| Dye wastewater from dye synthesis process has characteristics of complex constituents, high concentration and high colority. Moreover, it contains many biorefractory compounds and carcinogenic or teratogenic organic matters. With the increase of the variety of dye, the dye wastewater is becoming more difficult to treat since dyes are designed to be resistant to chemical oxidation, photochemical degradation and biodegradation. If the dye wastewater cannot be processed properly, they will not only pollute seriously the receiving water but also have the potential danger to the public health and ecologicalenvironment. Generally, azo dyes have the stable chemical structure and they are toxic to microorganism, as a result, the common physicochemical processes and biochemical processes can not achieve the sastisfactory results. In order to follow the environmental standard and achieve the purpose of comprehension treatment, it is necessary to develop a new and effective process aiming at treating this kind of dye wastewater. The ultrasound irradiation technology has been a study focus in the water pollution control field in recent years. It has the characteritis of the advanced oxidation processes including thermolysis, radical oxidation and supercritical oxidation. The ultrasound irradiation technology can be operated under the mild condition and the reaction is rapid. In addition, it can be applied alone or with other treatment technologies, so the ultrasound irradiation is considered a potential and promising technology.In this dissertation, azo dye Acid Green B was choosed as the model contaminant. Based on single parameter design, orthogonal design, Plackett-Burman design, Box-Behnken design and central composite design and response surface method, the degradation efficiency, the optimal experimental conditions, reaction kinetics and degradation mechanism of Acid Green B by ultrasound irradiation and ultrasound in combination with other treatment methods were investigated in detail. The purpose of this study is to expand the application range of sonochemistry in the field of wastewater treatment and to explore the new method to degrade the azo dye wastewater. At the same time, this study will provide experimental data for azo dye wastewater treatment and fundamental theory for the mechanism study of sonochemistry. Main results in this dissertation are summarized as follows:(1) In the case of degradation of Acid Green B by the single frequency ultrasonic irradiation, the experimental results showed that the degradation efficiency of Acid Green B was not satisfactory. The decolourity ratio of Acid Green B was just 41.8% under the optimal experimental conditions. The degradation efficieny was influenced by many factores, especially ultrasonic frequency and power density. the degradation efficiency of Acid Green B increased with the increase of power density, but it decreased when the ultrasonic frequency changed from 28 kHz to 45 kHz. In addition, the degradation efficiency was affected by Acid Green B concentration, initial pH value, bubbling gas and inorganic salts. The degradation efficiency of Acid Green B reduced greatly when the radical scavenger was added into the reaction system, which indicated the degradation of Acid Green B was achieved mainly through the radical oxidation reaction. The UV-Vis spectra of Acid Green B before and after degradation were analyzed and the following conclusions cound be drawn: Acid Green B was not completely mineralized to CO2 and H2O by the single frequency ultrasonic irradiation, instead, the chromophore in Acid Green B molecular structure was just destroyed under the attack of radicals. The degradation reaction of Acid Green B by single ultrasonic irradiation followed the first-order kinetics reaction.(2) In the case of degradation of Acid Green B by dual-frequency ultrasonic irradiation, the results showed that the degradation efficiency of Acid Green B by dual frequency ultrasound irradiation was proved to be superior to the total value of two single frequency ultrasound irradiation at the given experimental conditions, which indicated there was the synergistic effect in the dual frequency ultrasonic irradiation system. The decolouration ratio of 64.6% could be achieved when pH value was 4.0, input power was 490 W, the reaction time is 165 min and the initial concentration of dye wastewater is 100 mg/L. The detailed reasons and machanisms of the synergistic effect in the dual frequency ultrasonic irradiation system were studied on the base of the measurement of the quantity relationship of ?OH and analyzing the Rayleigh-Plesset equation of. the wall of cavitation bubbles.(3) In the case of degradation of Acid Green B by ultrasonic irradiation and H2O2. The decolourity ratio of Acid Green B was the objective response value, and the response surface methodology based on Box-Behnken design was employed to build the predictive mathematical model of Acid Green B degradation reaction. Under the optimum experimental conditions obtained by the predictive model, the predictive value of Acid Green B decolourity ratio is 96.82% according to the predictive model. The adequacy of the model equation for predicting the optimum response values was verified under the same experimental conditions and the experimental value is 93.34%, which was fitted to the predicted value by polynomial quadratic model with the deviation of just 3.48%. The confirmatory test showed that the predictive model has a significant difference and the experimental values agreed with the predicted values by the model. So the model can be used to the degradation reaction of Acid Green B. The response surface and contour plot was analyzed and the result showed that three factors: pH value, H2O2 dosage and ultrasonic power, were not linear relation, there is interaction reaction among these factors. The radical scavenger n-butanol was proved to inhibit the degradation reaction of Acid Green B. Moreover, there is proportional relationship between ?OH concentration and Acid Green B degration efficiency. So it can be drawn that the main degradation mechanism of Acid Green B was radical oxidation ?OH, and the reaction followed the apparent first-order kinetics reaction.(4) In the case of degradation of Acid Green B by ultrasonic irradiation and Fenton reaction, an orthogonal design L27(35) including 5 factors with 3 levels was applied in order to obtain the optimal experimental condtions of Acid Green B degradation by ultrasonic irradiation in combination with Fenton reation. The results showed that the effects order of 5 factors on decolourity were pH >reaction time > Fe2+ dosage > power density > H2O2 dosage > interaction effect of Fe2+ and H2O2. The optimal experimental conditions of Acid Green B decolouration reaction were as followed: Fe2+ dosage 7 mmol/L, H2O2 dosage 140mmol/L, pH value 3.5, power density 1.00 W/mL and reaction time 30 min. The effects orders of 5 factors on COD removal were reaction time> H2O2 dosage > pH > Fe2+ dosage > power density > interaction effect of Fe2+ and H2O2. The optimal experimental conditions of Acid Green B COD removal reaction were as followed: Fe2+ dosage 6 mmol/L, H2O2 dosage 120mmol/L, pH value 4.0, power density 1.00 W/mL and reaction time 40 min. The degradation mechanism is mainly radical oxidation of ?OH. The degradation path of Acid Green B by ultrasonic irradiation and Fenton reaction was explored. Firstly,. Acid Green was degraded into derivatives of benzene and naphthalene under the attack of ?OH, and then some small molecular organic intermediates were produced.(5) Fe-Ni-Mn/Al2O3 catalyst was prepared using Al2O3 as the carrier and the properties of Fe-Ni-Mn/Al2O3 catalyst were characterized. The effects of loaded solution concentration, loaded time and roast temperature on catalyst property were investigated by using an orthogonal experimental design. The experimental results showed that the best catalytic activity was obtained when loaded solution concentration, loaded time and roast temperature were 0.1mol/L,12 h and 550℃, respectively. The degradation efficiency of Acid Green B by ultrasonic irradiation was explored in the presence of catalyst Fe-Ni-Mn/Al2O3 and the oxidizer H2O2. The Plackett-Burman design was applied to study the effects of eight variables including catalyst dosage, the used times of catalyst, H2O2 dosage, reaction time, initial concentration and pH value of Acid Green B, power density and ultrasonic frequency and three pseudo variables. The Plackett-Burman design results gave three most important variables for Acid Green B degradation including catalyst dosage, H2O2 dosge and pH value. Then, the response surface methodology based on central composite disign was used to optimize the experimental conditions of Acid Green B degradation. UV-Vis spectra,ion chromatogram and GC-MS before and after reaction showed that Acid Green B had been completely decomposed, and the degradation path of Acid Green B was also inferred. It is deduced that the degradation mechanism of Acid Green B: The surface of Fe-Ni-Mn/Al2O3 catalyst was rubbed, rinsed and refreshed under the ultrasonic irradiation, as a result, the superficial area and the catalytic spot increased on the surface of Fe-Ni-Mn/Al2O3 catalyst, moreover, the mechanical effect of ultrasonic irradiation could speed up the transmitance of Acid Green B on the surface of catalyst and enhance the reaction efficiency.
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