Preparation methods and applications of iron / carbon quantum dot / biochar composite photocatalytic materials

Abstract

This invention discloses a method for preparing an iron / carbon quantum dot / biochar composite photocatalytic material and its application, belonging to the field of catalytic decomposition technology. Waste wolfberries are carbonized in an aqueous solution of 0.02–2 mol / L K₄[Fe(CN₆)]·3H₂O at 180–200°C for 6–8 hours. The resulting mixture is then centrifuged at 8000–10000 rpm for 10 minutes to separate the lower solid layer. This lower solid layer is dried at 60–80°C for 6 hours, ground, and sieved to obtain the iron / carbon quantum dot / biochar composite material. This invention uses a one-step synthesis method, eliminating the need for secondary composite processes and avoiding cumbersome and energy-intensive preparation steps. The resulting biochar material can be used as a purification material for sulfonamide and fluoroquinolone antibiotics in water, effectively solving the problem of sulfonamide and fluoroquinolone antibiotic pollution in aquatic environments requiring removal.

Description

Technical Field

[0001] This invention relates to the field of catalytic decomposition technology, specifically to the preparation method and application of iron / carbon quantum dot / biochar composite photocatalytic materials. Background Technology

[0002] Sulfonamides and fluoroquinolones are broad-spectrum and highly effective antibacterial drugs used as veterinary medicines to treat livestock and poultry diseases. However, in recent years, the overuse of antibiotics has been serious, leading to the presence of sulfonamide and fluoroquinolone antibiotic residues in the environment. In particular, antibiotics and their metabolites can enter environmental water bodies through multiple pathways, resulting in severe antibiotic residues in aquatic environments. Long-term exposure of aquatic microorganisms to antibiotic residues can lead to the evolution of drug resistance, posing a significant threat to human health and ecological balance. Therefore, it is essential to establish a green and efficient method for removing sulfonamides and fluoroquinolones.

[0003] Currently, the main methods for treating sulfonamides and fluoroquinolones in aquatic environments include chemical, physical, and biological methods. However, biological methods generally struggle to achieve complete mineralization of these antibiotics, and once they enter biological treatment units, they can easily cause secondary pollution. In recent years, photocatalytic oxidation has attracted attention as a novel heterogeneous chemical treatment method for degrading sulfonamides and fluoroquinolones.

[0004] Studies have shown that photocatalytic materials, after absorbing light energy, can catalyze the degradation of sulfonamides and fluoroquinolones, ultimately generating harmless or low-harm substances such as small molecules, CO2, and H2O, thus achieving environmentally friendly treatment of pollutants. Photocatalytic materials generally absorb solar energy, generating electron-hole pairs, which migrate to the catalyst surface to undergo redox reactions. Commonly used photocatalysts include metal oxides (TiO2, ZnO, WO3, MnO2, and BiVO4, etc.), metal sulfides (MoS2, MoSe2, CdS, and ZnS, etc.), metal-free photocatalysts (CQDs, SiC, and BP), and covalent metal frameworks. However, the visible light response range of single photocatalysts is relatively narrow, and the utilization rate of natural solar energy is only 5%.

[0005] Doping with highly conductive elements (such as transition metals, noble metals, and nonmetals) can expand the photoresponse range of semiconductor photocatalytic materials under visible light. Many carbon materials with excellent properties are considered as supports for improving the photocatalytic properties of semiconductor materials. Among them, biomass carbon-based materials are widely used due to their large surface area, high porosity, low cost, and environmental friendliness. However, research on the photocatalytic degradation of sulfonamides and fluoroquinolones in the aquatic environment based on carbon-based materials is relatively limited.

[0006] Patent CN202211310439.5 discloses a method for using red mud-supported biochar material to catalyze the degradation of sulfamethoxazole by sodium persulfate. This method uses coffee grounds as raw material and modifies and supports them with red mud, a type of iron-rich solid waste, to obtain red mud-supported biochar. The red mud-supported biochar catalyzes the formation of a persulfate complex, which then reacts with sulfamethoxazole on the material surface. While this method exhibits strong resistance to pH, various ions, and humic acids, the preparation temperature is high, and the addition of persulfate may cause secondary pollution.

[0007] Therefore, it is necessary to conduct systematic basic research on the preparation and performance improvement of photocatalytic materials for use in aquatic environments. The goal is to develop an environmentally friendly, low-cost, and practically applicable catalytic material for the effective purification of sulfonamide and fluoroquinolone antibiotics in aquatic environments. Summary of the Invention

[0008] Based on previous research and existing problems, this invention proposes a method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials after further research and analysis. The method uses a one-step synthesis, eliminating the need for secondary composite processes and saving the cumbersome and energy-intensive preparation process. The resulting biochar material can be used as a purification material for sulfonamide and fluoroquinolone antibiotics in water, and can be applied to water environments that require the removal of sulfonamide and fluoroquinolone antibiotics, effectively solving the problem of sulfonamide and fluoroquinolone antibiotic pollution in the water environment.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials, the method steps of which are as follows:

[0011] Step 1: Carbonize the waste wolfberries in an aqueous solution of K4[Fe(CN)6]•3H2O at 180-200℃ for 6-8 hours;

[0012] Step 2: Centrifuge the mixture obtained after hydrothermal treatment in Step 1 at 8000-10000 rpm for 10 min to separate the lower solid layer;

[0013] Step 3: Dry the lower solid obtained in Step 2 at 60-80℃ for 6 hours, grind it, and sieve it to obtain the iron / carbon quantum dot / biochar composite material.

[0014] Preferably, in step one, the concentration of K4[Fe(CN)6]•3H2O is 0.02~2mol / L.

[0015] Preferably, in step one, the mass ratio of the waste wolfberries to the volume ratio of the K4[Fe(CN)6]•3H2O solution is 3g:5mL.

[0016] Preferably, the heating rate for carbonization in step one is 10–15 °C / min.

[0017] The present invention also proposes an iron / carbon quantum dot / biochar composite photocatalytic material, which is prepared by the method mentioned above, and the particle size of the obtained iron / carbon quantum dot / biochar composite material is less than 100 mesh.

[0018] In addition, the present invention also applies the iron / carbon quantum dot / biochar composite material prepared above to the degradation of sulfonamide and fluoroquinolone antibiotics in water.

[0019] Furthermore, the steps for degrading sulfonamides and fluoroquinolones in water are as follows:

[0020] S1. Add the iron / carbon quantum dot / biochar composite photocatalyst to a mixed solution containing sulfonamides and fluoroquinolone antibiotics;

[0021] S2. Keep in darkness for 1 hour, then under visible light (natural light) for 1-9 hours to complete the photocatalytic degradation of sulfonamides and fluoroquinolones.

[0022] Preferably, the sulfonamide and fluoroquinolone antibiotic contaminants are one of norfloxacin, sulfamethoxazole, sulfathiazole, sulfamethoxazole, sulfamethoxypyrimidine, sulfadoxine, and sulfamethoxypyrimidine.

[0023] Preferably, the concentration of sulfonamides and fluoroquinolones in the mixed solution does not exceed 10 mg / L.

[0024] Preferably, the concentration of the iron / carbon quantum dot / biochar composite photocatalyst material in sulfonamide and fluoroquinolone antibiotic solutions is 0.4–1 g / L.

[0025] Compared with existing technologies, this invention provides a method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials and their applications, which have the following beneficial effects:

[0026] This invention uses waste wolfberry as a carbon source. While recycling the waste, it pyrolyzes the waste in K4[Fe(CN)6]•3H2O aqueous solution to synthesize an iron / carbon quantum dot / biochar composite material in one step. During the pyrolysis process, the organic compounds in the biochar of the iron / carbon quantum dot / biochar composite photocatalyst transfer electrons to the transition metal (Fe) to form stable free radicals. The upconversion properties of carbon quantum dots enable the composite photocatalyst to directly utilize the full spectrum of solar energy, while enhancing electron transfer and bandgap regulation.

[0027] Furthermore, this invention investigated the photocatalytic degradation performance of iron / carbon quantum dot / biochar composite materials on some sulfonamide and fluoroquinolone antibiotics. The results showed that the iron / carbon quantum dot / biochar composite material provided by this invention, using a 10 mg / L mixed solution of sulfonamide and fluoroquinolone antibiotics as the degradation target, achieved photocatalytic efficiencies of 84.20%, 21.39%, 86.51%, 89.23%, 76.88%, 77.44%, and 74.21% for norfloxacin, sulfamethoxazole, sulfathiazole, sulfamethoxazole, sulfamethoxypyrimidine, sulfadoxine, and sulfamethoxypyrimidine, respectively, after 9 hours of reaction under outdoor sunlight. Therefore, the iron / carbon quantum dot / biochar composite material prepared by this invention can degrade some sulfonamide and fluoroquinolone antibiotics in the aquatic environment in a green and low-cost manner. Attached Figure Description

[0028] Figure 1 The FTIR spectrum of the iron / carbon quantum dot / biochar composite material prepared in Example 1 of this invention;

[0029] Figure 2 This is a SEM image of the iron / carbon quantum dot / biochar composite material prepared in Example 1 of the present invention;

[0030] Figure 3 XPS spectrum of the iron / carbon quantum dot / biochar composite material prepared in Example 1 of this invention;

[0031] Figure 4 The XRD pattern of the iron / carbon quantum dot / biochar composite material prepared in Example 1 of this invention;

[0032] Figure 5 The BET plot of the iron / carbon quantum dot / biochar composite material prepared in Example 1 of this invention;

[0033] Figure 6 This is a schematic diagram showing the time and (CO-C) / CO of the photocatalytic degradation of norfloxacin, sulfamethoxazole, sulfathiazole, sulfamethoxazole, sulfamethoxypyrimidine, sulfadoxine, and sulfamethoxypyrimidine by the iron / carbon quantum dot / biochar composite material prepared in Example 1 of the present invention.

[0034] Figure 7 The image shows the electron paramagnetic resonance (EPR) spectrum of the phenyl radicals in the iron / carbon quantum dot / biochar composite photocatalyst material obtained in Example 1. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] To provide a clearer and more detailed description of the preparation method of the iron / carbon quantum dot / biochar composite photocatalytic material provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0037] Example 1

[0038] This embodiment proposes a method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials, the detailed steps of which are as follows:

[0039] (1) Place 3g of waste wolfberry into a reactor containing 5mL of 0.02mol / LK4[Fe(CN)6]•3H2O. Place the reactor in a muffle furnace and heat the muffle furnace to 200℃ at a heating rate of 10℃ / min. Keep the temperature for 8h.

[0040] (2) Centrifuge the mixture obtained after hydrothermal treatment in step (1) at 8000 rpm for 10 min to separate the lower solid layer.

[0041] (3) The lower solid obtained in step (2) is dried at 60°C for 6 hours, ground, and sieved to obtain an iron / carbon quantum dot / biochar composite material.

[0042] Example 2

[0043] This embodiment proposes a method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials, the detailed steps of which are as follows:

[0044] (1) Place 3g of waste wolfberry into a reactor containing 5mL of 0.2mol / L K4[Fe(CN)6]•3H2O. Place the reactor in a muffle furnace and heat the muffle furnace to 180℃ at a heating rate of 12℃ / min. Keep the temperature for 6h.

[0045] (2) Centrifuge the mixture obtained after hydrothermal treatment in step (1) at 10,000 rpm for 10 min to separate the lower solid layer.

[0046] (3) The lower solid obtained in step (2) is dried at 80°C for 6 hours, ground, and sieved to obtain an iron / carbon quantum dot / biochar composite material.

[0047] Example 3

[0048] This embodiment proposes a method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials, the detailed steps of which are as follows:

[0049] (1) Place 3g of waste wolfberry into a reactor containing 5mL of 2mol / LK4[Fe(CN)6]•3H2O. Place the reactor in a muffle furnace and heat the muffle furnace to 185℃ at a heating rate of 15℃ / min. Hold the temperature for 6.5h.

[0050] (2) Centrifuge the mixture obtained after hydrothermal treatment in step (1) at 9200 rpm for 10 min to separate the lower solid layer.

[0051] (3) The lower solid obtained in step (2) is dried at 72°C for 6 hours, ground, and sieved to obtain an iron / carbon quantum dot / biochar composite material.

[0052] The iron / carbon quantum dot / biochar composite photocatalytic materials prepared by the methods described in the above three embodiments all have a particle size of less than 100 mesh, and belong to microporous materials.

[0053] This invention also takes the iron / carbon quantum dot / biochar composite material prepared in Example 1 as an example to study and analyze its properties, wherein... Figure 1 The FTIR spectrum of the iron / carbon quantum dot / biochar composite material prepared in Example 1 of this invention is shown. The spectrum of iron / carbon quantum dot / biochar is as follows: 3370 cm⁻¹ -1 The left and right bands represent the stretching vibrations of OH / NH. (2360 and 1590 cm⁻¹) -1 The nearby absorption peaks correspond to the stretching vibrations of C=C and C=N, respectively. 2930 cm⁻¹ -1 and 1380cm -1 The absorption peaks at these locations correspond to the σC-H stretching vibration and the δC-H in-plane bending vibration stretching vibration peaks, respectively. In the FTIR of iron / carbon quantum dots / biochar, the Fe-O stretching vibration is located at 621 cm⁻¹. -1 The presence of Fe at this location indicates that Fe / carbon quantum dots / biochar are doped. Furthermore, the FTIR of Fe / BC / CQDs also shows a position at 775 cm⁻¹. -1 The γC-H absorption peaks around the left and right indicate that a benzene ring structure has been formed on the Fe / BC / CQDs.

[0054] Figure 2 The image shown is a SEM image of Example 1, which reveals the microstructure and structural features of the material. Figure 2 As can be seen in (a), wrinkles and pores appear in the iron / carbon quantum dot / biochar composite photocatalyst material, which indicates that the doping of heterogeneous elements leads to defects in the graphitization structure of the iron / carbon quantum dot / biochar composite photocatalyst material. Figure 2The smooth crystal structure observed in (b) indicates successful Fe ion doping. Furthermore... Figure 2 The (c_f)EDSmapping spectrum shows a high correlation between C, N, O, and Fe elements. N and O elements are uniformly distributed on the carbon substrate, and N and O elements are derived from biomass.

[0055] Figure 3 The XPS spectrum of Example 1 is shown below. Figure 3 (a) is the XPS full spectrum, from which the XPS characteristic peaks of C, N, O and Fe elements can be seen. Figure 3 (b) is the XPS spectrum of O1s. It can be seen from the figure that 531.2 eV, 532.04 eV and 533.3 eV correspond to the characteristic peaks of FeOOH, C=O and O=C=O, respectively. Figure 3 (c) is the XPS spectrum of N1s, from Figure 3 As can be seen in (c), 401 eV, 399.92 eV, and 398.67 eV correspond to the characteristic peaks of CN, N≡C, and CN=C, respectively. Figure 3 (d) is the XPS spectrum of C1s. It can be seen from the figure that the binding energy at 284.7 eV corresponds to C=C, which is consistent with the FTIR results.

[0056] Figure 4 The XRD pattern of Example 1 shows the broad peak at 2θ = 21.9°, corresponding to the graphite (002) plane. The characteristic peaks at 2θ = 24.8°, 2θ = 30.9°, and 2θ = 35.5° correspond to the (012), (104), and (110) planes, respectively, further demonstrating the presence of Fe. 3+ Doping.

[0057] Figure 5 The BET plot for Example 1 shows that the nitrogen adsorption-desorption curve is a type II isotherm. The average pore size of the iron / carbon quantum dot / biochar composite photocatalytic material is 1.985 nm, which is a microporous material.

[0058] The present invention also tested the photocatalytic degradation performance of sulfonamides and fluoroquinolones in water by the iron / carbon quantum dot / biochar composite material in Example 1. The specific steps are as follows:

[0059] Step 1: Weigh 20mg of photocatalytic composite material on a clean bench and place the weighed photocatalytic composite material into an Erlenmeyer flask containing a mixed solution of 50mL of sulfonamides and fluoroquinolones, wherein the concentration of sulfonamides and fluoroquinolones is 10mg / L.

[0060] Step 2: Place the conical flask under sunlight for 9 hours, and collect the supernatant at regular intervals.

[0061] Step 3: The supernatant collected every hour was filtered through a 0.22 μm hydrophilic membrane, and the concentrations of sulfonamides and fluoroquinolones were detected by HPLC-HRMS.

[0062] Step 4: Based on the detected concentrations C of sulfonamides and fluoroquinolones and the initial concentrations C0 of sulfonamides and fluoroquinolones, the photocatalytic degradation efficiency of the composite material is calculated as (C0-C) / C0. The photocatalytic composite material described in the above example is then used in the experiment.

[0063] Figure 6 This diagram illustrates the time and (CO-C) / CO ratio of the photocatalytic degradation of norfloxacin, sulfamethoxazole, sulfathiazole, sulfamethylisoxazole, sulfamethoxypyrimidine, sulfadoxine, and sulfamethoxypyrimidine by the iron / carbon quantum dot / biochar composite material prepared in Example 1 of this invention. As can be seen from the diagram, the photocatalytic degradation degree of norfloxacin, sulfamethoxazole, sulfathiazole, sulfamethoxypyrimidine, sulfadoxine, and sulfamethoxypyrimidine by the iron / carbon quantum dot / biochar composite photocatalytic material prepared in Example 1 gradually increases with time. After 9 hours of photodegradation, the photocatalytic efficiencies reached 84.20%, 21.39%, 86.51%, 89.23%, 76.88%, 77.44%, and 74.21%, respectively, demonstrating that the material synthesized in Example 1 has good photocatalytic degradation ability for these classes of sulfonamides and fluoroquinolones.

[0064] Figure 7 The image shows the electron paramagnetic resonance (EPR) spectrum of the phenyl radicals in the iron / carbon quantum dot / biochar composite photocatalyst obtained in Example 1. The iron / carbon quantum dot / biochar composite photocatalyst obtained in Example 1 forms phenyl radicals under illumination. It can be considered that the introduction of carbon quantum dots and iron significantly improves the absorption of visible light, thereby enhancing the photocatalytic activity and photothermal performance of the photocatalyst. Phenyl radicals are the main active substances that lead to the decomposition and eventual mineralization of some sulfonamide and fluoroquinolone antibiotics.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A method for preparing iron / carbon quantum dot / biochar composite photocatalytic materials, characterized in that, The steps are as follows: Step 1: Carbonize the waste wolfberries in an aqueous solution of K4[Fe(CN)6]•3H2O at 180-200℃ for 6-8 hours; Step 2: Centrifuge the mixture obtained after hydrothermal carbonization in Step 1 at 8000-10000 rpm for 10 min to separate the lower solid layer; Step 3: Dry the lower solid obtained in Step 2 at 60-80℃ for 6 hours, grind it, and sieve it to obtain the iron / carbon quantum dot / biochar composite material.

2. The preparation method of the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 1, characterized in that, The concentration of K4[Fe(CN)6]•3H2O in step one is 0.02~2mol / L.

3. The preparation method of the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 2, characterized in that, In step one, the mass ratio of discarded wolfberries to the volume ratio of K4[Fe(CN)6]•3H2O solution is 3g:5mL.

4. The method for preparing the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 2 or 3, characterized in that, The heating rate for carbonization in step one is 10–15 °C / min.

5. An iron / carbon quantum dot / biochar composite photocatalytic material, prepared by the method described in claim 4, characterized in that, The particle size of the prepared iron / carbon quantum dot / biochar composite photocatalytic material is less than 100 mesh.

6. An application of the iron / carbon quantum dot / biochar composite photocatalytic material as described in claim 5, characterized in that, It is used in the photocatalytic degradation of sulfonamides and fluoroquinolones in water.

7. The application of the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 6, characterized in that, The steps for degrading sulfonamide and fluoroquinolone antibiotics in water are as follows: S1. Add the iron / carbon quantum dot / biochar composite photocatalyst to a mixed solution containing sulfonamides and fluoroquinolone antibiotics; S2. Keep in darkness for 1 hour, then under visible light for 1-9 hours to complete the photocatalytic degradation of sulfonamides and fluoroquinolones.

8. The application of the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 7, characterized in that, The sulfonamide and fluoroquinolone antibiotic contaminants are norfloxacin and one of the following: sulfamethoxazole, sulfathiazole, sulfamethoxazole, sulfamethoxypyrimidine, sulfadoxine, and sulfamethoxypyrimidine.

9. The application of the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 7, characterized in that, The concentration of sulfonamides and fluoroquinolones in the mixed solution does not exceed 10 mg / L.

10. The application of the iron / carbon quantum dot / biochar composite photocatalytic material according to claim 9, characterized in that, The concentration of the iron / carbon quantum dot / biochar composite photocatalyst in a mixed solution of sulfonamides and fluoroquinolones is 0.4–1 g / L.

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