Adsorption and Oxidation of Elemental Mercury on Chlorinated ZnS

Jun 26, 2018 - Nano-ZnS particles are newly developed alternatives to activated carbons for Hg0 removal from flue gas. We investigated the Hg0 oxidati...
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Cite This: Energy Fuels 2018, 32, 7745−7751

Adsorption and Oxidation of Elemental Mercury on Chlorinated ZnS Surface Hailong Li,† Shihao Feng,† Wenqi Qu,† Jianping Yang,† Suojiang Liu,† and Yang Liu*,‡ †

School of Energy Science and Engineering, Central South University, Changsha 410083, China School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332-0100, United States

‡

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S Supporting Information *

ABSTRACT: Nano-ZnS particles are newly developed alternatives to activated carbons for Hg0 removal from flue gas. We investigated the Hg0 oxidation mechanisms in the presence of chlorine (Cl2) on the (110) surface of ZnS by first-principles calculations. The results show that the Cl2 molecule can dissociate into two Cl ions on the ZnS(110) surface, forming chlorinated ZnS surfaces. Compared to the clean ZnS surface, the chlorinated ZnS surface with dissociated Cl ions exhibit enhanced binding affinity over Hg0 with promoted Hg0 oxidation efficiency (Hg0 → HgCl2). The active Cl ions on ZnS surface can directly interact with Hg0 to form HgCl2, following the typical Eley−Rideal mechanism rather than the Langmuir− Hinshelwood mechanism.

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INTRODUCTION Mercury is harmful to human health and global environment.1,2 Mercury removal from large anthropogenic sources of mercury emissions, especially coal-fired boilers, has attracted the attention of governments around the world, including China and the United States.3,4 On August 16, 2017, the Minamata Convention on Mercury had entered into force to protect human health and environment from the anthropogenic emissions and releases of mercury compounds.5 Developing novel efficient mercury removal materials and technologies is critical to mercury removal. Activated carbon injection (ACI) combined with particle control is the commercialized method for mercury removal.6−9 However, it is still far from being widely applied among thermal power plants due to the following limitations: (1) high cost of activated carbons, ranging from $3810 to $166 000 per pound Hg removal;6 (2) high dependence on coal type and existing conventional air pollution control devices, lowering mercury capture performance for plants using sub-bituminous coal or plants equipped with a spray cooling system;10 (3) pollution of fly ash in coal-fired plants by the added activated carbons, a raw material for concrete.11 A promising approach to overcome the above limitations is to develop carbon-free adsorbent for mercury removal.12−20 Metal sulfide is one of the carbon-free adsorbents with superior mercury removal performance.21−26 Recent studies have revealed that zinc sulfide (ZnS) has shown promising mercury capture property21,27 with high equilibrium Hg0 adsorption capacity of 497.8 μg·g−1 at an optimal temperature of 180 °C because of the interactions between S2− and Hg0.21 Further studies explored that HCl, an important component in flue gas, has negligible effect on the mercury adsorption performance of nano-ZnS due to the fact that HCl is hard to dissociate on the surface.27,28 Beside HCl, Cl2 is another main constituent of Cl source in flue gas;29−33 however, the effects of Cl2 on Hg0 adsorption or oxidation on ZnS surface is still unclear. © 2018 American Chemical Society

The objective of this work is to investigate the adsorption of Cl2 on ZnS(110) face and its effect on Hg0 adsorption and oxidation. The interactions of Hg0 and Cl2 with ZnS are analyzed by the binding energies, adsorption geometries, partial densities of states (PDOS), and Mulliken population analysis. Different possible reaction routes are proposed by the reaction energy profiles with corresponding configurations. Finally, the oxidation mechanism of Hg0 over ZnS adsorbents is presented. This fundamental work is essential to the application of ZnS on Hg0 removal from coal combustion flue gas.

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COMPUTATIONAL DETAILS Consistent with our previous works, the ZnS(110) face with the lowest surface energy among all ZnS surfaces is chosen for all calculations.27,34 The cleaved (110) plane of ZnS based on 3 × 3 × 2 unit cells is shown in Figure 1. The atoms on the top two layers are allowed to relax, whereas those on the other layers are fixed in their bulk positions. The number of surface atoms is marked on the atom as shown in Figure 1c. All the calculations are performed using the DMol3 package.35 The generalized gradient approximation (GGA) with the Perdew− Burke−Ernzerhof (PBE) exchange correlation function and the double-numeric polarization (DNP)36 basis set is employed in all calculations. Spin polarization corrections are considered in all calculations. The core electrons are modeled using effective core potentials (ECP) method.37 A real space cutoff of 4.1 Å is used, and the convergence threshold parameters for the optimization are 1 × 10−5 (energy), 4 × 10−3 (gradient), and 5 × 10−3 (displacement), respectively. PBE is a high-precision functional and has been applied in many calculations.18,23,38,39 The optimized ZnS unit cell parameters (a = b = c = 5.490 Å) and Zn−S bond length (2.377 Å) using the PBE method are within Received: April 4, 2018 Revised: June 25, 2018 Published: June 26, 2018 7745

DOI: 10.1021/acs.energyfuels.8b01188 Energy Fuels 2018, 32, 7745−7751

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Figure 1. Slab models of ZnS(110) surface: (a) ZnS unit cell; (b) the establishment of the 3√2 × 2 crystal surface; (c) top view of ZnS(110); (d) side view of ZnS(110). Atoms are represented as yellow (S) and gray (Zn) spheres, respectively.

+1.5% error of the experimental determined lattice constants (a = b = c = 5.409 Å, Zn−S bond length is 2.342 Å),40 certifying the reliability of the results in this work. Binding energies (BEs) are calculated using the following equation: BE = E(AB) − [E(A) + E(B)]

(1)

where E(AB), E(A), and E(B) are the total energies of the adsorbate/substrate system, the isolated adsorbate, and the substrate, respectively. Transition states (TSs) along the reaction pathway were searched using the linear synchronous transit/ quadratic synchronous transit (LST/QST) combined with the Nudged-Elastic Band (NEB) algorithm.41

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RESULTS AND DISCUSSIONS Cl2 Binding on ZnS(110) Surface. Figure 2 shows the stable adsorption configurations of Cl2 adsorption on ZnS(110) surface. Obviously, the interaction strength of Cl2 on ZnS(110) surface is affected by the interacting configurations: with one end of the Cl2 molecule interacting with the ZnS surface (Figure 2a−c), the binding energy is in the range of −47.24 to −65.16 kJ/mol, while with both ends of the Cl2 molecule interacting with the ZnS surface (Figure 2d and 2e), the binding energies are in the range of −96.07 to −101.19 kJ/mol. Notably, in Figure 2d, the adsorbed Cl2 molecule tends to dissociate with bond length of Cl−Cl increasing from 2.02 Å (in Cl2) to 2.67 Å. In Figure 2e, Table 1. Comparison of BE (kJ/mol) of Cl2 Adsorbed on ZnS 2√2 × 4 Surface Cell and ZnS 2 × 3√2 Surface Cell

Figure 2. Stable optimized geometries of Cl2 on ZnS(110) surface. Atoms are represented as green (Cl), yellow (S) and gray (Zn) spheres, respectively. 7746

configuration

2√2 × 4 surface cell

2 × 3√2 surface cell

2(a) 2(b) 2(c) 2(d) 2(e)

−47.14 −51.93 −64.63 −90.14 −103.56

−47.24 −51.47 −65.16 −101.19 −96.07 DOI: 10.1021/acs.energyfuels.8b01188 Energy Fuels 2018, 32, 7745−7751

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Table 2. Mulliken Charge (e) Population Analysis for Clean ZnS(110) Surface, Hg0 Binding on ZnS(110) Surface, Cl Binding on ZnS(110) Surface, and Hg0 Binding on Chlorinated ZnS(110) Surface atoms

ZnS

ZnS−Hg

ZnS−Cl

ZnS−Cl−Hg

ZnS−2Cl(1)

ZnS−2Cl(2)

ZnS−2Cl−Hg

Zn(1) Zn(2) Zn(3) Zn(4) S(5) S(6) Cl(1) Cl(2) Hg

0.190 0.190 0.190 0.190 −0.229 −0.229 − − −

− 0.172 0.164 0.172 −0.212 −0.212 − − 0.074

− 0.200 0.223 0.201 −0.154 −0.153 −0.284 − −

− 0.144 0.200 − −0.169 − −0.297 − 0.199

0.203 0.218 0.218 0.203 −0.100 − −0.242 −0.242 −

0.201 0.219 0.209 0.220 −0.146 −0.146 −0.269 −0.269 −

− 0.192 0.192 − −0.113 − −0.235 −0.235 0.325

Figure 3. Mulliken charge (e) population analysis for (a) clean ZnS(110) surface, (b) chlorinated ZnS(110) surface with one Cl ion (ZnS−Cl), (c) chlorinated ZnS(110) surface with two Cl ions (ZnS−2Cl(1)), and (d) chlorinated ZnS(110) surface with two Cl ions (ZnS−2Cl(2)). Atoms are represented as green (Cl), yellow (S) and gray (Zn) spheres, respectively.

Figure 4. Initial placement configuration of Hg0 on chlorinated ZnS(110) surface Atoms are represented as green (Cl), pink (Hg), yellow (S) and gray (Zn) spheres, respectively.

the adsorbed Cl2 molecule completely dissociates into two ions on two adjacent Zn ions with increased Cl−Cl equilibrium distance from 2.02 to 4.15 Å and strongest binding energy among the configurations (Table 1). The dissociation of Cl2 molecule on ZnS surface introduces free Cl radicals on the surface, as named chlorinated surface. Such a process has also been observed in other materials, such as ZnO,42 W,43 Si,44−46 MgO,47 Au,48 GaAs,49 and CuO.50

The chlorinated surface turns to a strong electron acceptor due to the electron redistribution on the surface, as revealed by Mulliken charge population analysis of the clean and chlorinated ZnS(110) surfaces (Table 2 and Figure 3). With one Cl atom stabilized on the surface, the atomic charge of Zn(3) (atomic number is shown in Figure 1c) increases from 0.190 to 0.223 e, while that of Cl decreases from 0 (in Cl2) to −0.284 e, as shown in Figure 3a and Figure 3b. The atomic charges on other 7747

DOI: 10.1021/acs.energyfuels.8b01188 Energy Fuels 2018, 32, 7745−7751

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HgCl is formed directly on the chlorinated ZnS surface, as evidenced by the closing equilibrium distance (2.88 Å) between Hg and Cl on the chlorinated surface and the Hg−Cl bonding length (2.96 Å) in HgCl on clean ZnS(110) surface.27 Partial density of states (PDOS) studies reveal that the strong interactions are mainly due to the strong hybridization of the p-orbital of Cl and the s-, p-, and d-orbitals of Hg0 at approximately −5.7 and 0.3 eV, as shown in Figure 6. Such a phenomenon follows

neighboring atoms, e.g., Zn(2), Zn(4), S(5), and S(6), are also redistributed accordingly, demonstrating the significant role of Cl addition on the charge redistribution on ZnS surface. The electron redistribution on the ZnS(110) surface is attributed to the electron migration from the surface to the dissociated Cl atom. Moreover, the electron migration is enhanced by increasing the loading number of Cl atoms, as shown in Figure 3c and Figure 3d. The chlorination-induced electron redistribution affects the mercury heterogeneous oxidation process on ZnS surface, as shown in the following section. Hg 0 Adsorption and Oxidation on Chlorinated ZnS(110) Surface. Figure 4a and Figure 4b show the initial configurations of Hg0 on chlorinated ZnS(110) surface, while

Figure 6. PDOS for surface system of Hg0 adsorbed on chlorinated ZnS(110) surface with one Cl ion.

the Eley−Rideal (E−R) mechanism that Hg0 interacts with Cl radical intruded upon Cl2 adsorption on the surface of adsorbents to form HgCl, as shown in the following equation: 1/2Cl 2(g) + ZnS(s) → Cl−ZnS(s)

(2)

Cl−ZnS(s) + Hg(g) → HgCl−ZnS(s)

(3)

where g represents gas phase and s represents solid phase. We further investigated the adsorption of Hg0 on a chlorinated ZnS(110) surface with two Cl, representing excessive loading of chlorine on the surface, as shown in Figure 4c and Figure 4d. Interestingly, HgCl2 is directly formed following E−R mechanism with a binding energy as high as −223.17 kJ/mol, indicating strong Hg0 chemisorption on excessively chlorinated ZnS surface. Mulliken analysis reveals 0.325 e charge transfer from Hg to the excessively chlorinated ZnS(110) surface. The above oxidizing reaction of Hg0 on chlorinated ZnS belongs to mercury heterogeneous reaction, which eliminates the activation energy of the reaction between Hg0 and Cl2 and prominently promotes the reaction of Cl2 and Hg0. In contrast, homogeneous oxidation needs to overcome an energy barrier (typically 142− 181 kJ/mol)52,53 and occurs within a temperature window between 400 and 700 °C.54,55 Overcoming a significant high energy barrier for Hg0 oxidation is necessary for many reported catalysts, such as V2O5/TiO2(001) (91.53 kJ/mol),56,57 Au(111) (33−55 kJ/mol),48 Pd(100) (67.53 kJ/mol),58 MnO2(110) (66.27 kJ/mol),59 and CeO2(111) (59.39 kJ/mol).60 In this work, we further explored the oxidation from HgCl to HgCl2 (Supporting Information), whereas an energy barrier as high as 109.25 kJ/mol was revealed. This clearly demonstrates that the oxidation of Hg0 to HgCl2 in the presence of Cl2 follows the E−R mechanism rather than the Langmuir−Hinshelwood (L−H) mechanism, which is different from the process of Hg0 oxidation on CeO2,60 RuO2/ TiO2.61

Figure 5. Mulliken charge (e) population analysis for (a) Hg0 adsorption configuration on clean ZnS(110) surface (ZnS−Hg), (b) Hg0 adsorption configuration on chlorinated ZnS(110) surface with one Cl ion (ZnS−Cl−Hg), and (c) Hg0 adsorption configuration on chlorinated ZnS(110) surface with two Cl ions (ZnS−2Cl−Hg). (Atoms are represented as Cl, green; Hg, pink; S, yellow; Zn, gray.)

Figure 5b shows the geometry-optimized configurations. For comparison, Hg0 adsorption on clean ZnS surface is also studied, as shown in Figure 5a. Overall, compared to the clean ZnS surface, the chlorinated ZnS(110) surface exhibits enhanced Hg0 adsorption ability. The binding energy of Hg0 on the clean ZnS(110) surface is −65.28 kJ/mol, while that on chlorinated ZnS(110) surface is −80.87 kJ/mol, an enhancement of about 24%. This is due to the fact that more electrons transfer from Hg to the chlorinated ZnS(110) surface in comparison with the clean surface since the former is a stronger electron acceptor, as evidenced by the more positive atomic charge of Hg (0.199 e vs 0.074 e), as shown in Figure 5a and Figure 5b. The chlorines on the chlorinated ZnS(110) surface act as strong functional groups similar to the in-purpose bromine-functionalization on carbonaceous surface,51 whereas it requires no addition of chemicals since such a process happens naturally for ZnS in flue gas containing chlorine. 7748

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Figure 7. Potential energy diagram for different pathways of Hg0 on the chlorinated ZnS(110) surface.

Stability Analysis. The stability of HgCl and HgCl2 on ZnS(110) surface is analyzed to investigate the release of HgCl and HgCl2 from ZnS(100) surface. The energy diagram of Hg0 adsorption and possible desorption on ZnS(110) surface including reactants, intermediates, and products is shown in Figure 7. The energies of the optimized structures and possible desorption structures are relative to the reactants. ZnS_Cl/Hg0, ZnS_Hg/Cl, and ZnS/HgCl represent that Hg0, Cl, and HgCl dissociate from ZnS surface, respectively. The process of Hg0 adsorption on ZnS surface with one Cl emits heat 80.87 kJ/mol, and the desorptions of Hg0, Cl, and HgCl are endothermic with dissociation energies of 80.87, 153.65, and 217.48 kJ/mol, respectively, as shown in Figure 7a. Therefore, the product of Hg0 adsorption on chlorinated ZnS with one Cl is very stable. As shown in Figure 7b, more heat (223.17 kJ/mol) is released when Hg0 was adsorbed on the chlorinated ZnS(110) surface with two Cl, which suggests that the chlorinated ZnS(110) surface with two Cl has more affinity for Hg0 than the ZnS surface with one Cl and clean ZnS surface. Similarly, Hg0, Cl, HgCl, and HgCl2 are all very difficult to separate from ZnS(110) surface

because of the huge energy barrier. In conclusion, the products of HgCl and HgCl2 on ZnS surface are stable.

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CONCLUSIONS

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ASSOCIATED CONTENT

Cl2 shows significant dissociation effects on ZnS(110) surface, inducing chlorinated ZnS surface with electron redistribution. The chlorinated surface significantly promotes the adsorption of Hg0 by drawing more electrons from Hg0, forming HgCl or HgCl2 directly in line with E−R mechanism. The formed HgCl and HgCl2 are stabilized on the ZnS surface and are hardly to dissociate. Our future works will focus on the effects of Br on mercury adsorption and oxidation on ZnS.

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.8b01188. Description and Figure S1 (PDF) 7749

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(18) Suarez Negreira, A.; Wilcox, J. Role of WO3 in the Hg Oxidation across the V2O5-WO3-TiO2 SCR Catalyst: A DFT Study. J. Phys. Chem. C 2013, 117, 24397−24406. (19) Sasmaz, E.; Aboud, S.; Wilcox, J. Hg Binding on Pd Binary Alloys and Overlays. J. Phys. Chem. C 2009, 113, 7813−7820. (20) Sasmaz, E.; Wilcox, J. Mercury Species and SO2 Adsorption on CaO(100). J. Phys. Chem. C 2008, 112, 16484−16490. (21) Li, H.; Zhu, L.; Wang, J.; Li, L.; Shih, K. Development of NanoSulfide Sorbent for Efficient Removal of Elemental Mercury from Coal Combustion Fuel Gas. Environ. Sci. Technol. 2016, 50, 9551−9557. (22) Xu, Z.; Lv, X.; Chen, J.; Jiang, L.; Lai, Y.; Li, J. First Principles Study of Adsorption and Oxidation Mechanism of Elemental Mercury by HCl over MoS2(100) Surface. Chem. Eng. J. 2017, 308, 1225−1232. (23) Yang, Y.; Liu, J.; Liu, F.; Wang, Z.; Miao, S. Molecular-Level Insights into Mercury Removal Mechanism by Pyrite. J. Hazard. Mater. 2017, 344, 104−112. (24) Zhao, H.; Mu, X.; Yang, G.; George, M.; Cao, P.; Fanady, B.; Rong, S.; Gao, X.; Wu, T. Graphene-Like MoS2 Containing Adsorbents for Hg0 Capture at Coal-Fired Power Plants. Appl. Energy 2017, 207, 254−264. (25) Ozaki, M.; Uddin, M. A.; Sasaoka, E.; Wu, S. Temperature Programmed Decomposition Desorption of the Mercury Species over Spent Iron-Based Sorbents for Mercury Removal from Coal Derived Fuel Gas. Fuel 2008, 87, 3610−3615. (26) Wu, S.; Ozaki, M.; Uddin, M.; Sasaoka, E. Development of IronBased Sorbents for Hg0 Removal from Coal Derived Fuel Gas: Effect of Hydrogen Chloride. Fuel 2008, 87, 467−474. (27) Li, H.; Feng, S.; Liu, Y.; Shih, K. Binding of Mercury Species and Typical Flue Gas Components on ZnS(110). Energy Fuels 2017, 31, 5355−5362. (28) Li, H.; Zhu, L.; Wang, J.; Li, L.; Lee, P.-H.; Feng, Y.; Shih, K. Effect of Nitrogen Oxides on Elemental Mercury Removal by Nanosized Mineral Sulfide. Environ. Sci. Technol. 2017, 51, 8530−8536. (29) Miller, S. J.; Ness, S. R.; Weber, G. F.; Erickson, T. A.; Hassett, D. J.; Hawthorne, S. B.; Katrinak, K. A.; Louie, P. K. K. A Comprehensive Assessment of Toxic Emissions from Coal-Fired Power Plants: Phase I Results from the U.S. Department of Energy Study. Final Report to the Pittsburgh Energy Technology Center and the Morgantown Energy Technology Center of the U.S. Department of Energy on Contract No. DE-FC21-93MC30097; Energy and Environmental Research Center; University of North Dakota, Grand Forks, ND, October 1996. (30) Wang, Y.; Duan, Y.; Yang, L.; Zhao, C.; Shen, X.; Zhang, M.; Zhuo, Y.; Chen, C. Experimental Study on Mercury Transformation and Removal in Coal-Fired Boiler Flue Gases. Fuel Process. Technol. 2009, 90, 643−651. (31) Senior, C. L.; Sarofim, A. F.; Zeng, T.; Helble, J. J.; Mamani-Paco, R. Gas-Phase Transformations of Mercury in Coal-Fired Power Plants. Fuel Process. Technol. 2000, 63, 197−213. (32) Gutberlet, H.; Schluten, A.; Licata, A. SCR Impacts on Mercury Emissions from Coal-Fired Boilers. Presented at EPRI SCR Workshop, Memphis, TN, April 19−21, 2000. (33) Vosteen, B. W.; Straube, S.; Koser, H. Hg Sorption and Hg Oxidation by Cl and Br at SCR DeNOx Catalyst. Proceedings of the 9th Annual United States Environmental Protection Agency (EPA), Department of Energy (DOE), Electric Power Research Institute (EPRI), and Edison Electric Institute (EEI) Conference on Clean Air, Hg, Global Warming and Renewable Energy, Westin La Paloma Resort, Tucson, AZ, Jan 24, 2006. (34) Hamad, S.; Cristol, S.; Catlow, C. R. A. Surface Structures and Crystal Morphology of ZnS: Computational Study. J. Phys. Chem. B 2002, 106, 11002−11008. (35) Delley, B. An All-Electron Numerical Method for Solving the Local Density Functional for Polyatomic Molecules. J. Chem. Phys. 1990, 92, 508−517. (36) Delley, B. From Molecules to Solids with the Dmol3 Approach. J. Chem. Phys. 2000, 113, 7756−7764. (37) Bergner, A.; Dolg, M.; Küchle, W.; Stoll, H.; Preuss, H. Ab Initio Energy-Adjusted Pseudopotentials for Elements of Groups 13−17. Mol. Phys. 1993, 80, 1431−1441.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Yang Liu: 0000-0003-4313-0932 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The work was supported by the National Science Foundation of China (51476189) REFERENCES

(1) Clarkson, T. W. The Toxicology of Mercury. Crit. Rev. Clin. Lab. Sci. 1997, 34, 369−403. (2) Clarkson, T. W. Mercury: Major Issues in Environmental Health. Environ. Health. Perspect. 1993, 100, 31−38. (3) United States Environmental Protection Agency (U.S. EPA). Mercury and Air Toxics Standards (MATS) for Power Plants; U.S. EPA: Washington, DC, 2011. (4) Liu, J.; Abanades, S.; Gauthier, D.; Flamant, G.; Zheng, C.; Lu, J. Determination of Kinetic Law for Toxic Metals Release during Thermal Treatment of Model Waste in a Fluid-Bed Reactor. Environ. Sci. Technol. 2005, 39, 9331−9336. (5) U.N. Environment Programme, Minamata Convention on Mercury; http://www.mercuryconvention.org/Convention/tabid/ 3426/language/en-US/Default.aspx. (6) Jones, A. P.; Hoffmann, J. W.; Smith, D. N.; Feeley, T. J.; Murphy, J. T. DOE/NETL’s Phase II Mercury Control Technology Field Testing Program:Preliminary Economic Analysis of Activated Carbon Injection. Environ. Sci. Technol. 2007, 41, 1365−1371. (7) Pavlish, J. H.; Sondreal, E. A.; Mann, M. D.; Olson, E. S.; Galbreath, K. C.; Laudal, D. L.; Benson, S. A. Status Review of Mercury Control Options for Coal-Fired Power Plants. Fuel Process. Technol. 2003, 82, 89−165. (8) Wilcox, J.; Sasmaz, E.; Kirchofer, A.; Lee, S.-S. Heterogeneous Mercury Reaction Chemistry on Activated Carbon. J. Air Waste Manage. Assoc. 2011, 61, 418−426. (9) Padak, B.; Wilcox, J. Understanding Mercury Binding on Activated Carbon. Carbon 2009, 47, 2855−2864. (10) Feeley, T. J.; Brickett, L. A.; O’Palko, B. A.; Murphy, J. T. Field Testing of Mercury Control Technologies for Coal-Fired Power Plants, DOE/NETL Mercury R&D Program Review, May 2005. (11) Ding, F.; Zhao, Y.; Mi, L.; Li, H.; Li, Y.; Zhang, J. Removal of GasPhase Elemental Mercury in Flue Gas by Inorganic Chemically Promoted Natural Mineral Sorbents. Ind. Eng. Chem. Res. 2012, 51, 3039−3047. (12) Lee, J.-Y.; Ju, Y.; Keener, T. C.; Varma, R. S. Development of Cost-Effective Noncarbon Sorbents for Hg0 Removal from Coal-Fired Power Plants. Environ. Sci. Technol. 2006, 40, 2714−2720. (13) Granite, E. J.; Pennline, H. W.; Hargis, R. A. Novel Sorbents for Mercury Removal from Flue Gas. Ind. Eng. Chem. Res. 2000, 39, 1020− 1029. (14) Granite, E. J.; Myers, C. R.; King, W. P.; Stanko, D. C.; Pennline, H. W. Sorbents for Mercury Capture from Fuel Gas with Application to Gasification Systems. Ind. Eng. Chem. Res. 2006, 45, 4844−4848. (15) Yang, J.; Zhao, Y.; Zhang, J.; Zheng, C. Removal of Elemental Mercury from Flue Gas by Recyclable CuCl2 Modified Magnetospheres Catalyst from Fly Ash. Part 1. Catalyst Characterization and Performance Evaluation. Fuel 2016, 164, 419−428. (16) Yang, J.; Zhao, Y.; Zhang, J.; Zheng, C. Removal of Elemental Mercury from Flue Gas by Recyclable CuCl2 Modified Magnetospheres Catalyst from Fly Ash. Part 2. Identification of Involved Reaction Mechanism. Fuel 2016, 167, 366−374. (17) Jung, J.-E.; Geatches, D.; Lee, K.; Aboud, S.; Brown, G. E.; Wilcox, J. First-Principles Investigation of Mercury Adsorption on the α-Fe2O3(11̅02) Surface. J. Phys. Chem. C 2015, 119, 26512−26518. 7750

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(61) Liu, Z.; Sriram, V.; Li, C.; Lee, J.-Y. Mechanistic and Kinetic Studies of Elemental Mercury Oxidation over a RuO2/Rutile TiO2 Catalyst. Catal. Sci. Technol. 2017, 7, 4669−4679.

(38) Suarez Negreira, A.; Wilcox, J. DFT Study of Hg Oxidation across Vanadia-Titania SCR Catalyst under Flue Gas Conditions. J. Phys. Chem. C 2013, 117, 1761−1772. (39) Yang, Y.; Liu, J.; Zhang, B.; Liu, F. Mechanistic Studies of Mercury Adsorption and Oxidation by Oxygen over Spinel-Type MnFe2O4. J. Hazard. Mater. 2017, 321, 154−161. (40) Skinner, B. J. Unit-Cell Edges of Natural and Synthetic Sphalerites. Am. Mineral. 1961, 46, 1399−1411. (41) Govind, N.; Petersen, M.; Fitzgerald, G.; King-Smith, D.; Andzelm, J. A Generalized Synchronous Transit Method for Transition State Location. Comput. Mater. Sci. 2003, 28, 250−258. (42) Beheshtian, J.; Peyghan, A. A.; Bagheri, Z. Adsorption and Dissociation of Cl2 Molecule on ZnO Nanocluster. Appl. Surf. Sci. 2012, 258, 8171−8176. (43) Chen, H.-L.; Ju, S.-P.; Chen, H.-T.; Musaev, D. G.; Lin, M. C. Adsorption and Dissociation of the HCl and Cl2 Molecules on W(111) Surface: A Computational Study. J. Phys. Chem. C 2008, 112, 12342− 12348. (44) De Wijs, G. A.; De Vita, A.; Selloni, A. First-Principles Study of Chlorine Adsorption and Reactions on Si(100). Phys. Rev. B: Condens. Matter Mater. Phys. 1998, 57, 10021−10029. (45) Craig, B. I.; Smith, P. V. Chemisorption of HCl, Cl2 and F2 on the Si(100) Surface. Surf. Sci. 1992, 262, 235−244. (46) Lyubinetsky, I.; Dohnalek, Z.; Choyke, W. J.; Yates, J. T., Jr. Cl2 Dissociation on Si(100)-(2 × 1): A Statistical Study by Scanning Tunneling Microscopy. Phys. Rev. B: Condens. Matter Mater. Phys. 1998, 58, 7950−7957. (47) Xu, Y.; Li, J.; Zhang, Y.; Chen, W. The Adsorption and Dissociation of Cl2 on the MgO(001) Surface with Vacancies: Embedded Cluster Model Study. J. Chem. Phys. 2004, 120, 8753−8760. (48) Lim, D. H.; Wilcox, J. Heterogeneous Mercury Oxidation on Au(111) from First Principles. Environ. Sci. Technol. 2013, 47, 8515− 8522. (49) Ohno, T. Theory of Adsorption of Cl2 Molecules on GaAs(001) Surfaces. Surf. Sci. 1996, 357−358, 322−326. (50) Sun, S.; Zhang, D.; Li, C.; Wang, Y.; Yang, Q. Density Functional Theory Study of Mercury Adsorption and Oxidation on CuO(111) Surface. Chem. Eng. J. 2014, 258, 128−135. (51) Liu, J.; Qu, W.; Zheng, C. Theoretical Studies of MercuryBromine Species Adsorption Mechanism on Carbonaceous Surface. Proc. Combust. Inst. 2013, 34, 2811−2819. (52) Xu, M.; Qiao, Y.; Zheng, C.; Li, L.; Liu, J. Modeling of Homogeneous Mercury Speciation Using Detailed Chemical Kinetics. Combust. Flame 2003, 132, 208−218. (53) Wilcox, J. A Kinetic Investigation of High-Temperature Mercury Oxidation by Chlorine. J. Phys. Chem. A 2009, 113, 6633−6639. (54) Sliger, R. N.; Kramlich, J. C.; Marinov, N. M. Towards the Development of a Chemical Kinetic Model for the Homogeneous Oxidation of Mercury by Chlorine Species. Fuel Process. Technol. 2000, 65, 423−438. (55) Niksa, S.; Fujiwara, N. Predicting Extents of Mercury Oxidation in Coal-Derived Flue Gases. J. Air Waste Manage. Assoc. 2005, 55, 930− 939. (56) Liu, J.; He, M.; Zheng, C.; Chang, M. Density Functional Theory Study of Mercury Adsorption on V2O5(001) Surface with Implications for Oxidation. Proc. Combust. Inst. 2011, 33, 2771−2777. (57) Zhang, B.; Liu, J.; Dai, G.; Chang, M.; Zheng, C. Insights into the Mechanism of Heterogeneous Mercury Oxidation by HCl over V2O5/ TiO2 Catalyst: Periodic Density Functional Theory Study. Proc. Combust. Inst. 2015, 35, 2855−2865. (58) Zhang, B.; Liu, J.; Zhang, J.; Zheng, C.; Chang, M. Mercury Oxidation Mechanism on Pd(100) Surface from First-Principles Calculations. Chem. Eng. J. 2014, 237, 344−351. (59) Zhang, B.; Liu, J.; Yang, Y.; Chang, M. Oxidation Mechanism of Elemental Mercury by HCl over MnO2 Catalyst: Insights from First Principles. Chem. Eng. J. 2015, 280, 354−362. (60) Zhang, B.; Liu, J.; Shen, F. Heterogeneous Mercury Oxidation by HCl over CeO2 catalyst: Density Functional Theory Study. J. Phys. Chem. C 2015, 119, 15047−15055. 7751

DOI: 10.1021/acs.energyfuels.8b01188 Energy Fuels 2018, 32, 7745−7751