A comparative sonochemical reaction that is independent of the intensity of ultrasound and the geometry of the exposure apparatus

Abstract

Sonolysis of aqueous solutions of n-alkyl anionic surfactants results in the formation of secondary carbon-centered radicals (– CH–). The yield of – CH– depends on the bulk surfactant concentration up to a maximum attainable radical yield (the ‘plateau yield’) where an increasing surfactant concentration (below the critical micelle concentration) no longer affects the – CH– yield. In an earlier study it was found that the ratio of – CH– detected following sonolysis of aqueous solutions of sodium pentane sulfonate (SPSo) to that of sodium dodecyl sulfate (SDS) (i.e. CH SPSo/CH SDS) depended on the frequency of sonolysis, but was independent of the ultrasound intensity, at the plateau concentrations [J.Z. Sostaric, P. Riesz, Adsorption of surfactants at the gas/solution interface of cavitation bubbles: an ultrasound intensity-independent frequency effect in sonochemistry, J. Phys. Chem. B 106 (2002) 12537–12548]. In the current study, it was found that the CH SPSo/CH SDS ratio depended only on the ultrasound frequency and did not depend on the geometry of the ultrasound exposure apparatus considered.