Composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis and its preparation method

Abstract

The invention provides a composite material NaFeS2 / BiOCl for efficiently degrading formaldehyde under visible light catalysis and a preparation method thereof, belonging to the technical field of photocatalytic oxidation. The invention aims to prepare a photocatalyst with a wide light absorption range and high sunlight utilization rate by compounding NaFeS2 and BiOCl, so as to improve the formaldehyde removal effect. The method comprises: using Fe(NO3)3·9H2O and Na2S·9H2O as reactants, and preparing NaFeS2 by a hydrothermal synthesis method; adding Bi(NO3)3·5H2O and NaFeS2 to anhydrous ethanol, adding KCl solution to the solution, and adjusting the pH to 7 with KOH solution; placing the mixed solution at 70°C and stirring at a constant temperature for 3 hours, and then centrifuging, washing, and drying to obtain the NaFeS2 / BiOCl.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic oxidation, and in particular to a composite material NaFeS2 / BiOCl for efficiently degrading formaldehyde under visible light catalysis and a preparation method thereof. Background Art

[0002] The ecological environment encompasses both indoor and outdoor environments. Currently, concern about the ecological environment has entered the third generation of pollution: "indoor decoration pollution." Among the various indoor air pollutants derived from various interior decoration materials, formaldehyde (HCHO) has been identified as a carcinogen by the International Agency for Research on Cancer (IARC), an affiliate of the World Health Organization (WHO).

[0003] Generally speaking, HCHO has the characteristics of long release period, even at low concentrations (as low as 0.10 mg / m 3 ) can also cause great harm to the human body. Since most residents spend more than 80% of their time indoors every day, it is necessary to pay more attention to solving the problem of indoor formaldehyde pollution.

[0004] In view of this major problem, people have tried various strategies to remove indoor HCHO, such as ventilation, adsorption, thermal / ozone catalytic oxidation, plasma degradation and photocatalytic oxidation. Among them, the adsorption method uses the strong adsorption capacity of adsorbents such as activated carbon, molecular sieves, silica gel, etc. to remove formaldehyde, including physical adsorption and chemical adsorption. However, this method has limited adsorption capacity and cumbersome processing. Plasma degradation produces a large number of active species through gas discharge to react with formaldehyde to achieve the purpose of formaldehyde removal. This method is highly efficient, but the energy consumption is also high. Photocatalytic oxidation is a promising green technology for gaseous HCHO purification due to its advantages such as controllability, renewability, sustainability and no secondary pollution.

[0005] However, photocatalytic oxidation technology depends on the performance of the photocatalyst. Currently, photocatalysts have the problems of wide band gap and low utilization rate of sunlight, which leads to limited catalytic effect. Therefore, developing a photocatalyst with a wide band gap and high utilization rate of sunlight is the current research focus. Summary of the Invention

[0006] In view of this, the present invention aims to propose a composite material NaFeS2 / BiOCl for efficient visible light photocatalytic degradation of formaldehyde and a preparation method thereof, so as to solve the problem that the current photocatalyst has a wide band gap and low utilization rate of sunlight, resulting in limited catalytic effect.

[0007] The first aspect of the present invention provides a method for preparing a composite material NaFeS2 / BiOCl for efficient visible light photocatalytic degradation of formaldehyde, the method comprising:

[0008] Step 1, using Fe(NO3)3·9H2O and Na2S·9H2O as reactants, NaFeS2 is prepared by a hydrothermal synthesis method;

[0009] Step 2: After adding Bi(NO3)3·5H2O and NaFeS2 to anhydrous ethanol, adding KCl solution to the solution, and adjusting the pH to 7 with KOH solution; wherein the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:1-10:50;

[0010] The mixed solution was placed at a constant temperature of 70° C. and stirred for 3 hours, and then centrifuged, washed, and dried to obtain the NaFeS 2 / BiOCl.

[0011] Furthermore, in step 1, Fe(NO3)3·9H2O and Na2S·9H2O are used as reactants to prepare NaFeS2 by a hydrothermal synthesis method, comprising:

[0012] Step 1-1, adding Fe(NO3)3·9H2O and Na2S·9H2O in a molar ratio of 1:3 to distilled water, stirring at 100°C for 10 minutes, then reducing the stirring temperature to 60°C and continuing stirring for 30 minutes, and adding sodium hydroxide to the stirred solution to obtain a mixed solution;

[0013] Step 1-2, transferring the mixed solution obtained in step 1-1 to a hydrothermal reactor and performing a hydrothermal reaction at 180° C. for 24 hours;

[0014] Step 1-3: After the result of step 1-2 is cooled to room temperature, it is washed and dried to obtain the NaFeS2.

[0015] Furthermore, in step 1-1, the amount of sodium hydroxide added is 0.5 mol / L.

[0016] Furthermore, in steps 1-3, the washing and drying steps include:

[0017] The product obtained in step 1-2 was washed alternately with acetone and ethanol for 6-10 times to remove the by-product NaNO3;

[0018] The washed product was placed in an oven and vacuum dried at 60-80° C. for 12-24 h.

[0019] Furthermore, in step 2, the concentration of the KCl solution is 1-2 mol / L, and the concentration of the KOH is 2 mol / L.

[0020] Furthermore, in step 2, the washing includes:

[0021] Wash alternately with deionized water and ethanol 6-10 times.

[0022] Furthermore, in step 2, the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:1:50.

[0023] The second aspect of the present invention provides a composite material NaFeS2 / BiOCl prepared by the preparation method described in the first aspect above.

[0024] Furthermore, the NaFeS2 / BiOCl is a sheet structure.

[0025] The third aspect of the present invention provides an application of the composite material NaFeS2 / BiOCl prepared by the preparation method described in the first aspect above, comprising: applying the composite material NaFeS2 / BiOCl to remove formaldehyde in the air.

[0026] Compared with the prior art, the preparation method of the composite material NaFeS2 / BiOCl for efficient visible light photocatalytic degradation of formaldehyde of the present invention has the following advantages:

[0027] The invention provides a preparation method of a composite material NaFeS2 / BiOCl for efficient formaldehyde degradation by visible light catalysis, comprising: step 1, using Fe(NO3)3·9H2O and Na2S·9H2O as reactants to prepare NaFeS2 by a hydrothermal synthesis method; step 2, adding Bi(NO3)3·5H2O and NaFeS2 to anhydrous ethanol, adding a KCl solution to the solution, and adjusting the pH to 7 by using a KOH solution; wherein the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2, and the KCl is 50:1-10:50; placing the mixed solution at 70°C and stirring at a constant temperature for 3h, centrifuging, washing, and drying to obtain the NaFeS2 / BiOCl; thus, after preparing NaFeS2, adding the prepared NaFeS2 to the preparation process of BiOCl to prepare the composite material NaFeS2 / BiOCl, and utilizing BiOCl to obtain the composite material NaFeS2 / BiOCl. The composite material NaFeS2 / BiOCl has the advantages of unique layered structure, stable chemical properties and corrosion resistance. Since the addition of NaFeS2 causes the ultraviolet spectrum to red-shift, the overall light absorption range of the composite material NaFeS2 / BiOCl is relatively wide and can cover the entire visible spectrum. At the same time, since both NaFeS2 and BiOCl are semiconductor materials, the composite can form a heterojunction, which is conducive to the separation of photogenerated carriers in the photocatalytic process. Therefore, the obtained composite material has a wide light absorption range and a high sunlight utilization rate, and has a good formaldehyde removal effect when used as a photocatalyst. The composite material NaFeS2 / BiOCl prepared by the present invention is used as a photocatalyst for removing formaldehyde. Under the irradiation of visible light with 2 standard sunlight intensities (λ>400nm), the catalyst dosage is 0.1g, the reaction is carried out for 140min, and the formaldehyde degradation rate can reach 97.5%; at the same time, since the prepared NaFeS2 is added during the preparation of BiOCl, the preparation process is simple and easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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:

[0029] Figure 1 A flow chart showing the steps of preparing a composite material NaFeS2 / BiOCl for efficient formaldehyde degradation under visible light catalysis provided by an embodiment of the present invention;

[0030] Figure 2 SEM image of the composite material NaFeS2 / BiOCl for efficient formaldehyde degradation under visible light catalysis provided by an embodiment of the present invention;

[0031] Figure 3Ultraviolet diffuse reflectance spectra of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention, NaFeS2 prepared in Comparative Example 1, and BiOCl prepared in Comparative Example 2;

[0032] Figure 4 This is a graph showing the N2 adsorption-desorption isotherm of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention;

[0033] Figure 5 This is an infrared spectrum of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention;

[0034] Figure 6 This is a comparison chart of the performance of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention, NaFeS2 prepared in Comparative Example 1, and BiOCl prepared in Comparative Example 2 in visible light catalytic degradation of formaldehyde under the same conditions;

[0035] Figure 7 Schematic diagram of the catalytic performance stability test results of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] 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, formaldehyde, xylene, styrene, chlorinated organic compounds, ketones and lower alcohols.

[0038] Formaldehyde in the air mainly comes from decoration materials, furniture, incomplete combustion of traditional fuels, smoke and cosmetics. Short-term exposure to formaldehyde will irritate organs and cause adverse symptoms; long-term exposure to indoor air pollutants will be detrimental to health and may lead to sick building syndrome, building-related diseases, and in extreme cases, cancer. Generally speaking, formaldehyde has a long release cycle and can be released even at low concentrations (as low as 0.10 mg / m 3 Since most residents spend more than 80% of their time indoors every day, it is necessary to pay more attention to solving the problem of indoor formaldehyde pollution.

[0039] In response to this problem, various strategies have been developed to remove indoor formaldehyde, including ventilation, adsorption, thermal / ozone catalysis, plasma degradation, 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 degradation removes formaldehyde by generating a large number of active species through gas discharge, which react with formaldehyde. This method is highly efficient but also energy-intensive. Photocatalytic oxidation, on the other hand, offers advantages such as controllability, reproducibility, sustainability, and the absence of secondary pollution, making it a promising green technology for gaseous formaldehyde purification. Currently, photocatalytic oxidant technology primarily relies on photocatalysts for formaldehyde degradation. Therefore, the degradation effect is significantly affected by the catalytic performance of the photocatalyst.

[0040] However, currently used photocatalysts often suffer from problems such as a wide optical band gap and low sunlight utilization efficiency. For example, bismuth oxychloride (BiOCl), a new type of indirect band gap semiconductor, has become a research hotspot in the field of photocatalysis due to its unique layered structure, stable chemical properties, and corrosion resistance. However, BiOCl has an optical band gap of around 3.2 to 3.4 eV and only absorbs ultraviolet light, resulting in a low sunlight utilization efficiency. In addition, the recombination probability of photogenerated electron-hole pairs in bismuth-based photocatalysts is high, which seriously limits its application prospects. Using pure BiOCl as a photocatalyst to remove formaldehyde is not ideal.

[0041] In view of this, the present invention provides a composite material NaFeS2 / BiOCl for efficient formaldehyde degradation under visible light catalysis and a preparation method thereof. By compounding BiOCl with a narrow-bandgap magnetic semiconductor material NaFeS2, the composite material has a wider light absorption range and a higher utilization rate of sunlight. In addition, a heterojunction is formed between BiOCl and NaFeS2 to improve the separation efficiency of photogenerated electron-hole pairs, so that the prepared composite material NaFeS2 / BiOCl has good photocatalytic performance as a photocatalyst. The composite material NaFeS2 / BiOCl prepared by the present invention is used as a photocatalyst for removing formaldehyde from the air. Since the composite material NaFeS2 / BiOCl has adsorption properties and good photocatalytic performance, it has a good removal effect on formaldehyde in the air through the synergistic effect of photocatalysis and adsorption.

[0042] The following will describe in detail the composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis and its preparation method provided by the present invention with reference to the accompanying drawings and in combination with examples.

[0043] In a first aspect of an embodiment of the present invention, a method for preparing a composite material NaFeS2 / BiOCl for efficient formaldehyde degradation under visible light catalysis is provided.

[0044] Reference Figure 1 , Figure 1 The present invention provides a process flow chart of a method for preparing a composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde by visible light catalysis. Figure 1 As shown, the method includes:

[0045] Step 1: Using Fe(NO3)3·9H2O and Na2S·9H2O as reactants, NaFeS2 is prepared by a hydrothermal synthesis method.

[0046] Specifically, the steps for preparing NaFeS2 are:

[0047] Step 1-1, adding Fe(NO3)3·9H2O and Na2S·9H2O in a molar ratio of 1:3 to distilled water, stirring at 100°C for 10 minutes, then reducing the stirring temperature to 60°C and continuing stirring for 30 minutes, and adding sodium hydroxide to the stirred solution to obtain a mixed solution;

[0048] Step 1-2, transferring the mixed solution obtained in step 1-1 to a hydrothermal reactor and performing a hydrothermal reaction at 180° C. for 24 hours;

[0049] Step 1-3: After the result of step 1-2 is cooled to room temperature, it is washed and dried to obtain the NaFeS2.

[0050] The washing process uses acetone and deionized water for alternating washing, and acetone is used to remove the by-product NaNO3 of the reaction process.

[0051] In the embodiment of the present invention, sodium hydroxide is added to provide an alkaline environment to generate NaFeS2. Therefore, the amount of sodium hydroxide added does not need to be too much, as long as it can produce NaFeS2. In the embodiment of the present invention, the amount of sodium hydroxide added is 0.5 mol / L.

[0052] In some embodiments, since there are many methods for preparing NaFeS2, the reactants or preparation methods used can be adjusted as needed. For example, iron oxide and sodium thiosulfate can be used as reactants to prepare NaFeS2 by a hydrothermal method, or by a calcination method. The present invention does not impose any specific restrictions.

[0053] Step 2: After adding Bi(NO3)3·5H2O and NaFeS2 to anhydrous ethanol, adding KCl solution, and adjusting the pH to 7 with KOH solution to obtain a mixed solution; placing the mixed solution at a constant temperature of 70°C and stirring for 3 hours, centrifuging, washing, and drying to obtain the NaFeS2 / BiOCl.

[0054] Wherein, the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:1-10:50.

[0055] For example, the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:1:50;

[0056] The molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:3:50;

[0057] The molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:5:50;

[0058] The molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:7:50;

[0059] The molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:10:50.

[0060] Preferably, the composite material NaFeS2 / BiOCl is prepared by using the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl being 50:1:50. Under the conditions of an initial formaldehyde concentration of 100 ppm, 2 standard sun intensities, and a catalyst dosage of 0.1 g, the formaldehyde removal rate can reach 97.5% after 140 minutes.

[0061] The concentration of the added KCl solution is generally 1-2 mol / L, primarily serving as a Cl element for the preparation of BiOCl. The concentration of KOH is 2 mol / L. During the pH adjustment process, the pH is tested using precision pH test paper with a pH range of 5.5-9.0 until the solution reaches a pH of 7.0. It should be noted that since the added KCl needs to be evenly dispersed in the solution to prepare BiOCl, stirring is required during the addition of the KCl solution to achieve uniform mixing. Furthermore, due to its low solubility in ethanol, KCl is added as a solution rather than directly as a solid.

[0062] In the embodiment of the present invention, in order to reduce impurities in the prepared composite material NaFeS2 / BiOCl, after the reaction is completed and cooled to room temperature, the resultant is washed with deionized water and ethanol for 6-10 times.

[0063] In some embodiments, NaFeS2 and BiOCl can be prepared separately first, and then NaFeS2 and BiOCl are compounded by ultrasound or calcination to obtain a composite material NaFeS2 / BiOCl; wherein, NaFeS2 and BiOCl are commonly prepared by methods in related technologies, and the present invention does not impose specific limitations.

[0064] A second aspect of an embodiment of the present invention provides a composite material NaFeS2 / BiOCl prepared by the preparation method described in the first aspect above.

[0065] The prepared composite material was observed using a scanning electron microscope, and the obtained images are as follows: Figure 2 As shown, according to Figure 2 It can be seen that the prepared composite material NaFeS2 / BiOCl is a flaky nanostructure.

[0066] In the embodiments of the present invention, NaFeS2 and BiOCl form a heterojunction. A heterojunction is the interface region formed by the contact of two different semiconductors. Under light excitation, this heterojunction enables interfacial transfer and spatial separation of electrons and holes, preventing the rapid recombination of photogenerated carriers that can lead to low photocatalytic performance. Thus, the use of NaFeS2 and BiOCl overcomes the problem of BiOCl's low photocatalytic performance, which is caused by its narrow light absorption range and rapid recombination velocity of photogenerated carriers.

[0067] According to a third aspect of an embodiment of the present invention, there is provided a composite material NaFeS2 / BiOCl prepared by the preparation method described in the first aspect above, and the composite material NaFeS2 / BiOCl is used to remove formaldehyde in the air.

[0068] In the embodiment of the present invention, the composite material NaFeS2 / BiOCl can be applied to formaldehyde, SO2, ammonia, NO x Preferably, the modified nanocomposite material for high-efficiency visible light catalytic formaldehyde removal prepared in the embodiment of the present invention is used as a photocatalyst to remove formaldehyde.

[0069] The composite material NaFeS2 / BiOCl prepared by the embodiment of the present invention is used to remove formaldehyde. Under the conditions of a molar ratio of Bi(NO3)3·5H2O, NaFeS2 and KCl of 50:1:50, light irradiation of 2 standard suns, a catalyst dosage of 0.1 g and an initial formaldehyde concentration of 100 ppm, the formaldehyde removal efficiency reaches 97.5% after 140 minutes. It can be seen that the composite material NaFeS2 / BiOCl prepared by the preparation method provided by the embodiment of the present invention has good application prospects in the removal of formaldehyde in the air.

[0070] In the embodiment of the present invention, after preparing NaFeS2, the prepared NaFeS2 is added during the preparation of BiOCl, thereby obtaining the composite material NaFeS2 / BiOCl; thus, after preparing NaFeS2, the prepared NaFeS2 is added during the preparation of BiOCl, thereby obtaining the composite material NaFeS2 / BiOCl, utilizing the advantages of BiOCl's unique layered structure, stable chemical properties and corrosion resistance, and the addition of NaFeS2 causes a red shift in the ultraviolet spectrum, so that the overall light absorption range of the composite material NaFeS2 / BiOCl is wider and can cover the entire visible spectrum; at the same time, since NaFeS2 and BiOCl Both NaFeS2 and BiOCl are semiconductor materials, and their combination can form a heterojunction, which is conducive to the separation of photogenerated carriers in the photocatalytic process. Therefore, the obtained composite material has a wide light absorption range and a high sunlight utilization rate. It has a good formaldehyde removal effect when used as a photocatalyst. The composite material NaFeS2 / BiOCl prepared by the present invention is used as a photocatalyst for removing formaldehyde. Under the irradiation of visible light (λ>400nm) with an intensity of 2 standard sunlight, the catalyst dosage is 0.1g, the reaction time is 140min, and the formaldehyde degradation rate can reach 97.5%. At the same time, since the prepared NaFeS2 is added during the preparation of BiOCl, the preparation process is simple and easy.

[0071] In order to enable those skilled in the art to better understand the present invention, the following multiple specific examples are used to illustrate the composite material NaFeS2 / BiOCl for efficient visible light catalytic degradation of formaldehyde and its preparation method provided by the present invention.

[0072] Ferric nitrate nonahydrate (Fe(NO₃)₃·9H₂O), sodium sulfide nonahydrate (Na₂S·9H₂O), bismuth nitrate pentahydrate (Bi(NO₃)₃·H₂O), anhydrous ethanol, potassium hydroxide (KOH), potassium chloride (KCl), and sodium hydroxide (NaOH) were purchased from Aladdin (Shanghai, China). All reagents were used without further purification. Deionized water was used in all experiments.

[0073] Example 1

[0074] Step 1: Dissolve 40 mM Fe(NO₃)₃·9H₂O and 120 mM Na₂S·9H₂O in distilled water to prepare a 100 mL solution. Stir the solution at 100°C for 10 minutes and then at 60°C for 30 minutes. Then, add 0.5 mol NaOH to the mixture.

[0075] The solution mixture was transferred to a hydrothermal reactor and placed in an oven at 180°C for 24 hours. Subsequently, the reaction mixture was cooled to room temperature and washed several times with ethanol and acetone, and then dried at 80°C to obtain NaFeS2.

[0076] Step 2: Dissolve 5 mmol Bi(NO₃)₃·5H₂O and 0.1 mmol NaFeS₂ in 40 mL of anhydrous ethanol. Weigh 5 mmol KCl and dissolve it in 80 mL of distilled water. Slowly add the homogenized KCl solution to the uniformly stirred solution. Adjust the pH to 7 (5.5-9.0 precision pH paper) with 2 mol / L KOH solution. Stir the mixed solution at 70°C for 3 hours. After the reaction, centrifuge, wash, and dry to obtain the NaFeS₂ / BiOCl composite material.

[0077] Example 2

[0078] Step 1: Dissolve 40 mM Fe(NO₃)₃·9H₂O and 120 mM Na₂S·9H₂O in distilled water to prepare a 100 mL solution. Stir the solution at 100°C for 10 minutes and then at 60°C for 30 minutes. Then, add 0.5 mol NaOH to the mixture.

[0079] The solution mixture was transferred to a hydrothermal reactor and placed in an oven at 180°C for 24 hours. Subsequently, the reaction mixture was cooled to room temperature and washed several times with ethanol and acetone, and then dried at 80°C to obtain NaFeS2.

[0080] Step 2: Dissolve 5 mmol Bi(NO₃)₃·5H₂O and 0.5 mmol NaFeS₂ in 40 mL of anhydrous ethanol. Weigh 5 mmol KCl and dissolve it in 80 mL of distilled water. Slowly add the well-mixed KCl solution to the uniformly stirred solution. Adjust the pH to 7 (5.5-9.0 precision pH paper) with 2 mol / L KOH solution. The mixed solution is stirred at 70°C for 3 hours. After the reaction, centrifuge, wash, and dry to obtain the NaFeS₂ / BiOCl composite material.

[0081] Example 3

[0082] Step 1: Dissolve 40 mM Fe(NO₃)₃·9H₂O and 120 mM Na₂S·9H₂O in distilled water to prepare a 100 mL solution. Stir the solution at 100°C for 10 minutes and then at 60°C for 30 minutes. Then, add 0.5 mol NaOH to the mixture.

[0083] The solution mixture was transferred to a hydrothermal reactor and placed in an oven at 180°C for 24 hours. Subsequently, the reaction mixture was cooled to room temperature and washed several times with ethanol and acetone, and then dried at 80°C to obtain NaFeS2.

[0084] Step 2: Dissolve 5 mmol of Bi(NO₃)₃·5H₂O and 1 mmol of NaFeS₂ in 40 mL of anhydrous ethanol. Weigh 5 mmol of KCl and dissolve it in 80 mL of distilled water. Slowly add the well-mixed KCl solution to the uniformly stirred solution. Adjust the pH to 7 (5.5-9.0 precision pH paper) with 2 mol / L KOH solution. The mixed solution is stirred at 70°C for 3 hours. After the reaction, centrifuge, wash, and dry to obtain the NaFeS₂ / BiOCl composite material.

[0085] Comparative Example 1

[0086] 40 mM Fe(NO3)3·9H2O and 120 mM Na2S·9H2O were dissolved in distilled water to prepare 100 ml of a solution. The solution mixture was stirred at 100°C for 10 minutes and then at 60°C for 30 minutes, after which 0.5 mol of NaOH was added to the mixture.

[0087] The solution mixture was transferred to a hydrothermal reactor and placed in an oven at 180°C for 24 hours. Subsequently, the reaction mixture was cooled to room temperature and washed several times with ethanol and acetone, and then dried at 80°C to obtain NaFeS2.

[0088] Comparative Example 2

[0089] Dissolve 5 mmol of Bi(NO₃)₃·5H₂O in 40 mL of anhydrous ethanol. Weigh 5 mmol of KCl and dissolve it in 80 mL of distilled water. Slowly add the well-mixed KCl solution to the stirring Bi(NO₃)₃·5H₂O solution. Adjust the pH to 7 (5.5-9.0 with precision pH paper) with 2 mol / L KOH solution. Stir at 70°C for 3 hours. After the reaction, centrifuge, wash, and dry to obtain BiOCl.

[0090] The composite material NaFeS2 / BiOCl prepared in Example 1, the NaFeS2 prepared in Comparative Example 1 and the BiOCl prepared in Comparative Example 2 were tested by ultraviolet spectrometer, and the following results were obtained: Figure 3 The UV diffuse reflectance spectrum shown is based on Figure 3As can be seen, the BiOCl photocatalyst's absorption edge is around 300nm, while NaFeS2's optical absorption covers the entire visible spectrum. In the composite formed by adding BiOCl to NaFeS2, NaFeS2 compensates for BiOCl's shortcomings, demonstrating the successful synthesis of the composite. Furthermore, while the visible light absorption intensity of the NaFeS2 / BiOCl photocatalyst is slightly weakened, its absorption range still covers the entire visible spectrum, with a large absorption tail peak, indicating that it can utilize sufficient visible light. Therefore, the NaFeS2 / BiOCl composite prepared in this embodiment of the present invention exhibits high solar light utilization efficiency.

[0091] The adsorption and desorption test was carried out on Example 1. The test results are as follows: Figure 4 As shown, Figure 4 The N2 adsorption-desorption isotherm of the composite material NaFeS2 / BiOCl prepared in Example 1 is shown. Figure 4 It shows that the interaction between the adsorbent and the adsorbate is strong, and the adsorption effect on organic pollutants is good. Therefore, the composite material NaFeS2 / BiOCl prepared in the embodiment of the present invention can remove pollutants through the synergistic adsorption and photocatalytic properties.

[0092] In order to study the composition and structure of the synthesized sample, the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention was analyzed by infrared spectroscopy, and the following results were obtained: Figure 5 The Fourier infrared spectrum shown. Figure 5 It can be seen that for NaFeS2, 1100cm -1 is the characteristic peak of Fe-S; for BiOCl, 3445cm -1 The broad absorption peak at 527 cm is attributed to the stretching vibration mode of hydroxyl groups. -1 The spectral band corresponds to the symmetrical A2u-type vibration of the Bi-O bond; for NaFeS2 / BiOCl, the main typical absorption peaks of NaFeS2 and BiOCl are both present in NaFeS2 / BiOCl, further indicating the successful synthesis of the composite material NaFeS2 / BiOCl.

[0093] Test Example 1

[0094] This test example is used to verify the degradation performance of the composite material NaFeS2 / BiOCl prepared in Example 1, NaFeS2 prepared in Comparative Example 1, and BiOCl prepared in Comparative Example 2 as photocatalysts for formaldehyde.

[0095] Photocatalytic activity evaluation:

[0096] In a 1.5L quartz photocatalytic reactor, at room temperature, under visible light irradiation, a 5W fan was used to photocatalytically remove formaldehyde. A 350W xenon lamp was placed vertically outside the photoreactor. A UV cutoff filter (420nm) was used to remove ultraviolet rays. The average light intensity at the surface of the reaction solution in the reaction solution was measured by a photon density meter to be 200mW / cm 2 , i.e., 2 standard solar intensities (AM3G), 0.1 g of catalyst and 15 mL of deionized water were ultrasonically suspended in a Petri dish (7.0 cm diameter) for 25 minutes. 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. A certain amount of 38% formaldehyde aqueous solution was injected into the photoreactor. After reaching adsorption-desorption equilibrium in the dark, the initial concentration of evaporated HCHO was 100 ppm. During the irradiation process, the formaldehyde, CO2, and H2O concentrations in the reactor were monitored online using a photoacoustic infrared multi-gas monitor (INNOVA Air Tech 95 Instruments 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.

[0097] The test results show that under the irradiation of visible light (λ>400nm) with 2 standard solar intensities, the catalyst dosage is 0.1g, the initial formaldehyde concentration is 100ppm, and the initial temperature is room temperature, the formaldehyde degradation efficiency of NaFeS2 / BiOCl photocatalytic nanomaterials is as high as 97.5% after 140 minutes.

[0098] in, Figure 6 The performance comparison of the composite material NaFeS2 / BiOCl prepared in Example 1, NaFeS2 prepared in Comparative Example 1 and BiOCl prepared in Comparative Example 2 in the visible light catalytic degradation of formaldehyde under the same conditions is shown. Figure 6 It can be seen that when the catalytic test was carried out under the conditions of an initial formaldehyde concentration of 100 ppm and a catalyst dosage of 0.1 g, after 140 minutes of illumination, the degradation rate of formaldehyde using NaFeS2 / BiOCl as a photocatalyst could reach 97.5%; while when BiOCl alone was used as a photocatalyst after 140 minutes of illumination, formaldehyde was almost not degraded. This is because BiOCl does not absorb visible light, but only has a certain adsorption effect due to its layered structure, which reduces the formaldehyde content in the air through adsorption; and when NaFeS2 alone was used as a photocatalyst, the formaldehyde removal rate was only about 50% after 140 minutes of illumination.

[0099] Therefore, the composite material NaFeS2 / BiOCl prepared in the embodiment of the present invention has improved the separation efficiency of photogenerated carriers due to the formation of a heterojunction, so that the composite material has good photocatalytic performance. Compared with the use of NaFeS2 or BiOCl alone as a photocatalyst, it has a better effect on removing formaldehyde.

[0100] Test Example 2

[0101] Continuous degradation test:

[0102] When the composite material NaFeS2 / BiOCl prepared in Example 1 was used to degrade formaldehyde, after the first degradation reaction was completed, the culture dish containing the photocatalyst was dried at 60°C for 0.5 hour and then placed in the reactor again for the next formaldehyde removal reaction. Except for the materials, the other reaction conditions were kept consistent with the first time. After the second reaction was completed, the above steps were repeated to conduct a third degradation experiment.

[0103] The test results are as follows Figure 7 As shown, Figure 7 The formaldehyde removal rates of Example 1 in the first, second and third degradation tests are shown. Figure 7 It can be seen that in three consecutive degradation tests, the formaldehyde removal rate of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention is above 90%. Therefore, the photocatalytic activity of the composite material NaFeS2 / BiOCl prepared in Example 1 of the present invention remains good after three cycles, and its photocatalytic performance is stable.

[0104] It can be seen from the above experiments that the composite material NaFeS2 / BiOCl prepared by the preparation method of the embodiment of the present invention has a wide visible light absorption range and can cover the entire visible light range. Therefore, the utilization rate of sunlight is high. Since both NaFeS2 and BiOCl are semiconductors, the composite to form a heterojunction can improve the separation efficiency of photogenerated carriers, thereby obtaining a composite material with good photocatalytic performance. The composite material NaFeS2 / BiOCl prepared by the embodiment of the present invention has certain adsorption properties; therefore, the composite material prepared by the implementation of the present invention can remove formaldehyde through the synergistic effect of adsorption and photocatalysis.

[0105] The NaFeS2 / BiOCl composite material prepared in an embodiment of the present invention was used as a photocatalyst to remove indoor formaldehyde. Under irradiation with visible light (λ>400nm) of 2 standard solar intensities, a catalyst dosage of 0.1g, an initial formaldehyde concentration of 100ppm, and an initial temperature of room temperature, after 140 minutes of illumination, the formaldehyde removal rate reached 97.5%. In addition, the NaFeS2 / BiOCl composite material prepared in an embodiment of the present invention achieved a formaldehyde removal rate of 90% in three consecutive formaldehyde removal experiments, demonstrating its stable catalytic performance.

[0106] 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.

[0107] 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.

[0108] The above is a detailed introduction to the composite material NaFeS2 / BiOCl for efficient formaldehyde degradation catalyzed by visible light provided by the present invention and its preparation method. 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 composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis, characterized in that: The method comprises: Step 1, using Fe(NO3)3·9H2O and Na2S·9H2O as reactants, NaFeS2 is prepared by a hydrothermal synthesis method; Step 2: After adding Bi(NO3)3·5H2O and NaFeS2 to anhydrous ethanol, adding KCl solution, and adjusting the pH to 7 with KOH solution to obtain a mixed solution; wherein the molar ratio of the Bi(NO3)3·5H2O, the NaFeS2 and the KCl is 50:1:50; The mixed solution was placed at 70° C. and stirred for 3 hours, and then centrifuged, washed, and dried to obtain the NaFeS 2 / BiOCl.

2. The method for preparing the composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis according to claim 1, characterized in that: In the step 1, Fe(NO3)3·9H2O and Na2S·9H2O are used as reactants to prepare NaFeS2 by a hydrothermal synthesis method, comprising: Step 1-1, adding Fe(NO3)3·9H2O and Na2S·9H2O in a molar ratio of 1:3 to distilled water, stirring at 100°C for 10 minutes, then reducing the stirring temperature to 60°C and continuing stirring for 30 minutes, and adding sodium hydroxide to the stirred solution to obtain a mixed solution; Step 1-2, transferring the mixed solution obtained in step 1-1 to a hydrothermal reactor and performing a hydrothermal reaction at 180° C. for 24 hours; Step 1-3: After the result of step 1-2 is cooled to room temperature, it is washed and dried to obtain the NaFeS2.

3. The method for preparing the composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis according to claim 2, characterized in that: In the step 1-1, the amount of sodium hydroxide added is 0.5 mol / L.

4. The method for preparing the composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis according to claim 2, characterized in that: In steps 1-3, the washing and drying steps include: The product obtained in step 1-2 was washed alternately with acetone and ethanol for 6-10 times to remove the by-product NaNO3; The washed product was placed in an oven and vacuum dried at 60-80° C. for 12-24 h.

5. The method for preparing the composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis according to claim 1, characterized in that: In step 2, the concentration of the KCl solution is 1-2 mol / L, and the concentration of the KOH is 2 mol / L.

6. The method for preparing the composite material NaFeS2 / BiOCl for efficient degradation of formaldehyde under visible light catalysis according to claim 1, characterized in that: In the step 2, the cleaning comprises: Wash alternately with deionized water and ethanol 6-10 times.

7. A composite material NaFeS2 / BiOCl prepared by the preparation method according to any one of claims 1 to 6.

8. The composite material according to claim 7, characterized in that The NaFeS2 / BiOCl is a sheet-like structure.

9. An application of the composite material NaFeS2 / BiOCl prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The composite material NaFeS2 / BiOCl is applied to remove formaldehyde in the air.

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