Iron / nickel bimetallic amino-functionalized multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, preparation method and application

Abstract

The application provides an iron / nickel bimetallic aminated multi-walled carbon nanotube for adsorbing sulfonamide antibiotics, a preparation method and application, and relates to the field of sulfonamide antibiotic adsorbents.The preparation method comprises the following steps: adding multi-walled carbon nanotubes into DMF, and reacting with ethylenediamine and O-benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate to prepare aminated multi-walled carbon nanotubes; and dispersing the aminated multi-walled carbon nanotubes in ethylene glycol, and contacting with sodium acetate, a nickel salt and an iron salt to prepare the iron / nickel bimetallic aminated multi-walled carbon nanotube for adsorbing sulfonamide antibiotics.The iron / nickel bimetallic aminated multi-walled carbon nanotube for adsorbing sulfonamide antibiotics has the advantages of ordered pore structure, high mechanical strength, difficulty in plugging, large adsorption capacity, good economy, and the ability to effectively adsorb and remove sulfonamide antibiotics in wastewater; and after adsorption is completed, the iron / nickel bimetallic aminated multi-walled carbon nanotube can be quickly and efficiently separated from the wastewater, which is beneficial to subsequent recycling and reuse.

Description

Technical Field

[0001] This invention relates to the field of sulfonamide antibiotic adsorbent technology, and in particular to an iron / nickel bimetallic aminated multi-walled carbon nanotube for adsorbing sulfonamide antibiotics, its preparation method, and its application. Background Technology

[0002] Antibiotics are synthetic antibacterial drugs primarily used to effectively prevent and treat various infectious diseases in humans and animals. However, the use of antibiotics inevitably leads to their release and spread in the environment, which in turn affects the human body through the food chain, causing issues such as dysbiosis, digestive system dysfunction, and even death. Therefore, finding efficient, simple, and stable methods to remove antibiotics is of great significance.

[0003] Among various types of industrial wastewater, sulfonamide antibiotics are a very typical and frequently occurring class of antibiotics, widely found in pharmaceutical industrial wastewater, chemical production wastewater, and some medical-related industry wastewater. This is mainly due to the large-scale application of sulfonamide antibiotics in the pharmaceutical and veterinary drug fields, as well as their relatively complex synthesis processes and production procedures.

[0004] To date, numerous technologies (such as biodegradation, photocatalysis, and oxidation) and adsorbent materials have been used for the removal of sulfonamide antibiotics. However, sulfonamide antibiotics in industrial wastewater are difficult to completely remove using traditional wastewater treatment processes. For example, the activated sludge process typically has a low removal rate for sulfonamide antibiotics because sulfonamide antibiotics possess certain chemical stability and biological inertness, making them difficult for microorganisms to degrade. Furthermore, biodegradation methods are only applicable to sulfonamide antibiotics with biodegradable properties, and the specific degradation pathways, functional microbial communities corresponding to each reaction stage, and key enzyme structures are currently unclear. Photocatalysis and oxidation usually require advanced oxidation catalysis processes, resulting in poor overall economic efficiency and high engineering application costs.

[0005] Existing technologies disclose various adsorbents for adsorbing sulfonamide antibiotics, including traditional activated carbon materials, polymer materials, clay mineral materials, and biomass materials. However, traditional activated carbon materials have some disadvantages and limitations. For example, their disordered pore structure leads to relatively low adsorption capacity, and large quantities of activated carbon are required to treat high-concentration or large-volume wastewater, increasing treatment costs and complexity. Furthermore, the recovery and reuse of activated carbon is also a challenge. The preparation process of polymer materials is often complex and costly, hindering large-scale application. Clay mineral materials have a significant natural adsorption capacity bottleneck and low treatment efficiency. Chemical modification can easily introduce chemical impurities leading to secondary pollution and increase recovery costs. Biomass materials are easily attached to or decomposed by organisms in certain situations, leading to adverse biological reactions. Biomass materials such as straw and peanut shells require acid-base treatment to remove unnecessary components such as hemicellulose and lignin, and their adsorption rate is extremely low, with the adsorption process significantly affected by pH.

[0006] Existing technologies disclose a method of introducing amino groups onto the surface of activated carbon through a cross-coupling reaction initiated by a catalyst. The aim is to provide more negative charges to the activated carbon surface through these amino groups, thereby improving its adsorption capacity for cations. However, the inventors have found that activated carbon, as an amorphous carbon, has disordered pores, is prone to clogging, and has low mechanical strength, making it unsuitable for effective adsorption treatment of sulfonamide antibiotics. Summary of the Invention

[0007] To address the technical problems existing in the prior art, this invention provides a method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics. By controlling the reaction temperature, time, and precursor concentration, the multi-walled carbon nanotubes, amino functional groups, and metal precursors are fully mixed and contacted. Using multi-walled carbon nanotubes as a carrier provides stronger mechanical strength and thermal stability, which is beneficial for amination. The aminated multi-walled carbon nanotubes, as a carrier for iron and nickel bimetallic loading, enhance the hydrophilicity and dispersibility of carbon nanotubes, which is beneficial to the dispersibility and stability of the synthesized iron / nickel bimetallic aminated multi-walled carbon nanotubes used for adsorbing sulfonamide antibiotics. The aforementioned methods work together to effectively overcome the defects of existing sulfonamide antibiotic adsorption materials, achieving stable and efficient adsorption and removal of sulfonamide antibiotics from wastewater.

[0008] The present invention also provides iron / nickel bimetallic aminated multi-walled carbon nanotubes prepared by the aforementioned method for adsorbing sulfonamide antibiotics. These nanotubes have the characteristics of ordered pore structure, high mechanical strength, non-clogging, large adsorption capacity, and good economy. They can effectively adsorb and remove sulfonamide antibiotics from wastewater, and after adsorption, they are easy to separate from the wastewater quickly and efficiently, which is conducive to subsequent regeneration and recycling.

[0009] The present invention also provides the application of the iron / nickel bimetallic aminated multiwalled carbon nanotubes for adsorbing sulfonamide antibiotics in wastewater.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics includes the following steps: Step S01: Add multi-walled carbon nanotubes to N,N'-dimethylformamide, mix well, then add ethylenediamine, mix well, and continue to add O-benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate. Stir and heat the mixture to obtain a crude reaction solution. Dilute the crude reaction solution with ethanol and wash it. Separate and collect the solids. Wash and dry the solids to obtain aminated multi-walled carbon nanotubes. Step S02: Disperse aminated multi-walled carbon nanotubes in ethylene glycol, and add sodium acetate, nickel salt and iron salt in sequence. After the dispersion is uniform, heat to react. After the reaction is complete, collect the solid. Wash and dry the solid to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics.

[0011] Preferably, in step S01, the mass-to-volume ratio of multi-walled carbon nanotubes to ethylenediamine is 0.5-1 mg:1 mL; The weight ratio of multi-walled carbon nanotubes to O-benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate is 10-50:1.

[0012] Preferably, in step S01, the volume ratio of N,N'-dimethylformamide to ethylenediamine is 1:1-3.

[0013] Preferably, in step S01, the heating reaction temperature is 40-80℃ and the heating reaction time is 20-60 min.

[0014] Preferably, in step S02, the mass-to-volume ratio of aminated multi-walled carbon nanotubes to ethylene glycol is 2-10 mg:1 mL.

[0015] Preferably, in step S02, the nickel salt is one of the following: nickel nitrate hexahydrate, nickel chloride hexahydrate, or nickel acetate tetrahydrate; and the iron salt is one of the following: ferric chloride hexahydrate, ferric sulfate nonahydrate, or ferric nitrate nonahydrate.

[0016] Preferably, in step S02, the mass ratio of iron salt to aminated carbon nanotubes is 10-20:1; The molar ratio of iron salt to sodium acetate is 1:1-5; The molar ratio of iron salt to nickel salt is 1:1-2.

[0017] Preferably, in step S02, the heating reaction temperature is 120-200℃, and the heating reaction time is 2-12h.

[0018] An iron / nickel bimetallic aminated multiwalled carbon nanotube prepared by the aforementioned method for adsorbing sulfonamide antibiotics.

[0019] The application of the aforementioned iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics in wastewater.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the preparation of the iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics of the present invention, multi-walled carbon nanotubes are used as carriers. Compared with single-walled carbon nanotubes, in the amination process of first oxidizing to introduce -COOH / -OH and then introducing -NH2 through amidation reaction, multi-walled carbon nanotubes, due to their multi-walled structure, retain better conductive pathways on the inner wall after the outer wall is functionalized, which is more conducive to the uniform nucleation of metal precursors on their surface and reduces the final size of metal particles. Similarly, compared with other carbon materials, the one-dimensional hollow tubes of multi-walled carbon nanotubes can interweave with each other to form a relatively stable three-dimensional conductive network that is not easy to completely densely stack. The inter-tube channels between them are conducive to liquid phase mass transfer.

[0021] (2) In the preparation of the iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics in this invention, pre-aminated multi-walled carbon nanotubes are used as the carrier for the iron / nickel bimetallic loading. Amination not only enhances the hydrophilicity and dispersibility of the multi-walled carbon nanotubes, but also the amino groups contain lone pairs of electrons, which can react with Fe. 3+ / Fe 2+ Ni 2+ Coordination is formed, which increases the adsorption amount and uniformity of metal salt precursors on the support surface. As anchoring sites for metal ions, pre-amylation can avoid metal agglomeration and enhance the stability and adsorption selectivity of composite materials compared to direct metal loading.

[0022] (3) In the preparation of the iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics of the present invention, the iron / nickel bimetallic aminated multi-walled carbon nanotubes used for adsorbing sulfonamide antibiotics are modified by combining iron-nickel bimetallic particles with multi-walled carbon nanotubes, which successfully endows the adsorbent with excellent magnetic properties, thereby realizing the rapid and efficient separation of the adsorbent and the sample system to be treated under the action of an external magnetic field, fundamentally avoiding the inherent defects of the traditional separation process such as filtration and centrifugation.

[0023] (4) The iron / nickel bimetallic aminated multi-walled carbon nanotubes of the present invention for adsorbing sulfonamide antibiotics have a much higher adsorption capacity for sulfonamide antibiotics than the sum of iron-aminated multi-walled carbon nanotubes and nickel-aminated multi-walled carbon nanotubes. This is because the synergistic effect of the bimetals provides more active sites for the material. Specifically, the regulating effect of electron transfer between the iron / nickel bimetals can optimize the electron cloud density on the material surface, significantly improve the activity of amino functional groups, and make it easier to adsorb sulfonamide antibiotics through chemical action. At the same time, the synergistic dispersion effect of the bimetallic particles can effectively avoid the problem of active site shielding caused by the agglomeration of single metal particles, thereby greatly enhancing the material's specific adsorption capacity for sulfonamide antibiotics, breaking through the limitations of the adsorption performance of single metal modified carbon nanotubes, and further demonstrating the synergistic effect. For example, in Example 1 of this invention, the adsorption of the typical sulfonamide antibiotic sulfadiazine (SD) showed that, according to the Langmuir model which is more consistent with it, the adsorption capacity of bimetallic doping can reach 25.72 mg / g, which is much higher than the sum of 16.6 mg / g and 5.4 mg / g of single doping. Moreover, the effect of bimetallic doping is also better than that of single metal doping for the other 5 sulfonamide antibiotics, achieving excellent synergistic adsorption of sulfonamide antibiotics (Table 1). Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the aminated carbon nanotubes in Example 1 of the present invention.

[0025] Figure 2 The image shows a SEM-mapping image of the aminated carbon nanotubes in Example 1 of this invention. In the image, (A) is the surface scan morphology image, (B) is the C element distribution image, (C) is the N element distribution image, and (D) is the O element distribution image.

[0026] Figure 3 This is a SEM image of iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics according to Example 1 of the present invention.

[0027] Figure 4 This is a SEM-mapping image of the iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics according to Example 1 of the present invention; in the image, (A) is the surface scan morphology image, (B) is the elemental distribution map of Fe, (C) is the elemental distribution map of Ni, (D) is the elemental distribution map of C, (E) is the elemental distribution map of N, and (F) is the elemental distribution map of O.

[0028] Figure 5 The X-ray diffraction (XRD) patterns are shown for the aminated multi-walled carbon nanotubes in step (1) and the iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics in step (2) of Example 1 of the present invention.

[0029] Figure 6 This is a Langmuir diagram of the adsorption of sulfonamide antibiotics on iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics in Example 1 of the present invention.

[0030] Figure 7 This is a Freundlich diagram showing the individual adsorption of sulfonamide antibiotics on iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics in Example 1 of the present invention.

[0031] Figure 8 This is a zeta potential diagram of iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics in Example 1 of the present invention.

[0032] Figure 9 The Fourier transform infrared (FT-IR) spectra of iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics in Example 1 of the present invention before and after adsorption of sulfonamide antibiotics.

[0033] Figure 10 The thermogravimetric analysis (TGA) of iron / nickel bimetallic aminated multiwalled carbon nanotubes used for adsorbing sulfonamide antibiotics in Example 1 of the present invention before and after adsorption of sulfonamide antibiotics.

[0034] Figure 11 This is a magnetic recovery experiment diagram of iron / nickel bimetallic aminated multi-walled carbon nanotubes as adsorbents for adsorbing sulfonamide antibiotics in Example 1 of the present invention; in the diagram, (A) is a mixture of adsorbent and sulfonamide antibiotics, and (B) is an experimental diagram of magnetic adsorption of adsorbent after incubation.

[0035] Figure 12 This is a graph showing the reusability of iron / nickel bimetallic aminated multi-walled carbon nanotubes as an adsorbent in Example 1 of the present invention, used for adsorbing sulfonamide antibiotics.

[0036] Figure 13 The image shows the Langmuir plot of iron-aminated multi-walled carbon nanotubes adsorbed in Comparative Example 1 of this invention.

[0037] Figure 14 This is a Freundlich diagram of the adsorption of iron-aminated multi-walled carbon nanotubes in Comparative Example 1 of this invention.

[0038] Figure 15 The image shows the Langmuir plot of the adsorption of nickel-aminated multi-walled carbon nanotubes in Comparative Example 2 of this invention.

[0039] Figure 16 This is a Freundlich diagram of the adsorption of nickel-aminated multi-walled carbon nanotubes in Comparative Example 2 of this invention.

[0040] Figure 17 This is a SEM image of the unaminated multi-walled carbon nanotubes of Comparative Example 3 of the present invention.

[0041] Figure 18 This is a SEM image of the unaminated iron / nickel bimetallic multiwalled carbon nanotubes of Comparative Example 3 of this invention. Detailed Implementation

[0042] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0043] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] This invention provides a method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, comprising the following steps: Step S01: Add multi-walled carbon nanotubes to N,N'-dimethylformamide (DMF), mix well, then add ethylenediamine, mix well, and then add powdered O-benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate (HBTU). Stir and heat to react and obtain a crude reaction solution. Dilute the crude reaction solution with ethanol and wash it. Separate and collect the solid. Wash and dry the solid to obtain aminated multi-walled carbon nanotubes. Step S02: Disperse aminated multi-walled carbon nanotubes in ethylene glycol, and add sodium acetate, nickel salt and iron salt in sequence. After the dispersion is uniform, heat to react. After the reaction is complete, collect the solid. Wash and dry the solid to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics.

[0045] In this embodiment of the invention, step S01 uses multi-walled carbon nanotubes as a carrier. First, -COOH / -OH is introduced through oxidation, and then -NH2 is introduced through an amidation reaction. Due to its multi-walled structure, the inner wall of multi-walled carbon nanotubes retains good conductive pathways even after the outer wall is functionalized, which is more conducive to the uniform nucleation of metal precursors on its surface and reduces the final size of the metal particles. Similarly, compared with other carbon materials, the one-dimensional hollow tubes of multi-walled carbon nanotubes intertwine to form a relatively stable three-dimensional conductive network, making complete dense stacking difficult. The inter-tube channels facilitate liquid-phase mass transfer. Simultaneously, aminated multi-walled carbon nanotubes serve as a carrier for iron-nickel bimetallic loading. Amination not only enhances the hydrophilicity and dispersibility of multi-walled carbon nanotubes, but also, the amino groups contain lone pairs of electrons, which can interact with Fe... 3+ / Fe 2+ Ni 2+ Coordination is formed, increasing the adsorption capacity and uniformity of the metal salt precursor on the support surface. Serving as anchoring sites for metal ions, pre-ammoniation avoids metal agglomeration compared to direct metal loading, enhancing the stability and selectivity of the composite material. Then, in step S02, by composite modification of iron-nickel bimetallic particles with multi-walled carbon nanotubes, excellent magnetic properties are successfully endowed to the adsorbent, enabling rapid and efficient separation of the adsorbent from the sample system under an applied magnetic field. This fundamentally avoids the inherent defects of traditional separation processes such as filtration and centrifugation.

[0046] The aforementioned technical methods work together to produce iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics. These nanotubes have the characteristics of ordered pore structure, high mechanical strength, resistance to clogging, large adsorption capacity, and good economic efficiency. They can effectively adsorb and remove sulfonamide antibiotics from wastewater, and after adsorption, they are easy to separate from the wastewater quickly and efficiently, which is conducive to subsequent regeneration and recycling.

[0047] Preferably, in step S01, the mass-to-volume ratio of multi-walled carbon nanotubes to ethylenediamine is 0.5-1 mg:1 mL; the weight ratio of multi-walled carbon nanotubes to O-benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate is 10-50:1.

[0048] Preferably, in step S01, the volume ratio of N,N'-dimethylformamide to ethylenediamine is 1:1-3.

[0049] Preferably, in step S01, the heating reaction temperature is 40-80℃ and the heating reaction time is 20-60 min.

[0050] Preferably, in step S02, the mass-to-volume ratio of aminated multi-walled carbon nanotubes to ethylene glycol is 2-10 mg:1 mL.

[0051] Preferably, in step S02, the nickel salt is one of the following: nickel nitrate hexahydrate (Ni(NO3)2·6H2O), nickel chloride hexahydrate (NiCl2·6H2O), or nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O); and the iron salt is one of the following: ferric chloride hexahydrate (FeCl3·6H2O), ferric sulfate nonahydrate (Fe2(SO4)3·9H2O), or ferric nitrate nonahydrate (Fe(NO3)3·9H2O).

[0052] Preferably, in step S02, the mass ratio of iron salt to aminated carbon nanotubes is 10-20:1; the molar ratio of iron salt to sodium acetate is 1:1-5; and the molar ratio of iron salt to nickel salt is 1:1-2.

[0053] Preferably, in step S02, the temperature of the heating reaction is 120-200℃, and the heating reaction time is 2-12h.

[0054] The present invention also provides iron / nickel bimetallic aminated multiwalled carbon nanotubes prepared by the aforementioned method for adsorbing sulfonamide antibiotics.

[0055] This invention also provides the application of the iron / nickel bimetallic aminated multi-walled carbon nanotubes used for adsorbing sulfonamide antibiotics in wastewater.

[0056] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with some specific embodiments.

[0057] Example 1 This embodiment provides a method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, specifically as follows: (1) Preparation of aminated multi-walled carbon nanotubes: First, weigh 200 mg of multi-walled carbon nanotubes and add them to a beaker containing 100 mL of DMF, and disperse them until uniform; then add 300 mL of ethylenediamine to make the proportion of multi-walled carbon nanotubes in ethylenediamine reach 0.67 mg / mL, and continue to sonicate to mix them uniformly; after the sonication, add 10 mg of powdered HBTU to the mixture, and then transfer it to a 500 mL three-necked round-bottom flask. Then place the three-necked round-bottom flask in a constant temperature water bath, heat it to 60 °C, stir and reflux for 30 min to obtain a crude aminated multi-walled carbon nanotube solution. Dilute the obtained crude solution with ethanol and wash it. Filter and collect the solid. After washing the solid with ethanol, pure aminated multi-walled carbon nanotubes are obtained; finally, freeze-dry the aminated multi-walled carbon nanotubes for later use.

[0058] (2) Preparation of iron / nickel bimetallic doped aminated multi-walled carbon nanotubes: 300 mg of aminated multi-walled carbon nanotubes were weighed and added to a beaker containing 50 mL of ethylene glycol, so that the ratio of aminated multi-walled carbon nanotubes to ethylene glycol reached 6 mg / mL. The mixture was ultrasonically treated at room temperature until the aminated multi-walled carbon nanotubes were dispersed. Then, 0.05 mol 4.10 g sodium acetate, 0.01 mol 4.04 g Fe(NO3)3·9H2O and 0.01 mol 2.91 g Ni(NO3)2·6H2O were added sequentially. The mixture was ultrasonically treated again until the salts were completely dissolved into a black mixed solution. The black mixed solution was transferred to a polytetrafluoroethylene stainless steel reactor, and the temperature was controlled at 200 °C. The reaction was maintained at this temperature for 6 h. After the reaction was completed, the solid crude product was collected. The solid crude product was washed several times with deionized water and anhydrous ethanol to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics.

[0059] This embodiment also provides iron / nickel bimetallic aminated multiwalled carbon nanotubes prepared by the aforementioned method for adsorbing sulfonamide antibiotics.

[0060] Example 2 This embodiment provides a method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, specifically as follows: (1) Preparation of aminated multi-walled carbon nanotubes: First, weigh 300 mg of multi-walled carbon nanotubes and add them to a beaker containing 100 mL of DMF, and disperse them evenly; then add 300 mL of ethylenediamine to make the ratio of multi-walled carbon nanotubes in ethylenediamine reach 1 mg / mL, and continue to sonicate for 20 min to mix evenly; after the sonication, add 10 mg of powdered HBTU to the mixture, and then transfer it to a 500 mL three-necked round-bottom flask. Then place the three-necked round-bottom flask in a constant temperature water bath, heat it to 80 °C, stir and reflux for 20 min to obtain a crude aminated multi-walled carbon nanotube solution. Dilute the obtained crude solution with ethanol and wash it. Filter and collect the solid. After washing the solid with ethanol, pure aminated multi-walled carbon nanotubes are obtained; finally, freeze-dry the aminated multi-walled carbon nanotubes for later use.

[0061] (2) Preparation of iron / nickel bimetallic doped aminated multi-walled carbon nanotubes: 200 mg of aminated multi-walled carbon nanotubes were weighed and added to a beaker containing 50 mL of ethylene glycol, so that the ratio of aminated multi-walled carbon nanotubes to ethylene glycol reached 4 mg / mL. The mixture was ultrasonically treated at room temperature until the aminated multi-walled carbon nanotubes were dispersed. Then, 0.04 mol 3.28 g sodium acetate, 0.01 mol 2.70 g FeCl3·6H2O and 0.02 mol 4.75 g NiCl2·6H2O were added sequentially, and ultrasonic treatment was continued until the salts were completely dissolved into a black mixed solution. The black mixed solution was transferred to a polytetrafluoroethylene stainless steel reactor, and the temperature was controlled at 180 °C. The reaction was maintained at this temperature for 8 h. After the reaction was completed, the solid crude product was collected. The solid crude product was washed several times with deionized water and anhydrous ethanol to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics.

[0062] This embodiment also provides iron / nickel bimetallic aminated multiwalled carbon nanotubes prepared by the aforementioned method for adsorbing sulfonamide antibiotics.

[0063] Example 3 This embodiment provides a method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, specifically as follows: (1) Preparation of aminated multi-walled carbon nanotubes: First, weigh 50 mg of multi-walled carbon nanotubes and add them to a beaker containing 100 mL of DMF. Disperse the mixture until uniform. Then, add 100 mL of ethylenediamine to make the ratio of multi-walled carbon nanotubes in ethylenediamine reach 0.5 mg / mL. Continue ultrasonic treatment for 20 min to mix evenly. After ultrasonic treatment, add 5 mg of powdered HBTU to the mixture and transfer it to a 500 mL three-necked round-bottom flask. Then, place the three-necked round-bottom flask in a constant temperature water bath, heat it to 40 °C, stir and reflux for 1 h to obtain a crude aminated multi-walled carbon nanotube solution. Dilute the obtained crude solution with ethanol and wash it. Filter and collect the solid. After washing the solid with ethanol, pure aminated multi-walled carbon nanotubes are obtained. Finally, freeze-dry the aminated multi-walled carbon nanotubes for later use.

[0064] (2) Preparation of iron / nickel bimetallic doped aminated multi-walled carbon nanotubes: 300 mg of aminated multi-walled carbon nanotubes were weighed and added to a beaker containing 50 mL of ethylene glycol, so that the ratio of aminated multi-walled carbon nanotubes in ethylene glycol reached 6 mg / mL. The mixture was ultrasonically treated at room temperature until the aminated multi-walled carbon nanotubes were dispersed. Then, 0.03 mol 2.46 g sodium acetate, 0.01 mol 5.62 g Fe2(SO4)3·9H2O and 0.02 mol 5.82 g Ni(NO3)2·6H2O were added sequentially, and the mixture was ultrasonically treated until the salts were completely dissolved into a black mixed solution. The black mixed solution was transferred to a polytetrafluoroethylene stainless steel reactor, and the temperature was controlled at 120 °C. The reaction was kept at this temperature for 12 h. After the reaction was completed, the solid crude product was collected. The solid crude product was washed several times with deionized water and anhydrous ethanol to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics.

[0065] This embodiment also provides iron / nickel bimetallic aminated multiwalled carbon nanotubes prepared by the aforementioned method for adsorbing sulfonamide antibiotics.

[0066] Example 4 This embodiment provides a method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, specifically as follows: (1) Preparation of aminated multi-walled carbon nanotubes: First, weigh 150 mg of multi-walled carbon nanotubes and add them to a beaker containing 100 mL of DMF. Disperse the mixture until uniform. Then, add 300 mL of ethylenediamine to make the ratio of multi-walled carbon nanotubes in ethylenediamine reach 0.5 mg / mL. Continue ultrasonic treatment for 20 min to mix evenly. After ultrasonic treatment, add 3 mg of powdered HBTU to the mixture and transfer it to a 500 mL three-necked round-bottom flask. Then, place the three-necked round-bottom flask in a constant temperature water bath, heat it to 80 °C, stir and reflux for 40 min to obtain a crude aminated multi-walled carbon nanotube solution. Dilute the obtained crude solution with ethanol and wash it. Filter and collect the solid. After washing the solid with ethanol, pure aminated multi-walled carbon nanotubes are obtained. Finally, freeze-dry the aminated multi-walled carbon nanotubes for later use.

[0067] (2) Preparation of iron / nickel bimetallic doped aminated multi-walled carbon nanotubes: 404 mg of aminated multi-walled carbon nanotubes were weighed and added to a beaker containing 40.4 mL of ethylene glycol, so that the ratio of aminated multi-walled carbon nanotubes to ethylene glycol reached 10 mg / mL. The mixture was ultrasonically treated at room temperature until the aminated multi-walled carbon nanotubes were dispersed. Then, 0.01 mol of 0.82 g of sodium acetate, 0.01 mol of 4.04 g of Fe(NO3)3·9H2O, and 0.01 mol of 2.48 g of Ni(CH3COO)2·4H2O were added sequentially. The mixture was ultrasonically treated again until the salts were completely dissolved into a black mixed solution. The black mixed solution was transferred to a polytetrafluoroethylene stainless steel reactor, and the temperature was controlled at 160 °C. The reaction was maintained at this temperature for 2 h. After the reaction was completed, the solid crude product was collected. The solid crude product was washed several times with deionized water and anhydrous ethanol to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics.

[0068] This embodiment also provides iron / nickel bimetallic aminated multiwalled carbon nanotubes prepared by the aforementioned method for adsorbing sulfonamide antibiotics.

[0069] Comparative Example 1 Comparative Example 1 uses the technical solution of Example 1, the only difference being that in step (2), only Fe(NO3)3·9H2O is added, and the addition of Ni(NO3)2·6H2O is omitted to prepare iron-doped aminated multi-walled carbon nanotubes. Other conditions are the same as in Example 1.

[0070] Specifically, the iron-doped aminated multi-walled carbon nanotubes were prepared as follows: 300 mg of aminated multi-walled carbon nanotubes were weighed and added to a beaker containing 50 mL of ethylene glycol, achieving a ratio of 6 mg / mL of aminated multi-walled carbon nanotubes in ethylene glycol. The mixture was ultrasonically treated at room temperature until the aminated multi-walled carbon nanotubes were dispersed. Subsequently, 0.05 mol (4.10 g) of sodium acetate and 0.01 mol (4.04 g) of Fe(NO3)3·9H2O were added sequentially, and ultrasonic treatment continued until the salts were completely dissolved into a black mixed solution. This black mixed solution was transferred to a polytetrafluoroethylene stainless steel reactor, and the temperature was controlled at 200℃ for 6 hours. After the reaction, the solid crude product was collected. The solid crude product was washed multiple times with deionized water and anhydrous ethanol to obtain the iron-doped aminated multi-walled carbon nanotubes.

[0071] Comparative Example 2 Comparative Example 2 uses the technical solution of Example 1, the only difference being that in step (2), only Ni(NO3)2·6H2O is added, and the addition of Fe(NO3)3·9H2O is omitted to prepare nickel-doped aminated multi-walled carbon nanotubes. Other conditions are the same as in Example 1.

[0072] Specifically, nickel-doped aminated multi-walled carbon nanotubes were prepared as follows: 300 mg of aminated multi-walled carbon nanotubes were weighed and added to a beaker containing 50 mL of ethylene glycol, achieving a ratio of 6 mg / mL of aminated multi-walled carbon nanotubes in ethylene glycol. The mixture was ultrasonically treated at room temperature until the aminated multi-walled carbon nanotubes were dispersed. Subsequently, 0.05 mol of 4.10 g of sodium acetate and 0.01 mol of 2.91 g of Ni(NO3)2·6H2O were added sequentially, and ultrasonic treatment continued until the salts were completely dissolved into a black mixed solution. This black mixed solution was transferred to a polytetrafluoroethylene stainless steel reactor, and the temperature was controlled at 200 °C for 6 h. After the reaction, the solid crude product was collected. The solid crude product was washed multiple times with deionized water and anhydrous ethanol to obtain nickel-doped aminated multi-walled carbon nanotubes.

[0073] Comparative Example 3 Comparative Example 3 uses the technical solution of Example 1, except that step (1) is omitted and unaminated multi-walled carbon nanotubes are used in step (2). All other conditions are the same as in Example 1. Specifically, 300 mg of multi-walled carbon nanotubes (MWCNTs) were first weighed and added to a beaker containing 50 mL of ethylene glycol, achieving a MWCNT ratio of 6 mg / mL in ethylene glycol. The mixture was then sonicated at room temperature until the MWCNTs were dispersed. Subsequently, 0.05 mol (4.10 g) of sodium acetate, 0.01 mol (4.04 g) of Fe(NO3)3·9H2O, and 0.01 mol (2.91 g) of Ni(NO3)2·6H2O were added sequentially, and sonication continued until the salts were completely dissolved into a black mixed solution. This black mixed solution was transferred to a polytetrafluoroethylene (PTFE) stainless steel reactor, and the temperature was controlled at 200 °C for 6 hours. After the reaction, the solid crude product was collected. The solid crude product was washed multiple times with deionized water and anhydrous ethanol to obtain iron / nickel bimetallic doped MWCNTs.

[0074] Adsorption experiments were conducted on the products of Example 1 and Comparative Examples 1-3: The products of Example 1 and Comparative Examples 1-3 were used as adsorbents for adsorption experiments. 10 mg of each adsorbent from Example 1 and Comparative Examples 1-3 was added to 5 mL of sample solutions containing different types of sulfonamide antibiotics in glass bottles. The adsorption experiments were conducted in a constant-temperature water bath at 298 K with an amplitude of 200 rm / min. After magnetic separation, the supernatant was collected and filtered through a 0.45 μm filter membrane. Finally, the remaining sulfonamide antibiotic content was determined by HPLC. All adsorption experiments were repeated three times.

[0075] The adsorption capacity and removal rate of each adsorbent for antibiotics were calculated using the following formula: Qe=((C0-Ce)V) / m In the formula, C0 is the concentration of sulfonamide antibiotics; Ce (mg / L) and Qe (mg / g) represent the concentration of sulfonamide antibiotics in the solution at equilibrium and the amount of adsorption at adsorption equilibrium, respectively, and m is the mass of the adsorbent used in the experiment.

[0076] Adsorption isotherm Adsorption isotherms are used to describe the interaction between the adsorbent and the adsorbate. Two well-known adsorption isotherm models, Langmuir and Freundlich, are used to fit the experimental data. The specific formulas are as follows: Ce / qe=1 / (qmK L )+Ce / qm lnqe=lnK F +(1 / n)lnCe In the formula, Ce and qe represent the concentration (mg / L) of sulfonamide antibiotics in the solution at equilibrium and the adsorption amount (mg / g) at adsorption equilibrium, respectively; qm is the saturated adsorption capacity (mg / g); KL and KF are the Langmuir equilibrium constant (L / mg) and the Freundlich equilibrium constant (mg / g), respectively; and n is the Freundlich empirical coefficient (related to adsorption strength).

[0077] Repeatability and stability studies The regeneration performance of the adsorbent is an important parameter for evaluating the removal effect in practical applications, and it is usually determined by the desorption capacity of the adsorbent. Therefore, a desorption experiment was conducted on the iron / nickel bimetallic aminated multi-walled carbon nanotubes of Example 1 that had adsorbed sulfonamide antibiotics alone. Here, 4 mL of acetonitrile was used as the desorbent and added to the iron / nickel bimetallic aminated multi-walled carbon nanotubes that had adsorbed sulfonamide antibiotics. The mixture was sonicated for 3 min, separated by a magnet, the supernatant was poured off, and the adsorbent was dried. Then, the regenerated iron / nickel bimetallic aminated multi-walled carbon nanotubes (10 mg) were added to the sulfonamide antibiotic sample (5 mL, 100 mg / L) and allowed to reach adsorption equilibrium.

[0078] Figure 1 The image shows a single SEM image of the aminated multi-walled carbon nanotubes from Example 1. The results show that the synthesized aminated multi-walled carbon nanotubes exhibit a uniformly dispersed tubular morphology, with no obvious agglomeration or entanglement between the nanotubes, indicating that the amination modification effectively improved their dispersion performance. Observations also reveal that the carbon nanotubes have smooth, continuous walls, clear outlines, and a relatively uniform diameter distribution, maintaining an intact overall morphology. No obvious fractures, bends, or surface defects caused by ultrasonic treatment or chemical reactions were observed.

[0079] Figure 2This is a SEM-mapping image of the individual aminated multi-walled carbon nanotubes prepared in Example 1. The image clearly shows that the elemental distribution of the aminated multi-walled carbon nanotubes consists mainly of C and N elements. It is evident from the image that the synthesized aminated multi-walled carbon nanotubes are primarily composed of C and N elements. Carbon, as the main component of the multi-walled carbon nanotube framework, exhibits a continuous, dense, and uniform distribution throughout the field of view, corresponding to the tubular structure of the carbon nanotubes. Nitrogen is uniformly distributed over the carbon distribution area, without any local enrichment or significant deficiency. Since the nitrogen element originates from the ethylenediamine molecules used in the grafting reaction, its uniform and widespread distribution directly indicates that the amination modification has successfully covalently linked nitrogen-containing functional groups (i.e., amino groups) to the surface of the multi-walled carbon nanotubes, and the grafting process is relatively uniform, without selective deposition or aggregation.

[0080] Figure 3 The image shows an SEM image of the iron / nickel bimetallic aminated multi-walled carbon nanotubes from Example 1. As can be seen from the image, the doping of the bimetal did not significantly change the morphology of the multi-walled carbon nanotubes. No fractures or defects caused by the bimetallic doping were observed, and the nanotubes maintained a uniformly dispersed tubular morphology.

[0081] Figure 4 This is the SEM mapping image of the iron / nickel bimetallic supported aminated multi-walled carbon nanotubes in Example 1. The results show that five elements—Fe, Ni, C, N, and O—are uniformly distributed on the material surface. C and N are characteristic components of the aminated multi-walled carbon nanotube matrix, confirming that the matrix structure remained intact during metal loading. The presence of O may be related to residual oxygen-containing functional groups (such as carboxyl and hydroxyl groups) on the carbon nanotube surface or partial oxidation of metal oxides. More importantly, the signals of Fe and Ni elements show numerous discrete bright spot enrichment areas within the field of view, indicating that the metal is loaded onto the support in the form of tiny particles. These elemental distribution characteristics and the localization of metal particles collectively demonstrate that the iron / nickel bimetallic element has been successfully loaded onto aminated multi-walled carbon nanotubes, and that the loading process did not damage the matrix morphology, providing a reliable structural basis for subsequent adsorption applications.

[0082] Figure 5 The XRD patterns of the aminated multi-walled carbon nanotubes and iron / nickel bimetallic aminated multi-walled carbon nanotubes in Example 1 are shown in the figure. As can be seen from the figure, the iron / nickel bimetallic aminated multi-walled carbon nanotubes exhibit diffraction peaks of aminated multi-walled carbon nanotubes, iron and nickel metal particles and their oxides, which proves the successful synthesis of iron / nickel bimetallic aminated multi-walled carbon nanotubes.

[0083] Figure 6-7Langmuir and Freundlich plots of sulfonamide antibiotics adsorbed individually on the iron / nickel bimetallic aminated multi-walled carbon nanotubes of Example 1 were used to investigate the effect of iron / nickel bimetallic porous aminated multi-walled carbon nanotubes on the adsorption of six sulfonamide antibiotics individually. The isotherms are shown in the figure. As shown in the figure, the relationship between equilibrium adsorption capacity and equilibrium concentration in solution is provided. The relevant parameters of the adsorption model of individually adsorbed sulfonamide antibiotics are listed in Table 1. The Langmuir isotherm equations (0.996, 0.998, 0.996, 0.992, 0.996, 0.992) fit the adsorption process of sulfonamide antibiotics better than the Freundlich equations (0.969, 0.996, 0.998, 0.978, 0.996, 0.948), indicating that monolayer adsorption is dominant in the adsorption process of sulfonamide antibiotics. It is generally believed that the adsorption of sulfonamide antibiotics by iron / nickel bimetallic porous aminated multi-walled carbon nanotubes is dominated by π-π stacking interaction. At 298 K, the maximum adsorption capacities of sulfadiazine (SD), sulfapyridine (SPD), sulfathiazole (STZ), sulfamerazin (SM), sulfamethazine (SDM), and sulfisoxazole (SIZ) are 25.72, 53.11, 94.63, 93.60, 31.97, and 39.89 mg / g, respectively, with SD < SIZ < SDM < SPD < SM < STZ.

[0084] Figure 8 The diagram shows the Zeta potential of the iron / nickel bimetallic aminated multi-walled carbon nanotubes in Example 1. According to the diagram, at pH=4, sulfonamide antibiotics mainly exist in anionic form. The Zeta potential of the iron / nickel bimetallic aminated multi-walled carbon nanotubes used for adsorbing sulfonamide antibiotics is positive, indicating an electrostatic interaction between the two. Therefore, electrostatic interaction also contributes to the adsorption of sulfonamide antibiotics by the iron / nickel bimetallic aminated multi-walled carbon nanotubes.

[0085] Figure 9 To better understand the adsorption mechanism and the local patterns of chemical bond formation and binding during the adsorption process, FT-IR spectroscopy was used to characterize the iron / nickel bimetallic aminated multi-walled carbon nanotubes of Example 1, as well as the adsorbed iron / nickel bimetallic aminated multi-walled carbon nanotubes. SDZ was selected as a typical sulfonamide antibiotic. (See figure 524 cm⁻¹) -1 The peak at 1639 cm⁻¹ corresponds to the stretching vibration peak of the metal-oxygen bond formed by Fe-O and Ni-O bonds, while the peak at 1639 cm⁻¹ corresponds to the stretching vibration peak of the metal-oxygen bond formed by Fe-O and Ni-O bonds. -1The characteristic peak appearing at 987 cm⁻¹ corresponds to the skeletal vibrational peak of the –C=C– framework of iron / nickel bimetallic aminated multi-walled carbon nanotubes. After adsorption, the peak appears at 987 cm⁻¹. -1 The newly emerging characteristic peaks are related to CN, NH, and -SO2- bonds. The -NH2 and -NH- groups on the surface of the iron / nickel bimetallic aminated multi-walled carbon nanotubes make them π-electron donors, while the unsaturated structures (such as the sulfonamide group) present in sulfonamide antibiotics can act as strong π-electron acceptors. This π-πEDA interaction plays an important role in adsorption. Meanwhile, at 3469 cm⁻¹... -1 The NH peak appearing at [value] is a typical peak of iron / nickel bimetallic aminated multi-walled carbon nanotubes. After adsorption of sulfonamide antibiotics, it red-shifts to 3279 cm⁻¹. -1 Furthermore, the peak broadening intensity has increased, and at the same time, the peak width has increased to 500-600 cm. -1 The red shift and broadening of the -SO2NH- group in sulfonamide molecules further support the possibility of intermolecular hydrogen bond formation, proving that sulfonamide antibiotics have been stably attached to the material surface and interact with metal sites, forming a synergistic adsorption.

[0086] Figure 10 To further verify the possibility of intermolecular hydrogen bonding as an adsorption mechanism, the TGA of iron / nickel bimetallic aminated multi-walled carbon nanotubes in Example 1 before and after adsorption of sulfonamide antibiotics is shown in the figure. The TGA results show that, compared with the pure matrix material, the peak temperature of the maximum weight loss rate of the sample after adsorption and formation of hydrogen bonds shifts to higher temperatures. The decomposition temperature of 400℃-600℃ is significantly delayed, and the weight loss rate before the weight loss delay is reduced. This can be attributed to the fact that the hydrogen bonding effect restricts the thermal motion and volatilization escape of the guest molecules, requiring higher energy to break the intermolecular association structure. This further strengthens the possibility that the adsorption of sulfonamide molecules is a successful loading onto the material surface through hydrogen bonding, rather than simply physical adsorption.

[0087] Figure 11This diagram illustrates the experimental process of magnetic separation of the iron / nickel bimetallic aminated multi-walled carbon nanotube adsorbent of Example 1 using a magnet. As shown, after placing a permanent magnet on the outer wall of a container containing the adsorbent suspension, the black adsorbent particles, originally uniformly dispersed in the liquid phase, are rapidly attracted and aggregated near the inner wall of the container close to the magnet, and the solution becomes clear in a short time. This phenomenon clearly demonstrates that the prepared iron / nickel bimetallic aminated multi-walled carbon nanotubes possess excellent magnetic response performance. Since both iron and nickel are ferromagnetic metals, the adsorbent can be quickly and efficiently separated from the liquid phase system under the action of an external magnetic field, avoiding the high energy consumption and cumbersome operation required by traditional separation methods (such as centrifugation or filtration). Simultaneously, the magnet can completely adsorb and fix the adsorbent to the container wall, and the adsorbent is not easily lost when the solution is poured or removed, indicating that it has good "removal capability," i.e., convenient for recycling and subsequent processing. This magnetic separation property not only significantly improves the recovery efficiency of adsorbents in actual water treatment or catalytic reactions, but also provides a simple and economical way to achieve the recycling of adsorbents, fully demonstrating the practical value of magnetically separable functional materials.

[0088] Figure 12 The adsorption capacity of the regenerated iron / nickel bimetallic aminated multi-walled carbon nanotubes of Example 1 after five cycles. After two regenerations, the adsorption capacity remained at 40.46-97.7% of the initial cycle (SIZ 97.70%, SPD 94.68%, SDM 61.00%, SD 46.50%, STZ 40.59%, SM 40.46%). After five regenerations, the regenerated adsorption capacity was 5.23-69.1% of the initial cycle (SIZ 66.36%, SPD 60.00%, SDM 28.32%, SD 22.73%, STZ 12.27%, SM 10.90%).

[0089] Figure 13 , 14Experiments 15 and 16 investigated whether the adsorption effect of bimetallic porous carbon nanotubes was superior to that of monometallic aminated multi-walled carbon nanotubes. Iron-aminated and nickel-aminated multi-walled carbon nanotubes were prepared using the same method, and comparative experiments were conducted under the same conditions. The adsorption isotherms of six sulfonamide antibiotics on iron-aminated and nickel-aminated multi-walled carbon nanotubes are shown in the figure. Based on the parameters of the two models, the adsorption process of iron-aminated and nickel-aminated multi-walled carbon nanotubes is more consistent with the Langmuir model, with the maximum adsorbed pollutants being SPD 44.1 mg / g and SD 16.6 mg / g, respectively, lower than the adsorption capacity of sulfonamide antibiotics by iron / nickel bimetallic aminated multi-walled carbon nanotubes. It can be seen that the adsorption capacity of sulfonamide antibiotics increases with the addition of bimetallic oxides. When both metal oxides are present, the reaction sites of the material may further increase, which is inferred to be due to the synergistic effect of the bimetals.

[0090] Figure 17 The image shown is a scanning electron microscope (SEM) image of unaminated multi-walled carbon nanotubes (MWCNTs) in Comparative Example 3. The SEM reveals severe aggregation of the MWCNTs without amination modification. Specifically, the carbon nanotubes become entangled and stacked, forming large aggregates, with some areas even exhibiting clump-like aggregation. This is mainly because the unmodified MWCNTs lack active functional groups such as amino groups on their surface, resulting in higher surface energy and stronger intermolecular van der Waals forces. This leads to adsorption and entanglement between the carbon nanotubes, resulting in severe aggregation. This aggregation affects their subsequent loading capacity and application performance.

[0091] Figure 18 The image shown is a scanning SEM image of the unaminated iron / nickel bimetallic multi-walled carbon nanotubes in Comparative Example 3. Because the multi-walled carbon nanotubes were not pre-aminated, the direct loading of the iron / nickel bimetal resulted in severe agglomeration of the magnetic metal particles. Specifically, the iron / nickel metal particles did not achieve uniform dispersion but instead aggregated and fused together, forming large spherical agglomerates. These agglomerates were mostly attached to the surface of the carbon nanotubes and could not penetrate into the cavities of the carbon nanotubes. This metal agglomeration not only disrupts the effective bonding between the iron / nickel bimetal and the carbon nanotube carrier but also significantly reduces the specific surface area of ​​the material, weakens the adsorption activity of the metal particles, and severely affects the structural stability and durability of the material, thus hindering its subsequent adsorption applications.

[0092] Meanwhile, the performance of the materials in Example 1 and Comparative Examples 1-2 of this invention was compared and tested, as shown in Table 1.

[0093] Table 1. Comparison of the adsorption capacity of sulfonamide antibiotics between Example 1 and Comparative Examples 1-2.

[0094] Table 1 shows that the adsorption of six typical sulfonamide antibiotics was compared with that of the two models. The adsorption processes of iron / nickel bimetallic aminated multi-walled carbon nanotubes, iron-aminated multi-walled carbon nanotubes, and nickel-aminated multi-walled carbon nanotubes are more consistent with the Langmuir model. The maximum adsorption capacity of iron / nickel bimetallic aminated multi-walled carbon nanotubes for the six sulfonamide antibiotics is significantly higher than that of single iron doping and single nickel doping. This indicates that the bimetallic system is not a physical superposition of the adsorption effects of the two single metals, but rather produces a significant bimetallic synergistic adsorption effect, making its adsorption performance far superior to that of the single metal doping system.

[0095] Table 2, to demonstrate the excellent adsorption performance of the iron / nickel bimetallic aminated multi-walled carbon nanotubes of this invention, compares their adsorption capacity with that of sulfonamide antibiotic removal materials reported in the prior art, as shown in Table 2. The data in Table 2 show that the adsorption capacity of the iron / nickel bimetallic aminated multi-walled carbon nanotubes for sulfonamide antibiotics is higher than that of most existing removal materials. It can be seen that the iron / nickel bimetallic aminated multi-walled carbon nanotubes of this invention are indeed a potential material for removing sulfonamide antibiotics.

[0096] Table 2 Comparison of adsorption capacity for sulfonamide antibiotics

[0097] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0098] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics, characterized in that, Includes the following steps: Step S01: Using multi-walled carbon nanotubes as a carrier, first oxidize them to introduce -COOH / -OH, then add them to N,N'-dimethylformamide. After mixing evenly, add ethylenediamine, mix evenly, and then add O-benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate. Stir and heat the reaction to obtain the crude reaction solution. The crude reaction solution was diluted with ethanol and washed, and the solids were separated and collected. The solids were washed and dried to obtain aminated multi-walled carbon nanotubes. Step S02: Disperse aminated multi-walled carbon nanotubes in ethylene glycol, and add sodium acetate, nickel salt and iron salt in sequence. After the dispersion is uniform, transfer to a polytetrafluoroethylene stainless steel reactor and heat to react. After the reaction is complete, collect the solid. Wash and dry the solid to obtain iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics. In step S02, the temperature of the heating reaction is 120-200℃, and the heating reaction time is 2-12h.

2. The method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics according to claim 1, characterized in that, In step S01, the mass-to-volume ratio of multi-walled carbon nanotubes to ethylenediamine is 0.5-1 mg:1 mL. The weight ratio of multi-walled carbon nanotubes to O-benzotriazole-N,N,N',N'-tetramethylurea hexafluorophosphate is 10-50:

1.

3. The method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics according to claim 1, characterized in that, In step S01, the volume ratio of N,N'-dimethylformamide to ethylenediamine is 1:1-3.

4. The method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics according to claim 1, characterized in that, In step S01, the heating reaction temperature is 40-80℃, and the heating reaction time is 20-60min.

5. The method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics according to claim 1, characterized in that, In step S02, the mass-to-volume ratio of aminated multi-walled carbon nanotubes to ethylene glycol is 2-10 mg: 1 mL.

6. The method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics according to claim 1, characterized in that, In step S02, the nickel salt is one of the following: nickel nitrate hexahydrate, nickel chloride hexahydrate, or nickel acetate tetrahydrate; the iron salt is one of the following: ferric chloride hexahydrate, ferric sulfate nonahydrate, or ferric nitrate nonahydrate.

7. The method for preparing iron / nickel bimetallic aminated multi-walled carbon nanotubes for adsorbing sulfonamide antibiotics according to claim 1, characterized in that, In step S02, the mass ratio of iron salt to aminated carbon nanotubes is 10-20:

1. The molar ratio of iron salt to sodium acetate is 1:1-5; The molar ratio of iron salt to nickel salt is 1:1-2.

8. An iron / nickel bimetallic aminated multi-walled carbon nanotube for adsorbing sulfonamide antibiotics, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The application of iron / nickel bimetallic aminated multi-walled carbon nanotubes as described in claim 8 for the adsorption of sulfonamide antibiotics in wastewater.

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