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Degradation of Perfluoroalkyl Acids under 222 nm Irradiation in the Presence and Absence of Sulfite
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DOI：10.1021/acsestengg.6c00161.png)
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Abstract
En 中文
Krypton chloride excimer (KrCl*) lamps emitting at 222 nm have recently been shown to enhance the fluence-normalized rates of micropollutant abatement in UV-oxidation and -reduction systems relative to conventional, 254 nm light sources. Here, we investigated the destruction of short- and long-chain perfluoroalkyl acids under 222 nm irradiation from KrCl* lamps in the presence and absence of sulfite. At pH 12 under anaerobic conditions, all compounds were degraded under 222 nm irradiation with apparent quantum yields (Φapp,PFAS) increasing in the order 0.036 (perfluorobutanesulfonate (PFBS)), 0.124 (perfluorooctanesulfonate (PFOS)), 0.374 (perfluorooctanoic acid (PFOA)), and 0.822 (perfluorobutanoic acid (PFBA)), which are markedly higher than quantum yields reported previously at pH 8.5. Multiple lines of evidence suggest that the observed UV222 only degradation of perfluorocarboxylic acids is due to both direct photolysis and eaq–-based destruction, the latter enabled by photolysis of hydroxide ions at pH 12. In contrast, PFBS and PFOS degradation in the UV222 only system is due to eaq–-mediated destruction, not true direct photolysis. To compare the effectiveness of 222 nm KrCl* lamps with 254 nm, the UV/sulfite system was tested on two complex water matrices: (i) a reverse osmosis concentrate (ROC) spiked with short- and long-chain perfluoroalkyl acids and (ii) an aqueous film forming foam (AFFF). The extent of PFAS destruction in these complex matrices was greater for 222 nm irradiation relative to 254 nm by up to 6-fold when normalized to incident fluence. Overall, this study provides fundamental insight into the UV-based degradation of perfluoroalkyl acids at 222 nm and suggests that KrCl* lamps may provide improved performance compared to conventional 254 nm sources in UV/sulfite ARP for PFAS destruction in complex water matrices.
Keywords:
PFAS
PFBS
advanced reduction processes
hydrated electron
krypton chloride excimer lamp
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