Sustained-release of interlayer chloride in iron oxychloride for mercury oxidation from industrial flue gas

Abstract

Conversion of gaseous elemental mercury (Hg0) to its higher valence state is essential for mercury control using the current air pollution devices from industrial flue gas. Traditional technologies often use selective catalytic reduction (SCR) units to enhance the Hg0 oxidation performance but highly depend on the high-temperature catalysts, the presence of HCl, and the downstream liquid absorption system. This study proposes a novel method coupled with a low-temperature catalyst and a dust removal device to realize mercury immobilization. The iron oxychloride (FeOCl) 2D-nanosheets are put into practice as the low-temperature catalyst. The results indicate superior Hg0 oxidation performance at low oxidizing conditions and a wide temperature window (100–300 °C). The FeOCl catalyst can further combine with MnO2 to achieve mercury fixation. The outstanding property is attributed to the chloride with high activity between the Van Der Waals layer of FeOCl. The oxidative products HgCl2(g) in high yield are attributed to the low Fe-Cl bonding energy in FeOCl relative to metal chloride. This study highlights the conversion process of gaseous Hg0 to HgCl2 in oxidized form and provides a new idea that can be used in conjunction with dust removal equipment to expand the removal method of flue gas mercury.