High performance and K-poisoning resistance of CuCl2-MnOx/HZSM-5 adsorbent for elemental mercury removal

Manganese-based adsorbents have been extensively researched for the removal of Hg0 from coal-fired flue gas. However, the presence of K2O and K2SO4 in the flue gas significantly diminishes the Hg0 removal performance of the MnOx/HZSM-5 (MH) adsorbent, indicating a lack of tolerance to potassium species. To enhance its K-resistant and further improve the Hg0 removal performance, CuCl2 was applied to modify the MH adsorbent. The optimal CuCl2 loading of 5 wt% (noted as 5CCMH) and Hg0 removal efficiency reach 96.8–100 % between 150 and 250 °C. It was found that CuCl2 modification decreased the surface area, enhanced both reduction ability and surface acidity with two active sites Cu2+ and Cl−, facilitating effective reactions with Hg0 to form HgCl2 and HgO via active chlorine species (Cl*) and chemisorbed oxygen (Oα). Due to the preferential interaction of Cl species with K species, active Cu and Mn species are preserved, enhancing the K2O and K2SO4 resistance of 5CCMH absorbent with high performance for removal Hg0. Additionally, the presence of Cu2+ and Mn4+ contributes abundant acid sites and redox ability, allowing the 5CCMH adsorbents to maintain high Hg0 removal efficiency even after the introduction of K2O and K2SO4. This study provides guidance for designing active adsorbents in power plants using high-alkali-content coal and offers theoretical support for practical applications.