Determination of an Effective Perfluorinated Compounds (PFCs) Oxidation Method

Abstract:

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a stable synthetic class of chemicals ubiquitously spread in environmental media (i.e. air, soil, biota, surface water and groundwater). The substances’ strong polar carbon-fluorine bonds and their high thermal and chemical stability make them resistant to biological, chemical, and physical degradation. The purpose of this research is to identify the most effective oxidation method to treat perfluorinated compounds (PFCs) and their by-products that is suitable for in situ application. The laboratory oxidation study focuses on the more commonly detected and studied long-chain (C-8) PFAS; perfluorooctanoic acids (PFOA) and perfluorooctane sulfonic acid (PFOS).
Existing research evaluating oxidizing treatment effectiveness on perfluoroalkyl sulfoinoic acids (PFSAs) is limited. A review of the literature and results from preliminary studies indicate that activated persulfate and catalyzed hydrogen peroxide propagation (CHP) reactions appear to be promising oxidants for PFOA. It has been demonstrated that the reactivity of superoxide in water increases in the presence of hydrogen peroxide (H₂O₂) and solids. Superoxide generated in CHP reactions degrades PFOA seemingly similar to superoxide-mediated destruction of the perhalogenated compounds.
The goal of this study is to look at conditions that promote generation of superoxide and look at PFASs treatment effectiveness and byproduct generation. CHP reactions are conducted with varying amount of H₂O₂ and Fe(III) to determine the optimum conditions for PFC degradation. Results will be compared to those of another experiment using manganese dioxide as a CHP catalyst with varied H₂O₂ concentration to generate superoxide to degrade PFASs. Activated persulfate conditions to be compared include alkaline pH activation, heat activation, and dual oxidation (combined H₂O₂ and persulfate ). This presentation will focus on a comparison of oxidation effectiveness under the varied reaction conditions as well as on the oxidation intermediates and byproducts generated toward improved understanding of the potential for and limitations of in situ chemical oxidation (ISCO) for treatment of PFCs.