Abstract
Sorbent of αMnO2 nanorods coating TiO2 shell (denoted as αMnO2-NR@TiO2) was prepared to investigate the elemental mercury (Hg0) removal performance in the presence of SO2. Due the core-shell structure, αMnO2-NR@TiO2 has a better SO2 resistance when compared to αMnO2 nanorods (denoted as αMnO2-NR). Kinetic studies have shown that both the sorption rates of αMnO2-NR and αMnO2-NR@TiO2, which can be described by pseudo second-order models and SO2 treatment, did not change the kinetic models for both the two catalysts. In contrast, X-ray photoelectron spectroscopy (XPS) results showed that, after reaction in the presence of SO2, S concentration on αMnO2-NR@TiO2 surface is lower than on αMnO2-NR surface, which demonstrated that TiO2 shell could effectively inhibit the SO2 diffusion onto MnO2 surface. Thermogravimetry-differential thermosgravimetry (TG-DTG) results further pointed that SO2 mainly react with TiO2 forming Ti(SO4)O in αMnO2-NR@TiO2, which will protect Mn from being deactivated by SO2. These results were the reason for the better SO2 resistance of αMnO2-NR@TiO2.
Highlights
The emission of mercury from coal-fired power plants has drawn wide public concern in modern society
Conclusions αMnO2 -NR@TiO2 was prepared by versatile kinetics-controlled coating method to compare with αMnO2 -NR in the Hg0 removal process
Scanning electron microscopy (SEM), BET, and X-ray diffractometer diffractometer (XRD) results showed that TiO2 shell did not change the structure of αMnO2 -NR
Summary
The emission of mercury from coal-fired power plants has drawn wide public concern in modern society. Mercury emissions are a long-term threat to human health and the environment because of extreme toxicity, persistence, and bioaccumulation. Controlling mercury emitted from coal-fired power plants has practical significance. Mercury in coal combustion flue gas is mainly present in three forms: Elemental mercury (Hg0 ), oxidized mercury (Hg2+ ), and particulate-bound mercury (Hgp ). Particulate-bound mercury (Hgp ) can be removed by electrostatic precipitators (ESP). Fabric filters (FF), while oxidized mercury (Hg2+ ) can be captured by wet flue gas desulfurization system (WFGD). Existing air pollution control devices can hardly remove Hg0 due to its high volatility and low solubility
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