Preparation and sonophotocatalytic performance of hierarchical Bi2WO6 structures and effects of various factors on the rate of Rhodamine B degradation

Hierarchical Bi2WO6 structures with high surface area were prepared in the presence of polyvinylpyrrolidone by using an optimized hydrothermal method. The samples prepared were characterized by X-ray diffraction, field-emission scanning electron microscopy and N2 adsorption-desorption technique. The results of these characterizations showed the formation of the hierarchical Bi2WO6 structures with high surface area (51 m2/g). The degradation of Rhodamine B (RhB) with or without visible light was investigated under various experimental conditions to evaluate the sonophotocatalytic activity of the hierarchical Bi2WO6 structures. The result showed that the degradation efficiency was found to be in the following order: sonocatalysis < photocatalysis < sonophotocatalysis. The effects of various experimental factors such as light intensity, ultrasound pulse mode and catalyst dosage on the sonophotocatalysis efficiency were also investigated. Under the optimum condition (light intensity 140 W, ultrasound pulse mode: 9 s on/1 s off, Bi2WO6 catalyst dosage: 1.25 g/L), the excellent sonophotocatalytic activity on the degradation of RhB was observed: the degradation ratio achieved about 99.5% at 40 min. The mechanism of the sonophotocatalysis was also proposed.