A method for removing antibiotics from livestock and poultry wastewater using a COFs-based composite photocatalyst

Abstract

The present invention discloses a method for removing antibiotics from livestock and poultry wastewater by using a COFs-based composite photocatalyst, and the COFs-based composite photocatalyst comprises spherical vinyl-functionalized covalent organic frameworks and silver phosphate particles. In the present invention, the treatment method comprises: (1) introducing the livestock and poultry wastewater into the reaction pool of the catalytic reaction device, and then adding the COFs-based composite photocatalyst for catalytic reaction treatment, and the reaction time is 12 to 20 minutes; (2) overflowing the wastewater after the reaction in step (1) into the sedimentation tank, and the sedimentation time is 30 to 90 minutes; (3) discharging the supernatant after sedimentation from the catalytic reaction device; (4) pumping the catalyst after sedimentation back to the reaction pool, and simultaneously arranging a material regeneration tank to carry out activation and regeneration treatment on the catalyst after sedimentation with a period of 1 to 3 months. The present invention has the advantages of high treatment efficiency, simple operation, etc., can achieve complete degradation and removal of antibiotics in livestock and poultry wastewater under the stress of high concentration of COD, ammonia nitrogen and total phosphorus, and has excellent adaptability and good industrial application prospects.

Description

Technical Field

[0001] The present invention belongs to the fields of photocatalytic application of semiconductor materials and environmental protection technology, and relates to a method for treating livestock and poultry wastewater, in particular to a method for removing antibiotics in livestock and poultry wastewater by using a COFs-based composite photocatalyst. Background Art

[0002] China is a large country in livestock and poultry breeding. Data from the China Statistical Yearbook 2021 shows that in 2020, the number of fattening pigs slaughtered in China alone reached 530 million. According to the "Emission Source Statistical Survey Production Pollution Discharge Accounting Method and Coefficient Manual" and the "Pollutant Discharge Standard for Livestock and Poultry Industries" (GB18596-2001) of the second national pollution source census, the discharge of pig breeding wastewater in 2020 can reach 5.72 billion tons. To improve livestock and poultry production and disease prevention and control, antibiotics are added during the breeding process. Since antibiotics cannot be completely absorbed and metabolized in animals, 60% - 90% of the antibiotics will be discharged into livestock and poultry wastewater in the form of the original drug with feces and urine. Therefore, livestock and poultry wastewater not only has a large volume, but also contains antibiotics in addition to high concentrations of carbon, nitrogen, and phosphorus.

[0003] Currently, there are the following problems in the treatment of livestock and poultry wastewater: (1) Since the antibiotics and their intermediates contained in the wastewater will have a strong inhibitory effect on microorganisms, the anaerobic biological treatment process of livestock and poultry wastewater will become unstable or even ineffective; (2) The residual antibiotics in the wastewater are extremely likely to induce the enrichment of drug-resistant bacteria and the spread of antibiotic resistance genes (ARGs), thus posing a huge potential threat to the receiving environment and human health. In summary, due to the biological toxicity of antibiotics, the anaerobic biological treatment process of livestock and poultry wastewater is difficult to carry out efficiently, and it is necessary to carry out enhanced treatment to improve its biodegradability and at the same time eliminate the environmental risks caused by long-term exposure to antibiotics. Therefore, it is urgent to research and develop an economical and efficient livestock and poultry wastewater treatment technology to efficiently remove antibiotics in livestock and poultry wastewater.

[0004] Photocatalytic technology, with its advantages of mild reaction conditions and the ability to directly convert solar energy into chemical energy, has become a green technology that has received much attention in the fields of environment and energy. In recent years, scientific researchers have carried out a series of studies on photocatalytic technology as a pretreatment unit for biological treatment to enhance the bioavailability of wastewater. Numerous studies have shown that photocatalytic technology has the following significant advantages in the enhanced treatment of organic wastewater: 1) It has good oxidative decomposition performance for biotoxic substances such as antibiotics, and can significantly improve the bioavailability of organic wastewater; 2) The strongly oxidizing reactive species generated during the photocatalytic reaction endow the catalyst with good self-cleaning antibacterial function, making the catalyst have long-term stability during the treatment process of organic wastewater; 3) The reaction conditions are mild and no other chemical reagents need to be introduced. Therefore, using photocatalysis as a pretreatment unit in the biological treatment process to improve the bioavailability of livestock and poultry wastewater is a feasible and promising treatment technology.

[0005] The core of realizing efficient photocatalytic reaction is to select, design, and develop photocatalysts with high-efficiency and stable catalytic activity. Covalent organic frameworks (COFs) are a new type of crystalline porous polymer formed by covalently linking organic small molecule monomers. They have unique properties such as large specific surface area, high porosity, low density, good stability, high charge carrier mobility, and rich and adjustable structures, and have attracted much attention in the fields of photoelectrocatalysis, adsorption, energy storage, gas capture, etc. However, at present, the synthesis conditions of most COFs are generally relatively harsh and need to be carried out under high temperature, high pressure, and oxygen-free conditions; under complex water quality conditions, the selective affinity and adsorption capacity of COFs materials for specific target pollutants need to be improved; the intrinsic photogenerated carrier separation efficiency of COFs monomer materials is relatively low, and the photocatalytic activity needs to be further enhanced. Therefore, how to overcome the problems existing in the existing COFs materials, such as harsh preparation conditions, low separation efficiency of photogenerated electron-hole pairs, poor photocatalytic activity, poor selectivity, and poor tolerance to high COD and ammonia nitrogen, to obtain a COFs-based composite photocatalyst with simple preparation process, good photocatalytic performance, and high tolerance to high COD and ammonia nitrogen is of great significance for the efficient treatment of antibiotics in livestock and poultry wastewater. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for removing antibiotics in livestock and poultry wastewater using a COFs-based composite photocatalyst with a simple preparation process, high treatment efficiency, strong selectivity, and good performance in tolerating high COD and ammonia nitrogen.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for removing antibiotics in livestock and poultry wastewater using a COFs-based composite photocatalyst. Further, the method is to use the COFs-based composite photocatalyst to remove antibiotics in livestock and poultry wastewater; the COFs-based composite photocatalyst includes spherical vinyl-functionalized covalent organic frameworks, and silver phosphate particles are loaded on the vinyl-functionalized covalent organic frameworks.

[0009] For the above method, further improved, the mass ratio of the vinyl-functionalized covalent organic framework to the silver phosphate particles in the COFs-based composite photocatalyst is 1.0×10 -4 ~5.0×10 -3 ; the molar ratio of the vinyl functional group to the covalent organic framework in the vinyl-functionalized covalent organic framework is 10:1 to 15:1.

[0010] The preparation method of the COFs-based composite photocatalyst in the above method includes the following steps:

[0011] S1. Prepare a covalent organic framework dispersion from vinyl-functionalized covalent organic framework, add Ag + solution, stir to prepare a covalent organic framework / Ag + dispersion;

[0012] S2. Add the HPO4 2- solution to the covalent organic framework / Ag + dispersion prepared in step S1, stir under light-shielded conditions, wash, centrifuge, and dry to obtain a vinyl-functionalized covalent organic framework composite photocatalyst.

[0013] For the preparation method of the above COFs-based composite photocatalyst, further improved, in step S1, the preparation method of the vinyl-functionalized covalent organic framework includes the following steps:

[0014] (1) Charge 1,3,5-tris(4-aminophenyl)benzene and 1,4-dialdehyde-2,5-divinylbenzene with a molar ratio of 1:1 to 1:2 into acetonitrile, fully dissolve to obtain a mixed solution; the concentration of 1,3,5-tris(4-aminophenyl)benzene in the mixed solution is 5 to 20 mmol / L;

[0015] (2) Add a 10 - 15 mol / L acetic acid solution to the mixed solution obtained in step (1), stir vigorously for 10 - 45 s, then let it stand at room temperature for 48 - 80 h, wash, and vacuum dry to obtain a vinyl-functionalized covalent organic framework; the volume ratio of the acetic acid solution to acetonitrile is 0.04:1 to 0.2:1.

[0016] Further preferably, in step S1 of the above method, the concentration of the Ag + solution is 0.2 - 0.5 mol / L; the Ag + solution is AgNO3 solution; the covalent organic framework dispersion is obtained by mixing vinyl-functionalized covalent organic framework with water; the concentration of the covalent organic framework dispersion is 0.05 - 0.5 g / L; the dropping rate of the Ag + solution is 0.1 - 0.4 mL / min; the stirring time is 5 - 12 h;

[0017] In step S2, the molar ratio of HPO4 2- in the HPO4 2- solution to Ag + in the covalent organic framework / Ag + dispersion is 1:3; the HPO4 2- solution is Na2HPO4·12H2O solution; the HPO4 2-The dropping rate of the solution is 0.03 - 0.1 mL / min; the stirring time is 2 - 6 h; the drying process is carried out under vacuum conditions.

[0018] Further improved, when using the COFs-based composite photocatalyst to treat antibiotics in livestock and poultry wastewater, the following steps are included: mixing the COFs-based composite photocatalyst with livestock and poultry wastewater in a catalytic reaction device, and carrying out a degradation reaction under light conditions to complete the treatment of antibiotics in livestock and poultry wastewater; the addition amount of the COFs-based composite photocatalyst is 0.05 g - 0.5 g of the COFs-based composite photocatalyst added per liter of livestock and poultry wastewater; the livestock and poultry wastewater is wastewater containing COD, ammonia nitrogen, phosphorus, and antibiotics; the initial concentration of antibiotics in the livestock and poultry wastewater is 0.1 mg / L - 100 mg / L, the initial concentration of COD is 100 mg / L - 10,000 mg / L; the initial concentration of ammonia nitrogen is 10 mg / L - 1000 mg / L; the initial concentration of total phosphorus is 5 mg / L - 100 mg / L; the antibiotics in the livestock and poultry wastewater are at least one of tetracycline, oxytetracycline, chlortetracycline, sulfadiazine, sulfamerazine, sulfamethoxazole, sulfadimidine, gentamicin, erythromycin, clarithromycin, and azithromycin.

[0019] Furthermore, a catalytic reaction device is used to treat livestock and poultry wastewater; the catalytic reaction device includes a reaction tank, a sedimentation tank, a material regeneration tank, an aeration ring, a gas flow meter, and a liquid flow meter. Treating antibiotics in livestock and poultry wastewater includes the following steps:

[0020] (a1) Introduce the livestock and poultry wastewater into the reaction tank of the catalytic reaction device, and then add the COFs-based composite photocatalyst for treatment. The treatment time is 12 - 20 min; carry out a degradation reaction under light conditions;

[0021] (a2) Overflow and transport the reaction solution obtained after the degradation reaction in step (a1) to the sedimentation tank, and the sedimentation time is 30 - 90 min to obtain supernatant and sediment materials;

[0022] (a3) Filter the supernatant obtained in step (a2) and then discharge it from the catalytic reaction device;

[0023] (a4) Pump the sediment materials obtained in step (a2) back to the reaction tank to continue treating the livestock and poultry wastewater, and complete the continuous treatment of antibiotics in the livestock and poultry wastewater;

[0024] (a5) Transport the sediment materials after continuous treatment for 1 - 3 months in step (a4) to the material regeneration tank to carry out activation and regeneration treatment on the catalytic material. The specific regeneration treatment method is: add hydrogen peroxide solution and phosphoric acid solution, and react under stirring conditions for 10 - 30 min to obtain the regenerated COFs-based composite photocatalyst;

[0025] (a6) Return the regenerated COFs-based composite photocatalyst obtained in step (a5) to the reaction pool to continue treating the livestock and poultry wastewater.

[0026] Furthermore, a light source chamber is provided around and in the central area of the reaction pool, and the reaction pool is separated from the light source chamber by a light-transmitting partition; an aeration ring is installed at the bottom of the reaction pool; a xenon lamp or an LED energy-saving lamp is installed in the light source chamber.

[0027] Preferably, the material of the light-transmitting partition is polymethyl methacrylate; the aeration flow rate of the aeration ring is 5 - 20 m 3 / min.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] (1) The present invention provides a method for removing antibiotics from livestock and poultry wastewater by using a COFs-based composite photocatalyst. The COFs-based composite photocatalyst is used to treat the livestock and poultry wastewater, and the effective removal of antibiotics in the livestock and poultry wastewater is achieved through the degradation effect of the catalyst. In the present invention, the COFs-based composite photocatalyst used is composed of a vinyl-functionalized covalent organic framework and silver phosphate particles, and has the advantages of simple preparation process, mild preparation conditions, strong photocatalytic activity, good resistance to COD and ammonia nitrogen, etc. It is a new type of efficient visible-light photocatalyst that can be reused, and can achieve the degradation and removal of antibiotics in wastewater under visible light in a short time, and can still effectively degrade antibiotics in wastewater after being used multiple times. Therefore, the method for removing antibiotics from livestock and poultry wastewater by using the COFs-based composite photocatalyst of the present invention has the advantages of good antibiotic degradation performance and short reaction time. More importantly, the COFs-based composite photocatalyst used in the method of the present invention can be applied to the treatment of livestock and poultry wastewater containing high concentrations of COD, ammonia nitrogen, and total phosphorus, and can achieve the complete degradation and removal of antibiotics in wastewater under the stress of high COD, ammonia nitrogen, and total phosphorus, showing very good adaptability, having high application value and good application prospects.

[0030] (2) In the present invention, the mass ratio of the vinyl-functionalized covalent organic framework to the silver phosphate particles in the COFs-based composite photocatalyst used is 1.0×10 -4 ~5.0×10 -3, by optimizing the mass ratio of vinyl-functionalized covalent organic framework and silver phosphate particles, the catalytic activity of the catalyst can be more effectively improved, thereby more efficiently degrading antibiotics in wastewater; meanwhile, the molar ratio of vinyl functional groups to covalent organic framework in the vinyl-functionalized covalent organic framework is optimized to be 10:1 to 15:1, which can more effectively improve the selective adsorption and degradation performance of the covalent organic framework material against antibiotic molecules, and thus can also more efficiently achieve the effective degradation of antibiotics in wastewater.

[0031] (3) In the present invention, it also includes regenerating the photocatalyst after continuous cyclic use for 1 to 3 months. By using hydrogen peroxide solution and phosphoric acid solution to regenerate the used catalyst, the regeneration of the COFs-based composite photocatalyst can be achieved, enabling it to restore its photocatalytic activity, and thus the continuous treatment of livestock wastewater can be realized, further reducing the treatment cost.

[0032] (4) In the present invention, the preparation method of the COFs-based composite photocatalyst has the advantages of simple process, easy operation, low requirements for preparation conditions and equipment, high yield, green and pollution-free, etc. It is suitable for large-scale preparation and conducive to industrial application, thereby facilitating the low-cost and efficient treatment of livestock wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] Figure 1 It is a graph showing the degradation effect of the COFs-based composite photocatalyst on tetracycline under different time conditions in Embodiment 1 of the present invention.

[0035] Figure 2 It is a graph showing the degradation effect of the COFs-based composite photocatalyst on tetracycline under different COD concentrations in Embodiment 2 of the present invention.

[0036] Figure 3 It is a graph showing the degradation effect of the COFs-based composite photocatalyst on tetracycline under different ammonia nitrogen concentrations in Embodiment 3 of the present invention.

[0037] Figure 4 It is a graph showing the degradation effect of the COFs-based composite photocatalyst on tetracycline under different total phosphorus concentrations in Embodiment 4 of the present invention.

[0038] Figure 5 It is a graph showing the degradation effect of the COFs-based composite photocatalyst on tetracycline under different time conditions in Embodiment 5 of the present invention.

[0039] Figure 6Schematic structural diagram of the catalytic reaction device adopted in Example 5 of the present invention. Detailed implementation mode

[0040] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0041] The materials and instruments used in the following examples are all commercially available. In the examples of the present invention, unless otherwise specified, the processes used are conventional processes, the equipment used is conventional equipment, and the obtained data are all the averages of more than three tests.

[0042] Example 1

[0043] A method for treating antibiotic wastewater by using a COFs-based composite photocatalyst, specifically, a COFs-based composite photocatalyst is used to treat livestock and poultry wastewater containing tetracycline, including the following steps:

[0044] Weigh 50 mg of the COFs-based composite photocatalyst (10 mL COFs / Ag3PO4), add it to 100 mL of a tetracycline solution with a concentration of 20 mg / L, ultrasonicate for 1 min, stir and react in the dark for 30 min to reach the adsorption equilibrium, and then carry out the degradation reaction under the irradiation of a 300 W xenon lamp (λ>420 nm).

[0045] Blank group: Treat the tetracycline wastewater without adding the photocatalytic material, and the other conditions are the same.

[0046] During the degradation reaction, take the reaction solutions at different reaction times, measure the content of tetracycline in the reaction solutions by high performance liquid chromatography, and calculate the degradation effect of the COFs-based composite photocatalyst on the tetracycline solution at different times. The results are as Figure 1 shown.

[0047] Figure 1 It is the degradation effect curve diagram of different COFs-based composite photocatalysts on tetracycline under different time conditions in Example 1 of the present invention. As Figure 1 can be seen, under the condition of not adding the photocatalytic material, the concentration of tetracycline hardly changes and cannot degrade by itself under light irradiation; while after adding the photocatalytic material (COFs-based composite photocatalyst), after stirring in the dark for 30 min, about 3% of the tetracycline is adsorbed by the photocatalyst, and then the tetracycline is rapidly degraded and removed by the catalyst under visible light conditions (λ>420 nm). After 5 min of light irradiation, the removal rate of tetracycline can reach 100%.

[0048] In this example, the COFs-based composite photocatalyst (10 mL COFs / Ag3PO4) used includes spherical vinyl-functionalized covalent organic frameworks, on which silver phosphate particles are loaded. The mass ratio of the spherical vinyl-functionalized covalent organic frameworks to the silver phosphate particles is 4.97×10 -4 ; The molar ratio of vinyl functional groups to covalent organic frameworks in the vinyl-functionalized covalent organic frameworks is 12:1.

[0049] In this example, the preparation method of the COFs-based composite photocatalyst (10 mL COFs / Ag3PO4) used includes the following steps:

[0050] (1) Weigh 0.04 mmol of 1,3,5-tris(4-aminophenyl)benzene and 0.06 mmol of 1,4-dialdehyde-2,5-divinylbenzene and place them in a centrifuge tube. Then transfer 5 mL of acetonitrile into the centrifuge tube and ultrasonically treat the mixture for 20 s;

[0051] (2) Add 0.4 mL of acetic acid solution with a concentration of 12 mol / L to the mixed solution obtained in step (1). After shaking vigorously for 15 s, let it stand at room temperature for 72 h, centrifuge and wash, and then vacuum dry to obtain vinyl-functionalized covalent organic frameworks.

[0052] (3) Weigh 0.1 g of the vinyl-functionalized covalent organic frameworks obtained in step (2) and disperse them in 400 mL of ultrapure water to make a vinyl-functionalized covalent organic frameworks dispersion.

[0053] (4) Transfer 10.0 mL of the vinyl-functionalized covalent organic frameworks (COF) dispersion obtained in step (3), dilute it to 60 mL with ultrapure water, and add 15 mL of AgNO3 solution with a concentration of 0.6 mol / L at a dropping rate of 0.3 mL / min, and stir in the dark for 12 h to make a covalent organic frameworks / Ag + dispersion.

[0054] (5) Add 15 mL of Na2HPO4·12H2O solution with a concentration of 0.2 mol / L to the covalent organic frameworks / Ag + dispersion obtained in step (4) at a dropping rate of 0.1 mL / min, stir for 6 h under light-shielded conditions, wash several times with ultrapure water and ethanol, centrifuge, and vacuum dry at 60 °C for 12 h to obtain the COFs-based composite photocatalyst, 10 mL COFs / Ag3PO4.

[0055] For comparison, according to the above steps (1), (2) and (3), vinyl-functionalized covalent organic framework monomers without adding silver phosphate were prepared, denoted as COFs; according to the above steps (4) and (5), silver phosphate monomers without adding covalent organic frameworks were prepared, denoted as Ag3PO4.

[0056] Example 2

[0057] A method for removing antibiotics in livestock and poultry wastewater using a COFs-based composite photocatalyst is basically the same as Example 1, except that: the livestock and poultry wastewater solution in Example 2 contains different concentrations of COD, and the COD concentrations are 0, 100 mg / L, 2000 mg / L, 5000 mg / L, and 10000 mg / L respectively.

[0058] Figure 2 This is the removal efficiency diagram of tetracycline in livestock and poultry wastewater by the COFs-based composite photocatalyst in Example 2 of the present invention under different COD concentrations. From Figure 2 It can be seen that under the stress of different concentrations of COD, the COFs-based composite photocatalyst still maintains a good degradation effect on tetracycline. When the COD concentration is 100 - 2000 mg / L, the degradation efficiency of the catalyst does not change at all. When the COD concentration is as high as 100000 mg / L, the rate of the catalyst only decreases slightly, and the removal rate can still reach 93.2% at 12 min.

[0059] Example 3

[0060] A method for removing antibiotics in livestock and poultry wastewater using a COFs-based composite photocatalyst is basically the same as Example 1, except that: the livestock and poultry wastewater solution in Example 3 contains different concentrations of ammonia nitrogen, and the ammonia nitrogen concentrations are 0, 100 mg / L, 300 mg / L, 500 mg / L, and 1000 mg / L respectively.

[0061] Figure 3 This is the removal efficiency diagram of tetracycline in livestock and poultry wastewater by the COFs-based composite photocatalyst in Example 3 of the present invention under different ammonia nitrogen concentrations. From Figure 3 It can be seen that under the stress of different concentrations of ammonia nitrogen, the COFs-based composite photocatalyst still maintains a good degradation effect on tetracycline. When the ammonia nitrogen concentration is as high as 1000 mg / L, the removal rate can still reach 88.3% at 12 min.

[0062] Example 4

[0063] A method for removing antibiotics from livestock and poultry wastewater using a COFs-based composite photocatalyst is basically the same as Example 1, except that: the livestock and poultry wastewater solution in Example 3 contains different concentrations of total phosphorus, and the total phosphorus concentrations are 0, 5 mg / L, 30 mg / L, 50 mg / L, and 100 mg / L, respectively.

[0064] Figure 4 This is the removal efficiency graph of the COFs-based composite photocatalyst for tetracycline in livestock and poultry wastewater under different total phosphorus concentrations in Example 4 of the present invention. From Figure 4 It can be seen that under the stress of different concentrations of total phosphorus, the COFs-based composite photocatalyst still maintains a good degradation effect on tetracycline. When the total phosphorus concentration is as high as 100 mg / L, the removal rate can still reach 90.1% at 12 min.

[0065] Example 5

[0066] A method for removing antibiotics from livestock and poultry wastewater using a COFs-based composite photocatalyst is specifically to continuously treat livestock and poultry wastewater with a COFs-based composite photocatalyst, including the following steps:

[0067] (1) Add 1 kg of the COFs-based composite photocatalyst (10 mL COFs / Ag3PO4) prepared in Example 1 to the reaction pool of the catalytic reaction device (containing 10 m 3 of livestock and poultry wastewater containing 10 mg / L tetracycline, with a COD concentration of 3000 mg / L, an ammonia nitrogen concentration of 500 mg / L, and a total phosphorus concentration of 30 mg / L);

[0068] (2) Turn on the aeration ring and LED lamp, and carry out photocatalytic degradation reaction for 25 min under light;

[0069] (3) After the photocatalytic degradation reaction, the reaction solution is overflowed and transported to the sedimentation tank, and the sedimentation time is 60 min to obtain the supernatant and sediment materials;

[0070] (4) Filter the supernatant obtained in step (3) and then discharge it from the catalytic reaction device;

[0071] In this example, during the photocatalytic reaction process, the reaction solution at different reaction times was taken, and the content of tetracycline in the reaction solution was measured by high performance liquid chromatography, and the degradation effect of the COFs-based composite photocatalyst on the tetracycline solution at different times was calculated. The results are as Figure 5 shown.

[0072] Figure 5 This is the degradation effect curve graph of the COFs-based composite photocatalyst for tetracycline under different time conditions in Example 5 of the present invention. From Figure 5It can be seen that, under the condition of not adding photocatalytic materials, as the illumination time prolongs, the concentration of tetracycline hardly changes. After adding the COFs-based composite photocatalyst prepared in Example 1, the concentration of tetracycline decreases rapidly with the increase of illumination time. When the illumination time reaches 12 min, tetracycline is degraded and removed by 100%.

[0073] In this embodiment, the photocatalytic reaction device adopted is as Figure 6 shown. A light source chamber is provided around and in the central area of the reaction cell. The reaction cell and the light source chamber are separated by a light-transmitting partition board. An aeration ring is installed at the bottom of the reaction cell. A xenon lamp or an LED energy-saving lamp is installed in the light source chamber. The material of the light-transmitting partition board is polymethyl methacrylate. The aeration flow rate of the aeration ring is 5 - 20 m 3 / min.

[0074] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A method for removing antibiotics from livestock and poultry wastewater by using COFs-based composite photocatalysts, characterized in that, The method uses a COFs-based composite photocatalyst to remove antibiotics from livestock and poultry wastewater; the COFs-based composite photocatalyst includes spherical vinyl-functionalized covalent organic frameworks, and silver phosphate particles are loaded on the vinyl-functionalized covalent organic frameworks; the mass ratio of the vinyl-functionalized covalent organic frameworks to the silver phosphate particles in the COFs-based composite photocatalyst is 1.0×10 -4 ~5.0×10 -3 ; The preparation method of the vinyl-functionalized covalent organic frameworks includes the following steps: (1) adding 1,3,5-tri(4-aminophenyl)benzene and 1,4-dialdehyde-2,5-divinylbenzene in a molar ratio of 1:1 to 1:2 into acetonitrile and fully dissolving them to obtain a mixed solution; (2) Add 10-15 mol / L acetic acid solution to the mixed solution obtained in step (1), stir vigorously for 10-45 s, let stand at room temperature for 48-80 h, wash, and vacuum dry to obtain a vinyl functionalized covalent organic framework.

2. The method according to claim 1, characterized in that The molar ratio of the vinyl functional group to the covalent organic framework in the vinyl functionalized covalent organic framework is 10:1 to 15:

1.

3. The method according to claim 1, characterized in that, The preparation method of the COFs-based composite photocatalyst comprises the following steps: S1. Prepare a covalent organic framework dispersion from vinyl-functionalized covalent organic frameworks, add an Ag + solution, stir to prepare a covalent organic framework / Ag + dispersion; S2. Add HPO4 2- solution to the covalent organic framework / Ag + dispersion prepared in step S1, stir, wash, centrifuge and dry under light-shielding conditions to obtain a vinyl-functionalized covalent organic framework composite photocatalyst.

4. The method according to claim 1, wherein In step (1), the concentration of 1,3,5-tri(4-aminophenyl)benzene in the mixed solution is 5-20 mmol / L; in step (2), the volume ratio of the acetic acid solution to acetonitrile is 0.04:1-0.2:

1.

5. The method according to claim 3, wherein In step S1, the concentration of the Ag + solution is 0.2 - 0.5 mol / L; the Ag + solution is AgNO3 solution; the covalent organic framework dispersion is obtained by mixing vinyl-functionalized covalent organic framework with water; the concentration of the covalent organic framework dispersion is 0.05 - 0.5 g / L; the dropping rate of the Ag + solution is 0.1 - 0.4 mL / min; the stirring time is 5 - 12 h; In step S2, the HPO4 2- in the HPO4 2- solution and the Ag + in the covalent organic framework / Ag + dispersion have a molar ratio of 1:3; the HPO4 2- solution is a Na2HPO4·12H2O solution; the dropping rate of the HPO4 2- solution is 0.03 - 0.1 mL / min; the stirring time is 2 - 6 h; the drying process is carried out under vacuum conditions.

6. The method according to any one of claims 1 to 5, characterized in that, When using COFs-based composite photocatalyst to treat antibiotics in livestock and poultry wastewater, the method comprises the following steps: mixing the COFs-based composite photocatalyst with livestock and poultry wastewater in a catalytic reaction device, and performing a catalytic degradation reaction under light conditions to complete the treatment of antibiotics in the livestock and poultry wastewater; the addition amount of the COFs-based composite photocatalyst is 0.05-0.5g of the COFs-based composite photocatalyst per liter of livestock and poultry wastewater; the livestock and poultry wastewater is wastewater containing COD, ammonia nitrogen, phosphorus, and antibiotics; the initial concentration of antibiotics in the livestock and poultry wastewater is 0.1mg / L-100mg / L, the initial concentration of COD is 100mg / L-10000mg / L; the initial concentration of ammonia nitrogen is 10mg / L-1000mg / L; the initial concentration of total phosphorus is 5mg / L-100 mg / L; the antibiotic in the livestock and poultry wastewater is at least one of tetracycline, oxytetracycline, chlortetracycline, sulfadiazine, sulfamethoxazole, sulfamethoxazole, gentamicin, erythromycin, clarithromycin and azithromycin.

7. The method according to claim 6, characterized in that, A catalytic reaction device is used to treat livestock and poultry wastewater; the catalytic reaction device includes a reaction tank, a sedimentation tank, a material regeneration tank, an aeration ring, a gas flow meter, and a liquid flow meter. The treatment of antibiotics in livestock and poultry wastewater includes the following steps: (a1) introducing livestock and poultry wastewater into the reaction pool of the catalytic reaction device, and then adding COFs-based composite photocatalyst for catalytic reaction treatment, the reaction time is 12-20 min; the degradation reaction is carried out under light conditions; (a2) transferring the overflow of the reaction solution obtained after the catalytic reaction in step (a1) to a sedimentation tank for a sedimentation time of 30 to 90 minutes to obtain a supernatant and a precipitated material; (a3) filtering the supernatant obtained in step (a2) and discharging it from the catalytic reaction device; (a4) pumping the precipitated material obtained in step (a2) back into the reaction tank to continue treating the livestock and poultry wastewater, thereby completing the continuous treatment of antibiotics in the livestock and poultry wastewater; (a5) Transfer the precipitated material after continuous treatment for 1 to 3 months in step (a4) to the material regeneration pool, and perform activation and regeneration treatment on the catalytic material. The specific regeneration treatment method is as follows: Add hydrogen peroxide solution and phosphoric acid solution, and react under stirring conditions for 10 to 30 minutes to obtain a regenerated COFs-based composite photocatalyst; (a6) Return the regenerated COFs-based composite photocatalyst obtained in step (a5) to the reaction pool to continue treating livestock and poultry wastewater.

8. The method according to claim 7, wherein Light source chambers are provided around and in the central area of the reaction pool. The reaction pool is separated from the light source chambers by a light-transmitting partition; an aeration ring is installed at the bottom of the reaction pool; a xenon lamp or an LED energy-saving lamp is installed in the light source chamber.

9. The method according to claim 8, characterized in that, The light-transmitting partition is made of polymethyl methacrylate; the aeration flow rate of the aeration ring is 5 to 20 m 3 / min.

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