Wet process of elemental mercury removal using Ag@AgCl-BiOCl photocatalyst under fluorescent light irradiation

doi:10.11949/j.issn.0438-1157.20171235

Abstract

Abstract:

A series of Ag@AgCl-BiOCl photocatalysts were synthesized by a coprecipitation-photoreduction method and characterized by N₂ adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) techniques to understand their physical-chemical structures. The effects of AgCl content, pH value, reaction temperature, SO₂ and NO on the activities of elemental mercury (Hg⁰) removal were carried out in a wet Hg⁰ bubbling reactor under fluorescent light (FSL) irradiation. The results showed that a much higher Hg⁰ removal efficiency was obtained when the molar ratio of Ag to Bi was equal to 0.2 in the Ag@AgCl-BiOCl sample. With increasing pH value and reaction temperature, the Hg⁰ removal efficiency over Ag@AgCl_(0.2)-BiOCl under FSL irradiation became gradually worse. Compared with SO₂, NO showed a significant inhibitation on Hg⁰ removal. The mechanism analysis indicated that superoxide radicals (^·O₂^-), holes (h⁺), hydroxyl radicals (^·OH) and chlorine radicals (^·Cl) could be reactive species in the photocatalytic process of Hg⁰ removal, and in particular the ^·O₂^- played key role in Hg⁰ removal.

Key words: wet process, catalyst, Ag@AgCl-BiOCl, Hg⁰ removal, flue gas

摘要：

采用共沉淀-光还原法制备了系列Ag@AgCl-BiOCl可见光催化剂，利用N₂吸附-脱附、扫描电子显微镜（SEM）、X射线衍射（XRD）、紫外-可见漫反射光谱（DRS）、X射线光电子能谱（XPS）和电子自旋共振（ESR）等技术对光催化剂进行物化结构表征，在湿法脱汞装置上考察了荧光灯辐照下AgCl负载量、溶液pH、反应温度、SO₂和NO对单质汞（Hg⁰）脱除性能的影响。结果表明，在荧光灯辐照下，当Ag/Bi物质的量比为0.2时，光催化剂的脱汞效率最高。随着pH和反应温度的升高，脱汞效率逐渐降低。与SO₂相比，NO对脱汞效率的影响较大。在光催化氧化脱汞过程中，阴离子超氧自由基（^·O₂^-）、空穴（h⁺）、羟基自由基（^·OH）和氯自由基（^·Cl）等均可能发挥作用，但^·O₂^–作用较大。

关键词: 湿法, 催化剂, Ag@AgCl-BiOCl, 脱汞, 烟道气

CLC Number:

X511

LI Chengwei, LU Hao, ZHANG Anchao, XING Weibo, HU Song, XIANG Jun. Wet process of elemental mercury removal using Ag@AgCl-BiOCl photocatalyst under fluorescent light irradiation[J]. CIESC Journal, 2018, 69(5): 2217-2225.

李成伟, 路好, 张安超, 邢微波, 胡松, 向军. 荧光灯辐照下Ag@AgCl-BiOCl光催化剂湿法脱汞研究[J]. 化工学报, 2018, 69(5): 2217-2225.

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