Ag/BiOI光催化剂湿法脱除烟气中气态单质汞性能及机理

采用沉淀-光还原法制备了不同Ag含量的Ag/BiOI可见光催化剂，利用XRD、N₂吸附-脱附、SEM、TEM、XPS、DRS、光电流和ESR对其物化结构进行表征，在湿法鼓泡反应器脱汞装置上考察了Ag负载量、光照、SO₂和NO对气态单质汞（Hg⁰）脱除性能的影响。结果表明，与BiOI相比，Ag添加后光催化剂的脱汞效率大幅提高。当Ag负载质量分数为2%时，Ag/BiOI催化剂的脱汞效率高达98%。荧光灯辐照对Ag（2%）/BiOI催化剂的高效脱汞至关重要。与NO相比，SO₂对脱汞效率的影响颇为明显。与BiOI相比，Ag（2%）/BiOI中BiOI的边缘出现较多的Ag微颗粒，且Ag颗粒分散度较好；Ag的添加可以提高BiOI表面的化学吸附态氧含量和增强BiOI在可见光波段的吸收能力，有利于其高效脱汞。机理分析表明，超氧阴离子自由基（^•O₂^-）和空穴（h⁺）在光催化脱汞过程中起主要作用。

Mechanism and performance of wet process to remove gaseous elemental mercury from flue gas using Ag/BiOI photocatalyst

A series of Ag/BiOI visible-light-driven photocatalysts were successfully synthesized by the precipitation-photoreduction method. The physical-chemical structures of the composites were characterized by X-ray diffraction(XRD), N₂ adsorption-desorption, scanning electron microscope(SEM), transmission electron microscope(TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy(DRS), photocurrent test and electron spin resonance (ESR). The effects of Ag content, fluorescent lamp (FSL) irradiation, SO₂ and NO on the removal of gaseous elemental mercury(Hg⁰) were investigated in a wet bubbling reactor. The results showed that in comparison to BiOI, the mercury removal efficiency of Ag/BiOI was greatly improved when silver microparticles were added. In particular, with Ag content of 2% in Ag/BiOI, the mercury removal efficiency reached as high as 98%. The presence of FSL irradiation was very essential for keeping high Hg⁰ removal efficiency. Compared to NO, SO₂ showed a dramatic inhibition on Hg⁰ removal. The characterization results showed that some Ag microparticles were highly dispersed onto the surface of BiOI. The content of chemisorbed oxygen and absorption ability in visible light range were significantlyenhanced when Ag microparticles were doped onto the surface of BiOI, which could be beneficial for its high activity of mercury removal. The mechanism analysis indicated that superoxide radicals(^•O₂^-) and photoinduced holes(h⁺) were the primary active substances in the photocatalytic removal of Hg⁰.