A phosphorus-doped hollow spherical porous carbon material and its preparation method and application

Abstract

The present invention relates to the field of sewage treatment, and specifically to a phosphorus-doped hollow spherical porous carbon material, and a preparation method and application thereof. The present invention prepares porous carbon materials by non-metallic doping, which can increase the specific surface area of the material and increase the number of active sites. The phosphorus-doped hollow spherical porous carbon material is prepared by using dopamine hydrochloride and phytic acid as main reagents, tetraethoxysilane as a spherical structure directing agent, and is prepared by tubular furnace calcination, HF etching, and freeze drying. The present invention mainly generates polydopamine through the self-polymerization reaction of dopamine hydrochloride, and wraps it in a spherical structure directing agent. The amino group in the polydopamine combines with the phosphate group to form a phosphorus-doped hollow spherical porous structure heterogeneous catalyst with high catalytic performance and the ability to efficiently remove a variety of pollutants.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a phosphorus-doped hollow spherical porous carbon material and a preparation method and application thereof. Background Art

[0002] Antibiotics, a typical emerging pollutant, are secondary metabolites produced by microorganisms (including bacteria, fungi, and actinomycetes) or higher plants and animals during their life processes, with antipathogenic or other activities, as well as chemically synthesized or semi-synthetic compounds. They are chemicals that can interfere with the developmental functions of other living cells. Since their discovery in 1929, antibiotics have been widely used in medicine and aquaculture. Studies have shown that global antibiotic use has increased by 46% since 2000. However, the large-scale production and overuse of antibiotics can have certain ecotoxic effects on aquatic environments, disrupting the balance of aquatic ecosystems. Excessive discharge of antibiotics into the environment can lead to the emergence of new drug-resistant bacteria, ultimately posing a threat to public health and safety. Therefore, antibiotic contamination in aquatic environments poses a potential health risk to humans, making the development of efficient methods for removing sulfonamide antibiotics particularly important.

[0003] Currently, methods for removing sulfonamide antibiotic contaminants can be categorized into three main categories: physical removal (e.g., adsorption, flocculation, and membrane separation), biological removal, and advanced oxidation (AO) techniques. AO utilizes active oxidants to generate active species with higher redox potentials, thereby achieving rapid contaminant removal. Compared to other organic matter removal technologies, persulfate-based AO degrades or mineralizes virtually all organic contaminants into intermediates, CO₂, and H₂O. Therefore, persulfate-based AO is a highly promising process for treating sulfonamide antibiotics. Among various PMS activation strategies, activation with transition metals has demonstrated excellent efficiency in water treatment. However, metal activation is susceptible to secondary pollution, such as the dissolution of highly toxic Co ions, which severely hinders the long-term practical application of PMS. Therefore, alternative catalysts, such as other less toxic metal-based catalysts or metal-free catalysts, are urgently needed. However, metal-based catalysts struggle to completely overcome the secondary pollution problem caused by metal leaching. Compared to metal-based catalysts, metal-free catalysts are gaining increasing attention due to their lack of secondary metal pollution and environmental friendliness.

[0004] Among various metal-free materials, carbon-based materials have the advantages of diverse structures, good electrical conductivity, and superior mechanical properties. They have been widely used to construct metal-free catalysts. However, the active sites of carbon-based materials are limited, which restricts their catalytic performance. Currently, carbon-based catalysts doped with various heteroatoms (such as B, N, S, and P) are considered to be an effective way to improve catalytic activity because the doped heteroatoms can regulate the electronic properties of carbon materials, increase the active sites of carbon materials, and significantly improve structural defects, electrical conductivity, and the number of mesopores, thereby effectively removing antibiotics.

[0005] Therefore, how to provide a green and environmentally friendly non-metal-doped hollow spherical porous carbon material is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention prepares porous carbon materials through non-metallic doping, which can increase the number of material defect sites, increase the specific surface area, and enhance the current intensity. It aims to provide a non-metallic doped hollow spherical porous carbon material with large specific surface area, high activity, and green environmental protection, which can greatly improve the effective utilization rate of the catalyst.

[0007] It should be noted that since phosphorus atoms can act as electron donors and attach to carbon-based materials, and phytic acid contains six phosphate groups, is environmentally friendly, renewable, and easily obtained from grains, it is a promising source of P. Therefore, incorporating P into carbon-based materials can construct a new heterogeneous catalyst to activate PMS to remove organic pollutants.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The first technical purpose of the present invention is to provide a method for preparing the phosphorus-doped hollow spherical porous carbon material as described above, wherein the phosphorus-doped hollow spherical porous carbon material is prepared by using dopamine hydrochloride and phytic acid as main reagents and tetraethoxysilane as a directing agent, and is calcined in a tubular furnace, HF-etched, and freeze-dried; the method specifically comprises the following steps:

[0010] (1) adding tetraethoxysilane to a mixed solution containing aqueous ammonia, anhydrous ethanol, and deionized water, stirring, and adjusting the pH of the solution to obtain a tetraethoxysilane mixed solution for later use;

[0011] (2) dissolving dopamine hydrochloride in water, and adding the dopamine hydrochloride solution to the tetraethoxysilane mixed solution obtained in step (1) to react to obtain a black solution, i.e., a silica / polydopamine (PDA) mixed solution;

[0012] (3) After adding phytic acid to the silica / polydopamine (PDA) mixed solution obtained in step (2) for a period of time, a black flocculent is obtained, and then the obtained black flocculent is calcined at high temperature. After cooling to room temperature, it is etched with HF and washed with deionized water, and freeze-dried to obtain the phosphorus-doped hollow spherical porous carbon material.

[0013] Optionally, in step (1), the volume ratio of ammonia water, anhydrous ethanol, deionized water and tetraethoxysilane is (1-2):(20-25):(75-85):(1-2), and the pH of the solution is adjusted to 8-10.

[0014] Optionally, in step (2), the molar ratio of dopamine hydrochloride to water in the dopamine hydrochloride solution is (0.5-1 g):(5-10 mL), and the mass ratio of dopamine hydrochloride to tetraethoxysilane is (0.5-1):(1-2).

[0015] Furthermore, the reaction temperature in step (2) is 25°C-30°C, and the reaction time is 15-20 h.

[0016] Optionally, in step (3), the phytic acid solution is prepared by uniformly mixing 70% phytic acid and deionized water in equal volumes, and the amount of phytic acid solution added is 1-3 mL. Specifically, 1 mL, 2 mL, and 3 mL of the uniformly mixed phytic acid solution are added to the solution of step (2).

[0017] Furthermore, the high temperature calcination process is performed as follows:

[0018] Place under nitrogen atmosphere at 5 °C min -1 The samples were calcined at 400 °C for 1-2 h and then further calcined at 800 °C for 1-2 h.

[0019] Furthermore, the HF concentration is 5 wt %, and the etching time is 45-50 h.

[0020] The second technical purpose of the present invention is to provide a phosphorus-doped hollow spherical porous carbon material, which uses a spherical structure directing agent as a template to prepare a dopamine hydrochloride polymer, so that the polymer is evenly wrapped in the template to form a hollow spherical porous structure carbon material.

[0021] Specifically, polydopamine is generated by self-polymerization of dopamine hydrochloride and wrapped in a spherical structure directing agent. The amino groups in the polydopamine are combined with the phosphate groups to form a phosphorus-doped hollow spherical porous carbon material.

[0022] The third technical purpose of the present invention is to provide the application of the phosphorus-doped hollow spherical porous carbon material in sewage treatment.

[0023] Specifically, the phosphorus-doped hollow spherical porous carbon material is used as a heterogeneous catalyst to activate PMS to remove organic pollutants.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention is mainly to overcome the secondary pollution problem caused by traditional metal-doped materials, such as the high toxicity of iron sludge, cobalt ions, etc., and prepare porous carbon materials by non-metallic doping, which can increase the specific surface area of the material and increase the active sites. Phosphorus-doped hollow spherical porous carbon materials are prepared with dopamine hydrochloride and phytic acid as main reagents, tetraethoxysilane as spherical structure directing agent, and are prepared by tubular furnace calcination, HF etching, and freeze drying. This material and persulfate construct a catalytic oxidation system, and the used measurement can remove high-concentration antibiotics only at one-tenth of the catalyst amount in previous literature, truly achieving high efficiency, low cost, and green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0027] Figure 1 This is a scanning electron microscope image of phosphorus-doped hollow spherical porous carbon material.

[0028] Figure 2 This is a scanning electron microscope image of the carbon material of the comparative example.

[0029] Figure 3 This is a transmission electron microscope image of phosphorus-doped hollow spherical porous carbon material.

[0030] Figure 4 This is the elemental mapping of phosphorus-doped hollow spherical porous carbon materials.

[0031] Figure 5 It is a diagram showing the effect of catalytic degradation of sulfachloropyridazine by the carbon materials prepared in Example 1 and Comparative Examples 1-3.

[0032] Figure 6 This is a diagram showing the effect of the phosphorus-doped porous carbon material prepared in Example 1 on the adsorption and catalytic degradation of sulfachloropyridazine.

[0033] Figure 7 This is a diagram showing the effects of adsorption elution and catalytic degradation elution of the phosphorus-doped porous carbon material prepared in Example 1.

[0034] Figure 8 This is a cycle effect diagram of the catalytic degradation of sulfachloropyridazine by the phosphorus-doped porous carbon material prepared in Example 1. DETAILED DESCRIPTION

[0035] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0037] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0038] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0039] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0040] The invention discloses a phosphorus-doped hollow spherical porous carbon material and a preparation method thereof.

[0041] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0042] Example 1

[0043] A method for preparing a phosphorus-doped hollow spherical porous carbon material comprises the following steps:

[0044] First, ammonia water, anhydrous ethanol and deionized water were mixed and stirred at a volume ratio of 1:24:80 for 15 minutes. Then, tetraethoxysilane with an equal volume of ammonia water was added to the above solution, stirred for another 30 minutes, and the pH of the solution was adjusted to 9. Dopamine hydrochloride and deionized water were mixed and stirred at a mass ratio of 1:9 for 30 minutes, and the dopamine hydrochloride solution was added to the above mixture and stirred for 10 hours. Then, equal volumes of 70% phytic acid and deionized water were mixed evenly, 1 mL was added to the above solution and stirred at room temperature for 14 hours. The obtained sample was placed under a nitrogen atmosphere at 5 °C min -1 The samples were calcined at 400 °C for 2 h and further calcined at 800 °C for 1 h. After cooling to room temperature, they were etched with HF (5 wt%) for 48 h, washed with deionized water several times, and finally freeze-dried for 22 h.

[0045] Example 2

[0046] A method for preparing a phosphorus-doped hollow spherical porous carbon material comprises the following steps:

[0047] First, ammonia water, anhydrous ethanol and deionized water were mixed and stirred at a volume ratio of 1:24:80 for 15 minutes. Then, tetraethoxysilane with an equal volume to ammonia water was added to the above solution, stirred for another 30 minutes, and the pH of the solution was adjusted to 9. Dopamine hydrochloride and deionized water were mixed and stirred at a mass ratio of 1:9 for 30 minutes, and the dopamine hydrochloride solution was added to the above mixture and stirred for 10 hours. Then, equal volumes of 70% phytic acid and deionized water were mixed evenly, 2 mL was added to the above solution and stirred at room temperature for 14 hours. The obtained sample was placed under a nitrogen atmosphere at 5 ℃ min -1 The samples were calcined at 400 °C for 2 h and further calcined at 800 °C for 1 h. After cooling to room temperature, they were etched with HF (5 wt%) for 48 h, washed with deionized water several times, and finally freeze-dried for 22 h.

[0048] Example 3

[0049] A method for preparing a phosphorus-doped hollow spherical porous carbon material comprises the following steps:

[0050] First, ammonia water, anhydrous ethanol and deionized water were mixed and stirred at a volume ratio of 1:24:80 for 15 minutes. Then, tetraethoxysilane with an equal volume to ammonia water was added to the above solution, stirred for another 30 minutes, and the pH of the solution was adjusted to 9. Dopamine hydrochloride and deionized water were mixed and stirred at a mass ratio of 1:9 for 30 minutes, and the dopamine hydrochloride solution was added to the above mixture and stirred for 10 hours. Then, equal volumes of 70% phytic acid and deionized water were mixed evenly, 3 mL was added to the above solution and stirred at room temperature for 14 hours. The obtained sample was placed under a nitrogen atmosphere at 5 ℃ min-1 The samples were calcined at 400 °C for 2 h and further calcined at 800 °C for 1 h. After cooling to room temperature, they were etched with HF (5 wt%) for 48 h, washed with deionized water several times, and finally freeze-dried for 22 h.

[0051] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are provided to further illustrate the technical features disclosed in the present invention, but they should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above invention without inventive work are also considered to fall within the scope of protection of the present invention.

[0052] Comparative Example 1

[0053] The difference between Comparative Example 1 and Example 1 is that tetraethoxysilane and phytic acid are not added during the preparation of the material of Comparative Example 1, and the other contents remain unchanged.

[0054] Comparative Example 2

[0055] The difference between Comparative Example 2 and Example 1 is that tetraethoxysilane is not added during the preparation of the material of Comparative Example 1, and the other conditions remain unchanged.

[0056] Comparative Example 3

[0057] The difference between Comparative Example 3 and Example 1 is that phytic acid is not added to the materials of Comparative Example 1 during the preparation process, and the other conditions remain unchanged.

[0058] 1. Scanning electron microscope test

[0059] The phosphorus-doped hollow spherical porous carbon material prepared in Example 1 was tested by scanning electron microscopy. The test results are as follows: Figure 1 As shown. Figure 1 The results show that the material has a hollow spherical structure with an average particle size of 200-300nm, and the surface of the material is porous.

[0060] 2. Transmission electron microscopy test

[0061] The phosphorus-doped hollow spherical porous carbon material prepared in Example 1 was subjected to transmission electron microscopy and mapping tests. The test results are as follows: Figure 3-4 As shown. Figure 3 The results show that the material has a spherical structure with thin edges, thick middle and hollow. Figure 4 According to the mapping results analysis, the four elements C, P, N, and O are evenly distributed in the material.

[0062] The catalytic degradation effect and cyclic stability test of the catalytic materials prepared in Example 1 and Comparative Examples 1-3 were carried out. The results are as follows: Figure 5-8 shown.

[0063] Depend on Figure 5-7 It can be seen that the phosphorus-doped hollow spherical porous carbon material prepared in the present invention has an excellent catalytic degradation effect of sulfachloropyridazine.

[0064] In terms of catalytic degradation, the present invention uses phosphorus-doped hollow spherical porous carbon materials as catalytic carriers and forms a catalytic oxidation system with persulfate. Figure 5 As shown, within 40min, the removal rate of Example 1 to sulfachloropyridazine is 100%, while the removal effects of Comparative Examples 1-3 are respectively only 41%, 45%, 60%, indicating that tetraethoxysilane and phytic acid play a synergistic role in catalytic process. The removal effects of Comparative Example 1 and Comparative Example 2 are much lower than those of Example 1, indicating that the carbon material lacking tetraethoxysilane has no hollow spherical structure, and obvious agglomeration occurs, and the particles are larger and the active sites are less; After introducing phytic acid on this structure, the removal effect is not significantly improved. The removal effect of Comparative Example 3 is also relatively low, but is improved compared to Comparative Example 1 and Comparative Example 2, indicating that tetraethoxysilane plays an important role in catalytic process, and tetraethoxysilane can adjust the material to be a hollow spherical structure, which reduces particle size, increases specific surface area, and increases active sites.

[0065] Depend on Figure 6 It can be seen that the phosphorus-doped hollow spherical porous carbon material prepared by the present invention has an excellent adsorption effect of sulfachloropyridazine. Within 40 minutes, the adsorption effect of sulfachloropyridazine in Example 1 is about 50%. Figure 7 As can be seen, after the phosphorus-doped hollow spherical porous carbon material prepared in Example 1 adsorbed and catalytically degraded sulfachloropyridazine, the material was centrifuged and freeze-dried, and then sonicated in methanol for 1-2 hours. The antibiotic in the adsorption group was completely eluted, while the elution rate in the catalytic degradation group was less than 5%. This demonstrates that the phosphorus-doped hollow spherical porous carbon material of the present invention not only has good adsorption performance but also excellent catalytic degradation performance.

[0066] Depend on Figure 8 In terms of stability, the phosphorus-doped hollow spherical porous carbon material prepared by the present invention achieved a sulfachloropyridazine removal rate of over 97% after the first cycle. After four repeated cycles, the sulfachloropyridazine removal rate dropped to 78%. This result demonstrates that the material has significant stability and good recyclability.

[0067] In addition, Table 1 compares the PS activation performance of P2-MC with other reported SCP degradation catalysts. As can be seen from Table 1, the catalytic oxidation system constructed by the material of the present invention and persulfate can remove higher concentrations of antibiotics with a dosage of only one-tenth or even a few percent of the catalyst amount in previous literature.

[0068] Table 1

[0069]

[0070] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a phosphorus-doped hollow spherical porous carbon material, characterized in that: The phosphorus-doped hollow spherical porous carbon material is prepared by using dopamine hydrochloride and phytic acid as main reagents and tetraethoxysilane as a spherical structure directing agent, and is calcined in a tubular furnace, HF-etched, and freeze-dried. The process specifically comprises the following steps: (1) adding tetraethoxysilane to a mixed solution containing aqueous ammonia, anhydrous ethanol, and deionized water, stirring, and adjusting the pH of the solution to obtain a tetraethoxysilane mixed solution for later use; (2) dissolving dopamine hydrochloride in water, and adding the dopamine hydrochloride solution to the tetraethoxysilane mixed solution obtained in step (1) to react to obtain a black solution, i.e., a silica / polydopamine mixed solution; (3) adding phytic acid to the silica / polydopamine mixed solution obtained in step (2), calcining the obtained sample at high temperature, and after cooling to room temperature, etching with HF and washing with deionized water, and freeze-drying to obtain the phosphorus-doped hollow spherical porous carbon material; The high temperature calcination process is operated as follows: Place under nitrogen atmosphere at 5°C min -1 The sintered product was calcined at 400 °C for 1-2 hours and then further calcined at 800 °C for 1-2 hours. In step (1), the volume ratio of ammonia water, anhydrous ethanol, deionized water and tetraethoxysilane is (1-2):(20-25):(75-85):(1-2), and the pH of the solution is adjusted to 8-10; In step (2), the molar ratio of dopamine hydrochloride to water in the dopamine hydrochloride solution is (0.5-1 g):(5-10 mL), and the mass ratio of dopamine hydrochloride to tetraethoxysilane is (0.5-1):(1-2); The reaction temperature in step (2) is 25°C-30°C, and the reaction time is 15-20h; In step (3), the phytic acid solution is prepared by uniformly mixing 70% phytic acid and deionized water in equal volumes, and the amount of phytic acid solution added is 1-3 mL; The HF concentration is 5wt%, and the etching time is 45-50h; In terms of catalytic degradation, the phosphorus-doped hollow spherical porous carbon material is a catalytic carrier and constitutes a catalytic oxidation system with persulfate.

2. A phosphorus-doped hollow spherical porous carbon material prepared by the method of claim 1, characterized in that: Polydopamine is generated by the self-polymerization of dopamine hydrochloride and wrapped in a spherical structure-directing agent. The amino groups in the polydopamine are combined with the phosphate groups to form a phosphorus-doped hollow spherical porous carbon material.

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