Roles of Oxygen Functional Groups in Hydrogen Sulfide Adsorption

Mar 25, 2019 - The hydrogen sulfide (H2S) removal ability of activated carbon is closely related to surface oxygen groups, yet the roles of oxygen gro...
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Roles of Oxygen Functional Groups in Hydrogen Sulfide Adsorption on Activated Carbon Surface: A Density Functional Study Fenghua Shen, Jing Liu,* Chenkai Gu, and Dawei Wu

Ind. Eng. Chem. Res. Downloaded from pubs.acs.org by UNIV PARIS-SUD on 04/02/19. For personal use only.

State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China ABSTRACT: The hydrogen sulfide (H2S) removal ability of activated carbon is closely related to surface oxygen groups, yet the roles of oxygen groups in the process of H2S adsorption on activated carbon have heretofore been unclear. The interactions of H2S with various oxygen groups on activated carbon were detailed examined by density functional theory. The results indicate that pyrone, carbonyl, ester, and carboxyl groups are active sites for H2S adsorption, except for hydroxyl group. H2S can react directly with carbonyl oxygen atom in these oxygen groups leading to the formation of C−S, C−OH, and C−SH species. A pyrone group can improve the activity of surface carbon sites for H2S adsorption. The presence of non-neighboring epoxy oxygen atom increase evidently the activity of carbonyl oxygen atom for H2S adsorption. The relative position of the carbonyl oxygen atom and epoxy oxygen atom plays a key role in the activity of oxygen groups.

1. INTRODUCTION Hydrogen sulfide (H2S) is generally regarded as an acidic air pollutant produced in many industrial plants. H2S is harmful to the central nervous system of human bodies. In addition, H2S can destroy metallic catalysts and results in catalyst deactivation.1 Recently, the removal of H2S by using sorbents has attracted increasing attention. Among various materials, activated carbon is considered as a useful H2S sorbent.2,3 Clarification of the detailed interactions of H2S with activated carbon has great practical implication for achieving higher H2S removal efficiency. The surface chemistry property of activated carbon is one of the key points in H2S removal. Heteroatom oxygen on activated carbon surface is usually classified into different oxygen groups. These oxygen groups have significant effects on the surface chemistry of activated carbon,4−6 and thereby affect H2S adsorption. Various experimental studies were performed to investigate the influences of oxygen groups on H2S removal capacity of activated carbon.7−10 However, there is no general agreement on the role of different oxygen groups in H2S adsorption. Cal et al.11 studied the effect of oxygen content on H2S adsorption on activated carbon, and they found that H2S uptake capacity of activated carbon increased with the raising of oxygen content. They suggested that chemical reactions of H2S with C−O complexes were involved in H2S adsorption. Brazhnyk et al.12 investigated the oxidation of H2S by oxygen groups on activated carbon. They found that the H2S removal ability of activated carbon is mainly depending on the type of oxygen groups rather than the oxygen content. Bouzaza et al.13 suggested that some oxygen groups are active for H2S adsorption on activated carbon, whereas other oxygen groups are inert for H2S adsorption. Thus far, the detailed roles of different oxygen groups in H2S adsorption on activated carbon surface are still not clear. © XXXX American Chemical Society

Quantum chemistry methods based on density functional theory (DFT) have been increasingly used to clarify the interactions in both homogeneous and heterogeneous systems.14−17 Ashori et al.18 have studied the interactions of H2S with carbon nanocone, nanotube, and graphene by using DFT calculations. In our previous study,19 the adsorption mechanism of H 2 S on activated carbon surface was investigated. The results of DFT calculations indicated that activated carbon improved H2S decomposition and provided adsorption sites for H2S. However, to the best of the author’s knowledge, no theoretical study has been conducted to investigate the interactions of H2S with different oxygen groups on activated carbon at the molecular level. Such a study would help to give a better understanding of the effects of oxygen groups on H2S adsorption on activated carbon. The present study was conducted aiming to clarify the roles of different oxygen groups in the adsorption of H2S on activated carbon. The interactions of H2S with different oxygen groups (pyrone, carbonyl, ester, carboxyl, and hydroxyl) on carbon surface were studied by applying density functional theory. The adsorption energy of H2S on each oxygen groups is analyzed to determine their activity. This study provides an understanding of the interaction mechanism of H2S with oxygen groups, which is important for developing effective H2S removal technologies. Received: Revised: Accepted: Published: A

January 26, 2019 March 4, 2019 March 25, 2019 March 25, 2019 DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research

Figure 1. Activated carbon surface with and without oxygen functional groups.

neighboring sp2 carbonyl oxygen atom and sp3 epoxy oxygen atom and presents on activated carbon surfaces in a large number. The pyrone group would be the most important oxygen groups account for the basicity of activated carbon.29 It has been proposed that the basicity of activated carbon is mainly due to pyrone-type structures.30 Therefore, it is reasonable to use carboxyl, ester, and hydroxyl to simulate the acidic oxygen groups and to employ pyrone and carbonyl groups to simulate the basic oxygen groups on activated carbon. The optimized geometries of different oxygen groups are illustrated in Figure 1. Some pertinent bond lengths of C−O are also given. Mulliken population analysis is employed to evaluate the bond strength. A highly positive value of bond population means a strong interaction between the atoms, whereas no interaction exists if the bond population is close to zero.31,32 The bond populations of basic and acidic oxygen groups on activated carbon surface are listed in Table 1. The values of C−O bond populations in these oxygen groups are highly positive. This means a strong interaction of O atom with C atom, and the breaking of such C−O bond will be highly endothermic process.

2. COMPUTATIONAL METHODS All of the density functional theory calculations were performed using the Gaussian09 package.20 Full geometry optimizations of all structures were conducted at B3PW91/631G(d) level. The total adsorption energy can be calculated as following equation: Eads = E(AB) − (E(A) + E(B))

where E(A) is the total energy of the adsorbate and E(B) is the total energy of the substrate. E(AB) is the total energy of adsorbate/substrate system in the equilibrium state. Adsorption of the adsorbate is exothermic if Eads is negative.21,22 A more negative value of Eads corresponds to a stronger adsorption. Normally, if the adsorption energy is less than −30 kJ/mol, then the interaction belongs to physisorption. If the adsorption energy is higher than −50 kJ/mol, then the interaction belongs to chemisorption. Solid-state 13C NMR characterization experimental data showed that carbon had chemical structures consisting of 3−7 benzene rings.23 It was found that the reactivity of the active sites strongly depended on its local shape rather than on the size of the cluster models.24,25 Therefore, a seven-ring cluster model is used to represent the structure of activated carbon, as shown in Figure 1. This cluster model is suitable to simulate the activated carbon structure since its geometric parameters are close to the experimental data.26,27 It is important to establish reasonable models for oxygencontaining activated carbon surfaces in order to clarify the detailed interactions of H2S with oxygen groups. Oxygen groups can be divided into two groups according to their acidic or basic character. The well-defined acidic oxygen groups on carbon surface are carboxyl, ester, and hydroxyl groups. The basic oxygen groups are commonly assumed to be pyrone and carbonyl groups.28 The pyrone group, formed by air exposure of heat-treated activated carbon, is the combination of non-

Table 1. Mulliken Populations for Oxygen Functional Groups on Activated Carbon Surface

C(11)−C(8) C(8)−C(9) C(9)−C(10) C(10)−C(20) C(20)−C(23) C(23)−C(26) C−O B

pyrone

carbonyl

carboxyl

ester

hydroxyl

0.440 0.383 0.289 0.271 0.396 0.207 0.581

0.406 0.329 0.363 0.264 0.394 0.213 0.576

0.407 0.328 0.343 0.300 0.385 0.405 0.546

0.408 0.335 0.346 0.300 0.376 0.271 0.622

0.406 0.333 0.338 0.329 0.329 0.382 0.316

DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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3. RESULTS AND DISCUSSION 3.1. Adsorption of H2S on Activated Carbon. The adsorption of H2S on activated carbon surface was discussed.19 Two stable structures were obtained, including A and B, as shown in Figure 2. A C−S species is formed by H2S adsorption

dissociatively on pyrone. 1A and 1B represent the structures of H2S adsorption on neighboring C sites of O atom. C−S species is formed in 1A, and C−SH species is formed in 1B. C−S bond length is 1.664 Å in 1A, which is 0.098 Å shorter than that in 1B. The adsorption energy of H2S is −757.1 kJ/mol in 1A and −508.2 kJ/mol in 1B. The formations of C−S in 1A and C−SH in 1B are more exothermic than that in A and B. This indicates that pyrone group can improve the adsorption of H2S on activated carbon surface. O−H bond is formed by the reaction of H2S with O atom in 1C and 1D. The bond lengths of C−O in 1C and 1D have been elongated by the reaction of H2S with O atom, indicating that the interaction of C atom with O atom has been weakened. The adsorption energies of H2S in 1C and 1D are −557.7 and −259.1 kJ/mol, respectively, suggesting that the reaction of H2S with pyrone is highly exothermic. Therefore, although the adsorption energies of H2S in 1C and 1D are lower than that in A and B, there are still possibilities for their formation. The bond populations of H2S on pyrone are listed in Table 2. The values of C−S and C−O bond populations in these structures are highly positive. This implies the formations of strong covalent bonds in these structures, and the C−S, C− SH, and C−OH species formed by H2S adsorption on pyrone are very stable. The bond population of C−S in 1A is 0.498, which is higher than that in the other structures, suggesting the interaction of C atom with S atom in 1A is stronger. The C−S bond populations in 1B and 1D are lower than those in 1A and 1C. This means that the interaction of C atom with S atom in C−S species is stronger than that in C−SH species. Furthermore, the bond populations of C−O in 1C and 1D are lower than those in pyrone, indicating that the C−O bond has been weakened by the reaction of H2S with O atom. 3.3. Effect of Carbonyl Group on H2S Adsorption. The interactions of H2S with carbonyl were investigated by allowing H2S to approach carbonyl surface from different directions. Four stable surface complexes were obtained after optimization, as shown in Figure 3b. H2S adsorbs on neighboring C sites of O atom in structures 2A and 2B by forming C−S

Figure 2. H2S adsorption on activated carbon surface.

in A with an adsorption energy of −664.9 kJ/mol. H2S decomposes into SH and H atom in B, and then these two fragments adsorb separately on surface C sites. C−SH is formed by H2S adsorption in B. The adsorption energy of H2S in B is −442.0 kJ/mol, which is lower than that in A. This implies that C−S species is more likely to be formed by H2S adsorption. The adsorption of H2S on carbon is highly exothermic process, and belongs to chemisorption. Sun et al.33 performed H2S removal experiments by activated carbon, and suggested that chemisorption was involved in the adsorption process. 3.2. Effect of Pyrone Group on H2S Adsorption. The effects of basic oxygen groups on H2S adsorption were studied first. To exactly clarify the influence of pyrone group on H2S adsorption, all the possible locations and orientations of H2S approaching pyrone surface were considered. Four stable surface complexes were obtained after optimization, namely, 1A, 1B, 1C, and 1D, as shown in Figure 3a. It can be inferred from these surface complexes that H2S is likely to adsorb

Figure 3. Interactions of H2S with basic oxygen functional groups: (a) H2S on pyrone; (b) H2S on carbonyl. C

DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research Table 2. Mulliken Populations for H2S on Basic Oxygen Functional Groups pyrone

carbonyl

bond

1A

1B

1C

1D

2A

2B

2C

2D

C(11)−C(8) C(8)−C(9) C(9)−C(10) C(10)−C(20) C(20)−C(23) C(23)−C(26) C−O C−S

0.504 0.230 0.231 0.374 0.377 0.255 0.555 0.498

0.415 0.371 0.360 0.267 0.428 0.283 0.466 0.314

0.417 0.347 0.402 0.277 0.286 0.377 0.350 0.421

0.448 0.373 0.338 0.363 0.271 0.429 0.254 0.281

0.502 0.233 0.238 0.378 0.358 0.263 0.439 0.477

0.417 0.345 0.389 0.252 0.421 0.290 0.462 0.318

0.424 0.316 0.428 0.261 0.277 0.381 0.349 0.430

0.403 0.316 0.389 0.330 0.312 0.384 0.321 0.251

Figure 4. Interactions of H2S with acidic oxygen functional groups: (a) H2S on ester; (b) H2S on carboxyl; (c) H2S on hydroxyl.

that with pyrone. This is owing to the presence of nonneighboring epoxy O atom, which evidently increases the activity of carbonyl O atom for H2S adsorption. More information is derived from the bond population analyses, as listed in Table 2. It is clear that the C−S, C−SH, and C−OH species formed by H2S adsorption on carbonyl are very stable, since the values of the bond populations of them are highly positive. Shi et al.34 analyzed the adsorption of H2S on activated carbon by using XPS and they found that C−S groups can be formed by H2S adsorption.

species in 2A and C−SH species in 2B. The bond length of C−S is 1.676 Å in 2A and 1.761 Å in 2B. The adsorption energy of H2S in 2A is −674.7 kJ/mol, which is close to that in A. Meanwhile, H2S adsorption energy is −443.5 kJ/mol in 2B, which is only 1.5 kJ/mol higher than that in B. The above results suggest that carbonyl group has no obvious effect on H2S adsorption on neighboring C sites of O atom. Carbonyl group can also react with H2S by forming C−OH species, as indicated by 2C and 2D. The adsorption energy of H2S is −499.4 kJ/mol in 2C and −228.6 kJ/mol in 2D. However, the reaction of H2S with carbonyl is a less exothermic process than D

DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research Table 3. Mulliken Populations for H2S on Acidic Oxygen Functional Groups ester

carboxyl

hydroxyl

bond

3A

3B

3C

3D

4A

4B

4C

5A

5B

C(11)−C(8) C(8)−C(9) C(9)−C(10) C(10)−C(20) C(20)−C(23) C(23)−C(26) C−O C−S

0.504 0.227 0.227 0.415 0.356 0.294 0.605 0.497

0.421 0.355 0.391 0.366 0.328 0.332 0.518 0.303

0.422 0.319 0.440 0.245 0.267 0.423 0.278 0.480

0.400 0.316 0.433 0.309 0.363 0.366 0.352 0.265

0.505 0.225 0.217 0.401 0.347 0.437 0.535 0.503

0.420 0.340 0.386 0.305 0.352 0.421 0.530 0.297

0.400 0.308 0.363 0.271 0.415 0.364 0.347 0.210

0.504 0.234 0.228 0.422 0.305 0.405 0.310 0.490

0.421 0.357 0.386 0.384 0.274 0.433 0.248 0.282

the difference in H2S adsorption on pyrone and ester is closely related to the relative position of the carbonyl O atom and epoxy O atom, which plays a key role in the activity of oxygen groups. 3.5. Effect of Carboxyl Group on H2S Adsorption. The interactions of H2S with carboxyl via different approaches were investigated. The stable surface complexes of H2S on carboxyl are shown in Figure 4b, including 4A, 4B, and 4C. In 4A and 4B, the dissociated fragments of H2S adsorb on neighboring C sites of carboxyl. A C−S species is formed in 4A with an adsorption energy of −651.9 kJ/mol, which is close to the adsorption of H2S in A. The bond length of C−S is 1.663 Å in 4A. C−SH species is formed in 4B with a binding energy of −387.1 kJ/mol, which is lower than that in B, indicating that carboxyl group can inhibit the formation of C−SH on activated carbon. A carboxyl group can also react directly with H2S by forming C−OH species. However, the reaction of H2S with carboxyl is less exothermic than that of pyrone. This means that the pyrone group is more active for H2S adsorption than is the carboxyl group. The bond populations of H2S on carboxyl are listed in Table 3. It appears that the interaction of C atom with S atom in 4A is stronger than that in the other structures because of the higher C−S bond population. Moreover, C−O bond population decreases from 0.546 to 0.347 in 4C. This proves that C−O bond has been weakened by the reaction of H2S with carboxyl. 3.6. Effect of Hydroxyl Group on H2S Adsorption. The following discusses the interactions of H2S with hydroxyl, and two stable surface complexes are obtained, as shown in Figure 4c. It is clear that H2S tends to adsorb dissociatively on surface C sites by forming C−S and C−SH species. The adsorption energy of H2S is −672.5 kJ/mol in 5A and −409.1 kJ/mol in 5B. Hydroxyl group hinders the formation of C−SH species on activated carbon. Unlike the results of carboxyl and ester, H2S does not likely to react with hydroxyl. The hydroxyl like oxygen functionalities are not surface-active centers for H2S adsorption. For the purposes of the present discussion, it suffices to point out that H2S can react directly with carbonyl O atom in oxygen functional groups leading to the forming of C−OH species on activated carbon surface. The reactivity of oxygen groups for H2S adsorption is related to their acid−base properties. The pyrone group is more effective for H2S adsorption than the other oxygen groups. The presence of a pyrone group can improve H2S removal ability of activated carbon via enhancing the activity of neighboring C sites. Moreover, a pyrone group is an active center which can react directly with H2S. In addition, carboxyl and hydroxyl groups inhibit the formation of C−SH species on activated. This

The calculation results are in agreement with the experimental results that oxygen groups on carbon surface can take part in H2S adsorption and even react with H2S directly.35 Comparing the adsorption of H2S on pyrone, the formations of C−S, C−SH, and O−H species of H2S on carbonyl are less exothermic. It is thus sufficient to point out that the presence of epoxy O atom improves significantly the reactivity of carbonyl O atom in pyrone group for H2S adsorption. This makes pyrone group more effective for H2S adsorption than carbonyl group. The pyrone group plays a dual role, not only facilitating the adsorption of H2S on neighboring C sites but also offering an active site to react directly with H2S. The basic oxygen groups are effective sites on the carbon surface for H2S adsorption. H2S can react with carbonyl O atom in pyrone and carbonyl leading to the formation of C− OH species. Li et al.36 carried out an experiment to investigate the removal of H2S by activated carbon and suggested that pyrone groups can react with H2S. Feng et al.37 reported experimentally that H2S removal ability of activated carbon was correlated well with the amount of basic oxygen groups. They suggested that H2S could be oxidized by oxygen groups during the process of adsorption. Our calculation results are consistent with the experimental results. 3.4. Effect of Ester Group on H2S Adsorption. The roles of acidic oxygen groups in H2S adsorption on activated carbon were investigated in the similar manner. Four stable surface complexes, 3A, 3B, 3C, and 3D, were obtained by H2S adsorption on different sites of ester, as shown in Figure 4a. The adsorption energy of H2S is −674.2 kJ/mol in complex 3A, which is close to that in A. Meanwhile, the adsorption energy of H2S in 3B is only 2.7 kJ/mol higher than that of B. The results reveal that ester group has little effect on H2S adsorption on neighboring C sites. Ester can also act as active site to react with H2S, but the reaction of ester with H2S is less exothermic than that with pyrone. O−H bond is formed in 3C and 3D by the reactions of H2S with ester. The adsorption energies of H2S in 3C and 3D are −327.9 and −116.6 kJ/mol, respectively. The bond populations of H2S on ester are listed in Table 3. The values of C−S and C−O bond populations in these complexes are highly positive. This implies that C−S, C−SH, and C−OH species formed by H2S adsorption on ester are very stable. The interaction of C atom with S atom in 3A is stronger than that in the other structures, as indicated by the higher C−S bond population. The results of H2S on ester is different from those on pyrone. The exothermicity of the adsorption of H2S on ester is obviously lower than that on pyrone, indicating that pyrone is more active for H2S adsorption. Upon careful examination of the structures of pyrone and ester, it can be determined that E

DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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of microporous activated carbon on its electrochemical performance in supercapacitors. Adv. Funct. Mater. 2009, 19 (3), 438−447. (6) 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 (17), 9551−9557. (7) Shang, G.; Shen, G.; Liu, L.; Chen, Q.; Xu, Z. Kinetics and mechanisms of hydrogen sulfide adsorption by biochars. Bioresour. Technol. 2013, 133, 495−499. (8) Nowicki, P.; Skibiszewska, P.; Pietrzak, R. Hydrogen sulphide removal on carbonaceous adsorbents prepared from coffee industry waste materials. Chem. Eng. J. 2014, 248, 208−215. (9) Kazmierczak-Razna, J.; Gralak-Podemska, B.; Nowicki, P.; Pietrzak, R. The use of microwave radiation for obtaining activated carbons from sawdust and their potential application in removal of NO2 and H2S. Chem. Eng. J. 2015, 269, 352−358. (10) Shen, F.; Liu, J.; Zhang, Z.; Dai, J. On-line analysis and kinetic behavior of arsenic release during coal combustion and pyrolysis. Environ. Sci. Technol. 2015, 49 (22), 13716−13723. (11) Cal, M.; Strickler, B.; Lizzio, A. High temperature hydrogen sulfide adsorption on activated carbon: I. Effects of gas composition and metal addition. Carbon 2000, 38 (13), 1757−1765. (12) Brazhnyk, D. V.; Zaitsev, Y. P.; Bacherikova, I. V.; Zazhigalov, V. A.; Stoch, J.; Kowal, A. Oxidation of H2S on activated carbon KAU and influence of the surface state. Appl. Catal., B 2007, 70 (1), 557− 566. (13) Bouzaza, A.; Laplanche, A.; Marsteau, S. Adsorption−oxidation of hydrogen sulfide on activated carbon fibers: effect of the composition and the relative humidity of the gas phase. Chemosphere 2004, 54 (4), 481−488. (14) Wang, Z.; Liu, J.; Yang, Y.; Liu, F.; Ding, J. Heterogeneous reaction mechanism of elemental mercury oxidation by oxygen species over MnO2 catalyst. Proc. Combust. Inst. 2019, 37 (3), 2967−2975. (15) Yang, Y.; Liu, J.; Liu, F.; Wang, Z.; Miao, S. Molecular-level insights into mercury removal mechanism by pyrite. J. Hazard. Mater. 2018, 344, 104−112. (16) Hu, J.; Liu, Y.; Liu, J.; Gu, C.; Wu, D. High CO2 adsorption capacities in UiO type MOFs comprising heterocyclic ligand. Microporous Mesoporous Mater. 2018, 256, 25−31. (17) Joo, S. W.; Lee, S. Y.; Liu, J.; Qian, S. Diffusiophoresis of an elongated cylindrical nanoparticle along the axis of a nanopore. ChemPhysChem 2010, 11 (15), 3281−3290. (18) Ashori, E.; Nazari, F.; Illas, F. Adsorption of H2S on carbonaceous materials of different dimensionality. Int. J. Hydrogen Energy 2014, 39 (12), 6610−6619. (19) Shen, F.; Liu, J.; Zhang, Z.; Dong, Y.; Gu, C. Density functional study of hydrogen sulfide adsorption mechanism on activated carbon. Fuel Process. Technol. 2018, 171, 258−264. (20) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, revision D.01; Gaussian, Inc.: Wallingford, CT, 2009. (21) Shen, F.; Liu, J.; Wu, D.; Dong, Y.; Liu, F.; Huang, H. Design of O2/SO2 dual-doped porous carbon as superior sorbent for elemental mercury removal from flue gas. J. Hazard. Mater. 2019, 366, 321−328. (22) Yang, Z.; Li, H.; Qu, W.; Zhang, M.; Feng, Y.; Zhao, J.; Yang, J.; Shih, K. Role of Sulfur Trioxide (SO3) in Gas-Phase Elemental

indicates that the presence of carboxyl and hydroxyl groups has negative effect on H2S adsorption on activated carbon. Guo et al.38 investigated experimentally the removal of H2S by activated carbons derived from oil palm shell. They suggested that H atom in H2S can react with carbonyl (CO) oxygen groups. Leuch et al.35 studied the H2S adsorption on activated carbon surface. They found that the removal of H2S was produced mainly by oxidation reactions. The basic oxygen groups contribute particularly in H2S removal. Therefore, the calculation result is in agreement with the available experimental results.

4. CONCLUSION Density functional theory was used to investigate the interactions of H2S with different oxygen functional groups on activated carbon surface. This provides an insight into the roles of oxygen groups in the process of H2S adsorption. H2S can react directly with carbonyl oxygen atom in pyrone, carbonyl, ester, and carboxyl groups by forming C−S, C−SH, and C−OH species. A pyrone group can not only improve the adsorption of H2S by enhancing the activity of surface C sites but also react directly with H2S by forming C−OH species. Carbonyl and ester have no obvious effects on H2S adsorption on surface C sites, and they are weak active sites to react with H2S. Carboxyl and hydroxyl groups may inhibit the adsorption of H2S on activated carbon surface. The presence of nonneighboring epoxy oxygen atom can enhance the activity of carbonyl oxygen atom for H2S adsorption. The relative position of the carbonyl oxygen atom and epoxy oxygen atom governs the activity of oxygen groups. These calculation results serve to highlight the complexity of the interactions of H2S with oxygen groups on the carbon surface.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +86 27 87545526. Fax: +86 27 87545526. E-mail: [email protected]. ORCID

Jing Liu: 0000-0001-6520-9612 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by National Key R&D Program of China (2018YFC1901303), and National Natural Science Foundation of China (51606078).

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REFERENCES

(1) Fang, H.; Zhao, J.; Fang, Y.; Huang, J.; Wang, Y. Selective oxidation of hydrogen sulfide to sulfur over activated carbonsupported metal oxides. Fuel 2013, 108, 143−148. (2) Köchermann, J.; Schneider, J.; Matthischke, S.; Rönsch, S. Sorptive H2S removal by impregnated activated carbons for the production of SNG. Fuel Process. Technol. 2015, 138, 37−41. (3) Shen, F.; Liu, J.; Dong, Y.; Wu, D.; Gu, C.; Zhang, Z. Elemental mercury removal from syngas by porous carbon-supported CuCl2 sorbents. Fuel 2019, 239, 138−144. (4) Seredych, M.; Hulicova-Jurcakova, D.; Lu, G. Q.; Bandosz, T. J. Surface functional groups of carbons and the effects of their chemical character, density and accessibility to ions on electrochemical performance. Carbon 2008, 46 (11), 1475−1488. (5) Hulicova-Jurcakova, D.; Seredych, M.; Lu, G. Q.; Bandosz, T. J. Combined effect of nitrogen-and oxygen-containing functional groups F

DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research Mercury Immobilization by Mineral Sulfide. Environ. Sci. Technol. 2019, 53, 3250. (23) Perry, S.; Hambly, E.; Fletcher, T.; Solum, M.; Pugmire, R. Solid-state 13C NMR characterization of matched tars and chars from rapid coal devolatilization. Proc. Combust. Inst. 2000, 28 (2), 2313− 2319. (24) Chen, N.; Yang, R. T. Ab initio molecular orbital calculation on graphite: selection of molecular system and model chemistry. Carbon 1998, 36, 1061−1070. (25) Montoya, A.; Truong, T.T. T.; Mondragón, F.; Truong, T. N. CO desorption from oxygen species on carbonaceous surface: 1. Effects of the local structure of the active site and the surface coverage. J. Phys. Chem. A 2001, 105, 6757−6764. (26) Yang, F. H.; Yang, R. T. Ab initio molecular orbital study of the mechanism of SO2 oxidation catalyzed by carbon. Carbon 2003, 41 (11), 2149−2158. (27) Shen, F.; Liu, J.; Wu, D.; Dong, Y.; Zhang, Z. Development of O2 and NO co-doped porous carbon as high capacity mercury sorbent. Environ. Sci. Technol. 2019, 53, 1725−1731. (28) Fuente, E.; Menéndez, J.; Suarez, D.; Montes-Moran, M. Basic surface oxides on carbon materials: a global view. Langmuir 2003, 19 (8), 3505−3511. (29) Montes-Moran, M.; Suarez, D.; Menéndez, J.; Fuente, E. On the nature of basic sites on carbon surfaces: an overview. Carbon 2004, 42 (7), 1219−1225. (30) Boehm, H. Surface oxides on carbon and their analysis: a critical assessment. Carbon 2002, 40 (2), 145−149. (31) Liu, J.; Qu, W.; Joo, S. W.; Zheng, C. Effect of SO2 on mercury binding on carbonaceous surfaces. Chem. Eng. J. 2012, 184, 163−167. (32) Liu, Y.; Kasik, A.; Linneen, N.; Liu, J.; Lin, Y. S. Adsorption and diffusion of carbon dioxide on ZIF-68. Chem. Eng. Sci. 2014, 118, 32− 40. (33) Sun, T.; Shen, Y.; Jia, J. Gas cleaning and hydrogen sulfide removal for COREX coal gas by sorption enhanced catalytic oxidation over recyclable activated carbon desulfurizer. Environ. Sci. Technol. 2014, 48 (4), 2263−2272. (34) Shi, L.; Yang, K.; Zhao, Q.; Wang, H.; Cui, Q. Characterization and mechanisms of H2S and SO2 adsorption by activated carbon. Energy Fuels 2015, 29 (10), 6678−6685. (35) Le Leuch, L.; Subrenat, A.; Le Cloirec, P. Hydrogen sulfide adsorption and oxidation onto activated carbon cloths: applications to odorous gaseous emission treatments. Langmuir 2003, 19 (26), 10869−10877. (36) Li, H.; Monnell, J. D.; Alvin, M.; Vidic, R. D. Factors affecting activated carbon-based catalysts for selective hydrogen sulfide oxidation. Main Group Chem. 2008, 7 (3), 239−250. (37) Feng, W.; Kwon, S.; Borguet, E.; Vidic, R. Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry. Environ. Sci. Technol. 2005, 39 (24), 9744− 9749. (38) Guo, J.; Luo, Y.; Lua, A. C.; Chi, R.; Chen, Y.; Bao, X.; Xiang, S. Adsorption of hydrogen sulphide (H2S) by activated carbons derived from oil-palm shell. Carbon 2007, 45 (2), 330−336.

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DOI: 10.1021/acs.iecr.9b00507 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX