Preparation method and application of antibiotic bacteria residue-based magnetic biochar spheres doped with nitrogen in situ

Abstract

The application discloses a preparation method and application of antibiotic bacteria residue-based magnetic biochar spheres doped with nitrogen in situ, and belongs to the technical field of hazardous waste resource utilization and wastewater treatment. The application takes antibiotic bacteria residue as a precursor, takes ferric chloride as an iron source, and utilizes the rich nitrogen elements of the antibiotic bacteria residue to realize the degradation of residual antibiotics and in-situ nitrogen atom doping simultaneously through a "freeze-drying-pyrolysis" process without adding an external nitrogen source, so that the physicochemical properties of the biochar material are improved, and the adsorption performance of the biochar material is enhanced; and then, the cross-linking reaction of sodium alginate and calcium chloride is utilized to further prepare magnetic biochar spheres which are stable in structure and excellent in magnetism. The magnetic biochar spheres are applied to efficient treatment of antibiotic wastewater, have the characteristics of rapid separation and recycling, effectively reduce the wastewater treatment cost, realize harmless treatment and resource utilization of the antibiotic bacteria residue, and have excellent environmental benefits and economic values.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste resource utilization and wastewater treatment technology, specifically to a method for preparing and applying a highly efficient and easily recyclable antibiotic bacterial residue-based magnetic biocarbon ball. Background Technology

[0002] Antibiotic fermentation residue refers to the solid waste generated during the antibiotic fermentation process after extracting the effective components of the fermentation broth through a pressure filtration process. China's annual production of antibiotic fermentation residue exceeds 2 million tons. Due to the presence of residual antibiotics and other risk factors, it poses a serious threat to the environment and public health and has been included in the "National Hazardous Waste List," requiring strict supervision and proper disposal in accordance with the requirements for hazardous waste environmental management.

[0003] Currently, the main method for the harmless treatment of antibiotic bacterial residue is high-temperature incineration, which decomposes antibiotic residues through high temperatures to achieve harmlessness. However, due to the low calorific value of antibiotic bacterial residue, its incineration usually requires additional energy, leading to a significant increase in energy consumption and costs, with a treatment cost of approximately 3,000 yuan / ton. Furthermore, the incineration process generates substantial carbon emissions and releases persistent toxic pollutants such as dioxins, posing a risk of secondary environmental pollution. Simultaneously, the abundant crude protein in antibiotic bacterial residue results in a high nitrogen content; direct incineration leads to resource waste and does not align with the current green development requirements for solid waste resource utilization and carbon reduction. Therefore, developing a technology capable of achieving the harmless treatment and resource utilization of antibiotic bacterial residue is of significant practical importance.

[0004] Chinese patent application CN 115672951 A discloses a highly efficient and harmless treatment method for antibiotic bacterial residue. The method involves uniformly mixing a mixture of nitric acid and sulfuric acid with the antibiotic bacterial residue, followed by a hydrothermal reaction at 40–200°C to completely degrade the antibiotics. This technology suffers from strong acid corrosivity and safety hazards, and generates a large amount of strong acid waste liquid, easily causing secondary pollution. Chinese patent application CN 117025247 A discloses a method for the harmless and resource-based treatment of antibiotic bacterial residue. This method recovers bio-oil and biochar products from the pyrolysis-preheated and dried antibiotic bacterial residue powder. The biochar products can be used for soil remediation; however, the practical application feasibility of the biochar products has not been assessed. Chinese patent application CN 115138333 A discloses a method for the harmless and resource-based utilization of calcium / iron-rich antibiotic bacterial residue. This method involves mixing vancomycin fermentation residue with limestone, calcium sulfate, and polyferric sulfate, heating and drying it, and then carbonizing it to obtain magnetic biochar. This technology requires the addition of various reagents such as limestone, calcium sulfate, and polyferric sulfate to adjust the calcium and iron content and moisture content of the bacterial residue, increasing raw material costs and process complexity.

[0005] In conclusion, it is essential to develop a green, economical, and efficient technology for the harmless and resource-based utilization of antibiotic bacterial residue. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a green, economical, and efficient method for preparing and applying in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon spheres. This method can achieve the harmless treatment and resource utilization of hazardous waste, transforming antibiotic bacterial residue into in-situ nitrogen-doped magnetic biocarbon spheres with high adsorption performance and easy recycling, and applying them to the efficient treatment of antibiotic wastewater, thereby achieving the "triple" goals of harmless and resource-based solid waste treatment, wastewater treatment, and carbon emission reduction.

[0007] This invention uses antibiotic bacterial residue as a precursor and ferric chloride as an iron source. Utilizing the abundant nitrogen in the residue, it simultaneously degrades residual antibiotics and performs in-situ nitrogen atom doping through a "freeze-drying-pyrolysis" process without the need for an external nitrogen source, improving the physicochemical properties of the biochar material and thus enhancing its adsorption performance. Furthermore, to address the problems of difficult recovery and secondary pollution associated with traditional adsorption materials, this invention utilizes the cross-linking reaction of sodium alginate and calcium chloride to further prepare structurally stable and magnetically excellent magnetic biochar spheres. These magnetic biochar spheres are applied to the efficient treatment of antibiotic wastewater, exhibiting rapid separation and recycling characteristics, effectively reducing wastewater treatment costs, and achieving the harmless treatment and resource utilization of antibiotic bacterial residue. This demonstrates excellent environmental benefits and economic value, providing a new approach for the green treatment and high-value utilization of antibiotic bacterial residue.

[0008] Specifically, the preparation method of the present invention includes the following steps:

[0009] (1) After freezing the antibiotic bacterial residue, it is freeze-dried under vacuum, then crushed and sieved to obtain antibiotic bacterial residue powder;

[0010] (2) Mix and grind the antibiotic residue powder with anhydrous ferric chloride evenly, pyrolyze it under a nitrogen protective atmosphere with a gradient temperature increase, cool it to room temperature and grind it to obtain biochar powder.

[0011] (3) The biochar powder obtained in step (2) is acid washed, then washed with pure water until neutral, and dried to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar.

[0012] (4) Dissolve sodium alginate and polyvinyl alcohol in pure water, then add the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar obtained in step (3), stir evenly, and obtain a uniform composite slurry.

[0013] (5) The uniform composite slurry obtained in step (4) is added dropwise to the calcium chloride solution. After full cross-linking, it is washed with pure water to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon balls.

[0014] In step (1) above, the freezing temperature of the antibiotic bacterial residue is -25 to -15℃ and the freezing time is 12 to 48 hours; the vacuum freeze-drying temperature is -50 to -60℃; after pulverization, it is sieved using a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0015] In step (2) above, the mass ratio of antibiotic residue powder to anhydrous ferric chloride is 1:(0.5-2). The pyrolysis method is to heat to 400-800℃ at a heating rate of 4-10℃ / min and keep it at that temperature for 2-4 hours. The nitrogen gas flow rate is 20-50ml / min.

[0016] In step (3) above, the solution for acid washing of biochar powder is a 0.5-2M hydrochloric acid solution, and the acid washing time is 0.5-2h.

[0017] In step (4) above, the mass percentage of sodium alginate is 1% to 3%, the mass percentage of polyvinyl alcohol is 0.5% to 2%, and the mass percentage of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar is 1% to 3%.

[0018] In step (5) above, the mass percentage concentration of calcium chloride solution is 3% to 5%, and the cross-linking time is 24 to 48 hours.

[0019] The present invention has the following advantages and beneficial effects:

[0020] (1) This invention replaces the traditional heat pre-drying process with freeze-drying technology, avoiding the problems of volatile organic pollutants and odor pollution during heat pre-drying, thus reducing environmental pollution at the source. Then, the combined pyrolysis technology completely degrades the residual antibiotics in the antibiotic bacterial residue, realizing the harmless treatment of hazardous waste and converting it into high-value-added biocarbon materials, significantly reducing carbon emissions from solid waste treatment, and taking into account both environmental benefits and resource utilization.

[0021] (2) The present invention realizes in-situ nitrogen doping technology through the "freeze-drying-pyrolysis" process, introduces nitrogen-containing functional groups into the carbon skeleton of antibiotic bacterial residue-based magnetic biocarbon, achieves nitrogen doping without the need to add external sources, and significantly enhances the adsorption performance of biocarbon.

[0022] (3) This invention enables rapid separation and recycling through iron doping and magnetization and sodium alginate cross-linking process, avoiding the problems of difficult recycling and easy secondary pollution of traditional adsorption materials. It is applied to the efficient treatment of antibiotic wastewater and has significant environmental benefits and economic value. Attached Figure Description

[0023] Figure 1 The above are the EDS spectra of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon prepared in Examples 2-5 of this invention.

[0024] Figure 2 The N 1s high-resolution XPS spectrum of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon INBC700 prepared in this invention.

[0025] Figure 3 The hysteresis loops of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon prepared in Examples 2-5 of this invention.

[0026] Figure 4 The N 1s high-resolution XPS spectrum of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon INBC700 after adsorption of antibiotics prepared in this invention.

[0027] Figure 5 SEM image of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon INBC500 prepared according to the present invention.

[0028] Figure 6 SEM image of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon INBC600 prepared according to the present invention.

[0029] Figure 7 SEM image of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon INBC700 prepared according to the present invention.

[0030] Figure 8 SEM image of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon INBC800 prepared according to the present invention.

[0031] Figure 9 The N2 adsorption-desorption isotherms of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon prepared in Examples 2-5 of this invention are shown.

[0032] Figure 10 This is a magnetic attraction diagram of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon spheres prepared according to the present invention.

[0033] Figure 11 The diagram shows the cycling performance of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon balls prepared according to this invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings, comparative examples, and specific embodiments.

[0035] This invention uses protein-rich penicillin fermentation residue to prepare in-situ nitrogen-doped magnetic biochar. Through screening and optimization of carbonization conditions and in-situ nitrogen-doped magnetic biochar pelleting process, an in-situ nitrogen-doped antibiotic residue-based magnetic biochar pellet is prepared that can be used for efficient adsorption of antibiotic wastewater and is easy to recycle.

[0036] Example 1:

[0037] (1) After freezing the antibiotic bacterial residue at -25℃ for 12 to 24 hours, freeze-dry it under vacuum at -50 to -60℃, then pulverize it and pass it through a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0038] (2) Mix and grind the antibiotic residue powder with anhydrous ferric chloride at a mass ratio of 1:2. Under a nitrogen protective atmosphere with an aeration rate of 20-50 ml / min, heat to 400℃ for 2 hours at a heating rate of 4-10℃ / min. After cooling to room temperature, grind to obtain biochar powder.

[0039] (3) The obtained biochar powder was acid-washed with 1M hydrochloric acid solution for 1 hour, then washed with pure water until neutral, and dried to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar, denoted as INBC400.

[0040] Example 2:

[0041] (1) After freezing the antibiotic bacterial residue at -15℃ for 12 to 24 hours, freeze-dry it under vacuum at -50 to -60℃, then pulverize it and pass it through a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0042] (2) Mix and grind the antibiotic residue powder with anhydrous ferric chloride at a mass ratio of 1:1. Under a nitrogen protective atmosphere with an aeration rate of 20-50 ml / min, heat to 500℃ for 2 hours at a heating rate of 4-10℃ / min. After cooling to room temperature, grind to obtain biochar powder.

[0043] (3) The obtained biochar powder was acid-washed with 1M hydrochloric acid solution for 1 hour, then washed with pure water until neutral, and dried to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar, denoted as INBC500.

[0044] Example 3:

[0045] (1) After freezing the antibiotic bacterial residue at -20℃ for 12 to 24 hours, freeze-dry it under vacuum at -50 to -60℃, then pulverize it and pass it through a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0046] (2) Mix and grind the antibiotic residue powder with anhydrous ferric chloride at a mass ratio of 1:1. Under a nitrogen protective atmosphere with an aeration rate of 20-50 ml / min, heat to 600℃ for 2 hours at a heating rate of 4-10℃ / min. After cooling to room temperature, grind to obtain biochar powder.

[0047] (3) The obtained biochar powder was acid-washed with 1M hydrochloric acid solution for 1 hour, then washed with pure water until neutral, and dried to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar, denoted as INBC600.

[0048] Example 4:

[0049] (1) After freezing the antibiotic bacterial residue at -20℃ for 12 to 24 hours, freeze-dry it under vacuum at -50 to -60℃, then pulverize it and pass it through a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0050] (2) Mix and grind the antibiotic residue powder with anhydrous ferric chloride at a mass ratio of 1:1. Under a nitrogen protective atmosphere with an aeration rate of 20-50 ml / min, heat to 700℃ for 2 hours at a heating rate of 4-10℃ / min. After cooling to room temperature, grind to obtain biochar powder.

[0051] (3) The obtained biochar powder was acid-washed with 1M hydrochloric acid solution for 1 hour, then washed with pure water until neutral, and dried to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar, denoted as INBC700.

[0052] Example 5:

[0053] (1) After freezing the antibiotic bacterial residue at -20℃ for 12 to 24 hours, freeze-dry it under vacuum at -50 to -60℃, then pulverize it and pass it through a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0054] (2) Mix and grind the antibiotic residue powder with anhydrous ferric chloride at a mass ratio of 1:1. Under a nitrogen protective atmosphere with an aeration rate of 20-50 ml / min, heat to 800℃ for 2 hours at a heating rate of 4-10℃ / min. After cooling to room temperature, grind to obtain biochar powder.

[0055] (3) The obtained biochar powder was acid-washed with 1M hydrochloric acid solution for 1 hour, then washed with pure water until neutral, and dried to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar, denoted as INBC800.

[0056] The penicillin residue in dry-based antibiotic fermentation residue and the in-situ nitrogen-doped antibiotic fermentation residue-based magnetic biochar obtained in Examples 1-5 was determined, and the results are shown in Table 1. The penicillin residue content in the dry-based residue was 1218.63 µg / kg. After pyrolysis treatment at 400℃ to 800℃, no residual penicillin was detected in the in-situ nitrogen-doped antibiotic fermentation residue-based magnetic biochar INBC400, INBC500, INBC600, INBC700, and INBC800. These results indicate that penicillin can be completely eliminated during pyrolysis at 400℃ and above, effectively controlling the environmental risk of antibiotic residues in antibiotic fermentation residue.

[0057] Table 1. Penicillin Residue in Dry-Based Microbial Residue and In-situ Nitrogen-Doped Antibiotic Microbial Residue-Based Magnetic Biochar in Examples 1-5

[0058]

[0059] The elemental composition of the dry-based antibiotic bacterial residue and the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar obtained in Examples 2-5 was determined, and the results are shown in Table 2. The dry-based bacterial residue contained 54.23% rich crude protein, resulting in a high nitrogen content of 8.93%. INBC500, INBC600, INBC700, and INBC800 contained high nitrogen contents of 4.61%–7.47%, indicating that high-level in-situ nitrogen doping was achieved during the pyrolysis of the dry-based bacterial residue without the need for an external nitrogen source, which is beneficial for enhancing the pollutant removal performance of the biochar. The elemental distribution and speciation of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar were analyzed using energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). EDS results (…) Figure 1 This also confirmed the doping of N element in INBC500, INBC600, INBC700 and INBC800. Figure 2 XPS results further indicate that N in INBC700 mainly exists in the form of N oxide, graphitic N, pyrrole N, and pyridine N.

[0060] Table 2. Magnetic biocarbon elemental composition of dry-based bacterial residue and in-situ nitrogen-doped antibiotic bacterial residue in Examples 2-5

[0061]

[0062] The magnetic properties of biochar are very important for adsorbent separation. Figure 3The hysteresis loops of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar obtained in Examples 2–5 are shown. The saturation magnetizations of INBC500, INBC600, INBC700, and INBC800 are 1.50 emu / g, 6.21 emu / g, 15.46 emu / g, and 9.20 emu / g, respectively. This magnetic characteristic allows the biochar to be effectively separated from aqueous solution under the influence of an external magnetic field. In the absence of a magnetic field, its inherent superparamagnetism allows it to disperse uniformly and rapidly in aqueous solution, which is beneficial for the separation and reuse of biochar in practical applications.

[0063] Comparative Example 1:

[0064] (1) After freezing the antibiotic bacterial residue for 12 to 24 hours, freeze-dry it under vacuum at -50 to -60°C, then pulverize it and pass it through a 200-mesh sieve to obtain antibiotic bacterial residue powder with a particle size of less than 200 mesh.

[0065] (2) Mix and grind the antibiotic bacterial residue powder with anhydrous ferric chloride at a mass ratio of 1:1. Under a nitrogen protective atmosphere with an aeration rate of 20-50 ml / min, heat to 800℃ for 2 hours at a heating rate of 4-10℃ / min. After cooling to room temperature, grind to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon, denoted as INBC800-NA.

[0066] (3) INBC800-NA was added to an antibiotic solution with an initial concentration of 10 mg / L at a dosage of 0.3 g / L (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, tetracycline TC). The solution was adsorbed for 24 h at 25 °C and 200 rpm. After INBC800-NA was separated by applying a magnetic field, the concentration of the remaining antibiotic in the solution was measured, and the amount of antibiotic adsorbed by INBC800-NA was calculated.

[0067] Comparative Example 2:

[0068] The purchased commercial activated carbon was passed through a 200-mesh sieve and then added to antibiotic solutions with an initial concentration of 10 mg / L (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, and tetracycline TC) at a dosage of 0.3 g / L. The solutions were adsorbed for 24 h at 25 °C and 200 rpm. After filtering to separate the commercial activated carbon, the concentration of the remaining antibiotics in the solution was measured, and the adsorption capacity of the commercial activated carbon for the antibiotics was calculated.

[0069] Example 6:

[0070] The in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar obtained in Examples 1-5 was added at a dosage of 0.3 g / L to antibiotic solutions with an initial concentration of 10 mg / L (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, and tetracycline TC). After adsorption for 24 h at 25 °C and 200 rpm, the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar was separated by applying a magnetic field. The concentration of remaining antibiotics in the solution was measured, and the adsorption capacity of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar for antibiotics was calculated.

[0071] As shown in Table 3, within the temperature range of 400℃ to 700℃ in Examples 1-4, the adsorption capacity of antibiotics by in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar gradually increased with increasing temperature. With further temperature increases, the increase in antibiotic adsorption capacity at 800℃ in Example 5 was not significant. These results demonstrate the influence of pyrolysis temperature on the adsorption performance of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar. The pyrolysis condition of 700℃ in Example 4 better balances adsorption performance and energy consumption. Comparative Example 1, using a pyrolysis temperature of 800℃, showed a significant decrease in adsorption performance compared to Example 5, indicating that the acid washing process effectively improved the adsorption performance of the biochar. Compared to Comparative Example 2, the high adsorption capacity in Examples 2-5 proves the excellent adsorption performance of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar.

[0072] Table 3. Adsorption capacity of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar and commercial activated carbon for antibiotics.

[0073]

[0074] The mechanism of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon adsorption of antibiotics was analyzed using XPS. Figure 4 The image shows the 1s high-resolution XPS spectra of N after adsorption of SMX, NOR, OTC, and TC by in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar prepared under 700℃ pyrolysis conditions in Example 4. The drift of graphite N after antibiotic adsorption confirms the participation of graphite N in the adsorption process. The proportion of nitrogen oxides (14.47%) in INBC700 decreased to 7.87%, 9.57%, 12.90%, and 13.06% after adsorption of SMX, NOR, OTC, and TC, respectively (Table 4), indicating that N oxides play an important role in the antibiotic adsorption process. The drift of graphite N after SMX adsorption was the most significant, and the decrease in the proportion of N oxides was the most pronounced, which corresponds to the highest adsorption capacity exhibited by SMX compared to other antibiotics. This result confirms that the high content of N in-situ doped antibiotic bacterial residue-based biochar plays an important role in the adsorption of antibiotics.

[0075] Table 4. Changes in N-containing functional groups before and after adsorption of antibiotics by magnetic biochar based on nitrogen-doped antibiotic bacterial residue prepared at 700℃.

[0076]

[0077] To further illustrate the effect of in-situ nitrogen doping on the structure and properties of antibiotic bacterial residue-based magnetic biochar, scanning electron microscopy (SEM) and a fully automated specific surface area and porosity analyzer were used to analyze the biochar obtained in Examples 2-5. Comparative Example 2 ( Figure 5 ) and Example 3 ( Figure 6 SEM image of Example 4 () Figure 7 ) and Example 5 ( Figure 8 The SEM images of the biochar showed a rougher surface, exhibiting flocculent and sheet-like structures. This may be due to the collapse of the microporous structure under high-temperature conditions, which facilitates the diffusion of antibiotics within the biochar. Figure 9 The N2 adsorption-desorption isotherm diagram of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar is shown in Table 5. The calculated specific surface area and pore structure data are shown in Table 5. In Examples 2 and 3, the specific surface areas of INBC500 and INBC600 were 710.74 cm², respectively. 2 / g and 825.84 cm 2 / g, with the contribution of microporous structure being dominant, at 0.65 and 0.61 respectively. As the temperature continued to rise to 700-800°C in Examples 4-5, the specific surface area of ​​INBC700 and INBC800 decreased to 561.01 cm². 2 / g and 654.95 cm 2 / g, the contribution of microporous structure decreases. This is because the biocarbon skeleton is further etched under high temperature conditions, prompting more micropores to transform into mesopores, increasing the average pore size from 2.12 nm to 2.78 nm, which is beneficial to improving its adsorption performance for antibiotics.

[0078] Table 5. Specific surface area and pore size data of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar

[0079]

[0080] Example 7:

[0081] (1) Sodium alginate and polyvinyl alcohol were dissolved in pure water at a mass percentage of 2% and 1% respectively, and then 2% of antibiotic bacterial residue-based magnetic biochar INBC700 obtained in Example 4 was added and stirred evenly to obtain a composite slurry.

[0082] (2) The composite slurry obtained in step (1) is added dropwise to a 5% calcium chloride solution. After complete cross-linking, it is washed with pure water to obtain INBC700 carbon spheres, which are then stored in a pure aqueous solution for later use. INBC700 carbon spheres have good magnetic properties. Figure 10 It is easy to collect and facilitates recycling and reuse.

[0083] (3) The INBC700 wet carbon balls obtained in step (2) were added to an antibiotic solution (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, tetracycline TC) with an initial concentration of 10 mg / L at a dosage of 1.5 g / L (the effective dosage of INBC700 is 0.03 g / L). After adsorption for 24 h at 25 °C and 200 rpm, the INBC700 carbon balls were separated by applying a magnetic field.

[0084] The concentration of residual antibiotics in the solution was determined, and the adsorption capacity of INBC700 wet carbon beads for antibiotics was calculated. The adsorption capacities of INBC700 wet carbon beads for SMX, NOR, OTC, and TC were 120.77, 184.24, 67.35, and 48.07 mg / g, respectively (based on the effective dosage of INBC700), demonstrating excellent antibiotic removal capabilities.

[0085] The regeneration performance and stability of the INBC700 carbon spheres prepared in Example 7 were studied using methanol regeneration. One cycle consisted of antibiotic adsorption followed by methanol desorption, and a total of five cycles were performed. Figure 11 As shown, after 5 cycles, it still has good adsorption performance, indicating that the INBC700 carbon balls have good regeneration performance.

[0086] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered as equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A method for preparing in-situ nitrogen-doped antibiotic sludge-based magnetic biochar spheres, characterized in that, It comprises the following steps: (1) The antibiotic bacterial residue is frozen, then vacuum freeze-dried, the freezing temperature is-25 to-15℃, the freezing time is 12 to 48h, the vacuum freeze-drying temperature is-50 to-60℃, then crushed, sieved, and the antibiotic bacterial residue powder is obtained; (2) The antibiotic bacterial residue powder is mixed with anhydrous ferric chloride and uniformly ground, then pyrolyzed under a gradient temperature rise in a nitrogen protective atmosphere, and crushed after cooling to room temperature, and the bio-carbon powder is obtained; the pyrolysis method is to heat to 500 to 800℃ at a temperature rise rate of 4 to 10℃ / min, and keep the temperature for 2 to 4h, and the nitrogen gas flow rate is 20 to 50ml / min; (3) The bio-carbon powder obtained in step (2) is pickled, then washed with pure water until neutral, dried, and the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon containing 4.61% to 7.47% high content N is obtained; the N element exists in the form of oxidized N, graphite N, pyrrole N and pyridine N; (4) Sodium alginate and polyvinyl alcohol are dissolved in pure water, then the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon obtained in step (3) is added, stirred uniformly, and the uniform composite slurry is obtained; (5) The uniform composite slurry obtained in step (4) is added dropwise into a calcium chloride solution, crosslinked sufficiently, then washed with pure water, and the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon spheres are obtained.

2. The production method according to claim 1, characterized by, The antibiotic bacterial residue in step (1) is penicillin fermentation bacterial residue rich in protein.

3. The preparation method according to claim 1, characterized in that, The mass ratio of antibiotic bacterial residue powder to anhydrous ferric chloride in step (2) is 1:(0.5 to 2).

4. The method of claim 1, wherein, The solution for pickling the bio-carbon powder in step (3) is a 0.5 to 2M hydrochloric acid solution, and the pickling time is 0.5 to 2h.

5. The preparation method according to claim 1, characterized in that, The mass percentage of sodium alginate in step (4) is 1% to 3%, the mass percentage of polyvinyl alcohol is 0.5% to 2%, and the mass percentage of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon is 1% to 3%.

6. The method of claim 1, wherein, The mass percentage concentration of the calcium chloride solution in step (5) is 3% to 5%, and the crosslinking time is 24 to 48h.

7. The in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon spheres prepared by the preparation method in any one of claims 1 to 6.

8. The use of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon spheres in claim 7 for antibiotic wastewater treatment.

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