ABSTRACT
The enormous potential of sonochemical reactors in a wide variety of processes for chemical and allied industries is intact, whereas not exploited to date. A few ›elds use ultrasound in sonoreactors: They concern cleaning and decontamination, extraction and impregnation, crystallization and precipitation, and, to a greater or lesser extent, electrochemistry. In the majority of cases, some examples of large-scale use of sonoreactors are still valid, but generally, design is based on “intuition,” and the results quoted in yield are impossible to predict. Indeed, rare are the tentative to design in depth a sonoreactor (Hihn et al., 2000; Soon et al., 2006; Viennet et al., 2009). For many authors, the necessity to take care of the scale-up aspects is acknowledged, but most of the time this only concerns the cavitation activity and intensity, using solutions based on bubble dynamics equations
Reactor Design: A Crucial Step ..................................................................................................... 599 Heterogeneous Distribution of the Acoustic Field ....................................................................600 Electrode Presence Is “Intrusive” ..............................................................................................604
Direct Quanti›cation of Ultrasound Effects by Electrochemistry .................................................605 The Well-Known Electrodiffusional Method or What Happens during an Electrochemical Measurement for Mass-Transfer? .............................................................................................606 Reduce the Parameters In¢uence by Modeling .........................................................................609
A New Tool: The Equivalent Velocity............................................................................................ 613 Application to the Measurement of Acoustic Energy Distribution ........................................... 615 Use for Cavitation Quanti›cation ............................................................................................. 617
Physical Signi›cation for the Dimensionless Number .................................................................. 618 Toward the “Ideal” Sonoreactor? ................................................................................................... 620 References ...................................................................................................................................... 621
as well as experimentation with different reactor types and reactions. Design correlations for collapse pressure and its relation to cavitational yield should assist designers in choice of the operating parameters for a desired cavitational effect (Gogate and Pandit, 2004). In the meantime, it cannot be dissociated from the techniques useful for good understanding of cavitational activity distribution (Sutkar and Pandit, 2009). Cavitation is the phenomenon with the most important effect for intensi›cation of physical and chemical processing. However, even after a complete study of dynamic behavior of cavitation, this speci›city creates problems in proposing reliable design. Therefore, operating strategies are needed. Surprisingly, while the physics of the phenomenon is well covered and recommendation for optimum reactor parameters and design still exists (Sutkar and Pandit, 2009), a more global approach is needed, especially in the case of sonoelectrochemistry. There are many examples of large-scale processes assisted by ultrasound. Electrochemical reactions are often complex, but it can be considered essentially as mass transfer or ion transfer to or from the electrode surface that is highly sensitive to asymmetric bubble collapse. Nevertheless, even in this restricted community, a large choice of reactors are still available (Figure 23.1) and are mostly dedicated to the laboratory using them for the ›rst time.
