Preparation method of hollow type carbon-coated magnetic material and catalytic degradation application thereof

Abstract

The application relates to the sewage treatment field, and particularly discloses a preparation method of a hollow carbon-coated magnetic material and catalytic degradation application of the hollow carbon-coated magnetic material, the inner core of which is pretreated iron-manganese oxide, the catalytic reaction site is high, the water resistance is strong, a hydrochloric acid dopamine polymer is prepared to uniformly polymerize and coat to form a three-dimensional structure of a heterogeneous catalyst, the stability and dispersibility of the catalyst are high, the interface electron transfer path in a reaction process can be regulated and controlled, the reactivity and selectivity of the catalyst to target objects are improved, the adsorption and degradation reaction rate of the catalyst to antibiotics is high, and the catalyst has good circulation performance.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to a method for preparing hollow carbon-coated magnetic materials and their catalytic degradation application. Background Technology

[0002] Antibiotics are widely used in clinical and agricultural settings, making crucial contributions to the prevention and treatment of human and animal diseases. However, antibiotics are not completely metabolized by organisms, resulting in 30-90% of them remaining in feces and urine and being released into the environment. Furthermore, the long-term accumulation of antibiotics in the environment puts bacteria under pressure from human selection, thus promoting the emergence and spread of antibiotic resistance, posing a serious threat to human health and ecosystem security. Therefore, there is an urgent need to develop effective and environmentally friendly technologies to remove antibiotic residues from aquatic environments.

[0003] Antibiotic wastewater is typically characterized by hydrophobicity, biotoxicity, and recalcitrant degradation. Conventional removal methods include adsorption, activated sludge treatment, membrane treatment, and advanced oxidation technologies (AOTs). Among these, AOT based on activated persulfate utilizes highly reactive oxygen species with high redox potentials to transform large organic molecules, exhibiting strong mineralization capabilities and considered to have significant application potential in wastewater treatment plants. However, the concentration of antibiotics in actual wastewater is generally low (μg / mL). When antibiotics coexist with common substrates, AOTs show a significant inhibitory effect, with low-selectivity reactive free radicals preferentially reacting with the substrate, significantly reducing the removal efficiency of the target analyte. Therefore, it is necessary to further investigate the catalyst-mediated interfacial reaction process, modulate the interfacial electron transfer pathway at the molecular level, and improve the reactivity and selectivity of the catalyst for the target analyte.

[0004] Hollow nanomaterials have many advantages due to their structure, including a large specific surface area (hundreds of m²). 2 Hollow nanostructures, with their discrete voids, provide abundant accessible surface sites for catalytic reactions or to immobilize reaction centers. From a geometric evolution perspective, three-dimensional hollow nanostructures are considered to be formed by rolling and sealing two-dimensional nanosheets. Clearly, hollow nanomaterials possess the high activity of two-dimensional materials and the strong stability of three-dimensional network structures as effective catalysts: firstly, the three-dimensional structure enhances the robustness of the material structure, preventing the aggregation and degradation of reaction sites, while the highly accessible surface sites exhibit high activity due to their high unsaturated coordination; secondly, the discrete voids not only trap metastable reaction intermediates at the reaction sites for further reactions but also aggregate reactants through selective interactions. Therefore, this unique structural feature makes hollow nanomaterials an effective candidate for the rational design of efficient catalysts, and constructing uniform channel / pore structures to achieve rapid mass transfer and size sieving is a key research focus in the preparation of efficient catalysts. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for preparing hollow carbon-coated magnetic materials.

[0006] The technical content of this invention is as follows:

[0007] This invention provides a method for preparing hollow carbon-coated magnetic materials, comprising the following steps:

[0008] Step 1: Weigh out magnetic materials FeCl3·6H2O and MnCl2·4H2O in a mass ratio of 1:0-0.7 and pretreat them to obtain a mixed solution;

[0009] The pretreatment involves fully dispersing the magnetic material in a microemulsion with a volume of 4-6 times its volume, performing infrared heat treatment, and then immersing it in deionized water at a temperature of 0-10°C for supercooling treatment.

[0010] The microemulsion is formed by mixing cyclohexane, polyethylene glycol and manganese nitrate in a mass ratio of 5:(2-4):5.

[0011] The pretreatment enhances the reactivity of iron-manganese oxides by reacting ferric chloride hexahydrate and manganese dichloride tetrahydrate in a microemulsion rich in modifying groups such as sulfhydryl pyrimidines, and can also refine the grains and enhance water resistance, thereby improving the recyclability of magnetic materials.

[0012] Step 2: Under anaerobic conditions, NaHCO3 is added dropwise to the mixed solution while continuously stirring. The pH value is adjusted, and the mixture is continuously stirred to carry out a co-precipitation reaction to obtain a precipitate.

[0013] The pH value was adjusted to 8-12; the stirring time was 2-4 hours.

[0014] Step 3: Mix the precipitate prepared in Step 2 with the polymer raw material to undergo a polymerization reaction, and obtain the carbon-coated precursor precipitate.

[0015] The polymer raw material is composed of dopamine hydrochloride, a silane coupling agent, concentrated ammonia, a sugar alcohol solution, and deionized water in a volume ratio of 1:(0-20):(0-80); wherein the amount of dopamine hydrochloride added is 1-3g, and the amount of silane coupling agent used is 1.0-2.0%wt of dopamine hydrochloride; the silane coupling agent includes one or more of tetraethoxysilane, (3-aminopropyl)trimethoxysilane, and (3-isocyanopropyl)triethoxysilane;

[0016] The sugar alcohol solution is a polyol solution containing 20-40% by mass of glucose;

[0017] The sugar alcohol solution has dispersing properties and can also improve the strength of the polymer;

[0018] In the preparation method, dopamine hydrochloride is coupled and polymerized, and then introduced into a sugar alcohol solution to improve the dispersibility and uniformity of the polymer, which is beneficial to the adsorption of organic matter in water.

[0019] The polymerization reaction involves subjecting the precipitate prepared in step two to low-temperature plasma treatment, then adding the polymer from step two and stirring for 12-48 hours, followed by ultrasonic treatment.

[0020] The ultrasonic treatment frequency is 30-50KHz, and the time is 50-70min;

[0021] The polymerization reaction first involves low-temperature plasma treatment of the iron-manganese oxide, followed by ultrasonic treatment, which improves the interlayer dispersion of the polymer, increases the reaction sites, and results in higher polymerization uniformity.

[0022] Step 4: Place the obtained carbon-coated precursor precipitate under a nitrogen atmosphere and perform a two-stage temperature-increasing calcination heat treatment. After cooling the calcined product, perform HF etching, washing, and freeze drying to obtain the carbon-coated magnetic precipitate.

[0023] The calcination heat treatment is to calcine at 300-450℃ for 1-2 hours at a heating rate of 5-10℃ / min, and then continue calcining at 600-900℃ for 1-2 hours.

[0024] The magnetic material obtained through the calcination treatment via secondary calcination has a stable structure.

[0025] This invention also provides an application of hollow carbon-coated magnetic materials, including adsorption technology for the removal of sulfonamide antibiotics, catalytic degradation technology, and removal of one or more other organic substances in industrial wastewater in the environmental field.

[0026] Beneficial Effects: This invention provides a method for preparing hollow carbon-encapsulated magnetic materials. The method involves pretreating the magnetic material, chemically reacting iron-manganese oxides under infrared heat treatment to promote the connection of reaction sites on the surface, and then performing carbon encapsulation polymerization on the surface of the magnetic material. Dopamine hydrochloride, a sugar alcohol solution, and a silane coupling agent are reacted to form a uniformly dispersed polymer, which forms a three-dimensional hollow nanostructure with the magnetic material. This structure exhibits high robustness, preventing the aggregation and degradation of reaction sites. Simultaneously, the highly accessible surface sites exhibit high activity due to their high unsaturated coordination. Furthermore, the discrete voids not only trap metastable reaction intermediates at the reaction sites for further reactions but also allow reactants to aggregate through selective interactions. This invention aims to improve the removal efficiency of sulfonamide antibiotics while exploring the microscopic interfacial reaction characteristics between the catalyst and the target, revealing the electron transfer mechanism during the reaction process.

[0027] This invention also provides an application of hollow carbon-coated magnetic materials, offering more material options for the field of environmental governance, and providing important theoretical basis and technical support for the treatment of emerging pollutants in industrial wastewater.

[0028] Instruction manual illustrations

[0029] Figure 1 Scanning electron microscope image of carbon-coated magnetic material;

[0030] Figure 2 Transmission electron microscope image of carbon-coated magnetic material;

[0031] Figure 3 X-ray diffraction patterns of the carbon-coated magnetic materials prepared in Example 1 and Comparative Examples 1-2;

[0032] Figure 4 The graphs show the catalytic degradation effect of sulfamethoxazole by the carbon-coated magnetic materials prepared in Example 1 and Comparative Examples 1-2.

[0033] Figure 5 This is a stability diagram for the recycling of carbon-coated magnetic materials. Detailed Implementation

[0034] The present invention will be further described in detail below through specific implementation examples. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope of the appended claims.

[0035] Unless otherwise specified, all raw materials and reagents used in this invention are from the conventional market.

[0036] Example 1

[0037] A method for preparing a hollow carbon-coated magnetic material includes the following steps:

[0038] Step 1: Weigh out magnetic materials FeCl3·6H2O and MnCl2·4H2O in a mass ratio of 3.1:1 and pretreat them to obtain a mixed solution;

[0039] The pretreatment involves fully dispersing the magnetic material in a microemulsion of 5 times its volume, performing infrared heat treatment, and then immersing it in deionized water at a temperature of 5°C for supercooling treatment.

[0040] The microemulsion is a mixture of cyclohexane, polyethylene glycol, and manganese nitrate in a mass ratio of 5:3:5.

[0041] Step 2: Under anaerobic conditions, NaHCO3 is added dropwise to the mixed solution with continuous stirring to adjust the pH to 10, and the co-precipitation reaction is carried out with continuous stirring for 3 hours to obtain the precipitate.

[0042] Step 3: The precipitate from Step 2 is subjected to low-temperature plasma treatment, then a polymer raw material is added and stirred for 24 hours, followed by ultrasonic treatment at 40 kHz for 60 minutes to induce a polymerization reaction and obtain a carbon-coated precursor precipitate. The polymer raw material consists of 2 g of dopamine hydrochloride, 1.5% wt of tetraethoxysilane (dopamine hydrochloride), and concentrated ammonia, sugar alcohol solution, and deionized water in a volume ratio of 1:19:80.

[0043] The sugar alcohol solution is a propylene glycol solution containing 30% by mass of glucose;

[0044] Step 4: Place the carbon-coated precursor precipitate under a nitrogen atmosphere and perform a two-stage programmed calcination heat treatment. Calcinate at 350°C for 2 hours at a heating rate of 8°C / min, and then continue calcining at 800°C for 1 hour. After calcination, the product is cooled, etched with HF, washed, and freeze-dried to obtain the carbon-coated magnetic precipitate.

[0045] Example 2

[0046] A method for preparing a hollow carbon-coated magnetic material includes the following steps:

[0047] Step 1: Weigh out magnetic materials FeCl3·6H2O and MnCl2·4H2O in a mass ratio of 1:0.5 and pretreat them to obtain a mixed solution;

[0048] The pretreatment involves fully dispersing the magnetic material in a microemulsion of 4 times its volume, performing infrared heat treatment, and then immersing it in deionized water at 0°C for supercooling treatment.

[0049] The microemulsion is a mixture of cyclohexane, polyethylene glycol, and manganese nitrate in a mass ratio of 5:2:5.

[0050] Step 2: Under anaerobic conditions, NaHCO3 is added dropwise to the mixed solution with continuous stirring to adjust the pH to 8, and the co-precipitation reaction is carried out with continuous stirring for 2 hours to obtain the precipitate.

[0051] Step 3: The precipitate from Step 2 is subjected to low-temperature plasma treatment, followed by the addition of polymer raw materials and stirring for 12 hours. Then, it is ultrasonically treated at 30 kHz for 50 minutes to induce a polymerization reaction, yielding a carbon-coated precursor precipitate. The polymer raw materials consist of 1 g of dopamine hydrochloride, 1.0% wt of (3-isocyanopropyl)triethoxysilane, and concentrated ammonia, a sugar alcohol solution, and deionized water in a volume ratio of 1:10:40. The sugar alcohol solution is a polyol solution containing 20% ​​glucose by mass.

[0052] Step 4: Place the carbon-coated precursor precipitate under a nitrogen atmosphere and perform a two-stage programmed calcination heat treatment. Calcinate at 300℃ for 1 hour at a heating rate of 5℃ / min, and then continue calcining at 600℃ for 1 hour. After calcination, the product is cooled, etched with HF, washed, and freeze-dried to obtain the carbon-coated magnetic precipitate.

[0053] Example 3

[0054] A method for preparing a hollow carbon-coated magnetic material includes the following steps:

[0055] Step 1: Weigh out magnetic materials FeCl3·6H2O and MnCl2·4H2O in a mass ratio of 1:0.7 and pretreat them to obtain a mixed solution;

[0056] The pretreatment involves fully dispersing the magnetic material in a microemulsion of 6 times its volume, performing infrared heat treatment, and then immersing it in deionized water at a temperature of 10°C for supercooling treatment.

[0057] The microemulsion is a mixture of cyclohexane, polyethylene glycol, and manganese nitrate in a mass ratio of 5:4:5.

[0058] Step 2: Under anaerobic conditions, NaHCO3 is added dropwise to the mixed solution with continuous stirring to adjust the pH to 12, and the co-precipitation reaction is carried out with continuous stirring for 4 hours to obtain the precipitate.

[0059] Step 3: The precipitate from Step 2 is subjected to low-temperature plasma treatment, followed by the addition of polymer raw materials and stirring for 48 hours. Then, it is ultrasonically treated at 50 kHz for 70 minutes to induce a polymerization reaction, yielding a carbon-coated precursor precipitate. The polymer raw materials consist of 3 g of dopamine hydrochloride, 2.0% wt of (3-aminopropyl)trimethoxysilane (of dopamine hydrochloride), and concentrated ammonia, a sugar alcohol solution, and deionized water in a volume ratio of 1:20:80. The sugar alcohol solution is a polyol solution containing 40% glucose by mass.

[0060] Step 4: Place the carbon-coated precursor precipitate under a nitrogen atmosphere and perform a two-stage programmed calcination heat treatment. Calcinate at 450℃ for 2 hours at a heating rate of 10℃ / min, and then continue calcining at 900℃ for 2 hours. After calcination, the product is cooled, etched with HF, washed, and freeze-dried to obtain the carbon-coated magnetic precipitate.

[0061] Comparative Example 1

[0062] The difference between Comparative Example 1 and Example 1 is that carbon encapsulation is not introduced during the material preparation process of Comparative Example 1, that is, steps three and four are not performed, while other steps remain unchanged.

[0063] Comparative Example 2

[0064] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not add MnCl2·4H2O, while everything else remains the same.

[0065] Comparative Example 3

[0066] The difference between Comparative Example 3 and Example 1 is that the magnetic material of Comparative Example 3 is not pretreated, while everything else remains the same.

[0067] Comparative Example 4

[0068] The difference between Comparative Example 4 and Example 1 is that no sugar alcohol solution was added during the preparation of the polymer in Comparative Example 4; instead, an equal amount of deionized water was used.

[0069] Comparative Example 5

[0070] The difference between Comparative Example 5 and Example 1 is that Comparative Example 5 does not undergo low-temperature plasma treatment and ultrasonic treatment during the polymerization process. Instead, the solution from step 1 is directly added to the solution from step 2 and stirred for 24 hours, while other aspects remain unchanged.

[0071] I. Microstructure Testing

[0072] The hollow magnetic material prepared in Example 1 was tested using scanning electron microscopy and transparent electron microscopy. The test results are as follows: Figure 1 Figure 2 As shown. By Figure 1 The results show that the material exhibits a spherical structure with an average particle size between 400-500 nm, and a large number of particles are attached to its surface; while... Figure 2 Transmission electron microscopy analysis revealed that the material was thin and transparent in the middle, without obvious accumulation or agglomeration, and exhibited a hollow three-dimensional structure.

[0073] II. Crystal Structure Testing

[0074] The hollow magnetic materials prepared in Examples 1-3 were subjected to X-ray diffraction tests, and the test results are as follows: Figure 3As shown, the crystal structure of the material was obtained. Sharp diffraction peaks were detected at 2θ = 18.06°, 29.70°, 34.98°, 36.65°, 42.53°, 52.74°, 56.19°, and 61.65° in all examples, corresponding to the characteristic peaks of the MnFe2O4 (JCPDS no. 10-0319) standard card. Furthermore, broad peaks were detected around 20° in Comparative Examples 1 and 2, representing diffraction peaks of the amorphous graphitic carbon (002) crystal plane. These results indicate that the material has a hollow core-shell structure composed of iron-manganese oxide and an outer carbon coating.

[0075] III. Degradation Effect Test

[0076] The magnetic materials prepared in Example 1 and Comparative Examples 1-2 were tested for their catalytic degradation effect on sulfamethoxazole and their stability in repeated use. The results are as follows: Figure 4-5 As shown.

[0077] The effects of the examples and comparative examples on the catalytic degradation of sulfamethoxazole are shown in Table 1.

[0078] Table 1 Catalytic Degradation Tests of Sulfamethoxazole

[0079]

[0080] Based on Table 1 Figure 4 and Figure 5 It is evident that the hollow magnetic material prepared in this invention exhibits excellent adsorption and degradation performance for antibiotics and is recyclable. Regarding degradation efficiency, this invention uses the material as a carrier to mediate a catalytic oxidation system mediated by persulfate. After a 30-minute reaction, Example 1 showed a removal rate of over 93% for sulfamethoxazole, while Comparative Example 1 showed only 85%, indicating that Mn plays a crucial role in the catalytic process, stabilizing the crystal structure at the molecular level and thus regulating the interfacial electron transfer pathway, thereby affecting the removal efficiency of the target analyte. Comparative Example 2, after a 30-minute reaction, showed only approximately 56% removal of sulfamethoxazole, far lower than Example 1, indicating significant agglomeration and accumulation of iron oxides lacking carbon coating modification, leading to rapid degradation of active sites. In terms of material recycling stability, the carbon-coated magnetic material showed a sulfamethoxazole removal rate greater than 93% after the first cycle, and after five repeated uses, the removal rate only decreased to 75%. This result demonstrates that the material has significant recyclability and good cycle stability.

[0081] As can be seen from Comparative Example 3, the pretreatment of the iron-manganese oxide of the present invention significantly enhances the catalytic reaction by chemically linking the magnetic material surface;

[0082] As can be seen from Comparative Examples 4-5, adding a sugar alcohol solution to the coupling polymerization of dopamine hydrochloride in polymer polymerization, and performing low-temperature plasma treatment and ultrasonic treatment during the polymerization process, results in carbon layer structures with high stability, high uniformity and dispersion, and strong adsorption capacity.

Claims

1. A method for preparing a hollow carbon-coated magnetic material, characterized in that, Includes the following steps: Step 1: Weigh out magnetic materials FeCl3•6H2O and MnCl2•4H2O in a mass ratio of 1:0-0.7 and pretreat them to obtain a mixed solution. The mass of MnCl2•4H2O is not 0. The pretreatment involves fully dispersing the magnetic material in a microemulsion of 4-6 times its volume, performing infrared heat treatment, and then immersing it in deionized water at a temperature of 0-10°C for supercooling treatment. The microemulsion is formed by mixing cyclohexane, polyethylene glycol and manganese nitrate in a mass ratio of 5:(2-4):

5. Step 2: Under anaerobic conditions, adjust the pH value and continuously stir to carry out a co-precipitation reaction to obtain a precipitate; Step 3: Mix the precipitate prepared in Step 2 with the polymer raw material to undergo a polymerization reaction, and obtain the carbon-coated precursor precipitate. The polymer raw material is composed of dopamine hydrochloride and silane coupling agent, and concentrated ammonia, sugar alcohol solution and deionized water in a volume ratio of 1:(0-20):(0-80), wherein the volume of sugar alcohol solution and deionized water is not 0. The amount of dopamine hydrochloride added is 1-3g, and the amount of silane coupling agent used is 1.0-2.0%wt of dopamine hydrochloride; The silane coupling agent includes one or more of tetraethoxysilane, (3-aminopropyl)trimethoxysilane, and (3-isocyanopropyl)triethoxysilane; Step 4: Place the obtained carbon-coated precursor precipitate under a nitrogen atmosphere and perform a two-stage temperature-increasing calcination heat treatment. After cooling the calcined product, perform HF etching, washing, and freeze drying to obtain the carbon-coated magnetic precipitate. The polymerization reaction involves subjecting the precipitate prepared in step two to low-temperature plasma treatment, then adding the polymer from step two and stirring for 12-48 hours, followed by ultrasonic treatment. The ultrasonic treatment is performed at a frequency of 30-50 kHz for a duration of 50-70 minutes.

2. The method for preparing a hollow carbon-coated magnetic material according to claim 1, characterized in that, Step two involves adjusting the pH value to 8-12 and stirring for 2-4 hours.

3. The method for preparing a hollow carbon-coated magnetic material according to claim 1, characterized in that, The sugar alcohol solution is an ethanol solution containing 20-40% by mass of glucose.

4. The method for preparing a hollow carbon-coated magnetic material according to claim 1, characterized in that, The calcination heat treatment described in step four involves calcining at 300-450℃ for 1-2 hours at a heating rate of 5-10℃ / min, followed by calcination at 600-900℃ for another 1-2 hours.

5. The application of the carbon-coated magnetic material obtained by the preparation method according to any one of claims 1-4, characterized in that, The carbon-coated magnetic material is used to adsorb and catalytically degrade sulfonamide antibiotics.

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