Core-shell nanostructure α-Fe2O3/SnO2 binary oxides for the catalytic oxidation and adsorption of elemental mercury from flue gas

In this study, core-shell nanostructure alpha-Fe2O3/SnO2 binary oxides were prepared to for gaseous elemental mercury (Hg-0) removal. The composites were characterized and the results showed that alpha-Fe2O3/SnO2 was created with the SnO2 core and alpha-Fe2O3 shell nanostructure. alpha-Fe2O3/SnO2 had both 76% of Hg-0 removal efficiency and 80% of denitration efficiency during 120 min at 350 degrees C, which was much higher than the Hg-0 removal efficiency of alpha-Fe2O3 or SnO2 nanospheres. The O-2 played an active role in the Hg-0 removal over alpha-Fe2O3/SnO2 at high temperature, however, the SO2 and H2O vapor could reduce the Hg-0 removal efficiency of alpha-Fe2O3/SnO2 to 35% and 40%, respectively. The HCl in flue gas can greatly promote the Hg-0 removal efficiency to 95% interpreted as Deacon Reaction mechanism. When HCl is absent in flue gas, the mechanism of Hg-0 removal is concluded to catalytic oxidation and adsorption. The gaseous Hg-0 is oxidized by Fe3+ and surface-chemisorbed O2- to form HgO adsorbed on the surface and in the void of alpha-Fe2O3/SnO2. Meanwhile, the Fe2+ is re-oxidized by Sn4+ to form Fe3+ and Sn2+, and the Sn2+ is re-oxidized by O-2 in the flue gas.

Automated summary

The study found that α-Fe2O3/SnO2 binary oxides have high efficiency in removing gaseous elemental mercury, especially at high temperatures, with involvement of O-2. SO2 and H2O vapor can reduce the removal efficiency, while the presence of HCl greatly enhances it. The mechanisms of removal involve catalytic oxidation and adsorption processes, with involvement of Fe3+, O2-, Sn4+, and Sn2+.