The adsorption mechanisms of Hg0 on marcasite-type metal selenides: The influences of metal-terminated site

Compared with pyrite-type bulk, the anisotropic structure of marcasite-type bulk can produce more active sites, which may promote the performance on mercury removal. Therefore, the immobilization mechanisms of elemental mercury (Hg-0) on marcasite-type metal selenides (MSe2) with different metal-terminated sites (Fe, Co and Cu) were systematically investigated based on density functional theory. The calculated results indicate that the adsorptions of Hg-0 over different MSe2 surfaces belong to physisorption. The partial density of states analyses suggest that the Hg-0 adsorptions at metal sites are mainly caused by the hybridizations between the 6s orbital of Hg atom and the 4p orbital of metal atoms. The binding affinities of Hg atom at different metal sites are inversely proportional to the number of electrons in antibonding e(g) orbitals. In contrast, there are dual effects in the interactions between Hg-0 and Se sites: the attractions from the 5s orbital of Se atoms and the repulsions from the 4p orbital of Se atoms. The influences of metal-terminated sites on the adsorptions of Hg-0 at Se sites are relatively limited. Thus, this work provides guidance for the future design of marcasite-type metal selenide-based sorbents.

Automated summary

This study systematically investigated the immobilization mechanisms of elemental mercury on marcasite-type metal selenides based on density functional theory, finding that the adsorptions of Hg-0 at metal sites are mainly influenced by the 4p orbitals of metal atoms, while interactions at Se sites are affected by both the 5s and 4p orbitals of Se atoms. The influences of metal-terminated sites on Hg-0 adsorptions at Se sites are relatively limited.