Enhancement of perfluorooctanoate and perfluorooctanesulfonate activity at acoustic cavitation bubble interfaces

C. D. Vecitis, H. Park, J. Cheng, B. T. Mader, M. R. Hoffmann

Research output: Contribution to journalArticlepeer-review

122 Scopus citations

Abstract

Acoustic cavitation driven by ultrasonic irradiation decomposes and mineralizes the recalcitrant perfluorinated surfactants perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA). Pyrolytic cleavage of the ionic headgroup is the rate-determining step. In this study, we examine the sonochemical adsorption of PFOX, where X = S for PFOS and A for PFOA, by determining kinetic order and absolute rates over an initial PFOX concentration range of 20 nM to 200 μM. Sonochemical PFOX kinetics transition from pseudo-firstorder at low initial concentrations, [PFOX]i < 20 μM to zero-order kinetics at high initial concentrations, [PFOX]i < 40 μM, as the bubble interface sites are saturated. At PFOX concentrations below 100 μM, concentration-dependent rates were modeled with Langmuir-Hinshelwood (LH) kinetics. Empirically determined rate maximums, √Max PFOA = 2230 ± 560 nM min-1 and √ Max-PFOA = 230 ± 60 nM min-1, were used in the LH model, and sonochemical surface activities were estimated to be K PFOSSono = 120 000 M-1 and K PFOSSono = 28 500 M-1 60 and 80 times greater than equilibrium surface activities, KPFOSEq and K PFOAEq. These results suggest enhanced sonochemical degradation rates for PFOX when the bubble interface is undersaturated. The present results are compared to previously reported sonochemical kinetics of nonvolatile surfactants.

Original languageEnglish
Pages (from-to)16850-16857
Number of pages8
JournalJournal of Physical Chemistry C
Volume112
Issue number43
DOIs
StatePublished - 30 Oct 2008

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