Preparation of three-dimensional spherical BiOI/BiOBr heterojunction photocatalyst and its photocatalytic mercury removal performance

ZHANG Anchao; ZHANG Xu; ZHANG Qianqian; LI Haixia; WANG Hua; MEI Yanyang; ZHENG Haikun; CHEN Guoyan

doi:10.16186/j.cnki.1673-9787.2021100024

Abstract：Photocatalytic oxidation technology is an important strategy to control pollutant emission.Objective To enhance the utilization ratio of visible light and improve its photocatalytic activity of BiOBr,Methods the iodine doped three-dimensional spherical BiOI/BiOBr heterojunction photocatalysts were prepared by simple co-precipitation method.The structures of the samples were characterized by X-ray diffraction,UV-visible diffuse reflectance spectroscopy,scanning electron microscopy,N2 adsorption-desorption,X-ray photoelectron spectroscopy and electron spin resonance spectroscopy,and the performance of photocatalytic removal of elemental mercury(Hg0)was studied.Results The results showed that with the increase of iodine content,the diffraction peak intensity of BiOBr decreased,while the diffraction peak intensity of BiOI gradually in-creased.The BiOI/BiOBr composite photocatalyst retained the three-dimensional microsphere morphology of BiOBr,and BiOI was uniformly dispersed on the surface of BiOBr,meanwhile some new specific surface ar-eas were generated,which can provide more reaction space and promote the generation of active free radicals and improve the performance of the photocatalyst.Compared with BiOBr,the band gap energy of the composite photocatalyst was greatly reduced,and the visible light response ability was significantly enhanced.The pho-tocatalytic Hg0 removal performances of BiOI/BiOBr photocatalysts were higher than those of BiOI and BiOBr.When the molar ratio of BiOI to BiOBr was 2∶8,the Hg0 removal efficiency of the photocatalyst was up to 98%,which was 2.58 times that of BiOBr.The BiOI/BiOBr heterojunction photocatalyst prepared un-der acidic conditions would react with alkaline solution,which could cause the changes of the composition of the photocatalyst,and then affect the catalytic performance of the photocatalyst.The radicals capture ex-periment showed that anionic superoxide radicals(·O-2)and holes(h+)were important active substances in the process of Hg0 photocatalytic removal.Conclusion The research has laid a theoretical foundation for the composite preparation of bismuth halide oxide photocatalyst and its application in the field of mercury re-moval.