Disordered MoS₂ Nanosheets with Widened Interlayer Spacing for Elemental Mercury Adsorption from Nonferrous Smelting Flue Gas

Abstract

The development of a sorbent with a large elemental mercury (Hg0) adsorption capacity under a high SO2 concentration atmosphere is the key point for mercury emission control from nonferrous smelting (NFS) flue gas. By controlling the degree of crystallization, oxygen incorporation and disorder engineering were simultaneously realized to improve the Hg0 adsorption capacity of MoS2 nanosheets for the first time. The interlayer spacing of oxygen-incorporated MoS2 nanosheets reaches up to 9.4 Å from 6.4 Å of normal MoS2 nanosheets, which enhances the exposure of the active sites. Oxygen-incorporated MoS2 nanosheets display a disordered structure, indicating the declined crystallinity and increased active sites. Benefiting from the above synergistic advantages, oxygen incorporation and structure disorder increases significantly the equilibrium Hg0 adsorption capacity of MoS2 nanosheets to 16.26 mg·g–1 under 6% SO2 atmosphere, which is about 2.5 times larger than that of normal MoS2 nanosheets. Both external mass transfer and chemisorption control Hg0 adsorption on MoS2. Surface Mo5+ and S2 2– act as the main active sites generated by disorder engineering for capturing Hg0, and HgS is the final product of Hg0 adsorption. The simultaneous optimization of structural and chemical properties in this work provides an effective and convenient strategy to improve the Hg0 adsorption capacity of MoS2 nanosheets.

Mechanisms of Gas-Phase Mercury Immobilized by Metal Sulfides from Combustion Flue Gas: A Mini Review

“…The presence of surface vacancies can generally improve the Hg 0 adsorption performance of metal sulfides through reducing the saturation of active sites . For example, the Hg 0 removal efficiency of N–MoS 2 with surface defects was significantly better than that of B–MoS 2 , and DFT calculations suggested that the formation of S vacancy increased the positive potential of the MoS 2 (001) surface, which facilitated the capture of Hg valence electrons. , On the basis of the defect formation energy, the type of formed vacancies over metal sulfides can be determined. The formation of S vacancy can reduce the saturation of adjacent M sites, thereby facilitating the Hg 0 pre-adsorption process at low adsorption temperature .…”

In situ acid etching boosts mercury accommodation capacities of transition metal sulfides

“…6(a) & (b)). Both SO 2 and H 2 O slightly inhibited Hg 0 adsorption on pristine ZnS, probably because of competition for active sites among Hg 0 , SO 2 , and H 2 O 12,16,22 and/or coverage of active sites by the highly concentrated H 2 O 15,37 . O 2 gas is a highly enriched component in industrial flue gases, but it exhibits a negligible influence on Hg 0 adsorption by metal sulfides 10,15,[38][39][40] , so it was not studied in this work.…”

Edge-Enriched Molybdenum Disulfide Ultrathin Nanosheets with a Widened Interlayer Spacing for Highly Efficient Gaseous Elemental Mercury Capture

“…32 To enhance the exposure of the vast sulfur atoms on the basal plane, an oxygen insertion method has been developed previously to enlarge the interlayer spacing of MoS 2 . 33 However, due to the small volume of inserted oxygen atoms, this method cannot improve the thermal stability of MoS 2 . In this aspect, foreign molecule insertion provides a promising candidate because the larger volume of inserted molecules will be more helpful to prevent the structure collapse of MoS 2 nanosheets at a high temperature.…”