Preparation method and application of metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane

Abstract

The invention belongs to the technical field of photocatalysis, and relates to a metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane as well as a preparation method and application thereof. The invention relates to a metal organic framework AE / Fe-MOF-PVDF (Polyvinylidene Fluoride) photocatalytic membrane, which is formed by introducing AE (Aloe-emodin) into Fe-MOF to construct a heterojunction and immobilizing the heterojunction on a PVDF membrane. In the heterojunction, the mass ratio of AE to Fe is (0.5-2): 1. The metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane prepared by the method has a self-cleaning effect, pollution of the PVDF membrane is avoided, the utilization rate of the membrane is improved, meanwhile, the separation efficiency of photon-generated carriers can be promoted, and the photocatalytic degradation efficiency of macromolecular substances in traditional Chinese medicine wastewater is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photocatalysis, and relates to a metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane as well as a preparation method and application thereof. BACKGROUND

[0002] Water pollution and destruction have become one of the important factors restricting the development of environmental health, especially the wastewater generated by the traditional Chinese medicine pharmaceutical industry, because of the characteristics of complex and variable composition, a large number of types of organic pollutants, and significant differences in wastewater from different manufacturers, etc., it has become one of the high-concentration organic wastewater that is difficult to treat; these organic pollutants are difficult to degrade, have strong toxicity, and if they enter the water body, they will remain for a long time, and then cause a series of health problems. Therefore, realizing the recycling of traditional Chinese medicine pharmaceutical wastewater is not only a key research direction for comprehensive prevention and control of water pollution and purification of water environment, but also a necessary way for traditional Chinese medicine industry to realize green development and industrial upgrading.

[0003] At present, the common treatment methods of water pollution include flocculation sedimentation, adsorption and membrane separation method, etc., among which the membrane separation method has the characteristics of simple operation process, energy saving and high efficiency, green environmental protection, etc., and is one of the most promising treatment technologies. However, as we all know, the core of membrane separation technology is membrane material, and its performance directly determines the separation efficiency, operation cost, equipment life and application feasibility. Referring to the Chinese invention patent document with publication number CN105396468A, a PVDF separation membrane (PVDF membrane for short) is disclosed, which has a special molecular structure (-CF2-CH2-CF2-CH2-)n, and has the characteristics of high temperature resistance, aging resistance and organic solvent resistance, and is widely used in wastewater separation; however, it is mainly used for the separation of high-difficulty industrial wastewater, because when this membrane is used to treat traditional Chinese medicine wastewater for a long time, the macromolecular substances (such as tannins) in traditional Chinese medicine wastewater will adhere to the surface of the PVDF separation membrane, which cannot be degraded, so as to accumulate around the membrane holes or penetrate into the internal structure of the membrane, thereby causing membrane pollution, greatly reducing the utilization rate of the PVDF membrane, and thus limiting the application of the PVDF membrane.

[0004] The photocatalytic membrane is a functional composite material of photocatalysis technology and membrane separation technology, and the core is to combine the photocatalyst (TiO2) with the traditional membrane material (such as PVDF membrane, etc.), which solves the problem of membrane pollution of traditional membrane separation. Referring to the Chinese invention patent document with publication number CN111905811A, a PVDF / TiO2 composite photocatalytic membrane is disclosed, but the separation efficiency of photo-generated carriers of this composite photocatalytic membrane is low, which leads to low photocatalytic degradation efficiency of macromolecular substances in traditional Chinese medicine wastewater. SUMMARY

[0005] In view of the problems in the prior art that the PVDF membrane is easily polluted, the utilization rate is reduced, and the separation efficiency of photogenerated carriers of the composite photocatalytic membrane is low, resulting in low photocatalytic degradation efficiency of macromolecular substances in traditional Chinese medicine wastewater, a metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane and a preparation method and application thereof are provided.

[0006] The metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane is prepared by introducing an organic small molecule of an anthraquinone type of traditional Chinese medicine, aloe emodin (AE), into a metal organic framework Fe-MOF and supporting the aloe emodin (AE) on a PVDF membrane. The metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane has a self-cleaning effect, avoids pollution of the PVDF membrane, improves the utilization rate of the membrane, promotes the separation efficiency of photogenerated carriers, and improves the photocatalytic degradation efficiency of macromolecular substances in traditional Chinese medicine wastewater.

[0007] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0008] The metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane is prepared by introducing aloe emodin (AE) into Fe-MOF to construct a heterojunction and supporting the heterojunction on a PVDF membrane. In the heterojunction, the mass ratio of AE to Fe is (0.5-2):1.

[0009] The preparation method of the metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane comprises the following steps:

[0010] S1, membrane pretreatment

[0011] The PVDF membrane is soaked and pretreated to obtain a pretreated PVDF membrane.

[0012] S2, preparation of AE / Fe-MOF powder

[0013] S2.1, FeCl3·6H2O and terephthalic acid are dissolved in N,N-dimethylformamide to obtain a mixed solution A by ultrasonic treatment;

[0014] S2.2, aloe emodin (AE) is dispersed in the mixed solution A to obtain a mixed solution B by ultrasonic mixing;

[0015] S2.3, the mixed solution B is transferred to a reaction kettle for heating to obtain a solid precipitate; then the solid precipitate is washed, dried and ground to obtain the AE / Fe-MOF powder, i.e., the constructed heterojunction;

[0016] S3, preparation of the metal organic framework AE / Fe-MOF-PVDF photocatalytic membrane

[0017] The AE / Fe-MOF powder is dispersed in a water / absolute ethanol solution in a certain ratio, ultrasonic mixing is carried out, then the pretreated PVDF film in step S1 is put in, and ultrasonic treatment is carried out, so that the metal organic framework AE / Fe-MOF-PVDF photocatalytic film is obtained.

[0018] With further limitation, in the step S1, the soaking pretreatment is that the PVDF is soaked in absolute ethanol for 1h-12h.

[0019] With further limitation, in the step S2.1, the mass ratio of FeCl3.6H2O to terephthalic acid is (2.5-5):1 in every (10-50)mL N,N-dimethylformamide.

[0020] With further limitation, in the step S2.2, the power of ultrasonic is 30-100Hz, and the ultrasonic time is 40-80min.

[0021] With further limitation, in the step S2.3, the heating temperature is 90-150 DEG C, and the heating time is 24-40h.

[0022] With further limitation, in the step S3, the power of ultrasonic is all 30-100Hz, and the ultrasonic time is all 40-80min.

[0023] The application of the metal organic framework AE / Fe-MOF-PVDF photocatalytic film in the degradation of macromolecular substances in traditional Chinese medicine wastewater.

[0024] Compared with the prior art, the application has the beneficial effects that:

[0025] 1、The anthraquinone organic small molecule aloe emodin AE is reacted with the metal organic framework Fe-MOF to form the Fe metal organic framework AE / Fe-MOF, and a heterojunction is constructed; the aloe emodin is used as an electron transfer channel and has the characteristics of light-generated carriers, and based on the strong pi-electron delocalization effect of the AE, the Fe-MOF can be effectively activated, and the separation of the photo-generated electron-hole pairs of the Fe-MOF is accelerated, so that the separation efficiency of the carriers in the Fe-MOF and the circulation ability of the Fe 3+ / Fe 2+ are improved, and the photocatalytic degradation efficiency of the organic pollutants is improved, and the performance of the organic pollutants treated by the photo-Fenton process is significantly improved.

[0026] 2、The Fe metal organic framework AE / Fe-MOF is successfully loaded on the PVDF film to obtain the photocatalytic film, so that the in-situ photo-Fenton degradation of the pollutants on the surface and in the channel of the film can be realized, the self-cleaning of the contaminated film is realized, the service life of the film is enhanced, and after the photocatalyst is loaded, the photocatalyst is convenient to recycle, so that the whole reaction system can be continuously and effectively and stably operated.

[0027] 3. The Fe-based metal-organic framework AE / Fe-MOF-PVDF membrane of the present invention has a relatively stable structure and performance, and can be recycled in the photo-Fenton treatment of traditional Chinese medicine wastewater.

[0028] 4. This invention uses a co-precipitation ultrasonic method to construct and prepare Fe-based metal-organic frameworks AE / Fe-MOF-PVDF. The process is simple, fast, easy to implement, low in cost, high in yield, and has good prospects for industrialization.

[0029] 5. The Fe-based metal-organic framework AE / Fe-MOF-PVDF prepared by this invention has excellent photocatalytic degradation efficiency, degrades pollutants on the membrane in situ, gives the PVDF membrane self-cleaning properties and can maintain high membrane flux, promotes the degradation of macromolecular substances in traditional Chinese medicine wastewater, and improves photocatalytic degradation efficiency. Attached Figure Description

[0030] Figure 1 SEM surface and cross-sectional images of pure PVDF membrane and AE / Fe-MOF-PVDF prepared in Example 2 of this invention;

[0031] Figure 2 XRD patterns of Fe-MOF-PVDF and AE / Fe-MOF-PVDF prepared in the embodiments of the present invention;

[0032] Figure 3 Photocurrent-time (it) analysis charts (electrochemical test charts) of AE, Fe-MOF, and AE / Fe-MOF prepared for embodiments of the present invention;

[0033] Figure 4 The degradation effect of metal-organic frameworks AE / Fe-MOF-PVDF at different mass ratios prepared in the embodiments of the present invention on tannins is shown in the figure.

[0034] Figure 5 The graph shows the degradation effect of AE / Fe-MOF-PVDF prepared in Example 2 of this invention on tannins under different reaction conditions. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but the embodiments of the present invention are not limited thereto. Other methods for preparing the compounds of the present invention, with some conventional modifications to the reaction conditions according to the present invention, are considered to be within the scope of the present invention.

[0036] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0037] The technical concept of this invention is to introduce anthraquinone organic small molecules (AE) from traditional Chinese medicine into Fe-MOF and immobilize them on a PVDF membrane to prepare a metal-organic framework AE / Fe-MOF-PVDF membrane, which solves the problem of PVDF membranes being easily fouled during long-term use, and applies it to the degradation of traditional Chinese medicine wastewater.

[0038] Metal-organic frameworks (MOFs) have attracted widespread attention due to their excellent chemical and thermal stability, high porosity, and high surface area, providing abundant active sites for their interactions with surrounding molecules or ions. Fe-MOFs, in particular, possess abundant hydrogen-rich organic ligands and amino groups, further enhancing their compatibility with other molecules through hydrogen and covalent bonds. However, they still exhibit Fe... 3+ / Fe 2+ To address the shortcomings of low redox cycle and high electron-hole recombination rate, we modified it by adding a co-catalyst.

[0039] Aloe-emodin (AE) is a photosensitizer widely distributed in plants such as rhubarb, Polygonum multiflorum, aloe, madder, and cassia seed. It belongs to the hydroxyanthraquinone class, with hydroxyl groups flanking a benzene ring. It is a monoanthraquinone 1,8-dihydroxyanthraquinone derivative, possessing a phenolic hydroxyl group, a carbonyl group, and a complete large π-bond conjugated system in its molecular structure, exhibiting strong hyperlocalization and redox properties. More importantly, aloe-emodin has a quinone structure, belonging to the anthraquinone class of compounds, and can act as an electron transfer channel or a standalone main catalyst. It can not only function as an electron transfer channel, i.e., e - Within anthraquinone compounds, charge transfer occurs. Anthraquinone compounds can also act as host photocatalysts, absorbing light and generating photogenerated carriers, utilizing oxygen vacancies (h) in photoactive species. + It can also be oxidized to anthraquinone, which can effectively improve e - Increase the transfer rate, separate electron-hole pairs, and improve photocatalytic efficiency.

[0040] This invention introduces the anthraquinone organic small molecule aloe-emodin from traditional Chinese medicine into Fe-MOF to construct a heterojunction. The AE may be converted into the corresponding large conjugated ligand through a similar cyclodehydrogenation reaction, and react with Fe during the one-pot synthesis process. 3+ Coordination was performed and the substance was immobilized on a PVDF membrane. The photogenerated carriers and strong π-electron delocalization effect of aloe-emodin were utilized to effectively activate Fe-MOF, thereby improving the carrier separation efficiency and Fe content in Fe-MOF. 3+ / Fe 2+ The PVDF membrane's recycling capacity enhances its photocatalytic degradation efficiency for organic pollutants, enabling in-situ photo-Fenton degradation of pollutants on the PVDF membrane surface and within the channels, achieving self-cleaning of the contaminated membrane, and increasing the service life of the PVDF membrane.

[0041] The present invention provides a metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane, which is formed by introducing aloe-emodin AE into Fe-MOF to construct a heterojunction and immobilizing the heterojunction on a PVDF membrane; in the heterojunction, the mass ratio of AE to Fe is (0.5~2):1.

[0042] This invention provides a method for preparing a metal-organic framework (AE / Fe-MOF-PVDF) photocatalytic membrane, comprising the following steps:

[0043] S1, Membrane Pretreatment

[0044] PVDF is pretreated by immersion to obtain a pretreated PVDF membrane; preferably, the immersion pretreatment is to immerse PVDF in anhydrous ethanol for 1 h to 12 h.

[0045] S2. Preparation of AE / Fe-MOF powder

[0046] S2.1 Dissolve FeCl3·6H2O and terephthalic acid in N,N-dimethylformamide and sonicate to obtain mixed solution A; In this step, the mass ratio of FeCl3·6H2O to terephthalic acid added in each (10-50) mL of N,N-dimethylformamide is (2.5-5):1.

[0047] For example, when N,N-dimethylformamide is 10 mL, the added mass of FeCl3·6H2O is 0.025 g (or 0.05 g), and the added mass of terephthalic acid is 0.01 g. N,N-dimethylformamide can also be 20 mL, 30 mL, 40 mL, or 50 mL.

[0048] S2.2 Disperse AE in mixed solution A and ultrasonically mix to obtain mixed solution B; preferably, the ultrasonic power is 30-100Hz and the ultrasonic time is 40-80min.

[0049] S2.3. The mixed solution B is transferred to a reaction vessel and heated to obtain a solid precipitate; then washed, dried and ground to obtain AE / Fe-MOF powder, i.e. the constructed heterojunction;

[0050] S3. Preparation of metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane

[0051] AE / Fe-MOF powder is dispersed in a certain proportion of water / anhydrous ethanol solution and ultrasonically mixed; then placed into the pretreated PVDF membrane in step S1 and ultrasonically treated to obtain the final product.

[0052] Preferably, the heating temperature is 90–150°C, and the heating time is 24–40 h. The ultrasonic power is 30–100 Hz, and the ultrasonic time is 40–80 min.

[0053] This invention relates to the application of the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane in the degradation of macromolecules in traditional Chinese medicine wastewater.

[0054] The technical solution of the present invention will be described in detail below with reference to several embodiments.

[0055] It should be noted that, unless otherwise specified, the chemicals and reagents used in the following embodiments are all commercially available products commonly used in the field.

[0056] It should be noted that, unless otherwise specified, the operations used in the following embodiments are all conventional operations; for example, the operating temperature is always at room temperature unless otherwise specified. The test methods are all existing standard test methods in the art unless otherwise specified.

[0057] Example 1

[0058] The metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane provided in this embodiment is made by introducing AE into Fe-MOF and then immobilizing it on a PVDF membrane.

[0059] In this embodiment, the mass ratio of AE to Fe is 1:0.5.

[0060] This embodiment provides a method for preparing a metal-organic framework (AE / Fe-MOF-PVDF) photocatalytic membrane, including the following steps.

[0061] Step 1: Membrane Pretreatment

[0062] The PVDF membrane is pretreated by immersion to obtain a pretreated PVDF membrane.

[0063] Step 2: Dissolve 0.025g FeCl3·6H2O and 0.010g terephthalic acid in 40mL N,N-dimethylformamide (DMF) to prepare a solution, and sonicate to obtain mixed solution A;

[0064] Step 3: Disperse 0.05g of AE in the mixed solution A obtained in step 2, and sonicate to obtain mixed solution B.

[0065] Step 4: Transfer the mixed solution B obtained in Step 3 to a polytetrafluoroethylene-lined reactor and heat it at 120°C for 15 hours. The resulting solid precipitate is washed, dried, and ground to obtain AE / Fe-MOF powder.

[0066] Step 5: Disperse the AE / Fe-MOF powder obtained in Step 4 in 20 ml of water / anhydrous ethanol (V water:V ethanol = 1:1) solution and sonicate for 1 h to obtain a mixture.

[0067] Step 6: Place the PVDF membrane pretreated in Step 1 into the mixture from Step 5 and sonicate for 1 hour to obtain the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane.

[0068] Example 2

[0069] In this embodiment, the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane is made by introducing AE into Fe-MOF and then immobilizing it on a PVDF membrane.

[0070] In this embodiment, the mass ratio of AE to Fe is 1:1.

[0071] This embodiment provides a method for preparing a metal-organic framework (AE / Fe-MOF-PVDF) photocatalytic membrane, including the following steps.

[0072] Step 1: Membrane Pretreatment

[0073] The PVDF membrane is pretreated by immersion to obtain a pretreated PVDF membrane.

[0074] Step 2: Dissolve 0.05g FeCl3·6H2O and 0.010g terephthalic acid in 40mL N,N-dimethylformamide (DMF) to prepare a solution, and sonicate to obtain mixed solution A;

[0075] Step 3: Disperse 0.05g of AE in the mixed solution A obtained in step 2, and sonicate to obtain mixed solution B.

[0076] Step 4: Transfer the mixed solution B obtained in Step 3 to a polytetrafluoroethylene-lined reactor and heat it at 120°C for 15 hours. The resulting solid precipitate is washed, dried, and ground to obtain AE / Fe-MOF powder.

[0077] Step 5: Disperse the AE / Fe-MOF powder obtained in Step 4 in 20 mL of water / anhydrous ethanol (V water:V ethanol = 1:1) solution and sonicate for 1 h to obtain a mixture.

[0078] Step 6: Place the PVDF membrane pretreated in Step 1 into the mixture from Step 5 and sonicate for 1 hour to obtain the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane.

[0079] Example 3

[0080] In this embodiment, the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane is made by introducing AE into Fe-MOF and then immobilizing it on a PVDF membrane.

[0081] In this embodiment, the mass ratio of AE to Fe is 0.5:1.

[0082] This embodiment describes a method for preparing a metal-organic framework (AE / Fe-MOF-PVDF) photocatalytic membrane, comprising the following steps:

[0083] Step 1: Membrane Pretreatment

[0084] The PVDF membrane is pretreated by immersion to obtain a pretreated PVDF membrane.

[0085] Step 2: Dissolve 0.05g FeCl3·6H2O and 0.010g terephthalic acid in 40mL N,N-dimethylformamide (DMF) to prepare a solution, and sonicate to obtain mixed solution A;

[0086] Step 3: Disperse 0.025g of AE in the mixed solution A obtained in step 2, and sonicate to obtain mixed solution B.

[0087] Step 4: Transfer the mixed solution B obtained in Step 3 to a polytetrafluoroethylene-lined reactor and heat it at 120°C for 15 hours. The resulting solid precipitate is washed, dried, and ground to obtain AE / Fe-MOF powder.

[0088] Step 5: Disperse the AE / Fe-MOF powder obtained in Step 4 in 20 ml of water / anhydrous ethanol (V water:V ethanol = 1:1) solution and sonicate for 1 h to obtain a mixture.

[0089] Step 6: Place the PVDF membrane pretreated in Step 1 into the mixture from Step 5 and sonicate for 1 hour to obtain the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane.

[0090] To further illustrate the performance advantages of the AE / Fe-MOF-PVDF photocatalytic membrane prepared according to this invention, performance tests were conducted. Simultaneously, to verify the innovative aspects of this invention, the following comparative examples were designed.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing a Fe-MOF-PVDF photocatalytic membrane, including the following steps.

[0093] Step 1: Membrane Pretreatment

[0094] The PVDF membrane is pretreated by immersion to obtain a pretreated PVDF membrane.

[0095] Step 2: Dissolve 0.05g FeCl3·6H2O and 0.010g terephthalic acid in 40mL N,N-dimethylformamide (DMF) to prepare a solution, and sonicate to obtain mixed solution A;

[0096] Step 3: Transfer the mixed solution A obtained in Step 2 to a polytetrafluoroethylene-lined reactor and heat it at 120°C for 15 hours. The resulting solid precipitate is washed, dried, and ground to obtain Fe-MOF powder.

[0097] Step 4: Disperse the AE / Fe-MOF powder obtained in Step 3 in 20 ml of water / anhydrous ethanol (V water:V ethanol = 1:1) solution and sonicate for 1 h to obtain a mixture;

[0098] Step 5: Place the PVDF membrane pretreated in Step 1 into the mixture from Step 4 and sonicate for 1 hour to obtain the Fe-MOF-PVDF photocatalytic membrane.

[0099] Comparative Example 2

[0100] This comparative example provides a method for preparing a metal-organic framework material Fe-MOF, comprising the following steps:

[0101] Step 1: Dissolve 0.05g FeCl3·6H2O and 0.010g terephthalic acid in 40ml N,N-dimethylformamide (DMF) to prepare a solution, and sonicate to obtain mixed solution A;

[0102] Step 2: Transfer the mixed solution A obtained in Step 1 to a polytetrafluoroethylene-lined reactor and heat it at 120°C for 15 hours. The resulting solid precipitate is washed, dried, and ground to obtain a metal-organic framework material.

[0103] The performance tests of the products prepared in the comparative examples and embodiments are as follows.

[0104] Experiment 1, SEM test

[0105] SEM analysis was performed on pure PVDF membranes and the AE / Fe-MOF-PVDF photocatalytic membrane prepared in Example 2 with a mass ratio of AE to Fe of 1:1. The results are as follows: Figure 1 As shown in the figure. Where: a and b are scanning electron microscope images of the surface and cross-section of PVDF at 1 μm and AE / Fe-MOF-PVDF at 10 μm, respectively.

[0106] from Figure 1 The SEM images show that the pure PVDF membrane has a smooth surface and a porous structure. Compared with the pure PVDF membrane, the surface of the AE / Fe-MOF-PVDF photocatalytic membrane prepared in Example 2 is formed by irregular particle aggregation, indicating that the photocatalytic membrane prepared in this invention contains AE and Fe-MOF.

[0107] Experiment 2, XRD test

[0108] In this experiment, the Fe-MOF-PVDF prepared in the comparative example and the AE / Fe-MOF-PVDF photocatalytic membrane prepared in Example 2 with a mass ratio of AE to Fe of 1:1 were selected for XRD testing.

[0109] In this experiment, the XRD pattern of the self-cleaning membrane is as follows: Figure 2 As shown. The crystallinity and structure of the samples were analyzed by XRD. Both films exhibited characteristic peaks of PVDF reflection at 2θ = 18.2° and 20.3°, respectively. No composite characteristic peaks were observed on the films, which may be due to two reasons. Firstly, the signal from the PVDF film substrate itself was too strong, masking other peak signals. Secondly, only a portion of the catalyst entered the membrane pores.

[0110] Experiment 3: Photocurrent Time Analysis

[0111] The charge transfer performance of the catalyst was analyzed using transient photocurrent response.

[0112] AE, Fe-MOF, and the AE / Fe-MOF photocatalyst prepared in Example 2 with a mass ratio of 1:1 were analyzed for photocurrent time (It). The results are as follows: Figure 3 As shown.

[0113] Figure 3 The results show that, compared to AE and Fe-MOF, AE / Fe-MOF exhibits a higher photocurrent, implying the generation of more photogenerated electrons or a higher photogenerated electron transfer rate. These results indicate that the AE / Fe-MOF photocatalyst demonstrates excellent photocatalytic efficiency, which is beneficial for the efficient separation and transfer of the support.

[0114] Experiment 4. Degradation performance

[0115] The AE / Fe-MOF-PVDF photocatalytic membranes prepared in Examples 1 to 3 were used to degrade common high molecular weight tannins in traditional Chinese medicine wastewater.

[0116] The degradation experiment was conducted in a 500 mL glass beaker. The concentration of tannins in the herbal wastewater was 70 mg / L, and the total volume of the reaction system solution was 85 mL. First, dark adsorption was carried out for 1 hour in a dark room. Then, a 500 W xenon lamp (CEL-S500 / 350, Zhongjiao Jinyuan) was turned on, and 1.5 mL of H₂O₂ (0.01 M) was added for 1 hour of photo-Fenton degradation. Approximately 5 mL samples were taken every 15 minutes, filtered through a 0.45 μm needle filter, and the solution concentration was measured at 277 nm using a UV spectrophotometer.

[0117] See Figure 4 The AE / Fe-MOF-PVDF photocatalytic membranes prepared in Examples 1, 2, and 3 showed degradation rates of 80.14%, 86.88%, and 84.35% for common high molecular weight tannins in traditional Chinese medicine wastewater, respectively. The photocatalytic membrane in Example 2 showed the highest degradation efficiency for tannins in traditional Chinese medicine wastewater, indicating that the photocatalytic membrane formed when the mass ratio of AE to Fe is 1:1 has the best degradation effect.

[0118] Experiment 5: Degradation of common high molecular weight tannins in traditional Chinese medicine wastewater by photocatalytic membranes under different conditions

[0119] The AE / Fe-MOF photocatalyst membrane prepared in Example 2 with an AE to Fe mass ratio of 1:1 was degraded under different conditions; the concentration of tannins in the traditional Chinese medicine wastewater, the light source, H2O2 and other condition parameters during the degradation process were as described in Experiment 4.

[0120] (1) Blank group (AE / Fe-MOF-PVDF): Degradation of tannins in traditional Chinese medicine wastewater under conditions of no H2O2 and no light;

[0121] (2) AE / Fe-MOF-PVDF+H2O2: Degradation of tannins in traditional Chinese medicine wastewater by AE / Fe-MOF-PVDF photocatalytic membrane under conditions of adding H2O2 and not adding light;

[0122] (3) AE / Fe-MOF-PVDF+vis: Degradation of tannins in traditional Chinese medicine wastewater by AE / Fe-MOF-PVDF photocatalytic membrane under conditions of no H2O2 addition and light addition;

[0123] (4) AE / Fe-MOF-PVDF+vis+H2O2: Degradation of tannins in traditional Chinese medicine wastewater by AE / Fe-MOF-PVDF photocatalytic membrane under the conditions of adding H2O2 and light.

[0124] Figure 5 The degradation effects of the blank group, AE / Fe-MOF-PVDF+H2O2, AE / Fe-MOF-PVDF+vis, and AE / Fe-MOF-PVDF+vis+H2O2 were compared. The degradation rates were 1.276%, 57.80%, 65.09%, and 86.88%, respectively, demonstrating that the AE / Fe-MOF-PVDF photocatalytic membrane exhibited the best degradation rate for tannins under the combined effects of light and H2O2.

[0125] The above are several preferred embodiments of the preparation method of the present invention, but they should not be regarded as limitations on the technical solutions protected by the present invention. Any alternative solutions obtained by those skilled in the art based on the technical ideas of the present invention without creative labor should fall within the protection scope of the present invention.

Claims

1. A metal-organic framework (AE / Fe-MOF-PVDF) photocatalytic membrane, characterized in that, The heterojunction was constructed by introducing aloe-emodin (AE) into Fe-MOF and then immobilizing the heterojunction on a PVDF membrane; the mass ratio of AE to Fe in the heterojunction was (0.5–2):

1.

2. The method for preparing the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 1, characterized in that, Includes the following steps: S1, Membrane Pretreatment The PVDF membrane is pretreated by immersion to obtain a pretreated PVDF membrane; S2. Preparation of AE / Fe-MOF powder S2.1 Dissolve FeCl3·6H2O and terephthalic acid in N,N-dimethylformamide and sonicate to obtain mixed solution A; S2.2 Disperse aloe-emodin AE in mixed solution A and mix by ultrasonication to obtain mixed solution B; S2.

3. The mixed solution B is transferred to a reaction vessel and heated to obtain a solid precipitate; then washed, dried and ground to obtain AE / Fe-MOF powder, i.e. the constructed heterojunction; S3. Preparation of metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane AE / Fe-MOF powder was dispersed in a water-anhydrous ethanol solution and ultrasonically mixed; then placed into the pretreated PVDF membrane in step S1 and ultrasonically treated to obtain the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane.

3. The method for preparing the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 2, characterized in that, In step S1, the soaking pretreatment involves soaking PVDF in anhydrous ethanol for 1 to 12 hours.

4. The method for preparing the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 2, characterized in that, In step S2.1, the mass ratio of FeCl3·6H2O to terephthalic acid added in each (10-50) mL of N,N-dimethylformamide is (2.5-5):

1.

5. The method for preparing the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 2, characterized in that, In step S2.2, the ultrasonic power is 30-100Hz and the ultrasonic time is 40-80min.

6. The method for preparing the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 2, characterized in that, In step S2.3, the heating temperature is 90–150°C, and the heating time is 24–40 hours.

7. The method for preparing the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 2, characterized in that, In step S3, the ultrasonic power is 30-100Hz and the ultrasonic time is 40-80min.

8. The application of the metal-organic framework AE / Fe-MOF-PVDF photocatalytic membrane according to claim 1 in the degradation of macromolecular substances in traditional Chinese medicine wastewater.

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