In addition to chemical consequence, acoustic cavitation produces several physical events such as micro-jets with speed of ~100 m/s, shock waves, macro- and
micro-mixing (Hamdaoui 2009; Hamdaoui 2011; Hamdaoui and Naffrechoux
2007), as well as light emission, i.e., sonoluminescence (Suslick et al. 1999). SL
has been recently employed to estimate the bubble temperature and pressure reached
within the collapsing bubble as well as the bubble size (Lee et al. 2005; Suslick and
Flannigan 2008). Temperature of ~5000 K and pressure of up to 1700 atm were
estimated by Prof. Suslick’s group through analyzing SL spectrums obtained from
silicon oil and metal carbonyls (Suslick and Flannigan 2008).
5.3 Sonochemical Reactors
There are two most common types of sonochemical reactors used in sonochemical
processes (Yasui et al. 2005; Torres-Palma and Serna-Galvis 2018): (i) horn-type
systems, in which an immersed horn tip irradiates directly the liquid, as stated in
Fig. 5.3a, and (ii) a standing wave-type systems, in which the irradiating transducer
is mounted to the bottom surface of the reactor. This type includes the two common
configurations of Fig. 5.3b, c: bath system with indirect sonication, in which cell
containing the solution is dipped in the ultrasonic bath, and bath with direct
sonication in which irradiation travels directly to the solution via a transducer
fixed at the bottom of the bath, i.e., the cylindrical shape is mostly used herein. All
these systems are generally equipped with heating–cooling system to control the
temperature of the irradiating solution.
From the two main systems (horn and standing wave), continuous and pulsed
irradiation modes are possible, even though the continuous mode is often used. Also,
diverse configurations and geometries of reactors were developed (Keil and Swamy
1999). Sonochemical reactors may also be operated in continuous or batch modes
(Keil and Swamy 1999; Entezari et al. 2003). Detailed information about design
aspect of sonochemical reactors can be found in refs. (Keil and Swamy 1999; Gogate
et al. 2003; Gogate 2008; Sutkar and Gogate 2009).
5.3.1 Wave and Bubbles Characteristics in Sonochemical
Reactors
For an irradiation horn system, the generated wave is closely spherical, and its
amplitude falloffs immediately as the liquid depth, i.e., the distance from the horn
tip, increases (Yasui et al. 2005). In standing wave-type systems, the ultrasonic
amplitude is much lesser than that generated in horn-type systems. Bubbles in this
system gather at the location where the ultrasonic amplitude is near the critical point
at which the direction of the radiation force is inversed (Yasui et al. 2005).
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micro-mixing (Hamdaoui 2009; Hamdaoui 2011; Hamdaoui and Naffrechoux
2007), as well as light emission, i.e., sonoluminescence (Suslick et al. 1999). SL
has been recently employed to estimate the bubble temperature and pressure reached
within the collapsing bubble as well as the bubble size (Lee et al. 2005; Suslick and
Flannigan 2008). Temperature of ~5000 K and pressure of up to 1700 atm were
estimated by Prof. Suslick’s group through analyzing SL spectrums obtained from
silicon oil and metal carbonyls (Suslick and Flannigan 2008).
5.3 Sonochemical Reactors
There are two most common types of sonochemical reactors used in sonochemical
processes (Yasui et al. 2005; Torres-Palma and Serna-Galvis 2018): (i) horn-type
systems, in which an immersed horn tip irradiates directly the liquid, as stated in
Fig. 5.3a, and (ii) a standing wave-type systems, in which the irradiating transducer
is mounted to the bottom surface of the reactor. This type includes the two common
configurations of Fig. 5.3b, c: bath system with indirect sonication, in which cell
containing the solution is dipped in the ultrasonic bath, and bath with direct
sonication in which irradiation travels directly to the solution via a transducer
fixed at the bottom of the bath, i.e., the cylindrical shape is mostly used herein. All
these systems are generally equipped with heating–cooling system to control the
temperature of the irradiating solution.
From the two main systems (horn and standing wave), continuous and pulsed
irradiation modes are possible, even though the continuous mode is often used. Also,
diverse configurations and geometries of reactors were developed (Keil and Swamy
1999). Sonochemical reactors may also be operated in continuous or batch modes
(Keil and Swamy 1999; Entezari et al. 2003). Detailed information about design
aspect of sonochemical reactors can be found in refs. (Keil and Swamy 1999; Gogate
et al. 2003; Gogate 2008; Sutkar and Gogate 2009).
5.3.1 Wave and Bubbles Characteristics in Sonochemical
Reactors
For an irradiation horn system, the generated wave is closely spherical, and its
amplitude falloffs immediately as the liquid depth, i.e., the distance from the horn
tip, increases (Yasui et al. 2005). In standing wave-type systems, the ultrasonic
amplitude is much lesser than that generated in horn-type systems. Bubbles in this
system gather at the location where the ultrasonic amplitude is near the critical point
at which the direction of the radiation force is inversed (Yasui et al. 2005).
152
S. Merouani and O. Hamdaoui