Enhancing the catalytic oxidation of elemental mercury and suppressing sulfur-toxic adsorption sites from SO-containing gas in Mn-SnS.

It is difficult to stabilize gaseous elemental mercury (Hg°) on a sorbent from SO-containing industrial flue gas. Enhancing Hg° oxidation and activating surface-active sulfur (S*) can benefit the chemical mercury adsorption process. A Mn-SnS composite was prepared using the Mn modification of SnS nanosheets to expose more Mn oxidation and sulfur adsorption sites. The results indicate that Mn-Sn 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 Mn 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-SnS exhibits an excellent SO resistance when the SO concentration is lower than 1500 ppm. The effects of HO and O were also evaluated. The results show that O has no influence, while HO and SO coexisting in the flue gas have a toxic effect on the Hg° removal performance. The Mn-SnS has a great potential for the Hg° removal from SO-containing flue gas such as non-ferrous smelting gas.