Clean Coal Technology

2022, v.28;No.142(06) 110-119

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Performance of Ag/AgCl modified Bi_5O_7I/Bi_2O_3 composite for photocatalytic oxidation of elemental mercury

SHI Lei;ZHANG Anchao;ZHANG Huige;ZHANG Qianqian;ZHENG Hongxiang;ZHANG Xu;ZHANG Jingfan;School of Mechanical and Power Engineering,Henan Polytechnic University;

Abstract:

Mercury possesses the characteristics of hypertoxicity, atmospheric migration and bioaccumulation, which has posed a serious threat to the ecological environment and human health. The mercury emission in China from coal combustion ranks first in the world, therefore, it is imperative to strengthen the research on mercury control technology. It is the key to control mercury pollution by the efficient oxidation of elemental mercury(Hg0) from coal-fired flue gas. Using Ag/AgCl modified Bi_5O_7I/Bi_2O_3 composite as photocatalyst, the effects of experimental parameters such as Ag/Bi mass ratio, pH, inorganic anion, SO_2 and NO on the removal of gaseous elemental mercury by photocatalyst were studied in a wet photocatalytic reactor. The photocatalysts were characterized by N_2 adsorption-desorption, XRD,SEM,DRS,XPS and ESR. The results show that Ag/AgCl modified Bi_5O_7I/Bi_2O_3 composite possesses the superior photocatalytic oxidation performance and the mercury removal efficiency can reach as high as 98.5% when the Ag/Bi mass ratio is 0.03. With the increase of pH and the addition of inorganic carbonate ions, the efficiency of mercury removal decreases significantly. Compared with NO,SO_2 has a greater inhibitory effect on gaseous Hg0) from coal-fired flue gas. Using Ag/AgCl modified Bi_5O_7I/Bi_2O_3 composite as photocatalyst, the effects of experimental parameters such as Ag/Bi mass ratio, pH, inorganic anion, SO_2 and NO on the removal of gaseous elemental mercury by photocatalyst were studied in a wet photocatalytic reactor. The photocatalysts were characterized by N_2 adsorption-desorption, XRD,SEM,DRS,XPS and ESR. The results show that Ag/AgCl modified Bi_5O_7I/Bi_2O_3 composite possesses the superior photocatalytic oxidation performance and the mercury removal efficiency can reach as high as 98.5% when the Ag/Bi mass ratio is 0.03. With the increase of pH and the addition of inorganic carbonate ions, the efficiency of mercury removal decreases significantly. Compared with NO,SO_2 has a greater inhibitory effect on gaseous Hg0 removal. The chemical species of Bi and O in Bi_5O_7I/Bi_2O_3 will be varied due to the addition of Ag/AgCl, and a Z-scheme heterojunction structure is formed between Ag/AgCl and Bi_5O_7I/Bi_2O_3,which plays a crucial role in the activity of quaternary composite photocatalytic materials. The experiments of free radical capture show that superoxide radical(·O0 removal. The chemical species of Bi and O in Bi_5O_7I/Bi_2O_3 will be varied due to the addition of Ag/AgCl, and a Z-scheme heterojunction structure is formed between Ag/AgCl and Bi_5O_7I/Bi_2O_3,which plays a crucial role in the activity of quaternary composite photocatalytic materials. The experiments of free radical capture show that superoxide radical(·O-_2) and holes(h-_2) and holes(h+) were the main active substances for Hg+) were the main active substances for Hg0 removal.

Key Words: photocatalyst;heterojunction;catalytic oxidation;mercury removal;composite;pollutants

Abstract:

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Foundation: 国家自然科学基金资助项目(51676064);; 河南省高校科技创新人才资助项目(19HASTIT045);; 河南理工大学创新型科研团队资助项目(T2020-3);; 河南省科技攻关资助项目(182102310810)

Authors: SHI Lei;ZHANG Anchao;ZHANG Huige;ZHANG Qianqian;ZHENG Hongxiang;ZHANG Xu;ZHANG Jingfan;School of Mechanical and Power Engineering,Henan Polytechnic University;

DOI: 10.13226/j.issn.1006-6772.CE21040101

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