In Situ Emergency Disposal of Liquid Mercury Leakage by Fe-Containing Sphalerite: Performance and Reaction Mechanism

Abstract

The indoor concentration of mercury is often higher than the reference concentration due to the historic accidents with mercury-containing devices. Therefore, there is a great demand to develop a treatment for the accidental breakage of the devices containing liquid mercury. In this work, Fe-containing sphalerite was developed as a cost-effective sorbent for the in situ emergency disposal of liquid mercury leakage. Fe-containing sphalerite showed an excellent performance for elemental mercury capture at room temperature, with the capacity of much greater than 8.65 mg g–1 and the reaction rate of 4.82 μg g–1 min–1. The formed Hg species on Fe-containing sphalerite was HgS, so it was thermally stable at room temperature, poor leachable and low toxicity to microorganism. The chemical adsorption of elemental mercury on Fe-containing sphalerite mainly followed the Mars–Maessen mechanism and approximately followed a pseudo-zero-order kinetic reaction. The reaction rate of elemental mercury with Fe-containing sphalerite mainly depended on the concentration of Hg0 physically adsorbed on the surface. The physical adsorption of Hg0 on sphalerite was remarkably promoted after the incorporation of Fe, which may be mainly related to the presence of cation vacancies on Fe-containing sphalerite.

Sequestration of Gaseous Hg0 by Sphalerite with Fe Substitution: Performance, Mechanism, and Structure–Activity Relationship

“…Compared to fresh Fe-bearing sphalerite, no obvious change is observed over the Zn 2p, S 2p, O 1s, and Fe 2p regions after the reaction (Figure S5). The binding energy of Hg species on Fe-bearing sphalerite appears at 101.0 and 104.9 eV (Figure ), which is assigned to HgS . Due to the presence of surface lattice O in Fe-bearing sphalerite, the formation of HgO is possible, which was confirmed by TPD (Figure ).…”

“…The binding energy of Hg species on Fe-bearing sphalerite appears at 101.0 and 104.9 eV (Figure 7), which is assigned to HgS. 16 Due to the presence of surface lattice O in Fe-bearing sphalerite, the formation of HgO is possible, which was confirmed by TPD (Figure 8). The Hg-TPD profile displays two desorption peaks at 190 and 350 °C, which are ascribed to the decomposition of β-HgS and α-HgS, respectively, 38 without the appearance of the decomposition peak of HgO at 500 °C.…”

“…This result is consistent with a previous study in which Febearing sphalerite has better activity than sphalerite in the adsorption of liquid mercury at room temperature. 16 Moreover, compared to natural sphalerite, synthetic Fe-bearing sphalerite displayed higher activity in the sequestration of gaseous Hg 0 (Figure S1).…”

“…In a recent study, Liao et al demonstrates experimentally that the introduction of Fe 2+ into sphalerite greatly enhances the immobilization of Hg 0 . 16 This is made possible by the increase in cation vacancies, which results in the promotion of the physical adsorption of Hg 0 to active Zn sites. Moreover, due to the larger radius of Fe 2+ (0.077 nm) compared to Zn 2+ (0.074 nm), the incorporation of Fe 2+ enlarges the lattice of cubic sphalerite.…”

“…However, in most natural sphalerite, no strong correlation was observed between the concentrations of Hg and Fe. In a recent study, Liao et al demonstrates experimentally that the introduction of Fe 2+ into sphalerite greatly enhances the immobilization of Hg 0 . This is made possible by the increase in cation vacancies, which results in the promotion of the physical adsorption of Hg 0 to active Zn sites.…”