Preparation method of modified nano composite material and application of modified nano composite material in degradation of new pollutants

Abstract

The invention discloses a preparation method of a modified nano composite material and application of the modified nano composite material in degradation of new pollutants, and belongs to the field of new pollutant treatment. According to the preparation method disclosed by the invention, LaFeO3 is doped into MIL-88A to synthesize heterojunction MIL-88A-LaFeO3, and citric acid is added, so that the photocatalytic performance of the material is improved. The photo-Fenton degradation efficiency of the MIL-88A-coated LaFeO3 prepared by the preparation method disclosed by the invention on acetamiprid reaches 99.9% within 180 minutes, and the photo-Fenton degradation efficiency of the MIL-88A-coated LaFeO3 prepared by the preparation method disclosed by the invention on sulfamethoxazole reaches 100% within 180 minutes. The photo-Fenton degradation efficiency of the composite material modified by citric acid on acetamiprid reaches 100% within 75 min, and the composite material shows more excellent photocatalytic activity. The preparation method disclosed by the invention is simple in material and low in cost, and the prepared material is high in degradation rate, has broad spectrum and is applied to degradation of various types of neonicotinoid pesticides and antibiotics in a water body.

Description

Technical Field

[0001] The present invention belongs to the field of new pollutant treatment, and relates to a preparation method of a modified nanocomposite material and application thereof in degrading new pollutants. Background Art

[0002] With rapid socioeconomic development and advancements in science and technology, the types and quantities of chemicals used in production and daily life are constantly increasing. Some of these new chemicals and their metabolites, after entering the environment through various pathways, pose potential environmental risks and are not yet included in routine environmental monitoring systems or are difficult to effectively remove through traditional pollution control measures. These substances are collectively referred to as emerging contaminants (ECs). ECs primarily include pesticide residues, antibiotics, endocrine disruptors, perfluorinated compounds, and microplastics. These pollutants have a wide range of sources and are characterized by strong chemical stability, poor biodegradability, and potentially high ecotoxicity. Acetamiprid (a neonicotinoid pesticide) and sulfamethoxazole (an antibiotic) are typical examples. Due to their widespread use and environmental persistence, they have been widely detected in various aquatic environments. Studies have shown that these residual pollutants not only have acute and chronic toxic effects on organisms such as fish, amphibians, and aquatic insects, but also have profound impacts on the balance of aquatic ecosystems by disrupting food web structure and ecological functions. Therefore, the development of technology for efficiently degrading acetamiprid and sulfamethoxazole in water bodies is of great significance to maintaining aquatic ecological safety and protecting environmental health.

[0003] Currently, the degradation methods for acetamiprid and sulfamethoxazole mainly include biodegradation and adsorption technology. Biodegradation mainly relies on bacteria, fungi and their metabolic enzymes. Although it is green and environmentally friendly, it has strict requirements on temperature, pH and humidity conditions, otherwise the activity of microorganisms or enzymes will be significantly reduced. Adsorption technology relies on high-performance adsorbents (such as activated carbon, nanomaterials, etc.), which are relatively expensive and difficult to apply on a large scale. Low-cost adsorbents generally have problems such as insufficient adsorption capacity and poor selectivity, resulting in limited removal efficiency of target pollutants.

[0004] Compared to traditional pollutants such as dyes, the degradation of neonicotinoid pesticides (e.g., acetamiprid) and antibiotics (e.g., sulfamethoxazole) is more challenging due to their complex molecular structures (containing stable groups such as heterocyclic rings and halogens, resulting in high environmental persistence), bioinhibitory properties (antibiotics can inhibit the activity of degrading bacteria), and the risk of toxic intermediates (incomplete degradation of neonicotinoid pesticides may produce more toxic derivatives). These characteristics render conventional treatment methods ineffective, necessitating the urgent need for the development of new, efficient, cost-effective, and highly specific degradation technologies.

[0005] Compared with traditional treatment methods, advanced oxidation technologies (AOPs) have significant advantages such as high degradation efficiency and wide application range. They can effectively mineralize most organic pollutants and are not prone to secondary pollution. Among them, photo-Fenton oxidation technology has shown unique advantages in the field of emerging pollutant control because it can use clean solar energy to drive free radical reactions to degrade pollutants. As a photo-Fenton catalyst, MIL-88A has the characteristics of simple synthesis and high yield, but its practical application is restricted by its limited light absorption capacity and low electron-hole pair separation efficiency, resulting in the failure to fully exert its photocatalytic performance. Therefore, how to improve the photogenerated carrier separation efficiency of MIL-88A through modification methods such as constructing heterojunctions and introducing functional additives, while broadening its visible light absorption range, has become a key issue in breaking through the application of this material in photo-Fenton catalysis. This has important theoretical and practical significance for the efficient degradation and removal of new organic pollution. Summary of the Invention

[0006] To address these issues, the present invention provides a method for preparing a lanthanum ferrite-metal organic framework nanocomposite. LaFeO3 is hydrothermally incorporated into MIL-88A to create an effective heterojunction, promoting the separation of photogenerated electron-hole pairs. This heterojunction serves as a photo-Fenton catalyst, improving photocatalytic degradation efficiency. Furthermore, the addition of a modifier, citric acid, further enhances the composite's ability to remove new pollutants. The nanocomposite can be used to degrade the neonicotinoid pesticide acetamiprid and the antibiotic sulfamethoxazole in aquatic environments, demonstrating rapid degradation rates, broad-spectrum activity, and environmental friendliness.

[0007] The present invention provides a method for preparing a citric acid-modified lanthanum ferrite-metal organic framework nanocomposite material, comprising the following steps:

[0008] (1) Synthesis of perovskite (LaFeO3)

[0009] LaFeO3 was synthesized by sol-gel method using lanthanum nitrate and iron nitrate as raw materials;

[0010] (2) Synthesis of citric acid modified lanthanum ferrite-metal organic framework nanocomposite (N MIL-88A@LaFeO3)

[0011] LaFeO3 was added to a mixture of fumaric acid dissolved in ultrapure water / DMF, and then a solution of FeCl3·6H2O dissolved in the ultrapure water / DMF mixture was dropwise added to the mixture, and citric acid was added to prepare a modified nanocomposite material by a hydrothermal method.

[0012] In one embodiment of the present invention, in step (1), the molar ratio of lanthanum nitrate to ferric nitrate is 1:1.

[0013] In one embodiment of the present invention, in step (1), the sol-gel method is specifically as follows: 5 mmol of ferric nitrate and 10 mmol of citric acid are dissolved in 30 mL of distilled water to prepare a mixed solution, and then the solution obtained by dissolving 5 mmol of lanthanum nitrate in 30 mL of distilled water is mixed evenly, and heated at 80-100° C. for 4-6 hours until it becomes a dry gel-like precursor, and then the precursor is dried at 100-120° C. for 12-14 hours, and finally ground and calcined at 600-800° C. for 4-6 hours, and then washed and dried to obtain LaFeO3.

[0014] In one embodiment of the present invention, in step (2), LaFeO3 accounts for 4-36% of the mass of the composite material, and more preferably 8%.

[0015] In one embodiment of the present invention, in step (2), the molar ratio of fumaric acid to FeCl3·6H2O is 1:1.

[0016] In one embodiment of the present invention, in step (2), the volume ratio of ultrapure water to DMF is 1:1.

[0017] In one embodiment of the present invention, in step (2), the hydrothermal method conditions are: heating at 65-85° C. for 4-6 hours.

[0018] In one embodiment of the present invention, in step (2), the amount of citric acid added is 0.3-0.9 mmol, more preferably 0.9 mmol.

[0019] A method for preparing a citric acid-modified lanthanum ferrite-metal organic framework nanocomposite material capable of efficiently degrading acetamiprid and sulfamethoxazole comprises the following steps:

[0020] (1) Synthesis of perovskite (LaFeO3)

[0021] The sol-gel method was used to synthesize the LaFeO3 precursor. A mixed solution of 5 mmol of ferric nitrate and 10 mmol of citric acid was dissolved in 30 mL of distilled water. The mixture was then mixed with a solution of 5 mmol of lanthanum nitrate dissolved in 30 mL of distilled water. The solution was then heated at 80–100°C for 4–6 hours until it formed a xerogel-like precursor. The precursor was then dried in an oven at 100–120°C for 12–14 hours. Finally, the resulting precursor powder was ground with agate mortar, placed in an alumina crucible, and calcined in a muffle furnace at 600–800°C for 4–6 hours at a heating rate of 20°C / min. The product was then washed several times with distilled water and anhydrous ethanol and dried at 80–100°C for 12–14 hours to obtain LaFeO3 powder.

[0022] (2) Synthesis of citric acid modified lanthanum ferrite-metal organic framework nanocomposite (0.9N MIL-88A@LaFeO3): The synthesized LaFeO3 was added in a certain amount to a mixture of fumaric acid (2 mmol) dissolved in 15 mL of a (1:1 v / v) ultrapure water / DMF mixture for 1 h. Then, a solution of FeCl3·6H2O (2 mmol) dissolved in 15 mL of a (1:1 v / v) ultrapure water / DMF mixture was added dropwise to the above solution, followed by the addition of 0.9 mmol of citric acid and continuous stirring for 30–60 min. The resulting mixture was transferred to a 50 mL autoclave and heated at 65–85°C for 4–6 h. The product was collected by centrifugation, washed three times with DMF and deionized water, and dried in an oven at 60–80°C for 12–14 h to obtain 0.9N MIL-88A@LaFeO3.

[0023] The present invention provides a citric acid modified lanthanum ferrite-metal organic framework nanocomposite material prepared by the method described above.

[0024] The present invention provides the use of the above-mentioned citric acid-modified lanthanum ferrite-metal organic framework nanocomposite material in the degradation of acetamiprid and sulfamethoxazole.

[0025] In one embodiment of the present invention, the application of the above-mentioned citric acid modified lanthanum ferrite-metal organic framework nanocomposite in the degradation of acetamiprid, specifically: Degradation experiment is carried out in the acetamiprid aqueous solution (40mL) containing 50mg / L, the above-mentioned composite material is added, the solution is kept in the dark at room temperature, and stirred for 30min to reach adsorption-desorption equilibrium. Subsequently, under visible light (350W xenon lamp), 100 μL of H2O2 are added to the solution to carry out photo-Fenton reaction, and a sample is taken every 30min, and the acetamiprid content after degradation is subsequently determined by HPLC, so as to calculate the degradation rate of acetamiprid.

[0026] In one embodiment of the present invention, 100% degradation of acetamiprid can be completed in 75 minutes.

[0027] In one embodiment of the present invention, the application of the above-mentioned citric acid modified lanthanum ferrite-metal organic framework nanocomposite in the degradation of sulfamethoxazole is specially as follows: degradation experiment is carried out in a sulfamethoxazole aqueous solution (40mL) containing 20mg / L. 30mg of the above-mentioned composite material is added, the solution is kept in the dark at room temperature, and stirred for 30min to reach adsorption-desorption equilibrium. Subsequently, under visible light (10W) irradiation, 100 μL of H2O2 are added to the solution to carry out photo-Fenton reaction, and a sample is taken every 30min, and the sulfamethoxazole content after degradation is subsequently measured by HPLC, so as to calculate the degradation rate of sulfamethoxazole.

[0028] The present invention provides application of the above-mentioned lanthanum ferrite-metal organic framework nanocomposite material in the degradation of pesticides and antibiotics.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1) Compared with traditional pesticide degradation methods, the photo-Fenton degradation efficiency of acetamiprid achieved by the MIL-88A@LaFeO3 prepared in this invention reached 99.9% within 180 minutes. Furthermore, after centrifugation, washing, and drying, the catalyst remained at an efficiency of 85.9% even after four recycling cycles. This demonstrates the catalyst's high efficiency and stability, and its reusability.

[0031] 2) Compared with traditional antibiotic degradation methods, the photo-Fenton degradation efficiency of MIL-88A@LaFeO3 prepared in the present invention for sulfamethoxazole reached 100% in 180 min.

[0032] 3) The preparation method of the present invention has simple materials and low cost. The prepared MIL-88A@LaFeO3 has a fast degradation rate and a broad spectrum, and can be applied to the degradation of various types of pesticides and antibiotics in water bodies.

[0033] 4) The MIL-88A@LaFeO3 nanocomposite material modified with citric acid exhibited significantly enhanced photo-Fenton catalytic performance. Mechanism studies showed that citric acid modification not only effectively promoted the Fe 2+ / Fe 3+ cycle, and also increased the exposure of active sites, while improving the light absorption capacity and charge transfer efficiency. In the acetamiprid degradation experiment, the modified material showed excellent catalytic activity: compared with the unmodified material, which took 180 minutes to reach a degradation rate of 99.9%, the modified nanocomposite material only took 75 minutes to achieve complete degradation (100%), and the reaction cycle was shortened by 58.3%. In addition, the modified nanocomposite material exhibited a wider pH range of application (pH 3-11), maintained good stability in wastewater treatment under different acid and alkaline conditions, and has a wider range of practical application prospects. These performance improvements are mainly attributed to the fact that citric acid modification optimizes the surface properties of the material and enhances the interfacial reaction kinetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of photo-Fenton degradation of neonicotinoid pesticide acetamiprid by citric acid modified lanthanum ferrite-metal organic framework nanocomposite (0.9N MIL-88A@LaFeO3);

[0035] Figure 2Transmission electron microscopy characterization images of three nanomaterials of the present invention; (a) is perovskite LaFeO3, (b) is the metal organic framework MIL-88A, and (c) is the composite material 8% MIL-88A@LaFeO3 of Example 1;

[0036] Figure 3 X-ray diffraction patterns of LaFeO3, MIL-88A and 8% MIL-88A@LaFeO3 materials of the present invention;

[0037] Figure 4 Fourier transform infrared spectra of LaFeO3, MIL-88A and 8% MIL-88A@LaFeO3 materials of the present invention;

[0038] Figure 5 X-ray diffraction patterns of the MIL-88A@LaFeO3 material modified by adding different amounts of citric acid in the present invention;

[0039] Figure 6 This is the Fourier transform infrared spectra of the MIL-88A@LaFeO3 material modified by adding different amounts of citric acid in the present invention;

[0040] Figure 7 Degradation efficiency (a) and degradation rate constant (b) of acetamiprid by LaFeO3, MIL-88A and 8% MIL-88A@LaFeO3 of the present invention;

[0041] Figure 8 The effects of different key factors, pH (a) and catalyst dosage (b), on the degradation of acetamiprid by the photo-Fenton system of 8% MIL-88A@LaFeO3 of the present invention are shown;

[0042] Figure 9 Comparison of the degradation efficiency of LaFeO3, MIL-88A and 8% MIL-88A@LaFeO3 on sulfamethoxazole;

[0043] Figure 10 The effect of different key factors, pH, on the degradation of sulfamethoxazole by the photo-Fenton system was investigated by 8% MIL-88A@LaFeO3 of the present invention.

[0044] Figure 11 The degradation efficiency of acetamiprid by 0.3N, 0.6N and 0.9N MIL-88A@LaFeO3 of the present invention;

[0045] Figure 12 This is the effect of different key factors pH (a) and catalyst dosage (b) on the degradation of acetamiprid by the photo-Fenton system of 0.9N MIL-88A@LaFeO3 of the present invention. DETAILED DESCRIPTION

[0046] Example 1

[0047] Synthesis of lanthanum ferrite-metal organic framework nanocomposite (MIL-88A@LaFeO3):

[0048] (1) Synthesis of perovskite (LaFeO3)

[0049] 5 mmol of Fe(NO₃)₃·9H₂O and 10 mmol of citric acid were dissolved in 30 mL of ultrapure water, designated Solution A. 5 mmol of La(NO₃)₃·6H₂O was dissolved in 30 mL of ultrapure water, designated Solution B. Solution B was slowly added dropwise to Solution A, and the mixed solution was stirred at room temperature for 1 hour. The solution was then heated at 80°C for 4 hours to form a xerogel-like precursor, which was then dried in an oven at 100°C for 12 hours. The resulting powder was ground and calcined in air at 600°C in a muffle furnace at a heating rate of 20°C / min for 4 hours. The powder was washed several times with distilled water and ethanol and dried at 80°C for 12 hours.

[0050] (2) Synthesis of lanthanum ferrite-metal organic framework nanocomposite (MIL-88A@LaFeO3)

[0051] The synthesized LaFeO₃ was added to a mixture of fumaric acid (2 mmol) dissolved in 15 mL of a (1:1 v / v) ultrapure water / DMF mixture for 1 hour. A solution of FeCl₃·6H₂O (2 mmol) dissolved in 15 mL of a (1:1 v / v) ultrapure water / DMF mixture was added dropwise to the resulting solution, stirring continuously for 30 minutes. The resulting mixture was transferred to a 50 mL autoclave and heated at 65°C for 4 hours. The product was collected by centrifugation, washed three times with DMF and three times with deionized water, and dried in an oven at 60°C for 12 hours to obtain 4%, 8%, 12%, 24%, and 36% MIL-88A@LaFeO₃, respectively.

[0052] Example 2

[0053] Synthesis of citric acid modified lanthanum ferrite-metal organic framework nanocomposites:

[0054] (1) Synthesis of perovskite (LaFeO3)

[0055] 5 mmol of Fe(NO₃)₃·9H₂O and 10 mmol of citric acid were dissolved in 30 mL of ultrapure water, designated Solution A. 5 mmol of La(NO₃)₃·6H₂O was dissolved in 30 mL of ultrapure water, designated Solution B. Solution B was slowly added dropwise to Solution A, and the mixed solution was stirred at room temperature for 1 hour. The solution was then heated at 80°C for 4 hours to form a xerogel-like precursor, which was then dried in an oven at 100°C for 12 hours. The resulting powder was ground and calcined in air at 600°C in a muffle furnace at a heating rate of 20°C / min for 4 hours. The powder was washed several times with distilled water and ethanol and dried at 80°C for 12 hours.

[0056] (2) Synthesis of citric acid modified lanthanum ferrite-metal organic framework nanocomposite (0.9N MIL-88A@LaFeO3)

[0057] The synthesized LaFeO3, representing 8% of the total composite mass, was added to a solution of fumaric acid (2 mmol) dissolved in 15 mL of a (1:1 v / v) ultrapure water / DMF mixture for 1 hour. A solution of FeCl3·6H2O (2 mmol) dissolved in 15 mL of a (1:1 v / v) ultrapure water / DMF mixture was added dropwise to the solution, followed by 0.9 mmol of citric acid, and stirring continued for 30 minutes. The resulting mixture was transferred to a 50 mL autoclave and heated at 65°C for 4 hours. The product was collected by centrifugation, washed three times with DMF and three times with deionized water, and dried in an oven at 60°C for 12 hours to yield 0.9N MIL-88A@LaFeO3.

[0058] Example 3

[0059] The preparation method is the same as that of Example 2, with the only difference being that in step (2), the amount of citric acid added is 0.3 mmol and 0.6 mmol, respectively, to obtain 0.3N and 0.6N MIL-88A@LaFeO3, respectively.

[0060] Comparative Example 1

[0061] MIL-88A Synthesis:

[0062] FeCl₃·6H₂O (2 mmol) and fumaric acid (2 mmol) were dissolved in 30 mL of a 1:1 v / v mixture of distilled water and N,N-dimethylformamide (DMF) and magnetically stirred at 1000 rpm for 30 min. The mixture was then transferred to a 50 mL autoclave and hydrothermally treated at 65°C for 4 h. Finally, the product was washed three times with 20 mL each of DMF and deionized water and dried in an oven at 60°C for 12 h to obtain MIL-88A.

[0063] The prepared materials were analyzed, and TEM results showed that MIL-88A exhibited a spindle morphology and LaFeO3 exhibited irregular nanoparticles with an average size of 55±10.57nm. For 8% MIL-88A@LaFeO3, TEM images showed that LaFeO3 nanoparticles with a (101) corresponding plane spacing of 0.39nm were encapsulated by MIL-88A ( Figure 2 ).

[0064] X-ray diffraction (XRD) results show that Figure 3 As shown. The 8% MIL-88A@LaFeO3 composite material shows characteristic diffraction peaks of MIL-88A and LaFeO3, confirming the successful synthesis of the composite material. (100) and (002) correspond to the MIL-88A plane peaks, (101), (121), (220), (202), (240), (242) correspond to the perovskite structure of LaFeO3, and the composite sample has no additional prominent peaks, indicating that the composite material is synthesized with high purity. Fourier transform infrared (FTIR) results show that 8% MIL-88A@LaFeO3 has a peak at 542cm -1 , 1396cm -1 , 1604cm -1 The absorption peaks correspond to Fe-O, C=O asymmetric stretching vibration, symmetric C=O stretching vibration, and the infrared spectrum of 8% MIL-88A@LaFeO3 shows all the characteristic peaks of LaFeO3 and MIL-88A, which indicates the successful synthesis of the nanocomposite material ( Figure 4 ).

[0065] For the citric acid modified lanthanum ferrite-metal organic framework nanocomposites, XRD results show that, Figure 5 As shown. When citric acid modified MIL-88A, its crystal growth changed. 0.3N MIL-88A@LaFeO3 showed typical peaks similar to MIL-88A. However, as the citric acid continued to increase, the (100) crystal plane with the fastest growth rate gradually decreased. This is mainly due to the coordination competition between citric acid and fumaric acid. In this process, the generated coordination unsaturated iron sites acted as catalytic active centers to enhance the catalytic efficiency. FTIR results showed that Figure 6 The functional groups of MIL-88A@LaFeO3 after citric acid modification are similar to those of MIL-88A@LaFeO3, indicating that some citric acid carboxyl groups participate in the coordination and that the process of replacing the fumaric acid ligands does not change the core functional group type of the MOF skeleton.

[0066] Example 4

[0067] The application of lanthanum ferrite-metal organic framework nanocomposite (8% MIL-88A@LaFeO3) in photo-Fenton degradation of acetamiprid includes the following steps:

[0068] Degradation experiments were carried out in an acetamiprid aqueous solution (40 mL) containing 50 mg / L. 25 mg of catalyst was added, the solution was kept in the dark and stirred for 30 min at room temperature to reach adsorption-desorption equilibrium. Subsequently, under visible light (350 W xenon lamp), 100 μL of H2O2 was added to the solution to carry out a photo-Fenton reaction, and a sample was taken every 20 min. The acetamiprid content after degradation was then determined by HPLC to calculate the degradation rate of acetamiprid.

[0069] The results are as follows Figure 7 As shown in the figure, 4%, 8%, 12%, 24%, and 36% MIL-88A@LaFeO3 achieved acetamiprid degradation efficiencies of 75.9%, 90.5%, 87.8%, 72.9%, and 66.6%, respectively, with 8% MIL-88A@LaFeO3 showing the best degradation efficiency. In addition, the degradation rate constants were compared using the pseudo-first-order Langmuir-Hinshelwood kinetics. The apparent rate constant (k) of 8% MIL-88A@LaFeO3 was 0.015 min -1 The degradation rate constant is 1.1 to 2.1 times higher than that of other composite materials and 0.003 min higher than that of single LaFeO3. -1 ) is 5 times higher than MIL-88A (0.007min -1 ) was 2.2 times higher, which confirmed that the incorporation of LaFeO3 significantly enhanced the photocatalytic performance of MIL-88A, among which the synergistic degradation efficiency of 8% LaFeO3 and MIL-88A could achieve the best degradation effect.

[0070] Example 5

[0071] Effects of different factors on the degradation of acetamiprid by nanocomposites

[0072] Effect of pH value on degradation efficiency: Figure 8As shown in a, this study systematically investigated the degradation performance of 8% MIL-88A@LaFeO3 on acetamiprid under different pH conditions (pH 3-9). The experiment used 1mmol / L HCl and NaOH solutions to adjust the pH value, and the other conditions remained consistent with Example 4. The results showed that under strong acidic conditions (pH = 3), the material exhibited the best catalytic activity, and the degradation rate could reach 96.8% within 120 minutes. It is worth noting that even in a weakly alkaline environment (pH = 9), the system still maintained good degradation performance, and the degradation rate could reach 90.5% within 180 minutes. This result shows that 8% MIL-88A@LaFeO3 has a wide pH applicability range (pH 3-9) and can adapt to the treatment needs of wastewater with different acidity and alkalinity.

[0073] Catalyst dosage optimization study: Under pH=9, we further investigated the effect of catalyst dosage on degradation efficiency ( Figure 8 b) The experiment maintained all other conditions consistent with Example 4, with only the 8% MIL-88A@LaFeO3 dosage (0.1-1 g / L) varied. The results showed that when the catalyst dosage reached 0.75 g / L, the system achieved a 99.9% acetamiprid degradation rate within 180 minutes. Based on this, 0.75 g / L was determined to be the optimal dosage, which enables efficient acetamiprid degradation over a wide pH range.

[0074] Example 6

[0075] The application of lanthanum ferrite-metal organic framework nanocomposite (8% MIL-88A@LaFeO3) in photo-Fenton degradation of sulfamethoxazole includes the following steps:

[0076] Degradation experiments were performed in a 40 mL aqueous solution of 20 mg / L sulfamethoxazole. 30 mg of catalyst was added, and the solution was kept in the dark at room temperature and stirred for 30 min to reach adsorption-desorption equilibrium. Subsequently, under visible light (10 W), 100 μL of H2O2 was added to the solution to perform a photo-Fenton reaction. Samples were taken every 30 min, and the sulfamethoxazole content after degradation was subsequently determined by HPLC to calculate the degradation rate of sulfamethoxazole.

[0077] The results are as follows Figure 9 As shown in the figure, sulfamethoxazole will be degraded by about 10% under light, and 8% MIL-88A@LaFeO3 shows the best photo-Fenton degradation efficiency, achieving a sulfamethoxazole degradation efficiency of nearly 100%, which is a significant improvement compared to the photo-Fenton degradation efficiency of LaFeO3 (26.7%).

[0078] Example 7

[0079] Effect of pH on the degradation of sulfamethoxazole by nanocomposites

[0080] The effects of different pH on the degradation of sulfamethoxazole were studied. Figure 10 At pH 3, the nanocomposite achieved 100% degradation efficiency within 120 minutes. The acidic environment promoted the generation of ·OH radicals to attack sulfamethoxazole. At pH 7, the nanocomposite degradation efficiency also reached 100% within 180 minutes. At pH 9, the nanocomposite degradation efficiency began to decrease, indicating that the catalyst is more suitable for degrading acidic antibiotic wastewater.

[0081] Example 8

[0082] The application of citric acid modified lanthanum ferrite-metal organic framework nanocomposite material in photo-Fenton degradation of acetamiprid comprises the following steps:

[0083] Degradation experiments were carried out in an acetamiprid aqueous solution (40 mL) containing 50 mg / L. 30 mg of catalyst was added, the solution was kept in the dark and stirred for 30 min at room temperature to reach adsorption-desorption equilibrium. Subsequently, under visible light (350 W xenon lamp), 100 μL of H2O2 was added to the solution to carry out photo-Fenton reaction, and a sample was taken every 30 min. The acetamiprid content after degradation was subsequently determined by HPLC to calculate the degradation rate of acetamiprid.

[0084] like Figure 11 As shown in the data, the degradation efficiency of MIL-88A@LaFeO3 prepared with different citric acid modification concentrations (0.9N, 0.6N, and 0.3N) for acetamiprid within 120 minutes showed significant differences. Experimental data showed that the 0.9N modified sample exhibited the best catalytic performance, achieving 100% complete degradation; while the 0.6N and 0.3N samples only achieved degradation rates of 77.2% and 59.2%, respectively. It is worth noting that the degradation efficiency of the 0.9N modified sample was nearly 20% higher than that of the unmodified nanocomposite material. This result fully demonstrates the significant enhancement of the photocatalytic activity of the material by citric acid modification.

[0085] Example 9

[0086] Effects of different factors on the degradation of acetamiprid by nanocomposites

[0087] The effect of 0.9N MIL-88A@LaFeO3 catalyst dosage on the degradation efficiency of acetamiprid was systematically investigated. Figure 12a). The experimental results show that when the catalyst dosage is reduced from 0.75g / L to 0.375g / L, nearly 100% degradation of acetamiprid can still be achieved within 75min, indicating that the optimized catalyst still maintains high degradation efficiency when the dosage is reduced by 50%, significantly improving the catalytic efficiency and economy. In addition, the catalytic performance of 0.9N MIL-88A@LaFeO3 (0.375g / L) under different pH conditions was further investigated ( Figure 12 b). The results show that compared with 8% MIL-88A@LaFeO3, the modified material exhibits higher degradation efficiency under acidic (pH 3-5), neutral (pH 7), and alkaline (pH 9-11) conditions, indicating that it has a wider pH adaptability and is suitable for wastewater treatment in different acidic and alkaline environments, which has more advantages in practical applications.

[0088] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a nanocomposite material for efficiently degrading the neonicotinoid pesticide acetamiprid and the antibiotic sulfamethoxazole, characterized in that: The steps include: (1) Synthesis of LaFeO3 LaFeO3 was synthesized by sol-gel method using lanthanum nitrate and iron nitrate as raw materials; (2) Synthesis of citric acid modified lanthanum ferrite-metal organic framework nanocomposites LaFeO3 was added to a mixture of fumaric acid dissolved in ultrapure water / DMF, and then a solution of FeCl3·6H2O dissolved in the ultrapure water / DMF mixture was dropwise added to the mixture, and citric acid was added to prepare a modified nanocomposite material by a hydrothermal method.

2. The method according to claim 1, characterized in that In step (1), the molar ratio of lanthanum nitrate to ferric nitrate is 1:

1.

3. The method according to claim 1, characterized in that In step (1), the sol-gel method is specifically as follows: 5mmol of ferric nitrate and 10mmol of citric acid are dissolved in 30mL of distilled water to prepare a mixed solution, and then the solution obtained by dissolving 5mmol of lanthanum nitrate in 30mL of distilled water is mixed evenly, and heated at 80-100°C for 4-6h until it becomes a dry gel-like precursor, and then the precursor is dried at 100-120°C for 12-14h, and finally ground and calcined at 600-800°C for 4-6h, and LaFeO3 is obtained after washing and drying.

4. The method according to claim 1, wherein In step (2), LaFeO3 accounts for 4-36% of the mass of the composite material.

5. The method according to claim 1, wherein In step (2), LaFeO3 accounts for 8% of the mass of the composite material.

6. The method according to claim 1, characterized in that In step (2), the molar ratio of fumaric acid to FeCl3·6H2O is 1:1; and the hydrothermal method conditions are: heating at 65-85°C for 4-6h.

7. The method according to claim 1, characterized in that In step (2), the amount of citric acid added is 0.3-0.9 mmol.

8. The method according to claim 1, characterized in that The specific steps include: (1) Synthesis of LaFeO3 The sol-gel method is used for synthesis. 5mmol of ferric nitrate and 10mmol of citric acid are dissolved in 30mL of distilled water to prepare a mixed solution. The mixed solution is then mixed evenly with a solution obtained by dissolving 5mmol of lanthanum nitrate in 30mL of distilled water. The solution is then heated at 80-100°C for 4-6 hours until it becomes a dry gel-like precursor. The precursor is then dried at 100-120°C for 12-14 hours, ground, and calcined at 600-800°C for 4-6 hours. The powdered LaFeO3 is then washed and dried. (2) Synthesis of citric acid modified lanthanum ferrite-metal organic framework nanocomposite material: A certain amount of the synthesized LaFeO3 was added to a mixture of 2 mmol fumaric acid dissolved in 15 mL ultrapure water / DMF for 1 h. Then, a solution of 2 mmol FeCl3·6H2O dissolved in 15 mL ultrapure water / DMF mixture was added dropwise to the above solution, followed by addition of 0.9 mmol citric acid. The mixture was stirred continuously for 30 to 60 min. The resulting mixture was transferred to a 50 mL autoclave and heated at 65 to 85°C for 4 to 6 h. The mixture was centrifuged, washed, and dried to obtain citric acid modified lanthanum ferrite-metal organic framework nanocomposite material.

9. The nanocomposite material prepared by the method according to any one of claims 1 to 8.

10. Use of the nanocomposite material according to claim 9 in the degradation of pesticides and antibiotics.

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