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Kinetics and Mechanism of the Sonolytic Conversion of the Aqueous Perfluorinated Surfactants, Perfluorooctanoate (PFOA), and Perfluorooctane Sulfonate (PFOS) into Inorganic Products

Vecitis, Chad D. and Park, Hyunwoong and Cheng, Jie and Mader, Brian T. and Hoffmann, Michael R. (2008) Kinetics and Mechanism of the Sonolytic Conversion of the Aqueous Perfluorinated Surfactants, Perfluorooctanoate (PFOA), and Perfluorooctane Sulfonate (PFOS) into Inorganic Products. Journal of Physical Chemistry A, 112 (18). pp. 4261-4270. ISSN 1089-5639. https://resolver.caltech.edu/CaltechAUTHORS:20150805-151834195

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Abstract

The perfluorinated surfactants perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are recognized as widespread in the environment as well as recalcitrant toward most conventional water treatment technologies. In this study, acoustic cavitation as driven by high-frequency ultrasound is shown to be effective in the degradation of aqueous solutions of PFOS and PFOA and effective over a wide range of concentrations from 10 nM to 10 μM for a given compound. Sulfur, fluorine, and carbon mass balances indicate that mineralization occurs immediately following the degradation of the initial perfluorinated surfactant. Near complete conversion of PFOS and PFOA to CO, CO_2, F^-, and SO_4^(2-) occurs due to pyrolytic reactions at the surface and vapor phase of transiently collapsing cavitation bubbles. The initial PFOS or PFOA pyrolytic degradation occurs at the bubble−water interface and involves the loss of the ionic functional group leading to the formation of the corresponding 1H-fluoroalkane or perfluoroolefin. The fluorochemical intermediates undergo a series of pyrolytic reactions in the bubble vapor leading to C_1 fluoro-radicals. Secondary vapor-phase bimolecular reactions coupled with concomitant hydrolysis converts the C_1 fluoro-radicals to carbon monoxide, carbon dioxide, and HF, forming a proton and fluoride upon dissolution. Sonochemical half-lives, which are calculated from high-temperature gas-phase kinetics, are consistent with kinetic observations and suggest that mineralization occurs shortly after initial perfluorinated surfactant interfacial pyrolysis.


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http://dx.doi.org/10.1021/jp801081yDOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp801081yPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/jp801081yPublisherSupporting Information
ORCID:
AuthorORCID
Park, Hyunwoong0000-0002-4938-6907
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2008 American Chemical Society. Received: February 5, 2008. Published on Web 05/01/2008. We thank the 3M Company for ongoing research support. This support included the donation to Caltech of analytical standards and an Agilent LC-MS-Ion Trap mass spectrometer. Special thanks are given to Dale Bacon of the 3M Environmental Laboratory for his insight, useful comments, and guidance on this research project. The authors also thank Dr. A.J. Colussi for helpful discussions and Dr. Nathan Dalleska of the Environmental Analytical Center.
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3M CompanyUNSPECIFIED
Issue or Number:18
Record Number:CaltechAUTHORS:20150805-151834195
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150805-151834195
Official Citation:Kinetics and Mechanism of the Sonolytic Conversion of the Aqueous Perfluorinated Surfactants, Perfluorooctanoate (PFOA), and Perfluorooctane Sulfonate (PFOS) into Inorganic Products Chad D. Vecitis, Hyunwoong Park, Jie Cheng, Brian T. Mader, and Michael R. Hoffmann The Journal of Physical Chemistry A 2008 112 (18), 4261-4270 DOI: 10.1021/jp801081y
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59251
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:05 Aug 2015 22:45
Last Modified:09 Mar 2020 13:19

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