Elemental mercury removal from coal-fired flue gas using recyclable magnetic Mn-Fe based attapulgite sorbent

Magnetic manganese-iron modified attapulgite sorbents (xMnFAy) were synthesized and employed for Hg-0 removal from coal-fired flue gas. The effects of calcination temperature, MnO2 loading amount, reaction temperature, as well as the individual flue gas components on Hg-0 removal were investigated. The 0.1MnFA loaded with 10 wt% MnO2 and calcined at 450 degrees C exhibited the optimal Hg-0 removal activity, above 80% Hg-0 removal at a high GHSV of 4 x 10(5) h(-1)center dot O-2 promoted Hg-0 removal via recovering surface oxygen and high valence metal ions (Fe3+ and Mn4+). NO improved Hg-0 capture due to the formation of adsorbed NO2 and nitrate species, which functioned as active sites for mercury oxidation. SO2 prohibited Hg-0 retention because of its competitive adsorption against Hg-0 for the active sites and the sulfation of the sorbent. Besides, SO2 could reduce the high valence metal ions to a lower valence, which hampers Hg-0 oxidation. The presence of NO could overcome the inhibitive effect of SO2 on Hg-0 removal because the adsorbed NO2 and nitrate species were still retained on the sorbent surface in the case of SO2 existence center dot H2O inhibited Hg-0 removal because of the competitive adsorption. 0.1MnFA could maintain its good Hg-0 retention ability after five regeneration cycles. This work contributes to developing the cost-effective sorbents for Hg-0 removal from coal-fired flue gas, as well as maximizing the utilization of attapulgite clay.

Automated summary

Magnetic manganese-iron modified attapulgite sorbents were synthesized and shown to have optimal Hg-0 removal activity in coal-fired flue gas under certain conditions, which could potentially reduce costs and maximize the utilization of green energy sources.