Monatomic cobalt supported on carbon nitride catalyst, preparation method and application thereof

Abstract

The application discloses a single-atom cobalt loaded carbon nitride catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a mixed solution of 2-methyl imidazole and cyanuric acid and a melamine solution, adding a cobalt salt aqueous solution, preparing a supermolecular precursor loaded with a cobalt salt, and obtaining the single-atom cobalt loaded carbon nitride catalyst through calcination. The preparation method adopts a simple "supermolecular self-assembly-coordination / electrostatic adsorption-calcination" strategy, can firmly and uniformly load single-atom cobalt on carbon nitride, and the single-atom cobalt loaded carbon nitride catalyst prepared in the way has the advantages of high specific surface area, uniform active sites, high atom utilization rate and good stability, is a novel persulfate activator with excellent performance, and can realize efficient activation of persulfate under the condition of extremely low dosage, and has very important significance for rapid and thorough purification of a water environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental new materials, and particularly relates to a single-atom cobalt loaded carbon nitride catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] In people's production and life, antibiotics have been widely used, and a large amount of antibiotics that are not effectively utilized can easily enter the water environment through various channels, and the concentration of the detected antibiotics in natural water bodies is various from ng / L to g / L. At the same time, a large amount of antibiotics entering the environment can cause antibiotic resistance, thereby seriously threatening human health. Therefore, it is necessary to effectively remove the antibiotics in the water environment.

[0003] The advanced oxidation technology (PS-AOPs) based on persulfate can form high activity species, has the advantages of wide pH application range, long half-life, simple preservation, etc., and can quickly remove refractory organic pollutants in water bodies. However, persulfate is relatively stable at room temperature, and the degradation effect on organic pollutants is general, so it is particularly important to find a catalyst for efficiently activating persulfate.

[0004] The single-atom cobalt loaded carbon nitride material is a single-atom catalyst, which can be used as an activator for efficiently activating persulfate. However, the single-atom cobalt loaded carbon nitride material prepared by the conventional method still has the following defects: although the melamine-triazine acid supramolecule (g-C3N4 precursor) synthesized by self-assembly can load single-atom cobalt, it is difficult to firmly fix the single-atom cobalt due to the insufficient binding force of the g-C3N4 precursor, and it is also difficult to achieve uniform dispersion of the single-atom cobalt, thereby resulting in poor catalytic activity of the single-atom cobalt loaded carbon nitride material. At the same time, the single-atom cobalt is easily leached out, which leads to poor catalytic performance of the material and also easily causes secondary pollution to the water environment, so it is difficult to be widely used for activating persulfate and is not conducive to effectively purifying the water environment. Therefore, it is of great significance to obtain a single-atom cobalt loaded carbon nitride catalyst with high specific surface area, uniform active sites, high atom utilization rate and good stability for efficiently activating persulfate to degrade organic pollutants. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a preparation method of a single-atom cobalt loaded carbon nitride catalyst with high specific surface area, uniform active sites, high atom utilization rate and good stability, and application of the single-atom cobalt loaded carbon nitride catalyst in degrading organic pollutant wastewater.

[0006] To solve the above technical problems, the following technical solutions are adopted in the present application.

[0007] A preparation method of a single-atom cobalt loaded carbon nitride catalyst, comprising the following steps:

[0008] S1, mixing a mixed solution of 2-methyl imidazole and cyanuric acid, a melamine solution, and stirring to obtain a 2-methyl imidazole ligand doped supramolecular precursor suspension;

[0009] S2, mixing the 2-methyl imidazole ligand doped supramolecular precursor suspension obtained in step S1 with a cobalt salt aqueous solution, and stirring to obtain a cobalt salt loaded supramolecular precursor;

[0010] S3, calcining the cobalt salt loaded supramolecular precursor obtained in step S2 to obtain a single-atom cobalt loaded carbon nitride catalyst.

[0011] The preparation method described above is further improved, in step S1, the molar ratio of 2-methyl imidazole to cyanuric acid in the mixed solution of 2-methyl imidazole and cyanuric acid is 0.5-2.0:2.0-3.0.

[0012] The preparation method described above is further improved, in step S1, the molar ratio of cyanuric acid in the mixed solution of 2-methyl imidazole and cyanuric acid to melamine in the melamine solution is 2.0-3.0:2.0-3.0.

[0013] The preparation method described above is further improved, in step S2, the molar ratio of cyanuric acid in the mixed solution of 2-methyl imidazole and cyanuric acid to cobalt salt in the cobalt salt aqueous solution is 2.0-3.0:0.5-2.0, and the cobalt salt aqueous solution is a cobalt nitrate aqueous solution.

[0014] The preparation method described above is further improved, in step S1, the mixed solution of 2-methyl imidazole and cyanuric acid is prepared by dispersing 2-methyl imidazole and cyanuric acid in water, the molar volume ratio of 2-methyl imidazole, cyanuric acid to water is 0.5mmol-2.0mmol:2.0mmol-3.0mmol:20mL-45mL, the melamine solution is prepared by dispersing melamine in water, the molar volume ratio of melamine to water is 2.0mmol-3.0mmol:20mL-45mL, and the volume ratio of the mixed solution of 2-methyl imidazole and cyanuric acid to the melamine solution is 1:1.

[0015] The preparation method is further improved, in step S2, the volume ratio of the 2-methyl imidazole ligand doped supramolecular precursor suspension to the aqueous solution of cobalt salt is 8-20:1-4; the stirring time is 700 min-950 min, the stirring speed is 500 r / min-800 r / min, and after stirring, the following treatment is further included: filtering the stirring product, washing the filtered product with water and ethanol in sequence, and drying.

[0016] The preparation method is further improved, in step S3, the calcination temperature is 500 DEG C-600 DEG C, the calcination time is 120 min-240 min, the heating rate during the calcination process is 2 DEG C / min-10 DEG C / min, the calcination is carried out in an inert atmosphere, the flow rate of the inert atmosphere is 10 mL / min-40 mL / min, and the inert atmosphere is nitrogen.

[0017] As a general technical concept, the application further provides a single-atom cobalt loaded carbon nitride catalyst, which comprises carbon nitride and single-atom cobalt; the single-atom cobalt is loaded on the surface of the carbon nitride, and the single-atom cobalt loaded carbon nitride catalyst has a coral-like skeleton structure.

[0018] The single-atom cobalt loaded carbon nitride catalyst is prepared by the preparation method.

[0019] As a general technical concept, the application further provides an application of the single-atom cobalt loaded carbon nitride catalyst in degrading organic pollutant wastewater.

[0020] The application is further improved and includes the following steps: mixing the single-atom cobalt loaded carbon nitride catalyst with organic pollutant wastewater, adding a persulfate solution, carrying out a catalytic degradation reaction, and completing the degradation of organic pollutants in the wastewater; the mass-volume ratio of the single-atom cobalt loaded carbon nitride catalyst to the organic pollutant wastewater is 5 mg-20 mg:100 mL, the volume ratio of the persulfate solution to the organic pollutant wastewater is 0.25 mL-0.75 mL:100 mL, the concentration of the organic pollutants in the organic pollutant wastewater is 5 mg / L-20 mg / L, and the concentration of the persulfate solution is 100 mmol / L-200 mmol / L.

[0021] The application further improves the above-mentioned application, wherein the persulfate in the persulfate solution is at least one of sodium persulfate, potassium persulfate and potassium hydrogen persulfate, the organic pollutants in the organic pollutant wastewater are at least one of sulfamethoxazole, tetracycline hydrochloride, carbamazepine and p-acetylaminophenol, the mixing is performed under stirring, the stirring time is 30 min to 60 min, the catalytic degradation reaction time is 10 min to 40 min, and the catalytic degradation reaction temperature is 20 DEG C to 30 DEG C.

[0022] Compared with the prior art, the application has the following advantages:

[0023] (1) The application provides a preparation method of single-atom cobalt supported carbon nitride catalyst, which successfully prepares single-atom cobalt supported carbon nitride catalyst through the strategy of space confinement and ligand chelation. First, a mixed solution of 2-methyl imidazole and cyanuric acid and a melamine solution are mixed to perform supramolecular self-assembly, to obtain a 2-methyl imidazole ligand doped supramolecular precursor. The 2-methyl imidazole exists as a ligand and is uniformly dispersed on the material surface, which can play a strong chelation effect on the metal cobalt in the later stage. Then, a cobalt salt aqueous solution is added, and the cobalt ions are embedded in the coordination sites of the 2-methyl imidazole through coordination, and are supported on the surface and the internal network structure of the supramolecular body through adsorption. The space limitation of the supramolecular body and the strong chelation effect of the ligand are conducive to inhibiting the agglomeration of single-atom cobalt during calcination. Finally, the supramolecular precursor is converted into carbon nitride and the single-atom cobalt is firmly and uniformly dispersed on the carbon nitride through calcination, to obtain the single-atom cobalt supported carbon nitride catalyst. In the preparation method, the simple "supramolecular self-assembly-coordination / electrostatic adsorption-calcination" strategy can firmly and uniformly support the single-atom cobalt on the carbon nitride, and the single-atom cobalt supported carbon nitride catalyst prepared in this way has the advantages of high specific surface area, uniform active sites, high atom utilization rate and good stability, can exert the high catalytic activity of the single-atom cobalt and the synergistic catalytic effect of the carbon nitride carrier, has the advantages of heterogeneous catalysts and homogeneous catalysts, and can overcome the shortcomings of large catalyst and persulfate dosing amount, low persulfate activation efficiency, difficult recovery and secondary pollution in the heterogeneous catalysis process. The single-atom cobalt supported carbon nitride catalyst is a new type of persulfate activator with excellent performance, and can realize efficient activation of the persulfate under the condition of extremely low dosage. It has very important significance for rapid and thorough purification of water environment. Meanwhile, the preparation method has the advantages of simple process, low energy consumption, cheap and easily available raw materials, and is suitable for large-scale preparation and industrial application.

[0024] (2) The preparation method of the application also optimizes the amount of 2-methylimidazole, by optimizing the molar ratio of 2-methylimidazole to cyanuric acid to 0.5-2.0:2.0-3.0, so that the catalyst can provide more metal coordination sites while avoiding the destruction of the basic structure of carbon nitride, and greatly ensures that the prepared catalyst is a single-atom catalyst. When the amount of 2-methylimidazole is too high, the structure of the carbon nitride base will be destroyed to a greater extent, and it will be difficult to ensure that the catalyst formed is a single-atom structure, but will exist in the form of a heterojunction; when the amount of 2-methylimidazole is too low, the catalyst will not be able to provide more coordination sites, which will greatly reduce the degradation efficiency of the catalyst.

[0025] (3) The application also provides an application of a single-atom cobalt-loaded carbon nitride catalyst in degrading organic pollutant wastewater, by mixing the single-atom cobalt-loaded carbon nitride catalyst, persulfate and organic pollutant wastewater, the organic pollutants in the water body can be efficiently degraded, and the application has the advantages of simple process, convenient operation, fast degradation rate, good removal effect and the like, and has important significance for effectively removing organic pollutants in the environment. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Figure 1 is a transmission electron microscope image and element distribution map of the single-atom cobalt-loaded carbon nitride catalyst in Example 1 of the application.

[0027] Figure 2 Figure 2 is a SEM image of the single-atom cobalt-loaded carbon nitride catalyst in Example 1 of the application.

[0028] Figure 3 Figure 3 is a degradation effect diagram of different catalysts activating persulfate to degrade sulfamethoxazole in Example 2 of the application.

[0029] Figure 4 Figure 4 is a corresponding cycle number-degradation efficiency diagram of the single-atom cobalt-loaded carbon nitride catalyst activating persulfate to degrade sulfamethoxazole in Example 3 of the application.

[0030] Figure 5 Figure 5 is a degradation effect diagram of different catalyst addition amounts of the single-atom cobalt-loaded carbon nitride catalyst activating persulfate to degrade sulfamethoxazole in Example 4 of the application.

[0031] Figure 6 Figure 6 is a degradation effect diagram of different persulfate addition amounts of the single-atom cobalt-loaded carbon nitride catalyst activating persulfate to degrade sulfamethoxazole in Example 4 of the application.

[0032] Figure 7 Figure 7 is a degradation effect diagram of the single-atom cobalt-loaded carbon nitride catalyst activating persulfate to degrade different organic pollutants in Example 5 of the application. DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of the present application is not limited thereby. The materials and instruments used in the following examples are commercially available.

[0034] Example 1:

[0035] A method for preparing a single-atom cobalt loaded carbon nitride catalyst of the present application comprises the following steps:

[0036] (1) 0.6 mmol of 2-methylimidazole and 2.4 mmol of cyanuric acid were weighed and dispersed in 20 mL of water, and ultrasonic dispersion was performed for 15 min to obtain solution A; 3.0 mmol of melamine was weighed and dispersed in 20 mL of water, and ultrasonic dispersion was performed for 15 min to obtain solution B; at room temperature (25±2℃), solution B was transferred to solution A, and stirring was performed for 30 min to obtain a mixed solution of 2-methylimidazole ligand-doped melamine-cyanuric acid supramolecular precursor.

[0037] In this step, the dispersion of 2-methylimidazole and cyanuric acid in water and the dispersion of melamine in water are beneficial to the uniform dispersion of the substances, and the mixing of the two is beneficial to the formation of an ordered supramolecular structure.

[0038] (2) 10 mL of a cobalt nitrate aqueous solution with a concentration of 120 mmol / L was added dropwise to the mixed solution of the precursor, and stirring was performed at a rotation speed of 750 r / min for 900 min to obtain a uniform mixed solution; the mixed solution was then filtered, and was washed with ultrapure water and anhydrous ethanol in sequence, and was vacuum dried, and the dried solid was ground into a fine powder with a garnet mortar to obtain a cobalt salt loaded supramolecular precursor.

[0039] (3) The cobalt salt loaded supramolecular precursor was placed in a covered quartz boat, and was wrapped with tin paper tightly, and was placed in a tube furnace, and was calcined at 550℃ for 240 min under a nitrogen atmosphere at a heating rate of 2℃ / min, and after natural cooling, the sample was taken out to obtain a yellow-green powder sample, which was a single-atom cobalt loaded carbon nitride catalyst, and was named Co-MCAMeIm.

[0040] Figure 1 The transmission electron microscope (TEM) image and the element distribution map of the single-atom cobalt loaded carbon nitride catalyst in Example 1 of the present application. Figure 1 In the figure, (A) and (B) are TEM images, and (C), (D) and (E) are element distribution maps. From the figure, Figure 1 It can be seen that a large number of single-atom cobalt is uniformly distributed on the surface of the catalyst.

[0041] Figure 2 The SEM image of the single-atom cobalt loaded carbon nitride catalyst in Example 1 of the present application. From the figure, Figure 2It can be seen that the monatomic cobalt loaded carbon nitride catalyst as a whole presents a skeleton morphology similar to coral.

[0042] Comparative Example 1:

[0043] A preparation method of a pure carbon nitride catalyst, comprising the following steps:

[0044] (1) 2.4 mmol of cyanuric acid was weighed and dispersed in 20 mL of water, and ultrasonic dispersion was performed for 15 min to obtain solution A; 3.0 mmol of melamine was weighed and dispersed in 20 mL of water, and ultrasonic dispersion was performed for 15 min to obtain solution B; at room temperature (25±2℃), solution B was transferred to solution A, and stirring was performed for 30 min to obtain a mixed solution of melamine-cyanuric acid supramolecular precursor; the mixed solution was filtered, washed with ultrapure water and ethanol for at least 3 times in turn, vacuum dried, and the dried solid was ground into a fine powder with a agate mortar to obtain the precursor.

[0045] (2) The precursor was placed in a covered quartz boat, wrapped tightly with tin paper, and placed in a tube furnace, heated to 550℃ at a heating rate of 2℃ / min for calcination for 240 min, and then taken out after natural cooling to obtain a light yellow powder sample, which is a pure carbon nitride catalyst, named MCA.

[0046] Comparative Example 2:

[0047] A preparation method of a monatomic cobalt loaded pure carbon nitride catalyst, which is basically the same as the preparation method of the monatomic cobalt loaded carbon nitride catalyst (Co-MCAMeIm) in Example 1, except that no 2-methylimidazole is added in step (1); the monatomic cobalt loaded pure carbon nitride catalyst prepared thereby is named Co-MCA.

[0048] Comparative Example 3:

[0049] A preparation method of a cobalt nanoparticle loaded carbon material catalyst, comprising the following steps:

[0050] (1) 6 mmol of 2-methylimidazole was weighed and dispersed in 400 mL of water, and ultrasonic dispersion was performed for 15 min to obtain a 2-methylimidazole aqueous solution; then, 100 mL of a cobalt nitrate aqueous solution with a concentration of 120 mmol / L was added dropwise to the 2-methylimidazole aqueous solution, and uniform stirring was performed for 900 min to obtain a mixed solution; the mixed solution was then filtered, washed with ultrapure water and anhydrous ethanol for at least 3 times in turn, vacuum dried, and the dried solid was ground into a fine powder with a agate mortar to obtain the precursor.

[0051] (2) The above precursor was placed in a covered quartz boat and wrapped tightly with tin foil. It was placed in a tube furnace and heated to 550°C for 240 min at a heating rate of 2°C / min. After natural cooling, it was taken out to obtain a brown-green powder sample, which is the cobalt nanoparticle supported carbon material catalyst, named Co-MeIm.

[0052] Comparative Example 4:

[0053] A method for preparing a 2-methylimidazolium ligand-doped carbon nitride catalyst is basically the same as the method for preparing the single-atom cobalt-supported carbon nitride catalyst (Co-MCAMeIm) in Example 1, except that: in step (2), no aqueous solution of cobalt nitrate is added; the 2-methylimidazolium ligand-doped carbon nitride catalyst obtained is named MCAMeIm.

[0054] Example 2:

[0055] An application of the single-atom cobalt-supported carbon nitride catalyst of the present invention in the degradation of organic pollutant wastewater specifically involves activating persulfate to degrade sulfamethoxazole in water using the single-atom cobalt-supported carbon nitride catalyst, comprising the following steps:

[0056] 10 mg of each of the following catalysts were weighed: the single-atom cobalt-supported carbon nitride catalyst (Co-MCAMeIm) in Example 1, the pure carbon nitride catalyst (MCA) in Comparative Example 1, the single-atom cobalt-supported pure carbon nitride catalyst (Co-MCA) in Comparative Example 2, the cobalt nanoparticle-supported carbon material catalyst (Co-MeIm) in Comparative Example 3, and the 2-methylimidazolium ligand-doped carbon nitride catalyst (MCAMeIm) in Comparative Example 4. Each catalyst was placed in 100 mL of a 10 mg / L sulfamethoxazole solution and stirred for 30 min at room temperature (25 ± 2 °C) until adsorption-desorption equilibrium was reached. Then, 0.5 mL of a 200 mmol / L potassium persulfate composite salt solution was added, and the catalytic degradation reaction was carried out for 40 min to complete the degradation of sulfamethoxazole in the water.

[0057] During the catalytic degradation reaction, 0.5 mL of the reaction solution was taken at time points of 0 min (adsorption 30 min), 1 min, 5 min, 15 min, 20 min, 30 min, and 40 min. The solution was filtered through a 0.22 μm filter and immediately quenched with 1:1 anhydrous methanol. The concentration of sulfamethoxazole in the solution was determined by liquid chromatography. The degradation results for each catalyst are shown below. Figure 2 As shown.

[0058] Figure 3 This is a graph showing the degradation effect of sulfamethoxazole on persulfate activated by different catalysts in Example 2 of the present invention. Figure 3It can be seen that the removal rates of MCA, Co-MCA and Co-MCAMeIm to sulfamethoxazole are all 40% after 40 min of reaction, and it can be inferred that the removal ability of MCA without doping 2-methylimidazole (MeIm) or without loading metal cobalt is limited. The reason for the low removal rate of sulfamethoxazole by Co-MCA is that the MCA substrate without doping MeIm ligand has poor loading capacity for metal Co, so that the loading concentration of Co is extremely low. The removal rates of sulfamethoxazole by Co-MeIm and Co-MCAMeIm are both 100%. However, it should be noted that Co-MeIm prepared in Comparative Example 3 has a serious Co ion leaching problem. It can be seen that the single-atom cobalt loaded carbon nitride catalyst (Co-MCAMeIm) of the present application can efficiently and completely remove organic pollutants in water, and the metal ion leaching is extremely low, that is, the risk of secondary pollution can be ignored.

[0059] Example 3

[0060] The stability of the single-atom cobalt loaded carbon nitride catalyst was investigated, specifically that the single-atom cobalt loaded carbon nitride catalyst was repeatedly used to activate persulfate to degrade sulfamethoxazole in water, and the specific experiment was as follows.

[0061] (I) Cycle experiment

[0062] (1) 10 mg of the single-atom cobalt loaded carbon nitride catalyst in Example 1 was taken and placed in 100 mL of a sulfamethoxazole solution with a concentration of 10 mg / L, and stirred at room temperature for 30 min to reach adsorption-desorption equilibrium, then 0.5 mL of a potassium hydrogen persulfate composite salt solution with a concentration of 200 mmol / L was added for catalytic degradation reaction for 40 min to complete one cycle.

[0063] (2) After completing one cycle, the reaction system in step (1) was filtered, and the filtered product was sequentially washed with ultrapure water and anhydrous ethanol for 3 times, and vacuum dried at 60°C to obtain the single-atom cobalt loaded carbon nitride catalyst for recycling.

[0064] (3) Steps (1) and (2) were repeated for 4 times to complete the degradation cycle experiment.

[0065] (II) Regeneration experiment

[0066] (1) The material after the above cycle experiment, i.e. the reaction system after the fourth cycle in the cycle experiment is filtered, and the filtered product is washed with ultrapure water and anhydrous ethanol for 3 times respectively, and then dried at 60°C under vacuum. The dried solid is ground with a jade mortar, placed in a quartz boat with a cover, wrapped with tin paper tightly, heated to 550°C at a heating rate of 2°C / min in a tube furnace for 240 min, and then taken out after natural cooling to obtain a regenerated monatomic cobalt supported carbon nitride catalyst.

[0067] (2) 10 mg of the regenerated monatomic cobalt supported carbon nitride catalyst obtained in step (1) is placed in a 100 mL sulfamethoxazole solution with a concentration of 10 mg / L, stirred at room temperature for 30 min to reach adsorption-desorption equilibrium, and then 0.5 mL of a potassium hydrogen persulfate composite salt solution with a concentration of 200 mmol / L is added to carry out a catalytic degradation reaction for 40 min to complete the degradation of sulfamethoxazole in the water body.

[0068] The degradation efficiency of the monatomic cobalt supported carbon nitride catalyst in the cycle reuse in each cycle in the cycle experiment, and the degradation efficiency of the regenerated monatomic cobalt supported carbon nitride catalyst in the regeneration experiment are calculated.

[0069] Figure 4 The corresponding cycle number-degradation efficiency graph of the monatomic cobalt supported carbon nitride catalyst of Example 3 in the activation of persulfate for degrading sulfamethoxazole. From Figure 4 It can be seen that the removal rate of the monatomic cobalt supported tubular carbon nitride catalyst for sulfamethoxazole decreases from 100% to 85%; and after regeneration, the removal rate of the monatomic cobalt supported tubular carbon nitride catalyst for sulfamethoxazole is 100%. In addition, in each degradation cycle experiment and regeneration experiment, the leaching amount of Co ions of the monatomic cobalt supported tubular carbon nitride catalyst is relatively low, and is lower than the discharge limit value 0.75 mg / L of the standard GB25467-2010. It can be seen that the monatomic cobalt supported carbon nitride catalyst of the present application has excellent stability, is a catalyst with broad development prospects, and can be used for activating persulfate to degrade organic pollutants in water bodies.

[0070] Example 4:

[0071] The effects of different catalyst addition amounts and different persulfate addition amounts on the degradation effect of sulfamethoxazole are investigated, and the specific method is as follows: the monatomic cobalt supported carbon nitride catalyst is used to activate persulfate to degrade sulfamethoxazole in water body, which includes the following steps:

[0072] Take 5 mg, 10 mg, 15 mg, 20 mg of single-atom cobalt loaded carbon nitride catalyst (Co-MCAMeIm) in Example 1, respectively, into 100 mL of sulfamethoxazole solution with a concentration of 10 mg / L, stir for 30 min at room temperature (25±2℃), reach adsorption-desorption equilibrium, then add 0.5 mL of potassium hydrogen persulfate composite salt solution with a concentration of 200 mmol / L, and carry out catalytic degradation reaction for 40 min to complete the degradation of sulfamethoxazole in water.

[0073] Take four 10 mg of single-atom cobalt loaded carbon nitride catalyst (Co-MCAMeIm) in Example 1, respectively, into 100 mL of sulfamethoxazole solution with a concentration of 10 mg / L, stir for 30 min at room temperature (25±2℃), reach adsorption-desorption equilibrium, then add 0.25 mL, 0.5 mL, 0.75 mL, 1.0 mL of potassium hydrogen persulfate composite salt solution (concentration is 200 mmol / L), respectively, so that the concentration of potassium hydrogen persulfate composite salt in the reaction system is 0.5 mM, 1.0 mM, 1.5 mM, 2.0 mM, respectively, carry out catalytic degradation reaction for 40 min to complete the degradation of sulfamethoxazole in water.

[0074] Figure 5 The degradation effect diagram of single-atom cobalt loaded carbon nitride catalyst activated persulfate degrading sulfamethoxazole under different catalyst addition amounts in Example 4 of the application. Figure 6 The degradation effect diagram of single-atom cobalt loaded carbon nitride catalyst activated persulfate degrading sulfamethoxazole under different persulfate addition amounts in Example 4 of the application. Figure 5 And Figure 6 It can be seen that with the change of catalyst or persulfate addition amount, the degradation rate of single-atom cobalt loaded carbon nitride catalyst on sulfamethoxazole will change, and within a certain range, the reaction rate gradually increases with the increase of catalyst or persulfate addition amount.

[0075] Example 5:

[0076] The degradation effect of single-atom cobalt loaded carbon nitride catalyst on different organic pollutants was investigated, specifically, single-atom cobalt loaded carbon nitride catalyst activated persulfate was used to degrade sulfamethoxazole (SMX), tetracycline hydrochloride (TCH), carbamazepine (CBZ), and p-acetamidophenol (ACE) in water, including the following steps:

[0077] Take four 10mg single-atom cobalt loaded carbon nitride catalyst (Co-MCAMeIm) in example 1, respectively placed in 100mL, concentration of 10mg / L sulfonamides methylazole solution, tetracycline hydrochloride solution, carbamazepine solution, p-acetamidophenol solution, at room temperature (25±2℃), stirring for 30min, to reach adsorption-desorption equilibrium, then add 0.5mL, concentration of 200mmol / L potassium hydrogen persulfate composite salt solution, catalytic degradation reaction for 40min, complete the degradation of organic pollutants in water.

[0078] Figure 7 The degradation effect diagram of single-atom cobalt loaded carbon nitride catalyst in example 5 for activating persulfate to degrade different organic pollutants. Figure 7 It can be seen that the degradation rate of single-atom cobalt loaded carbon nitride catalyst on sulfonamides methylazole, tetracycline hydrochloride, carbamazepine, p-acetamidophenol is 100%, 100%, 100%, 98% respectively, which shows that the single-atom cobalt loaded carbon nitride catalyst of the present application has excellent removal effect on various toxic organic pollutants in water.

[0079] From the above results, in the preparation method of the present application, a simple "supramolecular self-assembly-coordination / electrostatic adsorption-calcination" strategy is used, which can firmly and uniformly load single-atom cobalt on carbon nitride. The single-atom cobalt loaded carbon nitride catalyst prepared thereby has the advantages of high specific surface area, uniform active sites, high atomic utilization rate, good stability, etc., can exert the high catalytic activity of cobalt single atom and the synergistic catalytic effect of carbon nitride carrier, has the advantages of heterogeneous catalyst and homogeneous catalysis, can overcome the shortcomings of large catalyst and persulfate dosage, low persulfate activation efficiency, difficult recovery and easy secondary pollution in the process of heterogeneous catalysis, is a new type of persulfate activator with excellent performance, and can achieve efficient activation of persulfate under extremely low dosage, which has great significance for rapid and thorough purification of water environment. At the same time, the preparation method of the present application also has the advantages of simple process, low energy consumption, cheap and easily available raw materials, etc., is suitable for large-scale preparation, and is convenient for industrial application.

[0080] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make many possible changes and modifications to the technical solutions of the present application, or modify equivalent embodiments with equivalent changes, without departing from the spirit and technical solutions of the present application. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present application, all still belong to the scope of protection of the technical solutions of the present application.

Claims

1. A method for preparing a single-atomic cobalt supported on carbon nitride catalyst, characterized by, Comprising the following steps: S1, mixing a mixed solution of 2-methyl imidazole and cyanuric acid, a melamine solution, stirring to obtain a 2-methyl imidazole ligand doped supramolecular precursor suspension; the molar ratio of 2-methyl imidazole and cyanuric acid in the mixed solution of 2-methyl imidazole and cyanuric acid is 0.5-2.0:2.0-3.0; S2, mixing the 2-methyl imidazole ligand doped supramolecular precursor suspension obtained in step S1 with a cobalt salt aqueous solution, stirring to obtain a cobalt salt loaded supramolecular precursor; S3, calcining the cobalt salt loaded supramolecular precursor obtained in step S2 to obtain a single-atom cobalt loaded carbon nitride catalyst.

2. The method for preparing a single-atom cobalt-supported carbon nitride catalyst according to claim 1, characterized in that, In step S1, the molar ratio of cyanuric acid in the mixed solution of 2-methyl imidazole and cyanuric acid and melamine in the melamine solution is 2.0-3.0:2.0-3.

0.

3. The method for preparing a single-atom cobalt-supported carbon nitride catalyst according to claim 2, characterized in that, In step S1, the molar ratio of cyanuric acid in the mixed solution of 2-methyl imidazole and cyanuric acid and cobalt salt in the cobalt salt aqueous solution in step S2 is 2.0-3.0:0.5-2.0, and the cobalt salt aqueous solution is a cobalt nitrate aqueous solution.

4. The production method of monatomic cobalt supported carbon nitride catalyst according to any one of claims 1 to 3, characterized by, In step S1, the mixed solution of 2-methyl imidazole and cyanuric acid is prepared by dispersing 2-methyl imidazole and cyanuric acid in water, and the molar volume ratio of 2-methyl imidazole, cyanuric acid and water is 0.5mmol-2.0mmol:2.0mmol-3.0mmol:20mL-45mL, and the melamine solution is prepared by dispersing melamine in water, and the molar volume ratio of melamine and water is 2.0mmol-3.0mmol:20mL-45mL, and the volume ratio of the mixed solution of 2-methyl imidazole and cyanuric acid and the melamine solution is 1:1; In step S2, the volume ratio of the 2-methyl imidazole ligand doped supramolecular precursor suspension to the cobalt salt aqueous solution is 8-20:1-4; the stirring time is 700min-950min, the stirring speed is 500r / min-800r / min, and after stirring, the stirring product is filtered, and the filtered product is washed with water and ethanol in sequence, and dried; In step S3, the calcination temperature is 500-600℃, the calcination time is 120-240min, the heating rate during calcination is 2-10℃ / min, the calcination is carried out in an inert atmosphere, the flow rate of the inert atmosphere is 10-40mL / min, and the inert atmosphere is nitrogen.

5. The single-atom cobalt loaded carbon nitride catalyst prepared by the preparation method of any one of claims 1-4 is used for degrading organic pollutant wastewater, the single-atom cobalt loaded carbon nitride catalyst comprises carbon nitride and single-atom cobalt; the single-atom cobalt is loaded on the surface of the carbon nitride, and the single-atom cobalt loaded carbon nitride catalyst has a coral-like skeleton structure.

6. Use according to claim 5, characterized in that, Comprising the following steps: The monatomic cobalt loaded carbon nitride catalyst is mixed with organic pollutant wastewater, a persulfate solution is added, and a catalytic degradation reaction is carried out to complete the degradation of the organic pollutants in the wastewater; the mass-volume ratio of the monatomic cobalt loaded carbon nitride catalyst to the organic pollutant wastewater is 1 mg-4 mg: 20 mL, the volume ratio of the persulfate solution to the organic pollutant wastewater is 0.25 mL-0.75 mL: 100 mL, the concentration of the organic pollutants in the organic pollutant wastewater is 5 mg / L-20 mg / L, and the concentration of the persulfate solution is 100 mmol / L-200 mmol / L.

7. Use according to claim 6, characterized in that, The persulfate in the persulfate solution is at least one of sodium persulfate, potassium persulfate, and potassium hydrogen persulfate complex salt, the organic pollutants in the organic pollutant wastewater are antibiotics, the antibiotics are at least one of sulfamethoxazole and tetracycline hydrochloride, the mixing is carried out under stirring, the stirring time is 30 min-60 min, the catalytic degradation reaction time is 10 min-40 min, and the catalytic degradation reaction temperature is 20 DEG C-30 DEG C.

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