Gaseous Elemental Mercury Removal by Magnetic Fe-Mn-Ce Sorbent in Simulated Flue Gas

摘要

A magnetic sorbent of Ce-doped Fe-Mn sorbent (Fe-Mn-Ce) was synthesized to capture gaseous elemental mercury from coal-fired flue gas. The physical and chemical properties of Fe-Mn-Ce sorbent were characterized by N2 adsorption, vibrating sample magnetometer, X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy (XPS). The mercury removal capability of Fe-Mn-Ce sorbent was tested in a fixed-bed system, and the effect of flue gas temperature and O-2 was investigated. The valence change of Fe 2,p, Mn 2p, Ce 3d, O 1s, and Hg 4f on the sorbent surface during mercury removal process was analyzed. Finally, the mechanism of mercury removal by the Fe-Mn-Ce sorbent was explored. The result shows that the synthesized Fe-Mn-Ce sorbent consists of many extremely small nanoparticles, contains a polycrystalline structure, and shows good mercury removal performance. High temperature is beneficial to mercury removal by the Fe-Mn-Ce sorbent, but the 6% O-2 in flue gas plays a negligible role. XPS analysis shows that the Mn existing in the Fe-Mn-Ce sorbet is mainly in the states of Mn3+ and Mn3+, and Ce is mainly present in the form of Ce4+ and Ce3+. The oxygen existing in the Fe-Mn-Ce sorbent includes adsorption oxygen and lattice oxygen. During the progress of mercury removal, some Mn4+ cations are reduced to Mn3(+ )cations, with part of adsorption oxygen converting into lattice oxygen, and there is no obvious change appearing in the spectral regions of Fe 2p and Ce 3d. Mercury capture by the Fe-Mn-Ce sorbent follows the Mars-Maessen mechanism with the adsorption product of mercurous oxide.