4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)

Sonochemical Degradation Of C4 Perfluorosurfactants: The Role Of Cavitation Bubble Surface Sorption

The kinetics of degradation of the aqueous-phase perfluoro-surfactants (PFBX) perfluorobutanoate (PFBA) and perfluorobutanesulfonate (PFBS) are investigated. Surface tension measurements are used to evaluate chain-length effects on equilibrium air-water interface partitioning. PFBX air-water interface partitioning coefficients were determined from the surface pressure equation of state for PFBA and PFBS. The relative surface activities expressed as Ksono are found to be dependent upon chain length when comparing the values for the or C4, C6 and C8 analogues, while the Γeq,max values change little with increasing chain length. The observed rates of sonolytic degradation are described in terms of a Langmuir-Hinshelwood kinetics model where Vmax (M s-1) is the maximum rate of reaction when all the available adsorption sites are occupied while the interfacial adsorption equilibrium constant, Kads, is the ratio of the PFBX concentration in the interfacial region to the bulk solution-phase concentration. Sonolytic degradations were carried out at 618 kHz at a power density of 250 W L-1 under a constant temperature of 10 °C in an argon-saturated solution and headspace. A Langmuir-type kinetic model can be applied to quantify the absolute rates of reaction over four orders of magnitude of initial concentration of PFYX (Y = H or B, X = A or S). The relative surface activities are 80 to 100 times greater than the equilibrium sorption activities. Depending on the initial concentrations over the range of nM to upper 𝜇M levels, the extent of C4 perfluoro-surfactant degradation varied from 100% for the nM concentration range to 20 to 40% degradation for the upper 𝜇M concentrations over 2 h of ultrasonic irradiation.
Tammy Campbell, Michael Hoffmann