Decolorization of dye Reactive Blue 19 using ozone and ultrasound.

摘要

In this research, the oxidation of the anthraquinone dye, Reactive Blue 19 was studied under conditions of varying pH, temperature, ultrasonic power, ozone concentration and initial dye concentration. The processes investigated were those of ozonation, ultrasound and ultrasound-enhanced ozonation. Laboratory experiments were performed using a semi-batch reactor by ozonating dye samples with and without ultrasound. This was done in order to determine whether ultrasound-enhanced ozonation is an effective method for enhancing reaction rates with ozone in the decolorization of the dye, Reactive Blue 19. The reactions of the dye with ozone and ultrasound-enhanced ozone were determined to occur through the OH· radical pathway. The effect of pH, temperature, ozone dosage, initial dye concentration and ultrasonic power were investigated. The rates of reaction are not sensitive to pH and increased between 14% to 22% for the temperature range between 12°C and 45°C. The mathematical model of the reaction pathway compared favorably with experimental results and indicated indirect oxidation by the OH· radicals. Under conditions of constant ultrasonic radiation and continuous gas application, decolorization rates were enhanced by ultrasound. The apparent rate constants increased between 34% to 203% for the ultrasonic powers between 40 W/L and 120 W/L compared to ozonation alone. The effects of ultrasonic power input on the gas-liquid mass transfer coefficient were also investigated and the results indicated that an increase in ultrasonic power input increased the mass transfer coefficient. The mass transfer coefficient increased between 89% and 93% for ozone inlet concentrations between 5.4 mg/L and 9.4 mg/L at an ultrasonic power of 120W/L. The significance of the key findings of this research include the demonstration of the technical feasibility of ultrasound-enhanced ozonation for decolorization of the dye, Reactive Blue 19. It also includes the development of the mathematical model which can be used for the design of ultrasound-enhanced ozonation systems and the favorable comparison of the model with experimental results.