SO₂ Tolerance and Mechanism of Elemental Mercury Removal from Flue Gas by a Magnetic Recyclable Fe₆Mn_0.8Ce_0.2O_y Sorbent

Abstract

A Ce-doped Fe−Mn magnetic sorbent (Fe 6 Mn 0.8 Ce 0.2 O y ) was developed using the coprecipitation method. The effects of O 2 , H 2 O, flue gas temperature, SO 2 concentration, and Ce doping on the SO 2 tolerance of the Fe 6 Mn 0.8 Ce 0.2 O y sorbent for mercury removal were explored in a fixed-bed system. Combined with mercury temperature-programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS) analysis, the mechanism of mercury removal by the Fe 6 Mn 0.8 Ce 0.2 O y sorbent in the presence of SO 2 was analyzed. The results show that the Fe 6 Mn 0.8 Ce 0.2 O y sorbent is a promising sorbent for circulating mercury removal with high SO 2 tolerance. Ce doping significantly enhances the SO 2 tolerance of the Fe 6 Mn 0.8 Ce 0.2 O y sorbent for mercury removal by protecting the Mn 4+ active sites from SO 2 poisoning. This is because Ce has a stronger affinity with SO 2 compared to that of Mn, and most of SO 2 will preferentially react with CeO 2 instead of MnO 2 to form Ce 2 (SO 4 ) 3 . O 2 in flue gas improves the SO 2 tolerance of the Fe 6 Mn 0.8 Ce 0.2 O y sorbent by timely supplementing the oxygen vacancies. H 2 O coexisting with SO 2 in flue gas further reduces the mercury removal rate because of the competitive adsorption between H 2 O and mercury. Mercury is mainly adsorbed by MnO 2 in the Fe 6 Mn 0.8 Ce 0.2 O y sorbent by the Mars−Maessen mechanism, and SO 2 in flue gas causes the generation of a small amount of Hg 2 SO 4 and HgSO 4 .

Mechanism‐based tuning of room‐temperature ferromagnetism in Mn‐doped β‐Ga2O3 by annealing atmosphere

“…By fitting the plot of ( αhν ) 2 versus hν , the bandgaps of GMO–air and GMO–O 2 are obtained as 4.98 and 5.18 eV, respectively. It is more V O s in GMO–air that results in lower optical transmittance and smaller bandgap, owing to the contributions of more occupied defect levels 28,29 . Figure 4B shows the PL spectra of the GMO films.…”

“…It is more V O s in GMO-air that results in lower optical transmittance and smaller bandgap, owing to the contributions of more occupied defect levels. 28,29 Figure 4B shows the PL spectra of the GMO films. The emission band can be divided into four bands centered at about 345, 415, 440, and 480 nm, respectively.…”

Graphitic Carbon Nitride for Gaseous Mercury Emission Control: A Review

“…As for noncarbon adsorbents, fly ash , and natural minerals − display low intrinsic Hg 0 affinity due to their low surface areas and pore volumes. Although some zeolites have large surface areas, they still exhibit low inherent Hg 0 affinity owing to inadequate active sites. − Metal oxides possess good Hg 0 oxidation ability; however, they are very sensitive to flue gas. − Carbonaceous materials have also been widely studied owing to their ample sources and luxuriant pore structures, such as activated carbon, − petroleum coke, − and biochar. − In addition, some novel adsorbents emerged recently, i.e., metal–organic frameworks (MOFs) and MXene (metal nitride or metal carbide) . However, their intrinsic Hg 0 affinities for pristine MOFs and MXene are very low.…”

The Synthesis of FeCl3-Modified Char from Phoenix Tree Fruit and Its Application for Hg0 Adsorption in Flue Gas

“…However, Hg 0 is hard to remove because of its chemical stability. Therefore, the removal of Hg 0 from flue gas is an important problem that poses several difficulties [11,12].…”