Remarkable effect of the incorporation of titanium on the catalytic activity and SO2 poisoning resistance of magnetic Mn–Fe spinel for elemental mercury capture

Abstract

Tiantium (Ti) was incorporated into non-stoichiometric Mn–Fe spinel to improve its performance for elemental mercury capture. Although the number of Mn4+ cations on (Fe2TixMn1−x)1−δO4 was less than that on the corresponding (Fe3−xMnx)1−δO4, the number of usable cation vacancies for elemental mercury oxidization obviously increased. As a result, elemental mercury capture by Mn–Fe spinel was generally promoted by the incorporation of Ti. Furthermore, SO2 mainly reacted with ≡FeIII–OH and few Mn4+ cations on the surface reacted with SO2 at lower temperatures (100–150°C), so SO2 poisoning resistance improved at lower temperatures due to the incorporation of Ti. Especially, (Fe2Ti0.5Mn0.5)1−δO4 showed an excellent capacity (4.2mgg−1) for elemental mercury capture in the presence of a high concentration of SO2 at 150°C. Meanwhile, (Fe2Ti0.5Mn0.5)1−δO4 with the saturation magnetization of 30.6emug−1 can be readily separated from the fly ash using magnetic separation, leaving the fly ash essentially free of catalyst and adsorbed HgO. Therefore, nanosized (Fe2Ti0.5Mn0.5)1−δO4 may be a promising candidate catalyst for elemental mercury capture.