Insights into the enhanced mechanism of selenium-doped iron nitride carbon catalysts for elemental mercury removal in flue gas

Abstract

This study developed a novel selenium-doped metal nitride carbon, Fe-NC-Se, via pyrolysis and impregnated hydrothermal methods for elemental mercury removal from coal-fired flue gas. The Fe-NC-Se demonstrated a remarkable mercury removal performance, achieving an average efficiency of 96.98% within 60 min at an optimal Se/Fe ratio of 2:1 and temperature of 110 °C, which was 2.5 times higher than that of the pristine Fe-NC (iron nitride carbon). Notably, Fe-NC-Se maintained an 84% efficiency in a high SO2 environment (1600 ppm), indicating strong resistance to SO2 poisoning. Long-term testing over 24 h showed a consistent removal efficiency of 84.75%, suggesting potential for recyclability. Advanced characterization techniques, including TEM (transmission electron microscopy) and XPS (X-ray photoelectron spectrometer), along with Density Functional Theory calculations, were employed to explore the removal mechanism. Results indicated that selenium doping enhanced surface charge transfer and the reactivity of surface atoms, facilitating mercury oxidation and sequestration. The oxidized Hg2+ was anchored by Se and partially stabilized by C, N, and Fe atoms, enhancing the catalyst’s effectiveness. This work not only advances the design of mercury abatement catalysts but also supports the industrial applicability of Fe-NC-Se in flue gas treatment.