Preparation method and application of heteroatom-doped carbon sphere catalyst

Abstract

The invention relates to the technical field of catalysts, and particularly discloses a preparation method and application of a heteroatom-doped carbon sphere catalyst, and the preparation method specifically comprises the following steps: S1, mixing and grinding urea and melamine, and calcining at 500-600 DEG C to obtain g-C3N4; s2, uniformly mixing g-C3N4, glucose and water, carrying out hydrothermal reaction, carrying out solid-liquid separation, washing, and drying a solid phase; s3, dissolving boric acid with water to prepare a solution, dispersing the solid phase obtained in S3 with water, heating, dropwise adding the boric acid solution, mixing, and evaporating to dryness to obtain a biochar precursor; and S4, calcining the biochar precursor in a nitrogen atmosphere, and finally washing and drying to obtain the heteroatom-doped carbon spheres. The preparation method is simple, the raw material source is wide, the cost is low, the obtained catalyst has a spherical microstructure and a large specific surface area, and PMS can be activated to generate a large amount of < 1 > O2 to realize efficient degradation of antibiotics.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly relates to a preparation method and application of a heteroatom-doped carbon sphere catalyst. Background Art

[0002] As a drug for treating infectious diseases, antibiotics are widely used and in large quantities. The presence of antibiotics has been detected in natural water environments in many regions of the world, and its potential harm to the ecosystem and human health cannot be ignored. Therefore, it is necessary to strengthen the degradation of organic pollutants such as antibiotics.

[0003] Carbon materials can efficiently activate persulfate to generate reactive oxygen species (ROS): sulfate radicals (SO4· - )、hydroxyl radicals (·OH), superoxide radicals (O2· - ) and singlet oxygen ( 1 O2), realizing the oxidative degradation of pollutants; and having the characteristics of high utilization rate, acid and alkali resistance, ultra-high pore volume and large specific surface area.

[0004] However, under high salinity conditions, free radical-based advanced oxidation technologies (AOPs) are easily severely inhibited during the oxidative degradation process and cannot show good degradation effects. Singlet oxygen ( 1 O2) has attracted much attention due to its long life cycle, electrophilicity and excellent selectivity, and has been widely used in fields such as photocatalytic oxidation, photodynamic therapy and oxidative degradation of organic pollutants.

[0005] Singlet oxygen is mainly synthesized by the photosensitization reaction of oxygen molecules. In recent years, graphene or graphene-like carbon nanomaterials (such as nanosheets, nanospheres, nanorods, nanotubes, nanodots, etc.) as non-metallic environmental protection materials are considered to be efficient and green catalysts for activating PMS to selectively generate 1 O2.

[0006] CN116174004A discloses a preparation method of a boron-doped carbon quantum dot-like graphitic carbon nitride porous heterostructure composite photocatalyst. After mixing and dispersing a carbon source, a nitrogen source and boric acid, a hydrothermal reaction is carried out, and then the supramolecular aggregate is obtained by filtration, washing and drying, and then calcined. The boron doping process of this method involves the use of a high-pressure vessel (2 MPa is about 20 atmospheres), and microwave assistance is required to achieve successful boronization of the material. The present invention realizes the boronization of the material by simply evaporating water in a low-temperature oil bath, avoiding the use of a high-pressure vessel and without other auxiliary means. Summary of the Invention

[0007] The present invention provides a preparation method and application of a heteroatom-doped carbon sphere catalyst. The preparation method is simple, the raw materials are widely sourced and inexpensive, and the obtained catalyst has a spherical microstructure, a large specific surface area, and can activate PMS to generate a large amount of 1 O2 to achieve efficient degradation of antibiotics.

[0008] The technical solution of the present invention is to provide a preparation method of a heteroatom-doped carbon sphere catalyst, comprising the following steps: S1. Mix and grind urea and melamine, and calcine at 500-600 °C to obtain g-C3N4; S2. Mix g-C3N4, glucose and water evenly, carry out a hydrothermal reaction, then separate the solid and liquid, wash, and dry the solid phase; S3. Dissolve boric acid in water to make a solution, disperse the solid phase obtained in S3 in water, heat and dropwise add the boric acid solution for mixing, and evaporate the water to obtain a biochar precursor; S4. Calcinate the biochar precursor in a nitrogen atmosphere, and finally wash and dry to obtain a heteroatom-doped carbon sphere.

[0009] Optionally, the mass ratio of urea to melamine is 1:1 to 1:3.

[0010] Optionally, during the calcination in S1, the heating rate is 4-6 °C / min, and the calcination time is 3-6 h.

[0011] Optionally, in S2, the mass ratio of g-C3N4 to glucose is 0.5-1:3-4; ultrasonic treatment is carried out for 2-4 h when adding water for mixing.

[0012] Optionally, during the hydrothermal reaction in S2, the temperature is 160-200 °C, and the duration is 8-12 h.

[0013] Optionally, the dosage of boric acid in S3 is 0.05-0.2 times the mass of the solid phase obtained in S3.

[0014] Optionally, in S3, oil bath heating is carried out, and the added temperature is 80-100 °C.

[0015] Optionally, in S4, the calcination temperature is 700-900 °C, the heating rate is 4-6 °C / min, the heat preservation time is 1-3 h, and the vacuum drying temperature is 50-80 °C.

[0016] The present invention also relates to a heteroatom-doped carbon sphere catalyst obtained by the above-mentioned preparation method.

[0017] The present invention also relates to the application of the described catalyst in activating PMS to degrade organic pollutants in water, which is characterized in that: the organic pollutants include but are not limited to sulfadiazine (SDZ), tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC).

[0018] The present invention has the following beneficial effects: 1. The present invention provides a preparation method of a heteroatom boron-doped carbon-based catalyst. By mixing urea, melamine, glucose, and boric acid, a catalyst with good morphology is prepared. The material is boronized by simply evaporating water through a low-temperature oil bath, avoiding the use of high-pressure containers and without other auxiliary means. Moreover, the raw materials are widely sourced and low in cost. The obtained catalyst has a large specific surface area, which is conducive to the recycling of resources, and has high application value and good application prospects.

[0019] 2. The carbon-based catalyst prepared by the present invention can effectively activate PMS. Compared with the comparative sample without doped atomic boron, the boron-doped carbon spheres can activate PMS to selectively generate a large amount of 1 O2, achieving rapid and efficient degradation and mineralization of antibiotics, and having extremely high environmental adaptability. Description of the Drawings

[0020] Figure 1 Scanning electron microscope images of biochars prepared at different temperatures in Example 1: (a) without boron doping, (b) with boron doping. It can be seen from the figure that both have regular spherical morphologies and certain pores on the surface.

[0021] Figure 2 Degradation graphs of plastic depolymerization to prepare biochar for different pollutant concentrations in Example 1.

[0022] Figure 3 Degradation graphs of plastic depolymerization to prepare biochar system for pollutants at different pH values in Example 1.

[0023] Figure 4 Catalytic degradation rate graphs of plastic depolymerization to prepare biochar system in Example 1 after repeating the cycle 4 times.

[0024] Figure 5 Influence graphs of environmental factor simulation on the activation of PMS by sample A to degrade SMX in Example 9 and Example 10.

[0025] Figure 6 Active oxygen species (ROS) capture kinetic curves and electron paramagnetic resonance (EPR) experimental results in Example 11 and Example 12. Detailed Embodiments

[0026] The experimental methods in the following examples are all conventional methods unless otherwise specified. The materials used in the following examples are all commercially available products unless otherwise specified.

[0027] The embodiments of the present invention will be described in detail below in conjunction with the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0028] Comparative Example 1 2.5 g of urea was ground into powder and evenly mixed with 2.5 g of melamine, and then calcined in an air atmosphere at 550 °C for 3 h at a heating rate of 5 °C / min to obtain Comparative Sample 1.

[0029] Comparative Example 2 2.5 g of urea was ground into powder and evenly mixed with 2.5 g of melamine, and then calcined at 550 °C for 3 h at a heating rate of 5 °C / min to obtain g-C3N4. 750 mg of g-C3N4 and 3.16 g of glucose were added to 60 mL of water, ultrasonicated for 4 h to disperse and dissolve, then transferred into a reaction kettle, hydrothermally treated at 180 °C for 10 h, centrifuged, washed with ethanol multiple times, and dried. 500 mg of the sample was calcined at 800 °C in a nitrogen atmosphere for 1 h at a heating rate of 5 °C / min to obtain Comparative Sample 2.

[0030] Comparative Example 3 3.16 g of glucose was added to 60 mL of water, ultrasonicated for 4 h to disperse and dissolve, then transferred into a reaction kettle, hydrothermally treated at 180 °C for 10 h, centrifuged, washed with ethanol multiple times, and dried. 1.0 g of the sample was added to 25 mL of water and ultrasonicated for 20 min to obtain suspension A. 100 mg of boric acid was dissolved in 25 mL of water to obtain solution B. After suspension A was placed in an oil bath and heated to the specified temperature, solution B was added dropwise to suspension A under magnetic stirring. After the addition was completed, magnetic stirring was maintained until the water was completely evaporated. 500 mg of the sample was calcined at 800 °C in a nitrogen atmosphere for 1 h at a heating rate of 5 °C / min to obtain Comparative Sample 3.

[0031] Example 1 After grinding 2.5 g of urea into powder, it was uniformly mixed with 2.5 g of melamine and calcined at 550 °C for 3 h at a heating rate of 5 °C / min to obtain g-C3N4. 750 mg of g-C3N4 and 3.16 g of glucose were added to 60 mL of water, ultrasonicated for 4 h to disperse and dissolve, then transferred into a reaction kettle, hydrothermally treated at 180 °C for 10 h, centrifuged, washed with ethanol multiple times, and dried to obtain g-C3N4@Glu. 1.0 g of g-C3N4@Glu was added to 25 mL of water and ultrasonicated for 20 min to obtain suspension A, and 100 mg of boric acid was dissolved in 25 mL of water to obtain solution B. After suspension A was heated to 90 °C in an oil bath, solution B was added dropwise to solution A under magnetic stirring. After the addition was completed, magnetic stirring was maintained until the water was completely evaporated to obtain B@g-C3N4@Glu. 500 mg of B@g-C3N4@Glu was heated to the specified temperature at a heating rate of 5 °C / min and calcined for 1 h in a nitrogen atmosphere to obtain Sample 1. According to different calcination temperatures, they were respectively denoted as Sample 1-1 (700 °C), Sample A (800 °C), and Sample 1-3 (900 °C).

[0032] Example 2 After grinding 2.5 g of urea into powder, it was uniformly mixed with 2.5 g of melamine and calcined at 550 °C for 3 h at a heating rate of 5 °C / min to obtain g-C3N4. 750 mg of g-C3N4 and 3.16 g of glucose were added to 60 mL of water, ultrasonicated for 4 h to disperse and dissolve, then transferred into a reaction kettle, hydrothermally treated at 180 °C for 10 h, centrifuged, washed with ethanol multiple times, and dried to obtain g-C3N4@Glu. 1.0 g of g-C3N4@Glu was added to 25 mL of water and ultrasonicated for 20 min to obtain suspension A, and 100 mg of boric acid was dissolved in 25 mL of water to obtain solution B. After suspension A was heated to the specified temperature in an oil bath, solution B was added dropwise to solution A under magnetic stirring. After the addition was completed, magnetic stirring was maintained until the water was completely evaporated to obtain B@g-C3N4@Glu. 500 mg of B@g-C3N4@Glu was heated to 800 °C at a heating rate of 5 °C / min and calcined for 1 h in a nitrogen atmosphere to obtain Sample 2. According to different evaporation temperatures, they were respectively denoted as Sample 2-1 (85 °C), Sample A (90 °C), and Sample 2-3 (95 °C).

[0033] Regarding the microscopic morphologies of the samples obtained in Comparative Example 2-3 and Example 1-2 as Figure 1As shown. It can be observed that Comparative Sample 2, Comparative Sample 3, and Example Sample A all have a regular spherical morphology. However, at the same scale (4 μm), the particle sizes of Example Sample A and Comparative Sample 2 are much larger than that of Comparative Sample 3, indicating that Example Sample A and Comparative Sample 2 will have a larger specific surface area, pore volume, and active sites than Comparative Sample 3. When treating water organic pollutants, they can more efficiently activate PMS to generate more reactive oxygen species (ROS).

[0034] Example 3 The catalysts obtained from Comparative Examples 1-3 and Examples 1-2 were used to activate PMS to degrade SMX (sulfamethoxazole). The specific operation steps are as follows: Step 1: Take multiple round-bottom flasks and add SMX solution (50 mL, 20 mg / L) respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add the oxidant PMS and the catalyst to the flask in sequence. The addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette. Use a UV-visible spectrophotometer to measure the peak shape of the UV-visible absorption spectrum of SMX.

[0035] The degradation effect was detected by the characteristic peak of SMX at a wavelength of 266 nm using a UV-visible spectrophotometer. Sampling was carried out at different time intervals, and sampling was stopped when the peak value of the characteristic peak of SMX at 266 nm no longer decreased. The comparative diagram of the degradation kinetic curves of SMX degraded by activating PMS with the catalysts obtained from Comparative Examples 1-3 and Examples 1-2 is shown in Figure 2 . Figure 2 a is the comparative kinetic curve of the degradation of SMX by activating PMS with the catalysts obtained from Comparative Samples 1-3 and Example Sample A, Figure 2 b is the comparative kinetic curve of the degradation of SMX by activating PMS with the catalyst obtained from Example 1, Figure 2 c is the comparative kinetic curve of the degradation of SMX by activating PMS with the catalyst obtained from Example 2.

[0036] Through Figure 2It can be seen that the implementation sample A with the simultaneous introduction of g-C3N4 and heteroatom boron has excellent PMS catalytic activity and can achieve nearly 100% SMX removal within 40 min. However, for the comparative sample 3 with the sole introduction of heteroatom boron or the comparative sample 2 with g-C3N4 alone, there are significant differences in activity compared to the implementation sample A, which can be attributed to: 1) Boron atoms are close in size to carbon atoms but have a lower electronegativity. The doping of boron atoms in the carbon skeleton can regulate the electron distribution of the carbon network and promote electron transfer. Moreover, the doping of boron atoms can introduce more defect sites in the carbon material, facilitating the activation of PMS by the catalyst and the adsorption of pollutants. While generating more reactive oxygen species, it also shortens the transport distance of reactive oxygen species and improves the utilization rate of reactive oxygen species. 2) The preparation of g-C3N4 introduces urea as a nitrogen source, and a larger amount of nitrogen doping greatly improves the electron migration ability of g-C3N4. The simultaneous introduction of the two greatly improves the catalytic activity of the implementation sample A, activating PMS to generate a large amount of 1 O2 for efficient degradation of pollutants.

[0037] Example 4 Application of using the implementation sample A of the present invention to activate PMS for the degradation of SDZ. The operation steps for the aforementioned catalyst to activate PMS for the degradation of SDZ are as follows: Step 1: Take multiple round-bottom flasks and add SDZ solution (50 mL, 20 mg / L) respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, sequentially add the oxidant PMS and the catalyst to the flask, where the addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette, and measure the peak shape of the SMX ultraviolet-visible absorption spectrum with a UV-visible spectrophotometer.

[0038] The degradation effect is detected by the characteristic peak of SDZ at a wavelength of 266 nm with a UV-visible spectrophotometer. Sampling is carried out at different time intervals, and sampling stops when the peak value of the SDZ characteristic peak at a wavelength of 266 nm no longer decreases.

[0039] Example 5 Application of using the implementation sample A of the present invention to activate PMS for the degradation of TC. The operation steps for the aforementioned catalyst to activate PMS for the degradation of TC are as follows: Step 1: Take multiple round-bottom flasks and add TC solution (50 mL, 20 mg / L) respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, sequentially add the oxidant PMS and the catalyst to the flask, where the addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, and 5 min respectively, add it to a cuvette, and measure the peak shape of the UV-visible absorption spectrum of SMX with a UV-visible spectrophotometer.

[0040] The degradation effect was detected by the characteristic peak of TC at a wavelength of 365 nm with a UV-visible spectrophotometer. Sampling was carried out at different time intervals, and sampling was stopped when the peak value of the TC characteristic peak at 365 nm no longer decreased.

[0041] Example 6 Application of activating PMS by the sample A of the present invention to degrade OTC. The operation steps for the aforementioned catalyst to activate PMS to degrade OTC are as follows: Step 1: Take multiple round-bottom flasks and add OTC solution (50 mL, 20 mg / L) respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PMS and catalyst to the flask in sequence. The addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, and 5 min respectively, add it to a cuvette, and measure the peak shape of the UV-visible absorption spectrum of OTC with a UV-visible spectrophotometer.

[0042] The degradation effect was detected by the characteristic peak of OTC at a wavelength of 361 nm with a UV-visible spectrophotometer. Sampling was carried out at different time intervals, and sampling was stopped when the peak value of the OTC characteristic peak at 361 nm no longer decreased.

[0043] Example 7 Application of activating PMS by the sample A of the present invention to degrade CTC. The operation steps for the aforementioned catalyst to activate PMS to degrade CTC are as follows: Step 1: Take multiple round-bottom flasks and add CTC solution (50 mL, 20 mg / L) respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PMS and catalyst to the flask in sequence. The addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, and 5 min respectively, add it to a cuvette, and measure the peak shape of the UV-visible absorption spectrum of CTC with a UV-visible spectrophotometer.

[0044] The degradation effect was detected by a UV-visible spectrophotometer at a wavelength of 364 nm for the characteristic peak of CTC. Sampling was carried out at different time intervals, and sampling was stopped when the peak value of the CTC characteristic peak at a wavelength of 364 nm no longer decreased.

[0045] Figure 3 It is a comparative curve graph of degradation kinetics for Examples 4 - 7. From Figure 3 It can be seen that the catalyst obtained by this preparation method is used to activate peroxymonosulfate (PMS) for efficient degradation of various common organic pollutants such as sulfadiazine (SDZ), chlortetracycline (CTC), oxytetracycline (OTC), tetracycline (TC), sulfamethoxazole (SMX), etc., and has excellent environmental adaptability and good reusability.

[0046] Example 8 The recycling performance test of Sample A described in the present invention is as follows.

[0047] Step 1: Take a round-bottom flask and add SMX solution (50 mL, 20 mg / L). After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PMS and catalyst to the flask in sequence. The addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette, and measure the peak shape of the UV-visible absorption spectrum of SMX with a UV-visible spectrophotometer.

[0048] Step 2: After the catalyst used in Step 2 is filtered by suction and washed with water, repeat Steps 1 - 2 twice. The catalyst after 3 experiments is washed with 2 mol / L hydrochloric acid (HCl) for 30 min, then washed with water until neutral and dried under vacuum, and repeat Steps 1 - 2 to complete the 3rd cycle experiment; after the 3rd cycle, heat it to 400 °C at a heating rate of 5 °C / min, calcine it for 1 h in a nitrogen atmosphere, wash it with water and dry it under vacuum to complete the 4th cycle.

[0049] Figure 4 It is the degradation kinetics of Sample A in the present invention for 4 cycles. It can be seen that the catalyst still has good catalytic activity after 4 cycles.

[0050] Example 9 Using Sample A, simulate the influence of various inorganic anions in environmental water bodies on the activation of PMS for the degradation of SMX, and test its anti-interference ability. The specific operation steps are as follows: Step 1: Take multiple round-bottom flasks and add SMX solution (50 mL, 20 mg / L) respectively. Add a small amount of inorganic anion solution to make the inorganic anion concentration in the system 20 mmol / L. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PMS and catalyst to the flask in sequence. The addition amounts of the oxidant and catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette. Use a UV-visible spectrophotometer to measure the peak shape of the UV-visible absorption spectrum of SMX.

[0051] The degradation effect is detected by the characteristic peak of SMX detected by a UV-visible spectrophotometer at a wavelength of 266 nm. Sampling is carried out at different time intervals, and sampling stops when the peak value of the SMX characteristic peak at 266 nm no longer decreases.

[0052] Example 10 Using Sample A, simulate the influence of different pH values of different environmental waters on the activation of PMS to degrade SMX, and test its anti-interference ability. The specific operation steps are as follows: Step 1: Take multiple round-bottom flasks and add SMX solution (50 mL, 20 mg / L) with the pH pre-adjusted (pH = 1, 3, 5, 6, 7, 9, 11) respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PMS and catalyst to the flask in sequence. The addition amounts of the oxidant and catalyst are 25 mg and 10 mg respectively; Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette. Use a UV-visible spectrophotometer to measure the peak shape of the UV-visible absorption spectrum of 3-AP.

[0053] The degradation effect is detected by the characteristic peak of SMX detected by a UV-visible spectrophotometer at a wavelength of 266 nm. Sampling is carried out at different time intervals, and sampling stops when the peak value of the SMX characteristic peak at 266 nm no longer decreases.

[0054] Figure 5To illustrate the influence of environmental factor simulation in Example 9 and Example 10 on the activation of PMS by Sample A for the degradation of SMX (reflected by the degradation kinetic curve), it can be seen that the degradation of sulfamethoxazole by the catalyst-activated PMS is not interfered by anions in the water body, showing good anti-interference ability. At the same time, the change in pH in the environment has no interfering ability on the degradation of sulfamethoxazole. Therefore, this catalyst has excellent environmental adaptability.

[0055] Example 11 Use the prepared Sample A.

[0056] Step 1: Take a round-bottom flask and add SMX solution (50 mL, 20 mg / L). Add appropriate amounts of reactive oxygen species (ROS) quenchers respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PDS and catalyst to the flask in sequence. The addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively. Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette. Use a UV-visible spectrophotometer to measure the peak shape of the UV-visible absorption spectrum of SMX.

[0057] Example 12 Use the prepared Comparative Sample 2.

[0058] Step 1: Take a round-bottom flask and add SMX solution (50 mL, 20 mg / L). Add appropriate amounts of reactive oxygen species (ROS) quenchers respectively. After preheating in a 30 °C water bath for 5 min, under magnetic stirring, add oxidant PDS and catalyst to the flask in sequence. The addition amounts of the oxidant and the catalyst are 25 mg and 10 mg respectively. Step 2: Take out 3 mL of the reaction solution at 0 min, 1 min, 3 min, 5 min, 10 min, 20 min, 30 min, and 40 min respectively and add it to a cuvette. Use a UV-visible spectrophotometer to measure the peak shape of the UV-visible absorption spectrum of SMX.

[0059] Figure 6 For the reactive oxygen species (ROS) capture kinetic curve and electron paramagnetic resonance (EPR) experimental results in Example 11 and Example 12, through Figure 6 a, it can be observed that the ROS in the system of Sample A activating PMS to degrade SMX is 1 O2 and a small amount of ·OH. The EPR result ( Figure 6 b) proves that 1 O2 is the main ROS; Figure 6It can be concluded that the ROS in the system of activating PMS by the comparative sample 2 to degrade SMX are 1 O2, ·OH, SO4· - , O2· - , and the EPR result ( Figure 6 d) proves that 1 O2 is the main ROS, and there is also a part of O2· - and ·OH.

[0060] The results of Example 11 and Example 12 show that the boron atom doping changes the activation mode of the material to PMS. After doping boron, the catalyst can activate PMS to generate 1 O2 with nearly 100% selectivity, and achieve the efficient and rapid removal of antibiotics through a non-radical pathway, without being interfered by various complex environmental factors.

[0061] The above embodiments describe the preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A preparation method of a heteroatom-doped carbon sphere catalyst, characterized in that It includes the following steps: S1. Mix and grind urea and melamine, and calcine at 500 - 600 °C to obtain g-C3N4; S2. Mix g-C3N4, glucose and water evenly, carry out hydrothermal reaction, then carry out solid-liquid separation and washing, and dry the solid phase; S3. Dissolve boric acid in water to make a solution, disperse the solid phase obtained in S3 with water, heat and dropwise add the boric acid solution for mixing, and evaporate the water to obtain a biochar precursor; S4. Calcine the biochar precursor in a nitrogen atmosphere, and finally wash with water and dry to obtain heteroatom-doped carbon spheres.

2. The preparation method according to claim 1, wherein: The mass ratio of urea to melamine is 1:1 - 3.

3. The preparation method according to claim 1, characterized in that: During the calcination in S1, the heating rate is 4 - 6 °C / min, and the calcination time is 3 - 6 h.

4. The preparation method according to claim 1, characterized in that: In S2, the mass ratio of g-C3N4 to glucose is 0.5 - 1:3 - 4; ultrasonic treatment is carried out for 2 - 4 h when mixing with water.

5. The preparation method according to claim 4, wherein: During the hydrothermal reaction in S2, the temperature is 160 - 200 °C, and the duration is 8 - 12 h.

6. The preparation method according to claim 1, characterized in that: In S3, the dosage of boric acid is 0.05 - 0.2 times the mass of the solid phase obtained in S3.

7. The preparation method according to claim 1, characterized in that: In S3, oil bath heating is carried out, the added temperature is 80 - 100 °C, and the oil bath time is 10 - 12 h.

8. The preparation method according to claim 1, characterized in that: In S4, the calcination temperature is 700 - 900 °C, the heating rate is 4 - 6 °C / min, the heat preservation time is 1 - 3 h, and the vacuum drying temperature is 50 - 80 °C.

9. The heteroatom-doped carbon sphere catalyst obtained by the preparation method according to any one of claims 1 - 8.

10. Use of the catalyst according to claim 9 in activating PMS for degrading organic pollutants in water body, characterized in that: The organic pollutants include but are not limited to sulfadiazine (SDZ), tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC).

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