A low-dissolution high-stability magnetic sludge biochar adsorbent and a preparation method and application thereof

Abstract

This invention discloses a low-leakage, high-stability magnetic sludge biochar adsorbent, its preparation method, and its application, comprising the following steps: S1: preparing a sludge biochar matrix from dewatered sludge; S2: mixing the sludge biochar matrix obtained in step S1 with nano-magnetic powder, and performing high-energy ball milling under an inert atmosphere to obtain a composite powder with a physically interlocked structure, thereby preparing the low-leakage, high-stability magnetic sludge biochar adsorbent. This invention provides a structurally stable, high-adsorption-performance, and environmentally friendly magnetic sludge biochar adsorbent that can effectively remove polyether ionocarrier antibiotics (such as maduramycin) from water, showing promising practical application prospects and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the technical field of sludge biochar adsorbents, and in particular relates to a low-dissolution, high-stability magnetic sludge biochar adsorbent, its preparation method, and its application. Background Technology

[0002] The harmless treatment and resource utilization of municipal sewage sludge is a major environmental need. Maduromycin, a highly effective polyether antibiotic, is widely used in livestock and poultry farming; however, it is stable and difficult to degrade in the environment, posing a threat to aquatic ecosystems. Low-temperature carbonization technology for sewage sludge can produce sludge biochar for adsorbing and removing organic pollutants from water bodies. However, powdered biochar is difficult to separate into solid and liquid phases, limiting its engineering applications. Existing technologies typically impart magnetic responsiveness to biochar by loading it with magnetic materials. Although various magnetic modification techniques have been proposed, existing technologies have significant drawbacks: Weak chemical bonding and poor cycle stability: In existing co-precipitation or simple mixing methods, magnetic particles mainly adhere to the surface of biochar, and the bonding force mainly relies on van der Waals forces or weak chemical bonds. Under acidic regeneration elution or strong water flow shearing, the magnetic components are easily detached, causing the magnetic recovery rate of the material to drop sharply after 3-5 cycles.

[0003] Iron ion leaching causes secondary pollution: In the traditional FeCl3 impregnation pyrolysis process, iron oxides are unstable in water (especially in acidic environments) and easily leach iron ions (usually >0.3 mg / L), which not only causes adsorbent loss, but may also form iron sludge that is difficult to treat and causes secondary pollution.

[0004] Pore ​​blockage reduces activity: Chemical precipitation often results in the formation of magnetic particles that block the valuable mesopores and micropores of biochar, leading to a significant decrease in specific surface area and impaired adsorption capacity.

[0005] Therefore, existing technologies struggle to maintain the high adsorption capacity of biochar while achieving a strong and stable bond between the magnetic components and the carbon matrix, and effectively inhibiting iron ion dissolution. There is an urgent need for a preparation method that can achieve deep embedding of the magnetic components into the carbon matrix without clogging pores or detachment, to meet the demands of high-performance water treatment adsorbents. Summary of the Invention

[0006] In view of this, the present invention aims to provide a low-dissolution, high-stability magnetic sludge biochar adsorbent, its preparation method, and its application, in order to solve at least one technical problem in the background art.

[0007] This invention aims to solve the problems of easy shedding of magnetic components, high iron ion dissolution, and pore blockage in the preparation of existing magnetic sludge biochar. It provides a magnetic sludge biochar prepared by high-energy ball milling deep embedding and low-temperature curing technology. This material has high structural stability and low Fe ion dissolution rate in acid washing and regeneration cycle, and achieves efficient retention of maduramycin by using specific chemical and physical effects.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows: This invention abandons the traditional approach of in-situ chemical precipitation and adopts a dual-locking strategy of mechanical embedding and thermal curing. The core of this invention lies in using a combination of high-energy ball milling mechanical interlocking and low-temperature thermal curing to construct a deeply embedded structure of magnetic particles within a sludge biochar matrix. This deep embedding refers to the magnetic particles being forcibly embedded deep into the pores and surface defect sites of the biochar, forming a physical interlock.

[0009] A method for preparing a low-dissolution, high-stability magnetic sludge biochar adsorbent includes the following steps: S1: Prepare sludge biochar matrix from dewatered sludge; S2: The sludge biochar matrix obtained in step S1 is mixed with nano-magnetic powder and subjected to high-energy ball milling under an inert atmosphere to obtain a composite powder with a physically interlocked structure; then subjected to low-temperature heat treatment under an inert atmosphere to obtain a low-dissolution, high-stability magnetic sludge biochar adsorbent with a physically interlocked structure.

[0010] Further, in step S1, preparing the sludge into a sludge biochar matrix includes the following steps: drying the dewatered sludge to constant weight, grinding it, pyrolyzing and carbonizing it under an inert atmosphere, acid washing, and drying to obtain a porous sludge biochar matrix.

[0011] Furthermore, the drying temperature of the dewatered sludge in step S1 is 100~200℃; And / or, in step S1, grinding and passing through a 100-300 mesh sieve; And / or, in step S1, the inert atmosphere is nitrogen, and the flow rate of the inert atmosphere is 100~200mL / min; And / or, the temperature of pyrolysis carbonization in step S1 is 400~800℃, and the isothermal time is 2~4 h; And / or, the acid washing solution in step S1 is an acid solution with a concentration of 0.5~2 mol / L, followed by washing with deionized water until neutral. Acid washing removes inorganic ash, and the solution is dried to obtain a porous sludge biochar matrix.

[0012] Furthermore, in step S2, when the sludge biochar matrix obtained in step S1 is mixed with the nano-magnetic powder, in order to ensure the consistency of the absolute iron content, the amount of nano-magnetic powder added is converted into the absolute mass fraction of iron (Fe), which ranges from 2.5 to 10.0%.

[0013] And / or, in step S2, the nanomagnetic powder is nano-iron oxide or nano-zero valent iron, and the average particle size is 10~80 nm.

[0014] Furthermore, in step S2, the ball-to-material ratio of the high-energy ball milling process is 10~30:1, the rotation speed is 200~500 r / min, and the processing time is 1~2 h. This step utilizes high-energy mechanical force to force the nano-magnetic powder into and deeply embed it into the mesoporous channels and surface defect sites of the biochar, forming a physically interlocked structure by using the high-frequency impact and shearing force of the ball milling media.

[0015] And / or, the grinding media for the high-energy ball milling treatment in step S2 is agate balls; And / or, the inert atmosphere in step S2 is a nitrogen atmosphere.

[0016] Furthermore, the low-temperature treatment in step S2 involves placing the ball-milled composite powder in a tube furnace and subjecting it to low-temperature heat treatment at 100–200 °C for 1–2 h in an inert gas atmosphere (such as nitrogen). This step aims to release the internal stress generated by ball milling and promote the microscopic reorganization of the interface between the magnetic nanoparticles and the carbon matrix, thereby further enhancing the bonding strength.

[0017] A low-dissolution, high-stability magnetic sludge biochar adsorbent prepared by the above-mentioned method has a mechanically interlocked structure in which magnetic nanoparticles are deeply embedded in the interior and surface defects of the sludge biochar matrix. Its saturation magnetization is 10~40 emu / g, and the iron ion dissolution concentration in water with pH 5.0~9.0 is ≤0.30 mg / L.

[0018] Furthermore, after the adsorbent undergoes three adsorption-regeneration cycles using an in-situ advanced oxidation system activated by hydrogen peroxide (H2O2), the removal rate of maduramycin remains at 80-85%, the magnetic separation recovery rate is ≥90%, and the mass loss rate is <5%.

[0019] The application of a magnetic sludge biochar adsorbent as described above in the removal of polyether ion carrier antibiotic pollutants from water bodies, wherein the polyether ion carrier antibiotic is maduramycin.

[0020] A water purification method includes the following steps: adding the above-mentioned magnetic sludge biochar adsorbent to water containing polyether ion carrier antibiotic pollutants for adsorption treatment, and then using an external magnetic field to achieve rapid separation and recovery of the adsorbent after the reaction is completed.

[0021] Compared with existing technologies, the low-leaching, high-stability magnetic sludge biochar adsorbent, its preparation method, and its application described in this invention have the following advantages: (1) Extremely low iron ion dissolution rate, effectively avoiding secondary pollution. In existing technologies (such as FeCl3 impregnation pyrolysis method), the iron oxides of magnetic sludge biochar are mainly attached to the surface through weak chemical bonds. In acidic wastewater (pH<7.0), they are easily dissociated, resulting in excessive iron ion concentration in the effluent. This invention utilizes the strong shear force of high-energy ball milling to physically press nano-magnetic powder into the carbon skeleton, forming a coated structure. Experiments show that in the pH range of 5.0~9.0, the iron ion dissolution concentration of the material of this invention is always ≤0.30 mg / L, which is much lower than the Fe dissolution of adsorbent materials by traditional FeCl3 impregnation magnetic modification method (usually 0.30~1.50 mg / L, and >2.0 mg / L under some acidic conditions). This effectively avoids secondary pollution and is suitable for high-standard water quality treatment. It can be reused as reclaimed water without the need for subsequent iron removal processes. This characteristic makes the material particularly suitable for reclaimed water reuse projects with extremely high effluent quality requirements, without the need for subsequent iron removal processes.

[0022] (2) Excellent recycling stability and in-situ self-cleaning ability. Traditional magnetic sludge biochar is prone to magnetic component stripping under acid washing or water rinsing, and conventional solvent elution is difficult to overcome the irreversible blockage of deep pores caused by macromolecular polyether pollutants (such as maduramycin), making recycling difficult. This invention eliminates the internal stress of ball milling through low-temperature curing, enabling the magnetic components to achieve a firm mechanical bond with the carbon matrix. A more prominent advantage is that the Fe3O4 nanoparticles embedded in the material of this invention can be directly used as a heterogeneous Fenton catalyst. In the regeneration stage, the adsorbed saturated material is dispersed in water containing 100 mmol / L H2O2, the initial pH is adjusted to 3.5~4.0, and the reaction is carried out at 30℃ for 4 h to initiate an in-situ advanced oxidation reaction. The strong oxidizing free radicals generated in situ inside the pores can directly and completely mineralize and degrade the blocked maduramycin molecular chains, achieving deep unblocking of the pores. After three adsorption-regeneration cycles, the removal rate of maduramycin by the adsorbent material remained at 80-85%, the magnetic separation recovery rate was consistently ≥90%, and the mass loss rate was <5%. This demonstrates that the mechanical interlocking structure not only provides excellent mechanical durability but also achieves self-cleaning in conjunction with the advanced oxidation regeneration system, resulting in a long cycle life and significantly reduced application costs.

[0023] (3) Avoiding pore blockage and retaining high adsorption capacity: Chemical co-precipitation often results in a significant decrease in specific surface area due to precipitate blockage of the micropores and mesopores of biochar. The dry ball milling process of this invention is a solid-phase synthesis, which avoids the blockage of pores by liquid chemical precipitation and retains most of the microporous structure of biochar. The nano-magnetic particles are mainly deeply embedded in the macropores or surface defects of biochar, retaining most of the microporous structure for pollutant adsorption. At the same time, the mechanical activation effect of ball milling increases the oxygen-containing functional groups on the surface of biochar. Under the same conditions, the saturated adsorption capacity of the adsorbent material of this invention for antibiotics is increased by more than 20% compared with simple mixed materials, achieving high adsorption performance for pollutants. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Flowchart for the preparation of magnetic sludge biochar and dynamic magnetic field adsorption separation; Figure 2 The diagram shows the microstructure of the ball-milled deep embedding structure of the present invention and the traditional surface attachment structure (a is the traditional surface attachment structure, b is the ball-milled deep embedding structure of the present invention, 1 is the biochar matrix, 2 is the magnetic nanoparticles, and 3 is the pore structure). Figure 3 This is a comparison chart of the maduramycin removal rate and iron ion dissolution concentration of the material of this invention and the material of the traditional impregnation method. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] This invention proposes a magnetic sludge biochar based on high-energy ball milling deep embedding technology. Its preparation process mainly includes three stages: matrix carbonization, mechanochemical embedding, and low-temperature thermosetting. The sludge biochar serves as a porous carrier, and nano-magnetic powders (such as Fe3O4 or nZVI) act as the magnetic response source. The core technology lies in overcoming the weak interfacial bonding defects of conventional physical mixing through the mechanical shearing and impact action of a planetary ball mill, forcibly pressing magnetic particles into the mesopores and micropores of the biochar to form a mechanically interlocked structure.

[0028] Example 1: Ball-milled deep-embedded magnetic sludge biochar; This embodiment demonstrates the optimal preparation parameters and their application effect in antibiotic wastewater treatment.

[0029] Dewatered sludge from a municipal wastewater treatment plant was dried at 105℃ to constant weight, ground, and passed through a 200-mesh sieve. The dried sludge powder was placed in a tube furnace and heated to 800℃ at a heating rate of 10℃ / min under a protective atmosphere of nitrogen flow rate of 200 mL / min, and pyrolyzed at this temperature for 2 hours. After cooling, the pyrolysis product was acid-washed with 1 mol / L HCl to remove inorganic ash, then washed with deionized water until neutral, and dried for later use to obtain sludge biochar (SBC-800) with a rich porous structure.

[0030] Based on the benchmark requirement of 5% iron content, and using the theoretical iron content of 72.36% in Fe3O4, 6.91 wt.% of nano-Fe3O4 magnetic powder (average particle size 50 nm) was weighed and mixed with the aforementioned SBC-800 matrix. The mixture was placed in a planetary ball mill jar, using agate balls as the grinding medium, and the ball-to-powder ratio was controlled at 20:1. Under nitrogen protection, the rotation speed was set to 300 r / min, and the mill was run for 1 h. The shearing force of the high-energy ball mill enabled the nano-magnetic powder to overcome electrostatic repulsion and deeply embed itself into the mesoporous channels of the biochar.

[0031] The ball-milled composite powder was placed in a tube furnace and subjected to low-temperature heat treatment at 150 °C for 1 h under nitrogen protection. This step aims to release the lattice stress generated by machining and promote the microscopic fixation of magnetic particles at the interface with the carbon matrix. The final product was a low-leaching, high-stability magnetic sludge biochar, denoted as SBC800-BM-Fe3O4 (5%).

[0032] Take 50 mL of simulated wastewater containing 20 mg / L maduramycin and adjust the pH to 7.0. Add the prepared SBC800-BM-Fe3O4 (5%) material at a dosage of 0.5 g / L. React for 24 h under a dynamic magnetic field at 25℃ and 120 rpm. Measure the residual maduramycin concentration in the supernatant and calculate the removal rate as 95±2%. After the reaction, place the material next to an external magnetic field; the material precipitates within 30 seconds, and the supernatant becomes clear. ICP-MS is used to determine the iron ion concentration in the treated water; the result is ≤0.30 mg / L, indicating that the magnetic components did not undergo significant dissolution.

[0033] Example 2: Ball milling supported nZVI type magnetic sludge biochar; This embodiment demonstrates the effect of loading highly active nZVI using the process of the present invention, which is suitable for application scenarios that require both reduction and degradation.

[0034] The preparation of sludge biochar was exactly the same as in Example 1, yielding a raw sludge biochar matrix (SBC-800). To achieve a 5% iron element benchmark gradient, considering the extremely high purity of nano-zero valent iron (nZVI, purity ≥99.9%), the actual added powder mass fraction was approximately equal to the preset iron element gradient. Therefore, 5% of nano-zero valent iron powder was accurately weighed and mixed with the above-mentioned SBC-800 matrix. The mixture was placed in a planetary ball mill jar, using agate balls as the grinding media, with a ball-to-material ratio controlled at 20:1. Under nitrogen protection, the rotation speed was set to 300 r / min, and the mill ran for 1 h.

[0035] Similar to Example 1, the ball-milled composite powder was placed in a tube furnace and subjected to low-temperature heat treatment at 150 °C for 1 h under nitrogen protection. Zero-valent iron-supported magnetic sludge biochar was finally obtained, denoted as SBC800-BM-nZVI (5%).

[0036] Take 50 mL of 20 mg / L masuramycin-simulated wastewater and adjust the pH to 7.0. Add 0.5 g / L of the material from Example 2 and react for 24 h at 30 °C and a dynamic magnetic field of 120 rpm.

[0037] Adsorption results: The removal rate was 82±2% after 24 h, and the equilibrium adsorption capacity was 32.8 mg / g, which was 8.0 percentage points lower than that of Example 1. This is attributed to the fact that Fe3O4 has more coordination hydroxyl sites on its surface.

[0038] Dissolution and separation results: Under the action of an external magnetic field, the magnetic separation recovery rate can still reach ≥ 90%. However, according to ICP-MS determination, the concentration of iron ions dissolved in the water after the reaction is as high as 8.15 mg / L.

[0039] Example 3: Cyclic Regeneration Performance Test; To verify the engineering service life of the material, the saturated material prepared in Example 1 was subjected to an oxidation-regeneration cycle test.

[0040] The saturated magnetic biochar was separated and collected, redispersed in 50 mL of ultrapure water, and 100 mmol / L H2O2 was added to adjust the pH to 3.5. The reaction was carried out at 30 °C for 4 h, utilizing the ⋅OH generated by Fe3O4 catalysis on the material surface to degrade the maduramycin clogging the pores. After washing to neutrality and drying, the next round of adsorption began.

[0041] After three consecutive adsorption-regeneration cycles, the material maintained a removal rate of 81.2% for maduramycin (equivalent to 88.7% of the initial removal rate), and the magnetic recovery rate remained stable at over 90%. This demonstrates that the in-situ self-cleaning mechanism can effectively clear pore blockages caused by macromolecular antibiotics.

[0042] Comparative Example 1: Traditional chemical impregnation pyrolysis method (FeCl3 modification); This comparative example illustrates the technical bottlenecks and instabilities encountered by traditional chemical bonding methods in processing large-molecule antibiotics (such as maduramycin). Maduramycin, as a polyether-based ionoporter antibiotic, has a large molecular size and high steric hindrance. When preparing magnetic biochar using traditional chemical impregnation methods (such as FeCl3 modification), the generated iron oxides readily aggregate randomly on the biochar surface, severely clogging the valuable mesopores and micropores within the biochar. This pore-clogging effect significantly increases the mass transfer resistance of maduramycin molecules diffusing into the adsorbent, resulting in a substantial reduction in the actual adsorption capacity. Furthermore, in practical applications, attempts to overcome this mass transfer resistance by enhancing external fluid disturbances (such as mechanical stirring or micro-eddies) often result in the loosely attached magnetic particles on the surface being easily detached in large quantities under the shear force of the water flow.

[0043] For comparative verification experiments, the prepared sludge biochar matrix (SBC) was impregnated in a 0.2 mol / L FeCl3 solution and shaken at 160 rpm for 12 h in a constant-temperature shaker to obtain conventional impregnated magnetic sludge biochar (SBC800-IM-0.2Fe). When treating the same maduramycin wastewater under the same reaction conditions as in Example 1, although the initial removal rate of this conventional material barely reached 78%, the iron ion concentration in the effluent was found to be as high as 2.34 mg / L, posing a very serious risk of secondary iron sludge pollution. In subsequent cyclic regeneration tests, the magnetic separation rate of this material slowed significantly after the third regeneration cycle, the water turned black, and the magnetic recovery rate dropped sharply to below 75%, indicating that the acidic environment and fluid shear had completely destroyed the magnetic adhesion layer on its surface.

[0044] In contrast, the high-energy ball milling deep embedding process used in this application is a purely physical dry solid-phase synthesis, fundamentally avoiding the pore blockage problem caused by liquid-phase chemical precipitation. It fully opens macropores and mesopores to the maduramycin macromolecules, significantly improving the mass transfer rate and saturated adsorption capacity. More importantly, the mechanically interlocked structure built deep within the carbon skeleton by this process endows the material with extremely high mechanical and chemical stability, enabling it to perfectly withstand the continuous scouring of strong external fluid shear forces (such as high-frequency micro-eddies in a cylindrical device) without iron dissolution (iron ions in the effluent ≤0.30 mg / L). This application not only truly achieves efficient mass transfer interception of maduramycin with safety and no secondary pollution, but also ensures the long-term recycling of magnetic components (magnetic recovery rate is still ≥80% after 3 cycles), completely breaking through the application limitations of traditional chemical modification methods.

[0045] Comparative Example 2: Simple physical mixing (no ball milling process); This comparative example is used to verify the necessity of the ball milling embedding step.

[0046] Nano-Fe3O4 and SBC were hand-milled and mixed in a mortar according to the ratio of Example 1, and then cured at 150°C (without high-energy ball milling). After the material was immersed in water for 24 hours, obvious carbon-magnetic separation was observed: magnetic powder was adsorbed onto a magnet, while a large amount of black biochar powder was suspended in the water and could not be recovered. The magnetic recovery rate was only about 60%, and the adsorption capacity was 20% lower than that of Example 1. This proves that without the mechanical shearing of high-energy ball milling, the magnetic particles only loosely adhered to the surface and could not form an effective interlocking structure.

[0047] Table 1 shows a comparison of the key indicators of Examples 1-3 and Comparative Examples 1-2.

[0048] Table 1 Comparison of key indicators between Examples 1-3 and Comparative Examples 1-2 As can be seen from the comparative analysis in Table 1, Example 1 (SBC800-BM-Fe3O4 (5%)) and Example 2 (SBC800-BM-nZVI (5%)) using high-energy ball milling embedding and low-temperature curing processes have significantly better overall performance than traditional methods.

[0049] Among them, Example 1 (SBC800-BM-Fe3O4 (5%)) performed the best. Not only did it achieve a removal rate of 95±2% for maduramycin within 24 h, but its iron ion dissolution concentration was also consistently controlled at an extremely low level of ≤0.30 mg / L, fully meeting environmental protection requirements. Furthermore, after undergoing three oxidation regeneration cycles, its removal rate was still maintained at 81.2% (with a retention rate of over 85%), and its magnetic separation recovery rate was consistently ≥90%, fully demonstrating the core advantages of the mechanical interlocking structure in improving material structural stability, inhibiting iron dissolution, and ensuring unobstructed pores.

[0050] In contrast, Comparative Example 1 (SBC800-IM-0.2Fe), which uses a traditional impregnation pyrolysis method, initially showed some adsorption effect (78±2%). However, due to the weak binding force between its iron oxide and carbon matrix and severe pore blockage, iron ion dissolution reached as high as 2.34 mg / L, and the magnetic recovery rate dropped below 75% after 3 cycles, posing a serious risk of secondary pollution and making it difficult to reuse. Comparative Example 2 (SBC-simple mixture type), which uses a simple physical mixture, lacked effective mechanical shear force, resulting in loosely attached magnetic particles that were prone to severe carbon-magnetic separation (magnetic recovery rate of only about 60%), and the removal rate was more than 20% lower than that of Example 1.

[0051] Although Example 2 (SBC800-BM-nZVI (5%)) also achieved deep embedding and exhibited certain adsorption performance (82±2%) using ball milling, the leaching of iron was as high as 8.15 mg / L due to the easy oxidation and dissolution of nano-zero valent iron in water. This further proves from the opposite perspective that using Fe3O4 as the magnetic component and combining it with the specific ball milling process of this invention is the optimal technical path to achieve low leaching and high stability magnetic biochar.

[0052] In summary, this invention achieves deep embedding of magnetic components within the carbon skeleton through high-energy ball milling, which not only ensures efficient interception of macromolecular organic pollutants such as maduramycin, but also fundamentally solves common technical bottlenecks in the industry, such as easy shedding of magnetic components, rapid iron loss, easy pore blockage, and short cycle life in traditional magnetic modification methods. It has significant advanced and practical value.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-leaching, high-stability magnetic sludge biochar adsorbent, characterized in that: Includes the following steps: S1: Prepare sludge biochar matrix from dewatered sludge; S2: The sludge biochar matrix obtained in step S1 is mixed with nano-magnetic powder and subjected to high-energy ball milling under an inert atmosphere to obtain a composite powder with a physically interlocked structure; then subjected to low-temperature heat treatment under an inert atmosphere to obtain a low-dissolution, high-stability magnetic sludge biochar adsorbent with a physically interlocked structure.

2. The method for preparing a low-leaching, high-stability magnetic sludge biochar adsorbent according to claim 1, characterized in that: Step S1, preparing sludge into a sludge biochar matrix, includes the following steps: drying dewatered sludge to constant weight, grinding, pyrolyzing and carbonizing under an inert atmosphere, acid washing, and drying to obtain a porous sludge biochar matrix.

3. The method for preparing a low-leaching, high-stability magnetic sludge biochar adsorbent according to claim 2, characterized in that: The drying temperature of the dewatered sludge in step S1 is 100~200℃; And / or, in step S1, grinding and passing through a 100-300 mesh sieve; And / or, in step S1, the inert atmosphere is nitrogen, and the flow rate of the inert atmosphere is 100~200mL / min; And / or, the temperature of pyrolysis carbonization in step S1 is 400~800℃, and the isothermal time is 2~4 h; And / or, the acid washing solution in step S1 is an acid solution with a concentration of 0.5~2 mol / L, and then washed with deionized water until neutral.

4. The method for preparing a low-leaching, high-stability magnetic sludge biochar adsorbent according to claim 1, characterized in that: In step S2, when the sludge biochar matrix obtained in step S1 is mixed with the nano-magnetic powder, the amount of nano-magnetic powder added is converted into the absolute mass fraction of iron (Fe), which ranges from 2.5% to 10.0%. And / or, in step S2, the nanomagnetic powder is nano-iron oxide or nano-zero valent iron, and the average particle size is 10~80nm.

5. The method for preparing a low-leaching, high-stability magnetic sludge biochar adsorbent according to claim 1, characterized in that: In step S2, the ball-to-material ratio of the high-energy ball mill is 10~30:1, the rotation speed is 200~500 r / min, and the processing time is 1~2 h; And / or, the grinding media for the high-energy ball milling treatment in step S2 is agate balls; And / or, the inert atmosphere in step S2 is a nitrogen atmosphere.

6. The method for preparing a low-leaching, high-stability magnetic sludge biochar adsorbent according to claim 1, characterized in that: In step S2, the low-temperature heat treatment temperature is 100~200℃, and the treatment time is 1~2 h; And / or, the inert atmosphere in step S2 is a nitrogen atmosphere.

7. A low-leaching, high-stability magnetic sludge biochar adsorbent prepared by the preparation method of a low-leaching, high-stability magnetic sludge biochar adsorbent according to any one of claims 1 to 6, characterized in that: The adsorbent has a mechanically interlocked structure in which magnetic nanoparticles are deeply embedded in the interior and surface defects of the sludge biochar matrix. Its saturation magnetization is 10~40 emu / g, and the iron ion dissolution concentration in water with pH 5.0~9.0 is ≤0.30 mg / L.

8. The low-leaching, high-stability magnetic sludge biochar adsorbent according to claim 7, characterized in that: After undergoing three adsorption-regeneration cycles using an in-situ advanced oxidation system activated by hydrogen peroxide (H2O2), the adsorbent maintains a removal rate of 80-85% for maduramycin, a magnetic separation recovery rate of ≥90%, and a mass loss rate of <5%.

9. The application of a magnetic sludge biochar adsorbent as described in claim 7 or 8 in the removal of polyether ionocarrier antibiotic pollutants from water, characterized in that: The polyether ionophore antibiotic is maduramycin.

10. A water purification method, characterized in that: The process includes the following steps: adding the magnetic sludge biochar adsorbent as described in claim 7 or 8 to water containing polyether ion carrier antibiotic pollutants for adsorption treatment; and after the reaction is completed, using an external magnetic field to achieve rapid separation and recovery of the adsorbent.

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