Perfluoro-2-propoxypropanoic acid (PFPrOPrA), “Gen X”, is an alternative perfluorinated alkyl substance (PFAS) for the legacy perfluorinated octanoic acid (PFOA). GenX is resistant to degradation a number of conventional and advanced oxidation wastewater treatment methods. We used pulse-radiolysis to determine a bimolecular rate constant of eaq- with “GenX” is near diffusion control, 5 × 1010 M-1●s-1. However complementary product studies using gamma radiolysis showed less than 2 % degradation after 8 hours of radiation under a variety of conditions. UV photocatalysis with TiO2 under alkali environment showed only slow conversion and no defluorination. Photoelectrochemical experiments are ongoing in an attempt to understand the possible degradation mechanisms by photocatalysis. The ultrasonic decomposition of “Gen X” at different initial concentrations, from 0.6 to 6 µmol/L at 640 Hz and 396 W, showed more than 80 % mineralization of the starting material to F-. We propose the ultrasonic-induced degradation of “Gen X” is primarily by pyrolysis. The reaction mechanisms and possible pyrolytic products were investigated using computational methods. The results indicated that pyrolysis induced by ultrasound could be an effective tool to remediation of Gen X. Enthalpies of the initial C-C and C-O bond cleavages of Gen X were calculated using density functional theory at the wb97xd/6-311G** level using the Gaussian 09 package. Similar computation studies for the thermal decomposition of a number of emerging perfluorinated alkyl substances are underway.

Comparison of radiolysis, TiO2 photocatalysis and sonolysis of “GenX”

2019 Spring National Meeting

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