TY - JOUR
T1 - Enhancement of perfluorooctanoate and perfluorooctanesulfonate activity at acoustic cavitation bubble interfaces
AU - Vecitis, C. D.
AU - Park, H.
AU - Cheng, J.
AU - Mader, B. T.
AU - Hoffmann, M. R.
PY - 2008/10/30
Y1 - 2008/10/30
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=56049125265&partnerID=8YFLogxK
U2 - 10.1021/jp804050p
DO - 10.1021/jp804050p
M3 - Article
AN - SCOPUS:56049125265
SN - 1932-7447
VL - 112
SP - 16850
EP - 16857
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 43
ER -