Preparation method and application of modified nanocomposite materials for efficient visible light catalytic formaldehyde removal

Abstract

The invention provides a preparation method and application of a modified nanocomposite material for efficient visible light catalytic formaldehyde removal, belonging to the technical field of photocatalytic oxidation. The invention aims to prepare a photocatalyst with a wide light absorption range and good catalytic performance through the preparation method, and avoid the situation in which the current photocatalyst has rapid photoinduced carrier recombination. The preparation method comprises: calcining a carbon-nitrogen source to prepare g-C3N4; wherein the carbon-nitrogen source is a nitrogen-containing organic matter with a carbon-nitrogen ratio of 1:2; preparing NaFeS2 by a hydrothermal synthesis method using Fe2O3 as an iron source and Na2S2O3·5H2O as a sodium source and a sulfur source; adding the g-C3N4 and the NaFeS2 in a mass ratio of 1-3:1 to anhydrous ethanol, ultrasonically vibrating for 4-6 hours, washing the resultant several times, vacuum drying it, and calcining it at 300-500°C for 1 hour to obtain the modified nanocomposite material, namely g-C3N4 / NaFeS2.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic oxidation, and in particular to a preparation method and application of a modified nanomaterial for efficient visible light catalytic formaldehyde removal. Background Art

[0002] Volatile organic compounds (VOCs) are precursors of atmospheric photochemical formation of O3 and fine particulate matter, posing a huge threat to human health and the ecological environment. They are mainly organic compounds with a boiling point of 50 to 260°C, including benzene, toluene, xylene, styrene, chlorinated organics, ketones and lower alcohols.

[0003] Formaldehyde in the air primarily comes from decoration materials, furniture, incomplete combustion of traditional fuels, smoke, and cosmetics. Short-term exposure to formaldehyde can irritate organs and cause adverse symptoms. Long-term exposure to indoor air pollutants is detrimental to health and can lead to sick building syndrome, building-related illnesses, and, in extreme cases, cancer. Formaldehyde has been designated a carcinogenic pollutant by various countries and urgently requires action.

[0004] Currently, a variety of technologies have been developed to control formaldehyde pollution, including adsorption, plasma, and photocatalytic oxidation. Adsorption, which utilizes the strong adsorption capacity of adsorbents such as activated carbon, molecular sieves, and silica gel, removes formaldehyde. Both physical and chemical adsorption methods are available, but these methods have limited adsorption capacity and are cumbersome to process. Plasma, through gas discharge, generates a large number of active species that react with formaldehyde to achieve formaldehyde removal. This method is highly efficient, but also consumes a lot of energy. Compared to the first two, photocatalytic oxidation offers simpler conditions, is green and energy-efficient, and can remove formaldehyde at room temperature and pressure.

[0005] However, in the actual application of photocatalytic oxidation, most of the existing photocatalysts have disadvantages such as wide bandgap, limited range of light absorption wavelength, and mismatch of energy band positions, which lead to limited catalytic effect of photocatalysts; therefore, improving the catalytic performance of photocatalysts is a hot topic of current research. Summary of the Invention

[0006] In view of this, the present invention aims to propose a preparation method and application of a modified nanomaterial for efficient visible light catalytic formaldehyde removal, so as to solve the problem of low catalytic performance of current photocatalysts.

[0007] The first aspect of the present invention provides a method for preparing a modified nanocomposite material for efficient visible light catalytic formaldehyde removal, the method comprising:

[0008] Step 1, calcining a carbon-nitrogen source to prepare g-C3N4; wherein the carbon-nitrogen source is a nitrogen-containing organic matter with a carbon-nitrogen ratio of 1:2;

[0009] Step 2, using Fe2O3 as an iron source and Na2S2O3·5H2O as a sodium source and a sulfur source, to prepare NaFeS2 by a hydrothermal synthesis method;

[0010] Step 3, adding the g-C3N4 and the NaFeS2 in a mass ratio of 1-3:1 to anhydrous ethanol, ultrasonically shaking for 4-6 hours, washing the resultant several times, vacuum drying, and calcining at 300-500°C for 1 hour to obtain the modified nanocomposite material - g-C3N4 / NaFeS2.

[0011] Furthermore, in step 1, the carbon and nitrogen source is calcined to prepare g-C3N4, comprising:

[0012] The crucible containing the carbon and nitrogen source is placed in a muffle furnace, heated to 500-600°C at a heating rate of 2-10°C / min, and calcined for 3-5h to obtain the g-C3N4.

[0013] Furthermore, in step 2, NaFeS2 is prepared by a hydrothermal synthesis method using Fe2O3 as an iron source, Na2S2O3·5H2O as a sodium source and a sulfur source, comprising:

[0014] Step 2-1, adding the Fe2O3 and the Na2S2O3·5H2O in a molar ratio of 1:1-2 to ethylenediamine, heating and stirring to mix uniformly;

[0015] Step 2-2, transferring the mixed solution obtained in step 2-1 into a high-pressure reactor and subjecting it to a hydrothermal reaction at 200° C. for 24 hours;

[0016] Step 2-3, cooling the result of step 2-2, washing, and vacuum drying to obtain the NaFeS2.

[0017] Furthermore, in step 1, the carbon and nitrogen source includes any one of cyanamide, dicyandiamide, melamine and urea.

[0018] Furthermore, in step 1, the carbon and nitrogen source is melamine.

[0019] Furthermore, in step 3, the mass ratio of the g-C3N4 and the NaFeS2 is 2:1.

[0020] Furthermore, in step 3, the washing of the obtained product several times and vacuum drying comprises:

[0021] After the resultant was washed alternately with ethanol and deionized water for 6-10 times, the resultant was placed in an oven and vacuum dried at 60-80° C. for 8-12 hours.

[0022] The second aspect of the present invention provides a modified nanocomposite material for efficient visible light catalytic formaldehyde removal prepared by the preparation method described in the first aspect.

[0023] Furthermore, in the modified nanocomposite material, the g-C3N4 and NaFeS2 form a heterojunction.

[0024] The third aspect of the present invention provides an application of a modified nano-composite material for efficient visible light catalytic formaldehyde removal, wherein the modified nano-composite material is prepared by the preparation method of the modified nano-composite material for efficient visible light catalytic formaldehyde removal described in the first aspect and is used to remove formaldehyde in the air.

[0025] Compared with the prior art, the preparation method of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal of the present invention has the following advantages:

[0026] The present invention provides a method for preparing a modified nanocomposite material for efficient visible light catalytic formaldehyde removal, comprising: step 1, calcining a carbon-nitrogen source to prepare g-C3N4; wherein the carbon-nitrogen source is a small molecular weight nitrogen-containing organic matter with a carbon-nitrogen ratio of 1:2; step 2, using Fe2O3 as an iron source and Na2S2O3·5H2O as a sodium source and a sulfur source, preparing NaFeS2 by a hydrothermal synthesis method; step 3, adding the g-C3N4 and the NaFeS2 in a mass ratio of 1-3:1 to anhydrous ethanol, ultrasonically shaking for 4-6 hours, washing the resultant several times, vacuum drying, and then heating at 3000 ℃ for 10 minutes. The modified nanocomposite material, g-C3N4 / NaFeS2, is calcined at 100-500°C for 1h. Thus, the present invention compounds NaFeS2 with g-C3N4 to form a heterojunction, thereby increasing the specific surface area of ​​g-C3N4 and expanding the light absorption range of g-C3N4, thereby preparing a modified nanocomposite material with a higher specific surface area, a higher visible light response capability and a longer photoexcited carrier lifetime. The modified nanocomposite material prepared by the present invention is applied to photocatalytic formaldehyde removal, and can achieve a removal rate of more than 97% within 2h, with good photocatalytic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 A flow chart showing the steps of a method for preparing a modified nanocomposite material for efficient visible light catalytic formaldehyde removal provided by an embodiment of the present invention is shown;

[0029] Figure 2The electron microscope scanning image of g-C3N4 / NaFeS2 prepared in Example 1 of the present invention is shown;

[0030] Figure 3 The UV diffuse reflectance spectra of g-C3N4 / NaFeS2 prepared in Example 1 of the present invention, g-C3N4 prepared in Comparative Example 1, and NaFeS2 prepared in Comparative Example 2 are shown;

[0031] Figure 4 The Fourier transform infrared spectra of g-C3N4 / NaFeS2 prepared in Example 1 of the present invention, g-C3N4 prepared in Comparative Example 1, and NaFeS2 prepared in Comparative Example 2 are shown;

[0032] Figure 5 A comparison chart of formaldehyde removal performance of g-C3N4 / NaFeS2 prepared in Examples 1, 2, and 3 of the present invention and g-C3N4 prepared in Comparative Example 1 and NaFeS2 prepared in Comparative Example 2 is shown;

[0033] Figure 6 A graph showing the photocatalytic performance of g-C3N4 / NaFeS2 prepared in Example 2 of the present invention is shown. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purpose, feature and a little bit of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Below is a detailed description of the embodiment of the present invention. This embodiment is implemented under the premise of the technical solution of the present invention, and provides detailed implementation methods and specific operating procedures, but the protection scope of the present invention is not limited to the following examples. If specific experimental steps or conditions are not specified in the embodiment, the operation or conditions of the conventional experimental steps described in the prior art in this area can be carried out. If the manufacturer of the reagents and other instruments is not specified, they are all conventional reagent products that can be obtained by commercial purchase.

[0035] Formaldehyde is a major indoor air pollutant and a major volatile organic compound (VOC). Formaldehyde in the air primarily comes from decoration materials, furniture, incomplete combustion of traditional fuels, smoke, and cosmetics. Short-term exposure to formaldehyde can irritate organs and cause adverse symptoms. Long-term exposure to indoor air pollutants is detrimental to health and may lead to sick building syndrome, building-related illnesses, and, in extreme cases, cancer. Therefore, effective formaldehyde removal is crucial for improving air quality and protecting human health.

[0036] Currently, methods for removing formaldehyde include adsorption, plasma, and photocatalytic oxidation. Adsorption, which utilizes the strong adsorption capacity of adsorbents such as activated carbon, molecular sieves, and silica gel, removes formaldehyde. This method includes both physical and chemical adsorption, but its adsorption capacity is limited and the process is cumbersome. Plasma removes formaldehyde by generating a large number of active species through gas discharge, which react with formaldehyde. This method is highly efficient but also consumes a lot of energy. Photocatalytic oxidation, driven by sunlight absorbed by a photocatalyst, offers advantages such as mild reaction conditions, environmental friendliness, energy conservation, and high multi-pollutant removal efficiency.

[0037] However, the catalytic performance of the photocatalyst in the photocatalytic oxidation method has a significant impact on its effectiveness in removing formaldehyde. Most photocatalysts currently used in photocatalytic oxidation methods suffer from shortcomings such as a wide bandgap, a limited range of light absorption wavelengths, and mismatched energy band positions. These shortcomings limit the catalytic performance of the photocatalyst, leading to low formaldehyde removal efficiency. For example, graphite carbon nitride (g-C3N4) has excellent thermal and chemical stability, a medium bandgap, and a structure similar to graphene. However, when used as a photocatalyst, the recombination rate of photoinduced charge carriers is too rapid, resulting in limited catalytic performance. Therefore, using pure g-C3N4 as a photocatalyst to remove formaldehyde has limited effectiveness.

[0038] In view of this, the present invention provides a method for preparing and applying a modified nanocomposite material for efficient visible light catalytic formaldehyde removal. The method comprises preparing g-C3N4, then preparing NaFeS2, and finally compounding NaFeS2 and g-C3N4 to obtain a modified nanocomposite material, namely g-C3N4 / NaFeS2. Thus, by forming a thin layer of NaFeS2 on the surface of g-C3N4, NaFeS2 is effectively coupled with g-C3N4, thereby increasing the specific surface area of ​​g-C3N4 and expanding the light absorption wavelength range. This avoids the situation where the photogenerated carrier recombination velocity is too fast when pure g-C3N4 is used as a photocatalyst, thereby improving the catalytic performance of g-C3N4. The g-C3N4 / NaFeS2 prepared by the present invention is used as a photocatalyst and has good application prospects in the removal of formaldehyde.

[0039] The preparation method and application of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal of the present invention will be described in detail below with reference to the accompanying drawings and in combination with examples.

[0040] A first aspect of the embodiments of the present invention provides a method for preparing a modified nanocomposite material for efficient visible light catalytic formaldehyde removal.

[0041] Reference Figure 1 , Figure 1The flowchart of the steps of the preparation method of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal provided by the embodiment of the present invention is shown as follows: Figure 1 As shown, the method includes:

[0042] S1, calcining the carbon and nitrogen source to prepare g-C3N4.

[0043] Among them, g-C3N4 is a polymer semiconductor, which is generally produced through a nitrogen-rich precursor (such as dicyandiamide, urea, melamine, thiourea, etc.). The generally used precursor is a carbon-nitrogen source, which is a nitrogen-containing organic matter with a carbon-nitrogen ratio of 1:2. The nitrogen-containing organic matter is a small molecular weight nitrogen-containing organic matter. The g-C3N4 is obtained by the polymerization of the small molecular weight nitrogen-containing organic matter.

[0044] Specifically, the steps of preparing g-C3N4 are: placing a crucible containing the carbon and nitrogen source in a muffle furnace, heating it to 500-600°C at a heating rate of 2-10°C / min, and calcining it for 3-5h to obtain the g-C3N4.

[0045] In an embodiment of the present invention, the carbon and nitrogen source includes any one of cyanamide, dicyandiamide, melamine, and urea, and the crucible is an alumina crucible. After calcination, a yellow block is obtained, and the yellow block is ground to obtain powdered g-C3N4.

[0046] For example, a crucible containing cyanamide is placed in a muffle furnace, heated to 500-600° C. at a heating rate of 2-10° C. / min, and calcined for 3-5 hours to obtain the g-C 3 N 4 .

[0047] The crucible containing melamine is placed in a muffle furnace, heated to 500-600°C at a heating rate of 2-10°C / min, and calcined for 3-5 hours to obtain the g-C3N4.

[0048] The crucible containing melamine is placed in a muffle furnace, heated to 500-600°C at a heating rate of 2-10°C / min, and calcined for 3-5 hours to obtain the g-C3N4.

[0049] The crucible containing urea is placed in a muffle furnace, heated to 500-600°C at a heating rate of 2-10°C / min, and calcined for 3-5 hours to obtain the g-C3N4.

[0050] Preferably, melamine is calcined as a carbon and nitrogen source to prepare g-C3N4. This is because melamine has the advantages of high hardness, wear resistance and heat resistance, and is not easily decomposed during the calcination process to produce impurities.

[0051] S2, NaFeS2 was prepared by hydrothermal synthesis using Fe2O3 as iron source and Na2S2O3·5H2O as sodium source and sulfur source.

[0052] Among them, NaFeS2 has inherent magnetic and photoelectric properties. Due to its excellent photoelectric properties, it has been used as glass carbon powder and positive electrode materials. However, the material properties and other applications of NaFeS2 are less studied. However, due to its deep valence band position and narrow band gap (2.01eV), NaFeS2 has good application prospects in the field of photocatalysis. Therefore, in the embodiment of the present invention, NaFeS2 is used in the preparation of photocatalysts and combined with other semiconductors to prepare photocatalysts with better formaldehyde removal effects.

[0053] Specifically, the steps of preparing NaFeS2 include:

[0054] S201, Fe2O3 and Na2S2O3·5H2O are added to ethylenediamine in a molar ratio of 1:1-2, and heated and stirred to mix uniformly.

[0055] For example, the molar ratio of Fe2O3 and Na2S2O3·5H2O is 1:1;

[0056] The molar ratio of Fe2O3 and Na2S2O3·5H2O is 1:1.5;

[0057] The molar ratio of Fe2O3 and Na2S2O3·5H2O is 1:2.

[0058] S202, transferring the mixed solution obtained in S201 to a high-pressure reactor and performing a hydrothermal reaction at 200° C. for 24 hours.

[0059] S203, cooling the product obtained in S202, washing it, and vacuum drying it to obtain NaFeS2.

[0060] S3, adding the g-C3N4 and the NaFeS2 in a mass ratio of 1-3:1 to anhydrous ethanol, ultrasonically shaking for 4-6 hours, washing the resultant several times, vacuum drying, and calcining at 300-500°C for 1 hour to obtain the modified nanocomposite material - g-C3N4 / NaFeS2.

[0061] Specifically, the steps of washing the resultant several times and vacuum drying are as follows: after the resultant is washed alternately with ethanol and deionized water for 6-10 times, the resultant is placed in an oven and vacuum dried at 60-80° C. for 8-12 hours.

[0062] In the embodiment of the present invention, considering that ultrasound can provide energy to cause liquid particles to interact violently, thereby accelerating the dissolution or reaction process of the substance, ultrasonic oscillation is used to accelerate the mixing process of g-C3N4 and NaFeS2, and then calcination is performed to obtain g-C3N4 / NaFeS2.

[0063] For example, the g-C3N4 and the NaFeS2 in a mass ratio of 1:1 are added to anhydrous ethanol;

[0064] Adding the g-C3N4 and the NaFeS2 in a mass ratio of 2:1 into anhydrous ethanol;

[0065] The g-C3N4 and the NaFeS2 in a mass ratio of 3:1 were added to anhydrous ethanol.

[0066] In the practice of the present invention, since the photocatalytic effect of the modified nanocomposite material prepared with a mass ratio of 2:1 is the best when g-C3N4 / NaFeS2 is used as a photocatalyst, it is preferred to use g-C3N4 and NaFeS2 with a mass ratio of 2:1 to prepare the modified nanocomposite material.

[0067] In some embodiments, in order to prepare the modified nanocomposite material in one step, after g-C3N4 is prepared, the prepared g-C3N4 can be directly added to the process of preparing NaFeS2 to directly obtain the modified nanocomposite material. For example, after Fe2O3 and Na2S2O3·5H2O are mixed, g-C3N4 is added, and then the mixture is transferred to a high-pressure reactor for hydrothermal reaction to prepare the modified nanocomposite material.

[0068] In some embodiments, since there are many methods for preparing NaFeS2, the reactants or preparation methods used can be adjusted as needed. For example, ferric nitrate and sodium sulfide can be used as iron source, sodium source and sulfur source respectively to prepare NaFeS2 by hydrothermal method, or calcination method can be used to prepare NaFeS2. The present invention does not impose specific restrictions.

[0069] A second aspect of the embodiments of the present invention provides a modified nanocomposite material prepared by the preparation method described in the first aspect.

[0070] Among them, the modified nanocomposite material is g-C3N4 / NaFeS2, whose light absorption range can cover the entire visible spectrum; its microscopic morphology is a block structure loaded with nanoparticles.

[0071] Furthermore, in the modified nanocomposite material, the g-C3N4 and the NaFeS2 form a heterojunction.

[0072] Among them, the heterojunction is the interface area formed by the contact between two different semiconductors. Under the condition of light excitation, the heterojunction can realize the interface transfer and spatial separation of electrons and holes, which can avoid the problem of low photocatalytic performance caused by rapid recombination of photoinduced carriers.

[0073] The modified nanocomposite material provided in the embodiment of the present invention has the same advantages as the preparation method of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal over the prior art, which will not be described in detail here.

[0074] The third aspect of the present invention provides an application of a modified nano-composite material for efficient visible light catalytic formaldehyde removal, wherein the modified nano-composite material is prepared by the preparation method of the modified nano-composite material for efficient visible light catalytic formaldehyde removal described in the first aspect and is used to remove formaldehyde in the air.

[0075] In an embodiment of the present invention, g-C3N4 / NaFeS2 can be applied to formaldehyde, SO2, ammonia, nitrogen oxides, etc. in the air. Preferably, the modified nanocomposite material for high-efficiency visible light catalytic formaldehyde removal prepared in an embodiment of the present invention is used as a photocatalyst to remove formaldehyde.

[0076] Formaldehyde was removed using g-C3N4 / NaFeS2 prepared by an embodiment of the present invention. Under the conditions of a mass ratio of g-C3N4 to NaFeS2 of 2:1, light irradiation of 2 standard suns, a catalyst dosage of 0.25 g / L, and an initial formaldehyde concentration of 15 ppm, the formaldehyde removal efficiency reached 97.2% after 2 hours. It can be seen that the modified nanocomposite material - g-C3N4 / NaFeS2 prepared by the preparation method provided by an embodiment of the present invention has good application prospects in the removal of formaldehyde in the air.

[0077] The application of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal provided by the embodiment of the present invention has the same advantages as the preparation method of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal over the prior art, which will not be elaborated here.

[0078] The embodiment of the present invention first prepares g-C3N4 and NaFeS2; then, adds the g-C3N4 and the NaFeS2 in a mass ratio of 1-3:1 to anhydrous ethanol, ultrasonically shakes for 4-6 hours, washes the resultant several times, vacuum-dries, and calcines at 300-500°C for 1 hour to obtain the modified nano-composite material - g-C3N4 / NaFeS2; thus, the present invention compounds NaFeS2 with g-C3N4 to form a heterojunction, increases the specific surface area of ​​g-C3N4, and expands the light absorption range of g-C3N4, thereby preparing a modified nano-composite material with a high specific surface area, a high visible light response ability, and a long photoexcited carrier lifetime. The modified nano-material prepared by the present invention is applied to photocatalytic formaldehyde removal, and can achieve a removal rate of more than 97% within 2 hours, with good photocatalytic effect.

[0079] In order to enable those skilled in the art to better understand the present invention, the preparation method and application of the modified nanocomposite material for efficient visible light catalytic formaldehyde removal of the present invention are described below through multiple specific examples.

[0080] Example 1

[0081] Step 1: Calcine 5g of melamine at 550°C for 4h at a heating rate of 10°C / min. After cooling to room temperature, grind the resulting yellow mass to obtain g-C3N4 powder.

[0082] Step 2: Dissolve 0.01 mol of Fe₂O₃ and 0.02 mol of Na₂S₂O₃·5H₂O in 30 mL of ethylenediamine. Stir vigorously at 60°C for 20 min, transfer to a 50 mL autoclave reactor, hydroheat at 200°C for 24 h, cool, and centrifuge. Rinse with water and ethanol. Dry in a vacuum oven at 80°C for 6 h.

[0083] Step 3: Separately, 50 mg of the prepared g-C3N4 and 50 mg of NaFeS2 were placed in 40 mL of anhydrous ethanol and subjected to continuous ultrasonication for 4 hours to allow for full reaction. Finally, the mixture was washed three times with ethanol and three times with water, then vacuum-dried at 80°C overnight. The dried product was calcined at 500°C for 1 hour to obtain g-C3N4 / NaFeS2, which was named CN / NFS-1.

[0084] Example 2

[0085] Step 1: Calcine 5g of melamine at 550°C for 4h at a heating rate of 10°C / min. After cooling to room temperature, grind the resulting yellow mass to obtain g-C3N4 powder.

[0086] Step 2: Dissolve 0.01 mol of Fe₂O₃ and 0.02 mol of Na₂S₂O₃·5H₂O in 30 mL of ethylenediamine. Stir vigorously at 60°C for 20 min, transfer to a 50 mL autoclave reactor, hydroheat at 200°C for 24 h, cool, and centrifuge. Rinse with water and ethanol. Dry in a vacuum oven at 80°C for 6 h.

[0087] Step 3: Separately, 100 mg of the prepared g-C3N4 and 50 mg of NaFeS2 were placed in 40 mL of anhydrous ethanol and subjected to continuous ultrasonication for 4 hours to allow for a complete reaction. Finally, the mixture was washed three times with ethanol and three times with water, then vacuum-dried at 80°C overnight. The dried product was calcined at 500°C for 1 hour to obtain g-C3N4 / NaFeS2, which was named CN / NFS-2.

[0088] Example 3

[0089] Step 1: Calcine 5g of melamine at 550°C for 4h at a heating rate of 10°C / min. After cooling to room temperature, grind the resulting yellow mass to obtain g-C3N4 powder.

[0090] Step 2: Dissolve 0.01 mol of Fe₂O₃ and 0.02 mol of Na₂S₂O₃·5H₂O in 30 mL of ethylenediamine. Stir vigorously at 60°C for 20 min, transfer to a 50 mL autoclave reactor, hydroheat at 200°C for 24 h, cool, and centrifuge. Rinse with water and ethanol. Dry in a vacuum oven at 80°C for 6 h.

[0091] Step 3: Separately, 150 mg of the prepared g-C3N4 and 50 mg of NaFeS2 were placed in 40 mL of anhydrous ethanol and subjected to continuous ultrasonication for 4 hours to allow for a complete reaction. Finally, the mixture was washed three times with ethanol and three times with water, then vacuum-dried at 80°C overnight. The dried product was calcined at 500°C for 1 hour to obtain g-C3N4 / NaFeS2, which was named CN / NFS-3.

[0092] Example 4

[0093] Step 1: Calcine 5g of melamine at 550°C for 4h at a heating rate of 10°C / min. After cooling to room temperature, grind the resulting yellow mass to obtain g-C3N4 powder.

[0094] Step 2: Dissolve 0.01 mol of Fe₂O₃ and 0.02 mol of Na₂S₂O₃·5H₂O in 30 mL of ethylenediamine. Stir vigorously at 60°C for 20 min, transfer to a 50 mL autoclave reactor, hydroheat at 200°C for 24 h, cool, and centrifuge. Rinse with water and ethanol. Dry in a vacuum oven at 80°C for 6 h.

[0095] Step 3: Separately, 75 mg of the prepared g-C3N4 and 50 mg of NaFeS2 were placed in 40 mL of anhydrous ethanol and subjected to continuous ultrasonication for 4 hours to allow for a complete reaction. Finally, the mixture was washed with ethanol and water three times each, then vacuum-dried at 80°C overnight. The dried product was calcined at 500°C for 1 hour to obtain g-C3N4 / NaFeS2.

[0096] Example 5

[0097] Step 1: Calcine 5g of melamine at 550°C for 4h at a heating rate of 10°C / min. After cooling to room temperature, grind the resulting yellow mass to obtain g-C3N4 powder.

[0098] Step 2: Dissolve 0.01 mol of Fe₂O₃ and 0.02 mol of Na₂S₂O₃·5H₂O in 30 mL of ethylenediamine. Stir vigorously at 60°C for 20 min, transfer to a 50 mL autoclave reactor, hydroheat at 200°C for 24 h, cool, and centrifuge. Rinse with water and ethanol. Dry in a vacuum oven at 80°C for 6 h.

[0099] Step 3: Separately, 125 mg of the prepared g-C3N4 and 50 mg of NaFeS2 were placed in 40 mL of anhydrous ethanol and subjected to continuous ultrasonication for 4 hours to allow for a complete reaction. Finally, the mixture was washed with ethanol and water three times each, then vacuum-dried at 80°C overnight. The dried product was calcined at 500°C for 1 hour to obtain g-C3N4 / NaFeS2.

[0100] Comparative Example 1

[0101] 5 g of melamine was calcined at 550°C for 4 h at a heating rate of 10°C / min. After cooling to room temperature, the resulting yellow mass was ground to produce g-C3N4 powder.

[0102] Comparative Example 2

[0103] Dissolve 0.01 mol of Fe₂O₃ and 0.02 mol of Na₂S₂O₃·5H₂O in 30 mL of ethylenediamine. Stir vigorously at 60°C for 20 minutes, then transfer to a 50 mL autoclave reactor and hydroheat at 200°C for 24 hours. Cool and centrifuge. Wash with water and ethanol. Dry in a vacuum oven at 80°C for 6 hours to obtain NaFeS₂.

[0104] Figure 2 The SEM image of the modified nanocomposite prepared in Example 2 is shown. Figure 2 It can be seen that the micromorphology of g-C3N4 is flake-like, the micromorphology of NaFeS2 is granular, and g-C3N4 / NaFeS2 is a block nanosheet-carrying nanoparticle structure.

[0105] Figure 3 The UV diffuse reflectance spectra of g-C3N4 / NaFeS2 prepared in Example 2, g-C3N4 prepared in Comparative Example 1, and NaFeS2 prepared in Comparative Example 2 are shown; Figure 3 It can be seen that the absorption edge of g-C3N4 is around 450nm, while in g-C3N4 / NaFeS2, due to the addition of NaFeS2, the light absorption range is extended to the entire visible light. Therefore, g-C3N4 / NaFeS2 has stronger light absorption ability, wider light absorption range, and improved photogenerated carrier separation efficiency, proving the successful synthesis of the modified nanocomposite material.

[0106] Figure 4 The Fourier transform infrared spectra of g-C3N4 / NaFeS2 prepared in Example 2, g-C3N4 prepared in Comparative Example 1 and NaFeS2 prepared in Comparative Example 2 are shown; Figure 4 It can be seen that g-C3N4, in 120-1700cm -1 , 3100-3300cm -1 Strong absorption bands appeared at 3100-3300cm -1 The broad absorption peak near 1200–1700 cm corresponds to the NH stretching vibration. -1 The band between 1554 cm and 1564 cm is attributed to the typical stretching vibrations of CN and C=N. -1 Corresponding to the stretching vibration of Fe-S, 3378 cm -1 and 3460cm -1 The main typical absorption peaks of pure g-C3N4 and NaFeS2 are present in the g-C3N4 / NaFeS2 sample, which further indicates the successful synthesis of the g-C3N4 / NaFeS2 composite catalyst.

[0107] Test Example 1

[0108] This test example is used to verify the formaldehyde removal performance of the g-C3N4 / NaFeS2 modified nanocomposite material prepared in Examples 1-3.

[0109] Photocatalytic activity evaluation:

[0110] In a 1.5L quartz photocatalytic reactor, at room temperature, under visible light irradiation, a 5W fan was used to accelerate the gas convection in the reactor. A 50mW / cm 2A 400W xenon lamp was used, with a UV cutoff filter (420nm) to remove UV rays. 25 mg of catalyst and 100 ml of deionized water were sonicated in a Petri dish (7.0 cm diameter) for 25 minutes to form a suspension. The dish was vacuum-dried at 60°C for 1 hour, forming a uniform photocatalyst film on the bottom of the dish. The dish was then placed in a photocatalytic reactor at a distance of 15 cm from the light source. A certain amount of 38% formaldehyde aqueous solution was injected into the photoreactor, and the initial concentration of HCHO evaporated after reaching adsorption-desorption equilibrium in the dark was 10 ppm. During irradiation, the formaldehyde, CO2, and H2O concentrations in the reactor were monitored online using a photoacoustic infrared multi-gas monitor (INNOVA AirTech 95Instruments Model 1412). The formaldehyde removal rate (Y) was calculated as Y (%) = (1-C / C0) × 100%, where C and C0 are the formaldehyde concentrations at 0 and t min, respectively.

[0111] The test results show that under the conditions of 2 standard solar intensities, a catalyst dosage of 0.25 g / L, and an initial formaldehyde concentration of 15 ppm, the g-C3N4 / NaFeS2 modified nanocomposite material has a formaldehyde removal efficiency of 97.2% after 2 hours.

[0112] in, Figure 5 The performance comparison of g-C3N4 / NaFeS2 prepared in Example 1, Example 2 and Example 3 and g-C3N4 prepared in Comparative Example 1 and NaFeS2 prepared in Comparative Example 2 in terms of visible light photocatalytic formaldehyde removal is shown. Figure 5 It can be seen that after 2 hours of illumination, the formaldehyde removal rates of pure g-C3N4 and NaFeS2 are only about 19.34% and 22.56%, respectively, while the formaldehyde removal rates of Example 1, Example 2 and Example 3 are much higher than those of Comparative Example 1 and Comparative Example 2, and the formaldehyde removal efficiency of g-C3N4 / NaFeS2 prepared in Example 2 is as high as 97.2% after 2 hours, which has a good formaldehyde removal effect.

[0113] Test Example 2

[0114] This test example is used to study the stability of the photocatalytic performance of the modified nanocomposite material g-C3N4 / NaFeS2 prepared in Example 2.

[0115] Continuous removal experiment:

[0116] After the first removal reaction was completed, the post-reaction solution was centrifuged and washed, and the recovered catalyst was dried in a freeze dryer for 48 hours, and then placed in the reactor again for the next removal experiment. Except for the materials, the other reaction conditions remained the same as the first time; after the second reaction was completed, the above steps were repeated and three removal experiments were performed.

[0117] The test results are as follows Figure 6 As shown, Figure 6 The following is a schematic diagram showing the photocatalytic performance of g-C3N4 / NaFeS2 prepared in Example 2; wherein each column represents the removal efficiency of the first removal test, the second removal test, and the third removal test from left to right. Figure 6 It can be seen that the formaldehyde removal efficiency is above 90% in the continuous removal experiments, which indicates that when the modified nanocomposite material g-C3N4 / NaFeS2 is used as a photocatalyst, its photocatalytic activity remains good after three cycles and has good stability.

[0118] According to the above experiments, the modified nano-composite material g-C3N4 / NaFeS2 prepared by the preparation method of the modified nano-composite material for high-efficiency visible light catalytic formaldehyde removal provided by the embodiment of the present invention has a wide light absorption range, can cover the entire visible spectrum range, and has a high formaldehyde removal efficiency. Under the conditions of 2 standard sunlight intensities, a catalyst dosage of 0.25 g / L and an initial formaldehyde concentration of 15 ppm, after 2 hours of reaction, the formaldehyde removal efficiency can reach 97.2%, which has a good application effect in the direction of photocatalytic formaldehyde removal.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

[0120] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and components involved are not necessarily required for the present invention.

[0121] The above is a detailed introduction to the preparation method and application of the modified nano-composite material for efficient visible light catalytic formaldehyde removal provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a modified nanocomposite material for efficient visible light catalytic formaldehyde removal, characterized in that: The method comprises: Step 1, calcining a carbon-nitrogen source to prepare g-C3N4; wherein the carbon-nitrogen source is a nitrogen-containing organic matter with a carbon-nitrogen ratio of 1:2; Step 2, using Fe2O3 as an iron source and Na2S2O3·5H2O as a sodium source and a sulfur source, to prepare NaFeS2 by a hydrothermal synthesis method, comprising: Step 2-1, adding the Fe2O3 and the Na2S2O3·5H2O in a molar ratio of 1:1-2 to ethylenediamine, heating and stirring to mix uniformly; Step 2-2, transferring the mixed solution obtained in step 2-1 into a high-pressure reactor and subjecting it to a hydrothermal reaction at 200° C. for 24 hours; Step 2-3, cooling the result of step 2-2, washing, and vacuum drying to obtain the NaFeS2; Step 3, adding the g-C3N4 and the NaFeS2 in a mass ratio of 1-3:1 to anhydrous ethanol, ultrasonically shaking for 4-6 hours, washing the resultant several times, vacuum drying, and calcining at 300-500°C for 1 hour to obtain the modified nanocomposite material - g-C3N4 / NaFeS2.

2. The method for preparing the modified nanocomposite material for efficient visible light catalytic formaldehyde removal according to claim 1, characterized in that: In the step 1, the carbon and nitrogen source is calcined to prepare g-C3N4, comprising: The crucible containing the carbon and nitrogen source is placed in a muffle furnace, heated to 500-600°C at a heating rate of 2-10°C / min, and calcined for 3-5h to obtain the g-C3N4.

3. The method for preparing the modified nanocomposite material for efficient visible light catalytic formaldehyde removal according to claim 1, characterized in that: In the step 1, the carbon and nitrogen source includes any one of cyanamide, dicyandiamide, melamine and urea.

4. The method for preparing the modified nanocomposite material for efficient visible light catalytic formaldehyde removal according to claim 3, characterized in that: In the step 1, the carbon and nitrogen source is melamine.

5. The method for preparing the modified nanocomposite material for efficient visible light catalytic formaldehyde removal according to claim 1, characterized in that: In the step 3, the mass ratio of the g-C3N4 and the NaFeS2 is 2:

1.

6. The method for preparing the modified nanocomposite material for efficient visible light catalytic formaldehyde removal according to claim 1, characterized in that: In the step 3, the obtained product is washed several times and vacuum dried, comprising: After the resultant was washed alternately with ethanol and deionized water for 6-10 times, the resultant was placed in an oven and vacuum dried at 60-80° C. for 8-12 hours.

7. A modified nanocomposite material for efficient visible light catalytic formaldehyde removal prepared by the preparation method according to any one of claims 1 to 6.

8. The modified nanocomposite material according to claim 7, characterized in that In the modified nanocomposite material, the g-C3N4 and NaFeS2 form a heterojunction.

9. Application of a modified nanocomposite material for efficient visible light catalytic formaldehyde removal, characterized in that: The modified nanocomposite material prepared by the method for preparing the modified nanocomposite material for efficient visible light catalytic formaldehyde removal according to any one of claims 1 to 6 is used for removing formaldehyde in the air.

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