Enhancing the catalytic oxidation of elemental mercury and suppressing sulfur-toxic adsorption sites from SO2-containing gas in Mn-SnS2

Abstract

It is difficult to stabilize gaseous elemental mercury (Hg°) on a sorbent from SO2-containing industrial flue gas. Enhancing Hg° oxidation and activating surface-active sulfur (S*) can benefit the chemical mercury adsorption process. A Mn-SnS2 composite was prepared using the Mn modification of SnS2 nanosheets to expose more Mn oxidation and sulfur adsorption sites. The results indicate that Mn-Sn2 exhibits better Hg° removal performances at a wide temperature range of 100–250 °C. A sufficient amount of surface Mn with a valance state of Mn4+ is favorable for Hg° oxidation, while the electron transfer properties of Sn can accelerate this oxidation process. Oxidized mercury primary exists as HgS with surface S*. A larger surface area, stable crystal structure, and active valance state of each element are favorable for Hg° oxidation and adsorption. The Mn-SnS2 exhibits an excellent SO2 resistance when the SO2 concentration is lower than 1500 ppm. The effects of H2O and O2 were also evaluated. The results show that O2 has no influence, while H2O and SO2 coexisting in the flue gas have a toxic effect on the Hg° removal performance. The Mn-SnS2 has a great potential for the Hg° removal from SO2-containing flue gas such as non-ferrous smelting gas.