全氟辛酸
过氧二硫酸盐
化学
降级(电信)
矿化(土壤科学)
水处理
激进的
环境化学
电化学
硫酸盐
三卤甲烷
无机化学
电极
水溶液
氯
有机化学
氮气
环境工程
电信
物理化学
计算机科学
工程类
作者
Melvin S. Samuel,K. Govindan,Donald R. Ryan,Sean T. McBeath,Brooke K. Mayer,Patrick J. McNamara
标识
DOI:10.1016/j.scitotenv.2024.173736
摘要
Improved 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−1 levels. The addition of peroxymonosulfate (PMS) during electrochemical oxidation (EO) can remove and destroy PFAS, but ng L−1 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 ng L−1 level perfluorooctanoic acid (PFOA) degradation. The influence of PDS concentration, temperature, and real water matrix effects, and PFOA concentration on PDS-EO performance were systematically examined. Batch reactor experiments revealed that 99.8 % of PFOA was degraded and 69.1 % defluorination was achieved, confirming PFOA mineralization. Scavenging experiments implied that sulfate radicals (SO4–) played a more important role for PFOA degradation than HO, 1O2, or electrons (e−). Further identification of PFOA degradation and transformation products by liquid chromatography-mass spectrum (LC-MS) analysis established plausible PFOA degradation pathways. The analysis corroborates that direct electron transfers at the electrode initiate PFOA oxidation and SO4– improves overall treatment by cleaving the CC bond between the C7F15 and COOH moieties in PFOA, leading to possible products such as C7F15 and F−. The perfluoroalkyl radicals can be oxidized by SO4– and HO, resulting in the formation of shorter chain perfluorocarboxylic acids (e.g., perfluorobutanoic acid [PFBA]), with eventual mineralization to CO2 and F−. At an environmentally relevant low initial concentration of 100 ng L−1 PFOA, 99 % degradation was achieved. The degradation of PFOA was slightly affected by the water matrix as less removal was observed in a real 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.
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