Effects of ultrasonic frequency and initial concentration on degradation of methylene blue

The ultrasonic degradation of hazardous organic compounds in an aqueous solution is an attractive technology for wastewater treatment. The kinetics of ultrasonic degradation has been investigated. However, there have been only a few quantitative studies of the effect of ultrasonic frequency on degradation rate. In this study, the ultrasonic degradation of methylene blue was performed at various frequencies, especially in the high frequency region, and various initial concentrations. From the results of the time dependence of the methylene blue concentration in this study, ultrasonic degradation was considered to be a pseudo-first-order reaction. The apparent degradation rate constant and sonochemical efficiency have a linear relationship, and the apparent rate constant and initial concentration have an inversely proportional relationship. These phenomena well agree with our proposed formula for estimating the apparent degradation rate constant. In addition, our proposed model is also applicable to the ultrasonic degradation of nonvolatile and hydrophilic compounds.