A preparation method of a poly-sulfone membrane modified by nano-gold based on a dopamine coating layer

Abstract

The application discloses a preparation method of a modified polysulfone membrane based on dopamine coating loaded nanometer gold, and the polysulfone membrane matrix is prepared through a phase inversion method and is soaked in an alkaline dopamine solution; after a self-polymerization reaction, a polydopamine (PDA) coating is modified on the surface of the polysulfone membrane matrix material; then the matrix material modified with the PDA is placed in a chloroauric acid solution, nanometer gold particles are prepared in situ by using weak reducibility and adhesion of the chloroauric acid solution, and finally the PDA@Au is modified on the surface of the polysulfone membrane matrix material to form a functional composite material. The material is applied to rhodamine B dye wastewater, has a good removal effect on the rhodamine B, and the functional composite material has good stability and high recycling rate.

Description

Technical Field

[0001] This invention belongs to the field of Rhodamine B dye wastewater removal technology, and relates to a method for preparing a dopamine-coated gold nanoparticle-modified polysulfone membrane. Background Technology

[0002] Dye wastewater is carcinogenic, teratogenic, and mutagenic, posing a significant threat to the environment and human health. Current methods for treating dye wastewater include flocculation sedimentation, physical adsorption, ion exchange, redox reactions, membrane separation, and biological treatment. While traditional adsorption and emerging catalytic technologies offer good removal efficiency, they suffer from challenges such as difficulty in recycling and the potential for secondary pollution. Therefore, finding recyclable and reusable dye wastewater treatment methods is of great importance.

[0003] Compared with traditional treatment methods such as adsorption, coagulation, oxidation, and biodegradation, membrane separation technology has great potential in treating dye wastewater with high color intensity and high COD values ​​due to its advantages such as operation at room temperature, simple operation, low energy consumption, high efficiency, small footprint, easy scale-up, and clean and efficient operation. Polysulfone membranes are a commonly used separation membrane. Due to their good temperature resistance and solvent resistance, they are often used as the base membrane for composite membranes such as ultrafiltration membranes. However, polysulfone membranes have poor hydrophilicity, which can lead to membrane fouling. Therefore, researchers have been dedicated to developing different membrane materials and modifying existing membrane materials to improve their hydrophilicity and efficiently adsorb pollutants in dye wastewater.

[0004] For example, Chinese invention patent application number 2022105223763 discloses the preparation and application of a CoS / Ti3C2MXene composite material. This material is prepared by solvothermal fixation of CoS nanoparticles onto a Ti3C2MXene film, forming a composite material in which CoS nanoparticles are uniformly loaded on the surface of Ti3C2MXene nanosheets. This document also describes the loading of cobalt sulfide nanoparticles onto a novel Ti3C2MXene material and its application in activating PMS for the degradation of Rhodamine B (RhB) under sunlight. This combines the advantages of cobalt sulfide and two-dimensional MXene materials in photocatalytic activation of PMS, achieving non-radical oxidation (… 1 The degradation process of photo-Fenton-like pollutants, mainly based on O2, overcomes the difficulty of the limitation of SO4· and ·OH in the degradation of organic pollutants by free radical quenchers in traditional research. It realizes the efficient and rapid degradation of colored pollutant RhB, and provides a green and efficient new approach for the field of photo-Fenton-like environmental remediation. Summary of the Invention

[0005] This invention aims to modify polysulfone membranes for efficient removal of Rhodamine B dye wastewater. It provides a method for preparing a polysulfone membrane modified with gold nanoparticles supported on a dopamine coating. The invention involves preparing a polysulfone membrane substrate via phase inversion and immersing it in an alkaline dopamine solution. After a self-polymerization reaction, a polydopamine (PDA) coating is applied to the surface of the polysulfone membrane substrate. The PDA-modified substrate is then placed in a chloroauric acid solution, utilizing its weak reducing and adhesive properties to prepare gold nanoparticles in situ. Finally, PDA@Au is applied to the surface of the polysulfone membrane substrate, forming a functional composite material. When applied to Rhodamine B fuel wastewater, this material exhibits good removal efficiency for Rhodamine B. The functional composite material also demonstrates good stability and high recyclability.

[0006] The technical solution of the present invention is as follows: A method for preparing a dopamine-coated gold nanoparticle-modified polysulfone film comprises the following steps in sequence: Preparation of S1, polysulfone-based film PSF S11. Place N,N-dimethylacetamide, polyethylene glycol and deionized water in a clean and dry conical flask, place a rotor in it, stir on a magnetic stirrer, add solid polysulfone particles, stir for a period of time, then transfer to a 65 ℃ constant temperature heating magnetic stirrer and stir for 24 h. After that, move the conical flask to room temperature, let it stand to remove bubbles, and obtain polysulfone film solution, which is then sealed and stored for later use. S12. Take the polysulfone film solution, place it on a clean glass plate, and use a scraper to evenly scrape the film solution. Immerse the scraped film in deionized water for 24 hours to obtain the polysulfone substrate material. S2. Preparation of polydopamine-coated PSF / PDA S21. Weigh 2 g of dopamine hydrochloride and disperse it evenly in 1000 ml of Tris-HCl solution. Stir on a magnetic stirrer for 1 h to obtain a dopamine solution. S22. The polysulfone substrate material prepared in S12 is washed with deionized water, dried at 40 °C for 1 h, and then immersed in dopamine solution. It is reacted at room temperature for 24 h. The coated dopamine-modified polysulfone film is taken out, and the residual solution on the film surface is washed away with deionized water. Finally, the dopamine-modified film is stored in deionized water. Preparation of S3 gold-supported composite material PSF / PDA@Au S31. Take the chloroauric acid mother solution prepared by vacuum-sealing chloroauric acid reagent in a glass tube, with deionized water as the solvent, transfer the prepared chloroauric acid mother solution to a brown bottle, and store it in a refrigerator at 4 ℃. S32. Pipette 20 mL of 0.01 mol / L chloroauric acid stock solution into a small beaker. Dilute the stock solution to prepare 100 mL of 2 mmol / L chloroauric acid solution. Immerse the dopamine-modified membrane prepared in S22 in the 2 mmol / L chloroauric acid solution for 3 h at room temperature. Take out the product and wash it with deionized water to remove residual reagents. Finally, store it in deionized water for later use to obtain the final dopamine-loaded gold-modified polysulfone membrane.

[0007] As a limitation of this invention: (i) In step S11, the mass ratio of N,N-dimethylacetamide, polyethylene glycol, deionized water and polysulfone particles is 180:20:1:45.

[0008] In this invention, the mass ratio of N,N-dimethylacetamide, polyethylene glycol, and polysulfone particles is crucial for the preparation of the polysulfone membrane. The membrane prepared according to the ratio of this invention has good mechanical properties, can be bent and wound, is easy to assemble, is simple to operate, and is easy to automate. The prepared polysulfone membrane provides good support for the formation of the dopamine coating and is not easily damaged during adsorption and desorption tests.

[0009] (ii) In step S21, the pH of the Tris-HCl solution is 8.5 and the concentration is 10 mmol / L.

[0010] In this step, the pH and concentration of the Tris-HCl solution have a significant impact on the self-polymerization reaction of dopamine on the sulfone film substrate. The modified polydopamine coating thickness is 0.005 mm. When the pH and concentration are not the values ​​specified in this invention, it affects the self-polymerization reaction of dopamine in the substrate material. Specifically, the concentration and pH mainly affect the particle size of dopamine. Under acidic conditions, a large amount of H+ in the solution... + The polymerization process of DA is inhibited. When pH = 5 to 8.5, the PDA particles formed are more obvious and the membrane surface is rougher as the pH increases, resulting in better modification effect. When pH > 8.5, the PDA particles become smaller and the roughness of the membrane surface decreases as the pH increases. This is mainly because PDA is unstable in strongly alkaline solutions and PDA particles are not easy to form on the membrane surface.

[0011] (iii) In step S31, the concentration of the chloroauric acid mother liquor is 0.01 mol / L.

[0012] The concentration of chloroauric acid mother liquor affects the number of gold nanoparticles loaded on the surface of the dopamine coating, which in turn affects the removal performance of the synthesized product of rhodamine B in the solution.

[0013] (iv) In step S12, the thickness of the polysulfone substrate material is 0.07-0.085 mm. In step S32, the thickness of the dopamine coating loaded with gold nanoparticles in the polysulfone film material based on dopamine coating loaded with gold nanoparticles is 0.005 mm.

[0014] The present invention also has a limitation: when the dopamine-loaded gold-modified polysulfone membrane composite material is applied to the removal of Rhodamine B dye wastewater, when the solution pH is 6, the reaction time is 100 min, and the initial concentration is 8.5 mg / L, the degradation rate of Rhodamine B is 98%, and after 4 adsorption cycles, the removal rate can still reach 92.67%.

[0015] The above-mentioned technical solution of the present invention, as a whole, is interconnected and mutually influential, and cannot be separated.

[0016] The beneficial effects achieved by the present invention after adopting the above technical solution are as follows: The preparation method of this invention is simple and the process is easy to control. A polysulfone-based film is prepared using a phase inversion method. Utilizing the adhesive and reducing properties of polydopamine, gold is successfully loaded onto the substrate to obtain a PSF / PAD@Au composite material. After modification with dopamine, the contact angle of this composite material decreases, and its hydrophilicity is significantly improved. Because dopamine is a small molecule with adhesive properties and contains amine and catechol functional groups, under the alkaline environment (pH=8.5) and the presence of oxygen in this invention, the catechol groups of dopamine are easily oxidized to quinone groups. Then, the phenolic hydroxyl groups and quinone groups undergo disproportionation, generating semiquinone free radicals, which couple to form cross-linking bonds, thereby forming a polydopamine layer on the surface of the substrate material. The polydopamine surface has strong adhesive properties and contains a large number of phenolic hydroxyl and amino groups, which are capable of secondary reactions. These active functional groups have strong adsorption properties and a certain degree of reducing properties, which can not only attach metal ions to the carrier but also reduce the adsorbed metal ions to elemental metals and load them onto the material surface to form a composite material. Because gold nanoparticles have a large number of highly active sites on their surface, they can easily combine with other atoms. Rhodamine B, which is positively charged in dye wastewater, can be adsorbed onto the surface of gold nanoparticles through electrostatic interaction. The unique Π-Π structure of polydopamine can highly enrich pollutants such as rhodamine B, thereby synergistically adsorbing rhodamine B pollutants with nano-sized gold, thus achieving a better removal effect of rhodamine B.

[0017] The composite material exhibits good removal efficiency for dye RhB. The optimal initial concentration for RhB removal is 8.5 mg / L, the optimal adsorption time is 100 min, and the optimal pH is 6. Solution temperature has little effect on the RhB removal rate. Cyclic experiments show that after four adsorption cycles, the removal rate can still reach 92.67%, indicating that PSF / PAD@Au has good stability and can be reused multiple times.

[0018] This invention is applicable to the preparation of dopamine-loaded gold-modified polysulfone membranes, which are further used to remove Rhodamine B from dye wastewater.

[0019] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a technical roadmap for the composite material prepared in Example 1 of the present invention; Figure 2 Rhodamine B standard curve; Figure 3 Infrared spectra of PSF, PSF / PDA, and PSF / PDA@Au; Figure 4 XPS plots for PSF, PSF / PDA, and PSF / PDA@Au; Figure 5 SEM images of PSF, PSF / PDA, and PDA-PSF / Au are shown, where: (a) - PSF membrane surface; (b) - PSF / PDA membrane surface; (c) - PSF / PDA@Au membrane surface; (d) - PSF / PDA@Au membrane surface after adsorption. Figure 6 The contact angle test results show the effect of dopamine modification on the hydrophilicity of polysulfone membranes before and after modification. Left panel: PSF membrane contact angle; Right panel: PSF / PDA membrane contact angle. Figure 7 This is a graph showing the effect of adsorption time on RhB removal rate. Figure 8 The graph shows the effect of different concentrations of Rhodamine B solution on the RhB removal rate at 25℃. Figure 9 The graph shows the effect of pH value of Rhodamine B solution on RhB removal rate. Figure 10 This is a graph showing the effect of temperature on RhB removal rate. Figure 11 The graph shows the effect of the number of adsorption cycles of the PSF / PDA@Au membrane on the removal rate of Rhodamine B. Detailed Implementation

[0021] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents, and all experimental and detection methods used in the following embodiments are existing experimental and detection methods.

[0022] Example: A method for preparing a dopamine-coated gold nanoparticle-modified polysulfone film. I. A method for preparing a dopamine-loaded gold-modified polysulfone film according to this embodiment, the technical route is as follows: Figure 1 As shown, proceed in the following order: Preparation of S1, polysulfone-based film (PSF) N,N-dimethylacetamide, polyethylene glycol, and deionized water were placed in a clean, dry conical flask. After placing the flask in the flask, the mixture was stirred on a magnetic stirrer. Solid polysulfone particles were then added, and the mixture was stirred for a period of time. After stirring for a period of time, the mixture was transferred to a 65 °C constant-temperature magnetic stirrer and stirred for 24 h. The conical flask was then moved to room temperature and allowed to stand to remove bubbles, resulting in a polysulfone film solution, which was then sealed and stored for later use. The mass ratio of N,N-dimethylacetamide, polyethylene glycol, deionized water, and polysulfone particles was 180:20:1:45.

[0023] Take a certain amount (2 mL) of polysulfone film solution, place it on a clean glass plate, and use a scraper to evenly scrape the film solution. Immerse the scraped film in deionized water for 24 h to obtain a polysulfone substrate material with a thickness of 0.079 mm.

[0024] S2, Preparation of polydopamine coating (PSF / PDA) The preparation process of 2 g / L dopamine solution is as follows: First, weigh 2 g of dopamine hydrochloride and uniformly disperse it in 1000 ml of Tris-HCl (pH=8.5, 10 mmol / L) solution. Stir on a magnetic stirrer for 1 h to obtain dopamine solution. Wash the polysulfone membrane obtained in the previous step with deionized water, dry it at 40 ℃ for 1 h, immerse it in dopamine solution, and react at room temperature for 24 h. Take out the coated dopamine-modified polysulfone membrane, wash off the residual solution on the membrane surface with deionized water, and finally store the dopamine-modified membrane in deionized water.

[0025] S3, Preparation of gold-supported composite material (PSF / PDA@Au) Preparation of chloroauric acid solution: Prepare a 0.01 mol / L chloroauric acid stock solution by vacuum-sealing 1 g of chloroauric acid crystals in a glass tube using deionized water as the solvent. Transfer the prepared chloroauric acid stock solution to a brown bottle and store it in a refrigerator at 4 ℃.

[0026] 20 mL of 0.01 mol / L chloroauric acid stock solution was pipetted into a small beaker and diluted to prepare a 100 mL 2 mmol / L chloroauric acid solution. The polydopamine-coated polysulfone membrane substrate was immersed in the 2 mmol / L chloroauric acid solution for 3 h at room temperature. The product was then removed and washed with deionized water to remove residual reagents. Finally, it was stored in deionized water for later use, yielding the final dopamine-loaded gold-modified polysulfone membrane (PSF / PDA@Au). The thickness of the dopamine coating loaded with gold nanoparticles in this material was 0.005 mm.

[0027] II. Performance Analysis and Measurement The performance of the above-mentioned dopamine-coated gold nanoparticle-modified polysulfone membrane (PSF / PDA@Au) and the control group were measured and characterized.

[0028] Control group: ① Prepare polysulfone-based film (PSF) using the same method as step S1 in this embodiment.

[0029] ② Prepare dopamine-modified polysulfone membrane PSF / PDA. The preparation method is the same as steps S1 and S2 in this embodiment.

[0030] 1. Rhodamine Standard Curve Weigh 0.1 g of Rhodamine B and dissolve it in a 1000 mL volumetric flask to prepare a 200 mg / L Rhodamine B solution. Dilute this solution to prepare 1, 2, 3, 4, 5, and 6 mg / L Rhodamine B solutions. Measure the absorbance at 554 nm and plot a concentration-absorbance curve. Figure 2 As shown), the standard curve equation is obtained as y = 0.2729x + 0.0529, R. 2 =0.9952.

[0031] 2. Performance Characterization 2.1. FT-IR analysis like Figure 3 The images show the infrared spectra of PSF, PSF / PDA, PSF / PDA@Au, and the spectra after adsorption. The figures indicate that PSF has a high adsorption capacity at 1250 cm⁻¹. -1 The S=O stretching vibration peak appears at 1591 cm. -1 The resonance peaks of aromatic hydrocarbons at C=C at this location are characteristic peaks of polysulfone films; in addition, the peak at 1439 cm⁻¹... -1 1522 cm -1 These two characteristic peaks are generated by PDA deposition on the PSF film surface. They correspond to the C=C stretching vibration and the NH bending vibration, respectively, indicating that PDA has been successfully modified onto the PSF base film. The S=O stretching vibration peak disappears after gold loading, which is due to the gold nanoparticles covering the base film surface.

[0032] 2.2 XPS Analysis XPS (extensive electron spectroscopy) is used to analyze the chemical composition of materials. Figure 4 As can be seen, the XPS full spectrum shows C1s peaks (284 eV) and O1s peaks (531 eV), indicating that the chemical composition of the modified material remains stable. The enhanced N1s peak on the material surface after treatment with dopamine solution indicates that polydopamine was successfully modified onto the base film surface. The appearance of an Au4f peak at 83 eV indicates that gold was successfully loaded onto the dopamine-modified polysulfone film. The appearance of a Cl2p peak (197 eV) after rhodamine B adsorption proves that rhodamine B was successfully adsorbed.

[0033] 2.3 SEM Analysis The microstructure of the polysulfone-based film (control group ①), the PDA-modified polysulfone film (control group ②), and the composite material (PSF / PDA@Au) prepared in this example were observed using SEM. The results are as follows: Figure 5 As shown in the figure, the PSF surface is relatively rough. Figure 5 a), while the polysulfone film modified by PDA has a denser and smoother surface ( Figure 5 b). From Figure 5 c. It can be observed that due to the adhesion and aggregation of dopamine, uniformly dispersed white spots appear, indicating that the gold particles on the PSF / PDA@Au surface are dispersed on the surface of the polysulfone film to which the PDA is attached. The PDA forms a complete covering layer on the surface of the PSF film, and gold loading on the polydopamine coating is successfully achieved. Figure 5 Image d is an electron microscope image after adsorption of Rhodamine B, which shows that the gold particles in the composite material are uniformly and stably dispersed.

[0034] 2.4 Contact Angle Analysis Since polymer materials are generally hydrophobic, affecting their adsorption and catalytic efficiency, their wetting properties are characterized by measuring the water contact angle on the material surface. The measurement results are as follows: Figure 6 As shown in the figure, the water contact angle of the base film (control group ①) is 65.19°, while the water contact angle of the polydopamine-modified film (control group ②) is reduced to 57.48°. This indicates that the contact angle is reduced after dopamine modification. This is because the polydopamine coating surface contains abundant hydrophilic catechol and amino active groups, which directly leads to an increase in the hydrophilicity of the composite material surface and significantly improves the hydrophilic properties of the modified material.

[0035] 3. Study on the adsorption and desorption properties of the material To investigate the dye removal effects of polysulfone-based films and modified materials, polysulfone-based films (control group ①), dopamine-modified polysulfone films (control group ②), and the nano-gold-loaded dopamine-coated modified polysulfone film (PSF / PDA@Au) prepared in this example were compared to test the removal effect of the composite materials on Rhodamine B. The specific process is as follows: Cut the membrane into 3×3 cm pieces respectively. 2 The effects of membrane size, initial concentration of Rhodamine B, adsorption time, pH, and temperature on the membrane's recyclability were investigated. The removal rate of Rhodamine B solution by the membrane after the adsorption reaction was expressed by the formula: M t (%) = C0 - C t / C0×100% Where: M t - Dye removal rate, % Initial concentration of C0 dye, mg / L; C t - Initial dye concentration at time t, mg / L; The composite membrane after adsorbing the dye was immersed in anhydrous ethanol for 12 h to desorb the dye. The absorbance of the supernatant before and after the reaction with Rhodamine B solution was measured using a UV-Vis spectrophotometer. The concentration of Rhodamine B was calculated according to the standard curve of Rhodamine B. The decolorization rate of the modified membrane with Rhodamine B solution is expressed by the formula: DR(%)=C t / C0×100% Wherein, DR is the decolorization rate (%), C0 is the initial concentration of the dye (mg / L); C t - Initial dye concentration at time t, mg / L; 3.1 Effect of adsorption time on removal rate The area is 3×3 cm 2 PSF, PSF / PDA, and PSF / PAD@Au with a thickness of 0.089 mm were added to a Rhodamine B solution (50 mL, 8.5 mg / L), and the relationship between removal amount and adsorption time was investigated at 10-minute intervals. Figure 7 It is evident that the PSF / PAD@Au membrane exhibits the best removal effect for Rhodamine B, while the PSF membrane and PSF / PDA membrane show almost no removal effect. With prolonged time, the removal rate of Rhodamine B by the Au-loaded composite membrane gradually increases, reaching a plateau at 100 min, indicating that the adsorption sites on the composite membrane surface have become saturated and the adsorption capacity has reached its maximum. Therefore, the optimal adsorption time was determined to be 100 min.

[0036] 3.2 Effect of initial concentration on removal rate Prepare 50 mL solutions of Rhodamine B with mass concentrations of 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, and 9.5 mg / L, respectively, and add water to a container with an area of ​​3 × 3 cm². 2 The PSF / PAD@Au material was subjected to adsorption by shaking at 25 °C for 100 min, and its absorbance A was measured. The results are as follows: Figure 8 As shown in the figure, the removal rate gradually increases with the increase of the initial dye concentration. When the initial concentration of Rhodamine B reaches 8.5 mg / L, the removal rate reaches 98.72%. Further increasing the initial concentration of Rhodamine B does not change the removal rate. This may be because the active adsorption sites on the material surface are limited. When the concentration of Rhodamine B in the solution is too high, some Rhodamine B molecules cannot approach the active sites. Therefore, with further increasing the initial dye concentration, the removal rate of Rhodamine B by the composite membrane remains unchanged.

[0037] 3.3 Effect of solution pH on removal rate Depend on Figure 9 It was found that the empty membrane and the dopamine-modified polysulfone membrane had almost no removal effect on Rhodamine B. Therefore, the removal effect of the PSF / PAD@Au membrane on Rhodamine B was only investigated in subsequent studies, using a membrane with an area of ​​3×3 cm. 2 A composite membrane with a thickness of 0.089 mm was dried and prepared for use. The pH of an 8.5 mg / L Rhodamine B solution was adjusted to 2, 4, 6, 8, 10, and 12 using 0.1 mol / L dilute sodium hydroxide and dilute hydrochloric acid, respectively. Then, a membrane with an area of ​​3 × 3 cm² was added. 2 The composite membrane was subjected to an adsorption experiment at a temperature of 25 °C, and the absorbance was measured and calculated.

[0038] The change in Rhodamine B removal rate of PSF / PAD@Au membrane with pH is as follows: Figure 9 As shown in the figure, in the initial stage, the removal rate of Rhodamine B by the composite membrane increased with increasing solution pH; the optimal removal rate of Rhodamine B was achieved at pH 6 (Mt = 98.72%), and the removal rate decreased somewhat with further increases in solution pH. The lower removal rate of Rhodamine B under acidic conditions is mainly due to the fact that Rhodamine B is a cationic dye, H... + Rhodamine B competes with it for adsorption and binding sites. As acidity decreases, the electrostatic attraction between the cationic molecules of Rhodamine B and the negative charge on the material surface increases, resulting in a high removal rate of Rhodamine B in the composite membrane, which reaches its maximum at pH 6. As the pH value continues to increase, the Rhodamine B molecules ionize, and Rhodamine B becomes a zwitterionic form, which weakens the electrostatic attraction between Rhodamine B and the material surface, thus reducing the removal rate.

[0039] 3.4 Effect of Temperature on Rhodamine B Removal Rate Transfer 50 mL of 8.5 mg / L Rhodamine B solution to a small beaker, and add a 3 × 3 cm² area... 2 The PSF / PAD@Au composites were subjected to adsorption at 25 ℃, 35 ℃, 45 ℃, 55 ℃, and 65 ℃ for 100 min with shaking. The removal efficiency curves of the composite material for Rhodamine B at different temperatures were obtained according to method 1.6. (See figure). Figure 10 .Depend on Figure 10 It can be seen that the removal rate of Rhodamine B by PSF / PDA@Au increases slightly with increasing solution temperature. At 65 ℃, the removal rate of Rhodamine B is 98.95%, which is 0.23% higher than the removal rate at 25 ℃ (98.72%), indicating that the solution temperature has little effect on the removal rate of Rhodamine B.

[0040] 3.5 Recycling performance The PSF / PAD@Au composite membrane, after adsorbing the dye, was immersed in anhydrous ethanol for 12 h, then washed with deionized water, and finally dried at 60 ℃ for 2 h. The regenerated PSF / PAD@Au composite membrane was then subjected to further adsorption experiments. The membrane was immersed in Rhodamine B solution and subjected to adsorption with shaking at 25 ℃ for 100 min. The absorbance was measured, and the removal rate of Rhodamine B by the composite membrane was calculated. The results are as follows: Figure 11 As shown in the figure, after four adsorption cycles, the removal rates of Rhodamine B by the PSF / PAD@Au composite membrane were 98.72%, 97.94%, 95.22%, and 92.67%, respectively. Therefore, the PSF / PAD@Au composite membrane can be regenerated and recycled within four adsorption cycles.

[0041] As described above, this invention uses a phase inversion method to prepare a polysulfone-based film. Utilizing the adhesive and reducing properties of polydopamine, gold was successfully loaded onto the substrate, resulting in a PSF / PAD@Au composite material. Tests using FESEM, FTIR, and XPS methods confirmed the successful synthesis of Au and its successful loading onto the substrate material. Contact angle testing results showed that dopamine modification reduced the contact angle and significantly improved hydrophilicity.

[0042] Experimental results show that the composite material has a good removal effect on dye RhB. The optimal initial concentration for RhB removal is 8.5 mg / L, the optimal adsorption time is 100 min, and the optimal pH is 6. Solution temperature has little effect on the RhB removal rate. Cyclic experiments show that after four adsorption cycles, the removal rate still reaches 92.67%, indicating that PSF / PAD@Au has good stability and can be reused multiple times.

[0043] Comparative Example In this embodiment, a series of composite membranes were prepared, and a series of adsorption and desorption performance studies were conducted on the membranes. The experimental process was the same as in the above embodiments, except that the composite membrane material and its preparation method were different, as detailed below: Group A: This group prepared a PSF / Au composite membrane. The preparation process of the PSF base membrane was the same as that in Example S1 of the present invention. After the PSF base membrane was prepared, it was immersed in 2 mmol / L chloroauric acid solution for 3 h to obtain the PSF / Au composite membrane.

[0044] Group B: PSF / PAD@Ag composite membrane, the preparation process is similar to the above embodiments of the present invention, the only difference being that the 2 mmol / L chloroauric acid solution is silver ammonia solution.

[0045] Group C: PVDF / PAD@Fe composite membrane, the preparation process is similar to the above embodiments of the present invention, the only difference is that: PSF in S1 is replaced by commercially available PVDF, and 2 mmol / L chloroauric acid solution is ferrous sulfate solution.

[0046] The composite membrane material prepared by the AC group above was used to study the adsorption and desorption performance of Rhodamine B. The removal of dye RhB was carried out at an initial concentration of 8.5 mg / L, an adsorption time of 100 min, and a pH of 6. After four adsorption cycles, the specific results of the Rhodamine B removal rate are as follows:

[0047] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a dopamine-coated gold nanoparticle-modified polysulfone film, characterized in that, Follow these steps in sequence: Preparation of S1, polysulfone-based film PSF S11. Place N,N-dimethylacetamide, polyethylene glycol and deionized water in a clean and dry conical flask, place a rotor in it, stir on a magnetic stirrer, add solid polysulfone particles, stir for a period of time, then transfer to a 65 ℃ constant temperature heating magnetic stirrer and stir for 24 h. After that, move the conical flask to room temperature, let it stand to remove bubbles, and obtain polysulfone film solution, which is then sealed and stored for later use. The mass ratio of N,N-dimethylacetamide, polyethylene glycol, deionized water, and polysulfone particles is 180:20:1:

45. S12. Take the polysulfone film solution, place it on a clean glass plate, and use a scraper to evenly scrape the film solution. Immerse the scraped film in deionized water for 24 hours to obtain the polysulfone substrate material. The thickness of the polysulfone substrate material is 0.07-0.085 mm; S2. Preparation of polydopamine-coated PSF / PDA S21. Weigh 2 g of dopamine hydrochloride and disperse it evenly in 1000 ml of Tris-HCl solution. Stir on a magnetic stirrer for 1 h to obtain a dopamine solution. S22. The polysulfone substrate material prepared in S12 is washed with deionized water, dried at 40 °C for 1 h, and then immersed in dopamine solution. It is reacted at room temperature for 24 h. The coated dopamine-modified polysulfone film is taken out, and the residual solution on the film surface is washed away with deionized water. Finally, the dopamine-modified film is stored in deionized water. S3. Preparation of dopamine-coated gold nanoparticle-modified polysulfone film S31. Take the chloroauric acid mother liquor prepared by vacuum-sealing chloroauric acid crystals in a glass tube, using deionized water as the solvent, and transfer the prepared chloroauric acid mother liquor to a brown bottle for refrigeration at 4 ℃. S32. Pipette 20 mL of 0.01 mol / L chloroauric acid stock solution into a small beaker. Dilute the stock solution to prepare 100 mL of 2 mmol / L chloroauric acid solution. Immerse the dopamine-modified membrane prepared in S22 in the 2 mmol / L chloroauric acid solution for 3 h at room temperature. Take out the product and wash it with deionized water to remove residual reagents. Finally, store it in deionized water for later use to obtain the final dopamine-coated gold nanoparticle-modified polysulfone membrane. The thickness of the dopamine-coated gold nanoparticle-modified polysulfone film material is 0.005 mm. The dopamine-coated gold nanoparticle-modified polysulfone membrane was applied to the removal of Rhodamine B dye wastewater. When the solution pH was 6, the reaction time was 100 min, and the initial concentration was 8.5 mg / L, the degradation rate of Rhodamine B was 98%. After 4 adsorption cycles, the removal rate could still reach 92.67%.

2. The method for preparing a dopamine-coated gold nanoparticle-modified polysulfone film according to claim 1, characterized in that, In step S21, the pH of the Tris-HCl solution is 8.5 and the concentration is 10 mmol / L.

3. The method for preparing a dopamine-coated gold nanoparticle-modified polysulfone film according to claim 1, characterized in that, In step S31, the concentration of the chloroauric acid mother liquor is 0.01 mol / L.

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