Magnetic copper-doped carbon nitride composite Fenton-like catalyst, preparation method thereof and application

Abstract

The present invention provides a magnetic copper-doped carbon nitride composite Fenton-like catalyst, a preparation method thereof, and an application thereof. The preparation method of the magnetic copper-doped carbon nitride composite Fenton-like catalyst of the present invention comprises the following steps: dispersing the prepared cuprous carbon nitride material and iron tetroxide in water, adding polyethylene glycol, stirring, separating, washing, and drying to obtain the magnetic copper-doped carbon nitride composite Fenton-like catalyst. The preparation method of the magnetic copper-doped carbon nitride composite Fenton-like catalyst of the present invention is simple in operation and easy to realize industrialization. The magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by this preparation method has high Fenton-like catalytic activity under alkaline conditions. When it is applied to the treatment of organic wastewater, it has good treatment effect, stable performance, can be quickly separated by a magnet after the reaction, is simple in operation, low in cost, and has high practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly relates to a magnetic copper-doped carbon nitride composite Fenton-like catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The traditional Fenton reaction can degrade most organic pollutants in water by generating strongly oxidizing hydroxyl radicals (HO·), so it is increasingly widely used in the treatment of wastewater in the chemical industry. However, this reaction needs to be carried out under the condition of pH 3-4. For a large amount of alkaline wastewater generated by petrochemical, pharmaceutical, papermaking, printing and dyeing industries, etc., acid needs to be added for pH adjustment before treatment. If the wastewater contains S 2- , CN - , additional risks of dangerous gas evolution will also be caused. In recent years, the heterogeneous Fenton-like system based on solid catalysts has extended its application scope to weak acidic and neutral through complexation and other means, but there are few reports on its research under alkaline conditions. The reason is that under alkaline conditions, Fe is easily converted into inert species, inhibiting the generation of HO·. In addition, CO3 2- and HCO3 - and other ions in the wastewater will also quench HO·, thus rapidly reducing the reaction rate. Therefore, it is urgent to develop a simple, efficient and Fenton-like treatment technology applicable to alkaline conditions.

[0003] Among common reactive oxygen species (ROS), singlet oxygen ( 1 O2) has better effects under alkaline conditions. Although the oxidation potential of HO· is higher than that of 1 O2, due to the oxidation of free radicals being more susceptible to the influence of pH, various anions, humic acid, etc. than non-free radicals such as 1 O2, in some cases, its treatment effect is actually inferior to that of 1 O2. However, 1 O2 is more common in persulfate and photocatalytic systems, and it is more difficult to be initiated by H2O2 in the Fenton system. Existing research has used the confinement effect of carbon nanotubes to load nanoscale Fe2O3 on them. Experiments have proved that the oxidizing agent in the system is 1 O2 rather than HO·, and the suitable pH range is 5-9. However, carbon nanotubes are expensive and not easy to promote.

[0004] Based on the defects of the catalysts in the current Fenton system, it is necessary to improve them. Summary of the Invention

[0005] In view of this, the present invention provides a magnetic copper-doped carbon nitride composite Fenton-like catalyst, a preparation method thereof, and an application thereof to solve the defects existing in the prior art.

[0006] In a first aspect, the present invention provides a method for preparing a cuprous carbon nitride material, comprising the following steps:

[0007] Add a carbon nitride precursor to a solvent, then add a copper salt. After stirring, evaporate the solvent and calcine in an inert atmosphere to obtain the cuprous carbon nitride material.

[0008] Preferably, in the method for preparing the cuprous carbon nitride material, the carbon nitride precursor comprises at least one of melamine, dicyandiamide, and 3-amino-1,2,4-triazole;

[0009] and / or, the copper salt comprises at least one of copper nitrate, copper sulfate, and copper chloride;

[0010] and / or, the solvent comprises at least one of an ethanol-water solvent, a methanol-water solvent, and a glycerol-water solvent.

[0011] and / or, in the step of adding the carbon nitride precursor to the solvent and then adding the copper salt, the molar mass ratio of the copper salt to the carbon nitride precursor is (0.01 - 2) mmol : (1 - 3) g.

[0012] Preferably, in the method for preparing the cuprous carbon nitride material, in the step of calcining in an inert atmosphere, the calcination temperature is 450 - 650 °C and the time is 2 - 4 h;

[0013] and / or, the inert atmosphere comprises at least one of nitrogen, helium, argon, and neon.

[0014] Preferably, in the method for preparing the cuprous carbon nitride material, heat from room temperature to the calcination temperature at a heating rate of 3 - 10 °C / min and then carry out the calcination.

[0015] In a second aspect, the present invention further provides a method for preparing a magnetic copper-doped carbon nitride composite Fenton-like catalyst, comprising the following steps:

[0016] Disperse the cuprous carbon nitride material prepared by the above-mentioned preparation method and magnetite in water, then add polyethylene glycol, stir, separate, wash, and dry to obtain the magnetic copper-doped carbon nitride composite Fenton-like catalyst.

[0017] Preferably, in the method for preparing the magnetic copper-doped carbon nitride composite Fenton-like catalyst, the relative molecular weight of the polyethylene glycol is 100 - 600.

[0018] Preferably, in the step of dispersing cuprous carbon nitride material and iron tetroxide in water and then adding polyethylene glycol in the preparation method of the magnetic copper-doped carbon nitride composite Fenton-like catalyst, the mass ratio of cuprous carbon nitride to iron tetroxide is (0.25-4):(0.25-4), the volume ratio of polyethylene glycol to water is (0.05-1):1, and the mass-volume ratio of cuprous carbon nitride to water is (0.03-0.12) g:(15-25) mL.

[0019] In a third aspect, the present invention also provides a magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by using the preparation method.

[0020] In a fourth aspect, the present invention also provides an application of the cuprous carbon nitride material prepared by the preparation method, or the magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by the preparation method, or the magnetic copper-doped carbon nitride composite Fenton-like catalyst in treating organic wastewater.

[0021] Preferably, the application includes the following steps: adding the cuprous carbon nitride material or the magnetic copper-doped carbon nitride composite Fenton-like catalyst to the organic wastewater, adjusting the pH of the organic wastewater to 3-12, and then adding H2O2.

[0022] The present invention has the following beneficial effects compared with the prior art:

[0023] 1. The cuprous carbon nitride material prepared by the present invention, in which, the graphitic carbon nitride is simple to prepare and has stable properties. At the same time, the unique N6 structure in the structure can effectively complex metal ions, thus playing a metal confinement role similar to the above-mentioned carbon nanotubes. The prepared cuprous graphitic carbon nitride material has a good degradation effect on pollutants (such as p-chlorophenol) in organic wastewater, especially has high catalytic activity under alkaline conditions; experiments show that the removal rate of p-chlorophenol by the cuprous carbon nitride material of the present invention is as high as 93.62%;

[0024] 2. The magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by the preparation method of the present invention has a good removal effect on pollutants in water, and its Fenton-like catalytic performance under alkaline conditions is better than that under acidic conditions; the principle is that the introduction of Cu can not only construct a Cu(I)-N electron bridge, making pyridine N continuously transfer electrons in g-C3N4 to Cu as an electron donor, promoting the regeneration of Cu(I)-N and the decomposition of H2O2, but also making the electron-deficient C atom adjacent to pyridine N act as a Lewis acid site. Under alkaline conditions, it adsorbs reactive oxygen or OH- together with Cu(II)-N to form a superoxide / hydroxyl complex, and then generates singlet oxygen through intramolecular electron transfer, reactive oxygen interaction or self-disproportionation reaction, converting the CuFe@PEG-H2O2 system from the traditional free radical pathway to the alkaline condition1 O2-dominated non-free radical system;

[0025] 3. The preparation method of the magnetic copper-doped carbon nitride composite Fenton-like catalyst of the present invention is simple in operation and easy to realize industrialization. The magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by this preparation method has high Fenton-like catalytic activity under alkaline conditions. When it is applied to the treatment of organic wastewater, the treatment effect is good, the performance is stable, and it can be quickly separated by a magnet after the reaction. The operation is simple, the cost is low, and it has high practical value. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 XRD patterns of Cu / CN in Example 1, Cu / CN-triazole, Cu / CN-dicyanamide, and Cu / CN in Comparative Examples 4-6 air ;

[0028] Figure 2 Image of the suspension formed by adding cuprous carbon nitride (Cu / CN) and Fe3O4 to ultrapure water;

[0029] Figure 3 Image of adding polyethylene glycol to the suspension system;

[0030] Figure 4 Image of the suspension of the magnetic copper-doped carbon nitride composite Fenton-like catalyst self-assembled after adding polyethylene glycol and stirring;

[0031] Figures 5 - 6 Scanning electron images of CuFe@PEG prepared in Example 7 at different magnifications;

[0032] Figure 7 Scanning electron image of Cu / CN in Example 1;

[0033] Figure 8 XRD patterns of CuFe@PEG in Example 7, Cu / CN in Example 1, Cu@PEG in Comparative Example 1, Fe@PEG in Comparative Example 2, and Fe3O4 in Comparative Example 3.

[0034] Figure 9The hysteresis loops of CuFe@PEG in Example 7 and Fe3O4 in Comparative Example 3;

[0035] Figure 10 The image of the solid-liquid separation of CuFe@PEG after the reaction in Example 7 by a magnet;

[0036] Figure 11 The removal rate of 4-chlorophenol catalyzed by CuFe@PEG in Example 7 and the leaching amounts of Fe and Cu at different pH values. Detailed implementation manners

[0037] Next, in combination with the implementation manners of the present invention, the technical solutions in the implementation manners of the present invention will be clearly and completely described. Obviously, the described implementation manners are only a part of the implementation manners of the present invention, rather than all the implementation manners. Based on the implementation manners in the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] It should be noted that the description order of the following examples does not limit the preferred order of the examples. In addition, in the description of the present application, the term "including" means "including but not limited to". The various embodiments of the present invention may exist in a range form; it should be understood that the description in a range form is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the counted range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0039] The embodiments of the present application provide a preparation method of a cuprous carbon nitride material, including the following steps:

[0040] Add a carbon nitride precursor to a solvent, then add a copper salt, stir, evaporate the solvent, and calcine under an inert atmosphere to obtain a cuprous carbon nitride material.

[0041] The cuprous carbon nitride material prepared by the present invention, wherein, graphitic carbon nitride is simple to prepare and has stable properties. At the same time, the unique N6 structure in the structure can effectively complex metal ions, thereby playing a metal confinement role similar to the above carbon nanotubes. The prepared cuprous graphitic carbon nitride material has a good degradation effect on pollutants (such as 4-chlorophenol) in organic wastewater, especially has high catalytic activity under alkaline conditions.

[0042] Based on the same inventive concept, the present invention also provides a method for preparing a magnetic copper-doped carbon nitride composite Fenton-like catalyst, comprising the following steps:

[0043] S1. Add a carbon nitride precursor to a solvent, then add a copper salt, stir, evaporate the solvent, and calcine in an inert atmosphere to obtain a cuprous carbon nitride material;

[0044] S2. Disperse the prepared cuprous carbon nitride material and magnetite in water, then add polyethylene glycol, stir, separate, wash, and dry to obtain the magnetic copper-doped carbon nitride composite Fenton-like catalyst.

[0045] Since the cuprous carbon nitride material is a powdery material, it is relatively difficult to recycle in practical applications, and there are disadvantages such as catalyst loss and reduced stability. Therefore, on the basis of the cuprous carbon nitride material, the present invention further prepares a magnetic copper-doped carbon nitride composite Fenton-like catalyst to overcome the above defects.

[0046] In some embodiments, the carbon nitride precursor includes at least one of melamine, dicyandiamide, and 3-amino-1,2,4-triazole, preferably melamine.

[0047] In some embodiments, the copper salt includes at least one of copper nitrate, copper sulfate, and copper chloride, preferably copper chloride, and more preferably copper chloride dihydrate.

[0048] In some embodiments, the solvent includes at least one of an ethanol-water solvent, a methanol-water solvent, and a glycerol-water solvent, preferably an ethanol-water solvent.

[0049] Specifically, the ethanol-water solvent is a mixed solution of ethanol and water; the methanol-water solvent is a mixed solution of methanol and water; the glycerol-water solvent is a mixed solution of glycerol and water.

[0050] In some embodiments, since the carbon nitride precursor has poor solubility in water, preferably, an ethanol aqueous solution is used for dissolution, wherein the volume ratio of ethanol to water is 1:1.

[0051] In some embodiments, the inert atmosphere includes at least one of nitrogen, helium, argon, and neon, preferably nitrogen.

[0052] In some embodiments, in the step of calcining in an inert atmosphere, the calcination temperature is 450-650°C and the time is 2-4 h; when the calcination temperature is too low, the degree of polymerization of carbon nitride is low and it is difficult to form an effective π-electron system; while when the calcination temperature is too high, the precursor decomposes excessively and it is also difficult to form an effective carbon nitride structure. Therefore, the calcination temperature of the present invention is 450-650°C.

[0053] In some embodiments, preferably, the calcination temperature is 600 °C and the time is 3 h.

[0054] In some embodiments, in step S1, the carbon nitride precursor is added to a solvent, and then a copper salt is added. After stirring, the solvent is evaporated, and then it is placed in a tube furnace or a muffle furnace for calcination to obtain a copper-doped graphitic carbon nitride material, i.e., cuprous carbon nitride material. To prevent the powder from being dispersed by the gas flow during calcination, preferably, the cuprous carbon nitride precursor is placed in a crucible with a lid for calcination. The cuprous material is relatively sensitive to air. When calcined in a muffle furnace, the surface layer of the precursor contacts the air and copper is converted into its oxide. When calcined in a tube furnace with an inert gas (such as nitrogen) passed through, the oxidation of copper can be prevented. As a further preference, the cuprous carbon nitride precursor is calcined in a tube furnace with nitrogen passed through.

[0055] In some embodiments, it is heated from room temperature to the calcination temperature at a heating rate of 3 - 10 °C / min and then calcined. Preferably, the heating rate is 10 °C / min.

[0056] In some embodiments, the relative molecular weight of polyethylene glycol is 100 - 600, and more preferably 400.

[0057] In some embodiments, in the step of adding the carbon nitride precursor to the solvent and then adding the copper salt, the molar mass ratio of the copper salt to the carbon nitride precursor is (0.01 - 2) mmol:(1 - 3) g. Preferably, the molar mass ratio of the copper salt to the carbon nitride precursor is (0.75 - 1.5) mmol:1 g, and more preferably 1.25 mmol:1 g.

[0058] In some embodiments, in step S1, the carbon nitride precursor is added to a solvent, and then a copper salt is added. After stirring, the solvent is evaporated and calcined under an inert atmosphere to obtain cuprous carbon nitride. Among them, the stirring time is 0.25 - 5 h, preferably 1 h.

[0059] In some embodiments, in step S2, the cuprous carbon nitride and iron trioxide are dispersed in water to obtain a suspension; then polyethylene glycol is added dropwise to the suspension. After stirring and self-assembly, it is separated, washed, and dried to obtain a magnetic copper-doped carbon nitride composite Fenton-like catalyst.

[0060] In some embodiments, in step S2, cuprous carbon nitride and iron oxide are dispersed in water, wherein the mass ratio of cuprous carbon nitride to iron oxide is (0.25 - 4):(0.25 - 4), preferably (1 - 4):(1 - 4), and more preferably (2 - 4):(2 - 4); in the magnetic copper-doped carbon nitride composite Fenton-like catalyst, cuprous carbon nitride is the main active component. When its content is small, the activity of the composite Fenton-like catalyst will be relatively small; while when the content of iron oxide is small, it will lead to insufficient cross-linking of polyethylene glycol and insufficient magnetism of the composite Fenton-like catalyst; as a further preference, the mass ratio of cuprous carbon nitride to iron oxide is 3:1.

[0061] In some embodiments, in step S2, the volume ratio of polyethylene glycol to water is (0.05 - 1):1, preferably (0.2 - 0.5):1, and more preferably 0.4:1.

[0062] In some embodiments, in step S2, the mass-volume ratio of cuprous carbon nitride to water is (0.03 - 0.12) g:(15 - 25) mL.

[0063] In some embodiments, in step S2, cuprous carbon nitride and iron oxide are dispersed in water, then polyethylene glycol is added, and after stirring, separation, washing, and drying, the magnetic copper-doped carbon nitride composite Fenton-like catalyst is obtained; wherein, the self-assembly stirring time is 1 - 4 h, preferably 3 h; as a preference, after the self-assembly is completed, a magnet is used to perform solid-liquid separation and washing on the above reaction solution, and after vacuum drying, the magnetic copper-doped carbon nitride composite Fenton-like catalyst is obtained.

[0064] The magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by the preparation method of the present invention has better Fenton-like catalytic performance under alkaline conditions than under acidic conditions; the principle is that the introduction of Cu can not only construct a Cu(I)-N electron bridge, enabling pyridine N to continuously transfer electrons in g-C3N4 to Cu as an electron donor, promoting the regeneration of Cu(I)-N and the decomposition of H2O2, but also enabling the electron-deficient C atom adjacent to pyridine N to act as a Lewis acid site. Under alkaline conditions, it adsorbs reactive oxygen or OH- together with Cu(II)-N to form a superoxide / hydroxyl complex, and then generates singlet oxygen through intramolecular electron transfer, reactive oxygen interaction, or self-disproportionation reaction, converting the CuFe@PEG-H2O2 system from the traditional free radical pathway to 1 an O2-dominated non-free radical system under alkaline conditions.

[0065] Polyethylene glycol (PEG) is a common low-cost linear polymer. Its terminal -OH can not only act as a Lewis acid site, but also the O atom in the monomer -CH2-O-CH2- can coordinate with metal ions. Therefore, when polyethylene glycol is added to the suspension system, the copper on the surface of cuprous carbon nitride and the Fe on the surface of magnetite will coordinate with polyethylene glycol, causing the polyethylene glycol to crosslink and form a network structure, and cuprous carbon nitride and magnetite are also coated therein, thus self-assembling to form a stable magnetic copper-doped carbon nitride composite Fenton-like catalyst.

[0066] Based on the same inventive concept, the present invention also provides a magnetic copper-doped carbon nitride composite Fenton-like catalyst, which is prepared by the above preparation method.

[0067] Based on the same inventive concept, the present invention also provides an application of the cuprous carbon nitride material prepared by the above preparation method, or the magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by the above preparation method, or the above magnetic copper-doped carbon nitride composite Fenton-like catalyst in treating organic wastewater.

[0068] Specifically, when using the cuprous carbon nitride material or the magnetic copper-doped carbon nitride composite Fenton-like catalyst for the pollutant degradation reaction, directly put the cuprous carbon nitride material or the magnetic copper-doped carbon nitride composite Fenton-like catalyst into the organic wastewater to be treated, and add H2O2; and the pollutant degradation rate is fast, and after the reaction, solid-liquid separation can be carried out by a magnet, and the operation is very simple, with great practical value.

[0069] In some embodiments, the above application includes the following steps: adding the cuprous carbon nitride material or the magnetic copper-doped carbon nitride composite Fenton-like catalyst to the organic wastewater, adjusting the pH of the organic wastewater to 3-12, and then adding H2O2.

[0070] In some embodiments, the pH of the organic wastewater is 3-12, more preferably 7-11, and even more preferably 11, that is, the wastewater to be treated is alkaline.

[0071] In some embodiments, the organic pollutant in the bag-treated organic wastewater is p-chlorophenol, and its concentration is 10-100 mg / L, more preferably 25-75 mg / L.

[0072] In some embodiments, the addition amount of the magnetic copper-doped carbon nitride composite Fenton-like catalyst is 0.25-2 g / L, preferably 0.75-1.75 g / L, and even more preferably 1.5 g / L.

[0073] In some embodiments, the concentration of the added H2O2 is 20 mM-70 mM, more preferably 40 mM.

[0074] In addition, during the treatment of organic wastewater, to ensure the uniform dispersion of the magnetic copper-doped carbon nitride composite Fenton-like catalyst in the Fenton-like reaction system, the reaction mixture was shaken by a constant temperature oscillator during the reaction, and the reaction temperature was 25°C.

[0075] The following further illustrates the magnetic copper-doped carbon nitride composite Fenton-like catalyst of the present application, its preparation method, and its application with specific examples. This part further illustrates the content of the present invention with specific examples, but should not be construed as a limitation to the present invention. Unless otherwise specified, the technical means adopted in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0076] The raw materials used in the following examples:

[0077] Melamine (analytical pure) and copper chloride dihydrate (analytical pure) were purchased from Macklin Biochemical Technology Co., Ltd. (Shanghai, China), iron oxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (Shanghai, China), hydrogen peroxide (30 wt.%) was purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China), and polyethylene glycol 400 (PEG-400) (analytical pure) was purchased from Shanghai Zhanyun Chemical Co., Ltd. (Shanghai, China). The water used in the experiments was ultrapure water (resistance ≥ 18.2 MΩ·cm -1 ).

[0078] Example 1

[0079] The present application provides a method for preparing a cuprous carbon nitride material, including the following steps:

[0080] Add 3 g of melamine to a mixed solution of 20 mL of ultrapure water and ethanol (the volume ratio of ultrapure water to ethanol is 1:1), then add 3.75 mmol of copper chloride dihydrate, continuously stir at 120°C, and after the water is evaporated, place it in a corundum crucible. Heat it to 600°C at a rate of 10°C / min in a nitrogen atmosphere and keep it for 3 h to obtain cuprous carbon nitride (Cu / CN).

[0081] Examples 2-8

[0082] The present application provides a method for preparing a magnetic copper-doped carbon nitride composite Fenton-like catalyst, including the following steps:

[0083] S1. Add 3 g of melamine to a mixed solution of 20 mL of ultrapure water and ethanol (the volume ratio of ultrapure water to ethanol is 1:1), then add 3.75 mmol of copper chloride dihydrate, continuously stir at 120°C, and after the water is evaporated, place it in a corundum crucible. Heat it to 600°C at a rate of 10°C / min in a nitrogen atmosphere and keep it for 3 h to obtain cuprous carbon nitride (Cu / CN);

[0084] S2. Add 20 mL of ultrapure water into a 100 mL beaker. Then add cuprous carbon nitride (Cu / CN) and Fe3O4 according to the mass in Table 1 below. After mechanical stirring evenly, add 4 mL of PEG - 400 dropwise and stir for 3 h. Finally, the solution turns dark green. Then, perform solid - liquid separation by a magnet, wash it 3 times with ultrapure water, put it into a vacuum drying oven and dry it at 50 °C. The sample obtained after grinding is the magnetic copper - doped carbon nitride composite Fenton - like catalyst (CuFe@PEG).

[0085] Table 1 - Dosages of Cu / CN and Fe3O4 in Examples 2 - 8

[0086] Example Mass of Cu / CN added (g) <![CDATA[Mass of Fe3O4 added (g)]]> 2 0.06 0.12 3 0.04 0.12 4 0.03 0.12 5 0.12 0.12 6 0.12 0.03 7 0.12 0.04 8 0.12 0.06

[0087] Comparative Example 1

[0088] This comparative example provides a catalyst, and its preparation method includes the following steps:

[0089] Add 20 mL of ultrapure water into a 100 mL beaker. Then add 0.12 g of the cuprous carbon nitride (Cu / CN) prepared in Example 1. After mechanical stirring evenly, add 4 mL of PEG - 400 dropwise and stir for 3 h. Then, perform centrifugation for solid - liquid separation, wash it 3 times with ultrapure water, put it into a vacuum drying oven and dry it at 50 °C. The catalyst Cu@PEG is obtained after grinding.

[0090] Comparative Example 2

[0091] This comparative example provides a catalyst, and its preparation method includes the following steps:

[0092] Add 20 mL of ultrapure water into a 100 mL beaker. Then add 0.12 g of Fe3O4 powder. After mechanical stirring evenly, add 4 mL of PEG - 400 dropwise and stir for 3 h. Then, perform solid - liquid separation by a magnet, wash it 3 times with ultrapure water, put it into a vacuum drying oven and dry it at 50 °C. The catalyst Fe@PEG is obtained after grinding.

[0093] Comparative Example 3

[0094] This comparative example provides a catalyst, which is Fe3O4 powder.

[0095] Comparative Examples 4 - 6

[0096] This comparative example provides a catalyst, and its preparation method includes the following steps:

[0097] Add 3 g of the carbon nitride precursor to a mixed solution of 20 mL of ultrapure water and ethanol (the volume ratio of ultrapure water to ethanol is 1:1) according to Table 2, then add 3.75 mmol of copper chloride dihydrate, continuously stir at 120 °C, and place it in a corundum crucible after the water has evaporated. As shown in Table 2, heat it to 600 °C at a rate of 10 °C / min in a nitrogen or air atmosphere and hold for 3 hours. The obtained powder is called Cu / CN-triazole, Cu / CN-dicyanamide, Cu / CN air .

[0098] Table 2 - Carbon nitride precursors and calcination atmospheres in the preparation of catalysts in Comparative Examples 4 to 6

[0099] Comparative Example Name of catalyst Cyanamide precursor used Calcination atmosphere 4 Cu / CN-triazole 3 - Amino - 1,2,4 - triazole Nitrogen 5 Cu / CN-dicyanamide Dicyandiamide Nitrogen 6 <![CDATA[Cu / CN air > Melamine Air

[0100] Comparative Example 7

[0101] This comparative example provides a catalyst, and its preparation method includes the following steps:

[0102] Put 3 g of melamine powder into a corundum crucible, heat it to 600 °C at a rate of 10 °C / min in a nitrogen atmosphere, and hold for 3 hours to obtain the catalyst g-C3N4.

[0103] Performance test

[0104] Characterization 1 of the catalyst

[0105] Figure 1 XRD patterns (XRD) of Cu / CN in Example 1, Cu / CN-triazole, Cu / CN-dicyanamide, and Cu / CN in Comparative Examples 4 to 6 air .

[0106] It can be seen from Figure 1 that the samples calcined in nitrogen formed a better graphite-phase carbon nitride structure. In the XRD patterns of Example 1, Comparative Example 4, and Comparative Example 5, the peaks at 2θ = 12.8 - 13.3° are attributed to the (100) crystal plane of the in-plane tris-s-triazine structure stacking of g-C3N4, and the sharp main peak at 27.9° corresponds to the interlayer stacking of the conjugated aromatic system; and in these three comparative example samples, no diffraction peaks corresponding to CuOx appeared, indicating that Cu was doped into the g-C3N4 lattice in a coordinated form. When calcined in an air atmosphere, Comparative Example 6 (Cu / CN air ), the color of the calcined material in the crucible showed "upper and lower stratification". The surface layer in contact with the air was fully oxidized to form reddish CuOx, while the interior was still grayish-green cuprous carbon nitride, and its in Figure 1The XRD in [it] also significantly differs from other comparative examples, with more CuO and Cu2O appearing, and the peaks of the carbon nitride lattice basically disappearing.

[0107] Characterization of the catalyst 2

[0108] In Example 7, during the preparation of the magnetic copper-doped carbon nitride composite Fenton-like catalyst, as Figures 2 - 4 shown, it is an image of a suspension formed by adding cuprous carbon nitride (Cu / CN) and Fe3O4 to ultrapure water; Figure 3 is an image of adding polyethylene glycol to the suspension system; ​ is an image of the suspension of the magnetic copper-doped carbon nitride composite Fenton-like catalyst self-assembled after adding polyethylene glycol and stirring. It can be seen from ​ that when the gray-green Cu / CN and black Fe3O4 are added to water, the two cannot spontaneously combine together. However, when polyethylene glycol is added and stirred, both can bind to the hydroxyl groups in the polyethylene glycol molecules. The linear polyethylene glycol is thus crosslinked to form a network structure, tightly binding Cu / CN and black Fe3O4 together to form a uniform composite material.

[0109] ​ are scanning electron images of CuFe@PEG prepared in Example 7 at different magnifications;

[0110] ​ is the scanning electron image of Cu / CN in Example 1.

[0111] From ​ it can be seen that for CuFe@PEG prepared in Example 7, the petal-like outward-extending flaky / lamellar stacking structure of the Cu / CN component can still be recognized, and the spherical nanoscale magnetite particles are evenly distributed / embedded on the surface of the catalyst.

[0112] Characterization of the catalyst 3

[0113] ​ are the X-ray diffraction patterns of CuFe@PEG in Example 7, Cu / CN in Example 1, Cu@PEG in Comparative Example 1, Fe@PEG in Comparative Example 2, and Fe3O4 in Comparative Example 3.

[0114] From ​ it can be seen that the XRD spectrum in Example 7 shows that the composite CuFe@PEG material retains the CNx(002) crystal plane at 27.8° and the vast majority of the crystal planes of magnetite, proving the successful composite of cuprous carbon nitride and Fe3O4.

[0115] ​ are the hysteresis loops of CuFe@PEG in Example 7 and Fe3O4 in Comparative Example 3;​ It is an image of the solid-liquid separation of CuFe@PEG after the reaction in Example 7 by a magnet.

[0116] From ​ it can be seen that the saturation magnetization of CuFe@PEG is 16.51 (emu / g), about 1 / 4 of that of Fe3O4 (76.44 emu / g), and is close to the combined ratio of Cu and Fe materials (3:1). From ​ it can be seen that after the catalytic reaction, CuFe@PEG can quickly achieve solid-liquid separation. After removing the external magnetic field, its relatively low residual magnetization compared to Fe3O4 enables it to redisperse into the solution faster (Fe3O4: 9.70 emu / g; CuFe@PEG: 1.72 emu / g).

[0117] Catalyst performance test

[0118] Add 50 mL of 50 mg / L 4-chlorophenol aqueous solution to a 100 mL conical flask, then add the prepared catalyst material (the addition amount is 1.0 g / L), place it in a constant temperature oscillator and oscillate for 15 min. Subsequently, add 40 mM of H2O2 to initiate the reaction (25 °C, 150 rpm); after oscillating for 2 h, take out some samples (i.e., the 4-chlorophenol aqueous solution after being treated with the catalyst) and filter them with a 0.22 μm polyethersulfone aqueous phase filter head, and analyze the content of the remaining 4-chlorophenol at 280 nm using an LC-2030C liquid chromatograph (LC, Shimadzu, Japan). Different initial pH values are adjusted with 0.1 M HCl and NaOH.

[0119] Catalytic performance test example 1

[0120] According to the above test method, using 4-chlorophenol (4-CP) as the target pollutant, the Fenton-like catalytic performance of the catalysts prepared in Example 1 and Comparative Examples 4-7 under alkaline conditions (pH = 11) was tested. As shown in Table 3, the catalyst prepared in Example 1 using melamine as the precursor has the highest catalytic activity, and 95% of 4-chlorophenol can be removed in 2 h; in contrast, the catalysts prepared in Comparative Examples 4 and 5 using 3-amino-1,2,4-triazole and dicyandiamide as the precursors have poor effects. Combining XRD analysis, the reason may be that the graphitic carbon nitride crystal structure formed by melamine is more complete and is more likely to combine with Cu to form more active sites; while Cu / CN prepared by calcination in air Air, the crystal structure of carbon nitride is not obvious, and Cu mainly exists in the form of oxides. Compared with being stabilized on carbon nitride through pyridine N, the former is more easily oxidized in water, resulting in a rapid decrease in the degradation reaction in the early stage and tending to stop in the later stage. In addition, g-C3N4 is usually used as a photocatalyst in the environmental remediation process. Therefore, the degradation activity of the catalyst Cu / CN prepared in Comparative Example 1 was tested under dark conditions. The results showed that the presence or absence of light had little effect on the degradation removal rate, indicating that the Fenton-like reaction played a dominant role in the degradation of pollutants.

[0121] Table 3 - Degradation removal rate of 4-CP by the catalyst prepared in the comparative example

[0122] ​ ​ ​ ​ ​ 93.62 ​ ​ 48.75 ​ ​ 71.49 ​ <![CDATA[Cu / CN Air > 63.42 ​ <![CDATA[g-C3N4]]> 35.02 ​ ​ 89.07

[0123] Catalytic performance test example 2

[0124] Add 50 mL of 50 mg / L 4-chlorophenol aqueous solution to a 100 mL conical flask, then add the Cu / CN prepared in Example 1 (the addition amount is 1.0 g / L), place it in a constant temperature oscillator and shake for 15 min. Subsequently, add 40 mM of H2O2 to start the reaction (25 °C, 150 rpm), and at the same time add furfuryl alcohol (FFA); different initial pH values are adjusted by 0.1 M HCl and NaOH.

[0125] Furfuryl alcohol (FFA) can react quantitatively with singlet oxygen 1 1O2. Therefore, add FFA to the reaction system, and perform pseudo-first-order reaction fitting with the change curve of FFA. The generation amount of 1 1O2 can be approximately obtained through its reaction rate constant. At different pH values, add the Cu / CN prepared in Example 1, and the generation amount of 1 1O2 in the system is shown in Table 4.

[0126] Table - 4 Generation amount of 1 1O2 under different pH conditions

[0127]

[0128]

[0129] As can be seen from Table 4 above, as the pH gradually increases (3 - 11), 1 the yield of 1O2 increases significantly. Thus, the Fenton system of the present invention has excellent catalytic degradation activity under strong alkaline conditions.

[0130] Catalytic performance test example 3

[0131] Add 50 mL of 50 mg / L 4-chlorophenol aqueous solution to a 100 mL conical flask, then add the prepared catalyst (the addition amount is 1.0 g / L) material, place it in a constant temperature oscillator and shake for 15 min, and then add 40 mM of H2O2 to initiate the reaction (25 °C, 150 rpm).

[0132] According to the above method, in order to explore the optimal composite ratio of cuprous carbon nitride and Fe3O4, the 4-CP degradation experiments were carried out on the catalysts prepared in Examples 2-8, Example 1, and Comparative Examples 1-3 under alkaline conditions (pH = 11). The results are shown in Table 5. As the proportion of the Fe3O4 component in the examples decreased and the proportion of the Cu / CN component increased, the 4-CP removal rate also increased accordingly. Combining the 4-CP removal rate results of the catalysts in Example 1 and Comparative Examples 1-3, it can be seen that in the catalytic reaction under alkaline conditions, the Cu / CN component plays a leading role, and the Fe3O4 component has limited contribution to the removal of 4-CP. When Cu / CN:Fe3O4 = 3:1 (i.e., Example 7), the catalytic removal ability of the raw material (Cu / CN) has reached 83.0%. However, when adding continuously, the remaining removal rate of 4-CP does not decrease but increases. At this time, the magnetic separation ability has been significantly reduced, and the loss of a large amount of Cu / CN components during the water washing process may conversely reduce the overall performance of the prepared material.

[0133] Table 5 - Degradation and removal rates of 4-CP by different samples

[0134]

[0135]

[0136] Performance test example 4

[0137] To evaluate the influence of the dosage of the composite catalyst prepared in Example 7 on the degradation of pollutants, the degradation experiment of 4-CP under different dosage conditions was carried out. The results are shown in Table 6.

[0138] The specific method is: add 50 mL of 50 mg / L 4-chlorophenol aqueous solution to a 100 mL conical flask, then add the catalyst prepared in Example 7 (the addition amount is 0.75 - 2.0 g / L) material, place it in a constant temperature oscillator and shake for 15 min, and then add 40 mM of H2O2 to initiate the reaction (25 °C, 150 rpm).

[0139] Table 6 - Removal rates of 4-CP by CuFe@PEG in Example 7 under different dosage conditions

[0140] ​ ​ 0.75 76.06 1 77.72 1.25 81.53 1.5 90.71 1.75 83.84 2 80.68

[0141] As can be seen from Table 7, when the dosage of CuFe@PEG in Example 7 was 0.75 - 1.5 g / L, with the increase of the catalyst dosage, due to the increase in active sites, the removal rate of 4-CP also increased accordingly; however, when the dosage exceeded 1.5 g / L, due to the rapid consumption of H2O2, the removal rate decreased slowly with the increase of the dosage. Therefore, under these conditions, 1.5 g / L was the optimal dosage of CuFe@PEG in Example 7.

[0142] Performance test example 5

[0143] To evaluate the catalytic performance and stability of the composite catalyst prepared in Example 7 under different pH conditions, at an addition amount of 1.5 g / L of the catalyst, the catalytic degradation performance of CuFe@PEG in Example 7 on 4-CP at different pH values, as well as the leaching of Cu and Fe in CuFe@PEG during this process, were tested. The results are as ​ shown. The specific method was as follows: 50 mL of 50 mg / L p-chlorophenol aqueous solution was added to a 100 mL conical flask, and then CuFe@PEG prepared in Example 7 (the addition amount was 1.5 g / L) was added. It was placed in a constant temperature oscillator and shaken for 15 min, and then 40 mM of H2O2 was added to initiate the reaction (25 °C, 150 rpm); different initial pH values were adjusted with 0.1 M HCl and NaOH.

[0144] As can be seen from ​ it, with the increase of pH, the degradation rate of 4-CP also increased accordingly, rising from 41.2% at pH = 3 to 90.7% at pH = 11. At the same time, the leaching amounts of Cu and Fe also gradually decreased, dropping to 0.007 mg / L and 0.056 mg / L respectively at pH = 11. In contrast, the leaching amount of Cu in the reaction of Cu / CN in Example 1 was 0.32 mg / L at pH = 11. It can be seen that after compounding, the stability of the active component cuprous carbonitride in the reaction was improved. This was because with the assistance of PEG, the copper in the cuprous carbonitride on the material surface coordinated with the O atom in the terminal hydroxyl group / monomer of PEG to form a PEG-metal complex, preventing the leaching of copper, thereby playing a role in stabilizing the active component.

[0145] Performance test example 6

[0146] To evaluate the recycling performance of the CuFe@PEG prepared in Example 7 (dosage 1.5 g / L), after each reaction, solid-liquid separation was carried out using a magnet, and then fresh 4-CP solution and H2O2 were added for the next recycling experiment. Meanwhile, Cu / CN in Example 1 (dosage 1.0 g / L) was used as a comparison. After each reaction, centrifugation was carried out, the catalyst was dried and then added to fresh 4-CP solution and H2O2 in proportion for the next recycling experiment. The recycling results are shown in Table 7.

[0147] Table 7 - Recycling effects of CuFe@PEG in Example 7 and Cu / CN in Example 1

[0148]

[0149]

[0150] As can be seen from Table 7, after 4 cycles, the removal rate of 4-CP by CuFe@PEG in Example 7 slightly decreased from 90.71% to 88.55%, with a decrease amplitude of only 2.16%; while that of Cu / CN decreased from 93.62% to 73.13%, with a decrease amplitude of 20.49%. It can be seen that after compounding, not only is the original cuprous carbon nitride easier to separate, but also its use stability is greatly improved.

[0151] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a magnetic copper-doped carbon nitride composite Fenton-like catalyst, characterized in that, It includes the following steps: Disperse cuprous carbon nitride material and magnetite in water, then add polyethylene glycol, stir, separate, wash, and dry to obtain a magnetic copper-doped carbon nitride composite Fenton-like catalyst; A preparation method of cuprous carbon nitride material, including the following steps: Add a carbon nitride precursor to a solvent, then add a copper salt, stir, evaporate the solvent, and calcine in an inert atmosphere to obtain cuprous carbon nitride material; The carbon nitride precursor is melamine; The copper salt includes at least one of copper nitrate, copper sulfate, and copper chloride; The solvent includes at least one of ethanol-water solvent, methanol-water solvent, and glycerol-water solvent; In the step of adding a copper salt after adding a carbon nitride precursor to a solvent, the molar mass ratio of the copper salt to the carbon nitride precursor is 3.75 mmol: 3 g; In the step of calcining in an inert atmosphere, the calcination temperature is 600 °C and the time is 3 h; The relative molecular weight of the polyethylene glycol is 400; in the step of dispersing cuprous carbon nitride material and magnetite in water and then adding polyethylene glycol, the mass ratio of cuprous carbon nitride to magnetite is 3:1, the volume ratio of polyethylene glycol to water is 0.2:1, and the mass-volume ratio of cuprous carbon nitride to water is 0.12 g: 20 mL.

2. The preparation method of the magnetic copper-doped carbon nitride composite Fenton-like catalyst according to claim 1, wherein, The inert atmosphere includes at least one of nitrogen, helium, argon, and neon; 3. The preparation method of the magnetic copper-doped carbon nitride composite Fenton-like catalyst according to claim 1, wherein Heat from room temperature to the calcination temperature at a heating rate of 3 - 10 °C / min and then conduct calcination; 4. A magnetic copper-doped carbon nitride composite Fenton-like catalyst, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 3; 5. Application of a magnetic copper-doped carbon nitride composite Fenton-like catalyst prepared by using the preparation method described in any one of claims 1 - 3 or the magnetic copper-doped carbon nitride composite Fenton-like catalyst described in claim 4 in treating organic wastewater.

6. The application according to claim 5, comprising the following steps: Add the magnetic copper-doped carbon nitride composite Fenton-like catalyst to organic wastewater, adjust the pH of the organic wastewater to 3 - 12, and then add H2O2.

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