Ag2WO4 / BiFeO3 heterojunction magnetic nano photocatalytic material and preparation method thereof

Abstract

The invention belongs to the field of nano photocatalysts, and particularly relates to an Ag2WO4 / BiFeO3 heterojunction magnetic nano photocatalytic material and a preparation method thereof. The preparation method comprises the following steps: firstly, carrying out hydrothermal reaction on Bi (NO3) 3.5 H2O and Fe (NO3) 3.9 H2O in KOH to prepare BiFeO3; and then carrying out ultrasonic dispersion and hydrothermal compounding on the Ag2WO4, AgNO3 and Na2WO4. 2H2O to form the heterojunction, wherein the mass fraction of Ag2WO4 is preferably 15%. The product is obtained by loading nanorod-shaped Ag2WO4 on polyhedral BiFeO3, the interface is tight, and the magnetic recoverability is good; and the degradation rate of 40mg / L LR5B under simulated sunlight for 100 minutes reaches 95.62%, which is 5.17 times, 1.71 times and 1.10 times of the loading capacity of pure BiFeO3 and 5% and 10%, so that the BiFeO3 / LR5B composite photocatalyst is suitable for high-efficiency treatment of dye wastewater.

Description

Technical Field

[0001] This invention relates to the field of nanophotocatalysts, specifically to an Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material and its preparation method. Background Technology

[0002] In recent years, the rapid development of industries such as textiles, dyeing and printing, and papermaking has exacerbated global water pollution problems. Dye wastewater, in particular, due to its complex composition, high toxicity, and difficulty in degradation, has become a major environmental problem posing a significant threat to the ecological environment and human health. Treatment methods for dye wastewater can be broadly categorized into physical, biological, and chemical methods. However, these traditional methods often suffer from low treatment efficiency, high costs, and the potential for secondary pollution, making them ill-suited to the increasingly stringent environmental standards under the "dual carbon" (carbon dioxide, carbon sequestration, and carbon emissions) goals.

[0003] Against this backdrop, photocatalysis technology, with its significant advantages such as high efficiency, low cost, and no secondary pollution, is gradually becoming a research hotspot as an emerging green treatment method. This technology refers to the process where, under illumination, a catalyst absorbs photon energy, exciting valence band electrons to transition to the conduction band, forming photogenerated electron-hole pairs. These pairs migrate to the catalyst surface, forming reactive species such as hydroxyl radicals and superoxide radicals, which then undergo redox reactions with organic pollutants in the water, effectively destroying the molecular structure of the pollutants and thus achieving the goal of pollutant degradation.

[0004] Among numerous photocatalysts, bismuth ferrite (BiFeO3), as a typical multiferroic material, exhibits both ferroelectricity and antiferromagnetism at room temperature, a unique physical property that has garnered significant attention in the field of photocatalysis. Furthermore, BiFeO3 possesses a narrow bandgap (approximately 2.2 eV), making it a promising candidate for photocatalytic applications. However, BiFeO3 suffers from drawbacks such as a narrow visible light response range and easy recombination of photogenerated electrons and holes, which affect its photocatalytic activity. Silver tungstate (Ag2WO4), as a member of the silver-based materials family, also holds immense potential in photocatalysis. As an important metal tungstate, Ag2WO4 is a wide-bandgap semiconductor (2.9–3.1 eV). Due to its unique crystal characteristics, such as high crystallinity, polymorphism, and abundant crystal defects, it exhibits excellent photocatalytic performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes an Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material and its preparation method. Nanorod-shaped Ag2WO4 is loaded onto irregularly polyhedral BiFeO3 to form an Ag2WO4 / BiFeO3 heterojunction with excellent photocatalytic performance. This solves the problems of low visible light utilization, easy recombination of photogenerated electron-hole pairs, and low recycling and reuse rates in photocatalytic materials.

[0006] The technical solution adopted in this invention is: a method for preparing Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic materials, mainly including the following steps: S1. Bismuth ferrite (BiFeO3) was prepared by a water bath method. Bismuth nitrate pentahydrate (Bi(NO3)3•5H2O) and ferric nitrate nonahydrate (Fe(NO3)3•9H2O) were dissolved in potassium hydroxide (KOH) solution and subjected to ultrasonic treatment to obtain a uniform suspension. The suspension was then transferred to a reaction vessel for hydrothermal reaction. After the reaction was completed, the resulting precipitate was washed, dried, and ground for later use. S2. Preparation of Ag2WO4 / BiFeO3 nanophotocatalyst. First, a BiFeO3 suspension was prepared using the BiFeO3 obtained in step S1. Then, AgNO3 was added to the BiFeO3 suspension and ultrasonic treatment was performed. After that, Na2WO4·2H2O was added and ultrasonic treatment was performed again. The resulting product was washed and dried to obtain the Ag2WO4 / BiFeO3 heterojunction nanophotocatalyst material. In the Ag2WO4 / BiFeO3 heterojunction nanophotocatalytic materials, the mass fractions of Ag2WO4 are 1%, 5%, 10%, and 15%, respectively.

[0007] As a preferred embodiment, in step S1, after dissolving Bi(NO3)3•5H2O and Fe(NO3)3•9H2O in KOH solution, the conditions for ultrasonic treatment of the suspension are as follows: first, stirring at room temperature for 50 to 60 minutes, and then ultrasonically treating the resulting solution for 30 to 40 minutes.

[0008] As a preferred option, in step S1, the hydrothermal reaction conditions are: reacting at 190°C for 6 to 7 hours.

[0009] As a preferred embodiment, in step S1, the precipitate after the reaction is completed is washed three times each with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 80°C.

[0010] As a preferred embodiment, in step S2, the preparation steps of the BiFeO3 suspension are as follows: first, 0.5g of BiFeO3 is added to 50ml of deionized water to obtain a suspension; then, 0.018g to 0.055g of AgNO3 is added to the suspension and the suspension is continuously sonicated for 30 to 40 minutes to form a uniform suspension.

[0011] As a preferred embodiment, in step S2, the step of performing ultrasonic treatment again is as follows: 0.01g to 0.055g of Na2WO4•2H2O is added to the suspension, ultrasonicated for 1 hour, and then the suspension is transferred to a high-pressure reactor and heated at 140°C for 6 hours.

[0012] As a preferred embodiment, in step S2, the precipitate is washed three times each with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven and vacuum dried at 60 to 70°C for 24 hours.

[0013] An Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material was prepared using the method described above.

[0014] The beneficial effects of this invention are: This invention prepares a BiFeO3 photocatalyst using a hydrothermal method, and then loads nanorod-shaped Ag2WO4 onto irregular polyhedral BiFeO3 via a hydrothermal-precipitation method to form an Ag2WO4 / BiFeO3 heterojunction with excellent photocatalytic performance. Experimental results show that when the Ag2WO4 loading is 15%, the Ag2WO4 / BiFeO3 heterojunction exhibits the best removal effect on 40 mg / L Lanazol Red 5B (LR5B) under simulated sunlight for 100 minutes, achieving a removal rate of 95.62%. This is 5.17, 1.71, and 1.10 times that of pure BiFeO3, the Ag2WO4 / BiFeO3 heterojunction with a 5% Ag2WO4 loading, and the Ag2WO4 / BiFeO3 heterojunction with a 10% Ag2WO4 loading, respectively. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The XRD patterns of the photocatalytic materials in each embodiment and comparative example are shown below. Figure 2 SEM images of the photocatalytic materials prepared in Comparative Examples 1, 2 and Example 3; Figure 3 XPS spectra of Comparative Examples 1, 2 and Example 3; Figure 4 This is the EDS element mapping diagram for Example 3; Figure 5 (a) Photocatalytic degradation spectrum of LR5B by the photocatalytic materials of each embodiment and comparative example; (b) Photocatalytic degradation spectrum of LR5B by the photocatalytic material prepared in Example 3 under control conditions; (c) Full spectrum of LR5B concentration change over time during degradation by the photocatalytic material prepared in Example 3; (d) Kinetic curve of degradation reaction of the photocatalytic materials of each embodiment and comparative example. Figure 6 The degradation rate of different pollutants by the photocatalytic material prepared in Example 3; Figure 7 The image shows the free radical capture experiment spectrum of the photocatalytic material prepared in Example 3. Detailed Implementation

[0017] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," or "the," and similar words used in the specification and claims of this patent application do not express a limitation of quantity, but rather indicate the presence of at least one; terms such as "comprising" or "including" indicate that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0019] Example 1 An Ag₂WO₄ / BiFeO₃ heterostructure magnetic nanophotocatalytic material, wherein the mass fraction of Ag₂WO₄ is 5%, is prepared by the following steps: S1. Preparation of Bismuth Ferrate (BiFeO3) by Water Bath Method First, 3.88 g of bismuth nitrate pentahydrate Bi(NO3)3•5H2O and 3.23 g of ferric nitrate nonahydrate Fe(NO3)3•9H2O were dissolved in 30 mL of 10 mol / L KOH solution and stirred at room temperature for 50 minutes, followed by sonication for 30 minutes to obtain a homogeneous suspension. Then, the suspension was transferred to an 80 mL high-pressure reactor and heated at 190 °C for 6 hours. After cooling to room temperature, the final product was washed three times with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 80 °C. After drying, it was ground for later use.

[0020] S2. Preparation of Ag2WO4 / BiFeO3 nanocatalysts 0.5 g of BiFeO3 was added to 50 mL of deionized water and sonicated for 30 minutes to form a homogeneous suspension. Then, 0.0183 g of AgNO3 was added and sonicated for another 30 minutes. Subsequently, 0.0178 g of Na2WO4·2H2O was added and sonicated for 1 hour. The suspension was then transferred to an 80 mL high-pressure reactor and heated at 140 °C for 6 hours. After cooling to room temperature, the final product was washed three times with deionized water and anhydrous ethanol, and then vacuum dried at 60 °C for 24 hours to obtain Ag2WO4 / BiFeO3 heterojunction nanomaterials.

[0021] Example 2 An Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material, wherein the mass fraction of Ag2WO4 is 10%.

[0022] The difference between Example 2 and Example 1 is as follows: In step S2, 0.5 g of BiFeO3 was added to 50 mL of deionized water and sonicated for 30 minutes to form a uniform suspension. Then, 0.0366 g of AgNO3 was added and sonicated for another 30 minutes. Subsequently, 0.0356 g of Na2WO4·2H2O was added and sonicated for 1 hour. The suspension was then transferred to an 80 mL high-pressure reactor and heated at 140°C for 6 hours. After cooling to room temperature, the final product was washed three times with deionized water and anhydrous ethanol, and then vacuum dried at 60°C for 24 hours to obtain Ag2WO4 / BiFeO3 heterojunction nanomaterials.

[0023] Example 3 An Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material, wherein the mass fraction of Ag2WO4 is 15%.

[0024] The difference between Example 3 and Example 1 is as follows: In step S2, 0.5 g of BiFeO3 was added to 50 mL of deionized water and sonicated for 30 minutes to form a uniform suspension. Then, 0.0550 g of AgNO3 was added and sonicated for another 30 minutes. Subsequently, 0.0534 g of Na2WO4·2H2O was added and sonicated for 1 hour. The suspension was then transferred to an 80 mL high-pressure reactor and heated at 140°C for 6 hours. After cooling to room temperature, the final product was washed three times with deionized water and anhydrous ethanol, and then vacuum dried at 60°C for 24 hours to obtain Ag2WO4 / BiFeO3 heterojunction nanomaterials.

[0025] Comparative Example 1: Pure BiFeO3 sample The difference between Comparative Example 1 and Example 1 is that it does not include step S2, and only pure BiFeO3 samples are prepared.

[0026] Comparative Example 2: Pure Ag2WO4 sample Add 0.0183 g of AgNO3 to 50 mL of deionized water, followed by 0.0178 g of Na2WO4·2H2O, and sonicate for 1 hour. Then, transfer the suspension to an 80 mL high-pressure reactor and heat at 140 °C for 6 hours. After cooling to room temperature, wash the final product three times with deionized water and anhydrous ethanol, and dry under vacuum at 60 °C for 24 hours.

[0027] Performance testing: For convenience, the prepared Ag2WO4 / BiFeO3 (with mass fractions of Ag2WO4 of 5%, 10%, and 15%) were named AB-5, AB-10, and AB-15, respectively.

[0028] Table 1. Required amounts of Ag₂WO₄ / BiFeO₃ heterojunctions with different ratios (unit: g) Heterojunction ratio BiFeO3 Ag2WO4 AgNO3 Na2WO4·2H2O 5% 0.5 0.025 0.0183 0.0178 10% 0.5 0.05 0.0366 0.0356 15% 0.5 0.075 0.0550 0.0534 The photocatalytic materials prepared in the above embodiments and comparative examples were characterized and tested for photocatalytic degradation performance. The specific test items are as follows: 1. Phase structure: The phase structure was analyzed using X-ray diffraction. Detailed test results are available in [link to relevant documentation]. Figure 1 .

[0029] The XRD pattern of the sample is as follows Figure 1As shown, pure BiFeO3 exhibits obvious diffraction peaks at 2θ = 22.49°, 31.81°, 32.14°, 39.51°, 45.81°, 51.37°, and 57.01°, which correspond to the (101), (012), (110), (021), (202), (113), and (122) crystal planes of the rhombohedral BiFeO3 (JCPDS20-0169), respectively. The Ag2WO4 sample exhibited diffraction peaks at 2θ = 18.43°, 27.23°, 30.08°, 32.24°, 44.69°, 55.40°, 56.20° and 59.20°, which correspond to the (020), (121), (022), (220), (042), (233), (242) and (224) crystal planes of Ag2WO4 (JCPDS 33-1195), respectively. Meanwhile, it can be seen from the Ag2WO4 / BiFeO3 heterostructure that the small amount of Ag2WO4 introduced did not significantly affect the diffraction peaks of BiFeO3. As the amount of Ag2WO4 increased, the peak intensity of BiFeO3 at 2θ=22.49°, 31.81°, and 32.14° decreased, indicating that the introduction of Ag2WO4 affected the growth of the (101), (012), and (110) crystal planes. Furthermore, the (022) crystal plane of Ag2WO4 was observed at 2θ=30.08° in the Ag2WO4 / BiFeO3 heterostructure, indicating the successful synthesis of the Ag2WO4 / BiFeO3 heterostructure. In addition, no other impurity peaks were detected in the figure, further indicating that the product has high purity.

[0030] The above phase structure analysis results show that the Ag2WO4 / BiFeO3 heterojunction photocatalytic material was successfully synthesized in the embodiments of the present invention.

[0031] 2. Morphology and Structure: The surface morphology of the catalyst was observed using field emission scanning electron microscopy. Detailed test results are available in [link to relevant documentation]. Figure 2 .

[0032] superior Figure 2 SEM images of BiFeO3, Ag2WO4, and AB-15 heterojunctions. From Figure 2 As can be seen in (a), pure BiFeO3 exhibits an irregular polyhedral structure with a diameter of about 8-10 μm. Figure 2 (b) In this study, Ag₂WO₄ exhibits a nanorod-like structure with an average length of approximately 500 nm and a width of approximately 80 nm. Figure 2 As shown in (c), nanorod-shaped Ag2WO4 is loaded on the surface of the irregular polyhedral BiFeO3, indicating that Ag2WO4 and BiFeO3 form a good interfacial contact, which is conducive to the interfacial reaction.

[0033] 3. Figure 3XPS spectra of Comparative Examples 1, 2 and Example 3.

[0034] from Figure 3 As can be seen from (a), the AB-15 heterojunction is mainly composed of Bi, Fe, O, Ag and W. Figure 3 In (b), the binding energies of Fe 2p in the AB-15 heterojunction are 711.00 eV, 718.50 eV, and 724.60 eV, respectively, which are slightly higher than the binding energies in pure BiFeO3. This indicates that charge exchange occurs between Ag2WO4 and BiFeO3 when they come into contact due to the difference in Fermi levels. Figure 3 In (c), Bi4f 7 / 2 and Bi 4f 5 / 2 The binding energies at 159.35 eV and 164.65 eV respectively proved the presence of Bi in AB-15. 3+ The existence of. For example... Figure 3 As shown in (d), in the O 1s spectrum, the two characteristic peaks at 530.22 eV and 531.90 eV correspond to lattice oxygen and surface oxygen, respectively. Figure 3 As shown in (e), in the high-resolution XPS spectrum of Ag 3d in AB-15, the peaks at 368.35 eV and 374.35 eV correspond to Ag 3d, respectively. 5 / 2 and Ag 3d 3 / 2 This indicates the presence of Ag in the composite material. + In the W 4f spectrum, the two characteristic peaks at 35.48 eV and 37.63 eV correspond to the W 4f values ​​of element W, respectively. 5 / 2 and W 4f 3 / 2 ( Figure 3 (f) Compared with pure BiFeO3 and Ag2WO4, the binding energies of the AB-15 heterojunction at Bi 4f, O 1s, Fe 2p and W 4f all show positive shifts. This may be attributed to the strong electronic interaction between BiFeO3 and Ag2WO4, which leads to a change in the electron cloud density of the elements. It also confirms the formation of the heterojunction between BiFeO3 and Ag2WO4.

[0035] 4. Figure 4 This is the EDS element mapping diagram for Example 3.

[0036] The EDS spectrum of the sample is as follows Figure 4 As shown, it can be seen from Figure 4 The results show that the five elements Bi, Fe, O, Ag, and W are uniformly distributed on the surface of the AB-15 heterojunction. This result clearly shows that the prepared composite material is composed of BiFeO3 and Ag2WO4, thus further verifying the successful synthesis of the Ag2WO4 / BiFeO3 heterojunction.

[0037] 5. Figure 5 (a) Photocatalytic degradation spectra of LR5B by the photocatalytic materials of each embodiment and comparative example. Figure 5 (b) is the photocatalytic degradation spectrum of LR5B by the photocatalytic material prepared in Example 3 under control conditions. Figure 5 (c) is the full spectrum of LR5B concentration change over time during the degradation of LR5B by the photocatalytic material prepared in Example 3. Figure 5 (d) shows the kinetic curves of the degradation reaction of the photocatalytic materials in each embodiment and comparative example.

[0038] LR5B is a widely used dye, commonly applied in textile printing and dyeing, leather coloring, and other industries. Due to wastewater discharge from these industries, the water pollution caused by LR5B is becoming increasingly prominent. Therefore, this experiment tested the photocatalytic performance of synthesized samples under simulated sunlight conditions, using Lanazon Red 5B (LR5B) as the target pollutant. Figure 5 As shown. To determine the adsorption-desorption characteristics of the synthesized material, a dark reaction was first conducted for 130 minutes during the experiment, as shown. Figure 5 As shown in (b). Experimental results show that the adsorption-desorption equilibrium of the AB-15 heterojunction was basically established after 30 minutes of dark reaction, and the removal rate remained relatively stable in the subsequent 100 minutes. Therefore, 30 minutes was used as the adsorption-desorption equilibrium point in this experiment. The control experiment results show that LR5B hardly degrades under simulated sunlight without the addition of any photocatalyst, indicating that LR5B is relatively stable. During the 100-minute photocatalytic reaction, the removal rate of LR5B by pure BiFeO3 was only 18.46%. However, under the same experimental conditions, Ag2WO4 / BiFeO3 heterojunctions with different amounts of Ag2WO4 loading all showed strong photocatalytic performance. Among them, the AB-15 heterojunction had the strongest photocatalytic activity, with a degradation rate of up to 95.62% for LR5B (e.g., ...). Figure 5 (a) This result shows that the introduction of Ag2WO4 plays a crucial role in improving the photocatalytic performance of the composite material. The main reason is that Ag2WO4 can significantly enhance the light absorption capacity of the photocatalyst and effectively promote the separation efficiency of photogenerated carriers.

[0039] To investigate the photocatalytic degradation process of LR5B by the AB-15 heterojunction under simulated sunlight, ultraviolet-visible absorption spectroscopy was used for analysis. The results are as follows: Figure 5As shown in (c), it is evident from the figure that the characteristic absorption peak of LR5B (located at 529 nm) gradually weakens with the extension of the photocatalytic reaction time. This phenomenon directly indicates that the concentration of LR5B continuously decreases during the photocatalytic reaction. During the photocatalytic reaction, due to the relatively low initial concentration of LR5B and the fewer interfering factors encountered in the early stages, the photocatalytic reaction conforms to a pseudo-first-order kinetic model, expressed as ln(C0 / C...). t =kt. For example... Figure 5 As shown in (d), the kinetic rate constant (k) of the AB-15 heterojunction is approximately 0.03053 min. -1 The concentrations were 22.12, 3.91, and 1.49 times that of pure BiFeO3, AB-5, and AB-10, respectively.

[0040] 6. Figure 6 The degradation rate of different pollutants by the photocatalytic material prepared in Example 3 is shown.

[0041] To evaluate the broad-spectrum nature of the synthesized material in the photocatalytic degradation process, the degradation capabilities of AB-15 for Rhodamine B (RhB), methyl orange (MO), methyl red (MR), Congo red (CR), and Safranin T (Saffron T) were determined. After 100 minutes of simulated sunlight irradiation, AB-15 achieved removal rates of 50.47% and 47.16% for CR and MR, respectively, demonstrating good removal capabilities for these two types of organic pollutants. However, for MO, RhB, and Safranin T, AB-15 achieved removal rates of only 3.04%, 8.07%, and 22.22%, respectively, indicating that these pollutants may exhibit higher stability or more complex removal pathways. The differences in removal efficiency may be due to the different adsorption characteristics and molecular structures of the pollutants themselves, leading to variations in adsorption capacity and adsorption sites on the photocatalyst surface, thus affecting the photocatalytic degradation efficiency.

[0042] 7. Free radical capture experiment: Figure 7 The image shows the free radical capture experiment spectrum of the photocatalytic material prepared in Example 3.

[0043] To further investigate the photocatalytic mechanism of the Ag2WO4 / BiFeO3 heterojunction, three different trapping agents were introduced in the experiment: disodium ethylenediaminetetraacetate (EDTA-2Na) was used to trap holes (h + p-Benzoquinone (BQ) captures superoxide radicals (·O2). -This study investigated the active substances that play a major role in the photocatalytic reaction of Ag2WO4 / BiFeO3 heterojunctions by using BQ to capture hydroxyl radicals (·OH) and isopropanol (IPA). After the addition of BQ, the degradation rate of LR5B decreased sharply to only 3.54%. This result indicates that BQ effectively captures superoxide radicals (·O2). - The addition of EDTA-2Na significantly inhibited the degradation of LR5B. The degradation rate of LR5B also decreased significantly to 30.41% after the addition of EDTA-2Na, indicating that EDTA-2Na may have effectively captured the holes generated during photocatalysis. In contrast, when the trapping agent IPA was added, the degradation rate of LR5B was 90.85%, slightly lower than the normal 95.62%. The trapping experiments showed that h + and O2 - It is the main active species, while ·OH plays a supporting role.

[0044] In summary, the Ag2WO4 / BiFeO3 photocatalytic material prepared in this invention achieves a degradation efficiency of 95.62% for LR5B within 100 minutes under simulated sunlight irradiation. This is 5.17, 1.71, and 1.10 times that of pure BiFeO3 and AB-5 and AB-10, respectively. The photocatalytic degradation efficiency of Ag2WO4 / BiFeO3 is significantly improved, with the Ag2WO4 / BiFeO3 heterojunction with 15% doping exhibiting the best photocatalytic degradation efficiency.

[0045] It should be noted that although the present invention has been described through the above embodiments, the present invention may have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and modifications to the present invention, but all such changes and modifications should fall within the scope of protection of the appended claims and their equivalents.

Claims

1. A method for preparing Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material, characterized in that, The main steps include the following: S1. Preparation of BiFeO3 by water bath method Bi(NO3)3•5H2O and Fe(NO3)3•9H2O were dissolved in KOH solution and subjected to ultrasonic treatment to obtain a uniform suspension. The suspension was then transferred to a reactor for hydrothermal reaction. After the reaction was completed, the resulting precipitate was washed, dried, and ground for later use. S2. Preparation of Ag2WO4 / BiFeO3 nanocatalysts First, a BiFeO3 suspension is prepared using the BiFeO3 obtained in step S1. Then, AgNO3 is added to the BiFeO3 suspension and ultrasonic treatment is performed. After that, Na2WO4·2H2O is added and ultrasonic treatment is performed again. The resulting product is washed and dried to obtain the Ag2WO4 / BiFeO3 heterojunction nanophotocatalytic material.

2. The preparation method of the Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material according to claim 1, characterized in that, In step S1, after dissolving Bi(NO3)3•5H2O and Fe(NO3)3•9H2O in KOH solution, the conditions for ultrasonic treatment of the suspension are as follows: first, stir at room temperature for 50-60 minutes, and then ultrasonically treat the stirred solution for 30-40 minutes.

3. The preparation method of the Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material according to claim 1, characterized in that, In step S1, the hydrothermal reaction conditions are: reacting at 190°C for 6-7 hours.

4. The preparation method of the Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material according to claim 1, characterized in that, In step S1, the precipitate after the reaction is completed is washed three times each with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 80°C.

5. The preparation method of the Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material according to claim 1, characterized in that, In step S2, the preparation steps of the BiFeO3 suspension are as follows: First, add 0.5g of BiFeO3 to 50ml of deionized water to obtain a suspension. Then, add 0.018~0.055g of AgNO3 to the suspension and continue to sonicate for 30~40 minutes to form a uniform suspension.

6. The preparation method of the Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material according to claim 1, characterized in that, In step S2, the ultrasonic treatment is performed again as follows: 0.01~0.055g of Na2WO4•2H2O is added to the suspension, ultrasonication is performed for 1 hour, and then the suspension is transferred to a high-pressure reactor and heated at 140°C for 6 hours.

7. The preparation method of the Ag2WO4 / BiFeO3 heterojunction magnetic nanophotocatalytic material according to claim 1, characterized in that, In step S2, the precipitate is washed three times each with deionized water and anhydrous ethanol, and then placed in a vacuum drying oven at 60~70℃ for 24 hours.

8. An Ag₂WO₄ / BiFeO₃ heterojunction magnetic nanophotocatalytic material, characterized in that... Prepared using the method described in any one of claims 1 to 7.

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