Characterization and application of a 1700-kHz acoustic cavitation field for water decontamination: a case study with toluidine blue

Abstract

This work aimed at the characterization and application of a cavitation field induced in water by an ultrasonic reactor operating at 1700 kHz and 15 W. It was found that the size of active bubbles varied from 0.23 to 3 µm. The number of active bubbles increased from 6.1142 × 10 8 s −1 L −1 at 25 °C to 4.4684 × 10 9 s −1 L −1 at 55 °C. The most active bubbles were those achieving temperature of 4000 K and pressure of 1000 atm at the collapse. The characterized cavitation field removed efficiently toluidine blue (TB), an emerging organic contaminant, through reaction with hydroxyl radical. The best TB-removal rate was obtained under argon saturation, but CO 2 completely suppressed the process. TB degradation rate sensitively enhanced with increasing initial substrate concentration and solution pH, whereas the liquid temperature did not affect the degradation rate. Formic acid, as an organic competitor, reduced considerably the degradation of the pollutant.

Toward understanding the mechanism of pure CO2‐quenching sonochemical processes

“…Not only the sonochemical effect but also sonobiological effects (Table ) and sonophysical effects, such as sonoluminescence and cavitation intensity, are suppressed under CO 2 reaction atmosphere. These observations were found for a wide range of ultrasound frequencies, ranging from 20 kHz to 1.7 MHz (Table ), which is the effective range of frequency used for sonochemistry …”

“…Sonochemistry may be applied for frequency ranging from 20 kHz to 1 MHz, with an optimum frequency being around 300 kHz . However, higher sonochemical efficiency, as measured by chemical dosimetries or pollutants destruction, has also been reported for up to 1.7 MHz . To evaluate the influence of frequency and acoustic intensity on the inhibiting effect of CO 2 toward the production rate of • OH, numerical simulations of chemical reactions occurring inside a CO 2 bubble and an air bubble have been conducted for various frequencies (20, 140, 213, 355, 515, 647, 1000 and 1100 kHz) and different acoustic intensities (0.5, 0.75 and 1 W cm ‐2 ).…”

Insight into the impact of excluding mass transport, heat exchange and chemical reactions heat on the sonochemical bubble yield: Bubble size-dependency

“…Pétrier et al [13] , examined the rate of phenol and carbon tetrachloride degradation over a range of ultrasonic frequencies from 20 to 800 kHz, where an optimal frequency of 200 kHz was determined for the maximal degradation of phenol, conversely, the decomposition of carbon tetrachloride increases proportionally with the frequency increase. In general, the effects of acoustic amplitude [14] , [15] , [16] , [17] , [18] , frequency [18] , [19] , [20] , [21] , [22] , saturating gas [18] , [23] , [24] , [25] , [26] , [27] , solution temperature [28] , [29] , static pressure [30] , [31] and other parameters have been widely investigated [32] .…”

Synthesis and Characterization of Amorphous Iron Oxide Nanoparticles by the Sonochemical Method and Their Application for the Remediation of Heavy Metals from Wastewater

“…The ultrasonic irradiation causes cavitation in an aqueous medium, which can generate a temperature of around 5000 • C and a pressure of over 1800 kPa, which enables many unusual chemical reactions to occur [39]. The cavitation is marked by the sequential events i.e., formation, growth and collapse of the microbubbles [40].…”