A dye-methylene blue (MB)-degraded by hydrodynamic cavitation (HC) and combined with other oxidants

As a kind of AOPs, hydrodynamic cavitation (HC) has the characteristics of energy savings and easy amplification. It is of great significance to study the degradation of dye molecules with HC, due to the toxicity, chroma and difficult biodegradation of dyes. In the present work, the HC treatment of methylene blue (MB) was investigated, and the effects of inlet pressure, solution pH, and initial concentration on the degradation of MB dye were explored. The maximum degradation rate of MB was obtained at 0.3 MPa, pH = 2, and an initial concentration of 10 mg/L. The combination of Na2S2O8 or O3 with HC were also conducted to explore their synergistic effect. The results indicated that the degradation performance of introducing ozone is better that of adding Na2S2O8. When the amount of O3 gas was 0.12 g/h, the MB degradation rate was over 99%, and the synergy index was 3.58. The intermediate products in the MB disintegration process were detected based on LC-MS, and the reaction mechanism and path of MB were proposed.