Preparation of Cu-Mn and Cu-Mn-Ce Oxide-incorporated Mesoporous Silica via Silicate Exfoliation for the Removal of NO and Hg^0

Cong-Jhen Lin ； Chuan-Lin Chang ； Chih-Fu Tseng ； Hong-Ping Lin ； Hsing-Cheng Hsi

《Aerosol and Air Quality Research》 19卷6期 (2019/06) Pp. 1421-1438

https://doi.org/10.4209/aaqr.2018.10.0389

摘要

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 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.

關鍵字

Silicate exfoliation ； Coal combustion ； Mercury ； Multi-pollutant ； Metal oxide