Elemental mercury removal over MnOx-CoOx-modified HZSM-5 adsorbents: Performance and characterizations

Abstract

In this study, MnOx-CoOx-modified HZSM-5 sorbents were prepared via the ultrasound-assisted impregnation method for Hg0 removal from the coal-fired flue gas. With the introduction of MnOx-CoOx, the Hg0 removal performance exhibited an increasing trend. Given that the mass content of MnOx-CoOx and the molar ratio of Mn/Co were fixed to 12 wt% and 1:3, the sorbent exhibited a relatively high Hg0 removal efficiency of 81% at 150 °C. Compared to virgin MnOx- or CoOx-modified HZSM-5 sorbent, the synergistic effect between MnOx and CoOx generated abundant surface acid sites and active oxygen species, which facilitated the adsorption of Hg0 and accelerated the oxidation of the adsorbed Hg0. Throughout the Hg0 capture cycles, Mn4+ and Co3+ acted as the active sites with HgO being the end product. Among the various gas constitutes, both O2 and NO demonstrated promotional effect on Hg0 removal, while SO2 interfered with the reaction to some degree. With the co-introduction of NO and SO2, an Hg0 removal efficiency of ∼94% was attained. Given its excellent recyclability, this sorbent system shows promising application potential.