Capture of gaseous elemental mercury from flue gas using a magnetic and sulfur poisoning resistant sorbent Mn/γ-Fe2O3 at lower temperatures

Abstract

A series of Mn/γ-Fe2O3 were synthesized to capture elemental mercury from the flue gas. Mn4+ cations and cation vacancies on the surface played important roles on elemental mercury capture by Mn/γ-Fe2O3. Furthermore, the reaction route of elemental mercury oxidization was dependent on the ratio of Mn4+ cations to cation vacancies. As a result, the capacities of 15%-Mn/γ-Fe2O3-250 for elemental mercury capture were generally higher than those of 30%-Mn/γ-Fe2O3-400. SO2 mainly reacted with ≡FeIII–OH and only a small amount of ≡Mn4+ reacted with SO2, so the presence of a high concentration of SO2 resulted in an insignificant effect on elemental mercury capture by 15%-Mn/γ-Fe2O3-250 at lower temperatures. The capacities of 15%-Mn/γ-Fe2O3-250 for elemental mercury capture in the presence of 2.8gNm−3 of SO2 were more than 2.2mgg−1 at <200°C. Meanwhile, 15%-Mn/γ-Fe2O3-250 can be separated from the fly ash using magnetic separation, leaving the fly ash essentially free of sorbent and adsorbed HgO. Therefore, 15% Mn/γ-Fe2O3-250 may be a promising sorbent for elemental mercury capture.