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 K 2 O and K 2 SO 4 in the flue gas significantly diminishes the Hg⁰ removal performance of the MnO x /HZSM-5 (MH) adsorbent, indicating a lack of tolerance to potassium species. To enhance its K-resistant and further improve the Hg⁰ removal performance, CuCl 2 was applied to modify the MH adsorbent. The optimal CuCl 2 loading of 5 wt% (noted as 5CCMH) and Hg⁰ removal efficiency reach 96.8–100 % between 150 and 250 °C. It was found that CuCl 2 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 HgCl 2 and HgO via active chlorine species (Cl*) and chemisorbed oxygen (O α). Due to the preferential interaction of Cl species with K species, active Cu and Mn species are preserved, enhancing the K 2 O and K 2 SO 4 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 K 2 O and K 2 SO 4. This study provides guidance for designing active adsorbents in power plants using high-alkali-content coal and offers theoretical support for practical applications. • The 5 wt% CuCl 2 -modified MnO x /HZSM-5 exhibited outstanding performance and resistance to K-poisoning for Hg⁰ removal. • Introducing of CuCl 2 into MnO x /HZSM-5 significantly enhances its reduction ability and surface acidity. • CuCl 2 doping inhibits the formation of Mn⁴⁺ on the adsorbent. • Cl species preferentially interact with K species, thereby protecting active Cu and Mn species. [ABSTRACT FROM AUTHOR]