Degradation of methyl green from wastewater with ultrasound synergized with Bi2O2CO3 catalysis: Kinetics, products, and pathways.

Bi 2 O 2 CO 3 is a Bi-based semiconductor catalyst. In this paper, microspherical Bi 2 O 2 CO 3 was prepared by hydrothermal method. The crystal structure, microscopic morphology and optical properties of the samples were characterized by X-ray Diffraction, Scanning Electron Microscope and UV–vis diffuse reflectance spectroscopy. The ultrasonic catalytic activity of Bi 2 O 2 CO 3 was evaluated using methyl green as a model contaminant. The degradation of methyl green by Bi 2 O 2 CO 3 adsorption, ultrasonic radiation, and ultrasound synergized with Bi 2 O 2 CO 3 catalysis were investigated. The results show that the degradation rates of the three methods are in order: Bi 2 O 2 CO 3 adsorption＜ultrasonic radiation＜ultrasound synergized with Bi 2 O 2 CO 3 catalysis. This indicates that the Bi 2 O 2 CO 3 microspheres showed good ultrasonic catalytic activity. In addition, the effects of ultrasonic power, ultrasonic duty ratio, Bi 2 O 2 CO 3 concentration and pH on the ultrasonic catalytic efficiency were also investigated. The optimal degradation conditions were determined (ultrasonic power is 400 W, ultrasonic duty ratio is 9:1, Bi 2 O 2 CO 3 concentration is 1.5 g/l, pH is 11, reaction time is 80 min). Active substances such as ·OH, 1O 2 , HO 2 ·, H 2 O 2 , and photogenerated holes may be produced in the process of methyl green degradation by ultrasound synergized with Bi 2 O 2 CO 3 catalysis. These active substances with strong oxidizing properties can decompose methyl green into CO 2 , HO 2 and other non-toxic small molecule compounds. Photogenerated holes can degrade methyl green directly or react with –OH in solution to produce more ·OH and thus significantly increase the degradation rate of methyl green. The results indicate that ultrasound synergized with Bi 2 O 2 CO 3 catalysis is of great potential application value in removal of organic pollution and environmental purification. Degradation mechanism of methyl green by US/Bi 2 O 2 CO 3. [Display omitted] [ABSTRACT FROM AUTHOR]