New insights into the effects of potassium species on the Hg0 removal performance of MnOx/HZSM-5 adsorbent

In this article, the effects of K species, including K2O, KCl, and K2SO4, on the Hg-0 removal capability of MnOx/HZSM-5 adsorbent were investigated. Adding K2O and K2SO4 interfered with the Hg-0 removal process; as the loading amount of these two K species increased, this adverse impact became more obvious. This was because the added K2O or K2SO4 lowered the acidity and oxidizability of the adsorbents via the interactions with MnOx, which exerted an inhibitory effect on the adsorption and oxidation of Hg-0. By contrast, introducing KCl made almost no adverse impacts on the Hg-0 elimination ability of the adsorbents. With rising the KCl content to 4 wt%, even similar to 92.7% Hg-0 removal efficiency was obtained. This could be attributed to the presence of Cl-; with the guidance of high-valence-state metal cations and O-2, Cl- could be converted to active chlorine species, which was capable of transforming Hg-0 to HgCl2. This finding supplied a theoretical basis for developing new adsorbents that were capable of stably operating in the power plants with high-alkali-content coal utilized.