Photocatalyst for degrading nitrogen-containing heteroaromatic ring pesticide as well as preparation method and application of photocatalyst

Abstract

The invention belongs to the technical field of nitrogen-containing heteroaromatic ring pesticide degradation, and discloses a photocatalyst for nitrogen-containing heteroaromatic ring pesticide degradation and a preparation method and application thereof. The preparation method comprises the following steps: calcining urea in a nitrogen atmosphere to obtain g-C3N4; the g-C3N4 and BiOBr form a heterojunction structure through aging treatment, and the composite heterojunction material is obtained; light ceramsite is used as a carrier, the composite heterojunction material is loaded on the light ceramsite, and the photocatalyst for degrading the nitrogen-containing heteroaromatic ring pesticide is obtained. The photocatalyst provided by the invention can realize ring-opening mineralization degradation of the nitrogen-containing heteroaromatic ring pesticide, so that the pollutant removal effect of the whole wetland is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen-containing heteroaromatic pesticide degradation, and particularly relates to a photocatalyst for nitrogen-containing heteroaromatic pesticide degradation, a preparation method thereof, and an application thereof. Background Art

[0002] During the use of nitrogen-containing heteroaromatic pesticides, residues will remain in soil, water bodies, and the air. These residues will pollute the environment, further affect crop cultivation, and even enter the human body through the food chain, posing a threat to human health. Moreover, nitrogen-containing heterocyclic pesticides have a stable structure and are difficult to degrade, and their degradation products are more toxic than the parent compounds. Wetlands are the key barriers to controlling land-source pollution from entering the sea, but wetlands are difficult to completely mineralize nitrogen-containing heterocyclic pesticides. Nitrogen heterocyclic pesticides and their degradation products accumulate in wetlands, leading to wetland degradation and pollutant accumulation, and thus causing serious ecological risks.

[0003] To solve the above technical problems, the existing technologies mainly adopt the following solutions: matrix enhancement, plant optimization, microbial enhancement, and photocatalysis-wetland combined treatment. Among them, the photocatalysis-wetland combined treatment has a high removal rate and mineralization degree for organic pollution, and is the main solution currently adopted.

[0004] Currently, the photocatalysts used in the photocatalysis-wetland combined treatment mainly include g-C 3 N 4 However, when using g-C 3 N 4 for photocatalytic degradation of nitrogen-containing heteroaromatic pesticides, for example, in the existing technology titled "Photodegradation of Imidacloprid in Aqueous Solution by the Metal-Free Catalyst Graphitic Carbon Nitride using an Energy-Saving Lamp" with the DOI number 10.1021 / acs.jafc.5b01105, under ultraviolet light conditions, using g-C 3 N 4 to photocatalytically degrade imidacloprid, after 5 hours of degradation treatment, the degradation efficiency reaches 90%. However, during the degradation process of this catalyst, the nitrogen-containing heterocyclic intermediate products do not undergo ring-opening degradation, resulting in the degradation products still having relatively high toxicity and being difficult to effectively achieve the degradation and removal of nitrogen-containing heteroaromatic pesticides. Moreover, the above degradation process needs to be carried out under ultraviolet light and is difficult to be used for the degradation of nitrogen-containing heteroaromatic pesticides in the actual wetland environment. In addition, g-C 3 N 4 is in the form of solid powder, and when used in the water body of the actual wetland environment, it is difficult to disperse the powdered catalyst and difficult to recover. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a photocatalyst for the degradation of nitrogen-containing heteroaromatic pesticides, a preparation method thereof, and an application thereof.

[0006] The photocatalyst for the degradation of nitrogen-containing heteroaromatic pesticides, the preparation method thereof, and the application thereof according to the present invention are realized through the following technical solutions: The first object of the present invention is to provide a photocatalyst for the degradation of nitrogen-containing heteroaromatic pesticides, including a carrier and a composite heterojunction material loaded on the carrier.

[0007] It should be noted that considering that the single g-C 3 N 4 photocatalyst has excessive complexation of photogenerated carriers, poor surface activity, insufficient visible light capture, and poor photocatalytic performance. Therefore, the present invention uses g-C 3 N 4 as a matrix, and forms a heterojunction structure by combining g-C 3 N 4 and BiOBr in the form of van der Waals force and electron-hole coupling to obtain a composite heterojunction material. And the present invention uses the formed composite heterojunction material with this heterojunction structure as the main active component of the photocatalyst, thereby improving the photocatalytic performance of the photocatalyst material.

[0008] In order to improve the dispersion effect of the composite heterojunction material in the subsequent used environmental water body and the convenience of recycling, the present invention preferably uses light expanded clay aggregate as the carrier, so that after the composite heterojunction material is loaded on the light expanded clay aggregate, it can not only improve the dispersion of the composite heterojunction material, but also can be used as a floating carrier, so that the formed photocatalyst can float on the water surface, which is beneficial to contact with sunlight, and thus improves the photocatalytic efficiency.

[0009] The present invention preferably controls the loading amount of the composite heterojunction material on the light expanded clay aggregate to be 3wt% - 7wt%, so as to make the heterojunction catalyst evenly loaded on the surface of the clay aggregate, reduce agglomeration, and balance the catalytic activity, the adsorption characteristics of the clay aggregate, and recyclability.

[0010] In some preferred embodiments of the present invention, the particle size of the light expanded clay aggregate is 0.8 cm - 1.1 cm, so that the light expanded clay aggregate used in the present invention is small-sized clay aggregate.

[0011] The second object of the present invention is to provide a preparation method of a photocatalyst for the degradation of nitrogen-containing heteroaromatic pesticides, including the following steps: Step 1, prepare a composite heterojunction material: 1.1) Using g-C 3 N 4 as a matrix, g-C3 N 4 g-C₃N₄ is dispersed in the aging solvent, and then aging treatment is carried out to enable g-C₃N₄ 3 N 4 and BiOBr to combine in the form of van der Waals force and electron-hole coupling to form a heterojunction structure, obtaining a mixed solution.

[0012] 1.2) After the solid-liquid separation of the mixed solution, it is washed and dried to obtain the composite heterojunction material.

[0013] It should be noted that the present invention does not limit the specific source of g-C₃N₄. The g-C₃N₄ prepared by using the preparation method of g-C₃N₄ in the existing technology in this field can be used. For example, in some preferred embodiments of the present invention, considering the problems of preparation cost and preparation efficiency, the g-C₃N₄ prepared by the following steps is used as the matrix: using urea as the g-C₃N₄ 3 N 4 precursor, and calcining it in a nitrogen atmosphere to convert urea into g-C₃N₄ 3 N 4 to obtain g-C₃N₄ 3 N 4 . The calcination temperature of the calcination treatment is 510°C to 530°C, and the calcination time is 4h to 6h. 3 N 4 For the matrix: Using urea as the g-C₃N₄ 3 N 4 precursor, and calcining it in a nitrogen atmosphere to convert urea into g-C₃N₄ 3 N 4 to obtain g-C₃N₄ 3 N 4 . The calcination temperature of the calcination treatment is 510°C to 530°C, and the calcination time is 4h to 6h.

[0014] In some preferred embodiments of the present invention, the molar ratio of g-C₃N₄ 3 N 4 to BiOBr is 1:0.8 to 1.2.

[0015] It should also be noted that during the exploration of the present invention, the solvothermal method was also used to prepare the mixed solution. Although the solvothermal method can also prepare the composite heterojunction material, the uniformity of the prepared composite heterojunction material is poor, and the interfacial bonding quality is poor, resulting in poor degradation efficiency of the photocatalyst for photocatalytic degradation of nitrogen-containing heteroaromatic pesticides. Therefore, the present invention optimizes the preparation process of the composite heterojunction material, and preferably adopts the aging treatment method for preparation. And in some preferred embodiments of the present invention, the aging treatment is carried out by ultrasonic wave combined with stirring, and the temperature of the aging treatment is room temperature, and the aging time is 4h to 6h, so as to achieve the purpose of preparing a more uniform, stable and active-site-rich heterojunction structure, optimizing the photocatalytic performance and reducing the preparation cost at the same time.

[0016] In some preferred embodiments of the present invention, the aging solvent is a mixed solvent of ethanol and water, and for every 1 g of g-C 3 N 4 0.15 L to 0.17 L of the aging solvent is added.

[0017] Step 2, loading light ceramsite: Using light ceramsite as a carrier, the composite heterojunction material is loaded onto the light ceramsite to obtain a photocatalyst for the degradation of nitrogen heterocyclic pesticides.

[0018] In some preferred embodiments of the present invention, when loading the composite heterojunction material onto the light ceramsite, the loading method used is the co-precipitation method, so that the composite material is evenly loaded on the surface of the light ceramsite to enhance the stability and catalytic performance of the composite material.

[0019] The co-precipitation method adopted in the present invention is an existing technology in the art, so the present invention will not elaborate here. Please refer to the existing technology: titled Enhanced remediation of PFAS-metal co-contaminated soil by ceramsite-supported Fe 3 O 4 -MoS 2 heterojunction as a high-performance piezocatalyst; DOI number: 10.1016 / j.jenvman.2024.121716.

[0020] The third object of the present invention is to provide an application of the above-mentioned photocatalyst for the degradation of nitrogen heterocyclic pesticides in the photocatalytic degradation of nitrogen heterocyclic pesticides.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses g-C 3 N 4The composite heterojunction material formed with BiOBr as the main active ingredient of the photocatalyst. On the one hand, BiOBr is a photocatalyst with appropriate conduction and valence bands, and its band gap type is an indirect transition band gap, which reduces the probability of recombination of photo-generated electrons and holes. As a result, there are a large number of un-recombined holes in the formed composite heterojunction material, which is beneficial for recombination with photoelectrons when it acts as a photocatalyst, thereby improving its photocatalytic performance. On the other hand, the introduction of BiOBr can effectively increase the specific surface area and pore structure of the photocatalyst material, and then effectively increase the contact area between the photocatalytic material and organic pollutants, which is conducive to the rapid diffusion of pollutants, thus effectively enhancing the photocatalytic performance of the photocatalytic material. And in the present invention, light ceramsite is used as a carrier. By loading the composite heterojunction material on the light ceramsite, not only can the aggregation of the composite heterojunction material be reduced, the dispersibility of the composite heterojunction material be improved to balance the catalytic activity and the adsorption characteristics of the ceramsite as well as recyclability, but also the light ceramsite can be used as a floating carrier, enabling the formed photocatalyst to float on the water surface, which is conducive to contact with sunlight, and then improving the photocatalytic efficiency. And through experimental verification, the photocatalyst of the present invention can achieve the ring-opening mineralization degradation of nitrogen-containing heteroaromatic pesticides, and then significantly improve the overall pollutant removal effect of the wetland.

[0022] In the present invention, by adopting an aging treatment method, g-C 3 N 4 and BiOBr are combined in the form of van der Waals force and electron-hole coupling to form a heterojunction structure with uniform, stable and rich active sites, thereby improving the photocatalytic performance of the photocatalyst material. Then, using light ceramsite as a carrier, the composite heterojunction material is loaded on the light ceramsite. Not only can the aggregation of the composite heterojunction material be reduced, the dispersibility of the composite heterojunction material be improved to balance the catalytic activity and the adsorption characteristics of the ceramsite as well as recyclability, but also the light ceramsite can be used as a floating carrier, enabling the formed photocatalyst to float on the water surface, which is conducive to contact with sunlight, and then improving the photocatalytic efficiency. Description of the Drawings

[0023] Figure 1 For the morphology test results of the photocatalysts of Example 1, Comparative Example 1 to Comparative Example 3, Figure 1 Among them, (a) is the scanning electron microscope image of Comparative Example 3, (b) is the scanning electron microscope image of Comparative Example 1, (c) is the scanning electron microscope image of Comparative Example 3, (d) is the scanning electron microscope image of Example 1, (e) is the distribution image of C element in (d), (f) is the distribution image of N element in (d), (g) is the distribution image of Bi element in (d), and (h) is the distribution image of Br element in (d).

[0024] Figure 2 X-ray diffraction spectra of the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0025] Figure 3 Fourier transform infrared spectra of the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0026] Figure 4 BET test results of the photocatalysts of Comparative Example 1 and Comparative Example 3. Figure 4 The inset in [figure number] is the porosity distribution map of the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0027] Figure 5 Fluorescence spectra of the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0028] Figure 6 UV-Vis diffuse reflectance spectra of the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0029] Figure 7 Relationship curve of (ahv) 1 / 2 versus the change of light energy for the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0030] Figure 8 Photocatalytic degradation curve of atrazine in indoor test.

[0031] Figure 9 Photocatalytic degradation curve of chlorpyrifos in indoor test.

[0032] Figure 10 Photocatalytic degradation curve of nicosulfuron in indoor test.

[0033] Figure 11 Schematic diagram of the group design for the field test. Among them, Figure A is the design schematic diagram of Group A, Figure B is the design schematic diagram of Group B, Figure C is the design schematic diagram of Group C, Figure D is the design schematic diagram of Group D, and Figure E is the design schematic diagram of Group E.

[0034] Figure 12 Setup diagram of the field experiment.

[0035] Figure 13 Test results of the in-situ field experiment. Among them, Figure a is the photocatalytic degradation curve of atrazine in the field test of different groups, Figure b is the photocatalytic kinetic fitting curve of atrazine in the field test of different groups, Figure c is the photocatalytic degradation curve of chlorpyrifos in the field test of different groups, Figure d is the photocatalytic kinetic fitting curve of chlorpyrifos in the field test of different groups, Figure e is the photocatalytic degradation curve of nicosulfuron in the field test of different groups, and Figure f is the photocatalytic kinetic fitting curve of nicosulfuron in the field test of different groups.

[0036] Figure 14It is the secondary ion mass spectrum of atrazine.

[0037] Figure 15 It is the secondary ion mass spectrum of partial degradation products of atrazine. Among them, Figures a - d are the secondary ion mass spectra of different degradation products of atrazine respectively.

[0038] Figure 16 It is the secondary ion mass spectrum of partial degradation products of atrazine. Among them, Figures a - f are the secondary ion mass spectra of different degradation products of atrazine respectively.

[0039] Figure 17 It is the secondary ion mass spectrum of partial degradation products of atrazine. Among them, Figures a - f are the secondary ion mass spectra of different degradation products of atrazine respectively.

[0040] Figure 18 It is the secondary ion mass spectrum of partial degradation products of atrazine. Among them, Figures a and b are the secondary ion mass spectra of different degradation products of atrazine respectively.

[0041] Figure 19 It is the secondary ion mass spectrum of chlorpyrifos and its partial degradation products. Among them, Figure a is the secondary ion mass spectrum of chlorpyrifos, and Figures b - d are the secondary ion mass spectra of different degradation products of chlorpyrifos respectively.

[0042] Figure 20 It is the secondary ion mass spectrum of partial degradation products of chlorpyrifos. Among them, Figures a - f are the secondary ion mass spectra of different degradation products of chlorpyrifos respectively.

[0043] Figure 21 It is the secondary ion mass spectrum of partial degradation products of chlorpyrifos. Among them, Figures a - f are the secondary ion mass spectra of different degradation products of chlorpyrifos respectively.

[0044] Figure 22 It is the secondary ion mass spectrum of partial degradation products of chlorpyrifos. Among them, Figures a - d are the secondary ion mass spectra of different degradation products of chlorpyrifos respectively.

[0045] Figure 23 It is the secondary ion mass spectrum of nicosulfuron and its partial degradation products. Among them, Figure a is the secondary ion mass spectrum of nicosulfuron, and Figures b - f are the secondary ion mass spectra of different degradation products of nicosulfuron respectively.

[0046] Figure 24 It is the secondary ion mass spectrum of partial degradation products of nicosulfuron. Among them, Figures a - f are the secondary ion mass spectra of different degradation products of nicosulfuron respectively.

[0047] Figure 25It is the secondary ion mass spectrum of the partial degradation products of nicosulfuron. Among them, Figure a and Figure b are the secondary ion mass spectra of different degradation products of nicosulfuron respectively. Specific implementation mode

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0049] Example 1 This example provides a photocatalyst for the degradation of nitrogen-containing heterocyclic pesticides, and it is prepared through the following steps: Step 1: Using urea as the g-C 3 N 4 precursor, calcining it in a nitrogen atmosphere at 520 °C for 5 h to obtain g-C 3 N 4 .

[0050] Step 2: Using a mixed solvent of ethanol and water as the aging solvent, dispersing 1.84 g of g-C 3 N 4 and 8.97 g of BiOBr in 300 mL of the aging solvent, and then carrying out aging treatment at 25 °C for 5 h to obtain a mixed solution. After the solid-liquid separation of the mixed solution obtained in the above step, wash it three times with deionized water and ethanol respectively, and dry it under vacuum at 80 °C for 12 h to obtain a composite heterojunction material.

[0051] Step 3: Using light expanded clay as the carrier, adopting the coprecipitation method, according to the ratio that the loading amount of the composite heterojunction material on the light expanded clay is 5 wt%, load the composite heterojunction material on the light expanded clay to obtain a photocatalyst, denoted as g-C 3 N 4 / BiOBr / LC.

[0052] Example 2 This example provides a photocatalyst for the degradation of nitrogen-containing heterocyclic pesticides, and it is prepared through the following steps: Step 1: Using urea as the g-C 3 N 4 precursor, calcining it in a nitrogen atmosphere at 510 °C for 6 h to obtain g-C 3 N 4 .

[0053] Step 2: Using an ethanol-water mixed solvent as the aging solvent, dispersing 1.84 g of g-C 3 N 48.97 g of BiOBr was dispersed in 300 mL of aging solvent, and then aged at 25 °C for 4 h to obtain a mixed solution. After the solid-liquid separation of the above-obtained mixed solution, it was washed three times with deionized water and ethanol respectively, and dried under vacuum at 80 °C for 12 h to obtain a composite heterojunction material.

[0054] Step 3: Using light expanded clay as a carrier, by means of coprecipitation, according to the ratio that the loading amount of the composite heterojunction material on the light expanded clay is 3 wt%, the composite heterojunction material was loaded on the light expanded clay to obtain a photocatalyst.

[0055] Example 3 This example provides a photocatalyst for the degradation of nitrogen-containing heteroaromatic pesticides, which is prepared by the following steps: Step 1: Using urea as the g-C 3 N 4 precursor, which was calcined at 530 °C for 4 h under a nitrogen atmosphere to obtain g-C 3 N 4 .

[0056] Step 2: Using an ethanol-water mixed solvent as the aging solvent, 1.84 g of g-C 3 N 4 and 8.97 g of BiOBr were dispersed in 300 mL of the aging solvent, and then aged at 25 °C for 6 h to obtain a mixed solution. After the solid-liquid separation of the mixed solution obtained in the above step, it was washed three times with deionized water and ethanol respectively, and dried under vacuum at 80 °C for 12 h to obtain a composite heterojunction material.

[0057] Step 3: Using light expanded clay as a carrier, by means of coprecipitation, according to the ratio that the loading amount of the composite heterojunction material on the light expanded clay is 7 wt%, the composite heterojunction material was loaded on the light expanded clay to obtain a photocatalyst.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is only that: In this comparative example, light expanded clay was not loaded, and the catalyst of this comparative example was denoted as g-C 3 N 4 / BiOBr.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is only that: In this comparative example, no photocatalyst was added, and the catalyst of this comparative example was denoted as LC.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is only that: This comparative example does not add BiOBr and does not load light ceramsite. The catalyst of this comparative example is denoted as g-C 3 N 4 .

[0061] Experimental section (I)Morphology test Taking the photocatalysts of Example 1 and Comparative Examples 1 to 3 of the present invention as examples, scanning electron microscope-energy dispersive spectrometer tests were respectively carried out on them, and the test results are as Figure 1 shown

[0062] Figure 1 are the scanning electron microscope-energy dispersive spectrometer test results of the photocatalysts of Example 1 and Comparative Examples 1 to 3 Figure 1 . In, Figure (a) is the scanning electron microscope image of Comparative Example 3, Figure (b) is the scanning electron microscope image of Comparative Example 1, Figure (c) is the scanning electron microscope image of Comparative Example 3, Figure (d) is the scanning electron microscope image of Example 1, Figure (e) is the distribution image of C element in Figure (d), Figure (f) is the distribution image of N element in Figure (d), Figure (g) is the distribution image of Bi element in Figure (d), and Figure (h) is the distribution image of Br element in Figure (d).

[0063] From Figure 1 Figure (a) in, it can be seen that the g-C prepared by the present invention 3 N 4 presents nanosheets with surface wrinkles. From Figure 1 Figure (b) in, it can be seen that the g-C prepared by the aging method of the present invention 3 N 4 / BiOBr presents uniformly dispersed and regular petal shapes. From Figure 1 Figure (c) in, it can be seen that many holes are observed on the surface of the light ceramsite used in the present invention. From Figure 1 Figure (d) in, it can be seen that compared with Figure (c), there are petal-shaped structures in the holes on the surface of the light ceramsite, and there are a small number of crystal grains around the holes, which indicates that the present invention has successfully loaded g-C 3 N 4 / BiOBr into the light ceramsite. And through Figure 1 Figures (e) to (h) in, it can be seen that C, N, Bi, and Br elements are uniformly distributed on the surface of the light ceramsite, which indicates that the present invention has successfully loaded g-C 3 N 4 / BiOBr into the light ceramsite

[0064] (II)X-ray diffraction test In order to verify that the preparation method of the present invention can make g-C3 N 4 Combines with BiOBr in the form of van der Waals forces and electron-hole coupling to form a heterojunction structure. Taking the photocatalysts of Comparative Example 1 and Comparative Example 3 as examples, the present invention respectively carried out X-ray diffraction tests on them, and the test results are as Figure 2 shown.

[0065] It can be seen from Figure 2 that the g-C 3 N 4 nanosheets of Comparative Example 3 have two typical characteristic peaks at 13.1° and 27.5°. The weaker (100) diffraction peak is caused by the stacking of the interlayer structure in the plane, while the superposition of the interlayer periodicity results in a larger intensity of the (002) diffraction peak. In the X-ray diffraction pattern of g-C 3 N 4 / BiOBr after compounding with BiOBr in Comparative Example 1, it can be seen that compared with Comparative Example 3, the diffraction peak of g-C 3 N 4 becomes less obvious under the interference of the strong diffraction peak of BiOBr, making the diffraction peaks of the g-C 3 N 4 / BiOBr heterojunction similar to those of BiOBr, with characteristic diffraction peaks at 10.9°, 25.2°, 32.3°, etc., and no other impurity peaks.

[0066] Based on the above, it can be known that the present invention can successfully realize the compounding of g-C 3 N 4 and BiOBr to form a composite heterojunction material, providing conditions for the subsequent preparation of photocatalysts for the degradation of nitrogen-containing heteroaromatic pesticides.

[0067] In order to explore the influence of the heterojunction structure formed between g-C 3 N 4 and BiOBr in the photocatalyst prepared by the present invention on its performance, the present invention also carried out the following test analysis.

[0068] (III) Fourier transform infrared spectroscopy test Taking the photocatalysts of Comparative Example 1 and Comparative Example 3 as examples, the present invention respectively carried out Fourier transform infrared spectroscopy tests on them, and the test results are as Figure 3 shown.

[0069] Figure 3 For the Fourier transform infrared spectra of the photocatalysts of Comparative Example 1 and Comparative Example 3, it can be seen that in g-C 3 N 4 / BiOBr of Comparative Example 1, there is g-C 3 N 4The absorption band, as well as the absorption band of BiOBr. For Comparative Example 1 and Comparative Example 3, the absorption bands at 808 cm -1 are both typical absorption bands of the triazine ring; at 1240 cm -1 ~1640 cm -1 The absorption band in the region is consistent with the typical stretching mode of the C-N heterocycle, corresponding to the triangular C-N (-C)-C unit or the bridging C-NH-C unit; while in the range of 3000 cm -1 ~3500 cm -1 The region is caused by the stretching vibration of the N-H bond; the infrared absorption band at 528 cm -1 is the typical stretching mode of the Bi-O bond. The above indicates that the g-C 3 N 4 / BiOBr heterojunction prepared in the present invention contains BiOBr and g-C 3 N 4 .

[0070] (IV) Pore structure test Taking the photocatalysts of Comparative Example 1 and Comparative Example 3 as examples, the present invention carried out BET tests and porosity distributions on them respectively using a fully automatic specific surface area and porosity analyzer, and the test results are as Figure 4 shown, where Figure 4 are the BET test results of the photocatalysts of Comparative Example 1 and Comparative Example 3, and the Figure 4 inset in is the porosity distribution diagram of the photocatalysts of Comparative Example 1 and Comparative Example 3.

[0071] From Figure 4 and the test results of the inset in Figure 4 , it can be seen that the BET results show that the specific surface area of g-C 3 N 4 / BiOBr in Comparative Example 1 increased from 15.63 m 3 N 4 / g of g-C 2 in Comparative Example 3 to 46.14 m 2 / g, and the g-C 3 N 4 / BiOBr material in Comparative Example 1 has a relatively high specific surface area and a large number of pore structures, which indicates that by combining g-C 3 N 4 and BiOBr in a heterojunction structure, the present invention can effectively increase the specific surface area and pore structure of the photocatalyst material, and further effectively increase the contact area between the photocatalytic material and the organic pollutants, which is beneficial to the rapid diffusion of pollutants, thereby effectively improving the photocatalytic performance of the photocatalytic material.

[0072] (V) Fluorescence performance test Taking the photocatalysts of Comparative Example 1 and Comparative Example 3 as examples, the fluorescence performance tests were respectively carried out on them by using a fluorescence spectrometer, and the test results are as Figure 5 shown.

[0073] From Figure 5 the test results, it can be seen that in the wavelength range of 400 nm to 600 nm, the emission peaks of g-C 3 N 4 of Comparative Example 3 and g-C 3 N 4 / BiOBr of Comparative Example 1 have similar shapes and both appear at 460 nm. Since the lower the emission peak intensity, the lower the recombination rate of photogenerated electron-hole pairs. Compared with g-C 3 N 4 of Comparative Example 3, the emission peak intensity of g-C 3 N 4 / BiOBr of Comparative Example 1 is significantly reduced, which indicates that the recombination rate of photoelectrons and holes of g-C 3 N 4 / BiOBr of Comparative Example 1 is low, which indicates that there are a large number of un-recombined holes in g-C 3 N 4 / BiOBr of Comparative Example 1. This is beneficial for the recombination with photoelectrons when it is used as a photocatalyst, so as to improve its photocatalytic performance.

[0074] (VI) Regarding the ultraviolet-visible diffuse reflection spectrum test and the curve of the change relationship of (ahv) 1 / 2 with light energy Taking the photocatalysts of Comparative Example 1 and Comparative Example 3 as examples, the ultraviolet-visible diffuse reflection spectrum tests were respectively carried out on them, and the test results are as Figure 6 shown, and the curves of the change relationship of (ahv) Figure 6 with light energy of Comparative Example 1 and Comparative Example 3 were drawn according to 1 / 2 the test results, and the results are as Figure 7 shown.

[0075] From Figure 6 and Figure 7 the test results, it can be seen that compared with g-C 3 N 4 of Comparative Example 3, the light absorption ability of g-C 3 N 4 / BiOBr of Comparative Example 1 is significantly improved in the wavelength range of 240 nm to 800 nm. In addition, with the synthesis of g-C 3 N 4 / BiOBr of Comparative Example 1, the light absorption ability of g-C 3 N 4The band gap is reduced from 2.63 eV to 2.00 eV. The lower band gap of g-C 3 N 4 / BiOBr makes the photo-electron transition easier and the catalytic activity stronger, which is attributed to the plasma effect of Bi metal and the heterojunction structure after compounding with carbon nitride, further verifying that by compounding g-C 3 N 4 and BiOBr in a heterojunction structure, the catalytic activity of the photocatalytic material can be effectively improved.

[0076] (VII) Photocatalytic performance test (1) Indoor photocatalytic degradation experiment setup: Using a xenon lamp to simulate sunlight, photocatalytic degradation kinetic experiments of the target pesticides were carried out on the successfully prepared photocatalysts of Comparative Example 1 to Comparative Example 3 and Example 1. The degradation time was generally 240 min, and the sampling interval was generally 10 min in the early stage and 60 min in the later stage.

[0077] Test method: Using a high-performance liquid chromatograph to identify and analyze the concentration and degradation products during the photocatalytic degradation of pesticides, and the test results are respectively as Figures 8 - 10 shown, where Figure 8 is the photocatalytic degradation curve of atrazine in the indoor experiment, Figure 9 is the photocatalytic degradation curve of chlorpyrifos in the indoor experiment, Figure 10 is the photocatalytic degradation curve of nicosulfuron in the indoor experiment.

[0078] From Figures 8 - 10 the indoor photocatalytic results, it can be seen that in the case of not adding any photocatalyst, the photocatalytic degradation efficiencies of atrazine, chlorpyrifos and nicosulfuron after 240 min are 97.61%, 95.86% and 95.48% respectively; in the case of adding LC of Comparative Example 2, the photocatalytic degradation efficiencies of atrazine, chlorpyrifos and nicosulfuron after 240 min are 94.46%, 91.56% and 93.69% respectively; in the case of adding g-C 3 N 4 of Comparative Example 3, the photocatalytic degradation efficiencies of atrazine, chlorpyrifos and nicosulfuron after 240 min are 78.51%, 65.85% and 61.67% respectively; in the case of adding g-C 3 N 4 / BiOBr of Comparative Example 1, the photocatalytic degradation efficiencies of atrazine, chlorpyrifos and nicosulfuron after 240 min are 5.35%, 11.21% and 3.24% respectively. In the case of adding g-C 3 N 4In the case of / BiOBr / LC, the photocatalytic degradation efficiencies of atrazine, chlorpyrifos, and nicosulfuron after 240 min were 2.34%, 7.21%, and 1.57%, respectively. According to the indoor experimental results, compared with Comparative Examples 1 to 3, the addition in Example 1 can significantly improve the photocatalytic degradation efficiency of nitrogen-containing heterocyclic pesticides such as atrazine, chlorpyrifos, and nicosulfuron.

[0079] (2) Outdoor photocatalytic degradation experiment setup: Using chlorpyrifos, atrazine, and nicosulfuron as the nitrogen-containing heteroaromatic pesticides to be degraded, and using the photocatalyst prepared in the present invention as the photocatalyst, five groups of experiments were set up in the manner described in Figure 11 : Group A is the in-situ matrix group, Group B is the in-situ matrix + plant group, Group C is the in-situ matrix + photocatalyst group, Group D is the in-situ matrix + plant + photocatalyst group, and Group E is the in-situ matrix + plant + photocatalysis + microorganism.

[0080] The above five groups of experiments were carried out in-situ in the coastal wetland, and the in-situ field experiment was as Figure 12 shown. Among them, the in-situ matrix and plants used 25 kg of in-situ sediments and in-situ plants Phragmites australis in the coastal wetland. The microorganisms were added to the experimental groups by the activated immobilization embedding method. The microorganisms were composite strains purchased from Shandong Pasteur Biotechnology (Qingdao) Co., Ltd. 100 μg / L of chlorpyrifos, nicosulfuron, and atrazine were enriched in each group. Water samples and sediment samples were collected on the 1st, 3rd, 5th, 7th, 10th, and 14th days respectively to analyze the treatment effect of the wetland system on the target pesticides. After the end of the experimental period, all plant samples were collected, then rinsed with deionized water and dried with paper towels, and weighed. The chopped plant samples and sediment samples were frozen and then placed in a freeze dryer for drying treatment. Subsequently, the pesticides were extracted by the QuEChERS method for determination, and the test results were as Figure 13 shown.

[0081] Figure 13 are the test results of the in-situ field experiment. Figure 13 In Figure 13 ​From the test results, it can be seen that atrazine, chlorpyrifos, and nicosulfuron have similar removal trends in each group of wetlands. The removal rates of the target pollutants in wetland group A after 14 days are 60%, 86%, and 63% respectively, and wetland group E has the highest removal rate for the target pollutants, reaching 93%, 94%, and 99% respectively. Moreover, the removal of atrazine, chlorpyrifos, and nicosulfuron in the wetland conforms to the first-order kinetics, and the degradation rates are katrazine = 0.076 d -1 ~0.406 d -1 , kchlorpyrifos = 0.133 d -1 ~0.177 d -1 and knicosulfuron = 0.067 d -1 ~0.339 d -1 . And it can also be seen from Figure 13 that after loading the catalyst, the overall pollutant removal effect of the wetland can be significantly improved.

[0082] After the above-mentioned on-site tests of atrazine, chlorpyrifos, and nicosulfuron, the present invention also detected the degradation products, and the detection results are respectively as Figures 19 - 25 shown. Among them, Figure 14 is the secondary ion mass spectrum of atrazine, Figures 15 - 18 is the secondary ion mass spectrum of some degradation products of atrazine. It can be seen from Figures 14 - 18 that the photocatalyst of the present invention can achieve the ring-opening mineralization degradation of atrazine. Figure 19 is the secondary ion mass spectrum of chlorpyrifos and its partial degradation products. Figure 19 Among them, figure a is the secondary ion mass spectrum of chlorpyrifos, and figures b - d are the secondary ion mass spectra of some degradation products of chlorpyrifos. Figures 20 - 22 is the secondary ion mass spectrum of some degradation products of chlorpyrifos. It can be seen from Figures 19 - 22 the test results that the photocatalyst of the present invention can achieve the mineralization degradation of chlorpyrifos. Figure 23 is the secondary ion mass spectrum of nicosulfuron and its partial degradation products. Figure 23 Among them, figure a is the secondary ion mass spectrum of nicosulfuron, and figures b - f are the secondary ion mass spectra of some degradation products of nicosulfuron. Figure 24 And Figure 25 are both the secondary ion mass spectra of some degradation products of nicosulfuron. It can be seen from Figures 23 - 25 the test results that the photocatalyst of the present invention can achieve the mineralization degradation of nicosulfuron.

[0083] In summary, the photocatalyst of the present invention can achieve the ring-opening mineralization degradation of nitrogen-containing heterocyclic aromatic pesticides, thereby significantly improving the overall pollutant removal effect of the wetland.

[0084] Obviously, the above embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides, characterized in that: It includes a carrier, and a composite heterojunction material loaded on the carrier; Wherein, the carrier is lightweight ceramsite; The composite heterojunction material is formed by combining g-C3N4 as a matrix with BiOBr in the form of van der Waals force and electron-hole coupling; The loading amount of the composite heterojunction material on the carrier is 3wt%~7wt%.

2. The photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to claim 1, characterized in that: The particle size of the lightweight ceramsite is 0.8 cm to 1.1 cm.

3. A method for preparing a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to any one of claims 1 to 2, characterized in that: The following steps are involved: Using g-C3N4 as a matrix, dispersing g-C3N4 and BiOBr in an aging solvent, and then performing an aging treatment so that g-C3N4 and BiOBr are combined in the form of van der Waals force and electron-hole coupling to form a heterojunction structure, thereby obtaining a mixed solution; The mixed solution is separated into solid and liquid, and then washed and dried to obtain a composite heterojunction material; The light ceramsite is used as a carrier and the composite heterojunction material is loaded on the light ceramsite by a coprecipitation method to obtain a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides.

4. The method for preparing a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to claim 3, characterized in that: The molar ratio of g-C3N4 to BiOBr is 1:0.8~1.

2.

5. The method for preparing a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to claim 3, characterized in that: The aging treatment is carried out by ultrasonic coordinated stirring; Among them, the power of ultrasound is 80W~120W.

6. The method for preparing a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to claim 3, characterized in that: The aging treatment temperature is room temperature, and the aging time is 4h~6h.

7. The method for preparing a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to claim 3, characterized in that: The aging solvent is a mixed solvent of ethanol and water in a volume ratio of 1:0.8-1.

2.

8. The method for preparing a photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to claim 7, characterized in that: Add 0.15L~0.17L of aging solvent for every 1g of g-C3N4.

9. Use of the photocatalyst for degradation of nitrogen-containing heteroaromatic pesticides according to any one of claims 1 to 2 in photocatalytic degradation of nitrogen-containing heteroaromatic pesticides.

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