Highly Dispersed Mn–Ce Binary Metal Oxides Supported on Carbon Nanofibers for Hg⁰ Removal from Coal-Fired Flue Gas

• Main Authors: Yongjun Xia, Zhiqiang Liao, Yan Zheng, Zijian Zhou
• Format: Article
• Language: English
• Published: MDPI AG 2018-12-01
• Series: Applied Sciences
• Subjects: coal-fired flue gas; mercury; carbon nanofibers; metal oxides; adsorption
• Online Access: https://www.mdpi.com/2076-3417/8/12/2501

Highly dispersed Mn⁻Ce binary metal oxides supported on carbon nanofibers (MnO_x⁻CeO₂/CNFs(OX)) were prepared for Hg⁰ removal from coal-fired flue gas. The loading value of the well-dispersed MnO_x⁻CeO₂ was much higher than those of many other reported supports, indicating that more active sites were loaded on the carbon nanofibers. In the present study, 30 wt % metal oxides (15 wt % MnO_x and 15 wt % CeO₂) were successfully deposited on the carbon nanofibers, and the sorbent yielded the highest Hg⁰ removal efficiency (>90%) within 120⁻220 °C under a N₂/O₂ atmosphere. An increase in the amount of highly dispersed metal oxides provided abundant active species for efficient Hg⁰ removal, such as active oxygen species and Mn⁴⁺ cations. Meanwhile, the carbon nanofiber framework provides the pathway for charge transfer during the heterogeneous Hg⁰ capture reaction processes. Under a N₂+6%O₂ atmosphere, a majority of Hg⁰ was removed via chemisorption reactions. The effects of flue gas composition were also investigated. O₂ replenished the active oxygen species on the surface and thus greatly promoted the Hg⁰ removal efficiency. SO₂ had an inhibitory effect on Hg⁰ removal, but NO facilitated Hg⁰ capture performance. Overall, carbon nanofibers seems to be a good candidate for the support and MnO_x⁻CeO₂/CNFs(OX) may be promising for Hg⁰ removal from coal-fired flue gas.