Abstract
Understanding the characteristics of pyrite-phase transition metal sulfides for the adsorption and desorption of gaseous elemental mercury (Hg0) is of vital significance for their applications in gaseous Hg0 capture. In this study, the adsorption and desorption of gaseous Hg0 onto pyrite-phase transition metal sulfides (i.e., FeS2/TiO2, CoS2/TiO2, and NiS2/TiO2) were compared, and the mechanisms of their differences were revealed by the kinetic analysis. The Co/NiS and SS bonds in dumbbell-shaped CoS2 and NiS2 were not entirely broken after oxidizing physically adsorbed Hg0, whereas the FeS and SS bonds in dumbbell-shaped FeS2 were. Thus, the activation energies of CoS2/TiO2 and NiS2/TiO2 for oxidizing physically adsorbed Hg0 were smaller than that of FeS2/TiO2, causing the stronger abilities of CoS2/TiO2 and NiS2/TiO2 to oxidize physically adsorbed Hg0 than that of FeS2/TiO2. However, the bonding strengths of Hg-S in HgS adsorbed on dumbbell-shaped CoS2 and NiS2 were relatively weaker because of the sharing of S2− in HgS with S− and Co2+/Ni2+, causing the decreases in heat stabilities of HgS adsorbed on CoS2/TiO2 and NiS2/TiO2. Therefore, HgS adsorbed on CoS2/TiO2 and NiS2/TiO2 can be voluntarily decomposed to release gaseous Hg0, which should be combined with FeS2/TiO2 for the emergency treatment of liquid Hg0 leakage indoors.
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