Simultaneous catalytic oxidation of nitric oxide and elemental mercury over Cu-Fe binary oxide treated by oxygen non-thermal plasma

Abstract

In this study, non-thermal plasma (NTP) was adopted to improve the catalytic oxidation performance of Cu-Fe binary oxides (CFs) for efficient simultaneous removal of NO and Hg0 from coal combustion flue gas. Sample characterization indicated that the pore structure, surface morphology, and crystalline phases of CF samples were not changed after plasma treatment whereas the contents of lattice oxygen (Ol), Fe3+, and Cu2+ were largely increased. The treated CF samples exhibited far better NO removal performance compared with raw CF over a wide reaction temperature range (150–450 °C). The influences of plasma discharge time, discharge power, discharge atmosphere, and reaction temperature on NO removal performance were analyzed. O2 facilitated Hg0 and NO removal·H2O had adverse effect on Hg0 and NO removal. To some extent, the CF samples exhibited better resistant to sulfur poisoning due to the presence of Fe species. Moreover, the simultaneous removal behavior of Hg0 and NO over the modified CF samples were analyzed. NO facilitated Hg0 removal, but Hg0 had a slight inhibitory impact on NO removal. The optimum reaction temperature of simultaneous removal of NO and Hg0 was 300 °C. Finally, the mechanism responsible for NO/Hg0 removal was revealed, where CuO and Fe2O3 served as active components. During NO removal process, Fe3+, Cu2+, and Ol were first consumed and then recovered due to the existence of O2. Hg0 catalytic oxidation dominated the Hg0 removal process because Hg0 adsorption equilibrium was reached in a short time.