RGO / CdS / MIL-101 (Fe) catalyst as well as preparation method and application thereof

Abstract

The invention discloses an rGO / CdS / MIL-101 (Fe) catalyst as well as a preparation method and application thereof, and belongs to the technical field of water treatment. The ternary heterojunction catalyst is prepared by adopting a two-step method: firstly, mixing ferric trichloride hexahydrate, terephthalic acid and reduced graphene oxide in N, N-dimethylformamide, and synthesizing rGO / MIL-101 (Fe) through solvothermal reaction; and dispersing the rGO / CdS / MIL-101 (Fe) catalyst in a cadmium chloride ethanol solution, adding sodium sulfide, and stirring for reaction to obtain the rGO / CdS / MIL-101 (Fe) catalyst. The degradation rate of the catalyst under the conditions of 0.3 g / L dosage and 30 mg / L antibiotic concentration after visible light irradiation for 30 min reaches 92.66%, the degradation rate is still kept to be close to 80% after circulation for 4 times, and the main active species are holes.

Description

A rGO / CdS / MIL-101(Fe) catalyst, its preparation method and application Technical Field

[0001] This invention belongs to the field of water treatment technology, and particularly relates to an rGO / CdS / MIL-101(Fe) catalyst, its preparation method, and its application. Background Technology

[0002] Water is the source of life and a core material resource upon which humankind depends for survival and development. However, with rapid socio-economic development, the widespread use of antibiotics has led to a large amount of antibiotic residues that are difficult to degrade or transform entering water bodies, causing increasingly serious water pollution problems and posing a serious threat to the ecological environment and human health. Therefore, the efficient removal of antibiotics from water bodies has become a key research topic in the field of environmental governance.

[0003] Photocatalysis based on metal-organic frameworks (MOFs) is one of the effective means to control organic pollutants. MOFs possess unique advantages such as large specific surface area, high porosity, and easily tunable pore structure, laying a solid foundation for their application in photocatalysis. Among numerous MOF materials, iron-based MOFs have become a research hotspot in photocatalysis due to their environmental friendliness, low cost, and significant photoresponse characteristics. MIL-101(Fe), as a typical iron-based MOF material, combines high specific surface area, good environmental compatibility, and excellent light absorption capacity, showing broad application prospects in the degradation of water pollutants.

[0004] However, the single MIL-101(Fe) photocatalyst has the shortcoming of low photogenerated electron migration efficiency, which seriously restricts the further improvement of its photocatalytic performance. Summary of the Invention

[0005] To address the aforementioned technical bottlenecks, this invention proposes an rGO / CdS / MIL-101(Fe) catalyst, its preparation method, and its applications. By combining reduced graphene oxide (rGO) and cadmium sulfide (CdS) with a heterojunction structure, the MIL-101(Fe) photocatalyst is efficiently modified, aiming to significantly improve its photogenerated electron mobility and photocatalytic efficiency, providing new strategies and ideas for technological innovation and development in the field of photocatalysis.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing an rGO / CdS / MIL-101(Fe) catalyst includes the following steps:

[0008] (1) Ferric chloride hexahydrate and terephthalic acid were dispersed in N,N-dimethylformamide, and reduced graphene oxide was added and stirred. Then, the mixture was subjected to a solvothermal reaction to obtain the rGO / MIL-101(Fe) composite.

[0009] (2) The rGO / MIL-101(Fe) complex was dispersed in a Cd-containing medium. 2+ Sodium sulfide was added to an ethanol solution and the mixture was stirred to obtain an rGO / CdS / MIL-101(Fe) heterojunction photocatalyst.

[0010] This invention constructs a multi-component heterojunction photocatalyst by introducing rGO and CdS to composite modify MIL-101(Fe). rGO, with its superior electronic conductivity, accelerates the migration rate of photogenerated electrons, effectively reducing electron-hole recombination. Meanwhile, the introduction of CdS forms a stable heterojunction structure with MIL-101(Fe), further reducing the recombination probability of photogenerated carriers. The synergistic effect of these two components significantly enhances the catalyst's degradation efficiency for antibiotics in water.

[0011] Further, in step (1), the conditions for the solvothermal reaction are: temperature 110°C and time 12h.

[0012] Further, in step (1), the molar ratio of ferric chloride hexahydrate to terephthalic acid is 1:0.5.

[0013] Furthermore, in step (1), the amount of reduced graphene oxide added is 5.2% of the mass of ferric chloride hexahydrate.

[0014] Further, in step (2), the Cd 2+ It is derived from cadmium chloride.

[0015] Further, in step (2), the Cd 2+ The molar ratio with sodium sulfide is 1:0.1.

[0016] The present invention also provides an rGO / CdS / MIL-101(Fe) catalyst, which is prepared by the above preparation method.

[0017] This invention also provides the application of an rGO / CdS / MIL-101(Fe) catalyst in the photocatalytic degradation of antibiotics.

[0018] Furthermore, the conditions for the photocatalytic degradation include: a catalyst dosage of 0.1-0.6 g / L, an antibiotic concentration of 10-50 mg / L, and the reaction being carried out under visible light irradiation.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] (1) This invention introduces rGO and CdS into the MIL-101(Fe) monomer catalyst to obtain an rGO / CdS / MIL-101(Fe) catalyst. The introduction of rGO and CdS enhances the light absorption capacity and catalytic performance of the rGO / CdS / MIL-101(Fe) heterojunction photocatalyst. The degradation effect is best when the catalyst dosage is 0.3 g / L and the TC solution concentration is 30 mg / L, with a total degradation rate as high as 92.66%. Cyclic degradation experiments were then conducted on TC, and the results showed that rGO / CdS / MIL-101(Fe) has good stability. After 4 cycles, the photodegradation performance is still good, and the degradation rate only decreases by about 10%.

[0021] (2) The photocatalytic mechanism of rGO / CdS / MIL-101(Fe) photocatalyst was investigated through free radical capture experiments. The analysis showed that rGO / CdS / MIL-101(Fe) generates h in the photocatalytic reaction. + , 1 O2、•OH、•O2 - Free radicals undergo photocatalytic degradation, in which free radical h + It plays a major role. Characterization by PL shows that the heterojunction formed by MIL-101(Fe), CdS and rGO can prevent the recombination of electron-hole pairs, prolong the lifetime of photogenerated carriers, and thus enhance photocatalytic efficiency. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 shows the XRD patterns of different catalysts;

[0024] Figure 2 shows the FT-IR spectra of different catalysts;

[0025] Figure 3 shows the SEM images and elemental mapping distributions of different catalysts; where (a) and (b) are SEM images of MIL-101(Fe); (c) is the SEM image of rGO / MIL-101(Fe); (d) is the SEM image of CdS / MIL-101(Fe); (e) is the SEM image of rGO / CdS / MIL-101(Fe); and (f), (g), (h), (i), and (j) are elemental mapping distributions of rGO / CdS / MIL-101(Fe).

[0026] Figure 4 shows the TEM (ac) and HRTEM (d) images of rGO / CdS / MIL-101(Fe).

[0027] Figure 5 shows (a) the UV-DRS spectra of different catalysts; and (b) the Tauc diagrams of CdS, MIL-101(Fe) and rGO / CdS / MIL-101(Fe).

[0028] Figure 6 shows the UV-Vis absorption spectrum of the TC solution;

[0029] Figure 7 shows the effect of different catalysts on the degradation of tetracycline hydrochloride;

[0030] Figure 8 shows the effect of the dosage of rGO / CdS / MIL-101(Fe) catalyst on the degradation effect of TC;

[0031] Figure 9 shows the effect of the rGO / CdS / MIL-101(Fe) catalyst on the degradation of TC solutions with different concentrations;

[0032] Figure 10 shows the reuse results of the rGO / CdS / MIL-101(Fe) catalyst;

[0033] Figure 11 shows the inhibitory effect of different quenchers on TC degradation;

[0034] Figure 12 shows the PL spectra of different catalysts. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0041] The experimental reagents and instruments used in the following embodiments of the present invention are shown in Tables 1 and 2.

[0042] Table 1 Major Chemical Drugs

[0043] Name, Specification, Manufacturer: Anhydrous Ethanol (Analytical Grade), Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd., Cadmium Chloride (Analytical Grade), Sinopharm Chemical Reagent Co., Ltd., Terephthalic Acid and Graphene (Analytical Grade), Sinopharm Chemical Reagent Co., Ltd., Ferric Chloride Hexahydrate (Analytical Grade), Sinopharm Chemical Reagent Co., Ltd., Sodium Sulfide (Analytical Grade), Sodium Sulfide Nonahydrate (Analytical Grade), Sinopharm Chemical Reagent Co., Ltd., N,N-Dimethylformamide (Analytical Grade), Shanghai Aladdin Biochemical Technology Co., Ltd., Tetracycline. surface

[0044] Table 2 Main Instruments

[0045] Instrument Name, Model or Specifications, Manufacturer: Electric Heating Blower Drying Oven 101-00S (Shaoxing Poyi Co., Ltd.), Electric Heating Constant Temperature Water Bath DF-101S (Gongyi Yuhua Instrument Co., Ltd.), Ultrasonic Cleaner CR-030S (Shenzhen Jiemeng Cleaning Equipment Co., Ltd.), Benchtop High-Speed ​​Centrifuge TG16-WS (Hunan Xiangyi Experimental Instrument Development Co., Ltd.), Heat Collector Constant Temperature Heating Magnetic Stirrer DF-101S (Gongyi Yuhua Instrument Co., Ltd.), Xenon Lamp Constant Current Power Supply PLS-SXE300 (Beijing Pofilai Technology Co., Ltd.), Electronic Analytical Balance (Youke Instrument Co., Ltd.) surface

[0046] Other instruments: beakers, centrifuge tubes, spatulas, cuvettes, graduated cylinders, weighing paper, droppers, volumetric flasks, medical injection needles, 1ml glass bottles, and filter membranes.

[0047] The technical solution of the present invention will be further illustrated by the following embodiments.

[0048] Example 1

[0049] A method for preparing an rGO / CdS / MIL-101(Fe) catalyst, comprising the following steps:

[0050] (1) First, weigh 40.5 mg of terephthalic acid and 135.2 mg of FeCl3·6H2O on an electronic analytical balance, and dissolve them in 60 mL of DMF solution on a magnetic stirrer. Then weigh 7.028 mg of rGO and add it to the solution and stir for 10 min. Then place it in a 100 mL high-temperature reactor and react at 110 °C for 12 h. After cooling to room temperature, centrifuge once, rinse three times with ethanol, and dry in a 65 °C oven to obtain rGO / MIL-101(Fe).

[0051] (2) 0.1 g of rGO / MIL-101(Fe) was dispersed in 2 mmol of CdCl2, 100 mL of anhydrous ethanol was added, and then 0.2 mmol of Na2S·9H2O was added. The mixture was magnetically stirred at 20 °C for 4 h, washed several times, and dried at 60 °C for 12 h to obtain the rGO / CdS / MIL-101(Fe) catalyst.

[0052] Comparative Example 1

[0053] A method for preparing a MIL-101(Fe) catalyst, comprising the following steps:

[0054] First, 40.5 mg of terephthalic acid and 135.2 mg of FeCl3·6H2O were weighed on an electronic analytical balance and dissolved in 60 mL of DMF solution on a magnetic stirrer. Then, the mixture was placed in a 100 mL high-temperature reactor and reacted at 110 °C for 12 h. After cooling to room temperature, the mixture was centrifuged once, washed three times with ethanol, and dried in a 65 °C oven to obtain the MIL-101(Fe) catalyst.

[0055] Comparative Example 2

[0056] A method for preparing an rGO / MIL-101(Fe) catalyst, comprising the following steps:

[0057] First, 40.5 mg of terephthalic acid and 135.2 mg of FeCl3·6H2O were weighed on an electronic analytical balance and dissolved in 60 mL of DMF solution on a magnetic stirrer. Then, 7.028 mg of rGO was weighed and added to the solution and stirred for 10 min. Subsequently, the solution was placed in a 100 mL high-temperature reactor and reacted at 110 °C for 12 h. After cooling to room temperature, the solution was centrifuged once, washed three times with ethanol, and dried in a 65 °C oven to obtain the rGO / MIL-101(Fe) catalyst.

[0058] Comparative Example 3

[0059] A method for preparing a CdS / MIL-101(Fe) catalyst, comprising the following steps:

[0060] (1) First, weigh 40.5 mg of terephthalic acid and 135.2 mg of FeCl3·6H2O on an electronic analytical balance. Dissolve them in 60 mL of DMF solution on a magnetic stirrer. Then place them in a 100 mL high-temperature reaction vessel and react at 110 °C for 12 h. After cooling to room temperature, centrifuge once, rinse three times with ethanol, and dry in a 65 °C oven to obtain MIL-101(Fe);

[0061] (2) Disperse 0.1g of MIL-101(Fe) in 2mmol of CdCl2, add 100mL of anhydrous ethanol, and then add 0.2mmol of Na2S·9H2O. Stir magnetically at 20℃ for 4h, wash repeatedly, and dry at 60℃ for 12h to obtain CdS / MIL-101(Fe) catalyst.

[0062] Comparative Example 4

[0063] A method for preparing an rGO / CdS catalyst, comprising the following steps:

[0064] 0.02 g of rGO was dispersed in 2 mmol of CdCl2, 100 mL of anhydrous ethanol was added, and then 0.2 mmol of Na2S·9H2O was added. The mixture was magnetically stirred at 20 °C for 4 h, washed several times, and dried at 60 °C for 12 h to obtain the rGO / CdS catalyst.

[0065] Characterization of catalysts

[0066] 1) XRD characterization

[0067] The crystal structure of the synthesized photocatalyst was characterized by powder X-ray diffraction (XRD, Rigaku Smartlab SE, Japan). Cu Kα radiation (λ = 1.54056 Å) was applied at 45 kV and 200 mA within a 2θ range of 10–80°, with a scan rate set at 4°min. -1 .

[0068] Figure 1 shows the XRD patterns of MIL-101(Fe) and its composite catalyst prepared by the solvothermal method. It can be seen that the MIL-101(Fe) material has high crystallinity between 5° and 20°, and sharp diffraction peaks appear at diffraction angles of 2θ = 8.91°, 9.80°, and 10.87°. These diffraction peaks are the main characteristic peaks of the MIL-101(Fe) material, proving that iron exists in the trivalent state in the material, indicating that MIL-101(Fe) was successfully synthesized and has a complete and good crystal structure. The characteristic peaks of pure CdS indicate the successful synthesis of CdS. The composite material CdS / MIL-101(Fe) contains characteristic peaks of both CdS and MIL-101(Fe), indicating that the crystal structure of the original material has not changed, proving the successful synthesis of CdS / MIL-101(Fe). Meanwhile, rGO / CdS / MIL-101(Fe) also contains characteristic peaks of rGO, MIL-101(Fe), and CdS, indicating that the material successfully loads CdS and rGO. However, the CdS peak is weaker. This result may be because MIL-101(Fe) and rGO reduce the grain size of CdS during the composite process, resulting in a weakening of the diffraction peak. The reduction in grain size increases the photocatalytic activity, which is consistent with the subsequent result that rGO / CdS / MIL-101(Fe) has the best photocatalytic activity.

[0069] 2) FT-IR Characterization: Fourier Transform Infrared Spectroscopy (FT-IR) is an effective characterization technique that identifies specific chemical bonds or functional groups in molecules by analyzing infrared spectra. The principle is that when infrared light shines on a material, the functional groups and chemical bonds within the material absorb specific wavelengths of infrared light due to the vibrations or rotations of their atoms, thus producing characteristic spectra. This invention uses a Bruker Alpha Fourier Transform Infrared Spectrometer (Bruker, Germany).

[0070] The MIL-101(Fe), CdS / MIL-101(Fe), rGO / MIL-101(Fe), and rGO / CdS / MIL-101(Fe) catalysts were analyzed by FT-IR spectroscopy. The results are shown in Figure 2. It can be seen that the infrared spectrum of MIL-101(Fe) is within the range of 750 cm⁻¹. -1 1396cm -1 1583cm -1 and 1680cm -1 There are relatively obvious characteristic peaks at nearby wavelengths. 750cm -1 The characteristic peak at 1396 cm⁻¹ is attributed to the CH bond of the benzene ring. -1 and 1583cm -1 The characteristic peak at 1680 cm⁻¹ represents the skeletal vibration of the C=C benzene ring. -1The characteristic peaks at 1396 cm⁻¹ are related to the C=O bonds present in the free carboxyl groups, indicating the presence of continuous dicarboxyl group linkages. This demonstrates the successful synthesis of MIL-101(Fe). The figure shows that the characteristic peaks of CdS are all present in the infrared spectrum of the CdS / MIL-101(Fe) photocatalyst, and the peak shapes of CdS / MIL-101(Fe) and MIL-101(Fe) remain almost unchanged, with only slight enhancement of each characteristic peak. The infrared spectra of rGO / MIL-101(Fe) and rGO / CdS / MIL-101(Fe) show that after loading rGO onto MIL-101(Fe), its structure did not change significantly, but rather remained at 1396 cm⁻¹. -1 and 1583cm -1 The relatively weakened intensity of the characteristic peak at [specific location] is likely due to the reaction of the carboxyl groups on MIL-101(Fe) with the numerous carbon-containing functional groups in rGO, resulting in the formation of a large number of long chains and reducing the amount of free dicarboxylic acids. However, the remaining characteristic peaks did not change significantly, further indicating the successful synthesis of the rGO / CdS / MIL-101(Fe) photocatalyst.

[0071] 3) SEM characterization: Field emission scanning electron microscope (SEM, Hitachi S-4800, Japan) and aberration-corrected transmission electron microscope (TEM, Titan G2 60-300, FEI, USA) were used for analysis.

[0072] The surface morphology of pure MIL-101(Fe) was analyzed using scanning electron microscopy. SEM images of the synthesized MIL-101(Fe) material are shown in Figure 3(a) and (b), with magnifications of 1500x and 5000x, and scale bars of 10μm and 1μm, respectively. The SEM images show that MIL-101(Fe) has a typical hexagonal octahedral morphology, with a smooth, flat surface, clear edges, and a uniform structure, proving the successful synthesis of MIL-101(Fe). Figure (c) clearly shows rGO attached to the crystalline MIL-101(Fe). The rGO / MIL-101(Fe) shape is similar to that of MIL-101(Fe), indicating that the loading of graphene did not affect the structure of MIL-101(Fe). Figure (d) shows that CdS exhibits severe aggregation and extremely poor dispersibility. Observation of Figure (e) reveals that rGO and CdS are attached to MIL-101(Fe), and the shape of MIL-101(Fe) does not change significantly. Furthermore, the EDS elemental mapping images of rGO / CdS / MIL-101(Fe) are shown in Figures (f)-(j), confirming the presence of C, Cd, S, O, and Fe in the heterojunction photocatalyst. The distribution of these five elements is extremely dense and clear, confirming the successful preparation of the rGO / CdS / MIL-101(Fe) heterojunction.

[0073] 4) The microstructure of rGO / CdS / MIL-101(Fe) was observed using TEM and HRTEM, as shown in Figures 4(a), (b), and (c). CdS and rGO are tightly attached to the surface of MIL-101(Fe). As shown in Figure 4(d), the lattice spacings of 0.34 nm and 0.25 nm correspond to the (002) plane of CdS and the (111) plane of rGO, respectively, indicating a tight interfacial contact between rGO, CdS, and MIL-101(Fe). TEM and HRTEM characterization further confirmed the successful fabrication of the rGO / CdS / MIL-101(Fe) heterostructure.

[0074] 5) UV-Vis DRS characterization: In this invention, UV-Vis diffuse reflectance spectra (DRS) were collected in the wavelength range of 240-800 nm using an Agilent Cary 60 UV-Vis spectrometer, and BaSO4 was used as the reflectance standard sample.

[0075] The light absorption performance of the prepared photocatalysts was characterized using UV-Vis diffuse reflectance spectroscopy (DRS). As shown in Figure 5(a), the light absorption band edges of MIL-101(Fe) and CdS are approximately 506 nm and 515 nm, respectively. After loading CdS, the light absorption capacity of the CdS / MIL-101(Fe) heterojunction photocatalyst was slightly improved. Due to the excellent light absorption performance of rGO, the visible light absorption capacity of the rGO / CdS / MIL-101(Fe) heterojunction photocatalyst was significantly increased after simultaneously loading rGO and CdS, thereby improving the light utilization rate and enhancing the photocatalytic activity. As shown in Figure 5(b), according to the Kubelka-Munk formula (αhѵ)... 1 / n =A(hѵ-Eg) was used to calculate the band gap (Eg) of CdS, MIL-101(Fe), and rGO / CdS / MIL-101(Fe), respectively. The results were 2.48 eV, 2.84 eV, and 2.15 eV, respectively, which further demonstrates that the photocatalytic performance of the rGO / CdS / MIL-101(Fe) heterojunction photocatalyst has been greatly improved.

[0076] Application Example 1

[0077] 1. Preparation of TC (Tetracycline, TC) solution: First, weigh 30 mg of TC and dissolve it in a 100 mL beaker. Then, transfer the solution to a 1000 mL volumetric flask and add deionized water to bring the volume to a final volume, obtaining a 30 mg / L TC solution. The 30 mg / L TC solution is then subjected to a UV-Vis spectrophotometer to determine the maximum absorption wavelength corresponding to the maximum absorption peak (Amax). Figure 6 shows that 356.5 nm is the maximum absorption wavelength of the 30 mg / L TC solution in the 200-400 nm range, at which point the maximum absorption peak appears.

[0078] 2. Degradation of tetracycline under different catalysts: The specific method is as follows: Take 5 groups of 50 mL and 30 mg / L TC solutions respectively, and weigh 15 mg each of MIL-101(Fe) (Comparative Example 1), rGO / MIL-101(Fe) (Comparative Example 2), CdS / MIL-101(Fe) (Comparative Example 3), rGO / CdS (Comparative Example 4), and rGO / CdS / MIL-101(Fe) (Example 1). Add them to the TC solution, sonicate in an ultrasonic cleaner for 10 min, stir on a magnetic stirrer for 10 min, and irradiate under a xenon lamp for 30 min. Take a sample every 6 min for a total of six times, and then measure the absorbance using a UV-Vis spectrophotometer.

[0079] The degradation of TC solution by photocatalysts MIL-101(Fe), rGO / MIL-101(Fe), CdS / MIL-101(Fe), rGO / CdS, and rGO / CdS / MIL-101(Fe) was studied when the initial concentration of TC solution was 30 mg / L, the catalyst dosage was 0.3 g / L, and the photoreaction time was 30 min. As shown in Figure 7, MIL-101(Fe) showed good dark adsorption of TC, but after 30 min of xenon lamp irradiation, the photocatalytic degradation efficiency of MIL-101(Fe) for 30 mg / L TC solution was only 17.4%, indicating poor photodegradation performance. The total degradation rate of CdS / MIL-101(Fe) was 78.11%, with a photocatalytic efficiency as high as 59.1%. This indicates that loading CdS onto MIL-101(Fe) reduced its specific surface area, resulting in a slightly lower adsorption capacity compared to MIL-101(Fe). After MIL-101(Fe) was loaded with rGO, the degradation rate increased to 46.63%, but the photocatalytic efficiency was only 19.5%, indicating that the dark adsorption effect was increased after loading with rGO. This shows that the addition of both substances improves the overall degradation performance, and the effect of loading CdS is more significant. Furthermore, the figure shows that the degradation rate reached 92.66% after loading MIL-101(Fe) with rGO and CdS, with both dark adsorption and photocatalytic effects increased. This indicates that rGO / CdS / MIL-101(Fe) has a greater effect on the degradation of TC, therefore rGO / CdS / MIL-101(Fe) is the optimal catalyst.

[0080] 3. Degradation of TC by different catalyst dosages: The initial concentration of TC solution was 30 mg / L. The dosages of rGO / CdS / MIL-101(Fe) were 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.5 g / L, and 0.6 g / L, respectively. These were then added to 50 mL and 30 mg / L TC solutions, respectively. The solutions were ultrasonically cleaned for 10 min, stirred on a magnetic stirrer for 10 min, and irradiated under a xenon lamp for 30 min. Samples were taken every 6 min for a total of six times. The absorbance was then measured using a UV-Vis spectrophotometer.

[0081] Using 30 mg / L TC as a model pollutant and a reaction time of 30 min, the effect of the dosage of rGO / CdS / MIL-101(Fe) heterojunction photocatalyst on the visible light degradation performance of TC was investigated. The results are shown in Figure 8. As can be seen from the figure, the degradation performance of TC by the rGO / CdS / MIL-101(Fe) heterojunction photocatalyst continuously increases with increasing dosage, because a larger dosage generates more active groups. When the dosage of rGO / CdS / MIL-101(Fe) heterojunction is 0.3 g / L, the TC degradation rate has increased to 92.66%. Further increasing the dosage of rGO / CdS / MIL-101(Fe) heterojunction photocatalyst no longer significantly improves the TC degradation performance. Therefore, the optimal dosage of rGO / CdS / MIL-101(Fe) heterojunction photocatalyst is 0.3 g / L, at which point the economic benefits of TC degradation are optimal.

[0082] 4. The degradation of TC by the catalyst at different concentrations was carried out as follows: The initial concentrations of TC solutions were 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, and 50 mg / L, respectively. 50 mL of each solution was taken. The dosage of rGO / CdS / MIL-101(Fe) was 0.3 g / L. The solutions were ultrasonicated for 10 min in an ultrasonic cleaner, stirred for 10 min on a magnetic stirrer, and irradiated under a xenon lamp for 30 min. Samples were taken every 6 min for a total of six times. The absorbance was then measured using a UV-Vis spectrophotometer.

[0083] The effect of a rGO / CdS / MIL-101(Fe) heterojunction photocatalyst at a dosage of 0.3 g / L and a reaction time of 30 min on the degradation performance of different concentrations of total TC under visible light was investigated. As shown in Figure 9, the degradation performance of the rGO / CdS / MIL-101(Fe) heterojunction photocatalyst decreased with increasing TC concentration. This is mainly because the amount of photocatalyst added remained constant, and the active free radicals generated by visible light also remained constant, thus reducing the TC degradation performance. Furthermore, with increasing TC concentration, more intermediate products were generated during the degradation process, and the degree of degradation tended to stabilize. Therefore, a catalyst dosage of 0.3 g / L resulted in the best economic efficiency for degrading a 30 mg / L TC solution.

[0084] 5. Repeat the experiment. The specific method is as follows: After degradation, the catalyst is washed three times with deionized water by centrifugation, dried in a 60℃ oven, and recovered. Then, the dried catalyst is cycled for degradation four times, and the total degradation rate after each cycle is recorded.

[0085] Catalyst stability and reusability are key indicators for evaluating the feasibility of catalysts in practical applications. To investigate the stability and reusability of rGO / CdS / MIL-101(Fe) in the rGO / CdS / MIL-101(Fe) / TC system, this invention conducted a cyclic experiment on the degradation of TC by rGO / CdS / MIL-101(Fe). The initial concentration of TC was set at 30 mg / L, the catalyst dosage at 0.3 g / L, the initial pH of the solution at 4.3, and the temperature at 25℃. Under these conditions, the TC degradation rate of rGO / CdS / MIL-101(Fe) was measured after four consecutive cycles. As shown in Figure 10, the degradation performance of the prepared rGO / CdS / MIL-101(Fe) heterojunction catalyst for TC gradually decreased with the increase of the number of cycles. This may be due to catalyst loss during centrifugation and washing, as well as loss during drying. This also leads to a decreasing trend in TC removal rate with the increase of the number of cycles. Simultaneously, residual TC is adsorbed on the catalyst surface, resulting in a decrease in catalytic performance. After four photodegradation experiments, the catalyst still achieved a degradation rate of nearly 80% for TC, indicating that it has good stability and can be reused. Moreover, the catalyst's degradation of TC is not due to adsorption, but rather photocatalytic degradation.

[0086] 6. Free radical capture experiment: The specific method is as follows: Under the conditions of an initial concentration of TC solution of 30 mg / L, an addition of rGO / CdS / MIL-101(Fe) of 0.3 g / L, and a 30 min light reaction, nitrogen (N2), tert-butanol (TBA), disodium ethylenediaminetetraacetate (EDTA-2Na), and furfuryl alcohol (FA) were selected as the free radical capture agents. 1 O2, h + •OH, •O2 - The trapping agent.

[0087] This invention introduces a free radical quencher into the photo / rGO / CdS / MIL-101(Fe) system. The main free radicals involved in the reaction are determined by the quencher's inhibition of the TC degradation reaction, and the reaction mechanism of TC degradation in the photo / rGO / CdS / MIL-101(Fe) system is analyzed. The experiment was conducted under optimal reaction conditions: initial TC concentration of 30 mg / L, catalyst dosage of 0.3 g / L, initial solution pH of 4.3, and T of 25 °C. Furfuryl alcohol, disodium ethylenediaminetetraacetate, tert-butanol, and nitrogen were used as catalysts, respectively. 1 O2, h + •OH, •O2 - The TC trapping agent. The experimental results are shown in Figure 11. After bubbling N2 into the solution and reacting for 60 min, the degradation rate of TC was 91.46%, a decrease of only 1.2%, indicating that •O2... -In the light / rGO / CdS / MIL-101(Fe) system, the degradation of TC did not play a significant role. However, after adding tert-butanol and reacting for 30 minutes, the degradation rate of TC reached 83.3%, only 9.36% lower than the original system. This indicates that •OH also underwent an oxidation reaction with pollutants during the degradation process. In the same reaction system, adding furfuryl alcohol resulted in a TC degradation rate of 68.1%, 24.56% lower than the original system. 1 O2 has a greater oxidizing effect than •OH in the degradation process. The degradation rate after adding disodium ethylenediaminetetraacetate (EDTA) to the reaction was only 24.9%, 67.76% lower than the original system. In the photoreaction, the degradation rate of TC was only 8%, indicating that H... + It plays a major role in the degradation process. Based on the above results, the active groups generated under visible light, from largest to smallest, are: H... + , 1 O2、•OH、•O2 - .

[0088] 7. Photoluminescence (PL) spectroscopy is an advanced method for studying the electronic band structure of materials. By analyzing PL spectra, a series of key data can be obtained, including peak position and peak intensity. Peak position directly reflects the color characteristics of fluorescence emission, while peak intensity reveals the dynamic processes of charge recombination and transfer within the material. This invention uses a Shimadzu RF-5301PC fluorescence spectrophotometer with an excitation wavelength of 243 nm. As shown in Figure 12, with an excitation wavelength of 243 nm, the fluorescence peak intensity of CdS / MIL-101(Fe) is significantly lower than that of CdS and MIL-101(Fe). This indicates that MIL-101(Fe) has a narrower visible light response range. This may be because after MIL-101(Fe) is excited by visible light, photogenerated electron-hole pairs separate. The inability of electrons to transfer in an orderly manner leads to the recombination of photogenerated electron-hole pairs, resulting in a decrease in the charge transfer rate and thus a narrower light response range for MIL-101(Fe). The heterojunction formed by MIL-101(Fe) loaded with CdS can prevent electron-hole recombination and prolong the lifetime of photogenerated carriers, thereby enhancing photocatalytic efficiency. The same applies to rGO / CdS / MIL-101(Fe). The heterojunction formed between MIL-101(Fe), CdS, and rGO enables effective charge separation and migration, effectively reducing the band gap width of the catalyst and increasing its visible light response range. Therefore, the fluorescence peak of rGO / CdS / MIL-101(Fe) is lower than that of CdS / MIL-101(Fe).

[0089] 8. Photocatalytic mechanism analysis

[0090] Based on the above experimental results, it can be seen that in the photocatalytic reaction, under visible light irradiation, electrons in the rGO / CdS / MIL-101(Fe) heterojunction photocatalyst migrate from the valence band to the conduction band, generating electron-hole pairs (Equation (2-1)). These electron-hole pairs generate a series of reactions, producing active substances that degrade TC. Details are as follows: the H generated by rGO / CdS / MIL-101(Fe)... + It can directly oxidize TC (Equation (2-8)) and simultaneously react with water molecules to produce •OH, which degrades TC (Equations (2-2) and (2-10)). Electrons migrating from rGO / CdS / MIL-101(Fe) react with oxygen to generate… 1 O2 (Equation (2-5)), the generation of these active ions plays a significant role in the degradation of TC (Equations (2-8) and (2-10)). Fe in the catalyst 3+ It will absorb electrons to generate Fe 2+ (Equation (2-3)) promotes Fe 3+ Fe 2+ The interconversion between these elements leads to the large-scale generation of hydroxyl radicals, accelerating the catalytic degradation process. The H+ in the valence band of MIL-101(Fe)... + It also undergoes oxidation with TC, resulting in degradation. Therefore, TC simultaneously reacts with multiple active groups to generate small molecules such as CO2 and H2O. Furthermore, the photoinduced electron-hole transfer in rGO / CdS / MIL-101(Fe) prolongs the lifetime of charge carriers and enhances the catalytic efficiency of the photocatalyst. rGO can rapidly form electron traps with electrons, improving the separation efficiency of electron-hole pairs and reducing the probability of electron-hole recombination (Equations (2-6) and (2-7)). rGO has a high specific surface area and conductivity, which can improve the adsorption performance and carrier (electron, hole) transport performance of rGO / CdS / MIL-101(Fe). These synergistic effects promote improved photocatalytic performance.

[0091] rGO / CdS / MIL-101(Fe)+ hv→e-+ H + (2-1)

[0092] H2O + H + → •OH (2-2)

[0093] Fe 3+ + e- → Fe 2+ (2-3)

[0094] e- + O2→ •O 2- (2-4)

[0095] •O2 - + •OH → 1 O2 (2-5)

[0096] rGO (e- ) + O2→ rGO- •O2- (2-6)

[0097] rGO- •O2-+•OH +TC→ Intermediate + H2O + CO2 (2-7)

[0098] H + + TC → Intermediate + CO2+ H2O (2-8)

[0099] 1 O2+ TC→ Intermediate + CO2+ H2O (2-9)

[0100] •OH + TC→ Intermediate + CO2+ H2O (2-10)

[0101] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an rGO / CdS / MIL-101(Fe) catalyst, characterized in that, The process includes the following steps: (1) dispersing ferric chloride hexahydrate and terephthalic acid in N,N-dimethylformamide, adding reduced graphene oxide and stirring, and then reacting with a solvothermal agent to obtain the rGO / MIL-101(Fe) composite; (2) dispersing the rGO / MIL-101(Fe) composite in a Cd-containing medium. 2+ Sodium sulfide was added to an ethanol solution and the mixture was stirred to obtain the rGO / CdS / MIL-101(Fe) catalyst.

2. The method for preparing the rGO / CdS / MIL-101(Fe) catalyst according to claim 1, characterized in that, In step (1), the conditions for the solvothermal reaction are: temperature 110℃ and time 12h.

3. The method for preparing the rGO / CdS / MIL-101(Fe) catalyst according to claim 1, characterized in that, In step (1), the molar ratio of ferric chloride hexahydrate to terephthalic acid is 1:0.

5.

4. The method for preparing the rGO / CdS / MIL-101(Fe) catalyst according to claim 1, characterized in that, In step (1), the amount of reduced graphene oxide added is 5.2% of the mass of ferric chloride hexahydrate.

5. The method for preparing the rGO / CdS / MIL-101(Fe) catalyst according to claim 1, characterized in that, In step (2), the Cd 2+ It is derived from cadmium chloride.

6. The method for preparing the rGO / CdS / MIL-101(Fe) catalyst according to claim 1, characterized in that, In step (2), the Cd 2+ The molar ratio with sodium sulfide is 1:0.

1.

7. An rGO / CdS / MIL-101(Fe) catalyst, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The application of the rGO / CdS / MIL-101(Fe) catalyst as described in claim 7 in the photocatalytic degradation of antibiotics.

9. The application according to claim 8, wherein the conditions for the photocatalytic degradation include: The rGO / CdS / MIL-101(Fe) catalyst was added at a rate of 0.1-0.6 g / L, the antibiotic concentration was 10-50 mg / L, and the reaction was carried out under visible light irradiation.

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