treatment goals are met. The implication of the HALT-PFAS technology for the site remediation will also be discussed.

Hydrothermal degradation of PFASs in AFFF-impacted groundwater and soil

ACS Spring 2022

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