A photocatalyst for degrading tetracycline and its preparation method

Abstract

This invention relates to a photocatalyst for the degradation of tetracycline and its preparation method. The preparation method involves first dissolving SnCl4•5H2O and NaOH in deionized water, stirring until homogeneous, adjusting the pH of the solution, heating to 60°C, adding ZnSO4•7H2O, and maintaining the temperature at 60°C for at least 8 hours. The reactants are centrifuged to obtain a solid product, which is washed with deionized water, dried at 60°C for 12 hours, and then calcined at 580°C for 2 hours to obtain ZnSnO3. Next, Na2WO4•H2O and ZnSnO3 are added to deionized water and stirred to obtain solution A. AgNO3 is dissolved in deionized water at a molar ratio of 2:1 to obtain solution B. Solution B is added to solution A and stirred until homogeneous. The resulting solid product is removed, washed, dried, and calcined at 400°C for 2 hours to obtain the photocatalyst ZnSnO3. 3 / Ag2WO4. This invention provides a new approach for designing highly efficient photocatalysts for environmental remediation.

Description

Technical Field

[0001] This invention relates to a method for preparing a photocatalyst, specifically a photocatalyst for degrading tetracycline and its preparation method. Background Technology

[0002] In recent years, with the rapid development of the pharmaceutical industry, the use of antibiotics has increased significantly. Antibiotics enter the aquatic environment through various pathways, including pharmaceutical wastewater, livestock wastewater, and medical wastewater. Tetracycline, a widely used antibiotic, can treat a variety of bacterial infections. However, residual antibiotics in the environment can enter surface water, groundwater, and even drinking water through surface runoff and leaching, leading to a series of water pollution problems and posing a serious threat to human health.

[0003] Methods for treating tetracycline-containing wastewater have gradually been developed. Currently, methods for removing tetracycline from water generally include physical adsorption, biodegradation, ozone oxidation, and photocatalytic oxidation. Among these, photocatalytic oxidation is a pollutant degradation technology that uses semiconductors as catalysts and solar energy to decompose organic matter, showing good degradation effects on antibiotics. Known photocatalysts include TiO2, ZnO, and In2O3; however, these traditional photocatalysts have wide band gaps, long light response times, low photocatalytic efficiency, and high regeneration costs, which limit their practical application.

[0004] ZnSnO3, as a multifunctional material, has been widely used in photocatalysis, gas sensing, and solar cells due to its high electronic conductivity, excellent optical properties, high stability, low cost, and non-toxicity. However, because ZnSnO3 has poor absorption of visible light, a fast electron-hole recombination rate, and a wide band gap, its photocatalytic activity remains unsatisfactory, thus limiting its application in the optical field.

[0005] Generally, for wide bandgap photocatalysts, coupling them with narrow bandgap photocatalysts with higher ECB values ​​than wide bandgap photocatalysts to construct heterojunctions is an effective way to overcome the above-mentioned shortcomings.

[0006] Ag₂WO₄ is widely used in many important fields, such as electronics, catalysis, environmental protection, and electrode materials. It exhibits good photocatalytic activity against pollutants under visible light irradiation. However, its application is severely limited by its limited visible light collection capacity and photocorrosion. To a certain extent, however, these drawbacks can be overcome by constructing composite photocatalysts. Summary of the Invention

[0007] The purpose of this invention is to provide a photocatalyst for degrading tetracycline and its preparation method, so as to solve the problem of antibiotic pollution caused by the use of tetracycline.

[0008] The objective of this invention is achieved as follows:

[0009] A method for preparing a photocatalyst for degrading tetracycline includes the following steps:

[0010] Synthesis of S1 and ZnSnO3: SnCl4•5H2O and NaOH were dissolved in deionized water and stirred until homogeneous. The pH of the solution was adjusted to 11.3, heated to 60℃, and ZnSO4•7H2O was added. The mixture was kept at 60℃ for at least 8 hours. The reactants were centrifuged to obtain a solid product, which was washed with deionized water and dried at 60℃ for 12 hours. The dried product was then calcined at 580℃ for 2 hours to obtain ZnSnO3.

[0011] Synthesis of S2 and ZA-2: Na2WO4•H2O and ZnSnO3 were added to deionized water and stirred to obtain solution A; AgNO3 was dissolved in deionized water at a molar ratio of 2:1 to obtain solution B; solution B was added to solution A and stirred evenly; the solid product obtained from the reaction was taken out, washed and dried, and then calcined at 400℃ for 2h to obtain the photocatalyst ZnSnO3 / Ag2WO4, which is called ZA-2.

[0012] Furthermore, the material ratio in step S1 is as follows:

[0013] SnCl4•5H2O NaOH Deionized water ZnSO4•7H2O

[0014] 0.32g 0.14g 40mL 0.26g.

[0015] Furthermore, the material ratio in step S2 is as follows:

[0016] Na2WO4•H2O ZnSnO3 Deionized water

[0017] 0.20g 0.56g 80mL.

[0018] Furthermore, in the preparation method of the present invention, the amount of Na2WO4•H2O added in step S2 is increased by 50%, and the photocatalyst ZnSnO3 / Ag2WO4 generated by the reaction is called ZA-1.

[0019] Furthermore, in the preparation method of the present invention, the amount of Na2WO4•H2O added in step S2 is reduced by 50%, and the photocatalyst ZnSnO3 / Ag2WO4 generated by the reaction is called ZA-3.

[0020] The objective of this invention can also be achieved in the following ways:

[0021] A photocatalyst for degrading tetracycline is prepared using the photocatalyst preparation method of this invention.

[0022] This invention prepared a ZnSnO3 / Ag2WO4 photocatalyst. SEM and TEM images confirmed the successful composite of ZnSnO3 and Ag2WO4. The chemical state and optical properties of the ZnSnO3 / Ag2WO4 photocatalyst were investigated using XRD, BET, and XPS. Furthermore, the photocatalytic activity of ZnSnO3 / Ag2WO4 was studied using transient photocurrent response, EIS Nyquist spectroscopy, and Mott-Schottky spectroscopy. The results showed that the ZnSnO3 / Ag2WO4 composite material possesses excellent photocarrier generation and transport capabilities, and its photocatalytic activity is significantly higher than that of pure ZnSnO3 and Ag2WO4. Moreover, photocatalytic degradation experiments demonstrated that the ZnSnO3 / Ag2WO4 composite material exhibited the best degradation effect and the highest reaction rate for tetracycline under visible light irradiation.

[0023] This invention prepares a ZnSnO3 / Ag2WO4 heterojunction photocatalyst, demonstrating the presence of interfacial chemical bonds, maximizing the advantages of the photocatalyst, improving the response to visible light, revealing the mechanism of photogenerated charge migration, and achieving effective separation of photogenerated carriers.

[0024] This invention provides a new approach for designing highly efficient photocatalysts for environmental remediation. Attached Figure Description

[0025] Figure 1 This is a process flow diagram for preparing the photocatalyst ZnSnO3 / Ag2WO4 of the present invention.

[0026] Figure 2 These are electron microscope (SEM) images, micrographs, and elemental mapping diagrams of the photocatalyst and its associated compounds; where (a) is a scanning electron microscope (SEM) image of ZnSnO3; (b) is a scanning electron microscope (SEM) image of Ag2WO4; (c) is a scanning electron microscope (SEM) image of ZnSnO3 / Ag2WO4; (d) is a high-resolution HRTEM (High-Resolution Electron Micrograph) photograph of ZnSnO3; (e) is a high-resolution HRTEM photograph of Ag2WO4; (f) is a high-resolution HRTEM photograph of ZnSnO3 / Ag2WO4; and (g)–(l) are elemental mapping diagrams of Zn, Sn, O, Ag, and W in ZnSnO3 / Ag2WO4.

[0027] Figure 3 These are the XRD patterns of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4.

[0028] Figure 4 These are optical characterization diagrams of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4; where (a) is a nitrogen adsorption-desorption isotherm diagram; and (b) is a pore size distribution diagram of the adsorption branch of the isotherm calculated using the Barrett-Joyner-Halenda method.

[0029] Figure 5 These are the XPS spectra of ZnSnO3 / Ag2WO4; where (a) is the survey, (b) is Zn 2p, (c) is Sn 3d, (d) is O 1s, (e) is Ag 3d, and (f) is W 4f.

[0030] Figure 6 The following are electrochemical characterization diagrams of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4; where (a) is the electrochemical impedance diagram; (b) is the transient photocurrent response diagram; (c) is the Mott-Schottky diagram; and (d) is the PL spectrum.

[0031] Figure 7 The diagram shows the photocatalytic degradation of tetracycline under visible light irradiation. (a) is a schematic diagram of tetracycline degradation in the presence of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4; (b) is a schematic diagram of the primary degradation kinetics of tetracycline in the presence of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4; and (c) is a schematic diagram of the photocatalytic degradation of tetracycline under visible light, showing the changes in photocatalytic activity of ZnSnO3 / Ag2WO4 over three consecutive usage cycles. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0033] like Figure 1 As shown, the preparation method of the photocatalyst of the present invention includes the following steps:

[0034] Synthesis of S1 and ZnSnO3: 0.32 g SnCl4•5H2O and 0.14 g NaOH were dissolved in 40 mL of deionized water and stirred. The pH of the solution was adjusted to 11.3, heated to 60 °C, and 0.26 g ZnSO4•7H2O was added. The mixture was kept at 60 °C overnight. The solid product was obtained by centrifugation, washed with deionized water, dried in an oven at 60 °C for 12 h, and then calcined at 580 °C for 2 h to obtain ZnSnO3.

[0035] Synthesis of S2 and ZA-2: 0.20 g Na2WO4•H2O and 0.56 g ZnSnO3 were added to 80 mL of deionized water and stirred for 15 min to obtain solution A; AgNO3 (the molar ratio of AgNO3 to Na2WO4•H2O was 2:1) was dissolved in 80 mL of deionized water to obtain solution B; solution B was added to solution A and stirred for 2 h; the obtained solid product was washed, dried, and calcined at 400 °C for 2 h to obtain the photocatalyst ZnSnO3 / Ag2WO4, named ZA-2.

[0036] In the preparation method of this invention, if the amount of Na2WO4•H2O added in step S2 is changed to 0.30g, the photocatalyst ZnSnO3 / Ag2WO4 generated by the reaction is called ZA-1.

[0037] In the preparation method of this invention, if the amount of Na2WO4•H2O added in step S2 is changed to 0.10g, the photocatalyst ZnSnO3 / Ag2WO4 generated by the reaction is called ZA-3.

[0038] Characterization of the photocatalyst ZnSnO3 / Ag2WO4 of this invention:

[0039] The morphology and microstructure of the photocatalyst ZnSnO3 / Ag2WO4 were obtained using scanning electron microscopy. The lattice information of the composite material was observed using transmission electron microscopy. X-ray diffraction analysis was used to determine the crystal structure of the samples. An automated BET analyzer was used to determine the BET specific surface area and its corresponding pore size distribution. X-ray photoelectron spectroscopy was used to analyze the chemical composition and surface state of the samples. A fluorescence spectrophotometer was used to study the photoluminescence properties.

[0040] Photocatalytic experiments of the photocatalyst ZnSnO3 / Ag2WO4 of this invention:

[0041] Using tetracycline as a model pollutant, photocatalytic experiments were conducted in a PL-X300D-FH photochemical reactor to evaluate the photocatalytic activity of the photocatalyst. The light source consisted of a 300W xenon lamp and an ultraviolet filter (wavelength <420 nm). 100 mg of catalyst was uniformly dispersed in 100 mL of tetracycline solution (20 mg / L) in a jacketed beaker connected to a circulating water system. Before illumination, the mixed solution was stirred in the dark for 30 min at 500 rpm / min using a magnetic stirrer to reach adsorption-desorption equilibrium. Subsequently, approximately 2 mL of the suspension was drawn using a 2 mL plastic syringe at 0 min, 2 min, 5 min, 10 min, and 15 min, and the catalyst particles were filtered through a 0.22 μm membrane filter. The concentration of tetracycline was determined by high-performance liquid chromatography (HPLC). The detection method was: A) acetonitrile (15%), B) 2% formic acid solution (85%), temperature 40 °C, flow rate 1 mL / min. The detection wavelength was 275 nm.

[0042] The morphology and microstructure of the photocatalyst prepared in this invention are as follows: Figure 2 As shown. The microstructures of ZnSnO3, Ag2WO4, and the photocatalyst ZnSnO3 / Ag2WO4 of this invention were observed using SEM. The SEM image of pure ZnSnO3 is shown below. Figure 2 As shown in (a), it consists of irregular blocky particles. Figure 2 (b) shows that Ag2WO4 exhibits a rod-like structure, which is consistent with previous reports. Figure 2 (c) is a SEM image of ZnSnO3 / Ag2WO4. It can be seen that blocky structures corresponding to ZnSnO3 and rod-shaped structures corresponding to Ag2WO4 appear, indicating the presence of both ZnSnO3 and Ag2WO4 in the composite material. Figure 2 (d)— Figure 2 As shown in (l), TEM and HRTEM images of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4 were analyzed and presented to further confirm the construction of the ZnSnO3 / Ag2WO4 composite material. TEM images are shown below. Figure 2 (d)— Figure 2 As shown in (e), there is a tight interfacial contact between ZnSnO3 and Ag2WO4, which facilitates effective charge transfer. The adjacent 0.26 nm and 0.48 nm lattice fringes in the HRTEM image belong to the (110) crystal plane of ZnSnO3 and the (111) crystal plane of Ag2WO4, respectively, indicating that ZnSnO3 and Ag2WO4 are tightly bonded. This directly confirms that the construction of heterojunctions can lead to semiconductor recombination and produce a synergistic effect. Figure 2 (g)— Figure 2(l) shows the elemental mapping of the ZnSnO3 / Ag2WO4 composite material, confirming the uniform distribution of elements Zn, Sn, O, Ag and W in the ZnSnO3 / Ag2WO4 composite material.

[0043] The crystal structures of pure ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4 were further verified by XRD. Figure 3 As shown, the diffraction peaks of all samples are relatively clear, indicating that all samples have a high degree of crystallinity. All diffraction peaks of pure ZnSnO3 material are highly consistent with the characteristic peaks of well-crystallized ZnSnO3 (JCPDS No. 01-089-0095). The characteristic diffraction peaks of pure ZnSnO3 centered at 32.0°, 33.9°, 37.4°, and 52.1° can correspond to the (104), (110), (015), and (11-6) crystal planes of hexagonal ZnSnO3, respectively. The prepared pure Ag₂WO₄ sample exhibited eight diffraction peaks at 30.2°, 31.5°, 32.8°, 45.2°, 54.4°, 55.3°, 57.0°, and 57.9°, corresponding to the (002), (231), (400), (060), (233), (352), (550), and (631) crystal planes of orthorhombic Ag₂WO₄ (JCPDS No. 70-1719), respectively. Furthermore, the diffraction peaks of the prepared ZnSnO₃ / Ag₂WO₄ were well attributed to ZnSnO₃ and Ag₂WO₄, indicating that Ag₂WO₄ was successfully incorporated into ZnSnO₃. The peak intensity of Ag₂WO₄ increased with increasing amounts of Na₂WO₄ and AgNO₃ used in the preparation process. In the XRD pattern of the ZnSnO3 / Ag2WO4 composite material, there were no other impurity peaks besides ZnSnO3 and Ag2WO4, indicating that the ZnSnO3 / Ag2WO4 material was successfully synthesized.

[0044] This invention uses nitrogen adsorption-desorption isotherms to study the BET specific surface area and pore size of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4. Figure 4 (a) and Figure 4 As shown in (b), ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4 all exhibit Type IV curves, conforming to the IUPAC classification criteria for mesoporous structures. The BET specific surface areas of ZnSnO3, Ag2WO4, and ZnSnO3 / Ag2WO4 are 31.86 m² / g. 2 / g, 5.96m 2 / g and 40.36m 2 / g, corresponding to pore volumes of 0.055cm. 3 / g, 0.011cm 3 / g and 0.069cm3 / g. The corresponding pore sizes are 4.34nm, 8.21nm, and 5.12nm, respectively. The specific surface area and pore volume of ZnSnO3 / Ag2WO4 are greater than those of ZnSnO3 and Ag2WO4, which endows ZnSnO3 / Ag2WO4 with more active sites for adsorption and photocatalytic degradation of tetracycline.

[0045] This invention employed XPS spectroscopy to investigate the surface composition and chemical state of the ZnSnO3 / Ag2WO4 composite material. The spectral analysis revealed peaks for Zn, Sn, O, Ag, and W in the ZnSnO3 / Ag2WO4 composite material, further supporting its formation. Compared to ZnSnO3, the Zn 2p peak in the ZnSnO3 / Ag2WO4 composite material exhibited a blue shift. Similarly, compared to the Sn 3d peak in ZnSnO3, the two characteristic Sn 3d peaks at 495.25 eV and 486.85 eV in the ZnSnO3 / Ag2WO4 composite material shifted towards lower binding energies. This shift can be attributed to the gain of electrons by Zn and Sn atoms after the formation of a heterojunction at the interface. The formation of OVs (Oxygen-Voltage-Oxygen) suppresses electron-hole recombination, thereby improving photocatalytic performance.

[0046] like Figure 5 As shown in figure a, the lattice oxygen, OVs, and surface adsorbed oxygen of ZnSnO3 / Ag2WO4 appear at 530.71 eV, 531.97 eV, and 532.91 eV in the O 1s spectrum, respectively, showing a significant red shift compared to ZnSnO3 and Ag2WO4. Compared to Ag2WO4, the Ag 3d peak in the ZnSnO3 / Ag2WO4 composite shows a significant blue shift, which may be due to the increased electron density of Ag atoms after the formation of a heterojunction at the interface by the Ag-O bond. Notably, compared to ZnSnO3 and Ag2WO4, the binding energies of Zn 2p, Sn 3d, and Ag 3d in the ZnSnO3 / Ag2WO4 composite show a slight downward shift. It can be inferred that OVs weaken the metallic bond, leading to a decrease in electron density around O, while increasing the electron density around Zn, Sn, and Ag. The Zn and Sn atoms in ZnSnO3 are bonded to the O atoms in Ag2WO4, and the Ag atoms in AgI are bonded to the O atoms in Ag2WO4. The two main peaks of W 4f at 37.66 eV and 35.51 eV indicate that W exists in the form of W(VI) in the ZnSnO3 / Ag2WO4 composite material.

[0047] To obtain more information about the transformation behavior and charge separation of the ZnSnO3 / Ag2WO4 heterostructure, several photoelectrochemical measurements were performed. Information on the sample's electron transport capability was provided via EIS. Furthermore, changes in EIS were related to the material's interfacial properties. The presence of an embedded electric field facilitates the migration and separation of photogenerated charges at the interface, one visual manifestation of which is a decrease in impedance.

[0048] Figure 6 The separation and recombination of photogenerated electrons and holes in the ZnSnO3 / Ag2WO4 composite material were elucidated. For example... Figure 6 As shown in (a), compared with pure ZnSnO3 and pure Ag2WO4, the ZnSnO3 / Ag2WO4 composite material exhibits the smallest radius of curvature in its EIS spectrum, indicating that it possesses the lowest electron conversion resistance, the highest charge separation efficiency, and the best photocatalytic performance. The photocurrent density curve reflects the separation and migration capabilities of photogenerated carriers. The transient photocurrent response of the sample under visible light irradiation was measured through five cycles of intermittent switching irradiation. Figure 6 As shown in (b), the transient photocurrent response of ZnSnO3 / Ag2WO4 exhibits a repeatable and relatively stable photocurrent curve over five consecutive on-off cycles. Furthermore, under the same testing conditions, the transient photocurrent density of the ZnSnO3 / Ag2WO4 composite material is significantly higher than that of pure ZnSnO3 and pure Ag2WO4, indicating that the ZnSnO3 / Ag2WO4 composite material has the best ability to generate and transport photocarriers. The semiconductor type and band structure of the ZnSnO3 / Ag2WO4 composite material were further investigated using Mott-Schottky plots. Figure 6 As shown in (c), the positive slope of the Mott-Schottky curves indicates that they belong to n-type semiconductors. The flat-band potentials (Efb) of ZnSnO3 and Ag2WO4 are –0.23V and 0.51V (relative to Ag / AgCl), respectively. For n-type semiconductors, the Efb values ​​are very close to the potentials of CB, which are –0.23V and 0.51V (relative to Ag / AgCl), respectively. According to the potential conversion relationship: E(NHE) = E(Ag / AgCl) + 0.197, the CB of ZnSnO3 and Ag2WO4 are –0.03V and 0.71V (relative to NHE), respectively. The separation of photogenerated charges is crucial to the photocatalytic activity of semiconductors, and luminescence is caused by the migration, transfer, and recombination of photoluminescent carriers in the semiconductor. Therefore, the separation efficiency of photogenerated carrier capture and migration separation in semiconductors is determined using emission spectra. Generally, the better the separation and migration efficiency of photoluminescent carriers, the lower the photoluminescence intensity in the emission spectrum, indicating a lower recombination rate of photoelectron-hole pairs and higher photocatalytic activity of the semiconductor catalyst. For example... Figure 6As shown in (d), pure ZnSnO3 has the highest emission peak intensity, indicating the highest carrier sufficiency efficiency. The ZnSnO3 / Ag2WO4 composite material has weaker PL emission, indicating that the ZnSnO3 / Ag2WO4 composite material has high photoinduced electron and hole separation efficiency, thus effectively promoting charge transfer.

[0049] The photocatalytic activity of the prepared photocatalysts was studied under visible light irradiation, targeting tetracycline as the pollutant. To improve the accuracy of the experiment, a blank experiment was also conducted. All mixed solutions were stirred in the dark for 30 min before light irradiation to reach adsorption-desorption equilibrium. The catalytic effects of different catalysts are shown below. Figure 7 As shown in (a), the tetracycline solution concentration remained almost unchanged without the addition of a photocatalyst, indicating that tetracycline is relatively stable. The catalytic activity of pure Ag₂WO₄ was not ideal; after 15 min of visible light irradiation, the degradation rate of tetracycline was only 12.14%. This may be due to the wide band gap of Ag₂WO₄ and its narrow response range to visible light, resulting in low photocatalytic efficiency. The catalytic activity of pure ZnSnO₃ was slightly better than that of pure Ag₂WO₄; after 15 min of visible light irradiation, the degradation rate of tetracycline was 39.03%. This is because the concentration of e- in a single catalyst... - and h + Under light irradiation, the material readily recombines, resulting in lower photocatalytic activity. Compared to pure Ag₂WO₄, the composite material exhibits better catalytic performance, with a degradation rate of over 45% for tetracycline after 15 min of visible light irradiation. Different molar ratios of ZnSnO₃ / Ag₂WO₄ composites showed different degradation rates, in the order ZA₂ > ZA₃ > ZA₁. Under the same reaction conditions, the degradation rate of ZA₂ reached its maximum of 62.87% after 15 min of visible light irradiation, due to the formation of heterojunctions and the increase in catalytically active sites. Furthermore, all photocatalysts used for the photocatalytic degradation of tetracycline conformed to a pseudo-first-order kinetic model.

[0050] ln(C t / C0)=–kt

[0051] Where t is the irradiation time, and k is the kinetic constant (min). -1 C0 is the initial concentration of tetracycline at 0 min, and C t The actual concentration of tetracycline at time t is given. Kinetic curves for different catalysts are shown below. Figure 7 As shown in (b), the k-constants for ZnSnO3, Ag2WO4, ZA-1, ZA-2, and ZA-3 are 0.02261 min. -1 0.00306min -1 0.028min -1 0.03739min -1and 0.02834min -1 The change in reaction rate was consistent with the photocatalytic activity. ZA-2 exhibited the highest reaction rate, 1.65 times that of ZnSnO3 and 12.22 times that of Ag2WO4, indicating that the heterojunction formed between ZnSnO3 and Ag2WO4 is beneficial for improving photocatalytic performance. The photostability and reusability of the photocatalyst are another important factor affecting its practical application. Under the same experimental conditions, the changes in the catalytic performance of ZnSnO3 / Ag2WO4 after three uses were obtained through continuous degradation experiments. Figure 7 As shown in (c), after three cycles, the photodegradation effect of the ZnSnO3 / Ag2WO4 composite material did not show significant loss, indicating that the prepared composite material maintains stable performance during repeated use and has good application prospects in actual industry.

Claims

1. A method for preparing a photocatalyst for degrading tetracycline, characterized in that, Includes the following steps: Synthesis of S1 and ZnSnO3: SnCl4•5H2O and NaOH were dissolved in deionized water, stirred until homogeneous, and the pH of the solution was adjusted to 11.

3. The solution was heated to 60℃, and ZnSO4•7H2O was added. The solution was kept at 60℃ for at least 8 hours. The reactants were centrifuged to obtain a solid product, which was washed with deionized water and dried at 60℃ for 12 hours. The product was then calcined at 580℃ for 2 hours to obtain ZnSnO3. Synthesis of S2 and ZA-2: Na2WO4•H2O and ZnSnO3 were added to deionized water and stirred to obtain solution A; AgNO3 was dissolved in deionized water with a molar ratio of AgNO3 to Na2WO4·H2O of 2:1 to obtain solution B; solution B was added to solution A and stirred evenly; the solid product obtained from the reaction was taken out, washed and dried, and then calcined at 400℃ for 2h to obtain the photocatalyst ZnSnO3 / Ag2WO4, named ZA-2.

2. The method for preparing the photocatalyst for degrading tetracycline according to claim 1, characterized in that, The material ratio in step S1 is as follows: SnCl4•5H2O NaOH Deionized water ZnSO4•7H2O 0.32g 0.14g 40mL 0.26g.

3. The method for preparing the photocatalyst for degrading tetracycline according to claim 1, characterized in that, The material ratio in step S2 is as follows: Na2WO4•H2O ZnSnO3 Deionized water 0.20g 0.56g 80mL.

4. The method for preparing the photocatalyst for degrading tetracycline according to claim 3, characterized in that, Increasing the amount of Na2WO4•H2O added in step S2 by 50% results in the photocatalyst ZnSnO3 / Ag2WO4 being generated and referred to as ZA-1.

5. The method for preparing the photocatalyst for degrading tetracycline according to claim 3, characterized in that, Reducing the amount of Na2WO4•H2O added in step S2 by 50% results in the photocatalyst ZnSnO3 / Ag2WO4 being generated, which is called ZA-3.

6. A photocatalyst for degrading tetracycline, characterized in that, It is prepared by the method of any one of claims 1-5.

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