Treatment method and treatment device for chloramphenicol wastewater

Abstract

The invention relates to the technical field of industrial wastewater treatment, and particularly discloses a chloramphenicol wastewater treatment method and a chloramphenicol wastewater treatment device. The treatment method comprises the following steps: simultaneously introducing ozone gas and chloramphenicol wastewater to be treated into a microbubble generator to obtain ozone microbubble wastewater; and adding the ozone microbubble wastewater and the nitrogen-doped monatomic iron-loaded graphene catalyst into a magnetizing reactor, and carrying out catalytic oxidation reaction to obtain treated wastewater. The nitrogen-doped monatomic iron-loaded graphene catalyst and a magnetic field mediated microbubble ozone system have a synergistic effect, so that a large amount of hydroxyl radicals (. OH) with strong oxidizing property can be generated, and chloramphenicol and complex refractory intermediate products thereof can be quickly and deeply oxidized; meanwhile, the catalytic effect can be further improved through the micro-bubble and monatomic catalyst near-scale effect. Compared with a traditional treatment method, the treatment method disclosed by the invention has the advantages that the degradation efficiency on complex pollutants is greatly improved, and the treatment method has a relatively high industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial wastewater treatment, and in particular to a method and a device for treating chloramphenicol wastewater. Background Art

[0002] With the development of the pharmaceutical industry, the production scale of chloramphenicol, an important broad-spectrum antibiotic, has continued to expand. However, the wastewater generated during the production process has become increasingly serious. Chloramphenicol production involves multiple complex chemical synthesis reactions, such as nitration, bromination, and acetylation of nitroacetophenone. Each step of the reaction is accompanied by the generation of large amounts of wastewater. These wastewaters, when combined, form industrial wastewater with complex composition and extremely high pollution loads.

[0003] Chloramphenicol wastewater has the following notable characteristics: First, it contains high concentrations of chloramphenicol and various difficult-to-degrade intermediates. These substances have stable chemical structures and are difficult to effectively decompose using conventional biological treatment methods. Second, the pH of the wastewater fluctuates greatly, often with strong acidity or strong alkalinity, which places extremely high demands on the corrosion resistance of treatment equipment and severely inhibits the activity of microorganisms, greatly affecting the effectiveness of biological treatment. Third, the wastewater also contains high concentrations of salt, with salinity typically ranging from 5% to 20%. This is due to the various inorganic salt raw materials added during the production process and the salts produced by acid-base neutralization. The high-salt environment not only dehydrates microbial cells, leading to metabolic disorders and even death of microorganisms, but also interferes with subsequent treatment processes, increasing the difficulty of treatment. Fourth, chloramphenicol and its related substances in the wastewater have strong biological toxicity and pose a serious threat to the ecological environment and human health. If discharged directly without effective treatment, it will disrupt the ecological balance of the water body and endanger human health after enrichment through the food chain.

[0004] Currently, traditional physical and chemical methods for treating chloramphenicol wastewater, such as adsorption and coagulation-sedimentation, can remove some pollutants but struggle to completely degrade organic pollutants like chloramphenicol, resulting in limited treatment effectiveness. Biological treatment methods, however, are inhibited by wastewater toxicity and high salinity, resulting in low microbial activity and low treatment efficiency, making it difficult to consistently achieve standard discharge. Therefore, there is an urgent need to develop an efficient, stable, and adaptable chloramphenicol wastewater treatment method to address the challenges of existing treatment technologies and achieve effective treatment of chloramphenicol wastewater. Summary of the Invention

[0005] To address the problems of poor treatment effects and inability to achieve consistent discharge standards in existing chloramphenicol wastewater treatment methods, the present invention provides a method and device for treating chloramphenicol wastewater. The present invention utilizes microbubble ozone catalytic oxidation technology, mediated by a magnetic field, in conjunction with a single-atom iron-supported graphene catalyst to treat chloramphenicol wastewater. This method achieves a chloramphenicol degradation rate exceeding 99% and a TOC removal rate exceeding 60%, with stable treatment effects. The method has broad application prospects in the field of chloramphenicol wastewater treatment.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

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

[0008] introducing ozone gas and chloramphenicol wastewater to be treated into a microbubble generator simultaneously to obtain ozone microbubble wastewater; adding the ozone microbubble wastewater and nitrogen-doped single-atom iron-supported graphene catalyst into 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 as raw materials and then supporting them on 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 0.05μm~0.1μm;

[0011] The number of graphene layers is 1 to 3, and the monolayer ratio is greater than 80%.

[0012] The invention relates to a method for treating chloramphenicol wastewater, wherein the ozone microbubbles produced by the microbubble generator have a large specific surface area and a longer residence time, effectively improving the mass transfer efficiency and utilization rate of ozone in wastewater, and accelerating the oxidative decomposition of chloramphenicol and its difficult-to-degrade intermediate products. The invention also provides ... catalytic oxidation is mediated by a magnetic field, thereby contributing to further improving the mass transfer efficiency and residence time of ozone microbubbles in wastewater, thereby increasing the chance of uniform contact of ozone microbubbles with pollutants, and under the action of the magnetic field, the iron atoms of the monatomic iron can be activated, further improving the catalytic activity. In addition, the nitrogen-doped monatomic iron-loaded graphene catalyst forms a synergistic effect with ozone, effectively promoting the decomposition of ozone to produce more highly active hydroxyl radicals (·OH), greatly enhancing the oxidizing capacity, achieving the deep degradation of chloramphenicol and its difficult-to-degrade intermediate products, and improving the TOC removal rate.

[0013] The treatment method provided by the present invention is not limited by the characteristics of chloramphenicol wastewater such as high salinity and large fluctuations in pH. Under complex water quality conditions, the magnetic field-assisted ozone dissolution and the efficient catalysis of the catalyst can still function stably, and exhibits good treatment effects on chloramphenicol wastewater of different sources and different components. It has wide applicability and potential for industrial application.

[0014] It's important to note that single-atom iron catalysts are catalysts in which active metallic iron atoms are uniformly dispersed on a support. Compared to traditional catalysts, single-atom catalysts have higher active site utilization and selectivity, enabling 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 50μm, thereby improving the efficiency of gas transfer to water. At the same time, microbubbles can also enhance the flotation effect and assist in removing oil and suspended matter in the water.

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

[0017] Dissolve tannic acid and iron salt in an alcohol solution, let it stand for complexation, then add melamine, mix evenly, dry, calcine at 600℃~800℃ under an inert atmosphere, pickle, and wash with water until neutral to obtain nitrogen-doped single-atom iron;

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

[0019] The preparation method of nitrogen-doped single-atom iron-supported graphene catalyst provided by the present invention can accurately control the dispersion state of iron atoms through the complexation of tannic acid and iron salt, and can prepare single-atom iron with a particle size of 0.05μm to 0.1μm by combining the calcination temperature of 600℃ to 800℃, ensuring that the iron atoms are highly active Fe 2+ In the subsequent loading process with graphene, the nitrogen-doped single-atom iron can be evenly dispersed on the graphene surface through freeze-drying technology, giving full play to the advantages of graphene's high specific surface area and excellent electronic conductivity, and improving the overall activity of the catalyst.

[0020] The nitrogen doping in the present invention can optimize the electronic structure of single-atom iron and enhance its adsorption and activation ability for ozone; the single-atom iron is highly dispersed on the graphene surface, providing abundant active sites, greatly improving the catalytic oxidation efficiency of pollutants in chloramphenicol wastewater; at the same time, the catalyst structure prepared by the method has high stability, and the active sites are not easily lost during multiple cycles of use, and can maintain efficient and stable catalytic performance, providing a catalyst with excellent performance for the treatment of highly toxic pharmaceutical wastewater, and has broad application prospects in the field of highly toxic pharmaceutical wastewater treatment.

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

[0022] Furthermore, the temperature of the static complexation is 20° C. to 40° C., and the complexation time is 5 min to 10 min.

[0023] Standing at room temperature for 5 to 10 minutes for complexation can fully coordinate tannic acid with iron ions, effectively inhibit the agglomeration of iron ions, and lay the foundation for the subsequent formation of single-atom iron active centers with uniform particle size.

[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] Nitrogen species produced by the decomposition of melamine at high temperature can react with Fe 2+ The formation of strong interactions can not only effectively inhibit the aggregation of iron atoms, but also construct Fe-N x active sites, thereby significantly improving the catalytic activity of the catalyst.

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

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

[0029] The preferred molar ratio of graphene to iron salt can ensure that the iron atoms are evenly dispersed in the form of single atoms, thereby increasing the number and accessibility of active sites. An appropriate amount of graphene can form a good electronic coupling effect with single-atom iron, promote the rapid transfer of electrons between the two, enhance the adsorption and activation ability of ozone, and improve the catalytic oxidation efficiency of chloramphenicol wastewater.

[0030] Furthermore, the mass 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 monatomic iron aqueous solution is (0.2-0.25) g / mL.

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

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

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

[0036] The optimal ozone gas introduction rate can ensure the removal rate of organic matter such as chloramphenicol in wastewater while ensuring that the oxygen introduction rate is minimized.

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

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

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

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

[0041] In a second aspect, the present invention also provides a device for treating chloramphenicol wastewater, comprising an ozone generator, a microbubble generator and a magnetizing reactor connected in sequence; wherein the water inlet of the microbubble generator is connected to the upper part of the magnetizing reactor, and the water outlet is connected to the bottom of the magnetizing reactor.

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

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

[0044] As a specific embodiment of the present invention, a gas flow meter is provided between the ozone generator and the microbubble generator for controlling the gas-water ratio entering the microbubble generator.

[0045] The present invention provides a method for treating chloramphenicol wastewater. The method couples a nitrogen-doped single-atom iron catalyst in a microbubble ozone catalytic oxidation treatment under magnetic field mediation, thereby achieving thorough treatment of refractory chloramphenicol wastewater. The removal rate of chloramphenicol in the wastewater reaches over 99%, and the TOC removal rate reaches over 60%. In addition, the method uses ozone as an oxidant, and the product after the reaction is mainly oxygen, which does not generate secondary pollution. The method not only solves the treatment problem of chloramphenicol wastewater and achieves standard discharge of wastewater, but also effectively reduces pollution to surrounding water bodies, soil and other ecological environments, and has high application value and environmental protection significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of a device for treating chloramphenicol wastewater according to an embodiment of the present invention;

[0047] Figure 2 TEM image of graphene used in the embodiment of the present invention;

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

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

[0050] Figure 5 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;

[0051] Figure 6 This is an XPS graph of the nitrogen-doped single-atom iron-supported graphene catalyst prepared in Example 2 of the present invention before use;

[0052] Figure 7 This is the XPS graph of the nitrogen-doped single-atom iron-supported graphene catalyst prepared in Example 2 of the present invention after use. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0054] The schematic diagram of the device for processing chloramphenicol wastewater used in the embodiment of the present invention is as follows Figure 1The device comprises an oxygen cylinder, an ozone generator, a microbubble generator, and a magnetized reactor. The magnetized reactor contains a nitrogen-doped single-atom iron-loaded graphene catalyst. The water inlet of the microbubble generator is connected to the upper portion of the magnetized reactor, while the water outlet is connected to the bottom of the reactor. The microbubble generator and the magnetized reactor form a circulation path.

[0055] Specifically, the magnetized reactor includes a reactor and two magnetic bars arranged on the outer wall of the reactor, and the two magnetic bars are arranged in parallel.

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

[0057] As a 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.

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

[0059] As a specific embodiment of the present invention, the magnetized reactor is also connected to a condenser for cooling the chloramphenicol wastewater. Ozone catalytic oxidation of chloramphenicol wastewater releases heat, so a condenser is provided to cool the wastewater to ensure a suitable reaction temperature and the safety of the treatment process.

[0060] The method for treating chloramphenicol wastewater using the above-mentioned device specifically comprises 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 generated ozone microbubble wastewater enters the reactor from the bottom of the magnetized reactor. Under the mediation 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 absorbed by another KI absorption bottle to prevent environmental pollution, and finally the tail gas emissions meet the standards.

[0062] In order to better illustrate the present invention, further examples are given below.

[0063] The number of graphene layers used in the following examples is 1 to 3, and the monolayer rate is greater than 80%. The chloramphenicol concentration in the chloramphenicol wastewater is about 50 mg / L.

[0064] Example 1

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

[0066] Step a: 5 g of tannic acid was dissolved in 50 mL of ethanol-water solution (v / v=1:1), and then 5 g of FeCl3·6H2O was added. The mixture was allowed to stand at room temperature for 5 min for complexation. Then, 20 g of melamine was added and stirred at room temperature for 30 min. The mixture was then dried in an oven at 80°C, ground, and placed in a tube furnace. Under nitrogen protection, the mixture was calcined at 800°C for 2 h, washed with 0.5 M sulfuric acid solution, and then washed with water until the pH of the washing solution was neutral. The mixture was dried to obtain nitrogen-doped single-atom iron, which was recorded as SAI.

[0067] Step b, weighing 3.54 g of graphene, adding it to 20 mL of deionized water, and ultrasonicating for 30 min to obtain a graphene dispersion;

[0068] Step c, dissolving 4 g of the nitrogen-doped single-atom iron prepared above in 20 mL of deionized water to obtain a nitrogen-doped single-atom iron solution; adding the nitrogen-doped single-atom iron solution to the graphene dispersion, magnetically stirring for 24 hours, and freeze-drying at -72°C to constant weight to obtain a nitrogen-doped single-atom iron-loaded graphene catalyst, recorded as SAG-Fe.

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

[0070] Figure 5 The XRD patterns of SAI and SAG-Fe prepared in this example show that the characteristic peaks of SAI and SAG-Fe are almost the same, and the peak positions have not changed. The surface SAI is successfully loaded onto the graphene surface, and the lamellar structure of the graphene is still retained after loading.

[0071] Figure 6 This is the XPS graph of SAG-Fe prepared in this example. It can be seen from the figure that two peaks of p orbital spin-orbit splitting are observed at 710.5eV and 724.1eV, which are respectively attributed to Fe 2+ 2p 3 / 2 and Fe 2+ 2p 1 / 2 Signal.

[0072] The above embodiment can also adopt other reaction conditions specified in the present invention to prepare SAG-Fe. As long as it is within the conditions specified in the present invention, the technical effect basically equivalent to the above can be achieved.

[0073] Example 2

[0074] The embodiment of the present invention provides a method for treating chloramphenicol wastewater, comprising the following steps:

[0075] Oxygen is introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater are simultaneously introduced into a microbubble generator, the mass ratio of ozone to chloramphenicol in the chloramphenicol wastewater is 0.2:1, the ozone flow rate is 0.3 L / min, the gas-water volume ratio of the microbubble generator is 1:5, and the pressure before the tube of the microbubble generator is not less than 0.25 MPa. The generated ozone microbubble wastewater is introduced into a magnetic reactor from the bottom, and a nitrogen-doped single-atom iron-loaded graphene catalyst is added, the mass volume ratio of the nitrogen-doped single-atom iron-loaded graphene catalyst to the chloramphenicol wastewater is 5 g:10 L, the magnetic field intensity is 12000 G, and after 30 minutes of reaction, the chloramphenicol degradation rate is detected to be 99.8%, and the TOC removal rate is 70.2%.

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

[0077] Example 3

[0078] The embodiment of the present invention provides a method for treating chloramphenicol wastewater, comprising the following steps:

[0079] Oxygen is introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater are simultaneously introduced into a microbubble generator, the mass ratio of ozone to chloramphenicol in the chloramphenicol wastewater is 0.25:1, the ozone flow rate is 0.3 L / min, the gas-water volume ratio of the microbubble generator is 1:8, and the pressure before the tube of the microbubble generator is not less than 0.25 MPa. The generated ozone microbubble wastewater is introduced into a magnetic reactor from the bottom, and a nitrogen-doped single-atom iron-loaded graphene catalyst is added, the mass volume ratio of the nitrogen-doped single-atom iron-loaded graphene catalyst to the chloramphenicol wastewater is 3 g:10 L, the magnetic field intensity is 15000 G, and after 40 minutes of reaction, the chloramphenicol degradation rate is detected to be 99.6%, and the TOC removal rate is 65.7%.

[0080] Example 4

[0081] The embodiment of the present invention provides a method for treating chloramphenicol wastewater, comprising the following steps:

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

[0083] In order to better illustrate the technical solution of the present invention, further comparison is made below through comparative examples and examples 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 no nitrogen-doped single-atom iron catalyst and magnetic field mediation are added. The method specifically comprises 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 chloramphenicol wastewater was 0.2:1, the ozone flow rate was 0.3 L / min, the gas-water volume ratio of the microbubble generator was 1:5, and the pressure before the tube of the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced into a common reactor from the bottom. After 70 minutes of reaction, the degradation rate of chloramphenicol was detected 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 no nitrogen-doped single-atom iron catalyst is added. The method specifically comprises 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 chloramphenicol wastewater was 0.2:1, the ozone flow rate was 0.3 L / min, the gas-water volume ratio of the microbubble generator was 1:5, and the pressure before the tube of the microbubble generator was not less than 0.25 MPa. The generated ozone microbubble wastewater was introduced into a magnetic reactor from the bottom with a magnetic field strength of 12000 G. After 60 minutes of reaction, the chloramphenicol degradation rate was detected to be 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. The method specifically comprises the following steps:

[0092] Oxygen is introduced into an ozone generator, and the generated ozone gas and chloramphenicol wastewater are simultaneously introduced into a microbubble generator, the mass ratio of ozone to chloramphenicol in the chloramphenicol wastewater is 0.2:1, the ozone flow rate is 0.3 L / min, the gas-water volume ratio of the microbubble generator is 1:5, and the pressure before the tube of the microbubble generator is not less than 0.25 MPa. The generated ozone microbubble wastewater is introduced into a magnetic reactor from the bottom, and activated carbon is added, the mass volume ratio of activated carbon to the chloramphenicol wastewater is 5 g:10 L, the magnetic field intensity is 12000 G, and after 30 minutes of reaction, the chloramphenicol degradation rate is detected to be 80.6%, and the TOC removal rate is 55.8%.

[0093] Comparative Example 4

[0094] This comparative example provides a method for treating chloramphenicol wastewater. The method differs from Example 2 only in that the method for preparing nitrogen-doped single-atom iron-loaded graphene is different, and the nitrogen source melamine is replaced by urea. The rest is identical. The method for preparing nitrogen-doped single-atom iron-loaded graphene comprises the following steps:

[0095] Step a: dissolving 5 g of tannic acid in 50 mL of ethanol-water solution (v / v=1:1), then adding 5 g of FeCl3·6H2O, standing at room temperature for complexation for 5 min, then adding 20 g of urea, stirring at room temperature for 30 min, then drying in an 80°C oven, grinding, placing in a tube furnace, calcining at 800°C for 2 h under nitrogen protection, washing with 0.5 M sulfuric acid solution, then washing with water until the pH of the washing solution is neutral, and drying to obtain nitrogen-doped iron;

[0096] Step b, weighing 3.54 g of graphene, adding it to 20 mL of deionized water, and ultrasonicating for 30 min to obtain a graphene dispersion;

[0097] Step c, dissolving 4 g of the nitrogen-doped iron prepared above in 20 mL of deionized water to obtain a nitrogen-doped iron solution; adding the nitrogen-doped iron solution to the graphene dispersion, magnetically stirring for 24 h, and freeze-drying at -72 ° C to constant weight to obtain a nitrogen-doped iron-loaded graphene catalyst.

[0098] The nitrogen-doped iron-supported graphene catalyst prepared above was used to treat chloramphenicol wastewater in exactly the same manner as in Example 1. After 50 minutes 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. The method differs from Example 2 only in that the preparation method of nitrogen-doped single-atom iron-loaded graphene is different, and the complexing agent tannic acid is replaced by polyacrylic acid. The rest is exactly the same. The preparation method of nitrogen-doped single-atom iron-loaded graphene comprises the following steps:

[0101] Step a: 5 g of polyacrylic acid is dissolved in 50 mL of ethanol-water solution (v / v=1:1), followed by the addition of 5 g of FeCl3·6H2O, and the mixture is allowed to stand at room temperature for 5 min for complexation. 20 g of melamine is then added, and the mixture is stirred at room temperature for 30 min. The mixture is then dried in an oven at 80° C., ground, and placed in a tube furnace. Under nitrogen protection, the mixture is calcined at 800° C. for 2 h, washed with 0.5 M sulfuric acid solution, and then washed with water until the pH of the washing solution is neutral, and dried to obtain nitrogen-doped iron.

[0102] Step b, weighing 3.54 g of graphene, adding it to 20 mL of deionized water, and ultrasonicating for 30 min to obtain a graphene dispersion;

[0103] Step c, dissolving 4 g of the nitrogen-doped iron prepared above in 20 mL of deionized water to obtain a nitrogen-doped iron solution; adding the nitrogen-doped iron solution to the graphene dispersion, magnetically stirring for 24 h, and freeze-drying at -72 ° C to constant weight to obtain a nitrogen-doped iron-loaded graphene catalyst.

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

[0105] In summary, the magnetic field can improve the solubility and stability of ozone in water, thereby improving the oxidation efficiency of ozone. Adding nitrogen-doped single-atom iron-loaded graphene catalyst under magnetic field mediation can provide more active sites; Compared with activated carbon, nitrogen-doped single-atom iron-loaded graphene has stronger catalytic activity; Increasing microbubble treatment can enhance ozone mass transfer efficiency, increase ozone utilization, and promote hydroxyl oxidation process. The present invention utilizes nitrogen-doped single-atom iron-loaded graphene catalyst and magnetic field-mediated microbubble ozone system synergistic effect, which can produce a large number of hydroxyl radicals (·OH) with strong oxidizing properties, quickly and deeply oxidize chloramphenicol and its complex and difficult-to-degrade intermediates; At the same time, the near-scale effect of microbubbles and single-atom catalysts can further enhance the catalytic effect. Compared with traditional treatment methods, the treatment method of the present invention greatly improves the degradation efficiency of complex pollutants and has a high prospect 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 in the scope of protection of the present invention.

Claims

1. A method for treating chloramphenicol wastewater, characterized in that, The steps include: introducing ozone gas and chloramphenicol wastewater to be treated into a microbubble generator simultaneously to obtain ozone microbubble wastewater; adding the ozone microbubble wastewater and nitrogen-doped single-atom iron-supported graphene catalyst into 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 as raw materials and then supporting them on graphene. The iron atom in the nitrogen-doped single-atom iron-supported graphene catalyst is Fe 2+ , the particle size of iron atoms is 0.05μm~0.1μm; The number of graphene layers is 1 to 3, and the monolayer ratio is greater than 80%.

2. the treatment method of chloramphenicol wastewater as claimed in claim 1, is characterized in that, The preparation method of the nitrogen-doped single-atom iron-supported graphene catalyst comprises the following steps: Dissolve tannic acid and iron salt in an alcohol solution, let it stand for complexation, then add melamine, mix evenly, dry, calcine at 600℃~800℃ under an inert atmosphere, pickle, and wash with water until neutral to obtain nitrogen-doped single-atom iron; Graphene is dispersed in water to obtain a graphene dispersion; a nitrogen-doped single-atom iron aqueous solution is added to the graphene dispersion, mixed evenly, and freeze-dried to obtain a single-atom iron-loaded graphene catalyst.

3. the treatment method of chloramphenicol waste water as claimed in claim 2, is characterized in that, The alcohol solution is a solution of anhydrous ethanol and water in a volume ratio of (1-2):1, and the volume mass ratio of the alcohol solution to tannic acid is 10 mL: (1-1.5) g; and / or The temperature of the static complexation is 20° C. to 40° C., and the complexation time is 5 min to 10 min.

4. the treatment method of chloramphenicol waste water as claimed in claim 2, is characterized in that, The molar ratio of the tannic acid to the 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 treatment method of chloramphenicol waste water as claimed in claim 2, is characterized in that, The molar ratio of graphene to iron salt is (1-3):1; and / or The mass volume ratio of the graphene to water is (3-4) g:20 mL; and / or The concentration of the nitrogen-doped monatomic iron aqueous solution is (0.2-0.25) g / mL.

6. The method for treating chloramphenicol wastewater as claimed in claim 1, wherein The mass ratio of the ozone gas to the chloramphenicol in the chloramphenicol wastewater is 0.2 to 0.3:1; and / or The mass 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 wastewater as claimed in claim 1, wherein The air-water volume ratio of the microbubble generator is 1:5 to 1:10, and the pressure before the tube of the microbubble generator is 0.25 MPa to 0.5 MPa.

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

9. The device for treating chloramphenicol wastewater according to any one of claims 1 to 8, characterized in that: The invention comprises an ozone generator, a microbubble generator and a magnetizing reactor which are connected in sequence; wherein the water inlet of the microbubble generator is connected to the upper part of the magnetizing reactor, and the water outlet is connected to the bottom of the magnetizing reactor.

10. The device for treating chloramphenicol wastewater according to claim 9, wherein The magnetized reactor comprises a reactor and parallel-arranged magnetic rods arranged on the outer wall of the reactor; the height of the magnetic rods is not lower than the wastewater level.

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