A method for synthesizing single-atom cobalt catalysts by ligand-assisted supramolecular thermal decomposition, the resulting catalysts, and their applications

Abstract

The invention discloses a method for synthesizing a single-atom cobalt catalyst by pyrolysis of a ligand-assisted supramolecular strategy and the resulting catalyst and application, and belongs to the field of water pollution control technology. The method provided by the present invention comprises the following steps: cobalt phthalocyanine and trimesic acid are mixed in water to obtain a cobalt phthalocyanine trimesic acid complex solution; then a dicyandiamide aqueous solution is added, and after stirring, an N-allylthiourea aqueous solution is added, and after the stirring reaction, the solid product obtained is washed and dried, and then pyrolysis is performed at high temperature, and the pyrolysis product is acid-leached and washed, and a single-atom cobalt catalyst is obtained after drying. The method of the present invention can obtain a single-atom cobalt catalyst with a high cobalt loading, and at the same time, it can achieve efficient degradation of sulfonamide antibiotics in sewage, and the removal rate of sulfonamide antibiotics can be made to reach more than 90% within 2 minutes, and the antibiotic removal rate within 5 minutes reaches more than 98%, and after multiple recycling, very high catalytic efficiency can still be maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution control, and in particular to a method for synthesizing a single-atom cobalt catalyst through ligand-assisted supramolecular strategy thermal decomposition, the obtained catalyst and its application. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Antibiotics, as a typical emerging pollutant, are widely used in large quantities and across a wide range of applications, and are widely detected in natural water environments. Although current environmental exposure levels are low, their stable structures, bioaccumulation, and amplification effects pose significant potential risks to ecosystems. Given the complex sources and composition of antibiotic contamination in water bodies, wastewater treatment requires targeted and sustainable purification of specific wastewater types to achieve precise oxidative degradation of trace antibiotics in diverse water environments. Therefore, the development of selectively tunable treatment technologies is imperative.

[0004] Advanced oxidation technology (AOPs) relies on the in situ generation of strong oxidizing active substances, which can efficiently degrade antibiotics or even completely mineralize them. Therefore, AOPs are widely used in the treatment of antibiotic pollution. In recent years, the peracetic acid (PAA) advanced oxidation technology (PAA-AOPs) based on the in situ generation of organic free radicals (RO·) has attracted the attention of more and more researchers. Due to its advantages such as simple operation, low cost and few toxic by-products, it has shown great potential in the field of water remediation. In addition, compared with the inorganic free radical active substances (such as ·OH, SO4·) generated in the traditional AOPs system, - ), RO has a longer survival time and is less affected by the complex matrix of the water body, so it has a stronger selective degradation ability for new antibiotic pollutants.

[0005] The construction of new and efficient catalytic systems is the main research direction of peracetic acid advanced oxidation technology. Its core lies in the development of high-activity and high-stability activation technology to enhance the efficiency of active substances. To date, a variety of methods have been used to activate peracetic acid to remove antibiotic pollutants in water. Metal ions (such as Fe 2+ and Co 2+) can effectively activate peracetic acid, but its recycling is difficult and the environmental hazards cannot be ignored. In contrast, heterogeneous catalysts containing metal-based and carbon-based materials can be easily recycled and reused after activating peracetic acid. Carbon-based catalysts such as carbon fibers, multi-walled carbon nanotubes (MWCNTs), activated carbon, etc. have been reported to be used to activate peracetic acid, but their catalytic performance is generally not outstanding and it is difficult to meet actual needs. Metal-based heterogeneous catalysts, especially those containing Co (such as Co3O4), generally exhibit excellent catalytic performance and have become a promising strategy to achieve efficient activation of peracetic acid and rapid degradation of pollutants. However, traditional Co-based transition metal catalysts only have surface metal sites that can play a catalytic role, resulting in low effective utilization of metal sites, large metal dosage, and high metal leaching. Therefore, it is crucial to develop and design new catalysts with high metal utilization, low metal dosage, and low metal ion leaching. Summary of the Invention

[0006] In view of this, the present invention provides a method for the pyrolysis synthesis of single-atom cobalt catalysts using a ligand-assisted supramolecular strategy, as well as the resulting catalyst and application. The single-atom cobalt catalyst prepared by the preparation method of the present invention can achieve maximum utilization of metal sites, low metal dosage, and extremely low metal leaching. When it is used to catalyze the activation of peracetic acid to degrade sulfonamide antibiotics in wastewater, no secondary pollution is generated during the catalytic process, the catalytic efficiency is high, and the catalyst can be recycled and reused multiple times.

[0007] In a first aspect, the present invention provides a method for synthesizing a single-atom cobalt catalyst by ligand-assisted supramolecular thermal decomposition strategy, comprising the following steps:

[0008] Cobalt phthalocyanine and trimesic acid are mixed in water to obtain a cobalt phthalocyanine-trimesic acid complex solution; a dicyandiamide aqueous solution is then added, stirred evenly, and then an N-allylthiourea aqueous solution is added. After stirring for reaction, the obtained solid product is washed and dried, and then subjected to high-temperature pyrolysis under the protection of an inert atmosphere. The pyrolysis product is then acid-leached, washed, and dried to obtain a single-atom cobalt catalyst.

[0009] In a second aspect, the present invention provides a single-atom cobalt catalyst prepared by the above method.

[0010] In a third aspect, the present invention provides the use of the above-mentioned single-atom cobalt catalyst in activating peracetic acid to degrade sulfonamide antibiotics.

[0011] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0012] (1) The present invention adopts a ligand-assisted supramolecular strategy, using metal cobalt salts and organic ligands to form a metal cobalt-ligand stable chelate under suitable conditions, and realizes the self-assembly process of the metal cobalt-ligand chelate with the carbon nitrogen substrate by means of intermolecular hydrogen bonds, thereby obtaining a metal supramolecular precursor with a high loading amount, and a single-atom cobalt catalyst can be obtained by high-temperature pyrolysis; the overall steps are relatively simple, achieving the maximum utilization of metal catalytic sites and reducing the amount of metal added in the catalyst synthesis; at the same time, in the single-atom catalyst obtained by this method, since a stable coordination structure is formed between the metal site and the ligand, the infiltration of the metal during the reaction is largely prevented, and the cobalt loading can reach up to 12wt%, which is significantly higher than the loading of most single-atom cobalt catalysts currently reported.

[0013] (2) The single-atom cobalt catalyst prepared by the method of the present invention has a rich and uniform symmetrical Co-N4-C coordination structure, which can catalyze the decomposition of peracetic acid to generate a variety of active oxygen species in situ, including ·OH, RO· and singlet oxygen ( 1 O2), can realize the efficient degradation of sulfonamide antibiotics in sewage, and the removal rate of sulfonamide antibiotics can reach more than 90% within 2 minutes, and the antibiotic removal rate can reach more than 98% within 5 minutes; and the single-atom cobalt catalyst prepared by the present invention will not produce secondary pollution during the catalytic process, and can still maintain extremely high catalytic efficiency after multiple recycling, and can realize efficient, stable and continuous degradation of sulfonamide antibiotics. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0015] Figure 1 This is a scanning electron microscope (SEM) image of the single-atom cobalt catalyst prepared in Example 1 of the present invention;

[0016] Figure 2 This is a spherical aberration correction-high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image of the single-atom cobalt catalyst prepared in Example 1 of the present invention;

[0017] Figure 3 This is a diagram showing the effect of sulfamethoxazole removal by activating peracetic acid with the single-atom cobalt catalyst prepared in Example 1 under different pH conditions of the present invention;

[0018] Figure 4This is a diagram showing the effect of sulfamethoxazole removal by activating peracetic acid in a system with different addition amounts of a single-atom cobalt catalyst according to Example 1 of the present invention;

[0019] Figure 5 This is a diagram showing the effect of sulfamethoxazole removal by activating peracetic acid in systems with different peracetic acid concentrations according to the present invention;

[0020] Figure 6 The results are a comparison of the effects of catalyst-activated peracetic acid on the degradation of sulfamethoxazole in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention;

[0021] Figure 7 The effects of activating peracetic acid and degrading sulfamethoxazole using single-atom cobalt catalysts in Example 1, Comparative Example 3, and Comparative Example 4 of the present invention are compared;

[0022] Figure 8 The effects of activating peracetic acid and degrading sulfamethoxazole using single-atom cobalt catalysts in Example 1, Comparative Example 5, and Comparative Example 6 of the present invention are compared;

[0023] Figure 9 The effects of activating peracetic acid and degrading sulfamethoxazole using single-atom cobalt catalysts in Example 1, Comparative Example 7, and Comparative Example 8 of the present invention are compared;

[0024] Figure 10 This is a bar chart showing the recycling effect of the single-atom cobalt catalyst of Example 1 of the present invention. DETAILED DESCRIPTION

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0026] The present invention provides a method for synthesizing a single-atom cobalt catalyst by ligand-assisted supramolecular strategy thermal decomposition, comprising the following steps:

[0027] Cobalt phthalocyanine and trimesic acid are mixed in water to obtain a cobalt phthalocyanine-trimesic acid complex solution; a dicyandiamide aqueous solution is then added, stirred evenly, and then an N-allylthiourea aqueous solution is added. After stirring for reaction, the obtained solid product is washed and dried, and then subjected to high-temperature pyrolysis under the protection of an inert atmosphere. The pyrolysis product is then acid-leached, washed, and dried to obtain a single-atom cobalt catalyst.

[0028] The present invention adopts a ligand-assisted supramolecular strategy. First, a stable metal-ligand chelate is formed using cobalt phthalocyanine and the organic ligand trimesic acid. Then, the self-assembly process of the metal-ligand chelate and the carbon-nitrogen substrate (dicyandiamide and N-allylthiourea) is realized by intermolecular hydrogen bonds to obtain a supramolecular precursor containing a high loading of metal cobalt, and a single-atom cobalt catalyst is obtained by high-temperature pyrolysis.

[0029] The present invention has discovered that the type of cobalt salt affects the catalytic effect of the single-atom cobalt catalyst. The present invention selects cobalt phthalocyanine because cobalt phthalocyanine, as an organic cobalt salt, has a structural formula of a cyclic molecule consisting of four benzene rings alternately connected by pyrrolidines and a central active metal ion. This organic coordination structure is conducive to the formation of a more stable metal-ligand chelate between the metal cobalt center and the carbon-nitrogen substrate. Therefore, compared with inorganic cobalt salts, a better catalytic effect can be achieved in the present invention.

[0030] In the present invention, the molar ratio of cobalt phthalocyanine, trimesic acid, dicyandiamide, and N-allylthiourea is (1-1.5):(4-6):(30-40):(20-30). Under the appropriate molar ratio, a single-atom cobalt catalyst with good catalytic effect can be obtained.

[0031] In the step of adding the N-allylthiourea aqueous solution after stirring, the stirring time is 10 to 60 minutes. The stirring process can be carried out at room temperature. The present invention does not impose any particular restriction on the stirring speed, as long as uniform mixing is ensured.

[0032] In the step of stirring reaction described in the present invention, the stirring reaction time is 3 to 8 hours, and the stirring reaction temperature is 10 to 40°C, preferably at room temperature. During the stirring reaction, the metal-ligand chelate and the carbon-nitrogen substrate form a metal cobalt supramolecular precursor precipitate by self-assembly. The present invention does not impose any special restrictions on the method of obtaining the solid product after the stirring reaction, for example, conventional methods such as filtration, suction filtration or centrifugation can be used. The present invention does not impose any special restrictions on the washing process, and preferably uses water and ethanol for alternating washing, and the number of washing times is 2 to 4 times. The present invention does not impose any special restrictions on the drying process, and can be carried out by freeze drying, vacuum drying, ordinary drying, etc.

[0033] In the present invention, the total molar concentration of the cobalt phthalocyanine-trimesic acid complex solution is 40 to 150 mM; the concentration of the dicyandiamide aqueous solution is 5 to 20 g / L; and the concentration of the N-allylthiourea aqueous solution is 5 to 20 g / L. The present invention imposes no particular restrictions on the preparation methods of the cobalt phthalocyanine-trimesic acid complex solution, the dicyandiamide aqueous solution, and the N-allylthiourea aqueous solution; commonly used methods in the art can be used.

[0034] In the present invention, the inert atmosphere is selected from argon or nitrogen to avoid the adverse effects of oxygen on the pyrolysis process. The present invention does not impose any particular restrictions on the flow rate of the inert atmosphere.

[0035] In the present invention, the high-temperature pyrolysis temperature is 650-750°C, and the high-temperature pyrolysis time is 3-6 hours. The high-temperature pyrolysis temperature will have a certain impact on the catalytic effect. Both too high and too low high-temperature pyrolysis temperatures will lead to a decrease in catalytic effect. The present invention does not impose any particular restrictions on the heating rate to the high-temperature pyrolysis temperature, but is preferably 2-8°C / min.

[0036] In the present invention, the acid leaching process uses hydrochloric acid or sulfuric acid solution with a concentration of 0.05 to 0.5 mol / L. The acid leaching process is to remove residual metallic cobalt on the surface of the catalyst (monoatomic cobalt does not react with acid). The acid leaching time is 40 to 120 minutes. After the acid leaching is completed, the catalyst is washed with water and ethanol multiple times and then dried. The present invention does not impose any particular restrictions on the drying process. In the present invention, vacuum drying at 50 to 80°C is preferred.

[0037] The present invention also provides a single-atom cobalt catalyst prepared by the above method. The single-atom cobalt catalyst prepared by the present invention has abundant single-atom cobalt catalytic sites, and the cobalt loading can reach up to 12 wt% or more.

[0038] The present invention also provides the use of the single-atom cobalt catalyst in activating peracetic acid to degrade sulfonamide antibiotics.

[0039] In the present invention, the ratio of the single-atom cobalt catalyst, peracetic acid and sulfonamide antibiotics is (100-200) mg: (0.2-0.6) mmol: (1-15) μmol; the concentration of the single-atom cobalt catalyst is 100-200 mg / L; and the pH is 6.8-7.2. The present invention uses peracetic acid as an oxidant. Compared with other oxidants, peracetic acid is less affected by organic matter and produces no or less toxic and harmful disinfection by-products. The single-atom cobalt catalyst of the present invention can catalyze the decomposition of peracetic acid to generate a variety of active oxygen species in situ, including ·OH, RO· and singlet oxygen ( 1 O2) can achieve efficient degradation of sulfonamide antibiotics in wastewater, with a removal rate of over 90% within 2 minutes. Furthermore, the single-atom cobalt catalyst prepared by this invention does not produce secondary pollution during the catalytic process and maintains extremely high catalytic efficiency after multiple recycling, achieving efficient, stable, and continuous degradation of sulfonamide antibiotics.

[0040] The technical solution of the present invention is further described below with reference to specific examples. The present invention has no particular limitation on the sources of the reagents used in the following examples, and commercially available products known to those skilled in the art can be used.

[0041] Example 1

[0042] This embodiment provides a method for synthesizing single-atom cobalt catalysts by thermal decomposition using a ligand-assisted supramolecular strategy.

[0043] (1) Weigh 3 g of N-allylthiourea (NA, 25.8 mmol) and 3 g of dicyandiamide (DCD, 35.7 mmol) and dissolve them in 300 ml of deionized water at 90°C to obtain NA solution and DCD solution, respectively.

[0044] (2) 4.8 mmol of trimesic acid (TA, 1.0 g) and 1.2 mmol of cobalt phthalocyanine (0.69 g) were dissolved in 75 mL of water to obtain a cobalt phthalocyanine-trimesic acid complex solution; the DCD solution and the cobalt-trimesic acid complex solution were mixed and stirred for 30 minutes, and finally the NA solution was added and stirred for 4 hours. The precipitate was separated by filtration and washed alternately with deionized water and ethanol twice each, and finally the precursor was obtained after freeze-drying.

[0045] (3) The precursor obtained above was heated to 700°C at a heating rate of 5°C / min under the protection of argon atmosphere (50 mL / min), kept at this temperature for 4 h, and then acid-leached in 0.1 M hydrochloric acid for 60 min to remove residual metals. It was then washed with deionized water and ethanol three times each, and dried in a vacuum oven at 65°C for 12 h to obtain a single-atom cobalt catalyst, which was recorded as Co SA -NC.

[0046] Figure 1 is a scanning electron microscope (SEM) image of the single-atom cobalt catalyst prepared in this embodiment; Figure 1 It can be seen that the prepared single-atom cobalt catalyst presents a typical nitrogen-carbon material flake structure, and there are no obvious nanoparticles.

[0047] Figure 2 This is a spherical aberration correction-high angle annular dark field-scanning transmission electron microscope (HAADF-STEM) image of the single-atom cobalt catalyst prepared in this example; Figure 2 The active metal sites are dispersed in single atoms, with a high loading density and no nanoparticles or metal clusters. The single atomic cobalt loading was determined to be 12.8 wt% by ICP-OES.

[0048] Example 2

[0049] This embodiment provides a method for synthesizing single-atom cobalt catalysts by thermal decomposition using a ligand-assisted supramolecular strategy.

[0050] (1) Weigh 3 g of N-allylthiourea (NA, 25.8 mmol) and 3 g of dicyandiamide (DCD, 35.7 mmol) and dissolve them in 300 ml of deionized water at 90°C to obtain NA solution and DCD solution, respectively.

[0051] (2) 6 mmol of trimesic acid (TA, 1.26 g) and 1.5 mmol of cobalt phthalocyanine (0.86 g) were dissolved in 75 mL of water to obtain a cobalt phthalocyanine-trimesic acid complex solution; the DCD solution and the cobalt-trimesic acid complex solution were mixed and stirred for 30 minutes, and finally the NA solution was added and stirred for 4 hours. The precipitate was separated by filtration and washed alternately with deionized water and ethanol twice each, and finally the precursor was obtained after freeze-drying.

[0052] (3) The precursor obtained above was heated to 700°C at a heating rate of 5°C / min under the protection of a nitrogen atmosphere (50 mL / min), kept warm for 4 h, and then acid-leached in 0.1 M hydrochloric acid for 60 min to remove residual metals. It was then washed with deionized water and ethanol three times each, and dried in a vacuum oven at 65°C for 12 h to obtain a single-atom cobalt catalyst; ICP-OES measurement showed that the cobalt loading was 11.6 wt%.

[0053] Example 3

[0054] This embodiment provides a method for synthesizing single-atom cobalt catalysts by thermal decomposition using a ligand-assisted supramolecular strategy.

[0055] (1) Weigh 3.2 g of N-allylthiourea (NA, 27.5 mmol) and 2.8 g of dicyandiamide (DCD, 33.3 mmol) and dissolve them in 300 ml of deionized water at 90°C to obtain NA solution and DCD solution, respectively.

[0056] (2) 4.8 mmol of trimesic acid (TA, 1.0 g) and 1.2 mmol of cobalt phthalocyanine (0.69 g) were dissolved in 75 mL of water to obtain a cobalt phthalocyanine-trimesic acid complex solution; the DCD solution and the cobalt-trimesic acid complex solution were mixed and stirred for 30 minutes, and finally the NA solution was added and stirred for 4 hours. The precipitate was separated by filtration and washed alternately with deionized water and ethanol twice each, and finally the precursor was obtained after freeze-drying.

[0057] (3) The precursor obtained above was heated to 700°C at a heating rate of 5°C / min under the protection of an argon atmosphere (50 mL / min), kept warm for 4 h, and then acid-leached in 0.1 M hydrochloric acid for 60 min to remove residual metals. It was then washed with deionized water and ethanol three times each, and dried in a vacuum oven at 65°C for 12 h to obtain a single-atom cobalt catalyst; ICP-OES measurement showed that the cobalt loading was 11.2 wt%.

[0058] Comparative Example 1

[0059] This comparative example provides a method for preparing a nitrogen-carbon catalyst.

[0060] (1) Weigh 3 g of N-allylthiourea (NA, 25.8 mmol) and 3 g of dicyandiamide (DCD, 35.7 mmol) and dissolve them in 300 ml of deionized water at 90°C to obtain NA solution and DCD solution, respectively.

[0061] (2) 4.8 mmol of trimesic acid (TA, 1.0 g) was dissolved in 75 mL of water; the DCD solution and the trimesic acid solution were mixed and stirred for 30 minutes, and finally the NA solution was added and stirred for 4 hours. The precipitate was separated by filtration and washed alternately with deionized water and ethanol twice each, and finally freeze-dried to obtain a solid.

[0062] (3) The solid obtained above was heated to 700°C at a heating rate of 5°C / min under argon atmosphere (50 mL / min), kept at this temperature for 4 h, and then cooled to obtain a nitrogen-carbon catalyst, which was recorded as NC.

[0063] Comparative Example 2

[0064] This comparative example provides a method for preparing a cobalt nanosphere catalyst.

[0065] 1.32g of cobalt phthalocyanine, 60g of urea, and 6g of polyvinylpyrrolidone (PVP) were mixed and ground into a powder. The mixture was then transferred to a quartz boat and placed in a tube furnace. The sample was heated to 500°C at a heating rate of 5°C / min and held at 500°C for 2 hours under flowing argon. After cooling, the cobalt nanosphere catalyst, designated Co-NPs, was obtained.

[0066] Comparative Example 3

[0067] The difference between this comparative example and Example 1 is that this comparative example is heated to 600° C. at a heating rate of 5° C. / min.

[0068] Comparative Example 4

[0069] The difference between this comparative example and Example 1 is that this comparative example is heated to 800° C. at a heating rate of 5° C. / min.

[0070] Comparative Example 5

[0071] The difference between this comparative example and Example 1 is that cobalt phthalocyanine is replaced by cobalt nitrate in this comparative example.

[0072] Comparative Example 6

[0073] The difference between this comparative example and Example 1 is that cobalt sulfate is used instead of cobalt phthalocyanine in this comparative example.

[0074] Comparative Example 7

[0075] This comparative example differs from Example 1 in that 2.4 mmol of trimesic acid (TA, 0.5 g) and 1.2 mmol of cobalt phthalocyanine (0.69 g) were dissolved in 75 mL of water to obtain a cobalt phthalocyanine-trimesic acid complex solution. That is, in this comparative example, the molar ratio of trimesic acid to cobalt phthalocyanine was 2:1.

[0076] Comparative Example 8

[0077] This comparative example differs from Example 1 in that 9.6 mmol of trimesic acid (TA, 2.0 g) and 1.2 mmol of cobalt phthalocyanine (0.69 g) were dissolved in 75 mL of water to obtain a cobalt phthalocyanine-trimesic acid complex solution. That is, in this comparative example, the molar ratio of trimesic acid to cobalt phthalocyanine was 8:1.

[0078] Test example

[0079] 1. Degradation experiments at different pH values:

[0080] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to reach a concentration of 0.26 mM. The pH of the wastewater was adjusted to 4.0-10.0 using 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution, which were 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, respectively. The single-atom cobalt catalyst prepared in Example 1 was added to the above solution to reach a concentration of 100 mg / L. The reaction was stirred at room temperature for 5 minutes. The removal rate of sulfamethoxazole over time was shown in the following table. Figure 3 shown.

[0081] from Figure 3As can be seen from the data, when the pH value of the wastewater is 4.0, after 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 61%. When the pH value of the wastewater is 5.0, after 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 85%. When the pH value of the wastewater is 6.0, after 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 94%. When the pH value of the wastewater is 7.0, after 2 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 96%. After 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 99%. When the pH value of the wastewater is 8.0, after 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 75%. When the pH value of the wastewater was 9.0, after 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was found to be 52%. Furthermore, it was confirmed that the peracetic acid system activated by the single-atom cobalt catalyst prepared by the present invention had a better removal effect on sulfamethoxazole at a neutral pH (pH=7), while both strongly acidic and strongly alkaline conditions were not conducive to the reaction.

[0082] 2. Degradation experiments with different catalyst addition amounts:

[0083] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole (SMX) to a concentration of 0.26 mM. The pH of the wastewater was adjusted to 7.0 using 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. The single-atom cobalt catalyst prepared in Example 1 was added to the above solution to concentrations of 25 mg / L, 50 mg / L, 75 mg / L, and 100 mg / L, respectively. The reaction was stirred at room temperature for 5 minutes, and the removal rate of sulfamethoxazole over time was recorded, as shown in FIG. Figure 4 As shown. Figure 4As can be seen, when the catalyst addition amount was 25 mg / L and the reaction time was 5 minutes at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was found to be 92%. When the catalyst addition amount was 50 mg / L and the reaction time was 5 minutes at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was found to be 94%. When the catalyst addition amount was 75 mg / L and the reaction time was 5 minutes at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was found to be 97%. When the catalyst addition amount was 100 mg / L and the reaction time was 2 minutes at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst reached 96%. After 5 minutes of reaction at room temperature, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was found to be 99%.

[0084] 3. Degradation experiment with different amounts of peracetic acid added:

[0085] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole (SMX) to achieve concentrations of 0.0325 mM, 0.065 mM, 0.13 mM, 0.20 mM, and 0.26 mM, respectively. The pH of the wastewater was adjusted to 7.0 using 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. The single-atom cobalt catalyst prepared in Example 1 was added to the above solution to achieve a concentration of 100 mg / L. The reaction was stirred at room temperature for 5 minutes, and the removal rate of sulfamethoxazole over time was recorded, as shown in FIG. Figure 5 As shown. Figure 5 As can be seen, when the peracetic acid addition amount was 0.0325 mM and the reaction was carried out at room temperature for 5 minutes, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was 45%. When the peracetic acid addition amount was 0.065 mM and the reaction was carried out at room temperature for 5 minutes, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was 68%. When the peracetic acid addition amount was 0.13 mM and the reaction was carried out at room temperature for 5 minutes, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was 88%. When the peracetic acid addition amount was 0.20 mM and the reaction was carried out at room temperature for 5 minutes, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was 90%. When the peracetic acid addition amount was 0.26 mM and the reaction was carried out at room temperature for 5 minutes, the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst was 99%.

[0086] 4. Degradation experiments with different catalyst types:

[0087] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to a concentration of 0.26 mM, and the pH value of the wastewater was adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. The catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 were then added to a concentration of 100 mg / L, and stirred for 5 minutes at room temperature. The pH value of wastewater containing 10 μM sulfamethoxazole was adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. The catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 were then added to a concentration of 100 mg / L, and stirred for 5 minutes at room temperature. The removal rates of sulfamethoxazole over time in systems containing and not containing PAA were shown in Figure 2. Figure 6 As shown. Figure 6 It can be seen that only the system in which the single-atom cobalt catalyst of Example 1 and peracetic acid are added simultaneously exhibits the best effect of removing sulfamethoxazole, and the removal rates of sulfamethoxazole in the other systems within 5 minutes are all below 50%.

[0088] 5. Degradation experiments of catalysts synthesized at different pyrolysis temperatures:

[0089] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to reach a concentration of 0.26 mM. The pH value of the wastewater was adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. Then, the single-atom cobalt catalyst prepared in Example 1, Comparative Example 3, and Comparative Example 4 was added to reach a concentration of 100 mg / L, and the reaction was stirred at room temperature for 5 minutes. Figure 7 As shown, it can be seen that the single-atom cobalt catalyst synthesized at a pyrolysis temperature of 700°C has the best catalytic degradation effect of sulfamethoxazole.

[0090] 6. Degradation experiments of catalysts synthesized from different cobalt salts:

[0091] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to reach a concentration of 0.26 mM. The pH value of the wastewater was adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. Then, the single-atom cobalt catalyst prepared in Example 1, Comparative Example 5, and Comparative Example 6 was added to the wastewater to reach a concentration of 100 mg / L. The reaction was stirred at room temperature for 5 minutes. Figure 8 As shown, it can be seen that the catalyst synthesized with cobalt phthalocyanine as the cobalt salt has the best catalytic degradation effect.

[0092] 7. Degradation experiment of catalysts synthesized with different molar ratios of benzoic acid and cobalt phthalocyanine:

[0093] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to reach a concentration of 0.26 mM. The pH value of the wastewater was adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. Then, the single-atom cobalt catalyst prepared in Example 1, Comparative Example 7, and Comparative Example 8 was added to the wastewater to reach a concentration of 100 mg / L. The reaction was stirred at room temperature for 5 minutes. Figure 9 As shown, it can be seen that the catalyst synthesized when the molar ratio of benzoic acid to cobalt phthalocyanine is 4:1 has the best catalytic degradation effect.

[0094] 8. Cyclic performance of the single-atom cobalt catalyst of Example 1:

[0095] Peracetic acid is added to wastewater containing 10 μM sulfamethoxazole to make its concentration reach 0.26 mM, and 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution is used to adjust the pH value of the wastewater to 7.0. The single-atom cobalt catalyst prepared in Example 1 is added to the above solution to make its concentration reach 100 mg / L, and the reaction is stirred at room temperature for 5 minutes. The concentration of sulfamethoxazole during the reaction is measured, and its removal rate is calculated. The continuous cycle catalytic experiment of the catalyst is operated as follows: the solid catalyst after the reaction is collected by filtration, repeatedly rinsed with deionized water 3-5 times, and then placed in a vacuum drying oven at 60°C for drying, and then the next catalytic reaction is started. The cycle is repeated and the changes in pollutant degradation are measured. The changes in the removal rate of sulfamethoxazole during the recycling of the catalyst are shown in Figure 10 .Depend on Figure 10 It can be seen that after four cycles, the removal rate of sulfamethoxazole in the system only decreased by about 4.6%, and its removal rate can still reach 95.4%, which shows that the single-atom cobalt catalyst prepared in Example 1 of the present invention has very good recyclability and is conducive to further promotion and application.

[0096] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for synthesizing single-atom cobalt catalysts by ligand-assisted supramolecular thermal decomposition, characterized in that: The steps include: Cobalt phthalocyanine and trimesic acid are mixed in water to obtain a cobalt phthalocyanine-trimesic acid complex solution; a dicyandiamide aqueous solution is then added, stirred evenly, and then an N-allylthiourea aqueous solution is added. After stirring for reaction, the obtained solid product is washed and dried, and then subjected to high-temperature pyrolysis under the protection of an inert atmosphere. The pyrolysis product is then acid-leached, washed, and dried to obtain a single-atom cobalt catalyst; The usage ratio of the cobalt phthalocyanine, trimesic acid, dicyandiamide and N-allylthiourea is (1-1.5) mmol: (4-6) mmol: (2.5-3.5) g: (2.5-3.5) g.

2. The method according to claim 1, wherein In the step of adding the N-allylthiourea aqueous solution after stirring evenly, the stirring time is 10 to 60 minutes.

3. The method according to claim 1, wherein In the stirring reaction step, the stirring reaction time is 3 to 8 hours, and the stirring reaction temperature is 10 to 40°C.

4. The method according to claim 1, wherein The total molar concentration of the cobalt phthalocyanine-trimellitic acid complex solution is 40-150 mM; the concentration of the dicyandiamide aqueous solution is 5-20 g / L; and the concentration of the N-allylthiourea aqueous solution is 5-20 g / L.

5. The method according to claim 1, wherein The inert atmosphere is selected from argon or nitrogen; the temperature of the high-temperature pyrolysis is 650-750° C., and the time of the high-temperature pyrolysis is 3-6 hours.

6. The method according to claim 1, wherein The acid leaching process uses hydrochloric acid or sulfuric acid solution with a concentration of 0.05-0.5 mol / L.

7. A single-atom cobalt catalyst prepared by the method according to any one of claims 1 to 6.

8. Use of the single-atom cobalt catalyst as claimed in claim 7 in activating peracetic acid to degrade sulfonamide antibiotics.

9. The use according to claim 8, characterized in that The ratio of the single-atom cobalt catalyst, peracetic acid, and sulfonamide antibiotic is (100-200) mg: (0.2-0.6) mmol: (1-15) μmol; the concentration of the single-atom cobalt catalyst is 100-200 mg / L; and the pH is 6.8-7.2.

Images