Method for preparing heterogeneous photocatalytic material for degrading fluoroquinolone antibiotics and application thereof

Abstract

The application belongs to the technical field of photocatalytic materials and the field of environmental governance, and discloses a preparation method and application of a heterojunction photocatalytic material for degrading fluoroquinolone antibiotics. The catalytic material is an S-type photocatalytic material, and the heterojunction photocatalytic material can be prepared through a simple hydrothermal method. By controlling the addition amount of NH2-MIL-68(In), Bi2MoO6 / NH2-MIL-68(In) heterojunctions with different component contents are obtained. Experimental results show that when the Bi2MoO6 / NH2-MIL-68(In) (BMN-2) photocatalytic material prepared by the application is applied to photocatalytic degradation of ofloxacin in water, 100% of the ofloxacin can be degraded after visible light irradiation for 90 minutes. In addition, the photocatalyst also has good photocatalytic degradation performance for ofloxacin in actual water. The heterojunction photocatalyst prepared by the application has good visible light response and excellent antibiotic degradation performance, and has good application prospect in the field of photocatalytic degradation of antibiotics.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method and application of a heterogeneous junction photocatalytic material for degrading fluoroquinolone antibiotics, and belongs to the technical field of photocatalytic materials and the field of environmental governance. BACKGROUND

[0002] Quinolone drugs, as a kind of synthetic broad-spectrum antibiotics, are widely used in the treatment of infectious diseases of human and animals. Ofloxacin, as a third-generation fluoroquinolone antibiotic, has been detected in water environment such as sewage, hospital wastewater, municipal sewage treatment plant, and surface water. Although the concentration of ofloxacin is not as high as other conventional pollutants, it still has a certain impact on the environment. Low-concentration ofloxacin can be enriched in the human body through the food chain. On the other hand, it can induce and select bacteria to develop drug resistance, which may weaken people's ability to resist these strains. Therefore, there is an increasing demand for developing an economical and effective method to remove ofloxacin in wastewater.

[0003] At present, various technologies, including biodegradation, adsorption, persulfate oxidation, photocatalysis, etc., have been widely tried for degrading ofloxacin from aqueous solution. Due to the stable chemical structure of ofloxacin, it is difficult to be biodegraded, and traditional wastewater treatment processes are not suitable for efficient and complete degradation of ofloxacin. In recent years, photocatalysis has been increasingly applied in the degradation of organic pollutants in water bodies due to its ecological friendliness, high efficiency, and good stability. It is crucial to synthesize efficient visible light-driven photocatalysts to utilize solar energy for treating antibiotic-containing wastewater. However, for most single-component semiconductors, the high recombination rate of electron-hole pairs generated under light excitation is still a common problem in practical applications. Therefore, it is a feasible strategy to construct a binary heterojunction structure to enhance the separation of electrons and holes.

[0004] Bismuth-based photocatalysts have always been the focus of attention due to their unique band structure and properties. Among these compounds, bismuth molybdate has attracted wide attention due to its performance in degrading organic pollutants. In addition, bismuth molybdate has visible light response and is very suitable for forming a heterojunction with other materials. However, single-component bismuth molybdate still has some drawbacks, such as poor visible light response and rapid recombination of photo-generated electron-hole pairs, which hinder its large-scale application in wastewater purification. NH2-MIL-68(In) is an emerging indium-MOF with great application potential and has been proven to be able to degrade antibiotics in water. However, the photocatalytic performance of NH2-MIL-68(In) is limited by its fast charge recombination rate. Therefore, selecting other types of semiconductors to form a heterojunction with NH2-MIL-68(In) can promote the separation of carriers to improve the photocatalytic efficiency. Therefore, how to combine NH2-MIL-68(In) with bismuth molybdate to construct a heterojunction to improve the degradation performance of antibiotics in water has become a technical problem to be solved at present. SUMMARY

[0005] In order to solve the above technical problems, the present application adopts the following technical scheme: a preparation method of a heterojunction photocatalytic material for degrading fluoroquinolone antibiotics, wherein Bi(NO3)3·5H2O and Na2MoO4·2H2O with a molar ratio of 2:1 are uniformly dispersed in 25 mL of ethylene glycol, 20-35 mg of NH2-MIL-68(In) is added to 20 mL of ethanol, after stirring for 0.5 h, the obtained NH2-MIL-68(In) ethanol solution is added to the ethylene glycol solution, after uniform stirring, the mixed solution is transferred to a polytetrafluoroethylene-lined autoclave, hydrothermal reaction is carried out for 24 h, after cooling, the material is washed with ethanol and water, and after separation and drying, the Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material can be obtained.

[0006] In order to solve the above technical problems, the present application adopts the following technical scheme: a preparation method of a heterojunction photocatalytic material for degrading fluoroquinolone antibiotics, wherein Bi(NO3)3·5H2O and Na2MoO4·2H2O with a molar ratio of 2:1 are uniformly dispersed in 25 mL of ethylene glycol, 20-35 mg of NH2-MIL-68(In) is added to 20 mL of ethanol, after stirring for 0.5 h, the obtained NH2-MIL-68(In) ethanol solution is added to the ethylene glycol solution, after uniform stirring, the mixed solution is transferred to a polytetrafluoroethylene-lined autoclave, hydrothermal reaction is carried out for 24 h, after cooling, the material is washed with ethanol and water, and after separation and drying, the Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material can be obtained.

[0007] In the above method, the method for preparing NH2-MIL-68(In) is as follows: NH2-BDC and In(NO3)3·4H2O are added in a molar ratio of 1:3 in 12.4 mL of DMF, and are ultrasonically dissolved, the homogeneous solution is transferred to a polytetrafluoroethylene-lined autoclave, hydrothermal reaction is carried out for 5 h, after natural cooling to room temperature, the material is washed with methanol and DMF, and after separation and drying, the NH2-MIL-68(In) is obtained.

[0008] In the above method, the stirring time of the mixed solution is 0.5 h.

[0009] In the above method, the hydrothermal reaction temperature is 125℃.

[0010] In the above method, the drying temperature of the material is 70℃.

[0011] Meanwhile, the present application also provides an application of the Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material obtained by the above preparation method in degrading fluoroquinolone antibiotics.

[0012] In the above application, the fluoroquinolone antibiotic is ofloxacin dissolved in water.

[0013] 1. The application adopts a hydrothermal method to prepare Bi2MoO6 / NH2-MIL-68(In) photocatalytic material, which is simple to prepare and convenient to operate.

[0014] 2. When the Bi2MoO6 / NH2-MIL-68(In) photocatalytic material is applied to photocatalytic degradation of ofloxacin in water, the degradation rate of ofloxacin reaches 100% after 90 min of visible light irradiation (300W xenon lamp), and has potential application prospect in the field of photocatalytic degradation of antibiotics.

[0015] 3. The photocatalytic material for degrading antibiotics prepared by the application has good photocatalytic performance, and the photocatalytic degradation efficiency of ofloxacin is still more than 90.0% after four cycles, indicating that the photocatalytic material has good stability and recyclability, and can effectively degrade antibiotics in water.

[0016] 4. The heterojunction photocatalytic material prepared by the application is excited under visible light, due to the difference between the work functions and Fermi levels of Bi2MoO6 and NH2-MIL-68(In), under the driving of the internal electric field, electrons will be directionally transferred between the two materials to achieve the balance of the Fermi level. Under visible light irradiation, Bi2MoO6 and NH2-MIL-68(In) are both excited, the internal electric field and band bending drive the photo-generated electrons of Bi2MoO6 to migrate from the conduction band to the valence band of NH2-MIL-68(In) and combine with holes. Therefore, the S-type heterojunction between Bi2MoO6 and NH2-MIL-68(In) is successfully prepared, the electrons are reserved in the conduction band of NH2-MIL-68(In), and the holes are reserved in the valence band of Bi2MoO6. In this way, the holes on the valence band of Bi2MoO6 can oxidize OH - to generate ·OH, and the electrons on the conduction band of NH2-MIL-68(In) can be captured by dissolved oxygen to form ·O2 - . Compared with single-component materials, the heterojunction material produces more active substances, effectively improving the photocatalytic degradation performance of the material on ofloxacin. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 XRD patterns of the materials Bi2MoO6, NH2-MIL-68(In) and Bi2MoO6 / NH2-MIL-68(In) of Example 1;

[0018] Figure 2 FTIR diffraction patterns of the materials Bi2MoO6, NH2-MIL-68(In) and Bi2MoO6 / NH2-MIL-68(In) of Example 1;

[0019] Figure 3SEM image of the material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) of Example 1;

[0020] Figure 4 Photocatalytic degradation graph of ofloxacin for the material Bi2MoO6, NH2-MIL-68(In) and Bi2MoO6 / NH2-MIL-68(In) of Example 2;

[0021] Figure 5 Photocatalytic removal graph of ofloxacin solution for different doses of Bi2MoO6 / NH2-MIL-68(In) (BMN-2) of Example 3;

[0022] Figure 6 Photocatalytic removal graph of ofloxacin solution of different concentrations for the material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) of Example 4;

[0023] Figure 7 Photocatalytic removal graph of ofloxacin solution of different pH values for the material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) of Example 5;

[0024] Figure 8 Corresponding cycle number-degradation efficiency graph of the photocatalytic material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) in Example 6 when degrading ofloxacin solution in cycles;

[0025] Figure 9 Photocatalytic degradation effect graph of ofloxacin in different actual water bodies for the photocatalytic material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) in Example 7. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with examples.

[0027] Example 1

[0028] Bi(NO3)3.5H2O (0.97 g) and Na2MoO4.2H2O (0.242 g) in a molar ratio of 2:1 were uniformly dispersed in 25 mL of ethylene glycol, while 20, 25, 30, 35 mg of NH2-MIL-68(In) was added to 20 mL of ethanol, respectively. After stirring for 0.5 h, the obtained NH2-MIL-68(In) ethanol solution was added to the ethylene glycol solution, and after stirring uniformly, the mixed solution was transferred to a polytetrafluoroethylene-lined autoclave, and hydrothermal reaction was carried out for 24 h. After cooling, it was washed with ethanol and water, and after separation, drying, the Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material was obtained. The prepared photocatalytic heterojunction material was named as BMN-x (x = 1, 2, 3, 4), wherein x = 1-4 represents the amount of NH2-MIL-68(In) added, which is 20, 25, 30, 35 mg, respectively.

[0029] The preparation method of the NH2-MIL-68(In) nanomaterial is as follows:

[0030] In 12.4 mL of DMF, 1.29 mmol of NH2-BDC and 3.84 mmol of In(NO3)3.4H2O were added and ultrasonically dissolved. The homogeneous solution was transferred to a polytetrafluoroethylene-lined autoclave, and hydrothermal reaction was carried out for 5 h. After natural cooling to room temperature, the material was washed with methanol and DMF, and after separation, drying, the NH2-MIL-68(In) was obtained.

[0031] Figures 1-3 The results of characterizing the material obtained in the above step are shown. The XRD pattern is shown in FIG. 1; the FTIR diffraction pattern is shown in FIG. 2; and the SEM image is shown in FIG. 3. Figure 1 The results of characterizing the material obtained in the above step are shown. The XRD pattern is shown in FIG. 1; the FTIR diffraction pattern is shown in FIG. 2; and the SEM image is shown in FIG. 3. Figure 2 The results of characterizing the material obtained in the above step are shown. The XRD pattern is shown in FIG. 1; the FTIR diffraction pattern is shown in FIG. 2; and the SEM image is shown in FIG. 3. Figure 3 The results of characterizing the material obtained in the above step are shown. The XRD pattern is shown in FIG. 1; the FTIR diffraction pattern is shown in FIG. 2; and the SEM image is shown in FIG. 3.

[0032] Example 2

[0033] The photocatalytic ability of the prepared material under visible light was evaluated by degrading ofloxacin in a quartz reactor equipped with circulating water. A 300 W xenon lamp and a 420 nm ultraviolet light cutoff filter (>420 nm) were used to provide visible light irradiation. 15 mg of photocatalyst was dispersed into a quartz photo-reactor containing 50 mL of ofloxacin solution (10 mg / L). The catalyst and the pollutant were allowed to reach adsorption equilibrium in the dark by stirring for 30 min. During light irradiation, about 2.5 mL of the suspension was taken every time interval (15 min), and then filtered with a syringe filter (0.22 μm) to remove the catalyst particles. The degradation rate of ofloxacin was determined by a high-performance liquid chromatograph.

[0034] Figure 4The figure is the photocatalytic degradation curve of the material prepared in Example 1 of the present application under visible light on ofloxacin. As can be seen from the figure, after 90 min of light, the degradation rates of ofloxacin using Bi2MoO6, NH2-MIL-68(In) alone are 78.5% and 52.9% respectively, and the photocatalytic degradation efficiency of the heterojunction material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) reaches 100%. It shows that the heterojunction material effectively improves the photocatalytic degradation rate of ofloxacin compared with single-component materials, and has good photocatalytic performance.

[0035] Example 3

[0036] The photocatalytic degradation of ofloxacin under visible light by different doses of the heterojunction material Bi2MoO6 / NH2-MIL-68(In) (BMN-2) was evaluated in a quartz reactor equipped with circulating water. A 300 W xenon lamp and a 420 nm ultraviolet light cutoff filter (>420 nm) were used to provide visible light irradiation. Different doses (100, 200, 300, 400 mg / L) of photocatalysts were dispersed into a quartz photo-reactor containing 50 mL of ofloxacin solution (10 mg / L). The catalyst and the pollutant were allowed to reach adsorption equilibrium by stirring for 30 min in the dark. During the light irradiation, about 2.5 mL of the suspension was taken every time interval (15 min) and then filtered with a syringe filter (0.22 μm) to remove the catalyst particles. The degradation rate of ofloxacin was determined by a high-performance liquid chromatograph.

[0037] Figure 5 The figure is the photocatalytic degradation curve of different doses of the Bi2MoO6 / NH2-MIL-68(In) (BMN-2) prepared in Example 1 of the present application under visible light on ofloxacin (10 mg / L). As can be seen from the figure, the adsorption rate of ofloxacin in the dark increases from 27.8% to 55.2% as the dose of BMC-30 increases from 100 mg / L to 400 mg / L, which is due to the increase in the number of available adsorption sites of BMN-2. The photocatalytic degradation of ofloxacin is enhanced (58.7% to 100%) as the dose of the sample increases, which is due to the fact that more photocatalytic materials provide more active sites and free radicals. When the dose of BMN-2 reaches 400 mg / L, the photocatalytic degradation rate of ofloxacin has only a small improvement compared with the adsorption efficiency. This phenomenon is due to the fact that the excessive dosage leads to the agglomeration of the photocatalyst, resulting in a decrease in the available active sites of the catalyst. Therefore, the photocatalytic material prepared in the present application has the optimal photocatalytic degradation effect when the dose is about 300 mg / L. Figure 5

[0038] Example 4

[0039] ​The effect of different antibiotic concentrations on the photocatalytic degradation of ofloxacin was evaluated in a quartz reactor with circulating water. A 300 W xenon lamp and a 420 nm UV cut-off filter (> 420 nm) were used to provide visible light irradiation. 15 mg of photocatalyst (BMN-2) was dispersed into a quartz photo-reactor containing 50 mL of ofloxacin solution. The catalyst and the pollutant were allowed to reach adsorption equilibrium by stirring in the dark for 30 min. During irradiation, about 2.5 mL of the suspension was taken every 15 min and filtered with a syringe filter (0.22 μm) to remove the catalyst particles. The degradation rate of ofloxacin was determined by high performance liquid chromatography.

[0040] Figure 6 The photocatalytic degradation effect curve of Bi2MoO6 / NH2-MIL-68(In) (BMN-2) prepared in Example 1 on different concentrations of ofloxacin solution under visible light is shown in the figure. As can be seen from the figure, as the concentration of ofloxacin increases from 5 mg / L to 20 mg / L, the photocatalytic degradation rate decreases from 100% to 65.8%. This is because the excess ofloxacin molecules will compete for the adsorption sites and reaction sites on the surface of the photocatalyst, resulting in a decrease in photocatalytic efficiency. Therefore, the photocatalytic material prepared in the present application has good photocatalytic degradation effect when the concentration of ofloxacin is less than 10 mg / L.

[0041] Example 5

[0042] The effect of different pH values on the photocatalytic degradation of ofloxacin was evaluated in a quartz reactor with circulating water. A 300 W xenon lamp and a 420 nm UV cut-off filter (> 420 nm) were used to provide visible light irradiation. 15 mg of photocatalyst (BMN-2) was dispersed into a quartz photo-reactor containing 50 mL of ofloxacin solution (10 mg / L). The catalyst and the pollutant were allowed to reach adsorption equilibrium by stirring in the dark for 30 min. During irradiation, about 2.5 mL of the suspension was taken every 15 min and filtered with a syringe filter (0.22 μm) to remove the catalyst particles. The degradation rate of ofloxacin was determined by high performance liquid chromatography.

[0043] Figure 7 The photocatalytic degradation effect curve of Bi2MoO6 / NH2-MIL-68(In) (BMN-2) prepared in Example 1 on different pH values of ofloxacin solution under visible light is shown in the figure. As can be seen from the figure, when the pH value increases from 5 to 9, the degradation rate remains above 85%, which indicates that the prepared material has strong usability in actual wastewater treatment processes. When pH = 3 or pH = 11, the adsorption and photocatalytic degradation efficiency decreases. The reason may be that a lower initial pH value (pH = 3) can accelerate the transformation of ·OH to H2O. In addition, when the pH value is high, the excess OH -Can be combined with active species (h + ) bind. When the pH value is extremely high (pH=11), excess OH groups... - It easily competes with ofloxacin for the limited active sites on the photocatalyst surface, resulting in poor degradation performance. Therefore, the photocatalytic material prepared in this invention exhibits good photocatalytic degradation effect at pH 5–9.

[0044] Example 6

[0045] The long-term reusability and stability of catalysts are key factors in practical water treatment processes. In this invention, four cycles of ofloxacin photocatalytic degradation were performed using BMN-2 nanocomposite materials. After each cycle, the collected catalyst was centrifuged, washed multiple times, and dried overnight at 70°C. Figure 8 As shown, after four cycles, the photodegradation efficiency of ofloxacin was still above 90.0%, indicating that BMN-2 has good stability and recyclability.

[0046] Example 7

[0047] The photocatalytic degradation of ofloxacin by BMN-2 in different environmental water bodies (lake water, river water, tap water, wastewater effluent, and ultrapure water) was evaluated in a quartz reactor containing circulating water. Visible light irradiation was provided using a 300W xenon lamp and a 420nm UV cutoff filter (>420nm). 15 mg of the photocatalyst (BMN-2) was dispersed in a quartz photoreactor containing 50 mL of ofloxacin solution (10 mg / L). Adsorption and stirring were performed in the dark for 30 min to allow the catalyst and contaminant to reach adsorption equilibrium. During illumination, approximately 2.5 mL of the suspension was collected every 15 min and filtered through a syringe filter membrane (0.22 μm) to remove catalyst particles. The degradation rate of ofloxacin was determined using high-performance liquid chromatography (HPLC).

[0048] like Figure 9 As shown, the photodegradation efficiency of ofloxacin in environmental water bodies decreased compared to ultrapure water. This is mainly because the active sites of BMN-2 were occupied by suspended solids and organic matter, thereby reducing the adsorption and photodegradation of ofloxacin by the material. The above results indicate that the prepared material still exhibits good photocatalytic degradation efficiency of ofloxacin in actual water bodies, demonstrating the promising application prospects of BMN-2 in wastewater treatment.

[0049] Example 8

[0050] The photocatalytic degradation of ofloxacin in real medical wastewater by BMN-2 was evaluated in a quartz reactor with circulating water. A 300 W xenon lamp and a 420 nm UV cut-off filter (>420 nm) were used to provide visible light irradiation. 15 mg of photocatalyst (BMN-2) was dispersed into a quartz photo-reactor containing 50 mL of medical wastewater. The catalyst was allowed to reach adsorption equilibrium with the pollutants in the dark by stirring for 30 min. After 90 min of irradiation, about 2.5 mL of the suspension was taken and then filtered with a syringe filter (0.22 μm) to remove catalyst particles and solid matter. The degradation rate of ofloxacin was determined by high performance liquid chromatography-mass spectrometry.

[0051] The photocatalytic degradation of ofloxacin in real medical wastewater by BMN-2 is shown in Table 1:

[0052] Table 1, Degradation performance of BMN-2 for ofloxacin in medical wastewater

[0053] Antibiotic Original concentration (ug / L) Concentration after light (ug / L) Removal rate (%) Ofloxacin 17.995 4.506 74.96

[0054] As shown in Table 1, the removal rate of ofloxacin in medical wastewater by BMN-2 reached 74.96%, which proved that the prepared material had good degradation effect on ofloxacin in real wastewater.

[0055] The above examples are merely examples for clearly illustrating the present application, and are not intended to limit the embodiments. Any technical solutions falling within the concept of the present application shall fall within the protection scope of the present application.

Claims

1. A method for preparing a heterogeneous photocatalytic material for degrading fluoroquinolone antibiotics, characterized by: Bi(NO3)3·5H2O and Na2MoO4·2H2O in a molar ratio of 2:1 were uniformly dispersed in 25 mL of ethylene glycol, 20-35 mg of NH2-MIL-68(In) was added to 20 mL of ethanol, after stirring for 0.5 h, the obtained NH2-MIL-68(In) ethanol solution was added to the ethylene glycol solution, after stirring uniformly, the mixed solution was transferred to a polytetrafluoroethylene-lined autoclave, and hydrothermal reaction was carried out for 24 h, after cooling, washing with ethanol and water, separation, drying, Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material was obtained; the method for preparing NH2-MIL-68(In) is as follows: NH2-BDC and In(NO3)3·4H2O were added to 12.4 mL of DMF in a molar ratio of 1:3, ultrasonic dissolution was carried out, the homogeneous solution was transferred to a polytetrafluoroethylene-lined autoclave, hydrothermal reaction was carried out for 5 h, after natural cooling to room temperature, the material was washed with methanol and DMF, after separation, drying, the NH2-MIL-68(In) was obtained.

2. Application of Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material obtained by the method of claim 1 in degrading fluoroquinolone antibiotics.

3. Use according to claim 2, characterized in that: The fluoroquinolone antibiotic is ofloxacin dissolved in water, and the dosage of the Bi2MoO6 / NH2-MIL-68(In) heterojunction photocatalytic material is 300 mg / L.

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