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Sonochemical Degradation of Perfluorooctanesulfonate in Aqueous Film-Forming Foams

Vecitis, Chad D. and Wang, Yajuan and Cheng, Jie and Park, Hyunwoong and Mader, Brian T. and Hoffmann, Michael R. (2010) Sonochemical Degradation of Perfluorooctanesulfonate in Aqueous Film-Forming Foams. Environmental Science and Technology, 44 (1). pp. 432-438. ISSN 0013-936X.

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Aqueous film-forming foams (AFFFs) are fire extinguishing agents developed by the Navy to quickly and effectively combat fires occurring close to explosive materials and are utilized today at car races, airports, oil refineries, and military locations. Fluorochemical (FC) surfactants represent 1−5% of the AFFF composition, which impart properties such as high spreadability, negligible fuel diffusion, and thermal stability to the foam. FC’s are oxidatively recalcitrant, persistent in the environment, and have been detected in groundwater at AFFF training sites. Ultrasonic irradiation of aqueous FCs has been reported to degrade and subsequently mineralize the FC surfactants perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS). Here we present results of the sonochemical degradation of aqueous dilutions of FC-600, a mixture of hydrocarbon (HC) and fluorochemical components including cosolvents, anionic hydrocarbon surfactants, fluorinated amphiphilic surfactants, anionic fluorinated surfactants, and thickeners such as starch. The primary FC surfactant in FC-600, PFOS, was sonolytically degraded over a range of FC-600 aqueous dilutions, 65 ppb < [PFOS]_i < 13100 ppb. Sonochemical PFOS−AFFF decomposition rates, R_(AFFF)^(−PFOS), are similar to PFOS−Milli-Q rates, R_(MQ)^(−PFOS), indicating that the AFFF matrix only had a minor effect on the sonochemical degradation rate, 0.5 < R_(AFFF)^(−PFOS)/R_(MQ)^(−PFOS) < 2.0, even though the total organic concentration was 50 times the PFOS concentration, [Org]_(tot)/[PFOS] ~50, consistent with the superior FC surfactant properties. Sonochemical sulfate production is quantitative, Δ[SO_4^(2−)]/Δ[PFOS] ≥ 1, indicating that bubble-water interfacial pyrolytic cleavage of the C−S bond in PFOS is the initial degradation step, in agreement with previous studies done in Milli-Q water. Sonochemical fluoride production is significantly below quantitative expectations, Δ[F^−]/Δ[PFOS] ~4 vs 17, suggesting that in the AFFF matrix, PFOS’ fluorochemical tail is not completely degraded, whereas Milli-Q studies yielded quantitative F− production. Measurements of time-dependent methylene blue active substances and total organic carbon indicate that the other FC-600 components were also sonolytically decomposed.

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Park, Hyunwoong0000-0002-4938-6907
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2009 American Chemical Society. Received August 17, 2009. Revised manuscript received October 22, 2009. Accepted November 2, 2009. Publication Date (Web): December 4, 2009. This work was supported by the 3M Co. The author’s thank 3M for the donation of the Agilent HPLC-MS ion trap used for all the analyses and for the donation of PFC calibration standards. The authors wish to thank Dr. Nathan Dalleska (Caltech Environmental Analytical Center) for comments and analytical support.
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Official Citation:Sonochemical Degradation of Perfluorooctanesulfonate in Aqueous Film-Forming Foams Chad D. Vecitis, Yajuan Wang, Jie Cheng, Hyunwoong Park, Brian T. Mader, Michael R. Hoffmann Environmental Science & Technology 2010 44 (1), 432-438
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17355
Deposited By: Tony Diaz
Deposited On:01 Feb 2010 03:24
Last Modified:09 Mar 2020 13:19

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