WHAT KINDS OF FACTORS WILL INFLUENCE THE ULTRASONIC DEGRADATION IN SEWAGE TREATMENT?
The main factors affecting ultrasonic degradation in sewage treatment include dissolved gas, pH value, reaction temperature, ultrasonic power intensity and ultrasonic frequency:
1. The presence of dissolved gases can provide cavitation nucleus, stabilize cavitation effects, and reduce cavitation thresholds. There are two main reasons for the impact of ultrasonic degradation rate and degradation: A. The nature and cavitation of dissolved gases on cavitation bubbles. The strength has an important influence; B, the free radicals produced by dissolved gases such as N2O2 also participate in the degradation reaction process, therefore, affect the reaction principle and the thermodynamic and kinetic behavior of the degradation reaction.
2. For the ultrasonic degradation of organic acid alkaline substances, the pH value of the solution has a great influence. When the pH value of the solution is small, the organic substances can evaporate into the cavitation bubbles and directly pyrolyze in the cavitation bubbles; at the same time, oxidation reactions can occur at the gas-liquid interface of the cavitation bubbles and the free radicals generated by the cavitation of the sewage. High degradation efficiency. When the pH value of the solution is large, organic substances cannot evaporate into the cavitation bubble, and the oxidation reaction occurs with the free radicals only at the gas-liquid interface of the cavitation bubbles, and the degradation efficiency is relatively low. Therefore, the adjustment of the pH of the solution should be as good as possible to the organic matter in the form of neutral molecules and easy to volatilize inside the bubble core.
3. Temperature has a very important influence on the intensity and dynamics of ultrasonic cavitation, resulting in changes in the rate and extent of ultrasonic degradation. The increase in temperature is helpful to speed up the reaction, but the ultrasonic-induced degradation is mainly due to the cavitation effect. When the temperature is too high, the water is boiled in the half-cycle of the sound pressure and the cavitation-induced high pressure is reduced. Bubbles are immediately filled with water vapor and reduce the high temperatures produced by cavitation, thus reducing degradation efficiency. General sonochemical efficiency decreases exponentially with increasing temperature. Therefore, the low temperature (less than 20 °C) is more conducive to ultrasonic degradation experiments, generally at room temperature.
4. Research shows that not the higher the frequency, the better the degradation effect. Ultrasonic frequency is related to the principle of degradation of organic pollutants, there is a good frequency of degradation reactions based on free radicals; degradation reactions based on pyrolysis, when the ultrasonic sound is stronger than the cavitation threshold, as the frequency increases , increase the efficiency of interpretation.
5. Ultrasonic power intensity refers to the total acoustic energy radiated into the reaction system per unit time by the area of the unit of ultrasonic emission. It is generally measured by the power per unit irradiation area. In general, the greater the ultrasonic power intensity is, the more favorable it is to the degradation reaction, but when it is too large, the cavitation bubbles will be shielded, and the ultrasonic power intensity can be used to reduce the energy and the degradation rate can be reduced.
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