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

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journal contribution
posted on 10.08.2016, 00:00 by Hailong Li, Lei Zhu, Jun Wang, Liqing Li, Kaimin Shih
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 m2·g–1 was then used to remove gas-phase elemental mercury (Hg0) from simulated coal combustion fuel gas at relatively high temperatures (140 to 260 °C). The Nano-ZnS exhibited far greater Hg0 adsorption capacity than the conventional bulk ZnS sorbent due to the abundance of surface sulfur sites, which have a high binding affinity for Hg0. Hg0 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 °C, the equilibrium Hg0 adsorption capacity of the Nano-ZnS (inlet Hg0 concentration of 65.0 μg·m–3) was greater than 497.84 μg·g–1. Compared with several commercial activated carbons used exclusively for gas-phase mercury removal, the Nano-ZnS was superior in both Hg0 adsorption capacity and adsorption rate. With this excellent Hg0 removal performance, noncarbon Nano-ZnS may prove to be an advantageous alternative to activated carbon for Hg0 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.