TiO2-ZnO photocatalyst for efficiently degrading neonicotinoid pesticides as well as preparation method and application of TiO2-ZnO photocatalyst

Abstract

The invention belongs to the field of pesticide pollution remediation. The invention provides a preparation method of a TiO2-ZnO photocatalyst for efficiently degrading neonicotinoid pesticides, which comprises the following steps: (1) grinding and fully mixing ZnO and 2-methylimidazole, transferring into a reaction kettle, and reacting to obtain an MOFs material ZIF-8; (2) adding polyethyleneimine and acetic acid into tetrabutyl titanate, stirring, then adding ZIF-8, and continuously stirring; (3) transferring the mixed solution in the step (2) into a polytetrafluoroethylene reaction kettle for reaction; (4) washing and drying the precursor substance after the reaction in the step (3); and (5) transferring the precursor substance obtained in the step (4) into a crucible, and carrying out high-temperature pyrolysis in a tubular furnace in an air atmosphere to obtain TiO2-ZnO. The invention further provides the TiO2-ZnO photocatalyst for efficiently degrading the neonicotinoid pesticide and application of the TiO2-ZnO photocatalyst. The TiO2-ZnO photocatalyst provided by the invention shows good degradation performance and long-term stability on the neonicotinoid pesticide. The synthesis steps are simple and suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of pesticide pollution remediation, and in particular relates to a highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides, its preparation method and application. Background Technology

[0002] Neonicotinic pesticides are neuroactive insecticides widely used in over 120 countries worldwide due to their highly effective pest control, accounting for approximately 25% of the global pesticide market. However, after application to farmland, only about 5% of neonicotinic pesticides are absorbed by crops. Residual neonicotinic pesticides migrate from farmland to rivers, lakes, and other water systems through various pathways, causing water pollution.

[0003] Traditional methods for removing neonicotinoid pesticides mainly include biological methods (microbial degradation, activated sludge adsorption), physical methods (sedimentation, filtration, physical adsorption), and electrochemical methods (electrophoresis, electrodialysis). These methods all have inherent drawbacks: electrochemical methods are energy-intensive, prone to losses, and costly during degradation; membrane separation methods have low adsorption capacity, low efficiency, and high cost; and microbial methods have long reaction times, are easily affected by the environment, and have unstable effects. Therefore, the effectiveness of traditional treatment methods for removing neonicotinoid pesticides from water bodies is not ideal.

[0004] Photocatalysis technology has become a research hotspot in recent years due to its mild reaction conditions, low energy consumption, and low cost. However, single-component photocatalysts still face some technical challenges: (1) poor light utilization efficiency and low response to visible light; (2) poor stability and easy deactivation; (3) environmentally unfriendly, as the preparation process causes pollution, which limits the practical application of this technology.

[0005] Therefore, existing technologies urgently need to be addressed. Summary of the Invention

[0006] This invention aims to address the shortcomings of existing technologies by providing a highly efficient TiO2-ZnO photocatalyst for the degradation of neonicotinoid pesticides, its preparation method, and its applications. By constructing a heterojunction, this invention effectively reduces the recombination rate of electron-hole pairs, while simultaneously broadening the utilization range of visible light and enhancing the photocatalytic effect. The TiO2-ZnO photocatalyst provided by this invention for the efficient degradation of neonicotinoid pesticides has advantages such as a wide visible light response range and high photogenerated carrier separation efficiency. Experiments demonstrate that the TiO2-ZnO photocatalyst exhibits excellent degradation performance and long-term stability for neonicotinoid pesticides.

[0007] To address the above problems, the present invention provides the following technical solution: A method for preparing a highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides includes the following steps: (1) ZnO and 2-methylimidazole were thoroughly mixed by grinding and then transferred into a reaction vessel to obtain MOF material ZIF-8; (2) Polyethyleneimine (or simply “PEI” in this invention) and acetic acid are added to tetrabutyl titanate and stirred, and then ZIF-8 is added and stirred again. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction to obtain the precursor material; (4) The precursor material after the reaction in step (3) is washed and dried; (5) The precursor material obtained in step (4) is transferred into a crucible and pyrolyzed at high temperature in an air atmosphere in a tube furnace to obtain TiO2-ZnO, which is the photocatalyst of the present invention.

[0008] In the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides as described above, in step (1), the mass ratio of ZnO to 2-methylimidazole is 1:(2-5).

[0009] As described above, in the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides, the reaction temperature in step (1) is 120-150 ℃ and the reaction time is 46-50 h.

[0010] In the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides as described above, in step (2), the stirring rate is 400-500 r / min and the stirring time is 5-20 min.

[0011] In the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides as described above, in step (2), the mass-volume ratio (g:mL) of ZIF-8 to tetrabutyl titanate is (0.5-3.5):10.

[0012] As described above, in the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides, in step (3), the reaction temperature is 170-190 ℃ and the reaction time is 22-24 h.

[0013] As described above, in the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides, in step (4), the washing is performed by washing the precursor material 3-5 times with deionized water and anhydrous ethanol respectively; the drying is performed by drying in an oven at a temperature of 55-60 ℃ for 6-10 h.

[0014] As described above, in the preparation method of TiO2-ZnO photocatalyst for efficient degradation of neonicotinoid pesticides, in step (5), the heating rate is 5-10 ℃ / min, the pyrolysis temperature is 450-600 ℃, and the reaction time is 2-4h.

[0015] Based on the same inventive concept, this invention provides a TiO2-ZnO photocatalyst for the efficient degradation of neonicotinoid pesticides, which is prepared by the preparation method described above.

[0016] Based on the same inventive concept, this invention provides an application of TiO2-ZnO photocatalyst, wherein the TiO2-ZnO photocatalyst prepared by the preparation method described above or the TiO2-ZnO photocatalyst described above is used for the photocatalytic degradation of neonicotinoid pesticides.

[0017] As described above, the neonicotinoid pesticide is any one of imidacloprid, thiamethoxam, acetamiprid, and dinotefuran.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The TiO2-ZnO photocatalyst for the efficient degradation of neonicotinoid pesticides provided by this invention can achieve rapid and efficient removal of neonicotinoid pesticides from water bodies, and still has high photocatalytic activity after repeated use.

[0019] 2. The TiO2-ZnO photocatalyst for the efficient degradation of neonicotinoid pesticides provided by this invention has unique advantages in wastewater purification compared to single-component catalysts, including a rapid and effective carrier separation rate, a broad absorption spectrum, and excellent chemical stability. Tests show that its degradation process generates a large number of hydroxyl radicals and photogenerated holes in water, which can completely mineralize neonicotinoid pesticides, achieving complete removal of neonicotinoid pesticides under natural light.

[0020] 3. The method for preparing the highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides provided by this invention does not require solvents, has many excellent properties such as being green, having high porosity, and having a large specific surface area, and can be reused, thus achieving true greenness and environmental friendliness. Attached Figure Description

[0021] Figure 1 This is a process diagram of preparing the TiO2-ZnO photocatalyst in Example 1; Figure 2 The SEM image of TiO2-ZnO prepared in Example 1; Figure 3 The XRD pattern of TiO2-ZnO prepared in Example 1; Figure 4XPS spectra of TiO2-ZnO prepared in Example 1 and TiO2 and ZnO prepared in Comparative Examples 1 and 2; Figure 5 The BET pore size distribution diagram of TiO2-ZnO prepared in Example 1 is shown. Figure 6 The N2 adsorption-desorption curve of TiO2-ZnO prepared in Example 1 is shown. Figure 7 The results show the photocatalytic performance of TiO2-ZnO prepared in Example 1 on imidacloprid solutions of different concentrations. Figure 8 The results show the photocatalytic performance of TiO2-ZnO prepared in Example 1 on neonicotinoid pesticides. Figure 9 The results show the photocatalytic stability of TiO2-ZnO prepared in Example 1. Figure 10 The visible light degradation test results are for TiO2-ZnO prepared in Example 1; Figure 11 The photocatalytic test results are for the TiO2-ZnO active substance scavenger prepared in Example 1 after its addition. Figure 12 The TiO2-ZnO prepared in Example 1 and the TiO2 and ZnO prepared in Comparative Examples 1 and 2, respectively. + EPR detection spectrum; Figure 13 EPR detection spectra of the ·OH of TiO2-ZnO prepared in Example 1 and TiO2 and ZnO prepared in Comparative Examples 1 and 2. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Polyethyleneimine, abbreviated as "PEI", was purchased from Aladdin, model number MW 600.

[0026] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0027] A method for preparing a highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides includes the following steps: (1) ZnO and 2-methylimidazole were thoroughly mixed by grinding and then transferred into a reaction vessel to obtain MOF material ZIF-8; (2) Add polyethyleneimine and acetic acid to tetrabutyl titanate and stir, then add ZIF-8 and continue stirring; (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction to obtain the precursor material; (4) The precursor material after the reaction in step (3) is washed and dried; (5) The precursor material obtained in step (4) is transferred into a crucible and pyrolyzed at high temperature in an air atmosphere in a tube furnace to obtain TiO2-ZnO, which is the photocatalyst of the present invention.

[0028] Preferably, in step (1), the mass ratio of ZnO to 2-methylimidazole is 1:(2-5). Under this condition, ZIF-8 material with good crystallinity can be formed.

[0029] Preferably, in step (1), the reaction temperature is 120-150 °C and the reaction time is 46-50 h. Most preferably, in step (1), the reaction temperature is 140 °C and the reaction time is 48 h.

[0030] Preferably, in step (2), the stirring rate is 400-500 r / min and the stirring time is 5-20 min, so that all components are fully mixed and uniform. If the speed is too low, below 400 r / min, the stirring will be insufficient and the stirring process will easily cause agglomeration; if the speed is too high, above 500 r / min, it will easily splash and cause material loss.

[0031] Preferably, in step (2), the mass-to-volume ratio (g:mL) of ZIF-8 to tetrabutyl titanate is (0.5-3.5):10. If the mass-to-volume ratio of ZIF-8 to tetrabutyl titanate is less than 0.5:10, the ZnO content in the prepared material is low, and the photolysis effect is poor; if the mass-to-volume ratio of ZIF-8 to tetrabutyl titanate is greater than 3.5:10, the preparation process cannot be stirred sufficiently, the TiO2 and ZnO in the obtained material are unevenly distributed, and the calcination process is prone to carbonization.

[0032] Preferably, in step (3), the reaction temperature is 170-190 ℃ and the reaction time is 22-24 h. The reaction is carried out at 170-190 ℃ for 22-24 h to form a precursor material with uniform texture. If the time is too short, less than 22 h, the reaction cannot be fully completed; if the time is too long, more than 24 h, the degradation performance of the obtained material will not be improved, and resources will be wasted.

[0033] Preferably, in step (4), the washing involves washing the precursor material 3-5 times with deionized water and anhydrous ethanol respectively to remove the impurities contained therein; the drying involves drying in an oven at a temperature of 55-60 ℃ for 6-10 hours to remove the water and ethanol mixed into the material during the washing process.

[0034] Preferably, in step (5), the heating rate is 5-10 ℃ / min, the pyrolysis temperature is 450-600 ℃, and the reaction time is 2-4 h. If the reaction time is less than 2 h, the prepared material is not fully calcined and still contains some precursor substances, resulting in poor photolysis effect. If the reaction time is more than 4 h, the material is over-calcined, the photolysis efficiency of the material decreases, and it is easily carbonized. Most preferably, in step (5), the heating rate is 5 ℃ / min, the pyrolysis temperature is 600 ℃, and the reaction time is 3 h.

[0035] Figure 1 This is a process diagram of preparing TiO2-ZnO photocatalyst in Example 1.

[0036] Based on the same inventive concept, this invention provides a TiO2-ZnO photocatalyst for the efficient degradation of neonicotinoid pesticides, which is prepared by the preparation method described above.

[0037] Based on the same inventive concept, this invention provides an application of TiO2-ZnO photocatalyst, wherein the TiO2-ZnO photocatalyst prepared by the preparation method described above or the TiO2-ZnO photocatalyst described above is used for the photocatalytic degradation of neonicotinoid pesticides.

[0038] As described above, the neonicotinoid pesticide is any one of imidacloprid, thiamethoxam, acetamiprid, and dinotefuran.

[0039] Example 1 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir for 10 min with a magnetic stirrer at a stirring rate of 450 r / min. Then add 2.66 g ZIF-8 and continue stirring for 10 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 180 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and twice with anhydrous ethanol, and then dried in an oven at 60 °C for 6 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 600 °C at a rate of 5 °C / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain a white solid TiO2-ZnO, denoted as TiO2-ZnO-1.

[0040] Example 2 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 150 °C and the reaction time is controlled at 50 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 8 min at a stirring rate of 450 r / min. Then add 2.66 g ZIF-8 and continue stirring for 5 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 175 °C and a reaction time of 24 h to obtain the precursor material. (4) The precursor material after the reaction in step (3) was washed 5 times with deionized water and 3 times with anhydrous ethanol, and then dried in an oven at 60 °C for 8 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 450 °C at a rate of 10 °C / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain a white solid TiO2-ZnO, denoted as TiO2-ZnO-2.

[0041] Example 3 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 120 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.8 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 500 r / min. Then add 2.66 g ZIF-8 and continue stirring for 5 min at a stirring rate of 400 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 175 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and three times with anhydrous ethanol, and then dried in an oven at 60 °C for 8 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 550 °C at a rate of 5 °C / min in a tube furnace under an air atmosphere. The mixture is then pyrolyzed for 3 h to obtain a white solid TiO2-ZnO, denoted as TiO2-ZnO-3.

[0042] Example 4 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.8 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 450 r / min. Then add 2.66 g ZIF-8 and continue stirring for 5 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 175 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed 5 times with deionized water and 4 times with anhydrous ethanol, and then dried in an oven at 60 °C for 8 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 500 °C at a rate of 10 °C / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain a white solid TiO2-ZnO, denoted as TiO2-ZnO-4.

[0043] Comparative Example 1 The difference from Example 1 is that the amount of ZIF-8 added was changed from 2.66 g to 0 g, and the rest is the same as in Example 1. The resulting photocatalyst is denoted as TiO2.

[0044] Comparative Example 2 ZIF-8 was directly passed through a tube furnace under air atmosphere, and the pyrolysis temperature was increased to 600 °C at a heating rate of 10 °C / min, with the reaction time controlled for 3 h. Finally, a white solid ZnO was obtained after pyrolysis, denoted as ZnO.

[0045] Comparative Example 3 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 450 r / min. Then add 0.5 g ZIF-8 and continue stirring for 10 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 180 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and twice with anhydrous ethanol, and then dried in an oven at 60 °C for 6 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 350 ℃, 450 ℃, 475 ℃, 500 ℃, 550 ℃, 600 ℃ and 700 ℃ at a rate of 5 ℃ / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain white solid TiO2-ZnO.

[0046] Comparative Example 4 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 450 r / min. Then add 1.5 g ZIF-8 and continue stirring for 10 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 180 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and twice with anhydrous ethanol, and then dried in an oven at 60 °C for 6 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 350 ℃, 450 ℃, 475 ℃, 500 ℃, 550 ℃, 600 ℃ and 700 ℃ at a rate of 5 ℃ / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain white solid TiO2-ZnO.

[0047] Comparative Example 5 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 450 r / min. Then add 2.66 g ZIF-8 and continue stirring for 10 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 180 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and twice with anhydrous ethanol, and then dried in an oven at 60 °C for 6 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 350 ℃, 450 ℃, 475 ℃, 500 ℃, 550 ℃, 600 ℃ and 700 ℃ at a rate of 5 ℃ / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain white solid TiO2-ZnO.

[0048] Comparative Example 6 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 450 r / min. Then add 3.5 g ZIF-8 and continue stirring for 10 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 180 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and twice with anhydrous ethanol, and then dried in an oven at 60 °C for 6 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 350 ℃, 450 ℃, 475 ℃, 500 ℃, 550 ℃, 600 ℃ and 700 ℃ at a rate of 5 ℃ / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain white solid TiO2-ZnO.

[0049] Comparative Example 7 (1) Weigh ZnO and 2-methylimidazole at a mass ratio of 1:2.67, mix them thoroughly by grinding, and then transfer them into a reaction vessel. The reaction temperature is 140 °C and the reaction time is controlled at 48 h to obtain MOF material ZIF-8. (2) Add 2.6 g PEI and 5.76 mL acetic acid to 10 mL tetrabutyl titanate and stir with a magnetic stirrer for 5 min at a stirring rate of 450 r / min. Then add 5 g ZIF-8 and continue stirring for 10 min at a stirring rate of 450 r / min. (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction at a temperature of 180 °C and a reaction time of 24 h to obtain the precursor. (4) The precursor material after the reaction in step (3) was washed three times with deionized water and twice with anhydrous ethanol, and then dried in an oven at 60 °C for 6 h. (5) The precursor material obtained in step (4) is transferred into a crucible and heated to 350 ℃, 450 ℃, 475 ℃, 500 ℃, 550 ℃, 600 ℃ and 700 ℃ at a rate of 5 ℃ / min in a tube furnace under air atmosphere. The mixture is then pyrolyzed for 3 h to obtain white solid TiO2-ZnO.

[0050] The following are the performance characterization data of TiO2-ZnO photocatalyst.

[0051] Figure 2 The SEM image of TiO2-ZnO-1 prepared in Example 1 is shown below. Figure 2 It can be seen that the photocatalyst TiO2-ZnO prepared in Example 1 of this invention is in particulate form.

[0052] Figure 3 The XRD pattern of TiO2-ZnO prepared in Example 1 is shown below. Figure 3It can be seen that the diffraction peaks with 2Thate values ​​of 31.21°, 35.37°, 36.24°, 48.11°, 57.18°, 63.67°, and 68.76° correspond to the (100), (002), (101), (102), (110), (103), and (112) crystal planes of the ZnO standard card (PDF 99-0008); the diffraction peaks with 2Thate values ​​of 25.35°, 36.24°, 37.30°, 48.11°, 54.23°, and 55.25° correspond to the (101), (103), (004), (200), (105), and (211) crystal planes of the anatase TiO2 standard card (PDF 99-0008). The correspondence of these peaks indicates the successful recombination of the two, and the strong and sharp diffraction peaks indicate that the grown catalyst is crystalline.

[0053] Figure 4 XPS spectra of TiO2-ZnO-1 prepared in Example 1 and TiO2 and ZnO prepared in Comparative Examples 1 and 2, respectively. Figure 4 It can be seen that the photocatalyst in Example 1 of the present invention contains O, Ti and Zn elements.

[0054] Figure 5 The image shows the BET pore size distribution of TiO2-ZnO prepared in Example 1. According to the IUPAC classification, this isotherm is a typical Type IV isotherm, accompanied by an H3 type hysteresis loop, indicating that the nanofibers have mesoporous properties.

[0055] Figure 6 The N2 adsorption-desorption curve of TiO2-ZnO prepared in Example 1 is shown below. Figure 6 It can be seen that the photocatalyst prepared in the embodiments of the present invention has a large number of mesopores with a size of about 2-3 nm, which endows the material with a well-defined mesoporous structure and highly porous characteristics.

[0056] The properties of TiO2-ZnO-2, TiO2-ZnO-3, and TiO2-ZnO-4 prepared in Examples 2, 3, and 4 are basically the same as those of TiO2-ZnO-1 prepared in Example 1.

[0057] Application Example 1: Photocatalysis Experiment (1) Experimental method: To test the activity of the composite photocatalyst, imidacloprid (hereinafter referred to as "IMM") was selected as a representative neonicotinoid pesticide for photocatalytic degradation experiments. 0.05 g of the photocatalyst prepared in the examples and comparative examples was weighed and dispersed in 25 mL of imidacloprid solution (concentration 50 mg / L). The reaction was carried out in the dark for 30 min to reach adsorption-desorption equilibrium. Subsequently, photocatalysis was performed in a photocatalytic reactor for 24 h. The concentration of imidacloprid was detected by high-performance liquid chromatography (HPLC), and the degradation rate was calculated as: degradation rate = (c0 - c) / c0, where c0 is the initial concentration and c is the concentration after 24 h of degradation.

[0058] (2) Experimental results and analysis: The results showed that after the adsorption equilibrium was reached in the dark reaction for 30 min, the light source was turned on, and photolysis was carried out under simulated natural light conditions at 300 W.

[0059] After 24 hours, the photocatalyst prepared in Example 1 achieved a degradation rate of 68.8% for imidacloprid, indicating that the composite photocatalyst has excellent catalytic degradation performance for imidacloprid. The visible light degradation rate of imidacloprid was 1.78 times higher than that of pure TiO2 and 1.92 times higher than that of pure ZnO. After five cycles of use, the activity remained above 65%, demonstrating good stability. It is also suitable for wastewater treatment of other neonicotinoid pesticides such as thiamethoxam and fipronil.

[0060] The TiO2-ZnO-2, TiO2-ZnO-3, and TiO2-ZnO-4 prepared in Examples 1, 2, 3, and 4 all exhibited a photodegradation performance of over 65% for 50 ppm neonicotinoid pesticides after 24 hours.

[0061] The photocatalyst prepared in Comparative Example 1 showed a degradation rate of 38.57% for imidacloprid; the photocatalyst prepared in Comparative Example 2 showed a degradation rate of 35.83% for imidacloprid.

[0062] As shown in Table 1, Comparative Examples 3-6 exhibited better photocatalytic effects when the ZIF-8 addition amount was between 0.5 and 3.5 g, i.e., the mass-to-volume ratio (g:mL) of ZIF-8 to tetrabutyl titanate was between (0.5-3.5):10, and the calcination temperature was between 450-600 °C. The degradation rate of the control (without photocatalyst) was 17.8%. As shown in Comparative Examples 3-7 in Table 1, the degradation rate was between 17.98% and 40.65% at temperatures below 350 °C or above 700 °C, which was not significantly different from the control degradation rate. A high mass-to-volume ratio (g:mL) of ZIF-8 to tetrabutyl titanate also resulted in a lower degradation rate of the final material. For example, the degradation rate of the material prepared in Comparative Example 7 was between 20.17% and 37.15%, which was significantly lower than that of Comparative Examples 3-6 at temperatures of 450-600 °C.

[0063] Table 1. Degradation rates of materials prepared in Comparative Examples 3-7

[0064] The photocatalytic process was repeated with the TiO2-ZnO prepared in Example 1 at concentrations of 10, 20, 30, and 40 ppm. The test results are as follows: Figure 7 As shown, when the concentration of imidacloprid is low, TiO2-ZnO in Example 1 can achieve complete degradation of imidacloprid.

[0065] The photocatalytic process was repeated with the TiO2-ZnO prepared in Example 1, using thiamethoxam, acetamiprid, and dinotefuran instead of imidacloprid. The test results are as follows. Figure 8 As shown, the TiO2-ZnO in Example 1 also exhibits certain degradation activity against other neonicotinoid pesticides.

[0066] Application Example 2: Cyclic Stability Experiment (1) Experimental method: At room temperature, 25 mL of a 50 ppm IMI solution was added to a quartz tube, followed by 5 mg of the photocatalyst prepared in Example 1. The mixture was stirred in the dark for 0.5 h to reach adsorption equilibrium, ensuring complete light protection during this process. After the dark reaction was complete, 1.5 mL of the mixed solution was filtered through a 0.45 μm aqueous filter membrane. The light source was then turned on, and after 24 h of illumination, a 1.5 mL sample of the IMI solution was taken and filtered, marking the first photocatalytic reaction. After the first photocatalytic reaction, the light source was turned off, the quartz tube containing the photocatalyst was removed, and the photocatalyst was separated by filtration. The sample was dried in a 60 °C oven for 6 h, and the photocatalytic experiment was repeated for the second photocatalytic reaction. The reaction was carried out for a total of 24 h, and this process was repeated a total of 5 times.

[0067] (2) Experimental results and analysis: The photocatalytic stability test results of TiO2-ZnO are as follows: Figure 9 As shown, TiO2-ZnO's performance did not decrease significantly after 5 cycles, indicating its good stability.

[0068] Application Example 3: Natural Light Degradation Experiment (1) Experimental method: At room temperature, 25 mL of a 50 ppm IMI solution was added to a quartz tube, followed by 5 mg of the photocatalyst prepared in Example 1. The solution was stirred in the dark for 0.5 h to reach adsorption equilibrium, ensuring complete light protection during this process. After the dark reaction was complete, 1.5 mL of the mixed solution was filtered through a 0.45 μm aqueous filter membrane. Subsequently, the solution was placed in a natural light irradiation area, and 1.5 mL of IMI solution was sampled after 1, 2, 3, 4, 5, 6, and 7 days of irradiation. The samples were also filtered through a 0.45 μm aqueous filter membrane, and the IMI content in the solution was detected by high-performance liquid chromatography (HPLC). An aqueous solution of imidacloprid without the added photocatalyst was used as a control, and the experimental procedure was the same.

[0069] (2) Experimental results and analysis: The natural light degradation test results of TiO2-ZnO are as follows: Figure 10 As shown, TiO2-ZnO still exhibits excellent degradation effects under natural light, and can completely degrade imidacloprid after a period of time.

[0070] Application Example 4: Experiment on the Addition of Active Substance Scavenger (1) Experimental method: At room temperature, 25 mL of 50 ppm IMI solution was added to a quartz tube, and 1 g of benzoquinone (·O2) was added to each tube. - (capture agent), 1g disodium ethylenediaminetetraacetate (h) + 1 mL isopropanol (·OH scavenging agent), 1 g potassium persulfate (e - After the capture agent was thoroughly mixed, 5 mg of the photocatalyst prepared in Example 1 was added to the solution, and the mixture was stirred in the dark for 0.5 h to reach adsorption equilibrium. This process required ensuring the reaction system was completely protected from light. After the dark reaction was complete, 1.5 mL of the mixed solution was filtered through a 0.45 μm aqueous filter membrane. The IMI content in the solution was detected by high-performance liquid chromatography (HPLC), and the degradation rate was then calculated. An aqueous solution of imidacloprid without the added photocatalyst was used as a control, and the experimental procedure was the same as above.

[0071] (2) Experimental results and analysis: Experimental results are as follows Figure 11 As shown, the active substance scavengers disodium ethylenediaminetetraacetate and isopropanol have an inhibitory effect on the degradation of TiO2-ZnO, indicating that hydroxyl radicals and photogenerated holes are the main active substances that play a role in the degradation process.

[0072] Figures 12-13Further EPR detection chromatograms show that its degradation process generates a large number of hydroxyl radicals and photogenerated holes in water, which can mineralize neonicotinoid pesticides and remove them under natural light.

[0073] It should be noted that the specific embodiments are merely representative examples of the present invention, and the technical solution of the present invention is obviously not limited to the above embodiments, and there can be many variations. Those skilled in the art who obtain the present invention based on its explicit disclosure or without objection from the written description should consider it to be within the scope of protection of this patent.

Claims

1. A method for preparing a highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides, characterized in that, Includes the following steps: (1) ZnO and 2-methylimidazole were thoroughly mixed by grinding and then transferred into a reaction vessel to obtain MOF material ZIF-8; (2) Add polyethyleneimine and acetic acid to tetrabutyl titanate and stir, then add ZIF-8 and continue stirring; (3) The mixture from step (2) is transferred to a polytetrafluoroethylene reactor for reaction to obtain the precursor material; (4) The precursor material after the reaction in step (3) is washed and dried; (5) The precursor material obtained in step (4) is transferred into a crucible and pyrolyzed at high temperature in an air atmosphere in a tube furnace to obtain TiO2-ZnO, which is the photocatalyst of the present invention.

2. The method for preparing the highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides according to claim 1, characterized in that, In step (1), the mass ratio of ZnO to 2-methylimidazole is 1:(2-5).

3. The method for preparing the highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides according to claim 1, characterized in that, In step (1), the reaction temperature is 120-150 °C and the reaction time is 46-50 h.

4. The method for preparing the highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides according to claim 1, characterized in that, In step (2), the stirring rate is 400-500 r / min and the stirring time is 5-20 min.

5. The method for preparing the highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides according to claim 1, characterized in that, In step (2), the mass-volume ratio (g:mL) of ZIF-8 to tetrabutyl titanate is (0.5-3.5):

10.

6. The method for preparing the TiO2-ZnO photocatalyst for efficiently degrading neonicotinoid pesticides according to claim 1, characterized in that, In step (3), the reaction temperature is 170-190 ℃ and the reaction time is 22-24 h.

7. The method for preparing the highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides according to claim 1, characterized in that, In step (5), the heating rate is 5-10 ℃ / min, the pyrolysis temperature is 450-600 ℃, and the reaction time is 2-4h.

8. A highly efficient TiO2-ZnO photocatalyst for degrading neonicotinoid pesticides, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7 above.

9. An application of a TiO2-ZnO photocatalyst, characterized in that, The application is as follows: using the TiO2-ZnO photocatalyst prepared by any one of the preparation methods described in claims 1 to 7 or the TiO2-ZnO photocatalyst described in claim 8 for the photocatalytic degradation of neonicotinoid pesticides.

10. The application according to claim 9, characterized in that, The neonicotinoid pesticides mentioned are any one of imidacloprid, thiamethoxam, acetamiprid, and dinotefuran.

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