Enhanced mercury removal performance of Cu-Fe binary oxide sorbents modified by non-thermal plasma

In this work, magnetic Cu-Fe binary oxide (CF) sorbents synthesized by sol gel method are modified by oxygen non-thermal plasma for efficient removal of elemental mercury (Hg-0) from coal-fired flue gas. Sample characterization indicates that plasma treatment has very little impact on the physical properties, magnetization characteristics, and crystalline phases of CF sorbents. But the content of Fe3+, Cu2+, and lattice oxygen in CF sorbents are significantly improved after plasma treatment. Mercury adsorption experiments suggest that the modified sorbents show higher Hg-0 removal efficiency in comparison with raw sorbents, and longer treatment time leads to higher Hg-0 removal efficiency. The effect of plasma discharge power (32-96 VA), discharge atmosphere (N-2, air, 50% N-2(+) 50% O-2, and O-2), and reaction temperature (50-350 degrees C) on mercury removal performance are also explored in a fixed-bed reactor. The presence of O-2, NO, and HCl promote Hg-0 removal. SO2 and H2O suppress Hg-0 removal, but O-2 addition can obviously weaken such inhibitory effects. Both experimental results and kinetic model indicate that chemisorption is the decisive factor for Hg-0 removal over CF sorbents. Moreover, the mechanism of Hg-0 removal over the modified CF sorbents is also investigated. The results indicate that Fe2O3 and CuO serving as active sites are greatly consumed in Hg-0 removal process. The multiple regeneration cycles testify that the combination of thermal desorption and non-thermal plasma treatment can realize the efficient regeneration of CF sorbents.

Automated summary

In this study, magnetic Cu-Fe binary oxide sorbents were modified by oxygen non-thermal plasma for efficient removal of elemental mercury from coal-fired flue gas. Plasma treatment improved the Fe3+, Cu2+, and lattice oxygen content in the sorbents, leading to higher Hg-0 removal efficiency. Both experimental results and kinetic model confirmed that chemisorption is the dominant factor for Hg-0 removal over the modified sorbents.