Method for synthesizing monatomic cobalt catalyst through ligand-assisted supramolecular strategy pyrolysis, obtained catalyst and application

Abstract

The invention discloses a method for synthesizing a monatomic cobalt catalyst through ligand-assisted supramolecular strategy pyrolysis, the obtained catalyst and application, and belongs to the technical field of water pollution control. The method provided by the invention comprises the following steps: mixing cobalt phthalocyanine and trimesic acid in water to obtain a cobalt phthalocyanine-trimesic acid complex solution; the preparation method comprises the following steps: adding an aqueous solution of dicyandiamide, uniformly stirring, adding an aqueous solution of N-allylthiourea, stirring to react, washing and drying an obtained solid product, carrying out high-temperature pyrolysis, and carrying out acid leaching, washing and drying on a pyrolysis product to obtain the monatomic cobalt catalyst. According to the method, the monatomic cobalt catalyst with high cobalt loading capacity can be obtained, meanwhile, the sulfonamide antibiotics in sewage can be efficiently degraded, the removal rate of the sulfonamide antibiotics can reach 90% or above within 2 min, the removal rate of the antibiotics can reach 98% or above within 5 min, and very high catalytic efficiency can still be kept after multiple times of cyclic utilization.

Description

Technical Field

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

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

[0003] As a typical emerging pollutant, antibiotics are widely used in large quantities and in a wide range of applications. They are widely detected in natural water environments. Although the current exposure level of antibiotics in the environment is low, their structure is stable and they have bioaccumulation and amplification effects. Their potential harm to the ecosystem cannot be ignored. Given the complex sources and components of antibiotic pollution in water bodies, wastewater treatment needs to purify specific types of wastewater in a targeted and sustainable manner to achieve precise oxidative degradation of trace antibiotics in different water environments. Therefore, it is imperative to develop selectively adjustable treatment technologies.

[0004] Advanced oxidation techniques (AOPs) rely 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. It has shown great potential in the field of water remediation due to its advantages such as simple operation, low cost and few toxic by-products. 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 highly active and stable activation technologies to enhance the efficiency of active substances. So far, 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 its 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 show 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 pyrolysis synthesis of single-atom cobalt catalysts by a ligand-assisted supramolecular strategy, the obtained catalyst and applications. The single-atom cobalt catalyst prepared by the preparation method of the present invention can achieve maximum utilization of metal sites, lower metal dosage and extremely low metal filtration. When it is used to catalyze and activate peracetic acid to degrade sulfonamide antibiotics in sewage, no secondary pollution is generated during the catalytic process, the catalytic efficiency is high, and the catalyst can be recycled and reused many times.

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

[0008] 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, stirred evenly, and then an N-allylthiourea aqueous solution is added, and after stirring for reaction, the obtained solid product is washed and dried, and then high-temperature pyrolysis is carried out under the protection of an inert atmosphere, and then the pyrolysis product is 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 and the carbon nitrogen substrate by means of intermolecular hydrogen bonds, thereby obtaining a metal supramolecular precursor containing a high loading amount, and a single-atom cobalt catalyst can be obtained by high-temperature pyrolysis; the overall steps are relatively simple, and the maximum utilization of metal catalytic sites is achieved, 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 process is largely prevented, and the cobalt loading amount can reach more than 12wt%, which is significantly higher than the loading amount 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, 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 constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0015] Figure 1 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 microscope (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 removal effect of sulfamethoxazole 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 activating peracetic acid to degrade sulfamethoxazole using different addition amounts of single-atom cobalt catalyst in Example 1 of the present invention;

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

[0020] Figure 6 The effect of catalyst-activated peracetic acid on the degradation of sulfamethoxazole is compared between Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0021] Figure 7 The effect 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 is compared;

[0022] Figure 8 The effect 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 is compared;

[0023] Fig. 9 The effect of activating peracetic acid and degrading sulfamethoxazole by single-atom cobalt catalyst of Example 1, Comparative Example 7 and Comparative Example 8 of the present invention is compared;

[0024] Fig.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 are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those 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 pyrolysis using a ligand-assisted supramolecular strategy, comprising the following steps:

[0027] 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, stirred evenly, and then an N-allylthiourea aqueous solution is added, and after stirring for reaction, the obtained solid product is washed and dried, and then high-temperature pyrolysis is carried out under the protection of an inert atmosphere, and then the pyrolysis product is acid-leached, washed, and dried to obtain a single-atom cobalt catalyst.

[0028] The present invention adopts a ligand-assisted supramolecular strategy. First, cobalt phthalocyanine and an organic ligand trimesic acid are used to form a stable metal-ligand chelate. Then, the self-assembly process of the metal-ligand chelate and a carbon-nitrogen substrate (dicyandiamide and N-allylthiourea) is realized by means of 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 finds that the type of cobalt salt will affect 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 pyrrolidine-connected benzene rings 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 evenly, 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 special restrictions on the stirring speed, as long as it can ensure even mixing.

[0032] In the step of stirring reaction described in the present invention, the time of stirring reaction is 3 to 8 hours, and the temperature of stirring reaction 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 specifically limit the method for 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 specifically limit 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 specifically limit 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 does not impose any special restrictions on the preparation methods of the cobalt phthalocyanine-trimesic acid complex solution, the dicyandiamide aqueous solution and the N-allylthiourea aqueous solution, and the 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 temperature of the high temperature pyrolysis is 650-750°C, and the time of the high temperature pyrolysis is 3-6 hours. The temperature of the high temperature pyrolysis will have a certain influence on the catalytic effect. Too high or too low a high temperature pyrolysis temperature will lead to a decrease in the catalytic effect. The present invention does not impose any special restrictions on the heating rate of heating to the high temperature pyrolysis temperature, and 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 0.05-0.5 mol / L. The acid leaching process is to remove the residual metal cobalt on the surface of the catalyst (monoatomic cobalt does not react with acid). The acid leaching time is 40-120 minutes. After the acid leaching is completed, water and ethanol are used for multiple washings, and then drying is performed. The present invention does not impose any special restrictions on the drying process. The present invention is preferably vacuum drying at 50-80°C.

[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 loading amount of cobalt can reach up to more than 12wt%.

[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 sewage, and the removal rate of sulfonamide antibiotics can reach more than 90% within 2 minutes. Moreover, 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 achieve efficient, stable and continuous degradation of sulfonamide antibiotics.

[0040] The technical solution of the present invention is further described below in conjunction with specific examples. The present invention has no particular limitation on the source 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, denoted as Co. SA -NC.

[0046] Figure 1 is a scanning electron microscope (SEM) image of the single-atom cobalt catalyst prepared in this example; 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 : 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 It can be seen that the active metal sites are dispersed in single atoms, with high loading density and no nanoparticles or metal clusters. The single atomic cobalt loading was measured by electron coupled plasma optical emission spectroscopy (ICP-OES) to be 12.8 wt%.

[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), and kept warm for 4 h. After cooling, it was acid-leached in 0.1 M hydrochloric acid for 60 min to remove residual metals, and then washed with deionized water and ethanol for 3 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 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 after cooling. 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 a solid was obtained after freeze-drying.

[0062] (3) The solid 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 that 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] First, 1.32 g of cobalt phthalocyanine, 60 g of urea, and 6 g of polyvinyl pyrrolidone (PVP) were mixed and ground into powder, 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 kept at 500 ° C for 2 hours under flowing argon. After cooling, cobalt nanosphere catalysts were obtained, recorded as Co-NPs.

[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 phthalocyanine is replaced by cobalt sulfate in this comparative example.

[0074] Comparative Example 7

[0075] The difference between this comparative example and Example 1 is that in this comparative example, 2.4 mmol of trimesic acid (TA, 0.5 g) and 1.2 mmol of cobalt phthalocyanine (0.69 g) are 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 is 2:1.

[0076] Comparative Example 8

[0077] Compared with Example 1, the difference between this comparative example and Example 1 is that in this comparative example, 9.6 mmol of trimesic acid (TA, 2.0 g) and 1.2 mmol of cobalt phthalocyanine (0.69 g) are 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 is 8:1.

[0078] Test example

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

[0080] Peracetic acid was added to the wastewater containing 10 μM sulfamethoxazole to make its concentration reach 0.26 mM, and the pH value of the wastewater was adjusted to 4.0-10.0 with 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 make its concentration reach 100 mg / L, and the reaction was stirred at room temperature for 5 minutes. The removal rate of sulfamethoxazole over time was as follows: Figure 3 shown.

[0081] from Figure 3It can be seen that when the pH value of the sewage is 4.0, after 5 minutes of reaction at room temperature, it is found that 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 sewage is 5.0, after 5 minutes of reaction at room temperature, it is found that 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 sewage is 6.0, after 5 minutes of reaction at room temperature, it is found that 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 sewage is 7.0, after 2 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst can reach 96%, and after 5 minutes of reaction at room temperature, it is found that 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 sewage is 8.0, after 5 minutes of reaction at room temperature, it is found that 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 sewage is 9.0, after reacting at room temperature for 5 minutes, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 52%. It can be determined that the peracetic acid system activated by the single-atom cobalt catalyst prepared by the present invention has a better removal effect on sulfamethoxazole when the pH is neutral (pH=7), and both strong acidic and strong alkaline conditions are not conducive to the reaction.

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

[0083] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole (SMX) to make its concentration reach 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 single-atom cobalt catalyst prepared in Example 1 was added to the above solution to make its concentration reach 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 4It can be seen that when the catalyst addition amount is 25 mg / L, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 92%. When the catalyst addition amount is 50 mg / L, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 94%. When the catalyst addition amount is 75 mg / L, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 97%. When the catalyst addition amount is 100 mg / L, after 2 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst can reach 96%. After 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 99%.

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

[0085] Peracetic acid was added to wastewater containing sulfamethoxazole (SMX) at a concentration of 10 μM to make its concentration reach 0.0325 mM, 0.065 mM, 0.13 mM, 0.20 mM, and 0.26 mM, respectively, 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 single-atom cobalt catalyst prepared in Example 1 was added to the above solution to make its concentration reach 100 mg / L, and 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 It can be seen that when the amount of peracetic acid added is 0.0325mM, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 45%. When the amount of peracetic acid added is 0.065mM, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 68%. When the amount of peracetic acid added is 0.13mM, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 88%. When the amount of peracetic acid added is 0.20mM, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 90%. When the amount of peracetic acid added is 0.26mM, after 5 minutes of reaction at room temperature, it is found that the removal rate of sulfamethoxazole in the peracetic acid system activated by the single-atom cobalt catalyst is 99%.

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

[0087] Peracetic acid was added to the wastewater containing 10 μM sulfamethoxazole to make its concentration reach 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, and then the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were added to make their concentration reach 100 mg / L, and stirred for 5 minutes at room temperature. The pH value of the wastewater containing 10 μM sulfamethoxazole was adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution, and then the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were added to make their concentration reach 100 mg / L, and stirred for 5 minutes at room temperature. The removal rate of sulfamethoxazole over time in the system containing PAA and not containing PAA is shown as follows: 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 experiment of catalysts synthesized at different pyrolysis temperatures:

[0089] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to make its concentration reach 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. Then, the single-atom cobalt catalyst prepared in Example 1, Comparative Example 3 and Comparative Example 4 was added to make its concentration reach 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 experiment of catalysts synthesized from different cobalt salts:

[0091] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to make its concentration reach 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. Then, the single-atom cobalt catalyst prepared in Example 1, Comparative Example 5 and Comparative Example 6 was added to make its concentration reach 100 mg / L, and the reaction was stirred at room temperature for 5 minutes. Figure 8 As shown, it can be seen that the catalyst synthesized using cobalt phthalocyanine as the cobalt salt has the best catalytic degradation effect.

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

[0093] Peracetic acid was added to wastewater containing 10 μM sulfamethoxazole to make its concentration reach 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. Then, the single-atom cobalt catalyst prepared in Example 1, Comparative Example 7 and Comparative Example 8 was added to make its concentration reach 100 mg / L, and the reaction was stirred at room temperature for 5 minutes. Fig. 9 As shown, it can be seen that when the molar ratio of benzoic acid to cobalt phthalocyanine is 4:1, the synthesized catalyst 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 the pH value of the wastewater is adjusted to 7.0 with 0.1 mM sulfuric acid or 0.1 mM sodium hydroxide solution. 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, and it is repeatedly rinsed with deionized water for 3-5 times, and then placed in a vacuum drying oven at 60°C for drying. After that, the next catalytic reaction is started, and the cycle is repeated to measure the changes in pollutant degradation. The changes in the removal rate of sulfamethoxazole during the recycling of the catalyst are shown in Fig.10 .Depend on Fig.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 above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for synthesizing single-atom cobalt catalysts by ligand-assisted supramolecular strategy 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; then a dicyandiamide aqueous solution is added, stirred evenly, and then an N-allylthiourea aqueous solution is added, and after stirring for reaction, the obtained solid product is washed and dried, and then high-temperature pyrolysis is carried out under the protection of an inert atmosphere, and then the pyrolysis product is acid-leached, washed, and dried to obtain a single-atom cobalt catalyst.

2. The method according to claim 1, characterized in that The dosage 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.

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

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

5. The method according to claim 1, characterized in that 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.

6. The method according to claim 1, characterized in that 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.

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

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

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

10. The use according to claim 9, characterized in that 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.

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