FeOOH quantum dot / CuFe2O4 composite material, its preparation method and application

Abstract

This invention discloses a FeOOH quantum dot / CuFe2O4 composite material, its preparation method, and its applications. The FeOOH quantum dot / CuFe2O4 composite material comprises CuFe2O4 nanosheets and FeOOH quantum dots supported on the CuFe2O4 nanosheets. The FeOOH quantum dot / CuFe2O4 composite material provided by this invention exhibits excellent degradation rate and cycling stability of methylene blue as a photocatalyst.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst preparation, and particularly to FeOOH quantum dot / CuFe2O4 composite materials, their preparation methods, and applications. Background Technology

[0002] Methylene blue is a commonly used organic dye, widely applied in printing and dyeing, medical applications, and analytical identification, particularly in the textile industry where it is a crucial alkaline dye. Methylene blue can cause cancer and gene mutations, and the wastewater generated from its use, if discharged untreated, poses a significant threat to environmental safety and human health. Therefore, the efficient, rational, and safe treatment of this wastewater is of great importance for both environmental protection and human health. In recent years, the environmentally friendly, economical, and efficient photocatalytic technology for dye degradation has received widespread attention.

[0003] B. Janani et al. (Physica E:Low-dimensional Systems and Nanostructures, 2021, 130, 114664) used sonochemical-coprecipitation technology to prepare ZnO heterojunction nanocomposites (NCs) decorated with CuFe2O4 to degrade methylene blue, achieving a degradation rate of 86% in 3 hours. Summary of the Invention

[0004] The purpose of this invention is to provide FeOOH quantum dot / CuFe2O4 composite materials, their preparation methods and applications, so as to achieve high-efficiency degradation of organic dyes such as methylene blue.

[0005] To achieve the above objectives, the first aspect of the present invention provides a FeOOH quantum dot / CuFe2O4 composite material, comprising:

[0006] CuFe2O4 nanosheets, and

[0007] FeOOH (iron hydroxy oxide) quantum dots loaded on the CuFe2O4 nanosheets.

[0008] In some embodiments, the FeOOH quantum dots and the CuFe2O4 nanosheets form a heterojunction.

[0009] In some embodiments, the FeOOH quantum dot / CuFe2O4 composite material is prepared by CuFe2O4 and trivalent iron salt at a mass ratio of 1:(0.1-0.3).

[0010] In some embodiments, the trivalent iron salt is FeCl3·6H2O.

[0011] In some embodiments, based on energy-dispersive X-ray spectroscopy, in the FeOOH quantum dot / CuFe2O4 composite material, O accounts for 62.89% of the total number of atoms, Fe accounts for 21.19%, and Cu accounts for 15.92%.

[0012] The second aspect of this invention provides a method for preparing the aforementioned FeOOH quantum dot / CuFe2O4 composite material, comprising:

[0013] CuFe₂O₄ and a ferric salt were mixed in an organic solvent, sonicated, and then KHCO₃ was added to obtain a reaction mixture.

[0014] The reaction mixture was stirred for 6-10 hours to obtain the FeOOH quantum dot / CuFe2O4 composite material.

[0015] In some embodiments, the CuFe2O4 is mixed with the ferric salt at a mass ratio of 1:(0.1-0.3), and KHCO3 is in molar excess relative to the ferric salt.

[0016] In some embodiments, the organic solvent is ethanol.

[0017] In some embodiments, the reaction mixture is stirred at 20-30°C.

[0018] A third aspect of the present invention provides the use of the aforementioned FeOOH quantum dot / CuFe2O4 composite material as a photocatalyst.

[0019] A fourth aspect of the present invention provides a method for treating wastewater containing organic dyes, comprising:

[0020] Wastewater containing organic dyes, such as methylene blue, is mixed with the aforementioned FeOOH quantum dot / CuFe2O4 composite material to obtain a mixture to be treated.

[0021] The mixture to be treated is kept under visible light irradiation for at least 120 minutes.

[0022] Beneficial effects

[0023] The FeOOH quantum dot / CuFe2O4 composite material provided by this invention accelerates the separation of photogenerated electron-hole pairs by forming a Fe-O-Fe electron rapid transfer channel between FeOOH quantum dots and CuFe2O4, generating more active free radicals to degrade methylene blue. After 180 min of photocatalysis using FeOOH quantum dot / CuFe2O4 as a photocatalyst, the degradation rate of methylene blue is significantly higher than that of previously reported CuFe2O4-ZnO heterojunction nanocomposites.

[0024] Moreover, the FeOOH quantum dot / CuFe2O4 composite material provided by this invention also exhibits excellent cycle stability as a photocatalyst.

[0025] Furthermore, since FeOOH and CuFe2O4 possess a certain degree of magnetism, the FeOOH quantum dot / CuFe2O4 composite material provided by this invention is easy to recycle as a photocatalyst, making it more environmentally friendly. Attached Figure Description

[0026] Figure 1 The structure and morphology of FeOOH quantum dots / CuFe2O4 are shown, in which, Figure 1 In the middle (a) and (b), SEM images of CuFe2O4 and 20% FeOOH quantum dots / CuFe2O4 prepared in Example 2 are respectively. Figure 1 (c) is a TEM image of 20% FeOOH quantum dots / CuFe2O4. Figure 1 The middle (d) image shows the energy-dispersive X-ray spectrum of 20% FeOOH quantum dots / CuFe2O4. Figure 1 (e)-(h) show the high-frequency elemental mapping of 20% FeOOH quantum dots / CuFe2O4, where (e) is the SEM image corresponding to the high-frequency elemental mapping;

[0027] Figure 2 XRD patterns of different materials are shown;

[0028] Figure 3 The X-ray photoelectron spectroscopy (XPS) of 20% FeOOH quantum dots / CuFe2O4 is shown, in which... Figure 3 In the image, (a) is the full spectrum, (b) is the C1s spectrum, (c) is the Cu 2p spectrum, (d) is the O1s spectrum, and (e) is the Fe 2p spectrum.

[0029] Figure 4 The degradation performance of methylene blue by different catalysts is shown;

[0030] Figure 5 Figure (a) shows the degradation effect of 20% FeOOH / CuFe2O4 as a photocatalyst on methylene blue after 5 cycles. Figure 5 Figure (b) shows a bar chart illustrating the degradation effect after five cycles;

[0031] Figure 6 The effect of methylene blue concentration on degradation performance is shown;

[0032] Figure 7 The effect of different pH values ​​of wastewater on degradation performance is shown;

[0033] Figure 8The UV-Vis diffuse reflectance spectra (a), band gap (b), impedance spectra (c), and transient photocurrent plots (d) of different catalysts are shown. Detailed Implementation

[0034] Example

[0035] To provide a clearer understanding of the technical solution, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in conjunction with the accompanying drawings.

[0036] It should be noted that, unless otherwise specified in the following examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0037] Preparation of FeOOH quantum dot / CuFe2O4 composite material

[0038] Example 1

[0039] 0.01M Cu(NO3)2·3H2O and 0.02M Fe(NO3)3·9H2O were weighed and dissolved in 30mL of deionized water. Then, 4g of citric acid was added, and the mixture was stirred magnetically until dissolved, at which point the solution was light green. The pH of the solution was then adjusted to approximately 7 using ammonia, at which point the solution should be dark green. The mixture was then magnetically stirred and heated to 70℃ to evaporate the liquid until it transformed into a green gel. The gel was then dried in an oven at 130℃ for 5 hours. During this process, the colloid preheated and expanded, forming a dry black gel. The product was transferred to a crucible, a small amount of anhydrous ethanol was added, and the mixture was ignited. During this process, the gel transformed into a black, tree-like structure. After grinding, the product was transferred to a muffle furnace and calcined at 500℃ for 3 hours under flowing air, with a heating rate of 5℃ / min. The resulting powder was reddish-brown, yielding CuFe2O4.

[0040] 0.2 g of CuFe2O4 was weighed and dispersed in 40 mL of anhydrous ethanol. 0.02 g of FeCl3·6H2O was added and sonicated for 10 min. The mixture was then stirred mechanically at 25 °C for 8 h, with sufficient KHCO3 added simultaneously (molar ratio of FeCl3·6H2O:KHCO3 = 1:3) over 10 min. The resulting composite material was then centrifuged in a centrifuge tube at 8000 r / min for 5 min. It was then washed three times with deionized water and finally dried in a drying oven at 60 °C for 10 h to obtain the FeOOH quantum dot / CuFe2O4 composite material, which is also referred to as 10% FeOOH quantum dot / CuFe2O4 in this paper.

[0041] Example 2

[0042] The only difference between Example 2 and Example 1 is that 0.02g FeCl3·6H2O in Example 1 is replaced with 0.04g FeCl3·6H2O. The resulting FeOOH quantum dot / CuFe2O4 composite material is also referred to as 20% FeOOH quantum dot / CuFe2O4 in this article.

[0043] Example 3

[0044] The only difference between Example 3 and Example 1 is that 0.02g FeCl3·6H2O in Example 1 is replaced with 0.06g FeCl3·6H2O. The resulting FeOOH quantum dot / CuFe2O4 composite material is also referred to as 30% FeOOH quantum dot / CuFe2O4 in this article.

[0045] Preparation of FeOOH quantum dots

[0046] 0.02 g FeCl3·6H2O was dispersed in 40 mL of anhydrous ethanol and sonicated for 10 min. The mixture was then stirred with a magnetic stirrer at 25 °C for 8 h, while simultaneously adding sufficient KHCO3 (molar ratio of FeCl3·6H2O:KHCO3 = 1:3) over 10 min. The resulting composite material was then poured into a centrifuge tube and centrifuged at 8000 r / min for 5 min. The mixture was then washed three times with deionized water and finally dried in a drying oven at 60 °C for 10 h to obtain FeOOH quantum dots.

[0047] Characterization of FeOOH quantum dot / CuFe2O4 composite materials

[0048] First, the structure and morphology of individual CuFe2O4 and the 20% FeOOH quantum dot / CuFe2O4 prepared in Example 2 were characterized using scanning electron microscopy (SEM). Figure 1 As shown in (a), individual CuFe₂O₄ particles are mainly composed of spherical particles with a size of 60 to 70 nm. Figure 1 As shown in photo (b), in the 20% FeOOH quantum dot / CuFe2O4 composite, CuFe2O4 has a multilayered sheet structure, and there are many pores between the layered nanosheets, which enhances the material's dye adsorption capacity; FeOOH quantum dots are uniformly loaded on CuFe2O4; as shown in the photo (b), the CuFe2O4 composite ... enhancing the material's dye adsorption capacity; FeOOH quantum dots are uniformly loaded on CuFe2O4; as shown in the photo (b), the CuFe2O4 composite has a multilayered sheet structure, and there are many pores between the layered nanosheets, Figure 1As shown in the TEM image (c), the FeOOH quantum dots have an average diameter of about 3-4 nm and are uniformly dispersed on CuFe2O4 nanosheets. Based on energy-dispersive X-ray spectroscopy, it is roughly determined that in a 20% FeOOH quantum dot / CuFe2O4 structure, O accounts for 62.89% of the total atoms, Fe accounts for 21.19%, and Cu accounts for 15.92%. Figure 1 (d)). Furthermore, according to the high-frequency element mapping ( Figure 1 In the composite material, Cu, Fe, and O are uniformly distributed (e-h).

[0049] X-ray diffraction (XRD) analysis further confirmed the crystal structures of FeOOH, CuFe2O4, and FeOOH quantum dots / CuFe2O4. Figure 2 In the study, the diffraction peaks of pure CuFe2O4 at 2θ = 24.1°, 35.9°, 62.1°, 71.9°, 73.2°, and 76.0° correspond to crystal planes (112), (211), (224), (332), (305), and (422), respectively. The characteristics of the diffraction peaks are consistent with the structure of tetragonal spinel CuFe2O4 (PDF#34-0425). FeOOH quantum dots / CuFe2O4 also exhibit these peaks, indicating the presence of CuFe2O4. The absence of diffraction peaks in FeOOH is due to its low crystallinity and high dispersibility. With increasing FeOOH doping concentration, the diffraction peaks at 2θ = 35.9° and 76.0° gradually disappear, possibly due to the formation of chemical bonds between CuFe2O4 and FeOOH, leading to a change in the crystal structure of the composite material. In summary, FeOOH has been successfully incorporated into CuFe2O4 layered nanosheets.

[0050] X-ray photoelectron spectroscopy (XPS) was used to evaluate the elemental valence states and chemical composition of the FeOOH quantum dot / CuFe2O4 surface, such as... Figure 3 As shown. According to Figure 3 In (a), the broad-spectrum XPS spectrum of FeOOH quantum dots / CuFe2O4 shows the main peaks for carbon (C), oxygen (O), iron (Fe), and copper (Cu). Figure 3 (b) shows the high-resolution spectrum in the C1s region. The C1s signals of 288.8 eV, 286.3 eV, and 284.8 eV are attributed to the C=O, CO, and CC components in the citric acid added during synthesis, respectively. For the Cu 2p spectrum (… Figure 3 (c)), Cu 2p 3 / 2 and Cu 2p 1 / 2The spin-orbit component exhibited two strong peaks at 933.2 eV and 953.2 eV, respectively, with a splitting width of approximately 20.0 eV, indicating the presence of Cu in the FeOOH quantum dot / CuFe2O4 composite material. 2+ The values ​​of 941.7 eV and 961.4 eV are attributed to satellite observations. For the high-resolution spectrum of O1s (… Figure 3 In the middle (d) spectrum, 533.4 eV is attributed to HOH in the adsorbed water, 531.4 eV to Fe-OH in FeOOH, and 529.9 eV to the Fe-O-Fe fast electron transfer channel formed between FeOOH and CuFe2O4, indicating that FeOOH was successfully doped onto CuFe2O4. The high-resolution spectrum of Fe 2p ( Figure 3 The middle (e) shows two strong peaks. Fe 2p 3 / 2 The binding energy is at 710.6 eV, and the oscillating satellite energy is at 719.8 eV. Fe 2p 1 / 2 The peaks were observed at 724.0 eV, while the satellite observed them at 732.7 eV. These two peaks are attributed to Fe in the FeOOH quantum dot / CuFe2O4 composite material. 3+ .

[0051] Photocatalytic performance testing of FeOOH quantum dot / CuFe2O4 composite material

[0052] Taking the degradation of methylene blue as an example, the degradation performance of the FeOOH quantum dot / CuFe2O4 composite material provided by this invention as a photocatalyst for organic dyes was tested. Specifically, a 300W xenon lamp with a cutoff filter (λ≥420nm) was used as a visible light source to degrade methylene blue to evaluate the performance of the FeOOH / CuFe2O4 photocatalyst.

[0053] First, the general testing process will be explained.

[0054] 100 mL of simulated methylene blue wastewater of a certain concentration was added to a 200 mL reactor. Under reaction conditions of room temperature and 150-200 rpm, 30 mg of photocatalyst was used to degrade methylene blue. The solution was stirred in the dark for 60 min to allow adsorption equilibrium. Then, the photocatalytic reaction was carried out for 3 hours under a 300 W xenon lamp and a 420 nm cutoff filter, with absorbance measured every 30 min. The remaining methylene blue content in the filtered methylene blue degradation solution was analyzed using a UV-Vis spectrophotometer (λ = 663 nm). (The sample was filtered using a 0.45 μm syringe filter before absorbance measurement).

[0055] The formula for calculating the degradation rate of methylene blue is as follows:

[0056] D(%)=[(C0-C t) / C0]×100%

[0057] Where D is the degradation rate of methylene blue, C0 is the initial concentration of methylene blue, and C t This represents the concentration of methylene blue after degradation.

[0058] Test Example 1 examines the methylene blue degradation performance of different catalysts.

[0059] 100 mL of 10 mg / L methylene blue simulated wastewater (pH = 7) was poured into the reactor. The above-mentioned test process was performed using 10% FeOOH quantum dots / CuFe2O4 prepared in Example 1, 20% FeOOH quantum dots / CuFe2O4 prepared in Example 2, 30% FeOOH quantum dots / CuFe2O4 prepared in Example 3, and pure CuFe2O4 as catalysts, respectively. The results are as follows: Figure 4 As shown.

[0060] from Figure 4 It can be seen that after stirring for 60 min in the dark, none of the catalysts showed any adsorption effect on methylene blue (MB). After 180 min of photoreaction, the degradation rate of methylene blue by CuFe2O4 was 52.7%. For 10% FeOOH quantum dots / CuFe2O4, the degradation rate of methylene blue after 180 min of photoreaction was 88.67%, which may be due to the limited number of active sites. The 20% FeOOH quantum dot / CuFe2O4 photocatalyst showed the best degradation ability, with a degradation rate of 91.5% of methylene blue after 180 min of photoreaction. However, for 30% FeOOH quantum dots / CuFe2O4, the degradation rate of methylene blue after 180 min of photoreaction was 87.42%. This may be because excessive FeOOH tends to aggregate, thus preventing the formation of fast channels, reducing the number of active sites, and leading to a decrease in degradation ability.

[0061] Test Example 2: Catalyst Stability Test

[0062] Furthermore, taking 20% ​​FeOOH quantum dots / CuFe2O4 as an example, the stability of the FeOOH quantum dot / CuFe2O4 composite material provided by this invention as a photocatalyst was investigated, and the results are as follows: Figure 5 As shown in (a) and (b), the figure demonstrates relatively good long-term stability over five consecutive operations (20 h). Fresh simulated wastewater was replaced periodically each time. It can be seen that the degradation rate of 20% FeOOH quantum dots / CuFe2O4 decreased by only 10.85% after five cycles, exhibiting good stability.

[0063] Test Example 3 investigated the effect of methylene blue concentration on degradation performance.

[0064] Using 30 mg of 20% FeOOH quantum dots / CuFe2O4 as a photocatalyst, degradation experiments were conducted on methylene blue solutions (pH=7) at concentrations of 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, and 30 mg / L, respectively, following the commonly used testing procedure described above. The degradation rates at different methylene blue concentrations are shown below. Figure 6 As shown.

[0065] from Figure 6 As can be seen, when the methylene blue concentration is 10 mg / L, the 20% FeOOH quantum dot / CuFe2O4 photocatalyst has the highest degradation rate, and the methylene blue degradation rate reaches 91.5% after 180 min of visible light irradiation.

[0066] Test Example 4 examines the effect of wastewater pH on the degradation performance of methylene blue.

[0067] Simulated wastewater with a methylene blue concentration of 10 mg / L and pH values ​​of 3, 5, 7, 9, and 11 was prepared. Following the general testing procedure described above, 30 mg of 20% FeOOH quantum dot / CuFe2O4 photocatalyst was used for degradation. The degradation rates at different wastewater pH values ​​are as follows: Figure 7 As shown.

[0068] from Figure 7 As can be seen, when the pH value is 9, the 20% FeOOH quantum dot / CuFe2O4 photocatalyst exhibits the best degradation performance for methylene blue, with a degradation rate of 99.99% after 180 min of visible light irradiation.

[0069] To understand the electron transfer pathway during the photocatalytic reaction, electrochemical analysis was performed on the material. First, the visible light absorption capacity of the material was tested, and the ultraviolet-visible diffuse reflectance spectrum was measured (e.g., ...). Figure 8 In Figure (a), all five materials exhibit good light absorption in the visible light range. The maximum absorption wavelength of CuFe₂O₄ is around 550 nm, while that of FeOOH quantum dots is around 450 nm. Combining the two materials shifts the maximum absorption wavelength to around 500 nm, and the FeOOH quantum dot-loaded CuFe₂O₄ material shows even stronger light absorption. This indicates that the loading of FeOOH quantum dots enhances the visible light absorption range of CuFe₂O₄. Different percentages of FeOOH quantum dot loading also affect visible light absorption: the 20% FeOOH quantum dot / CuFe₂O₄ composite material shows the strongest absorption, followed by the 10% FeOOH quantum dot / CuFe₂O₄ composite material, and the 30% FeOOH quantum dot / CuFe₂O₄ composite material shows the weakest absorption. Furthermore, the band gap of each material is calculated based on the diffuse reflectance spectra. Figure 8As shown in (b), the band gap of CuFe2O4 is 1.579 eV, while that of FeOOH quantum dots is 1.698 eV. With the introduction of FeOOH quantum dots, the band gap of the FeOOH quantum dot / CuFe2O4 composite material begins to increase, reaching a maximum of 1.616 eV with 20% FeOOH quantum dots / CuFe2O4, while the band gap of 30% FeOOH quantum dots / CuFe2O4 begins to decrease. Introducing different proportions of FeOOH quantum dots also has different effects on the band gap width of the samples. To study the transfer of photogenerated electrons at the semiconductor-electrolyte interface, electrochemical impedance spectroscopy (EIS) was performed. Figure 8 Figure (c) shows the electrochemical impedance of five materials. The impedances of FeOOH quantum dots and CuFe2O4 are significantly higher, indicating that the electron-hole recombination rate of FeOOH quantum dots and CuFe2O4 is extremely high. However, when the two materials are combined, the electrochemical impedance decreases significantly, with the 20% FeOOH quantum dot / CuFe2O4 composite material exhibiting the lowest electrochemical impedance. Due to the introduction of FeOOH quantum dots, the photogenerated electrons in the FeOOH quantum dot / CuFe2O4 composite material transfer more rapidly, reducing electron-hole recombination and thus generating more active free radicals, thereby improving photocatalytic activity. The recombination rate of photogenerated electrons and holes in a photocatalyst is inseparable from its photoelectric conversion performance. The transient photocurrent response is used to evaluate the carrier separation ability and the separation rate of photogenerated holes and electrons in a photocatalyst. Therefore, to study the electron-hole pair separation efficiency of the prepared materials, their transient photocurrent performance (e.g., ...) was investigated. Figure 8 As shown in Figure (d), all five materials exhibit significant and relatively stable photocurrent responses. However, the photocurrent response of pure CuFe2O4 is significantly lower than that of the composite material. This is because the introduction of FeOOH quantum dots excites photogenerated electrons from the valence band to the conduction band of CuFe2O4, which then rapidly transfer to the working electrode. The photogenerated electrons in the conduction band quickly transfer to the FeOOH quantum dots, thereby improving the efficiency of charge separation. The 20% FeOOH quantum dot / CuFe2O4 composite material shows the best photocurrent response, followed by 10% FeOOH quantum dot / CuFe2O4, while 30% FeOOH quantum dot / CuFe2O4 shows the worst response, which is consistent with previous electrochemical impedance spectroscopy results.

[0070] The above analysis and tests demonstrate that the FeOOH quantum dot / CuFe2O4 composite material provided by this invention accelerates the separation of photogenerated electron-hole pairs by forming a Fe-O-Fe electron rapid transfer channel between FeOOH quantum dots and CuFe2O4, thereby generating more active free radicals to degrade methylene blue. After 180 min of photoreaction with the FeOOH quantum dot / CuFe2O4 catalyst, the degradation rate of methylene blue is 99.99%, significantly higher than that of previously reported CuFe2O4-ZnO heterojunction nanocomposites.

[0071] Moreover, the FeOOH quantum dot / CuFe2O4 composite material provided by this invention also exhibits excellent cycle stability as a photocatalyst.

[0072] Furthermore, since FeOOH and CuFe2O4 possess certain magnetic properties, the FeOOH quantum dot / CuFe2O4 composite photocatalyst provided by this invention is easy to recycle and is more environmentally friendly.

[0073] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A FeOOH quantum dot / CuFe2O4 composite material, characterized in that, include: CuFe2O4 nanosheets, and FeOOH quantum dots loaded on the CuFe2O4 nanosheets; The FeOOH quantum dot / CuFe2O4 composite material is prepared by CuFe2O4 and trivalent iron salt at a mass ratio of 1:0.

2.

2. The FeOOH quantum dot / CuFe2O4 composite material according to claim 1, characterized in that, The FeOOH quantum dots and the CuFe2O4 nanosheets form a heterojunction.

3. The FeOOH quantum dot / CuFe2O4 composite material according to claim 1, characterized in that, The ferric salt is FeCl3·6H2O.

4. The FeOOH quantum dot / CuFe2O4 composite material according to claim 1, characterized in that, According to energy-dispersive X-ray spectroscopy, in the FeOOH quantum dot / CuFe2O4 composite material, O accounts for 62.89% of the total number of atoms, Fe accounts for 21.19%, and Cu accounts for 15.92%.

5. The method for preparing the FeOOH quantum dot / CuFe2O4 composite material according to any one of claims 1-4, characterized in that, include: CuFe₂O₄ and a ferric salt were mixed in an organic solvent, sonicated, and then KHCO₃ was added to obtain a reaction mixture. The CuFe₂O₄ and the ferric salt were mixed at a mass ratio of 1:0.2, and KHCO₃ was in molar excess relative to the ferric salt. The reaction mixture was stirred for 6-10 hours to obtain the FeOOH quantum dot / CuFe2O4 composite material.

6. The preparation method according to claim 5, characterized in that, The organic solvent is ethanol.

7. Use of the FeOOH quantum dot / CuFe2O4 composite material according to any one of claims 1-4 as a photocatalyst.

8. A method for treating wastewater containing organic dyes, characterized in that, include: Wastewater containing organic dyes is mixed with the FeOOH quantum dot / CuFe2O4 composite material according to any one of claims 1-4 to obtain a mixture to be treated; The mixture to be treated is kept under visible light irradiation for at least 120 minutes.

9. The processing method according to claim 8, characterized in that, The organic dye is methylene blue.

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