Sonochemistry industrial applications

L.A. Crum, T.J. Mason, J.L. Reisse, and K.S. Suslick (eds.), Industrial applications of sonochemistry and power ultrasonics, Sonochemistry and Sonoluminescence, NATO ASI Series, Kluwer Academic Publishers, 1999, 377-390, ISBN 0-7923-5549-0. 

All of the preceding dosimeters for sonochemistry (both chemical and physical) are applicable in, and have been studied under, homogeneous conditions. On the other hand, most of the potential industrial applications of ultrasound concern solid-liquid mixtures. The use of such dosimeters under heterogeneous conditions could lead to some discrepancies, however, since the presence of a suspended solid may result in scattering and dampening of the wave. For this reason the search for accurate dosimeters working under heterogeneous conditions is of considerable interest. 

The various advantages of using ultrasound (as can be inferred from Table 22.1) notwithstanding, sonochemistry continues to be a laboratory curiosity with few industrial applications. The chief reasons are the lack of a scale-up rationale and economics. 

For general aspects on sonochemistry the reader is referred to references [174,180], and for cavitation to references [175,186]. Cordemans [187] has briefly reviewed the use of (ultra)sound in the chemical industry. Typical applications include thermally induced polymer cross-linking, dispersion of Ti02 pigments in paints, and stabilisation of emulsions. High power ultrasonic waves allow rapid in situ copolymerisation and compatibilisation of immiscible polymer melt blends. Roberts [170] has reviewed high-intensity ultrasonics, cavitation and relevant parameters (frequency, intensity,... 

The principles of sonochemistry can also be applied to disrupt different species of oil-bearing microalgae cells. Detailed experimental results are necessary to support the cost-effectiveness and industrial scale applicability of ultrasound for microbial lipid extraction, and subsequent biodiesel production in comparison to conventional methods (Mata et al., 2010). 

The term sonochemistry indicates the use of sound waves to generate chemical and physical effects which can be harnessed in multiple applications (Fig. 1). Although such effects can be obtained at a wide range of frequencies, the word sonochemical is invariably linked to ultrasound, i.e. sound we cannot hear (typically above 20 kHz). Natural phenomena are good sources of both ultrasonic (e.g. animal communication or navigation) and infrasonic waves (such as earthquakes and tidal motion). Ultrasonics is currently of interest to lay people because of medical imaging, metal cleaning, industrial and dental drills and non-destructive material characterisation. 

Sonochemistry has a very broad spread of applications throughout academia and industry with many of significance in environmental issues some of which will be considered in this chapter (Table 10.1). 

The progress of sonochemistry in waste minimisation is dependent upon the possibility of scaling up the excellent laboratory results for industrial use. There are currently several systems available commercially with configurations to suit most applications [63, 64]. 

Several examples of Type la sonochemical activation are found in the literature. It should be clear that the main advantage of the present classification is to open the route to a multitude of experiments within the application of the "approximative correspondence principles". The heuristic richness of these principles precisely originates in their looseness. This looseness has several origins, but the practical application is that a reaction recognized as a photochemically or electrochemically induced chain reaction may lead to far better yields of products under sonication. This bonus may be again amplified by the fact that industrial scaling-up of reactions seems better mastered in sonochemistry than in photochemistry or electrochemistry. To find a reservoir of reactions where sonochemical activation could possibly lead to ameliorations, one may consult a number of reviews. ... 

This is of great importance when considering the potential for application of sonochemistry to industrial processes given the current degree of interest in this rapidly expanding field of chemistry. 

The explanation for these phenomena was similar to that of Xu et al. [44]. According to sonochemistry, ultrasound can cause high-energy chemical reactions and increase the reactivity of particles. Therefore, lead zirconate tita-nate (PZT) phase can be formed at lower calcination temperature (400 °C) in the created gels. This advantage, together with low-cost starting materials used, will make the hybrid method an attractive approach for industrial febrication of PZT ceramics. It is also believed to be applicable to other materials similar to PZT. 

Ultrasound is sound pitched above the frequency bond of human hearing. It is a part of sonic spectrum ranging from 20 kHz to 10 MHz (wavelengths from 10 to 10 cm). The application of ultrasound in association with chemical reactions is called sonochemistry. The range from 20 kHz to aroimd 1 MHz is used in sonochemistry, since acoustic cavitation in liquids can be efficiently generated within this frequency range. However, common laboratory and industrial equipment typically utilize a range between 20 and 40 kHz. 

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