Sonic intensity

The sonication intensity is directly proportional to the square of the vibration amplitude of the ultrasonic source. As a rule, increasing the intensity increases the sonoohemioal effeots however, the ultrasonic energy a system can take is limited. Thus, cavitation bubbles, which are initially difficult to create at the higher frequencies as a result of the shorter duration of rarefaction cycles, are now possible by virtue of the collapse time, temperature and pressure on collapse being mutually dependent. However, the sonication intensity cannot be increased indefinitely as the maximum possible bubble size is also dependent on the pressure amplitude. As the pressure amplitude is increased, bubbles may grow so large on rarefaction that the time available for collapse will be inadequate. In fact, it has been unequivocally established that ... 

A minimum sonication intensity level is required to reach the cavitation threshold. 

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 frequency effect of ultrasonic waves with frequencies around 1 MHz (0.76, 1.0, and 1.7 MHz) was studied using the electrical detection method described above [88], The experimental data and theoretical analysis of the results indicated that there was an optimum ultrasonic frequency corresponding to a maximum in sonochemical yield according to the bubble distribution in liquid. A Gaussian distribution of gas bubble radii was expected for a water sample exposed to a normal air atmosphere. In addition, experimental data also showed that any comparison of the frequency effect on the sonochemical efficiency should be under the conditions of not only the same sonic power but also the same sonic intensity. 

A study on the cavitation effect of 28-kHz ultrasound on sonic intensity and sonication time was completed using the electrical method [89]. The experimental... 

As in most other cases of reactor design with distributed properties in the reaction field (e.g, distributed sonic intensity, distributed photo energy), the reaction field in a microwave reactor is also a distributed system (with respect to temperature, through which alone the microwave effect seems to be manifested in most cases). The results from a domestic microwave reactor can... 

Electroacoustic unit for generating high sonic and ultra-sonic intensities in gases and interphases. US patent 5,299,175. 

The value of Afii depends on mechanochemical conditions the more severe the shearing action, the lower is. It may also depend on the presence of radical acceptors [50]. If branching reactions occur, tends to be higher [40]. A larger has been obtained in good versus poor solvents in stirring experiments [13]. In the solid state, correlates with particle size (Volume 2, Section VIIA.A). In ultrasonic experiments there is an optimum frequency [37] at which is a minimum. Results on the influence of sonic intensity are contrasting [32, 33, 64, 65]. The influence of process parameters on is discussed in Chapter IV. 

Sonic. Gas generates an intense sound Beld into which liquid is directed. Similar to two-fluid hut with greater tolerance for solids. Similar to two-fluid. 

In addition to the deposition mechanisms themselves, methods for preliminary conditioning of aerosols may be used to increase the effectiveness of the deposition mechanisms subsequently apphed. One such conditioning method consists of imposing on the gas nigh-intensity acoustic vibrations to cause collisions and flocculation of the aerosol particles, producing large particles that can be separated by simple inertial devices such as cyclones. This process, termed sonic (or acoustic) agglomeration, has attained only hmited commercial acceptance. 

In order to increase the overall extraction efficiency during SFE sonication has been applied [352]. Ultrasound creates intense sinusoidal variations in density and pressure, which improve solute mass transfer. Development of an SFE method is a time-consuming process. For new methods, analysts should refer the results to a traditional sample preparation method such as Soxhlet or LLE. 

The sonochemical reduction of Au(III) has been investigated under Ar in the presence of 20 mM 1-propanol at different frequencies, where two types of ultrasound irradiation systems were used one is a horn type sonicator (Branson 450-D, frequency 20 kHz, diameter of Ti tip 19 mm) and the other is a standing wave sonication system with a series of transducers operating at different ultrasound frequencies (L-3 Communication ELAK Nautik GmbH, frequency 213, 358, 647, and 1,062 kHz, diameter of oscillator 55mm) [33]. All experiments were performed at a constant ultrasound intensity ((0.1+/—0.01 W mL-1), which was determined by calorimetry. 

SnO has received much attention as a potential anode material for the lithium-ion-secondary-battery. The conventional techniques require temperatures above 150°C to form phase pure SnO. Whereas, sonication assisted precipitation technique has been used to prepare phase-pure SnO nanoparticles at room temperature by Majumdar et al. [25]. In this study, ultrasonic power has been found to play a key role in the formation of phase pure SnO as with a reduction in the ultrasonic power authors have observed a mixed phase. For the case of high ultrasonic power, authors have proposed that, intense cavitation and hence intense collapse pressure must have prevented the conversion of SnO to Sn02-... 

The turbidity gradually increased as shown in Table 9.19, with an increase in the volume of solution or amount of CH3COONa in all samples (control, sonicated and boiled). But the increase in precipitation was not in proportion to the reagent added to the A12(S04)3 solution. The turbidity in the first solution for unsonicated, sonicated and boiled solution was roughly in the ratio 1 lVi 3. Turbidity in sonicated and boiled samples was almost equal in solution containing 10 ml of aluminium sulphate and 5.0 ml of sodium acetate. Turbidity in sonicated samples (10 + 10) increased marginally compared to the boiled sample. This trend of sonicated samples, as seen in Table 9.19, indicated the role of ultrasonic power to be important. When 20 ml of A12(S04)3 solution was mixed with 5 ml of sodium acetate and sonicated, the amount of precipitate formed was negligible compared to the precipitation in a mixture of 10 ml of A12(S04)3 and 2.5 ml of sodium acetate, where the intensity of the ultrasonic power was almost double. 

In the first experiment 10 ml of 500 ppm solutions of FeCl3 were sonicated for 15, 30, 45 and 60 min. To examine the reduction of Fe(III) to Fe(II), 0.1 ml of the sonicated sample was transferred to a 10 ml volumetric flask and mixed with 0.5 ml of 2,000 ppm K3[Fe(CN)6] solution before making up to the mark with distilled water. Final concentration of this sonicated sample in 10 ml of volumetric flask was 5 ppm. UV-vis absorbance at >.max 795 was recorded. Sonication reduced Fe3+ to Fe2+, which reacted with K3[Fe(CN)6], already added in the solution, to form blue colour due to prussian blue. Continuous sonication gradually increased the concentration and intensity of prussian blue complex, as is clear from the Table 10.1. 

To examine the oxidation of Fe2+ to Fe3+, in the second experiment, 10 ml solution of 0.1 M ferrous ammonium sulphate was taken separately in four different beakers and sonicated for 15, 30, 45 and 60 min, before transferring the solution to a 25 ml volumetric flask and adding to it 10 ml of 0.01 M KSCN and making upto the mark with deionised water. The absorbance of these solutions was measured at 4-,iax 451 nm. Sonication of ferrous ammonium sulphate solutions oxidised ferrous ions to ferric ions, which in the presence of thiocyanate ions, produced an intense red coloured complex Fe(SCN)63, in proportions to the oxidation of ferrous ions to ferric ions, as could be seen in Fig. 10.1. 

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