Catalytic sludge biochar for strengthening iron-nitrogen anchoring through spatial constraint as well as preparation method and application of catalytic sludge biochar

Abstract

The invention discloses catalytic sludge biochar for strengthening iron-nitrogen anchoring through spatial constraint as well as a preparation method and application of the catalytic sludge biochar, and belongs to the technical field of organic solid waste recycling. The preparation method comprises the following steps: mixing an iron source, sludge and urea according to a certain mass ratio, adjusting the water content to 7-25%, and extruding, granulating and molding into granules with compact structures in a specific manner; and then pyrolyzing in an inert atmosphere to prepare the catalytic sludge biochar. The preparation method provided by the invention can effectively inhibit the volatilization loss of nitrogen element in the pyrolysis process and promote the reaction of iron and nitrogen, so that a rich FexN active structure is efficiently and directionally generated under the extremely low level that the use amount of urea is only 1-12% of the mass of sludge. The catalytic sludge biochar disclosed by the invention is excellent in performance, and the degradation removal rate of levofloxacin is as high as 98.94%. The method is simple in process and low in cost, and a brand new technical scheme is provided for high-value resource utilization of the sludge and efficient and economic treatment of the antibiotic wastewater difficult to degrade.

Description

Technical Field

[0001] This invention relates to the field of organic solid waste resource utilization technology, specifically to a method for preparing catalytic sludge biochar with enhanced iron and nitrogen anchoring through spatial constraint and its application in treating wastewater containing antibiotics. Background Technology

[0002] The wastewater treatment sector faces the dual demands of sludge resource utilization and the control of emerging pollutants. On the one hand, the large amount of excess sludge generated during wastewater treatment presents immense challenges in its disposal. Traditional methods such as landfilling and incineration are prone to causing secondary pollution and fail to achieve high-value resource utilization. On the other hand, emerging pollutants such as residual antibiotics in water bodies are difficult to remove effectively by conventional biological treatment processes due to their bioinhibitory properties, posing a potential threat to the ecological environment and human health. The use of advanced oxidation technologies such as persulfate catalytic oxidation for the deep treatment of antibiotic-containing wastewater is becoming a development trend, and the core of this technology lies in the development of efficient, stable, and economical heterogeneous catalysts.

[0003] The technical approach of converting sludge into biochar through pyrolysis and using it as a catalyst in the persulfate advanced oxidation system aligns with the environmental protection concept of "treating waste with waste." However, unmodified sludge biochar typically suffers from limited specific surface area, a lack of active sites, and weak electron conduction, resulting in generally low catalytic activity.

[0004] To enhance the catalytic performance of biochar, doping with elements such as iron and nitrogen has been extensively studied. Iron doping can introduce Fenton or Fenton-like active sites, while nitrogen doping can modulate the electronic structure of carbon materials, enhancing their conductivity and activation ability against persulfate. The Fe-N composite structure formed by iron and nitrogen during pyrolysis can significantly improve catalytic performance.

[0005] Existing methods for preparing iron-nitrogen co-doped sludge biochar still have significant shortcomings. ZL202210996097.0 discloses a method for preparing Fe-rich biochar from pharmaceutical sludge via iron-nitrogen co-doping pyrolysis. x The method of producing Fe-N structured biochar. While this method can achieve certain catalytic performance, it requires the addition of a large amount of exogenous nitrogen source to form sufficient Fe-N active structures, with the amount of urea added being 1 to 4 times the mass of the sludge itself. This significantly increases raw material costs and greatly limits the practical application of the technology. It also increases the emission of nitrogen-containing gases during pyrolysis, bringing new environmental burdens. The fundamental reason is that in traditional mixed-pyrolysis processes, iron and nitrogen elements are easily volatilized and lost in gaseous form at high temperatures, resulting in low reaction efficiency between them and a low Fe-N structure formation rate. To achieve the expected catalytic effect, it is necessary to significantly increase the amount of nitrogen source added.

[0006] Therefore, it is necessary to develop a new preparation method, which can greatly reduce the amount of nitrogen source, strengthen the reaction between iron and nitrogen in the pyrolysis process, promote the directional generation of Fe-N active structure, and prepare high-performance and low-cost catalytic sludge biochar. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the application provides a preparation method of catalytic sludge biochar with simple process, low cost and excellent catalytic performance and application thereof. The method effectively solves the key problems of large amount of nitrogen source, easy loss of elements and low formation efficiency of Fe-N active structure in the traditional iron and nitrogen co-doping process through the physical "space constraint" strategy. The sludge biochar with high catalytic performance is obtained under the condition of low urea usage, which provides an economically feasible technical solution for sludge resource utilization and efficient treatment of antibiotic pollutants.

[0008] The first aspect of the application provides a preparation method of catalytic sludge biochar with space-constrained iron and nitrogen anchoring, characterized in that the method comprises the following steps: S1. mixing iron source, sludge and urea in proportion to obtain a mixture; S2. adjusting the moisture content of the mixture to 7%-20%, and then granulating and molding, and then drying to constant weight to obtain granular sludge; S3. pyrolyzing the granular sludge under the protection of inert atmosphere, the pyrolysis temperature is 750-850℃, and the pyrolysis time is 60-120 minutes, to obtain the catalytic sludge biochar; In some embodiments, the mass ratio of the sludge and urea in step S1 is 10:(0.1-1.2), preferably 10:(0.2-1.2). In some more preferred embodiments, the mass ratio of the sludge and urea is 10:1.

[0009] In some embodiments, in step S1, the mass ratio of the iron source and sludge is 1:(8-12); In some embodiments, in step S1, the iron source is Fe 3+ salt, selected from one or a combination of FeCl3, Fe3O4, Fe2O3 and Fe(OH)3.

[0010] Further, the sludge is derived from residual sludge of a municipal sewage treatment plant; Further, in step S2, the granular sludge is in the shape of granules with a volume of 0.5-2.5cm 3 ; In some embodiments, the granular sludge is a cube, a cuboid, a sphere, a columnar body or an irregular shape with an aspect ratio less than 5.

[0011] In some preferred embodiments, the granular sludge is a columnar granule with a diameter of 0.5-1 cm and a length of 1-3 cm.

[0012] In some embodiments, step S1 further comprises a sludge pretreatment step; the residual sludge is dried, crushed, and then sieved; in a preferred embodiment, the crushed sludge is sieved through a 60-mesh sieve.

[0013] In some embodiments, step S2, the granulation molding is performed by a screw extrusion granulator, and the columnar granule has an apparent density of 1.45-1.80 g / cm 3 , preferably 1.65-1.75 g / cm 3 . In some preferred embodiments, step S2, after adjusting the moisture content, further comprises a step of allowing the mixture to stand and age for 20-40 minutes.

[0014] Further, in step S3, the pyrolysis is performed under an inert atmosphere, and the heating rate is 8-12℃ / min.

[0015] The second aspect of the present application provides a catalytic sludge biochar prepared by the preparation method, which is rich in iron and nitrogen active sites and forms a high proportion of FexN structures, which can be one or more of FeN, Fe2N, Fe3N, and Fe4N.

[0016] The third aspect of the present application provides the use of the catalytic sludge biochar in the treatment of antibiotic-containing wastewater by activated persulfate.

[0017] Further, in the treatment of antibiotic-containing wastewater, the dosage of the catalytic sludge biochar is 0.05-0.15 g / L, and the dosage of the persulfate is 1-10 mM. In some embodiments, the antibiotics in the antibiotic-containing wastewater include fluoroquinolone antibiotics or macrolide antibiotics; the fluoroquinolone antibiotics are selected from one or a combination of levofloxacin, ofloxacin, enrofloxacin, ciprofloxacin, norfloxacin, and difloxacin; and the macrolide antibiotics are selected from one or a combination of erythromycin and roxithromycin.

[0018] In some embodiments, the antibiotic degradation rate is ≥97% in 90 minutes; in some preferred embodiments, the degradation rate is ≥98%.

[0019] Advantages: Compared with the prior art, the present application has the following advantages: (1) This invention effectively inhibits the volatilization and loss of iron and nitrogen elements during pyrolysis by means of physical spatial constraint of "granulation molding", strengthens the anchoring of iron and nitrogen elements and the reaction between iron and nitrogen, increases the iron and nitrogen content in biochar, strengthens the directional generation of Fe-N active sites, and improves the Fe-N abundance and catalytic performance of biochar. (2) The preparation method of the present invention is simple, economical and efficient, and easy to scale up: its core process is simple, and the equipment used is all conventional industrial equipment, which is easy to operate. In particular, the method effectively promotes the directional generation of Fe-N active structure with extremely low urea dosage (only 1%-12% of the sludge mass), and produces sludge biochar with high catalytic performance.

[0020] (3) The biochar prepared by this invention has excellent catalytic performance and high degradation efficiency. The water treatment method based on the catalytic sludge biochar of this invention has a degradation and removal rate of up to 98.94% for levofloxacin. (4) The method of the present invention “treats waste with waste”, with significant environmental benefits: The present invention uses urban residual sludge as the main raw material, transforms it into high-value-added environmental functional materials, and uses it to treat antibiotic wastewater that is difficult to degrade, realizing the synergistic treatment of solid waste and water pollutants, which is in line with the green and circular environmental protection concept. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the application and do not constitute a limitation thereof. In the drawings: Figure 1 XRD pattern of sludge biochar as an exemplary embodiment 1 of the present invention; Figure 2 XRD pattern of sludge biochar as an exemplary embodiment 2 of the present invention; Figure 3 High-resolution N 1s spectra of biochar from exemplary embodiments 1-3 and comparative example 1 of the present invention; Figure 4 The degradation curves of LEV catalyzed by biochar in exemplary Examples 1-3 and Comparative Example 1 are shown. Detailed Implementation

[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; the reagents and instruments described, unless otherwise specified, are commercially available.

[0023] Sludge source: The sludge was taken from the residual sludge of a wastewater treatment plant after dewatering by a belt filter press.

[0024] Example 1 This embodiment provides a method for preparing catalytic sludge biochar with enhanced iron-nitrogen anchoring through spatial constraint and a method for deep treatment of antibiotic wastewater. The specific steps are as follows: (1) Select the residual sludge produced by the urban sewage treatment plant, dry it in a constant temperature oven at 105℃ for 24 hours, and then cool it naturally to room temperature; put the cooled dried sludge into a high-speed crusher and crush it at a speed of 36000 r / min for 30 seconds. The crushed product is screened through a 60-mesh standard sieve, and the powder under the sieve is collected and sealed in a desiccator for later use.

[0025] (2) Mix ferric chloride, pretreated sludge, and urea at a mass ratio of 1:10:1 until homogeneous; add deionized water dropwise to the mixture while stirring, adjusting the moisture content of the system to 20%, and let it stand for 30 minutes to allow the water to fully soak the material particles; feed the aged material into a screw extruder, adjust the extrusion knob to make the output particles cylindrical with a diameter of 0.5-1cm and a length of 1-3cm, with an apparent density of 1.74g / cm³. 3 The shaped columnar particles were dried in a 105℃ constant temperature oven until constant weight, and then set aside for later use.

[0026] (3) The extruded and dried sludge columnar particles are placed into the reaction chamber of a tubular furnace and nitrogen is introduced to replace the inert atmosphere for 30 minutes (flow rate 100 mL / min) to ensure that there is no oxygen residue in the furnace; then the heating rate is set to 10℃ / min, and the temperature is raised to 800℃ under continuous nitrogen protection, and the temperature is maintained for 90 minutes to complete the pyrolysis and carbonization; after the pyrolysis is completed, the temperature is naturally cooled to room temperature; crushed and ground to a particle size of less than 60 mesh, thus obtaining the space-constrained enhanced iron and nitrogen anchored sludge biochar FBC800-H.

[0027] (4) Take 10 mg of the biochar (FBC800-H) prepared in step (3) and add it to 100 mL of wastewater containing levofloxacin. In this embodiment of the invention, the initial concentration CO of the levofloxacin wastewater is 80 mg / L, the pH value is 6.5, and the amount of persulfate added to the wastewater is 5 mM. In this embodiment of the invention, the catalytic degradation reaction is carried out in a 250 mL stoppered conical flask. The stoppered conical flask is placed in a constant temperature shaker and shaken in the dark at 25°C and 220 r / min. After the catalytic degradation reaction, the treated effluent is obtained.

[0028] Example 2 This embodiment provides a method for preparing catalytic sludge biochar with enhanced iron-nitrogen anchoring through spatial constraint and a method for deep treatment of antibiotic wastewater. The specific steps are as follows: (1) Select the residual sludge produced by the urban sewage treatment plant, dry it in a constant temperature oven at 105℃ for 24 hours, and then cool it naturally to room temperature; put the cooled dried sludge into a high-speed crusher and crush it at a speed of 36000 r / min for 30 seconds. The crushed product is screened through a 60-mesh standard sieve, and the powder under the sieve is collected and sealed in a desiccator for later use.

[0029] (2) Mix ferric chloride, pretreated sludge, and urea at a mass ratio of 1:10:1 until homogeneous; add deionized water dropwise to the mixture while stirring, adjusting the moisture content of the system to 15%, and let it stand for 30 minutes after stirring until the water fully wets the material particles; feed the aged material into a screw extruder granulator, adjust the extrusion knob to make the output particles cylindrical with a diameter of 0.5-1cm and a length of 1-3cm, with an apparent density of 1.69g / cm³. 3 The shaped columnar particles were dried in a 105℃ constant temperature oven until constant weight, and then set aside for later use.

[0030] (3) The extruded and dried sludge columnar particles are placed into the reaction chamber of a tubular furnace and nitrogen is introduced to replace the inert atmosphere for 30 minutes (flow rate 100 mL / min) to ensure that there is no oxygen residue in the furnace; then the heating rate is set to 10℃ / min, and the temperature is raised to 800℃ under continuous nitrogen protection, and the temperature is maintained for 90 minutes to complete the pyrolysis and carbonization; after the pyrolysis is completed, the temperature is naturally cooled to room temperature; crushed and ground to a particle size of less than 60 mesh, thus obtaining the space-constrained enhanced iron and nitrogen anchored sludge biochar FBC800-M.

[0031] (4) Take 10 mg of the biochar (FBC800-M) prepared in step (3) and add it to 100 mL of wastewater containing levofloxacin. In this embodiment of the invention, the initial concentration CO of the levofloxacin wastewater is 80 mg / L, the pH value is 6.5, and the amount of persulfate added to the wastewater is 5 mM. In this embodiment of the invention, the catalytic degradation reaction is carried out in a 250 mL stoppered conical flask. The stoppered conical flask is placed in a constant temperature shaker and shaken in the dark at 25°C and 220 r / min. After the catalytic degradation reaction, the treated effluent is obtained.

[0032] Example 3 This embodiment provides a method for preparing catalytic sludge biochar with enhanced iron-nitrogen anchoring through spatial constraint and a method for deep treatment of antibiotic wastewater. The specific steps are as follows: (1) Select the residual sludge produced by the urban sewage treatment plant, dry it in a constant temperature oven at 105℃ for 24 hours, and then cool it naturally to room temperature; put the cooled dried sludge into a high-speed crusher and crush it at a speed of 36000 r / min for 30 seconds. The crushed product is screened through a 60-mesh standard sieve, and the powder under the sieve is collected and sealed in a desiccator for later use.

[0033] (2) Mix ferric chloride, pretreated sludge, and urea at a mass ratio of 1:10:0.2 until homogeneous; add deionized water dropwise to the mixture while stirring, adjusting the moisture content of the system to 7.5%, and let it stand for 30 minutes after stirring until the water fully soaks the material particles; feed the aged material into a screw extruder, adjust the extrusion knob to make the output particles cylindrical with a diameter of 0.5-1cm and a length of 1-3cm, with an apparent density of 1.53g / cm³. 3 The shaped columnar particles were dried in a 105℃ constant temperature oven until constant weight, and then set aside for later use.

[0034] (3) The extruded and dried sludge columnar particles are placed into the reaction chamber of a tubular furnace and nitrogen is introduced to replace the inert atmosphere for 30 minutes (flow rate 100 mL / min) to ensure that there is no oxygen residue in the furnace; then the heating rate is set to 10℃ / min, and the temperature is raised to 800℃ under continuous nitrogen protection, and the temperature is maintained for 90 minutes to complete the pyrolysis and carbonization; after the pyrolysis is completed, the temperature is naturally cooled to room temperature; crushed and ground to a particle size of less than 60 mesh, thus obtaining the space-constrained enhanced iron and nitrogen anchored sludge biochar FBC800-0.2.

[0035] (4) Take 10 mg of the biochar (FBC800-L) prepared in step (3) and add it to 100 mL of wastewater containing levofloxacin. In this embodiment of the invention, the initial concentration CO of the levofloxacin wastewater is 80 mg / L, the pH value is 6.5, and the amount of persulfate added to the wastewater is 5 mM. In this embodiment of the invention, the catalytic degradation reaction is carried out in a 250 mL stoppered conical flask. The stoppered conical flask is placed in a constant temperature shaker and shaken in the dark at 25°C and 220 r / min. After the catalytic degradation reaction, the treated effluent is obtained.

[0036] Example 4 This embodiment provides a method for preparing catalytic sludge biochar with enhanced iron-nitrogen anchoring through spatial constraint and a method for deep treatment of antibiotic wastewater. The specific steps are as follows: (1) Select the residual sludge produced by the urban sewage treatment plant, dry it in a constant temperature oven at 105℃ for 24 hours, and then cool it naturally to room temperature; put the cooled dried sludge into a high-speed crusher and crush it at a speed of 36000 r / min for 30 seconds. The crushed product is screened through a 60-mesh standard sieve, and the powder under the sieve is collected and sealed in a desiccator for later use.

[0037] (2) Mix ferric chloride, pretreated sludge, and urea at a mass ratio of 1:10:0.1 until homogeneous; add deionized water dropwise to the mixture while stirring, adjusting the moisture content of the system to 7.5%, and let it stand for 30 minutes after stirring until the water fully wets the material particles; feed the aged material into a screw extruder, adjust the extrusion knob to make the output particles cylindrical with a diameter of 0.5-1cm and a length of 1-3cm, with an apparent density of 1.49g / cm³. 3 The shaped columnar particles were dried in a 105℃ constant temperature oven until constant weight, and then set aside for later use.

[0038] (3) The extruded and dried sludge columnar particles are placed into the reaction chamber of a tubular furnace and nitrogen is introduced to replace the inert atmosphere for 30 minutes (flow rate 100 mL / min) to ensure that there is no oxygen residue in the furnace; then the heating rate is set to 10℃ / min, and the temperature is raised to 800℃ under continuous nitrogen protection, and the temperature is maintained for 90 minutes to complete the pyrolysis and carbonization; after the pyrolysis is completed, the temperature is naturally cooled to room temperature; crushed and ground to a particle size of less than 60 mesh to obtain the space-constrained enhanced iron and nitrogen anchored sludge biochar FBC800-0.1.

[0039] (4) Take 10 mg of the biochar (FBC800-L) prepared in step (3) and add it to 100 mL of wastewater containing levofloxacin. In this embodiment of the invention, the initial concentration CO of the levofloxacin wastewater is 80 mg / L, the pH value is 6.5, and the amount of persulfate added to the wastewater is 5 mM. In this embodiment of the invention, the catalytic degradation reaction is carried out in a 250 mL stoppered conical flask. The stoppered conical flask is placed in a constant temperature shaker and shaken in the dark at 25°C and 220 r / min. After the catalytic degradation reaction, the treated effluent is obtained.

[0040] Comparative Example 1 This comparative example provides a method for preparing and applying sludge biochar, the specific steps of which are as follows: (1) Select the residual sludge produced by the urban sewage treatment plant, dry it in a constant temperature oven at 105℃ for 24 hours, and then cool it naturally to room temperature; put the cooled dried sludge into a high-speed crusher and crush it at a speed of 36000 r / min for 30 seconds. The crushed product is screened through a 60-mesh standard sieve, and the powder under the sieve is collected and sealed in a desiccator for later use.

[0041] (2) Mix ferric chloride, pretreated sludge, and urea in a mass ratio of 1:10:1 until homogeneous; place the mixture into the reaction chamber of a tubular furnace, and purge with nitrogen to create an inert atmosphere for 30 minutes (flow rate 100 mL / min) to ensure no oxygen remains in the furnace; then set the heating rate to 10℃ / min and raise the temperature to 800℃ under continuous nitrogen protection, and maintain the constant temperature for 90 minutes to complete the pyrolysis and carbonization; after pyrolysis, allow the mixture to cool naturally to room temperature; thus, obtain sludge biochar FBC800 without spatially constrained enhanced iron-nitrogen anchoring.

[0042] (3) Take 10 mg of the biochar (FBC800) prepared in step (2) and add it to 100 mL of wastewater containing levofloxacin. In this embodiment of the invention, the initial concentration of levofloxacin wastewater CO is 80 mg / L, the pH value is 6.5, and the amount of persulfate added to the wastewater is 5 mM. In this embodiment of the invention, the catalytic degradation reaction is carried out in a 250 mL stoppered conical flask. The stoppered conical flask is placed in a constant temperature shaker and shaken in the dark at 25°C and 220 r / min. After the catalytic degradation reaction, the treated effluent is obtained.

[0043] Test case To evaluate the degradation performance of the prepared catalytic sludge biochar, the degradation process of Examples 1 to 4 and Comparative Example 1 was monitored. Specifically, at set time points, 2 mL of water sample was taken from each conical flask, filtered, and 1 mL of the filtrate was taken. The remaining concentration of levofloxacin was determined using liquid chromatography. Based on the concentration changes over time, degradation kinetic curves were plotted, and the removal rate results are shown in Table 4.

[0044] The XRD patterns of the sludge biochar prepared in Examples 1 and 2 are as follows: Figure 1 and Figure 2 As shown, by analyzing the position and intensity of the diffraction peaks, it can be proven that under the spatially constrained process conditions, a high abundance of Fe was successfully formed in the pyrolysis products. x N-structures (such as Fe₂N, Fe₄N, etc.) These Fe x The N-structure is the key catalytic active site.

[0045] As shown in Table 1, based on XPS analysis, the relative abundance of Fe in Examples 1 and 2 is higher than that in Comparative Example 1. Elemental analysis in Table 2 shows that the nitrogen content in Examples 1 and 2 is also higher than that in Comparative Example 1, demonstrating the anchoring effect of spatial constraints on iron and nitrogen. This iron-nitrogen anchoring also enhances the reaction between iron and nitrogen. Figure 3 A comparison of the fine N 1s spectra obtained from XPS analysis shows that the Fe-N peaks in Examples 1 and 2 are significantly stronger than those in Comparative Example 1. Table 3 also shows that the relative content of Fe-N in the N 1s peaks in Examples 1 and 2 is higher than that in Comparative Example 1, indicating a significant enhancement of Fe-N active sites in Examples 1 and 2. Spatial confinement enhances iron-nitrogen anchoring, thereby significantly improving the catalytic performance of biochar. Figure 4 The degradation rates and degradation percentages of Examples 1 and 2 were significantly better than those of Comparative Example 1. Table 4 shows that the degradation percentages of all Examples 1 to 4 were significantly better than those of Comparative Example 1.

[0046] In summary, this invention strengthens the anchoring of iron and nitrogen elements in biochar during pyrolysis through spatial constraint, effectively inhibiting the escape of iron and nitrogen elements, enhancing the reaction between iron and nitrogen during pyrolysis, promoting the directional formation of Fe-N active structures, and simultaneously optimizing the structural characteristics and catalytic performance of biochar. This results in sludge biochar with high catalytic performance under low urea usage conditions, providing an economical and feasible technical solution for sludge resource utilization and efficient treatment of antibiotic pollutants.

[0047] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A process for the preparation of catalytic sludge biochar reinforced by spatial confinement of iron-nitrogen anchoring characterized by, The method comprises the following steps: S1. mixing an iron source, sludge and urea in a certain proportion to obtain a mixture; S2. adjusting the moisture content of the mixture to 7%-20%, and then granulating and molding, and then drying to constant weight to obtain granular sludge; S3. pyrolyzing the granular sludge under the protection of an inert atmosphere, the pyrolysis temperature being 750-850℃, and the pyrolysis time being 60-120 minutes, to obtain the catalytic sludge biochar. The mass ratio of the sludge to urea in step S1 is 10:(0.1-1.2).

2. The production method according to claim 1, characterized by, In step S1, the mass ratio of the iron source to sludge is 1:(8-12); and / or, In step S1, the iron source is an iron-containing compound selected from one or a combination of FeCl3, Fe3O4, Fe2O3 and Fe(OH)3.

3. The preparation method according to claim 1, characterized in that, The sludge is derived from residual sludge of a sewage treatment plant; In step S2, the granular sludge is in a granular shape with a volume of 0.5-2.5 cm 3 The granular sludge is in a cubic, cuboid, spherical, cylindrical or irregular shape with an aspect ratio of less than 5.

4. The preparation method according to claim 3, characterized in that, In step S1, the residual sludge is dried, crushed and sieved.

5. The preparation method according to claim 1, characterized in that, In step S2, the granulation molding is performed by a compression / extrusion granulator, and the apparent density of the granulated sludge is 1.45 to 1.80 g / cm 3 , preferably 1.65 to 1.75 g / cm 3 . In step S2, after adjusting the moisture content, the mixture is allowed to stand for 20-40 minutes.

6. The method of claim 1, wherein, In step S3, the pyrolysis is carried out under an inert atmosphere, and the heating rate is 8-12℃ / min.

7. Catalytic sludge biochar produced by the method of any one of claims 1-6, characterized by, The catalytic sludge biochar is rich in iron and nitrogen active sites, and a high proportion of FexN structures are formed, wherein the FexN structures can be one or more of FeN, Fe2N, Fe3N and Fe4N.

8. The catalytic sludge biochar prepared by the method of any one of claims 1-6, or the use of the catalytic sludge biochar of claim 7 in the activated persulfate treatment of antibiotic-containing wastewater.

9. Use according to claim 8, characterized in that, The dosage of the catalytic sludge biochar is 0.05-0.15 g / L, and the dosage of the persulfate is 1-10 mM.

10. Use according to claim 8, characterized in that, The antibiotics in the antibiotic-containing wastewater include fluoroquinolone antibiotics or macrolide antibiotics; The fluoroquinolone antibiotics are selected from one or a combination of levofloxacin, ofloxacin, enrofloxacin, ciprofloxacin, norfloxacin and difloxacin; The macrolide antibiotics are selected from one or a combination of erythromycin and roxithromycin.

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