Bi2o2co3-mil-68(in) heterojunction composite material and preparation method and application thereof

Abstract

The application provides a Bi2O2CO3-MIL-68(In) heterojunction composite material and a preparation method and application thereof, and belongs to the technical field of photocatalytic materials, the field of persulfate catalysis and the field of environmental governance. The composite material is obtained by loading Bi2O2CO3 on the surface of MIL-68(In) to form a Z-type heterojunction structure; the Bi2O2CO3 is a spherical body with a diameter of 200-500 nm, and the surface is a stacked granular structure; the MIL-68(In) is a regular hexahedral rhombic rod-shaped structure with a particle size of 5-10 mu m, and the Bi2O2CO3 is dispersedly loaded on the surface of the MIL-68(In). The application has the advantages of simple operation, strong visible light absorption capacity of the heterojunction material, stable photocatalytic performance, high degradation efficiency and the like, and has a potential application prospect in the field of photocatalytic persulfate.

Description

Technical Field

[0001] This invention relates to the fields of photocatalytic materials technology, persulfate catalysis, and environmental remediation, and in particular to a Bi2O2CO3-MIL-68(In) heterojunction composite material, its preparation method, and its application in photocatalytic coupling of persulfate degradation of antibiotics. Background Technology

[0002] In recent years, antibiotics have been widely used in the prevention and treatment of diseases in agriculture, animals, and humans, especially those with ideal antibacterial effects and relatively low side effects. However, the incomplete absorption, overuse, and pollution of antibiotics in organisms pose a potential threat to ecological and environmental safety, which is also one of the major threats to biological health. Ofloxacin (OFL) is a third-generation broad-spectrum antibacterial fluoroquinolone drug, widely used to treat human and animal diseases and can enter environmental water bodies through various routes. Due to its stable structure and low biodegradability, its detection rate and concentration are relatively high in various aquatic environments.

[0003] Ofloxacin in the aquatic environment can induce and select bacteria to develop resistance to the drug, which may impair human resistance to these bacterial strains. Even low concentrations of ofloxacin can accumulate in the human body through the food chain. Therefore, there is a growing need to develop a cost-effective method for removing ofloxacin from wastewater.

[0004] Currently, antibiotic treatment technologies in water can be mainly divided into biological, physical, and chemical methods. Due to their stable chemical structure and non-biodegradable characteristics, traditional wastewater treatment processes are not suitable for the efficient removal of ofloxacin. In recent years, chemical removal methods, including persulfate oxidation and photocatalysis, have been widely explored for removing ofloxacin from aqueous solutions. Photocatalysis, due to its environmental friendliness, high efficiency, and excellent stability, can also be used to remove ofloxacin. However, at this stage, the rapid recombination of photogenerated electrons and holes makes it difficult for traditional photocatalytic semiconductors to be widely applied in practical wastewater treatment. For sustainable development, the synthesis of highly efficient visible light-driven photocatalysts has become a research hotspot.

[0005] Photocatalysis has shown great potential in environmental pollution control due to its mild reaction conditions, stable chemical properties, and low secondary pollution. However, its severe recombination of photogenerated electron-hole pairs leads to a low number of effective photogenerated charges, and the large migration barrier between photogenerated charges limits the separation of photogenerated electron-hole pairs. Persulfate generates a large number of sulfate radicals by breaking its own O-O bonds. These radicals have strong oxidizing properties and react with organic pollutants to achieve removal. However, the persulfate activation process is energy-intensive and prone to secondary pollution and metal leaching.

[0006] Therefore, there is an urgent need to explore materials that can effectively combine photocatalysis and persulfate catalysis, improve photocatalytic performance while reducing the energy consumption of persulfate activation, so that the two can have a positive synergistic effect to efficiently degrade pollutants. Summary of the Invention

[0007] To address the aforementioned problems in existing technologies, this invention provides a Bi2O2CO3-MIL-68(In) heterojunction composite material, its preparation method, and its applications. This invention offers advantages such as a simple preparation method, strong visible light absorption capacity of the heterojunction material, stable photocatalytic performance, and high degradation efficiency, demonstrating potential application prospects in the field of photocatalytic persulfate treatment.

[0008] The technical solution of the present invention is as follows:

[0009] A Bi2O2CO3-MIL-68(In) heterojunction composite material, wherein Bi2O2CO3 is loaded onto the surface of MIL-68(In) to form a Z-shaped heterojunction structure;

[0010] The Bi2O2CO3 is a sphere with a diameter of 200-500nm and a stacked granular structure on the surface; the MIL-68(In) is a regular hexahedral rhombic rod-shaped structure with a particle size of 5-10μm, and the Bi2O2CO3 is dispersed and loaded on the surface of the MIL-68(In).

[0011] The present invention also provides a method for preparing the Bi2O2CO3-MIL-68(In) heterojunction composite material, comprising the following steps:

[0012] (1) Preparation of MIL-68(In):

[0013] Dissolve In(NO3)3·4H2O in DMF, stir until homogeneous, add 1,4-phthalic acid, stir until homogeneous again, and then transfer to a polytetrafluoroethylene (PTFE) liner. Seal the PTFE liner in a stainless steel autoclave and perform a hydrothermal reaction at 100-150°C for 40-48 hours. After cooling, wash and dry the resulting solid to obtain MIL-68(In).

[0014] (2) Preparation of Bi2O2CO3-MIL-68(In) heterojunction composite material:

[0015] Mannitol C6H 14 O is uniformly dispersed in deionized water to obtain mannitol solution. Bi(NO3)3·5H2O and MIL-68(In) prepared in step (1) are then added to the solution. The solution is ultrasonically treated for 10-30 min and then magnetically stirred for 30-40 min.

[0016] Then, saturated Na2CO3 solution is added to the above solution, and the mixture is stirred for 30-50 minutes. The mixture is then transferred to a high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 160-200℃ for 12-18 hours. After cooling, the mixture is washed with ethanol and water, and after separation and drying, the Bi2O2CO3-MIL-68(In) heterojunction composite material can be obtained.

[0017] Preferably, in step (1), the molar ratio is In(NO3)3·4H2O:1-4 phthalic acid = 1-1.5:1-2.

[0018] Preferably, in step (1), the mass ratio of In(NO3)3·4H2O to the volume ratio of DMF is 1-1.5:0.045-0.5 mg / mL.

[0019] Preferably, in step (2), the mass ratio is Bi(NO3)3·5H2O:C6H 14 O: Na2CO3: MIL-68(In)=1-1.4: 0.9-1.2: 1.8-2.2: 0.05-0.1.

[0020] Preferably, in step (2), the concentration of the mannitol solution is 18-25 mg / mL.

[0021] This invention further provides the application of the Bi2O2CO3-MIL-68(In) heterojunction composite material in the degradation of antibiotics, specifically, the Bi2O2CO3-MIL-68(In) heterojunction composite material in a photocatalytically coupled persulfate system generates h + , O2 - , 1 O2, SO4 - • and ·OH reactive substances degrade pollutants.

[0022] Preferably, the antibiotic is ofloxacin.

[0023] Preferably, the antibiotic is an antibiotic that is soluble in water.

[0024] More preferably, the water in which the antibiotic is dissolved is a mobile phase water.

[0025] The beneficial technical effects of this invention are as follows:

[0026] 1. This invention utilizes a simple hydrothermal method to load Bi₂O₂CO₃ nanoparticles onto the surface of MIL-68(In) to form a heterojunction composite material. Bi₂O₂CO₃ semiconductors possess advantages such as simple composition, low toxicity, high photostability, and excellent photocatalytic activity, with a band gap typically around 3.0 eV. Constructing a heterojunction composite material with Bi₂O₂CO₃ and MIL-68(In) can improve problems such as low visible light response, low electronic conductivity, and annihilation of photogenerated carriers, exhibiting excellent photocatalytic coupling performance for the degradation of antibiotics by persulfate.

[0027] 2. The invention produces a heterostructure consisting of stacked nanoparticles encapsulating bar-shaped structures. The hexahedral bar-shaped MIL-68(In) possesses advantages such as a large specific surface area and stable framework morphology, while the Bi2O2CO3 nanoparticles are small spherical particles. Several granular Bi2O2CO3 clusters are grouped together, embedded or encapsulated on the surface of MIL-68(In), increasing the contact area with contaminants and exposing more active sites in the composite structure.

[0028] 3. This invention influences local charge distribution and reduces band gap by introducing oxygen vacancies, which then act as important adsorption and active sites. Oxygen vacancies can also capture photogenerated electrons and inhibit the recombination of electrons and holes in the surface and bulk, thereby improving the catalytic and degradation performance of the material.

[0029] 4. This invention is innovative in terms of material preparation and compounding. During the hydrothermal synthesis process, mannitol decomposes into levulinic acid (CH3COCH2CH2COOH) and formic acid (HCOOH). Levulinic acid is very stable and can be used as a structure-directing agent to control the morphology of Bi2O2CO3. Formic acid is further oxidized to CO2, and the resulting CO2 and Na2CO3 act as carbon sources, causing Bi2O2CO3 to form a stacked and aggregated shape of many particles. Such a structure can increase the absorption of light energy and the contact area with pollutants during photocatalysis, exposing more active sites and greatly improving the photocatalytic efficiency.

[0030] 5. Regarding process parameters such as raw material preparation, precursor ratio, and reaction temperature and time, our laboratory has determined the optimal parameters through numerous experiments. For example, in the synthesis method of Bi2O2CO3-MIL-68(In), adding MIL-68(In) as a precursor results in a hexahedral rhomboid rod-like structure, allowing particulate Bi2O2CO3 to adhere to its surface and form a more stable framework morphology. If too little or too much MIL-68(In) is added, the degradation efficiency of the composite material will decrease.

[0031] 6. The Bi2O2CO3-MIL-68(In) composite material of this invention can be used in mobile water. When applied to the photocatalytic-persulfate degradation of ofloxacin in flowing water, it significantly improves the degradation rate of single-treatment technologies. After the material is added and stirred for 30 minutes to reach adsorption equilibrium, persulfate is added. Under visible light irradiation (300W xenon lamp), the degradation rate of ofloxacin reaches 98% after 40 minutes of illumination, showing potential application prospects in the field of photocatalytic-persulfate coupled degradation of antibiotics. Furthermore, the composite material has a high reusability rate; after four photocatalytic-persulfate experiments, its degradation rate remains above 80%, indicating that the composite material has high stability and excellent reusability in the degradation of antibiotics in water. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0033] Figure 1 SEM images of granular Bi2O2CO3 (a), hexahedral MIL-68 (In) (b), and composite materials Bi2O2CO3-MIL-68 (In) (c) and (d) in Example 1;

[0034] Figure 2 XRD patterns of Bi2O2CO3, MIL-68(In) and Bi2O2CO3-MIL-68(In);

[0035] Figure 3 A comparison of the degradation rates of ofloxacin by Bi2O2CO3, MIL-68(In) and Bi2O2CO3-MIL-68(In) in a photocatalytically coupled persulfate system in Test Example 1;

[0036] Figure 4 To test the degradation rate of ofloxacin solutions of different concentrations by Bi2O2CO3-MIL-68(In) in Example 2;

[0037] Figure 5 A comparison of the degradation rates of ofloxacin by Bi2O2CO3-MIL-68(In) at different pH values ​​in Test Example 3;

[0038] Figure 6 The graph shows the recycling performance of Bi2O2CO3-MIL-68(In) in test example 4 for degrading of ofloxacin. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0040] Example 1:

[0041] (1) Dissolve 631 mg (2.09 mmol) of In(NO3)3·4H2O in 30 ml of DMF, sonicate, stir evenly, add 425 mg (2.50 mmol) of 1,4-phthalic acid, stir for 20-40 minutes to mix evenly, transfer the resulting solution to a high-pressure reactor lined with polytetrafluoroethylene, and hydrothermally react at 100 °C for 48 h. After cooling, wash and dry the resulting solid to obtain MIL-68(In).

[0042] (2) 910 mg of mannitol (C6H) 14 O) was uniformly dispersed in 50 mL of deionized water to form a mannitol solution with a concentration of 18.2 mg / mL. At the same time, 970 mg Bi(NO3)3·5H2O and 25, 50, 100 and 150 mg of MIL-68(In) prepared in step (1) were added. After sonication for 10 min, the mixture was magnetically stirred for 30 min to obtain a mixed solution.

[0043] 2000 mg of Na2CO3 was added to 10 mL of deionized water to obtain a saturated Na2CO3 solution, which was then added dropwise to the mixed solution. After stirring at 1000 rpm with a magnetic force for 30 min, the mixed solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 180 °C for 15 h. After cooling, the solution was washed with ethanol and water, separated, and dried to obtain the Bi2O2CO3-MIL-68(In) photocatalytic material for later use, and named BCM-X (where X = 25, 50, 100, 150).

[0044] The surface morphology of the prepared Bi2O2CO3-MIL-68(In) is as follows: Figure 1 As shown. From Figure 1 (a) As can be seen, the Bi₂O₂CO₃ consists of spheres with a diameter of 200-500 nm, and its surface has a stacked granular structure. Several granular Bi₂O₂CO₃ clusters are grouped together, embedded in or encapsulated on the surface of MIL-68(In). From... Figure 1 (b) It can be seen that the MIL-68(In) has a hexahedral rhombic rod-like structure with a particle size of 5-10 μm. From Figure 1 As can be seen in (c) and (d), Bi2O2CO3 is dispersed and loaded on the surface of the MIL-68(In).

[0045] The XRD patterns of Bi2O2CO3, MIL-68(In), and Bi2O2CO3-MIL-68(In) prepared by the above method are shown in the figure. Figure 2 As shown.

[0046] Test Example 1:

[0047] The ability of the prepared material to activate persulfate under visible light was evaluated by degrading ofofloxacin in a quartz reactor filled with circulating water. The prepared Bi2O2CO3-MIL-68(In) composite photocatalyst material was used for photocatalytic-persulfate degradation of the target pollutant ofofloxacin, and a comparison was made between a single cluster of Bi2O2CO3 with a particle size of 200-500 nm and a single hexagonal rod-shaped MIL-68(In) material with a particle size of 5-10 μm.

[0048] The experimental method was as follows: 30 mg of each of the three composite materials mentioned above were added to 100 ml of ofloxacin solution with an initial concentration of 5 mg / L, maintaining the mass concentration of the composite materials at 0.3 g / L. A 300 W xenon lamp with λ > 420 nm was used to simulate visible light. Adsorption experiments were conducted under dark conditions before the light irradiation began. After adsorption equilibrium was reached, 30 mg of PMS was added to maintain the molar concentration of persulfate at 0.5 mmol / L. The light irradiation was then turned on for a 40-minute photodegradation experiment. Samples were taken every 10 minutes. After filtration using a 0.22 μm filter, the remaining ofloxacin concentration was measured using a high-performance liquid chromatograph, and the degradation rate was calculated.

[0049] The measurement results are as follows Figure 3 As shown, the horizontal axis represents degradation time (Time), and the vertical axis represents ofloxacin degradation rate (C). t / C0), where C0 is the initial concentration of ofloxacin, C t This is the real-time concentration. (From...) Figure 3 It can be seen that after irradiation with visible light for 40 min, the total degradation rates of the single materials Bi2O2CO3 and MIL-68(In) were only 78.15% and 30.54%, respectively. Under the same conditions, the photocatalytic efficiency of Bi2O2CO3-MIL-68(In) after combining the two materials was significantly improved, and the degradation rate was increased to 98.12%.

[0050] This indicates that the material exhibits superior photocatalytic-persulfate degradation performance after being composite-formed into a heterojunction. The heterojunction interface formed by Bi₂O₂CO₃ and MIL-68(In) promotes the migration of photogenerated electrons and reduces the recombination rate of photogenerated carriers, thereby improving photocatalytic performance. Simultaneously, persulfate in the coupled system can capture photogenerated electrons, generating sulfate radicals through self-activation. Furthermore, the enhanced reactivity is further amplified by the promoted separation of photogenerated electron-hole pairs.

[0051] Test Example 2:

[0052] The effect of varying antibiotic concentrations on the photocatalytic degradation efficiency of Bi₂O₂CO₃ / MIL-68(In) persulfate was evaluated by adjusting the antibiotic concentration. The experiment was conducted at room temperature. Ofloxacin solutions of 1, 5, 10, and 20 mg / L were added to beakers, and a magnetic stirrer was used under illumination to ensure adequate contact between the added catalyst and the antibiotic solution. Adsorption experiments were conducted in the dark before illumination began. After the catalyst and ofloxacin reached adsorption equilibrium, illumination was turned on and 30 mg of persulfate was added. Illumination lasted for 40 min. Sampling points were taken every 5 minutes on average for the first two stages, and every 10 minutes thereafter. The remaining ofloxacin concentration was measured using high-performance liquid chromatography (HPLC), and the degradation rate was calculated.

[0053] The measurement results are as follows Figure 4 As shown, the horizontal axis represents degradation time (Time), and the vertical axis represents ofloxacin degradation rate (C). t / C0), where C0 is the initial concentration of ofloxacin, C t This is the real-time concentration. (From...) Figure 4 It can be seen that when the concentration of ofloxacin increased from 5 mg / L to 10 mg / L, the degradation efficiency of BCM-50 decreased from 98.25% to 78.52%. This is because as the concentration of ofloxacin increases, more ofloxacin molecules consume the free radicals and holes of the catalytic material, resulting in a decrease in the photocatalytic-persulfate performance of the composite material.

[0054] Test Example 3:

[0055] The effect of different pollutant concentrations on the photocatalytic degradation efficiency of Bi2O2CO3 / MIL-68(In) persulfate by adjusting the solution pH was evaluated. The experiment was conducted at room temperature. A 5 mg / L ofloxacin solution was added to a beaker, and a magnetic stirrer was turned on under light to ensure sufficient contact between the added catalyst and the antibiotic solution. Adsorption experiments were conducted in the dark before the start of light exposure. After the catalyst and ofloxacin adsorption reached equilibrium, the light was turned on and a certain amount of persulfate was added. The light exposure time was 40 min. Sampling points were taken every 5 min on average for the first two points, and then every 10 min on average thereafter. The residual ofloxacin concentration was measured using high-performance liquid chromatography (HPLC), and the degradation rate was calculated.

[0056] The measurement results are as follows Figure 5 As shown, the horizontal axis represents degradation time (Time), and the vertical axis represents ofloxacin degradation rate (C). t / C0), where C0 is the initial concentration of ofloxacin, C t This is the real-time concentration. (From...) Figure 5 It is known that the optimal degradation pH for BCM-50 is between 7 and 9. When the degradation solution is acidic, especially at pH=3, the degradation rate drops to 85.29%. This is due to the free radical O2 excited by the photocatalyst under acidic conditions. - Easily H + Consumption leads to a decrease in the concentration of reactive oxygen species, resulting in a reduction in the efficiency of photocatalytic persulfate degradation.

[0057] Test Example 4:

[0058] Based on the photocatalytic-persulfate activity of the Bi2O2CO3-MIL-68(In) composite material, its cyclic stability in the photocatalytic degradation of ofloxacin can be investigated to further explore its feasibility in practical applications. Cyclic degradation experiments were conducted on the BCM-50 composite material using a xenon lamp setup. 30 mg of the Bi2O2CO3-MIL-68(In) composite material was added to a 5 mg / L ofloxacin solution. After adsorption equilibrium was reached, 30 mg of PMS was added, and the xenon lamp was turned on to initiate the photocatalytic coupled persulfate reaction. The cycle was repeated four times, with each cycle consisting of 30 min of dark adsorption and 40 min of photodegradation. After each cycle, the composite material was washed with deionized water before immediately starting the next cycle.

[0059] The measurement results are as follows Figure 6 As shown, after four cycles, the total degradation efficiency of BCM-50 for ofloxacin can still reach more than 80%, which indicates that the prepared Bi2O2CO3 / MIL-68(In) composite material has stable performance and good practical application feasibility.

[0060] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, and for those of ordinary skill 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. Therefore, the present invention is not limited to the specific details without departing from the general concept defined by the claims and their equivalents.

Claims

1. A Bi2O2CO3-MIL-68(In) heterojunction composite material, characterized in that, The composite material is formed by loading Bi2O2CO3 onto the surface of MIL-68(In) to form a Z-shaped heterojunction structure; The Bi2O2CO3 is a sphere with a diameter of 200-500nm and a stacked granular structure on the surface; the MIL-68(In) is a regular hexahedral rhombic rod-shaped structure with a particle size of 5-10μm, and the Bi2O2CO3 is dispersed and loaded on the surface of the MIL-68(In).

2. The method for preparing the Bi2O2CO3-MIL-68(In) heterojunction composite material according to claim 1, characterized in that, Includes the following steps: (1) Preparation of MIL-68(In): Dissolve In(NO3)3·4H2O in DMF, stir until homogeneous, add 1,4-phthalic acid, stir until homogeneous again, and then transfer to a polytetrafluoroethylene (PTFE) liner. Seal the PTFE liner in a stainless steel autoclave and perform a hydrothermal reaction at 100-150°C for 40-48 hours. After cooling, wash and dry the resulting solid to obtain MIL-68(In). (2) Preparation of Bi2O2CO3-MIL-68(In) heterojunction composite material: Mannitol C6H 14 O is uniformly dispersed in deionized water to obtain mannitol solution. Bi(NO3)3·5H2O and MIL-68(In) prepared in step (1) are then added to the solution. The solution is ultrasonically treated for 10-30 min and then magnetically stirred for 30-40 min. Then, a saturated Na2CO3 solution was added to the above solution, and the mixture was stirred for 30-50 minutes. The mixture was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 160-200℃ for 12-18 hours. After cooling, the mixture was washed with ethanol and water, and after separation and drying, the Bi2O2CO3-MIL-68(In) heterojunction composite material was obtained.

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio is In(NO3)3·4H2O:1-4 phthalic acid = 1-1.5:1-2.

4. The preparation method according to claim 2, characterized in that, In step (1), the mass ratio of In(NO3)3·4H2O to the volume ratio of DMF is 1-1.5:0.045-0.5 mg / mL.

5. The preparation method according to claim 2, characterized in that, In step (2), the mass ratio is Bi(NO3)3·5H2O:C6H 14 O: Na2CO3: MIL-68(In)=1-1.4: 0.9-1.2: 1.8-2.2: 0.05-0.

1.

6. The preparation method according to claim 2, characterized in that, In step (2), the concentration of the mannitol solution is 18-25 mg / mL.

7. The application of the Bi2O2CO3-MIL-68(In) heterojunction composite material according to claim 1 in the degradation of antibiotics, characterized in that, The Bi2O2CO3-MIL-68(In) heterojunction composite material generates h in a photocatalytically coupled persulfate system. + , O2 - , 1 O2, SO4 - • and ·OH reactive substances degrade pollutants.

8. The application according to claim 7, characterized in that, The antibiotic in question is ofloxacin.

9. The application according to claim 7, characterized in that, The antibiotic is an antibiotic that is soluble in water.

10. The application according to claim 9, characterized in that, The water in which the antibiotics are dissolved is a mobile phase water body.

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