Adsorption of Surfactants at the Gas/Solution Interface of Cavitation Bubbles: An Ultrasound Intensity-Independent Frequency Effect in Sonochemistry

Abstract

A major limitation in determining the effects of ultrasound frequency in sonochemistry in relation to cavitation is that no reliable relationship exists between the energy supplied to the system and the energy converted by the cavitation process in producing a sonochemical effect. However, the current study presents a frequency effect that is independent of the energy supplied to the system. Spin-trapping of secondary carbon radicals with 3,5-dibromo-4-nitrosobenzenesulfonic acid-d2 (DBNBS-d2) and electron paramagnetic resonance (EPR) have been used to determine the relative ability of two nonvolatile surfactants [sodium 1-pentanesulfonic acid (SPSo) and sodium dodecyl sulfate (SDS)] to scavenge •H atoms and •OH radicals at the gas/solution interface of cavitation bubbles. The results obtained at 354 and 1057 kHz are compared to those observed previously at 47 kHz (Sostaric, J. Z.; Riesz, P. J. Am. Chem. Soc. 2001, 123, 11010−11019). At particular bulk surfactant concentrations, both surfactants reached a...