A method and device for treating chloramphenicol wastewater

Abstract

This invention relates to the field of industrial wastewater treatment technology, specifically disclosing a method and apparatus for treating chloramphenicol wastewater. The treatment method includes the following steps: simultaneously introducing ozone gas and the chloramphenicol wastewater to be treated into a microbubble generator to obtain ozone microbubble wastewater; adding the ozone microbubble wastewater and a nitrogen-doped single-atom iron-supported graphene catalyst into a magnetically charged reactor for catalytic oxidation to obtain treated wastewater. This invention utilizes the synergistic effect of a nitrogen-doped single-atom iron-supported graphene catalyst and a magnetically mediated microbubble ozone system to generate a large number of highly oxidizing hydroxyl radicals (·OH), rapidly and deeply oxidizing chloramphenicol and its complex, recalcitrant intermediates; simultaneously, the near-scale effect between the microbubbles and the single-atom catalyst further enhances the catalytic effect. Compared to traditional treatment methods, this invention significantly improves the degradation efficiency of complex pollutants and has high prospects for industrial application.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method and apparatus for treating chloramphenicol wastewater. Background Technology

[0002] With the development of the pharmaceutical industry, chloramphenicol, as an important broad-spectrum antibiotic, has seen its production scale continuously expand. However, the wastewater problem generated during the production process is becoming increasingly serious. The production of chloramphenicol involves multiple complex chemical synthesis reactions, such as the nitration, bromination, and acetylation of nitroacetophenone. Each reaction is accompanied by the generation of a large amount of wastewater. After mixing, this wastewater forms industrial wastewater with complex composition and extremely high pollution load.

[0003] Chloramphenicol wastewater has the following significant characteristics: First, it contains high concentrations of chloramphenicol and various recalcitrant intermediates. These substances have stable chemical structures, making them difficult to decompose effectively using conventional biological treatment methods. Second, the wastewater exhibits large fluctuations in pH, often being strongly acidic or alkaline, requiring extremely high corrosion resistance from treatment equipment and severely inhibiting microbial activity, significantly impacting the effectiveness of biological treatment. Third, the wastewater also contains high concentrations of salt, typically between 5% and 20%, stemming from various inorganic salts added during production and salts produced during acid-base neutralization. High-salt environments not only cause dehydration of microbial cells, leading to metabolic disorders and even death, but also interfere with subsequent treatment processes, increasing treatment difficulty. Fourth, chloramphenicol and related substances in the wastewater possess strong biotoxicity, posing a serious threat to the ecological environment and human health. Direct discharge without effective treatment will disrupt the aquatic ecological balance and, through bioaccumulation in the food chain, endanger human health.

[0004] Currently, traditional physicochemical methods for treating chloramphenicol wastewater, such as adsorption and coagulation sedimentation, can remove some pollutants, but they are insufficient to completely degrade organic pollutants like chloramphenicol, resulting in limited treatment effectiveness. Biological treatment methods suffer from low microbial activity due to the toxicity and high salinity of the wastewater, leading to low treatment efficiency and the inability to consistently meet discharge standards. Therefore, there is an urgent need to develop a highly efficient, stable, and adaptable method for treating chloramphenicol wastewater to address the limitations of existing technologies and achieve effective treatment of chloramphenicol wastewater. Summary of the Invention

[0005] To address the problems of poor treatment efficiency and inability to consistently meet discharge standards in existing chloramphenicol wastewater treatment methods, this invention provides a method and apparatus for treating chloramphenicol wastewater. This invention employs microbubble ozone catalytic oxidation technology, synergistically using a single-atom iron-supported graphene catalyst under magnetic field guidance to treat chloramphenicol wastewater. This results in a chloramphenicol degradation rate exceeding 99% and a TOC removal rate exceeding 60%, with stable treatment performance, demonstrating broad application prospects in the field of chloramphenicol wastewater treatment.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] A method for treating chloramphenicol wastewater includes the following steps:

[0008] Ozone gas and chloramphenicol wastewater to be treated are simultaneously introduced into a microbubble generator to obtain ozone microbubble wastewater; ozone microbubble wastewater and nitrogen-doped single-atom iron-supported graphene catalyst are added to a magnetic reactor for catalytic oxidation reaction to obtain treated wastewater;

[0009] The nitrogen-doped single-atom iron-supported graphene catalyst is prepared by calcining tannic acid complexed iron and melamine and then loading them onto graphene.

[0010] The iron atom in the nitrogen-doped single-atom iron-supported graphene catalyst is Fe. 2+ The particle size of iron atoms is 0.05 μm to 0.1 μm;

[0011] Graphene has 1 to 3 layers, with a single-layer ratio of >80%.

[0012] Compared to existing technologies, the chloramphenicol wastewater treatment method provided by this invention employs microbubble ozone catalytic oxidation technology to treat chloramphenicol wastewater. The ozone microbubbles generated by the microbubble generator have a large specific surface area and a long residence time, effectively improving the mass transfer efficiency and utilization rate of ozone in the wastewater, and accelerating the oxidative decomposition of chloramphenicol and its recalcitrant intermediates. Simultaneously, the magnetic field-mediated ozone catalytic oxidation further enhances the mass transfer efficiency and residence time of the ozone microbubbles in the wastewater, thereby increasing the opportunity for uniform contact between the ozone microbubbles and pollutants. Furthermore, the magnetic field activates the iron atoms of single-atom iron, further improving catalytic activity. In addition, the nitrogen-doped single-atom iron-supported graphene catalyst forms a synergistic effect with ozone, effectively promoting ozone decomposition to generate more highly active hydroxyl radicals (·OH), significantly enhancing oxidation capacity, achieving deep degradation of chloramphenicol and its recalcitrant intermediates, and improving TOC removal rate.

[0013] The treatment method provided by this invention is not limited by the characteristics of chloramphenicol wastewater such as high salinity and large pH fluctuations. Under complex water quality conditions, the magnetic field-assisted ozone dissolution and the efficient catalysis of the catalyst can still play a stable role. It shows good treatment effect on chloramphenicol wastewater of different sources and different compositions, and has broad applicability and industrial application potential.

[0014] It should be noted that single-atom iron catalysts refer to catalysts formed by uniformly dispersing active metallic iron atoms on a support. Compared with traditional catalysts, single-atom catalysts have higher utilization of active sites and selectivity, and can carry out efficient catalytic reactions at lower temperatures, making them particularly suitable for the degradation of organic pollutants.

[0015] Microbubble technology refers to increasing the gas-liquid contact area by generating bubbles with a diameter of less than 50 μm, thereby improving the efficiency of gas transfer into water. At the same time, microbubbles can also enhance the flotation effect and help remove oil and suspended solids from water.

[0016] As a specific embodiment of the present invention, the preparation method of the nitrogen-doped single-atom iron-supported graphene catalyst includes the following steps:

[0017] Tannic acid and iron salt were dissolved in an alcohol solution, allowed to stand and complex, then melamine was added, mixed evenly, dried, and calcined at 600℃~800℃ under an inert atmosphere. After acid washing, the mixture was washed with water until neutral to obtain nitrogen-doped single-atom iron.

[0018] Graphene was dispersed in water to obtain a graphene dispersion; nitrogen-doped single-atom iron aqueous solution was added to the graphene dispersion, mixed evenly, and freeze-dried to obtain a single-atom iron-supported graphene catalyst.

[0019] The method for preparing nitrogen-doped single-atom iron-supported graphene catalyst provided by this invention precisely controls the dispersion state of iron atoms through the complexation of tannic acid and iron salt. Combined with a calcination temperature of 600℃~800℃, single-atom iron particles with a particle size of 0.05μm~0.1μm can be prepared, ensuring that the iron atoms are in a highly active Fe... 2+ The catalyst exists in a certain form; in the subsequent loading process with graphene, through freeze-drying technology, nitrogen-doped single-atom iron can be uniformly dispersed on the graphene surface, giving full play to the advantages of graphene's high specific surface area and excellent electronic conductivity, thereby improving the overall activity of the catalyst.

[0020] In this invention, nitrogen doping optimizes the electronic structure of single-atom iron, enhancing its adsorption and activation capabilities for ozone. The highly dispersed single-atom iron on the graphene surface provides abundant active sites, significantly improving the catalytic oxidation efficiency of pollutants in chloramphenicol wastewater. Simultaneously, the catalyst prepared by this method exhibits high structural stability; the active sites are not easily lost during repeated cycles, maintaining efficient and stable catalytic performance. This provides a high-performance catalyst for the treatment of highly toxic pharmaceutical wastewater, showing broad application prospects in this field.

[0021] Furthermore, the alcohol solution is a solution of anhydrous ethanol and water in a volume ratio of (1-2):1, and its volume-to-mass ratio with tannic acid is 10 mL:(1-1.5) g.

[0022] Furthermore, the temperature for static complexation is 20℃~40℃, and the complexation time is 5min~10min.

[0023] Allowing the tannic acid to fully coordinate with iron ions by standing at room temperature for 5 to 10 minutes can effectively inhibit the aggregation of iron ions and lay the foundation for the subsequent formation of uniform single-atom iron active centers.

[0024] Furthermore, the molar ratio of the tannic acid to the iron salt is 1:(6-7).

[0025] Furthermore, the molar ratio of the iron salt to melamine is 1:(8-9).

[0026] The nitrogen species produced by the decomposition of melamine at high temperatures can react with Fe. 2+ The formation of strong interactions can effectively inhibit the aggregation of iron atoms and construct Fe-N on the graphene surface. x Active sites, which are beneficial to significantly improve the catalytic activity of the catalyst.

[0027] Furthermore, the calcination time is 2 to 3 hours.

[0028] Furthermore, the molar ratio of graphene to iron salt is (1-3):1.

[0029] The optimal molar ratio of graphene to iron salt ensures that iron atoms are uniformly dispersed in single-atom form, thereby increasing the number and accessibility of active sites. An appropriate amount of graphene can form a good electronic coupling with single-atom iron, promoting the rapid transfer of electrons between the two, enhancing the adsorption and activation capacity of ozone, and improving the catalytic oxidation efficiency of chloramphenicol wastewater.

[0030] Furthermore, the mass-to-volume ratio of the graphene to water is (3-4) g: 20 mL.

[0031] Furthermore, the resistivity of the graphene is 0.02 μΩ / m to 0.03 μΩ / m.

[0032] Furthermore, the concentration of the nitrogen-doped single-atom iron aqueous solution is (0.2–0.25) g / mL.

[0033] Furthermore, the freeze-drying temperature is -70℃ to -80℃.

[0034] Vacuum freeze drying can effectively prevent iron atom aggregation, improve dispersion, and to some extent enhance the mechanical strength of the catalyst, increase its service life, and thus improve catalytic activity.

[0035] Furthermore, the mass ratio of ozone gas to chloramphenicol in the chloramphenicol wastewater is 0.2–0.3:1.

[0036] The optimal ozone gas flow rate ensures the removal rate of organic matter such as chloramphenicol in wastewater while minimizing the amount of oxygen introduced.

[0037] Furthermore, the gas-to-water volume ratio of the microbubble generator is 1:5 to 1:10, and the inlet pressure of the microbubble generator is 0.25 MPa to 0.5 MPa.

[0038] Furthermore, the mass-to-volume ratio of the nitrogen-doped single-atom iron-supported graphene catalyst to chloramphenicol wastewater is (3-5) g: 10 L.

[0039] Furthermore, the magnetic field strength of the magnetic reactor is 10000G to 15000G.

[0040] Furthermore, the catalytic oxidation reaction takes 30 to 60 minutes.

[0041] Secondly, the present invention also provides an apparatus for treating chloramphenicol wastewater, comprising an ozone generator, a microbubble generator, and a magnetic reactor connected in sequence; wherein the inlet of the microbubble generator is connected to the upper part of the magnetic reactor, and the outlet is connected to the bottom of the magnetic reactor.

[0042] In one specific embodiment of the present invention, the magnetic reactor includes a reactor and parallel magnetic rods arranged on the outer wall of the reactor; the height of the magnetic rods is not lower than the wastewater level.

[0043] In one specific embodiment of the present invention, the magnetic rod is 300mm long and has a diameter of 19mm.

[0044] In one specific embodiment of the present invention, a gas flow meter is provided between the ozone generator and the microbubble generator to control the gas-water ratio entering the microbubble generator.

[0045] The chloramphenicol wastewater treatment method provided by this invention couples a nitrogen-doped single-atom iron catalyst into a microbubble ozone catalytic oxidation process mediated by a magnetic field, achieving complete treatment of recalcitrant chloramphenicol wastewater. The removal rate of chloramphenicol in the wastewater reaches over 99%, and the TOC removal rate reaches over 60%. In addition, this method uses ozone as an oxidant, and the main product after the reaction is oxygen, which does not produce secondary pollution. It not only solves the problem of chloramphenicol wastewater treatment and achieves the standard discharge of wastewater, but also effectively reduces pollution to the surrounding water bodies, soil and other ecological environments, and has high application value and environmental protection significance. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the apparatus for treating chloramphenicol wastewater used in an embodiment of the present invention;

[0047] Figure 2 These are TEM images of graphene used in embodiments of the present invention;

[0048] Figure 3 This is a TEM image of nitrogen-doped single-atom iron prepared in Example 2 of the present invention;

[0049] Figure 4 This is a TEM image of the nitrogen-doped single-atom iron-supported graphene catalyst prepared in Example 2 of the present invention;

[0050] Figure 5 The XRD patterns of graphene (GO), nitrogen-doped single-atom iron (SAI), and nitrogen-doped single-atom iron supported graphene catalyst (SAG-Fe) in Example 2 of the present invention are shown.

[0051] Figure 6 XPS image of the nitrogen-doped single-atom iron-supported graphene catalyst prepared in Example 2 of this invention before use;

[0052] Figure 7 XPS image of the nitrogen-doped single-atom iron-supported graphene catalyst prepared in Example 2 of this invention after use. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0054] A schematic diagram of the apparatus for treating chloramphenicol wastewater used in this embodiment of the invention is shown below. Figure 1As shown, it includes an oxygen cylinder, an ozone generator, a microbubble generator, and a magnetic reactor. The magnetic reactor is equipped with a nitrogen-doped single-atom iron-supported graphene catalyst. The inlet of the microbubble generator is connected to the upper part of the magnetic reactor, and the outlet is connected to the bottom of the reactor. The microbubble generator and the magnetic reactor form a circulation path.

[0055] Specifically, the magnetic reactor includes a reactor and two magnetic rods disposed on the outer wall of the reactor, with the two magnetic rods arranged in parallel.

[0056] In one specific embodiment of the present invention, the magnetic rod has a length of 300mm, a magnetic field strength of 12000G, a diameter of 19mm, and a height not lower than the wastewater level.

[0057] In one specific embodiment of the present invention, a gas flow meter is provided between the ozone generator and the microbubble generator to control the gas-to-water ratio entering the microbubble generator.

[0058] In one specific embodiment of the present invention, a KI absorption bottle is also provided between the ozone generator and the microbubble generator to absorb unreacted oxygen or excess ozone.

[0059] In one specific embodiment of the present invention, the magnetic reactor is also connected to a condenser for cooling the chloramphenicol wastewater. The ozone catalytic oxidation of chloramphenicol wastewater releases heat; therefore, a condenser is installed to cool the wastewater, ensuring a suitable reaction temperature and the safety of the treatment process.

[0060] The method for treating chloramphenicol wastewater using the above-mentioned device specifically includes the following steps:

[0061] Oxygen is introduced into the ozone generator, and the generated ozone gas and chloramphenicol wastewater are simultaneously introduced into the microbubble generator. The ozone microbubble wastewater enters the reactor from the bottom of the magnetized reactor. Under the guidance of the magnetic field, the enhanced mass transfer of microbubbles, and the action of the catalyst, ozone efficiently oxidizes and degrades the pollutants in the chloramphenicol wastewater. After the reaction, the tail gas is discharged from the reactor and then the residual ozone is absorbed by another KI absorption bottle to prevent environmental pollution. Finally, the tail gas is discharged in compliance with the emission standards.

[0062] To better illustrate the present invention, further examples are provided below.

[0063] The graphene used in the following examples has 1 to 3 layers and a single-layer ratio of >80%; the concentration of chloramphenicol in the chloramphenicol wastewater is about 50 mg / L.

[0064] Example 1

[0065] This invention provides a method for preparing a nitrogen-doped single-atom iron-supported graphene catalyst, the specific steps of which are as follows:

[0066] Step a: Dissolve 5g of tannic acid in 50mL of ethanol aqueous solution (v / v = 1:1), then add 5g of FeCl3·6H2O, let it stand at room temperature for 5min to complex, then add 20g of melamine, stir at room temperature for 30min, then dry in an oven at 80℃, grind, place in a tube furnace, calcine at 800℃ for 2h under nitrogen protection, wash with 0.5M sulfuric acid solution, then wash with water until the pH of the washing solution is neutral, dry, and obtain nitrogen-doped single-atom iron, denoted as SAI;

[0067] Step b: Weigh 3.54g of graphene and add it to 20mL of deionized water, sonicate for 30min to obtain graphene dispersion;

[0068] Step c: Dissolve 4g of nitrogen-doped single-atom iron prepared above in 20mL of deionized water to obtain nitrogen-doped single-atom iron solution; add nitrogen-doped single-atom iron solution to graphene dispersion, stir magnetically for 24h, and freeze dry at -72℃ to constant weight to obtain nitrogen-doped single-atom iron supported graphene catalyst, denoted as SAG-Fe.

[0069] The TEM image of graphene (GO) in this embodiment is as follows: Figure 2 As shown, the TEM image of the prepared nitrogen-doped single-atom iron (SAI) is as follows. Figure 3 As shown, the TEM image of the nitrogen-doped single-atom iron-supported graphene catalyst (SAG-Fe) is as follows. Figure 4 As shown in the figure, graphene has a single-layer structure with a large specific surface area; Fe in SAI and SAG-Fe is atomically dispersed, and single-atom iron is successfully loaded onto graphene.

[0070] Figure 5 The XRD patterns of SAI and SAG-Fe prepared in this embodiment are shown. As can be seen from the figure, the characteristic peaks of SAI and SAG-Fe are almost the same, and the peak positions have not changed. The surface SAI was successfully loaded onto the graphene surface, and the sheet structure of graphene was still retained after loading.

[0071] Figure 6 The XPS plot of SAG-Fe prepared in this embodiment shows two peaks at 710.5 eV and 724.1 eV, indicating p-orbital spin-orbit splitting, which are attributed to Fe. 2+ 2p 3 / 2 and Fe 2+ 2p 1 / 2 Signal.

[0072] The above embodiments can also be used to prepare SAG-Fe using other reaction conditions defined by the present invention. As long as the conditions are within the range defined by the present invention, the technical effects can be basically equivalent to those described above.

[0073] Example 2

[0074] This invention provides a method for treating chloramphenicol wastewater, comprising the following steps:

[0075] Oxygen was introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater were simultaneously introduced into a microbubble generator. The mass ratio of ozone to chloramphenicol in the wastewater was 0.2:1, the ozone flow rate was 0.3 L / min, the gas-to-water volume ratio in the microbubble generator was 1:5, and the inlet pressure of the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced from the bottom into a magnetic reactor, where nitrogen-doped single-atom iron-supported graphene catalyst was added at a mass-to-volume ratio of 5 g to chloramphenicol wastewater. The magnetic field strength was 12000 G. After reacting for 30 min, the degradation rate of chloramphenicol was 99.8%, and the TOC removal rate was 70.2%.

[0076] Figure 7 This is the XPS image of the nitrogen-doped single-atom iron-supported graphene catalyst (SAG-Fe) used in this embodiment, compared with... Figure 6 The comparison shows that two peaks of p-orbital spin splitting were observed at 710.5 eV and 724.1 eV before and after the treatment, respectively, which were attributed to Fe. 2+ 2p 3 / 2 and Fe 2+ 2p 1 / 2 The signal indicates that the valence state of Fe did not change significantly before and after use, proving that the material has good reusability.

[0077] Example 3

[0078] This invention provides a method for treating chloramphenicol wastewater, comprising the following steps:

[0079] Oxygen was introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater were simultaneously introduced into a microbubble generator. The mass ratio of ozone to chloramphenicol in the wastewater was 0.25:1, the ozone flow rate was 0.3 L / min, the gas-to-water volume ratio in the microbubble generator was 1:8, and the inlet pressure of the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced from the bottom into a magnetic reactor, where nitrogen-doped single-atom iron-supported graphene catalyst was added at a mass-to-volume ratio of 3 g to chloramphenicol wastewater. The magnetic field strength was 15000 G. After reacting for 40 min, the degradation rate of chloramphenicol was 99.6%, and the TOC removal rate was 65.7%.

[0080] Example 4

[0081] This invention provides a method for treating chloramphenicol wastewater, comprising the following steps:

[0082] Oxygen was introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater were simultaneously introduced into a microbubble generator. The mass ratio of ozone to chloramphenicol in the wastewater was 0.3:1, the ozone flow rate was 0.3 L / min, the gas-to-water volume ratio in the microbubble generator was 1:10, and the pressure at the inlet of the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced from the bottom into a magnetic reactor, where nitrogen-doped single-atom iron-supported graphene catalyst was added. The mass-to-volume ratio of the catalyst to the chloramphenicol wastewater was 4 g:10 L, the magnetic field strength was 10000 G, and after 40 min of reaction, the degradation rate of chloramphenicol was 99.4%, and the TOC removal rate was 60.8%.

[0083] To better illustrate the technical solution of the present invention, further comparisons are made below using comparative examples and instances of the present invention.

[0084] Comparative Example 1

[0085] This comparative example provides a method for treating chloramphenicol wastewater, which differs from Example 2 only in that it does not include a nitrogen-doped single-atom iron catalyst or magnetic field mediation. Specifically, it includes the following steps:

[0086] Oxygen was introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater were simultaneously introduced into a microbubble generator. The mass ratio of ozone to chloramphenicol in the wastewater was 0.2:1, the ozone flow rate was 0.3 L / min, the gas-to-water volume ratio in the microbubble generator was 1:5, and the pressure before the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced into a conventional reactor from the bottom. After reacting for 70 minutes, the degradation rate of chloramphenicol was found to be 99.5%, and the TOC removal rate was 50.3%.

[0087] Comparative Example 2

[0088] This comparative example provides a method for treating chloramphenicol wastewater, which differs from Example 2 only in that it does not include a nitrogen-doped single-atom iron catalyst. Specifically, it includes the following steps:

[0089] Oxygen was introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater were simultaneously introduced into a microbubble generator. The mass ratio of ozone to chloramphenicol in the wastewater was 0.2:1, the ozone flow rate was 0.3 L / min, the gas-to-water volume ratio in the microbubble generator was 1:5, and the pressure before the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced from the bottom into a magnetic reactor with a magnetic field strength of 12000 G. After 60 min of reaction, the degradation rate of chloramphenicol was 99.6%, and the TOC removal rate was 55.4%.

[0090] Comparative Example 3

[0091] This comparative example provides a method for treating chloramphenicol wastewater, which differs from Example 2 only in that the nitrogen-doped single-atom iron catalyst is replaced with activated carbon. Specifically, it includes the following steps:

[0092] Oxygen was introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater were simultaneously introduced into a microbubble generator. The mass ratio of ozone to chloramphenicol in the wastewater was 0.2:1, the ozone flow rate was 0.3 L / min, the gas-to-water volume ratio in the microbubble generator was 1:5, and the pressure at the inlet of the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced from the bottom into a magnetic reactor, and activated carbon was added at a mass-to-volume ratio of 5 g to chloramphenicol wastewater. The magnetic field strength was 12000 G. After reacting for 30 min, the degradation rate of chloramphenicol was measured to be 80.6%, and the TOC removal rate was 55.8%.

[0093] Comparative Example 4

[0094] This comparative example provides a method for treating chloramphenicol wastewater, which differs from Example 2 only in the preparation method of nitrogen-doped single-atom iron-supported graphene, replacing melamine as the nitrogen source with urea. The rest is identical. The preparation method of the nitrogen-doped single-atom iron-supported graphene includes the following steps:

[0095] Step a: Dissolve 5g of tannic acid in 50mL of ethanol aqueous solution (v / v = 1:1), then add 5g of FeCl3·6H2O, let it stand at room temperature for 5min to complex, then add 20g of urea, stir at room temperature for 30min, then dry in an oven at 80℃, grind, place in a tube furnace, calcine at 800℃ for 2h under nitrogen protection, wash with 0.5M sulfuric acid solution, then wash with water until the pH of the washing solution is neutral, dry, and obtain nitrogen-doped iron;

[0096] Step b: Weigh 3.54g of graphene and add it to 20mL of deionized water, sonicate for 30min to obtain graphene dispersion;

[0097] Step c: Dissolve 4g of nitrogen-doped iron prepared above in 20mL of deionized water to obtain a nitrogen-doped iron solution; add the nitrogen-doped iron solution to the graphene dispersion, stir magnetically for 24h, and freeze-dry at -72℃ to constant weight to obtain a nitrogen-doped iron-supported graphene catalyst.

[0098] The nitrogen-doped iron-supported graphene catalyst prepared above was used to treat chloramphenicol wastewater in the same way as in Example 1. After 50 min of reaction, the degradation rate of chloramphenicol was 99.7% and the degradation rate of TOC was 55.2%.

[0099] Comparative Example 5

[0100] This comparative example provides a method for treating chloramphenicol wastewater, which differs from Example 2 only in the preparation method of nitrogen-doped single-atom iron-supported graphene, replacing the complexing agent tannic acid with polyacrylic acid; otherwise, the methods are identical. The preparation method of the nitrogen-doped single-atom iron-supported graphene includes the following steps:

[0101] Step a: Dissolve 5g of polyacrylic acid in 50mL of ethanol aqueous solution (v / v = 1:1), then add 5g of FeCl3·6H2O, let it stand at room temperature for 5min to complex, then add 20g of melamine, stir at room temperature for 30min, then dry in an oven at 80℃, grind, place in a tube furnace, calcine at 800℃ for 2h under nitrogen protection, wash with 0.5M sulfuric acid solution, then wash with water until the pH of the washing solution is neutral, dry, and obtain nitrogen-doped iron;

[0102] Step b: Weigh 3.54g of graphene and add it to 20mL of deionized water, sonicate for 30min to obtain graphene dispersion;

[0103] Step c: Dissolve 4g of nitrogen-doped iron prepared above in 20mL of deionized water to obtain a nitrogen-doped iron solution; add the nitrogen-doped iron solution to the graphene dispersion, stir magnetically for 24h, and freeze-dry at -72℃ to constant weight to obtain a nitrogen-doped iron-supported graphene catalyst.

[0104] The nitrogen-doped iron-supported graphene catalyst prepared above was used to treat chloramphenicol wastewater in the same way as in Example 1. After 50 min of reaction, the degradation rate of chloramphenicol was 99.6% and the degradation rate of TOC was 55.6%.

[0105] In summary, magnetic fields can improve the solubility and stability of ozone in water, thereby increasing ozone oxidation efficiency. Adding nitrogen-doped single-atom iron-supported graphene catalysts under magnetic field guidance can provide more active sites. Compared to activated carbon, nitrogen-doped single-atom iron-supported graphene exhibits stronger catalytic activity. Increasing microbubble treatment can enhance ozone mass transfer efficiency, increase ozone utilization, and promote the hydroxyl oxidation process. This invention utilizes the synergistic effect of nitrogen-doped single-atom iron-supported graphene catalysts and magnetic field-mediated microbubble ozone systems to generate a large number of highly oxidizing hydroxyl radicals (·OH), rapidly and deeply oxidizing chloramphenicol and its complex, recalcitrant intermediates. Simultaneously, the near-scale effect between microbubbles and single-atom catalysts further enhances the catalytic effect. Compared to traditional treatment methods, the method of this invention significantly improves the degradation efficiency of complex pollutants and has high prospects for industrial application.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating chloramphenicol waste water, characterized by, Includes the following steps: Ozone gas and chloramphenicol wastewater to be treated are simultaneously introduced into a microbubble generator to obtain ozone microbubble wastewater; ozone microbubble wastewater and nitrogen-doped single-atom iron-supported graphene catalyst are added to a magnetic reactor for catalytic oxidation reaction to obtain treated wastewater; The nitrogen-doped single-atom iron-supported graphene catalyst is prepared by calcining tannic acid complexed iron and melamine and then loading them onto graphene. The iron atom in the nitrogen-doped monatomic iron supported graphene catalyst is Fe 2+ The particle size of the iron atom is 0.05-0.1 μm. Graphene has 1 to 3 layers, with a single-layer ratio of >80%.

2. The method for treating chloramphenicol waste water according to claim 1, wherein The preparation method of the nitrogen-doped single-atom iron-supported graphene catalyst includes the following steps: Tannic acid and iron salt were dissolved in an alcohol solution, allowed to stand and complex, then melamine was added, mixed evenly, dried, and calcined at 600℃~800℃ under an inert atmosphere. After acid washing, the mixture was washed with water until neutral to obtain nitrogen-doped single-atom iron. Graphene was dispersed in water to obtain a graphene dispersion; nitrogen-doped single-atom iron aqueous solution was added to the graphene dispersion, mixed evenly, and freeze-dried to obtain a single-atom iron-supported graphene catalyst.

3. The method for treating chloramphenicol waste water according to claim 2, wherein The alcohol solution is a solution of anhydrous ethanol and water in a volume ratio of (1~2):1, and its volume-to-mass ratio with tannic acid is 10 mL: (1~1.5) g; and / or The temperature for static complexation is 20℃~40℃, and the complexation time is 5min~10min.

4. The method for treating chloramphenicol waste water according to claim 2, wherein The molar ratio of tannic acid to iron salt is 1:(6~7); and / or The molar ratio of the iron salt to melamine is 1:(8~9); and / or The calcination time is 2h to 3h.

5. The method for treating chloramphenicol waste water according to claim 2, wherein The molar ratio of graphene to iron salt is (1~3):1; and / or The mass-to-volume ratio of the graphene to water is (3~4) g:20 mL; and / or The concentration of the nitrogen-doped single-atom iron aqueous solution is (0.2~0.25) g / mL.

6. The method for treating chloramphenicol waste water as claimed in claim 1, wherein, The mass ratio of ozone gas to chloramphenicol in the chloramphenicol wastewater is 0.2~0.3:1; and / or The mass-to-volume ratio of the nitrogen-doped single-atom iron-supported graphene catalyst to chloramphenicol wastewater is (3~5) g:10L.

7. The method for treating chloramphenicol waste water as claimed in claim 1, wherein, The gas-to-water volume ratio of the microbubble generator is 1:5 to 1:10, and the inlet pressure of the microbubble generator is 0.25 MPa to 0.5 MPa.

8. The method for treating chloramphenicol waste water as claimed in claim 1, wherein, The magnetic field strength of the magnetized reactor is 10000G~15000G; and / or The catalytic oxidation reaction takes 30 to 60 minutes.

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