Kinetics analysis for development of a rate constant estimation model for ultrasonic degradation reaction of methylene blue.
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.
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan. Electronic address: dkobayashi@ci.kagu.tus.ac.jp.
Daisuke
D
Kobayashi
Department of Chemical Science and Technology, Graduate School of Chemical Science and Technology, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
Chiemi
C
Honma
Department of Chemical Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama 2-12-1, Meguro-ku, Tokyo 152-8550, Japan.
Hideyuki
H
Matsumoto
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
Tomoki
T
Takahashi
Department of Chemical Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama 2-12-1, Meguro-ku, Tokyo 152-8550, Japan.
Chiaki
C
Kuroda
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
Katsuto
K
Otake
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
Atsushi
A
Shono
Degradation rate constant; Frequency; Initial concentration; Kinetic analysis; Methylene blue; Sonochemical efficiency value