Preparation method and application of in-situ nitrogen-doped antibiotic mushroom dreg-based magnetic biological carbon spheres

Abstract

The invention discloses a preparation method and application of in-situ nitrogen-doped antibiotic mushroom dreg-based magnetic biological carbon spheres, and belongs to the technical field of hazardous waste recycling and wastewater treatment. According to the method, the antibiotic mushroom dregs are used as a precursor, ferric trichloride is used as an iron source, the degradation of residual antibiotics and in-situ nitrogen atom doping are synchronously realized through a'freeze drying-pyrolysis' process under the condition of not adding an external nitrogen source by utilizing rich nitrogen elements of the antibiotic mushroom dregs, and the physical and chemical properties of the biological carbon material are improved; therefore, the adsorption performance is enhanced; and further preparing the magnetic biological carbon spheres with stable structure and excellent magnetism by utilizing a cross-linking reaction of sodium alginate and calcium chloride. The magnetic biological carbon sphere is applied to efficient treatment of antibiotic wastewater, has the characteristics of rapid separation and cyclic utilization, effectively reduces the wastewater treatment cost, realizes harmless treatment and resource utilization of antibiotic residues, and shows excellent environmental benefits and economic values.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hazardous waste resource utilization and wastewater treatment, and particularly relates to a preparation method and application of antibiotic bacteria residue-based magnetic biochar spheres with high efficiency and easy recovery. BACKGROUND

[0002] Antibiotic bacteria residue refers to solid waste generated after the effective components of fermentation liquor are extracted through filter pressing technology in the process of antibiotic fermentation production. The annual output of antibiotic bacteria residue in China 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 listed in the National Hazardous Waste List, which needs to be strictly monitored and properly treated in accordance with the requirements of hazardous waste environmental management.

[0003] At present, the harmless treatment of antibiotic bacteria residue mainly adopts high-temperature incineration technology to realize harmless treatment through high-temperature decomposition of antibiotic residues. However, due to the low calorific value of antibiotic bacteria residue, additional energy is usually needed for its incineration treatment, which leads to significant increase in energy consumption and cost, with a treatment cost of about 3000 yuan / ton. In addition, a large amount of carbon emissions and release of dioxin and other refractory toxic pollutants will occur during the incineration process, which poses a risk of secondary environmental pollution. At the same time, the rich crude protein in antibiotic bacteria residue makes it have a high nitrogen content, and direct incineration treatment causes waste of resources, which does not meet the current green development requirements of solid waste resource utilization and carbon emission reduction. Therefore, it is of great practical significance to develop a technology that can realize the harmless treatment and resource utilization of antibiotic bacteria residue.

[0004] Chinese patent application CN 115672951 A discloses an efficient harmless treatment method for antibiotic bacteria residue, which uniformly mixes a mixture of nitric acid and sulfuric acid with antibiotic bacteria residue, and then completely degrades the antibiotics through 40-200℃ hydrothermal reaction. This technology has strong acid corrosion and safety hazards, and will produce a large amount of strong acid waste liquid, which is easy to cause secondary pollution. Chinese patent application CN 117025247 A discloses a harmless and resourceful treatment method for antibiotic bacteria residue, which recovers bio-oil and biochar products by pyrolyzing preheated and dried antibiotic bacteria residue powder, and the biochar products can be used for soil remediation treatment. However, the actual application feasibility of the biochar products has not been evaluated. Chinese patent application CN 115138333 A discloses a harmless and resourceful utilization method for calcium / iron-rich antibiotic bacteria residue, which mixes vancomycin fermentation residue with limestone, calcium sulfate and polymeric ferric sulfate, and then carbonizes the mixture after drying to obtain magnetic biochar. This technology needs to add limestone, calcium sulfate, polymeric ferric sulfate and other reagents to adjust the calcium and iron content and water content of the bacteria residue, which increases the raw material cost and process complexity.

[0005] In summary, it is particularly necessary to develop a green, economical and efficient harmless and resource utilization technology of antibiotic bacterial residue. SUMMARY

[0006] In view of the problems existing in the prior art, the purpose of the present application is to provide a green, economical and efficient preparation method and application of in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar spheres. The method can realize the harmless treatment and resource utilization of hazardous waste, convert antibiotic bacterial residue into in-situ nitrogen-doped magnetic biochar spheres with high adsorption performance and easy recovery, and apply the magnetic biochar spheres to efficient treatment of antibiotic wastewater, thereby realizing the "triple" goals of harmless and resource utilization of solid waste, wastewater treatment and carbon emission reduction.

[0007] The present application uses antibiotic bacterial residue as a precursor, ferric chloride as an iron source, and utilizes the rich nitrogen elements of antibiotic bacterial residue to realize the degradation of residual antibiotics and in-situ nitrogen atom doping simultaneously under the condition of not adding external nitrogen source through the "freeze-drying-pyrolysis" process, thereby improving the physicochemical properties of biochar materials and enhancing the adsorption performance thereof. In addition, in order to solve the problems of difficult recovery and easy secondary pollution of traditional adsorption materials, the cross-linking reaction of sodium alginate and calcium chloride is utilized to further prepare magnetic biochar spheres with stable structure and excellent magnetism. The magnetic biochar spheres are applied to efficient treatment of antibiotic wastewater, have the characteristics of rapid separation and cyclic utilization, effectively reduce the cost of wastewater treatment, realize the harmless treatment and resource utilization of antibiotic bacterial residue, exhibit excellent environmental benefits and economic value, and provide a new idea for green treatment and high-value utilization of antibiotic bacterial residue.

[0008] Specifically, the preparation method of the present application comprises the following steps:

[0009] (1) freeze the antibiotic bacterial residue, perform vacuum freeze-drying, then crush, sieve and obtain antibiotic bacterial residue powder;

[0010] (2) mix and grind the antibiotic bacterial residue powder and anhydrous ferric chloride uniformly, perform pyrolysis under a gradient temperature rise in a nitrogen protective atmosphere, grind after cooling to room temperature, and obtain biochar powder;

[0011] (3) perform acid pickling on the biochar powder obtained in step (2), then wash to neutral with pure water, dry and 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 uniformly and obtain a uniform composite slurry;

[0013] (5) The uniform composite slurry obtained in step (4) is dropped into a calcium chloride solution drop by drop, and after sufficient crosslinking, pure water is used for washing to obtain antibiotic-straw-based magnetic biochar spheres with in-situ nitrogen doping.

[0014] The freezing temperature of the antibiotic straw in the above step (1) is -25 to -15 DEG C, and the freezing time is 12 to 48 h; the vacuum freeze-drying temperature is -50 to -60 DEG C; after crushing, a 200-mesh screen is used for screening to obtain antibiotic straw powder with a particle size of less than 200 mesh.

[0015] In the above step (2), the mass ratio of the antibiotic straw powder to anhydrous ferric chloride is 1:(0.5-2), the pyrolysis method is heating at a heating rate of 4-10 DEG C / min to 400-800 DEG C and holding for 2-4 h, and the nitrogen gas flow rate is 20-50 ml / min.

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

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

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

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

[0020] (1) The present application replaces the traditional thermal pre-drying process with freeze-drying technology, avoiding the problems of volatile organic pollutants and odor pollution in the thermal pre-drying process, and reducing environmental pollution from the source. Then, combined with pyrolysis technology, the residual antibiotics in antibiotic straw are completely degraded, realizing the harmless treatment of hazardous waste, and converting it into high-value biochar materials, significantly reducing the carbon emissions of solid waste treatment, and taking into account environmental benefits and resource utilization.

[0021] (2) The present application realizes in-situ nitrogen doping technology through the "freeze-drying-pyrolysis" process, introducing nitrogen-containing functional groups into the carbon skeleton of antibiotic-straw-based magnetic biochar, without the need for external addition to achieve nitrogen doping, significantly enhancing the adsorption performance of biochar.

[0022] (3) The present application realizes rapid separation and recycling function through the balling process of iron doping and sodium alginate crosslinking, avoiding the problems of difficult recovery and easy secondary pollution of traditional adsorbent materials, and is applied to efficient treatment of antibiotic wastewater, having significant environmental benefits and economic value. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 This is the EDS energy spectrum of the in-situ nitrogen-doped antibiotic bacteria residue-based magnetic biocarbon prepared in Examples 2-5 of the present invention.

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

[0025] Figure 3 This is the hysteresis loop of the in-situ nitrogen-doped antibiotic bacteria residue-based magnetic biocarbon prepared in Examples 2-5 of the present invention.

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

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

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

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

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

[0031] Figure 9 This is the N2 adsorption-desorption isotherm of the in situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar prepared in Examples 2-5 of the present invention.

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

[0033] Figure 11 This is a cycle performance diagram of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon spheres prepared in the present invention. DETAILED DESCRIPTION

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

[0035] The application selects penicillin fermentation residue rich in protein to prepare in-situ nitrogen-doped magnetic biochar, and through screening and optimization of carbonization conditions and in-situ nitrogen-doped magnetic biochar ball forming process, in-situ nitrogen-doped antibiotic residue-based magnetic biochar balls which can be used for efficient adsorption of antibiotic wastewater and are easy to recover are prepared.

[0036] Example 1

[0037] (1) The antibiotic residue is frozen at -25 DEG C for 12-24 h, vacuum freeze-dried at -50 to -60 DEG C, then crushed, and sieved through a 200-mesh screen to obtain antibiotic residue powder with a particle size of less than 200 mesh;

[0038] (2) The antibiotic residue powder is mixed with anhydrous ferric chloride at a mass ratio of 1:2, uniformly ground, heated to 400 DEG C at a heating rate of 4-10 DEG C / min under a nitrogen atmosphere with a ventilation rate of 20-50 ml / min, pyrolyzed for 2 h, crushed after cooling to room temperature, and the biochar powder is obtained;

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

[0040] Example 2

[0041] (1) The antibiotic residue is frozen at -15 DEG C for 12-24 h, vacuum freeze-dried at -50 to -60 DEG C, then crushed, and sieved through a 200-mesh screen to obtain antibiotic residue powder with a particle size of less than 200 mesh;

[0042] (2) The antibiotic residue powder is mixed with anhydrous ferric chloride at a mass ratio of 1:1, uniformly ground, heated to 500 DEG C at a heating rate of 4-10 DEG C / min under a nitrogen atmosphere with a ventilation rate of 20-50 ml / min, pyrolyzed for 2 h, crushed after cooling to room temperature, and the biochar powder is obtained;

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

[0044] Example 3

[0045] (1) The antibiotic residue is frozen at -20 DEG C for 12-24 h, vacuum freeze-dried at -50 to -60 DEG C, then crushed, and sieved through a 200-mesh screen to obtain antibiotic residue powder with a particle size of less than 200 mesh;

[0046] (2) The antibiotic bacteria residue powder and anhydrous ferric chloride are mixed and ground uniformly at a mass ratio of 1:1, heated to 600°C at a heating rate of 4-10°C / min under a nitrogen protective atmosphere with a ventilation rate of 20-50 ml / min, pyrolyzed for 2 h, ground after cooling to room temperature, and antibiotic bacteria residue-based magnetic biochar powder is obtained;

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

[0048] Example 4:

[0049] (1) The antibiotic bacteria residue is frozen at -20°C for 12-24 h, vacuum freeze-dried at -50 to -60°C, then crushed and sieved through a 200-mesh screen to obtain antibiotic bacteria residue powder with a particle size of less than 200 mesh;

[0050] (2) The antibiotic bacteria residue powder and anhydrous ferric chloride are mixed and ground uniformly at a mass ratio of 1:1, heated to 700°C at a heating rate of 4-10°C / min under a nitrogen protective atmosphere with a ventilation rate of 20-50 ml / min, pyrolyzed for 2 h, ground after cooling to room temperature, and antibiotic bacteria residue-based magnetic biochar powder is obtained;

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

[0052] Example 5:

[0053] (1) The antibiotic bacteria residue is frozen at -20°C for 12-24 h, vacuum freeze-dried at -50 to -60°C, then crushed and sieved through a 200-mesh screen to obtain antibiotic bacteria residue powder with a particle size of less than 200 mesh;

[0054] (2) The antibiotic bacteria residue powder and anhydrous ferric chloride are mixed and ground uniformly at a mass ratio of 1:1, heated to 800°C at a heating rate of 4-10°C / min under a nitrogen protective atmosphere with a ventilation rate of 20-50 ml / min, pyrolyzed for 2 h, ground after cooling to room temperature, and antibiotic bacteria residue-based magnetic biochar powder is obtained;

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

[0056] Penicillin residues were measured in dry antibiotic bacterial residue and in situ nitrogen-doped antibiotic bacterial residue-based magnetic biochars obtained in Examples 1-5. The results are shown in Table 1. The penicillin residue in the dry bacterial residue was 1218.63 µg / kg. After pyrolysis at 400°C to 800°C, no penicillin residue was detected in the in situ nitrogen-doped antibiotic bacterial residue-based magnetic biochars (INBC400, INBC500, INBC600, INBC700, and INBC800). These results demonstrate that penicillin can be completely eliminated during pyrolysis at temperatures of 400°C and above, effectively controlling the environmental risk of antibiotic residues in antibiotic fermentation bacterial residues.

[0057] Table 1 Penicillin residues in dry-based fungus residue and in-situ nitrogen-doped antibiotic fungus residue-based magnetic biocarbon in Examples 1 to 5

[0058]

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

[0060] Table 2 Elemental composition of dry-based fungus residue and in-situ nitrogen-doped antibiotic fungus residue-based magnetic biocarbon in Examples 2 to 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-straw-based magnetic biochar obtained in Examples 2-5 are shown. The saturation magnetization of INBC500, INBC600, INBC700 and INBC800 is 1.50 emu / g, 6.21 emu / g, 15.46 emu / g and 9.20 emu / g, respectively. This magnetic characteristic makes the biochar effectively separated from the aqueous solution under the action of an external magnetic field, and its inherent superparamagnetism when no magnetic field is present makes it uniformly and rapidly dispersed in the aqueous solution, which is conducive to the separation and reuse of the biochar in practical applications.

[0063] Comparative Example 1:

[0064] (1) The antibiotic straw was frozen for 12-24 h, then vacuum freeze-dried at -50 to -60°C, then ground and sieved through a 200-mesh screen to obtain antibiotic straw powder with a particle size of less than 200 mesh;

[0065] (2) The antibiotic straw powder was mixed with anhydrous ferric chloride at a mass ratio of 1:1 and ground uniformly, then pyrolyzed at 800°C for 2 h under a nitrogen protective atmosphere with a gas flow rate of 20-50 ml / min and a heating rate of 4-10°C / min, then ground after cooling to room temperature to obtain in-situ nitrogen-doped antibiotic-straw-based magnetic biochar, denoted as INBC800-NA.

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

[0067] Comparative Example 2:

[0068] Commercial activated carbon purchased was sieved through a 200-mesh screen, then added to antibiotic solutions (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, tetracycline TC) with an initial concentration of 10 mg / L at a dosage of 0.3 g / L, and adsorbed for 24 h at 25°C and 200 rpm, then the commercial activated carbon was separated by filtration, the residual antibiotic concentration in the solution was determined, and the adsorption capacity of the commercial activated carbon for antibiotics was calculated.

[0069] Example 6:

[0070] The in-situ nitrogen-doped antibiotic-straw-based magnetic biochar obtained from Examples 1-5 was added into antibiotic solutions (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, tetracycline TC) with initial concentrations of 10 mg / L at a dosage of 0.3 g / L. After adsorption for 24 h at 25°C and 200 rpm, the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar was separated by applying a magnetic field. The residual antibiotic concentrations in the solutions were determined, and the adsorption capacities of the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar for antibiotics were calculated.

[0071] As shown in Table 3, in Examples 1-4, within the temperature range of 400-700°C, the adsorption capacities of the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar for antibiotics gradually increased as the temperature increased. As the temperature continued to increase, the increase in the adsorption capacity of antibiotics in Example 5 at 800°C was not significant. The above results illustrate the effect of pyrolysis temperature on the adsorption performance of the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar. The pyrolysis conditions of 700°C in Example 4 can better balance the adsorption performance and energy consumption. The adsorption performance of Comparative Example 1, which used a pyrolysis temperature of 800°C, was significantly lower than that of Example 5, indicating that the acid washing process effectively improved the adsorption performance of the biochar. Compared with Comparative Example 2, the high adsorption capacities of Examples 2-5 demonstrate the excellent adsorption performance of the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar.

[0072] Table 3 Adsorption capacities of in-situ nitrogen-doped antibiotic-straw-based magnetic biochar and commercial activated carbon for antibiotics

[0073]

[0074] The mechanism of adsorption of antibiotics by the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar was analyzed by XPS. Figure 4 N 1s high-resolution XPS spectra of the in-situ nitrogen-doped antibiotic-straw-based magnetic biochar prepared under pyrolysis conditions of 700°C in Example 4 after adsorption of SMX, NOR, OTC, and TC. The shift of graphitic N after adsorption of antibiotics confirms the involvement of graphitic N in the adsorption process. The proportion of oxidized nitrogen in INBC700 (14.47%) decreased to 7.87%, 9.57%, 12.90%, and 13.06% after adsorption of SMX, NOR, OTC, and TC, respectively (Table 4), indicating that oxidized N played an important role in the antibiotic adsorption process. The shift of graphitic N after adsorption of SMX was the most obvious, and the decrease in the proportion of oxidized N was the most significant, which also corresponded to the highest adsorption capacity exhibited by SMX in the adsorption process compared to other antibiotics. This result confirms that the high content of N in the in-situ nitrogen-doped antibiotic-straw-based biochar plays an important role in the adsorption of antibiotics.

[0075] Table 4 Changes of N-containing functional groups of antibiotic-straw-based magnetic biochar prepared at 700℃ before and after adsorbing antibiotics

[0076]

[0077] To further illustrate the influence of in-situ nitrogen doping on the structure and performance of antibiotic-straw-based magnetic biochar, scanning electron microscopy (SEM), automatic specific surface and porosity analyzer were used to analyze the biochar obtained in Examples 2-5. Comparing the SEM images of Comparative Example 2 ( Figure 5 ) and Example 3 ( Figure 6 ), the SEM images of Example 4 ( Figure 7 ) and Example 5 ( Figure 8 ) have a rougher surface, showing flocculent structure and sheet structure. This may be due to the collapse of microporous structure under high temperature conditions, which is beneficial to the diffusion of antibiotics inside the biochar. Figure 9 The N2 adsorption-desorption isotherm graph of in-situ nitrogen-doped antibiotic-straw-based magnetic biochar is shown in Figure 5. The specific surface area and pore structure data calculated are shown in Table 5. The specific surface areas of INBC500 and INBC600 in Examples 2-3 are 710.74 cm 2 / g and 825.84 cm 2 / g, respectively, in which the contribution of microporous structure occupies a dominant position, which is 0.65 and 0.61, respectively. As the temperature continues to rise to 700-800℃ in Examples 4-5, the specific surface areas of INBC700 and INBC800 decrease to 561.01 cm 2 / g and 654.95 cm 2 / g, respectively, and the contribution of microporous structure decreases. This is because the biochar skeleton is further etched under high temperature conditions, promoting more micropores to transform into mesopores, and the average pore size increases from 2.12 nm to 2.78 nm, which is beneficial to improve its adsorption performance for antibiotics.

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

[0079]

[0080] Example 7:

[0081] (1) Dissolve sodium alginate and polyvinyl alcohol in pure water according to 2% and 1% mass percentage, respectively, then add 2% antibiotic-straw-based magnetic biochar INBC700 obtained in Example 4, and stir uniformly to obtain a composite slurry;

[0082] (2) The composite slurry obtained in step (1) is dropped into 5% calcium chloride solution drop by drop, and INBC700 carbon spheres are obtained after sufficient crosslinking and pure water washing, and are stored in pure water solution for standby use. The INBC700 carbon spheres have good magnetism Figure 10 , are easy to collect, and are conducive to recycling and reuse.

[0083] (3) The INBC700 wet carbon spheres obtained in step (2) are added into antibiotic solutions (sulfamethoxazole SMX, norfloxacin NOR, oxytetracycline OTC, and 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), and are adsorbed for 24 h at 25°C and 200 rpm, and then the INBC700 carbon spheres are separated by applying a magnetic field.

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

[0085] The regeneration performance and stability of the INBC700 carbon spheres prepared in Example 7 are studied by using methanol regeneration. Antibiotic adsorption-methanol desorption is one cycle, and a total of five cycles are performed. As shown in Figure 11 , the INBC700 carbon spheres still have good adsorption performance after five cycles, indicating that the INBC700 carbon spheres have good regeneration performance.

[0086] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be considered as equivalent replacement modes, and all are included in the protection scope of the present application.

Claims

1. A method for preparing in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon spheres, characterized in that: The steps include: (1) Freezing the antibiotic residue, performing vacuum freeze drying, and then crushing and sieving to obtain antibiotic residue powder; (2) The antibiotic residue powder and anhydrous ferric chloride are mixed and ground evenly, and then pyrolyzed by increasing the temperature gradually under a nitrogen atmosphere. After cooling to room temperature, the powder is ground to obtain biochar powder; (3) acid-washing the biochar powder obtained in step (2), then washing it with pure water until it is neutral, and drying it to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biochar; (4) dissolving sodium alginate and polyvinyl alcohol in pure water, then adding the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon obtained in step (3), stirring evenly to obtain a uniform composite slurry; (5) The uniform composite slurry obtained in step (4) is added dropwise into a calcium chloride solution, and after sufficient cross-linking, it is washed with pure water to obtain in-situ nitrogen-doped antibiotic bacterial residue-based magnetic biocarbon balls.

2. The preparation method according to claim 1, characterized in that 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 In step (1), the freezing temperature of the antibiotic bacterial residue is -25 to -15°C, and the freezing time is 12 to 48 hours; the vacuum freeze-drying temperature is -50 to -60°C.

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

5. The preparation method according to claim 1, characterized in that The pyrolysis method in step (2) is to heat to 400-800°C at a heating rate of 4-10°C / min and keep warm for 2-4h, with a nitrogen ventilation rate of 20-50ml / min.

6. The preparation method according to claim 1, characterized in that In step (3), the solution for pickling the biochar powder is a 0.5-2M hydrochloric acid solution, and the pickling time is 0.5-2h.

7. The preparation method according to claim 1, characterized in that In step (4), 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%.

8. The preparation method according to claim 1, characterized in that The mass percentage concentration of the calcium chloride solution in step (5) is 3% to 5%, and the cross-linking time is 24 to 48 hours.

9. In situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon spheres prepared by the preparation method according to any one of claims 1 to 9.

10. Use of the in-situ nitrogen-doped antibiotic bacterial residue-based magnetic bio-carbon spheres according to claim 10 for treating antibiotic wastewater.

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