Preparation method of AgBr / BiFeO3 magnetic nano photocatalyst
Patent Information
- Application Number
- CN202510999026.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-11-07
AI Technical Summary
BiFeO3 photocatalytic materials suffer from low visible light utilization, low efficiency in separating photogenerated electrons and holes, and easy recombination, resulting in low photocatalytic activity.
By constructing AgBr/BiFeO3 heterojunctions, AgBr was loaded onto BiFeO3 nanorods using a hydrothermal method to form AgBr/BiFeO3 magnetic nanocatalysts, thereby improving photocatalytic performance.
AgBr/BiFeO3 magnetic nanophotocatalysts achieved a degradation rate of 95.72% for Lanazon Red 5B under simulated sunlight, which is 5.66 times that of pure BiFeO3. Moreover, the preparation process is simple and low-cost.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a nano-photocatalyst preparation technology, in particular to a preparation method of an AgBr / BiFeO3 magnetic nano-photocatalyst. BACKGROUND
[0002] As an important industry for people's livelihood, the textile industry not only meets consumer demand but also brings significant resource and environmental pressure, including high energy consumption, high chemical dependence and serious pollution emissions. According to the China Textile Industry Green Development Report (2021-2022), the energy consumption of the textile industry accounts for 4.3% of the total industrial energy consumption in China, and the wastewater discharge accounts for 11% of the total industrial wastewater discharge in China. In particular, organic dyes in the industry are not only toxic but also difficult to decompose, making them one of the major global pollution sources. Due to the high loss rate of dyes during production, about 15% of the dyes will enter the water environment through wastewater discharge and other means. The toxins in some dyes can cause various diseases in the human body, including water-borne diseases, and even increase the risk of cancer.
[0003] The treatment technology of dye wastewater can be roughly divided into biological treatment, physical treatment and chemical treatment. However, the conventional treatment method generally has poor treatment effect and is prone to secondary pollution, which poses a hidden danger to public health and safety. Therefore, it is particularly urgent to develop new technologies that can efficiently remove dyes from wastewater. Photocatalytic technology has shown great potential in water pollution due to its green, efficient and low-cost advantages. This technology can use clean and renewable solar energy to treat water pollution and convert pollutants into harmless substances. With the increasingly severe situation of environmental pollution and energy shortage, photocatalytic technology has become an important frontier technology in wastewater treatment.
[0004] BiFeO3 is considered to be one of the promising photocatalytic materials for degrading organic matter. BiFeO3 has a narrow band gap (about 2.1-2.8 eV) and high utilization rate of sunlight. BiFeO3 also has strong redox ability and strong degradation ability for organic matter, and is inherently magnetic. However, BiFeO3 has problems such as easy recombination of photo-generated electrons and holes, which leads to low photocatalytic activity. AgBr has a band gap of about 2.6 eV and can effectively utilize visible light, and has good catalytic activity, showing great potential in environmental remediation, energy conversion and biomedical fields. By constructing a heterojunction, the absorption capacity of the material for visible light can be improved, and the separation of photo-generated electrons and holes can be effectively promoted, thereby improving the photocatalytic performance.
[0005] By constructing a heterojunction between BiFeO3 and AgBr, the technical advantages of both can be combined to improve the performance of the photocatalyst, but there are few reports on this aspect of technology. SUMMARY
[0006] The application aims at the deficiency of the prior art, and provides a preparation method of an AgBr / BiFeO3 magnetic nano photocatalyst.
[0007] The technical scheme adopted by the application is as follows: A preparation method of an AgBr / BiFeO3 magnetic nano photocatalyst, comprising the following steps: Step S1, a certain amount of BiFeO3 is added into deionized water, and is ultrasonically treated for 20-30 min to realize dispersion, to obtain a dispersion liquid a; Step S2, AgNO3 solution is added dropwise into the dispersion liquid a obtained in step S1, and is ultrasonically treated for 20-30 min to obtain a suspension A; wherein the dropwise adding amount of AgNO3 is 9-20% of the mass of BiFeO3; Step S3, 6-13% of the mass of BiFeO3 is dissolved into deionized water to obtain a solution B; Step S4, the solution B obtained in step S3 is added dropwise into the suspension A and is ultrasonically treated for 20-30 min to obtain a suspension C; Step S5, the suspension C obtained in step S4 is transferred into a polytetrafluoroethylene-lined reaction kettle, and is subjected to hydrothermal reaction at 130-140 DEG C to obtain a target product mixture, and the hydrothermal reaction time is 5.5-6.5 h; Step S6, the target product mixture is subjected to centrifugation, washing and drying to obtain the AgBr / BiFeO3 catalyst.
[0008] In the preparation method, the dropwise adding amount of AgNO3 is 9% of the mass of BiFeO3 in step S2; and the adding amount of KBr is 6% of the mass of BiFeO3 in step S3.
[0009] In the preparation method, the dropwise adding amount of AgNO3 is 13.6% of the mass of BiFeO3; and the adding amount of KBr is 9.5% of the mass of BiFeO3 in step S3.
[0010] In the preparation method, the dropwise adding amount of AgNO3 is 18.2% of the mass of BiFeO3; and the adding amount of KBr is 13% of the mass of BiFeO3 in step S3.
[0011] In the preparation method, the BiFeO3 is prepared according to the following process in step S1: Step S1.1, 3.88g Bi (NO3) 3*5H2O and 3.23g Fe (NO3) 3*9H2O were dissolved in 30mL 10mol / L KOH solution, stirred at room temperature for 50min, and then ultrasonic for 30min to obtain a uniform suspension; Step S1.2, the suspension obtained in step S11 was transferred to a 80mL polytetrafluoroethylene lined autoclave, and heated at 190℃ for 6h; Step S1.3, after the reaction was completed, after cooling to room temperature, the brown-red precipitate was collected by centrifugation, and dried at 80℃ for 12h to obtain BiFeO3.
[0012] Advantages of the application: 1. The preparation method of the AgBr / BiFeO3 magnetic nano photocatalyst, BiFeO3 is prepared by hydrothermal method, AgBr is loaded on the BiFeO3 nanorod by precipitation method, and AgBr / BiFeO3 heterojunction with good photocatalytic performance is formed. The experimental results show that when the loading amount of AgBr is 15%, the degradation rate of laranine red 5B of AgBr / BiFeO3 composite material reaches 95.72% within 60 minutes of simulated sunlight irradiation, which is 5.66 times of pure BiFeO3.
[0013] 2. The preparation method of the AgBr / BiFeO3 magnetic nano photocatalyst is simple in operation process, low in production cost, and economic and environmental protection. Bismuth ferrite is synthesized by solvent thermal deposition method, without high temperature annealing, and compared with chemical synthesis method, without conductive glass and other high-cost and complicated steps in the synthesis process, the method is simple and low in cost. DETAILED DESCRIPTION
[0014] Figure 1 The XRD pattern of the photocatalytic material prepared in Example 1 and the comparative example of the application is shown; Figure 2 The SEM patterns of the photocatalytic materials prepared in each example and the comparative example are shown in (a), (b) and (c), respectively; Figure 3 The XPS pattern of the photocatalytic material prepared in Example 1 and the comparative example of the application is shown; Figure 4 The EDS-mapping pattern of the photocatalytic material of Example 1 of the application is shown; Figure 5 The degradation of laranine red 5B of the photocatalytic material of Example 1 and the comparative example of the application is shown; Figure 6 The effect of different ions on the photocatalytic performance of the photocatalytic material of Example 1 is shown; Figure 7The figure shows the degradation of different pollutants by the photocatalytic material of Example 1 of the application. Figure 8 The figure shows the radical capture experiment of the photocatalytic material prepared in Example 1 of the application. DETAILED DESCRIPTION
[0015] In order to make the technical concept and advantages of the invention to achieve its purpose more clear and explicit, the technical solutions of the application will be further described in detail below with reference to the drawings. It should be understood that the following examples are only used to explain and illustrate the preferred embodiments of the application, and should not be considered as limiting the scope of the patent protection required by the application. EXAMPLE
[0016] The preparation method of the AgBr / BiFeO3 magnetic nano-photocatalyst of the application is as follows: A certain amount of BiFeO3 was added to 40 ml of deionized water and ultrasonically treated for 30 min to achieve dispersion. Then a certain amount of AgNO3 solution was added dropwise to the above suspension, and ultrasonically treated for 30 min to obtain suspension A. A certain amount of KBr was dissolved in 10 ml of deionized water to obtain solution B, which was added dropwise to suspension A and ultrasonically treated for 30 min to obtain suspension C. The mixed suspension C was transferred to an 80 mL polytetrafluoroethylene-lined reaction kettle, and a hydrothermal reaction was carried out at 140℃ for 6 h. After the reaction was completed, it was naturally cooled to room temperature, and the precipitate was separated by centrifugation, washed with deionized water and anhydrous ethanol three times each, and finally placed in a constant temperature drying oven at 80℃ for heat treatment for 6 h to obtain the AgBr / BiFeO3 photocatalytic composite material as shown in Figure 2 (c). As shown in Table 1, by changing the amount of AgBr (10%, 15% and 20%), a series of samples were obtained, which are denoted as AB-10, AB-15 and AB-20, respectively.
[0017] Table 1 Amount of materials required for different proportions of AgBr / BiFeO3 heterojunctions (unit: g)
[0018] BiFeO3 can be prepared by a simple hydrothermal method: First, 3.88 g of Bi(NO3)3•5H2O and 3.23 g of Fe(NO3)3•9H2O were dissolved in 30 mL of 10 mol / L KOH solution, stirred at room temperature for 50 min, and then ultrasonically treated for 30 min to obtain a uniform suspension. Then, the suspension was transferred to an 80 mL polytetrafluoroethylene-lined high-pressure reaction kettle, and heated at 190℃ for 6 h. After cooling to room temperature, the brown-red precipitate was collected by centrifugation, and dried at 80℃ for 12 hours to obtain BiFeO3. Embodiment
[0019] The application discloses a preparation method of an AgBr / BiFeO3 magnetic nano-photocatalyst. Step S1, a certain amount of BiFeO3 is added into deionized water, and ultrasonic treatment is performed for 20-30 min to realize dispersion, so as to obtain a dispersion liquid a; Step S2, AgNO3 solution is added drop by drop into the dispersion liquid a obtained in step S1, and ultrasonic treatment is performed for 20-30 min, so as to obtain a suspension A; wherein the dropwise adding amount of AgNO3 is 9-20% of the mass of BiFeO3; Step S3, 6-13% of the mass of BiFeO3 is dissolved in deionized water to obtain a solution B; Step S4, the solution B obtained in step S3 is added drop by drop into the suspension A and ultrasonic treatment is performed for 20-30 min, so as to obtain a suspension C; Step S5, the suspension C obtained in step S4 is transferred into a polytetrafluoroethylene-lined reaction kettle, and hydrothermal reaction is performed at 130-140 DEG C, so as to obtain a target product mixture, and the hydrothermal reaction time is 5.5-6.5 h; Step S6, the target product mixture is centrifuged, washed and dried to obtain the AgBr / BiFeO3 catalyst.
[0020] Comparative Example 1: AgBr.
[0021] Comparative Example 2: BiFeO 3。
[0022] The photocatalytic materials AgBr / BiFeO3 (the loading amount of AgBr is 10%, 15% and 20%) prepared by the comparative examples 1 and 2 and the embodiment 1 of the application are subjected to performance characterization and photocatalytic degradation performance test, and the specific performance, test items and results are as follows: 1, phase structure: the phase structure is analyzed by means of an X-ray diffractometer, and the test results are shown in Table 1. Figure 1 .
[0023] The composition and structure of AgBr, BiFeO3 and a series of AgBr / BiFeO3 composite materials are studied by means of XRD test, as shown in Table 2. Figure 1As shown, pure BiFeO3 sample shows obvious diffraction peaks at 2θ = 22.49°, 31.81°, 32.14°, 39.51°, 45.81°, 51.37°, and 57.01°, respectively, corresponding to the (101), (012), (110), (021), (202), (113), (122) crystal planes of BiFeO3 standard card (JCPDS 20-0169), and the sample is rhombohedral system. AgBr shows characteristic diffraction peaks at 2θ = 30.94°, 44.33°, 55.04°, 73.24°, respectively, corresponding to the (200), (220), (222) and (420) crystal planes of AgBr standard card (JCPDS 06-0438). The overall diffraction peaks of AgBr / BiFeO3 composite material are consistent with those of rhombohedral BiFeO3. With the loading of AgBr, the diffraction peaks of AgBr at 2θ = 44.33°, 55.04° appear and correspond to the (220), (222) of AgBr. When the content of AgBr gradually increases, the diffraction peak gradually increases, proving the formation of AgBr / BiFeO3 heterojunction.
[0024] 2. Morphology structure: The surface morphology of the catalyst was observed by field emission scanning electron microscope, and the test results are shown in Figure 2 .
[0025] Figure 2 (a), (b), (c) are SEM images of BiFeO3, AgBr and AgBr / BiFeO3 heterojunction, respectively. As can be seen from Figure 2 (a), pure BiFeO3 is stacked by a large number of irregular polyhedrons, and the diameter is about 8-10 μm. Figure 2 In (b), pure AgBr presents a nano-block structure with a diameter of about 1-5 μm. In Figure 2 (c), nano-block AgBr is attached to the surface of BiFeO3, which confirms that AgBr and BiFeO3 have good interface contact, which is beneficial to the interface reaction.
[0026] Phase structure: XPS was used to analyze the elemental composition and valence state of the sample surface, and the test results are shown in Figure 3 .
[0027] In order to study the elemental composition and valence state of the synthesized material, BiFeO3, AgBr and AB-15 were analyzed by XPS, and all the spectra were taken with C 1s (284.8 eV) as the reference. As shown in Figure 3 (e), AB-15 heterojunction is mainly composed of Bi, Fe, O, Ag and Br elements. As shown in Figure 3 (a), the peaks with binding energy of 68.7 eV and 69.5 eV are respectively attributed to Br 3d5 / 2 and Br3d 3 / 2 The orbital pattern confirms that bromine in the composite material is represented by Br. − The valence state exists. For example... Figure 3 As shown in (b), Bi 4f 7 / 2 and Bi4f 5 / 2 The binding energies at 159.2 eV and 164.5 eV indicate that bismuth in BiFeO3 is in a trivalent oxidation state. Figure 3 In (c), the characteristic peaks at 530.0 eV and 531.8 eV in the O 1s spectrum correspond to lattice oxygen and surface oxygen, respectively. Figure 3 In (d), the binding energies of 367.9 eV and 373.9 eV correspond to Ag 3d, respectively. 5 / 2 and Ag 3d 3 / 2 Energy levels, proving Ag + The presence of [missing information]. Furthermore, after loading AgBr, the binding energy of Bi 4f shifts slightly compared to BiFeO3. This may be due to the alteration of the electron cloud density of BiFeO3 when AgBr binds to it, thus affecting its electronic structure. Compared to pure BiFeO3 and AgBr, the binding energies of Br 3d, Bi 4f, O 1s, and Ag 3d in AB-15 all show significant shifts, confirming the formation of a heterojunction between BiFeO3 and AgBr.
[0028] 4. Figure 4 This is the EDS-mapping spectrum of the photocatalytic material in Example 1 of the present invention.
[0029] exist Figure 4 The EDS spectrum shows that five elements, Ag, Br, Bi, Fe, Br, and O, are distributed on the surface of AB-15, indicating that the composite material is composed of AgBr and BiFeO3, further proving the formation of AgBr / BiFeO3 heterojunction.
[0030] 5. Figure 5 The photocatalytic degradation spectra of Lanazol Red 5B by the photocatalytic materials of Example 1 and the comparative example of the present invention are shown.
[0031] Lanazor Red 5B is a synthetic dye traditionally used for dyeing protein fibers such as wool and silk. However, due to its vibrant color and high stability, it has also been widely used in the colored glass and fireworks industries in recent years. However, due to unregulated discharges during the production and use of fireworks, large amounts of wastewater containing Lanazor Red 5B are directly discharged into rivers, leading to increasingly serious water pollution problems. This dye is chemically stable and difficult to degrade naturally; long-term accumulation may damage aquatic ecosystems and even affect human health through the food chain. Therefore, this experiment tested the photocatalytic performance of synthesized samples under simulated sunlight conditions, using Lanazor Red 5B as the target pollutant. Figure 5 As shown in (b), the experiment first conducted a 90-minute dark reaction to determine the adsorption-desorption characteristics of the composite material. It was found that the removal rate of LR5B remained essentially unchanged at 30 and 90 minutes, indicating that the composite material reached adsorption-desorption equilibrium at 30 minutes. Therefore, 30 minutes was used as the adsorption-desorption equilibrium point in this experiment. The control experiment results showed that without the addition of a photocatalyst, LR5B hardly degraded under simulated sunlight irradiation. Figure 5 As shown in (a), within a 60-minute reaction time, the degradation rate of LR5B by the pure BiFeO3 photocatalyst was 16.89%. However, with increasing AgBr content, the degradation efficiency of LR5B by the AgBr / BiFeO3 composite material first increased and then decreased. The 15% AgBr / BiFeO3 composite material exhibited the best photocatalytic activity, achieving a degradation rate of 95.72% for LR5B. This indicates that AgBr plays a crucial role in the photocatalytic degradation process, primarily because increasing AgBr enhances light absorption and promotes the separation of photogenerated charge carriers. However, excessive AgBr may form electron-hole recombination centers, thereby inhibiting the photocatalytic degradation of LR5B. Due to factors such as the low initial concentration of LR5B, the photocatalytic reaction follows a pseudo-first-order kinetic equation. Figure 5 As shown in (c), the kinetic rate constant (k) of the AB-15 heterojunction is approximately 0.03908 min. -1 It is 18.10 times that of pure BiFeO3. Further observation of the photocatalytic degradation of LR5B by the AB-15 heterojunction under simulated sunlight was conducted using real-time monitoring of UV-Vis absorption spectroscopy. Figure 5 As shown in (d), the results indicate that the characteristic absorption peak of LR5B (529 nm) gradually weakens with increasing reaction time, confirming that the concentration of LR5B gradually decreases. The following experiments all used AB-15 heterojunctions for degradation analysis.
[0032] 6. Figure 6 The graphs show the degradation effects of the photocatalytic materials of Example 1 and the comparative example of this invention on Lanazon Red 5B in the presence of different ions.
[0033] As to the influence of different ions on the degradation effect of Rhodamine B, the experiment selected PO4 3- , HPO4 2- , H2PO4 - , SO4 2- , the concentration of which is 1mmol / L, to influence the photocatalytic degradation of RhB, and the experimental results are shown in Figure 6 . After PO4 3- , HPO4 2- , H2PO4 - , the degradation rate of LR5B is reduced to 66.31%, 82.66%, 84.41% respectively, which may be because these ions react with the holes generated in the photocatalytic process. Among them, PO4 3- has the strongest ability to capture holes, which significantly reduces the degradation rate of LR5B. The inhibitory effect of SO4 2- is relatively weak, and after adding it, the degradation rate of LR5B is 89.19%.
[0034] 7、 Figure 7 The degradation map of the photocatalytic material prepared in Example 1 of the present application for different pollutants.
[0035] Figure 7 As shown in (a) and (b), when Lannasun Red 5B and methylene blue coexist, the adsorption of the mixed solution is enhanced, and the degradation is inhibited, and the removal rate of Lannasun Red 5B is 59.69%. This may be due to the mutual competition of active species caused by organic pollutants. Figure 7 As shown in (c), the AgBr / BiFeO3 heterojunction exhibits significant photocatalytic activity for different organic pollutants. The removal rates of LR5B and MR are 95.72% and 87.14% respectively at 60 minutes, indicating that the heterojunction has good mineralization ability for these two types of organic pollutants. For RhB and MB, the degradation rates are only 8.45% and 6.52%, which indicates that these pollutants may have higher stability or more complex degradation path. These differentiated degradation effects may be due to the difference in the chemical structure of various pollutants, resulting in the difference in the adsorption capacity of the photocatalyst surface, and thus affecting the photocatalytic reaction rate.
[0036] 8、Free radical capture experiment: Figure 8 The free radical capture experiment map of the photocatalytic material prepared in Example 1 of the present application.
[0037] The capture experiment is used to study the main active substances involved in the photocatalytic process, which is of great significance to explore the mechanism of photocatalytic reaction. Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), p-benzoquinone (BQ) and isopropyl alcohol (IPA) are used as hole (h + ), superoxide radical (•O 2−) and active substances such as hydroxyl radicals (•OH). As shown in Figure 8 Figure 6, the degradation rate of LR5B is significantly reduced to only 5.86% in the presence of BQ, which indicates that BQ can capture •O 2− , thereby hindering the further degradation of LR5B. When EDTA-2Na is added, the degradation rate of LR5B is reduced to 41.27%, which indicates that EDTA-2Na can effectively capture the holes generated in the photocatalytic process. When IPA is used as a capture agent, the degradation rate of LR5B is 91.27%, which has little effect on the degradation of LR5B. The results show that h + and •O 2− are the main active species in this photocatalytic reaction, and •OH plays an auxiliary degradation role.
[0038] As can be seen from the above, the degradation rate of laranin red 5B reaches 95.72% within 60 minutes under simulated sunlight irradiation, which is 5.66 times that of pure BiFeO3. The photocatalytic degradation efficiency of AgBr / BiFeO3 is significantly improved, and the heterojunction photocatalytic degradation efficiency of AgBr / BiFeO3 doped with 15% is the best.
Claims
1. A method for preparing AgBr / BiFeO3 magnetic nanocatalysts, characterized in that: Comprising Step S1, a certain amount of BiFeO3 is added to deionized water, and ultrasonic treatment is carried out for 20-30 min to achieve dispersion, and a dispersion liquid a is obtained; Step S2, AgNO3 solution is added dropwise to the dispersion liquid a obtained in step S1, and ultrasonic treatment is carried out for 20-30 min, and a suspension A is obtained; wherein the dropwise amount of AgNO3 is 9-20% of the mass of BiFeO3; Step S3, 6-13% of the mass of BiFeO3 of KBr is dissolved in deionized water to obtain solution B; Step S4, the solution B obtained in step S3 is added dropwise to the suspension A and ultrasonic treatment is carried out for 20-30 min to obtain a suspension C; Step S5, the suspension C obtained in step S4 is transferred to a polytetrafluoroethylene lined reaction kettle, and hydrothermal reaction is carried out at 130-140℃, and a target product mixture is obtained, and the hydrothermal reaction time is 5.5-6.5h; Step S6, the target product mixture is centrifuged, washed and dried to obtain the AgBr / BiFeO3 catalyst.
2. The method of claim 1, wherein: In step S2, the dropwise amount of AgNO3 is 9% of the mass of BiFeO3; in step S3, the amount of KBr added is 6% of the mass of BiFeO3.
3. The method of claim 1, wherein: In step S2, the dropwise amount of AgNO3 is 13.6% of the mass of BiFeO3; in step S3, the amount of KBr added is 9.5% of the mass of BiFeO3.
4. The method of claim 1, wherein: The dropwise amount of AgNO3 is 18.2% of the mass of BiFeO3; in step S3, the amount of KBr added is 13% of the mass of BiFeO3.
5. The method of any one of claims 1-4, wherein: In step S1, the BiFeO3 is prepared as follows: step S1.1, 3.88g Bi(NO3)3·5H2O and 3.23g Fe(NO3)3·9H2O are dissolved in 30mL 10mol / L KOH solution, stirred at room temperature for 50min, and then ultrasonic treatment is carried out for 30min to obtain a uniform suspension; Step S1.2, the suspension obtained in step S11 is transferred to an 80mL polytetrafluoroethylene lined high-pressure reaction kettle, and heated at 190℃ for 6h; Step S1.3, after the reaction is completed, the temperature is cooled to room temperature, the brown-red precipitate is collected by centrifugation, and dried at 80℃ for 12h to obtain BiFeO3.