Enhanced perfluorooctanoic acid (PFOA) degradation by electrochemical activation of peroxydisulfate (PDS) during electrooxidation for water treatment
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2024-06-04 |
| Journal | The Science of The Total Environment |
| Authors | Melvin S. Samuel, K. Govindan, Donald R. Ryan, Sean T. McBeath, Brooke K. Mayer |
| Institutions | Marquette University, University of Massachusetts Amherst |
| Citations | 29 |
Abstract
Section titled āAbstractāImproved treatment of per- and polyfluoroalkyl substances (PFAS) in water is critically important in light of the proposed United States Environmental Protection Agency (USEPA) drinking water regulations at ng L<sup>-1</sup> levels. The addition of peroxymonosulfate (PMS) during electrooxidation (EO) can remove and destroy PFAS, but ng L<sup>-1</sup> levels have not been tested, and PMS itself can be toxic. The objective of this research was to test peroxydisulfate (PDS, an alternative to PMS) activation by boron-doped diamond (BDD) electrodes for perfluorooctanoic acid (PFOA) degradation. The influence of PDS concentration, temperature, and environmental water matrix effects, and PFOA concentration on PDS-EO performance were systematically examined. Batch reactor experiments revealed that 99 % of PFOA was degraded and 69 % defluorination was achieved, confirming PFOA mineralization. Scavenging experiments implied that sulfate radicals (SO<sub>4</sub><sup>-</sup>) and hydroxyl radicals (HO) played a more important role for PFOA degradation than <sup>1</sup>O<sub>2</sub> or electrons (e<sup>-</sup>). Further identification of PFOA degradation and transformation products by liquid chromatography-mass spectrometry (LC-MS) analysis established plausible PFOA degradation pathways. The analysis corroborates that direct electron transfers at the electrode initiate PFOA oxidation and SO<sub>4</sub><sup>-</sup> improves overall treatment by cleaving the CC bond between the C<sub>7</sub>F<sub>15</sub> and COOH moieties in PFOA, leading to possible products such as C<sub>7</sub>F<sub>15</sub> and F<sup>-</sup>. The perfluoroalkyl radicals can be oxidized by SO<sub>4</sub><sup>-</sup> and HO, resulting in the formation of shorter chain perfluorocarboxylic acids (e.g., perfluorobutanoic acid [PFBA]), with eventual mineralization to CO<sub>2</sub> and F<sup>-</sup>. At an environmentally relevant low initial concentration of 100 ng L<sup>-1</sup> PFOA, 99 % degradation was achieved. The degradation of PFOA was slightly affected by the water matrix as less removal was observed in an environmental river water sample (91 %) compared to tests conducted in Milli-Q water (99 %). Overall, EO with PDS provided a destructive approach for the elimination of PFOA.
Tech Support
Section titled āTech SupportāOriginal Source
Section titled āOriginal SourceāReferences
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