Mercury adsorbent, its preparation method and application

Abstract

The present invention provides a mercury adsorbent. The mercury adsorbent has a two-dimensional nanosheet structure and includes 1 / 4 CuS-MoS2, 1 / 6 CuS-MoS2, and 1 / 9 CuS-MoS2. The composition of the mercury adsorbent includes molybdenum disulfide, copper sulfide, and dimethylformamide. The molybdenum disulfide is in a two-dimensional nanosheet structure, and the molybdenum disulfide nanosheets are stacked layer by layer. The dimethylformamide is located between at least two adjacent molybdenum disulfide nanosheets in the molybdenum disulfide nanosheets. The interlayer spacing between two adjacent molybdenum disulfide nanosheets is 0.90 to 1.00 nanometers, and the copper sulfide is uniformly dispersed on the surface of the molybdenum disulfide nanosheets and in the lattice of the molybdenum disulfide. The present invention utilizes the coupling of in-plane S defects and copper element doping to achieve atomic reorganization on the basal plane, and activates the mercury adsorption activity of sulfur atoms on the basal plane of MoS2 by means of electron reconstruction caused by Cu atoms replacing Mo atoms and the exposure of internal metal sites, thereby realizing a stepwise optimization of the mercury removal effect.

Description

Technical Field

[0001] The present invention belongs to the field of mercury-containing flue gas treatment, and particularly relates to a mercury adsorbent, a preparation method thereof, and an application thereof. Background Art

[0002] As an important index of Hg 0 adsorption capacity, the adsorption activity determines the adsorption effect of MoS2 on Hg 0 However, the adsorption activity is often restricted by the number of unsaturated edge sites and the defect of S inertness on the basal plane, and it is difficult to achieve breakthrough optimization.

[0003] In order to increase the number of unsaturated edge sites, some common techniques are dedicated to the design of surface defects of MoS2. For example, surface etching methods such as H2O2, NaClO, oxygen plasma, and H2 annealing are used to create defects on the surface to generate S defect sites (Sv) on the basal plane. Based on the unsaturated S-Mo bonds exposed by the S defect sites Sv on the basal plane of MoS2, the exposure of metal sites on the MoS2 surface is optimized, and the chemical reaction activity is further improved.

[0004] In order to improve the defect of S inertness on the basal plane, common techniques incorporate metal or non-metal heteroatoms into the basal plane of MoS2 to improve the reaction activity of the basal plane by changing the electron density of Mo and S atoms near the dopant.

[0005] However, this method has limited improvement in reaction activity. Summary of the Invention

[0006] Aiming at solving the technical problem of limited improvement in the reaction activity of molybdenum disulfide in the above common techniques, the present invention provides a mercury adsorbent. The mercury adsorbent has a two-dimensional nanosheet structure and includes 1 / 4CuS-MoS2, 1 / 6CuS-MoS2, and 1 / 9CuS-MoS2. The composition of the mercury adsorbent includes molybdenum disulfide, copper sulfide, and dimethylformamide;

[0007] Among them, the molybdenum disulfide has a two-dimensional nanosheet structure, and the molybdenum disulfide nanosheets are stacked layer by layer. The dimethylformamide is located between at least two adjacent layers of the molybdenum disulfide nanosheets;

[0008] The layer spacing between two adjacent molybdenum disulfide nanosheets is 0.90 to 1.00 nanometers, and the copper sulfide is uniformly dispersed on the surface of the molybdenum disulfide nanosheets and in the crystal lattice of the molybdenum disulfide.

[0009] Further, in terms of mass fraction, the contents of Cu 2+ and Cu + in the mercury adsorbent are 31 to 33% and 66 to 68% respectively, and the contents of Mo 4+ and Mo5+ , the contents of Mo 6+ are 28 - 30%, 33 - 35%, and 35 - 37% respectively, and the content of S2 2- on the surface of the mercury adsorbent is 27 - 30%.

[0010] The present invention also provides a preparation method of a mercury adsorbent, including the steps of:

[0011] Mixing a molybdenum-containing reagent, a sulfur-containing reagent, and dimethylformamide to obtain a first mixed solution; wherein, the molar ratio of molybdenum element in the molybdenum-containing reagent to sulfur element in the sulfur-containing reagent is 1:0.5 - 9; the molybdenum-containing reagent includes ammonium heptamolybdate, and the sulfur-containing reagent includes thiourea;

[0012] Heat-treating the first mixed solution, and then performing solid-liquid separation on the precipitate to obtain DMF-expanded molybdenum disulfide; wherein, the treatment temperature of the heat treatment is 120 - 260 °C, and the treatment time is 4 - 20 h;

[0013] Disperse the DMF-expanded molybdenum disulfide in a solvent to obtain a dispersion liquid, and sequentially add a copper sulfate solution and a sodium sulfide solution to the dispersion liquid, and perform solid-liquid separation to obtain the mercury adsorbent; wherein, the addition ratio of DMF-expanded molybdenum disulfide to the copper sulfate and the sodium sulfide is 0.3 g: 0.0001 - 0.0015 mol: 0.0001 - 0.0015 mol.

[0014] Further, the addition ratio of DMF-expanded molybdenum disulfide to the copper sulfate and the sodium sulfide is 0.3 g:0.0004 - 0.0006:0.0004 - 0.0006.

[0015] Further, the concentration of the dimethylformamide is 50% - 100%, and the mass-volume ratio of the molybdenum-containing reagent to the dimethylformamide is 1 g:10 - 30 ml.

[0016] Further, the treatment temperature of the heat treatment is 140 - 200 °C, and the treatment time is 8 - 16 h.

[0017] Further, the solvent includes water, and the mass-volume ratio of the DMF-expanded molybdenum disulfide to the solvent is 0.3 g / 30 - 70 ml; the step of dispersing the DMF-expanded molybdenum disulfide in a solvent to obtain a dispersion liquid further includes: placing the DMF-expanded molybdenum disulfide in the solvent and performing ultrasonic dispersion for 10 - 30 min.

[0018] Further, the sequential addition of copper sulfate solution and sodium sulfide solution to the dispersion liquid includes the steps of: after adding the copper sulfate solution to the dispersion liquid, stirring at a speed of 500 revolutions per minute for 2 to 6 hours, and then adding the sodium sulfide solution to the dispersion liquid and reacting for 40 - 80 minutes.

[0019] The present invention also provides an application of the mercury adsorbent as described above or the mercury adsorbent prepared by the preparation method as described above in any of the above in treating mercury-containing flue gas, including the steps of:

[0020] The mercury adsorbent contacts the mercury-containing flue gas to adsorb Hg in the mercury-containing flue gas 0 ;

[0021] wherein, the composition of the mercury-containing flue gas includes: sulfur dioxide 0 - 20%, oxygen 0 - 20%, water vapor 0 - 20%, nitric oxide 0 - 1000 ppm, hydrogen chloride 0 - 50 ppm; the mercury concentration in the mercury-containing flue gas is 0 - 10 mg / m 3 , the flow rate of the mercury-containing flue gas is 0.5 - 3 L / min, and the mass-volume ratio of the mercury adsorbent to the mercury-containing flue gas is 1 - 15 mg / L.

[0022] Further, the treatment time of the mercury-containing flue gas is less than 5400 minutes, and the treatment temperature of the mercury-containing flue gas is 40 - 160 °C.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] In the present invention, the high-valence Cu 2+ , Mo 6+ and unsaturated sulfur S2 2- on the surface of the adsorbent all participate in the adsorption of mercury as active sites.

[0025] 1. In the present invention, an appropriate amount of copper ions is incorporated into the mercury adsorbent. Due to the stronger electron gain ability and electron transfer ability of divalent copper ions, the electron loss process of oxidized Hg 0 is accelerated, effectively enhancing the high-temperature mercury capture activity of MoS2; the doping of copper ions also increases the valence state of molybdenum, and copper ions obtain electrons from molybdenum, enhancing the reduction ability.

[0026] By precisely controlling the amount of copper ions incorporated, the mercury adsorbent is divided into 1 / 4CuS-MoS2, 1 / 6CuS-MoS2, and 1 / 9CuS-MoS2 according to the proportion of copper sulfide. Most copper ions enter the molybdenum disulfide lattice and are evenly distributed on the surface and within the lattice of molybdenum disulfide, providing abundant anchor sites for the growth of sulfur ions while avoiding the loss of active sites covered by the accumulation of copper sulfide, and synergistically optimizing the Hg of copper ions and unsaturated sulfur S2 2- ​0 adsorption effect and simultaneously enhance the activity of sulfur atoms on the basal plane of MoS2. In addition, the sulfided copper sulfide can also effectively increase the content of short-chain sulfur S2 2- , and these elemental changes further promote the oxidative adsorption of mercury adsorbent for Hg 0 .

[0027] 2. The present invention realizes the atomic reorganization of the basal plane by coupling in-plane S defects and copper element doping, and activates the mercury adsorption activity of sulfur atoms on the basal plane of MoS2 by using the electron reconstruction caused by defects and the exposure of internal metal sites; the copper element doping on MoS2 can further optimize the oxidation ability of adjacent unsaturated S and Mo atoms through strong electron coupling.

[0028] 3. In the mercury adsorbent prepared by the present invention, the interlayer spacing of molybdenum disulfide after intercalation is widened, thereby improving the exposure degree and accessibility of active sites on the surface and inside of molybdenum disulfide nanosheets, and greatly enhancing the adsorption activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on the structures shown in these drawings without creative efforts.

[0030] Figure 1 XRD diffraction patterns of the CuS-MoS2 nanosheets prepared in Examples 3-4 and Comparative Example 1 of the present invention and the DMF-MoS2 obtained in Example 1.

[0031] Figure 2 XRD diffraction patterns of the modified MoS2 nanosheets with different metal ions prepared in Examples 3-4 and Comparative Example 1 of the present invention.

[0032] Figure 3 SEM images of the modified MoS2 nanosheets prepared in Examples 3-4 and Comparative Example 1 of the present invention; among them, Figure 3 (a): 1 / 2CuS-MoS2; Figure 3 (b): 1 / 4CuS-MoS2; Figure 3 (c): 1 / 6CuS-MoS2; Figure 3 (d) 1 / 9CuS-MoS2; Figure 3 (e): 1 / 6S-MoS2; Figure 3 (f): 1 / 6Cu-MoS2; Figure 3 (g): 1 / 6FeS-MoS2; Figure 3(h): 1 / 6 ZnS-MoS2.

[0033] Figure 4 TEM and EDS spectra of the modified MoS2 nanosheets of 1 / 6 CuS-MoS2 prepared in Example 4 of the present invention and 1 / 6 Cu-MoS2 prepared in Comparative Example 1; among them, Figure 4 (a) is 1 / 6 Cu-MoS2; Figure 4 (b): 1 / 6 CuS-MoS2.

[0034] Figure 5 Cu 2p XPS spectra of the modified MoS2 nanosheets of 1 / 6 CuS-MoS2 prepared in Example 4 of the present invention and 1 / 6 Cu-MoS2 prepared in Comparative Example 1.

[0035] Figure 6 Mo 3d XPS spectra of the modified MoS2 nanosheets of 1 / 6 CuS-MoS2 prepared in Example 4 of the present invention and 1 / 6 Cu-MoS2 prepared in Comparative Example 1.

[0036] Figure 7 S 2p XPS spectra of the modified MoS2 nanosheets of 1 / 6 CuS-MoS2 prepared in Example 4 of the present invention and 1 / 6 Cu-MoS2 prepared in Comparative Example 1.

[0037] Figure 8 Composition ratio diagrams of Cu, Mo and S elements of the modified MoS2 nanosheets of 1 / 6 CuS-MoS2 prepared in Example 4 of the present invention and 1 / 6 Cu-MoS2 prepared in Comparative Example 1.

[0038] Figure 9 Adsorption capacity versus time curve of DMF-MoS2 at 80 °C for a long time in Example 2 of the present invention after adsorbing Hg 0

[0039] Figure 10 Raman spectra of the modified MoS2 prepared in Example 1 and Examples 4-5 and Comparative Example 1 of the present invention.

[0040] Figure 11 In Analytical Example 5, DMF-MoS2 prepared in Example 1 of the present invention, 1 / 4 CuS-MoS2 prepared in Example 3, 1 / 6 CuS-MoS2 prepared in Example 4, 1 / 2 CuS-MoS2 and 1 / 9 CuS-MoS2 prepared in Comparative Example 1 for Hg 0 Adsorption curves.

[0041] Figure 12 ​For Analytical Example 6, the adsorption curves of DMF-MoS2 prepared in Example 1, 1 / 6CuS-MoS2 prepared in Example 4, 1 / 6FeS-MoS2 prepared in Comparative Example 1, and 1 / 6ZnS-MoS2 for Hg at 160 °C 0 are shown in

[0042] Figure 13 In Example 5 of the present invention, the adsorption curve of 1 / 6CuS-MoS2 prepared in Example 1 for Hg in simulated smelting flue gas at different temperatures 0 is shown in

[0043] Figure 14 In Example 5 of the present invention, the adsorption rate curve of 1 / 6CuS-MoS2 prepared in Example 1 for Hg in simulated smelting flue gas at different temperatures 0 is shown in

[0044] Figure 15 In Example 6 of the present invention, the long-term saturation adsorption curve of 1 / 6CuS-MoS2 prepared in Example 1 for Hg in simulated smelting flue gas at 160 °C 0 is shown in

[0045] Figure 16 In Example 6 of the present invention, the comparison chart of Hg adsorption performance between 1 / 6CuS-MoS2 prepared in Example 1 and the modified adsorbent in simulated smelting flue gas at 160 °C 0 is shown in

[0046] Figure 17 For Analytical Example 7, the XPS spectra after adsorption of 1 / 6Cu-MoS2 prepared in Comparative Example 1 and 1 / 6CuS-MoS2 prepared in Example 4, where Figure 17 (a)Cu 2p, Figure 17 (b)Mo 3d, Figure 17 (c)S 2p and Figure 17 (d)Hg 4f.

[0047] Figure 18 For Analytical Example 8, the Hg-TPD curves of 1 / 6Cu-MoS2 prepared in Comparative Example 1 and 1 / 6CuS-MoS2 prepared in Example 4

[0048] Figure 19 For Analytical Example 9, the optimized configurations of Hg adsorption on the (001) plane of Cu x -MoS2 in Comparative Example 1, where 0 (a)is Cu-MoS2, Figure 19 (b)is Cu2-MoS2, Figure 19 (c)is Cu3-MoS2, Figure 19 (d)is shown in Figure 19(d) is Cu-S-MoS2).

[0049] Figure 20 For the analysis in Example 10, the optimized configuration of Hg adsorbed on the (100) plane of Cu-MoS2, where 0 Figure 20 (a) is the Cu top site, Figure 20 (b) is the Mo bridge site, Figure 20 (c) is the S boundary site, Figure 20 (d) is the S-Mo bridge site. Specific Embodiments

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0051] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0052] When the embodiments give a numerical range, it should be understood that unless otherwise specified in the present invention, any value at both ends of each numerical range and any value between the two ends can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention, based on the understanding of those skilled in the art of the prior art and the description of the present invention, can also use any methods, devices and materials of the prior art similar or equivalent to those described in the embodiments of the present invention to implement the present invention.

[0053] The present invention provides a mercury adsorbent, which is a two-dimensional nanosheet structure and includes molybdenum disulfide and copper sulfide; wherein, the molybdenum disulfide nanosheets are stacked, and N,N-dimethylformamide is intercalated between two adjacent molybdenum disulfide nanosheets, and the interlayer spacing between two adjacent molybdenum disulfide nanosheets is 0.90 - 1.00 nanometers; the copper sulfide is uniformly dispersed on the surface of the molybdenum disulfide and in the crystal lattice of the molybdenum disulfide.

[0054] In some embodiments, according to the division of the copper ion doping amount, the mercury adsorbent includes 1 / 6CuS-MoS2, 1 / 4CuS-MoS2, and 1 / 9CuS-MoS2, where 1 / X represents the atomic molar ratio of Cu and Mo in the composite material.

[0055] Specifically, as Figure 1 ​, Figure 2 As shown in the figure, the present invention uses XRD to analyze the phase structures of 1 / 6CuS-MoS2, 1 / 4CuS-MoS2, and 1 / 9CuS-MoS2. It can be seen that all three have two characteristic structures of 2H-phase MoS2 and CuS. As the amount of copper ion compounding decreases, the peak intensity of CuS gradually weakens; when the compounding amount is 1 / 6CuS-MoS2 and 1 / 9CuS-MoS2, the characteristic peak of CuS is difficult to observe in the XRD diffraction pattern, indicating that the high specific surface structure of MoS2 causes CuS to be highly dispersed, and Cu atoms enter the MoS2 lattice. After the material is sulfided, the formed CuS microparticles are difficult to detect.

[0056] It can also be observed that the diffraction peak of the plane in the XRD pattern of the mercury adsorbent is 8.7°, corresponding to an interlayer distance of 9.8 Å. The results of XRD analysis show that the basal interlayer distance of the mercury adsorbent remains in an expanded state, and highly dispersed CuS enters the MoS2 structure.

[0057] As Figure 3 shown, in order to observe the microscopic morphology of the mercury adsorbent, SEM was used to analyze the mercury adsorbent. It can be seen that as the amount of copper element compounding decreases, most of the copper ions enter the lattice, and the amount of copper sulfide particles on the surface of molybdenum disulfide decreases significantly. This further corroborates Figure 1 the research situation of the XRD pattern in

[0058] As Figure 4 shown, in order to explore the microscopic structure and surface element distribution of the sample, TEM was used to observe the microscopic structure of the material, and EDS was used to perform a surface element area scan analysis. It can be observed that 1 / 6CuS-MoS2 has a graphene-like two-dimensional sheet structure, and the surface elements are evenly distributed, confirming that copper ions can be evenly distributed on the two-dimensional MoS2 nanosheets, and these copper ions provide potential anchoring sites for the growth of sulfide ions during the sulfidation process.

[0059] In some embodiments, by mass fraction, the contents of Cu 2+ and Cu + in the mercury adsorbent are 31-33% and 66-68% respectively, and the contents of Mo 4+ and Mo 5+ and Mo 6+ are 28-30%, 33-35%, and 35-37% respectively, and the content of S2 2- on the surface of the mercury adsorbent is 27-30%.

[0060] Exemplarily, by mass fraction, the contents of Cu 2+ and Cu +The contents are 32.88% and 67.12% respectively for [element name replaced by 'Mo' in Chinese], Mo 4+ 、Mo 5+ 、Mo 6+ The contents are 29.70%, 34.26% and 36.04% respectively, and the surface S2 2- content of the mercury adsorbent is 28.35%. Among them, the mercury adsorbent is 1 / 6CuS-MoS2.

[0061] As Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 shown, in order to analyze the surface chemical states of Cu, Mo and S elements in 1 / 6CuS-MoS2, XPS was used to analyze 1 / 6CuS-MoS2. As Figure 4 shown, four peaks appeared in the high-resolution Cu 2p spectrum at binding energies of 955.3, 933.9, 952.4 and 932.5 eV, which are attributed to Cu 2+ 2p 1 / 2 、Cu 2+ 2p 3 / 2 and Cu + 2p 1 / 2 、Cu + 2p 3 / 2 , and the contents of Cu 2+ and Cu + in 1 / 6CuS-MoS2 are 32.88% and 67.12% respectively.

[0062] As Figure 5 shown, two peaks at 228.8 and 232.0 eV in 1 / 6CuS-MoS2 can be attributed to Mo3d 5 / 2 and Mo 3d 3 / 2 orbitals, corresponding to the characteristic peaks of Mo 4+ on MoS2. Two peaks with binding energies at 229.2 and 232.7 eV correspond to Mo 5+ , and the peaks at 231.5 and 234.6 eV belong to Mo 6+ . The binding energy peak positions of its Mo 6+ are 233.6 (Mo3d 5 / 2 ) and 237.0 eV (Mo 3d 3 / 2 ), and the contents of Mo 4+ 、Mo 5+ and Mo 6+ in 1 / 6CuS-MoS2 are 29.70%, 34.26% and 36.04% respectively.

[0063] As Figure 6As shown, the results indicate that S mainly exists in two forms, including S 2- and S2 2- . The content of S2 2- on the surface of 1 / 6CuS-MoS2 is 28.35%.

[0064] Compared with common technologies, the mercury adsorbent prepared by the present invention has the following advantages:

[0065] In the present invention, the high-valence Cu 2+ , Mo 6+ and unsaturated sulfur S2 2- on the surface of the adsorbent all participate in the adsorption of mercury as active sites.

[0066] 1. In the present invention, an appropriate amount of copper ions is incorporated into the mercury adsorbent. Due to the stronger electron gain ability and electron transfer ability of divalent copper ions, the electron loss process of oxidized Hg 0 is accelerated, effectively enhancing the high-temperature mercury capture activity of MoS2; the doping of copper ions also increases the valence state of molybdenum, and copper ions obtain electrons from molybdenum, enhancing the reduction ability.

[0067] By precisely controlling the doping amount of copper ions, most copper ions enter molybdenum disulfide and are evenly distributed on the surface and within the lattice of molybdenum disulfide. While providing abundant anchoring sites for the growth of sulfur ions, it avoids the loss of active sites covered by the accumulation of copper sulfide, and synergistically optimizes the Hg 2- adsorption effect of copper ions and unsaturated sulfur S2 0 . In addition, the sulfided copper sulfide can effectively increase the content of short-chain sulfur S2 2- , and these elemental changes further promote the oxidative adsorption of mercury adsorbent for Hg 0 .

[0068] The coupling of in-plane S defects and transition metal doping elements realizes the atomic reconstruction of the basal plane, and activates the mercury adsorption activity of the MoS2 basal plane by using the electron reconstruction caused by the defects and the exposure of internal metal sites.

[0069] 2. The present invention realizes the atomic reconstruction of the basal plane by coupling in-plane S defects and copper element doping, and activates the mercury adsorption activity of the MoS2 basal plane by using the electron reconstruction caused by the defects and the exposure of internal metal sites; the doping of copper elements at the boundary positions of MoS2 can further optimize the oxidation ability of adjacent unsaturated S and Mo atoms through strong electron coupling.

[0070] 3. In the present invention, the interlayer spacing of the intercalated molybdenum disulfide is widened, thereby increasing the exposure degree and accessibility of the active sites on the surface and inside of the molybdenum disulfide nanosheets, and greatly enhancing the adsorption activity.

[0071] The present invention provides a preparation method of a mercury adsorbent, comprising the steps:

[0072] S1. Mix a molybdenum-containing reagent, a sulfur-containing reagent, and dimethylformamide to obtain a first mixed solution; wherein, the molar ratio of molybdenum element to sulfur element in the molybdenum-containing reagent and the sulfur-containing reagent is 1:0.5 - 9; the molybdenum-containing reagent includes ammonium heptamolybdate, and the sulfur-containing reagent includes thiourea.

[0073] The molybdenum-containing reagent includes ammonium heptamolybdate. As an inorganic substance, ammonium heptamolybdate has the chemical formula (NH4)6Mo7O 24 , and is a colorless to light green crystalline solid. It is usually used to prepare catalysts, metallic molybdenum, pigments, metal surface treatment agents, corrosion inhibitors, and trace element fertilizers. In the present invention, it is used as the molybdenum source for synthesizing molybdenum disulfide materials. Due to the characteristics of ammonium heptamolybdate such as being easy to purify, dissolve, and thermally dissociate, the NH3 thermally dissociated from it can escape fully with heating, thus avoiding the pollution of molybdenum products. Therefore, ammonium heptamolybdate is widely used as the basic raw material for producing high-purity molybdenum products.

[0074] The sulfur-containing reagent includes thiourea. As an organic sulfur-containing compound, thiourea has the chemical formula CH4N2S and is a white and shiny crystal. It is usually used to manufacture drugs, dyes, resins, molding powders, etc. In the present invention, it is used as the sulfur source for synthesizing molybdenum disulfide.

[0075] Dimethylformamide, also known as DMF, is a colorless transparent liquid. As a chemical raw material and solvent with extremely wide applications, it can be arbitrarily mixed with water and most organic solvents, and has good solubility for a variety of organic and inorganic compounds.

[0076] In some embodiments, the concentration of dimethylformamide is 50% - 100%, and the mass-to-volume ratio of the molybdenum-containing reagent to dimethylformamide is 1 g:10 - 30 ml.

[0077] In some embodiments, ammonium heptamolybdate and thiourea can be first mixed in proportion and then dissolved in the DMF solvent. After vigorously stirring for 30 min, a first mixed solution is obtained, so that ammonium heptamolybdate, thiourea, and DMF can be fully mixed to promote the efficient progress of subsequent reactions.

[0078] S2. Heat-treat the first mixed solution, and then perform solid-liquid separation of the precipitate to obtain the DMF-expanded molybdenum disulfide; wherein, the treatment temperature of the heat treatment is 120 - 260 °C, and the treatment time is 4 - 20 h.

[0079] In some embodiments, the treatment temperature of the heat treatment is 140 - 200 °C, and the treatment time is 8 - 16 h.

[0080] The DMF-expanded molybdenum disulfide is a two-dimensional nanosheet structure. The DMF-expanded molybdenum disulfide includes stacked molybdenum disulfide nanosheets and dimethylformamide inserted between adjacent two layers of molybdenum disulfide nanosheets. The layer spacing between adjacent two layers of molybdenum disulfide nanosheets is 0.90 - 1.00 nanometers. Among the active sites on the surface of the molybdenum disulfide nanosheets that make up the DMF-expanded molybdenum disulfide, the proportion of the number of molybdenum sites is 30% - 60%, and the proportion of the number of sulfur sites is 30% - 50%.

[0081] In some embodiments, among the active sites on the surface of the molybdenum disulfide nanosheets that make up the DMF-expanded molybdenum disulfide, the proportion of the number of molybdenum sites is 30% - 50%, and the proportion of the number of sulfur sites is 20% - 40%.

[0082] The DMF-expanded molybdenum disulfide can be applied to Hg 0 adsorption.

[0083] During the Hg 0 adsorption process, part of the mercury-containing flue gas fills into the two-dimensional nanosheet structure of the DMF-expanded molybdenum disulfide, and the active sites in the DMF-expanded molybdenum disulfide adsorb Hg in the mercury-containing flue gas 0 .

[0084] Specifically, the DMF-expanded molybdenum disulfide can be placed in a reaction device such as an adsorbent bed, and then the mercury-containing flue gas is introduced into the above reaction device.

[0085] Exemplarily, the composition of the mercury-containing flue gas includes: sulfur dioxide 0 - 20%, oxygen 0 - 20%; the mercury concentration in the mercury-containing flue gas is 0 - 10 mg / m 3 .

[0086] Also exemplarily, the flow rate of the mercury-containing flue gas is 0.5 - 3 L / min, and the mass-volume ratio of the DMF-expanded molybdenum disulfide to the mercury-containing flue gas is 0.1 - 10 mg / L.

[0087] In some embodiments, the mercury-containing flue gas contacts the DMF-expanded molybdenum disulfide at a temperature of 20 - 200 °C.

[0088] S3. Disperse the DMF-expanded molybdenum disulfide in a solvent to obtain a dispersion liquid. Add a copper sulfate solution and a sodium sulfide solution to the dispersion liquid in sequence, and perform solid-liquid separation to obtain the mercury adsorbent; wherein, the addition ratio of the DMF-expanded molybdenum disulfide to the copper sulfate and the sodium sulfide is 0.3 g : 0.0001 - 0.0015 mol : 0.0001 - 0.0015 mol.

[0089] In some embodiments, when the mercury adsorbent is 1 / 6CuS-MoS2, the ratio of the addition amounts of the DMF-expanded molybdenum disulfide, copper sulfate, and sodium sulfide is 0.3 g: 0.0004 - 0.0006: 0.0004 - 0.0006.

[0090] Specifically, the solvent includes water, and the mass-volume ratio of the DMF-expanded molybdenum disulfide to the solvent is 0.3 g / 30 - 70 ml; the step of dispersing the DMF-expanded molybdenum disulfide in the solvent to obtain a dispersion liquid further includes: placing the DMF-expanded molybdenum disulfide in the solvent and ultrasonically dispersing it for 10 - 30 min.

[0091] Exemplarily, the DMF-expanded molybdenum disulfide can be placed in the solvent and ultrasonically dispersed for 15 min

[0092] In some embodiments, adding the copper sulfate solution and the sodium sulfide solution to the dispersion liquid in sequence includes the steps: after adding the copper sulfate solution to the dispersion liquid, stirring at a speed of 500 revolutions per minute for 2 - 6 h, and then adding the sodium sulfide solution to the dispersion liquid and reacting for 40 - 80 min.

[0093] Exemplarily, the concentration of the copper sulfate solution can be 1 mol·L -1 , and the concentration of sodium sulfide can be 1 mol·L -1 .

[0094] Another exemplarily, a 1 mol·L -1 CuSO4 solution can be added dropwise to the dispersion liquid, stirred vigorously for 4 h, and then a corresponding 1 mol·L -1 NaS solution is continuously added dropwise and reacted for 60 min.

[0095] The present invention also provides an application of the mercury adsorbent as described above or the mercury adsorbent prepared by the preparation method as described in any one of the above in treating mercury-containing flue gas, including the steps:

[0096] The mercury adsorbent is contacted with the mercury-containing flue gas to adsorb Hg in the mercury-containing flue gas 0 ;

[0097] Among them, the composition of the mercury-containing flue gas includes: sulfur dioxide 0 - 20%, oxygen 0 - 20%, nitrogen monoxide 0 - 1000 ppm, hydrogen chloride 0 - 50 ppm, water vapor 0 - 20%; the mercury concentration in the mercury-containing flue gas is 0 - 10 mg / m 3 , the flow rate of the mercury-containing flue gas is 0.5 - 3 L / min, and the mass-volume ratio of the mercury adsorbent to the mercury-containing flue gas is 1 - 15 mg / L.

[0098] Exemplarily, in addition to sulfur dioxide, oxygen, nitrogen monoxide, hydrogen chloride, and water vapor, the mercury-containing flue gas may further include nitrogen.

[0099] Furthermore, the treatment time of the mercury-containing flue gas is less than 5400 min, and the treatment temperature of the mercury-containing flue gas is 40~160 °C.

[0100] For the convenience of those skilled in the art to further understand the present invention, the following is an example for illustration:

[0101] It should be noted that in the attached drawings, Hg 0 concentration (μg·m -3 ) is the Hg concentration value at the outlet of the equipment after the mercury-containing flue gas is purified by the mercury adsorbent (including the DMF-expanded molybdenum disulfide prepared in the present invention, the same hereinafter); Adsorption capacity (mg / g) in the attached drawings is the adsorption capacity of the mercury adsorbent after long-term adsorption of Hg 0 ; Hg 0 removealefficiency is the adsorption efficiency of the mercury adsorbent for Hg 0 ; Heat Flow (W / g) is the heat flow of the mercury adsorbent. 0

[0102] Example 1

[0103] Prepare DMF-MoS2: Dissolve 1.33 g of ammonium heptamolybdate and 2.45 g of thiourea completely in 25 mL of deionized water, stir vigorously for 30 minutes, and then add 25 mL of DMF solution to the solution to obtain a first mixture. Subsequently, transfer the first mixture to a 100 mL autoclave lined with Teflon and maintain it at 180 °C for 12 hours. After centrifugation, a black precipitate is obtained, and then wash the black precipitate with deionized water and alcohol. After washing, dry it at 80 °C for 10 h to obtain disordered structure DMF-expanded molybdenum disulfide nanosheets, namely DMF-expanded molybdenum disulfide (DMF-MoS2).

[0104] Example 2

[0105] Place the DMF-expanded molybdenum disulfide prepared in Example 1 in an adsorbent bed, and pass mercury-containing flue gas into it at a flow rate of 0.5~3 L / min at temperatures of 80 °C and 160 °C respectively. Among them, the mass-volume ratio of DMF-expanded molybdenum disulfide to the mercury-containing flue gas is 5 mg / L, and the dosage of the mercury removal adsorbent is 5 mg. Among them, the sulfur dioxide concentration in the mercury-containing flue gas is 6%, the oxygen concentration is 6%, and the mercury concentration is 5 mg / m 3 .

[0106] As Figure 9 can be seen, further measure the adsorption of Hg by DMF-MoS2 at 80 °C for a long time0 The adsorption capacity after that is as follows: MoS2-DMF adsorbs Hg for a long time at 80°C 0 The adsorption capacity reaches 46.91 mg·g -1 . Figure 9 In it, the arrow points to the ordinate corresponding to the corresponding curve.

[0107] Example 3

[0108] Take 0.3 g of DMF-expanded molybdenum disulfide (DMF-MoS2) prepared in Example 1, place it in 50 mL of deionized water and ultrasonically disperse it for 15 min, then add 0.8 ml of 1 mol·L -1 of CuSO4 solution, stir vigorously for 4 h, and then continue to add 0.8 ml of 1 mol·L -1 of NaS solution. After reacting for 60 min, collect the product by filtration, wash it several times with ethanol and deionized water, and freeze-dry it for 12 h to obtain 1 / 4CuS-MoS2.

[0109] Example 4

[0110] Take 0.3 g of DMF-expanded molybdenum disulfide (DMF-MoS2) prepared in Example 1, place it in 50 mL of deionized water and ultrasonically disperse it for 15 min, then add 0.5 ml of 1 mol·L -1 of CuSO4 solution, stir vigorously for 4 h, and then continue to add 0.5 ml of 1 mol·L -1 of NaS solution. After reacting for 60 min, collect the product by filtration, wash it several times with ethanol and deionized water, and freeze-dry it for 12 h to obtain 1 / 6CuS-MoS2.

[0111] Example 5

[0112] Take 3 mg of 1 / 6CuS-MoS2 prepared in Example 4 and place it in the adsorbent bed. Pass the mercury-containing flue gas into it at a flow rate of 0.5 - 3 L / min under the simulated flue gas conditions of 40°C, 80°C, 120°C, 160°C, and 200°C respectively; among them, the mass-volume ratio with the mercury-containing flue gas is 8 mg / L, and the composition of the mercury-containing flue gas includes: sulfur dioxide 6%, oxygen 6%, nitric oxide 200 ppm, hydrogen chloride 20 ppm, water vapor 10%, and the mercury concentration in the mercury-containing flue gas is 5 mg / m 3 .

[0113] As Figure 13 shown, under the simulated smelting flue gas conditions, 1 / 6CuS-MoS2 shows excellent Hg 0Removal ability, nearly 100% of Hg can be achieved within 4 h 0 Adsorption efficiency. When the temperature rises to 200 °C, the outlet Hg during the test stage 0 concentration gradually rises to 20 μg·m −3 . Figure 14 Among them, in the temperature range of 40 to 160 °C, the Hg adsorption rate of 1 / 6CuS-MoS2 0 is about 21 μg·g −1 ·min −1 , while the Hg adsorption rate of DMF-MoS2 at the same temperature 0 is about 12 μg·g −1 ·min −1 . When the temperature is 200 °C, the Hg adsorption rate of 1 / 6CuS-MoS2 0 is about 19 μg·g −1 ·min −1 . The above results prove that copper atoms are doped and sulfided, strong active sites are formed on the surface and have extremely strong thermal stability, further expanding the applicable temperature window of MoS2.

[0114] Example 6

[0115] Take 3 mg of 1 / 6CuS-MoS2 prepared in Example 4 and place it in the adsorbent bed. Under the simulated flue gas conditions at 160 °C, pass the mercury-containing flue gas into it at a flow rate of 0.5 - 3 L / min; among them, the mass-volume ratio with the mercury-containing flue gas is 8 mg / L, and the composition of the mercury-containing flue gas includes: sulfur dioxide 6%, oxygen 6%, nitric oxide 200 ppm, hydrogen chloride 20 ppm, water vapor 10%, and the mercury concentration in the mercury-containing flue gas is 5 mg / m 3 .

[0116] As Figure 15 shown, in the initial 1000 min test at 160 °C, the outlet Hg 0 concentration is lower than 20 μg·m −3 , and the time to reach saturated adsorption is about 5400 min. After calculation, the adsorption capacity of 1 / 6CuS-MoS2 measured at 160 °C is 47.67 mg·g −1 . As Figure 16 shown, 1 / 6CuS-MoS2 greatly improves the adsorption capacity of sulfides at high temperatures. Compared with other sulfide adsorptions, 1 / 6CuS-MoS2 has significant advantages in terms of high temperature and high capacity. Under similar conditions, the adsorption capacity of 1 / 6CuS-MoS2 is 1.7 times that of DMF-MoS2 and 3 times that of O-MoS2. The above results show that copper atom doping and sulfidation can significantly improve the Hg adsorption capacity of MoS2 nanosheets 0Adsorption capacity and adsorption rate.

[0117] Comparative Example 1

[0118] Take 0.3 g of DMF-expanded molybdenum disulfide (DMF-MoS2) prepared in Example 1, disperse it in 50 mL of deionized water by ultrasonic for 15 min, and control the product type by changing the type and addition amount of sulfate and the addition amount of sodium sulfide. The specific parameters are shown in Table 1. The specific products include 1 / 2CuS-MoS2, 1 / 9CuS-MoS2, 1 / 6S-MoS2, 1 / 6Cu-MoS2, 1 / 6FeS-MoS2, 1 / 6ZnS-MoS2.

[0119] Table 1 Synthesis parameters

[0120]

[0121] Analysis Example 1

[0122] The phase structures of all modified MoS2 samples (including 1 / 6CuS-MoS2 and 1 / 4CuS-MoS2 prepared in Examples 1 and 2 of the present invention, and 1 / 2CuS-MoS2, 1 / 9CuS-MoS2, 1 / 6S-MoS2, 1 / 6Cu-MoS2, 1 / 6FeS-MoS2, 1 / 6ZnS-MoS2 prepared in Comparative Example 1 of the present invention) were analyzed by XRD.

[0123] As Figure 1 shown, the synthesized CuS-MoS2 (including 1 / 6CuS-MoS2, 1 / 4CuS-MoS2, 1 / 2CuS-MoS2, and 1 / 9CuS-MoS2) all have two characteristic structures of 2H-phase MoS2 and CuS. During the process of reducing the composite amount, the peak intensity of CuS gradually weakens. When the composite amount is 1 / 6CuS-MoS2, the characteristic peak of CuS is difficult to observe in the XRD diffraction pattern, which indicates that the high specific surface structure of MoS2 leads to the highly dispersed CuS, and most of the Cu atoms enter the MoS2 lattice. After the material is sulfided, the formed CuS microparticles are difficult to be detected.

[0124] In addition, the diffraction peak of the (001) plane in the XRD pattern of the modified MoS2 is 8.7°, corresponding to an interlayer distance of 9.8 Å. The results of XRD analysis show that the interlayer spacing of the modified MoS2 base layer remains in an expanded state, and the highly dispersed CuS enters the MoS2 structure.

[0125] As Figure 2As shown, to compare the effects of different ion modifications, other transition metal sulfides were also used to modify MoS2. It can be seen that very similar diffraction peaks exist in different diffraction curves. This indicates that the sulfides are distributed on the surface of MoS2 in a highly dispersed form, and the crystal structure of MoS2 remains intact to a large extent, which also proves the stability of the properties of the DMF-expanded molybdenum disulfide material.

[0126] Analysis Example 2

[0127] As Figure 3 shown, SEM was used to analyze the modified MoS2. It can be seen that Figure 3 in the 1 / 2CuS-MoS2 two-dimensional nanolayer structure of (a), there are large-sized particles. These particles are formed by the reaction of a large amount of copper ions that did not enter the MoS2 lattice with sulfide ions to form massive CuS.

[0128] As the incorporation amount of copper ions decreases, most of the ions enter the lattice, and the part that forms copper sulfide alone decreases significantly. In 1 / 6CuS-MoS2 ( Figure 3 c) and 1 / 9CuS-MoS2 ( Figure 3 d), almost no large particles can be observed.

[0129] When no copper ions are incorporated, in 1 / 6S-MoS2 ( Figure 3 e), some regions show higher brightness. This is because the poor conductivity of sulfur leads to the accumulation of electrons on the sulfur surface. This is mainly due to the lack of sites on the molybdenum sulfide surface for direct anchoring of sulfide ions. A large amount of S is deposited on the surface of the lamellar structure, while suppressing the exposure of the sites on the molybdenum sulfide surface.

[0130] By adding an appropriate amount of cations, in 1 / 6Cu-MoS2 ( Figure 3 f), 1 / 6FeS-MoS2 ( Figure 3 g), 1 / 6ZnS-MoS2 ( Figure 3 h), some heteroatom metals enter the molybdenum sulfide lattice, and the formed modified MoS2 maintains its two-dimensional lamellar structure.

[0131] Analysis Example 3

[0132] To explore the microstructure and surface element distribution of the samples, as Figure 4 shown, TEM was used to observe the microstructure of the modified MoS2, and EDS was used to perform area scanning analysis of the surface elements. It can be seen that both 1 / 6Cu-MoS2 and 1 / 6CuS-MoS2 have a graphene-like two-dimensional lamellar structure, and the surface elements are evenly distributed, confirming that copper ions can be evenly distributed on the two-dimensional MoS2 nanosheets. At the same time, these copper ions provide potential anchoring sites for the growth of sulfide ions during the sulfidation process.

[0133] Analysis Example 4

[0134] As Figure 10 shown, Raman spectroscopy was used to analyze the structural changes of modified MoS2. Two typical stretching vibration modes could be observed in different MoS2 samples, corresponding to the out-of-plane atomic vibration A -1 mode at 371 cm 1g and the in-plane atomic vibration E1 2g mode at 403 cm -1 .

[0135] Compared with the original DMF-MoS2, the E1 2g peaks of copper ion-modified MoS2 (including 1 / 6CuS-MoS2, 1 / 4CuS-MoS2, 1 / 2CuS-MoS2, and 1 / 9CuS-MoS2) showed redshift and broadening, indicating a weakening of the Mo-S bond strength on the basal plane. This was due to the substitution of Mo atoms by Cu in the plane, resulting in a decrease in the number of Mo-S bonds. At the same time, the interval between the E1 2g peak and the A 1g peak of copper ion-modified MoS2 increased, indicating a weakening of the in-layer bonding and an enhancement of the interaction between adjacent MoS2 layers. The peak centered at 466 cm -1 was the vibration of the S2 dimer A 1g in the modified MoS2, which mainly originated from the S2 dimer formed by the anchoring of sulfur ions at the copper sites.

[0136] Due to the low Cu content in 1 / 9CuS-MoS2, S was difficult to be anchored and grown at the Cu sites, resulting in a small amount of short-chain sulfur that was difficult to detect.

[0137] Analysis Example 5

[0138] As Figure 11 shown, after 120 min of adsorption, the outlet Hg 0 concentration of 1 / 2CuS-MoS2 rapidly increased to 40 μg·m −3 ; when the doping amount was reduced, the outlet Hg 0 concentration of 1 / 4CuS-MoS2 was 14 μg·m −3 , and the outlet Hg 0 concentration of 1 / 6CuS-MoS2 was close to 0 μg·m −3 . This might be because with the increase in the doping amount, the content of bulk CuS increased, and a large amount of CuS accumulated and covered the effective surface active sites of MoS2. When the doping amount was further reduced, the outlet Hg 0 concentration of 1 / 9CuS-MoS2 was 9 μg·m −3 , indicating that too low a doping amount reduced the number of surface active sites.

[0139] To further explore the role of copper atom doping, the mercury removal performance of DMF-MoS2, 1 / 6Cu-MoS2, and 1 / 6CuS-MoS2 was compared. As Figure 11 shown in (b), the mercury removal performance of DMF-MoS2 was the worst. After 120 min of adsorption, the outlet Hg 0 concentration rose to 50 μg·m −3 , and was still rising; for 1 / 6Cu-MoS2 doped with copper atoms, the outlet mercury concentration decreased to 27 μg·m −3 , indicating that the incorporation of copper atoms effectively improved the high-temperature mercury capture activity of MoS2. It is speculated that the possible reason is that divalent copper ions have stronger electron gain ability and electron transport ability, accelerating the electron loss process of oxidized Hg 0 .

[0140] For 1 / 6CuS-MoS2 formed by further sulfidation of 1 / 6Cu-MoS2, the outlet Hg 0 concentration remained at about 0 μg·m −3 during the test, which may be related to the S2 2- active sites formed by 1 / 6CuS-MoS2. Therefore, compared with other CuS-MoS2 adsorbents, 1 / 6CuS-MoS2 has a significant advantage in site activity, thus showing the best Hg 0 removal performance.

[0141] Analysis Example 6

[0142] Take 3 mg of DMF-MoS2 prepared in Example 1, 1 / 6CuS-MoS2 prepared in Example 4, 1 / 6FeS-MoS2 and 1 / 6ZnS-MoS2 prepared in Comparative Example 1, and place them in the adsorbent bed respectively. Pass the mercury-containing flue gas into it at a flow rate of 0.5 - 3 L / min in a nitrogen environment at 160 °C; among them, the mercury concentration in the mercury-containing flue gas is 5 mg / m 3 .

[0143] As Figure 12 shown, at the end of the 120-min test, 1 / 6FeS-MoS2 showed the worst Hg 0 removal performance, and the outlet Hg 0 concentration rose to about 60 μg·m −3 , and the outlet Hg 0 concentration of 1 / 4ZnS-MoS2 was 33 μg·m −3 . The order of mercury removal performance of different doping elements is 1 / 6CuS-MoS2 > 1 / 6ZnS-MoS2 > 1 / 6FeS-MoS2, which may be related to the electron gain and loss ability of ions. Cu 2+ is more inclined to gain electrons and has an effect on Hg0 It can play an oxidizing role, but Fe 2+ has reducibility and loses electrons during the reaction, which inhibits the mercury removal performance of 1 / 6FeS-MoS2.

[0144] Analysis of Example 7

[0145] The surface chemical element state changes of 1 / 6Cu-MoS2 and 1 / 6CuS-MoS2 after the Hg 0 removal experiment were analyzed by XPS. Figure 17 The Cu 2p spectrogram in (a) can be divided into four peaks, which are Cu + and Cu 2+ species.

[0146] As shown in Table 2, after adsorbing Hg 0 , the proportion of high-valent Cu 2+ on the surface of 1 / 6Cu-MoS2 decreased from 26.60% to 22.79%, and the proportion of high-valent Cu 2+ on the surface of 1 / 6CuS-MoS2 decreased from 32.88% to 25.64%. The proportion of low-valent Cu + increased in both, indicating that surface Cu 2+ participated in the oxidation of Hg 0 .

[0147] As Figure 17 shown in (b), the high-resolution Mo 3d XPS spectrum of 1 / 6Cu-MoS2 after adsorption can be divided into six peaks, which are attributed to Mo 6+ , Mo 5+ and Mo 4+ . After Hg 0 capture, the peak position of Mo 6+ did not change significantly, but its proportion decreased from 36.08% to 29.07%, indicating that Mo 6+ can react directly with Hg 0 . The atomic proportion of Mo 5+ slightly increased from 30.77% to 32.24%, and the atomic proportion of Mo 4+ increased from 33.15% to 38.69%. This is because Mo 0 is reduced to Mo 6+ and Mo 5+ and Mo 4+ during the oxidation of Hg 6+ . The results show that the Mo 5+ site may be more active in oxidizing Hg 0 than the Mo 6+The proportion decreased from 36.04% to 31.37%, and the consumption ratio of high-valence molybdenum decreased, indicating that after sulfurization regulation, new sites were generated on the surface that could be used for the 0 oxidative adsorption of Hg.

[0148] Figure 17 The S 2p XPS spectrum in (c) contains four peaks, corresponding to S2 2− and S 2− . After adsorption, the proportion of unsaturated S2 2− on the surface of 1 / 6Cu-MoS2 decreased from 21.94% to 19.72%, and the atomic proportion of S 2− increased from 78.06% to 80.28%. In 1 / 6CuS-MoS2, the proportion of unsaturated S2 2− decreased from 28.35% to 22.50%, indicating that during the adsorption process of 1 / 6CuS-MoS2 formed after sulfurization, Hg 0 would preferentially bind to the unsaturated S2 2− sites, while in 1 / 6Cu-MoS2, more high-valence metal sites exposed on the surface would be consumed.

[0149] The chemical state of mercury adsorbed on 1 / 6Cu-MoS2 and 1 / 6CuS-MoS2 was analyzed by XPS (d). Peaks centered at 105.44 eV (Hg 4f 5 / 2 ) and 101.39 eV (Hg 4f 7 / 2 ) corresponded to Hg 2+ , proving that an oxidation reaction occurred during the adsorption of Hg 0 on DMF-MoS2.

[0150] Table 2 Chemical composition of different modified MoS2 surfaces

[0151]

[0152] Analysis Example 8

[0153] In order to analyze the product composition of mercury adsorbed on the surfaces of 1 / 6Cu-MoS2 and 1 / 6CuS-MoS2 samples, temperature-programmed desorption (Hg-TPD) tests were carried out.

[0154] Comparing the initial decomposition temperatures of different adsorbents, the initial decomposition temperature of DMF-MoS2 was the lowest, about 60 °C. Mercury formed a weakly bound Hg-Mo amalgam on the surface, which was not conducive to the efficient mercury removal of the adsorbent at high temperatures. For 1 / 6Cu-MoS2 modified with copper ions, the initial decomposition temperature was about 100 °C, while the initial decomposition temperature of 1 / 6CuS-MoS2 increased significantly to 130 °C. The increase in the initial decomposition temperature indicated that the weak adsorption sites on the surface of 1 / 6CuS-MoS2 were transformed into strong adsorption sites.

[0155] Comparing the curve distributions of 1 / 6Cu-MoS2 and 1 / 6CuS-MoS2, the mercury adsorbed by 1 / 6Cu-MoS2 is rapidly decomposed and released at 150 °C. The decomposition range is mainly between 200-250 °C, and the temperature corresponding to the maximum decomposition peak is 251 °C. The temperature at which the mercury in 1 / 6CuS-MoS2 decomposes rapidly is approximately 200 °C, and the maximum peak appears at 273 o °C, and the overall decomposition range is concentrated in the high-temperature section. Under the same pre-adsorption conditions, 1 / 6CuS-MoS2 has the highest decomposition temperature, indicating that regulating the basal plane structure of MoS2 effectively increases the number of strong adsorption sites on the surface.

[0156] Analysis Example 9

[0157] The above analysis examples have demonstrated that doping with copper ions can reduce the generation of weak adsorption sites on the surface and effectively improve the high-temperature adsorption activity of MoS2 nanosheets. To further analyze the changes in adsorption sites, density functional theory calculations were used to study the effect of copper ion doping on the adsorption activity of MoS2.

[0158] As Figure 19 shown, the basal plane sites of copper ion-doped MoS2 were simulated using the Cu-MoS2(001) plane. Different numbers of copper atoms were used to replace the molybdenum atoms on the basal plane of MoS2. As the number of copper atom substitutions increased, the adsorption energy also gradually increased, reaching -22.2, -33.7, and -59.9 kJ∙mol -1 -1, respectively. When three copper atoms replaced the molybdenum atoms, the mercury atom could directly bond with the surface S sites to form a bicoordinated S-Hg-S structure, with bond lengths of 2.403 Å and 2.520 Å, respectively. In the absence of copper ion doping, the adsorption energies at different sites on the basal plane were all lower than 11 kJ∙mol -1 -1, indicating that copper ion doping can effectively enhance the adsorption activity of the MoS2 basal plane towards mercury. The binding energy between the activated basal plane sites and mercury is enhanced, thereby improving the high-temperature mercury removal performance of the material. When copper atoms are adsorbed on the S sites of the MoS2(001) plane, the surface adsorption energy reaches -104.6 kJ∙mol -1 -1, indicating that the copper sites distributed on the MoS2(001) surface can also directly interact strongly with mercury atoms, which is beneficial for the formation of stable HgS products after Hg is oxidized.

[0159] Analysis Example 10

[0160] To study the adsorption of Hg 0 on different sites of the Cu-MoS2(100) plane, four stable adsorption structures, including A, B, C, and D, were constructed, as Figure 20 shown. Configurations A and B represent Hg0 Adsorbed on the metal edge sites of the Cu-MoS2(100) surface. In Structure A, the Hg atom is adsorbed on the top site of the Cu atom, and the Hg-Cu bond length is 2.923 Å; in Structure B, the Hg atom is adsorbed on the bridge site of Mo, forming two Hg-Mo bonds with a bond length of 2.889 Å.

[0161] The calculation results show that for Hg in Configurations A and B 0 the adsorption energies are -38.5 and -96.0 kJ∙mol -1 respectively, indicating that mercury binds stronger to the molybdenum element at the boundary sites in this structure. This may be because after the electron transfer from the molybdenum atom to the copper atom, the molybdenum atom in the high valence state has a stronger mercury-binding ability. Structures C and D represent the binding of Hg 0 to the S edge sites of the Cu-MoS2(100) surface, and their Hg 0 adsorption energies are -25.0 and -150.4 kJ∙mol -1 respectively. In Structure D, the mercury atom forms bonds with S and Mo respectively, with bond lengths of 2.541 and 2.756 Å, while the binding energies of the S edge sites of the undoped MoS2(100) surface are all lower than 16 kJ∙mol -1 This indicates that the doping of copper atoms retains the activity of the metal boundary sites while enhancing the activity of the S edge sites. The calculation results show that on the (100) surface and (001), the adsorption capacity of different sites for Hg 0 has been enhanced. Further proved, the activation effect of copper atom doping on the basal plane and edge sites, the initial decomposition temperature of the adsorbed mercury is significantly increased, and the high-temperature adsorption activity is stronger.

[0162] In the above technical solutions of the present invention, the above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A mercury adsorbent, characterized in that, The mercury adsorbent has a two-dimensional nanosheet structure, including 1 / 4CuS-MoS2, 1 / 6CuS-MoS2, 1 / 9CuS-MoS2, where 1 / 4, 1 / 6, and 1 / 9 are the atomic molar ratios of Cu and Mo in the mercury adsorbent. The composition of the mercury adsorbent includes molybdenum disulfide, copper sulfide, and dimethylformamide; Among them, the molybdenum disulfide has a two-dimensional nanosheet structure, and the molybdenum disulfide nanosheets are stacked layer by layer. The dimethylformamide is located between at least two adjacent layers of the molybdenum disulfide nanosheets; The layer spacing between two adjacent molybdenum disulfide nanosheets is 0.90 - 1.00 nanometers, and the copper sulfide is uniformly dispersed on the surface of the molybdenum disulfide nanosheets and in the lattice of the molybdenum disulfide.

2. The mercury adsorbent according to claim 1, characterized in that, In terms of mass fraction, Cu in the mercury adsorbent 2+ , Cu + has contents of 31-33% and 66-68% respectively, Mo 4+ , Mo 5+ , Mo 6+ has contents of 28-30%, 33-35% and 35-37% respectively, and the content of S2 2- on the surface of the mercury adsorbent is 27-30%.

3. A preparation method of a mercury adsorbent, characterized in that, It includes the steps: Mix a molybdenum-containing reagent, a sulfur-containing reagent, and dimethylformamide to obtain a first mixed solution; where the molar ratio of the molybdenum element in the molybdenum-containing reagent to the sulfur element in the sulfur-containing reagent is 1:0.5 - 9; the molybdenum-containing reagent includes ammonium heptamolybdate, and the sulfur-containing reagent includes thiourea; Heat-treat the first mixed solution, and then perform solid-liquid separation of the precipitate to obtain DMF-expanded molybdenum disulfide; where the treatment temperature of the heat treatment is 120 - 260 °C, and the treatment time is 4 - 20 h; Disperse the DMF-expanded molybdenum disulfide in a solvent to obtain a dispersion liquid. Sequentially add a copper sulfate solution and a sodium sulfide solution to the dispersion liquid, and perform solid-liquid separation to obtain the mercury adsorbent; where the addition ratio of the DMF-expanded molybdenum disulfide to the copper sulfate and the sodium sulfide is 0.3 g:0.0001 - 0.0015 mol:0.0001 - 0.0015 mol.

4. The preparation method according to claim 3, characterized in that, The addition ratio of the DMF-expanded molybdenum disulfide to the copper sulfate and the sodium sulfide is 0.3 g:0.0004 - 0.0006:0.0004 - 0.0006.

5. The preparation method according to claim 3, characterized in that, The concentration of the dimethylformamide is 50% - 100%, and the mass-volume ratio of the molybdenum-containing reagent to the dimethylformamide is 1 g:10 - 30 mL.

6. The preparation method according to claim 3, wherein The treatment temperature of the heat treatment is 140 - 200 °C, and the treatment time is 8 - 16 h.

7. The preparation method according to claim 3, characterized in that, The solvent includes water, and the mass-volume ratio of the DMF-expanded molybdenum disulfide to the solvent is 0.3 g / 30 - 70 mL; the step of dispersing the DMF-expanded molybdenum disulfide in a solvent to obtain a dispersion liquid further includes: placing the DMF-expanded molybdenum disulfide in the solvent and ultrasonically dispersing it for 10 - 30 min.

8. The preparation method according to claim 3, characterized in that, The step of sequentially adding the copper sulfate solution and the sodium sulfide solution to the dispersion liquid includes: after adding the copper sulfate solution to the dispersion liquid, stirring it at a speed of 500 revolutions per minute for 2 - 6 h, and then adding the sodium sulfide solution to the dispersion liquid and reacting for 40 - 80 min.

9. Use of a mercury adsorbent as described in claim 1 or 2 or a mercury adsorbent prepared by the preparation method described in any one of claims 3 to 8 in treating mercury-containing flue gas, characterized in that, It includes the steps: The mercury adsorbent contacts the mercury-containing flue gas and adsorbs Hg in the mercury-containing flue gas 0 ; Among them, the composition of the mercury-containing flue gas includes: sulfur dioxide 0-20%, oxygen 0-20%, nitrogen monoxide 0-1000 ppm, hydrogen chloride 0-50 ppm, water vapor 0-20%; the mercury concentration in the mercury-containing flue gas is 0-10 mg / m 3 , the flow rate of the mercury-containing flue gas is 0.5-3 L / min, and the mass-volume ratio of the mercury adsorbent to the mercury-containing flue gas is 1-15 mg / L.

10. The application according to claim 9, characterized in that The treatment time of the mercury-containing flue gas is less than 5400 min, and the treatment temperature of the mercury-containing flue gas is 40 - 160 °C.

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