A SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane and its preparation method and application

Abstract

The present invention relates to the field of ultrafiltration membrane technology, and in particular to an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane, and a preparation method and application thereof. Based on the Michael addition reaction, the present invention modifies MIL-101 nanoparticles with sulfonated dopamine, and prepares a hydrophilic polyethersulfone (PES) membrane by a blending modification method. First, an SPDA-modified MIL-101 nanomaterial is synthesized, and a PES ultrafiltration membrane is modified by blending and used to improve the filtration performance and anti-fouling performance of extracellular organic matter (EOM) of algae cells. The effects of SPDA-modified MIL-101 nanomaterials on the performance structure of ultrafiltration membranes at different addition amounts are further analyzed. The permeability and separation performance of the membrane are evaluated by pure water flux and pollution flux. The anti-fouling performance of the membrane is evaluated by the proportion of reversible pollution and irreversible pollution and the flux recovery rate through three cycles of alternating filtration of EOM solution and pure water.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrafiltration membranes, in particular to an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane and a preparation method and application thereof. Background Art

[0002] In recent years, the increasing frequency of algal blooms in surface waters has posed a significant challenge to drinking water safety. Suspended pollutants in high-algae water bodies, such as algal cells and their secreted extracellular organic matter (EOM), particularly the easily soluble and dispersible nature of EOM and its complex composition, are the primary cause of deteriorating effluent quality, impacting the effectiveness of conventional water treatment processes. Ultrafiltration has been proven to be an efficient, reliable, and feasible technology for treating high-algae water. Ultrafiltration technology can maintain the integrity of algal cells and avoid the problem of algal cell fragmentation, but problems such as low organic matter retention and severe membrane fouling still exist in high-algae water bodies.

[0003] Previous studies have shown that hydrophilic modification of ultrafiltration membranes can effectively mitigate membrane fouling. Mixed-matrix membranes are typically fabricated using methods such as blending with hydrophilic polymers, grafting hydrophilic monomers, coating, and blending with hydrophilic nanoparticles. Metal-organic frameworks (MOFs) offer significant advantages, including large surface area, structural tunability, and ease of functionalization, effectively improving the hydrophilicity and filtration capacity of ultrafiltration membranes. Wang et al. modified ultrafiltration membranes by blending UIO-66, improving humic acid removal while mitigating membrane fouling. Muayad et al. significantly improved the membrane's pure water flux and flux recovery rate by adding metal-organic frameworks (UIO-66 and UIO-66-NH2) to polyethersulfone, demonstrating enhanced anti-fouling properties. Furthermore, due to the poor compatibility of nanoparticles with the membrane matrix and their tendency to agglomerate, researchers often modify the nanoparticles to produce mixed-matrix membranes with improved performance. For example, nanoparticles have been modified with tannic acid or polydopamine to improve compatibility with the membrane matrix.

[0004] There are few reports on the preparation of mixed matrix membranes by modifying nanoparticles with sulfonated polydopamine. Summary of the Invention

[0005] The present invention is based on the Michael addition reaction, and MIL-101 nanoparticles are modified with sulfonated dopamine, and a hydrophilic polyethersulfone (PES) membrane is prepared by a blending modification method. First, SPDA-modified MIL-101 nanomaterials are synthesized, and the PES ultrafiltration membrane is modified by blending and used to improve the filtration performance and anti-fouling performance of extracellular organic matter (EOM) of algae cells. The effects of SPDA-modified MIL-101 nanomaterials on the performance and structure of ultrafiltration membranes at different addition amounts are further analyzed. The permeability and separation performance of the membrane are evaluated by pure water flux and pollution flux. The anti-fouling performance of the membrane is evaluated by the proportion of reversible pollution and irreversible pollution and the flux recovery rate through three cycles of alternating filtration of EOM solution and pure water.

[0006] The first aspect of the present invention provides a method for preparing an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane, comprising the following steps:

[0007] S1. Preparation of MIL-101: A CrCl3·6H2O aqueous solution and a PTA aqueous solution were stirred, heated to react, cooled to room temperature, centrifuged, and the precipitate was collected, washed, and dried to obtain MIL-101;

[0008] S2. Preparation of SPDA-modified MIL-101: MIL-101 was dispersed in the mixture and sonicated to form a suspension. Dopamine hydrochloride was added to the suspension, stirred, and Tris-HCl buffer was injected. After stirring for 12-24 hours, sodium 3-mercapto-1-propanesulfonate was added and the reaction was continued for 10-30 hours. The mixture was washed and centrifuged, and then vacuum-dried to obtain SPDA-modified MIL-101.

[0009] S3. Preparation of SPDA-modified MIL-101-modified polyethersulfone ultrafiltration membrane: PVP and SPDA-modified MIL-101 were dissolved in NMP, ultrasonically dispersed, and then added with dry PES and stirred for 10-30 hours. The membrane was allowed to stand for degassing, and a scraper was used to scrape the membrane on a glass plate to obtain the SPDA-modified MIL-101-modified polyethersulfone ultrafiltration membrane.

[0010] As a preferred embodiment, the mass ratio of CrCl3·6H2O to PTA is (2-3): (1-2).

[0011] As a preferred embodiment, the heating reaction is carried out at 200-220° C. for 10-15 hours.

[0012] As a preferred embodiment, the mass ratio of MIL-101 to dopamine hydrochloride is (0.05-1): (0.05-1).

[0013] As a preferred embodiment, the mixed liquid is a mixed liquid of deionized water and anhydrous ethanol, and the mass ratio of deionized water to anhydrous ethanol is (1-2): (1-2).

[0014] As a preferred embodiment, the mass ratio of the SPDA-modified MIL-101, PVP and PES is (0.05-0.2):1:16.

[0015] The second aspect of the present invention provides an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane obtained by the above preparation method.

[0016] The third aspect of the present invention provides an application of an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane in sewage treatment.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention uses MIL-101 as raw material, synthesizes SPDA-modified MIL-101 nanomaterials by adhesion modification of sulfonated polydopamine, adds SPDA-modified MIL-101 into PES casting solution by blending modification method, and prepares modified ultrafiltration membrane by non-solvent-induced phase separation.

[0019] 2. This study successfully prepared a SPDA-modified MIL-101 nanomaterial by modifying the surface of MIL-101 with sulfonated polydopamine. This material not only possesses the structural characteristics of MIL-101 but also shares the hydrophilicity and electronegativity of sulfonated polydopamine, providing a foundation for the subsequent preparation of ultrafiltration membranes.

[0020] 3. Through the study of water contact angle, membrane surface electronegativity, irreversible contamination degree, etc., it is proved that the addition of SPDA modified MIL-101 improves the membrane pore structure of ultrafiltration membrane, increases hydrophilicity and electronegativity, and thus increases the water flux of ultrafiltration membrane. 254 Retention rate and anti-pollution ability.

[0021] 4. By comparing the modified membranes, the ultrafiltration membrane with 0.1wt% SPDA modified MIL-101 has the best comprehensive performance, with a membrane water contact angle of 54.89° and a water flux of 540L / (m 2 h), UV 254 The rejection rate increased by 16%, and the flux recovery rate after three cycles reached 89%, providing a solid foundation for the application of ultrafiltration in high-algae water. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The micromorphology and elemental surface distribution spectrum of MIL-101 and SPDA modified MIL-101, Figure 1(a) is MIL-101, Figure 1 (b) SPDA-modified MIL-101.

[0023] Figure 2 This is the elemental composition diagram of SPDA-modified MIL-101.

[0024] Figure 3 XPS and FTIR spectra of MIL-101 and SPDA-modified MIL-101.

[0025] Figure 4 The surface morphology and structure analysis diagram of the ultrafiltration membrane at different addition amounts of SPDA-modified MIL-101.

[0026] Figure 5 This is the water contact angle and Zeta potential diagram of the ultrafiltration membrane.

[0027] Figure 6 This is a graph showing ultrafiltration membrane flux and UV254 rejection rate.

[0028] Figure 7 This is the ultrafiltration membrane flow rate diagram and pollution degree diagram.

[0029] Figure 8 The absorbance diagram of EOM solution and permeate measured by UV-visible spectrophotometer. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] Polyethersulfone PES (Mn = 100000) was purchased from BASF AG, Germany, analytical grade;

[0032] N-Methylpyrrolidone (NMP) was provided by Aladdin and was of analytical grade;

[0033] Polyvinylpyrrolidone (PVP) K30 was purchased from Tianjin Zhonglian Chemical Reagent Co., Ltd. and was of analytical grade;

[0034] Dopamine hydrochloride (PDA) was purchased from Shanghai McLean Reagent with a purity of 98%;

[0035] Tris-HCl buffer was purchased from Xiamen Aimimanni Biotechnology Co., Ltd. and was analytical grade;

[0036] Chromium trichloride hexahydrate (CrCl3·6H2O) was purchased from Shanghai Aladdin Reagent with a purity of 98%;

[0037] Terephthalic acid (PTA) was purchased from Shanghai Aladdin Reagent with a purity of 99%;

[0038] Sodium 3-mercapto-1-propanesulfonate was purchased from Shanghai Aladdin Reagent with a purity of 98%.

[0039] Example 1

[0040] This embodiment provides an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane, the preparation method of which includes the following steps:

[0041] S1. Preparation of MIL-101: 2.66 g of CrCl3·6H2O was dissolved in 45 mL of deionized water, and 1.66 g of PTA was dissolved in 45 mL of deionized water. The two solutions were mixed and stirred, dried in an oven at 210°C for 12 hours, cooled to room temperature, centrifuged, and the precipitate was collected. The precipitate was washed alternately with deionized water and ethanol to remove impurities and dried to obtain MIL-101.

[0042] S2. Preparation of SPDA-modified MIL-101: 0.1 g of MIL-101 was dispersed in 60 mL of a mixture (V(deionized water) : V(ethanol) = 1:1) and sonicated for 10 min to form a suspension. 0.1 g of dopamine hydrochloride was added to the suspension, stirred, and 20 mL of Tris-HCl buffer was injected. After stirring for 12 h, 0.1 g of sodium 3-mercapto-1-propanesulfonate was added and the reaction continued for 12 h. The suspension was washed, centrifuged, and vacuum-dried to obtain SPDA-modified MIL-101.

[0043] S3. Preparation of SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane: According to the mass percentage, 1% PVP and 0.1% SPDA-modified MIL-101 were dissolved in 82.95% NMP, and after ultrasonic dispersion, 16% dry PES was added and stirred for 12 hours. The membrane was allowed to stand for degassing, and a 150μm scraper was used to scrape the membrane on a glass plate to obtain the SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane. The membrane was stored in deionized water, and the water was changed every 12 hours.

[0044] Example 2

[0045] This embodiment provides a SPDA-modified MIL-101-modified polyethersulfone ultrafiltration membrane. The specific implementation is the same as that of Example 1, except that 0% SPDA is added to S3 to modify MIL-101.

[0046] Example 3

[0047] This embodiment provides a SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane. The specific implementation is the same as that of Example 1, except that 0.05% SPDA is added to S3 to modify MIL-101.

[0048] Example 4

[0049] This embodiment provides a SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane. The specific implementation is the same as that of Example 1, except that 0.15% SPDA is added to S3 to modify MIL-101.

[0050] Example 5

[0051] This embodiment provides a SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane. The specific implementation is the same as that of Example 1, except that 0.2% SPDA is added to S3 to modify MIL-101.

[0052] Performance Testing

[0053] The following tests were performed on the MIL-101, SPDA-modified MIL-101 (hereinafter referred to as modified nanoparticles), and SPDA-modified MIL-101-modified polyethersulfone ultrafiltration membrane (hereinafter referred to as ultrafiltration membrane) prepared in the above examples:

[0054] (1) Structure and performance characterization

[0055] ① The microstructure and element distribution spectrum of the modified nanoparticles were analyzed by SEM. Figure 1 . Figure 1 (a) It can be observed that MIL-101 exhibits an octahedral morphology with a particle size between 200 nm and 300 nm, which is a typical feature of MIL-101 crystals. Figure 1 (b) SPDA-modified MIL-101 exhibits a similar octahedral morphology with little change in particle size, but the lattice plane is slightly rough, and is a structure wrapped in a polydopamine shell.

[0056] ② Use XPS to analyze the elemental composition of modified nanoparticles. Figure 2 As can be seen from the figure, MIL-101 contains Cr, O, and C elements, and N and S elements appear in the dopamine after oxidation self-healing, further indicating that the sulfonated polydopamine coating is successfully coated on MIL-101. Figure 3 (a) The N1s and S2P characteristic peaks appearing in the XPS graph also indicate the successful loading of sulfonic acid groups.

[0057] ③ Use FTIR to analyze the functional group composition of modified nanoparticles with a scanning range of 4000-500 cm -1 The results are shown in Figure 3 From the FTIR spectrum Figure 3 (b) It can be seen that 1018 and 748 cm -1 The characteristic peak appears due to the vibration of the benzene ring inside the nanoparticles. -1 The peak at 1168cm is the characteristic peak of Cr-O stretching vibration. -1 The characteristic peak at 3400cm is caused by the vibration of sulfonic acid group. -1 The broad absorption peak is caused by the vibration of -OH or -NH functional groups in dopamine. The above results show that the modification of sulfonated polydopamine nanoparticles (SPDA modified MIL-101) is successful.

[0058] ④Use SEM to analyze the microstructure of the ultrafiltration membrane; use AFM to analyze the surface roughness of the ultrafiltration membrane. Figure 4 . When added in small amounts, such as M1 (Example 3) and M2 (Example 1), the membrane surfaces show a smooth and flat morphology; with the further addition of nanoparticles, nanoparticles gradually appear on the surfaces of M3 (Example 4) and M4 (Example 5). At an addition amount of 0.1wt%, as shown in Figure M2 (Example 1), the nanoparticles are evenly dispersed and the surface is smooth and flat. This is because polydopamine increases the compatibility between the membrane matrix and the nanoparticles. However, when the addition amount is greater than 0.1wt%, the nanoparticles agglomerate on the surface and the surface is noticeably rough. Membrane surface roughness AFM, such as Figure 4 As shown in the figure, the surface roughness of the membrane shows a trend of first decreasing and then increasing. The high hydrophilicity of the nanoparticles leads to the acceleration of the phase separation process, resulting in a smoother surface. The subsequent increase in roughness is because the nanoparticles increase the viscosity of the casting solution, delay the phase separation process, and cause the aggregation of nanoparticles, resulting in greater roughness.

[0059] ⑤Analysis of membrane pore structure of all membranes Figure 4 As shown in the cross-sectional SEM. As can be seen from the figure, all ultrafiltration membranes are composed of three parts: bottom voids, middle finger-like pores and a dense sponge-like pore structure at the top of the membrane. From M0 (Example 2) to M2 (Example 1), with the addition of nanoparticles, the pore structure changes from an inclined to a straight form. The straight pore structure is more conducive to the passage of water molecules, thereby improving the water permeability of the ultrafiltration membrane. From M2 (Example 1) to M4 (Example 5), with the continued addition of nanoparticles, the pore structure continues to change to an inclined state, and the voids in the bottom layer of the ultrafiltration membrane are all improved. This enhanced structure can improve the mechanical properties of the ultrafiltration membrane and is more conducive to practical applications.

[0060] ⑥ Use contact angle / surface tension meter to analyze the water contact angle of ultrafiltration membrane; use solid surface Zeta potential tester to analyze the surface Zeta potential of ultrafiltration membrane. Figure 5Generally speaking, membrane surface hydrophilicity is an important indicator for evaluating membrane performance, and it plays a vital role in improving permeability and anti-fouling performance. Figure 5 The water contact angle of membrane M0 (Example 2) shown in (a) is 71°. After adding varying amounts of SPDA to modify MIL-101, the membrane contact angles initially decrease and then increase, with the lowest being 54.89° for membrane M2 (Example 1). Because sulfonated polydopamine-modified MIL-101 has good hydrophilicity, the addition of nanoparticles can enhance the membrane's surface hydrophilicity.

[0061] Since most pollutants carry negative charges, increasing the electronegativity of the membrane surface can enhance the charge repulsion between pollutants and the membrane surface, thereby improving the membrane's anti-pollution ability. Figure 5 (b) The membrane surface carries a negative charge at pH = 7. This is because the number of hydroxyl and sulfonic acid groups in the modified nanoparticles increases, which increases the electronegativity of the membrane surface. As the pH increases from 5 to 9, the Zeta potential of the original membrane decreases from -19mV to -41mV, while the M2 (Example 1) membrane decreases from -21mV to -60mV. Compared with the unmodified membrane, the electronegativity of the Zeta potential of the modified membrane increases by 1.77 times. This is related to the abundant hydroxyl and sulfonic acid groups provided by sulfonated polydopamine. The increased electronegativity can better repel negatively charged pollutants and provide better anti-pollution ability.

[0062] ⑦Use UV-visible spectrophotometer to measure the absorbance of EOM solution and permeate. Figure 8 .

[0063] (2) Porosity and pore size analysis of ultrafiltration membrane

[0064] The porosity and average pore size of the ultrafiltration membrane were measured using the wet-dry gravimetric method. The wet membrane was the ultrafiltration membrane prepared in Example S3 and stored in water, and the dry membrane was the wet membrane dried to a constant weight.

[0065] Wet film (4cm 2 ) was first weighed and then dried at 100°C for 12 hours. The porosity (ε) was calculated as:

[0066]

[0067] Where W1 and W2 are the weights of wet and dry films, respectively, and ρ is the density of water (g / cm 3 ), A is the membrane area (cm 2 ), l (cm) is the thickness of the film.

[0068] The average pore size r of the membrane was calculated by the Guerout-Elford-Ferry equation (2).

[0069]

[0070] Where η is the viscosity of water (pa·s), Q is the volume of permeated water (m 3 / s), ΔP is the working pressure (Pa).

[0071] The results are shown in Table 1.

[0072] Table 1

[0073]

[0074] (3) Pure water flux and UV of ultrafiltration membrane 254 Retention rate test

[0075] The pure water flux test uses Shanghai Mosu ultrafiltration cup for dead-end filtration. First, the membrane sample is pre-pressed at 0.15 MPa for 30 minutes. After the test system is stable, the pure water flux is measured at 0.1 MPa and calculated using formula (3):

[0076]

[0077] Where: J W is the pure water flux, L / (m 2 ·h); V is the volume of the filtrate during the measurement time, L; A is the effective filtration area of ​​the ultrafiltration membrane, m 2 ; t is the ultrafiltration membrane filtration time, h.

[0078] EOM solution retention rate test: Microcystis aeruginosa solution cultured in the laboratory was used as a simulated natural water body, and the EOM solution was extracted by high-speed centrifugation. 254 =0.030~0.035; DOC=5.0mg / L. Use UV-visible spectrophotometer at wavelength 254nm to measure the absorbance of the permeate, and obtain the concentration of the permeate and the original solution through the standard curve. Calculate UV by formula (4) 254 Retention rate.

[0079]

[0080] The test results are as follows Figure 6 As shown in Figure 2, with the addition of nanoparticles, the pure water flux of the modified membrane, the EOM solution contamination flux and the UV 254 The retention rate is higher than that of the unmodified membrane. The water flux of M2 (Example 1) reaches 540L / (m 2 ·h), equivalent to the original membrane 287L / (m 2 ·h) is 1.88 times. The water flux of ultrafiltration membrane is often affected by many factors. The M2 (Example 1) membrane has a straight pore structure, increased porosity, increased hydrophilicity, etc. In addition, the metal organic framework is a porous material. MIL-101 has Pore ​​diameter, much larger than the diameter of water molecules This structure is conducive to the transport of water molecules. The reduction in pure water flux of M3 (Example 4) and M4 (Example 5) can be attributed to the reduction in porosity and hydrophilicity.

[0081] UV of M0 (Example 2) film 254 The rejection rate is only 14%, while the modified membrane M2 (Example 1) can reach up to 30%. There are a lot of small molecular organics in the algae pollutants, which can easily pass through the membrane, resulting in the unmodified PES membrane being sensitive to UV. 254 The size repulsion effect of the extracellular organic matter and the surface of the nanocomposite membrane are both negatively charged. Compared with pure PES membrane, the nanocomposite membrane has a stronger charge repulsion between the extracellular organic matter and the membrane surface. Figure 5 (b), thereby enhancing the repulsion of extracellular organic matter and improving the effluent quality.

[0082] (IV) Anti-pollution performance test

[0083] In order to test the anti-fouling performance of the modified ultrafiltration membrane, deionized water and EOM contaminated solution were alternately used for dead-end filtration. 200 mL of pure water was first filtered at 0.1 MPa, and then the solution was replaced with 300 mL of EOM contaminated solution. The flux change was recorded by an electronic balance; then 200 mL of deionized water was used for in-situ backwashing; the solution was converted to pure water again, and the alternating cycle filtration was repeated three times. The flux recovery rate (FRR) after three cycles of the membrane was calculated.

[0084] R ir , R r , R t They are irreversible pollution, reversible pollution and total pollution, calculated according to formulas (5) to (8):

[0085]

[0086] R r =(R t -R ir )×100% (8)

[0087] Where: J e3 Terminal flux at the end of the third cycle; J s4 Initial flux of the 4th cycle; initial flux of J0 ultrafiltration membrane.

[0088] In order to evaluate the anti-fouling performance of the membrane, the flux changes of the modified membrane in filtering EOM contaminated solution and pure water were investigated for three filtration cycles. The results are shown in Figure 2. Figure 7 shown. Figure 7(a) is the result of five membrane circulation filtration tests. Due to the interaction between the secretions of algae cells and the membrane surface during the filtration process, the flux of EOM solution is lower than that of pure water, and shows a gradually decreasing trend, indicating that small molecular pollutants in the EOM solution will gradually block the membrane pores, and large molecular pollutants will gradually form a filter cake layer, resulting in a decrease in membrane flux. Due to the increased hydrophilicity and electronegativity, the water flux recovery rate of the modified membrane is as follows Figure 7 (b), which is better than the 72% flux recovery rate of the unmodified M0 (Example 2) membrane. The flux recovery rate of M2 (Example 1) reached 89% after three cycles. The flux recovery rate trend also showed a trend of first increasing and then decreasing. The flux recovery rate change trend is consistent with the membrane hydrophilicity trend. The irreversible fouling of the modified membrane accounts for Figure 7 (b), wherein the irreversible contamination Rir of the modified membrane was significantly reduced after three cycles, with irreversible contamination of M0 (Example 2) being 28% and that of M2 (Example 1) being 11%, and irreversible contamination being reduced by 17%. The effective mitigation of the modified membrane is mainly attributed to the increase in the hydrophilicity and electronegativity of the membrane. The hydration layer formed on the membrane surface reduces the contamination layer formed by the contact between the pollutants and the membrane. The negative charge on the membrane surface increases the repulsion between the pollutants and the membrane surface, thereby improving the anti-pollution ability of the membrane. Among them, the SPDA-modified MIL has the best anti-pollution effect at 0.1wt% addition, and its flux recovery rate is 89%.

[0089] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing an SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane, characterized in that: The steps include: S1. Preparation of MIL-101: A CrCl3·6H2O aqueous solution and a PTA aqueous solution were stirred, heated to react, cooled to room temperature, centrifuged, and the precipitate was collected, washed, and dried to obtain MIL-101; S2. Preparation of SPDA-modified MIL-101: MIL-101 was dispersed in the mixture and sonicated to form a suspension. Dopamine hydrochloride was added to the suspension, stirred, and Tris-HCl buffer was injected. After stirring for 12-24 hours, sodium 3-mercapto-1-propanesulfonate was added and the reaction was continued for 10-30 hours. The mixture was washed and centrifuged, and then vacuum-dried to obtain SPDA-modified MIL-101. S3. Preparation of SPDA-modified MIL-101-modified polyethersulfone ultrafiltration membrane: PVP and SPDA-modified MIL-101 were dissolved in NMP, ultrasonically dispersed, and then added with dry PES and stirred for 10-30 hours. The membrane was allowed to stand for degassing, and a scraper was used to scrape the membrane on a glass plate to obtain the SPDA-modified MIL-101-modified polyethersulfone ultrafiltration membrane.

2. The preparation method according to claim 1, characterized in that The mass ratio of the CrCl3·6H2O to PTA is (2-3): (1-2).

3. The preparation method according to claim 2, characterized in that The heating reaction condition is to place the mixture at 200-220° C. for 10-15 hours.

4. The preparation method according to claim 3, characterized in that The mass ratio of the MIL-101 to dopamine hydrochloride is (0.05-1): (0.05-1).

5. The preparation method according to claim 4, characterized in that The mixed liquid is a mixed liquid of deionized water and anhydrous ethanol, and the mass ratio of the deionized water to the anhydrous ethanol is (1-2): (1-2).

6. The preparation method according to claim 5, characterized in that The mass ratio of the SPDA-modified MIL-101, PVP and PES is (0.05-0.2):1:

16.

7. A SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the SPDA-modified MIL-101 modified polyethersulfone ultrafiltration membrane according to claim 7 in sewage treatment.

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