Degradation of Perfluorooctanoic Acid by Reactive Species Generated through Catalyzed H₂O₂ Propagation Reactions

Abstract

Perfluorinated compounds, which are environmentally persistent and bioaccumulative contaminants, cannot currently be treated in the subsurface by in situ technologies. Catalyzed H 2 O 2 propagation (CHP) reactions, which generate hydroxyl radical, hydroperoxide anion, and superoxide anion, were investigated for treating perfluorooctanoic acid (PFOA) as a basis for in situ chemical oxidation remediation of groundwater. Using 1 M H 2 O 2 and 0.5 mM iron(III), PFOA was degraded by 89% within 150 min. Hydroxyl radical does not react with PFOA, but systems producing only superoxide promoted 68% PFOA degradation within 150 min. In systems producing only hydroperoxide, the level of PFOA degradation was 80% over 150 min. The generation of near-stoichiometric equivalents of fluoride during PFOA degradation and the lack of detectable degradation products suggest PFOA may be mineralized by CHP. CHP process conditions can be adjusted during treatability studies to increase the flux of superoxide and hydroperoxide to treat PFOA, providing an easily implemented technology.

The effect of oxygen in the photocatalytic oxidation pathways of perfluorooctanoic acid

“…These intermediates are strong oxidizing species able to mineralize organic compounds [37,38]. However, an extensive debate on the oxidative pathway of PFOA exists nowadays, because it has been demonstrated that ·OH radicals generated by Fenton reagent are not very effective in the PFOA mineralization [30,39] and that Ti IV OH· + can take an active part in the mineralization reaction [27,40,41].…”

Electrochemical Advanced Oxidation Processes (EAOP) to degrade per- and polyfluoroalkyl substances (PFASs)

“…This is true in the case of the remediation of PFASs [12]. The fluoro-carbon skeletons is so stable that it can resist the attack of •HO [28]. However, the EAOP has been proven to be an effective method for breaking down PFASs.…”

“…As said, there are various degradation approaches [12], for example Fenton reaction of hydrogen peroxide [28], persulphate [12], chemical oxidation [56], sonolytic conversion [57], etc. This review focuses on EAOP [58] that is summarised in Table 2.…”

“…This oxidation capacity will be enhanced in the EAOP cell where the oxidant of •HO can be in-situ generated and refreshed, as discussed previously. Although the radical of •HO is one of the strongest oxidants [41], it has been reported to have a limited capacity to break down PFOA / PFOS alone [28]. That is, the vital contribution for the degradation is the PFOA / PFOS's direct oxidation occurred on the electrode surface, or at least this direct oxidation initialises the degradation process, which is then followed by the subsequent steps [11].…”

Temperature effect on photolysis decomposing of perfluorooctanoic acid

“…For direct photolysis, the electrophilic oxidants are oxygen in the reaction solution or water molecules of the reaction solution (Niu et al, 2013;Gatto et al, 2015;Mitchell et al, 2013). The C 6 F 13 C 16 O 18 O and C 6 F 13 C 18 O 18 O are the main intermediates resulting from direct irradiation of PFOA in H 2 18 O solutions under high oxygen pressure (Hori et al, 2004a).…”