Comparison of ultrasonic degradation rates constants of methylene blue at 22.8 kHz, 127 kHz, and 490 kHz

Abstract

Techniques such as solvent extraction, incineration, chemical dehalogenation, and biodegradation have been investigated for the degradation of hazardous organic compounds. We found ultrasound to be an attractive technology for the degradation of hazardous organic compounds in water. However, the effects of ultrasonic frequency on degradation rate constants were not investigated quantitatively. In this study, the degradation process of a model for hazardous organic compound methylene blue was investigated using ultrasonic irradiation. The study focused on the effects of ultrasonic frequency and ultrasonic power on the degradation rate constant. The apparent degradation rate constants were estimated based on time dependence of methylene blue concentration assuming pseudo-first-order kinetics for the decomposition. A linear relationship between the apparent degradation rate constant and ultrasonic power was identified. In addition, the apparent degradation rate constants at frequencies of 127 and 490 kHz were much larger than those at 22.8 kHz. A relationship between the apparent degradation rate constant and the sonochemical efficiency value (SE value) was also found. Based on these results, a simple model for estimating the apparent degradation rate constant of methylene blue based on the ultrasonic power and the SE value is proposed in this study.

The use of power ultrasound for water treatment

“…The optimum appears to occur between 200 and 400 kHz for nonvolatile molecules, while the yield increases for volatile molecules as the frequency increases (Kobayashi et al, 2012;Pétrier and Francony, 1997). …”

Comparison of Threshold Power between Methylene Blue Degradation and KI Oxidation Reaction Using Ultrasound

“…From the results of our previous study, the apparent rate constant of ultrasonic degradation of methylene blue was evaluated using a pseudo-first-order reaction model [14] [15] [16]. kHz [15].…”

“…However, when the frequency is higher than 500 kHz, the value of threshold power of KI oxidation is higher than that of methylene blue degradation, and the difference becomes large with increasing frequency. In our previous study, there is a relationship between SE KI value and degradation rate constant of methylene blue [14] [15] [16]. In addition, it has been reported that the ultrasonic degradation of methylene blue is enhanced by TiO 2 particle addition under dark condition [23] [24] [25], and the presence of TiO 2 particle accelerates the generation of hydroxyl radicals during ultrasonic irradiation even in the absence of UV irradi- ation [26].…”

“…In our previous study, the effects of frequency on ultrasonic degradation of methylene blue as a model hazardous organic compound have been investigated, and a simple model for estimating the apparent degradation rate constant using SE KI value, ultrasonic power, initial concentration, and sample solution volume is proposed [14] [15] [16]. Moreover, it is observed that a threshold power is required for degradation reaction to progress, and frequency has less influence on threshold power for degradation reaction of methylene blue.…”

Modeling methylene blue oxidation by means of Fenton chemistry enhanced by UV irradiation at mild conditions

“…However, the advanced chemical oxidation processes, based on the generation of extremely reactive hydroxyl radicals are among the promising techniques for the environmental destruction organic dyes, including MB, in aqueous solution. MB has been oxidized by the generation of hydroxyl radicals using different techniques, among them ultrasonic degradation [11][12][13] and sonophotocatalysis [14][15][16][17] can be mentioned.…”