Binding of Mercury Species and Typical Flue Gas Components on ZnS(110)

Abstract

Environmentally benign zinc sulfide (ZnS), consisting entirely of “active” sites, has shown promising efficiency for capturing mercury from flue gas in recent experimental studies. In this work, the binding mechanism of Hg0 on the ZnS(110) surface was investigated by the density functional theory (DFT) method. Meanwhile, the binding of two additional mercury forms, HgCl and HgCl2, and three essential flue gas components, H2O, SO2, and HCl, and their further effects on the strength of Hg0 binding on the ZnS(110) surface were also evaluated. The results showed that, consistent with experimental observations, Hg0 can be chemisorbed on the ZnS(110) surface with binding energies (BEs) as high as −87.80 kJ/mol. The enhanced electrostatic characteristics on the activated surface, especially the Zn sites, are beneficial to exciting the outer-shell electrons of Hg0 and thereby enhancing the binding strength of the material. HgCl and HgCl2 were found to be chemisorbed with the highest BEs of −174.33 and −132.79 kJ/mol, respectively. Moreover, H2O was found to have a positive effect on Hg0 binding, whereas SO2 and HCl have negligible effects. Our theoretical calculations demonstrate that ZnS has great potential to serve as a novel sorbent for the efficient removal of mercury from coal-combustion flue gas.

Multiform Sulfur Adsorption Centers and Copper-Terminated Active Sites of Nano-CuS for Efficient Elemental Mercury Capture from Coal Combustion Flue Gas

“…The activation energies of Hg 0 adsorbed on the Cu-terminated sites of CuO and on Zn of ZnS are around 100 kJ/mol. ,, This value is lower than that for mercury sulfides. Therefore, it is quite possible that the desorption peak at 120 °C was assigned to Hg–Cu amalgam over nano-CuS, like the Hg–Zn amalgam on the ZnS surface . Moreover, this desorption temperature is quite near the desorption temperature of the Hg–Ag amalgam .…”

“…Therefore, it is quite possible that the desorption peak at 120 °C was assigned to Hg−Cu amalgam over nano-CuS, like the Hg−Zn amalgam on the ZnS surface. 61 Moreover, this desorption temperature is quite near the desorption temperature of the Hg−Ag amalgam. 62 To further confirm this point, extensive Hg-TPD testing was conducted over copper powder.…”

“…The peak centered at 201 °C was assigned to metacinnabar (β-HgS), and the peak located at 303 °C was due to the decomposition of cinnabar (α-HgS). ,, The decomposition energy for mercury sulfides has been reported to be from 135 to 185 kJ/mol . The activation energies of Hg 0 adsorbed on the Cu-terminated sites of CuO and on Zn of ZnS are around 100 kJ/mol. ,, This value is lower than that for mercury sulfides. Therefore, it is quite possible that the desorption peak at 120 °C was assigned to Hg–Cu amalgam over nano-CuS, like the Hg–Zn amalgam on the ZnS surface .…”

Efficient Removal of Elemental Mercury from Coal-Fired Flue Gas over Sulfur-Containing Sorbent at Low Temperatures

“…There was a well-resolved peak at about 200 °C, which could be ascribed to the release of β-HgS. 29,30…”

Nanosized Copper Selenide Functionalized Zeolitic Imidazolate Framework‐8 (CuSe/ZIF‐8) for Efficient Immobilization of Gas‐Phase Elemental Mercury

“…The desorption/decomposition peak in the Hg‐TPD pattern of Hg‐laden 0.8NC‐ZIF centering at 265 °C indexed to the characteristic decomposition temperature of HgSe . Although the Cu‐terminated sites in CuSe probably acted as the adsorption center for Hg 0 capture in metal chalcogenides, the mercury in as‐formed amalgam will be trapped by Se 2− immediately due to the exceedingly high affinity between mercury and Se 2− . This contributes to that the adsorbed mercury exists primarily as HgSe instead of Hg‐Cu amalgam over the 0.8NC‐ZIF surface.…”