However, in horn-tip system, cavities are concentrated near the tip where the
amplitude is large (Renaudin et al. 1994). Additionally, in a horn-type sonochemical
systems, bubbles are mostly of vaporous nature, whereas gaseous type of bubbles are
dominant in a standing wave reactor since the bubbles density in this system is
concentrated at the region where the radiation amplitude is low (Yasui et al. 2005).
In general, chemiluminescence of luminol or sonochemiluminescence has been used
for visualizing the reaction zones in sonochemical reactors (Renaudin et al. 1994;
Pétrier et al. 2008; Son et al. 2011, 2012; Choi 2015).
Transducers
Ultrasound
control
Cooler/heater
device
Tank
Solution to
treat
Water
(B)
(A)
Ultrasound control
Transducer
Probe tip
Solutionto treat
Coolant in
Coolant out
(C)
Ultrasound control
Transducer/vibrating
plate
Solution to treat
Coolant in
Coolant out
Fig. 5.3 Main types of sonochemical reactors. (a) Probe system, (b) bath system with indirect
sonication, and (c) standing wave reactor with direct sonication. Reprinted with permission from
(Torres-Palma and Serna-Galvis 2018)
5 Sonochemical Treatment of Textile Wastewater
153