Composite adsorbent for removing tetracycline in wastewater and preparation method thereof

Abstract

The invention discloses a composite adsorbent for removing tetracycline in wastewater and a preparation method thereof, and relates to the field of wastewater treatment.The preparation method comprises the following steps that gasified slag and corn roots are pretreated and then mixed and pyrolyzed to prepare a magnetic biochar substrate, the magnetic biochar substrate is dispersed in a solvent, copper salt and organic ligands are added, and the magnetic biochar substrate is obtained; and collecting products through an external magnetic field to obtain the composite adsorbent for removing tetracycline in wastewater. A copper-based metal organic framework material grows in situ on a gasified slag / corn root biochar substrate, and the specific surface area of the material is increased by using a highly ordered porous structure of MOF; through the combined action of various mechanisms, the adsorbent shows extremely high adsorption capacity and good selectivity on tetracycline molecules.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to a composite adsorbent for removing tetracycline from wastewater and its preparation method. Background Technology

[0002] Tetracycline (TC), the second most widely used antibiotic globally, is difficult to completely degrade after its extensive use in medicine and animal husbandry. Most of it enters the aquatic environment through excretion, causing persistent pollution and inducing antibiotic resistance genes, seriously threatening ecological security and public health. Therefore, removing TC from the aquatic environment has become an urgent task. Currently, the main methods for TC removal include biotechnology, chemical oxidation, catalysis, membrane separation, and adsorption. Among these, adsorption has become one of the most effective methods for removing tetracycline from aquatic systems due to its high cost-effectiveness, ease of operation, lack of secondary pollution, and high purification efficiency.

[0003] Previous studies have confirmed that metallic components such as aluminum, iron, calcium, and magnesium exhibit excellent adsorption properties for tetracycline. However, these aluminum, iron, calcium, and magnesium species are exogenous metals, significantly increasing the production cost of tetracycline adsorbents. Gasification slag (GS), a large-scale solid waste generated by the coal gasification industry, is an ideal candidate material for the green design of tetracycline adsorbents due to its rich multi-metallic composition and porous structure. According to incomplete statistics, China generates approximately 35 million tons of GS annually. Current disposal methods (stockpiling / landfilling) not only consume land resources but also pose environmental risks. Therefore, there is an urgent need to develop new utilization technologies. GS is rich in Al2O3, Fe2O3, SiO2, and residual carbon. This chemical diversity gives GS a unique advantage in preparing TC adsorbents—the active metal components serve as a library of active sites for capturing tetracycline, SiO2 forms a silicon-oxygen network framework, and residual carbon contributes to its porous structure and adsorption performance.

[0004] Although GS contains a large number of metal components, these metals mainly exist in the form of silicate / aluminosilicate crystalline phases, exhibiting low reactivity. Therefore, they are often removed as impurities to prepare porous GS-based materials. Thus, effectively utilizing the abundant multi-metal components in GS is crucial for developing highly efficient GS-based adsorbent materials. Studies have shown that the reconstruction of the biomass carbon framework can form a hierarchical porous network, and the resulting carbon matrix exhibits abundant active functional groups. These functional groups can anchor and disperse metal components through coordination and precipitation mechanisms. Therefore, introducing biomass-derived carbon can not only enhance the specific surface area of ​​GS-based adsorbents but also improve the utilization rate of active metal components in the GS matrix.

[0005] This invention focuses on a specific biomass resource: maize root. Notably, the unique vascular bundle structure of maize root (CR) contributes to increasing its specific surface area, while its abundant lignin / cellulose components can be converted into numerous surface-active sites. However, to date, few studies have reported the construction of GS-based metal-rich adsorbents for tetracycline adsorption using a composite system of GS and maize root. Here, this invention couples multi-metal-rich GS with maize root biomass via a one-step co-pyrolysis method to prepare a GS / CR-derived metal-rich biochar adsorbent. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a composite adsorbent for removing tetracycline from wastewater and its preparation method.

[0007] The objective of this invention can be achieved through the following technical solutions: A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 60-80 parts of gasification slag, 20-40 parts of corn root, 2-6 parts of copper salt, 3-8 parts of organic ligand, and 200-300 parts of solvent.

[0008] Furthermore, the main components of the gasification slag are SiO2, Al2O3, CaO, Fe2O3 and residual carbon.

[0009] Furthermore, the copper salt is one of copper nitrate, copper chloride, copper sulfate, copper iodide, copper acetate, and copper carbonate.

[0010] Furthermore, the organic ligand is one of pyromellitic acid, trimellitic acid, trimethyl pyromellitic acid, and terephthalic acid.

[0011] Furthermore, the solvent is one or more of deionized water, ethanol, methanol, and toluene.

[0012] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) The gasification slag is washed, dried and then crushed to obtain pretreated gasification slag; (2) The corn roots are washed, dried and then crushed to obtain pretreated corn roots; (3) Mix the pretreated corn roots and pretreated gasification slag to obtain a mixed powder. Place the mixed powder into a tube furnace and heat it to 500-700℃ at a rate of 4-6℃ / min under N2 atmosphere. Hold the temperature for 0.5-1.5h. After cooling, obtain the product. After post-treatment, obtain a magnetic biochar substrate. (4) Disperse the magnetic biochar substrate in a solvent, add copper salt and stir for 3-5 hours, then add organic ligands, reflux in a water bath at 60-80℃ for 4-8 hours, cool to room temperature, collect the product by applying an external magnetic field, wash and dry to obtain a composite adsorbent for removing tetracycline from wastewater.

[0013] Furthermore, the specific steps for drying and pulverizing the gasification slag in step (1) are as follows: place the washed gasification slag in an oven at 100-110℃ and dry it for 22-26 hours, then pulverize it and pass it through a 180-220 mesh sieve.

[0014] Furthermore, the specific steps for drying and crushing the corn roots in step (2) are as follows: place the washed corn roots in an oven at 70-90℃ to dry to constant weight, crush them, and then pass them through a 40-80 mesh sieve.

[0015] Furthermore, the specific post-processing steps in step (3) are as follows: soak and stir with hydrochloric acid solution of 9-10 times the volume of the product for 1-3 hours, then wash with deionized water until the filtrate is neutral, place the filter cake in an oven at 100-110℃ and dry for 10-14 hours, then crush and pass through an 80-120 mesh sieve.

[0016] Furthermore, in step (4), the drying temperature is 50-70℃, and the time is 10-14 hours. The beneficial effects of this invention are: (1) The core raw material gasification slag is a solid waste generated during the coal gasification process, and corn roots are a typical agricultural waste. This invention realizes the high-value-added resource utilization of the two wastes, which not only reduces the raw material cost of the adsorbent, but also alleviates the environmental pressure caused by the accumulation of industrial solid waste and agricultural straw, and meets the requirements of green and sustainable development.

[0017] (2) The composite material prepared by this invention solves the two major problems of adsorption efficiency and separation and recovery. The iron oxide in the gasification slag is converted into magnetic material (such as Fe3O4) after pyrolysis, which makes the material have intrinsic magnetism. It can achieve rapid and low-energy solid-liquid separation by applying an external magnetic field, which improves the disadvantages of traditional powder adsorbents such as difficult filtration and high energy consumption.

[0018] (2) Synergistic adsorption through multiple mechanisms: corn root biochar provides a large specific surface area and abundant pores; gasification slag provides active sites for metal oxides; and copper-based MOFs provide a large number of specific adsorption sites. These three elements work synergistically through multiple mechanisms to exhibit extremely high adsorption capacity and good selectivity for tetracycline molecules. The Fe in the gasification slag... 3+ Ca 2+ Mg 2+ Al 3+ Metal ions, and Cu introduced by post-modification 2+It can undergo strong complexation with the carbonyl, enol, and amide groups on the tetracycline molecule to form stable surface complexes; the oxygen-containing functional groups such as hydroxyl and carboxyl groups remaining on the surface of biochar form a dense hydrogen bond network with the -NH2, -OH, and -CONH2 groups on the tetracycline molecule, firmly capturing pollutant molecules; the tetracycline molecule has multiple conjugated aromatic rings, which are good electron acceptors, and the organic ligands of MOF are electron donors. A strong π-π interaction will occur between the two, thereby adsorbing tetracycline; the triple action of complexation (metal), hydrogen bonding (functional group), and π-π (aromatic carbon) is used to achieve efficient capture of TC. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The gasification slag used in the embodiments and comparative examples of this invention was purchased from Yili Xintian Coal Chemical Co., Ltd., China.

[0021] Example 1 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 60 parts of gasification slag, 20 parts of corn root, 2 parts of copper nitrate, 3 parts of trimesic acid, and 200 parts of ethanol and deionized water in a volume ratio of 1:1.

[0022] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in a 100℃ oven for 22h, crush it and pass it through a 180-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 1 cm, place the washed corn roots in a 70℃ oven to dry to constant weight, crush them and pass them through a 40-mesh sieve to obtain pretreated corn roots. (3) The pretreated corn roots and pretreated gasification residue were mixed to obtain a mixed powder. The mixed powder was placed in a tube furnace and heated to 500°C at a rate of 4°C / min under N2 atmosphere and kept at that temperature for 0.5h. After cooling, the product was obtained. The product was soaked and stirred in 0.1mol / L hydrochloric acid solution with 9 times its volume for 1h. Then it was washed with deionized water until the filtrate was neutral. The filter cake was placed in a 100°C oven and dried for 10h. After crushing, it was passed through an 80-mesh sieve to obtain a magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Copper nitrate was added and stirred for 3 hours, followed by the addition of trimesic acid. The mixture was refluxed in a water bath at 60°C for 4 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, the product was dried at 50°C for 10 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0023] Example 2 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 64 parts of gasification slag, 24 parts of corn root, 3 parts of copper nitrate, 4 parts of trimesic acid, and 220 parts of ethanol and deionized water in a volume ratio of 1:1.

[0024] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 102℃ for 23h, crush it and pass it through a 190-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 2cm, dry the washed corn roots in a 75℃ oven until constant weight, crush them and pass them through a 50-mesh sieve to obtain pretreated corn roots; (3) Mix the pretreated corn roots and pretreated gasification residue to obtain mixed powder. Place the mixed powder in a tube furnace and heat it to 550°C at a rate of 5°C / min under N2 atmosphere. Keep it at that temperature for 1 hour. After cooling, obtain the product. Soak and stir the product in 0.1 mol / L hydrochloric acid solution with 10 times its volume for 2 hours. Then wash it with deionized water until the filtrate is neutral. Place the filter cake in an oven at 105°C and dry it for 12 hours. After crushing, pass it through a 90-mesh sieve to obtain magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Copper nitrate was added and stirred for 4 hours, and then trimesic acid was added. The mixture was refluxed in a water bath at 65°C for 5 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, it was dried at 55°C for 12 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0025] Example 3 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 70 parts of gasification slag, 30 parts of corn root, 4 parts of copper nitrate, 5 parts of trimesic acid, and 240 parts of ethanol and deionized water in a volume ratio of 1:1.

[0026] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 110℃ for 24h, crush it and pass it through a 200-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 1 cm, place the washed corn roots in an 80℃ oven to dry to constant weight, crush them and pass them through a 60-mesh sieve to obtain pretreated corn roots. (3) Mix the pretreated corn roots and pretreated gasification residue to obtain mixed powder. Place the mixed powder in a tube furnace and heat it to 600°C at a rate of 5°C / min under N2 atmosphere. Keep it at the temperature for 1 hour. After cooling, obtain the product. Soak and stir the product in 0.1 mol / L hydrochloric acid solution with 10 times its volume for 2 hours. Then wash it with deionized water until the filtrate is neutral. Place the filter cake in an oven at 105°C and dry it for 12 hours. After crushing, pass it through a 100-mesh sieve to obtain magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Copper nitrate was added and stirred for 4 hours, then trimesic acid was added. The mixture was refluxed in a water bath at 70°C for 6 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, it was dried at 60°C for 12 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0027] Example 4 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 75 parts of gasification slag, 35 parts of corn root, 5 parts of copper nitrate, 7 parts of trimesic acid, and 260 parts of ethanol and deionized water in a volume ratio of 1:1.

[0028] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 105℃ for 24 hours, crush it and pass it through a 210 mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 2cm, place the washed corn roots in an 80℃ oven to dry to constant weight, crush them and pass them through a 70-mesh sieve to obtain pretreated corn roots; (3) The pretreated corn roots and pretreated gasification residue were mixed to obtain a mixed powder. The mixed powder was placed in a tube furnace and heated to 650°C at a rate of 5°C / min under N2 atmosphere and kept at the temperature for 1.2h. After cooling, the product was obtained. The product was soaked and stirred in 0.1mol / L hydrochloric acid solution with 9.5 times its volume for 2.5h. Then it was washed with deionized water until the filtrate was neutral. The filter cake was placed in an oven at 105°C and dried for 12h. After being crushed and passed through a 110-mesh sieve, a magnetic biochar substrate was obtained. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Copper nitrate was added and stirred for 4 hours, then trimesic acid was added. The mixture was refluxed in a water bath at 70°C for 6 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, it was dried at 60°C for 12 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0029] Example 5 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 80 parts of gasification slag, 40 parts of corn root, 6 parts of copper nitrate, 8 parts of trimesic acid, and 300 parts of ethanol and deionized water in a volume ratio of 1:1.

[0030] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 110℃ for 26h, crush it and pass it through a 220-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 2cm, dry the washed corn roots in a 90℃ oven until constant weight, crush them and pass them through an 80-mesh sieve to obtain pretreated corn roots; (3) The pretreated corn roots and pretreated gasification residue were mixed to obtain a mixed powder. The mixed powder was placed in a tube furnace and heated to 700°C at a rate of 6°C / min under N2 atmosphere and kept at the temperature for 1.5h. After cooling, the product was obtained. The product was soaked and stirred in 0.1mol / L hydrochloric acid solution with 10 times its volume for 3h. Then it was washed with deionized water until the filtrate was neutral. The filter cake was placed in an oven at 110°C and dried for 14h. After crushing, it was passed through a 120-mesh sieve to obtain a magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Copper nitrate was added and stirred for 5 hours, and then trimesic acid was added. The mixture was refluxed in a water bath at 80°C for 8 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, it was dried at 70°C for 14 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0031] Comparative Example 1 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 70 parts of gasification slag, 30 parts of corn root, 4 parts of zinc nitrate, 5 parts of trimesic acid, and 240 parts of ethanol and deionized water in a volume ratio of 1:1.

[0032] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 110℃ for 24h, crush it and pass it through a 200-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 1 cm, place the washed corn roots in an 80℃ oven to dry to constant weight, crush them and pass them through a 60-mesh sieve to obtain pretreated corn roots. (3) Mix the pretreated corn roots and pretreated gasification residue to obtain mixed powder. Place the mixed powder in a tube furnace and heat it to 600°C at a rate of 5°C / min under N2 atmosphere. Keep it at the temperature for 1 hour. After cooling, obtain the product. Soak and stir the product in 0.1 mol / L hydrochloric acid solution with 10 times its volume for 2 hours. Then wash it with deionized water until the filtrate is neutral. Place the filter cake in an oven at 105°C and dry it for 12 hours. After crushing, pass it through a 100-mesh sieve to obtain magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Zinc nitrate was added and stirred for 4 hours, then trimesic acid was added. The mixture was refluxed in a water bath at 70°C for 6 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, the product was dried at 60°C for 12 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0033] Comparative Example 2 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 70 parts of gasification slag, 30 parts of corn root, 5 parts of trimesic acid, and 240 parts of ethanol and deionized water in a volume ratio of 1:1.

[0034] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 110℃ for 24h, crush it and pass it through a 200-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 1 cm, place the washed corn roots in an 80℃ oven to dry to constant weight, crush them and pass them through a 60-mesh sieve to obtain pretreated corn roots. (3) Mix the pretreated corn roots and pretreated gasification residue to obtain mixed powder. Place the mixed powder in a tube furnace and heat it to 600°C at a rate of 5°C / min under N2 atmosphere. Keep it at the temperature for 1 hour. After cooling, obtain the product. Soak and stir the product in 0.1 mol / L hydrochloric acid solution with 10 times its volume for 2 hours. Then wash it with deionized water until the filtrate is neutral. Place the filter cake in an oven at 105°C and dry it for 12 hours. After crushing, pass it through a 100-mesh sieve to obtain magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1, pyromellitic acid was added, and after stirring for 4 hours, the mixture was refluxed in a water bath at 70°C for 6 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, it was dried at 60°C for 12 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0035] Comparative Example 3 A composite adsorbent for removing tetracycline from wastewater comprises, by weight, the following components: 70 parts of gasification slag, 30 parts of corn root, 4 parts of copper nitrate, and 240 parts of ethanol and deionized water in a volume ratio of 1:1.

[0036] A method for preparing a composite adsorbent for removing tetracycline from wastewater includes the following steps: (1) Wash the gasification slag, dry the washed gasification slag in an oven at 110℃ for 24h, crush it and pass it through a 200-mesh sieve to obtain the pretreated gasification slag. (2) Wash the corn roots, cut them into small sections of about 1 cm, place the washed corn roots in an 80℃ oven to dry to constant weight, crush them and pass them through a 60-mesh sieve to obtain pretreated corn roots. (3) Mix the pretreated corn roots and pretreated gasification residue to obtain mixed powder. Place the mixed powder in a tube furnace and heat it to 600°C at a rate of 5°C / min under N2 atmosphere. Keep it at the temperature for 1 hour. After cooling, obtain the product. Soak and stir the product in 0.1 mol / L hydrochloric acid solution with 10 times its volume for 2 hours. Then wash it with deionized water until the filtrate is neutral. Place the filter cake in an oven at 105°C and dry it for 12 hours. After crushing, pass it through a 100-mesh sieve to obtain magnetic biochar substrate. (4) The magnetic biochar substrate was dispersed in ethanol and deionized water in a volume ratio of 1:1. Copper nitrate was added and stirred for 4 hours. The mixture was then refluxed in a water bath at 70°C for 6 hours. After cooling to room temperature, the magnetic product was collected by strong magnetic adsorption of neodymium iron boron. After washing, the product was dried at 60°C for 12 hours to obtain a composite adsorbent for removing tetracycline from wastewater.

[0037] The following is a further performance test of the composite adsorbent prepared in this invention for removing tetracycline from wastewater. Adsorption conditions: initial tetracycline concentration: 50 mg / L; solution pH: 7.0 (simulating neutral wastewater); temperature: 25℃; adsorption time: 24 h (ensuring adsorption equilibrium); adsorbent dosage: 0.1 g / L; test index: adsorption capacity (Q...). e (mg / g): the mass of tetracycline adsorbed per unit adsorbent at equilibrium; removal rate (%): the percentage of the difference between the initial concentration and the equilibrium concentration of tetracycline.

[0038] The test results are shown below and recorded in Table 1.

[0039] Table 1: Test Results According to the data in Table 1, a comparison of the embodiments and comparative examples of the present invention shows that the adsorption capacity and removal rate of Examples 1-5 are significantly higher than those of Comparative Examples 1-3. Comparative Example 1 (Zn-MOF modified biochar) shows that the zinc-based MOF has the ability to adsorb tetracycline, but it is not as good as the copper-based MOF, and its performance is second best. Comparative Example 2 (no copper salt, biochar substrate) relies only on the pores and surface functional groups of biochar, and its adsorption performance is the worst. Comparative Example 3 (no organic ligand, CuO / biochar) does not form MOF. Although copper oxide can provide some adsorption sites, its performance is poor.

[0040] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A composite adsorbent for removing tetracycline from wastewater, characterized by comprising, By weight parts, including the following components: gasification slag 60-80 parts, corn root 20-40 parts, copper salt 2-6 parts, organic ligand 3-8 parts, solvent 200-300 parts.

2. The composite adsorbent for removing tetracycline from wastewater according to claim 1, characterized by, The main components of the gasification slag are SiO2, Al2O3, CaO, Fe2O3 and residual carbon.

3. The composite adsorbent for removing tetracycline from wastewater according to claim 1, characterized by, The copper salt is one of copper nitrate, copper chloride, copper sulfate, copper iodide, copper acetate and copper carbonate.

4. The composite adsorbent for removing tetracycline from wastewater according to claim 1, characterized by, The organic ligand is one of trimesic acid, trimellitic acid, trimethyl trimesate and terephthalic acid.

5. The composite adsorbent for removing tetracycline from wastewater according to claim 1, characterized by, The solvent is a combination of one or more of deionized water, ethanol, methanol and toluene.

6. A method for preparing a composite adsorbent for removing tetracycline from wastewater according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) The gasification slag is washed, dried and crushed to obtain pretreated gasification slag; (2) The corn root is washed, dried and crushed to obtain pretreated corn root; (3) The pretreated corn root and the pretreated gasification slag are mixed to obtain a mixed powder, which is placed in a tube furnace and heated to 500-700℃ at a rate of 4-6℃ / min under N2 atmosphere, and kept for 0.5-1.5h, and the product is obtained after cooling, and the magnetic biochar substrate is obtained after post-treatment of the product; (4) The magnetic biochar substrate is dispersed in a solvent, and the copper salt is first added and stirred for 3-5h, and then the organic ligand is added, and the reaction is refluxed at 60-80℃ for 4-8h, and the product is collected by an external magnetic field after cooling to room temperature, and the composite adsorbent for removing tetracycline from wastewater is obtained after washing and drying.

7. The method according to claim 6, wherein the method is characterized by, In step (1), the specific steps of drying and crushing the gasification slag are drying the washed gasification slag in an oven at 100-110℃ for 22-26h, and then crushing and sieving through a 180-220 mesh sieve.

8. The method according to claim 6, wherein the method is characterized by, In step (2), the specific steps of drying and crushing the corn root are drying the washed corn root in an oven at 70-90℃ until the weight is constant, and then crushing and sieving through a 40-80 mesh sieve.

9. The method according to claim 6, wherein the method is characterized by, In step (3), the specific steps of post-treatment are soaking and stirring the product in a hydrochloric acid solution with a volume of 9-10 times that of the product for 1-3h, then washing with deionized water until the filtrate is neutral, drying the filter cake in an oven at 100-110℃ for 10-14h, and then crushing and sieving through an 80-120 mesh sieve.

10. The method of claim 6, wherein the method is characterized by: In step (4), the drying temperature is 50-70℃, and the drying time is 10-14h.

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