The influences of selenium species on mercury removal over pyrite surface: A density functional theory study

摘要

Elemental mercury (Hg0) and selenium species (Se0 and SeO2) are two typical unsolved pollutants in coal combustion flue gas due to their high volatility. The interactions between Hg0 and selenium species play an important role in the mercury pollution control. Thus, the co-adsorption of Hg0 and selenium species on pyrite surface was calculated based on density functional theory (DFT), and the role of selenium species on Hg0 adsorption was systematically investigated. Although there is a weak attraction between Hg0 and Se0, the extremely high affinity from pyrite (FeS2) surface to Se0 results in the powerful occupation for Fe sites. Eventually, the competitive adsorption inhibits the mercury removal performance of pyrite. On the other hand, the effect of SeO2 on Hg0 adsorption is determined by its concentration. Since the low concentration of SeO2 in flue gas, the dissociation of SeO2 can produce a right amount of coordination-absent active sites, which is beneficial for mercury elimination. Therefore, this study is of great significance to the development and regulation of pyrite-based sorbents.