Molecular-Level Insights into Efficient Immobilization of Gas-Phase Elemental Mercury by a Selenium Cluster-Functionalized Carbon Surface: A DFT Study

Abstract

Reducing mercury emissions from industrial discharge gases remains an insurmountable challenge. Selenides have been shown to be promising Hg0 sorbents, and the structure of the selenide cluster is one of the determining factors for the absorption capacity of Hg0. In this study, density functional theory was adopted to reveal the removal mechanism of mercury from selenium cluster-loaded activated carbon (AC) at the molecular level. It is found that the mercury adsorption performance of AC functionalized by a Se n (n ≤ 8) cluster varies greatly. The effect of a single Se atom on the adsorption efficacy of mercury on the AC surface is minimal. Especially, Se6 and Se8 cyclic clusters supported on the AC surface can promote the physical adsorption of mercury. Notably, the AC surface modified by chain clusters composed primarily of Se2 dimers, and Se3 trimers can transform physical adsorption into chemisorption with superior adsorption performance to Hg0. Additionally, all selenium-functionalized AC surfaces have high affinity for HgO molecules. The Se2 and Se3 cluster-functionalized AC surface shows superior performance for the efficient sequestration of mercury. By providing a comprehensive understanding of mercury removal by Se n /AC, these results could aid in the design and development of Se-based adsorbents for industrial applications of mercury removal.