Removal of elemental mercury from simulated flue gas by ZSM-5 modified with Mn-Fe mixed oxides

Zeolite (ZSM-5), as a kind of carbon-free sorbent or catalyst, has been widely applied in many fields due to its big surface area, good chemical and thermal stability, and excellent adsorption performance. In this study, Mn-Fe modified ZSM-5 are synthesized via sol-gel approach and employed for elemental mercury (Hg-0) removal from simulated flue gas at low temperature. The results show that pure ZSM-5 shows poor mercury capture ability with Hg-0 removal efficiency of similar to 8.5-18.8% at 100-300 degrees C. Mn or Fe modification can both efficiently enhance the Hg-0 removal efficiency of the ZSM-5. The sorbent with Mn/Fe molar ratio of 1:2 exhibits the optimal mercury capture ability with the highest Hg-0 removal efficiency near 100% at temperatures of 200 and 250 degrees C due to the significant synergy effect between Mn2O3 and Fe2O3. The presence of NO has a negligible effect on the Hg-0 removal performance of Mn/ZSM-5 and Mn1Fe2/ZSM-5, while the existence of SO2 considerably degrades the Hg-0 capture performance of Mn/ZSM-5 owing to competing adsorption and side reactions. Fe addition can protect Mn active sites from SO2 poisoning and thereby enhancing the SO2 resistance of Mn/ZSM-5 to some extent.