Molecular-level insights into the immobilization of vapor-phase mercury on Fe/Co/Ni-doped hierarchical molybdenum selenide

A novel and efficient adsorbent (TM-MoSe2, TM = Fe, Co, Ni) for mercury removal was developed and studied. The adsorption of mercury species (Hg-0, HgCl, and HgCl2) and the oxidation of Hg-0 by HCl on TM-MoSe2 (001) surface were explored at molecular level by density functional theory (DFT). The results shown that the Hg-0 adsorption capacity of MoSe2 was improved by the doping of Fe/Co/Ni, which was also confirmed by experiments. The initial Hg-0 removal efficiency of MoSe2-based adsorbents reached 96.4-100.0%. In addition, HgCl was mainly adsorbed on TM-MoSe2 (001) surface in the form of dissociation. The escape of Hg atom from HgCl resulted in the release of Hg-0 again. However, HgCl2 could be fixed well on the surface of adsorbent through molecular adsorption or dissociative adsorption. For the oxidation process of Hg-0 by HCl, it abided with the Langmuir-Hinshelwood mechanism. In comparison with direct oxidation (Hg. HgCl2), two-step pathway (Hg. HgCl. HgCl2) was an achievable reaction route with lower energy. Furthermore, the Hg. HgCl process was the rate-limiting step of the two-step pathway. The proposed adsorption and oxidation mechanism of mercury species on TM-MoSe2 (001) provide advanced strategies on the development of adsorbents for industrial mercury removal.

Automated summary

A novel and efficient adsorbent TM-MoSe2 (TM = Fe, Co, Ni) was developed for mercury removal. The doping of Fe/Co/Ni was found to enhance the Hg-0 adsorption capacity of MoSe2, leading to initial Hg-0 removal efficiency of 96.4-100.0%. The adsorption mechanism of HgCl and HgCl2 varied on the TM-MoSe2 (001) surface, with HgCl2 being fixed well through molecular or dissociative adsorption.