Oxidative immobilization of gaseous mercury by [Mo3S(S2)6]2- functionalized layered double hydroxide

Every year, thousands of tons of gaseous mercury are released globally, prompting the World Health Organization (WHO) in 2020 to designate mercury as one of the top 10 chemicals posing severe health risks. Therefore, the removal of Hg0 from the environment is imperative. Our study introduces [Mo3S(S2)6]2- ≡ [Mo3S13]2- functionalized layered double hydroxides nanoparticles, (LDH─Mo3S13), as an excellent sorbent for gaseous Hg0. This material achieved a remarkable sorption capacity of ~2.33×103 mg/g for gaseous elemental Hg0. Such an enormously high sorption capacity makes this material the lead non-platinum-based Hg0 gas sorbent known to date. Though sulfides of the Mo3S(S2)6 species of the LDH predominantly serve as active sites for capturing gaseous Hg, their integration is essential for the accessibility of gaseous Hg0 to the individual reactive active site between the LDH lamella. A heterogeneous reaction between the gaseous Hg0 vapor and the solid LDH─Mo3S13 sorbent enables the oxidation of gaseous Hg0 to Hg2+ and the reduction of the S22- groups to 2S2- yield redox-driven formation of the nanocrystalline HgS onto the solid sorbents. Density Functional Theory (DFT) calculations provide further insights into the interactions between Hg0 and S indicating adsorption energy ranging from -8 kJ/mol to -19 kJ/mol. Moreover, the overall reaction enthalpy was calculated as -4048 kJ/mol, suggesting the spontaneous formation of HgS. This investigation unveils an atomistic understanding of the redox-driven interactions between Hg0 vapor and Mo3S(S2)6 species, as well as the remarkably high mercury sorption capacity of LDH─Mo3S13, highlighting the potential of metal sulfide functionalized LDHs for the efficient immobilization of gaseous elemental mercury.

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, Copyright © 2024 American Chemical Society, after peer review and technical editing by the publisher. To access the final edited and published work see [https://pubs.acs.org/doi/10.1021/acs.chemmater.4c01098].”