Different Crystal Forms of ZnS Nanomaterials for the Adsorption of Elemental Mercury

Abstract

ZnS is a promising sorbent in recovering Hg0 from industrial flue gas due to its excellent Hg0 adsorption capacity. However, the internal structure–activity relationship still needs to be further clarified. In this work, ZnS sorbents with different structures were synthesized with the hydrothermal method by tuning the temperature. The samples had significant differences in the crystallinity, morphology, particle size, and sulfur (S) active sites. The results indicated that Hg0 removal performance was determined by the specific surface area and S active sites. ZnS synthesized at low temperatures (80-ZnS and 120-ZnS) had a larger surface area, while the S sites on the high-temperature-synthesized sample (160-ZnS) were more active for Hg0 adsorption. The 160-ZnS sample exhibited a much higher Hg0 adsorption amount per unit surface area. Further characterization revealed that S2 2– and S x were the main active sites for Hg0 adsorption. S x existed in the form of long-chain polysulfur (L-S x ) on 80-ZnS and 120-ZnS, while it exhibited in the form of short-chain polysulfur (S-S x ) on 160-ZnS. L-S x had negligible adsorption ability, while S-S x had a high affinity for Hg0. Hg0 can react with S2 2– and S-S x , forming α-HgS and β-HgS, respectively. The new insight in this work can provide theoretical guidance for the design and structure optimization of ZnS, facilitating its practical industrial application.

Favorably adjusting the pore characteristics of copper sulfide by template regulation for vapor-phase elemental mercury immobilization

“…Compared with that under pure N 2 , both O 2 and SO 2 slightly inhibited the Hg 0 adsorption activity of 9CuS-BTC, which was probably attributed to the competitive adsorption between flue gas components and Hg 0 for the active ligands. 20,43 In addition, due to an identical competitive mechanism, 14 H 2 O in SFG played a more dominant role in suppressing the Hg 0 adsorption efficiency of 9CuS-BTC, which was decreased by approximately 10% when 8% H 2 O was added. It should be noted that, although the primary flue gas components possibly existing at the tail part of the industrial flue gas treatment process exhibited inhibitive effects, more or less, on the Hg 0 removal performance of 9CuS-BTC, all the experiments were conducted with a 9CuS-BTC dosage as low as 1 mg.…”

“…14,19 In this case, Hg 0 can be readily oxidized and subsequently immobilized over unsaturated suldes in an in situ manner, e.g., Hg 0 + S 1À / HgS + S 2À . 20 Contrarily, for most of the other MSs, due to the absence of unsaturated suldes, only metal cations can accept the electrons donated by Hg 0 , e.g., Hg 0 + M 2+ / Hg 2+ + M 0 , where M represents the metal cation, while the reaction Hg 0 + S 2À / HgS goes against the electron conservation principle, and the oxidized mercury (Hg 2+ ) must migrate along the MSs surface to be nally immobilized by divalent saturated suldes in an ex situ manner, e.g., (Hg 2+ + S 2À / HgS). 21 Thus, based on the previously mentioned mechanistic and theoretical analyses, CuS should exhibit an outstanding performance for Hg 0 capture if the unsaturated ligands are adequately accessible during the adsorption process.…”

“…, Hg 0 + S 1− → HgS + S 2− . 20 Contrarily, for most of the other MSs, due to the absence of unsaturated sulfides, only metal cations can accept the electrons donated by Hg 0 , e.g. , Hg 0 + M 2+ → Hg 2+ + M 0 , where M represents the metal cation, while the reaction Hg 0 + S 2− → HgS goes against the electron conservation principle, and the oxidized mercury (Hg 2+ ) must migrate along the MSs surface to be finally immobilized by divalent saturated sulfides in an ex situ manner, e.g.…”

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

“…Based on the above analyses, two possible pathways can be deduced for Hg 0 2− to form HgS (2Hg 0 + S 2 2− → 2HgS). 39,40 HgS is the final product of Hg 0 adsorption. In order to clarify the detailed effect of O 2 on Hg 0 adsorption, the surface chemistry of O-MoS 2 after adsorbing Hg 0 under 6% O 2 (used O-MoS 2 under O 2 ) was analyzed by XPS.…”

“…Based on the above analyses, two possible pathways can be deduced for Hg 0 adsorption over O-MoS 2 nanosheets: (i) Hg 0 first reacts with Mo 5+ to form [Hg·Mo] and then migrates to neighboring sulfur sites by forming HgS (Hg 0 + Mo 5+ –S → [Hg·Mo]–S, [Hg·Mo]–S → [Mo 4+ ] + HgS); (ii) Hg 0 directly reacts with S 2 2– to form HgS (2Hg 0 + S 2 2– → 2HgS). , HgS is the final product of Hg 0 adsorption.…”