Density functional theory study on the structural evolution of mercury sulfide adsorbed on zinc sulfide

The unclear structure evolution of mercury sulfides on metal sulfides (MSs) impedes the mechanistic understanding of the mercury immobilization processes on MSs-based sorbents. This work adopted the earth-abundant ZnS to investigate the transformation of the compositional unites of cinnabar comprised of repeated ...S-Hg-SHg-S-Hg... sequences, on ZnS(1 1 0) surface. The results show that mercury mono-sulfide (HgS) was stable on ZnS (110) surface, indicating it would further grow into HgS2 or Hg2S unit. However, after exploring the stability of HgS2 and Hg2S, it was found that HgS2 was relatively stable, while Hg2S dissociated into HgS and an isolated Hg atom on ZnS(1 1 0) surface. This phenomenon suggests that no ...S-Hg-S-Hg-S-Hg... chain was formed. The mechanistic understanding of the transformation of metal sulfide species on the ZnS surface is of great help to not only explain the evolution of mercury on metal sulfides, but also design efficient metal sulfides for mercury removal from anthropogenic sources.