A bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent, a preparation method and application thereof

Abstract

The application belongs to the field of magnetic adsorption materials, and specifically discloses a magnetic hierarchical porous carbon nanotube composite adsorbent derived from a bimetallic ZIF, a preparation method and application thereof. The composite adsorbent is synthesized by a one-pot method and an in-situ pyrolysis method. The method first synthesizes bimetallic ZIFs by a one-pot method at room temperature. Then, the bimetallic ZIFs are subjected to in-situ pyrolysis under high-temperature and oxygen-free conditions to obtain magnetic hierarchical porous carbon nanotubes. The method has the advantages of low preparation cost, strong operability, controllable composition and structure, easy recovery, high adsorption efficiency, etc. The method can be mass-produced, overcomes the difficulty in recycling of traditional powder adsorbents, is easy to operate in the process of adsorbing and removing tetracycline hydrochloride, has low cost, can efficiently adsorb tetracycline hydrochloride, and has good adsorption performance, structural stability and recyclable performance. The method has a wide application prospect in the field of wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and relates to magnetic adsorption materials, specifically to a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent, its preparation method, and its application. Background Technology

[0002] Tetracycline hydrochloride, a representative tetracycline antibiotic, is widely used as a broad-spectrum antibiotic for the treatment of human and animal diseases. However, due to the overuse of antibiotics, they are frequently detected in aquatic environments such as groundwater, river water, surface water, and drinking water. Even at low concentrations, residual tetracycline hydrochloride can induce the formation of resistant bacteria. Furthermore, 50%–80% of tetracycline hydrochloride is discharged into aquatic ecosystems as parent or intermediate products through wastewater and animal feces. Long-term residual tetracycline hydrochloride leads to the generation and spread of drug-resistant bacteria and resistance genes, damaging ecosystems and threatening human health. Traditional wastewater treatment technologies are insufficient to completely remove tetracycline hydrochloride; therefore, research into new methods and materials for removing tetracycline hydrochloride has received widespread attention from researchers in order to reduce the harm of antibiotics to humans and the environment.

[0003] Currently, advanced oxidation methods, membrane methods, electrochemical methods, and adsorption methods have been used for the removal of tetracycline hydrochloride. Among them, adsorption is considered one of the most effective methods for removing tetracycline hydrochloride due to its advantages such as high efficiency, ease of operation, low cost, and minimal secondary pollution. The adsorbent is key to adsorption methods; materials with large specific surface areas, abundant adsorption sites, and porous structures are promising adsorbents. Commonly used porous materials include resins, metal oxides, carbon-based materials, natural minerals, and metal-organic frameworks. Carbon-based materials are widely used in pharmaceutical wastewater treatment due to their structural stability, wide availability of raw materials, and high specific surface area; however, their poor regeneration performance, high preparation cost, and low adsorption efficiency further limit their large-scale application. Therefore, constructing adsorbents with high adsorption efficiency, large adsorption capacity, and strong recovery performance is of great significance for the treatment of pharmaceutical wastewater.

[0004] Carbon nanotubes (CNTs) have wide applications in wastewater treatment due to their abundant oxygen-containing functional groups, strong charge transfer capabilities, accessible active sites, and low carbon layer packing density. Zeolite-like imidazolium ester (ZIF) frameworks are simple to synthesize, possess large specific surface areas, high porosity, high stability, and abundant carbon and nitrogen sources, making them widely used in the preparation of carbon-based materials. Carbon-based materials derived from ZIFs have become a research hotspot due to their high specific surface area, tunable pore structure and morphology, ease of doping with atoms, and abundant active sites. Compared to traditional carbon nanotube preparation methods (such as arc discharge, chemical deposition, and laser evaporation), ZIF-derived in-situ prepared carbon nanotubes offer advantages such as simple synthesis, tunable structure, and high specific surface area. However, the pore structure of ZIF-derived carbon nanotubes remains predominantly microporous, and nitrogen is easily lost and the structure collapses during pyrolysis, resulting in poor adsorption performance for antibiotics. Furthermore, the synthesized ZIFs carbon nanotubes are in powder form, and the difficulty in separating them in aqueous solution and the difficulty in recycling them further limit their application in the field of adsorption. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent, its preparation method, and its application. This bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent not only possesses a good pore structure, high specific surface area, and abundant active sites, exhibiting excellent adsorption performance, but also allows for magnetic separation, structural stability, and recyclability.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent includes the following steps:

[0008] Step 1: Place 10g-15g of 2-methylimidazole in 80mL-120mL of ultrapure water and stir until well mixed. Then add 0.1g-0.5g of sodium cetylbenzenesulfonate and stir to form a homogeneous solution for later use.

[0009] Step 2: Add zinc acetate dihydrate to 10mL-20mL of ultrapure water and stir until completely dissolved. Then add ferrous chloride tetrahydrate and sonicate to form a homogeneous solution for later use. The total mass of zinc acetate dihydrate and ferrous chloride tetrahydrate is 2.5g, and the molar ratio of zinc acetate dihydrate to ferrous chloride tetrahydrate is (2.5-9):1.

[0010] Step 3: Under stirring conditions, the solution prepared in Step 2 is added dropwise to the solution prepared in Step 1. After the addition is complete, the reaction vessel is sealed with sealing film and stirred continuously for 24 hours to form a light orange suspension. After the reaction is complete, the suspension is washed and dried to obtain bimetallic ZIFs.

[0011] Step 4: Place the bimetallic ZIFs prepared in Step 3 into a quartz boat, then place it in a tube furnace. Under a nitrogen or argon atmosphere, heat the furnace to 400℃~500℃ at a heating rate of 2℃ / min~5℃ / min for 1h~2h, then heat it again to 900~1100℃ for 3h~5h. Finally, cool the furnace to room temperature and collect the black product, which is the magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs.

[0012] The present invention also has the following technical features:

[0013] Preferably, the stirring time in both step one and step two is 30 min to 60 min.

[0014] Preferably, the ultrasound time in step two is 10 min to 20 min.

[0015] Preferably, the washing in step three involves washing with ultrapure water and ethanol or methanol 3 to 5 times respectively.

[0016] This invention also protects a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared by the method described above, and its application in the adsorption of tetracycline hydrochloride. The application method includes the following steps:

[0017] S1. The magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs is added to an aqueous solution of tetracycline hydrochloride with a concentration of 5 mg / L to 100 mg / L according to the mass ratio of (1 to 15):1. The adsorbent is then added to the aqueous solution of tetracycline hydrochloride with a concentration of 5 mg / L to 100 mg / L and adsorbed for 15 h to 24 h.

[0018] S2. After the adsorption is completed, an external magnetic field is used to separate the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent containing the drug.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] This invention employs an in-situ pyrolysis room temperature aqueous phase synthesis method to synthesize bimetallic ZIFs precursors. The synthesis method is simple and highly controllable. The magnetic hierarchical porous carbon nanotube composite adsorbent derived from the bimetallic ZIFs prepared by in-situ temperature-controlled pyrolysis of the precursors has excellent magnetic properties and hierarchical pore structure. This material possesses excellent characteristics such as superior hierarchical pore structure, high specific surface area, large adsorption capacity, and high recovery rate.

[0021] The bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent of the present invention has low preparation cost, strong operability, controllable composition and structure, high adsorption efficiency, and can be mass-produced. Under an external magnetic field, it can achieve rapid separation from the solution, has good magnetic properties and can be used for a long time. It can be widely applied to various pharmaceutical wastewater treatment fields and has excellent economic and environmental benefits.

[0022] The bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent of the present invention is easy to operate and has low cost for adsorbing and removing tetracycline hydrochloride. It can efficiently adsorb tetracycline hydrochloride and exhibits good adsorption performance, structural stability and recyclability. Attached Figure Description

[0023] Figure 1 The hysteresis curve of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 1.

[0024] Figure 2 Transmission electron microscopy image of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 2.

[0025] Figure 3 The graph shows the adsorption performance of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 2 on tetracycline hydrochloride at different times.

[0026] Figure 4 Nitrogen adsorption-desorption experiment of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 3.

[0027] Figure 5 The pore size distribution diagram of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 3 is shown.

[0028] Figure 6 The graph shows the adsorption performance of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 3 on tetracycline hydrochloride under different pH conditions.

[0029] Figure 7 The Fourier transform infrared spectrum of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 4. Detailed Implementation

[0030] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0031] Example 1

[0032] A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent includes the following steps:

[0033] 1) Preparation of ligand solution: Weigh 12g of 2-methylimidazole using an electronic balance and add it to 80mL of ultrapure water. Stir for 30min until dissolved, then add 0.1g of sodium cetylbenzenesulfonate and stir for 30min until completely dissolved. Set aside for use.

[0034] 2) Preparation of metal salt solution: Weigh 2.0g of zinc acetate dihydrate using an electronic balance and add it to 10mL of ultrapure water. Stir for 30min until dissolved. Then add 0.5g of ferrous chloride tetrahydrate and sonicate for 10min to form a homogeneous solution for later use.

[0035] 3) Preparation of bimetallic ZIFs: Add the solution from 2) dropwise to 1), and stir for 24 hours after forming a light orange suspension. During the stirring process, the reaction vessel needs to be sealed with a sealing film. After the reaction is completed, centrifuge and then wash with ultrapure water and ethanol or methanol 4 times, each time with a volume of 30 mL.

[0036] 4) Preparation of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent: The quartz boat containing the sample prepared in step 3) was placed in a tube furnace and subjected to two-step pyrolysis under a nitrogen atmosphere. First, pyrolysis was carried out at 500℃ for 1 h with a heating rate of 3℃ / min, and then at 1000℃ for 4 h with a heating rate of 5℃ / min. After the tube furnace cooled to room temperature, the sample was taken out to obtain the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent.

[0037] The above-prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent is used to adsorb tetracycline hydrochloride, specifically including the following steps:

[0038] 25 mg of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent was added to 150 mL of tetracycline hydrochloride solution with a concentration of 60 mg / L. The mixture was reacted at 25 °C for 24 h. After adsorption saturation, magnetic separation was performed under an external magnetic field. Then, 5 mL of the supernatant was filtered through a membrane, and the concentration of tetracycline hydrochloride in the filtrate was determined by ultraviolet spectrophotometer. The concentration of the remaining tetracycline hydrochloride was calculated based on the tetracycline hydrochloride standard curve. Finally, the adsorption efficiency of tetracycline hydrochloride was calculated, which was 85%.

[0039] The hysteresis loop of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in this embodiment is as follows: Figure 1 As shown, from Figure 1It can be seen that the magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs has a strong response to external magnetic fields and has a certain degree of magnetism, indicating that the constructed magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs has certain advantages in solution separation and recycling.

[0040] Example 2

[0041] A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent includes the following steps:

[0042] 1) Preparation of ligand solution: Weigh 13g of 2-methylimidazole using an electronic balance and add it to 95mL of ultrapure water. Stir for 60min until dissolved, then add 0.4g of sodium cetylbenzenesulfonate and stir for 60min until completely dissolved. Set aside for use.

[0043] 2) Preparation of metal salt solution: Weigh 2.2g of zinc acetate dihydrate using an electronic balance and add it to 15mL of ultrapure water. Stir for 60min until dissolved. Then add 0.3g of ferrous chloride tetrahydrate and sonicate for 15min to form a homogeneous solution for later use.

[0044] 3) Preparation of bimetallic ZIFs: Add the solution in 2) dropwise to 1), and stir for 30 h after forming a light orange suspension. During the stirring process, the reaction vessel needs to be sealed with sealing film. After the reaction is completed, centrifuge and then wash with ultrapure water and ethanol or methanol 5 times, each time with a volume of 40 mL.

[0045] 4) Preparation of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent: After placing the quartz boat containing the sample into a tube furnace, two-step pyrolysis was carried out under a nitrogen atmosphere. First, pyrolysis was performed at 450℃ for 2h with a heating rate of 2℃ / min, and then at 1000℃ for 3h with a heating rate of 5℃ / min. After the tube furnace cooled to room temperature, the sample was taken out to obtain the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent.

[0046] The above-prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent is used to adsorb tetracycline hydrochloride, specifically including the following steps:

[0047] 45 mg of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent was added to 150 mL of a 30 mg / L tetracycline hydrochloride solution. The mixture was reacted at 30 °C for 24 h. After adsorption saturation, magnetic separation was performed under an external magnetic field. 5 mL of the supernatant was then filtered through a membrane, and the concentration of tetracycline hydrochloride in the filtrate was determined using a UV spectrophotometer. The remaining tetracycline hydrochloride concentration was calculated based on the tetracycline hydrochloride standard curve. Finally, the adsorption efficiency of tetracycline hydrochloride was calculated, which was 92%.

[0048] The transmission electron microscope (TEM) image of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in this embodiment is shown below. Figure 2 As shown, from Figure 2 It can be seen that the prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent exhibits a bamboo-like nanotube shape with a width of about 20 nm, and displays a structure with alternating light and dark areas or a "worm-like" structure, indicating that magnetic carbon nanotubes with a hierarchical porous structure have been successfully prepared.

[0049] The adsorption performance of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in this embodiment for tetracycline hydrochloride at different adsorption times is shown in the figure below. Figure 3 As shown, by Figure 3 It can be seen that, within the range of 0–15 h, the adsorption capacity of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent for tetracycline hydrochloride first increases and then tends to level off over time.

[0050] Example 3

[0051] A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent includes the following steps:

[0052] 1) Preparation of ligand solution: Weigh 15g of 2-methylimidazole using an electronic balance and add it to 100mL of ultrapure water. Stir for 50min until dissolved, then add 0.5g of sodium cetylbenzenesulfonate and stir for 50min until completely dissolved. Set aside for use.

[0053] 2) Preparation of metal salt solution: Weigh 1.9g of zinc acetate dihydrate using an electronic balance and add it to 15mL of ultrapure water. Stir for 50min until dissolved. Then add 0.7g of ferrous chloride tetrahydrate and sonicate for 20min to form a homogeneous solution for later use.

[0054] 3) Preparation of bimetallic ZIFs: Add the solution in 2) dropwise to 1), and stir for 30 h after forming a light orange suspension. During the stirring process, the reaction vessel needs to be sealed with a sealing film. After the reaction is completed, centrifuge and then wash 5 times with ultrapure water and ethanol or methanol, each time with a volume of 30 mL.

[0055] 4) Preparation of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent: A quartz boat containing the sample was placed in a tube furnace and subjected to two-step pyrolysis under a nitrogen atmosphere. First, pyrolysis was carried out at 500℃ for 1 h with a heating rate of 2℃ / min, and then at 950℃ for 4 h with a heating rate of 3℃ / min. After the tube furnace cooled to room temperature, the sample was removed to obtain the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent.

[0056] The above-prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent is used to adsorb tetracycline hydrochloride, specifically including the following steps:

[0057] 20 mg of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent was added to 200 mL of a 20 mg / L tetracycline hydrochloride solution. The mixture was reacted at 35 °C for 25 h. After adsorption saturation, magnetic separation was performed under an external magnetic field. 5 mL of the supernatant was then filtered through a membrane, and the concentration of tetracycline hydrochloride in the filtrate was determined using a UV spectrophotometer. The remaining tetracycline hydrochloride concentration was calculated based on the tetracycline hydrochloride standard curve. Finally, the adsorption efficiency of tetracycline hydrochloride was calculated, and it was found to be 92%.

[0058] Figure 4 Nitrogen adsorption-desorption experiment of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 3. Figure 5 The pore size distribution diagram of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in Example 3 is shown below; Figure 4 and Figure 5 It can be seen that the nitrogen adsorption isotherm of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent exhibits type-I characteristics, and the high nitrogen adsorption capacity in the low-pressure region indicates that the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent has a microporous and mesoporous structure.

[0059] The adsorption performance of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in this embodiment for tetracycline hydrochloride under different pH conditions is shown in the figure below. Figure 6 As shown, from Figure 6 As can be seen from the data, within the range of 2–12 h, the adsorption capacity of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent for tetracycline hydrochloride first increases and then decreases with increasing pH.

[0060] Example 4

[0061] A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent includes the following steps:

[0062] 1) Preparation of ligand solution: Weigh 10g of 2-methylimidazole using an electronic balance and add it to 120mL of ultrapure water. Stir for 60min until dissolved, then add 0.5g of sodium cetylbenzenesulfonate and stir for 60min until completely dissolved. Set aside for use.

[0063] 2) Preparation of metal salt solution: Weigh 2.1g of zinc acetate dihydrate using an electronic balance and add it to 20mL of ultrapure water. Stir for 60min until dissolved. Then add 0.4g of ferrous chloride tetrahydrate and sonicate for 20min to form a homogeneous solution for later use.

[0064] 3) Preparation of bimetallic ZIFs: Add the solution in 2) dropwise to 1), and stir for 36 hours after forming a light orange suspension. During the stirring process, the reaction vessel needs to be sealed with a sealing film. After the reaction is completed, centrifuge and then wash three times with ultrapure water and ethanol or methanol, each time with a volume of 40 mL.

[0065] 4) Preparation of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent: A quartz boat containing the sample was placed in a tube furnace and subjected to two-step pyrolysis under a nitrogen atmosphere. First, pyrolysis was carried out at 400℃ for 1.5h with a heating rate of 5℃ / min, and then at 900℃ for 5h with a heating rate of 2℃ / min. After the tube furnace cooled to room temperature, the sample was removed to obtain the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent.

[0066] The above-prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent is used to adsorb tetracycline hydrochloride, specifically including the following steps:

[0067] 30 mg of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent was added to 150 mL of a 10 mg / L tetracycline hydrochloride solution. The mixture was reacted at 30 °C for 18 h. After adsorption saturation, magnetic separation was performed under an external magnetic field. 5 mL of the supernatant was then filtered through a membrane, and the concentration of tetracycline hydrochloride in the filtrate was determined using a UV spectrophotometer. The remaining tetracycline hydrochloride concentration was calculated based on the tetracycline hydrochloride standard curve. Finally, the adsorption efficiency of tetracycline hydrochloride was calculated, and it was found to be 90%.

[0068] The Fourier transform infrared spectrum of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared in this embodiment is shown below. Figure 7 As shown, from Figure 7 It can be seen that the surface of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent has abundant oxygen- or nitrogen-containing functional groups, indicating that the constructed bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent has a large number of active sites, which has a certain promoting effect on the adsorption of tetracycline hydrochloride.

[0069] The adsorption performance of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent for tetracycline hydrochloride under different temperature conditions prepared in this embodiment is shown in Table 1. As can be seen from Table 1, in the range of 25℃ to 35℃, the adsorption capacity of the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent for tetracycline hydrochloride increases with increasing temperature.

[0070] Table 1 Adsorption capacity of tetracycline hydrochloride at different temperatures

[0071]

[0072] Example 5

[0073] A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent includes the following steps:

[0074] 1) Preparation of ligand solution: Weigh 10g of 2-methylimidazole using an electronic balance and add it to 120mL of ultrapure water. Stir for 60min until dissolved, then add 0.5g of sodium cetylbenzenesulfonate and stir for 60min until completely dissolved. Set aside for use.

[0075] 2) Preparation of metal salt solution: Weigh 3g of zinc acetate dihydrate using an electronic balance and add it to 20mL of ultrapure water. Stir for 60min until dissolved. Then add 0.3g of ferrous chloride tetrahydrate and sonicate for 20min to form a homogeneous solution for later use.

[0076] 3) Preparation of bimetallic ZIFs: Add the solution in 2) dropwise to 1), and stir for 36 hours after forming a light orange suspension. During the stirring process, the reaction vessel needs to be sealed with a sealing film. After the reaction is completed, centrifuge and then wash three times with ultrapure water and ethanol or methanol, each time with a volume of 40 mL.

[0077] 4) Preparation of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent: A quartz boat containing the sample was placed in a tube furnace and subjected to two-step pyrolysis under a nitrogen atmosphere. First, pyrolysis was carried out at 400℃ for 1.5h with a heating rate of 5℃ / min, and then at 900℃ for 5h with a heating rate of 2℃ / min. After the tube furnace cooled to room temperature, the sample was removed to obtain the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent.

[0078] The above-prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent is used to adsorb tetracycline hydrochloride, specifically including the following steps:

[0079] 15 mg of bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent was added to 200 mL of a 5 mg / L tetracycline hydrochloride solution. The mixture was reacted at 30 °C for 15 h. After adsorption saturation, magnetic separation was performed under an external magnetic field. 5 mL of the supernatant was then filtered through a membrane, and the concentration of tetracycline hydrochloride in the filtrate was determined using a UV spectrophotometer. The remaining tetracycline hydrochloride concentration was calculated based on the tetracycline hydrochloride standard curve. Finally, the adsorption efficiency of tetracycline hydrochloride was calculated, and it was found to be 90%.

[0080] The bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent provided by this invention features a simple synthesis process, large-scale production capability, low synthesis cost, easy recovery, and low toxicity of the raw materials used in the preparation process, thus exhibiting good environmental friendliness. The prepared bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent possesses excellent hierarchical porous structure, high nitrogen doping content, large specific surface area, and abundant active sites. The preparation of this bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent for adsorbing tetracycline hydrochloride is simple and easy to operate, exhibits high adsorption efficiency, large adsorption capacity, and easy recovery, demonstrating strong advantages in treating antibiotic wastewater.

Claims

1. A method for preparing a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent, characterized in that, Includes the following steps: Step 1: Place 10 g to 15 g of 2-methylimidazole in 80 mL to 120 mL of ultrapure water and stir until well mixed. Then add 0.1 g to 0.5 g of sodium cetylbenzenesulfonate and stir to form a homogeneous solution for later use. Step 2: Add zinc acetate dihydrate to 10 mL ~ 20 mL of ultrapure water and stir until completely dissolved. Then add ferrous chloride tetrahydrate and sonicate to form a homogeneous solution for later use. The total mass of zinc acetate dihydrate and ferrous chloride tetrahydrate is 2.5 g, and the molar ratio of zinc acetate dihydrate to ferrous chloride tetrahydrate is (2.5~9):

1. Step 3: Under stirring conditions, the solution prepared in Step 2 is added dropwise to the solution prepared in Step 1. After the addition is complete, the reaction vessel is sealed with sealing film and stirred continuously for 24 h to form a light orange suspension. After the reaction is complete, the suspension is washed and dried to obtain bimetallic ZIFs. Step 4: Place the bimetallic ZIFs prepared in Step 3 into a quartz boat, then place it in a tube furnace. Under a nitrogen or argon atmosphere, heat the furnace to 400℃~500℃ at a heating rate of 2℃ / min~5℃ / min for 1 h~2 h, then heat it again to 900~1100℃ for 3 h~5 h. Finally, cool the furnace to room temperature and collect the black product, which is the magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs. The magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs has a microporous and mesoporous structure.

2. The method for preparing the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent as described in claim 1, characterized in that, The stirring time mentioned in both Step 1 and Step 2 is 30 min to 60 min.

3. The method for preparing the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent as described in claim 1, characterized in that, The ultrasound time mentioned in step two is 10 min to 20 min.

4. The method for preparing the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent as described in claim 1, characterized in that, The washing described in step three involves washing with ultrapure water and ethanol or methanol 3 to 5 times respectively.

5. A bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent prepared by the method described in any one of claims 1 to 4.

6. The application of a bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent as described in claim 5 in the adsorption of tetracycline hydrochloride, characterized in that, Includes the following steps: S1. The magnetic hierarchical porous carbon nanotube composite adsorbent derived from bimetallic ZIFs was added to an aqueous solution of tetracycline hydrochloride with a concentration of 5 mg / L to 100 mg / L according to the mass ratio of (1~15):

1. The adsorbent was then added to the aqueous solution of tetracycline hydrochloride with a concentration of 5 mg / L to 100 mg / L and adsorbed for 15 h to 24 h. S2. After the adsorption is completed, an external magnetic field is used to separate the bimetallic ZIFs-derived magnetic hierarchical porous carbon nanotube composite adsorbent containing the drug.

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