[Opinion] The Need to Include a Fluorine Mass Balance in the Development of Effective Technologies for PFAS Destruction
By Sanne J. Smith, Mélanie Lauria, Christopher P. Higgins, Kurt D. Pennell, Jens Blotevogel, and Hans Peter H. Arp
Environ. Sci. Technol.
February 5, 2024
DOI: 10.1021/acs.est.3c10617
Many emerging technologies, including electrochemical oxidation, plasma, hydrothermal alkaline treatment, supercritical water oxidation, photocatalytic degradation, sonolysis, and thermal treatment, are being developed and marketed for the destruction of per- and polyfluoroalkyl substances (PFAS) in environmental media. (1) In contrast to conventional treatment methods designed to capture and concentrate PFAS, the goal of these technologies is to actually destroy PFAS. As a consequence, there is the potential to generate and unintentionally release transformation products, such as ultra-short-chain PFAS (e.g., C2–C3) or longer-chain fluorinated compounds.
The importance of transformation (by)product formation during the destructive treatment of PFAS has been recognized in the literature. (2,3) Nonetheless, studies describing destructive technologies may still report concentrations of only the parent compound or a small set of target PFAS and often confuse “transformation of target species” with “mineralization”. In contrast to that of other organic micropollutants, the degradation of PFAS can be readily monitored by tracing the fluorine element. When technologies are tested in spiked, laboratory-prepared solutions or solids, PFAS concentrations are usually sufficiently high and background fluoride concentrations sufficiently low to allow tracking of defluorination with fluoride measurements. This type of confirmation is often achieved using fluoride-selective electrodes, sometimes verified by ion chromatography (IC) or other methods.
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