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Preparation of Cu-Mn and Cu-Mn-Ce Oxide/Mesoporous Silica via Silicate Exfoliation for Removal of NO and Hg0

Category: Control Techniques and Strategy

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DOI: 10.4209/aaqr.2018.10.0389
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Cong-Jhen Lin1, Chuan-Lin Chang2, Chih-Fu Tseng1,3, Hong-Ping Lin 2, Hsing-Cheng Hsi 1

  • 1 Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 10617, Taiwan
  • 2 Department of Chemistry, National Cheng-Kung University, Tainan 70101, Taiwan
  • 3 Taiwan Power Research Institute, Taiwan Power Company, New Taipei City 23847, Taiwan

Highlights

  • Cu-Mn and Cu-Mn-Ce silica were prepared via silicate-exfoliation method.
  • Silicate-exfoliation caused large surface area and uniform metal oxide dispersion.
  • Ce promoted NO removal with presence of SO2 by increasing Brønsted acid sites.
  • Oxidation followed by adsorption resulted in Hg0 removal for the tested samples.
  • Adsorbed HCl was the key component responsible for Hg0 oxidation and adsorption.

Abstract

Cu-Mn and Cu-Mn-Ce oxide/mesoporous silica samples were fabricated through silicate-exfoliation method and their physicochemical properties and NO/Hg0 removal effectiveness were investigated. Silicate-exfoliation method was shown to induce structural reformation, leading to the large specific surface area and uniform dispersion of metal oxides on the silicate surface. The valence transition between Cu2+ and Mn3+ in Cu-Mn silica contributed to the single reduction peaks presented in the H2-temperature programmed reduction profiles and high Mn4+/Mn and Cu+/Cu ratios observed by the XPS examinations. The labile valence states may lead to the inhibition of NO removal for Cu-Mn samples. In contrast, Ce modification promoted NO removal efficiency in the presence of SO2 due to the increase of Brønsted acid sites. In Hg0 removal tests, adsorption was shown to be the primary removal mechanism for the tested Cu-Mn and Cu-Mn-Ce silica samples. Cu2Mn8 had the greatest Hg removal performance, suggesting that the effect of Ce modification on enhancing Hg0 adsorption was less significant when Mn was present in a great content. The adsorbed HCl was found to be the key gas component responsible for Hg0 oxidation and the subsequent adsorption. Additionally, the competitive adsorption between the possible formed HgCl2 and SO2 did not show to inhibit the Hg0 oxidation by Cu-Mn silica, but the oxidized Hg is less adsorptive by the sample with the presence of SO2.

Keywords

Silicate exfoliation Coal combustion Mercury Multipollutant Metal oxide


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