Sonocrystallization

Cavitation bubbles work as nucleation sites of particles. For example, in a supercooled sucrose solution, nucleation of ice crystals induced by cavitation bubbles has been experimentally observed [72], This phenomenon has been called sonocrys-tallization [73]. Although there are some papers on the mechanism of sonocrystal-lization, it has not yet been fully understood [74, 75]. It has been reported that the distribution of crystal size in sonocrystallization is narrower than that without ultrasound [73]. It may be related to the narrower size distribution of sonochemi-cally synthesized particles compared to that without ultrasound [76, 77]. Further studies are required for the mechanism of particle nucleation by ultrasound. 

Theoretical Aspects Crystallization and Sonocrystallization to Form Inorganic Nanoparticles... 

Some of the reports are as follows. Mizukoshi et al. [31] reported ultrasound assisted reduction processes of Pt(IV) ions in the presence of anionic, cationic and non-ionic surfactant. They found that radicals formed from the reaction of the surfactants with primary radicals sonolysis of water and direct thermal decomposition of surfactants during collapsing of cavities contribute to reduction of metal ions. Fujimoto et al. [32] reported metal and alloy nanoparticles of Au, Pd and ft, and Mn02 prepared by reduction method in presence of surfactant and sonication environment. They found that surfactant shows stabilization of metal particles and has impact on narrow particle size distribution during sonication process. Abbas et al. [33] carried out the effects of different operational parameters in sodium chloride sonocrystallisation, namely temperature, ultrasonic power and concentration sodium. They found that the sonocrystallization is effective method for preparation of small NaCl crystals for pharmaceutical aerosol preparation. The crystal growth then occurs in supersaturated solution. Mersmann et al. (2001) [21] and Guo et al. [34] reported that the relative supersaturation in reactive crystallization is decisive for the crystal size and depends on the following factors. 

To understand the effect of various parameters during sonocrystallization process following process was adapted, the experimental setup is shown in Fig. 7.1. The carbonation reaction was carried out in a semibatch reactor consisting of... 

Fig. 7.5 Plausible mechanism of nano CaC03 particle synthesis during sonocrystallization in presence of surfactants [43]...

Fig. 7.8 Transmission electron micrograph of nano CaC03 particles synthesized using polyacrylic acid as surfactant using sonocrystallization method [43]...

Castro M, Capote P (2007) Ultrasound-assisted crystallization (sonocrystallization). Ultrason Sonochem 14(6) 717-724... 

McCausland LJ, Cains PW (2002) Sonocrystallization - ultrasonically promoted crystallization for the optimal Isolation of drug actives, Dmg Delivery Systems Sciences 2(2) 47... 

Chow et al. (2004) reported dynamic video images of the influence of ultrasonic cavitation on the sonocrystallization of ice at a microscopic level. The ultrasonic device was used in combination both with an optical... 

Chow, R., Blindt, R., Kamp, A., Grocutt, P., andChivers, R. 2004. The microscopic visualization of the sonocrystallization of ice using a novel ultrasonic cold stage. Ultrason. Sonochem. 11, 245-250. 

Ruecroft, G., Hipkiss, D., Ly, T., Maxted, N., and Cains, PW. 2005. Sonocrystallization The use of ultrasound for improved industrial crystallization. Organic Process Research Development, 9 923-32. 

Ultrasound-assisted formation of a solid phase sonocrystallization and sonoprecipitation... 

Sonocrystallization is the currently accepted name for the use of power ultrasound to control and accelerate the course of a crystallization process. This effect had previously been used in the salting-out process for years, and has been found to have a favourable... 

Crystallization in the presence of an ultrasonic wave (sonocrystallization) exhibits a number of features specific to the US wave that clearly distinguishes it from crystallization in its absence. For most materials, such features include, (a) faster primary nucleation, which is fairiy uniform thorough the sonicated volume (b) relatively easy nucleation in materials which are usually difficult to nucleate otherwise (c) the initiation of secondary nucleation and (d) the production of smaller, purer crystals that are more uniform in size. 

Low-frequency US waves of variable frequency (namely, 15, 20, 25 and 30 kHz) used for sonocrystallization were found to result in no substantiai differences in shape, mean size or size distribution in the resulting crystals. Therefore, these wavelengths seem to have the same influence on nucieation and crystal growth. One possible explanation is that they are much larger than the size of the nuclei and crystals. 

Other emerging crystallization techniques, such as supercritical fluid crystallization and sonocrystallization (ultrasound in crystallization), are also mentioned. Potential applications for these emerging technologies are present in the pharmaceutical industry. 

New approaches are currently being analyzed to induce crystallization and control the crystal size. An example of these novel approaches is crystallization in the presence of an ultrasonic wave or sonocrystallization, which is discussed in Section 7.4.1. 

Sander JRG, Zeiger BW, Suslick KS (2014) Sonocrystallization and sonofiagmentation. Ultrason Sonochem 21 1908-1915... 

Chow, R., Blindt R Chivers, R., Povey, M 2003. The sonocrystallization of ice in sucrose solutions Primary and secondary nucleation. Ultrasonics 41 (8) 595-604. 

Bund, R.K. and Pandit, A.B. 2007. Sonocrystallization Effect on lactose recovery and crystal habit, Ultrason. Sonochem. 14 143-152. 

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