Fe-doped carbon nitride photocatalyst, preparation method and application thereof

Abstract

The application belongs to the field of photocatalytic materials and wastewater treatment technology, and particularly relates to a Fe-doped carbon nitride photocatalyst, a preparation method and application. The catalytic material takes graphite-like carbon nitride as a substrate, introduces surface Fe sites and interlayer Fe sites through a "supramolecular assembly-thermal polymerization method", and develops a Fe sur+lat -CN catalyst with iron-nitrogen coordination structure. The surface Fe sites and interlayer Fe sites can synergistically control the electronic structure of the catalyst, promote the separation and transmission of photo-generated charges. The catalyst is combined with peroxoacetic acid (PAA) to construct a photocatalytic Fenton-like synergistic system based on Fe sur+lat -CN under visible light irradiation. The constructed synergistic degradation system has the advantages of high degradation efficiency, wide application range, good stability and low secondary pollution risk, and has good application prospect in the field of deep treatment of organic pollutants in industrial wastewater, aquaculture wastewater, seawater and other water bodies.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials and wastewater treatment technology, specifically relating to an Fe-doped carbon nitride photocatalyst, its preparation method, and its application. Background Technology

[0002] With industrialization and urbanization, various recalcitrant organic pollutants, such as phenolic compounds, antibiotics, drug residues, and endocrine disruptors, are continuously released into the aquatic environment. Their environmental persistence, bioaccumulation, and potential toxicity pose a serious threat to the ecological environment and human health. Traditional biological treatment processes are insufficient for the deep removal of these pollutants. Against this backdrop, advanced oxidation technologies capable of generating reactive oxygen species (ROS) have gradually become a research hotspot in the field of water treatment.

[0003] Compared with traditional oxidants, peracetic acid (PAA) has a lower O2 bond dissociation energy (159 kJ·mol⁻¹). -1 The concentration of H2O2 was significantly lower than that of H2O2 (213 kJ·mol⁻¹). -1 ) and persulfate (PMS) (317 kJ·mol -1 Therefore, it is more easily activated by light, heat, or catalysts to generate ROS. Besides ·OH, the activation process of PAA can also produce CH3COO·, CH3COOO·, and... 1 O2 and various reactive species, including high-valence metal oxygen species (Fe(IV)=O), are present. Among them, organic free radicals and non-free radical species exhibit longer lifespans, higher selectivity, and stronger resistance to water matrix interference, demonstrating significant advantages in complex aquatic environments. Furthermore, the final decomposition products of PAA are mainly acetic acid, water, and oxygen, avoiding the problems of sulfate accumulation in PMS systems and iodine-containing byproducts in periodate (PI) systems. Therefore, it is considered a green oxidant that combines high efficiency and environmental friendliness.

[0004] Currently, transition metal-catalyzed PAA activation has become an important research direction. However, traditional homogeneous metal ion systems generally suffer from metal loss and secondary pollution problems, while metal oxide nanoparticle catalysts are difficult to further improve catalytic efficiency due to particle agglomeration, insufficient exposure of active sites, and limited atom utilization. In contrast, single-atom catalysts (SACs) exhibit significant advantages in advanced oxidation reactions due to their isolated and uniform active centers, high atom utilization, and tunable local electronic structures. In particular, iron-based single-atom catalysts (FeSACs) not only possess environmental friendliness, abundant resources, and low cost, but also can achieve Fe-N xThe coordination structure effectively promotes the formation of Fe(IV)=O and the Fe(III) / Fe(II) cycling process, and is considered a key material for constructing efficient Fenton-like systems.

[0005] Graphitic carbon nitride (CN), as a typical visible light-responsive photocatalyst, possesses abundant sp... 2 The hybrid N sites and unique layered structure not only enable stable anchoring of isolated Fe atoms to form Fe-N x The active sites can also promote photogenerated electron transport and redox cycles. Existing studies have mostly focused on the activation of PAA or peroxides by surface Fe sites, but the catalytic activity is still limited and requires further research. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, this invention proposes an Fe-doped carbon nitride photocatalyst, its preparation method, and its application. This catalyst is a carbon nitride (Fe2+) photocatalyst with synergistic surface and interlayer Fe sites. sur+lat -CN) photocatalyst, which provides a Fe-based sur+lat -CN photocatalytic-Fenton-like synergistic degradation method. This invention constructs a catalyst with active centers on the surface and between layers of Fe sites via a "supramolecular assembly-thermal polymerization method". The surface Fe sites serve as photosensitive centers, broadening the visible light response range, enhancing light absorption and photogenerated carrier yield, and assisting the between-layer Fe sites as active centers for Fenton-like reactions, providing a fast electron transfer channel. The catalyst's own good conductivity further accelerates the migration of photogenerated electrons from the support to the Fe sites, effectively suppressing carrier recombination and improving PAA utilization efficiency.

[0007] The present invention further improves upon Fe sur+lat Adding an oxidant to the -CN photocatalytic system to construct an Fe-based system sur+lat -CN photocatalytic-Fenton-like synergistic reaction system, utilizing Fe sur+lat -CN enhances light absorption performance, promoting the generation of ROS such as Fe(IV)=O and ·OH, which together achieve efficient oxidation removal and deep mineralization of organic pollutants in water.

[0008] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing an Fe-doped carbon nitride photocatalyst, the method comprising the following steps: S1. Preparation of precursor solution: Melamine is mixed with a first solvent and heated and stirred to form a melamine solution; cyanuric acid is mixed with a second solvent and heated and stirred to form a cyanuric acid solution; S2. Preparation of metal complex solution: Acid, Fe... 3+Salt is mixed with a third solvent and stirred to dissolve, thus preparing an Fe metal complex solution; S3. Supramolecular self-assembly and calcination: The Fe metal complex solution obtained in step S2 is added to the cyanuric acid solution in step S1 and mixed to obtain a mixed solution. Then, it is added to the melamine solution in step S1 and stirred continuously under heating conditions to generate a supramolecular precursor. The precursor is separated, washed, dried and ground, and then calcined under a certain atmosphere. After cooling to room temperature, the product is collected to obtain the Fe-doped carbon nitride photocatalyst.

[0009] Furthermore, in step S1, the molar ratio of melamine to cyanuric acid is (0.5~2):1; The concentration of the melamine solution is 1~100 mg / mL; the concentration of the cyanuric acid solution is 1~100 mg / mL; The heating temperature is 40~100 ℃, the stirring speed is 100~2000 r / min, and the time is 0.1~10 h.

[0010] Furthermore, the first solvent, the second solvent, and the third solvent are each independently selected from one or more of water, ethanol, or methanol.

[0011] Further, in step S2, the acid is selected from one or more of oxalic acid, citric acid, or ammonium thiocyanate; when oxalic acid is selected, the oxalic acid reacts with Fe... 3+ The molar ratio of salts is (3~10):1; The mass-to-volume ratio of oxalic acid to the third solvent is 1~2:1 mg / mL; the Fe 3+ The mass-to-volume ratio of salt to the third solvent is 0.3~2:1 mg / mL; The Fe 3+ The salt is selected from one or more of ferric nitrate, ferric chloride, and ferric acetate. And / or, the stirring speed is 100~2000 r / min, and the time is 0.5~10 h.

[0012] Furthermore, in step S3, the volume ratio of the cyanuric acid solution to the Fe metal complex solution is 0.1~50:1; the volume ratio of the melamine solution to the Fe metal complex solution is 0.2~25:1. The heating temperature is 40~100℃, the stirring speed is 100~2000 r / min, and the stirring time is 0.5~10 h.

[0013] Furthermore, in step S3, the separation method is centrifugal separation, and the centrifugal speed is 1000~13000 r / min; The drying method is atmospheric pressure drying, vacuum drying, or freeze drying, with a drying temperature of -80~100℃ and a drying time of 5~60 h; the grinding time is 0.1~10 h. The calcination temperature is 300~800℃, the calcination time is 0.5~10 h, and the heating rate is 1~10 ℃ / min; The calcination atmosphere is nitrogen, argon, or carbon dioxide, and the gas flow rate is 0.5~10 mL / min.

[0014] Secondly, the present invention provides an Fe-doped carbon nitride photocatalyst prepared by the preparation method described in the present invention.

[0015] Furthermore, in the application of the Fe-doped carbon nitride photocatalyst of the present invention in the preparation of organic pollutant degrading agents, the organic pollutant degrading agent further includes an oxidant containing peracetic acid; the organic pollutant is selected from at least one of phenol (PhOH), bisphenol A (BPA), 4-chlorophenol (4-CP), tetracycline (TC), atrazine (ATZ), moxifloxacin (MXF), rhodamine (RhB), or methylene blue (MB).

[0016] Thirdly, the present invention provides a method for degrading organic pollutants based on the Fe-doped carbon nitride photocatalyst described in the present invention. The photocatalyst is ultrasonically dispersed into the system to be treated, the pH and temperature of the reaction system are adjusted, and the system is stirred in the dark to reach adsorption-desorption equilibrium. An oxidant is added to the reaction system to construct a photocatalytic-Fenton-like system, and then the reaction system is placed under a light source to irradiate and degrade the organic pollutants. The oxidant is an aqueous solution containing peracetic acid. The final concentration of the photocatalyst in the system to be treated is 0.1~1 g / L; The final concentration of peracetic acid in the system to be treated is 50~1000 μM; The mass ratio of the photocatalyst to the oxidant is 1:(0.05~1); And / or, the ultrasonic power is 200-800 W, the frequency is 10-50 kHz, and the ultrasonic treatment time is 0.1-5 h; And / or, the pH of the reaction system is 3.0~10.0; the temperature of the reaction system is 4~60℃; And / or, the stirring speed is 100~2000 r / min, and the time is 0.1~5 h; And / or, the light source is a xenon lamp, LED lamp, high-pressure mercury lamp, metal halide lamp, or sunlight.

[0017] Furthermore, the oxidant also includes one or more of hydrogen peroxide, acetic acid, or a stabilizer; the stabilizer includes one or more of phosphonic acid stabilizers, aminocarboxylic acid chelating agents, or phosphate stabilizers, preferably one or more of hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, or sodium pyrophosphate.

[0018] Beneficial effects: (1) This invention provides a Fe sur+lat -CN photocatalyst (sur represents surface, lat represents interlayer), in which Fe is highly dispersed in single-atom form on a CN substrate; the surface Fe sites significantly enhance visible light absorption, improve charge separation and migration efficiency, suppress electron-hole recombination, and also enhance the photocatalyst's absorption capacity for visible light and photogenerated carrier yield; the interlayer Fe sites act as Fenton-like reaction active centers and provide fast electron transfer channels, effectively suppressing carrier recombination, together endowing Fe with... sur+lat -CN exhibits excellent photocatalytic activity.

[0019] (2) Fe prepared in this invention sur+lat Compared to CN photocatalysts, -CN photocatalysts exhibit superior performance in degrading organic matter. Under conditions of visible light and PAA coexistence, this catalyst can dominate the generation of an advanced oxidation system dominated by Fe(IV)=O and synergistically with ·OH. Furthermore, the catalyst preparation method of this invention is green and safe, uses readily available raw materials, and has a simple process, thus possessing high application prospects and practical value.

[0020] (3) The photocatalytic-Fenton-like synergistic degradation method developed in this invention is highly efficient, broad-spectrum, and widely applicable: based on Fe sur+lat -CN photocatalysis-Fenton-like (Fe sur+lat The CN / PAA / Vis system exhibits highly efficient simultaneous removal capabilities for multiple pollutants: phenol removal rate >90% within 30 min, and removal rate of organic compounds such as BPA, MXF, RhB, and MB >90%. Furthermore, the catalyst demonstrates good cycle stability and has broad application prospects. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the application and do not constitute a limitation thereof. In the drawings: Figure 1 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur Comparison of the photocatalytic degradation performance of PhOH by -CN under visible light; Figure 2 For the Fe-based examples 9-14sur+lat The CN-based photocatalytic Fenton water treatment method in Comparative Example 4 and the Fe-based photocatalytic Fenton water treatment method in Comparative Example 5 sur Comparison of PhOH degradation performance of photocatalytic Fenton water treatment methods in -CN; where (a) is the degradation curve of photocatalytic Fenton water treatment in Examples 9-14; (b) is the pseudo-first-order kinetic fitting graph of photocatalytic Fenton water treatment in Examples 9-14; (c) is the degradation curve of photocatalytic Fenton water treatment in Examples 9, Comparative Example 4, and Comparative Example 5; (d) is the pseudo-first-order kinetic fitting graph of photocatalytic Fenton water treatment in Examples 9, Comparative Example 4, and Comparative Example 5.

[0022] Figure 3 For example 9, based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method and Comparative Example 6's Fe-based method sur+lat -CN's photocatalytic water treatment method and Comparative Example 9 based on Fe sur+lat Comparison chart of the performance of Fenton-like water treatment methods for degrading PhOH in CN; Figure 4 For example 9, based on Fe sur+lat Performance diagram of the photocatalytic Fenton water treatment method of CN for degrading different organic pollutants; Figure 5 As in Example 17, based on Fe sur+lat Comparison of PhOH degradation performance of CN's photocatalytic Fenton water treatment method under different PAA dosages; Figure 6 For example 9, based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method for degrading PhOH is shown in the graph; where (a) is the cyclic degradation activity graph and (b) is the degradation activity graph in different water environments. Figure 7 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur TEM comparison images of -CN; where (a) is the TEM image of CN, and (b) is the TEM image of Fe. sur+lat TEM image of -CN, (c) Fe sur -CN TEM image; Figure 8 Fe prepared in Example 1 sur+lat HAADF-STEM image of -CN; Figure 9 Fe prepared in Example 1 sur+latX-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra of the -CN catalyst; where (a) is the XANES spectrum, (b) is the EXAFS spectrum, and (c) is the EXAFS fitting curve.

[0023] Figure 10 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur XRD comparison chart of -CN; Figure 11 Fe prepared in Example 1 sur+lat XPS comparison charts of -CN; where (a) is the C 1s spectrum, (b) is the N 1s spectrum, and (c) is the Fe 2p spectrum; Figure 12 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur DRS comparison chart for -CN; Figure 13 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur Comparison of photoelectric conversion performance of -CN; where (a) is the photocurrent response under alternating light and dark conditions; (b) is the electrochemical impedance Nyquist plot under visible light and dark conditions; Figure 14 For example 9, based on Fe sur+lat Comparison of PhOH degradation performance of the -CN photocatalytic Fenton-like water treatment method after adding different active species capture agents; Figure 15 Fe in Example 9 sur+lat -CN / PAA / Vis, CN / PAA / Vis in Comparative Example 4, and Fe in Comparative Example 5 sur ESR comparison chart of CN / PAA / Vis; where (a) is TEMP- 1 The signal intensity diagram of O2, (b) is DMPO-·O2 - (c) Signal intensity diagram; (d) Signal intensity diagram of DMPO-X;

[0024] Figure 16 For example 9, based on Fe sur+lat -CN, CN-based in Comparative Example 4, and Fe-based in Comparative Example 5 sur -CN's photocatalytic Fenton-like water treatment method, the changes in PMSO and PMSO2 concentrations during the reaction process, and the Fe-based method in Example 9.sur+lat -CN's photocatalytic Fenton water treatment method shows a comparison of PMSO and PMSO2 concentration changes during the reaction process under different atmospheres; where (a) is the PMSO concentration diagram and (b) is the PMSO2 concentration diagram. Detailed Implementation

[0025] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; the reagents and instruments described, unless otherwise specified, are commercially available.

[0026] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0027] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0028] Unless otherwise specified, the wastewater volume in the examples / comparative examples is 50 mL for the wastewater degradation steps.

[0029] Example 1 Fe sur+lat Preparation of -CN photocatalyst (1) Disperse 756.8 mg of melamine in 80 mL of ultrapure water and stir at 800 r / min at 85 °C for 0.5 h until it is completely dissolved to form solution A; disperse 620 mg of cyanuric acid in 64 mL of ultrapure water and stir at 800 r / min at 85 °C for 0.5 h until it is completely dissolved to form solution B.

[0030] (2) Disperse 40 mg of oxalic acid and 30 mg of ferric nitrate nonahydrate in 30 mL of ultrapure water and mix them. Stir at 800 r / min for 1 h at room temperature to completely dissolve them, and obtain solution C.

[0031] (3) Add solution C to solution B and stir until homogeneous to obtain mixture B+C. Then transfer it to solution A and stir mixture A+B+C at 800 r / min for 4 h at 85 ℃ to complete supramolecular self-assembly and generate supramolecular precursor. Wash with ultrapure water by centrifugation (centrifugation speed 10000 r / min), collect the supramolecular precursor precipitate, and dry it by vacuum drying at 65 ℃ for 24 h. Grind the dried supramolecular precursor for 1 h, and then calcine it at 600 ℃ for 4 h under a nitrogen atmosphere (gas flow rate 1 mL / min) (heating rate 5 ℃ / min). After cooling to room temperature, collect the obtained product, namely Fe sur+lat -CN photocatalyst.

[0032] Example 2 Fe sur+lat Preparation of -CN photocatalyst Example 2 is basically the same as Example 1, except for the mass of ferric nitrate nonahydrate. In Example 2, the mass of ferric nitrate nonahydrate is 10 mg. The remaining steps and raw materials are the same as in Example 1. The product obtained is denoted as 10Fe. sur+lat -CN photocatalyst.

[0033] Example 3 Fe sur+lat Preparation of -CN photocatalyst Example 3 is basically the same as Example 1, except for the mass of ferric nitrate nonahydrate. In Example 3, the mass of ferric nitrate nonahydrate is 20 mg. The remaining steps and raw materials are the same as in Example 1. The product obtained is denoted as 20Fe. sur+lat -CN photocatalyst.

[0034] Example 4 Fe sur+lat Preparation of -CN photocatalyst Example 4 is basically the same as Example 1, except for the mass of ferric nitrate nonahydrate. In Example 4, the mass of ferric nitrate nonahydrate is 40 mg. The remaining steps and raw materials are the same as in Example 1. The product obtained is denoted as 40Fe. sur+lat -CN photocatalyst.

[0035] Example 5 Fe sur+lat Preparation of -CN photocatalyst Example 5 is basically the same as Example 1, except for the mass of ferric nitrate nonahydrate. In Example 5, the mass of ferric nitrate nonahydrate is 50 mg. The remaining steps and raw materials are the same as in Example 1. The product obtained is denoted as 50Fe. sur+lat -CN photocatalyst.

[0036] Example 6 Fe sur+lat Preparation of -CN photocatalyst Example 6 is basically the same as Example 1, except for the mass of ferric nitrate nonahydrate. In Example 6, the mass of ferric nitrate nonahydrate is 60 mg. The remaining steps and raw materials are the same as in Example 1. The product obtained is denoted as 60Fe. sur+lat -CN photocatalyst.

[0037] Example 7 Fe sur+lat Preparation of -CN photocatalyst (1) Disperse 195.5 mg of melamine in 195.5 mL of ethanol and stir at 100 r / min for 0.1 h at 40 °C until it is completely dissolved to form solution A; disperse 100 mg of cyanuric acid in 100 mL of ethanol and stir at 100 r / min for 0.1 h at 40 °C until it is completely dissolved to form solution B.

[0038] (2) Disperse 7.8 mg oxalic acid and 7.8 mg ferric chloride hexahydrate in 3.9 mL ethanol and mix them. Stir at 100 r / min for 0.5 h at room temperature to completely dissolve them, and obtain solution C.

[0039] (3) Add solution C to solution B and stir until homogeneous to obtain mixture B+C. Then transfer it to solution A and stir mixture A+B+C at 40℃ and 100 r / min for 0.5 h to complete supramolecular self-assembly and generate supramolecular precursor. Wash with ultrapure water by centrifugation (centrifugation speed 1000 r / min), collect the supramolecular precursor precipitate, and freeze-dry it at -80℃ for 2 h. Grind the dried supramolecular precursor for 0.1 h, and then calcine it at 300℃ for 0.5 h (heating rate 1℃ / min) under an argon atmosphere (gas flow rate 0.5 mL / min). After cooling to room temperature, collect the obtained product, namely Fe. sur+lat -CN photocatalyst.

[0040] Example 8 Fe sur+lat Preparation of -CN photocatalyst (1) Disperse 756.8 mg of melamine in 7.57 mL of methanol and stir at 2000 r / min at 100℃ for 10 h until it is completely dissolved to form solution A; disperse 1549.0 mg of cyanuric acid in 15.49 mL of methanol and stir at 2000 r / min at 100℃ for 10 h until it is completely dissolved to form solution B.

[0041] (2) Disperse 65.6 mg of oxalic acid and 20 mg of ferric acetate tetrahydrate in 60 mL of methanol and mix them. Stir at 2000 r / min for 10 h at room temperature to completely dissolve them, and obtain solution C.

[0042] (3) Add solution C to solution B and stir until homogeneous to obtain mixture B+C. Then transfer it to solution A and stir mixture A+B+C at 100℃ and 2000 r / min for 10 h to complete supramolecular self-assembly and generate supramolecular precursor. Wash with ultrapure water by centrifugation (centrifugation speed 13000 r / min), collect the supramolecular precursor precipitate, and dry it by atmospheric pressure drying at 100℃ for 60 h. Grind the dried supramolecular precursor for 10 h, and then calcine it at 800℃ for 10 h in a carbon dioxide atmosphere (gas flow rate 10 mL / min) (heating rate 10℃ / min). After cooling to room temperature, collect the obtained product, namely Fe. sur+lat -CN photocatalyst.

[0043] Comparative Example 1: Preparation of CN photocatalyst (1) Disperse 756.8 mg of melamine in 80 mL of ultrapure water and stir at 800 r / min at 85℃ for 0.5 h until it is completely dissolved to form solution A; disperse 620 mg of cyanuric acid in 64 mL of ultrapure water and stir at 800 r / min at 85℃ for 0.5 h until it is completely dissolved to form solution B.

[0044] (2) Add solution A to solution B and stir until homogeneous to obtain mixture A+B. Stir at 800 r / min for 4 h at 85℃ to complete supramolecular self-assembly and generate supramolecular precursor. Wash with ultrapure water by centrifugation (centrifugation speed of 10000 r / min), collect the supramolecular precursor precipitate, and dry it by vacuum drying at 65℃ for 24 h. Grind the dried supramolecular precursor for 1 h, and then calcine it at 600℃ for 4 h under a nitrogen atmosphere (gas flow rate of 1 mL / min) (heating rate of 5℃ / min). After cooling to room temperature, collect the obtained product, i.e., CN photocatalyst.

[0045] Comparative Example 2 Fe sur Preparation of -CN photocatalyst 100 mg of CN was dispersed in 50 mL of anhydrous ethanol and ultrasonically dispersed for 1 h. Then, Fe was added as described in Example 1. sur+latEquimolar amounts of ferric nitrate nonahydrate (-CN) were evaporated to dryness at 95 °C and 800 r / min with stirring. The supramolecular precursor precipitate was collected and dried under vacuum at 65 °C for 24 h. The dried supramolecular precursor was then ground for 1 h and subsequently calcined at 300 °C for 4 h (heating rate 10 °C / min) under a nitrogen atmosphere (gas flow rate 1 mL / min). After cooling to room temperature, the resulting product, Fe, was collected. sur -CN photocatalyst.

[0046] Comparative Example 3: Preparation of F200CN Photocatalyst Comparative Example 3 prepared iron-doped graphitic carbon nitride according to the method disclosed in patent (CN202211050834.4) and used it as a comparative catalyst. The raw material composition, reaction temperature, reaction time, calcination atmosphere, and calcination procedure of this comparative catalyst were strictly carried out according to the method described in the aforementioned patent.

[0047] 45 mL of anhydrous ethanol and 5 mL of 12 mol / L hydrochloric acid were mixed and stirred continuously until completely homogeneous. 200 mg of ferric nitrate nonahydrate and 3 g of melamine were added to the mixture to obtain mixed solution A. Mixed solution A was stirred continuously for 6 h at a temperature of 65℃ and a rotation speed of 550 r / min. After all the solutions were evaporated to dryness, a yellow powder was obtained. The powder was ground evenly and placed in a quartz boat. Under a nitrogen atmosphere, it was calcined at 550℃ for 4 h in a sealed quartz tube at a heating rate of 5℃ / min. After cooling to room temperature, the obtained material was rinsed with deionized water and ethanol and dried under vacuum at 60℃. The obtained powder was placed in a quartz boat and calcined at 550°C for 1.5 h in a sealed quartz tube under a nitrogen atmosphere, with a heating rate of 5°C / min. After cooling to room temperature, the obtained material was rinsed with deionized water and ethanol and dried under vacuum at 60°C to obtain iron-doped graphitic carbon nitride (F200CN).

[0048] The following are the characterization tests for the photocatalyst: Transmission electron microscopy (TEM) images were captured using a JEOL JEM-2100 microscope with an electron beam acceleration voltage of 200 kV. Figure 7 As shown, the Fe prepared in Example 1 of this invention sur+lat -CN photocatalyst and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur -CN atoms all exhibit a typical stacked nanosheet morphology. The preparation method of this invention successfully introduces Fe atoms without altering the structural characteristics of the CN support itself. sur+lat No obvious metal particles or aggregates were observed in the TEM images of -CN.

[0049] High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images were captured using a JEM ARM200F thermal field emission microscope at a voltage of 200 kV. Figure 8 As shown, the Fe prepared in Example 1 sur+lat Isolated atom bright spots were observed on the CN substrate, indicating that Fe is loaded on the CN substrate in the form of highly dispersed single atoms.

[0050] Fe was determined using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods. sur+lat The coordination structure of Fe-N in -CN catalysts. For example... Figure 9 As shown in (a), Fe sur+lat The K-edge absorption position of Fe in -CN is close to Fe3O4 and higher than that of the Fe foil, indicating that Fe sur+lat Fe in CN 2+ and Fe 3+ Coexistence. Furthermore... Figure 9 (b) Display Fe sur+lat -CN Fe's K-edge k 3 The weighted R-space Fourier transform EXAFS (FT-EXAFS) spectrum showed a characteristic peak at 1.50 Å at which was attributed to Fe-N coordination, while no Fe-Fe (2.20 Å) or Fe-O (1.41 Å) scattering signals were detected, confirming the absence of iron oxides and iron clusters in the material. Figure 9 (c) The fitting parameters indicate that the Fe-N coordination number is approximately 3.66 and the Fe-N bond length is 2.00 Å. EXAFS fitting results further indicate that Fe... sur+lat The Fe site in -CN has an approximate Fe-N4 type single-atom structure.

[0051] The X-ray diffraction spectra (XRD) of the samples were studied using a Bruker D2-phaser X-ray diffractometer (CuKα, 30 kV, 10 mA). Figure 10 Fe prepared in Example 1 sur+lat -CN, CN prepared in Comparative Example 1, and Fe prepared in Comparative Example 2 sur XRD comparison chart of -CN. (See attached image.) Figure 10 As shown, the diffraction peaks at 13.1° and 27.9° belong to the (100) and (002) crystal planes of CN, respectively. Fe sur+lat -CN and Fe sur -CN exhibits a shift in diffraction peaks at 13.1° and 27.9° due to the doping of more Fe atoms in the repeated stacking of 3-s-triazine units, with both peaks showing lower intensities than CN. sur+latThe lack of obvious diffraction peaks for Fe in CN further indicates that Fe is mainly uniformly dispersed in CN in the form of single atoms.

[0052] The X-ray photoelectron spectroscopy (XPS) of the samples was tested using a Thermo Scientific K-Alpha spectrometer. Figure 11 Fe prepared in Example 1 sur+lat -CN, CN prepared in Comparative Example 1, and Fe prepared in Comparative Example 2 sur XPS comparison chart for -CN. (See attached image) Figure 11 As shown in (a), the C 1s spectrum of CN can be fitted to two peaks located around 284.8 eV and 288.1 eV, corresponding to the C C bond and sp bond, respectively. 2 C atoms in a hybrid N=CN group. Fe sur+lat -CN and Fe sur The NC=N peaks in -CN shifted to 287.9 ​​and 288.0 eV, respectively, indicating that the introduction of Fe altered the local electronic environment of CN and enhanced the electronic interaction between Fe and the support. Specifically, Fe... sur+lat -CN exhibits a more pronounced binding energy shift, indicating that interlayer Fe sites have a stronger regulatory effect on the electronic structure. For example... Figure 11 As shown in (b), the N 1s spectrum of CN can be decomposed into three characteristic peaks at 398.6, 400.0, and 401.2 eV, which are respectively attributed to sp. 2 Hybridized CN=C, N-(C)3, and incompletely condensed -NH / -NH2 groups. Compared to CN, Fe... sur+lat The shift of the N 1s peak in -CN to lower binding energies may be due to the formation of coordinate bonds between N and Fe. Furthermore, as... Figure 11 As shown in (c), Fe sur In the Fe 2p spectrum of -CN, two characteristic peaks at 710.9 eV and 723.6 eV can be observed, which belong to Fe 2p. 3 / 2 and Fe2p 1 / 2 And Fe sur+lat -CN did not detect the corresponding Fe 2p signal. Considering that XPS can only detect elemental information in the nanometer range of the material surface, this result confirms that Fe sur+lat Fe species in CN are not primarily exposed on the surface, but are more likely to be stably embedded in the CN layers.

[0053] The diffuse reflectance (DRS) spectrum of the sample was measured using a UV-Vis spectrophotometer (Shimadzu UV-3600 Plus). Figure 12 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur-CN's DRS comparison chart. (By...) Figure 12 It can be seen that, compared to CN, Fe sur+lat -CN and Fe sur The absorbance and absorption edge wavelength of CN are improved in the 200-800 nm range, indicating that modifying CN with Fe is beneficial to improving light absorption capacity and broadening the spectral response range, which can generate more photogenerated carriers and thus improve photocatalytic performance.

[0054] The following are the photoelectric conversion performance tests: Photoelectric conversion performance was tested on a CHI660D electrochemical workstation (Chenhua Instrument). A standard three-electrode system was used, consisting of a counter electrode (platinum wire), a reference electrode (saturated calomel electrode), and a working electrode, with 0.1 mol / L Na₂SO₄ solution as the electrolyte. The working electrode was prepared as follows: 5 mg of sample powder was ultrasonically dispersed in 1 mL of ultrapure water. The suspension was coated onto an indium tin oxide (ITO) glass surface, dried at room temperature, and heated at 180 °C for 5 h. A 300 W xenon lamp with a 400 nm cutoff filter was used as the visible light source. Photocurrent response was measured at 0.0 V; electrochemical impedance spectroscopy (EIS) was performed at 5 mV AC voltage from 0.01 Hz to 10 Hz. 5 Recorded within the Hz range.

[0055] Figure 13 Fe prepared in Example 1 sur+lat -CN and CN prepared in Comparative Example 1 and Fe prepared in Comparative Example 2 sur Comparison chart of photoelectric conversion performance of -CN. (Source: [Insert chart here]) Figure 13 (a) It can be seen that Fe sur+lat The photocurrent response values ​​of -CN are CN and Fe, respectively. sur The 3.7-fold and 2.6-fold increases in -CN indicate that interlayer Fe site modification further enhances the separation efficiency of CN photogenerated charges. Figure 13 (b) It can be seen that under dark and light conditions, the R of CN ct The value decreased from 16.4 kΩ in darkness to 13.9 kΩ under illumination, Fe sur -CN's R ct The value decreased from 9.3 kΩ in darkness to 6.8 kΩ under illumination, Fe sur+lat -CN's R ct The value decreased from 2.8 kΩ in darkness to 1.4 kΩ under illumination. This is in contrast to CN and Fe. sur -CN, Fe sur+lat -CN exhibits lower R values ​​in both dark and light conditions. ctThe value indicates that co-modification of surface and interlayer Fe sites can reduce the internal resistance of photogenerated electron migration and improve conductivity, and better conductivity can play a greater role in promoting photogenerated electron transfer.

[0056] The following are water treatment methods for the photocatalysts prepared in Examples 1-8 and Comparative Examples 1-3.

[0057] Example 9 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 15 mg of Fe prepared in Example 1 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0058] Example 10 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 15 mg of 10Fe prepared in Example 2 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0059] Example 11 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 15 mg of 20Fe prepared in Example 3 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0060] Example 12 Based on Fe sur+lat-CN's photocatalytic Fenton-like water treatment method 15 mg of 40Fe prepared in Example 4 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0061] Example 13 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 15 mg of the 50Fe prepared in Example 5 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0062] Example 14 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 15 mg of 60Fe prepared in Example 6 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0063] Example 15 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 5 mg of Fe prepared in Example 1 was used. sur+lat-CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (200 W, 10 kHz) for 0.1 h. The pH of the reaction system was adjusted to 3 and the temperature to 4ºC. The mixture was stirred at 100 r / min for 6 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 50 μM. The reaction system was then placed under an LED lamp for irradiation to initiate Fe-based... sur+lat -CN photocatalytic Fenton-like reaction.

[0064] Example 16 Based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method 50 mg of Fe prepared in Example 1 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (800 W, 50 kHz) for 5 h. The pH of the reaction system was adjusted to 10 and the temperature to 60ºC. The mixture was stirred at 2000 r / min for 5 h to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 1000 μM. The reaction system was then irradiated under a high-pressure mercury lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic Fenton-like reaction.

[0065] Comparative Example 4: CN-based photocatalytic Fenton-like water treatment method 15 mg of the CN photocatalyst prepared in Comparative Example 1 was added to 50 mL of wastewater to be treated and dispersed by ultrasonication (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then placed under a xenon lamp for irradiation to initiate a CN-based photocatalytic Fenton-like reaction.

[0066] Comparative Example 5 Based on Fe sur -CN's photocatalytic Fenton-like water treatment method 15 mg of Fe prepared in Comparative Example 2 was used sur -CN photocatalyst was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur -CN photocatalytic Fenton-like reaction.

[0067] Comparative Example 6 Based on Fe sur+lat-CN's photocatalytic water treatment method 15 mg of Fe prepared in Example 1 was used. sur+lat -CN photocatalyst was added to 50 mL of wastewater to be treated and ultrasonically dispersed (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur+lat -CN photocatalytic reaction.

[0068] Comparative Example 7: CN-based photocatalytic water treatment method 15 mg of the CN photocatalyst prepared in Comparative Example 1 was added to 50 mL of wastewater to be treated and dispersed by ultrasonication (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The system was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. The reaction system was then placed under a xenon lamp for irradiation to initiate a CN-based photocatalytic reaction.

[0069] Comparative Example 8 Based on Fe sur -CN's photocatalytic water treatment method 15 mg of Fe prepared in Comparative Example 2 was used sur -CN photocatalyst was added to 50 mL of wastewater to be treated and ultrasonically dispersed (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. The reaction system was then irradiated under a xenon lamp to initiate the adsorption-desorption process based on Fe. sur -CN photocatalytic reaction.

[0070] Comparative Example 9 Based on Fe sur+lat -CN's Fenton-like water treatment method 15 mg of Fe prepared in Example 1 was used. sur+lat -CN was added to 50 mL of wastewater to be treated and ultrasonically dispersed (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM, initiating the Fe-based adsorption-desorption process. sur+lat -CN-like Fenton reaction.

[0071] Comparative Example 10: A CN-based Fenton-like water treatment method 15 mg of CN prepared in Comparative Example 1 was added to 50 mL of wastewater to be treated and dispersed by ultrasonication (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM, thus initiating a CN-based Fenton-like reaction.

[0072] Comparative Example 11 Based on Fe sur -CN's Fenton-like water treatment method 15 mg of Fe prepared in Comparative Example 2 was used sur -CN was added to 50 mL of wastewater to be treated and dispersed ultrasonically (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25ºC. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM, initiating the Fe-based adsorption-desorption process. sur -CN-like Fenton reaction.

[0073] Comparative Example 12: A Photocatalytic Fenton-like Water Treatment Method Based on F200CN 15 mg of the F200CN photocatalyst prepared in Comparative Example 3 was added to 50 mL of wastewater to be treated and dispersed by ultrasonication (500 W, 40 kHz) for 0.5 h. The pH of the reaction system was adjusted to 7 and the temperature to 25 °C. The mixture was stirred at 800 r / min for 15 min to reach adsorption-desorption equilibrium. PAA was added to maintain the PAA concentration in the reaction system at 250 μM. The reaction system was then placed under a xenon lamp for irradiation to initiate a Fenton-like photocatalytic reaction based on Fe200CN.

[0074] Example 17 Different PAA Dosages The experimental steps were basically the same as in Example 9, except that the amount of PAA added was 62.5 μM, 125.0 μM, 250.0 μM and 500.0 μM, respectively.

[0075] The following are the performance tests for degrading organic pollutants: Phenol (PhOH), bisphenol A (BPA), 4-chlorophenol (4-CP), tetracycline (TC), atrazine (ATZ), moxifloxacin (MXF), rhodamine (RhB), or methylene blue (MB) were selected as target degradation products at 10 ppm. Visible light was provided by a xenon lamp (300 W, Zhongjiao Jinyuan CEL-HXF300). The pH of the reaction system was adjusted to 7, and the temperature was 25 ºC. In the photocatalytic Fenton-like reaction system, the photocatalyst concentration was 0.3 g / L, and the PAA concentration was 250 μM. After the degradation reaction started, 1 mL of the reaction solution was taken at regular intervals, mixed with 1 mL of methanol, centrifuged (10000 r / min) to remove the photocatalyst from the reaction solution, and the supernatant was filtered through a 0.22 μm Millipore filter. The concentration of organic matter in the supernatant was determined by high performance liquid chromatography (Waters 1525); the total organic carbon content in the supernatant was determined by a total organic carbon analyzer (Shimadzu, TOC-V CPH).

[0076] Figure 1 Fe prepared in Example 1 sur+lat -CN, CN prepared in Comparative Example 1, and Fe prepared in Comparative Example 2 sur Comparison of the photocatalytic degradation performance of PhOH by -CN under visible light. Figure 1 It can be seen that the unmodified CN photocatalyst achieved a PhOH removal rate of 10.1% after 30 min of visible light irradiation; after introducing single-atom Fe, Fe... sur The degradation activity of -CN was improved to 12.5%, indicating that surface Fe site modification alone can improve the photogenerated charge separation efficiency of CN to a certain extent; Fe sur+lat The CN (Example 1) catalyst exhibited superior photocatalytic activity, with a PhOH removal rate as high as 27.7%. This indicates that the synergistic modification of surface and interlayer Fe sites can more efficiently improve the photocatalytic performance of CN materials.

[0077] Figure 2 For example 9, based on Fe sur+lat -CN photocatalytic Fenton water treatment method (Fe sur+lat Comparison chart of the performance of PhOH degradation of each comparative system in Examples 10-14 and Comparative Examples 4-5 (CN / PAA / Vis) with that in Examples 10-14. Figure 2 (ab) The results showed that the addition amount of ferric nitrate nonahydrate was 30 mg Fe sur+lat -CN (Example 1) demonstrated the best performance, achieving a PhOH removal rate of up to 90.8%. Its first-order reaction kinetic constant k is 0.0858 min. -1 Superior to 10Fe sur+lat-CN (59.2%), 20Fe sur+lat -CN (61.3%), 40Fe sur+lat -CN (77.6%), 50Fe sur+lat -CN (83.7%) and 60Fe sur+lat -CN (77.6%). By Figure 2 (c) It can be seen that after 30 min of illumination, CN / PAA / Vis (Comparative Example 4) and Fe sur The removal rates of phenol in the CN / PAA / Vis (Comparative Example 5) system were 37.0% and 62.2%, respectively; while Fe... sur+lat The -CN / PAA / Vis (Example 9) system achieved a PhOH removal rate of up to 90.8% within the same timeframe. Figure 2 (d) It can be seen that, by fitting the pseudo-first-order kinetic equation ln(C / C0)=-kt, we obtain: Fe sur+lat The reaction rate constant of the CN / PAA / Vis system (k = 0.0858 min) -1 (These are CN / PAA / Vis and Fe respectively) sur -5.4 times and 2.7 times that of the CN / PAA / Vis system. This invention is based on Fe sur+lat -CN's photocatalytic Fenton-like water treatment method can more efficiently activate PAA through the unique synergistic effect of surface and interlayer Fe sites. It achieves superior organic matter degradation through photocatalysis-Fenton-like synergy, and its technical effect far exceeds that of surface Fe site modification systems.

[0078] Meanwhile, the iron-doped graphitic carbon nitride F200CN prepared in Comparative Example 3 was compared with the Fe prepared in Example 1. sur+lat -CN catalysts were used in the degradation experiments of organic pollutants. Under the same reaction conditions, their degradation performance on PhOH, BPA, and 4-CP was investigated. During the experiments, the initial pollutant concentration, catalyst dosage, PAA concentration, light intensity, reaction volume, and reaction time were kept completely consistent to eliminate the influence of differences in reaction conditions. Experimental results showed that, under the same reaction conditions, the Fe-CN catalyst prepared in Example 1... sur+lat -CN catalysts exhibited superior degradation performance for PhOH, BPA, and 4-CP compared to the F200CN prepared in Comparative Example 3. Specifically, for PhOH, the Fe200CN catalyst prepared in Example 1... sur+lat The apparent first-order reaction rate constant of the -CN catalyst is 0.0858 min. -1 Comparative Example 3 was 0.030 min. -1 The former is approximately 2.9 times that of the latter. For BPA and 4-CP, the Fe prepared in Example 1... sur+lat-CN catalysts also exhibited superior removal efficiency.

[0079] Figure 3 This is a comparison chart showing the performance of each system in Example 9, Comparative Example 6, and Comparative Example 9 in degrading PhOH. (Source: [Insert chart here]) Figure 3 It can be seen that in pure photocatalysis of Fe without PAA participation and relying solely on visible light, sur+lat In the -CN / Vis system (Comparative Example 6), the removal rate of PhOH was 27.7%. In the Fenton-like Fe system, which relied solely on catalyst activation of PAA without light exposure... sur+lat In the -CN / PAA system (Comparative Example 9), the removal rate of PhOH was 8.1%. However, in the Fe of this invention... sur+lat In the -CN / PAA / Vis synergistic system, the removal rate reached 90.8% after 30 min, exhibiting superior PhOH degradation activity. This indicates that the synergy between photocatalysis and Fenton-like reaction is key to enhancing degradation activity. These results suggest that Fe... sur+lat The CN / PAA / Vis water treatment method, by coupling photocatalysis with Fenton-like reactions, can achieve better pollutant purification effects and greater practical application potential than single photocatalysis or simple Fenton-like technologies.

[0080] Figure 4 Fe for Example 9 sur+lat The activity diagram of the CN / PAA / Vis system for degrading various organic pollutants shows that the method of this invention exhibits excellent degradation ability for a variety of organic pollutants with different structures and properties. After 30 min of reaction, the removal rates of PhOH, 4-CP, BPA, TC, MXF, RhB, and MB reached 90.8%, 88.8%, 100%, 83.5%, 91.2%, 100%, and 98.2%, respectively; while for ATZ, a more difficult pollutant to degrade, the removal rate also reached 84.8%. This demonstrates the Fe... sur+lat The -CN / PAA / Vis system exhibits broad-spectrum and highly efficient degradation activity against a variety of organic pollutants, including phenols, antibiotics, and dyes.

[0081] Figure 5 This is a graph showing the effect of different PAA concentrations on the degradation performance of PhOH in Example 17. Figure 5It can be seen that when the PAA concentration increased from 62.5 μM to 250.0 μM, the removal rate of PhOH within 30 min significantly increased from 62.8% to 90.8%. This indicates that when the PAA concentration is below 250.0 μM, increasing the PAA concentration can provide more oxidant molecules that can be activated by the Fe active sites on the catalyst surface and participate in the reaction, thereby accelerating the catalytic reaction process and improving the pollutant removal efficiency. However, when the PAA concentration continued to increase to 500.0 μM, the degradation efficiency of PhOH did not further improve. Therefore, the preferred PAA concentration of this invention is 250.0 μM, which allows for the removal of Fe... sur+lat The -CN / PAA / Vis system can achieve optimal pollutant degradation with high oxidant utilization.

[0082] Figure 6 For example 9, based on Fe sur+lat PhOH degradation activity diagram of the photocatalytic Fenton-like water treatment method of -CN. Figure 6 (a) It can be seen that after 5 consecutive cycles of degradation, Fe sur+lat The -CN / PAA / Vis system showed no significant decrease in its activity in degrading PhOH, indicating good stability. Figure 6 (b) It can be seen that Fe sur+lat -CN / PAA / Vis achieved a 96.8% degradation rate of PhOH in the Bohai Sea, while maintaining a PhOH degradation rate of over 70.0% in actual water environments such as the Yellow Sea, East China Sea, and South China Sea. This indicates that Fe... sur+lat The -CN / PAA / Vis system exhibits strong anti-interference performance.

[0083] It should be noted that the experimental results based on Example 9 demonstrate the excellent performance of the method of the present invention under the preferred parameter combination. Using the schemes described in Examples 10-14, under correspondingly optimized reaction conditions, similar technical effects can be achieved, efficiently activating PAA and synergistically combining photocatalysis and Fenton-like reactions to effectively remove organic pollutants from water.

[0084] Figure 14 For example 9, based on Fe sur+lat The photocatalytic Fenton-like water treatment method of -CN compares the performance of PhOH degradation after adding different active species capture agents. 10 mM methanol (MeOH), 10 mM tert-butanol (TBA), 1 mM p-benzoquinone (p-BQ), 200 μM furfuryl alcohol (FFA), 1 mM manganese chloride (MnCl2), 1 mM dimethyl sulfoxide (DMSO), 1 mM 2,4-hexadiene (2-HD), and sodium oxalate (Na2C2O4) are used as RO·, ·OH, and ·O2, respectively. - , 1O2, CH3C(O)OO·, Fe(Ⅳ)=O, RO·, and photogenerated hole scavengers. (From...) Figure 14 (a) It can be seen that the addition of FFA and p-BQ affects Fe sur+lat The effect of the -CN / PAA / Vis system on PhOH removal is negligible, indicating that... 1 O2 and ·O2 - It has no effect on the degradation of PhOH. The addition of Na₂C₂O₄ inhibited the degradation of PhOH, possibly due to Fe. sur+lat The -CN / PAA / Vis system exhibits higher separation efficiency of photogenerated electron-hole pairs, releasing more photogenerated holes to participate in the reaction, thereby improving degradation efficiency. The addition of both MeOH and TBA leads to Fe... sur+lat The -CN / PAA / Vis system showed a decrease in PhOH removal rate, preliminarily confirming the formation of ·OH and RO· in the system. Combined with the quenching results of 2,4-HD and MnCl2 experiments, RO· participated in Fe... sur+lat The degradation process of PhOH in the -CN / PAA / Vis system. The addition of DMSO significantly affected PhOH removal, preliminarily verifying the presence of Fe(Ⅳ)=O. These results indicate that Fe... sur+lat The main active species in the -CN / PAA / Vis system is Fe(Ⅳ)=O, followed by ·OH, while photogenerated holes and RO· contribute less than the former two.

[0085] The electron spin resonance (ESR) spectra of the samples were measured using a Bruker EMXplus electron spin resonance spectrometer. Figure 15 Fe in Example 9 sur+lat -CN / PAA / Vis, CN / PAA / Vis in Comparative Example 4, and Fe in Comparative Example 5 sur ESR comparison chart of -CN / PAA / Vis. Under visible light irradiation, 2,2,6,6-tetramethyl-4-piperidinone (TEMP) and 5,5-dimethyl-1-pyrrolidone-N-oxide (DMPO) were used as... 1 O2 and ·O2 - Spin probes, such as Figure 15 As shown in (ab), under visible light irradiation, Fe sur -CN / PAA / Vis system generated 1 O2 and ·O2 - Signal strength ratio of CN and Fe sur+lat -CN is more pronounced, indicating that the system can produce more 1 O2 and ·O2 - .Depend on Figure 15 (cd) indicates that, compared to CN and Fe sur -CN, Fesur+lat Distinct DMPO-X and DMPO-·OH signals were observed in the -CN / PAA / Vis system, indicating that Fe sur+lat -CN can efficiently activate PAA, promote the generation of Fe(Ⅳ)=O and ·OH, thereby significantly improving the pollutant removal capacity.

[0086] Quantitative analysis of high-priced ferrous oxide species.

[0087] Methyl phenyl sulfoxide (PMSO) is often used as a probe molecule to recognize Fe(Ⅳ)=O because it reacts with Fe(Ⅳ)=O to form methyl phenyl sulfone (PMSO2). First, 15 mg of catalyst was added to 50 mL of ultrapure water, and the mixture was sonicated for 30 min. PMSO was then added to maintain a concentration of 40 μM, and the mixture was stirred in the dark for 15 min to reach adsorption-desorption equilibrium. Next, PAA was added to the mixture to adjust its concentration to 250 μM. Irradiation was initiated, and at regular intervals, 1 mL of the reaction solution was taken, and 1 mL of methanol was added to terminate the reaction. Catalyst particles were removed by centrifugation and filtration, and the concentrations of PMSO and PMSO2 were detected by high-performance liquid chromatography (Waters 1525).

[0088] Figure 16 For example 9, based on Fe sur+lat -CN, Comparative Example 4 based on CN and Comparative Example 4 based on Fe sur A comparison of PMSO and PMSO2 concentration changes during the reaction process in the -CN photocatalytic Fenton water treatment method. Figure 16 It can be seen that after 30 minutes of reaction, Fe sur+lat In the CN / PAA / Vis system, the PMSO concentration decreased from 10.0 μM to 4.1 μM, while the PMSO2 concentration increased from 0.0 μM to 5.3 μM. The η(ΔPMSO2 / ΔPMSO) conversion rate reached as high as 90.1%, far exceeding that of the CN / PAA / Vis system (4.8%) and Fe. sur -CN / PAA / Vis(30.0%) system, the above results confirm that in the Fe of this invention sur+lat The -CN / PAA / Vis system contains Fe(IV)=O. To demonstrate the source of O in Fe(IV)=O, the presence of Fe under different atmospheric conditions was investigated. sur+lat The formation of PMSO and PMSO2 in the CN / PAA / Vis system was investigated. When dissolved oxygen was removed by N2 purging and N2 was continuously introduced, the removal of PhOH and the reduction of PMSO concentration were significantly inhibited, and the formation of PMSO2 was also significantly reduced, with a conversion efficiency of only 38.2%, lower than that under air atmosphere conditions. This result directly indicates that some dissolved oxygen in the water participates in the formation of Fe.sur+lat The formation of high-valence metal species in the CN / PAA / Vis system. Combined with... Figure 14 and Figure 15 The conclusion is that Fe sur+lat The mechanism by which the -CN / PAA / Vis system degrades organic pollutants is the result of the synergistic effect of multiple active species, namely: the synergistic activation of PAA by surface and interlayer Fe sites, simultaneously generating ·OH via the free radical pathway and Fe(IV)=O via the high-valence metal species pathway, confirming the role of Fe. sur+lat -CN / PAA / Vis follows a photocatalytic activation mechanism for PAA degradation, rather than being dominated by a single reaction pathway.

[0089] In summary, this invention provides a Fe sur+lat Preparation method of -CN photocatalytic material and a Fe-based method sur+lat A photocatalytic-Fenton-like synergistic degradation method for -CN. This invention utilizes a "supramolecular assembly-thermal polymerization method" to precisely anchor Fe atoms in single-atom form onto a CN substrate, constructing an Fe substrate with excellent light absorption and charge separation properties. sur+lat -CN composite photocatalyst. This catalyst was coupled with PAA, and Fe was constructed under visible light irradiation. sur+lat -CN / PAA / Vis synergistic reaction system. The interlayer Fe sites significantly broaden the material's response range to visible light and enhance the separation efficiency of photogenerated charges. The synergistic surface Fe sites, acting as highly efficient Fenton-like reactive centers, activate PAA, leading to the generation of a higher oxidation system with ·OH and Fe(IV)=O. These synergistic effects jointly promote the continuous generation of both free radicals and non-free radicals, synergistically enhancing the Fe... sur+lat The CN / PAA / Vis system demonstrates high efficiency in the oxidation removal and deep mineralization of pollutants. This method achieves a phenol removal rate exceeding 91% within 30 minutes and a removal rate of over 90% for multiple pollutants, with no significant performance degradation after five cycles, thus realizing highly efficient removal of organic pollutants from water. This invention achieves efficient coupling of photocatalysis and Fenton-like reactions, solving the problems of high electron-hole recombination rates and low oxidant utilization efficiency in traditional technologies, providing an innovative solution for efficient, stable, and green water treatment technology.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing an Fe-doped carbon nitride photocatalyst, characterized in that, The preparation method includes the following steps: S1. Preparation of precursor solution: Melamine is mixed with a first solvent and heated and stirred to form a melamine solution; cyanuric acid is mixed with a second solvent and heated and stirred to form a cyanuric acid solution; S2. Preparation of metal complex solution: Acid, Fe... 3+ Salt is mixed with a third solvent and stirred to dissolve, thus preparing an Fe metal complex solution; S3. Supramolecular self-assembly and calcination: The Fe metal complex solution obtained in step S2 is added to the cyanuric acid solution in step S1 and mixed to obtain a mixed solution. Then, it is added to the melamine solution in step S1 and stirred continuously under heating conditions to generate a supramolecular precursor. The precursor is separated, washed, dried and ground, and then calcined under a certain atmosphere. After cooling to room temperature, the product is collected to obtain the Fe-doped carbon nitride photocatalyst.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of melamine to cyanuric acid is (0.5~2):1; The concentration of the melamine solution is 1~100 mg / mL; the concentration of the cyanuric acid solution is 1~100 mg / mL; The heating temperature is 40~100 ℃, the stirring speed is 100~2000 r / min, and the time is 0.1~10 h.

3. The preparation method according to claim 1, characterized in that, The first solvent, the second solvent, and the third solvent are each independently selected from one or more of water, ethanol, or methanol.

4. The preparation method according to claim 3, characterized in that, In step S2, the acid is selected from one or more of oxalic acid, citric acid, or ammonium thiocyanate; when oxalic acid is selected, the oxalic acid reacts with Fe... 3+ The molar ratio of salts is (3~10):1; The mass-to-volume ratio of oxalic acid to the third solvent is 1~2:1 mg / mL; the Fe 3+ The mass-to-volume ratio of salt to the third solvent is 0.3~2:1 mg / mL; The Fe 3+ The salt is selected from one or more of ferric nitrate, ferric chloride, and ferric acetate. And / or, the stirring speed is 100~2000 r / min, and the time is 0.5~10 h.

5. The preparation method according to claim 3, characterized in that, In step S3, the volume ratio of the cyanuric acid solution to the Fe metal complex solution is 0.1~50:1; the volume ratio of the melamine solution to the Fe metal complex solution is 0.2~25:

1. The heating temperature is 40~100℃, the stirring speed is 100~2000 r / min, and the stirring time is 0.5~10 h.

6. The preparation method according to claim 3, characterized in that, In step S3, the separation method is centrifugal separation, and the centrifugal speed is 1000~13000 r / min; The drying method is atmospheric pressure drying, vacuum drying, or freeze drying, with a drying temperature of -80~100℃ and a drying time of 5~60 h; the grinding time is 0.1~10 h. The calcination temperature is 300~800℃, the calcination time is 0.5~10 h, and the heating rate is 1~10 ℃ / min; The calcination atmosphere is nitrogen, argon, or carbon dioxide, and the gas flow rate is 0.5~10 mL / min.

7. The Fe-doped carbon nitride photocatalyst prepared by the preparation method according to any one of claims 1-6.

8. The application of the Fe-doped carbon nitride photocatalyst according to claim 7 in the preparation of organic pollutant degrading agents, characterized in that, The organic pollutant degrading agent also includes an oxidant containing peracetic acid; the organic pollutant is selected from at least one of phenol, bisphenol A, 4-chlorophenol, tetracycline, atrazine, moxifloxacin, rhodamine, or methylene blue.

9. A method for degrading organic pollutants based on the Fe-doped carbon nitride photocatalyst of claim 7, characterized in that, The photocatalyst was ultrasonically dispersed into the system to be treated. The pH and temperature of the reaction system were adjusted, and the system was stirred in the dark to reach adsorption-desorption equilibrium. An oxidant was added to the reaction system to construct a photocatalytic-Fenton-like system. The reaction system was then placed under a light source to irradiate and degrade organic pollutants. The oxidant was an aqueous solution containing peracetic acid. The final concentration of the photocatalyst in the system to be treated is 0.1~1 g / L; The final concentration of peracetic acid in the system to be treated is 50~1000 μM; The mass ratio of the photocatalyst to the oxidant is 1:(0.05~1); And / or, the ultrasonic power is 200-800 W, the frequency is 10-50 kHz, and the ultrasonic treatment time is 0.1-5 h; And / or, the pH of the reaction system is 3.0~10.0; the temperature of the reaction system is 4~60℃; And / or, the stirring speed is 100~2000 r / min, and the time is 0.1~5 h; And / or, the light source is a xenon lamp, LED lamp, high-pressure mercury lamp, metal halide lamp, or sunlight.

10. The degradation method according to claim 9, characterized in that, The oxidant also includes one or more of hydrogen peroxide, acetic acid, or stabilizers; the stabilizers include one or more of phosphonic acid stabilizers, aminocarboxylic acid chelating agents, or phosphate stabilizers, preferably one or more of hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, or sodium pyrophosphate.

Images