A two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst, its preparation method and application

Abstract

The application discloses a two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst and a preparation method and application thereof. The preparation method comprises the following steps: dispersing two-dimensional single-crystal Bi2Fe4O9 nanosheets in a solvent, adding thioacetamide (TAA), stirring, and obtaining a reddish-brown suspension; placing the reddish-brown suspension in a reaction kettle, heating and performing a hydrothermal reaction, washing and drying the reaction product after the reaction is completed, and obtaining the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material. The preparation method is simple, the reaction condition is easy to control, and is suitable for large-scale production in industry. The two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst prepared by the method has a large specific surface area and good stability, can activate PS under visible light, and can degrade 20 mg / L of RhB to 98% within 50 min, and has a wide application prospect in the field of organic dye wastewater degradation.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation technology, specifically relating to a two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst, its preparation method, and its application. Background Technology

[0002] With socio-economic development, industrial production and human activities have placed increasing pressure on the environment. The direct discharge of wastewater from industries such as printing waste, landfill leachate, and the cosmetics and pharmaceutical industries has led to a severe imbalance in the water environment. In particular, the types and compositions of pollutants in wastewater are becoming increasingly complex, making it difficult for conventional chemical oxidation methods to achieve deep treatment of organic wastewater. Organic wastewater purification methods based on photo-assisted advanced oxidation technologies (AOPs) mainly include Fenton oxidation, photochemical oxidation, and persulfate (PS) advanced oxidation. Among these, photo-assisted activated PS advanced oxidation technology is a catalytic technology that can efficiently remove organic pollutants. Compared with traditional oxidation technologies, it has advantages such as environmental friendliness, high reaction efficiency, and mild reaction conditions, and it shows particularly good degradation effects on some recalcitrant organic pollutants.

[0003] Bi₂Fe₄O₉ is a typical multiferroic oxide semiconductor material with a narrow band gap of approximately 2.1 eV, exhibiting excellent absorption and response to visible light. Due to its high chemical stability, non-toxicity, and environmental friendliness, it is widely used in photo-assisted advanced oxidation technologies. However, defects such as oxygen vacancies in Bi₂Fe₄O₉ easily become recombination centers for electron-hole pairs, significantly reducing its catalytic activity. To minimize this limitation and suppress the recombination of photogenerated carriers, composite materials are typically constructed by combining it with semiconductors to enhance its catalytic activity. For example, Chinese patent document CN110227475A discloses a method for preparing a BiFeO₃ / Bi₂Fe₄O₉ heterostructure catalyst and its application. This invention obtains the BiFeO₃ / Bi₂Fe₄O₉ heterostructure catalyst via a hydrothermal method. Under visible light assistance, the catalyst activates PMS to degrade oxytetracycline, achieving a degradation rate of 82% within 40 minutes.

[0004] Bi₂S₃ is a thin-layer, narrow-bandgap semiconductor material commonly used in applications such as pollutant degradation and hydrogen desorption from water. Due to its bandgap of only 1.3-1.7 eV, it exhibits excellent visible light response, making it suitable for composite formation with other semiconductor materials, thereby effectively suppressing the recombination of photogenerated carriers during the catalytic process. For example, Chinese patent document CN105854899A discloses a Bi₂S₃ / TiO₂ composite visible light catalyst and its preparation method. This method uses Bi₂S₃ as the semiconductor composite material and employs a two-step (sol-gel) hydrothermal method to form a "rod-spherical" Bi₂S₃ / TiO₂ composite structure, achieving a RhB degradation rate of up to 98.2% within 120 minutes.

[0005] Based on the above analysis, this invention, by strictly controlling the reaction conditions, successfully synthesized for the first time a "sheet-needle" Bi2Fe4O9-Bi2S3 nanosheet composite catalyst with a special morphology by combining Bi2Fe4O9 and Bi2S3 using a solvothermal method. The preparation process of this composite catalyst is simple, the reaction conditions are easy to control, and it can activate PS under visible light to efficiently degrade organic wastewater, making it very suitable for the deep treatment of organic wastewater. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst. This method is simple, the reaction conditions are easy to control, and the equipment requirements are low, making it suitable for large-scale industrial production.

[0007] A method for preparing a two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst includes the following steps:

[0008] (1) Two-dimensional single-crystal Bi2Fe4O9 nanosheets were dispersed in a solvent, thioacetamide (TAA) was added, and the mixture was stirred to obtain a reddish-brown suspension.

[0009] (2) The reddish-brown suspension was placed in a reaction vessel and heated to carry out a hydrothermal reaction. After the reaction was completed, the reaction product was washed and dried to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material.

[0010] This invention uses Bi2Fe4O9 nanosheets as a sacrificial template and TAA as an etchant, employing an ion exchange method to grow Bi2S3 in situ on the surface, forming a complex hierarchical Bi2Fe4O9-Bi2S3 composite catalyst with needle-like Bi2S3 coating Bi2Fe4O9 nanosheets. Specifically, during the hydrothermal reaction in step (2), TAA in the mixed solution generates S... 2- Bi with Bi2Fe4O9 nanosheets surface 3+Anion exchange reaction occurs to generate needle-like Bi2S3, ultimately forming a Bi2Fe4O9-Bi2S3 composite catalyst.

[0011] Preferably, in step (1), the solvent is a mixture of ethanol and ethylene glycol, wherein the volume ratio of ethanol to ethylene glycol in the mixture is 1:2-5.

[0012] Preferably, in step (1), the ratio of the two-dimensional single-crystal Bi2Fe4O9 nanosheets, thioacetamide (TAA), and solvent is 0.1-0.2g:0.5-0.7mmol:30-60mL.

[0013] Preferably, in step (1), the two-dimensional single-crystal Bi2Fe4O9 nanosheets are prepared by hydrothermal reaction using Bi(NO3)3·5H2O and Fe(NO3)3·9H2O as raw materials and NaOH as a mineralizing agent in a solution system of deionized water and acetic acid.

[0014] Preferably, the preparation method of the two-dimensional single-crystal Bi2Fe4O9 nanosheets is as follows: Bi(NO3)3·5H2O is added to a mixed solvent of water and acetic acid and stirred, then Fe(NO3)3·9H2O is added and stirred to obtain a red mixed solution; NaOH is added to the red mixed solution to make the NaOH concentration reach 8-12 mol / L and stirred to obtain a precursor suspension; the precursor suspension is kept at 120-180℃ for 6-12 h for hydrothermal reaction, and after the reaction is completed, the reaction product is taken out, filtered, washed and dried to obtain the two-dimensional single-crystal Bi2Fe4O9 nanosheets.

[0015] Preferably, the volume ratio of water to acetic acid in the mixed solvent is 15-80:1.

[0016] Preferably, the ratio of Bi(NO3)3·5H2O, Fe(NO3)3·9H2O to the mixed solvent is 1mmol:1.5-2mmol:40mL.

[0017] Preferably, in step (2), the hydrothermal reaction temperature is 120-180℃ and the reaction time is 4-12h.

[0018] More preferably, in step (2), the hydrothermal reaction temperature is 150°C and the reaction time is 6 hours. Under these reaction conditions, the hydrothermal reaction can be made more complete.

[0019] Preferably, the washing process involves cleaning with deionized water and anhydrous ethanol, respectively.

[0020] This invention also provides a two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst prepared by the above-described method. The two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst of this invention is plate-needle shaped, has a large specific surface area, good dispersibility, good stability, and high PS activation ability, and exhibits good degradation effect on pollutants in organic dye wastewater.

[0021] This composite catalyst is suitable for photo-assisted PS activation, and its principle is that PS reacts with Fe. 2+ The reaction produces SO4 - The photogenerated carriers, under the excitation of visible light, cause the separation of electrons and holes inside the semiconductor, providing more Fe(II) for the activation of PS, thus accelerating the PS activation process and improving the degradation efficiency.

[0022] This invention also provides the application of the aforementioned two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst in the treatment of organic dye wastewater. The two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst of this invention has a large specific surface area, enabling it to adsorb more dye molecules and provide more activation sites for PS. It can activate PS to degrade RhB aqueous solutions under visible light assistance, degrading 98% of a 20 mg / L Rhodamine B (RhB) solution in 50 minutes. Furthermore, it exhibits good chemical stability and is a highly promising novel catalytic activation material for treating organic dye wastewater.

[0023] Preferably, the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst is applied by adding the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst into dye wastewater, and undergoing a degradation reaction through photo-assisted PS activation.

[0024] More preferably, visible light assists in the oxidation of PS during the degradation reaction. During the degradation process, PS reacts with Fe... 2+ The reaction produces SO4 - With ·OH, photogenerated electrons with Fe 3+ The reaction provides more Fe for PS activation. 2+ This will further improve the degradation efficiency of organic pollutants.

[0025] In the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst, needle-like Bi₂S₃ is tightly coated on the surface of Bi₂Fe₄O₉ nanosheets, forming an interface. During the activation process of PS under visible light assistance, Fe(II) reacts with PS to generate ·SO₄. - And ·HO, thereby degrading organic pollutants. With the assistance of visible light, photogenerated carriers provide more Fe(II) for the activation of PS, accelerating the activation process of PS.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] (1) The preparation process of the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst of the present invention is simple, the equipment requirements are low, and the reaction conditions are easy to control, making it suitable for large-scale industrial production.

[0028] (2) The two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst prepared by the present invention has a large specific surface area, which can adsorb more dye molecules and provide more sites for activating PS. At the same time, it has good stability and can maintain high stability after three cycles of degradation.

[0029] (3) This invention activates PS with the assistance of visible light, during which PS reacts with Fe. 2+ The reaction produces SO4 - The photogenerated carriers, along with ·OH and excited by visible light, cause the separation of electrons and holes inside the semiconductor. These photogenerated carriers provide more Fe(II) for the activation of PS, thus accelerating the activation process of PS.

[0030] (4) The two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst prepared by the present invention has strong PS activity. When PS is activated under visible light, it degrades 98% of 20mg / L RhB within 50min. It can be used to treat environmental pollutants, especially wastewater, and can greatly reduce the residue of pollutants. Attached Figure Description

[0031] Figure 1 The images show SEM images of the samples prepared in the examples and comparative examples. (a) is an SEM image of the two-dimensional single-crystal Bi2Fe4O9 nanosheets prepared in Comparative Example 1. (b) is an SEM image of the Bi2S3 material system synthesized in aqueous phase prepared in Comparative Example 2 (the sample was prepared by hydrothermal reaction under the same conditions as in Example 2). (c) and (d) are SEM images of the Bi2Fe4O9-Bi2S3 composite catalyst prepared in Example 2 at different scales.

[0032] Figure 2 The image shows the XRD pattern of the Bi2S3 material system synthesized in aqueous phase as prepared in Comparative Example 2.

[0033] Figure 3 The image shows the XRD pattern of the Bi2Fe4O9-Bi2S3 composite catalyst prepared in Example 2.

[0034] Figure 4Fourier transform infrared spectra of the two-dimensional single-crystal Bi2Fe4O9 nanosheets prepared in Comparative Example 1 and the Bi2Fe4O9-Bi2S3 nanosheet composite catalyst prepared in Example 2.

[0035] Figure 5 The figures show the degradation efficiency curves and the bar charts of the reaction rate constants of the catalysts prepared in the examples and comparative examples for degrading 20 mg / L RhB solutions in different systems, where (a) is the degradation efficiency curve and (b) is the reaction rate constant bar chart.

[0036] Figure 6 The graph shows the cyclic degradation efficiency of the Bi2Fe4O9-Bi2S3 nanosheet composite catalyst prepared in Example 2. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0038] Example 1

[0039] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 20 mL ethylene glycol and 10 mL ethanol, and then 0.5 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0040] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 150°C for 6 hours. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. Then the sample was dried at 60°C for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-0.5.

[0041] Example 2

[0042] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 20 mL ethylene glycol and 10 mL ethanol, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0043] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 150°C for 6 hours. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. Then the sample was dried at 60°C for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-0.6.

[0044] The SEM image of the Bi2Fe4O9-Bi2S3 composite catalyst prepared in this embodiment is shown below. Figure 1 As shown in (c) and (d), the morphology of Bi2S3 is observed to be a nanoneedle-like structure coated on the surface of Bi2Fe4O9; the XRD pattern of this Bi2Fe4O9-Bi2S3 composite catalyst is shown in Figure 1. Figure 3 As shown, the diffraction peaks of pure Bi2Fe4O9 appear at 2θ values ​​of 14.8°, 28.2°, and 28.9°, which are very consistent with the (001), (121), and (211) crystal planes of orthogonal Bi2Fe4O9 (JCPDS:25-0090). In the XRD pattern of the Bi2Fe4O9-Bi2S3 composite catalyst, the diffraction peaks belonging to Bi2Fe4O9 (JCPDS:25-0090) and Bi2S3 (JCPDS:84-0279) are clearly observed at 17.6°, 25.2°, 31.8°, and 33°, corresponding to the (012), (031), (122), and (041) crystal planes, respectively. In the Fourier transform infrared spectrum of the Bi2Fe4O9-Bi2S3 composite catalyst, at 814 cm⁻¹... -1 1132cm -1 1382cm -1 The infrared absorption peak at that location is attributed to the vibration of the Bi-S bond. This also indicates the presence of Bi2Fe4O9 and Bi2S3 components in the composite catalyst.

[0045] Example 3

[0046] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 20 mL ethylene glycol and 10 mL ethanol, and then 0.7 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0047] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 150°C for 6 hours. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. Then the sample was dried at 60°C for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-0.7.

[0048] Example 4

[0049] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 10 mL ethylene glycol and 20 mL ethanol, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0050] (2) The above reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 150°C for 6 hours. After the reaction was completed, the reaction vessel was cooled with the oven and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. The sample was then dried at 60°C for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-0.6(2).

[0051] Example 5

[0052] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 10 mL ethylene glycol and 20 mL ethanol, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0053] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 140℃ for 6 hours. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. Then the sample was dried at 60℃ for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-140℃-0.6.

[0054] Example 6

[0055] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 10 mL ethylene glycol and 20 mL ethanol, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0056] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 160℃ for 6 hours. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. Then the sample was dried at 60℃ for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-160℃-0.6.

[0057] Example 7

[0058] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 10 mL ethylene glycol and 20 mL ethanol, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0059] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 150°C for 2 hours using hydrothermal methods. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was removed. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. The sample was then dried at 60°C for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-0.6-2h.

[0060] Example 8

[0061] (1) Mullite phase two-dimensional single crystal Bi2Fe4O9 nanosheets were uniformly dispersed in a mixed solvent of 10 mL ethylene glycol and 20 mL ethanol, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0062] (2) The above-mentioned reddish-brown suspension was placed in a reaction vessel and placed in an oven. The reaction was carried out at 150°C for 4 hours. After the reaction was completed, the reaction vessel was cooled with the oven, and the sample was taken out. The sample was washed with deionized water and anhydrous ethanol until the washing solution was neutral. Then the sample was dried at 60°C for 12 hours to obtain a black powder sample, which is the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material, denoted as BBs-0.6-4h.

[0063] Comparative Example 1: Preparation of Bi2Fe4O9 nanosheets

[0064] (1) Add 1 mmol Bi(NO3)3·5H2O to a mixed solvent of 37.5 mL deionized water and 2.5 mL acetic acid, and dissolve it completely by magnetic stirring. Then add 1.5 mmol Fe(NO3)3·9H2O and stir to obtain a red mixed solution. Then add NaOH to the red mixed solution to make the NaOH concentration reach 10 mol / L and stir for 2 h to obtain a reddish-brown precursor suspension.

[0065] (2) The reddish-brown precursor suspension was placed in a polytetrafluoroethylene liner and then placed in a reaction vessel. The vessel was sealed and kept at 180°C for 12 hours for hydrothermal reaction. After the reaction was completed, the product was naturally cooled to room temperature. The product was then removed, washed with deionized water and anhydrous ethanol until neutral, and dried for 12 hours to obtain the two-dimensional single crystal Bi2Fe4O9 nanosheets.

[0066] The SEM image of the two-dimensional single-crystal Bi₂Fe₄O₉ nanosheets (BFO) prepared in this comparative example is shown below. Figure 1As shown in (a), the two-dimensional single-crystal Bi2Fe4O9 nanosheets prepared by the method of the present invention have smooth surfaces, uniform morphology, and good dispersion; as shown in the Fourier transform infrared spectrum... Figure 4 As shown in the figure, 441cm -1 490cm -1 628cm -1 810cm -1 The infrared absorption peaks at these locations correspond to the octahedral FeO6 group and the tetrahedral FeO4 group in Bi2Fe4O9, respectively.

[0067] Comparative Example 2: Bi2S3 material system synthesized in aqueous phase

[0068] (1) Two-dimensional single-crystal Bi2Fe4O9 nanosheets of mullite phase were uniformly dispersed in 30 mL of deionized water, and then 0.6 mmol TAA was added and stirred thoroughly to obtain a reddish-brown suspension.

[0069] (2) The above reddish-brown suspension was placed in a reaction vessel and hydrothermally reacted in an oven at 150°C for 6 hours. After the reaction was completed, the sample was cooled with the furnace and washed with deionized water and anhydrous ethanol until the washing liquid was neutral. The sample was then dried at 60°C for 12 hours to obtain a black powder sample, which is the target product of aqueous synthesis.

[0070] like Figure 1 (b) shows the SEM image of the sample prepared in this comparative example. The SEM image reveals that the prepared sample has a nanoneedle-like morphology with a length of approximately 300 nm, and the sample tends to be aggregated. No Bi2Fe4O9 nanosheet morphology was observed in the SEM image, nor was any second phase morphology grown on the nanosheet surface observed, indicating that the aqueous synthesis method in Comparative Example 2 could not successfully prepare the composite material system.

[0071] like Figure 2The XRD pattern of the sample prepared in this comparative example is shown. The XRD pattern clearly shows very strong diffraction peaks for Bi2S3 and Fe2O3 in the sample prepared in this comparative example. No diffraction peaks for Bi2Fe4O9 were found. The Fe2O3 diffraction peaks at 49.6°, 54.2°, 62.6°, and 64.3° correspond to the (220), (132), (130), and (-211) crystal planes, respectively. The results indicate that using deionized water instead of ethylene glycol / ethanol as the solvent for hydrothermal reaction cannot yield the expected Bi2Fe4O9-Bi2S3 nanosheet composite material system. During the hydrothermal reaction in the aqueous system, the Bi2Fe4O9 nanosheets may completely dissolve to form active materials due to the high temperature and pressure conditions provided by the hydrothermal reaction. These materials then participate in the nucleation and crystallization of new substances, ultimately generating agglomerated nanoneedle-shaped Bi2S3 and some iron oxide impurities, such as… Figure 1 As shown in (b). This is because, under hydrothermal conditions, water, as a highly polar reaction medium, inhibits the nucleation and crystal growth of Bi2S3 crystals on the surface of Bi2Fe4O9, making it impossible to obtain monodisperse Bi2Fe4O9-Bi2S3 nanosheet composite materials with regular morphology.

[0072] Sample Analysis

[0073] The catalyst (20 mg) prepared in Example 2 was added to 50 mL of RhB (20 mg / L) solution and stirred in the dark for 30 min. Samples were taken, and before the xenon lamp was started to irradiate, 1.5 mM PS was added to the RhB solution to start the degradation reaction. The solution was kept at about 25 °C throughout the process. Samples were taken every 10 min and mixed with 50 mg of Na2S2O3 to quench the reaction. After centrifugation, the change in absorbance of the catalyst to the RhB solution was tested using a UV-Vis spectrophotometer.

[0074] from Figure 5The results show that the removal rates of RhB under different systems (Vis-PS, Vis-BBs, Vis-PS-BFO, PS-BBs, Vis-PS-BBs) were compared. Under PS alone, the RhB degradation rate was 21%, as some PS was activated by the heat generated under light intensity. Secondly, pure Bi2Fe4O9 assisted PS activation and degradation of RhB under visible light, achieving a degradation rate of 70% within 50 minutes. However, the Bi2Fe4O9-Bi2S3 composite catalyst alone only achieved a 36% degradation rate of RhB under visible light, and 80% without light-assisted PS activation. In contrast, the Bi2Fe4O9-Bi2S3 composite catalyst achieved a 98% PS degradation rate under visible light, demonstrating that the photo-assisted Bi2Fe4O9-Bi2S3 composite catalyst can effectively activate PS and degrade RhB. The bar chart of the reaction rate constants of the prepared composite catalysts shows that the calculated values ​​for different systems (Vis-PS, Vis-BBs, Vis-PS-BFO, PS-BBs, Vis-PS-BBs) are 0.00476, 0.00862, 0.0238, 0.0314, and 0.0744 min, respectively. -1 .

[0075] To evaluate the reproducibility and stability of the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanocomposite catalyst in the photo-assisted activation of PS for RhB degradation, the experiment was repeated three times under the same conditions. After each repetition, the catalyst was thoroughly washed with deionized water and ethanol and dried at 60°C. The cyclic degradation curve of the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanocomposite catalyst prepared in Example 2 is shown below. Figure 6 As shown, after three cycles of degradation experiments, the removal rate of RhB in the composite material decreased from 98% to 86%, without a particularly significant decrease. Therefore, this indicates that the Bi2Fe4O9-Bi2S3 composite catalyst has good stability and reusability in activating PS.

[0076] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst in the treatment of organic dye wastewater, characterized in that, The preparation method of the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst includes the following steps: (1) Two-dimensional single-crystal Bi2Fe4O9 nanosheets are dispersed in a solvent, thioacetamide is added, and the mixture is stirred to obtain a reddish-brown suspension. The ratio of the two-dimensional single-crystal Bi2Fe4O9 nanosheets, thioacetamide and solvent is 0.1-0.2 g: 0.5-0.7 mmol: 30-60 mL. The solvent is a mixed solvent of ethanol and ethylene glycol, and the volume ratio of ethanol to ethylene glycol in the mixed solvent is 1:2-5. (2) The reddish-brown suspension was placed in a reaction vessel and heated to carry out a hydrothermal reaction. After the reaction was completed, the reaction product was washed and dried to obtain the two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst material. The reaction temperature of the hydrothermal reaction was 120-180 °C and the reaction time was 4-12 h.

2. The application of the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst according to claim 1 in the field of organic dye wastewater treatment, characterized in that, In step (1), the two-dimensional single-crystal Bi2Fe4O9 nanosheets are prepared by hydrothermal reaction using Bi(NO3)3·5H2O and Fe(NO3)3·9H2O as raw materials and NaOH as a mineralizing agent in a solution system of deionized water and acetic acid.

3. The application of the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst according to claim 2 in the field of organic dye wastewater treatment, characterized in that, The preparation method of the two-dimensional single-crystal Bi2Fe4O9 nanosheets is as follows: Bi(NO3)3·5H2O is added to a mixed solvent of water and acetic acid and stirred. Then Fe(NO3)3·9H2O is added and stirred to obtain a red mixed solution. NaOH is added to the red mixed solution to make the NaOH concentration reach 8-12 mol / L and stirred to obtain a precursor suspension. The precursor suspension is kept at 120-180 ℃ for 6-12 h for hydrothermal reaction. After the reaction is completed, the reaction product is taken out, filtered, washed and dried to obtain the two-dimensional single-crystal Bi2Fe4O9 nanosheets.

4. The application of the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst according to claim 1 in the field of organic dye wastewater treatment, characterized in that, The two-dimensional Bi2Fe4O9-Bi2S3 nanosheet composite catalyst was added to the dye wastewater, and a degradation reaction was carried out by photo-assisted persulfate activation.

5. The application of the two-dimensional Bi₂Fe₄O₉-Bi₂S₃ nanosheet composite catalyst according to claim 4 in the field of organic dye wastewater treatment, characterized in that, The degradation reaction process utilizes visible light-assisted persulfate activation to oxidize and degrade organic matter.

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