Preparation method and application of pyrrole nitrogen-doped iron monatomic catalyst modified by water vapor etching

Abstract

The application discloses a preparation method of a pyrrole nitrogen-doped iron monatomic catalyst modified by a water vapor etching method and application thereof, and relates to the technical field of catalytic material preparation. The application takes Fe-ZIF as a precursor, and successfully prepares a water vapor etching high-load iron monatomic catalyst through a cage encapsulation method and a water vapor etching method. The catalyst prepared by the application not only effectively overcomes the shortcomings that the specific surface energy of a monatomic catalyst is large, the monatomic catalyst is prone to form agglomeration, and the load of a metal catalyst is usually low, but also improves the catalytic performance of the catalyst, effectively increases the pyrrole nitrogen-doping content, and can quickly degrade antibiotics. The catalyst prepared by the application has strong applicability, mild reaction conditions, and excellent performance in catalyzing and activating a persulfate advanced oxidation reaction to degrade antibiotics, and the water vapor etching iron monatomic catalyst still maintains good structure and catalytic performance after five cycles of degrading antibiotics.

Description

Technical Field

[0001] This invention relates to the field of catalytic material preparation technology, specifically to a method for preparing a water vapor etching modified pyrrole nitrogen-doped iron single-atom catalyst and its application. Background Technology

[0002] Most antibiotics are not metabolized and absorbed by humans or animals, but are excreted into the environment. Antibiotics are widely used and consumed in large quantities; numerous studies have shown that various antibiotics have been detected in natural water environments. Antibiotics in surface water can be broadly classified into six categories based on their chemical structure and properties: sulfonamides, tetracyclines, macrolides, quinolones, aminoglycosides, and β-lactams. Sulfonamides are the longest-used class of synthetic antibiotics and are among the most widely used antibiotics in my country. Sulfasalazine (SSZ), belonging to the sulfadiazine class, is a widely used drug for treating inflammatory bowel disease and rheumatoid arthritis. It is important to note that bacteria easily develop resistance to sulfonamides; in the long run, increasing dosages is the only way to maintain treatment or efficacy. Most sulfonamides that cannot be completely metabolized and absorbed by organisms enter the environment as metabolites or even as the parent compound.

[0003] In the field of sulfonamide antibiotic pollution treatment, activated persulfate advanced oxidation technology has received widespread attention. In recent years, carbon nitride, graphene, and carbon nanotubes have been used as supports to improve transition metal defects, and the resulting catalysts have been widely used in advanced oxidation treatment of water pollution due to their good economics and relatively stable chemical structure. However, their strong metal leaching activity, small specific surface area, and limited pH application range restrict their practical application in the catalytic activation of persulfate for antibiotic pollution treatment.

[0004] Single-atom catalysts exhibit the highest metal atom utilization rate. Their uniform catalytic active site geometry avoids side reactions caused by inhomogeneous composition and structure of active components, significantly improving the selectivity of target products. They also allow for good identification of catalytic active centers and possess unsaturated coordination environments. Furthermore, single-atom catalysts combine high activity, high selectivity, and recyclability, endowing them with superior catalytic performance and making them a research hotspot in the field of catalysis. Among single-atom catalysts, iron-based single-atom catalysts are receiving increasing attention due to their green, environmentally friendly, and highly efficient characteristics, making them potential candidates for various applications such as drug detection and pollutant degradation. They show significant advantages in degrading toxic and persistent emerging organic pollutants in aquatic environments. However, due to their large specific surface energy, single atoms are prone to migration and aggregation, often resulting in low loadings in the prepared single-atom metal catalysts, posing numerous challenges to their synthesis.

[0005] To overcome this problem, developing iron single-atom catalysts with high metal utilization, excellent activation performance, and stable co-catalytic effects has become a challenge in the field of advanced oxidative antibiotic pollution treatment. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching. The catalyst prepared by this method has high degradation efficiency and stable catalytic performance for the antibiotic sulfasalazine.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching includes the following steps:

[0009] Step 1: Dissolve a certain amount of 2-methylimidazole in methanol to obtain solution A; mix a certain amount of zinc nitrate hexahydrate and acetylacetone iron in methanol and then dissolve them in an ultrasonic machine to obtain solution B; slowly add solution B dropwise to solution A and stir to obtain a turbid liquid containing Fe-ZIF.

[0010] Step 2: The turbid Fe-ZIF solution was washed with 5,5-dimethyl-1-pyrrolline-N-oxide and methanol, and then separated by centrifugation and dried in an oven to obtain the Fe-ZIF precursor.

[0011] Step 3: After grinding the Fe-ZIF precursor, place it in a tube furnace filled with nitrogen and water vapor for calcination. In the tube furnace, water vapor etching is used to allow the molecules to react with carbon at high temperature to generate gaseous H2 and CO, forming micropores and expanding the micropore size; the water vapor etching time is 0.5-2 hours.

[0012] In the above-mentioned method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching, in step one, the mass ratio of zinc nitrate hexahydrate, iron acetylacetone, and 2-methylimidazole is 0.8-1:0.25-0.35:1-1.5, respectively.

[0013] In the above-mentioned method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching, in step three, the calcination temperature in a tube furnace is 900-950℃, the calcination heating rate is 5-15℃ / min, the calcination time is 3-5h, and the calcination atmosphere is argon or nitrogen.

[0014] In the above-mentioned method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching, the solvent methanol in step one can be replaced by N,N-dimethylformamide; the dissolution time in the ultrasonic machine is 10-20 min.

[0015] Another objective of this invention is to provide a water vapor etching method for modifying pyrrole nitrogen-doped iron single-atom catalysts, which are prepared using the above-described preparation method.

[0016] Another object of the present invention is to provide the application of the above-mentioned water vapor etching modified pyrrole nitrogen-doped iron single-atom catalyst in the catalytic degradation of the antibiotic sulfasalazine.

[0017] The preparation principle of the catalyst of this invention is as follows:

[0018] A pyrrole nitrogen-doped iron single-atom catalyst prepared by a cage encapsulation method and a steam etching method allows the molecules to react with carbon at high temperatures to generate gaseous H2 and CO, forming micropores. This increases the micropore size, improves the density of accessible active sites on the iron single-atom catalyst, enhances the charge transfer rate, and effectively improves the catalytic performance of the material. The catalyst prepared by this invention provides abundant metallic iron single-atom active sites, effectively dops with pyrrole nitrogen, improves the activation efficiency of persulfate, and achieves highly efficient catalytic degradation of sulfasalazine by activated persulfate advanced oxidation reactions.

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

[0020] (1) The raw materials of this invention are widely available and inexpensive; the preparation method of this invention is simple, mild, green and safe.

[0021] (2) Compared to the original iron single-atom catalyst, this invention modifies and increases the density of accessible active sites in the iron single-atom catalyst through water vapor etching, effectively increasing the pyrrole nitrogen doping content. The combination of the material phases clearly demonstrates that this single-atom structure can optimize the interfacial co-catalytic effect, reduce mass transfer resistance, increase the specific surface area of ​​the material, enhance pollutant adsorption, improve structural stability, increase electron transfer efficiency, and increase single-atom active sites, thereby improving the activation efficiency of persulfate advanced oxidation of the catalyst and achieving efficient degradation of sulfasalazine.

[0022] (3) This invention opens up a new way to rationally design iron single-atom catalysts, improve electron transfer efficiency and enhance the performance of catalytic persulfate advanced oxidation degradation of pollutants.

[0023] (4) When the catalyst prepared in this invention is applied to the catalytic degradation of the antibiotic sulfasalazine, it exhibits efficient and stable advanced oxidation water treatment catalytic performance, has good environmental friendliness, and has good application prospects. Attached Figure Description

[0024] Figure 1The XRD patterns are of the catalysts prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 in the specific implementation embodiments.

[0025] Figure 2 Raman spectroscopy for the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0026] Figure 3 XPS plots of N1s in the catalysts prepared in Example 1 and Comparative Example 2.

[0027] Figure 4 The graphs show the performance of activated persulfate in degrading sulfonamide antibiotics in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2.

[0028] Figure 5 The graph shows the degradation performance of sulfonamide antibiotics in a cyclic experiment using activated persulfate in Example 1. Detailed Implementation

[0029] This invention proposes a method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching and its application. In order to make the advantages and technical solutions of this invention clearer and more explicit, the invention will be further described below with reference to specific embodiments.

[0030] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0031] The ZIF mentioned in this invention refers to the zeolite imidazole ester skeleton.

[0032] Example 1:

[0033] A method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching includes the following steps:

[0034] (1) First, weigh 1.5 g of 2-methylimidazole and simultaneously measure 15 mL of methanol solution, stirring until it becomes transparent, as solution A; weigh 1.3 g of zinc nitrate hexahydrate and 0.4 g of acetylacetone iron, simultaneously measure 30 mL of methanol solution, dissolve and mix them, and then place them in an ultrasonic machine for 15 minutes, as solution B. Slowly add the prepared solution B dropwise into solution A, and continue stirring for 1 hour to obtain a turbid liquid containing Fe-ZIF.

[0035] (2) The turbid liquid containing Fe-ZIF was washed three times by centrifugation with 5,5-dimethyl-1-pyrrolline-N-oxide and methanol respectively, and then dried in an oven to obtain the Fe-ZIF precursor.

[0036] (3) The Fe-ZIF precursor was ground and then calcined in a tube furnace purged with nitrogen and water vapor. The temperature was increased at a rate of 5℃ / min, and the calcination was carried out at 900℃ for 3 hours. During the calcination, the water vapor etching time was 1 hour. The resulting sample was modified by water vapor etching with pyrrole nitrogen-doped iron single-atom catalyst, denoted as Fe. SA -60-CN supported single-atom catalyst.

[0037] Example 2:

[0038] The difference between this embodiment and Embodiment 1 is as follows: In step (3), the dried solid obtained in step (2) is ground and then placed in a tube furnace purged with nitrogen and water vapor for calcination. The temperature is increased at a rate of 5°C / min, and the calcination is carried out at 900°C for 3 hours. During the calcination, the water vapor etching time is 0.5 hours. After that, a sample of pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching is obtained, denoted as Fe. SA -30-CN supported single-atom catalyst.

[0039] Example 3:

[0040] The difference between this embodiment and Embodiment 1 is as follows: In step (1), the stirring time is 2 hours, and the dissolution time in the ultrasonic machine is 20 minutes; in step (3), the dried solid obtained in step (2) is ground and then placed in a tube furnace purged with nitrogen and water vapor for calcination. The temperature is increased at a rate of 7°C / min, and the calcination is carried out at 950°C for 3 hours. During the calcination, the water vapor etching time is 2 hours. After that, a sample of pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching is obtained, denoted as Fe. SA -120-CN supported single-atom catalyst.

[0041] Example 4:

[0042] The difference between this embodiment and Embodiment 1 is that in step one, the mass ratio of zinc nitrate hexahydrate, ferric acetylacetone, and 2-methylimidazole is 0.8:0.25:1.5, respectively.

[0043] Example 5:

[0044] The difference between this embodiment and Embodiment 1 is that in step one, the mass ratio of zinc nitrate hexahydrate, ferric acetylacetone, and 2-methylimidazole is 1:0.35:1.

[0045] Comparative Example 1:

[0046] A catalyst, whose preparation method is basically the same as that of Example 1, except that iron acetylacetone is not added in step (2), and is referred to as CN catalyst.

[0047] Comparative Example 2:

[0048] An iron single-atom catalyst was prepared using a method basically the same as in Example 1, except that in step (3), the dried solid obtained in step (2) was ground and then placed in a tube furnace under a nitrogen atmosphere for calcination. The temperature was increased at a rate of 5°C / min, and the catalyst was calcined at 900°C for 3 hours. The resulting sample of the iron single-atom catalyst was then obtained and denoted as Fe. SA -CN supported single-atom catalyst.

[0049] The XRD patterns of the catalysts prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 are shown below. Figure 1 As shown.

[0050] X-ray diffraction (XRD) patterns show that Fe SA -30-CN, Fe SA -60-CN, Fe SA -120-CN, Fe SA -CN and CN have only one C peak at approximately 26° (2θ), indicating that no peak representing metallic Fe was found, proving that Fe... SA -30-CN, Fe SA -60-CN, Fe SA -120-CN, Fe SA The -CN catalyst did not exhibit clusters or nanoparticles. The catalyst after the Fenton reaction also did not show any Fe-related peaks, indicating that the catalyst after the reaction also lacked clusters and nanoparticles.

[0051] Figure 2 Raman spectroscopy for the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0052] At 1340cm -1 and 1580cm -1 The two dominant peaks nearby are the disorder peak (D peak) and the graphite peak (G peak), respectively. The intensities of the D peak (ID) and the G peak (IG) indicate the degree of disorder and graphitization of the carbon substrate, respectively. The ID / IG value of Example 1 is 0.98, that of Comparative Example 1 is 0.88, and that of Comparative Example 2 is 0.93, indicating that the degree of disorder of the carbon substrate increases with the gradual formation of carbon defects. This demonstrates that water vapor etching increases the formation of carbon defects and improves the catalytic performance of the catalyst.

[0053] Figure 3 XPS plots of N1s in the catalysts prepared in Example 1 and Comparative Example 2.

[0054] Three types of nitrogen were formed: pyrrole nitrogen (399.78 eV), pyridine nitrogen (398.08 eV), and graphitic nitrogen (401.38 eV). In Example 1, the relative content of pyrrole N was the highest among the three, and significantly higher than the other two types of nitrogen. In Comparative Example 2, the relative content of pyridine N was the highest among the three, and significantly higher than the other two types of nitrogen, demonstrating that water vapor etching alters the type of nitrogen doping within the material.

[0055] Figure 5 The graph shows the degradation performance of sulfonamide antibiotics in a cyclic experiment using activated persulfate in Example 1.

[0056] The application of this method will be tested below, taking into account the above embodiments and comparative examples.

[0057] Example 6:

[0058] Performance testing of persulfate advanced oxidation catalytic degradation of sulfasalazine:

[0059] All degradation reactions were carried out in 100 mL glass vials, with an initial concentration of sulfasalazine in the reaction solution set at 20 μM. The pH of the solution was adjusted with sulfuric acid (50 mM) and sodium hydroxide (50 mM). 50 mg of the catalysts prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 were added, and the reaction solutions were reacted in the dark. Persulfate was added initially to initiate the degradation reaction. Next, at specified time points of 1 min, 2 min, 3 min, 4 min, 5 min, 7.5 min, 10 min, and 15 min, 0.5 mL of the reaction solution was aspirated using a syringe and immediately filtered through a 0.22 μm polytetrafluoroethylene filter. Residual oxidizing substances were quenched with sodium thiosulfate solution. The concentration of sulfasalazine was determined using high-performance liquid chromatography (HPLC, PerkinElmer Flexar, USA) on a C18 column (4.6 × 150 mm, 5 μm, Perkin Elmer, USA). Figure 4 As can be seen, Example 1 almost completely catalyzes the degradation of sulfasalazine within 7.5 min. After 15 min of reaction, the catalytic degradation efficiencies of the catalysts prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 for sulfasalazine were 100% (Fe). SA -60-CN), 98.5% (Fe SA -30-CN), 99.1% (Fe SA -120-CN), 15.9% (CN) and 72.9% (Fe SA -CN). The water vapor etching-doped pyrrole nitrogen iron single-atom catalyst prepared in this application has a much higher efficiency in catalytic degradation of pollutants than the catalysts provided in Comparative Examples 1 and 2.

[0060] The initial concentration of sulfasalazine in the reaction solution was set to 20 μM. The pH of the solution was adjusted using sulfuric acid (50 mM) and sodium hydroxide (50 mM). 50 mg of the water vapor etching process for the doped pyrrole-doped iron nitride single-atom catalyst Fe prepared in Example 1 above was added. SA The reaction solution was subjected to five cycles of -60-CN under dark and room temperature conditions, with each reaction lasting 15 minutes. After the fifth cycle, the degradation efficiency of sulfasalazine still reached 94.4%.

[0061] Example 7:

[0062] Fe was tested according to the method in Example 4. SA -30-CN, Fe SA -120-CN activated the catalytic performance of sulfasalazine degradation. After reacting for 15 min in the dark, Fe... SA The -30-CN catalyst exhibited a 98.5% degradation efficiency for sulfasalazine, and after five cycles, the degradation efficiency remained at 90.5%. After reacting for 15 minutes in the dark, Fe... SA The -120-CN catalyst exhibited a degradation efficiency of 99.1% for sulfasalazine, and after five cycles, its degradation efficiency for sulfasalazine still reached 91.4%.

[0063] The solvent methanol in this invention can also be replaced by N,N-dimethylformamide.

[0064] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0065] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A method for preparing a pyrrole nitrogen-doped iron single-atom catalyst modified by water vapor etching, characterized in that, The steps are as follows: Step 1: Dissolve a certain amount of 2-methylimidazole in methanol to obtain solution A; mix a certain amount of zinc nitrate hexahydrate and acetylacetone iron in methanol and then dissolve them in an ultrasonic machine to obtain solution B; slowly add solution B dropwise to solution A and stir to obtain a turbid liquid containing Fe-ZIF. Step 2: The turbid Fe-ZIF solution was washed with 5,5-dimethyl-1-pyrrolline-N-oxide and methanol, and then separated by centrifugation and dried in an oven to obtain the Fe-ZIF precursor. Step 3: After grinding the Fe-ZIF precursor, it is placed in a tube furnace with nitrogen and water vapor and calcined to obtain the product. In the tube furnace, water vapor etching is used to make the molecules react with carbon at high temperature to generate gaseous H2 and CO, forming micropores and expanding the micropore size; the water vapor etching time is 0.5-2 h.

2. The method for preparing a water vapor etching modified pyrrole nitrogen-doped iron single-atom catalyst according to claim 1, characterized in that: In step one, the mass ratio of zinc nitrate hexahydrate, ferric acetylacetone, and 2-methylimidazole is 0.8-1: 0.25-0.35: 1-1.5, respectively.

3. The method for preparing a water vapor etching modified pyrrole nitrogen-doped iron single-atom catalyst according to claim 1, characterized in that: In step three, the calcination temperature in the tube furnace is 900-950 ℃, the calcination heating rate is 5-15 ℃ / min, and the calcination time is 3-5h.

4. The method for preparing a water vapor etching modified pyrrole nitrogen-doped iron single-atom catalyst according to claim 1, characterized in that: In step one, methanol is replaced with N,N-dimethylformamide as the solvent; the dissolution time in the ultrasonic machine is 10-20 minutes.

5. A water vapor etching method for modifying pyrrole nitrogen-doped iron single-atom catalysts, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 4.

6. The application of the water vapor etching method modified pyrrole nitrogen-doped iron single-atom catalyst according to claim 5 in the catalytic degradation of the antibiotic sulfasalazine.

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