A phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, a preparation method and application thereof

Abstract

The application discloses a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material and a preparation method and application thereof, and belongs to the technical field of sewage treatment. The preparation method comprises the following steps: pyrolyzing agricultural waste to obtain biochar; dispersing the biochar, soluble copper salt, soluble cobalt salt, urea and a phosphorus source, i.e., disodium hydrogen phosphate, in water, and preparing a composite material through ultrasonic treatment, hydrothermal reaction and freeze-drying. The composite material prepared by the application builds a stable phosphorus-oxygen-metal interface through phosphorus doping, optimizes the electrical conductivity and pore structure of the biochar, realizes targeted adsorption of pollutants through the pi-pi conjugation and electrostatic interaction between the biochar and neonicotinoid insecticides, and efficiently activates persulfate through a free radical and non-free radical synergistic path. The composite material has the advantages of stable structure, low metal leaching amount and strong anti-interference capability, has a broad-spectrum degradation effect on various neonicotinoid insecticides such as imidacloprid and thiamethoxam, and is suitable for the treatment of neonicotinoid insecticides in complex water environments.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and particularly relates to a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, its preparation method and application. Background Technology

[0002] Neonicotinic insecticides (such as imidacloprid and thiamethoxam) are widely used in agricultural production due to their high insecticidal activity and relatively low acute toxicity to mammals. However, these compounds are characterized by stable molecular structures, high water solubility, and long environmental half-lives, making them prone to accumulation in water bodies. They pose a persistent ecological risk to aquatic ecosystems and non-target organisms by acting on nicotinic acetylcholine receptors in aquatic organisms. Pollutants like imidacloprid, with their nitrogen heterocyclic structures, are difficult to remove effectively by traditional wastewater treatment processes (such as conventional biological treatment and flocculation sedimentation). While physical adsorption can temporarily transfer pollutants, it suffers from problems such as difficulty in regeneration after adsorption saturation and the potential for secondary pollution. Therefore, developing novel water treatment technologies that can efficiently and effectively degrade neonicotinic insecticides has become an important research direction in the fields of environmental engineering and pollution control.

[0003] Persulfate advanced oxidation technology, through activation to generate highly reactive oxidizing species such as sulfate radicals, hydroxyl radicals, and singlet oxygen, can efficiently destroy the molecular structure of organic pollutants. This technology also has a wide pH adaptability range and is easy to operate, making it one of the effective methods for treating recalcitrant organic pollutants. Layered bimetallic hydroxides, due to their unique layered crystal structure and tunable metal composition, show potential application value in persulfate activation. However, pure-phase layered bimetallic hydroxides still face several bottlenecks in practical applications: their nanosheets are prone to aggregation, leading to a decrease in specific surface area and masking of active sites; the intrinsic electronic conductivity of the material is poor, limiting electron transfer efficiency; in addition, metal ions are easily leached during the reaction, which not only reduces the stability of the catalyst but may also cause secondary metal pollution.

[0004] To overcome these shortcomings, researchers have attempted to combine layered bimetallic hydroxides (BHOHs) with biochar, utilizing the abundant pore structure and good conductivity of biochar to inhibit nanomaterial aggregation and promote interfacial electron transfer. Biochar is typically derived from the pyrolysis of biomass waste, making it inexpensive and environmentally friendly. However, most existing BHOH-biochar composite systems still suffer from several key deficiencies: First, the bonding between the BHOH and the biochar carrier relies heavily on weak physical interactions (such as van der Waals forces) or hydrogen bonds, resulting in weak interfacial chemical bonds, leading to high resistance to electron transfer and low efficiency in metal redox cycles. Second, the dispersion of active components remains unsatisfactory, and local aggregation cannot be completely avoided, limiting the full exposure of active sites. Third, existing composite materials generally lack the ability to target and degrade specific pollutants. The activated active species often indiscriminately attack pollutant molecules, potentially destroying only side chains or non-core structures, while failing to completely destroy the most toxic parent structure or key functional groups. This can lead to the generation of still toxic intermediate products during degradation, and the environmental risks are not fundamentally eliminated.

[0005] Heteroatom doping is an effective strategy for controlling the interfacial properties and electronic structure of carbon-based composite materials. Phosphorus, as an ideal dopant atom, possesses oxygen-containing functional groups (such as phosphate) that can form stable covalent bonds (such as POM bonds) with metal sites in layered bimetallic hydroxides and oxygen-containing functional groups on the surface of biochar. This provides new possibilities for constructing strongly bonded and functionally synergistic adsorption-catalysis interfaces. Although phosphorus doping has been studied in materials science, its specific mechanism of action in layered bimetallic hydroxide-biochar composite systems, particularly how precise phosphorus doping can optimize interfacial electronic structure, enhance material stability, and achieve efficient targeted oxidative degradation of specific pollutants such as neonicotinoids, still lacks systematic and in-depth research and clear technical solutions. Therefore, there is an urgent need to develop a novel composite material that enhances interfacial bonding and catalytic performance through a controllable phosphorus doping strategy, while possessing broad-spectrum and efficient degradation capabilities, to promote the application of advanced oxidation technologies in practical water environment management. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, its preparation method, and its application. The composite material prepared by this invention has a stable structure, low metal leaching, and strong anti-interference ability. It can efficiently degrade neonicotinoid pesticides through adsorption-catalysis synergy and has a broad-spectrum degradation effect, making it suitable for the treatment of complex water environments.

[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 phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, comprising the following steps: S1. Biochar preparation: Agricultural waste is crushed and sieved, then subjected to programmed temperature pyrolysis under an inert atmosphere, cooled, and ground to obtain biochar; S2. Preparation of the mixed system: The biochar, soluble copper salt, soluble cobalt salt and urea are dispersed together in water, stirred to form a homogeneous solution, and then a phosphorus source is added. The mixture is then dispersed by ultrasonication to obtain the mixed system. S3. Hydrothermal reaction and post-treatment: The mixed system is subjected to a hydrothermal reaction. After the reaction is completed, the product is washed and freeze-dried to obtain a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material.

[0008] Further, in step S1, the agricultural waste is selected from at least one of peanut shells, walnut shells, and grapefruit peels; in step S2, the soluble copper salt is copper nitrate trihydrate, the soluble cobalt salt is cobalt nitrate hexahydrate, and the phosphorus source is disodium hydrogen phosphate. Agricultural waste is widely available and inexpensive. The biochar formed after high-temperature pyrolysis has a rich porous structure, which can provide a stable carrier for metal component loading. Copper nitrate trihydrate and cobalt nitrate hexahydrate have excellent solubility and can be uniformly dispersed in aqueous solution. Disodium hydrogen phosphate, as a phosphorus source, can slowly release phosphate ions during hydrothermal processes and form stable coordination bonds with metal ions.

[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, in step S2, based on 1g of biochar, the amount of soluble copper salt added is 1 mmol, the amount of soluble cobalt salt added is 2 mmol, the amount of urea added is 10 mmol, and the amount of phosphorus source added is 0.2~0.4 g.

[0011] Furthermore, in step S2, the composite material exhibits optimal catalytic performance when the phosphorus source is added at a concentration of 0.3 g, denoted as 0.3PCuCoBC. If the phosphorus source addition is too low, a sufficient phosphorus-oxygen-metal interface cannot be formed, resulting in insufficient interfacial electron transfer efficiency; if the addition is too high, phosphorus agglomeration will cover the active sites, thus reducing catalytic activity. An addition of 0.3 g achieves a balance between the interfacial structure and the exposure of active sites.

[0012] Furthermore, in step S3, the hydrothermal reaction temperature is 140℃~170℃, and the reaction time is 8 h~14 h. Hydrothermal temperature and time are key parameters for controlling the crystal structure of the layered double hydroxide and the efficiency of phosphorus-oxygen-metal covalent bond formation: below 140℃, the reaction between metal ions and the phosphorus source is incomplete, resulting in insufficient crystallinity of the layered structure and weak interfacial covalent bond bonding; above 170℃, the layered nanosheets are prone to agglomeration, damaging the porous biochar support structure and increasing energy consumption. A reaction time of 8~14 h ensures that the metal components are fully assembled within the biochar pores, forming a uniformly dispersed layered structure, balancing preparation efficiency and material performance. The optimal parameter combination is 160℃ for 12 h, maximizing the catalytic activity and structural stability of the composite material.

[0013] Furthermore, in step S3, the freeze-drying temperature is -60℃ to -50℃, and the vacuum degree is 10 Pa to 30 Pa; the hydrothermal reaction temperature in step S3 is 160℃, and the reaction time is 12 h. Freeze-drying can avoid the collapse of the material's pore structure during traditional drying, while reducing the agglomeration of metal components, preserving the material's high specific surface area and porous characteristics, and providing favorable conditions for subsequent adsorption and catalytic reactions; this temperature and vacuum degree range can ensure that water is fully sublimated without damaging the phosphorus-oxygen-metal covalent bond structure of the material.

[0014] The introduction of phosphorus source in this invention achieves multiple regulatory effects: on the one hand, the phosphate ions provided by disodium hydrogen phosphate form stable phosphorus-oxygen-metal covalent bonds with divalent copper and trivalent cobalt, strengthening the interfacial bonding force between layered double hydroxides and biochar, and reducing the risk of metal ion leaching; on the other hand, phosphorus doping can optimize the conductivity of biochar, promote the transfer of electrons between metal sites and carbon carriers, and increase the number of defect sites in the carbon matrix, thereby improving the activation efficiency of persulfate; in addition, the introduction of phosphorus can also regulate the pore structure of the material, increase the specific surface area, and enhance the adsorption capacity for pollutants.

[0015] Secondly, the present invention provides a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, which is prepared by the above-mentioned preparation method. The composite material has a phosphorus-oxygen-metal covalent bond interface, and Cu and Co metal active components are uniformly dispersed in the porous biochar framework.

[0016] Thirdly, the present invention provides the application of the above-mentioned phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material in the activation of persulfate.

[0017] Fourthly, the present invention provides the application of the above-mentioned phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material in the degradation of neonicotinoid insecticides in water.

[0018] Furthermore, the phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material and persulfate are added together to water containing neonicotinoid insecticides to react and degrade the neonicotinoid insecticides.

[0019] Further, the dosage of the phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material is 0.1 g / L to 0.3 g / L; the dosage of the persulfate is 0.04 g / L to 0.08 g / L; the reaction time is 40 min to 80 min; the initial concentration of the neonicotinoid insecticide is 1 mg / L to 20 mg / L; and the persulfate is permonosulfate and / or perdisulfate.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects: The phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material prepared in this invention exhibits stable structure, low metal leaching, and strong anti-interference ability. A stable phosphorus-oxygen-metal interface is constructed through phosphorus doping, optimizing the conductivity and pore structure of the biochar. Furthermore, the π-reactivity between biochar and neonicotinoid insecticides is utilized. π-conjugation and electrostatic interaction enable targeted adsorption of pollutants, and persulfate is efficiently activated through a synergistic pathway of free radicals and non-free radicals.

[0021] The composite material exhibits broad-spectrum degradation effects on various neonicotinoid insecticides such as imidacloprid and thiamethoxam. In a 10 mg / L imidacloprid solution, the degradation rate reaches 97.4% in 60 minutes, which is significantly better than the undoped and other heteroatom-doped composite systems.

[0022] When applied in actual water bodies, this composite material achieves a removal rate of over 89% for neonicotinoid insecticides, exhibits minimal interference from the water matrix, and demonstrates strong resistance to interference. Furthermore, the preparation method of this invention uses agricultural waste as biochar raw material, resulting in low cost, simple process, no secondary pollution, and suitability for large-scale production.

[0023] This invention not only provides a novel composite material for the efficient degradation of neonicotinoid insecticides in water, but also clarifies the mechanism by which phosphorus doping regulates the interfacial behavior of layered double hydroxide-biochar, providing new ideas for the interfacial design and controllable preparation of carbon-based composite catalysts. Attached Figure Description

[0024] Figure 1 The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of 0.3PCuCoBC prepared in Example 1, where (a) is a scanning electron microscope image and (b) and (c) are TEM images.

[0025] Figure 2XRD comparison images of 0.3PCuCoBC prepared in Example 1, CuCoBC prepared in Comparative Example 1, 0.2PCuCoBC prepared in Example 4, and 0.4PCuCoBC prepared in Example 4.

[0026] Figure 3 FTIR comparison images of 0.3PCuCoBC prepared in Example 1, CuCoBC prepared in Comparative Example 1, 0.2PCuCoBC prepared in Example 4, and 0.4PCuCoBC prepared in Example 4.

[0027] Figure 4 Raman comparison charts of 0.3PCuCoBC prepared in Example 1, CuCoBC prepared in Comparative Example 1, 0.2PCuCoBC prepared in Example 4, and 0.4PCuCoBC prepared in Example 4.

[0028] Figure 5 Comparison of nitrogen adsorption-desorption for 0.3PCuCoBC prepared in Example 1, CuCoBC prepared in Comparative Example 1, 0.2PCuCoBC prepared in Example 4, and 0.4PCuCoBC prepared in Example 4, wherein (a) is a nitrogen adsorption-desorption isotherm diagram and (b) is a pore size distribution diagram.

[0029] Figure 6 The image shows a comparison of electron paramagnetic resonance (EPR) of 0.3PCuCoBC prepared in Example 1 and CuCoBC prepared in Comparative Example 1.

[0030] Figure 7 A comparison of the degradation efficiency of potassium persulfate in water by different catalytic systems.

[0031] Figure 8 The graph shows the effect of different dosages of 0.3PCuCoBC activated potassium persulfate on the degradation efficiency of imidacloprid in water in Example 7.

[0032] Figure 9 The graph shows the effect of 0.3PCuCoBC activation of different concentrations of potassium persulfate on the degradation efficiency of imidacloprid in water in Example 8.

[0033] Figure 10 The graph shows the effect of 0.3PCuCoBC activated potassium persulfate on the degradation efficiency of imidacloprid in water bodies with different initial pH values ​​in Example 9.

[0034] Figure 11 This is a graph showing the broad-spectrum degradation effect of 0.3PCuCoBC activated potassium persulfate on different types of neonicotinoid insecticides in water in Example 11.

[0035] Figure 12This is a stability test diagram of the recycling of 0.3PCuCoBC activated potassium persulfate for degrading imidacloprid in water in Example 12. Detailed Implementation

[0036] 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.

[0037] All raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0038] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably uses raw materials of analytical grade or purity commonly used in the field of chemical synthesis.

[0039] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0040] Example 1 This embodiment provides a preferred method for preparing a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material of the present invention, which is designated as 0.3PCuCoBC.

[0041] The specific steps are as follows: S1. Biochar Preparation: Peanut shells, agricultural waste, are washed, dried, crushed, and sieved through a 100-mesh sieve. An appropriate amount of powder is placed in a tube furnace and heated to 700°C at a heating rate of 5°C / min under a nitrogen protective atmosphere, and maintained at this temperature for 2 hours for pyrolysis. After natural cooling to room temperature, the resulting black solid is ground to obtain biochar (denoted as BC), which is then set aside.

[0042] S2. Preparation of the mixing system: Accurately weigh 1.0 g of the above biochar BC and disperse it in 60 mL of ultrapure water. Then, add 1 mmol of copper nitrate trihydrate, 2 mmol of cobalt nitrate hexahydrate, and 10 mmol of urea sequentially. Stir the mixture at room temperature for 30 minutes to form a homogeneous suspension. Then, add 0.3 g of disodium hydrogen phosphate (a phosphorus source) to the system, continue stirring to achieve initial dispersion, and then transfer the mixture to an ultrasonic processor for ultrasonic dispersion for 15 minutes to obtain a homogeneous and stable mixing system.

[0043] S3. Hydrothermal Reaction and Post-treatment: The mixture obtained in step S2 was transferred to a hydrothermal reactor and reacted at 160°C for 12 hours. After the reaction, it was allowed to cool naturally to room temperature. The resulting product was washed three times each with ultrapure water and anhydrous ethanol by centrifugation (centrifugation conditions: 8000 rpm, 5 min) to thoroughly remove unreacted ions and impurities. Finally, the washed wet material was freeze-dried at -55°C and a vacuum of 20 Pa for 24 hours to obtain a black phosphorus-doped copper-cobalt layered double hydroxide-biochar composite powder, namely 0.3PCuCoBC.

[0044] The morphology and structure of the 0.3PCuCoBC material obtained in this embodiment were characterized. Its scanning electron microscope (SEM) image (…) Figure 1 a) shows that the porous honeycomb structure of the biochar substrate was completely preserved, with no obvious framework collapse. High-magnification SEM and transmission electron microscopy (TEM) images ( Figure 1 As can be clearly observed in b and 1c), the sheet-like or flower-like copper-cobalt layered double hydroxide nanoparticles are uniformly attached to the surface of biochar and the inner walls of its pores, without obvious accumulation or agglomeration, indicating that the introduction of phosphorus effectively promotes the dispersion of active components.

[0045] Example 2 This embodiment aims to illustrate the substitutability of biochar raw materials. The preparation steps are the same as in Example 1, except that the agricultural waste raw material in step S1 is changed.

[0046] S1a. Biochar was prepared using walnut shells as raw material, using the same method (passing through a 100-mesh sieve, under N2 atmosphere, heating to 700℃ at 5℃ / min and holding for 2h), denoted as BC-W.

[0047] S1b. Biochar was prepared from grapefruit peel using the same method (passing through a 100-mesh sieve, under N2 atmosphere, heating to 700℃ at 5℃ / min and holding for 2h), denoted as BC-P.

[0048] Composite materials were prepared using BC-W and BC-P under the same conditions as S2 (addition of 0.3g disodium hydrogen phosphate) and S3 in Example 1, and were denoted as 0.3PCuCoBC-W and 0.3PCuCoBC-P, respectively.

[0049] XRD and nitrogen adsorption-desorption tests revealed that both materials successfully formed layered double hydroxide structures with specific surface areas reaching 195.4 m². 2 / g and 187.6 m 2 / g, although slightly lower than 0.3PCuCoBC (208.89 m) using peanut shell biochar as a carrier. 2 / g), but still much higher than the undoped material in Comparative Example 1. In the degradation experiment (under the same conditions as Experiment 5), the degradation rates of 10 mg / L imidacloprid by 0.3PCuCoBC-W and 0.3PCuCoBC-P were 95.1% and 93.8% respectively after 60 minutes, indicating that various agricultural wastes such as peanut shells, walnut shells, and grapefruit peels are suitable for preparing the composite material of this invention, demonstrating the universality and cost advantage of the raw materials.

[0050] Example 3 This embodiment investigates the effect of biochar pyrolysis temperature on the properties of composite materials. The preparation steps are the same as in Example 1, except that the pyrolysis temperature in step S1 is changed.

[0051] S1c. Using peanut shells as raw material, biochar was prepared by pyrolysis at final temperatures of 500℃ and 900℃ respectively (other conditions were the same: passing through a 100-mesh sieve, N2 atmosphere, heating at 5℃ / min, and holding for 2h). The biochar was denoted as BC-500 and BC-900 respectively.

[0052] Using BC-500 and BC-900, composite materials were prepared under the same conditions as S2 and S3 in Example 1, and were denoted as 0.3PCuCoBC-500 and 0.3PCuCoBC-900, respectively.

[0053] Characterization results show that pyrolysis temperature directly affects the pore structure and graphitization degree of biochar. 0.3PCuCoBC-500 has a relatively high specific surface area (215.3 m²). 2 / g), but the carbon structure has a lower degree of order; 0.3PCuCoBC-900 has a higher degree of graphitization, but the specific surface area decreases slightly (198.7 m). 2 / g). In the imidacloprid degradation test, the degradation rates of 0.3PCuCoBC-500, 0.3PCuCoBC (700℃), and 0.3PCuCoBC-900 at 60 minutes were 94.5%, 97.4%, and 96.0%, respectively. This indicates that biochar prepared in the range of 500-900℃ can all serve as effective carriers, with 700℃ being a relatively optimal balance point that can balance high specific surface area and good conductivity.

[0054] Example 4 This embodiment systematically examines the effect of the amount of phosphorus source (disodium hydrogen phosphate) added on the material structure and properties, which is the key to supporting the range of phosphorus source addition (0.2~0.4g) in the claims.

[0055] The preparation method is the same as in Example 1, except that the amount of disodium hydrogen phosphate added is changed in step S2: Add 0g, and the resulting material is denoted as CuCoBC.

[0056] Add 0.2g, and the resulting material is recorded as 0.2PCuCoBC.

[0057] Add 0.3g, and the resulting material is recorded as 0.3PCuCoBC.

[0058] Add 0.4g, and the resulting material is recorded as 0.4PCuCoBC.

[0059] The above series of materials were systematically characterized.

[0060] XRD patterns ( Figure 2 The results show that the CuCoBC composite system has a 2θ value of 12.8. ° (003), 25.9 ° (006), 33.6 ° (009) and 37.2 ° The (012) peak exhibits typical characteristic peaks of layered bimetallic hydroxides, confirming the successful formation of the layered structure. For the phosphorus-doped sample (PCuCoBC), the characteristic peaks of layered bimetallic hydroxides remain clearly distinguishable. This phenomenon can be attributed to interfacial coordination, which promotes the orderly growth of the layered bimetallic hydroxides and enhances their crystallinity. Notably, the (003) peak of 0.3PCuCoBC shifts slightly to a higher angle, corresponding to a decrease in interlayer spacing. This is due to the partial embedding of phosphorus-oxygen groups between the layers of the layered bimetallic hydroxide, further strengthening the interlayer interaction.

[0061] FTIR spectra ( Figure 3 The data shows that at 3550 cm... -1 There is a broad absorption band nearby, corresponding to the O2 of surface hydroxyl groups and adsorbed water. The H stretching vibration shows a significantly enhanced absorption band intensity in 0.3PCuCoBC, indicating that phosphorus doping improves the surface hydrophilicity of the material. This improvement is due to the increased oxygen-containing groups introduced by phosphorus, which facilitates the adsorption and mass transfer of imidacloprid and persulfate at the material interface. In the low wavenumber region, at 670 cm⁻¹... -1 and 504 cm -1 The vibration bands at the locations belong to Co. O and Cu The stretching vibration of the O bond, at 422 cm -1 The weak peak at that location can be attributed to Cu. O The bridging vibrations of Co confirmed the presence of metal-oxygen bonds in the 0.3PCuCoBC layer.

[0062] Raman spectroscopy ( Figure 4 The data shows that all four materials are at 1331cm. -1 (D-band, carbon defect) and 1578cm-1 A characteristic peak appears at (G band, graphitized carbon). Notably, the I value of 0.3PCuCoBC is... D / I G The ratio reached 1.04, significantly higher than that of undoped CuCo / BC (0.82). This I D / I G The increase in the ratio is due to the formation of additional defect sites. During the hybridization process of P 3p and C 2p orbitals, the difference in electronegativity leads to a local charge imbalance, thereby inducing more defects.

[0063] Nitrogen adsorption-desorption test ( Figure 5 This indicates that the specific surface area of ​​0.3PCuCoBC reaches 208.89 m². 2 / g, significantly higher than CuCoBC (40.79m 2 / g), 0.2PCuCoBC (143.55m 2 / g) and 0.4PCuCoBC (118.44m 2 / g); 0.3PCuCoBC exhibits the highest specific surface area due to optimal phosphorus doping that prevents the aggregation of layered bimetallic hydroxides without excessive phosphorus covering the biochar pores, thus exposing more active sites.

[0064] Electron paramagnetic resonance (EPR) testing further verified the number of active sites. Comparison of EPR images of 0.3PCuCoBC prepared in Example 1 and CuCoBC prepared in Comparative Example 1 are shown below. Figure 6 The CuCoBC peak intensity is weak at g=2.007, while the 0.3PCuCoBC peak intensity is the strongest. This phenomenon is closely related to phosphorus coordination. When phosphorus binds to the metal site of the layered bimetallic hydroxide through phosphorus-oxygen-metal bonds, it alters the electronic configuration of the metal. The lone pair electrons of phosphorus are transferred to the d orbitals of the metal ion, increasing the unpaired electron density around the metal center and forming a local spin-enriched region. This enhanced spin signal does not originate from conventional oxygen vacancies, but rather from the unique electronic state induced by the phosphorus-oxygen-metal coordination environment regulated by phosphorus, thus providing additional electron donor centers for persulfate activation.

[0065] Example 5 This embodiment is used to support the description of the adjustable range of hydrothermal reaction conditions in the claims and specification.

[0066] Based on the formulation of Example 1, with the phosphorus source added at a fixed amount of 0.3g, the hydrothermal reaction temperature and time were varied: Hydrothermal temperature changes: The hydrothermal reaction temperatures were set to 140℃, 150℃, 160℃, and 170℃ respectively, and the reaction time was fixed at 12 hours. The resulting materials were denoted as PCuCoBC-140℃-12h, PCuCoBC-150℃-12h, 0.3PCuCoBC (160℃-12h), and PCuCoBC-170℃-12h respectively.

[0067] Hydrothermal time variation: With the hydrothermal temperature fixed at 160℃, the reaction was carried out for 8 hours, 10 hours, 12 hours (optimal), and 14 hours, respectively. The resulting materials were denoted as PCuCoBC-160℃-8h, PCuCoBC-160℃-10h, 0.3PCuCoBC (160℃-12h), and PCuCoBC-160℃-14h, respectively.

[0068] Performance tests showed that at excessively low hydrothermal temperatures (140℃), the layered structure crystallized incompletely, resulting in low catalytic activity (imidacloprid degradation rate 86.2%). Excessively high temperatures (170℃) could lead to excessive growth and aggregation of nanosheets, resulting in a slight decrease in activity (degradation rate 94.7%). Regarding time, 8 hours of reaction time was insufficient, achieving a degradation rate of 90.1%. Extending the reaction to 12 hours yielded optimal performance (97.4%). Further extending to 14 hours maintained performance at approximately 96.9%, but increased energy consumption. Therefore, hydrothermal reactions at 140-170℃ for 8-14 hours can yield materials with excellent performance, with 160℃ for 12 hours being the optimal combination. This range represents the preferred process window of this invention.

[0069] Comparative Example 1 The preparation method was exactly the same as in Example 1, except that disodium hydrogen phosphate was not added in step S2. All other conditions (including the amounts of biochar, metal salt, and urea, as well as hydrothermal and post-treatment conditions) remained consistent. The resulting material was denoted as CuCoBC.

[0070] Its XRD pattern ( Figure 2 The sample exhibits characteristic peaks, confirming the formation of a layered structure, but the position of the (003) peak differs from that of the doped sample. Its specific surface area is only 40.79 m². 2 / g ( Figure 5 The concentration of electron paramagnetic resonance (EPR) was significantly lower than that of the phosphorus-doped sample, indicating severe nanosheet aggregation. Figure 6 The signal was weak. In the degradation experiment ( Figure 7 Its removal rate of imidacloprid in 60 minutes was only about 75%, which was significantly lower than that of 0.3PCuCoBC (97.4%).

[0071] Comparative Example 2 In step S1, peanut shells were heated to 700°C at a rate of 5°C / min and held for 2 hours in air (not nitrogen). The resulting material was ash, not porous biochar. Using this carrier, composites were attempted according to steps S2 (with 0.3g phosphorus source) and S3 of Example 1. The resulting product had an extremely low specific surface area (<10 μm). 2 The metal components were severely aggregated. Under the same degradation conditions, the removal rate of imidacloprid was less than 30%, proving that the formation of a porous conductive biochar carrier by pyrolysis under an inert atmosphere is a necessary prerequisite for this invention.

[0072] Comparative Example 3 In this comparative example, disodium hydrogen phosphate in step S2 of Example 1 was replaced with an equimolar amount of sodium dihydrogen phosphate. Other conditions remained unchanged, and the resulting material was denoted as PCuCoBC-NaH2PO4.

[0073] Characterization revealed that the material can also form a layered structure, but its specific surface area (165.4 m²) is smaller. 2 Both the ( / g) and EPR signal intensities were lower than those of 0.3PCuCoBC using disodium hydrogen phosphate. Degradation experiments showed that its 60-minute imidacloprid removal rate was 91.5%, which was better than Comparative Example 1, but lower than the 97.4% of the optimal example. This indicates that disodium hydrogen phosphate has unique advantages in controlling the phosphate release rate and adjusting pH to facilitate interfacial reactions, which is one of the reasons why it is a preferred phosphorus source.

[0074] Comparative Example 4 To highlight the synergistic effect of the copper-cobalt bimetallic combination, a single metal control was included in this comparative example.

[0075] D4-1: Only copper salts are used. In step S2, only 2 mmol of copper nitrate trihydrate is added (keeping the total metal molar amount constant at 3 mmol), and no cobalt salt is added. Everything else is the same as in Example 1. The resulting material is denoted as PCuBC.

[0076] D4-2: Cobalt salt only. In step S2, only 3 mmol of cobalt nitrate hexahydrate was added, without adding copper salt. Everything else was the same as in Example 1, and the resulting material was denoted as PCoBC.

[0077] Degradation tests showed that PCuBC and PCoBC achieved removal rates of 82.7% and 79.4% for imidacloprid within 60 minutes, respectively. The copper-cobalt bimetallic system with 0.3PCuCoBC achieved a removal rate of 97.4%. This confirms the electronic synergistic effect between copper and cobalt, which can more efficiently activate persulfate. The bimetallic combination is one of the key features of this invention.

[0078] Example 6 The composite materials prepared above are used to activate potassium persulfate to degrade imidacloprid in water: Experimental group: 0.0075g of 0.3PCuCoBC was added to 50mL of imidacloprid solution (initial concentration of 10mg / L, initial pH of 7), and then 0.0025g of potassium persulfate was added to the system to carry out catalytic degradation reaction for 60min to complete the degradation of imidacloprid in the water.

[0079] Control group 1: The only difference from the experimental group is that 0.3 PCuCoBC is omitted.

[0080] Control group 2: The only difference from the experimental group is that potassium persulfate is omitted.

[0081] Control group 3: The only difference from the experimental group was that 0.3PCuCoBC was replaced with an equal mass of CuCoBC.

[0082] Control group 4: The only difference from the experimental group was that 0.3 PCuCoBC was replaced with an equal mass of 0.2 PCuCoBC.

[0083] Control group 5: The only difference from the experimental group was that 0.3 PCuCoBC was replaced with an equal mass of 0.4 PCuCoBC.

[0084] 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 calculated, and the results are as follows: Figure 7 As shown.

[0085] Depend on Figure 7 It is evident that the 0.3PCuCoBC prepared in this invention can efficiently activate potassium persulfate, achieving a removal rate of 97.4% for imidacloprid, significantly superior to the undoped system. This advantage stems from the enhanced electron transfer achieved by the phosphorus-oxygen-metal interface constructed by phosphorus doping, the improved activation efficiency of persulfate through the synergistic effect of copper-cobalt bimetals, and the synergistic adsorption-catalysis effect achieved by abundant defect sites and optimized pore structure. In contrast, CuCoBC, lacking heteroatom regulation, suffers from weak interfacial bonding and insufficient active sites. Furthermore, the heteroatom-metal interaction forces of 0.2PCuCoBC and 0.4PCuCoBC are weaker, failing to achieve the catalytic effect of 0.3PCuCoBC.

[0086] Example 7 The degradation of imidacloprid in water by 0.3 PCuCoBC activated potassium persulfate prepared in Example 1 using different dosages: 0.005 g, 0.0075 g, 0.010 g, 0.0125 g and 0.015 g of 0.3 PCuCoBC were added to 50 mL of imidacloprid solution (initial concentration 10 mg / L, initial pH 7), respectively. Then, 0.0025 g of potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 60 min to complete the degradation of imidacloprid in the water.

[0087] During the catalytic degradation process, the supernatant was periodically aspirated, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography (HPLC) at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The degradation rates of imidacloprid by different dosages of 0.3 PCuCoBC are shown in the figure. Figure 8 .from Figure 8 As can be seen, with the catalyst dosage increasing from 0.1 g / L to 0.15 g / L, the imidacloprid removal rate increased from 60.7% to 97.4%. This is because the number of active sites increases with the catalyst dosage, which can fully activate persulfate. When the catalyst dosage exceeds 0.15 g / L, the removal rate does not improve significantly and even decreases slightly. This is because excessive catalyst leads to the self-quenching of active species and increases treatment costs. Therefore, a catalyst dosage of 0.15 g / L can achieve efficient degradation at low cost.

[0088] Example 8 The 0.3PCuCoBC prepared in Example 1 was used to activate potassium persulfate of different concentrations to degrade imidacloprid in water: Five 0.0075g portions of 0.3PCuCoBC were added to five 50mL portions of imidacloprid solution (initial concentration 10mg / L, initial pH 7). Then, 0.002g, 0.0025g, 0.003g, 0.0035g, and 0.004g of potassium persulfate were added to each system, respectively, and the catalytic degradation reaction was carried out for 60min to complete the degradation of imidacloprid in the water.

[0089] During the catalytic degradation process, the supernatant was periodically aspirated, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography (HPLC) at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The degradation rates of imidacloprid by different concentrations of potassium persulfate are shown in the figure. Figure 9 .from Figure 9 It can be seen that when the concentration of potassium persulfate increased from 0.04 g / L to 0.05 g / L, the removal rate of imidacloprid increased from 85.9% to 97.4%; when the concentration was further increased to 0.08 g / L, the removal rate remained basically unchanged, and the reaction rate decreased slightly. Excess potassium persulfate can cause self-quenching of active species and increase the cost of the agent. Therefore, the optimal effect is achieved when the potassium persulfate addition is 0.05 g / L.

[0090] Example 9 The degradation of imidacloprid in water bodies with different pH values ​​was achieved using 0.3PCuCoBC activated potassium persulfate prepared in Example 1. Six 0.0075g portions of 0.3PCuCoBC were added to six 50mL portions of imidacloprid solution (initial concentration of 10mg / L, initial pH values ​​of 4, 5, 7, 9, 10, and 11, respectively). Then, 0.0025g of potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 60min to complete the degradation of imidacloprid in the water.

[0091] During the catalytic degradation process, the supernatant was periodically aspirated, filtered through a 0.45 μm filter membrane, and the concentration of imidacloprid was determined using high-performance liquid chromatography (HPLC) at a wavelength of 260 nm. The removal rate of imidacloprid was then calculated. The degradation rates of imidacloprid at different pH values ​​are shown in the figure. Figure 10 .Depend on Figure 10 It can be seen that the catalytic system maintains high degradation efficiency in the pH range of 4 to 11, with removal rates exceeding 90%.

[0092] Example 10 The degradation of imidacloprid in different water bodies using 0.3PCuCoBC activated potassium persulfate prepared in Example 1: Four 0.0075g samples of 0.3PCuCoBC were added to four 50mL samples of imidacloprid solution (initial concentration 10mg / L, initial pH 7, solvents: ultrapure water, tap water, school lake water, and river water, respectively). Then, 0.0025g of potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 60min to complete the degradation of imidacloprid in the water.

[0093] After the catalytic degradation reaction was completed, the supernatant was aspirated, 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.

[0094] Table 1. Removal rate of imidacloprid by the same catalytic system under different water conditions As shown in Table 1, the 0.3PCuCoBC prepared by this invention still maintains a high degradation efficiency in actual water bodies, with a removal rate of over 89%. It is less affected by water matrix interference, has strong anti-interference ability, and is suitable for complex water environment treatment.

[0095] Example 11 The degradation of different neonicotinoid insecticides in water using 0.3PCuCoBC activated potassium persulfate prepared in Example 1: Five 0.0075g portions of 0.3PCuCoBC were added to five 50mL portions of solutions of imidacloprid, thiamethoxam, chlorpyrifos, dinotefuran, and acetamiprid (initial concentration 10mg / L, initial pH 7). Then, 0.0025g of potassium persulfate was added to each system, and the catalytic degradation reaction was carried out for 60min.

[0096] During the catalytic degradation process, the supernatant was periodically aspirated, filtered through a 0.45 μm filter membrane, and the concentration of each insecticide was determined using high-performance liquid chromatography at the corresponding wavelength to calculate the removal rate. The degradation rates of different neonicotinoid insecticides are shown in [reference needed]. Figure 11 .Depend on Figure 11 It can be seen that the composite material has a removal rate of over 85% for all five neonicotinoid insecticides, demonstrating excellent broad-spectrum degradation effect.

[0097] Example 12 Cyclic experiment on the degradation of imidacloprid in water using 0.3PCuCoBC activated potassium persulfate prepared in Example 1: 0.0075 g of 0.3 PCuCoBC was added to 50 mL of imidacloprid solution (initial concentration 10 mg / L, initial pH 7), and 0.0025 g of potassium persulfate was added. After reacting for 60 min, the catalyst was centrifuged to recover it. After washing and freeze-drying, it was used for the next experiment. A total of 5 cycles were performed.

[0098] After each reaction, the imidacloprid removal rate was measured, and the results are as follows: Figure 12 As shown. By Figure 12 It can be seen that after 5 cycles, the removal rate of imidacloprid by 0.3PCuCoBC remains at 80%, which confirms that the composite material has excellent structural stability and renewability, and reduces the cost of practical application.

[0099] Example 13 This embodiment aims to illustrate that the composite material of the present invention has the ability to activate different types of persulfates.

[0100] Under the same conditions (10 mg / L imidacloprid, pH=7, 0.3PCuCoBC 0.15 g / L, oxidant 0.05 g / L, reaction 60 min), potassium persulfate (PMS, KHSO5) and sodium persulfate (PDS, Na2S2O8) were used as oxidants, respectively.

[0101] Experimental results show that the degradation rate is 97.4% when using PMS and 93.2% when using PDS. Both achieved excellent degradation effects, proving that the composite material of the present invention can activate both PMS and PDS. In practical applications, the type of persulfate can be flexibly selected according to cost and availability.

[0102] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, characterized in that, Includes the following steps: S1. Biochar preparation: Agricultural waste is crushed and sieved, then subjected to programmed temperature pyrolysis under an inert atmosphere, cooled, and ground to obtain biochar; S2. Preparation of the mixed system: The biochar, soluble copper salt, soluble cobalt salt and urea are dispersed together in water, stirred to form a homogeneous solution, and then a phosphorus source is added. The mixture is then dispersed by ultrasonication to obtain the mixed system. S3. Hydrothermal reaction and post-treatment: The mixed system is subjected to a hydrothermal reaction. After the reaction is completed, the product is washed and freeze-dried to obtain a phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material.

2. The preparation method according to claim 1, characterized in that, In step S1, the agricultural waste is selected from at least one of peanut shells, walnut shells, and grapefruit peels; in step S2, the soluble copper salt is copper nitrate trihydrate, the soluble cobalt salt is cobalt nitrate hexahydrate, and the phosphorus source is disodium hydrogen phosphate.

3. The preparation method according to claim 1 or 2, characterized in that, In step S2, based on 1g of biochar, the amount of soluble copper salt added is 1 mmol, the amount of soluble cobalt salt added is 2 mmol, the amount of urea added is 10 mmol, and the amount of phosphorus source added is 0.2~0.4 g.

4. The preparation method according to claim 3, characterized in that, In step S3, the hydrothermal reaction temperature is 140℃~170℃, and the reaction time is 8 h~14 h.

5. The preparation method according to claim 1, characterized in that, In step S3, the freeze-drying temperature is -60℃ to -50℃ and the vacuum degree is 10 Pa to 30 Pa; in step S3, the hydrothermal reaction temperature is 160℃ and the reaction time is 12 h.

6. A phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material, characterized in that, It is prepared by any one of claims 1 to 5.

7. The application of the phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material according to claim 6 in the activation of persulfate.

8. The application of the phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material according to claim 6 in the degradation of neonicotinoid insecticides in water.

9. The application according to claim 8, characterized in that, The phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material was added together with persulfate to water containing neonicotinoid insecticides to react and degrade the neonicotinoid insecticides.

10. The application according to claim 9, characterized in that, The dosage of the phosphorus-doped copper-cobalt layered double hydroxide-biochar composite material is 0.1 g / L to 0.3 g / L; the dosage of the persulfate is 0.04 g / L to 0.08 g / L; the reaction time is 40 min to 80 min; the initial concentration of the neonicotinoid insecticide is 1 mg / L to 20 mg / L; and the persulfate is permonosulfate and / or perdisulfate.

Images