Development of Nano-Sulfide Sorbent for Efficient Removal of Elemental Mercury from Coal Combustion Fuel Gas

The surface area of zinc sulfide (ZnS) was successfully enlarged using nanostructure particles synthesized by a liquid-phase precipitation method. The ZnS with the highest surface area (named Nano-ZnS) of 196.1 m(2).g(-1) was then used to remove gas-phase elemental mercury (Hg) from simulated coal combustion fuel gas at relatively high temperatures (140 to 260 degrees C). The Nano-ZnS exhibited far greater Hg adsorption capacity than the conventional bulk ZnS sorbent due to the abundance of surface sulfur sites, which have a high binding affinity for Hg-0.Hg-0 was first physically adsorbed on the sorbent surface and then reacted with the adjacent surface sulfur to form the most stable mercury compound, HgS, which was confirmed by X-ray photoelectron spectroscopy analysis and a temperature-programmed desorption test. At the optimal temperature of 180 degrees C, the equilibrium Hg-0 adsorption capacity of the Nano-ZnS (inlet Hg concentration of 65.0 mu gm(-3)) was greater than 497.84 mu g.g(-1) Compared with several commercial activated carbons used exclusively for gas-phase mercury removal, the Nano-ZnS was superior in both Hg adsorption capacity and adsorption rate. With this excellent Hg-0 removal performance, noncarbon Nano-ZnS may prove to be an advantageous alternative to activated carbon for Hg-0 removal in power plants equipped with particulate matter control devices, while also offering a means of reusing fly ash as a valuable resource, for example as a concrete additive.