ZHANG A C, ZHANG J F, ZHANG D, et al. Study on the removal of elemental mercury using microspherical Br-doped BiOCl composite photocatalyst[J]. Journal of Henan Polytechnic University (Natural Science), 2024, 43(6): 90-99.

doi：10.16186/j.cnki.1673-9787.2022020067

Received:2022/02/27

Revised:2022/04/13

Online:2024/09/24

Study on the removal of elemental mercury using microspherical Br-doped BiOCl composite photocatalyst

ZHANG Anchao,  ZHANG Jingfan,  ZHANG Dan,  SUN Zhijun,  ZHANG Xu,  LIU Yanwen,  ZHENG Haikun

School of Mechanical and Power Engineering，Henan Polytechnic University，Jiaozuo 454000，Henan，China

Abstract: Photocatalytic oxidation is an effective technology for controlling atmospheric mercury pollution. Objectives To develop a low-cost visible-light-driven mercury removal catalyst. Methods Microspherical BiOBrxCl1-x composite photocatalysts with different molar contents of bromine (Br) were synthesized by a one-step coprecipitation method, and their photocatalytic performances for Hg0 removal under fluorescent lamp (FSL) irradiation were evaluated in a wet photocatalytic mercury removal device. The physical and chemical structures of the samples were analyzed using N2 adsorption-desorption, XRD, UV-Vis DRS, SEM, HRTEM, XPS, and ESR techniques. Moreover, the charge transfer between BiOCl and BiOBr was studied using density functional theory. Results The results showed that compared with BiOCl and BiOBr, the photocatalytic performances of BiOBrxCl1-x composites were significantly improved, with the Hg0 removal efficiency of the BiOBr0.2Cl0.8 photocatalyst reaching as high as 90.3%, which was approximately 50% higher than that of pure BiOCl. Compared with NO3- and SO42-, Cl- and CO32- exhibited more significant inhibition on Hg0 removal. The specific surface area of the BiOBr0.2Cl0.8 composites was slightly larger than that of BiOBr and BiOCl, which would be beneficial for providing more reactive sites. With the gradual increase of Br content, the intensity of the XRD characteristic peaks of BiOCl gradually decreased, and the photocatalytic absorption capacity exhibited a regular redshift, indicating a strong interaction between BiOBr and BiOCl rather than a simple mechanical mixture. Both Bi 4f and O 1s of the BiOBr0.2Cl0.8 composite material shifted towards higher binding energies, indicating that the introduction of Br affected the states of Bi and O in BiOCl. Mechanism analysis showed that three active species were involved in the oxidative process of Hg0 removal, in the order of effectiveness: •O2-, h+, •OH. Conclusions The improvement in photocatalytic activity was primarily due to the formation of a Z-type heterojunction between BiOCl and BiOBr, which effectively enhanced the separation of photo-generated charges. This study provides a new approach for the development of low-cost and efficient bismuth oxyhalide-based photocatalysts for mercury removal.

Key words: photocatalyst; BiOCl; BiOBr; the removal of elemental mercury