Preparation of Cu-Mn and Cu-Mn-Ce Oxide/Mesoporous Silica via Silicate Exfoliation for Removal of NO and Hg0
Aerosol and Air Quality Research
Cu-Mn and Cu-Mn-Ce oxide-incorporated mesoporous silica was formed by hydrothermally exfoliating silicate, and the physicochemical properties and NO/Hg 0 removal efficiency were investigated. The exfoliation induced structural reformation, resulting in a large specific surface area and the uniform dispersion of metal oxides on the surface. The transfer of valences between Cu 2+ and Mn 3+ in the Cu-Mn silica contributed to the single reduction peak displayed in the H 2 temperature-programmed
... ture-programmed reduction profiles and the high Mn 4+ /Mn and Cu + /Cu ratios observed via X-ray photoelectron spectroscopy (XPS). The high oxygen lability of the Cu-Mn silica may have inhibited its ability to remove NO. By contrast, when SO 2 was present, incorporating Ce enhanced the NO removal efficiency due to the increased number of Brønsted acid sites. Hg 0 removal tests indicated that adsorption was the primary removal mechanism for both the Cu-Mn and the Cu-Mn-Ce silica samples. Cu2Mn8 exhibited the highest Hg removal efficiency, suggesting that Ce's enhancing effect on Hg 0 adsorption was diminished when a large amount of Mn was present. Of the gaseous components, the adsorbed HCl was mainly responsible for the oxidation and subsequent adsorption of Hg 0 . Furthermore, with the addition of SO 2 , the competitive adsorption of SO 2 and the resulting HgCl 2 did not decrease the Cu-Mn silica's efficiency in oxidizing Hg 0 , but the oxidized Hg was less adsorptive.