posted on 2020-07-15, 12:04authored byHassan Javed, Jordin Metz, Toprak C. Eraslan, Jacques Mathieu, Bo Wang, Gang Wu, Ah-Lim Tsai, Michael S. Wong, Pedro J. J. Alvarez
Perfluorooctanoic
acid (PFOA) is a widely distributed recalcitrant
contaminant. In recent years, advanced oxidation processes have been
explored for PFOA degradation, yet factors influencing their efficacy
and degradation mechanism are not fully understood. Here, we resolve
ambiguity in the literature regarding the role of superoxide in PFOA
degradation (e.g., by nucleophilic attack) by considering three pure
superoxide-producing systems: KO2 in dimethyl sulfoxide,
xanthine oxidase with hypoxanthine, and WOx/ZrO2 catalyst with H2O2. Superoxide
production was confirmed in all systems by electron paramagnetic resonance
spectroscopy and by precipitation of nitroblue tetrazolium, a common
superoxide probe. Positive control experiments showed that the produced
superoxide degrades ∼48% of bisphenol A within 1 day, corroborating
the fact that superoxide was sufficiently stable and available for
reaction in the test systems. However, no PFOA degradation was observed,
which was corroborated by the absence of fluoride and degradation
byproducts in all three systems. Therefore, other reaction pathways
should be explored for PFOA degradation.