Bismuth oxybromide promoted detoxification of cylindrospermopsin under UV and visible light illumination

Bismuth oxybromide (BiOBr) was prepared and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). The BiOBr promoted detoxification of cylindrospermopsin (CYN) under UV ( λ   <   350   nm) and visible light ( λ   >   420   nm) illumination was studied. The results revealed that the toxic uracil unit of CYN was removed, and the carboxylic group of the degraded product was also decomposed, to give the innoxious tricyclic guanidine product under the title conditions. In contrast, the traditional Fenton reagents (Fe 2+ and H 2 O 2 ) limited to remove the uracil moiety of CYN with the carboxylic group intact. Presumably, the decarboxylation ability of BiOBr was induced by Br 4 p valence band hole ( h Br   4 p + ), and the degradation mechanism was also proposed based on the experimental results and theoretical calculation.