Kinetics analysis for development of a rate constant estimation model for ultrasonic degradation reaction of methylene blue

Abstract

Ultrasound has been used as an advanced oxidation method for wastewater treatment. Sonochemical degradation of organic compounds in aqueous solution occurs by pyrolysis and/or reaction with hydroxyl radicals. Moreover, kinetics of sonochemical degradation has been proposed. However, the effect of ultrasonic frequency on degradation rate has not been investigated. In our previous study, a simple model for estimating the apparent degradation rate of methylene blue was proposed. In this study, sonochemical degradation of methylene blue was performed at various frequencies. Apparent degradation rate constant was evaluated assuming that sonochemical degradation of methylene blue was a first-order reaction. Specifically, we focused on effects of ultrasonic frequency and power on rate constant, and the applicability of our proposed model was demonstrated. Using this approach, maximum sonochemical degradation rate was observed at 490 kHz, which agrees with a previous investigation into the effect of frequency on the sonochemical efficiency value evaluated by KI oxidation dosimetry. Degradation rate increased with ultrasonic power at every frequency. It was also observed that threshold power must be reached for the degradation reaction to progress. The initial methylene blue concentration and the apparent degradation rate constant have a relation of an inverse proportion. Our proposed model for estimating the apparent degradation rate constant using ultrasonic power and sonochemical efficiency value can apply to this study which extended the frequency and initial concentration range.

Ultrasound-assisted electrochemical treatment of wastewaters containing organic pollutants by using novel Ti/Ta2O5–SnO2 electrodes

“…Only a few studies used ultrasound frequency higher than 1000 kHz [129] [130] [131] [132]. Thus it was shown that irradiation of solution containing 10 mol/L MB dye in ultrasonic bath type reactor with 1640 kHz frequency (0.08 W/mL actual power) for 1 h provided 25% of dye degradation efficiency [133]. To the best of our knowledge, 1640 kHz was the highest frequency tested in MB degradation.…”

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].…”

“…The effect of ultrasonic power on apparent degradation rate constant of methylene blue for various frequencies[15].…”

Study on the efficiency of a transducer for sonochemistry by calorimetry

“…26,27) The sonochemical efficiency (SE) defines the ratio of the amount of substance in the reacted material to the ultrasonic energy input to the sample. 26) The SE is usually determined by the KI method, and can be increased by optimizing ultrasonic frequency 26,28) and the liquid height 29) in a reactor. Ultrasonic power, which is the ultrasonic energy per unit time, is used to study the frequency dependence of chemical reactions by ultrasonic irradiation.…”