I have been trying to read up a bit and find a plausible explanation to link of higher ultrasound frequency to the cavitation phenomenon and its effect on sono-chemical reactions. Does it promote the rate of reaction in any way or degrade it?
Also, one thing I am not clear is whether the stable cavitation aids in these reactions or not. I am aware that transient caviation helps in disruptive phenomenon so probably it helps in preventing aggregations and destroying weak bonds. But does the frequency of ultrasound increase the threshold to reach the transient cavitation?
Any help would be appreciated. Thank you in advance.
At constant intensity, the pressure pulse generated with cavity collapse increases with increase in ultrasonic frequency which leads to enhanced cavitational efficiency. At high frequencies the cavities generated are smaller in size and require few acoustic cycles before reaching resonant size. As the process of cavity collapse is adiabatic (hot-spot theory), the local temperature increases with increase in frequency resulting in higher rate of reaction. The reaction rates increases upto an optimum frequency and with further increase in frequency the rate decreases.
The stable cavitation causes the oscillation of cavities without significant release of energy and consequently the reaction does not take place. And for high frequencies the requirement of threshold intensity for onset of cavitation is large which also increases the energy consumption.
At constant intensity, the pressure pulse generated with cavity collapse increases with increase in ultrasonic frequency which leads to enhanced cavitational efficiency. At high frequencies the cavities generated are smaller in size and require few acoustic cycles before reaching resonant size. As the process of cavity collapse is adiabatic (hot-spot theory), the local temperature increases with increase in frequency resulting in higher rate of reaction. The reaction rates increases upto an optimum frequency and with further increase in frequency the rate decreases.
The stable cavitation causes the oscillation of cavities without significant release of energy and consequently the reaction does not take place. And for high frequencies the requirement of threshold intensity for onset of cavitation is large which also increases the energy consumption.
I think the answer is YES. however, it is very difficult to describe the relationship between ultrasound and chemical reaction with a clear rule or math model.
see
Optimization of solid food waste oil biodiesel by ultrasound-assisted transesterification
https://www.sciencedirect.com/science/article/pii/S001623611931169X
Kinetic Model of Biodiesel Processing Using Ultrasound
http://journal.ipb.ac.id/index.php/jtep/article/view/7349
Synthesis of Biodiesel Using Microwave Absorption Catalysts
Article Synthesis of Biodiesel Using Microwave Absorption Catalysts
Kinetics for the Synthesis of Biodiesel Based on the Calculation of Hot Spot Temperatures in the Catalyst. Article Kinetics for the Synthesis of Biodiesel Based on the Calcula...
Kailas Naresh
This process depends on intensity of sonic flow of energy, ultrasonic wave frequency, temperature and time of a solution sonication, in particular. These parameters are expected to increase possibility of water molecules decomposition into Н∙and ∙ОН free radicals. https://www.researchgate.net/publication/329834665_Ultrasound_Effect_on_Molecules_of_Sodium_Dodecyl_Sulphate_as_Systems_of_Nanoparticles
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