Self-template synthesis of Co3O4 nanotube for efficient Hg0 removal from flue gas

Abstract

The adsorption of elemental mercury (Hg0) is a widely used technology to remove Hg0 from flue gas. The morphology and structure of sorbents, which have serious impacts on the number and availability of adsorption sites and the mass transfer of Hg0, play an important role in Hg0 removal process. Nanotube materials have through-pore structures leading to lower mass transfer resistance and more adsorption sites for Hg0. Given this, organic–inorganic hybrid nanowires were prepared by hydrothermal method as self-template. After calcination with a controlling heating rate and temperature, a series mesoporous Co3O4 nanotube sorbents were obtained. Characterization results show that the heating rate mainly affects the pore structure of the sorbents, while the calcination temperature mainly affects the surface morphology. When the calcination temperature is 400 °C and the calcination rate is 0.5 °C /min, the sorbent (Co3O4-T400-R0.5) has a clear 1D tubular structure which can effectively reduce the mass transfer resistance. And the unique internal surface of the tubular structure can provide more active sites, which can effectively avoid the competitive adsorption of Hg0 and other gas components. Furthermore, Co3O4-T400-R0.5 has the highest Co3+/Co2+ ratio leading to a better redox property, which is of benefit to Hg0 removal process. Therefore, the Hg0 removal efficiency of Co3O4-T400-R0.5 can reach more than 90% with a high gas hourly space velocity of 90,000 h− 1 and 0.02 g loading amount at 250 °C. Furthermore, Co3O4-T400-R0.5 has excellent Hg0 removal efficiencies in different flue gas condition showing a high stability.