The paper presents an insight into the mechanism of the ultrasonic enhancement of solvent extraction through the effect of ultrasound on the vegetal material involved. Thus, a series of experiments has been developed to investigate the effect of ultrasonic energy on the vegetal material and the solvent used. Several results concerning the ultrasonic extractive value, ultrasonic swelling index and the effects of frequency on vegetal material are presented.

The paper presents our results concerning the ultrasonically assisted extraction of bioactive principles from plant material. A comparison with classical methodologies is presented and technological aspects of ultrasonically assisted extraction are discussed.

This paper shows a systematic study of the 500 kHz frequency ultrasound efficiency on the microbial inactivation as a function of ultrasonic power delivered into the bacterial suspension. The inactivation of Escherichia coli IAM 12058, a Gram-negative bacterium and Streptococcus mutans JCM 5175, a Gram-positive bacterium is enhanced by increasing the ultrasonic power in the range of 1.7-12.4W and the logarithm of survival ratio decreases linearly with irradiation time, except for E. coli sonicated with the highest power level. The rate constants were estimated in the linear region of the plots representing survival ratio logarithm vs. sonication time. A better understanding of the inactivation process at 500kHz could be gained by suppressing the chemical effects with a radical scavenger. We find out that the rate constants increase with the ultrasonic power delivered into the solution and dramatically decrease by the addition of t-butanol as a radical scavenger to the bacterial suspension. For comparison, experiments were carried out at a low frequency level of 20kHz. It was found out that for the same ultrasonic power delivered into the bacterial suspension, the inactivation was slightly enhanced at 500kHz frequency. The examinations of bacterium performed with a TEM revealed lethal damages arising from the interaction of bacterial cells with the cavitational bubbles. A significant amount of empty cell envelopes as well as their cytoplasmatic content was detected. Thus, based on these new data, the mechanism of bacterial inactivation by ultrasounds at high frequency is discussed here.

It would seem that the economic viability is yet to be established for a great number of sonochemical processes, owning to their perfectible ultrasonic equipments. Industrial scale sonoreactors may become more important as a result of mastering the parameters with influence on their energy balance. This work related the solvent type to the energy efficiency as the first step of a complex study aiming to assess the energy balance of sonochemical reactors at 500 kHz. Quantitative measurements of ultrasonic power for water and 10 pure organic solvents were performed by calorimetry for a cylindrically shaped sonochemical reactor with a bottom mounted vibrating plate. It was found that the ultrasonic power is strongly related to the solvent, the energy conversion for organic liquids is half from that of water and there is a drop in energy efficiency for filling levels up to 250 mm organic solvents. Surface tension, viscosity and vapor pressure influence the energy conversion for organic solvents, but it is difficult explain these findings based on physical properties of solvents alone. The apparent intensity of the atomization process shows a good agreement with the experimentally determined values for energy conversion for water and the solvent group studied here. This study revealed that to attain the same ultrasonic power level, more electrical energy is need for organic solvents as compared to water. The energy balance equation has been defined based on these findings by considering an energy term for atomization.

In this work, the efficiency of 20 kHz frequency ultrasounds versus the classical stirring procedure was investigated on the solvent extraction of Jordanian El-Lajjun oil shale by employing a horn type sonicator. The influence of sonication parameters (sonication time and ultrasonic power) and extraction parameters (extraction solvent and oil shale particle size) on the solubilization of organic matter (bitumen) from oil shale are reported here. The influence of seven individual solvents, namely: tetrahydrofuran, benzene, carbon tetrachloride, chloroform, kerosene, toluene, acetone and a mixture of methanol _ acetone _ chloroform on the fraction extracted was investigated and it was found that the fraction extracted was 90％ after only ten minutes of sonication at 33 W when tetrahydrofuran was used as extraction solvent. It was found that the fraction extracted percentage is strongly influenced by the solvent extraction, ultrasonic power and exposure time and less influenced by the particle size. Under the current experimental conditions and using the tetrahydrofuran as extraction solvent, the extraction time was decreased by four folds while the fraction extracted percentage (E％) was increased by three times.

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A mixture of benzoyl chloride and nitrobenzene is not known to be chemically reactive, indeed the mixture is chemically inert when subjected individually to either ultrasonic irradiation or heating. However, if this system is initially subjected to ultrasound and then heated for several hours at 200 degrees C, a reaction does occur and the products are benzoic anhydride, hydrochloric acid, nitrous and nitric acid together with some minor products. To the best of our knowledge, this is the first example of a reaction where the effect of ultrasound does not appear to be the consequence of the direct action of acoustic cavitation bubbles. A possible explanation of this behaviour is advanced which involves an electron transfer reaction in which nitrobenzene is first activated by ultrasound and then acts as oxidant in the thermal stage of reaction.

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