汞具有剧毒性、大气迁移性和生物累积性等特征，对生态环境和人类健康构成严重威胁。我国燃煤汞排量居世界首位，加强汞控制技术研究势在必行。燃煤烟气中单质汞(Hg0)的高效氧化是治理汞污染的关键。以Ag/AgCl改性的Bi5O7I/Bi2O3复合材料为光催化剂，在湿法光催化反应器中研究了Ag/Bi质量比、pH、无机阴离子、SO2和NO等参数对光催化剂脱除气态单质汞的影响；采用N2吸附-脱附、XRD、SEM、DRS、XPS和ESR等手段对光催化剂进行表征。结果表明，当Ag/Bi质量比为0.03时，Ag/AgCl改性Bi5O7I/Bi2O3复合材料的光催化氧化能力最佳，脱汞效率可达98.5%；随反应溶液pH的升高和无机碳酸根离子的添加，脱汞效率明显降低；与NO相比，SO2对气态单质汞脱除性能影响较大。添加Ag/AgCl改变了Bi5O7I/Bi2O3中Bi和O的化学存在形态，Ag/AgCl与Bi5O7I/Bi2O3之间可能形成了Z型异质结，这对四元复合光催化材料的活性起着至关重要的作用；自由基捕获试验表明超氧自由基（·O-2）和空穴（h+）是脱除Hg0的主要活性物质。

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 Bi5O7I/Bi2O3 composite as photocatalyst,the effects of experimental parameters such as Ag/Bi mass ratio,pH,inorganic anion,SO2 and NO on the removal of gaseous elemental mercury by photocatalyst were studied in a wet photocatalytic reactor. The photocatalysts were characterized by N2 adsorption-desorption,XRD,SEM,DRS,XPS and ESR. The results show that Ag/AgCl modified Bi5O7I/Bi2O3 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,SO2 has a greater inhibitory effect on gaseous Hg0 removal. The chemical species of Bi and O in Bi5O7I/Bi2O3 will be varied due to the addition of Ag/AgCl,and a Z-scheme heterojunction structure is formed between Ag/AgCl and Bi5O7I/Bi2O3,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+) were the main active substances for Hg0 removal. 

0 引言

1 材料与方法

   1.1 光催化剂的制备

   1.2 表征方法

   1.3 光催化剂活性分析

2 结果与讨论

   2.1 光催化剂的脱汞性能

   2.2 表征分析

   2.3 机理分析

3 结论