Sulfur-doped carbon-based confinement composite material as well as preparation method and application thereof

Abstract

The invention discloses a sulfur-doped carbon-based confinement composite material as well as a preparation method and application thereof, and belongs to the technical field of sewage treatment. The preparation method comprises the following steps: jointly dispersing biochar, soluble copper salt, soluble iron salt and sodium sulfate into water to obtain a mixed solution A; adjusting the pH value of the mixed solution to 4.8-5.2 by using a pH regulator and a pH buffer agent to obtain a mixed solution B; performing hydrothermal reaction on the mixed solution B, and then filtering, washing, drying and calcining to obtain the sulfur-doped carbon-based confinement composite material. The prepared sulfur-doped carbon-based confinement composite material is low in price, stable in structure and high in catalytic activity. When the catalyst is used for activating persulfate, the decomposition reaction of the persulfate can be accelerated through a free radical and non-free radical synergistic path. When a catalytic oxidation system formed by the catalyst and persulfate is used for degrading the neonicotinoid insecticides in water, the degradation efficiency is high, and the catalyst has a broad-spectrum degradation effect on various neonicotinoid insecticides such as thiamethoxam and clothianidin.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a sulfur-doped carbon-based confined composite material, its preparation method, and its application. Background Technology

[0002] Neonicotinic insecticides are synthetic nicotine derivatives that combine high insecticidal activity, broad-spectrum control effects, and low toxicity to mammals, making them widely used in agricultural pest control. However, due to their small molecular structure, high water solubility, and long environmental half-life, these insecticides are easily adsorbed by soil particles and migrate with water, eventually seeping into groundwater or surface water and accumulating in aquatic ecosystems, posing a potential threat to aquatic organisms and ecological balance. Imidacloprid, as a first-generation neonicotinic insecticide, works by specifically targeting nicotinic acetylcholine receptors in the insect nervous system, causing excitation, paralysis, and even death in pests. However, imidacloprid is a nitrogen-containing heterocyclic compound that is difficult to biodegrade, and conventional wastewater treatment processes are ineffective in removing it, leading to its continuous accumulation in the aquatic environment.

[0003] Compared to traditional oxidation technologies that generate hydroxyl radicals by activating hydrogen peroxide, the persulfate advanced oxidation process has become an important technological direction for the degradation of organic pollutants due to its unique advantages. This process breaks the peroxy bond of persulfate through specific activation methods, generating a large number of highly oxidizing species, including sulfate radicals, hydroxyl radicals, superoxide radicals, and singlet oxygen, which can efficiently destroy the chemical structure of organic pollutants. At the same time, this process has higher reaction stability, is less demanding on the pH value of the reaction system, and maintains good applicability in acidic, neutral, and even weakly alkaline water environments, with significantly better environmental tolerance than traditional oxidation technologies.

[0004] In recent years, researchers have focused on the activation of peroxymonosulfate for the treatment of organic wastewater using layered bimetallic hydroxide and biochar composite catalysts. These catalysts are typically prepared by directly mixing and drying biochar and layered bimetallic hydroxide, aiming to combine the adsorption properties of biochar with the catalytic activity of layered bimetallic hydroxide. However, existing preparation processes have significant drawbacks: firstly, van der Waals forces easily cause particle aggregation between the layered bimetallic hydroxide nanosheets, leading to the covering of active sites on the catalyst surface and reducing catalytic efficiency; secondly, during aqueous reactions, metal ions in the layered bimetallic hydroxide are prone to leaching, resulting not only in the loss of active catalyst components and shortened catalyst lifespan but also potential secondary pollution of water bodies.

[0005] In summary, the core problem with existing layered bimetallic hydroxide and biochar composite catalysts lies in the lack of a spatial confinement mechanism for the metal active component. This prevents the stable loading of layered bimetallic hydroxides or metal active sites into the biochar matrix through structural design, leading to recurring aggregation and leaching issues. Therefore, developing a biochar-based composite catalyst with a spatially confined structure to inhibit metal particle aggregation and reduce ion leaching through confinement, while simultaneously enhancing persulfate activation, is of significant practical importance for achieving deep degradation of neonicotinoid pesticides and mitigating water environment risks. It is also a key breakthrough for promoting the industrial application of persulfate processes. Summary of the Invention

[0006] In view of this, the present invention aims to provide a sulfur-doped carbon-based confined composite material, its preparation method, and its application. The sulfur-doped carbon-based confined composite material prepared by the present invention is inexpensive, structurally stable, and exhibits strong catalytic activity. When this catalyst is used to activate persulfate, the decomposition reaction of persulfate can be accelerated through a synergistic pathway of free radicals and non-free radicals. When the catalytic oxidation system composed of this catalyst and persulfate is used to degrade neonicotinoid insecticides in water, it exhibits high degradation efficiency and a broad-spectrum degradation effect on various neonicotinoid insecticides such as thiamethoxam and thiamethoxam.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing a sulfur-doped carbon-based confined composite material, comprising the following preparation steps: S1. A mixed solution A is obtained by dispersing biochar, soluble copper salt, soluble iron salt and sodium sulfate together in water; S2. Adjust the pH of the mixed solution to 4.8~5.2 using a pH adjuster and a pH buffer to obtain mixed solution B; S3. The mixed solution B is subjected to a hydrothermal reaction, then filtered, washed, dried and calcined to obtain a sulfur-doped carbon-based confined composite material.

[0008] Preferably, the concentration of biochar in the mixed solution A in S1 is 10~50 g / L, and Cu 2+ The concentration is 0.04~0.10 mol / L, Fe 3+ The concentration of sodium sulfide is 0.06~0.15 mol / L, and the concentration of sodium sulfide is 0.005~0.02 mol / L.

[0009] Furthermore, the biochar has a mesh size of 60-150 mesh. The biochar used in this invention can be prepared by calcining agricultural waste under an inert atmosphere. Agricultural waste includes, but is not limited to, biomass raw materials such as peanut shells, walnut shells, and melon seed shells. The calcination temperature is 500-900℃, the holding time is 1-3h, and the heating rate is 5-10℃ / min, which can yield biochar with excellent performance.

[0010] Further, the soluble copper salt includes, but is not limited to, at least one of CuCl2, Cu(NO3)2, and CuSO4; the soluble iron salt includes, but is not limited to, at least one of FeCl3, Fe(NO3)3, and Fe(CH3COO)3. The cations of the soluble copper and soluble iron salts in this invention are Cu... 2+ Source and Fe 3+ Sodium sulfide is used as a sulfur source and reducing agent to achieve sulfur doping and bimetallic valence state control.

[0011] The introduction of sodium sulfide in this invention achieves multiple regulatory effects. On the one hand, sodium sulfide releases sulfur at high temperatures. 2- Cu 2+ It is reduced to highly active, low-valence copper, while also reducing some of the Fe. 3+ Fe reduction 2+ To form Fe3O4, these active metal components are confined in the carbon framework or channels of biochar, constructing a stable heterojunction and enhancing the electron transfer between the metal and the support. On the other hand, sulfur doping can increase the defect sites in the carbon matrix, and at the same time, through the coordination of sulfur with metal, it can further anchor and confine the metal particles, effectively inhibit their aggregation, and make the active sites uniformly exposed.

[0012] Preferably, the pH adjuster in S2 is sodium hydroxide, potassium hydroxide, or ammonia; the pH buffer is sodium bicarbonate, potassium bicarbonate, sodium dihydrogen phosphate, or disodium hydrogen phosphate. The main function of the pH adjuster and pH buffer used in this invention is to regulate the pH value of the reaction system. The buffering effect of the pH buffer can stabilize the pH value within a narrow range of 4.8 to 5.2. This condition is crucial for the directional assembly of metal ions into a layered structure within the confined space of biochar, directly affecting the confinement effect and the stability of subsequent heterojunction formation.

[0013] During the preparation process of this invention, the pH value is controlled between 4.8 and 5.2. If the pH value exceeds 5.2, it may cause Cu in the reaction system to... 2+ Fe 3+ Excessive hydrolysis outside the confined space of biochar forms amorphous precipitates, disrupting the ordered structure of the confined space. If the pH value is below 4.8, it may not be sufficient to completely precipitate metal ions, resulting in insufficient active metal content in the catalyst and inadequate binding of metals with biochar, thus reducing the overall stability of the material.

[0014] Preferably, the hydrothermal reaction temperature in S3 is 80~150℃ and the time is 4~10h.

[0015] Preferably, the calcination in S3 is carried out under nitrogen atmosphere; the calcination temperature is 400~600℃, the time is 1~4h; the nitrogen flow rate is 0.1~0.5mL / min, and the heating rate is 2~10℃ / min.

[0016] This invention uses a hydrothermal-calcination method to prepare sulfur-doped carbon-based confined composite materials. In the hydrothermal stage, the porous structure of biochar enables the initial confined assembly of metal components. In the calcination stage, the confining effect is enhanced by carbon skeleton shrinkage and sulfur lattice doping. Compared with the traditional single hydrothermal method, it is easier to form a stable confined structure. It not only has lower energy consumption, but also has more active sites in the confined space and more uniform dispersion.

[0017] Secondly, the present invention provides a sulfur-doped carbon-based confined composite material, which is prepared by the above-described preparation method.

[0018] Thirdly, the present invention provides the application of the above-mentioned sulfur-doped carbon-based confined composite material in activated persulfate.

[0019] Fourthly, the present invention provides the application of the above-mentioned sulfur-doped carbon-based confined composite material in the degradation of neonicotinoid insecticides in water.

[0020] Preferably, the steps for degrading neonicotinoid pesticides in water include: adding sulfur-doped carbon-based confined composite material and persulfate to water containing neonicotinoid pesticides, and the degradation treatment of the neonicotinoid pesticides in water is completed after the reaction.

[0021] Preferably, the amount of sulfur-doped carbon-based confined composite material added is 0.05–0.5 g / L; the persulfate is permonosulfate and / or perdisulfate; the amount of persulfate added is 0.01–0.1 g / L; the reaction time is 10–30 min; and the concentration of the neonicotinoid insecticide is 1–20 mg / L.

[0022] It contains at least the following beneficial technical effects: The sulfur-doped carbon-based confined composite material prepared in this invention is inexpensive, structurally stable, and exhibits strong catalytic activity. When this catalyst is used to activate persulfate, the decomposition reaction of persulfate can be accelerated through a synergistic pathway of free radicals and non-free radicals. When the catalytic oxidation system composed of this catalyst and persulfate is used to degrade neonicotinoid pesticides in water, it exhibits high degradation efficiency and a broad-spectrum degradation effect on various neonicotinoid pesticides such as thiamethoxam and thiamethoxam.

[0023] In the sulfur-doped carbon-based confined composite material prepared by this invention, the copper-iron bimetallic component is uniformly loaded on the surface of biochar in nanosheet form, which effectively solves the problem of monomer agglomeration and deactivation. Sulfur forms metal-sulfur bonds with the metal, and after 5 cycles, the Cu and Fe leaching concentrations are as low as 0.057 mg / L and 0.041 mg / L, respectively, showing excellent stability.

[0024] In practical wastewater treatment applications, it exhibits good degradation capabilities for neonicotinoid insecticides, with removal rates exceeding 80% in actual water bodies such as tap water, school lake water, and Songhua River water samples. Furthermore, the preparation method provided by this invention is simple, produces no secondary pollution, and is suitable for large-scale production.

[0025] This invention not only provides a novel catalyst for the efficient degradation of neonicotinoid insecticides in water, but also provides a sulfur-doped carbon-based confined composite material with stable structure and excellent performance, offering new ideas for the design and controllable preparation of carbon-based composite catalysts. Attached Figure Description

[0026] Figure 1 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the SCuFeBC prepared in Example 1, where (a) is a scanning electron microscope image, and (b) and (c) are TEM images.

[0027] Figure 2 The XRD comparison diagrams show the SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3.

[0028] Figure 3 The image shows a comparison of FTIR values ​​for SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3.

[0029] Figure 4 Raman comparison diagrams of SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3.

[0030] Figure 5 The N2 adsorption-desorption comparison diagrams are shown for SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3. Among them, (a) is the N2 adsorption-desorption diagram and (b) is the pore size distribution diagram.

[0031] Figure 6Comparison of electron paramagnetic resonance (EPR) images of SCuFeBC prepared in Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3.

[0032] Figure 7 The degradation rate of imidacloprid in water by different amounts of SCuFeBC-activated potassium persulfate in Example 3 is shown.

[0033] Figure 8 The degradation rate of imidacloprid in water by different concentrations of potassium persulfate activated by SCuFeBC in Example 4 is shown.

[0034] Figure 9 The degradation rate of imidacloprid in water bodies with different pH values ​​was achieved by SFCBC-activated potassium persulfate in Example 5.

[0035] Figure 10 The degradation rate of different neonicotinoid insecticides in water by SFCBC-activated potassium persulfate in Example 7 is shown.

[0036] Figure 11 This is a cyclic experiment of SFCBC activating potassium persulfate to degrade imidacloprid in water in Example 8. Detailed Implementation

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0040] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0041] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0042] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0043] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.

[0044] Activated carbon preparation: 40g of grapefruit peel raw material was washed, dried, crushed and sieved. The temperature was raised to 600℃ in a nitrogen atmosphere at a heating rate of 10℃ / min and held for 2h for high-temperature pyrolysis. After cooling, it was ultrasonically cleaned and dried to obtain 100-mesh biochar, denoted as BC.

[0045] It should be noted that other types of biochar can also achieve the technical objectives of this invention.

[0046] Example 1 Preparation of sulfur-doped carbon-based confined composite materials: 1 g of biochar was dispersed in 100 mL of ultrapure water, followed by the addition of 0.005 mol of copper nitrate trihydrate, 0.015 mol of ferric nitrate nonahydrate, and 0.001 mol of sodium sulfide. A mixed solution of 0.4 mol / L sodium hydroxide and 0.4 mol / L sodium bicarbonate was added dropwise to adjust the pH to 5. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 110 °C for 5 h. After the hydrothermal reaction was completed, the sample was removed, washed three times by centrifugation with water and ethanol, and dried in an oven at 80 °C. Subsequently, the precursor was placed in a tube furnace and pyrolyzed at 500 °C under nitrogen atmosphere at a heating rate of 5 °C / min for 2 h to prepare a sulfur-doped carbon-based confined composite material, denoted as SCuFeBC.

[0047] The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the SCuFeBC prepared in Example 1 are shown below. Figure 1 In the image, (a) is a scanning electron microscope image, and (b) and (c) are transmission electron microscope images.

[0048] from Figure 1As can be seen, the natural structure of the SCuFeBC-based biochar prepared by this invention is completely preserved, with a large number of interconnected pores distributed on the surface. The framework does not collapse or the structure is destroyed due to the loading of the bimetallic component. Nanosheet particles with a thickness of about 20-50 nm are uniformly attached to the surface of the biochar and the inner wall of the pores. There is no obvious agglomeration of all nanocomponents. The transmission electron microscopy image further reveals the microstructure and confinement characteristics of the material. The crystal lattice fringes of the nanosheet components can be clearly observed under high magnification, corresponding to the characteristic interplanar spacing of the heterojunction, which confirms that the bimetallic active component has good crystallinity.

[0049] Example 2 Preparation of sulfur-doped carbon-based confined composite materials: 5 g of biochar was dispersed in 100 mL of ultrapure water. Then, 0.01 mol of copper nitrate trihydrate, 0.015 mol of ferric nitrate nonahydrate, and 0.0005 mol of sodium sulfide were added. After stirring for 2 h, a mixed solution of 0.4 mol / L sodium hydroxide and 0.4 mol / L sodium bicarbonate was added dropwise to adjust the pH to 4.8. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 80 °C for 10 h. After the hydrothermal reaction was complete, the sample was removed, washed three times by centrifugation with water and ethanol, and dried in an oven at 80 °C. Subsequently, the precursor was placed in a tube furnace and pyrolyzed at 400 °C under nitrogen atmosphere at a heating rate of 2 °C / min for 4 h to prepare a sulfur-doped carbon-based confined composite material, denoted as SCuFeBC-2. Example 3 Preparation of sulfur-doped carbon-based confined composite materials: 3g of biochar was dispersed in 100mL of ultrapure water, followed by the addition of 0.008mol of copper nitrate trihydrate, 0.008mol of ferric nitrate nonahydrate, and 0.002mol of sodium sulfide. After stirring for 2 hours, a mixed solution of 0.4mol / L sodium hydroxide and 0.4mol / L sodium bicarbonate was added dropwise to adjust the pH to 5.2. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 150℃ for 4 hours. After the hydrothermal reaction was completed, the sample was removed, washed three times by centrifugation with water and ethanol, and dried in an oven at 80℃. Subsequently, the precursor was placed in a tube furnace and pyrolyzed at 600℃ under nitrogen atmosphere at a heating rate of 10℃ / min for 4 hours to prepare a sulfur-doped carbon-based confined composite material, denoted as SCuFeBC-3. Comparative Example 1 Preparation of carbon-based composite catalysts: 1 g of biochar was dispersed in 100 mL of ultrapure water, followed by the addition of 0.005 mol of copper nitrate trihydrate and 0.015 mol of ferric nitrate nonahydrate. After stirring for 2 h, a mixed solution of 0.4 mol / L sodium hydroxide and 0.4 mol / L sodium bicarbonate was added dropwise to adjust the pH to 5. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 110 °C for 5 h. After the hydrothermal reaction was completed, the sample was removed, washed three times by centrifugation with water and ethanol, and dried in an oven at 80 °C. Subsequently, the precursor was placed in a tube furnace and pyrolyzed at 500 °C under nitrogen conditions at a heating rate of 5 °C / min for 2 h to prepare a sulfur-doped carbon-based confined composite material, denoted as CuFeBC.

[0050] Comparative Example 2 Preparation of carbon-based composite catalysts: 1 g of biochar was dispersed in 100 mL of ultrapure water. Then, 0.005 mol of copper nitrate trihydrate, 0.015 mol of ferric nitrate nonahydrate, and 0.01 mol of melamine were added. After stirring for 2 h, a mixed solution of 0.4 mol / L sodium hydroxide and 0.4 mol / L sodium bicarbonate was added dropwise to adjust the pH to 5. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 110 °C for 5 h. After the hydrothermal reaction was completed, the sample was removed, washed three times by centrifugation with water and ethanol, and dried in an oven at 80 °C. Subsequently, the precursor was placed in a tube furnace and pyrolyzed at 500 °C under nitrogen atmosphere at a heating rate of 5 °C / min for 2 h to prepare a sulfur-doped carbon-based confined composite material, denoted as NCuFeBC.

[0051] Comparative Example 3 Preparation of carbon-based composite catalysts: 1 g of biochar was dispersed in 100 mL of ultrapure water. Then, 0.005 mol of copper nitrate trihydrate, 0.015 mol of ferric nitrate nonahydrate, and 0.01 mol of thiourea were added. After stirring for 2 h, a mixed solution of 0.4 mol / L sodium hydroxide and 0.4 mol / L sodium bicarbonate was added dropwise to adjust the pH to 5. The mixture was then transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 110 °C for 5 h. After the hydrothermal reaction was completed, the sample was removed, washed three times by centrifugation with water and ethanol, and dried in an oven at 80 °C. Subsequently, the precursor was placed in a tube furnace and pyrolyzed at 500 °C under nitrogen conditions at a heating rate of 5 °C / min for 2 h to prepare a sulfur-doped carbon-based confined composite material, denoted as NSCuFeBC.

[0052] Experimental Example 1 The XRD comparison images of SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3 are shown below. Figure 2 .

[0053] After calcination at 500℃, the crystal phase of CuFeBC undergoes a significant transformation, with new diffraction peaks appearing at 2θ of 35.61°, 38.78°, and 48.92°, which are characteristic crystal planes of CuO. The CuO crystal phase also exists in NCuFeBC and NSCuFeBC, indicating that without sodium sulfide modification, copper is more likely to exist in the form of inert CuO, while the sodium sulfide-modified SCuFeBC exhibits unique crystal phase characteristics. The diffraction peaks of 2θ at 43.37°, 50.54°, and 74.21° correspond to the (111), (200), and (220) crystal planes of metallic Cu (JCPDS 04-8636), while the diffraction peaks of the (220), (311), (400), and (440) crystal planes of Fe3O4 appear at 2θ at 30.29°, 35.60°, 43.37°, and 62.93° (JCPDS 89-3854). This result confirms that the sulfur element introduced by sodium sulfide can effectively regulate the metallic phase and promote Cu… 2+ Reduced to Cu 0 and Cu + At the same time, some Fe 3+ Fe reduction 2+ To form Fe3O4, these active metal components are confined in the carbon framework or channels of biochar, constructing a stable heterojunction, enhancing the electron transfer between the metal and the support, and providing a crystal structure basis for the dynamic redox cycle between Cu(0) and Cu(I).

[0054] Experiment Example 2 The FTIR comparison images of SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3 are shown below. Figure 3 .

[0055] from Figure 3 As can be seen from this, NSCuFeBC is at 530 cm. -1 and 624 cm -1 The strong characteristic peak appearing at 3500 cm⁻¹ is attributed to the stretching vibration of the metal-oxygen bond. -1 The broadened absorption peaks nearby correspond to the bending vibrations of hydroxyl groups on the catalyst surface and the OH bonds in adsorbed water molecules. It is noteworthy that the sulfur-doped material exhibits a peak at 500 cm⁻¹. -1 The presence of characteristic vibrational peaks of metal-sulfur bonds, although less intense than those of metal-oxygen bonds, directly confirms that sodium sulfide modification can locally form metal-sulfur bonds while retaining the metal-oxygen framework, thus constructing sulfur-oxygen dual active sites. This structure optimizes electron transfer efficiency and multi-pathway activation capability while maintaining material structural stability.

[0056] Experimental Example 3 Raman spectroscopy can be used to verify non-sp in the graphite structure. 2 Defects induced by hybrid carbon. Raman comparison graphs of SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3 are shown below. Figure 4 .

[0057] from Figure 4 As can be seen from this, all four materials are at 1336 cm. -1 (D band, corresponding to carbon structural defects) and 1592 cm -1 (G-band, corresponding to sp) 2 A characteristic peak appears at the plane stretching vibration of hybrid carbon, where the intensity ratio of the D band to the G band of SCuFeBC is (I D / I G =0.99) is significantly higher than CuFeBC (0.68), NCuFeBC (0.81) and NSCuFeBC (0.96), confirming that sulfur doping introduces richer structural defects.

[0058] Experiment Example 4 N2 adsorption-desorption tests further revealed the regulatory effect of sulfur doping on the pore structure of the materials. Comparison figures of N2 adsorption-desorption for SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3 are shown in the figure. Figure 5 .

[0059] The specific surface area of ​​SCuFeBC reaches 77.3 m². 2 / g, significantly higher than CuFeBC (28.4 m 2 / g), NCuFeBC (57.6m) 2 / g) and NSCuFeBC (37.1 m 2 The pore size distributions of SCuFeBC, CuFeBC, NCuFeBC, and NSCuFeBC were 6.9 nm, 6.4 nm, 3.3 nm, and 4.7 nm, respectively. This difference stems from two factors: firstly, the release of gases such as H2S and sulfur vapor from Na2S decomposition forms micropores and network structures within the carbon matrix; secondly, sulfur doping inhibits carbon layer stacking, promoting the formation of loose, sheet-like, or porous structures. Ultimately, SCuFeBC, through pore size adjustment, effectively optimizes the exposure of active sites and mass transfer efficiency while increasing the specific surface area. Electron paramagnetic resonance (EPR) of oxygen vacancies further confirms the lattice defect characteristics. Comparison images of EPR of SCuFeBC prepared in Example 1, CuFeBC prepared in Comparative Example 1, NCuFeBC prepared in Comparative Example 2, and NSCuFeBC prepared in Comparative Example 3 are shown below. Figure 6 .

[0060] At g=2.005, the signal intensity of SCuFeBC is the most prominent, indicating that its defect and vacancy density is significantly higher. These sites can serve as active centers for PMS activation, providing favorable conditions for catalytic reactions.

[0061] Experimental Example 5 The carbon-based composite catalysts prepared above are used to activate potassium persulfate to degrade imidacloprid in water: Experimental group: 0.010g SCuFeBC was added to 50mL of imidacloprid solution (initial concentration of 5mg / L, initial pH of 7), and then 0.0025g potassium persulfate was added to the system to carry out catalytic degradation reaction for 20min to complete the degradation of imidacloprid in the water.

[0062] Control group 1: The only difference from the experimental group is that SCuFeBC is omitted.

[0063] Control group 2: The only difference from the experimental group is that PMS is omitted.

[0064] Control group 3: Compared with the experimental group, the only difference is that SCuFeBC was replaced with an equal mass of CuFeBC and PMS was omitted.

[0065] Control group 4: The only difference from the experimental group was that SCuFeBC was replaced with an equal mass of CuFeBC.

[0066] Control group 5: Compared with the experimental group, the only difference is that SCuFeBC was replaced with an equal mass of NCuFeBC and PMS was omitted.

[0067] Control group 6: The only difference from the experimental group was that SCuFeBC was replaced with an equal mass of NCuFeBC.

[0068] Control group 7: Compared with the experimental group, the only difference is that SCuFeBC was replaced with an equal mass of NSCuFeBC and PMS was omitted.

[0069] Control group 8: The only difference from the experimental group was that SCuFeBC was replaced with an equal mass of NSCuFeBC.

[0070] After the catalytic degradation reaction was completed, the supernatant was aspirated with a syringe, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined by high performance liquid chromatography at a wavelength of 260 nm. The removal rate of imidacloprid was calculated, and the results are shown in Table 1.

[0071] Table 1. Removal rate of imidacloprid by different catalytic systems As shown in Table 1, the SCuFeBC prepared in this invention can efficiently activate peroxymonosulfate, significantly improving the degradation effect on imidacloprid, with a removal rate of up to 93.7%. This is significantly superior to undoped CuFeBC+PMS (71.9%), nitrogen-doped NCuFeBC+PMS (69.6%), and nitrogen-sulfur co-doped NSCuFeBC+PMS (82.8%). This advantage stems from the sulfur provided by sodium sulfide. 2- Cu 2+ Reduced to highly active, low-valence Cu 0 and Cu + Furthermore, it synergistically forms a heterojunction with Fe, combining the defect sites introduced by sulfur doping and the optimized pore structure to achieve highly efficient activation of PMS. In contrast, NCuFeBC, due to nitrogen coordination with the metal covering some active sites, and NSCuFeBC, whose thiourea pyrolysis products have weaker reduction capabilities than sodium sulfide, cannot achieve the catalytic effect of SCuFeBC. Compared to single-metal modified biochar catalysts, the CuFe bimetallic synergistic strategy employed in this invention, combined with the valence state regulation effect of sulfur doping, further enhances electron transfer efficiency and the number of active sites, significantly improving degradation efficiency.

[0072] The leaching concentrations of Cu and Fe ions in the solution after the reaction in the experimental group were detected by inductively coupled plasma mass spectrometry and were 0.057 mg / L and 0.041 mg / L, respectively, which are far below the heavy metal emission limits in the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002). This result confirms that the metal-sulfur bonds and bimetallic heterostructure formed by sulfur and metal in SCuFeBC can effectively inhibit the leaching of metal ions; at the same time, the CuFe bimetallic compound is uniformly loaded on the surface of biochar in nanosheet form, avoiding particle agglomeration and detachment, and ensuring the stability of the catalyst during recycling.

[0073] Experimental Example 6 SCuFeBC-activated potassium persulfate, prepared using different dosages in Example 1, degrades imidacloprid in water: 0.0025 g, 0.005 g, 0.01 g, 0.015 g and 0.025 g of SCuFeBC were added to 50 mL of imidacloprid solution (initial concentration 5 mg / L, initial pH 7), respectively. Then, 2.5 mg of potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 20 min to complete the degradation of imidacloprid in the water.

[0074] During the catalytic degradation process, the supernatant was aspirated with a syringe, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The degradation rates of imidacloprid in water by different dosages of SCuFeBC-activated potassium persulfate in Example 3 are shown in [reference needed]. Figure 7 .from Figure 7 As can be seen, the degradation efficiency of imidacloprid increased from 53.4% ​​to 93.7% with increasing catalyst dosage. This is because when the catalyst concentration is too low, the number of Cu and Fe active sites exposed on the PMS surface is insufficient to fully activate PMS, resulting in less total active material production. Meanwhile, when the catalyst dosage continues to increase from 0.2 g / L, the improvement in imidacloprid degradation is not significant and even shows a slight decrease. This is because excessive catalyst may reduce the PMS allocated per unit active site, and some sites cannot effectively activate PMS. Furthermore, free radicals generated on the surface of excessive catalyst cannot attack imidacloprid molecules due to their spatial proximity, easily leading to ineffective self-reactions and reduced utilization of reactive substances. Therefore, a catalyst dosage of 0.2 g / L can achieve efficient treatment of imidacloprid under lower cost conditions.

[0075] Experimental Example 7 The SCuFeBC prepared in Example 1 was used to activate different amounts of potassium persulfate to degrade imidacloprid in water: Four 0.01g SCuFeBC solutions were added to four 50mL imidacloprid solutions (initial concentration 5mg / L, initial pH 7). Then, 0.5mg, 1mg, 1.5mg, 2.5mg and 5mg of potassium persulfate were added to each system, respectively, and the catalytic degradation reaction was carried out for 20min to complete the degradation of imidacloprid in the water.

[0076] During the catalytic degradation process, the supernatant was aspirated with a syringe, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The degradation rates of imidacloprid in water by different amounts of potassium persulfate activated by SCuFeBC in Example 4 are shown below. Figure 8 .from Figure 8 It can be seen that when the PMS concentration increases from 10 mg / L... -1 Increase to 50 mg / L -1At that time, the removal rate of imidacloprid significantly increased from 42.8% to 93.7%. The higher PMS concentration provided more HSO5 for activation. - The increased concentration of PMS leads to the generation of more free radicals, directly oxidizing imidacloprid. Furthermore, the increased concentration of PMS enhances its diffusion-driven action on the catalyst surface, shortens the pathway of reactants to the active sites, and accelerates the reaction rate. However, when the PMS concentration is further increased to 100 mg / L... -1 At that time, the removal rate of imidacloprid remained basically unchanged, but the reaction rate decreased. Excessive PMS led to the removal of SO42-. - Excessive concentration triggers free radical self-quenching, reducing the concentration of effective active substances; SO4 - With excessive HSO5 - The reaction produces S2O8, which has a weak oxidizing ability. 2- This weakens the degradation ability. Therefore, when the amount of potassium persulfate added is 2.5 mg, potassium persulfate can be efficiently activated with less catalyst, and efficient treatment of imidacloprid can be achieved.

[0077] Experimental Example 8 The SCuFeBC activated potassium persulfate prepared in Example 1 was used to degrade imidacloprid in water bodies with different pH values: Five 0.01g SCuFeBC samples were added to 50mL of imidacloprid solution (initial concentration 5mg / L, initial pH values ​​3, 4, 5, 7, 9 and 11 respectively). Then, 2.5mg potassium persulfate was added to each system and the catalytic degradation reaction was carried out for 20min to complete the degradation of imidacloprid in the water.

[0078] During the catalytic degradation process, the supernatant was aspirated with a syringe, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The degradation rate of imidacloprid in water bodies with different pH values ​​by SCuFeBC-activated potassium persulfate in Example 5 is shown in [reference needed]. Figure 9 .Depend on Figure 9 It can be seen that when the initial pH value of the imidacloprid solution is 3, 4, 5, 7, 9 and 11, the removal rates of imidacloprid within 15 min are 39.2%, 88.7%, 90.9%, 93.7%, 91.4% and 91.0%, respectively.

[0079] Experimental Example 9 Degradation of imidacloprid in different water bodies using SCuFeBC activated potassium persulfate prepared in Example 1: Four 0.01g SCuFeBC samples were added to four 50mL imidacloprid solutions (initial concentration 5mg / L, initial pH 7, solvents: ultrapure water, tap water, school lake water, and Songhua River water sample, respectively). Then, 2.5mg potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 20min to complete the degradation of imidacloprid in the water.

[0080] After the catalytic degradation reaction was completed, the supernatant was aspirated with a syringe, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined by high performance liquid chromatography at a wavelength of 260 nm. The removal rate of imidacloprid was calculated, and the results are shown in Table 2.

[0081] Table 2. Removal rate of imidacloprid by the same catalytic system under different water conditions As shown in Table 2, the SCuFeBC prepared by this invention exhibits rapid and efficient catalytic degradation of imidacloprid under both laboratory conditions and in actual water bodies, demonstrating excellent adaptability.

[0082] Experimental Example 10 Using SCuFeBC-activated potassium persulfate prepared in Example 1 to treat different neonicotinoid insecticides in water: Five 0.01g SCuFeBC samples were added to 50mL of solutions of imidacloprid, thiamethoxam, thiamethoxam, dinotefuran, and acetamiprid (initial concentration 5mg / L, initial pH 7). Then, 2.5mg of potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 20min to complete the degradation of imidacloprid in the water.

[0083] During the catalytic degradation process, the supernatant was aspirated with a syringe and filtered through a 0.45 μm filter membrane. The concentrations of imidacloprid, thiamethoxam, thiamethoxam, dinotefuran, and acetamiprid were determined using high-performance liquid chromatography (HPLC) at wavelengths of 260 nm, 260 nm, 254 nm, 254 nm, and 270 nm. The removal rates of imidacloprid, thiamethoxam, thiamethoxam, dinotefuran, and acetamiprid were calculated. The degradation rates of different neonicotinoid insecticides in water by SCuFeBC-activated potassium persulfate in Example 7 are shown in [reference needed]. Figure 10 .Depend on Figure 10 It is evident that the SCuFeBC prepared by this invention exhibits rapid and efficient catalytic degradation of various neonicotinoid insecticides, demonstrating excellent application value.

[0084] Experimental Example 11 Cyclic experiment on the degradation of imidacloprid in water by SCuFeBC-activated potassium persulfate prepared in Example 1: 0.01g of SCuFeBC was added to 50mL of imidacloprid solution (initial concentration 5mg / L, initial pH 7), and then 2.5mg of potassium persulfate was added to each system. The catalytic degradation reaction was carried out for 20min to complete the degradation of imidacloprid in the water.

[0085] After the catalytic degradation reaction was completed, the supernatant was aspirated with a syringe, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The catalyst used in the previous reaction was recovered for the next degradation experiment. A total of 5 cycles were performed, and the results are as follows: Figure 11 As shown. By Figure 11 It can be seen that the SCuFeBC catalyst prepared by this invention can still maintain good catalytic activity during multiple cycles, demonstrating its excellent structural stability and regenerability.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a sulfur-doped carbon-based confined composite material, characterized in that, The preparation method comprises the following steps: S1. dispersing biochar, a soluble copper salt, a soluble iron salt and sodium sulfate in water to obtain a mixed solution A; S2. adjusting the pH of the mixed solution to 4.8-5.2 using a pH adjuster and a pH buffer to obtain a mixed solution B; S3. performing a hydrothermal reaction on the mixed solution B, and then filtering, washing, drying and calcining to obtain a sulfur-doped carbon-based confined composite material.

2. The production method according to claim 1, characterized by, The concentration of the biochar in the mixed solution A in the S1 is 10-50 g / L, the concentration of Cu 2+ is 0.04-0.10 mol / L, the concentration of Fe 3+ is 0.06-0.15 mol / L, and the concentration of the sodium sulfide is 0.005-0.02 mol / L.

3. The preparation method according to claim 1, characterized in that, The pH adjuster in S2 is sodium hydroxide, potassium hydroxide or ammonia water; and the pH buffer is sodium bicarbonate, potassium bicarbonate, sodium dihydrogen phosphate or disodium hydrogen phosphate.

4. The method of claim 1, wherein, The hydrothermal reaction temperature in S3 is 80-150℃, and the time is 4-10h.

5. The preparation method according to claim 1, characterized in that, The calcination in S3 is performed under a nitrogen atmosphere; the calcination temperature is 400-600℃, the time is 1-4h; the nitrogen flow rate is 0.1-0.5mL / min, and the temperature rising rate is 2-10℃ / min.

6. A sulfur-doped carbon-based confined composite, characterized in that, The sulfur-doped carbon-based confined composite material is prepared by the preparation method of any one of claims 1-6.

7. The sulfur-doped carbon-based confined composite material of claim 6 is used in activating persulfate.

8. The sulfur-doped carbon-based confined composite material of claim 6 is used in degrading neonicotinoid insecticides in water.

9. Use according to claim 9, characterized in that, The step of degrading neonicotinoid insecticides in water comprises: adding the sulfur-doped carbon-based confined composite material and persulfate to water containing neonicotinoid insecticides, and completing the degradation of the neonicotinoid insecticides in the water after the reaction.

10. The use according to claim 10, characterized in that, The addition amount of the sulfur-doped carbon-based confined composite material is 0.05-0.5g / L; the persulfate is peroxymonosulfate and / or peroxodisulfate; the addition amount of the persulfate is 0.01-0.1g / L; the reaction time is 10-30min; and the concentration of the neonicotinoid insecticides is 1-20mg / L.

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