Coralline carbon nitride-based manganese catalyst as well as preparation method and application thereof

Abstract

The invention provides a coralline carbon nitride-based manganese catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst preparation and pollutant degradation. The preparation method of the coralline carbon nitride-based manganese catalyst comprises the following steps: under a first heating condition, dissolving melamine in ethylene glycol to obtain a melamine solution, and mixing the melamine with the ethylene glycol to obtain a cyanuric acid suspension; under a second heating condition, slowly dropwise adding the melamine solution into the cyanuric acid suspension, mixing, centrifuging and drying to obtain a carbon nitride precursor solid; grinding the carbon nitride precursor solid, and mixing the ground carbon nitride precursor solid with a manganese source to obtain a carbon nitride-manganese blended precursor; under an inert atmosphere, the carbon nitride-manganese blended precursor is calcined to obtain the coralline-shaped carbon nitride-based-manganese catalyst, the coralline-shaped carbon nitride-based-manganese catalyst has a larger specific surface area and more active sites, and transition metal manganese is doped in carbon nitride, so that the catalytic capability is effectively improved, and rapid degradation of pollutants is realized.

Description

Technical Field

[0001] The present disclosure belongs to the fields of catalyst preparation and pollutant degradation, and particularly relates to a coral-like carbon nitride-based manganese catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, with the rapid development of the pharmaceutical and washing and chemical industries, pharmaceutical and personal care products (PPCPs) have gradually come into people's sight as a class of emerging pollutants. Such substances are continuously introduced into the environment, and the resulting water pollution problem has become increasingly prominent. Therefore, how to efficiently treat wastewater containing PPCPs has become an urgent task.

[0003] Although the current carbon nitride catalysts have certain adsorption properties, their ability to remove PPCPs is limited and there is still room for further improvement. Summary of the Invention

[0004] In view of this, the present disclosure provides a coral-like carbon nitride-based manganese catalyst, a preparation method thereof, and an application thereof, in order to at least partially solve the above technical problems. For this, the technical solutions provided by the present disclosure are as follows.

[0005] As a first aspect of the present disclosure, a preparation method of a coral-like carbon nitride-based manganese catalyst is provided, including: dissolving melamine in ethylene glycol to obtain a melamine solution under a first heating condition, and mixing cyanuric acid with ethylene glycol to obtain a cyanuric acid suspension; slowly dropping the melamine solution into the cyanuric acid suspension under a second heating condition, and obtaining a carbon nitride precursor solid through mixing, centrifuging, and drying; grinding the carbon nitride precursor solid and mixing it with a manganese source to obtain a carbon nitride-manganese co-blended precursor; calcining the carbon nitride-manganese co-blended precursor in an inert atmosphere to obtain a coral-like carbon nitride-based manganese catalyst.

[0006] As a second aspect of the present disclosure, a coral-like carbon nitride-based manganese catalyst prepared by the above preparation method is provided, wherein the coral-like carbon nitride-based manganese catalyst includes: carbon nitride and manganese oxide loaded on the carbon nitride, and the carbon nitride has a coral-like structure.

[0007] As a third aspect of the present disclosure, an application of a coral-like carbon nitride-based manganese catalyst in degrading pollutants is provided.

[0008] Based on the above technical solutions, the coral-like carbon nitride-based manganese catalyst, a preparation method thereof, and an application thereof provided by the present disclosure have at least one of the following beneficial effects:

[0009] (1) In the embodiments of the present disclosure, a melamine solution and a cyanuric acid suspension are prepared, and the melamine solution is slowly dropped into the cyanuric acid suspension. By controlling the mixing method of reaction raw materials, heating conditions, etc., a carbon nitride precursor solid can be obtained. Subsequently, the carbon nitride precursor solid is admixed with a manganese source, and during the admixing process, manganese is uniformly dispersed on the carbon nitride. By calcining and controlling the calcination temperature, a coral-like carbon nitride-based manganese catalyst can be prepared. The method for preparing the coral-like carbon nitride-based manganese catalyst in the present disclosure is relatively simple, the process is easy to control, the catalytic performance of the prepared carbon nitride-based manganese catalyst is stable, the comprehensive cost is low, and it is easy to realize batch preparation.

[0010] (2) In the embodiments of the present disclosure, the prepared carbon nitride-based manganese catalyst has a coral-like structure, which has a larger specific surface area, can expose more Mn active sites, effectively improves the catalytic ability of carbon nitride, and can achieve rapid degradation of pollutants. Description of the Drawings

[0011] Figure 1 It is the scanning electron microscope image (SEM) and element distribution map of the coral-like carbon nitride-based manganese (Mn20-CN) catalyst in Example 1 of the present disclosure;

[0012] Figure 2 It is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 1 of the present disclosure;

[0013] Figure 3 It is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 2 of the present disclosure;

[0014] Figure 4 It is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 3 of the present disclosure;

[0015] Figure 5 It is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 4 of the present disclosure;

[0016] Figure 6 It is the cyclic stability test diagram of the catalyst in Example 1 of the present disclosure;

[0017] Figure 7 It is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 6 of the present disclosure. Detailed Embodiments

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0019] Carbon nitride is a carbon-nitrogen polymer material composed of carbon and nitrogen. In related technologies, carbon nitride is usually prepared by thermal polymerization. However, the prepared carbon nitride usually has problems such as low comparative area, poor metal loading dispersion and insufficient stability. It is impossible to improve the catalytic performance of the carbon nitride catalyst, resulting in poor degradation effect of PPCPs.

[0020] Ozonation technology is an advanced oxidation technology that produces hydroxyl radicals (·OH) with strong oxidizing properties to quickly remove organic matter in water without secondary pollution, thereby achieving the purpose of water purification. However, the slower ·OH generation rate reduces the removal rate of pollutants and cannot quickly and effectively remove pollutants.

[0021] In view of the above problems, the present invention introduces transition metal manganese (Mn) into carbon nitride-based materials and controls the synthesis conditions to prepare a coral-like carbon nitride-based-manganese catalyst with a larger specific surface area. Finally, the catalyst is combined with advanced oxidation technology to achieve rapid degradation of organic pollutants.

[0022] Specifically, as a first aspect of the present disclosure, a method for preparing a coral-like carbon nitride-based-manganese catalyst is provided, comprising: under a first heating condition, dissolving melamine in ethylene glycol to obtain a melamine solution, and mixing cyanuric acid with ethylene glycol to obtain a cyanuric acid suspension; under a second heating condition, slowly dropping the melamine solution into the cyanuric acid suspension, mixing, centrifuging, and drying to obtain a carbon nitride precursor solid; grinding the carbon nitride precursor solid and mixing it with a manganese source to obtain a carbon nitride-manganese blended precursor; and calcining the carbon nitride-manganese blended precursor under an inert atmosphere to obtain a coral-like carbon nitride-based-manganese catalyst.

[0023] In an embodiment of the present disclosure, a melamine solution and a cyanuric acid suspension are prepared, and the melamine solution is slowly dropped into the cyanuric acid suspension. By controlling the mixing method of reaction raw materials, heating conditions, etc., a carbon nitride precursor solid can be obtained. Subsequently, the carbon nitride precursor solid is mixed with a manganese source. During the mixing process, manganese is uniformly dispersed on the carbon nitride. After calcination and controlling the calcination temperature, the prepared coral-like carbon nitride-based manganese catalyst has a larger specific surface area, thereby being able to expose more active sites. Moreover, appropriately doping transition metal manganese in the carbon nitride effectively improves the catalytic ability of the carbon nitride, and rapid degradation of pollutants can be achieved. In addition, the preparation method of the coral-like carbon nitride-based manganese catalyst of the present disclosure is simple, the process is easy to control, the catalytic performance of the prepared carbon nitride-based manganese catalyst is stable, the comprehensive cost is low, and it is easy to realize batch preparation.

[0024] According to an embodiment of the present disclosure, the heating temperature under the first heating condition is 90 - 100 °C, for example, it can be 90 °C, 91 °C, 93 °C, 95 °C, 97 °C, and 99 °C, so that melamine can dissolve in hot ethylene glycol to form a melamine solution, and cyanuric acid can be dispersed in hot ethylene glycol to form a cyanuric acid suspension. The respective mixing time for forming the melamine solution and the cyanuric acid suspension is 20 - 40 min, for example, 25 min, 30 min, and 35 min. Further, the concentration of the melamine solution is 20 - 25 g / L, for example, 21 g / L, 22 g / L, 23 g / L, and 24 g / L; the concentration of the cyanuric acid suspension is 20 - 25 g / L, for example, 21 g / L, 22 g / L, 23 g / L, and 24 g / L.

[0025] According to an embodiment of the present disclosure, under the second heating condition, the mixing temperature of the melamine solution and the cyanuric acid suspension is 105 - 125 °C, for example, 110 °C, 115 °C, and 120 °C, the mixing time is 20 - 40 min, for example, 25 min, 30 min, and 35 min; the mixing volume ratio of the melamine solution and the cyanuric acid suspension is 5:4 - 4:5.

[0026] For example: Add 1 g of melamine to 50 mL of ethylene glycol solvent, mix at 100 °C for 20 min to obtain a melamine solution with a concentration of 20 g / L; similarly, add 1 g of cyanuric acid to 40 mL of ethylene glycol solvent, mix at 100 °C for 20 min to obtain a cyanuric acid suspension with a concentration of 25 g / L. Subsequently, slowly drop the melamine solution into the cyanuric acid suspension, add it according to the volume ratio of melamine:cyanuric acid = 5:4, and mix well at 105 °C for 20 min to obtain a carbon nitride precursor solution.

[0027] According to an embodiment of the present disclosure, after obtaining the carbon nitride precursor solution, it is centrifuged, washed multiple times, and dried to obtain a carbon nitride precursor solid. Among them, the centrifugation speed is 10,000 r, 4 °C, for 5 min; it is washed multiple times by oscillating alternately with ethanol and ultrapure water, such as 3 times; drying can be carried out in a vacuum drying oven, such as drying at 80 °C for 12 h.

[0028] According to an embodiment of the present disclosure, the addition amount of the manganese source is 0.5 - 2.5 mmol; the manganese source is selected from any one of Mn(NO3)2·4H2O, Mn(NO3)2·6H2O, Mn(NO3)3, and Mn(NO3)3·9H2O. After the carbon nitride precursor solid is sufficiently ground, it is then ground and mixed with the manganese source for 20 min to obtain a carbon nitride-manganese co-blended precursor.

[0029] According to an embodiment of the present disclosure, the calcination temperature is 450 - 600 °C, such as 450 °C, 470 °C, 500 °C, 520 °C, 550 °C, and 600 °C, and the calcination time is 1 - 3 h, such as 1 h, 1.5 h, 2 h, 2.5 h, and 3 h.

[0030] As a second aspect of the present disclosure, there is provided a coral-like carbon nitride-based manganese catalyst prepared by the above method. Among them, the coral-like carbon nitride-based manganese catalyst includes: carbon nitride and a manganese compound supported on the carbon nitride, and the carbon nitride has a coral-like structure.

[0031] In an embodiment of the present disclosure, the coral-like carbon nitride-based manganese catalyst has a larger specific surface area, exposes more active sites, and manganese is uniformly dispersed in the carbon nitride, which can enhance the removal effect of pollutants. In addition, the catalyst with a coral-like structure has coexisting micropores, mesopores, and macropores, which can accelerate the diffusion and mass transfer of reactants (such as O3, H2O2, ibuprofen), and improve the catalytic reaction kinetics. The mechanical strength of the coral-like skeleton is relatively high, and it is not easy to collapse in the long-term catalytic reaction, and the porous structure can buffer the dissolution of Mn metal to ensure the activity of the catalyst.

[0032] As a third aspect of the present disclosure, there is provided an application of the above coral-like carbon nitride-based manganese catalyst in degrading pollutants.

[0033] In an embodiment of the present disclosure, an Mn-N coordination bond can be formed between Mn and carbon nitride, and an active interface can be formed to stabilize active Mn, avoiding the dissolution or inactivation of Mn. Therefore, when the coral-like carbon nitride-based manganese catalyst degrades pollutants, it can achieve rapid degradation of pollutants while having a high degradation rate.

[0034] According to an embodiment of the present disclosure, the application of the above-mentioned coral-like carbon nitride-based-manganese catalyst in the degradation of pollutants includes: introducing ozone (O3) and hydrogen peroxide (H2O2) into organic pollutants, and adding the above-mentioned coral-like carbon nitride-based-manganese catalyst to react to achieve the degradation of organic pollutants.

[0035] O3 can directly oxidize pollutants or decompose to generate reactive oxidative species (ROS) such as hydroxyl radicals (·OH), which can degrade pollutants. However, the reaction rate is slow, and the generation of ·OH needs to be initiated under alkaline conditions or with a catalyst, which is costly and has a low yield of ·OH, thus affecting the degradation effect. H2O2 generates ·OH (H2O2→2·OH) under the catalytic action of the catalyst, but ·OH is limited by the catalytic efficiency of the catalyst or the reaction conditions. The present disclosure addresses the problems existing in the use of O3 or H2O2 alone, utilizes a method of using O3 in conjunction with H2O2, and uses the above-mentioned coral-like carbon nitride-based-manganese catalyst as a catalyst for degrading pollutants, thereby achieving rapid removal of pollutants in water without causing secondary pollution. Specifically, in the catalytic system of the coral-like carbon nitride-based-manganese catalyst, Mn has Mn 2+ / Mn 3+ / Mn 4+ Multiple valence states can simultaneously activate O3 and H2O2, achieving multivalent redox cycle generation On the other hand, the electron-rich properties of carbon nitride (g-C3N4) can enhance the adsorption of O3 and H2O2. The π-conjugated structure of carbon nitride can accelerate the transfer of interface electrons from O3 or H2O2 to the Mn active site, promoting the generation of free radicals. The Mn-N bond formed between Mn and g-C3N4 can stabilize the Mn active site by strong coordination, preventing Mn from dissolving or precipitating and affecting the catalytic performance of the catalyst.

[0036] According to an embodiment of the present disclosure, the organic pollutant includes ibuprofen, the concentration of ozone is 7.5±1 mg / L, and the concentration of hydrogen peroxide is 0.5-1.5 μL / L.

[0037] The following will take the degradation process of ibuprofen as an example to briefly describe the reaction mechanism in the degradation reaction process.

[0038] Specifically, O3 and H2O2 form a free radical network through a cascade reaction, achieving a synergistic effect. That is, O3 activates H2O2 to generate ·OH; H2O2 acts as an electron donor to promote the decomposition of O3 into , and then converted into ·OH, the generated ·OH further reacts with O3 or H2O2 to form a chain cycle, continuously generating active oxygen. In the coral-like carbon nitride-based manganese catalyst (Mn / g-C3N4) catalytic system, the unique property of manganese with multiple valence states can be used to further enhance the synergistic effect, that is, Mn2+ / Mn 3+ / Mn 4+ It can simultaneously activate O3 and H2O2 to generate reactive species. The electron-rich surface of g-C3N4 enhances the adsorption of O3 and H2O2, promoting interfacial electron transfer; Mn forms Mn-N bonds with g-C3N4, stabilizing the active sites and reducing the dissolution or inactivation of manganese, which affects the catalytic performance of the catalyst. The degradation efficiency of ibuprofen (C 13 H 18 O2) is closely related to its molecular characteristics. The benzene ring and carboxylic acid group of ibuprofen are vulnerable to attack by electrophilic free radicals such as ·OH, triggering ring-opening or decarboxylation reactions; among them, O3 preferentially oxidizes double bonds or electron-rich regions (such as benzene rings), and ·OH can attack organic substances indiscriminately, completely mineralizing intermediate products and reducing the accumulation of toxic by-products. In addition, the nitrogen-rich surface of g-C3N4 adsorbs the carboxylic acid group of ibuprofen through hydrogen bonds or electrostatic interactions, enriching pollutants near the manganese (Mn) active sites, increasing the local reaction concentration, and improving the degradation effect.

[0039] The reaction processes involved are as follows:

[0040]

[0041] The specific technical solutions and beneficial effects of the present disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1

[0043] Step S1: Prepare the carbon nitride precursor solution: Weigh 1 g of melamine and add it to 50 mL of ethylene glycol solvent, mix at 100 °C for 20 min to obtain a melamine solution with a concentration of 20 g / L, named solution A; weigh 1 g of cyanuric acid and add it to 40 mL of ethylene glycol solvent, mix at 100 °C for 20 min to obtain a cyanuric acid suspension with a concentration of 25 g / L, named suspension B. Then, use a dropper to slowly drip solution A into suspension B, add it according to a volume ratio of A:B of 5:4, and mix well at 100 °C for 20 min to obtain the carbon nitride precursor solution.

[0044] Step S2: Prepare the carbon nitride precursor solid: Centrifuge the carbon nitride precursor solution obtained in step S1, and then add ethanol and ultrapure water and wash it three times with a shaker respectively. The centrifuge parameters are: 10000 r, 4 °C, 5 min. After washing, put the obtained precipitate into a vacuum drying oven and dry it at 80 °C for 12 h to obtain the carbon nitride precursor solid.

[0045] Step S3 Preparation of carbon nitride-manganese blended precursor: After thoroughly grinding the obtained carbon nitride precursor solid in a mortar in Step S2, weigh 2 mmol of Mn(NO3)2·4H2O and add it to the carbon nitride precursor solid, then grind it thoroughly for another 20 min to obtain the carbon nitride-manganese blended precursor.

[0046] Step S4 Preparation of coral-like carbon nitride-based manganese catalyst: Load the carbon nitride-manganese blended precursor into a crucible and place it in a tube furnace. Under a nitrogen atmosphere, calcine it at 500 °C with a heating rate of 5 °C·min -1 for 2 h to obtain the coral-like carbon nitride-based manganese catalyst, named Mn20-CN.

[0047] Use a scanning electron microscope (SEM) to characterize the Mn20-CN catalyst prepared in Example 1, and the test results are as Figure 1 shown.

[0048] Figure 1 This is the scanning electron microscope (SEM) image and elemental distribution map of the coral-like carbon nitride-based manganese (Mn20-CN) catalyst in Example 1 of the present disclosure.

[0049] As Figure 1 shown, the Mn20-CN catalyst exhibits a uniform coral-like morphology, and the four elements of Mn, C, N, and O are evenly distributed in the Mn20-CN material.

[0050] Comparative Example 1

[0051] Step S1 Carbon nitride precursor solution: Weigh 1 g of melamine and add it to 50 mL of ethylene glycol solvent, mix it at 100 °C for 20 min to obtain a melamine solution with a concentration of 20 g·L -1 named Solution A; weigh 1 g of cyanuric acid and add it to 40 mL of ethylene glycol solvent, mix it at 100 °C for 20 min to obtain a cyanuric acid suspension with a concentration of 25 g·L -1 named Suspension B. Then, use a dropper to slowly drip Solution A into Solution B and add it in a volume ratio of A:B of 5:4, and mix it thoroughly at 100 °C for 20 min to obtain the carbon nitride precursor solution.

[0052] Step S2 Preparation of carbon nitride precursor solid: Centrifuge the carbon nitride precursor solution obtained in Step S1, then add ethanol and ultrapure water and wash it thoroughly three times with an oscillator respectively. The centrifuge parameters are: 10000 r, 4 °C, 5 min. After washing, put the obtained precipitate into a vacuum drying oven and dry it at 80 °C for 12 h to obtain the carbon nitride precursor solid.

[0053] Step S3: Preparation of coral-like carbon nitride catalyst: The carbon nitride precursor solid is loaded into a crucible and placed in a tube furnace. Under a nitrogen atmosphere, it is calcined at a temperature of 500 °C with a heating rate of 5 °C·min -1 for 2 h to obtain a coral-like carbon nitride catalyst, named CN.

[0054] Example 2

[0055] The coral-like carbon nitride-based manganese catalyst is prepared by the same method as in Example 1. The difference from Example 1 is that in step S3, the dosage of Mn(NO3)2·4H2O is 0.5 mmol. A coral-like carbon nitride-based manganese catalyst is obtained and named Mn5-CN.

[0056] Example 3

[0057] The coral-like carbon nitride-based manganese catalyst is prepared by the same method as in Example 1. The difference from Example 1 is that in step S3, the dosage of Mn(NO3)2·4H2O is 1 mmol. A coral-like carbon nitride-based manganese catalyst is obtained and named Mn10-CN.

[0058] Example 4

[0059] The coral-like carbon nitride-based manganese catalyst is prepared by the same method as in Example 1. The difference from Example 1 is that in step S3, the dosage of Mn(NO3)2·4H2O is 1.5 mmol. A coral-like carbon nitride-based manganese catalyst is obtained and named Mn15-CN.

[0060] Example 5

[0061] The coral-like carbon nitride-based manganese catalyst is prepared by the same method as in Example 1. The difference from Example 1 is that in step S3, the dosage of Mn(NO3)2·4H2O is 2.5 mmol. A coral-like carbon nitride-based manganese catalyst is obtained and named Mn25-CN.

[0062] Example 6

[0063] The coral-like carbon nitride-based manganese catalyst is prepared by the same method as in Example 1. The difference from Example 1 is that in step S4, the calcination temperature is 450 °C. A coral-like carbon nitride-based manganese catalyst is obtained and named Mn-CN-450.

[0064] Example 7

[0065] The coral-like carbon nitride-based manganese catalyst is prepared by the same method as in Example 1. The difference from Example 1 is that in step S4, the calcination temperature is 550 °C. A coral-like carbon nitride-based manganese catalyst is obtained and named Mn-CN-550.

[0066] Example 8

[0067] The coral-like carbon nitride-based manganese catalyst was prepared by the same method as in Example 1. The difference from Example 1 was that in step S4, the calcination temperature was 600 °C. The coral-like carbon nitride-based manganese catalyst was obtained and named Mn-CN-600.

[0068] Comparative Example 2

[0069] The coral-like carbon nitride-based manganese catalyst was prepared by the same method as in Example 1. The difference from Example 1 was that in step S3, the carbon nitride precursor solid obtained in step S2 was sufficiently ground in a mortar, and then 2 mmol of Fe(NO3)3·9H2O was weighed and added to the precursor and ground for 20 min to obtain a carbon nitride-iron blended precursor, and the carbon nitride-iron catalyst was prepared from this carbon nitride-iron precursor and named Fe20-CN.

[0070] Comparative Example 3

[0071] The coral-like carbon nitride-based manganese catalyst was prepared by the same method as in Example 1. The difference from Example 1 was that in step S3, the carbon nitride precursor solid obtained in step S2 was sufficiently ground in a mortar, and then 2 mmol of Cu(NO3)2·3H2O was weighed and added to the precursor and ground for 20 min to obtain a carbon nitride-copper blended precursor, and the carbon nitride-copper catalyst was prepared from this carbon nitride-copper precursor and named Cu20-CN.

[0072] Comparative Example 4

[0073] The coral-like carbon nitride-based manganese catalyst was prepared by the same method as in Example 1. The difference from Example 1 was that in step S3, the precursor obtained in step S2 was sufficiently ground in a mortar, and then 2 mmol of Co(NO3)2·6H2O was weighed and added to the precursor and ground for 20 min to obtain a carbon nitride-cobalt blended precursor, and the carbon nitride-cobalt catalyst was prepared from this carbon nitride-cobalt precursor and named Co20-CN.

[0074] Test Example 1

[0075] The degradation experiment was carried out using the Mn20-CN catalyst prepared in Example 1 and the CN catalyst prepared in Comparative Example 1. Specifically, four groups of ibuprofen pollutants with an initial concentration of 20 mg / L were provided, and ozone with a dose of 7.5 ± 1 mg / L and 1 μL of H2O2 were introduced into 3 groups of the ibuprofen pollutants respectively. 0.01 g / L of the CN catalyst was added to one group of ozone and H2O2, 0.01 g / L of the Mn20-CN catalyst was added to one group, and one group was used as a blank without adding any catalyst; 0.01 g / L of the Mn20-CN catalyst was added to the group without ozone and H2O2 (i.e., only ibuprofen pollutants), and the reaction time for the degradation of pollutants in the four groups was 30 min. After the reaction ended, the concentrations of ibuprofen in the four groups of solutions at different reaction times were detected respectively, and the specific test results are as Figure 2 shown.

[0076] Figure 2 This is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 1 of the present disclosure.

[0077] As Figure 2 shown, the Mn20-CN catalyst prepared in Example 1 can completely degrade ibuprofen. Compared with other reaction conditions and the CN catalyst, it significantly improves the treatment efficiency of organic pollutants, proving that the coral-like carbon nitride-based manganese catalyst prepared in the present disclosure and the co-ozonation technology can quickly and efficiently remove organic pollutants.

[0078] Test Example 2

[0079] The degradation test was carried out using the catalysts prepared in Examples 1 to 5. Specifically, five groups of ibuprofen pollutants with an initial concentration of 20 mg / L were provided. After introducing ozone with a dose of 7.5 ± 1 mg / L and 1 μL of H2O2 into the five groups of ibuprofen pollutants respectively, 0.01 g / L of the Mn5-CN, Mn10-CN, Mn15-CN, Mn20-CN, and Mn25-CN catalysts were added to them respectively and differently, and the reaction time for the degradation of pollutants was 30 min. After the reaction ended, the concentrations of ibuprofen in the five groups of solutions at different reaction times were detected respectively, and the specific test results are as Figure 3 shown.

[0080] Figure 3 This is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 2 of the present disclosure.

[0081] As Figure 3As shown, the coral-like carbon nitride-based manganese catalysts prepared in Examples 1-5 can all improve the degradation rate and effect of ibuprofen, and it is shown that when the addition amount of manganese source is 2-2.5 mmol, the prepared Mn-CN catalyst has a high degradation efficiency. Especially when the addition amount of manganese source is 2 mmol, its degradation efficiency is the highest.

[0082] Test Example 3

[0083] The catalysts prepared in Example 1 and Examples 6-8 were subjected to degradation tests. Specifically, 4 groups of ibuprofen pollutants with an initial concentration of 20 mg / L were provided. After introducing ozone with a dose of 7.5 ± 1 mg / L and 1 μL of H2O2 into the 4 groups of ibuprofen pollutants respectively, 0.01 g / L of Mn-CN-450, Mn20-CN (i.e., Mn-CN-500), Mn-CN-550, and Mn-CN-600 catalysts were added to them respectively and differently. The reaction for pollutant degradation was 30 min. After the reaction ended, the concentrations of ibuprofen in the 4 groups of solutions at different reaction times were detected respectively. The specific test results are as Figure 4 shown.

[0084] Figure 4 This is the degradation effect diagram of different catalysts for ibuprofen pollutants in Test Example 3 of the present disclosure.

[0085] As Figure 4 shown, the coral-like carbon nitride-based manganese catalysts prepared in Example 1 and Examples 6-8 can all improve the degradation rate and effect of ibuprofen, and it is shown that when the calcination temperature is 500-550 °C, the prepared Mn-CN catalyst has a high treatment efficiency for organic pollutants. Especially when the calcination temperature is 500 °C, the degradation effect of ibuprofen is the highest.

[0086] Test Example 4

[0087] The catalysts prepared in Example 1 and Comparative Examples 2-4 were subjected to degradation tests. Specifically, 4 groups of ibuprofen pollutants with an initial concentration of 20 mg / L were provided. After introducing ozone with a dose of 7.5 ± 1 mg / L and 1 μL of H2O2 into the 4 groups of ibuprofen pollutants respectively, 0.01 g / L of Fe20-CN, Mn20-CN, Cu20-CN, and Co20-CN catalysts were added to them respectively and differently. The reaction time for pollutant degradation was 30 min. After the reaction ended, the concentrations of ibuprofen in the 4 groups of solutions at different reaction times were detected respectively. The specific test results are as Figure 5 shown.

[0088] Figure 5 This is the degradation effect diagram of different catalysts for ibuprofen pollutants in Test Example 4 of the present disclosure.

[0089] As Figure 5 shown, the degradation rate and effect of ibuprofen by the catalyst prepared in Example 1 are significantly higher than those of the catalysts prepared in Comparative Examples 2-4, indicating that compared with other metals, manganese can more effectively improve the catalytic ability of carbon nitride. The reason is analyzed as follows: The surface of g-C3N4 is rich in nitrogen and can preferentially adsorb the carboxylic acid group of ibuprofen. Mn has multiple valence states (Mn 2+ / Mn 3+ / Mn 4+ ), and it is more likely to undergo redox reactions in the field of peroxide technology, promoting the decomposition of O3 to generate active species ( , ·OH, H2O2), and it can also activate H2O2 to generate active species. For Cu, it is easy to form Cu 2+ , with low redox activity and difficult to efficiently catalyze the decomposition of ozone; for Fe, the Fe 3+ / Fe 2+ cycle may be limited by reaction conditions (such as pH), and it is easy to generate iron hydroxide precipitation, resulting in catalyst deactivation; for Co, Co 3+ has high stability, but weak oxidation ability, difficult to effectively activate ozone or H2O2, and no active oxidation species are generated, resulting in lower catalytic effects of Co, Fe, and Cu than Mn.

[0090] The specific surface areas S BET (m² / g) of Fe20-CN, Mn20-CN, Cu20-CN, Co20-CN, g-C3N4, and coral-like g-C3N4 in Test Example 4 are shown in Table 1 below.

[0091] Table 1

[0092]

[0093] Note: In Table 1, g-C3N4 was obtained by grinding 2 g of melamine and directly calcining it in a tube furnace at 500 °C, and the calcination conditions were the same as those in Example 1.

[0094] As can be seen from Table 1, the coral-like g-C3N4 provided by the present disclosure has a relatively high specific surface area. In addition, although the Mn20-CN of the present disclosure does not have a large specific surface area compared with Cu20-CN and Co20-CN, its catalytic performance is the highest, and the performance of degrading ibuprofen pollutants is the highest. Thus, it shows that the combined action of Mn and coral-like g-C3N4 in the present disclosure has a high performance in degrading pollutants in catalytic ozone and H2O2.

[0095] Test Example 5

[0096] The cyclic stability of the Mn20-CN catalyst prepared in Example 1 was tested. Specifically, five groups of ibuprofen pollutants with an initial concentration of 20 mg / L were provided. After introducing ozone with a dose of 7.5 ± 1 mg / L and 1 μL of H2O2 into one of the groups, 0.01 g / L of the Mn20-CN catalyst was added thereto, and the reaction time for the degradation of the pollutants was 30 min. After the reaction ended, the used Mn20-CN catalyst was collected and dried at 60 °C for 12 h and then used again. The regenerated catalyst was repeatedly cycled five times, and the concentrations of ibuprofen in the five groups of solutions at different reaction times were detected respectively. The specific test results are as Figure 6 shown.

[0097] Figure 6 This is the cyclic stability test diagram of the catalyst in Example 1 of the present disclosure.

[0098] As Figure 6 shown, after 5 cycles of testing, the degradation efficiency of the Mn20-CN catalyst for ibuprofen still remains at a high level, indicating that the coral-like carbon nitride-based manganese catalyst prepared in the present disclosure has high catalytic stability.

[0099] Preparation process of Test Example 6 Mn20-BC: Biochar (BC) was obtained by grinding banyan tree roots and calcining them in a tube furnace at 500 °C, at a rate of 5 °C / min for 2 h. The obtained BC was fully mixed and ground with 2 mmol of Mn(NO3)2·4H2O for 20 min, and then calcined in a tube furnace at 500 °C for 2 h at a rate of 5 °C / min to prepare.

[0100] The degradation tests were carried out on the above-prepared Mn20-BC catalyst and Mn20-CN in Example 1. Specifically, three groups of ibuprofen pollutants with an initial concentration of 20 mg / L were provided. After introducing ozone with a dose of 7.5 ± 1 mg / L and 1 μL of H2O2 into the three groups of ibuprofen pollutants respectively, one of the groups was used as a blank without adding any catalyst; one group was added with 0.01 g / L of the Mn20-CN catalyst in Example 1, and the other group was added with 0.01 g / L of the Mn20-BC catalyst. The reaction time for the degradation of the ibuprofen pollutants was 30 min. After the reaction ended, the concentrations of ibuprofen in the three groups of solutions at different reaction times were detected respectively. The specific test results are as Figure 7 shown.

[0101] Figure 7 This is the degradation effect diagram of different catalysts for degrading ibuprofen pollutants in Test Example 6 of the present disclosure.

[0102] As Figure 7 shown, the Mn20-CN catalyst in Example 1 of the present disclosure has high degradation performance.

[0103] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not used to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A preparation method of a coral-like carbon nitride-based manganese catalyst, comprising: Under a first heating condition, dissolving melamine in ethylene glycol to obtain a melamine solution, and mixing cyanuric acid with ethylene glycol to obtain a cyanuric acid suspension; Under a second heating condition, slowly dropping the melamine solution into the cyanuric acid suspension, and obtaining a carbon nitride precursor solid through mixing, centrifuging, and drying; Grinding the carbon nitride precursor solid and mixing it with a manganese source to obtain a carbon nitride-manganese blend precursor; Under an inert atmosphere, calcining the carbon nitride-manganese blend precursor to obtain a coral-like carbon nitride-based manganese catalyst.

2. The preparation method according to claim 1, wherein, The heating temperature under the first heating condition is 90-100 °C, and the respective mixing time for forming the melamine solution and the cyanuric acid suspension is 20-40 min; The concentration of the melamine solution is 20-25 g / L, the concentration of the cyanuric acid suspension is 20-25 g / L, and the mixing volume ratio of the melamine solution to the cyanuric acid suspension is 5:4-4:

5.

3. The preparation method according to claim 1, wherein, Under the second heating condition, the mixing temperature of the melamine solution and the cyanuric acid suspension is 105-125 °C, and the mixing time is 20-40 min.

4. The preparation method according to claim 1, wherein, The addition amount of the manganese source is 0.5-2.5 mmol; The manganese source is selected from any one of Mn(NO3)2·4H2O, Mn(NO3)2·6H2O, Mn(NO3)3, and Mn(NO3)3·9H2O.

5. The preparation method according to claim 1, wherein, The calcining temperature is 450-600 °C, and the calcining time is 1-3 h.

6. A coral-like carbon nitride-based manganese catalyst prepared by the preparation method according to any one of claims 1-5, wherein, The coral-like carbon nitride-based manganese catalyst comprises: carbon nitride and manganese oxide loaded on the carbon nitride, and the carbon nitride has a coral-like structure.

7. An application of the coral-like carbon nitride-based manganese catalyst as described in claim 6 in degrading pollutants.

8. The application according to claim 7, wherein The application of the coral-like carbon nitride-based manganese catalyst in degrading pollutants comprises: Introducing ozone and hydrogen peroxide into an organic pollutant, and adding the coral-like carbon nitride-based manganese catalyst as described in claim 6 for reaction to achieve the degradation of the organic pollutant.

9. The application according to claim 8, wherein The organic pollutant includes ibuprofen; The concentration of the ozone is 7.5±1 mg / L, and the concentration of the hydrogen peroxide is 0.5-1.5 μL / L.

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