Copper-doped iron sulfide, method for producing the same, and use thereof

Abstract

The application provides copper-doped iron sulfide and a preparation method and application thereof, wherein the preparation method of the copper-doped iron sulfide comprises the following steps: S1. configuring iron nitrate and copper nitrate into a metal salt solution; wherein the sum of the molar concentrations of iron ions and copper ions in the metal salt solution is 0.003-0.06 mol / 25 ml; S2. dissolving a sulfur source in the metal salt solution to obtain a mixed solution, heating the mixed solution to 120-180 DEG C under high pressure for 12 h, and separating the solid substance in the mixed solution to obtain the copper-doped iron sulfide; the molar concentration of the sulfur source in the mixed solution is 0.01-0.1 mol / 50 ml; or, the metal salt solution is heated to 120-180 DEG C under high pressure for 12 h to obtain a precursor, the precursor is mixed with elemental sulfur and then heated to 400 DEG C for 2 h to obtain the copper-doped iron sulfide. The mercury adsorption capacity of the iron sulfide is improved, and the Hg 0 removal has a significant economic advantage.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal control technology, specifically relating to a copper-doped iron sulfide, its preparation method, and its application. Background Technology

[0002] Metal sulfides possess strong resistance to SO2 poisoning and are rich in mercury-loving sulfur, making them the most promising adsorbent materials for mercury removal from high-sulfur flue gas. As the cheapest metal sulfide, iron sulfide has a significant cost advantage over copper sulfide and molybdenum sulfide. However, its mercury removal performance is far weaker than other metal sulfides; researchers have found that hydrothermally synthesized iron disulfide has a mercury adsorption capacity of only 2.7 mg·g⁻¹. -1 .

[0003] Therefore, it is necessary to provide a copper-doped iron sulfide, its preparation method, and its application to solve the technical problems existing in the above-mentioned commonly used technologies. Summary of the Invention

[0004] To address the technical problems of weak mercury removal performance and low mercury adsorption capacity of iron sulfide in the aforementioned commonly used technologies, this invention provides a method for preparing copper-doped iron sulfide, comprising the following steps:

[0005] S1. Prepare a metal salt solution by dissolving ferric nitrate and copper nitrate; wherein the sum of the molar concentrations of ferric ions and copper ions in the metal salt solution is 0.003 to 0.06 mol / 25 ml.

[0006] S2. Dissolve the sulfur source in a metal salt solution to obtain a mixture. Heat the mixture under high pressure to 120-180°C and keep it at that temperature for 12 hours. Separate the solids to obtain copper-doped iron sulfide. The molar concentration of the sulfur source in the mixture is 0.01-0.1 mol / 50 ml.

[0007] Alternatively, the metal salt solution is heated to 120–180°C under high pressure and held for 12 hours to obtain a precursor. The precursor is then mixed with elemental sulfur and heated to 400°C and held for 2 hours to obtain copper-doped iron sulfide.

[0008] Furthermore, the sulfur source includes thiourea and sodium sulfide.

[0009] Furthermore, when the sulfur source is the thiourea, heating the mixture to 120-180°C under high pressure and holding it at that temperature for 12 hours includes heating the mixture to 120-140°C under high pressure and holding it at that temperature for 12 hours.

[0010] Furthermore, when the sulfur source is sodium sulfide, heating the mixture to 120-180°C under high pressure and holding it at that temperature for 12 hours includes heating the mixture to 160-180°C under high pressure and holding it at that temperature for 12 hours.

[0011] Furthermore, the mass ratio of the precursor to the elemental sulfur is 1:1 to 2.

[0012] Furthermore, in the copper-doped iron sulfide, the molar ratio of iron ions to copper ions is 0.9–0.95:0.05–0.1.

[0013] This invention provides a copper-doped iron sulfide, prepared by any of the methods described above.

[0014] The present invention also provides an application of the copper-doped iron sulfide described above in mercury removal from flue gas, comprising the steps of passing mercury-containing flue gas into the copper-doped iron sulfide to carry out a mercury removal reaction, wherein the reaction temperature of the mercury removal reaction is 25℃~50℃, and the flow rate of the mercury-containing flue gas is 600 mL·min. -1 The mercury-containing flue gas contains Hg 0 Concentration 100–200 μg / m -3 .

[0015] Furthermore, the mercury-containing flue gas includes sulfur-containing flue gas, wherein the volume fraction of sulfur dioxide in the sulfur-containing flue gas is 4-8% and the volume fraction of oxygen is 4-8%.

[0016] Furthermore, the concentration of HCl in the mercury-containing flue gas is 2–6 ppm.

[0017] Compared with the prior art, the present invention has at least the following advantages:

[0018] This invention provides a method for preparing copper-doped iron sulfide, in which copper is uniformly dispersed within the iron sulfide. The applicant discovered that Fe... 3+ Cu 2+ and S2 2- These are the active sites for mercury removal from copper-doped iron sulfide, which participate in Hg through different pathways. 0 The oxidation and adsorption of copper lead to the final fixation of HgS, while copper doping results in the formation of more S2 on the surface of iron sulfide. 2- This part S2 2- It is formed by the coordination of S and Cu. In addition, high-valence Cu is introduced into the surface of copper-doped iron sulfide. 2+ That accounts for 26.61%.

[0019] The applicant also found that copper doping reduced the band gap of FeS2 from 0.647 eV to 0.10 eV, significantly shifted the d-band center negatively, and promoted Hg...0 Adsorption and electron transport: Compared to individual Fe and Cu sites, the increased charge density in the Fe-Hg and Cu-Hg bond regions enhances Hg atom charge transfer and strengthens the interaction between Hg and the Fe and Cu sites of copper-doped iron sulfide. The d orbitals of Fe and Cu sites overlap with the s orbitals of Hg, playing a synergistic role in mercury removal. The adsorption energy decreases from -55.85 kJ·mol⁻¹. -1 (Fe site) and -39.61 kJ·mol -1 (Cu site) increased to -68.70 kJ·mol -1 Furthermore, the Cu sites pre-adsorbed on the FeS2(100) surface synergistically with the Fe sites to inhibit Hg. 0 The adsorption energy reaches -96.52 kJ·mol⁻¹ -1 Cu sites on Hg 0 The adsorption energy also reaches -80.89 kJ·mol⁻¹. -1 .

[0020] Based on the above, copper-doped iron sulfide achieves Hg 0 The adsorption performance was optimized, and its mercury adsorption capacity was significantly improved compared with other metal sulfides, reaching that of ordinary ferric disulfide (2.7 mg·g⁻¹). -1 It is about 9 times more effective than iron sulfide, while also taking into account the advantages of iron sulfide's strong resistance to SO2 poisoning. It can maintain high mercury removal performance in a high sulfur dioxide atmosphere with SO2 volume fraction of 6%, and is suitable for mercury removal from high SO2 smelting flue gas.

[0021] In addition, Fe 0.9 Cu 0.1 SS deHg 0 The cost is 471.00 yuan / (kg Hg) 0 (Considering only the raw material cost of adsorbent preparation), it is only 2 / 5 of that of ordinary iron disulfide and 1 / 250 of that of carbon-based adsorbents. Therefore, copper doping achieves an increase in the adsorption capacity of iron sulfide for mercury, while also improving the adsorption capacity of Hg. 0 It has significant economic advantages in terms of removal and has good application potential. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 (a) is a scanning electron micrograph of FeS2-S in Example 1 of this invention. Figure 1(b) Fe in Example 1 of the present invention 0.9 Mo 0.1 Scanning electron micrographs of SS. Figure 1 (c) Example 1 Fe of the present invention 0.9 Cu 0.1 Scanning electron micrograph of SS.

[0024] Figure 2 (a) is the X-ray diffraction pattern of iron sulfide before and after metal cation doping in Example 1 of the present invention; Figure 2 (b) is the X-ray diffraction pattern of copper-doped iron sulfide with different copper addition amounts in Example 1 of the present invention.

[0025] Figure 3 For the analysis of FeS2-S and Fe in Example 1 of this invention 0.9 Cu 0.1 Raman spectrum of SS.

[0026] Figure 4 (a) is the Fe 2p orbital X-ray photoelectron spectrum of iron sulfide before and after doping in Example 1 of this invention; Figure 4 (b) is the S2p orbital X-ray photoelectron spectrum of iron sulfide before and after doping in Example 1 of this invention: Figure 4 (c) X-ray photoelectron spectra of Mo 3d orbitals of iron sulfide before and after doping in Example 1 of this invention; Figure 4 (d) is the Cu 2p orbital X-ray photoelectron spectrum of iron sulfide before and after doping in Example 1 of this invention.

[0027] Figure 5 (a) Hg of FeS2 prepared by thiourea as a sulfur source at different sulfidation temperatures in Example 2 of this invention at 50°C and 6% SO2 + 6% O2. 0 Adsorption performance; Figure 5 (b) Fe prepared at different sulfidation temperatures using thiourea as a sulfur source in Example 2 of this invention. 0.9 Cu 0.1 Hg at 50℃ and 6% SO2 + 6% O2 0 Adsorption performance; Figure 5 (c) Fe prepared by using thiourea as a sulfur source at different sulfidation temperatures in Example 2 of this invention. 0.9 Mo 0.1 Hg at 50℃ and 6% SO2 + 6% O2 0 Adsorption performance; Figure 5 (d) Fe prepared at different sulfidation temperatures using sodium sulfide as a sulfur source in Example 2 of this invention. 0.9 Cu 0.1 S at 50℃, 6% SO2 + 6% O2, Hg 0 Adsorption performance.

[0028] Figure 6 The Hg of iron sulfide prepared by dry sulfidation in Example 3 of this invention is analyzed under 6% SO2 + 6% O2. 0 Adsorption performance.

[0029] Figure 7 For the analysis of the Hg of iron sulfide doped with different copper addition amounts in Example 4 of this invention under 6% SO2 + 6% O2 conditions. 0 Adsorption performance.

[0030] Figure 8 (a) Fe in Example 5 of the present invention 0.9 Cu 0.1 SS under different flue gas components Hg 0 Adsorption performance; Figure 8 (b) Fe in Example 5 of the present invention 0.9 Cu 0.1 SS under different flue gas components Hg 0 Adsorption performance.

[0031] Figure 9 Fe in Example 6 of this invention 0.9 Cu 0.1 SS and FeS2-S under the conditions of 6% SO2 + 6% O2 and 50℃, FeS2-S and Fe 0.9 Cu 0.1 Long-term adsorption curve of SS.

[0032] Figure 10 (a) FeS2-S and Fe in Example 6 of the present invention 0.9 Cu 0.1 SS adsorption Hg 0 pseudo-level one and Figure 10 (b) Analyzing FeS2-S and Fe in Example 6 of this invention 0.9 Cu 0.1 SS adsorption Hg 0 The pseudo-second-order dynamics model.

[0033] Figure 11 (a) Hg adsorption in Example 7 of the present invention 0 Fe before and after 0.9 Cu 0.1 X-ray photoelectron spectroscopy of SS in the Fe 2p orbital, Figure 11 (b) Hg adsorption in Example 7 of the present invention 0 Fe before and after 0.9 Cu 0.1 X-ray photoelectron spectrum of SS in the S2p orbit Figure 11 (c) Hg adsorption in Example 7 of the present invention0 Fe before and after 0.9 Cu 0.1 X-ray photoelectron spectroscopy of SS in Cu 2p orbitals Figure 11 (d) shows the adsorption of Hg in Example 7 of this invention. 0 Fe before and after 0.9 Cu 0.1 X-ray photoelectron spectrum of SS in the Hg 4f orbital.

[0034] Figure 12 Fe in Example 8 of this invention 0.9 Cu 0.1 Mercury desorption curves for SS under programmed temperature rise. Detailed Implementation

[0035] The technical solutions of 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, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0037] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0038] This invention provides a method for preparing copper-doped iron sulfide, comprising the following steps:

[0039] S1. Prepare a metal salt solution by mixing ferric nitrate and copper nitrate; wherein the sum of the molar concentrations of ferric ions and copper ions in the metal salt solution is 0.003 to 0.006 mol / 25 ml.

[0040] For example, the sum of the molar concentrations of iron ions and copper ions is 0.005 mol / 25 ml.

[0041] S2. Wet sulfidation: The sulfur source is dissolved in a metal salt solution to obtain a mixed solution. The mixed solution is heated to 120-180℃ under high pressure and kept at that temperature for 12 hours. Copper-doped iron sulfide is obtained by filtration. The molar concentration of the sulfur source in the mixed solution is 0.01-0.1 mol / 50 ml.

[0042] In some embodiments, the sulfur source can be first dissolved in deionized water to form a sulfur source solution with a sulfur source molar concentration of 0.01 to 0.1 mol / 50 ml, and then the sulfur source solution is mixed with a metal salt solution and stirred for 2 to 3 hours to obtain a mixed solution.

[0043] In some specific embodiments, heating the mixture to 120-180°C under high pressure and holding for 12 hours, and then filtering to obtain copper-doped iron sulfide may include the following steps: transferring the mixture into a 100ml Teflon-lined autoclave, heating to 120-180°C and holding for 12 hours, obtaining a black powder by filtration, washing the black powder several times with deionized water and ethanol alternately, and then drying to obtain copper-doped iron sulfide.

[0044] The drying temperature can be 60℃, and the drying time can be 12 hours.

[0045] In some embodiments, the molar concentration of the sulfur source in the mixture can be 0.01 to 0.05 mol / 50 ml; in some more specific embodiments, the molar concentration of the sulfur source in the mixture can be 0.02 mol / 50 ml.

[0046] In some embodiments, the sulfur source includes thiourea and / or sodium sulfide.

[0047] When the sulfur source is thiourea, heating the mixture to 120-180°C under high pressure and holding it at that temperature for 12 hours includes heating the mixture to 120-140°C under high pressure and holding it at that temperature for 12 hours.

[0048] When the sulfur source is sodium sulfide, heating the mixture to 120-180°C under high pressure and holding it at that temperature for 12 hours includes heating the mixture to 160-180°C under high pressure and holding it at that temperature for 12 hours.

[0049] Alternatively, dry sulfidation: the metal salt solution is heated to 120-180°C under high pressure and held for 12 hours to obtain a precursor. The precursor is mixed with elemental sulfur and then heated to 400°C and held for 2 hours to obtain copper-doped iron sulfide.

[0050] In some specific embodiments, the metal salt solution can be transferred to a 100 mL Teflon-lined autoclave, heated to 120–180 °C and held for 12 h, and a reddish-brown precursor can be obtained by filtration, washing and drying. The precursor is then mixed evenly with elemental sulfur and fed into a tube furnace, and then heated to 400 °C under a N2 atmosphere and held for 2 h.

[0051] The mass ratio of the precursor to the elemental sulfur can be 1:1 to 2; in some embodiments, the mass ratio of the precursor to the elemental sulfur can be 1:1.5.

[0052] In some embodiments, the molar ratio of iron ions to copper ions in copper-doped iron sulfide is 0.9–0.95:0.05–0.1.

[0053] In some more specific embodiments, the molar ratio of iron ions to copper ions in copper-doped iron sulfide can be 0.9:0.1.

[0054] When the molar ratio of iron ions to copper ions in copper-doped iron sulfide is 0.9–0.95:0.05–0.1, the molar ratio of iron nitrate to copper nitrate in the metal salt solution is 0.9–0.95:0.05–0.1.

[0055] When the molar ratio of iron ions to copper ions in copper-doped iron sulfide is 0.9:0.1, the molar ratio of iron nitrate to copper nitrate in the metal salt solution is also 0.9:0.1.

[0056] This invention provides a copper-doped iron sulfide, prepared by any of the methods described above.

[0057] This invention provides an application of copper-doped iron sulfide as described above in mercury removal from flue gas, comprising the steps of passing mercury-containing flue gas into the copper-doped iron sulfide to carry out a mercury removal reaction, wherein the reaction temperature of the mercury removal reaction is 25℃~50℃, and the flow rate of the mercury-containing flue gas is 600 mL·min. -1 The mercury-containing flue gas contains Hg 0 Concentration 100–200 μg / m -3 .

[0058] For example, the mercury-containing flue gas can be cooled to a temperature of 25–50°C to provide a reaction environment of 25–50°C for the mercury removal reaction.

[0059] In some embodiments, Hg in mercury-containing flue gas 0 Concentration 120–180 μg / m -3 In some more specific embodiments, Hg in mercury-containing flue gas 0 Concentration 150 μg.m -3 .

[0060] Furthermore, the mercury-containing flue gas includes sulfur-containing flue gas, wherein the volume fraction of sulfur dioxide in the sulfur-containing flue gas is 4-8% and the volume fraction of oxygen is 4-8%.

[0061] In some embodiments, the volume fraction of sulfur dioxide in the sulfur-containing flue gas is 5-7% and the volume fraction of oxygen is 5-7%. In some specific embodiments, the volume fraction of sulfur dioxide in the sulfur-containing flue gas is 6% and the volume fraction of oxygen is 6%.

[0062] Furthermore, the concentration of HCl in the mercury-containing flue gas is 2 to 6 ppm, and in some specific embodiments, the concentration of HCl in the mercury-containing flue gas is 5 ppm.

[0063] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided:

[0064] Example 1: One-step hydrothermal synthesis of copper-doped iron sulfide using wet sulfidation

[0065] S1. Dissolve 0.005 mol of ferric nitrate and copper nitrate in 25 mL of deionized water to form a metal salt solution;

[0066] S2. Thiourea (0.02 mol, A) and sodium sulfide (0.02 mol, B) were dissolved separately in 25 mL of deionized water to form two sulfur source solutions. The sulfur source solutions were then stirred with a metal salt solution for 2 hours to form a mixture. This mixture was then transferred to a 100 mL Teflon-lined autoclave and kept at a certain temperature for 12 hours. A black powder was obtained by filtration, washed several times alternately with deionized water and ethanol, and then dried at 60 °C for 12 hours. The obtained copper-doped iron sulfide is denoted as Fe. x Cu (1-x) Syz, where x represents the molar amount of Fe / (Fe+Cu) molar amount, y represents the sulfur source, and z represents the sulfidation temperature.

[0067] Copper-doped iron sulfide using thiourea as the sulfur source is denoted as Fe. x Cu (1-x) SA; Copper-doped iron sulfide with sodium sulfide as the sulfur source is denoted as Fe. x Cu (1-x) SB;

[0068] By changing the molar ratio of ferric nitrate to copper nitrate in the metal salt solution, and achieving a molar ratio of 0.95:0.05, Fe was prepared. 0.95 Cu 0.05 SA or Fe 0.95 Cu 0.05 SB;

[0069] Fe was prepared when the molar ratio of ferric nitrate to copper nitrate in a metal salt solution was 0.9:0.1. 0.9 Cu 0.1 SA or Fe 0.9 Cu 0.1 SB;

[0070] Fe was prepared when the molar ratio of ferric nitrate to copper nitrate in a metal salt solution was 0.85:0.15. 0.85 Cu 0.15 SA or Fe 0.85 Cu 0.15 SB.

[0071] Example 2: Dry sulfidation synthesis of copper-doped iron sulfide

[0072] S1. Dissolve 0.005 mol of ferric nitrate and copper nitrate in 25 mL of deionized water to form a metal salt solution;

[0073] S2. The metal salt solution was transferred to a 100 mL Teflon-lined autoclave, heated to 160 °C and held for 12 h. A reddish-brown precursor was obtained by filtration, washing, and drying. The precursor was then mixed uniformly with elemental sulfur (mass ratio 2:3) and fed into a tube furnace. The furnace was then heated to 400 °C under a N2 atmosphere and held for 2 h. The resulting copper-doped iron sulfide was denoted as Fe. x Cu (1-x) SS.

[0074] By changing the molar ratio of ferric nitrate to copper nitrate in the metal salt solution, and achieving a molar ratio of 0.95:0.05, Fe was prepared. 0.95 Cu 0.05 SS;

[0075] Fe was prepared when the molar ratio of ferric nitrate to copper nitrate in a metal salt solution was 0.9:0.1. 0.9 Cu 0.1 SS;

[0076] Fe was prepared when the molar ratio of ferric nitrate to copper nitrate in a metal salt solution was 0.85:0.15. 0.85 Cu 0.15 SS.

[0077] Comparative Example 1: Molybdenum-doped iron sulfide synthesized by wet sulfidation

[0078] S1. Dissolve 0.005 mol of ferric nitrate and ammonium molybdate in 25 mL of deionized water to form a metal salt solution;

[0079] S2. Thiourea (0.02 mol, A) and sodium sulfide (0.02 mol, B) were dissolved separately in 25 mL of deionized water to form two sulfur source solutions. One of the sulfur source solutions was stirred with a metal salt solution for 2 h to form a mixture. The mixture was then transferred to a 100 mL Teflon-lined autoclave and kept at a certain temperature for 12 h. A black powder was obtained by filtration, washed several times alternately with deionized water and ethanol, and then dried at 60 °C for 12 h. The obtained copper-doped iron sulfide is denoted as Fe. x Mo (1-x) Syz, where x represents the molar amount of Fe / (Fe+Cu) molar amount, y represents the sulfur source, and z represents the sulfidation temperature.

[0080] That is, molybdenum-doped iron sulfide with thiourea as the sulfur source is denoted as Fe. x Mo (1-x) SA; molybdenum-doped iron sulfide with sodium sulfide as the sulfur source is denoted as Fe. x Mo (1-x) SB;

[0081] Fe was prepared when the molar ratio of ferric nitrate to copper nitrate in a metal salt solution was 0.9:0.1. 0.9 Mo 0.1 SA or Fe 0.9 Mo 0.1 SB.

[0082] Comparative Example 2: Molybdenum-doped iron sulfide was synthesized using a dry sulfidation method.

[0083] S1. Dissolve 0.005 mol of ferric nitrate and ammonium molybdate in 25 mL of deionized water to form a metal salt solution;

[0084] S2. The metal salt solution was transferred to a 100 mL Teflon-lined autoclave, heated to 160 °C and held for 12 h. A reddish-brown precursor was obtained by filtration, washing, and drying. The precursor was then mixed uniformly with elemental sulfur (mass ratio 2:3) and fed into a tube furnace. The furnace was then heated to 400 °C under a N2 atmosphere and held for 2 h. The resulting copper-doped iron sulfide was denoted as Fe. x Mo (1-x) SS.

[0085] When the molar ratio of ferric nitrate to copper nitrate in a metal salt solution is 0.9:0.1, Fe 0.9 Mo 0.1 SS.

[0086] Comparative Example 3 uses wet sulfidation to synthesize copper-doped iron sulfide.

[0087] S1. Dissolve 0.005 mol of ferric nitrate in 25 mL of deionized water to form a metal salt solution;

[0088] S2. Thiourea (0.02 mol, A) and sodium sulfide (0.02 mol, B) were dissolved separately in 25 mL of deionized water to form two sulfur source solutions. The sulfur source solutions were then stirred with a metal salt solution for 2 hours to form a mixture. This mixture was then transferred to a 100 mL Teflon-lined autoclave and kept at a certain temperature for 12 hours. A black powder was obtained by filtration, washed several times alternately with deionized water and ethanol, and then dried at 60 °C for 12 hours. The obtained copper-doped iron sulfide is denoted as Fe. x Cu (1-x) Syz, where x represents the molar amount of Fe / (Fe+Cu) molar amount, y represents the sulfur source, and z represents the sulfidation temperature.

[0089] Iron sulfide with thiourea as the sulfur source is denoted as FeS2-A; copper-doped iron sulfide with sodium sulfide as the sulfur source is denoted as FeS2-B.

[0090] Comparative Example 4: Iron sulfide was synthesized using a dry sulfidation method.

[0091] S1. Dissolve 0.005 mol of ferric nitrate in 25 mL of deionized water to form a metal salt solution;

[0092] S2. The metal salt solution was transferred to a 100 mL Teflon-lined autoclave, heated to 160 °C and held for 12 h. The precursor was obtained by filtration, washing and drying. The precursor was then mixed with elemental sulfur (mass ratio 2:3) and fed into a tube furnace. The furnace was then heated to 400 °C under N2 atmosphere and held for 2 h. The obtained iron sulfide was denoted as FeS2-S.

[0093] Fe mentioned in the following analysis example x Cu (1-x) SA, Fe x Cu (1-x) SB, Fe 0.95 Cu 0.05 SA, Fe 0.95 Cu 0.05 SB, Fe 0.9 Cu 0.1 SA or Fe 0.9 Cu 0.1 SB, Fe 0.85 Cu 0.15 SA, Fe 0.85 Cu 0.15 SB was prepared in Example 1, and the Fe mentioned in the following analytical examples... x Cu (1-x) SS, Fe 0.95 Cu 0.05 SS, Fe 0.9 Cu 0.1 SS, Fe0.85 Cu 0.15 SS was prepared in Example 2, and the Fe mentioned in the following analytical examples x Mo (1-x) SA, Fe x Mo (1-x) SB, Fe 0.9 Mo 0.1 SA, Fe 0.9 Mo 0.1 SB was prepared from Comparative Example 1, and the Fe mentioned in the following analytical examples... x Mo (1-x) SS, Fe 0.9 Mo 0.1 SS was prepared from Comparative Example 2, FeS2-A and FeS2-B mentioned in the following analytical examples were prepared from Comparative Example 3, and FeS2-S mentioned in the following analytical examples were prepared from Comparative Example 4.

[0094] Analysis Example 1: Analyzing the effect of copper / molybdenum doping on the structure of iron sulfide.

[0095] The effects of copper / molybdenum doping on the morphology and structure of iron sulfide were analyzed using SEM, such as... Figure 1 As shown, the present invention provides a comparison of ordinary iron sulfide (FeS2-S) prepared in Comparative Example 4 and molybdenum / copper doped iron sulfide (FeS2-S prepared in Comparative Example 2). 0.9 Mo 0.1 SS and Fe prepared in Example 2 0.9 Cu 0.1 The morphology of the SS (ferric sulfide) particles consisted of irregular clusters formed by the aggregation of small particles, with a cluster size of approximately 4-6 μm, indicating that copper and molybdenum doping did not alter the macroscopic morphology of the iron sulfide. Energy dispersive spectroscopy (EDS) showed a uniform distribution of Fe and S elements on the particle surface, along with uniformly distributed copper or molybdenum, indicating that molybdenum / copper was uniformly dispersed within the iron sulfide. The BET specific surface areas of the iron sulfide, copper-doped iron sulfide, and molybdenum-doped iron sulfide were all the same, at 3 m². 2 ·g -1 This indicates that metal cation doping has no significant effect on the specific surface area of ​​iron sulfide.

[0096] The phase structures of iron sulfide, copper-doped iron sulfide, and molybdenum-doped iron sulfide were analyzed by XRD, such as... Figure 2 As shown in (a), the characteristic diffraction peaks of the XRD pattern of FeS2-S at 2θ = 28.5, 33.0, 37.1, 40.8, 47.4, and 56.3° correspond to the (111), (200), (210), (211), (220), and (311) crystal planes of pyrite-type FeS2 (JCPDS PDF 42-1340), respectively. After doping with the metal cation (Cu / Mo), Fe... 0.9 Cu0.1 SS and Fe 0.9 Mo 0.1 The diffraction peaks of SS also highly match the characteristic peaks of pyrite, and no obvious impurity peaks were observed in the XRD patterns of the three types of iron sulfides, indicating that metal cation doping does not affect the phase structure of iron sulfides. Figure 2 As shown in (b), copper-doped iron sulfide prepared with different amounts of copper ions also have XRD diffraction peak patterns that match those of pyrite-type FeS2 (JCPDS PDF 42-1340), indicating that the phase structure of copper-doped iron sulfide studied in this invention is pyrite-type FeS2.

[0097] SEM analysis revealed that Cu and Mo ions were incorporated into the FeS2 crystal without significantly affecting its overall structure.

[0098] The effect of copper doping on the structural characteristics of iron sulfide was analyzed using Raman spectroscopy, such as... Figure 3 As shown. Undoped FeS2-S at 320-420 cm⁻¹ -1 Two distinct vibration peaks appeared within the range, located at 343 cm. -1 The peak at that point corresponds to the E of FeS2. g Vibration mode, located at 379cm -1 The peak at that location corresponds to the A peak of FeS2. g Vibration modes. After the introduction of copper, Fe... 0.9 Cu 0.1 No new characteristic peaks were observed in SS, which remained at 343 cm⁻¹. -1 and 379cm -1 Neither of the two characteristic peaks showed significant shift or broadening, and the corresponding peak intensity ratios were quite close, further indicating that copper doping did not change the structure of iron sulfide.

[0099] XPS was used to analyze the effects of copper and molybdenum doping on the valence state distribution of elements on the surface of iron sulfide. Figure 4 As shown in (a), the peaks at 707.2 and 708.1 eV in the Fe 2p spectrum of FeS2-S correspond to Fe 2+ Fe 2p 3 / 2 The two peaks at 708.3 and 710.6 eV correspond to Fe orbitals. 3+ Fe 2p 3 / 2 The peak at 713.1 eV corresponds to the satellite peak, and the other five peaks correspond to Fe 2p. 1 / 2 Orbit. After molybdenum and copper doping, Fe... 0.9 Mo 0.1 SS and Fe 0.9 Cu 0.1 The peak positions in the Fe 2p spectrum of SS did not change significantly. For example... Figure 4 As shown in (b), there are three peaks at S2p in FeS2-S, with the peak at 161.7 eV corresponding to S. 2- The peaks at 162.7 and 163.8 eV correspond to S2. 2-12 .like Figure 4 As shown in (c), Fe 0.9 Mo 0.1 The peaks at 225.7 and 226.9 eV in the Mo 3d spectrum of SS correspond to S, respectively. 2- 2s and S2 2- The peaks at 228.7 and 232.7 eV correspond to Mo, respectively. 4+ Mo3d 5 / 2 and Mo 3d 3 / 2 The orbital indicates that the introduced molybdenum is mainly in the form of Mo. 4+ It exists in the form of... (e.g.) Figure 4 As shown in (d), Fe 0.9 Cu 0.1 In the Cu 2p spectrum of SS, the peaks at 932.6 and 952.4 eV correspond to Cu, respectively. + 2p 3 / 2 and Cu + 2p 1 / 2 The orbitals, with peaks at 933.9 and 955.1 eV, correspond to Cu, respectively. 2+ 2p 3 / 2 and Cu 2+ 2p 1 / 2 track.

[0100] The valence state distribution of each element changed significantly before and after copper doping, as shown in Table 1. The S valence state of FeS2... 2- The proportion is as high as 33.87%, after doping S 2- The proportion decreased significantly, Fe 0.9 Mo 0.1 SS and Fe 0.9 Cu 0.1 SS decreased to 10.08% and 8.36% respectively, while S2 2- The percentage increased significantly from 65.73% to 89.97% and 91.69%, respectively, indicating that metal cation doping can generate more S2 on the surface of iron sulfide. 2- This part S2 2- This is clearly due to the coordination of S with Cu and Mo. After doping, Fe... 3+ The percentages decreased from 28.44% to 26.75% and 26.71%, respectively. Furthermore, Fe... 0.9 Cu 0.1 High-valence Cu was introduced onto the SS surface. 2+ That accounts for 26.61%. 15 .

[0101] Table 1 Surface chemical composition before and after iron sulfide doping

[0102]

[0103] Analysis Example 2: Effect of Sulfur Source on Mercury Removal Performance in Copper / Molybdenum Doped Iron Sulfide

[0104] At 50℃, in a 6% SO2 + 6% O2 atmosphere, Hg 0 Concentration 150 μg·m -3 Under the conditions specified, a mercury removal test was conducted for 60 minutes, with an adsorbent dosage of 10 mg. For example... Figure 5 (a)~ Figure 5 As shown in (c), molybdenum-doped iron sulfide exhibits poor mercury removal performance, Fe 0.9 Mo 0.1 Hg at 60 min for SA-180 0 The adsorption efficiency was only 32%, indicating that molybdenum doping actually inhibited the mercury removal performance of iron sulfide.

[0105] Thiourea is used as a sulfur source, and iron sulfide has Hg. 0 The adsorption performance is relatively less affected by the sulfidation temperature. FeS2-A-160 with a sulfidation temperature of 160℃ exhibits the best mercury removal performance, but its Hg removal performance is significantly reduced after 60 min. 0 The adsorption efficiency is only 63.5%.

[0106] The mercury removal performance of copper-doped iron sulfide is significantly affected by the sulfidation temperature; the higher the sulfidation temperature, the worse the mercury removal performance of the adsorbent. Fe prepared at a sulfidation temperature of 120℃... 0.9 Cu 0.1 SA-120 exhibited the best mercury removal performance, with Hg at 60 min. 0 The adsorption efficiency is still 92%, indicating that copper doping can improve the mercury removal performance of iron sulfide. The optimal sulfidation temperature for copper-doped iron sulfide with thiourea as the sulfur source is 120-140℃.

[0107] The effect of sodium sulfide as a sulfur source on mercury removal performance, such as Figure 5 As shown in (d), copper-doped iron sulfide prepared using sodium sulfide as the sulfur source exhibits different trends in mercury removal performance. The copper-doped iron sulfide synthesized at 160℃ shows the best mercury removal performance, with the lowest Hg level at 60 min. 0 The adsorption efficiency is still 96%, indicating that sodium sulfide is more suitable as a sulfur source for hydrothermal sulfidation than thiourea, and the optimal sulfidation temperature for copper-doped iron sulfide with sodium sulfide as the sulfur source is 160-180℃.

[0108] Analysis of the effect of preparation method on mercury removal performance in copper / molybdenum doped iron sulfide in Example 3

[0109] The effect of dry sulfidation on the mercury removal performance of iron sulfide was studied, and the results are as follows: Figure 6 As shown. All three types of iron sulfide synthesized by dry sulfidation of elemental sulfur exhibit better mercury removal performance than those obtained by wet sulfidation, with copper-doped iron sulfide showing the best mercury removal performance at Hg levels below 60 min. 0 The adsorption efficiency remained at 98%, and was still 95% after 120 minutes.

[0110] Molybdenum-doped iron sulfide has slightly weaker mercury removal performance; Hg at 120 min is lower. 0 The adsorption efficiency is 91%.

[0111] This indicates that the sulfidation method is an important factor affecting the mercury removal performance of iron sulfide. Compared with wet sulfidation, the adsorbent obtained by dry sulfidation of elemental sulfur has better mercury removal performance. Molybdenum / copper doping can further improve the mercury removal efficiency of iron sulfide, and the improvement effect of copper doping is more significant.

[0112] Analysis of the effect of copper doping amount in copper-doped iron sulfide in Example 4

[0113] like Figure 7 As shown, the mercury removal performance of copper-doped iron sulfide exhibits a trend of first increasing and then decreasing with the amount of copper added. The mercury removal performance of undoped iron sulfide within 120 minutes... 0 The adsorption efficiency is 80%. After the introduction of copper, Fe 0.95 Cu 0.05 The efficiency of SS was increased to 90% after increasing the copper doping amount, Fe 0.9 Cu 0.1 SS achieved a maximum mercury removal efficiency of 98%. However, further increasing the copper doping concentration resulted in Fe... 0.85 Cu 0.15 SS's Hg 0 The adsorption efficiency actually decreased to 85%. Furthermore, the efficiency of copper sulfide was only 81%, and the chemical formula of copper-doped iron sulfide is Fe. 0.9 Cu 0.1 Mercury adsorption performance is optimal when the molar ratio of copper to iron (SS) is 0.9:1.

[0114] Analysis of the Influence of Flue Gas Composition and Temperature in Example 5

[0115] Non-ferrous smelting flue gas contains various components such as O2, SO2, HCl, and H2O, and flue gas temperature may also affect the mercury removal performance of copper-doped iron sulfide. For example... Figure 8 As shown in (a), Fe was tested under different atmospheres. 0.9 Cu 0.1 SS's Hg 0 Adsorption performance, and Figure 8 The mercury concentration was 150 μg / m under all atmospheric conditions. -3It is evident that both 6% SO2 and 5ppm HCl promote the removal of mercury from copper-doped iron sulfide, and the average Hg within 1 hour... 0 The adsorption efficiency increased from 85% to 97% and 98%, respectively; 6% O2 and 10% H2O had no significant effect on the mercury removal performance of the adsorbent, indicating that copper-doped iron sulfide has good resistance to flue gas poisoning.

[0116] Subsequently, mercury removal tests were conducted under simulated smelting flue gas conditions (SFG: 6% SO2 + 6% O2 + 5ppm HCl + 10% H2O), and Hg was measured. 0 The adsorption efficiency is as high as 100%, indicating that Fe 0.85 Cu 0.15 SS can maintain good mercury removal performance in complex smelting flue gas environments. For example... Figure 8 As shown in (b), the effect of mercury-containing flue gas on the adsorption performance of copper-doped iron sulfide was investigated. It can be seen that Fe... 0.9 Cu 0.1 SS exhibits good mercury removal performance at both 25℃ and 50℃. However, the mercury removal performance gradually decreases with increasing temperature; at 100℃, after 120 minutes of mercury removal testing, the mercury removal efficiency drops to 67%. This is due to Fe... 0.9 Cu 0.1 This is due to the relatively weak mercury adsorption capacity of some active sites on the SS surface.

[0117] Example 6: Mercury Adsorption Capacity Test

[0118] Mercury adsorption capacity is an important indicator for evaluating the mercury removal performance of adsorbents. This study investigated the effect of copper-doped iron sulfide on mercury adsorption. 0 The adsorption capacity was determined at 50℃, under a 6% O2 + 6% SO2 atmosphere, and a gas flow rate of 600 mL / min. -1 Hg 0 Concentration 150 μg.m -3 Under the conditions, FeS2-S prepared in Comparative Example 4 and Fe prepared in Example 2 were compared respectively. 0.9 Cu 0.1 SS undergoes prolonged Hg 0 Adsorption test results are as follows Figure 9 As shown: FeS2-S reached 90% penetration after 45 hours. Hg was calculated by integration. 0 The adsorption capacity is 8.3 mg·g. -1 In comparison, Fe 0.9 Cu 0.1 SS only achieved 90% breakthrough after 120 hours, with an effective adsorption time 2.7 times longer than FeS2-S. Hg 0 The adsorption capacity is 25.0 mg·g. -1 It is 3 times that of FeS2-S.

[0119] The pseudo-first-order and pseudo-second-order kinetic models were used to further analyze FeS2-S and Fe. 0.9 Cu 0.1 SS's Hg 0 Adsorption characteristics were studied, and their adsorption kinetics were investigated, as shown in Equations 1, 2 and 3.

[0120] Pseudo-first-order dynamics model:

[0121]

[0122] Pseudo-second-order dynamics model:

[0123]

[0124] or

[0125] In the formula, q t and q e k1(min) represents the mercury adsorption capacity at time t (min) and adsorption equilibrium, respectively. -1 ) and k2(g·mg -1 ·min -1 ) represent the reaction rate constants of the two kinetic models, respectively.

[0126] like Figure 10 As shown in Table 2, the pseudo-first-order kinetic model affects FeS2-S and Fe 0.9 Cu 0.1 The goodness of fit (R) of the SS mercury-capturing adsorption curve 2 The goodness of fit of the pseudo-second-order kinetic model improved to 0.9284 and 0.9404, respectively, indicating that FeS2-S and Fe... 0.9 Cu 0.1 SS to Hg 0 The adsorption characteristics of Hg are more consistent with the pseudo-second-order kinetic model, i.e., Hg 0 Chemical adsorption is the key reason for the removal of mercury by the two iron sulfide adsorbents. According to Table 2, FeS2 and Fe... 0.9 Cu 0.1 S adsorbs Hg 0 The kinetic parameters, and the saturated mercury adsorption capacity (q) obtained under the pseudo-second-order kinetic model. e The concentrations were 9.1 and 27.5 mg / g, respectively. -1 This is closer to the experimental data. Kinetic studies show that FeS2 and Fe... 0.9 Cu 0.1 SS to Hg 0 The adsorption mainly depends on the active sites on the iron sulfide surface for Hg. 0 Chemical adsorption.

[0127] Table 2 Model parameters for pseudo-first-order and pseudo-second-order dynamics

[0128]

[0129] Table 3 shows a comparison of the mercury adsorption performance of copper-doped iron sulfide with other typical metal sulfides. Copper-doped iron sulfide exhibits better Hg adsorption performance. 0 Its adsorption performance is significantly improved compared to other metal sulfides, exceeding that of ordinary ferric disulfide (2.7 mg·g⁻¹). -1 It is 9 times more effective than Fe and can maintain high mercury removal performance under a 6% SO2 + 6% O2 atmosphere, making it suitable for mercury removal from high SO2 smelting flue gas. Furthermore, Fe... 0.9 Cu 0.1 SS deHg 0 The cost is 471.00 yuan / (kg Hg) 0 (Considering only the raw material cost of adsorbent preparation), it is only 2 / 5 of that of ordinary iron disulfide and 1 / 250 of that of carbon-based adsorbents. Therefore, copper doping achieves an increase in the adsorption capacity of iron sulfide for mercury, while also improving the adsorption capacity of Hg. 0 It has significant economic advantages in terms of removal and has good application potential.

[0130] Table 3 Adsorption capacity of different sulfide adsorbents

[0131]

[0132]

[0133] Analysis of Example 7: Investigating the Mercury Adsorption Mechanism of Copper-Doped Iron Sulfide

[0134] Hg was compared using XPS. 0 Fe before and after adsorption 0.9 Cu 0.1 SS surface element valence state changes, such as Figure 11 As shown in Table 4, copper-doped iron sulfide (Fe) 0.9 Cu 0.1 Cu in SS) 2+ Fe 3+- It is the main Hg 0 Adsorption active sites can directly adsorb Hg 0 Oxidized to Hg 2+ .

[0135] Figure 11 (a) shows the Fe 2p XPS spectrum of the adsorbent, which can be decomposed into eight peaks. The two peaks at 707.2 and 708.1 eV correspond to Fe 2+ Fe 2p 3 / 2The two peaks at 708.3 and 710.6 eV correspond to Fe orbitals. 3 + Fe 2p 3 / 2 The peak at 713.1 eV corresponds to the Fe2p peak of the satellite peak. 3 / 2 The orbital, the other five peaks correspond to Fe2p 1 / 2 Orbital. Adsorption of Hg 0 After that, Fe 2+ and Fe 3+ The peak position did not shift significantly, Fe 3+ The proportion decreased from 26.71% to 23.44%, Fe 2+ The increased proportion indicates that Fe 3+ It is Hg 0 The oxidation active sites.

[0136] like Figure 11 As shown in (b), the S2p XPS spectrum of the adsorbent contains three peaks, with the peak at 161.9 eV corresponding to S. 2- The peaks at 162.7 and 163.9 correspond to S2. 2- Adsorption of Hg 0 After that, S2 2- and S 2- The proportion did not change significantly, indicating that S2 2- Not Hg 0 The oxidation active sites.

[0137] like Figure 11 As shown in (c), the Cu 2p XPS spectrum of the adsorbent contains four peaks, with the peaks at 932.6 and 952.4 eV corresponding to Cu. + The peaks at 933.9 and 955.1 eV correspond to Cu. 2+ Adsorption of Hg 0 After that, Cu 2+ The proportion decreased from 26.61% to 22.85%, Cu + The increased proportion of Cu indicates 2+ Also Hg 0 The oxidation active sites.

[0138] like Figure 11 As shown in (d), the Hg 4f XPS spectrum contains two peaks, with peaks at 104.7 eV and 100.8 eV corresponding to Hg, respectively. 2+ Hg 4f 5 / 2 and Hg 4f 7 / 2 Orbits indicate that in Fe 0.9 Cu 0.1 S adsorbs Hg through chemical oxidation. 0 This is consistent with the results of adsorption kinetic analysis.

[0139] Table 4 Fe 0.9 Cu 0.1 Surface chemical composition before and after SS adsorption

[0140]

[0141] Analysis of Example 8: Investigating the Mercury Adsorption Mechanism of Copper-Doped Iron Sulfide

[0142] Mercury adsorption in the Fe prepared in Example 2 was analyzed by mercury-programmed temperature desorption (Hg-TPD). 0.9 Cu 0.1 The morphology of SS surface, such as Figure 12 As shown in the figure, the Hg-TPD curve exhibits a significant mercury desorption peak at 270℃, indicating that Hg... 0 After oxidation and adsorption, HgS is formed on the surface of the adsorbent.

[0143] Combining material characterization and theoretical calculations, it can be seen that S2 2- Fe 3+ and Cu 2+ It is the active component for mercury removal in copper-doped iron sulfide, where Cu is formed by substituting Fe or S to form copper doping. Copper doping promotes the synergistic effect between Fe and Cu sites and Hg atoms in iron sulfide, and the adsorption energy increases from -55.85 kJ·mol⁻¹. -1 Increased to -68.70 kJ·mol -1 Furthermore, the pre-adsorbed Cu sites, alone or in conjunction with Fe sites, further enhance the adsorption energy of Hg to -80.89 and -96.52 kJ·mol⁻¹. -1 .

[0144] It can be inferred that Hg 0 In Fe 0.9 Cu 0.1 There are two pathways for adsorption on SS. The first pathway is via Hg. 0 With metal site Cu 2+ -Fe 3+ The reaction forms [Fe-Hg-Cu], eventually producing HgS, as follows:

[0145] Hg 0 +Cu 2+ -Fe 3+ -S→[Fe·Hg·Cu]-S

[0146] [Fe·Hg·Cu]-S→[Cu + ]+Fe 2+ +HgS

[0147] The second route is Hg 0 Directly with the metal site Fe 3+The reaction forms [Fe-Hg], as follows:

[0148] Hg 0 +Fe 3+ -S→[Fe·Hg]-S

[0149] [Fe·Hg]-S→[Fe 2+ ]+HgS

[0150] Under both pathways, Hg 0 Both will form stable HgS through chemical adsorption on the surface of copper-doped iron sulfide.

[0151] This invention synthesizes various iron sulfides using a molybdenum / copper doping strategy, including copper-doped iron sulfides (Fe2+) under high SO2 flue gas conditions. 0.9 Cu 0.1 SS) deHg 0 The study investigated the effects of cation doping on the surface chemical properties of iron sulfide, elucidating the enhancement mechanism of mercury removal active sites on the iron sulfide surface, thereby significantly improving the mercury adsorption capacity of iron sulfide. The main conclusions are as follows:

[0152] (1) Copper / molybdenum doping did not change the original pyrite (FeS2) phase structure and specific surface area of ​​iron sulfide, but it achieved the regulation of surface chemical properties through elemental doping. Hydrothermal and elemental sulfur sulfidation can increase the proportion of unsaturated sulfur on the surface of doped iron sulfide, and the doping of chalcophilic metal cations copper / molybdenum will increase the S2 content of iron sulfide. 2- The proportions increased from 65.73% to 91.69% and 89.97% respectively, Fe 3+ The proportions decreased from 28.44% to 26.75% and 26.71%, respectively. Compared to molybdenum doping, which only introduces low-valence Mo... 4+ Copper doping introduces the high-valence state Cu as an active component. 2+ .

[0153] (2) By doping Hg of iron sulfide before and after doping 0 Adsorption experiments revealed that copper-doped iron sulfide exhibited superior mercury removal performance compared to iron sulfide, molybdenum-doped iron sulfide, and copper sulfide. Under simulated smelting flue gas (6% SO2 + 6% O2 + 5ppm HCl + 10% H2O) atmosphere, its mercury removal efficiency approached 100%. Copper-doped iron sulfide is suitable for use at temperatures of 50℃ and below, and is applicable to smelting flue gas after washing or condensation treatment. Under a 6% SO2 + 6% O2 atmosphere, copper-doped iron sulfide effectively removed mercury from Hg. 0 The adsorption capacity reaches 25.0 mg·g -1 It is three times that of undoped iron sulfide and nine times that of ordinary iron disulfide. Copper-doped iron sulfide undergoes Hg removal. 0 The cost is only 471.00 yuan / (kg Hg) 0The cost is less than 1 / 250th that of industrial carbon-based adsorbents, demonstrating a significant economic advantage. Adsorption kinetic analysis shows that chemisorption is the main rate-determining step in the mercury removal process.

[0154] (3)Fe 3+ Cu 2+ and S2 2- These are the active sites for mercury removal from copper-doped iron sulfide, which participate in Hg through different pathways. 0 The copper doping process oxidizes and adsorbs FeS2, ultimately fixing it as HgS. DFT calculations show that copper doping reduces the band gap of FeS2 from 0.647 eV to 0.10 eV, significantly shifts the d-band center negatively, and promotes HgS oxidation and adsorption. 0 Adsorption and electron transport: Compared to individual Fe and Cu sites, the increased charge density in the Fe-Hg and Cu-Hg bond regions enhances Hg atom charge transfer and strengthens the interaction between Hg and the Fe and Cu sites of copper-doped iron sulfide. The d orbitals of Fe and Cu sites overlap with the s orbitals of Hg, playing a synergistic role in mercury removal. The adsorption energy decreases from -55.85 kJ·mol⁻¹. -1 (Fe site) and -39.61 kJ·mol -1 (Cu site) increased to -68.70 kJ·mol -1 Furthermore, the Cu sites pre-adsorbed on the FeS2(100) surface synergistically with the Fe sites to inhibit Hg. 0 The adsorption energy reaches -96.52 kJ·mol⁻¹ -1 Cu sites on Hg 0 The adsorption energy also reaches -80.89 kJ·mol⁻¹. -1 .

[0155] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing copper-doped iron sulfide, characterized in that, Including the following steps: S1. Prepare a metal salt solution by dissolving ferric nitrate and copper nitrate; wherein, in the metal salt solution, the sum of the molar concentrations of iron ions and copper ions is 0.003~0.06 mol / 25 ml, and the molar ratio of copper to iron in the metal salt solution is 0.9:0.1; S2. Dissolve the sulfur source in a metal salt solution to obtain a mixture. Heat the mixture to 120~180℃ under high pressure and keep it at that temperature for 12h. Separate the solids to obtain copper-doped iron sulfide. The molar concentration of the sulfur source in the mixture is 0.01~0.1mol / 50ml. The sulfur source includes thiourea and sodium sulfide; when the sulfur source is thiourea, the mixture is heated to 120~140℃ under high pressure and kept at that temperature for 12h; when the sulfur source is sodium sulfide, the mixture is heated to 160~180℃ under high pressure and kept at that temperature for 12h. Alternatively, the metal salt solution is heated to 120~180℃ under high pressure and held for 12h to obtain a precursor. The precursor is mixed with elemental sulfur and then heated to 400℃ and held for 2h to obtain copper-doped iron sulfide. The mass ratio of the precursor to the elemental sulfur is 1:1~2.

2. A copper-doped iron sulfide, characterized in that, It is prepared by the method for preparing copper-doped iron sulfide as described in claim 1.

3. An application of copper-doped iron sulfide as described in claim 2 in mercury removal from flue gas, characterized in that, The process includes passing mercury-containing flue gas into the copper-doped iron sulfide to carry out a mercury removal reaction, wherein the reaction temperature is 25℃~50℃ and the flow rate of the mercury-containing flue gas is 600 mL·min. -1 The mercury-containing flue gas contains Hg 0 Concentration 100~200 μg.m -3 .

4. The application according to claim 3, characterized in that, The mercury-containing flue gas includes sulfur-containing flue gas, wherein the volume fraction of sulfur dioxide in the sulfur-containing flue gas is 4-8% and the volume fraction of oxygen is 4-8%.

5. The application according to claim 3, characterized in that, The concentration of HCl in the mercury-containing flue gas is 2-6 ppm.

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