A Fe 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalysts, their preparation methods and applications

Abstract

This invention discloses a Fe 3+ This invention relates to an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material, its preparation method, and its application, belonging to the field of emerging pollutant degradation. The catalytic material in this invention is produced using Fe... 3+ It is formed by anchoring tubular carbon nitride doped with phosphorus and potassium; wherein, the Fe in the catalyst material 3+ The anchoring amount is 1wt% to 9wt%. The preparation method provided by this invention is simple, easy to implement, has good repeatability, and high yield. The obtained iron ions are uniformly distributed in the graphitic phase carbide ring network and will not be oxidized, effectively avoiding the problems of easy oxidation and uneven distribution of iron ions. This catalytic material has good performance and strong versatility, and can be used in the field of water pollution degradation and purification.

Description

Technical Field

[0001] This invention belongs to the field of emerging pollutant degradation, specifically relating to a Fe 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalytic materials, their preparation methods, and applications. Background Technology

[0002] In recent years, my country's urban population has been growing rapidly, leading to a surge in demand for urban construction. The urban construction industry has experienced sustained and rapid development, making significant contributions to my country's infrastructure development. However, at the same time, the increase in housing and population concentration has also resulted in a sharp increase in pollution, with wastewater treatment becoming a major challenge. Wastewater containing organic pollutants is discharged from residential, urban sewage, and industrial processes, causing significant water pollution. Aquatic organic pollutants include natural organic matter and synthetic organic matter (SOCs), with synthetic organic matter including dyes, pharmaceuticals, pesticides, phenols, and personal care products (PPCPs).

[0003] PPCPs (Probiotic-Consumable Pollutants) are closely related to urban residents' lives and include various antibiotics, cosmetics, hair dyes, shampoos, etc. Although these pollutants are present in small quantities, they have low biodegradability and are discharged into the natural environment through building sewage pipes. Wastewater treatment plants are unable to remove trace amounts of these pollutants, thus causing these antibiotics to have harmful effects on human health. With the increase in population and the impact of the global pandemic, the use of pharmaceutical antibiotics has become increasingly frequent.

[0004] Tetracycline (TC), a cheap and widely used antibiotic, is extensively used. However, its long half-life of approximately 180 days leads to the emergence of resistant strains in water bodies, which are difficult to eradicate, posing a significant threat to human quality of life. Tetracycline is a yellow crystalline powder, odorless and tasteless, soluble in dilute acids and alkalis, and relatively stable chemically, but easily destroyed and inactivated in alkaline solutions. Residents ingest or use antibiotics in their daily lives, which are then excreted in feces and urine, eventually reaching sewage treatment plants through building sewers. However, due to its bioaccumulation in water sources and its difficulty in metabolism, complete removal of tetracycline using traditional technologies is not easy. The widespread use of these antibiotics may exert strong selective pressure on human and natural microbial systems. Studies have found resistance genes in microorganisms, possibly induced by excessive tetracycline. These resistance genes may spread through soil and water sources, posing a threat to food safety and human health. Due to the frequent and widespread use and continuous emissions of tetracycline, tetracycline residues in the environment can be considered a "persistent" organic pollutant. However, the current abuse and overuse of tetracycline stimulates bacterial evolution and the spread of drug resistance; the more we use this class of antibiotics, the greater the likelihood that they will lose their effectiveness over time. Therefore, there is an urgent need to develop an efficient and rapid method for tetracycline removal to ensure that humans are free from the effects of this class of antibiotics.

[0005] Graphitic carbon nitride (g-C3N4), as a metal-free organic semiconductor material, has attracted widespread attention in the photocatalytic degradation of pollutants due to its simple synthesis strategy, low cost, good stability, and tunable band structure. However, the bulk g-C3N4 formed by traditional high-temperature thermal polymerization exhibits severe aggregation, small surface area, inherently low light-harvesting ability, fast electron-hole recombination rate, and generally low surface carrier migration efficiency. Furthermore, the intense thermal shock caused by high temperatures leads to disorder or poor crystallinity of g-C3N4 crystals, causing significant damage to its ordered structure, primarily due to the disordered S-triazine ring structure in the g-C3N4 framework. Due to these limiting factors, the efficiency of carbon nitride-based photocatalytic degradation systems for antibiotics is often extremely low. Therefore, modification treatment is necessary to improve its catalytic performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a Fe 3+Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalytic material, its preparation method, and its application are presented. This composite photo-Fenton catalytic material exhibits highly efficient photo-Fenton synergistic effects and can degrade antibiotics in water. By adjusting the amount of elemental doping, the separation efficiency of photogenerated electrons and holes, the interfacial charge transfer rate, and the photo-Fenton synergistic degradation activity are improved, achieving optimal control of the photocatalytic-Fenton synergistic effect.

[0007] In a first aspect, the present invention provides an Fe 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalytic material, the catalytic material being produced by Fe... 3+ It is formed by anchoring tubular carbon nitride doped with phosphorus and potassium.

[0008] In the catalytic material, the total doping amount of phosphorus and potassium is 0.17 wt% to 1.3 wt%, and Fe... 3+ The anchoring amount is 1wt% to 9wt%.

[0009] Fe in this invention 3+ Anchored potassium-phosphorus doped tubular carbon nitride composite photo-Fenton catalyst material, abbreviated as F-PKCN, with potassium-phosphorus doped tubular carbon nitride simply referred to as PKCN. The key points in the preparation of F-PKCN are twofold: first, to prepare potassium-phosphorus doped carbon nitride with cyano groups and nitrogen vacancies with the assistance of potassium dihydrogen phosphate; and second, to combine iron ions with carbon nitride and incorporate them into PKCN to synthesize a photo-Fenton synergistic catalyst. The resulting iron ions are uniformly distributed in the graphitic carbon nitride azine ring network and are not oxidized, effectively avoiding the problems of easy oxidation and uneven distribution of iron ions. Its performance in degrading tetracycline and other antibiotics was investigated, providing theoretical support for further development of novel catalysts for the degradation of antibiotics in wastewater.

[0010] Secondly, the present invention provides an Fe 3+ A method for preparing an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material includes the following steps:

[0011] A first suspension was obtained by hydrothermal reaction of a solution of melamine and potassium dihydrogen phosphate. The first suspension was freeze-dried to obtain an intermediate. The intermediate was calcined to obtain tubular carbon nitride doped with phosphorus and potassium.

[0012] The tubular carbon nitride was dispersed in a solvent to form a second suspension. FeCl3·6H2O was added to the second suspension, followed by ultrasonication, stirring, and drying to obtain Fe. 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalyst.

[0013] The freeze-drying process slightly inhibits the formation of tubular morphology in the carbon nitride, but the phosphorus and potassium elements are better integrated with the carbon nitride with almost no element loss. This promotes the generation of more active sites, enabling redox reactions with pollutants and thus enhancing degradation efficiency.

[0014] During the drying process, iron ions form coordination bonds with nitrogen in C3N4 and are fixed within the C3N4 azine ring network, preventing diffusion to the surface. This promotes the stability of the catalyst and improves its degradation performance.

[0015] Furthermore, the weight ratio of melamine to potassium dihydrogen phosphate is 75–600:1; the temperature of the hydrothermal reaction is 190–210°C; and the time of the hydrothermal reaction is 10–14 h.

[0016] Furthermore, the calcination temperature is 530–570°C, the calcination time is 3–6 h, and the calcination temperature gradient is 1–3°C / min.

[0017] Furthermore, the amount of FeCl3·6H2O added is based on Fe 3+ The mass calculation shows that the amount added is 1 wt% to 9 wt% of the tubular carbon nitride; the drying temperature is 180 to 220°C, and the drying time is 3 to 6 hours.

[0018] Thirdly, this invention provides the application of the above-mentioned composite photo-Fenton catalytic material in the degradation of antibiotics in wastewater.

[0019] Furthermore, the application of composite photo-Fenton catalytic materials in the degradation of antibiotics in wastewater includes the following steps:

[0020] Adjust the pH of the wastewater to 3-9, and add the Fe... 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalysts were subjected to dark-field adsorption under light-free conditions to reach adsorption equilibrium.

[0021] Add hydrogen peroxide and carry out a photo-Fenton reaction under xenon lamp irradiation.

[0022] Furthermore, the antibiotic includes at least one of tetracycline, chlortetracycline hydrochloride, norfloxacin, and amoxicillin.

[0023] Beneficial effects under simulated natural light conditions:

[0024] This invention modifies tubular carbon nitride by elemental doping. The doping of alkali metals and nonmetals has a certain influence on the initial tubular morphology. Fe... 3+Anchoring has a greater impact on the morphology of carbon nitride, but correspondingly, its degradation efficiency for antibiotics in wastewater can reach a relatively high level in a short time. This method is simple, easy to implement, has good repeatability, and high yield. The obtained iron ions form coordination bonds with nitrogen in C3N4 and are uniformly distributed in the graphitic carbon nitride azine ring network without diffusing to the surface. Therefore, they are not oxidized, effectively avoiding the problems of easy oxidation and uneven distribution of iron ions. Simultaneously, during the dark adsorption process, due to Fe... 3+ The anchored catalyst has more metal active sites, resulting in a strong affinity of oxygen-containing functional groups on antibiotic molecules for iron-containing active sites. Simultaneously, the abundant in-plane vacancies in F-PKCN enable antibiotics to rapidly migrate to carbon nitride, achieving strong and rapid adsorption of antibiotics on the carbon nitride surface. This catalyst overcomes the pH limitation of traditional Fenton catalysts, exhibiting high degradation efficiency over a wide pH range, and shows great promise for applications in photocatalysis and the degradation of emerging pollutants. Attached Figure Description

[0025] Figure 1 The images are scanning electron microscope (SEM) images, where A is the SEM image of tubular-CN in the control group; B is the SEM image of PKCN-3 in Example 1; and C is the SEM image of 5F-PKCN in Example 2.

[0026] Figure 2 The images show X-ray diffraction (XRD) patterns, where A is the XRD pattern of PKCN-x in Example 1; and B is the XRD pattern of XF-PKCN in Example 2.

[0027] Figure 3 The graphs show the degradation efficiency of tetracycline pollutants in tubular-CN, PKCN-x, and XF-PKCN wastewater, where A represents the degradation efficiency of tubular-CN and PKCN-x, and B represents the degradation efficiency of tubular-CN and XF-PKCN.

[0028] Figure 4 The graphs show the degradation efficiency of 5F-PKCN for different antibiotic contaminants. A represents the degradation efficiency of chlortetracycline hydrochloride, B represents the degradation efficiency of norfloxacin, and C represents the degradation efficiency of amoxicillin.

[0029] Figure 5 The graph shows the degradation efficiency of 5F-PKCN on antibiotic pollutants at different pH levels. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the test reagents, consumables, devices, and equipment used are all commercially available unless otherwise specified. It should be understood that the following description is only for explaining the present invention and does not limit its content.

[0031] Example 1

[0032] This embodiment provides a method for preparing carbon nitride doped with different amounts of potassium dihydrogen phosphate, including the following steps:

[0033] (1) Mix 3g of melamine and X mg of potassium dihydrogen phosphate (X = 5, 10, 20, 30, 40) evenly, dissolve in 60ml of deionized water, sonicate for 10min to disperse evenly, and magnetically stir at room temperature for 2 hours to obtain a white suspension.

[0034] (2) Transfer the suspension obtained in step (1) to a reaction vessel (100 ml), and then put it into a forced-air drying oven for hydrothermal reaction at 200°C for 12 hours. After the reaction, cool the product to room temperature.

[0035] (3) The product obtained in step (2) was subjected to freeze treatment, and then dried in a vacuum freeze dryer to obtain a white powder sample. The dried sample was calcined in a muffle furnace at 550℃ for 4 hours with a temperature gradient of 2℃ / min. A light yellow powder sample, namely PKCN-x, was obtained. According to the different weights of potassium dihydrogen phosphate used, the product PKCN was named PKCN-1, PKCN-2, PKCN-3, PKCN-4 and PKCN-5 in sequence, where the weight of potassium dihydrogen phosphate in PKCN-1 was 5mg, and so on.

[0036] A control group was set up in which CN was not doped with potassium dihydrogen phosphate, and the preparation method was the same as in Example 1.

[0037] Figure 1 A is a scanning electron microscope image of the control group CN. Figure 1 Image B is a scanning electron microscope (SEM) image of PKCN-3. The image shows that the basic carbon nitride is tubular. After elemental doping modification, its morphology is slightly altered. This is because during the freeze-drying process, phosphorus and potassium dopants fuse with the carbon nitride. The amorphous phase of this solid undergoes internal movement before reaching its melting point, resulting in slight morphological damage or collapse. However, the significance of the freeze-drying step lies in better preserving the phosphorus and potassium dopant content, preventing element loss, and thus promoting the modification and bridging of carbon nitride by the two elements, achieving optimal elemental doping.

[0038] Example 2

[0039] This embodiment provides samples with different Fe contents. 3+ A method for preparing an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material includes the following steps:

[0040] (1) Mix 0.5g PKCN and Xwt% FeCl3·6H2O and add to deionized water. Sonicate for 30min to disperse evenly, and then magnetically stir at room temperature for 8 hours to obtain a yellow suspension. Wherein X is Fe... 3+ The mass percentages, X = 1, 3, 5, 7.

[0041] (2) The product obtained in step (1) was placed in a drying oven at 200℃ and dried for 4 hours to finally obtain the XF-PKCN composite photo-Fenton catalyst. Based on Fe... 3+ The composite photo-Fenton catalysts were named 1F-PKCN, 3F-PKCN, 5F-PKCN, 7F-PKCN, and 9F-PKCN according to different mass percentages. Among them, 1F-PKCNFe 3+ The mass percentage is 1, and so on.

[0042] Figure 2 The X-ray diffraction (XRD) pattern shows only the characteristic peaks of graphitic carbon nitride at 13.2° and 27.5°, without any characteristic peaks related to iron. This indirectly proves that iron exists in an ionic state and exists in the g-C3N4 azine ring network through coordination bonds.

[0043] Example 3

[0044] This embodiment provides the application of the materials prepared in Example 1 and Example 2 in the degradation of tetracycline wastewater.

[0045] (1) Prepare 100 mL of tetracycline solution with a concentration of 20 mg / L, adjust the pH of the tetracycline solution to 5, weigh 20 mg of PKCN-x prepared in Example 1 and XF-PKCN catalyst prepared in Example 2, and add them to the tetracycline solution.

[0046] (2) A dark adsorption reaction process was carried out for 30 minutes. After the dark adsorption process was completed, 0.2 mM hydrogen peroxide was added, and the wastewater was subjected to a photo-Fenton reaction under simulated natural light irradiation conditions (a xenon lamp was used in this embodiment). A sample of 2 mL was taken every 15 minutes, centrifuged, and the absorbance of the supernatant was measured using a UV spectrophotometer. The absorbance was calculated using the formula X = (C0 - C) / C0 × 100%, where X is the degradation rate of the pollutant, C0 is the initial concentration of the pollutant, and C is the concentration of the pollutant after degradation.

[0047] Figure 3In this example, the initial tubular CN showed a certain improvement in antibiotic degradation efficiency compared to traditional Bulk carbon nitride. Doping with potassium dihydrogen phosphate further enhanced the degradation activity. The PKCN-3 catalyst (KH₂PO₄) exhibited the best degradation effect with a doping amount of 20 mg, achieving a degradation efficiency of 75% within 60 minutes. Anchoring Fe ions to PKCN-3 improved the degradation performance to over 88%, and the 5F-PKCN catalyst with the optimal Fe doping ratio achieved a degradation rate of 92% within 60 minutes.

[0048] Example 4

[0049] This embodiment provides the application of the material 5F-PKCN prepared in Example 2 in the degradation of different antibiotic wastewater.

[0050] (1) Prepare 100 mL of tetracycline solution, chlortetracycline hydrochloride solution, norfloxacin solution and amoxicillin solution with a concentration of 20 mg / L, adjust their pH to 5, weigh 20 mg of the 5F-PKCN catalyst prepared in Example 2, and add it to the above solution.

[0051] (2) The dark adsorption reaction process was carried out for 30 minutes. After the dark adsorption process was completed, 0.2 mM hydrogen peroxide was added, and the xenon lamp used in the experiment was turned on to allow the wastewater to undergo a full photo-Fenton reaction. A sample of 2 mL was taken every 15 minutes, centrifuged, and the supernatant was measured using a UV spectrophotometer. The absorbance was calculated using the formula X = (C0 - C) / C0 × 100%, where X is the degradation rate of the pollutant, C0 is the initial concentration of the pollutant, and C is the concentration of the pollutant after degradation. The degradation results are as follows: Figure 4 As shown, the degradation targets were tetracycline-like chlortetracycline hydrochloride, norfloxacin (a fluoroquinolone), and amoxicillin (a β-lactam). Experiments demonstrated that the F-PKCN catalytic material exhibited high degradation capabilities for different types of antibiotic pollutants within 60 minutes. Particularly for antibiotic pollutants with an initial concentration of 20 mg / L, the degradation efficiencies were 93%, 90%, and 88%, respectively. Increasing the pollutant concentration to 50 mg / L, the degradation efficiency of the F-PKCN catalytic material remained at least 80% within 60 minutes, further illustrating the relatively superior versatility and high efficiency of this catalytic material in catalytic oxidation.

[0052] Example 5

[0053] (1) After preparing 100 mL of tetracycline solution with a concentration of 20 mg / L, stir magnetically and connect a pH meter. Add a small amount of HCl solution to lower the pH value or a small amount of KOH solution to raise the pH value. After stirring evenly, perform pH value testing until the desired pH value is reached.

[0054] (2) 20 mg of the 5F-PKCN catalyst prepared in Example 2 was added to the tetracycline solution after the pH value was adjusted, and then the dark adsorption reaction process was carried out. The subsequent process was the same as in Example 4 (2).

[0055] Figure 5 The pH experiment results show that this catalyst overcomes the pH limitation of traditional Fenton catalysts and has high degradation efficiency over a wide pH range.

[0056] In summary, this invention successfully synthesized Fe 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalysts broaden the photoresponse range of the catalyst through appropriate band matching, suppress the recombination of photogenerated carriers, and improve the catalytic oxidation performance of the catalyst in a photo-synergistic Fenton system.

[0057] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A Fe 3+ Anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material, characterized in that... The catalyst material is Fe 3+ It is formed by anchoring tubular carbon nitride doped with phosphorus and potassium. In the catalytic material, the total doping amount of phosphorus and potassium is 0.17 wt% to 1.3 wt%, and Fe... 3+ The anchoring amount is 1wt% to 9wt%, and the Fe 3+ It is anchored within the carbon nitride framework by forming coordinate bonds with nitrogen atoms in the triazine ring structure of carbon nitride.

2. The Fe according to claim 1 3+ A method for preparing an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material, characterized in that... Includes the following steps: A first suspension was obtained by hydrothermal reaction of a solution of melamine and potassium dihydrogen phosphate. The first suspension was freeze-dried to obtain an intermediate. The intermediate was calcined to obtain tubular carbon nitride doped with phosphorus and potassium. The tubular carbon nitride was dispersed in a solvent to form a second suspension. FeCl3·6H2O was added to the second suspension, followed by ultrasonication, stirring, and drying to obtain Fe. 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalyst.

3. The Fe according to claim 2 3+ A method for preparing an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material, characterized in that... The weight ratio of melamine to potassium dihydrogen phosphate is 75–600:1; the temperature of the hydrothermal reaction is 190–210°C; and the time of the hydrothermal reaction is 10–14 h.

4. The Fe according to claim 2 3+ A method for preparing an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material, characterized in that... The calcination temperature is 530–570℃, the calcination time is 3–6 h, and the calcination temperature gradient is 1–3℃ / min.

5. The Fe according to claim 2 3+ A method for preparing an anchored phosphorus and potassium-doped tubular carbon nitride composite photo-Fenton catalytic material, characterized in that... The amount of FeCl3·6H2O added is based on Fe 3+ The mass calculation shows that the amount added is 1 wt% to 9 wt% of the tubular carbon nitride; the drying temperature is 180 to 220°C, and the drying time is 3 to 6 hours.

6. The application of the composite photo-Fenton catalytic material according to claim 1 or the composite photo-Fenton catalytic material prepared by the preparation method according to any one of claims 2 to 5 in the degradation of antibiotics in wastewater, characterized in that, Adjust the pH of the wastewater to 3-9, and add the Fe... 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalytic material undergoes photo-Fenton synergistic degradation reaction in the presence of hydrogen peroxide and under light irradiation.

7. The application according to claim 6, characterized in that, Includes the following steps: Adjust the pH of the wastewater to 3-9, and add the Fe... 3+ Anchored phosphorus and potassium doped tubular carbon nitride composite photo-Fenton catalyst material was subjected to dark field adsorption under light-free conditions to reach adsorption equilibrium. Add hydrogen peroxide and conduct a photo-Fenton reaction under simulated natural light conditions.

8. The application according to claim 6, characterized in that, The antibiotics include at least one of tetracycline, chlortetracycline hydrochloride, norfloxacin, and amoxicillin.

Images