The motion characteristic of cavitation bubble is one of the major factors affecting acoustic cavitation. In this paper, a cavitation model coupled with acoustic pressure is established using lattice Boltzmann pseudopotential model. Aimed at demonstrating the feasibility of applying LB method in acoustic cavitation, the acoustic cavitation simulations are compared with the predictions of Keller equation. The comparison of theoretical prediction and numerical simulation shows that LB method is suitable for acoustic cavitation simulation.
This paper reports a design proposal of a sonochemical setup for pesticide wastewater degradation. Multi-parameters obtained by multi-sensors of the setup were utilized to control experimental variables and analyze degradation effect. Based on the setup and method designed, degradation experiments of deltamethrin were set up. In the work, treatments using ultrasonic, ozone, and the combination of them were carried out respectively, and parameters including ultrasonic frequency, pH, electrical conductivity, temperature as well as mass were taken into consideration. Results indicated that deltamethrin could be degraded efficiently under the irradiation of 589 kHz US/O3 combined and the degradation rate could reach 91%.
Dual-frequency ultrasonic assisted ozonation was proposed to degrade pesticide wastewater. The frequencies of ultrasound were 28 kHz and low-MHz (208 kHz, 495 kHz, 679 kHz and 890 kHz). The influence of ultrasound frequency was investigated in this paper. The electrical conductivity of deionized water was measured under different conditions, and degradation rate of acephate solution was used to verify degradation effect of the treatment. The results implied that the 208 kHz system was suitable for ozone dissolving and 495 kHz system was suitable for acephate degradation.
The degradation of chlorpyrifos is investigated with the treatments of sonolysis, ozonolysis, and sonolytic ozonolysis at various frequencies. Results show that there exists frequency effect in sonolytic ozonolysis. In sonolytic ozonolysis, the maximum degradation rate is obtained at 495 kHz, and the degradation kinetics is fitted to the first-order kinetics model well. However, the most significant synergistic effect between ultrasonic and ozone is at 124 kHz. The kinetics parameters indicate that chlorpyrifos is much more labile to ultrasonic at 495 kHz, while ozone is much more soluble at 124 kHz. The hydrolysis and oxidation are deduced to contribute to the degradation reaction and the degradation pathway for chlorpyrifos degradation is proposed.
Ultrasonic intensity has a great influence on the concentration of cavitation bubbles. Considering the characteristic of cavitation, in this paper, we propose a method of measuring the amount of cavitation bubbles to identify the change of cavitation intensity indirectly. First, acquires images of reaction liquid under the action of the certain power ultrasonic through machine vision technology; then, obtains micro bubbles quantity generated by ultrasonic cavitation; finally, establish the mathematical model between cavitation intensity and amount of cavitation bubbles to indirectly detect the change of ultrasonic cavitation intensity.
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