Power density modulated ultrasonic degradation of perfluoroalkyl substances with and without sparging Argon

Abstract

The power density modulates the dynamics of the chemical reactions during the ultrasonic breakdown of organic compounds. We evaluated the ultrasonic degradation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) at various power densities (30 W/L–262 W/L) with and without sparging Argon. We observed pseudo-first-order degradation kinetics at an initial PFASs concentration of 100 nM over a range of power density. The rate kinetics of degradation shows a non-linear increase with an increase in power density. We proposed a four-parameter logistic regression (4PLR) equation that empirically fits the degradation rate kinetics with the power density. The 4PLR equation predicts that the maximum achievable half-life of PFOA and PFOS sonochemical degradation are 1 and 10 min under a given set of experimental conditions. The high bulk-water temperature (i.e., 30 °C) of the aqueous sample helps increase the degradation rate of PFOA and PFOS. The addition of oxidants such as iodate and chlorate help enhance PFOA degradation in an argon environment at an ultrasonic frequency of 575 kHz.