Degradation of azo dye wastewater by dual-frequency ultrasoundsynergized with H2O2
双频超声辐射协同H2O2降解偶氮染料废水的研究

The degradation of azo dye Acid Green 20 was studied by dual frequency ultrasound in the presence of H2O2. The effects of ultrasonic power density, initial concentration and pH of dyestuff solution, bubbling gas and H2O2 addition on degradation of Acid Green 20 were investigated. The results show that degradation efficiency at dual-frequency ultrasound mode is proved to be superior to that at single frequency mode under the given experimental conditions. Degradation efficiency increases with increasing ultrasonic power density. The degradation rate of Acid Green 20 is highly dependent on pH value and acidic condition helps to promote the degradation of Acid Green 20. The optimum degradation rate of Acid Green 20 can be achieved when pH value is 4.0. However, the degradation rate decreases with the increase of dye initial concentration and the optimal concentration 40 mg/L. Degradation rate of Acid Green 20 is enhanced significantly in the presence of saturated gases and H2O2. Although 94.6% of decolorization is achieved after 5 h degradation under the optimum conditions, Acid Green 20 is not completely mineralized to CO2 and H2O, instead, some organic intermediates are produced.