Comprehensive experimental and numerical investigations of the effect of frequency and acoustic intensity on the sonolytic degradation of naphthol blue black in water
No Thumbnail Available
Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
In the present work, comprehensive experimental and numerical investigations of the effects of frequency
and acoustic intensity on the sonochemical degradation of naphthol blue black (NBB) in water have
been carried out. The experiments have been examined at three frequencies (585, 860 and 1140 kHz)
and over a wide range of acoustic intensities. The observed experimental results have been discussed
using a more realistic approach that combines the single bubble sonochemistry and the number of active
bubbles. The single bubble yield has been predicted using a model that combines the bubble dynamics
with chemical kinetics consisting of series of chemical reactions (73 reversible reactions) occurring inside
an air bubble during the strong collapse. The experimental results showed that the sonochemical degradation
rate of NBB increased substantially with increasing acoustic intensity and decreased with increasing
ultrasound frequency. The numerical simulations revealed that NBB degraded mainly through the
reaction with hydroxyl radical ( OH), which is the dominant oxidant detected in the bubble during collapse.
The production rate of OH radical inside a single bubble followed the same trend as that of NBB
degradation rate. It increased with increasing acoustic intensity and decreased with increasing frequency.
The enhancing effect of acoustic intensity toward the degradation of NBB was attributed to the rise of
both the individual chemical bubble yield and the number of active bubbles with increasing acoustic
intensity. The reducing effect of frequency was attributed to the sharp decrease in the chemical bubble
yield with increasing frequency, which would not compensated by the rise of the number of active bubbles
with the increase in ultrasound frequency.