A supported iron-cobalt diatomic coral-like carbon nitride catalyst, its preparation method and application

Abstract

This invention provides a supported iron-cobalt diatomic coral-like carbon nitride catalyst, its preparation method, and its application. The preparation method includes: uniformly mixing an oxygen-containing organic precursor and a metal precursor, followed by ball milling to obtain a supported cobalt acetate / iron acetate supramolecular precursor; calcining the supramolecular precursor to obtain a diatomic cobalt and iron supported coral-like carbon nitride catalyst. The supported iron-cobalt diatomic coral-like carbon nitride catalyst prepared by this invention has advantages such as high specific surface area, abundant reactive sites, good catalytic performance, and high metal atom utilization rate. It can be widely used to activate persulfate to degrade organic pollutants, with good degradation effect and good application value and prospects. At the same time, the preparation method of this invention also has the advantages of simple process, convenient operation, readily available raw materials, low cost, and easy industrial production, showing great application prospects in the field of environmental catalysis.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control, specifically relating to a supported iron-cobalt diatomic coral-like carbon nitride catalyst, its preparation method, and its application. Background Technology

[0002] In livestock and aquaculture, the overuse of antibiotics can lead to antibiotic resistance in farmed animals. While animals can excrete 30%-90% of ingested antibiotics through feces and urine, many unmetabolized antibiotics contribute to increased antibiotic concentrations in the natural environment, ultimately posing significant risks to human health and ecosystems. Residual antibiotics in the environment not only inhibit microbial growth but also exert toxic effects on plants and animals, disrupting ecosystem stability. Furthermore, the high presence of antibiotics can lead to the development of resistance genes in microorganisms. These genes can spread within plants and animals and in environmental media (air, water, and soil), posing potential risks to human health.

[0003] Currently, the technologies used to treat antibiotic wastewater mainly include novel advanced oxidation technologies as well as traditional biological and physical technologies. Advanced oxidation technologies, through electron transfer processes, induce strong oxidants to generate various reactive free radicals (·OH, ·O2). - SO4 - Advanced oxidation technologies (AORs) continuously degrade and even mineralize antibiotic pollutants into smaller molecules. Due to their high efficiency, environmental friendliness, and ease of operation, AORs have become a research hotspot for removing antibiotics from water. In recent years, there have been numerous research reports on AORs based on persulfate (PMS) for the remediation of recalcitrant organic pollutants in water. Persulfate is a powerful and economically viable oxidant that can serve as a stable in-situ chemical oxidation agent to remediate recalcitrant organic pollutants in water. Compared to hydroxyl radicals (·OH), sulfate radicals (·SO4) are more effective. - It has advantages such as a wider pH range, a longer half-life, and a higher redox potential. Therefore, PMS-activated advanced oxidation technology has broad application prospects in the remediation of antibiotic-contaminated water bodies due to its high efficiency, low energy consumption, and low pollution.

[0004] Single-atom catalysts (SACs) are a class of supported catalysts containing only relatively isolated single metal atoms as catalytic active centers. Compared with traditional homogeneous and heterogeneous catalysts, SACs can significantly reduce the amount of metal used, and their uniform distribution can maximize the exposure of metal active sites. Therefore, they are considered to combine the advantages of both homogeneous and heterogeneous catalysis. In recent years, graphitic carbon nitride (g-C3N4) has been considered one of the ideal catalysts for single-atom support. Its unique structure can be considered as an extended ligand that coordinates with a single metal atom, thereby simulating the coordination environment of homogeneous metal catalysts. g-C3N4 has a π-conjugated structure similar to nitrogen-doped graphene, in which nitrogen-rich microheterocycles can anchor single atoms well. Nevertheless, the preparation of atomic-level catalysts supported on carbon nitride still faces the following problems: (1) Existing preparation methods are complex and expensive; (2) Existing preparation methods focus on the support of single-atom catalysts, while the metal loading is low and the metal is prone to agglomeration; (3) Existing atomic-level catalysts supported on carbon nitride have low specific surface area, few activation sites, and low catalytic efficiency. The aforementioned problems limit the widespread application of atomically supported carbon nitride catalysts. Therefore, overcoming the shortcomings of existing technologies and obtaining diatomic supported carbon nitride catalysts with high metal loading, high catalytic activity, good stability, and high specific area is of great significance for the efficient utilization of persulfate to degrade antibiotics in water. Summary of the Invention

[0005] To address the aforementioned technical issues, this solution provides a supported iron-cobalt diatomic coral-like carbon nitride catalyst, its preparation method, and its application. This supported iron-cobalt diatomic coral-like carbon nitride catalyst has a high specific surface area, numerous reactive sites, high single-atom metal loading, fast reaction rate, good stability, and can efficiently activate persulfate. The preparation process is simple, convenient, low-cost, efficient, and yields high efficiency.

[0006] To achieve the above objectives, this solution first provides a method for preparing a supported iron-cobalt diatomic coral-like carbon nitride catalyst, comprising the following steps:

[0007] S1. Mix and grind the nitrogen source with acidic organic matter to obtain an oxygen-containing organic precursor;

[0008] S2. Cobalt acetate and iron acetate are mixed to obtain a metal precursor. The oxygen-containing organic precursor obtained in S1 is ball-milled with the metal precursor to obtain a supported cobalt acetate / iron acetate supramolecular precursor.

[0009] S3. The product obtained in S2 is heated and calcined, then naturally cooled and ground into powder to obtain the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe.

[0010] The nitrogen source includes any one of melamine, urea, or dicyandiamide;

[0011] The acidic organic compounds include any one of cyanuric acid, uric acid, and benzoic acid.

[0012] Preferably, the mass ratio of nitrogen source to acidic organic matter in step S1 is 1:0.25-3.

[0013] Preferably, in step S2, the mass ratio of cobalt acetate to iron acetate is 1:1-2; and in step S2, the mass ratio of the oxygen-containing organic precursor to the metal precursor is 1:0.5-0.01.

[0014] Preferably, in step S2, the ball milling speed is 20-600 rpm / min, and the ball milling time is 1-24 hours; the ball milling program is set to grind clockwise for 5 minutes, grind counterclockwise for 5 minutes, and rest for 5 minutes.

[0015] Preferably, the heating rate in step S3 is 1℃ / min to 10℃ / min; the calcination temperature is 450℃ to 650℃; and the calcination time is 1h to 10h.

[0016] Based on a general inventive concept, this solution also provides a supported iron-cobalt diatomic coral-like carbon nitride catalyst.

[0017] Based on a general inventive concept, this solution also provides an application of a supported iron-cobalt diatomic coral-like carbon nitride catalyst in the treatment of organic pollutant wastewater.

[0018] Preferably, the application involves: mixing and stirring a supported iron-cobalt diatomic coral-like carbon nitride catalyst with organic pollutant wastewater, adding a persulfate solution to carry out a catalytic degradation reaction, thereby completing the degradation of organic pollutants in the water; the organic pollutants include one or more of antibiotics, dyes, and phenols.

[0019] Preferably, the mass-to-volume ratio of the supported iron-cobalt diatomic coral-like carbon nitride catalyst to the organic pollutant wastewater is 5 mg to 20 mg: 100 mL; the volume ratio of the persulfate solution to the organic pollutant wastewater is 0.5 to 2: 50; the concentration of the persulfate solution is 10 mmol / L to 100 mmol / L; the persulfate in the persulfate solution is potassium peroxymonosulfate; and the concentration of organic pollutants in the organic pollutant wastewater is 5 mg / L to 20 mg / L.

[0020] Preferably, the antibiotic includes one or more of ciprofloxacin, sulfadiazine, tetracycline, and norfloxacin; the stirring time is 30 min to 120 min; and the catalytic degradation reaction time is 5 s to 30 min.

[0021] The preparation principle of the catalyst of this invention is as follows:

[0022] A nitrogen source (melamine, urea, or dicyandiamide) is mixed with an acid compound (cyanuric acid, uric acid, or benzoic acid) to obtain an oxygen-containing organic precursor. This precursor is then mixed with a metal precursor and ball-milled. During high-energy ball milling, the oxygen-containing organic molecules collide and mix uniformly with the metal molecules. Simultaneously, mechanochemical forces allow the oxygen atoms in the organic molecules to effectively capture and stably isolate the metal molecules. The metal molecules and the oxygen-containing organic precursor are fully coupled to form a supported cobalt acetate / iron acetate supramolecular precursor. This precursor contains oxygen-containing functional groups, which is beneficial for oxygen doping. This not only facilitates the formation of coral-like carbon nitride morphology but also provides more anchoring sites for the loading of diatomic atoms. This is one of the key technologies for preparing single-atom cobalt-supported tubular carbon nitride catalysts. It not only increases the specific surface area and active sites but also forms a micro-confined environment on the catalyst surface, accelerating the reaction rate. Further calcination to introduce cobalt and iron diatoms can significantly improve the material's activation performance against persulfate. At the same time, this stable supported catalyst has a large specific surface area, coral-like structure, and numerous reactive active sites, enabling efficient and rapid activation of persulfate to degrade organic pollutants.

[0023] Coral-like carbon nitride has coral-like protrusions and internal porous structures embedded with diatomic sites, forming a micro-reaction environment at the nanoscale confinement level. In the diatomic sites, iron and cobalt diatoms exist in a Co-N-Fe adjacent manner through nitrogen-rich micro-heterocyclic rings in carbon nitride, forming active sites with synergistic effects.

[0024] This method utilizes the adsorption and coordination of oxygen-containing organic precursors with metal precursors during high-energy ball milling, which is more conducive to introducing metal precursors into organic precursors and dispersing them uniformly. This improves the dispersibility of the metal precursors and avoids the aggregation of cobalt and iron atoms on the catalyst surface during subsequent calcination. Consequently, it improves the dispersibility and utilization rate of the two atoms in the catalyst, significantly enhancing the catalytic efficiency. Therefore, the preparation method of this invention can prepare a cobalt and iron supported coral-like carbon nitride catalyst with high cobalt and iron loading, high utilization rate, good dispersibility, and high catalytic activity.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) This invention creatively uses a combination of ball milling and calcination to prepare a high-performance supported iron-cobalt diatomic coral-like carbon nitride catalyst with higher specific surface area, surface micro-reaction domain and unique diatomic reaction sites. It has high metal atom utilization rate and can accelerate the reaction rate, thus exhibiting better catalytic performance.

[0027] (2) The catalyst prepared by this method can be widely used to activate persulfate to degrade organic pollutants (such as antibiotics) and can achieve good degradation effect, with good application value and application prospects. At the same time, the preparation method of this invention is simple, easy to operate, has readily available raw materials, low cost, and is easy to realize industrial production, with great application prospects, especially in the field of environmental catalysis. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The images show the XRD patterns of the diatomic cobalt and iron supported coral-like carbon nitride catalyst prepared in Example 1 of this invention, the coral-like carbon nitride catalyst (OCN) prepared in Comparative Example 1, the layered carbon nitride (CN) prepared in Comparative Example 2, the single-atom cobalt supported coral-like carbon nitride catalyst (OCN-Co) prepared in Comparative Example 3, the single-atom iron supported coral-like carbon nitride catalyst (OCN-Fe) prepared in Comparative Example 4, and the cobalt and iron metal oxide supported layered carbon nitride catalyst (CN-Co / Fe) prepared in Comparative Example 5.

[0030] Figure 2 The images show SEM images of the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) prepared in Example 1 of the present invention, the coral-like carbon nitride (OCN) prepared in Comparative Example 1, and the layered carbon nitride (CN) prepared in Comparative Example 2, where (a) is OCN, (bc) is OCN Co / Fe, and (d) is CN.

[0031] Figure 3 The images show TEM images of the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) prepared in Example 1 of this invention and the cobalt and iron metal oxide supported layered carbon nitride catalyst (CN-Co / Fe) in Comparative Example 5. (a) and (b) are TEM images of OCN Co / Fe in the range of 1 μm and 10 nm, (c) and (d) are TEM images of CN-Co / Fe in the range of 100 nm and 5 nm, and (e) and (f) are TEM images of non-OCN Co / Fe in the range of 50 nm and 5 nm.

[0032] Figure 4The images show STEM images of the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) prepared in Example 1 of this invention, the monoatomic cobalt supported coral-like carbon nitride (OCN-Co) prepared in Comparative Example 3, and the monoatomic iron supported coral-like carbon nitride (OCN-Fe) prepared in Comparative Example 4, where (a) is OCN-Co, (b) is OCN-Fe, and (c) is OCN Co / Fe.

[0033] Figure 5 Synchrotron radiation spectra of the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) prepared in Example 1 of the present invention, the monoatomic cobalt supported coral-like carbon nitride (OCN-Co) prepared in Comparative Example 3, and the monoatomic iron supported coral-like carbon nitride (OCN-Fe) prepared in Comparative Example 4; (a) is the XANES spectrum, and (b) is the EXAFS spectrum;

[0034] Figure 6 The above are BET diagrams of the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) prepared in Example 1 of the present invention, the monoatomic cobalt supported coral-like carbon nitride (OCN-Co) prepared in Comparative Example 3, the monoatomic iron supported coral-like carbon nitride (OCN-Fe) prepared in Comparative Example 4, and the cobalt and iron metal oxide supported layered carbon nitride catalyst (CN-Co / Fe) prepared in Comparative Example 5.

[0035] Figure 7 This is a time-degradation efficiency graph showing the activation of persulfate to degrade ciprofloxacin solution by various catalysts in Experimental Example 2 of this invention.

[0036] Figure 8 This is a time-degradation efficiency graph showing the activation of persulfate degradation of ciprofloxacin solution by the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) in different water bodies in Experimental Example 2 of the present invention.

[0037] Figure 9 This is a time-degradation efficiency graph showing the activation of persulfate degradation of different pollutant solutions using a diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) in Experimental Example 2 of this invention.

[0038] Figure 10 This is a graph showing the cycle number versus degradation efficiency when the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) is activated to degrade ciprofloxacin solution with persulfate in Experiment Example 3 of this invention. Detailed Implementation

[0039] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0040] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.

[0041] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art; unless otherwise specified, the reagents used in the embodiments are all commercially available.

[0042] Example 1: Preparation of the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe:

[0043] S1. Take 10g of melamine and 30g of cyanuric acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0044] S2. Add 249 mg of cobalt acetate and 180 mg of ferric acetate to the ball mill jar, and grind continuously in the ball mill for 8 hours at a speed of 480 rpm / min, clockwise for 5 min, counterclockwise for 5 min, and rest for 5 min to obtain a supramolecular precursor with uniformly mixed cyanuric acid, melamine and metal small molecules.

[0045] S3. Place the precursor in a crucible, put it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt diatomic coral-like carbon nitride catalyst, named OCN-Co / Fe-1.

[0046] Example 2: Preparation of the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe:

[0047] S1. Take 10g of dicyandiamide and 30g of benzoic acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0048] S2. Add 249 mg of cobalt acetate and 180 mg of ferric acetate to the ball mill jar, and grind continuously in the ball mill for 8 hours at a speed of 480 rpm / min, clockwise for 5 min, counterclockwise for 5 min, and rest for 5 min to obtain a supramolecular precursor with uniformly mixed cyanuric acid, melamine and metal small molecules.

[0049] S3. Place the precursor in a crucible, put it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt diatomic coral-like carbon nitride catalyst, named OCN-Co / Fe-2.

[0050] Example 3: Preparation of the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe:

[0051] S1. Take 10g of urea and 30g of cyanuric acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0052] S2. Add 249 mg of cobalt acetate and 180 mg of ferric acetate to the ball mill jar, and grind continuously in the ball mill for 8 hours at a speed of 480 rpm / min, clockwise for 5 min, counterclockwise for 5 min, and rest for 5 min to obtain a supramolecular precursor with uniformly mixed cyanuric acid, melamine and metal small molecules.

[0053] S3. Place the precursor in a crucible, place it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt diatomic coral-like carbon nitride catalyst, named OCN-Co / Fe-3.

[0054] Example 4: Preparation of the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe:

[0055] S1. Take 10g of melamine and 30g of benzoic acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0056] S2. Add 249 mg of cobalt acetate and 180 mg of ferric acetate to the ball mill jar, and grind continuously in the ball mill for 8 hours at a speed of 480 rpm / min, clockwise for 5 min, counterclockwise for 5 min, and rest for 5 min to obtain a supramolecular precursor with uniformly mixed cyanuric acid, melamine and metal small molecules.

[0057] S3. Place the precursor in a crucible, put it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt diatomic coral-like carbon nitride catalyst, named OCN-Co / Fe-4.

[0058] Example 5: Preparation of the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe:

[0059] S1. Take 10g of dicyandiamide and 30g of uric acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0060] S2. Add 249 mg of cobalt acetate and 180 mg of ferric acetate to the ball mill jar, and grind continuously in the ball mill for 8 hours at a speed of 480 rpm / min, clockwise for 5 min, counterclockwise for 5 min, and rest for 5 min to obtain a supramolecular precursor with uniformly mixed cyanuric acid, melamine and metal small molecules.

[0061] S3. Place the precursor in a crucible, place it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt diatomic coral-like carbon nitride catalyst, named OCN-Co / Fe-5.

[0062] Comparative Example 1: Preparation of atom-free coral-like carbon nitride OCN:

[0063] Take 10g of melamine and 30g of cyanuric acid, transfer them to a 200ml ball mill jar, and grind continuously for 8 hours at 480rpm / min, clockwise for 5min, counterclockwise for 5min, and rest for 5min to obtain a cyanuric acid-melamine supramolecular precursor. Place the precursor in a crucible and put it in a muffle furnace, heat it to 550℃ at a heating rate of 2.3℃ / min, and hold it at 550℃ for 3h. After natural cooling, remove it and grind it in a mortar to obtain a light gray powder sample, which is coral-like carbon nitride, named OCN.

[0064] Comparative Example 2: Preparation of layered carbon nitride catalyst CN:

[0065] Take 5g of melamine and put it into a crucible. Place it in a muffle furnace and heat it to 550℃ at a heating rate of 2.3℃ / min. Keep it at 550℃ for 3 hours. After it cools naturally, take it out and grind it with a mortar and pestle to obtain a yellow powder sample, which is layered carbon nitride, named CN.

[0066] Comparative Example 3: Preparation of a single-atom cobalt-supported coral-like carbon nitride catalyst OCN-Co:

[0067] S1. Take 10g of melamine and 30g of cyanuric acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0068] S2. Add 0.5g of cobalt acetate to the ball mill jar, and grind at 480rpm / min, clockwise for 5min, counterclockwise for 5min, rest for 5min. Run the program continuously in the ball mill for 8 hours to obtain a supramolecular precursor with uniformly mixed cyanuric acid-melamine-cobalt acetate molecules.

[0069] S3. Place the precursor prepared in S2 into a crucible, place it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the single-atom cobalt-supported coral-like carbon nitride catalyst of the present invention, named OCN-Co.

[0070] Comparative Example 4: Preparation of a single-atom iron-supported coral-like carbon nitride catalyst OCN-Fe:

[0071] S1. Take 10g of melamine and 30g of cyanuric acid, grind them evenly, and then transfer them to a 200ml ball mill jar;

[0072] S2. Add 0.34g of ferric acetate to the ball mill jar, and grind at 480rpm / min, clockwise for 5min, counterclockwise for 5min, rest for 5min. Run the program continuously in the ball mill for 8 hours to obtain a supramolecular precursor with uniformly mixed cyanuric acid-melamine-ferric acetate molecules.

[0073] S3. Place the precursor prepared in S2 into a crucible, place it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the single-atom iron-supported coral-like carbon nitride catalyst of the present invention, named OCN-Fe.

[0074] Comparative Example 5: Preparation of supported iron-cobalt two-atom layered carbon nitride catalyst CN-Co / Fe:

[0075] S1. Take 40g of melamine, grind it evenly, and then transfer it to a 200ml ball mill jar;

[0076] S2. Add 249 mg cobalt acetate and 180 mg ferric acetate to the ball mill jar, and grind at 480 rpm / min, clockwise for 5 min, counterclockwise for 5 min, and rest for 5 min. Run the program continuously in the ball mill for 8 hours to obtain a supramolecular precursor with uniformly mixed cyanuric acid and metal small molecules.

[0077] S3. Place the precursor in a crucible, put it in a muffle furnace, heat it to 550°C at a heating rate of 2.3°C / min, and hold it at 550°C for 3 hours. After it cools naturally, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt two-atom layered carbon nitride catalyst, named CN-Co / Fe.

[0078] Comparative Example 6: Preparation of supported iron-cobalt diatomic carbon nitride catalyst non-OCN-Co / Fe using a ball mill-free process:

[0079] S1. Grind 10g of melamine and 30g of cyanuric acid evenly, and add 249mg of cobalt acetate and 180mg of ferric acetate.

[0080] S3. Place the system from S1 into a crucible, place it in a muffle furnace, heat it to 550℃ at a heating rate of 2.3℃ / min, and hold it at 550℃ for 3 hours. After natural cooling, take it out and grind it with a mortar to obtain a brown powder sample, which is the supported iron-cobalt diatomic carbon nitride catalyst, named non-OCN-Co / Fe.

[0081] Experimental Example 1

[0082] (1) Examine the X-ray diffraction (XRD) patterns of the catalysts prepared in Example 1 and Comparative Examples 1-6.

[0083] X-ray diffraction analysis was performed on the OCN Co / Fe catalyst prepared in Example 1 and the OCN, CN, OCN-Co, OCN-Fe, CN-Co / Fe, and non-OCN-Co / Fe catalysts prepared in Comparative Examples 1-6.

[0084] The results are as follows Figure 1 As shown, the OCN Co / Fe-1 catalyst prepared by this method exhibits two distinct XRD diffraction peaks at 13.0° and 27.5°, at which they are attributed to the (100) and (002) crystal planes of graphitic carbon nitride, confirming that the prepared product is graphitic carbon nitride (g-C3N4). Meanwhile, the XRD patterns also show that... Figure 1 It can be seen that the XRD patterns of the iron-cobalt diatomic coral-like carbon nitride catalyst (OCN Co / Fe) and the single-atom metal supported coral-like carbon nitride catalysts OCN-Co and OCN-Fe do not change much, indicating that cobalt atoms and iron atoms are uniformly distributed on the carbon nitride support.

[0085] Compared with Example 1, the catalysts prepared in Comparative Examples 3, 4 and 5 showed a slight increase in diffraction peak intensity at 13.0° and 27.5°, while the diffraction peak intensity of Comparative Examples 1, 2 and 6 showed a slight decrease. This indicates that the loading of metal atoms, oxygen-containing precursors and ball milling processes all affect the framework structure of carbon nitride.

[0086] (2) Scanning electron micrographs (SEM images) of the catalysts prepared in Example 1 and Comparative Examples 1-2 and 6.

[0087] Scanning electron microscopy (SEM) images were analyzed of the OCN-Co / Fe catalyst prepared in Example 1, the OCN and CN catalysts prepared in Comparative Examples 1-2, and the non-OCN-Co / Fe catalyst in Comparative Example 6.

[0088] The results are as follows Figure 2As shown in the figure, (a) is OCN, (b) is OCN Co / Fe, (c) is CN, and (d) is non-OCN Co / Fe. Compared with the dense and stacked layered carbon nitride structure shown in Figure (c), the OCN and OCN Co / Fe catalysts generated by adding cyanuric acid, or by loading metal atoms, ball milling and calcining, have a unique twisted lamellar coral-like layered structure. However, the catalyst generated without ball milling only makes the surface structure of carbon nitride rougher and lacks the unique twisted lamellar coral-like layered structure, which reduces the active sites and active area of ​​the catalyst.

[0089] (3) Transmission electron microscopy (TEM) images of the catalysts prepared in Example 1 and Comparative Examples 5-6.

[0090] The OCN Co / Fe catalyst prepared in Example 1 and the CN-Co / Fe and non-OCN Co / Fe catalysts prepared in Comparative Examples 5-6 were analyzed by transmission electron microscopy.

[0091] The results are as follows Figure 3 As shown, 3a and 3b are TEM images of OCN-Co / Fe in the range of 1µm and 10nm, respectively, and 3c and 3d are TEM images of CN-Co / Fe in the range of 100nm and 5nm, respectively. Figure 3 e and 3f are TEM images of non-OCN Co / Fe in the 50 nm and 5 nm ranges; from Figure 3 As can be seen from the af data, OCN Co / Fe exhibits a curled, coral-like layered structure. These layered structures are divided into regions of varying sizes due to the twisting and fragmentation of the lamellae, and obvious pore structures are observed. Furthermore, no cobalt or iron nanoparticles or clusters were observed, indicating that cobalt and iron diatoms are uniformly anchored on the carbon nitride matrix. Compared with OCN Co / Fe, lattice fringes of cobalt or iron nanoparticles were clearly observed in CN-Co / Fe and non-OCN Co / Fe.

[0092] These results indicate that adding cyanuric acid during ball milling not only alters the morphology of the support but also introduces numerous doping sites, thereby providing a strong ability to anchor metal atoms and effectively capture and stabilize cobalt and iron diatoms.

[0093] (4) Scanning transmission electron microscopy (STEM) images of the catalysts prepared in Example 1 and Comparative Examples 3-4.

[0094] The results are as follows Figure 4As shown in the figure, 4a is OCN-Co, 4b is OCN-Fe, and 4c is OCN-Co / Fe. As can be seen from the figure, there are many isolated bright spots that are different from the support (circled) in the three figures. This indicates that the cobalt and iron atoms in the support are dispersed in the g-C3N4 support in an atomic-level form.

[0095] (5) Examine the synchrotron radiation spectra of the catalysts prepared in Example 1 and Comparative Examples 3-4.

[0096] The results are as follows Figure 5 As shown, from Figure 5 The aXANES spectra show that the oxidation state of cobalt atoms in the OCN Co / Fe diatomic catalyst is lower than that in the OCN-Co monoatomic catalyst, while the oxidation state of iron atoms in the OCN Co / Fe catalyst is higher than that in the OCN-Fe catalyst. This indicates a synergistic effect in the diatomic catalyst, leading to changes in the electronic structure of cobalt and iron atoms. Figure 5 As can be seen from the EXAFS spectra, in OCN Co / Fe, OCN-Co, and OCN-Fe, no metal atoms were observed compared to the metal and its oxides. The nearby metal-metal peaks indicate the formation of a uniformly dispersed atomic-level structure. Simultaneously, we can observe slight changes in the lengths of both the Co-N(O) and Fe-N(O) bonds at the OCN Co / Fe diatomic sites, suggesting that the formation of the binuclear metal sites also affects the coordination structure of the metal atomic sites.

[0097] (6) Examine the BET plots of the catalysts prepared in Example 1 and Comparative Examples 3-5.

[0098] from Figure 6 As can be seen from the data, the specific surface area of ​​the CN-Co / Fe catalyst prepared in Comparative Example 5 is 13.47 m². 2 / g, while the specific surface areas of the OCN-Co and OCN-Fe catalysts prepared in Comparative Examples 3-4 were 103.57m², respectively. 2 / g, 100.49m 2 / g, while the specific surface area of ​​the OCN Co / Fe catalyst prepared in Example 1 of this scheme is 115.76m². 2 / g, significantly higher than other comparative examples.

[0099] Therefore, the OCN Co / Fe-1 catalyst prepared by the method of the present invention has a larger specific surface area, which makes the diatomic cobalt and iron supported coral-like carbon nitride catalyst have more reactive sites, which is beneficial to improving the catalytic performance of the catalyst.

[0100] Table 1 below shows the OCN-Co / Fe catalyst prepared in Example 1 of this invention, the OCN-Co catalyst prepared in Comparative Examples 3-5, the OCN-Fe and CN-Co / Fe catalysts, and the mass fractions of cobalt and iron elements as determined by ICP.

[0101] As shown in Table 1, the OCN Co / Fe catalyst prepared by the method of the present invention has a higher metal loading, with the metal atom loading all exceeding 3%, which is more conducive to improving the catalytic performance of the catalyst.

[0102] Table 1. Comparison of catalyst performance between Example 1 and Comparative Examples 3-5

[0103] sample <![CDATA[Specific surface area (m 2 / g)]]> Co content (wt%) Fe content (wt%) Comparative Example 5CN Co / Fe 13.47 1.18％ 1.47％ Comparative Example 3OCN Co 103.57 7.11％ / Comparative Example 4OCN Fe 100.49 / 5.21％ Example 1: OCN Co / Fe 115.76 3.34％ 3.45％

[0104] Experiment Example 2

[0105] The application of the catalysts prepared in Example 1 and Comparative Examples 1-6 in the treatment of antibiotic wastewater was investigated.

[0106] Weigh 5 mg each of the OCN Co / Fe catalyst prepared in Example 1 and the OCN, CN, OCN-Co, OCN-Fe, CN-Co / Fe, and non-OCN Co / Fe catalysts prepared in Comparative Examples 1-6, and place them in 100 mL of ciprofloxacin solution with a concentration of 5 mg / L. Stir in the dark for 30 minutes to reach adsorption equilibrium. Then add 1 mL of PMS (potassium persulfate) solution with a concentration of 50 mmol / L to the solution to carry out catalytic degradation reaction. By using the catalyst to activate persulfate to degrade ciprofloxacin in the water, the degradation of ciprofloxacin in the water is completed.

[0107] During the persulfate activation reaction, 1 ml of ciprofloxacin solution was taken at time points of 1 min, 3 min, 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min. The characteristic peak value of ciprofloxacin in the solution was measured by liquid chromatography, and the degradation efficiency of ciprofloxacin solution by different catalysts under different time conditions was calculated.

[0108] The results are as follows Figure 7-9 As shown, Figure 7The diagram shows the time-degradation efficiency of the catalysts prepared in Examples 1 and 1-4 for the degradation of ciprofloxacin solution by activated persulfate. The results show that after 30 min of reaction, the degradation efficiencies of CN and OCN catalysts for activated persulfate on ciprofloxacin were 12.1% and 21.5%, respectively. The degradation efficiencies of OCN Co / Fe, OCN-Co, OCN-Fe, CN-Co / Fe, and non-OCN Co / Fe on ciprofloxacin were 100%, 95.2%, 78.2%, 51.1%, and 37.5%, respectively. Furthermore, OCN Co / Fe achieved 100% degradation of ciprofloxacin within 25 min. These results indicate that coral-like carbon nitride can provide more specific surface area and active sites, while diatomic catalytic sites can significantly improve the catalyst degradation efficiency. Simultaneously, the results show that the absence of ball milling significantly affected the degradation results, indicating insufficient binding and thus low degradation efficiency.

[0109] Figure 8 The graph shows the time-degradation efficiency of the OCN Co / Fe catalyst prepared in Example 1 of this invention when activated in different water bodies to degrade ciprofloxacin solution with persulfate. Figure 8 As shown, the catalytic reaction rate of OCN Co / Fe activated persulfate degradation of ciprofloxacin was not significantly affected in pure water, tap water, river water, and pure water with added humic acid, all reaching 100% within 30 minutes, indicating that the catalyst has good environmental interference resistance.

[0110] Figure 9 This is a time-degradation efficiency graph showing the OCN Co / Fe catalyst prepared in Example 1 of this invention during the activation of persulfate to degrade different pollutant solutions; as shown. Figure 9 As shown, after 15 min of reaction, the degradation efficiency of the diatomic cobalt and iron supported coral-like carbon nitride catalyst (OCN Co / Fe) for sulfamethoxazole, carbamazepine, atrazine, bisphenol A and phenol all reached 100%, indicating that the catalyst has a wide range of applicability.

[0111] In summary, the iron-cobalt diatomic coral-like carbon nitride catalyst prepared by this invention significantly improves the degradation efficiency of organic pollutants and can efficiently and thoroughly remove organic pollutants from water. This also demonstrates that the iron-cobalt diatomic coral-like carbon nitride catalyst of this invention has good persulfate activation ability, stability and practicality.

[0112] Experimental Example 3

[0113] The stability of the OCN Co / Fe catalyst prepared in Example 1 was investigated.

[0114] The specific steps for activating persulfate degradation of organic pollutants in water through multiple recycling of the OCN Co / Fe catalyst are as follows:

[0115] Step 1: Take 5 mg of the OCN Co / Fe catalyst prepared in Example 1 and place it in 100 mL of ciprofloxacin solution with a concentration of 5 mg / L. Stir in the dark for 30 minutes to reach adsorption equilibrium. Then add 1 mL of PMS solution with a concentration of 50 mmol / L to the solution to carry out catalytic degradation reaction for 20 minutes. The degradation of organic pollutants in the water is completed by activating persulfate, thus completing one cycle.

[0116] Step 2: After completing one cycle, filter the reaction system from Step 1 to obtain the catalyst. Filter and wash the catalyst five times with deionized water, and dry it at 60℃ for 12 hours to obtain the regenerated catalyst.

[0117] Step 3: Repeat steps 1 and 2 five times in total, using an iron-cobalt diatomic coral-like carbon nitride catalyst to cycle the ciprofloxacin solution and complete the degradation cycle experiment.

[0118] During the persulfate activation reaction, 1 mL of ciprofloxacin solution was taken at time points of 1 min, 3 min, 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min. The characteristic peak value of ciprofloxacin in the solution was measured by liquid chromatography, and the degradation efficiency of the catalyst on the ciprofloxacin solution under different time conditions in each cycle was calculated.

[0119] The results are as follows Figure 10 As shown, Figure 10 This is a graph showing the cycle number versus degradation efficiency when the OCN Co / Fe catalyst prepared in Example 1 activates persulfate to degrade ciprofloxacin solution; as shown. Figure 10 As shown, after five cycles of reaction, the OCN Co / Fe catalyst still maintained an efficiency of 99.7% in activating persulfate to degrade ciprofloxacin within 30 minutes. The results indicate that the OCN Co / Fe catalyst has excellent stability and is a promising catalyst for activating persulfate to degrade antibiotics.

[0120] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, any improvements and modifications obtained without departing from the technical concept of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a supported iron-cobalt diatomic coral-like carbon nitride catalyst, characterized in that, The preparation steps are as follows: S1. A nitrogen source is mixed and ground with an acidic organic compound to obtain an oxygen-containing organic precursor; the nitrogen source includes any one of melamine, urea, and dicyandiamide; the acidic organic compound includes any one of uric acid and benzoic acid; the mass ratio of the nitrogen source to the acidic organic compound is 1:0.25~3. S2. Cobalt acetate and ferric acetate are mixed to obtain a metal precursor. The oxygen-containing organic precursor obtained in S1 is ball-milled with the metal precursor at a speed of 480 rpm for 8 hours. The ball-milling program is set to grind clockwise for 5 minutes, counterclockwise for 5 minutes, and rest for 5 minutes to obtain a loaded cobalt acetate / ferric acetate supramolecular precursor. The mass ratio of cobalt acetate to ferric acetate is 1:1~2; the mass ratio of the oxygen-containing organic precursor to the metal precursor is 1:0.5~0.

01. S3. The product obtained in S2 is heated and calcined, then naturally cooled and ground into powder to obtain the supported iron-cobalt diatomic coral-like carbon nitride catalyst OCN-Co / Fe.

2. The preparation method according to claim 1, characterized in that, The heating rate in step S3 is 1℃ / min to 10℃ / min; the calcination temperature is 450℃ to 650℃, and the calcination time is 1h to 10h.

3. A supported iron-cobalt diatomic coral-like carbon nitride catalyst prepared by the preparation method according to any one of claims 1 to 2.

4. The application of a supported iron-cobalt diatomic coral-like carbon nitride catalyst prepared by the preparation method according to any one of claims 1 to 2 in the treatment of organic pollutant wastewater.

5. The application according to claim 4, characterized in that, The application steps are as follows: the iron-cobalt diatomic coral-like carbon nitride catalyst is mixed and stirred with organic pollutant wastewater, and persulfate solution is added to carry out catalytic degradation reaction to complete the degradation of organic pollutants in the water; the organic pollutants include one or more of antibiotics, dyes, and phenols.

6. The application according to claim 5, characterized in that, The mass-to-volume ratio of the supported iron-cobalt diatomic coral-like carbon nitride catalyst to the organic pollutant wastewater is 5 mg to 20 mg: 100 mL; the volume ratio of the persulfate solution to the organic pollutant wastewater is 0.5 to 2: 50; the concentration of the persulfate solution is 10 mmol / L to 100 mmol / L; the persulfate in the persulfate solution is potassium peroxymonosulfate; and the concentration of organic pollutants in the organic pollutant wastewater is 5 mg / L to 20 mg / L.

7. The application according to claim 5, characterized in that, The antibiotics include one or more of ciprofloxacin, sulfadiazine, tetracycline, and norfloxacin; the stirring time is 30 min to 120 min; and the catalytic degradation reaction time is 5 s to 30 min.

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