Ultrasonic mixing

Mixing can be achieved by ultrasound using lead zirconate titanate (PZT), a piezoelectric ceramic, operated in the kHz region [22], In this way, liquid streams can be moved and even turbulent-like eddies are induced. Favorably, ultrasonic action is coupled into a closed volume, a micro chamber. Here, the creation of standing waves has been reported. 

Compared with other means of creating turbulence in closed chambers, such as mixing by valves, ultrasonic mixing is said to have advantages with regard to sensitivity towards the presence of bubbles and can freely choose the flow ratio between the two liquids to be mixed (which is not given for valve mixing) [22], 

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Ozonation can be enhanced by the addition of ultraviolet (uv) radiation. This combination can be effective in degrading chlorinated organic compounds and pesticides. In addition, metal ions such as iron, nickel, chromium, and titanium [7440-32-6] can act as catalysts, as can ultrasonic mixing. 

Unlike the known approaches we develop the use of water- fuel emulsions with the soluble in water catalytic non- corroding additions and ultrasonic mixing by the sharp superheated steam for reduction of the oxides of nitrogen and soot emission in the combustion engines. Our know how is also the use of the electro-activated water for emulgation. The first results testily the technical and economic expedience of the chosen direction. 

For interesterification to the n-butyl esters, 100 yl of n-butanol HC1 is mixed ultrasonically in the reaction vial. The solution is heated for 2 hr, 30 min in the 100°C sand bath with ultrasonic mixing every 30 min. This reaction mixture is evaporated just to dryness under nitrogen as described above. 

This micro device for ultrasonic mixing was made from two plates, one of which has a shallow open volume to give a micro chamber after assembly (see Figure 1.31) [22], The area that actually covers the micro chamber is considerably thinned compared with the remaining thickness of the top plate. On this diaphragm, a thin PZT membrane is deposited, which acts as ultrasonic wave generator. The micro chamber is connected to two inlet channels and one outlet channel. 

Upon ultrasonic action, turbulence occurred, moving material throughout the whole mixing chamber [22], After termination of ultrasonic mixing, the initial pattern rapidly developed, the two zones being separated by a straight interface. 

Relationship between PZT excitation frequency and ultrasonic mixing... 

FIGURE 3.47 The ultrasonic mixing process, (a) Videocamera scene at standby state. Ethanol and water were in laminar flow. Limited diffusion occurred at the interface of the ethanol and water flows, (b) Ultrasonic vibration ON. The laminar flow changed and turbulence occurred, (c) After 2 s of ultrasonic vibration, ethanol was mixed well with water, (d) Ultrasonic vibration OFF. The laminar flow resumed [327]. Reprinted with permission from Wiley-VCH Verlag. 

Yaralioglu, G.G., Wygant, I.O., Marentis, T.C., Khuri-Yakub, B.T., Ultrasonic mixing in microfluidic channels using integrated transducers. Anal. Chem. 2004, 76, 3694-3698. 

Colucci, J.A., Borrero, E.E., and Alape, F. 2005. Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing. Journal of the American Oil Chemists Society, 82 525-530. 

Miller-Ihli N. J. (1989) Automated ultrasonic mixing accessory for slurry sampling into a graphite furnace atomic absorption spectrometer, J Anal At Spectrom 4 295-297. 

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