Multiscale Investigation of 3D Morphology SnSe2 for Mercury Removal from Flue Gas: Experimental and Simulation Studies

Mercury, a toxic heavy metal, poses significant risks to human health. Coal-fired power plants are the largest anthropogenic sources of mercury emissions, making mercury removal from flue gas imperative. Among various mercury adsorbents, metal selenides show promising potential in mercury capture. Here, we reported the synthesis of a novel three-dimensional hierarchical flower-like material, SnSe2, and its debut application in flue gas mercury capture. Under the influence of low-coordinated selenium, the introduction of abundant selenium vacancy defects led to the exposure of additional active sites in the adsorbent. Additionally, the presence of Sn enhanced gas selectivity and promoted electron transfer processes, thereby augmenting Hg0 adsorption and oxidation performance. Benefiting from these advantages, SnSe2 exhibited superior mercury removal performance over a wide temperature range (30–180 °C), with a saturated mercury adsorption capacity of 2027.23 μg/g, surpassing that of commercial activated carbon. Furthermore, the presence of NO in flue gas improved mercury adsorption performance, while high concentrations of SO2 do not affect mercury removal efficiency, as elucidated by adsorption kinetics models. Moreover, the mercury adsorption mechanism was demonstrated through mercury temperature-programmed desorption (Hg-TPD) and density functional theory (DFT) calculations. Finally, toxicity characteristic leaching procedure (TCLP) experiments confirmed SnSe2 as an efficient and permanent adsorbent for mercury, offering insights into the application of novel mercury removal materials.