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

Abstract In this study, core-shell nanostructure α-Fe2O3/SnO2 binary oxides were prepared to for gaseous elemental mercury (Hg0) removal. The composites were characterized and the results showed that α-Fe2O3/SnO2 was created with the SnO2 core and α-Fe2O3 shell nanostructure. α-Fe2O3/SnO2 had both 76% of Hg0 removal efficiency and 80% of denitration efficiency during 120 min at 350 ℃, which was much higher than the Hg0 removal efficiency of α-Fe2O3 or SnO2 nanospheres. The O2 played an active role in the Hg0 removal over α-Fe2O3/SnO2 at high temperature, however, the SO2 and H2O vapor could reduce the Hg0 removal efficiency of α-Fe2O3/SnO2 to 35% and 40%, respectively. The HCl in flue gas can greatly promote the Hg0 removal efficiency to 95% interpreted as Deacon Reaction mechanism. When HCl is absent in flue gas, the mechanism of Hg0 removal is concluded to catalytic oxidation and adsorption. The gaseous Hg0 is oxidized by Fe3+ and surface-chemisorbed O2- to form HgO adsorbed on the surface and in the void of α-Fe2O3/SnO2. Meanwhile, the Fe2+ is re-oxidized by Sn4+ to form Fe3+ and Sn2+, and the Sn2+ is re-oxidized by O2 in the flue gas.