A Novel Adsorption/Saturation Approach to Ultrasonic Degradation of Phenol

Abstract

AbstractThe study describes development and application of a kinetic model based on the local concentration of solutes and hydroxyl radicals to predict the rate of ultrasonically induced oxidative degradation of phenol at 300 kHz. The results reveal that the degradation follows saturation kinetics. The rate is slow at low concentrations of the solute, increases with concentration and reaches a maximum at what we defined as “the critical concentration”. At higher concentrations (than the “critical”) the rate slows down and stabilizes at a plateau as it becomes concentration-independent. Owing to the similarity of sonochemical reactions in water to chemical reactions in heterogeneous systems, a kinetic model based on Langmuir adsorption isotherm is developed to predict the rate of reaction in terms of the initial concentration of the solute. The similarity of the model to models describing catalytic and adsorptive reaction kinetics is explained by reduced mass transfer limitations under ultrasonic irradiation, and localization of the solute at the bubble-liquid interface as a function of concentration.