The all important sonochemical and sonoelectrochemical effects, such as mass transfer enhancement, surface activation of reactant, catalyst or electrode, change of (electro)chemical mechanism and/or the initiation of novel coupled chemical reactions, are connected with cavitation [1-4]. The presence of cavitation is thus the necessary condition for expression of these effects. The cavitation can take place only if the intensity of ultrasound is higher than cavitation threshold. That is why an intensity of ultrasonic power is the most significant parameter characterizing an ultrasonic field.

Whereas in the case of low intensity ultrasound the measurement of intensity and its distribution is well solved [5], in the case of high intensity (when cavitation takes place) the measurement is much more complicated. That is why the prediction of distribution of ultrasound within the cell based on theory is desirable.

This poster will show how numerical solution of the wave equation can predict the distribution of intensity within the reactor [6].

The calculations together with experimental verification have shown that the whole reactor behaves like a resonator and the energy distribution depends strongly on its shape. Therefore, the simulation of the intensity distribution has been used for optimization of the shape of ultrasonic reactor. The optimal geometry resulted in a strong increase in intensity along a large part of the cell.

The advantages of such optimised geometry are:

- the ultrasonic power necessary for obtaining cavitation is low, consequently, the erosion of the transducer face is minimized;

- low power delivered to the system results in only weak heating, consequently, no cooling is necessary;

- the "active volume" is large, i.e. the fraction of the reactor volume with high intensity is large and is not limited to a vicinity close to the horn tip.

For sonoelectrochemistry two main advantages are evident:

-it is not necessary to place the electrodes into a small area near the horn surface but anywhere in the cell where the intensity is high;

-an electrochemical cell can be simply immersed into the ultrasonic bath. The electrode system is electrically isolated from the horn by the walls of the cell. Consequently, the metallic horn cannot work like an electrode and a four-electrode potentiostat (which is necessary in the case of non-isolated immersed horn) is not required.

This work was financially supported by COST (D32/004/04), the Ministry of Education of the Czech Republic (grant number 1P05OC074) and Generalidad Valenciana (Project GV05/104).

[1] Suslick, K. S., Science 247 (1990) 1439

[2] Luche, J. L., Ultrasonics Sonochemistry 1 (1994) S111-S118

[3] Klíma, J. et al., J. Electroanal. Chem. 399 (1995) 147-155

[4] Lepoint, T. et al., Synthetic Organic Sonochemistry, Plenum Press, 1998, pp. 8-11

[5] J. Berlan, J.; Mason, T. J., Adv. in Sonochemistry, 4 (1996) 1-73

[6] Sáez, V. et al., Ultrason. Sonochem., 12(1-2) (2005) 59-65

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1. Electrochemistry with ultrasound: Report on WG4 activity
2. Research in the group "New Technological Development in Electrochemistry: Sonoelectrochemistry and Bioelectrochemistry" Alicante University