In-situ synthesis of Bi2WO6/AgBr/Ag4V2O7 with double Z-scheme heterojunction for oxytetracycline degradation and weakening toxicity

A novel double Z-scheme heterojunction Bi2WO6/AgBr/Ag4V2O7 composite catalyst was successfully prepared by the ultrasonic-assisted coprecipitation method, and the Bi2WO6/AgBr/Ag4V2O7 composite catalyst shows better photocatalytic activity for oxytetracycline. The increased photocatalytic activity is due to the combination of AgBr and Ag4V2O7, which enables Bi2WO6/AgBr/Ag4V2O7 to have a wider range of visible light absorption, as well as the construction of double Z-scheme heterojunction, which enables Bi2WO6/AgBr/Ag4V2O7 to have stronger photogenerated e--h+ pairs separation efficiency. The reactive species trapping experiments found that ·O2–, h+ and ·OH all participated in the reaction to varying degrees. [Display omitted] •A novel Bi2WO6/AgBr/Ag4V2O7 photocatalyst has been successfully prepared by the ultrasonic-assisted coprecipitation method.•Bi2WO6/AgBr/Ag4V2O7 photocatalyst exhibits better photocatalytic activity to oxytetracycline.•The formation of double Z-scheme electron transfer mechanism accelerates the separation of charge carriers.•The toxicity of oxytetracycline to wheat decreased significantly after degradation by Bi2WO6/AgBr/Ag4V2O7. Herein, a novel Bi2WO6/AgBr/Ag4V2O7 double Z-scheme heterojunction photocatalytic material was synthesized by the ultrasonic-assisted coprecipitation method. When the content of AgBr in Bi2WO6/AgBr/Ag4V2O7 is 30 wt% and the content of Ag4V2O7 is 1 wt%, under the optimized reaction conditions, the degradation rate of Bi2WO6/AgBr/Ag4V2O7 to oxytetracycline (OTC) reached 88.13 % within 60 min, and the photocatalytic activity decreased only slightly after repeated use for three times, other than that, the toxicity of OTC to wheat decreased significantly after degradation. The morphology, composition, crystal structure and visible light absorption capacity of the samples are investigated by a series of characterization techniques. Furthermore, free radical capture experiment, electron paramagnetic resonance (EPR) experiment and liquid chromatography-mass spectrometry (LC-MS) were used to explore the possible photocatalytic mechanism and degradation path of OTC. The results show that the improvement of photocatalytic activity is attributed to the construction of a double Z-scheme heterojunction, which provides a more effective structural space for the separation of photogenerated e--h+ pairs. This study provides a new idea for the separation of photogenerated e--h+ pairs and broadens the response range of visible li