Application of peroxymonosulfate assisted g-c3n4 / cooh composite photocatalyst in degradation of norfloxacin

Abstract

The application belongs to the technical field of photocatalysis, and discloses application of peroxymonosulfate assisted g-C3N4 / CoOOH composite photocatalyst in degrading norfloxacin; g-C3N4 is prepared by taking melamine as raw material, then g-C3N4 is added in the preparation of CoOOH to carry out compounding, and g-C3N4 / CoOOH catalyst is prepared by a plurality of hydrothermal methods; g-C3N4 and CoOOH construct heterojunction to improve the electron transfer capacity, have good energy band structure, greatly improve the photocatalytic degradation capacity, and have excellent activation peroxymonosulfate (PMS) capacity, which is used for exciting PMS to generate ·SO4 2‑ , and is used for degrading norfloxacin, has good degradation effect, and has stronger degradation activity.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic nanomaterial preparation, and relates to a method for preparing a peroxymonosulfate-assisted g-C3N4 / CoOOH composite photocatalyst for removing norfloxacin. Background Technology

[0002] With the development of industrialization and pharmaceuticals, an increasing number of antibiotics are being used to combat bacteria, and norfloxacin (NOR) is one of them. Although norfloxacin has a positive effect against bacteria, it is not easily degraded and accumulates in the environment over a long period, posing a significant threat to human health and the ecological environment, and also contributing to drug resistance in pathogens. Therefore, the removal and treatment of norfloxacin is particularly important. Photocatalysis technology has attracted widespread attention due to its green, economical, and efficient characteristics. Among various advanced oxidation processes (AOPS), persulfate is particularly prominent due to its significant redox potential, wide pH range, and low price. Peroxymonosulfate (PMS), in particular, has attracted widespread attention due to its water solubility, environmental friendliness, and ease of activation.

[0003] Graphitic carbon nitride (g-C3N4) is a non-metallic polymer composed of covalently bonded carbon and nitrogen atoms arranged in a conjugated layer structure. It is an n-type semiconductor with a band gap of 2.7 eV, exhibiting good visible light absorption, physicochemical stability, and a suitable electronic band structure. However, it also has some drawbacks, such as low photogenerated carrier mobility and low surface area. To mitigate these issues, methods such as elemental doping, morphology manipulation, and heterojunction formation are commonly used. These methods can significantly enhance the photocatalytic performance of graphitic carbon nitride.

[0004] This invention utilizes a hydrothermal method to prepare activated persulfate g-C3N4 supported nano-CoOOH catalysts, which differs from the traditional thermal precipitation method. For example, patent CN202211412505.X describes a biochar-supported nano-CoOOH catalyst prepared using a traditional thermal precipitation method. In this method, biochar is dispersed in a solution during CoOOH catalyst preparation. Composite catalyst samples prepared using this method are prone to agglomeration, have poor dispersibility, and low composite ratios. In contrast, the hydrothermal method allows for the coexistence of gas and liquid phases in a closed environment. Liquid and gaseous water act as pressure-transferring media under high temperature and pressure, ensuring the reactants are fully dissolved in the water and the reaction is complete. Simultaneously, the hydrothermal method also offers advantages such as dispersed material particle size, avoiding impurities introduced by ball milling, increasing the specific surface area of ​​the material, and enhancing catalyst activity.

[0005] Currently, there is no comparative study on the hydrothermal method and the thermal precipitation method for preparing peroxymonosulfate-assisted g-C3N4 / CoOOH composite photocatalysts. Summary of the Invention

[0006] The technical problem to be solved by this invention is as follows: Based on the above-mentioned problem, this invention provides a method for preparing a peroxymonosulfate-assisted g-C3N4 / CoOOH composite photocatalyst for the removal of norfloxacin. This invention prepares a peroxymonosulfate-assisted g-C3N4 / CoOOH composite photocatalyst through an in-situ growth method for the degradation of norfloxacin by sunlight. The introduction of g-C3N4 successfully improves the separation effect of photogenerated electron-hole pairs and the electron transfer capacity of CoOOH, resulting in a higher norfloxacin degradation effect.

[0007] To achieve the above effects, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a peroxymonosulfate-assisted g-C3N4 / CoOOH composite photocatalyst for removing norfloxacin includes the following steps:

[0009] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. After the calcined light yellow sample is cooled naturally, carbon nitride powder is obtained.

[0010] (2) Preparation of g-C3N4 / CoOOH: Co(NO3)3·6H2O was weighed and dissolved in deionized water, and ultrasonically treated to obtain solution A. Simultaneously, a certain mass of g-C3N4 powder was weighed and added to solution A, and ultrasonically treated again. Then, sodium hydroxide solution was added dropwise, and the mixture was stirred in a water bath at 40–60°C for 1–3 minutes. Next, 30% hydrogen peroxide was added dropwise to the mixed solution, and the mixture was kept at 40–60°C for 4–6 hours. Finally, the solution was centrifuged to obtain the precipitate.

[0011] Furthermore, the concentration of the sodium hydroxide solution is 0.01 g / mL, and the concentration of the cobalt nitrate solution is 0.01–0.02 g / mL. The volume ratio of cobalt nitrate solution to sodium hydroxide solution and 30% hydrogen peroxide is 20:10:0.5.

[0012] Furthermore, in step (2), the mass ratio of g-C3N4 to CoOOH is 0.3 to 0.9:1. More preferably, it is 0.7:1.

[0013] (3) Pour the precipitate from step (2) into a reaction vessel and add ethanol solvent. React at 70-130℃ for 8-12 hours. Finally, centrifuge and dry the precipitate to obtain g-C3N4 / CoOOH; denoted as x-CN / Co (x = 30%-90%), where x is the weight percentage of g-C3N4 and CoOOH.

[0014] Furthermore, the preferred reaction conditions are: reaction at 80℃ for 10 hours.

[0015] The prepared g-C3N4 / CoOOH composite photocatalyst has the ability to activate peroxymonosulfate (PMS) and degrade norfloxacin.

[0016] The technical advantages of this invention are as follows: Firstly, by using melamine as a precursor to prepare g-C3N4 and constructing a heterojunction with CoOOH, the electron transfer capability is improved, resulting in a favorable band structure and significantly enhanced photocatalytic degradation ability. Secondly, CoOOH possesses excellent activation ability for peroxymonosulfate (PMS), enabling the generation of SO4 from PMS. 2- The main components are... This preparation method is simple and easy to implement, with easily controllable conditions. The hydrothermal method ensures the reactants are fully dissolved in water, leading to a complete reaction. Simultaneously, the hydrothermal method also offers advantages such as dispersed particle size, avoiding impurities introduced by ball milling, increasing the specific surface area of ​​the material, and enhancing catalyst activity. Furthermore, the prepared Z-type composite photocatalyst g-C3N4 / CoOOH shows promising application prospects. Attached Figure Description

[0017] The invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1 These are X-ray diffraction patterns of g-C3N4, CoOOH, and 0.7-g-C3N4 / CoOOH composite photocatalysts.

[0019] Figure 2 The images show the degradation effects of g-C3N4, CoOOH, and the 0.7-g-C3N4 / CoOOH composite photocatalyst.

[0020] Figure 3 This is a photocatalytic experiment cycle diagram of the 0.7-g-C3N4 / CoOOH composite photocatalyst.

[0021] Figure 4 These are scanning images of g-C3N4, CoOOH, and the 0.7-g-C3N4 / CoOOH composite photocatalyst.

[0022] Figure 5 The study aimed to investigate the effects of different solvents and temperatures on the preparation of the composite sample 0.7CN / Co.

[0023] Figure 6 The degradation effect of CN / Co composite material prepared by hydrothermal reaction using water as solvent on norfloxacin is shown. Detailed Implementation

[0024] The present invention will now be further described with reference to specific embodiments. The following embodiments are intended to further illustrate the present invention, but not to further limit the present invention.

[0025] Example 1

[0026] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. After the calcined light yellow sample is naturally cooled, carbon nitride powder (g-C3N4) is obtained.

[0027] (2) Preparation of 0.3-g-C3N4 / CoOOH: Weigh 0.291g Co(NO3)2·6H2O and dissolve it in 20mL of deionized water, and sonicate it. This is called step A. At the same time, weigh 0.027g of g-C3N4 and add it to step A for sonication. Then weigh 0.1g NaOH in 10mL of deionized water and add it dropwise to step A and place it in a water bath at 50℃. After two minutes, add 0.5mL of 30% H2O2 to the mixed solution and keep it at 50℃ for 5h. Then centrifuge the solution to obtain the precipitate.

[0028] (3) Pour the obtained precipitate into a reaction vessel and add 30 mL of ethanol solvent. React at 80 °C for 10 h. Finally, centrifuge and dry the precipitate. A composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.3:1 can be obtained.

[0029] Example 2

[0030] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. Let the calcined light yellow sample cool naturally to obtain carbon nitride powder.

[0031] (2) Preparation of 0.5-g-C3N4 / CoOOH: Weigh 0.291g Co(NO3)2·6H2O and dissolve it in 20mL of deionized water, and sonicate it, which is called step A; at the same time, weigh 0.045g of g-C3N4 and add it to step A for sonication. Then weigh 0.1g NaOH in 10mL of deionized water, add it dropwise to step A and place it in a water bath at 50℃; after two minutes, add 0.5mL of 30% H2O2 to the mixed solution and keep it at 50℃ for 5h. Then centrifuge the solution to obtain the precipitate.

[0032] (3) Pour the obtained precipitate into a reaction vessel and add 30 mL of ethanol solvent. React at 80 °C for 10 h. Finally, centrifuge and dry the precipitate. A composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.5:1 can be obtained.

[0033] Example 3

[0034] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. Let the calcined light yellow sample cool naturally to obtain carbon nitride powder.

[0035] (2) Preparation of 0.7-g-C3N4 / CoOOH: Weigh 0.291g Co(NO3)2·6H2O and dissolve it in 20mL of deionized water, and perform ultrasonic treatment, which is called step A; at the same time, weigh 0.063g of g-C3N4 and add it to step A for ultrasonic treatment together. Then weigh 0.1g NaOH in 10mL of deionized water, add it dropwise to step A and place it in a water bath at 50℃; after two minutes, add 0.5mL of 30% H2O2 to the mixed solution and keep it at 50℃ for 5h. Then centrifuge the solution to obtain the precipitate.

[0036] (3) Pour the obtained precipitate into a reaction vessel and add 30 mL of ethanol solvent. React at 80 °C for 10 h. Finally, centrifuge and dry the precipitate. A composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.7:1 can be obtained.

[0037] Example 4

[0038] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. Let the calcined light yellow sample cool naturally to obtain carbon nitride powder.

[0039] (2) Preparation of 0.9-g-C3N4 / CoOOH: Weigh 0.291g Co(NO3)2·6H2O and dissolve it in 20mL of deionized water, and sonicate it, which is called step A; at the same time, weigh 0.081g of g-C3N4 and add it to step A for sonication. Then weigh 0.1g NaOH in 10mL of deionized water, add it dropwise to step A and place it in a water bath at 50℃; after two minutes, add 0.5mL of 30% H2O2 to the mixed solution and keep it at 50℃ for 5h. Then centrifuge the solution to obtain the precipitate.

[0040] (3) Pour the obtained precipitate into a reaction vessel and add 30 mL of ethanol solvent. React at 80 °C for 10 h. Finally, centrifuge and dry the precipitate. A composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.9:1 can be obtained.

[0041] Example 5

[0042] The difference between Example 5 and Example 3 is that the phrase "the obtained precipitate is poured into the reaction vessel and 30 mL of ethanol solvent is added, and the reaction is carried out at 80°C for 10 h" in step (3) is replaced with "the obtained precipitate is poured into the reaction vessel and 30 mL of ethanol is added, and the reaction is carried out at 130°C for 10 h". The other operations are the same as in Example 3.

[0043] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. Let the calcined light yellow sample cool naturally to obtain carbon nitride powder.

[0044] (2) Preparation of 0.7-g-C3N4 / CoOOH: Weigh 0.291g Co(NO3)3·6H2O and dissolve it in 20mL of deionized water, and sonicate it. This is called step A. At the same time, weigh 0.063g of g-C3N4 and add it to step A for sonication. Then weigh 0.1g NaOH in 10mL of deionized water and add it dropwise to step A and place it in a water bath at 50℃. After two minutes, add 0.5mL of 30% H2O2 to the mixed solution and keep it at 50℃ for 5h. Then centrifuge the solution to obtain the precipitate.

[0045] (3) Pour the obtained precipitate into a reaction vessel and add 30 mL of ethanol solvent. React at 130 °C for 10 h. Finally, centrifuge and dry the precipitate. A composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.7:1 can be obtained.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 3 is that the obtained precipitate was not poured into the reactor for hydrothermal reaction.

[0048] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. Let the calcined light yellow sample cool naturally to obtain carbon nitride powder.

[0049] (2) Preparation of 0.7-g-C3N4 / CoOOH: 0.291g of Co(NO3)2·6H2O was dissolved in 20mL of deionized water and subjected to ultrasonic treatment, referred to as step A; simultaneously, 0.063g of g-C3N4 was added to step A and subjected to ultrasonic treatment together. Then, 0.1g of NaOH was weighed into 10mL of deionized water and added dropwise to step A and placed in a water bath at 50℃. After two minutes, 0.5mL of 30% H2O2 was added dropwise to the mixed solution and kept at 50℃ for 5h. The solution was then centrifuged, and the precipitate was dried. The composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.7:1 was thus obtained.

[0050] Comparative Example 2

[0051] Compared with Example 3, Comparative Example 2 differs in that the phrase "the obtained precipitate is poured into the reaction vessel and 30 mL of ethanol solvent is added, and the reaction is carried out at 80°C for 10 h" in step (3) is replaced with "the obtained precipitate is poured into the reaction vessel and 30 mL of water solvent is added, and the reaction is carried out at 80°C for 10 h". The other operations are the same as in Example 3.

[0052] Comparative Example 3

[0053] The difference between Comparative Example 3 and Example 3 is that the precipitate obtained was subjected to hydrothermal treatment at 130°C in water-soluble conditions, while other operations were the same as in Example 3.

[0054] (1) Preparation of g-C3N4: Weigh an appropriate amount of melamine into a crucible, place it in a tube furnace at 550°C, and calcine it in air at a heating rate of 5°C / min for 5 hours. Let the calcined light yellow sample cool naturally to obtain carbon nitride powder.

[0055] (2) Preparation of 0.7-g-C3N4 / CoOOH: Weigh 0.291g Co(NO3)2·6H2O and dissolve it in 20mL of deionized water, and perform ultrasonic treatment, which is called step A; at the same time, weigh 0.063g of g-C3N4 and add it to A for ultrasonic treatment together. Then weigh 0.1g NaOH in 10mL of deionized water, add it dropwise to step A and place it in a water bath at 50℃; after two minutes, add 0.5mL of 30% H2O2 to the mixed solution and keep it at 50℃ for 5h. Then centrifuge the solution to obtain the precipitate.

[0056] (3) Pour the obtained precipitate into a reaction vessel and add 30 mL of water solvent. React at 130 °C for 10 h. Finally, centrifuge and dry the precipitate. A composite photocatalyst with a g-C3N4 / CoOOH mass ratio of 0.7:1 can be obtained.

[0057] In this experiment, after the dark reaction was completed, 20 mg of PMS was added as an auxiliary oxidant. 10 mg of photocatalyst was used to degrade 1 L of a 10 mg / L NOR (norfloxacin) aqueous solution. A 500 W xenon lamp was used as the light source to simulate sunlight. First, during the dark reaction phase, samples were taken every 10 minutes, repeated three times, to determine if adsorption equilibrium had been reached. During the light reaction phase, samples were taken every 5 minutes, repeated four times. Each sample was 3 mL and filtered. The absorbance of the filtered solution was measured using a liquid ultraviolet spectrophotometer to determine the degradation rate of norfloxacin within 50 minutes.

[0058] Table 1

[0059] Example Photocatalyst Degradation rate Example 1 0.3CN / Co 81％ Example 2 0.5CN / Co 68％ Example 3 0.7CN / Co 97.6％ Example 4 0.9CN / Co 93％ Example 5 0.7CN / Co 94％ <![CDATA[g-C3N4]]> 10％ CoOOH 60％ Comparative Example 1 0.7CN / Co 78％ Comparative Example 2 0.7CN / Co 84％ Comparative Example 3 0.7CN / Co 78％

[0060] Figure 1 The X-ray diffraction pattern of the CN / Co composite photocatalyst prepared in Example 3 is shown by X-ray diffraction analysis. The (100) and (002) crystal planes of g-C3N4 correspond to diffraction peaks at 13.1° and 27.3°, respectively. The peak position of CoOOH matches the standard card. In the CN / Co composite sample, peaks consistent with the pure sample are clearly observed, indicating successful sample preparation.

[0061] Figure 2 a and b are the blank control and PMS-assisted photocatalytic degradation diagrams of NOR (norfloxacin) by the prepared CN / Co composite photocatalyst, respectively. Figure 2 As can be seen from graph a, without the addition of PMS, the catalyst has almost no degradation effect on norfloxacin solution. Figure 2As shown in b, after the dark reaction was completed and 20 mg of PMS was added, the 0.7-CN / Co composite photocatalyst achieved a degradation effect of 97.6% on norfloxacin within 50 min, indicating that 0.7-CN / Co has a high photocatalytic degradation effect.

[0062] pass Figure 2 As can be seen, the photocatalytic effect is greatly limited under conditions of only adding PMS and traditional photocatalysis. Figure 2 In step b, the introduction of PMS as an auxiliary activator significantly improves the photocatalytic effect. This is because the Z-type heterojunction photocatalytic composite material prepared in this invention accelerates the electron transfer rate and reduces the recombination efficiency of electron-hole pairs. Furthermore, CoOOH, as a transition metal hydroxide, has a good activation effect on PMS. This invention proposes a simple method for preparing the g-C3N4-CoOOH composite catalyst and explores the activation mechanism of PMS, providing a new possibility for PMS-assisted photocatalytic degradation.

[0063] Figure 3 The figure shows the photocatalytic degradation cycle experiment of NOR aqueous solution by the 0.7-CN / Co composite photocatalyst prepared in Example 3. It can be seen from the figure that after five cycles, the degradation effect of the composite photocatalyst does not differ by more than 6%, indicating that the composite photocatalyst has high stability.

[0064] Figure 4 This is a scanning electron microscope (SEM) image of the g-C3N4, CoOOH, 0.7-CN / Co composite photocatalyst prepared in Example 3. From... Figure 4 As can be seen in (a), g-C3N4 exhibits a regular blocky structure; from Figure 4 (b) shows that CoOOH exhibits blocky particles; from Figure 4 (c) clearly shows that two different blocks are combined together, indicating that the sample composite was successful.

[0065] Figure 5 The effect of the 0.7-CN / Co composite photocatalyst prepared in Example 3 on the degradation effect of norfloxacin solution under different solvents and temperatures was investigated. Figure 5 The results show that the samples without photocatalytic degradation and those treated with water at 130°C showed only a 78% degradation rate of norfloxacin within the same timeframe. The sample treated with ethanol at 80°C exhibited the best photocatalytic degradation performance, reaching 97%. Overall, the ethanol-treated sample outperformed the water-treated sample, and at 80°C, it outperformed the 130°C sample.

[0066] Figure 6The CN / Co composite photocatalyst was prepared by a hydrothermal reaction at 80℃ using water as a solvent after a thermal precipitation reaction. The figure shows that the degradation effect of CN / Co on norfloxacin solution differs from that of the sample prepared using ethanol as a solvent at 80℃. Specifically, the 0.7CN / Co prepared with water as a solvent showed a degradation rate of only 84% within the same time period, while the sample prepared with ethanol as a solvent achieved 97.6%.

Claims

1. An application of a g-C3N4 / CoOOH composite photocatalyst, characterized in that: (1) Weigh out cobalt nitrate and dissolve it in deionized water and sonicate it. During the sonication process, add g-C3N4 and then add sodium hydroxide solution. After heating in a water bath for a period of time, add hydrogen peroxide solution and continue the hydrothermal reaction at 40~60℃ for 4~6h. After the reaction, centrifuge to obtain the precipitate. (2) Pour the precipitate into a reaction vessel and add ethanol solvent. Perform hydrothermal reaction at 80~130℃ for 8~12h. Centrifuge and dry the precipitate to obtain g-C3N4 / CoOOH composite photocatalyst; the mass ratio of g-C3N4 to CoOOH is 0.7~0.9:

1. Application of the g-C3N4 / CoOOH composite photocatalyst in the photocatalytic degradation of norfloxacin by activated peroxymonosulfate.

2. The application according to claim 1, characterized in that: The preparation method of g-C3N4 is as follows: melamine is weighed and heated to 550℃ in air at a heating rate of 5℃ / min for 5 h. After calcination, it is naturally cooled to obtain g-C3N4.

3. The application according to claim 1, characterized in that: The sodium hydroxide solution has a concentration of 0.01 g / mL, and the hydrogen peroxide solution has a mass concentration of 30%.

4. The application according to claim 1, characterized in that: The mass ratio of g-C3N4 to CoOOH is 0.7:

1.

5. The application according to claim 1, characterized in that: After adding sodium hydroxide solution in step (1), add hydrogen peroxide after bathing in a water bath at 40~60℃ for 1~3 minutes.

6. The application according to claim 1, characterized in that: Step (2) The hydrothermal conditions are 80℃ for 10 h.

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