Hierarchical Ag-SiO_2@Fe_3O_4magnetic composites for elemental mercury removal from non-ferrous metal smelting flue gas

摘要

Hierarchical Ag-SiO_2@Fe_3O_4 magnetic composites were selected for elemental mercury(Hg^0) removal from non-ferrous metal smelting flue gas in this study. Results showed that the hierarchical Ag-SiO_2@Fe_3O_4 magnetic composites had favorable Hg^0 removal ability at low temperature. Moreover, the adsorption capacity of hierarchical magnetic composite is much larger than that of pure Fe_3O_4 and SiO_2@Fe_3O_4. The Hg^0 removal efficiency reached the highest value as approximately 92% under the reaction temperature of 150°C, while the removal efficiency sharply reduced in the absence of O_2. The characterization results indicated that Ag nanoparticles grew on the surface of SiO_2@Fe_3O_4 support. The large surface area of SiO_2 supplied efficient reaction room for Hg and Ag atoms. Ag–Hg amalgam is generated on the surface of the composites. In addition, this magnetic material could be easily separated from fly ashes when adopted for treating real flue gas, and the spent materials could be regenerated using a simple thermal-desorption method.