Sonocatalytic degradation of methylene blue with TiO2 pellets in water

A series of experiments were carried out to study the degradation of methylene blue by the irradiation of ultrasound onto TiO2 in aqueous solution. A statistically significant decrease in the concentration of methylene blue was observed after 60 min irradiation. While the reduction was 22% of the initial concentration without H2O2, addition of H2O2 significantly enhanced the degradation of methylene blue for the TiO2 containing system (85% reduction of the initial concentration). The addition of H2O2 had no effect on the methylene blue degradation when the system contained Al2O3. The degradation ratio of methylene blue was dependent on the amount of TiO2 and also the specific surface area of TiO2 in the solution. The effects of radical scavenging agents on the degradation of methylene blue were also investigated for the system with TiO2. It was found that the radical scavenging agents dimethyl sulfoxide (DMSO), methanol, and mannitol suppressed the degradation, with DMSO being the most effective. The effect of pH on the degradation of methylene blue was further investigated. An U-shaped change in the concentration of methylene blue in the presence of TiO2 was observed along with the change in pH values (pH 3–12), and the highest degradation ratio was observed at around pH 7. In conclusion, ultrasound irradiation of TiO2 in aqueous solution resulted in significant generation of hydroxyl radicals, and this process may have potential for the treatment of organic dyes in wastewater.