Removal of gas-phase Hg0 by Mn/montmorillonite K 10

Abstract

Mn/montmorillonite K 10 (Mn/MK10) prepared by impregnation method was studied to remove Hg⁰ in simulated coal-fired flue gas. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). Effects of manganese loading value, reaction temperature and flue gas components on Hg⁰ removal efficiency were investigated. The results indicated that 4% Mn/MK10 was the optimal sample with outstanding Hg⁰ removal efficiency over the temperature range of 100–400 °C. The characteristic analysis demonstrated that amorphous MnO₂ and active oxygen were crucial for Hg⁰ removal. Besides, NO had a promoting effect due to the formation of Hg(NO₃)₂. The addition of only 5 ppm HCl led to excellent Hg⁰ removal performance as HCl enhanced Hg⁰ conversion to HgCl_x. The inhibition effect of SO₂ could be counteracted in the presence of NO and/or HCl. The Hg⁰ removal capacity showed a relative decrease when H₂O (g) was added to simulated flue gas. Moreover, Hg⁰ removal performance was maintained at 80–99% (NO/SO₂ = 0.26–1.71) in simulated flue gas without HCl, which appeared to be promising in industrial application.