Surface sulfidation modification of magnetospheres from fly ash for elemental mercury removal from coal combustion flue gas.

• Magnetospheres was modified through H 2 S as an efficient sorbent for Hg0. • Elemental sulfur derived from H 2 S oxidation was responsible high-efficient Hg0 adsorption. • Gaseous Hg0 was immobilized as stable HgS with extremely low leaching ratio. • The application route for Hg0 removal by using magnetospheres with suface sulfidation modification was proposed. Reduction of elemental mercury (Hg0) emission from coal-fired power plants is an enormous challenge. In this work, magnetospheres separated from fly ash was modified through H 2 S as an efficient sorbent (i.e., S-MS) for Hg0. Elemental sulfur with high affinity towards Hg0 was formed on the S-MS surface through selective catalytic oxidation of H 2 S. The sulfidation temperature played an important role in Hg0 adsorption over S-MS, ascribing to the variation of sulfur species on S-MS. The S-MS exhibited above 80% Hg0 adsorption efficiency with a sulfidation temperature of 150 °C for 30 min. The optimal Hg0 adsorption performance was obtained at 50 and 75 °C, implying that the S-MS could be adopted by injecting into the duct upstream of wet electrostatic precipitator (WESP) system. The gaseous Hg0 was immobilized by S-MS as stable mercury sulfide (HgS) owing to the presence of abundant sulfur species that is active for binding Hg0. The leaching ratio of mercury from spent S-MS in WESP effluent was as low as 1%, hence minimizing the secondary mercury pollution from the industrial waste. The cost analysis demonstrates that the mercury removal technology on the basis of magnetospheres adsorbents exhibited much superiority in operation cost compared with commercial activated carbon injection technology. Thus, the S-MS, with specific features, such as high Hg0 adsorption performance, minimized environmental hazardous and recyclability, displayed great potential in Hg0 sequestration. [ABSTRACT FROM AUTHOR]