Modified sludge biochar as well as preparation method and application thereof

Abstract

The invention discloses modified sludge biochar as well as a preparation method and application thereof, and belongs to the technical field of sludge treatment. The preparation method of the modified sludge biochar comprises the following steps: carrying out gravity concentration on sludge, adding an iron-based dehydration conditioner, and stirring to obtain conditioned sludge; dehydrating the conditioned sludge to obtain dehydrated sludge cakes; pyrolyzing and carbonizing the dewatered cement cake, cooling, and sequentially crushing, grinding, sieving, cleaning and drying to obtain powdery charcoal; and carrying out modification treatment on the powdery biochar by adopting a modifier to obtain the modified sludge biochar. The invention also discloses the modified sludge biochar prepared by the preparation method and application of the modified sludge biochar in antibiotic wastewater treatment. The modified biochar prepared through a synergistic path of'dehydration strengthening, pyrolysis stabilization and functional modification 'has efficient adsorbability, environmental safety and economic feasibility, and the purpose of'treating waste with waste' is achieved when the modified biochar is used for adsorption and degradation of sulfamethoxazole.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and specifically relates to a modified sludge biochar and a preparation method and application thereof. Background Art

[0002] With the rapid economic development and the acceleration of urbanization, the amount of sewage and sludge generated worldwide each year has also increased dramatically. Sludge has a high water content and complex composition, and is rich in pollutants that have not been completely degraded during sewage treatment, such as bacteria, viruses, protozoa, parasites and other pathogenic organisms, heavy metals, nitrogen, phosphorus and other conventional pollutants and new pollutants. If the sludge cannot be effectively treated and disposed of in a timely manner, it will not only occupy valuable land resources, but may also pose risks to the environment and human health.

[0003] Sludge landfill and land use have high requirements for sludge. Although the cost is low and the operation is simple, the pollutants in the sludge cannot be completely removed; incineration is currently the most thorough way to dispose of sludge, but the ash and dioxins produced by combustion are harmful substances. Such treatment and disposal methods will have a certain impact on the ecological environment. Sludge pyrolysis, as an emerging thermochemical treatment technology, can achieve sludge reduction, stabilization and resource utilization under low environmental impact; the pyrolysis product sludge biochar is a cheap carbon-rich porous material with good adsorption properties and specific structural characteristics.

[0004] At the same time, my country's antibiotic pollution problems mainly come from three major areas: first, the high-concentration wastewater containing antibiotic mother liquor and intermediates generated during the production process of the pharmaceutical industry; second, the medical wastewater carrying unmetabolized antibiotics discharged during the diagnosis and treatment process of the medical system; and third, the agricultural non-point source pollution caused by the large-scale use of antibiotic feed additives in the aquaculture industry. At present, adsorption is considered to be the preferred process for treating wastewater containing antibiotics, because the adsorption method is simple and easy to operate, cost-effective and reusable, and different adsorbents can be selected according to actual economic needs to achieve the effect of both economic and performance.

[0005] How to modify sludge biochar and use it for antibiotic-contaminated wastewater to achieve “waste treatment with waste” is one of the current research hotspots in this field. Summary of the invention

[0006] The purpose of the present invention is to provide a modified sludge biochar and a preparation method and application thereof, so as to solve the problems of complex preparation process and poor adsorption performance of existing sludge biochar materials.

[0007] The technical solution adopted to achieve the above object is to provide a method for preparing modified sludge biochar, comprising the following steps: (1) After gravity concentrating the sludge, an iron-based dehydration conditioning agent is added and stirred to obtain conditioned sludge; (2) dehydrating the conditioned sludge to obtain a dehydrated sludge cake having a moisture content of 65-75%; (3) pyrolyzing and carbonizing the dehydrated cake, and then cooling it, crushing, grinding, sieving, washing and drying it in sequence to obtain powdered biochar; (4) The powdered biochar is modified by a modifier to obtain modified sludge biochar; the modifier is a phosphoric acid solution or a sodium hydroxide solution.

[0008] The beneficial effects of the above technical solution adopted in the present invention are as follows: the addition of the iron-based conditioning agent in the present invention combined with gravity concentration significantly improves the sludge dehydration efficiency and reduces the sludge adhesion effect; and through dehydration treatment, most of the surface adsorbed water and interstitial water in the sludge are removed, and the dehydrated water cake formed after dehydration is moist inside but not covered by a water layer, avoiding the sludge adhesion problem generated in the subsequent pyrolysis process. Using the dehydrated water cake with a water content of 65-75% for pyrolysis, the water molecules in the sludge continuously escape during the pyrolysis process, which is conducive to the formation of pores in the sludge biochar, so that it has a larger specific surface area; at the same time, the iron element provided by the iron-based conditioning agent can further catalyze the pyrolysis reaction, optimize the carbon structure and enhance the complexing ability of pollutants, so that the prepared powdered biochar itself has a good adsorption effect. On this basis, phosphoric acid solution or sodium hydroxide solution is used as a modifier to further optimize its pore structure and adsorption capacity. Phosphoric acid solution modification can etch the biochar surface to form a rich pore structure (such as mesopores / micropores), greatly improving the specific surface area and pollutant adsorption capacity; sodium hydroxide modification increases functional groups through surface hydroxylation, which can enhance the chemical adsorption of heavy metals or organic matter; the modified sludge biochar obtained in this way has a strong adsorption capacity.

[0009] Preferably, in step (1), the iron-based dehydration conditioning agent is a polyferric sulfate solution with a mass fraction of 30-35%; the addition amount of the iron-based dehydration conditioning agent is 8-12% of the dry mass of the sludge.

[0010] More preferably, in step (1), the iron-based dehydration conditioning agent is a 33.3% by mass polyferric sulfate solution; and the dosage of the iron-based dehydration conditioning agent is 10% of the dry mass of the sludge.

[0011] Preferably, the stirring in step (1) comprises the following steps: stirring at 300-500 rpm for 20-40 s, stirring at 50-200 rpm for 2-5 min, and standing for 20-40 min after the stirring is completed.

[0012] More preferably, the stirring in step (1) comprises the following steps: stirring at 400 rpm for 30 seconds, stirring at 100 rpm for 3 minutes, and standing for 30 minutes after the stirring is completed.

[0013] Preferably, the dehydration in step (2) is carried out by suction filtration and pressure filtration in sequence.

[0014] More preferably, the filtration is carried out using a Buchner funnel with a vacuum pump condition of 0.05 MPa; the pressure condition for the filter press is 240 kg.

[0015] Preferably, the pyrolysis carbonization in step (3) is carried out under an inert atmosphere, with a heating rate of 8-12°C / min, a temperature of 700-900°C, and a time of 50-80min.

[0016] More preferably, the pyrolysis carbonization in step (3) is carried out in a nitrogen atmosphere, with a heating rate of 10°C / min, a temperature of 800°C, and a time of 60 min.

[0017] More preferably, the cooling in step (3) is performed under a nitrogen atmosphere.

[0018] Preferably, step (4) comprises the following steps: adding the powdered biochar to a phosphoric acid solution or a sodium hydroxide solution and shaking and soaking it for 3 to 5 hours, washing the precipitate until the washing solution is neutral, and then drying it to a constant weight to obtain modified sludge biochar.

[0019] More preferably, step (4) comprises the following steps: adding the powdered biochar to a phosphoric acid solution or a sodium hydroxide solution and soaking it at 150 rpm for 4 hours, washing the precipitate with deionized water until the washing solution is neutral, and then drying it to a constant weight to obtain modified sludge biochar.

[0020] Preferably, the mass fraction of the phosphoric acid solution is 45-55%, and the molar concentration of the sodium hydroxide solution is 1.8-2.2 mol / L.

[0021] More preferably, the mass fraction of the phosphoric acid solution is 50%, and the molar concentration of the sodium hydroxide solution is 2 mol / L.

[0022] Preferably, the mass ratio of powdered biochar to modifier is 1:40~60.

[0023] More preferably, the mass ratio of powdered biochar to modifier is 1:50.

[0024] The present invention also provides modified sludge biochar prepared by the above preparation method.

[0025] The present invention also provides application of the modified sludge biochar in the treatment of antibiotic wastewater.

[0026] Preferably, the antibiotic wastewater is sulfamethoxazole wastewater.

[0027] The present invention has the following beneficial effects: (1) The present invention uses polyferric sulfate to condition and dehydrate the sludge, and attaches iron elements to the sludge surface, which can effectively assist the sludge dehydration and provide more adsorption sites for the biochar after pyrolysis. The modified sludge biochar obtained in this way can not only effectively adsorb pollutants, but the attachment of iron elements also makes its adsorption effect better.

[0028] (2) The preparation method of the present invention first obtains wet sludge by concentrating and dehydrating the sludge, and then directly pyrolyzes the wet sludge under anaerobic conditions at high temperature to obtain sludge biochar material. Compared with other sludge-based biochars, the sludge biochar material has a better adsorption effect and can effectively remove antibiotics in wastewater, thereby achieving the purpose of sludge disposal and resource utilization.

[0029] (3) The present invention solves the pain points of high pollution risk and low utilization value in sludge treatment through the synergistic path of "dehydration enhancement-pyrolysis stabilization-functional modification". The modified biochar obtained has high adsorption efficiency, environmental safety and economic feasibility. It is used for the adsorption and degradation of sulfamethoxazole, achieving the purpose of "treating waste with waste". BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The flowchart of the preparation of modified sludge biochar; Figure 2 are SEM images of sludge biochar; wherein, (a) is the SEM image of the sludge biochar of comparative example 1; (b) is the SEM image of the modified sludge biochar of comparative example 2; (c) is the SEM image of the modified sludge biochar of example 1; (d) is the SEM image of the modified sludge biochar of example 2; Figure 3 This is the adsorption and desorption curve of the sludge biochar of Comparative Example 1; Figure 4 This is the adsorption and desorption curve of the modified sludge biochar in Example 1; Figure 5 This is the adsorption and desorption curve of the modified sludge biochar in Example 2; Figure 6 This is the pore size and volume diagram of the sludge biochar in comparative example 1; Figure 7 This is the pore size and volume diagram of the modified sludge biochar in Example 1; Figure 8 This is the pore size and pore volume diagram of the modified sludge biochar in Example 2. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0032] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0033] The features and performance of the present invention are further described in detail below in conjunction with the examples. The coconut shell activated carbon is from Pingdingshan Lvlin Activated Carbon Co., Ltd., with a specification of 2-4 mm.

[0034] Example 1 A method for preparing modified sludge biochar comprises the following steps: (1) After the municipal sludge is allowed to stand for 24 hours, the supernatant is removed to obtain concentrated sludge; 200 mL of concentrated sludge is taken into a 250 mL beaker, and a polyferric sulfate solution of 10% of the dry weight of the sludge is added thereto, and the mixture is placed on a magnetic stirrer and stirred at 400 rpm for 30 seconds, and then stirred at 100 rpm for 3 minutes. After the stirring is completed, the mixture is allowed to stand for 30 minutes to obtain conditioned sludge; (2) Pour the conditioned sludge into a Buchner funnel for sludge filtration, set the vacuum pump to 0.05 MPa, and continue to filter until the mud cake cracks; take the filtered mud cake and wrap it in a filter cloth for pressure filtration, press filter at 240 kg until its water content is 70%, and obtain a dehydrated mud cake; (3) 50 g of dehydrated water cake was placed in a porcelain boat, which was placed in a tube furnace. Under a nitrogen atmosphere, the temperature was raised to 800 °C at a heating rate of 10 °C / min, and then kept warm for 60 min for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the sample was cooled to room temperature. The nitrogen flow should be maintained during the cooling process. After cooling, the sample was removed and crushed, ground and sieved through a 100-mesh sieve in turn. The surface ash was washed off with deionized water and then dried to constant weight and stored to obtain powdered biochar. (4) Prepare 100 mL of 50% phosphoric acid solution, add 2 g of powdered biochar into the phosphoric acid solution, and soak at room temperature at a speed of 150 r / min for 4 h. Then take the precipitate and repeatedly rinse it with deionized water until the washing solution is neutral, and dry it to constant weight to obtain modified sludge biochar.

[0035] The preparation process of modified sludge biochar in this embodiment is as follows: Figure 1 shown.

[0036] Example 2 A method for preparing modified sludge biochar comprises the following steps: (1) After the municipal sludge is allowed to stand for 24 hours, the supernatant is removed to obtain concentrated sludge; 200 mL of concentrated sludge is taken into a 250 mL beaker, and a polyferric sulfate solution of 10% of the dry weight of the sludge is added thereto, and the mixture is placed on a magnetic stirrer and stirred at 400 rpm for 30 seconds, and then stirred at 100 rpm for 3 minutes. After the stirring is completed, the mixture is allowed to stand for 30 minutes to obtain conditioned sludge; (2) Pour the conditioned sludge into a Buchner funnel for sludge filtration, set the vacuum pump to 0.05 MPa, and continue to filter until the mud cake cracks; take the filtered mud cake and wrap it in a filter cloth for pressure filtration, press filter at 240 kg until its water content is 70%, and obtain a dehydrated mud cake; (3) 50 g of dehydrated water cake was placed in a porcelain boat, which was placed in a tube furnace. Under a nitrogen atmosphere, the temperature was raised to 800 °C at a heating rate of 10 °C / min, and then kept warm for 60 min for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the sample was cooled to room temperature. The nitrogen flow should be maintained during the cooling process. After cooling, the sample was removed and crushed, ground and sieved through a 100-mesh sieve in turn. The surface ash was washed off with deionized water and then dried to constant weight and stored to obtain powdered biochar. (4) Prepare 100 mL of 2 mol / L sodium hydroxide solution, add 2 g of powdered biochar into the phosphoric acid solution, and soak at room temperature at a speed of 150 r / min for 4 h. Then take the precipitate and repeatedly rinse it with deionized water until the washing solution is neutral, and dry it to constant weight to obtain modified sludge biochar.

[0037] Example 3 (1) After the municipal sludge is allowed to stand for 24 hours, the supernatant is removed to obtain concentrated sludge; 200 mL of concentrated sludge is taken into a 250 mL beaker, and a polyferric sulfate solution of 8% of the dry weight of the sludge is added thereto, and the mixture is placed on a magnetic stirrer and stirred at 300 rpm for 40 seconds, and then stirred at 50 rpm for 5 minutes. After the stirring is completed, the mixture is allowed to stand for 40 minutes to obtain conditioned sludge; (2) Pour the conditioned sludge into a Buchner funnel for sludge filtration, set the vacuum pump to 0.05 MPa, and continue to filter until the mud cake cracks; take the filtered mud cake and wrap it in a filter cloth for pressure filtration, press filter at 240 kg until its water content is 65%, and obtain a dehydrated mud cake; (3) 50 g of dehydrated water cake was placed in a porcelain boat, which was placed in a tube furnace. Under a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 8 °C / min, and then kept warm for 80 min for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the sample was cooled to room temperature. The nitrogen flow should be maintained during the cooling process. After cooling, the sample was removed and crushed, ground and sieved through a 100-mesh sieve in turn. The surface ash was washed off with deionized water and then dried to constant weight and stored to obtain powdered biochar. (4) Prepare 80 mL of a 45% phosphoric acid solution, add 2 g of powdered biochar into the phosphoric acid solution, and oscillate and soak at 200 r / min for 3 h at room temperature. Take the precipitate and repeatedly rinse it with deionized water until the washing solution is neutral, and dry it to constant weight to obtain the modified sludge biochar.

[0038] Example 4 (1) After the municipal sludge is allowed to stand for 24 hours, the supernatant is removed to obtain concentrated sludge; 200 mL of the concentrated sludge is taken into a 250 mL beaker, and a polyferric sulfate solution of 12% of the dry weight of the sludge is added thereto, and the mixture is placed on a magnetic stirrer and stirred at 500 rpm for 20 seconds, and then stirred at 200 rpm for 2 minutes. After the stirring is completed, the mixture is allowed to stand for 20 minutes to obtain conditioned sludge; (2) Pour the conditioned sludge into a Buchner funnel for sludge filtration, set the vacuum pump to 0.05 MPa, and continue to filter until the mud cake cracks; take the filtered mud cake and wrap it in a filter cloth for pressure filtration, press filter at 240 kg until its water content is 75%, and obtain a dehydrated mud cake; (3) 50 g of dehydrated water cake was placed in a porcelain boat, which was placed in a tube furnace. Under a nitrogen atmosphere, the temperature was raised to 900 °C at a heating rate of 12 °C / min, and then kept warm for 50 min for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the sample was cooled to room temperature. The nitrogen flow should be maintained during the cooling process. After cooling, the sample was removed and crushed, ground and sieved through a 100-mesh sieve in turn. The surface ash was washed off with deionized water and then dried to constant weight and stored to obtain powdered biochar. (4) Prepare 120 mL of a sodium hydroxide solution with a molar concentration of 2 mol / L, add 2 g of powdered biochar into the sodium hydroxide solution, and oscillate and soak at a speed of 100 r / min for 5 h at room temperature. Then take the precipitate and repeatedly rinse it with deionized water until the washing solution is neutral, and dry it to constant weight to obtain the modified sludge biochar.

[0039] Comparative Example 1 A method for preparing sludge biochar comprises the following steps: (1) After the municipal sludge is allowed to stand for 24 hours, the supernatant is removed to obtain concentrated sludge; 200 mL of concentrated sludge is taken into a 250 mL beaker, and a polyferric sulfate solution of 10% of the dry weight of the sludge is added thereto, and the mixture is placed on a magnetic stirrer and stirred at 400 rpm for 30 seconds, and then stirred at 100 rpm for 3 minutes. After the stirring is completed, the mixture is allowed to stand for 30 minutes to obtain conditioned sludge; (2) Pour the conditioned sludge into a Buchner funnel for sludge filtration, set the vacuum pump to 0.05 MPa, and continue to filter until the mud cake cracks; take the filtered mud cake and wrap it in a filter cloth for pressure filtration, press filter at 240 kg for 30 minutes to obtain a dehydrated mud cake with a moisture content of 70%; (3) 50 g of dehydrated water cake was placed in a porcelain boat, which was placed in a tubular furnace. Under a nitrogen atmosphere, the temperature was increased to 800 °C at a heating rate of 10 °C / min and then kept warm for 60 min for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the sample was cooled to room temperature. Nitrogen flow must be maintained during the cooling process. After cooling, the sample was removed and crushed, ground and sieved through a 100-mesh sieve in turn. The surface ash was washed off with deionized water and then dried to constant weight and stored to obtain sludge biochar.

[0040] Comparative Example 2 A method for preparing modified sludge biochar comprises the following steps: (1) After the municipal sludge is allowed to stand for 24 hours, the supernatant is removed to obtain concentrated sludge; 200 mL of concentrated sludge is taken into a 250 mL beaker, and a polyferric sulfate solution of 10% of the dry weight of the sludge is added thereto, and the mixture is placed on a magnetic stirrer and stirred at 400 rpm for 30 seconds, and then stirred at 100 rpm for 3 minutes. After the stirring is completed, the mixture is allowed to stand for 30 minutes to obtain conditioned sludge; (2) Pour the conditioned sludge into a Buchner funnel for sludge filtration, set the vacuum pump to 0.05 MPa, and continue to filter until the mud cake cracks; take the filtered mud cake and wrap it in a filter cloth for pressure filtration, press the filter at 240 kg for 30 minutes, take it out and dry it to constant weight to obtain a dry mud cake; (3) 50 g of dry mud cake was placed in a porcelain boat, which was placed in a tubular furnace. In a nitrogen atmosphere, the temperature was increased to 800 °C at a heating rate of 10 °C / min and then kept warm for 60 min for pyrolysis and carbonization. After the pyrolysis and carbonization were completed, the mixture was cooled to room temperature. Nitrogen flow must be maintained during the cooling process. After cooling, the sample was removed and crushed, ground and sieved through a 100-mesh sieve. The surface ash was washed off with deionized water and then dried to constant weight and stored to obtain modified sludge biochar.

[0041] Experimental example 1. Morphology analysis The morphology of the sludge biochar prepared in Examples 1-2 and Comparative Examples 1-2 was characterized by scanning electron microscopy (SEM). Figure 2 shown.

[0042] contrast Figure 2 (a)~(d) show that the sludge biochar has obvious changes in microscopic morphology and pore structure before and after modification. Compared with the sludge biochar material prepared in comparative examples 1~2, the modified sludge biochar material obtained in examples 1~2 has more open pores and a more significant porous structure.

[0043] 2. Adsorption and desorption performance and pore size and volume analysis The specific surface area of ​​the sludge biochar prepared in Examples 1-2 and Comparative Example 1 was characterized by the N2 adsorption-desorption curve method (BET), and the pore size and pore volume distribution were analyzed. The results are as follows: Figures 3~8 shown.

[0044] contrast Figures 3-5 As shown in Figures 6-8, the adsorption performance of the modified sludge biochar material (Examples 1-2) is greatly improved compared with that before modification, and the pore volume is larger, which is more conducive to adsorption; after phosphoric acid elution, the pores of the material are opened, and the specific surface area increases from 136.47m 2 / g increased to 377.78 m 2 / g; after modification by sodium hydroxide, the specific surface area of ​​the material increased to 298.91 m 2 / g.

[0045] 3. Analysis of the adsorption effect of antibiotics in wastewater Under the same conditions, the sludge biochar prepared in Examples 1-2, Comparative Examples 1 and 2 and the coconut shell activated carbon ground and sieved through a 100-mesh sieve were added to the simulated wastewater at a dosage of 0.2 g / L to carry out an adsorption experiment. The initial concentration of sulfamethoxazole in the simulated wastewater was 20 mg / L. After adsorption for 4 hours, the concentration of sulfamethoxazole in the simulated wastewater was detected. The comparative experimental results are shown in Table 1 below.

[0046] Table 1 Comparison of adsorption effects of different carbon materials

[0047] As can be seen from Table 1, after adding phosphoric acid-modified sludge biochar (Example 1) to 20 mg / L sulfamethoxazole antibiotic wastewater, the sulfamethoxazole concentration in the wastewater decreased from 20 mg / L to 11.41 mg / L 4 hours later, and after adding sodium hydroxide-modified sludge biochar (Example 2) 4 hours later, the sulfamethoxazole concentration in the wastewater decreased from 20 mg / L to 13.81 mg / L, while the unmodified sludge biochar (Comparative Example 1) reduced the wastewater concentration to 16.98 mg / L, which is similar to the effect of coconut shell activated carbon. More specifically, the removal rate of sulfamethoxazole by the biochar modified with phosphoric acid (Example 1) was 42.95%, which was 27.85% higher than that of the unmodified sludge biochar in Comparative Example 1 (15.1% removal rate of sulfamethoxazole). The removal rate of sulfamethoxazole by coconut shell activated carbon was 16.15%, which was similar to the performance of the sludge biochar before modification (Comparative Example 1). This was because the doping of the dehydrating agent Fe element effectively improved the adsorption performance of the sludge biochar. However, the adsorption effect of the biochar obtained by directly drying the sludge after preliminary dehydration and pyrolysis of the dry sludge was only 1.47%, which was much lower than the adsorption effect of the sludge biochar in Example 1 and Comparative Example 1 on sulfamethoxazole.

[0048] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the scope of the present invention.

Claims

1. A method for preparing modified sludge biochar, characterized in that: The following steps are involved: (1) After gravity concentrating the sludge, an iron-based dehydration conditioning agent is added and stirred to obtain conditioned sludge; (2) dehydrating the conditioned sludge to obtain a dehydrated sludge cake having a moisture content of 65-75%; (3) pyrolyzing and carbonizing the dehydrated cake, and then cooling it, crushing, grinding, sieving, washing and drying it in sequence to obtain powdered biochar; (4) The powdered biochar is modified by a modifier to obtain modified sludge biochar; the modifier is a phosphoric acid solution or a sodium hydroxide solution.

2. The method for preparing modified sludge biochar according to claim 1, characterized in that: In the step (1), the iron-based dehydration conditioning agent is a polyferric sulfate solution with a mass fraction of 30-35%; the dosage of the iron-based dehydration conditioning agent is 8-12% of the dry mass of the sludge.

3. The method for preparing modified sludge biochar according to claim 1, characterized in that: In step (1), stirring The method comprises the following steps: stirring at 300-500 rpm for 20-40 seconds, stirring at 50-200 rpm for 2-5 minutes, and standing for 20-40 minutes after the stirring is completed.

4. The method for preparing modified sludge biochar according to claim 1, characterized in that: In the step (2), dehydration is carried out by suction filtration and pressure filtration in sequence.

5. The method for preparing modified sludge biochar according to claim 1, characterized in that: In the step (3), the pyrolysis carbonization is carried out under an inert atmosphere, with a heating rate of 8-12° C. / min, a temperature of 700-900° C., and a time of 50-80 min.

6. The method for preparing modified sludge biochar according to claim 1, characterized in that: The step (4) comprises the following steps: adding the powdered biochar to a phosphoric acid solution or a sodium hydroxide solution and shaking and soaking for 3 to 5 hours, washing the precipitate until the washing solution is neutral, and then drying to a constant weight to obtain the modified sludge biochar.

7. The method for preparing modified sludge biochar according to claim 6, characterized in that: The mass fraction of the phosphoric acid solution is 45-55%, and the molar concentration of the sodium hydroxide solution is 1.8-2.2 mol / L.

8. The method for preparing modified sludge biochar according to claim 1, characterized in that: The mass ratio of the powdered biochar to the modifier is 1:40-60.

9. Modified sludge biochar prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the modified sludge biochar according to claim 9 in the treatment of antibiotic wastewater.

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