Iron-cobalt bimetal and nitrogen-doped sludge biochar composite catalytic material, preparation method and application thereof

Abstract

This invention discloses an iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material, its preparation method, and its application, belonging to the field of catalytic materials technology. This composite catalytic material uses municipal sludge-based biochar as a carrier, with iron and cobalt elements loaded on the surface of the carrier and doped with nitrogen. The iron and cobalt elements exist in the form of metal oxides. This invention successfully prepares bimetallic and nitrogen-doped biochar using a low-temperature hydrothermal method. This material exhibits excellent cycle stability, antibiotic degradation, and water body compatibility, while also demonstrating environmental safety and excellent anti-interference ability. FeCo-NBC has broad application prospects in practical water treatment, providing new strategies and theoretical support for the research and development of waste biomass resource conversion and efficient removal technologies for recalcitrant organic pollutants.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, and particularly relates to a composite catalytic material of iron-cobalt bimetallic and nitrogen-doped sludge biochar, its preparation method and its application. Background Technology

[0002] Currently, urban wastewater treatment faces two major challenges: the resource utilization and disposal of municipal sludge and the deep reduction of new pollutants. On the one hand, municipal sludge, as a byproduct of wastewater treatment, is being produced on a continuously increasing scale. Traditional disposal methods such as landfill and incineration not only pose high environmental risks but also fail to achieve high-value conversion of solid waste. On the other hand, quinolone antibiotics such as ofloxacin persist in water bodies. Due to their strong bioinhibitory properties and stable structure, conventional biochemical treatment processes are unable to effectively degrade them, posing a potential threat to aquatic ecosystem safety and human health. Advanced oxidation technologies based on persulfate (PMS), with their advantages of strong oxidation capacity and mild reaction conditions, have become an important development direction for the deep treatment of antibiotic wastewater. Developing efficient, economical, and easily recyclable PMS catalytic materials is therefore crucial for research.

[0003] Using municipal waste sludge as raw material for pyrolysis to prepare biochar, and then using it to activate persulfate treatment of recalcitrant wastewater, is an important technical approach to implement the "waste-to-waste" concept. Sludge-based biochar raw materials are readily available and inexpensive, and have a stable carbon skeleton structure, giving them a natural advantage as a catalytic carrier; however, raw sludge biochar generally suffers from insufficient pore development, low specific surface area, few available active sites on the surface, and weak electron transfer capacity, which limits its activation performance for PMS.

[0004] To enhance the catalytic performance of biochar, transition metal loading and nitrogen doping have been extensively studied. Iron (Fe) loading can introduce Fenton-like active sites, while cobalt (Co) loading is considered a preferred metal for PMS activation due to its higher electron transfer efficiency. Nitrogen doping can modulate the electronic structure of carbon materials, enhancing their conductivity and PMS adsorption and activation capabilities. Studies have shown that a synergistic effect can occur between the Fe and Co bimetallic groups, accelerating PMS activation and significantly improving catalytic efficiency through the valence state cycling of Fe(II) / Fe(III) and Co(II) / Co(III).

[0005] Existing methods for preparing iron-cobalt bimetallic and nitrogen-doped carbon-based catalytic materials still have significant shortcomings. Chinese patent application CN109482219A uses concentrated sludge from a coking plant as raw material, first converting it into sludge-based activated carbon, and then using cobalt and iron nitrates as precursors and acrylamide as a nitrogen source to prepare a CoFe2O4 / nitrogen-doped sludge-based activated carbon catalyst via a gel-calcination method. Chinese patent application CN121669294A uses sludge as raw material, mixing an iron source, sludge, and urea, followed by extrusion granulation and pyrolysis to prepare iron-nitrogen anchored catalytic sludge biochar. The paper (Bimetallic and nitrogen co-doped biochar for peroxymonosulfate (PMS) activation to degrade emerging contaminants, Separation and Purification Technology, 2023, 307: 122807) prepared Fe-Co and nitrogen co-doped biochar (FeCo-BC) using agricultural waste as raw material via impregnation-pyrolysis. The paper (Activation of peroxymonosulfate by cobalt-iron nanoparticles sanchored on nitrogen-doped biochar for efficient removal of tetracycline from water: free radical and non-free radical pathways, Process Safety and Environmental Protection, 2025: 107856) also prepared FeCo@NBC composite material using agricultural waste as raw material.

[0006] Although the above methods can achieve certain catalytic performance, they still have the following shortcomings: (1) Using agricultural waste or commercial activated carbon as carriers, the raw material cost is high or the source is unstable; although using coking sludge as raw material realizes some solid waste utilization, the source of coking sludge is special and the output is limited, so it is not universal; (2) Most of them adopt impregnation-pyrolysis, gel-calcination or one-step carbonization methods, which involve multiple steps, high temperature energy consumption and easy agglomeration and poor dispersibility of metal particles; (3) The gel-calcination method uses acrylamide as nitrogen source, which is costly and the gel process control requirements are strict; in the pyrolysis method, nitrogen element is easy to volatilize and lose in gaseous form at high temperature, resulting in low nitrogen doping efficiency. The root cause of the above limitations is that the existing process has failed to achieve synergistic control of nitrogen doping and bimetallic loading under mild conditions. The high temperature treatment process leads to agglomeration of active components and serious nitrogen loss. Moreover, the process flow is complicated, which limits the large-scale application and promotion of the technology.

[0007] Therefore, it is necessary to develop a new preparation method that uses municipal sludge, which has a large output and wide availability, as raw material to simultaneously achieve efficient co-loading of nitrogen doping and Fe-Co bimetal under mild conditions. This would simplify the process, reduce energy consumption, prepare high-performance, low-cost catalytic sludge biochar materials, and expand their application in the treatment of ofloxacin-type antibiotic wastewater. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a composite catalytic material of iron-cobalt bimetallic and nitrogen-doped sludge biochar, its preparation method, and its applications. Using sludge as biomass raw material, urea as nitrogen source, and Fe(NO3)3·9H2O and Co(NO3)2·6H2O as bimetallic precursors, this invention successfully prepared bimetallic and nitrogen-doped biochar (FeCo-NBC) using a low-temperature hydrothermal method. The synergistic mechanism of nitrogen doping and bimetallic co-modification in regulating specific surface area and enhancing active sites is systematically elucidated. Using the typical quinolone antibiotic ofloxacin as the target pollutant, the degradation performance of the FeCo-NBC / PMS system for OFL under different reaction conditions was systematically investigated. Simultaneously, the cycling stability of FeCo-NBC and its universality in degrading different types of organic pollutants were examined.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A composite catalytic material of iron-cobalt bimetallic and nitrogen-doped sludge biochar is disclosed, using municipal sludge-based biochar as a carrier. The carrier surface is loaded with iron and cobalt elements and doped with nitrogen. The iron and cobalt elements exist in the form of metal oxides, forming Fe-N and Co-N coordination bonds. The specific surface area of ​​the composite material is 150-170 m² / g. 2 / g, ID / IG value is 1.0~1.2, and it is magnetic.

[0010] Furthermore, the iron element is derived from Fe(NO3)3·9H2O, the cobalt element is derived from Co(NO3)2·6H2O, and the nitrogen element is derived from urea; in the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material, Fe(II) / Fe(III) and Co(II) / Co(III) coexist, forming redox cycle active sites.

[0011] This invention also provides a method for preparing a composite catalytic material of iron-cobalt bimetal and nitrogen-doped sludge biochar, comprising the following steps: (1) After drying, crushing and sieving municipal sludge, it is pyrolyzed at high temperature under an inert atmosphere to obtain raw sludge biochar; (2) Add the original sludge biochar, urea, iron salt and cobalt salt obtained in step (1) to water, mix evenly, adjust the pH to 11~12, and continue stirring to obtain a mixed solution; (3) The mixture obtained in step (2) is transferred into the reactor for hydrothermal reaction. After the reaction is completed, it is cooled, washed and dried to obtain the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material.

[0012] Further, the high-temperature pyrolysis temperature is 600~800℃, the heating rate is 5~15℃ / min, the holding time is 60~150min, the inert gas is nitrogen, and the flow rate is 0.3~1.0L / min; preferably, the high-temperature pyrolysis temperature is 700℃, the heating rate is 10℃ / min, the holding time is 120min, the inert gas is nitrogen, and the flow rate is 0.5L / min.

[0013] Further, the temperature of the hydrothermal reaction is 180~220℃, and the reaction time is 10~14h; preferably, the temperature of the hydrothermal reaction is 200℃, and the reaction time is 12h.

[0014] Furthermore, the ratio of the original sludge biochar, urea, iron salt, and cobalt salt is 1g:1g:2mmol:1mmol.

[0015] This invention also provides the application of an iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material in the activation of persulfate to degrade antibiotics in water.

[0016] Furthermore, the antibiotic is at least one of ofloxacin (OFL), tetracycline (TC), ciprofloxacin (CIP), malachite green (MG), and sulfamethoxazole (SMX).

[0017] Furthermore, in the application system, the dosage of the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalyst is 0.05~1g / L, the persulfate concentration is 0.5~4mmol / L, the reaction time is ≤60min, the initial pH of the reaction system is 3~11, and the temperature is 10~40℃.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: (1) This invention achieves simultaneous co-loading of nitrogen doping and Fe-Co bimetal by low-temperature hydrothermal method, which is different from the traditional impregnation-pyrolysis or gel-calcination process. Under hydrothermal conditions, the nitrogen-containing active species generated by urea decomposition form coordination precursors with iron and cobalt in situ. After crystallization, they are firmly anchored on the surface of biochar support, which effectively avoids metal agglomeration and nitrogen loss caused by high temperature treatment, promotes the directional generation of Fe-N / Co-N active sites, and improves the abundance of active components and catalytic performance in the material.

[0019] (2) The preparation method of the present invention is simple, mild and cost-controllable. It uses municipal sludge, which has a large output and wide availability, as raw material. It does not require complicated multi-step operations. It can be completed in just two steps: "pyrolysis carbonization-low temperature hydrothermal loading". The hydrothermal temperature is only 180~220℃. It does not require high-temperature calcination and the energy consumption is significantly lower than the existing gel-calcination method. Urea is used as the nitrogen source. It is widely available and inexpensive, which greatly reduces the cost of raw materials. The process is simple. The required equipment is all conventional industrial equipment. It is easy to operate and can be promoted on a large scale.

[0020] (3) The FeCo-NBC catalytic material prepared in this invention exhibits excellent performance and high degradation efficiency. Benefiting from the synergistic effect of Fe-Co bimetallic materials (Fe(II) / Fe(III) and Co(II) / Co(III) valence state cycling) and the synergistic regulation of the electronic structure of carbon materials by nitrogen doping, FeCo-NBC has excellent activation performance for PMS. Under optimal reaction conditions, the degradation rate of OFL can reach more than 95% within 60 min, and it also has good removal effects on a variety of recalcitrant pollutants such as tetracycline, ciprofloxacin, and sulfamethoxazole.

[0021] (4) This invention has the dual environmental benefits of “treating waste with waste” and resource utilization. High-value-added water treatment catalysts are prepared using municipal waste sludge as the core raw material, which simultaneously realizes the reduction and high-value utilization of sludge. It is then applied to the deep treatment of antibiotic wastewater, providing a new technical path for sludge resource utilization and antibiotic pollution control, and has good environmental and social benefits. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The images show scanning electron microscope (SEM) and X-ray diffraction (SEM-EDS) images of different catalytic materials; where a is the SEM image of BC; b is the SEM image of SBC; c is the SEM image of NBC; d is the SEM image of Fe-NBC; e is the SEM image of Co-NBC; f is the SEM image of FeCo-NBC; f1 is the EDS image of C; f2 is the EDS image of N; f3 is the EDS image of O; f4 is the EDS image of Fe; and f5 is the EDS image of Co. Figure 2 Raman spectra of SBC, NBC, and FeCo-NBC; Figure 3 VSM diagram of FeCo-NBC; Figure 4 The images show the characteristic peak spectra of XPS before and after the SBC, NBC, and FeCo-NBC catalytic reactions; where a represents C1s and b represents O1s. Figure 5 The XPS peak spectra before and after the NBC and FeCo-NBC catalytic reactions are shown; where a represents N1s, b represents Fe2p, and c represents Co2p. Figure 6 The removal efficiency of ofloxacin by different catalytic systems is shown; where a represents the comparison of catalytic performance and b represents the catalytic rate. Figure 7 The effects of different FeCo-NBC dosages, different PMS concentrations, and different initial pH values ​​of the reaction system on the degradation of ofloxacin are shown; where a is the catalyst dosage; b is the PMS concentration; and c is the pH (Zeta potential). Figure 8 The results show the effects of different ions and humic acids on the catalytic effect of FeCo-NBC. Figure 9 The degradation efficiency of FeCo-NBC / PMS system for different antibiotics (a) and degradation efficiency of OFL under different water quality conditions (b). Figure 10 The reusability of PMS for OFL degradation activated by FeCo-NBC (a) and Fe-NBC (b); Figure 11 FTIR plots (a) and XPS performance comparison (b) before and after using FeCo-NBC. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0029] The raw materials used in this invention are: municipal sewage sludge, provided by a large wastewater treatment plant in Zhengzhou, Henan Province; ofloxacin (OFL), sodium hydroxide (NaOH), ferric nitrate nonahydrate (Fe(NO3)3•9H2O), tert-butanol (TBA), tetracycline, ciprofloxacin, and sulfamethoxazole, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; and chemical oxidants PMS (OXONE, KHSO5-KHSO4-K2SO4, ≥47% KHSO5basis), cobalt nitrate hexahydrate Co(NO3)2·6H2O, and spin traps (5,5-Dimethyl-1-pyrroline N-oxide (DMPO, 97%), 2,2,6,6-tetramethyl-4-piperidinol (TEM, greater than 100%)). 98% sodium chloride (NaCl), anhydrous sodium sulfate (Na2SO4), sodium bicarbonate (NaHCO3), and disodium hydrogen phosphate (Na2HPO4) were purchased from Shanghai Aladdin Chemical Technology Co., Ltd.; hydrochloric acid (HCl, 37%) was purchased from Luoyang Chemical Reagent Factory; sodium chloride (NaCl), anhydrous sodium sulfate (Na2SO4), sodium bicarbonate (NaHCO3), and disodium hydrogen phosphate (Na2HPO4) were purchased from Tianjin Kemei Chemical Reagent Co., Ltd.; methanol (MeOH), tert-butanol (TBA, 99%), sodium thiosulfate (Na2S2O8, PS, 99%), and ethanol (EtOH, 99.9%) were purchased from Tianjin Damao Chemical Reagent Co., Ltd.; sodium nitrate (NaNO3) was purchased from Tianjin Hongyan Chemical Reagent Factory; malachite green was purchased from Sinopharm Chemical Reagent Co., Ltd.; L-histidine (L-his) was purchased from Shanghai Lanji Technology Development Co., Ltd.; and superoxide dismutase (SOD) was purchased from Shanghai Yuanye Biotechnology Co., Ltd. All chemical reagents were analytical grade and used as is without further purification. Deionized water was prepared in the laboratory using an EPED-10TF pure water instrument.

[0030] The technical solution of the present invention will be further illustrated by the following embodiments.

[0031] Example 1 (1) Take an appropriate amount of raw sludge, dry it in an oven at 200℃ for 12 hours, crush it and pass it through a 200-mesh sieve to obtain sludge powder, which is denoted as BC; put 10g of BC into a quartz boat and place it in the middle of the tube furnace, and then start the pyrolysis program: set the heating rate to 10℃ / min, the target pyrolysis temperature to 700℃, and keep the temperature constant for 120min after reaching the set temperature; during the heating, pyrolysis and cooling process, nitrogen is continuously introduced at a flow rate of 0.5L / min. After the tube furnace cools naturally to room temperature, take out the obtained sludge biochar and label it as SBC. (2) Add 1.0 g of SBC, 1.0 g of urea, 2 mmol of Fe(NO3)3·9H2O (0.808 g), and 1 mmol of Co(NO3)2·6H2O (0.291 g) to 50 mL of water. Shake the resulting mixture in a constant force shaker for 30 min. Adjust the pH of the solution to between 11 and 12 with NaOH solution, and then continue shaking for 30 min. Transfer the resulting mixture to a reaction vessel and perform a hydrothermal reaction at 200 °C for 12 hours. Finally, wash the cooled precipitate with deionized water until neutral and dry it at 60 °C. Grind the resulting black particles and label them as FeCo-NBC.

[0032] Comparative Example 1 Similar to Example 1, except that Fe(NO3)3·9H2O and Co(NO3)2·6H2O are not added in step (2), and the final product is named NBC.

[0033] Comparative Example 2 Similar to Example 1, except that Fe(NO3)3·9H2O is not added in step (2), and the final product is named Fe-NBC.

[0034] Comparative Example 3 Similar to Example 1, except that Co(NO3)2·6H2O is not added in step (2), and the final product is named Co-NBC.

[0035] Characterization analysis 1. SEM Analysis The surface morphology and elemental composition of the catalyst were characterized using scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (SEM-EDS), such as... Figure 1 As shown, a is the SEM image of BC; b is the SEM image of SBC; c is the SEM image of NBC; d is the SEM image of Fe-NBC; e is the SEM image of Co-NBC; f is the SEM image of FeCo-NBC; f1 is the EDS image of C; f2 is the EDS image of N; f3 is the EDS image of O; f4 is the EDS image of Fe; and f5 is the EDS image of Co. Firstly, from the perspective of overall morphological differences, compared with unmodified BC, SBC exhibits a more porous and loose structure. After nitrogen doping modification, the morphology of NBC undergoes a significant change, forming a unique layered structure; this structure can further expand the specific surface area of ​​the material, providing a basis for subsequent metal loading and catalytic reactions. In the morphological comparison of metal-doped biochar, single-metal-doped Fe-NBC (… Figure 1 d) Co-NBC Figure 1In both cases, large particle agglomeration was observed on the surface of the e), while bimetallic doped FeCo-NBC ( Figure 1 The surface of f) in the image is uniformly dispersed with a large number of nanoparticles. To further quantify this morphological difference, the particle size of the metal particles in the SEM images was statistically analyzed (Table 1). The results show that the average particle sizes of Fe-NBC and Co-NBC are 0.484 μm and 0.599 μm, respectively, with large standard deviations (0.252 μm and 0.386 μm), indicating that the metal particles are widely distributed and have obvious agglomeration. In contrast, the average particle size of the metal particles on the FeCo-NBC surface is significantly reduced to 0.396 μm, with a standard deviation of only 0.117 μm, indicating a more uniform particle size distribution and significantly improved metal dispersion. These results indicate that the simultaneous introduction of Fe and Co bimetals enables the metal particles to be uniformly distributed on the surface and in the pores of the carbon material, significantly improving the surface roughness of FeCo-NBC and forming an entangled spatial structure, which is beneficial to enhancing the material's ability to remove antibiotics. EDS images ( Figure 1 Figure 1f) further demonstrates that FeCo-NBC maintains a stable overall morphology after being loaded with iron and cobalt bimetals, and that Fe and Co elements are uniformly distributed within the material without significant agglomeration, which is highly consistent with SEM observations and particle size statistics. Combined with phase analysis of the carbon materials, it is known that most metal / nitrogen-doped biochars are predominantly amorphous carbon, with active metals widely dispersed and embedded within the channels of the nitrogen-doped biochar. This embedded structure effectively inhibits the shedding and agglomeration of metal particles, improving the structural stability of the material. The excellent metal dispersion of FeCo-NBC is one of the key factors in its improved catalytic performance. This phenomenon can be attributed to the introduction of iron, which enhances the interaction between the active metal and the carbon support, suppressing the migration and agglomeration of cobalt particles through electronic regulation effects.

[0036] Table 1 Particle size statistics 2. BET Analysis The specific surface area, pore size distribution, and pore volume of SBC, NBC, and FeCo-NBC were evaluated using N2 adsorption-desorption technology. Specific parameters are shown in Table 2.

[0037] All three samples exhibited Langmuir type IV isotherms, indicating a uniform mesoporous structure. The results show that the specific surface areas of SBC, NBC, and FeCo-NBC are 37.67 m² / s. 2 / g, 106.19m 2 / g and 150.056m 2The pore sizes of FeCo-NBC were 5.9804 nm, 5.613 nm, and 10.1276 nm, respectively. Compared with NBC, FeCo-NBC has a larger specific surface area and total pore volume, which is beneficial for pollutant adsorption and exposure of active sites, thereby improving catalytic efficiency. These structural features may be related to the uniform distribution of FeCo alloy on the biochar surface; uniformly dispersed metal particles can effectively increase the exposed area and provide more active sites. Pore size distribution analysis showed that the pore sizes of the three biochars were mainly concentrated between 5 nm and 11 nm, indicating that they have a mesoporous structure. Compared with SBC, FeCo-NBC exhibited more significant mesoporous characteristics at 10 nm, with a pore volume approximately five times that of SBC. In summary, the co-doping of iron, cobalt, and nitrogen significantly increased the specific surface area of ​​the biochar, and the porous structure of FeCo-NBC provided abundant active sites for subsequent catalytic reactions.

[0038] Table 2 Basic Parameters of BET 3. Raman analysis To investigate the changes in carbon structure, Raman spectroscopy was further used to characterize the material, such as... Figure 2 As shown. All materials are at 1315.4cm. -1 and 1590.0cm -1 Characteristic peaks appeared at the peaks, corresponding to the D and G peaks of carbon materials, reflecting the defect structure and ordered graphite structure in biochar. The ID / IG intensity ratio was calculated by fitting the peak area. This ratio can be used to evaluate the surface defect degree of carbon-based materials. The larger the ratio, the higher the disorder and the more defect structures in the material. Compared with SBC (0.65), NBC (0.84), and FeCo-NBC after the reaction (0.89), FeCo-NBC before the reaction had the largest ID / IG ratio, 1.08, indicating that it has more abundant structural defects, which is conducive to the binding and degradation of pollutant molecules. After multiple cycles of reaction, the ID / IG ratio of FeCo-NBC decreased to 0.89, corresponding to a certain degree of catalytic performance decay, but it was still higher than that of undoped SBC and NBC, indicating that the introduction of Fe and Co bimetals plays an important role in maintaining the structural defects and catalytic activity of the material. The above results are consistent with the literature reports, that is, the co-doping of nitrogen and bimetals can effectively improve the defect degree of carbon materials. In addition, at 1200~1400 cm⁻¹, the surface defect ratio of FeCo-NBC was significantly increased. -1 In this region, the Raman peak shapes of different samples showed some differences. The peak shape of FeCo-NBC was broader than that of other samples in this region, which may be related to the local structural changes caused by Fe and Co doping, indicating that metal doping has affected the microscopic chemical bonding environment of carbon materials. Abundant structural defects and unique local structures together provide the structural basis for the high catalytic efficiency of FeCo-NBC.

[0039] 4. VSM Analysis The magnetic properties of FeCo-NBC were characterized using a vibrating sample magnetometer (VSM), and the results are as follows: Figure 3 As shown in the figure, the remanent magnetization (Mr) and coercivity (Hc) of FeCo-NBC are 2.04 emu / g and 237.14 Oe, respectively, indicating that the material has good magnetic response performance. The introduction of iron and cobalt bimetals successfully endowed biochar with magnetism. This property enables the catalyst to be efficiently separated and recovered under the action of an external magnetic field, which is consistent with the experimental results of continuous recovery of the catalyst through a permanent magnet in subsequent recycling experiments. The excellent magnetic separation performance not only simplifies the catalyst recovery process, but also effectively avoids the secondary pollution problems that may be caused by catalyst residues, showing good prospects for practical applications.

[0040] 5. XPS Analysis Figure 4 The XPS peak spectra of SBC, NBC and FeCo-NBC are shown, where a is the C1s high-resolution spectrum and b is the O1s high-resolution spectrum.

[0041] The C1s high-resolution spectrum can be fitted with three characteristic peaks, corresponding to different carbon species: CC (~284.8 eV), CO (~285.2 eV), and C=O (~289.6 eV). Quantitative analysis results show that the relative content of CC bonds gradually increases from SBC to NBC and then to FeCo-NBC, indicating that the aromaticity of the material is continuously enhanced, which helps to improve the conductivity and structural stability of the material and provides favorable conditions for electron transfer and active site protection during the catalytic process. In addition, the proportion of CC bonds after the FeCo-NBC catalytic reaction only slightly decreases, indicating that the surface carbon skeleton of the material is not significantly damaged during recycling, confirming its good cycle stability. The O1s high-resolution spectrum can also be fitted with three characteristic peaks: O 2- (~530.4 eV), CO (~531.6 eV), and C=O (~532.9 eV). Quantitative results show that O 2- The relative content of SBC is ranked as follows: <NBC<FeCo-NBC,O 2- This is usually closely related to the defect sites and metal active centers on the material surface. The increase in their content directly proves that more oxygen-rich active sites have been formed on the FeCo-NBC surface. These sites can serve as active sites for PMS, and promote the decomposition of PMS to generate highly active oxide species by regulating the electron transfer process, thereby significantly improving the catalytic performance.

[0042] To further explore the microstructural advantages of FeCo-NBC and the regulatory mechanism of elemental chemical states on catalytic performance, detailed characterization analysis was carried out using XPS N 1s, Fe 2p, and Co 2p high-resolution spectra. The results are as follows: Figure 5 As shown.

[0043] Combination Figure 5 XPS analysis of the N 1s spectra of FeCo-NBC revealed that nitrogen in NBC mainly exists in the form of graphitic nitrogen (73.2%), pyrrole nitrogen (8.9%), and pyridine nitrogen (7.9%). In FeCo-NBC, the proportion of pyrrole nitrogen significantly increased, while the proportion of pyridine nitrogen decreased to 4.84%, and a characteristic peak of metal-coordinated nitrogen (Metal-N) appeared at a binding energy of 397 eV. This change suggests that some pyridine nitrogen, acting as active sites, coordinated with Fe / Co ions and was transformed into metal-coordinated nitrogen. Simultaneously, the increase in pyrrole nitrogen reflects the reconstruction of the nitrogen structure on the support surface, both of which jointly confirm the formation of Fe-N / Co-N bonds. Quantitative results showed that compared to NBC, the relative content of graphitic nitrogen in FeCo-NBC was slightly decreased; while Fe and Co dual doping significantly increased the relative content of pyrrole-N. Generally, increasing the pyrrole-N content can enhance the adsorption affinity of materials for pollutants, thereby improving degradation efficiency. In addition, the introduction of nitrogen can build more metal-loaded defect sites on the surface of bimetallic doped composite materials. These defect sites can not only enhance the interaction between the metal and the carbon support and reduce the metal dissolution loss during the catalytic process, but also avoid secondary pollution caused by the release of metal ions.

[0044] Figure 5 Figure b shows the high-resolution Fe 2p spectrum before and after the FeCo-NBC reaction, containing four main characteristic peaks with binding energies at 710.5 eV, 713.5 eV, 723.7 eV, and 726.3 eV, respectively, corresponding to Fe(II)2p. 3 / 2 Fe(III)2p 3 / 2 Fe(II)2p 1 / 2 and Fe(III)2p 1 / 2 Notably, the characteristic peak of Fe(III) at 713.5 eV is also related to the Fe-N coordination structure, confirming that Fe is anchored to the carbon support surface through coordination bonds with nitrogen atoms. This structure enhances the stability of Fe and improves its catalytic activity. The coexistence of Fe(III) and Fe(II) indicates that Fe... 0 During material preparation or catalytic reaction, partial oxidation occurs to generate Fe(III) and Fe(II); the introduction of Co can significantly promote the reduction conversion of Fe(III) to Fe(II), effectively alleviate the problem of catalytic activity decay caused by the accumulation and aggregation of Fe(III), and thus solve the bottleneck of difficult Fe(II) regeneration in traditional Fe-based materials.

[0045] Figure 5 Figure c shows the high-resolution Co 2p spectrum before and after the FeCo-NBC reaction. The fitted peak at 786.5 eV corresponds to metallic Co, while the characteristic peaks at 779.88 eV and 795.67 eV belong to Co(II). Furthermore, the binding energy at 779.88 eV can be attributed to the Co-N coordination bond, further confirming that Co forms a stable coordination structure with nitrogen atoms and the carbon support. In addition, the characteristic peaks at 781.41 eV and 796.33 eV correspond to Co 2p, respectively. 3 / 2 and Co2p 1 / 2 This indicates that both Co(II) and Co(III) valence states exist simultaneously in FeCo-NBC. The efficient redox cycle between Co(II) and Co(III) can significantly promote the conversion of Co(III) to Co(II) and form a synergistic effect with the redox cycle of Fe(II) / Fe(III), driving the electron transfer process inside the bimetal, thereby inducing the generation of abundant oxygen vacancies, significantly enhancing the adsorption and activation capacity of PMS, and ultimately greatly improving the catalytic activity of FeCo-NBC.

[0046] Application Example 1 The catalytic materials prepared in Example 1 and Comparative Examples 1-3 were used in the degradation of antibiotics in water by activated persulfate. The specific method was as follows: Batch experiments were conducted in 250 mL Erlenmeyer flasks containing 25 mL of ofloxacin (OFL), 0.5 g / L of catalyst, and 2 mM PMS. The initial concentration of the contaminant solution was 20 mg / L, with an initial pH of 9. Deionized water was used as the solvent for the solution preparation. After preparation, the Erlenmeyer flasks were placed in a constant-temperature shaker at 25 °C and 180 rpm. During the reaction, 1 mL samples were periodically drawn at fixed time intervals. The extracted samples were filtered through a 0.45 µm Teflon membrane and then added to a sample bottle containing 40 µL of Na₂S₂O₈ to stop the reaction. All experiments were repeated three times to ensure the accuracy of the results.

[0047] Based on the experimental procedure, the following groups were established: Group 1: Add PMS only; Group 2: Only FeCo-NBC prepared in Example 1 was added; Group 3: Add SBC and PMS; Group 4: NBC and PMS prepared in Comparative Example 1 were added; Group 5: Fe-NBC and PMS prepared in Comparative Example 2 were added; Group 6: Co-NBC and PMS prepared in Comparative Example 3 were added; Group 7: FeCo-NBC prepared in Example 1 and PMS are added.

[0048] Performance test The removal effect of different catalytic systems on ofloxacin (OFL) is shown in Figure 6 the figure, where a is the comparison of catalytic performance, and b is the catalytic rate.

[0049] The adsorption of pure FeCo-NBC on OFL is limited, indicating that adsorption alone is not the main way for OFL removal; the removal of OFL by the PMS system alone is also weak. Therefore, comparative experiments on the catalytic degradation performance of each system were further carried out. The results show that the FeCo-NBC / PMS system has the highest removal rate of OFL, showing the optimal catalytic activity. This may be attributed to Fe 3+ / Fe 2+ and Co 3+ / Co 2+ constructed efficient redox cycle, and the synergistic effect of the two can accelerate the decomposition process of PMS and generate more highly active oxidized species. To further quantify the kinetic characteristics of the catalytic reaction, the pseudo-first-order kinetic fitting was performed on the OFL removal processes of different systems ( Figure 6 b in the figure). The results show that the apparent rate constants (k) of the Fe-NBC / PMS system with single Fe doping and the Co-NBC / PMS system with single Co doping are both significantly lower than that of the FeCo-NBC / PMS system, which further confirms the synergistic enhancement effect of Fe and Co in the FeCo-NBC material. Based on the comprehensive performance experimental results, the order of OFL removal performance of different systems is: Fe-NBC < FeCo-NBC ≈ Co-NBC. Since the metal loading in each sample remains consistent, the interference of the difference in metal loading on the catalytic performance can be excluded. It can be inferred that the introduction of Co can effectively make up for the defect of low activity of Fe-based catalytic materials, while the doping of Fe can reduce the amount of Co in the system on the premise of ensuring the catalytic performance, achieving a balance between the material preparation cost and the catalytic activity, and providing a reference for the design of high-efficiency and low-cost catalytic materials. To deeply reveal the internal mechanism of the excellent catalytic activity exhibited by FeCo-NBC, a series of exploration experiments were subsequently carried out.

[0050] Application Example 2 To explore the most suitable experimental conditions, the dosage of different catalysts, the dosage of PMS and the pH value were tested in the FeCo-NBC / PMS system, and the specific method is as follows: Different catalyst dosages: the scheme is the same as that of Group 7 in Application Example 1, with the difference that the dosage of the catalytic material is adjusted to 0.05g / L, 0.1g / L, 0.3g / L, 0.5g / L, and 1g / L respectively.

[0051] Different PMS dosages: Same as the regimen for group 7 in Application Example 1, except that the dosage of PMS was adjusted to 0.5mM, 1mM, 2mM, 3mM and 4mM respectively.

[0052] Initial pH of different reaction systems: Same as group 7 in application example 1, except that the pH is adjusted to 3, 5, 7, 9 and 11 respectively.

[0053] The effects of different FeCo-NBC dosages, PMS concentrations, and pH on OFL degradation are as follows: Figure 7 Where a is the amount of catalyst added; b is the PMS concentration; and c is the pH (Zeta potential).

[0054] When the mass of FeCo-NBC increased from 0.05 g / L to 0.50 g / L, the removal rate of OFL increased significantly within 60 minutes, and the reaction rate constant also increased accordingly. This indicates that appropriately increasing the catalyst dosage can enhance the activation level of PMS, thereby generating more free radicals and non-free radicals (such as •OH, SO4•). - , 1 O2) accelerates the degradation of pollutants. However, when the FeCo-NBC dosage was further increased from 0.5 g / L to 1.0 g / L, the OFL removal rate did not show a significant improvement. This may be because the excessive metal species loaded on the catalyst surface lead to over-coverage of active sites, thereby weakening the utilization efficiency per unit mass of catalyst. The above results indicate that FeCo-NBC can achieve a relatively ideal catalytic effect at a dosage of 0.50 g / L (see Figure a).

[0055] When the PMS concentration increased from 0.5 mmol / L to 2 mmol / L, the removal rate of OFL significantly improved (Figure b). The relevant rate constant value increased from 0.0274 min... -1 Increased to 0.0856 min -1 When the PMS concentration further increased to 4 mmol / L, the OFL removal rate decreased, and the relevant rate constant dropped to 0.0559 min. -1 This may be because excessively high PMS concentrations can trigger the self-quenching effect of reactive oxygen species, leading to a decrease in the concentration of effective oxide species. Simultaneously, due to the limited number of catalytically active sites on the FeCo-NBC surface, excessive PMS is difficult to activate effectively. The combined effect of these two factors results in high-concentration PMS failing to achieve the expected removal effect of OFL. Considering both catalytic efficiency and reagent cost, a PMS concentration of 2 mmol / L was selected as the PMS concentration for subsequent experiments.

[0056] The initial pH of the solution significantly modulates the removal efficiency of OFL in the FeCo-NBC / PMS system (see Figure c). As the initial pH increases from 3 to 11, the OFL removal rate gradually increases. Zeta potential analysis shows that when the initial pH < 4.0, the FeCo-NBC surface is positively charged; when the initial pH > 4.0, the surface becomes negatively charged. Lower pH results in higher Zeta potential and stronger electrostatic repulsion between particles; conversely, higher pH results in lower Zeta potential and weaker interparticle repulsion, which is beneficial for improving degradation efficiency. Under strongly acidic conditions (pH = 3), the degradation reaction is significantly inhibited. This is partly due to the fact that acidic environments induce quenching reactions of sulfate free radicals (Equation 1), which inhibits the formation of reactive oxygen species (ROS) and reduces the number of effective catalytic sites. On the other hand, positively charged OFL molecules (pKa ≈ 5.5~8.0) and the similarly positively charged FeCo-NBC surface generate electrostatic repulsion, hindering the contact between pollutants and catalytic sites. Furthermore, under acidic conditions, PMS mainly exists as HSO5. - It exists in form, and it is related to SO4• - The free radical generation pathway is affected by pH, further limiting the yield of active species. As pH increases, the FeCo-NBC surface gradually becomes negatively charged, weakening the electrostatic repulsion between it and the amphoteric OFL molecule, which facilitates the enrichment of contaminants onto the catalyst surface. Simultaneously, OH groups in the system... - The increase can promote its interaction with HSO5 - The reaction (Equation 2) occurs, generating more reactive oxygen species, thereby enhancing the degradation reaction. At pH=11, PMS mainly utilizes SO52-. 2- SO5 exists in the form of [unclear] under strongly alkaline conditions. 2- SO4 can be generated 2- With OH - (Equation 3) Both of these active species can participate in the degradation of OFL. Although there is electrostatic repulsion between FeCo-NBC and OFL under strongly alkaline conditions, the removal efficiency of OFL still reaches 95.11%. This result indicates that in an alkaline environment, pH plays a dominant role in regulating the PMS activation pathway, and its influence exceeds that of the electrostatic interaction between the material and the pollutant.

[0057] .

[0058] Application Example 3 Natural water bodies contain various anions and organic matter, which often have an adverse effect on the degradation of pollutants. Therefore, this invention utilizes inorganic anions (Cl-) commonly found in actual aquatic environments. - NO3 - HCO3 - HPO42- and SO4 2- The effects of humic acid (HA) and humic acid (HA) on the degradation efficiency of the FeCo-NBC / PMS system were investigated using the following methods: Different inorganic anions: Same as Group 7 in Application Example 1, except that the dosage of the catalyst is 0.5 g / L, the dosage of PMS is 2 mM, the initial pH of the reaction system is adjusted to 11, and the inorganic anion (Cl... - NO3 - HCO3 - HPO4 2- and SO4 2- The concentrations of the ions were adjusted to 1 mM, 10 mM and 40 mM, respectively.

[0059] Different concentrations of HA: Same as the scheme in Group 7 of Application Example 1, except that the amount of catalyst added is 0.5 g / L, the amount of PMS added is 2 mM, the initial pH of the reaction system is adjusted to 11, and the concentration of HA is adjusted to 2 mg / L, 5 mg / L and 10 mg / L respectively.

[0060] The effects of different ions and humic acids on the catalytic effect are shown in the figure. Figure 8 As can be seen from the figure, Cl - and SO4 2- FeCo-NBC / PMS inhibited the degradation of OFL by concentrations of 1 mM, 10 mM, and 40 mM. This inhibitory effect did not significantly change with increasing concentration of the anion, which may be due to the presence of Cl... - The reaction with persulfate produces chlorine free radicals, which have weak oxidizing power, thereby inhibiting the degradation of pollutants. Furthermore, Cl... - and SO4 2- It will react with PMS (as shown in Equations 4 and 5). This reaction consumes PMS and inhibits the formation of reactive oxides.

[0061] .

[0062] NO3 - and HCO 3- It also adversely affected the oxidative degradation process of OFL in the FeCo-NBC / PMS system. 3- The higher the concentration of NO3, the more significant the inhibitory effect on OFL degradation. - With SO4• - The reaction of OH produces NO3- free radicals with low redox potential. - This reduces the degradation effect on OFL; the specific reaction process can be found in Equations 6 and 7.

[0063] .

[0064] HCO3 - At low concentrations, the inhibitory effect on OFL degradation is very weak; at 40 mmol / L, HCO3... - The system's OFL removal rate decreased slightly, which may be related to HCO3. - It quenched SO42- in the reaction solution as a free radical scavenger. - And •OH. Overall, NO3 - HCO3 - The concentration of these anions in water has little effect on the removal of OFL by the FeCo-NBC / PMS system. This system can still effectively degrade OFL in the presence of these anions.

[0065] HPO4 2- Concentration produced different effects on FeCo-NBC / PMS. Adding 1 mmol / L HPO4... 2- It has a slight inhibitory effect, while high concentrations of HPO4... 2- The addition of [a specific ingredient] did not further inhibit the reaction; instead, it slightly promoted the removal of OFL. Adding 1 mmol / L HPO4 [a specific ingredient]... 2- At that time, the degradation rate decreased slightly, which may be due to HPO4 2- The charge repulsion between FeCo-NBC and the competitive adsorption with OFL after ionization. When 10 mM HPO4 is added... 2- The degradation efficiency was significantly improved to 95.72%, which may be due to the large amount of HPO4. 2- Promotes OH - The ionization of HPO4 and the initial pH results showed that alkaline conditions were favorable for OFL removal. However, when the concentration increased to 40 mM, the degradation rate was only 91.65%. 2- While still showing a promoting effect on the FeCo-NBC / PMS system, the degradation rate was slightly lower compared to the low concentration (10 mM). This may be due to the fact that HPO42- was released in the early stages of the degradation reaction. 2- Ionization produces OH - The reaction efficiency with PMS is greater than that with HPO4. 2- and SO4• - The reaction efficiency is shown in Equations 8 and 9. At lower concentrations, Equation 8 remains the dominant reaction, and the solution environment is alkaline, thus continuously improving the degradation efficiency of OFL. However, with the increase of HPO4... 2- As the concentration increases to excess, OH- is gradually depleted, and the reaction changes from Equation 8 to Equation 9, thereby reducing the reaction efficiency.

[0066] .

[0067] These results indicate that the FeCo-NBC / PMS system has strong resistance to inorganic anions.

[0068] At a concentration of 2 mg / L HA, OFL removal was slightly inhibited. The inhibitory effect on OFL removal efficiency became increasingly significant with increasing HA concentration. HA typically contains various functional groups (such as carboxyl and quinone groups) and is considered a free radical scavenger. On the FeCo-NBC surface, HA can compete with OFL for oxidation, thereby consuming some of the active species generated after PMS activation. Furthermore, as a typical soluble organic compound, HA can quench some free radicals. Although HA has some impact on the system, its inhibitory effect is acceptable; at a concentration of 10 mg / L, more than 80% of OFL can still be degraded through oxidation.

[0069] Application Example 4 To investigate the universality of the FeCo-NBC / PMS system, the degradation efficiency of the FeCo-NBC / PMS system for different antibiotics and for OFL under different water quality conditions was examined. The antibiotics used were: ofloxacin (OFL), tetracycline (TC), ciprofloxacin (CIP), malachite green (MG), and sulfamethoxazole (SMX). The different water quality conditions included: deionized water, municipal tap water, natural lake water, and actual industrial wastewater. The specific methods were as follows: Different antibiotics: The regimen is the same as that in group 7 of application example 1, except that the antibiotics are replaced with tetracycline (TC), ciprofloxacin (CIP), malachite green (MG) and sulfamethoxazole respectively at the same dosage. Different water quality: The scheme is the same as that in Group 7 of Application Example 1, except that the volume of deionized water is replaced with actual industrial wastewater, natural lake water and municipal tap water.

[0070] Figure 9 The degradation efficiency of FeCo-NBC / PMS system for different antibiotics (a) and degradation efficiency of OFL under different water quality conditions (b) are shown.

[0071] As shown in Figure a, the FeCo-NBC / PMS system can achieve a degradation rate of over 98% for TC and MG within 60 min, and a removal rate of over 73% for CIP and SMX, indicating that the system has excellent degradation efficiency for typical antibiotic pollutants.

[0072] To systematically evaluate the practical application potential of the FeCo-NBC / PMS system and further explore its degradation stability in real water substrates, this invention conducted parallel degradation experiments using actual industrial wastewater, natural lake water, and municipal tap water as background water samples, strictly adhering to the experimental parameters of the pure water system. OFL was used as the target degradant to examine the system's water quality adaptability. The experimental results are shown in Figure b. In the three real water substrates mentioned above, the degradation rate of OFL by the FeCo-NBC / PMS system was not significantly different from the results of the pure water system, indicating that the degradation efficiency of this system is less affected by coexisting components in the actual water substrate, possessing good environmental adaptability and anti-interference ability. This provides experimental support for its application in the remediation of antibiotic pollution in real water bodies.

[0073] Application Example 5 This invention investigated the reusability of FeCo-NBC-activated PMS for OFL degradation through a five-cycle experiment. The specific method was as follows: after each run (operating conditions were the same as group 7 in Application Example 1), the FeCo-NBC was recovered by filtration, washed three times with deionized water, and dried at 80°C for future use. The results are as follows: Figure 10 As shown in 'a'.

[0074] Experimental results show that the degradation efficiency of FeCo-NBC for OFL gradually decreases with increasing cycle number. This indicates that the active sites of FeCo-NBC are gradually consumed. One possible reason is that intermediate products generated during catalytic degradation are easily adsorbed onto the catalyst surface, occupying some active sites and hindering effective contact between PMS and active sites, thus inhibiting the activation process of PMS and the generation of reactive oxygen species (ROS). Another reason is the distinct stage-based degradation of catalyst activity during cycling; the degradation performance of the material declines significantly after the third cycle, and the removal rate drops drastically by the fifth cycle. This may be closely related to the disruption of the Fe(II) / Fe(III) and Co(II) / Co(III) redox cycles. It is speculated that excessive loss of trivalent metal ions (Fe(III) and Co(III)) occurs in the system during the third cycle, disrupting the self-circulation equilibrium of the bimetallic compounds and drastically reducing the number of active sites, thereby significantly reducing the degradation capacity for OFL. Notably, even after four cycles, the degradation efficiency of FeCo-NBC for OFL can still be maintained above 70%, fully demonstrating its good reusability and structural stability.

[0075] To further verify the effect of bimetallic doping on improving the stability of iron-based materials, this invention simultaneously conducted a comparative experiment on the cyclic regeneration of Fe-NBC (operating conditions were the same as group 5 in Application Example 1). The results are as follows: Figure 10As shown in b): After three cycles, Fe-NBC exhibited a degradation performance retention rate of only 45%, indicating severe loss of its surface active sites; while FeCo-NBC retained over 90% of its performance after three cycles. This comparative result clearly confirms that the Fe-Co bimetallic synergistic system can effectively inhibit the loss of active sites and significantly improve the cycling stability of iron-based materials by strengthening the interaction between the metal and the carbon support (such as Fe-N and Co-N coordination structures), thereby alleviating the material deactivation process.

[0076] To further verify the cyclic regeneration stability of FeCo-NBC at the microscopic level, FTIR and XPS full-spectrum characterization were performed on fresh and recycled samples, respectively. The results are as follows: Figure 11 As shown in the FTIR spectrum, the positions and relative peak intensities of the main characteristic peaks of FeCo-NBC before and after use are basically consistent, indicating that the surface functional group structure of the material has not changed significantly after multiple catalytic reactions, demonstrating excellent structural stability. XPS full-spectrum results show that the peak intensities of the main elemental characteristic peaks in the cycled sample are slightly lower than those in the fresh sample. This phenomenon can be attributed to the slight damage to the locally ordered structure on the catalyst surface during advanced oxidation. Nevertheless, the positions of the elemental characteristic peaks in the cycled sample and the fresh sample are almost identical, indicating that the main chemical composition and elemental valence state distribution of the material have not changed significantly, further confirming the excellent chemical stability of FeCo-NBC. In summary, FeCo-NBC is an environmentally friendly and reusable high-efficiency catalytic material with broad application prospects in the field of organic pollutant degradation.

[0077] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite catalytic material of iron-cobalt bimetallic material and nitrogen-doped sludge biochar, characterized in that, The iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material uses municipal sludge-based biochar as a carrier. The surface of the carrier is loaded with iron and cobalt elements and doped with nitrogen elements. The iron and cobalt elements exist in the form of metal oxides.

2. The iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material according to claim 1, characterized in that, The iron element is derived from Fe(NO3)3·9H2O, the cobalt element is derived from Co(NO3)2·6H2O, and the nitrogen element is derived from urea; in the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material, Fe(II) / Fe(III) and Co(II) / Co(III) coexist, forming redox cycle active sites.

3. A method for preparing a composite catalytic material of iron-cobalt bimetallic and nitrogen-doped sludge biochar as described in claim 1 or 2, characterized in that, Includes the following steps: (1) After drying, crushing and sieving municipal sludge, it is pyrolyzed at high temperature under an inert atmosphere to obtain raw sludge biochar; (2) Add the original sludge biochar, urea, iron salt and cobalt salt obtained in step (1) to water, mix evenly, adjust the pH to 11~12, and continue stirring to obtain a mixed solution; (3) The mixture obtained in step (2) is transferred into the reactor for hydrothermal reaction. After the reaction is completed, it is cooled, washed and dried to obtain the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material.

4. The preparation method according to claim 3, characterized in that, The high-temperature pyrolysis temperature is 600~800℃, the heating rate is 5~15℃ / min, the holding time is 60~150min, the inert gas is nitrogen, and the flow rate is 0.3~1.0L / min; The hydrothermal reaction is carried out at a temperature of 180~220℃ for 10~14h.

5. The preparation method according to claim 4, characterized in that, The high-temperature pyrolysis temperature is 700℃, the heating rate is 10℃ / min, the holding time is 120min, the inert gas is nitrogen, and the flow rate is 0.5L / min. The hydrothermal reaction was carried out at a temperature of 200°C for 12 hours.

6. The preparation method according to claim 3, characterized in that, The ratio of the original sludge biochar, urea, iron salt, and cobalt salt used is 1g:1g:2mmol:1mmol.

7. The application of the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalytic material as described in claim 1 or 2 in the activated persulfate degradation of antibiotics in water.

8. The application according to claim 7, characterized in that, The antibiotic is at least one of ofloxacin, tetracycline, ciprofloxacin, malachite green, and sulfamethoxazole.

9. The application according to claim 7, characterized in that, In the application system, the dosage of the iron-cobalt bimetallic and nitrogen-doped sludge biochar composite catalyst is 0.05~1g / L, the concentration of persulfate is 0.5~4mmol / L, the reaction time is ≤60min, the initial pH of the reaction system is 3~11, and the temperature is 10~40℃.

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