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

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-delta)O-4 was less than that on the corresponding (Fe3-xMnx)(1-delta)O-4, 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 equivalent to Fe-III-OH and few Mn4+ cations on the surface reacted with SO2 at lower temperatures (100-150 degrees C), so SO2 poisoning resistance improved at lower temperatures due to the incorporation of Ti. Especially, (Fe2Ti0.5Mn0.5)(1-delta)O-4 showed an excellent capacity (4.2 mg g(-1)) for elemental mercury capture in the presence of a high concentration of SO2 at 150 degrees C. Meanwhile, (Fe2Ti0.5Mn0.5)(1-delta)O-4 with the saturation magnetization of 30.6 emu g(-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-delta)O-4 may be a promising candidate catalyst for elemental mercury capture. (c) 2010 Elsevier B.V. All rights reserved.