Irradiation and Sonication

Irradiation energy and sound waves have also been used for insect control. These treatments cause mutations, sterilization, and death, depending on intensity, frequency, and exposure time. The gamma rays are the most effective and promising but their use is expensive today. 

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Briefly discuss the advantages and disadvantages of the following control methods biological control, controlled atmosphere, irradiation, and sonication. 

The experimental configuration in Figure 4.1 does not provide in situ capability for sono-, photo- and microwave-induced homogeneous catalysis. The chemistry occurring in the fluid elements of an irradiated or sonicated CSTR are not similar to the fluid elements in the recycle stream and sample cells. However, Figure 4.1 maintains the potential for on-line measurement capability, particularly for product, and for some side-products. The issue concerning intermediates is more complex. 

Cation radical cyclization can be performed (and accelerated significantly) under sonication. Thus, the reaction of methyl vanillate with phenyliodonium bis(acetate) is initiated by ultrasonic irradiation and gives rise to the corresponding oquinone monoketal, which is trapped by a series of furanes. Monoadducts are formed reactions can be conducted at room temperature and are essentially complete within 15-50 min (Avalos et al. 2000). 

For any radiation-based AOP such as UV, UV/O3, UV/H2O2, PCO, and sonication, intensity and frequency (for sonication) of irradiation are important parameters. At low intensity, homogeneous photooxidation rate increases with the increase in intensity and the quantum efficiency is independent of intensity. At intermediate intensity, the rate varies as P and the quantum efficiency varies with the inverse of However, at high intensity, recombination of hydroxyl radical occurs which reduces the quantum yield of the process. 

The effects of ultrasonic treatment and ultrasonic irradiation on the extraction of cottonseed meal have been assessed [56], Results indicated that a combination of enzyme treatment and sonication produced a significantly greater yield of extracted protein than traditional methodologies. 

For benzaldehyde there was always some 30% yield of unidentified products, whether the reaction was sonicated or not. These side products are thought to be hydroquinoid dimers. p-Methyl benzaldehyde, which also shows the substantial sonoelectrochemical switch to the hydrodimer, has a blocked para-position and is less affected by side reactions (results are summed up in Table 7). Similar effects were obtained by ultrasonic irradiation from a horn probe (20 kHz), and by employing a range of different silent and sonicated conditions (powers, sources, cell geometries) and comparing product ratios and limiting current densities from... 

In contrast to traditional energy sources, microwave, laser, and sonic energy can be delivered to specific solid sites or small areas by fine-tuning frequencies and energy levels. It is especially suitable for preparation of nano-structured catalyst. For example, inherent eggshell catalysts can be produced with sonochem-ical preparation by which nano-dispersed metal particles are formed with instantaneous decomposition of metal solution by high-intensity irradiation of ultrasound in local area. In the preparation of M02C on ZSM-5 with ultrasound at 20 kHz, narrowly distributed particles of about 2nm in diameter are uniformly dispersed on the outer surface of the ZSM-5 support. ... 

Fig. 9 TEM images and D/G Raman bands for (a) pristine MWCNT, (b) after MW irradiation (2.45 GHz), (c) after sequential MW-US (20 kHz) irradiation, (d) sonication at 20 kHz, and (e) sonication at 300 kHz. Reproduced with permission from [69]. Copyright 2011 The Royal Society of Chemistry...

The reaction of spiro[indole-3,2 -oxiranes] (174) with thioacetamide in the presence of LiBr as a catalyst in an aqueous medium produced substituted 2 -amino-4 -benzoyl-2-methylspiro[indole-3,5 -[l,3]oxathiolane]-2(lH)-ones (175). The reaction was carried out under both microwaves and sonication, and the results were also compared with the conventional method (Dandia et al. 2010). In general, improvement in rate and yields were observed when reaction was carried out under sonication as compared to microwave irradiation and the conventional method (Scheme 8.56). 

Several instruments are available to perform semiautomated particle sizing by sieving. Modes of agitation include shaking, forced air, and sonic irradiation. The first two types are suited for large sample sizes (10 g or more), and the third type is suited for smaller samples size (< 1 g). These instruments may be interfaced to a balance with software for collection of data by a PC. Particle size analysis by these approaches may require the use of rifflers to generate representative powder sample if the product is not uniform to begin with. 

Plate 3a-c. Scanning electron micrographs showing the reduction of particle size obtained on sonication of TaS2 a TaS2 before ultrasonic irradiation, b after 10 min irradiation, and c 120 min irradiation (Note change in scale)... 

A sensor for nitric oxide was constructed utilizing multiwaUed carbon nanotubes that were previously modified with ethylenediamine and sonicated in a solution containing Co -TSPP. Drop cast electrodes were prepared and characterized by field-emission transmission electron microscopy, X-ray photoelectron spectroscopy and by electrochemical techniques [220]. Cyclic voltammetry, electrochemical impedance, and chronoamperometry were utilized to evaluate the electrocatalytic activity of the hybrid sensor that exhibited linear response in the 6.6 x 10 to 1.3 X 10 mol L range, with a detection limit of 6.6 x 10 mol L. Electrodes composed of porphyrins, platinum nanowires, and Nafion were proposed for photocatalytic reduction of water [221]. After an extensive search for optimization of each component and under the best conditions (—350 mV and visible light irradiation) a detectable amount of hydrogen was produced, but Nafion can diminish the diffusion of ions to the porphyrin active sites. 

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