Anti-fouling ultrafiltration membrane and method for preparing the same

Abstract

The application relates to the technical field of anti-pollution of ultrafiltration membranes, and discloses an anti-pollution ultrafiltration membrane and a preparation method thereof. The anti-pollution ultrafiltration membrane comprises an ultrafiltration membrane base film and Mn-N-Cu-TiO2 visible light catalyst dispersed in the ultrafiltration membrane base film; the Mn-N-Cu-TiO2 visible light catalyst is an anatase TiO2 doped with Mn, N and Cu. In the anti-pollution ultrafiltration membrane, the Mn-N-Cu-TiO2 visible light catalyst is adopted, Mn, N and Cu can cooperate with each other, a synergistic effect is generated, the light catalyst is close to black or presents black, and a smaller band gap energy is obtained, so that the ultrafiltration membrane can effectively degrade the organic pollutants adsorbed in the membrane under visible light, the membrane pollution degree is reduced, the irreversible pollution is reduced, and the service life of the membrane is prolonged.

Description

Technical Field

[0001] This invention relates to the field of antifouling technology for ultrafiltration membranes, and more particularly to an antifouling ultrafiltration membrane and its preparation method. Background Technology

[0002] Ultrafiltration is an important separation and purification technology. Because it mainly separates materials physically and does not produce secondary pollution, it has wide applications in water treatment, pharmaceuticals, chemicals, and the food industry. However, the treatment efficiency of ultrafiltration membranes is limited by the microporous structure and surface properties of the membrane. Furthermore, since most ultrafiltration membranes are made of organic materials such as polysulfone (PSF), polyvinylidene fluoride (PVDF), and polyvinyl chloride (PVC), these materials have good membrane-forming properties but are highly hydrophobic. During use, they easily adsorb organic pollutants in the water, such as sugars, fats, and proteins, leading to irreversible membrane fouling, flux loss, reduced membrane lifespan, and increased investment costs.

[0003] Currently, most research focuses on improving membrane antifouling performance by modifying materials to increase the hydrophilicity of the membrane surface. However, improving membrane antifouling performance solely through surface hydrophilicity has limitations; organic membrane fouling still occurs with increasing membrane operating time, leading to irreversible pollution. Therefore, how to reduce the degree of membrane fouling, minimize irreversible pollution, and extend membrane lifespan through innovation in membrane materials and appropriate external conditions is considered a key technical challenge that needs to be addressed.

[0004] Patent CN109289550A discloses a method for preparing and applying an antifouling polyvinylidene fluoride hybrid ultrafiltration membrane. This method introduces polytannic acid / polyethyleneimine / titanium dioxide composite nanoparticles into the polyvinylidene fluoride ultrafiltration membrane to enhance its antifouling performance. While titanium dioxide can utilize its photocatalytic activity to degrade adsorbed organic pollutants in the ultrafiltration membrane, thereby reducing pollution, titanium dioxide is white and has a large band gap, resulting in very low photocatalytic activity under visible light. This makes it difficult for the ultrafiltration membrane to degrade organic pollutants under visible light. Summary of the Invention

[0005] To address the technical problem of poor degradation of organic pollutants by existing TiO2-modified ultrafiltration membranes under visible light, this invention provides an antifouling ultrafiltration membrane and its preparation method. This antifouling ultrafiltration membrane can effectively degrade adsorbed organic pollutants in the membrane under visible light, reducing membrane fouling, minimizing irreversible fouling, and extending membrane lifespan.

[0006] The specific technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides an antifouling ultrafiltration membrane, comprising an ultrafiltration membrane base and a Mn-N-Cu-TiO2 visible light catalyst dispersed within the ultrafiltration membrane base; wherein the Mn-N-Cu-TiO2 visible light catalyst is anatase TiO2 doped with Mn, N and Cu.

[0008] In the ultrafiltration membrane of this invention, anatase TiO2 co-doped with Mn, N, and Cu is used. The synergistic effect of Mn, N, and Cu enables the photocatalyst to effectively degrade adsorbed organic pollutants in the ultrafiltration membrane under visible light, reducing organic and irreversible pollution of the ultrafiltration membrane. Specifically, the doping of Mn, N, and Cu achieves the following effects: The doping of Mn, N, and Cu facilitates a more disordered crystal orientation and lattice arrangement in TiO2. When external light enters the catalyst, it is scattered, absorbed, and not reflected. Therefore, the doping of Mn, N, and Cu helps to obtain a photocatalyst with a near-black or black appearance, allowing it to absorb more visible light and thus improving visible light utilization. Furthermore, compared to TiO2 doped with a single element or two of Mn, N, and Cu, Mn-N-Cu-TiO2 has a smaller band gap energy, below 2.0 eV, and can absorb a wider range of light wavelengths, thus achieving photocatalysis under visible light.

[0009] Furthermore, when treating biochemical effluent (such as secondary biochemical effluent), bacteria can adhere to the surface of the ultrafiltration membrane, reducing its performance. The Mn-N-Cu-TiO2 visible light catalyst used in this patent has good antibacterial properties. When bacteria come into contact with this catalyst, their cell membranes are disrupted, thereby inhibiting bacterial growth on the ultrafiltration membrane and reducing contamination from the biocommunity on the membrane surface. Therefore, when used to treat biochemical effluent, the ultrafiltration membrane of this invention can achieve filtration under light-protected conditions. When the ultrafiltration membrane surface becomes contaminated, exposing it to visible light or sunlight allows for the self-degradation of the fouling layer, restoring membrane flux.

[0010] Preferably, the preparation method of the Mn-N-Cu-TiO2 visible light catalyst includes the following steps: dissolving a manganese source, a copper source, and a titanium dioxide precursor in solvent I, mixing them evenly to form solution A; dissolving a nitrogen source in solvent I, mixing them evenly, and adjusting the pH to 1.7-2.5 to form solution B; adding solution B dropwise to solution A under stirring conditions, mixing evenly, and then performing an ultrasonic-low temperature solvothermal reaction; after the reaction is completed, separating the product to obtain the Mn-N-Cu-TiO2 visible light catalyst.

[0011] In the above process, the order of adding raw materials will affect the color of the final Mn-N-Cu-TiO2 visible light catalyst. Specifically, the present invention controls the pH and adjusts the pH by adding acid when preparing solution B, rather than after mixing solution A and solution B. This can prevent TiO2 from precipitating prematurely, thus facilitating the acquisition of a black Mn-N-Cu-TiO2 visible light catalyst.

[0012] Furthermore, the doping of Mn, N, and Cu, combined with ultrasonic treatment, can make the crystal orientation of TiO2 disordered and the lattice arrangement disordered, thereby making the obtained Mn-N-Cu-TiO2 visible light catalyst appear black or close to black.

[0013] Further, the molar ratio of the manganese source, nitrogen source, and copper source, respectively, is 1.0–1.5:87–95:1, calculated as Mn, N, and Cu, respectively. Further, the molar ratio of the copper source and titanium dioxide precursor, respectively, is 1:20–25, calculated as Cu and Ti, respectively.

[0014] The dosage of manganese, nitrogen, and copper sources, as well as their ratio, affects the color and band gap of the Mn-N-Cu-TiO2 visible light catalyst, thus influencing its catalytic performance under visible light. Based on theoretical analysis and extensive experiments, this invention found that when the molar ratio of manganese, nitrogen, and copper sources is controlled at 1.0–1.5:87–95:1, and the molar ratio of copper source to titanium dioxide precursor is controlled at 1:20–25, combined with ultrasonic treatment, the Mn-N-Cu-TiO2 visible light catalyst can achieve a black color and a smaller band gap, thereby further improving its catalytic activity under visible light and giving the ultrafiltration membrane better antifouling properties.

[0015] Furthermore, the manganese source is a manganese salt, the nitrogen source is urea, the copper source is a copper salt, and the titanium dioxide precursor is tetrabutyl titanate.

[0016] Furthermore, after dissolving the nitrogen source in solvent I, the mixture is ultrasonically treated for 4–8 hours, and then the pH is adjusted to 1.7–2.5.

[0017] Furthermore, the temperature of the ultrasonic-low temperature solvothermal reaction is 150-300℃, the reaction time is 5-8h, during which ultrasonication is performed for 2.5-4h, and the ultrasonic frequency is 10000-15000Hz.

[0018] The extent of the ultrasonic-low-temperature solvothermal reaction affects the color of the final Mn-N-Cu-TiO2 visible light photocatalyst. This invention controls the temperature at 150–300℃ and the reaction time at 5–8 hours, resulting in a black appearance of the obtained Mn-N-Cu-TiO2 visible light photocatalyst, thus enabling it to exhibit good photocatalytic activity under visible light.

[0019] Furthermore, the process of separating the product includes the following steps: after solid-liquid separation, washing, freezing for 10-24 hours, and then freeze-drying for 36-48 hours.

[0020] Furthermore, solvent I is an organic alcohol.

[0021] Preferably, the mass ratio of the ultrafiltration membrane base to the Mn-N-Cu-TiO2 visible light catalyst is 1:0.03 to 0.08.

[0022] Secondly, the present invention provides a method for preparing the antifouling ultrafiltration membrane, comprising the following steps: adding the ultrafiltration membrane base material, the pore-forming agent and the Mn-N-Cu-TiO2 visible light catalyst to solvent II, dissolving them completely, and then degassing and aging them to obtain a casting solution; transferring the casting solution to a nonwoven fabric, scraping out a liquid film, and then transferring the nonwoven fabric and the liquid film together to a liquid bath for a phase inversion reaction; after the membrane is completely solidified, transferring it to water to remove excess solvent II to obtain the antifouling ultrafiltration membrane.

[0023] Preferably, the ultrafiltration membrane base material is one or more of polysulfone, polyvinylidene fluoride, and polyvinyl chloride.

[0024] Preferably, the porogen is polyethylene glycol with a weight-average molecular weight of 5000 to 20000 Da.

[0025] Preferably, the mass ratio of the ultrafiltration membrane base material to the pore-forming agent is 1:0.10 to 0.15.

[0026] Preferably, the mass ratio of the ultrafiltration membrane base material to solvent II is 1:4.5 to 5.0.

[0027] Preferably, solvent II is N,N-dimethylacetamide (DMAc).

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) In the antifouling ultrafiltration membrane of the present invention, Mn-N-Cu-TiO2 visible light catalyst is used. Mn, N and Cu can cooperate with each other to produce a synergistic effect. Combined with ultrasonic action, the photocatalyst is close to black or appears black and has a small band gap energy. Under visible light, it can effectively degrade organic pollutants adsorbed in the ultrafiltration membrane, reduce membrane fouling, and restore membrane flux.

[0030] (2) In the process of preparing Mn-N-Cu-TiO2 visible light catalyst, by controlling the order of raw material addition, the amount of manganese source, nitrogen source and copper source added and the ratio of the three, as well as the temperature and time of ultrasonic-low temperature solvothermal reaction, the Mn-N-Cu-TiO2 visible light catalyst obtained can be black in appearance and have a small band gap, thereby further improving its catalytic effect under visible light and giving the ultrafiltration membrane better anti-fouling performance;

[0031] (2) The antifouling ultrafiltration membrane of the present invention has good antifouling performance, as well as good membrane separation performance and high permeation flux. Attached Figure Description

[0032] Figure 1 This is a scanning electron microscope (SEM) image of the Mn-N-Cu-TiO2 visible light catalyst in this invention.

[0033] Figure 2 This is a schematic diagram of the structure of the Mn-N-Cu-TiO2 visible light catalyst in this invention.

[0034] Figure 3 The degradation curves of methyl orange by the Mn-N-Cu-TiO2 visible light catalyst and TiO2 photocatalyst of Example 1 under simulated sunlight are shown.

[0035] Figure 4 The images show surface SEM images of the antifouling ultrafiltration membrane (right) and PVC ultrafiltration membrane (left) used in Example 1 after treating the secondary biochemical effluent. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments.

[0037] The following description of the embodiments is provided to enable those skilled in the art to understand and use the invention, and is not intended to limit the scope of protection of the invention. Variations and advantages that may occur to those skilled in the art without departing from the spirit and scope of the inventive concept are included in this invention, and the scope of protection of this invention is defined by the appended claims and any equivalents thereof.

[0038] General Implementation Examples

[0039] An antifouling ultrafiltration membrane includes an ultrafiltration membrane base and a Mn-N-Cu-TiO2 visible light catalyst dispersed within the ultrafiltration membrane base; the Mn-N-Cu-TiO2 visible light catalyst is anatase TiO2 doped with Mn, N and Cu.

[0040] In one specific embodiment, the mass ratio of the ultrafiltration membrane base to the Mn-N-Cu-TiO2 visible light catalyst is 1:0.03 to 0.08.

[0041] As one specific embodiment, the preparation method of the Mn-N-Cu-TiO2 visible light catalyst includes the following steps: dissolving a manganese source, a copper source, and a titanium dioxide precursor in solvent I, mixing them evenly to form solution A; dissolving a nitrogen source in solvent I, mixing them evenly, and adjusting the pH to 1.7-2.5 to form solution B; adding solution B dropwise to solution A under stirring conditions, mixing evenly, and then performing an ultrasonic-low temperature solvothermal reaction; after the reaction is completed, separating the product to obtain the Mn-N-Cu-TiO2 visible light catalyst.

[0042] In one specific embodiment, in the preparation method of the Mn-N-Cu-TiO2 visible light catalyst, the molar ratio of the manganese source, nitrogen source, copper source and titanium dioxide precursor is 1.0-1.5:87-95:1:20-25, respectively, based on Mn, N, Cu and Ti.

[0043] In one specific embodiment, in the preparation method of the Mn-N-Cu-TiO2 visible light catalyst: the manganese source is a manganese salt, the nitrogen source is urea, the copper source is a copper salt, and the titanium dioxide precursor is tetrabutyl titanate.

[0044] In one specific embodiment, in the preparation method of the Mn-N-Cu-TiO2 visible light catalyst: after dissolving the nitrogen source in solvent I, ultrasonic treatment is performed for 4 to 8 hours, and then the pH is adjusted to 1.7 to 2.5.

[0045] In one specific embodiment, in the preparation method of the Mn-N-Cu-TiO2 visible light catalyst: the temperature of the ultrasonic-low temperature solvothermal reaction is 150-300℃, the reaction time is 5-8h, during which ultrasonication is performed for 2.5-4h, and the ultrasonic frequency is 10000-15000Hz.

[0046] In one specific embodiment, in the preparation method of the Mn-N-Cu-TiO2 visible light catalyst: the solvent I is an organic alcohol.

[0047] In one specific embodiment, the preparation method of the Mn-N-Cu-TiO2 visible light catalyst includes the following steps: after solid-liquid separation, washing, freezing for 10-24 hours, and then freeze-drying for 36-48 hours.

[0048] A method for preparing the antifouling ultrafiltration membrane includes the following steps: adding the ultrafiltration membrane base material, pore-forming agent, and Mn-N-Cu-TiO2 visible light catalyst to solvent II, dissolving them completely, and then degassing and aging them to obtain a casting solution; transferring the casting solution to a nonwoven fabric, scraping out a liquid film, and then transferring the nonwoven fabric and the liquid film together to a liquid bath for a phase inversion reaction; after the membrane is completely solidified, transferring it to water to remove excess solvent II to obtain the antifouling ultrafiltration membrane.

[0049] In one specific embodiment, the ultrafiltration membrane base material is one or more of polysulfone, polyvinylidene fluoride, and polyvinyl chloride.

[0050] In one specific embodiment, the porogen is polyethylene glycol with a weight-average molecular weight of 5000 to 20000 Da.

[0051] In one specific embodiment, the mass ratio of the ultrafiltration membrane base material to the pore-forming agent is 1:0.10 to 0.15.

[0052] In one specific embodiment, the mass ratio of the ultrafiltration membrane base material to solvent II is 1:4.5 to 5.0.

[0053] In one specific embodiment, solvent II is N,N-dimethylacetamide (DMAc).

[0054] Example 1

[0055] The following steps were used to prepare a Mn-N-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0056] (1) Preparation of Mn-N-Cu-TiO2 visible light catalyst:

[0057] Solution A was prepared by dissolving 1.16 mmol of manganese chloride, 1 mmol of copper chloride, and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 45 mmol of urea solution in 30 mL of anhydrous ethanol for 6 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 6 hours. The temperature was controlled at 200°C during the reaction, and sonication was performed every 30 seconds for a total duration of 3 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-N-Cu-TiO2 visible light catalyst, which appeared as shown in the image. Figure 1As shown, the structure is as follows Figure 2 As shown.

[0058] (2) Preparation of antifouling ultrafiltration membrane:

[0059] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-N-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-N-Cu-TiO2-0.6wt%, DMAc-80.4wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the solution was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / L polyethylene terephthalate (PET) nonwoven fabric. A liquid film with a thickness of 200 μm was scraped out using a film scraper. The nonwoven fabric and the liquid film were then transferred together to a liquid bath at room temperature for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water for preservation.

[0060] The Mn-N-Cu-TiO2 visible light catalyst obtained in this embodiment is black in appearance. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 160 minutes. In contrast, the original TiO2 catalyst cannot (see...). Figure 3 ).

[0061] Using the antifouling ultrafiltration membrane obtained in this embodiment, bovine serum albumin (BSA) aqueous solution was treated, and the pure water flux was measured to reach 416 L / m³. 2 At h bar, the retention rate of bovine serum albumin reached 96.0%.

[0062] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 80%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 87%.

[0063] In a wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat secondary biological wastewater. Compared with a PVC ultrafiltration membrane without the addition of a Mn-N-Cu-TiO2 visible light catalyst, the antifouling ultrafiltration membrane reduced the E. coli adhesion rate by 90% (see...). Figure 4 ).

[0064] Example 2

[0065] The following steps were used to prepare a Mn-N-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0066] (1) Preparation of Mn-N-Cu-TiO2 visible light catalyst:

[0067] Solution A was prepared by dissolving 1.48 mmol of manganese chloride, 1.1 mmol of copper chloride, and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 52.2 mmol of urea solution in 30 mL of anhydrous ethanol for 6 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 8 hours. The temperature was controlled at 150 °C during the reaction, and sonication was performed every 30 seconds for a total duration of 4 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-N-Cu-TiO2 visible light catalyst.

[0068] (2) Preparation of antifouling ultrafiltration membrane:

[0069] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-N-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-N-Cu-TiO2-0.8wt%, DMAc-80.2wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the mixture was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a liquid bath at room temperature for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0070] The Mn-N-Cu-TiO2 visible light catalyst obtained in this embodiment is black in appearance. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 280min.

[0071] Using the antifouling ultrafiltration membrane obtained in this embodiment, the pure water flux for treating bovine serum albumin (BSA) aqueous solution reached 483 L / m³. 2At h bar, the retention rate of bovine serum albumin reached 92%.

[0072] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 78%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 82%.

[0073] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of Mn-N-Cu-TiO2 visible light catalyst, the adhesion rate of E. coli in the antifouling ultrafiltration membrane was reduced by 92%.

[0074] Example 3

[0075] The following steps were used to prepare a Mn-N-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0076] (1) Preparation of Mn-N-Cu-TiO2 visible light catalyst:

[0077] Solution A was prepared by dissolving 1.32 mmol of manganese chloride, 0.88 mmol of copper chloride, and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 38.3 mmol of urea solution in 30 mL of anhydrous ethanol for 4 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 5 hours. The temperature was controlled at 300 °C during the reaction, and sonication was performed every 30 seconds for a total duration of 2.5 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-N-Cu-TiO2 visible light catalyst.

[0078] (2) Preparation of antifouling ultrafiltration membrane:

[0079] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-N-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-N-Cu-TiO2-1.3wt%, DMAc-79.7wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, they were degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a liquid bath at room temperature for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0080] The Mn-N-Cu-TiO2 visible light catalyst obtained in this embodiment is black in appearance. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 240min.

[0081] Using the antifouling ultrafiltration membrane obtained in this embodiment, bovine serum albumin (BSA) aqueous solution was treated, and the pure water flux was measured to reach 521 L / m³. 2 At h bar, the retention rate of bovine serum albumin reached 90%.

[0082] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 72%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 78%.

[0083] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of Mn-N-Cu-TiO2 visible light catalyst, the adhesion rate of E. coli of the antifouling ultrafiltration membrane was reduced by 86%.

[0084] Example 4

[0085] The following steps were used to prepare a Mn-N-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0086] (1) Preparation of Mn-N-Cu-TiO2 visible light catalyst:

[0087] Solution A was prepared by dissolving 3.0 mmol of manganese chloride, 2.98 mmol of copper chloride, and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 42.09 mmol of urea solution in 30 mL of anhydrous ethanol for 8 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 6 hours. The temperature was controlled at 200°C during the reaction, and sonication was performed every 30 seconds for a total duration of 3 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-N-Cu-TiO2 visible light catalyst.

[0088] (2) Preparation of antifouling ultrafiltration membrane:

[0089] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-N-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-N-Cu-TiO2-0.6wt%, DMAc-80.4wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the mixture was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a liquid bath at room temperature for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0090] The Mn-N-Cu-TiO2 visible light catalyst obtained in this embodiment is black in appearance. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 380min.

[0091] Using the antifouling ultrafiltration membrane obtained in this embodiment, bovine serum albumin (BSA) aqueous solution was treated, and the pure water flux was measured to reach 420 L / m³. 2 The retention rate of bovine serum albumin reached 96% at h bar.

[0092] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 80%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 83%.

[0093] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of Mn-N-Cu-TiO2 visible light catalyst, the adhesion rate of E. coli in the antifouling ultrafiltration membrane was reduced by 93%.

[0094] Example 5

[0095] The following steps were used to prepare a Mn-N-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0096] (1) Preparation of Mn-N-Cu-TiO2 visible light catalyst:

[0097] Solution A was prepared by dissolving 0.9 mmol of manganese chloride, 2.0 mmol of copper chloride, and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 44.13 mmol of urea solution in 30 mL of anhydrous ethanol for 8 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 6 hours. The temperature was controlled at 200°C during the reaction, and sonication was performed every 30 seconds for a total duration of 3 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-N-Cu-TiO2 visible light catalyst.

[0098] (2) Preparation of antifouling ultrafiltration membrane:

[0099] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-N-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-N-Cu-TiO2-0.6wt%, DMAc-80.4wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the mixture was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a liquid bath at room temperature for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0100] The Mn-N-Cu-TiO2 visible light catalyst obtained in this embodiment is black in appearance. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 300min.

[0101] Using the antifouling ultrafiltration membrane obtained in this embodiment, the pure water flux for treating bovine serum albumin (BSA) aqueous solution reached 418 L / m³. 2 The retention rate of bovine serum albumin reached 96% at h bar.

[0102] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 80%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 84%.

[0103] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of Mn-N-Cu-TiO2 visible light catalyst, the adhesion rate of E. coli in the antifouling ultrafiltration membrane was reduced by 91%.

[0104] Results Analysis: The Mn-N-Cu-TiO2 visible light photocatalysts of Examples 1-3 were black and exhibited high catalytic degradation efficiency of methyl orange under simulated sunlight. When used in antifouling ultrafiltration membranes, they enabled good flux recovery of fouled ultrafiltration membranes after sunlight irradiation. Compared to Example 1, the Mn-N-Cu-TiO2 visible light photocatalysts obtained in Examples 4-5 showed significantly weaker catalytic degradation effects on methyl orange under simulated sunlight, and the flux recovery rate of the antifouling ultrafiltration membranes after simulated sunlight irradiation was lower. This indicates that the amounts of manganese, nitrogen, and copper sources, as well as the degree of reaction in the ultrasonic-low-temperature solvothermal method, affect the photocatalytic performance of the Mn-N-Cu-TiO2 visible light photocatalyst under visible light (sunlight), thereby affecting the antifouling performance of the ultrafiltration membrane.

[0105] Comparative Example 1

[0106] The following steps were used to prepare an N-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0107] (1) Preparation of N-Cu-TiO2 visible light catalyst:

[0108] Solution A was prepared by dissolving 1.0 mmol of copper chloride and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 45.0 mmol of urea solution in 30 mL of anhydrous ethanol for 8 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 6 hours. The temperature was controlled at 200°C during the reaction, and sonication was performed every 30 seconds for a total duration of 3 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the N-Cu-TiO2 visible light catalyst.

[0109] (2) Preparation of antifouling ultrafiltration membrane:

[0110] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and N-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, N-Cu-TiO2-0.6wt%, DMAc-80.4wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the mixture was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a room temperature liquid bath for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0111] The N-Cu-TiO2 visible light catalyst obtained in this embodiment is coffee-colored. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 420min.

[0112] Using the antifouling ultrafiltration membrane obtained in this embodiment, bovine serum albumin (BSA) aqueous solution was treated, and the pure water flux was measured to reach 411 L / m³. 2 At h bar, the retention rate of bovine serum albumin reached 96%.

[0113] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 80%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 82%.

[0114] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of N-Cu-TiO2 visible light catalyst, the adhesion rate of E. coli in the antifouling ultrafiltration membrane was reduced by 90%.

[0115] Comparative Example 2

[0116] The following steps were used to prepare a Mn-Cu-TiO2 visible light catalyst, which was then applied to an ultrafiltration membrane:

[0117] (1) Preparation of Mn-Cu-TiO2 visible light catalyst:

[0118] 1.16 mmol of manganese chloride, 1.0 mmol of copper chloride, and 22 mmol of tetrabutyl titanate were dissolved together in 30 mL of anhydrous ethanol to form solution A. 30 mL of anhydrous ethanol was sonicated for 8 hours, and hydrochloric acid was added to adjust the pH to 2 to form solution B. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 6 hours. The temperature was controlled at 200℃ during the reaction, with sonication occurring every 30 seconds for a total duration of 3 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-Cu-TiO2 visible light catalyst.

[0119] (2) Preparation of antifouling ultrafiltration membrane:

[0120] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-Cu-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-Cu-TiO2-0.6wt%, DMAc-80.4wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the mixture was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a room temperature liquid bath for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0121] The Mn-Cu-TiO2 visible light catalyst obtained in this embodiment is coffee-colored. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 320min.

[0122] Using the antifouling ultrafiltration membrane obtained in this embodiment, the pure water flux for treating bovine serum albumin (BSA) aqueous solution reached 413 L / m³. 2 The retention rate of bovine serum albumin reached 96% at h bar.

[0123] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 80%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 83%.

[0124] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of Mn-Cu-TiO2 visible light catalyst, the adhesion rate of E. coli of the antifouling ultrafiltration membrane was reduced by 90%.

[0125] Comparative Example 3

[0126] The following steps were used to prepare a Mn-N-TiO2 visible light catalyst and apply it to an ultrafiltration membrane:

[0127] (1) Preparation of Mn-N-TiO2 visible light catalyst:

[0128] Solution A was prepared by dissolving 1.16 mmol of manganese chloride and 22 mmol of tetrabutyl titanate in 30 mL of anhydrous ethanol. Solution B was prepared by sonicating 45.0 mmol of urea solution in 30 mL of anhydrous ethanol for 8 hours and adjusting the pH to 2 with hydrochloric acid. Solution B was then slowly added dropwise to solution A under stirring. After the mixture became transparent, it was transferred to a polytetrafluoroethylene (PTFE) liner, which was then placed in a reaction vessel, sealed, and transferred to an oven for an ultrasonic-low-temperature solvothermal reaction for 6 hours. The temperature was controlled at 200°C during the reaction, and sonication was performed every 30 seconds for a total duration of 3 hours at a frequency of 12500 Hz. After the reaction, the mixture was cooled to room temperature, centrifuged, and washed with anhydrous ethanol three times. The precipitate was then frozen for 12 hours and freeze-dried for 48 hours to obtain the Mn-N-TiO2 visible light catalyst.

[0129] (2) Preparation of antifouling ultrafiltration membrane:

[0130] In a water bath (temperature controlled within the range of 60–90°C), 50,000 Da of PVC, 10,000 Da of PEG, and Mn-N-TiO2 visible light catalyst were added to DMAc (PVC-17wt%, PEG-2wt%, Mn-N-TiO2-0.6wt%, DMAc-80.4wt%) and stirred for 6 hours to dissolve. After the PVC and PEG were completely dissolved, the mixture was degassed using a compressor pump and allowed to stand in a water bath for 12 hours to form a casting solution. The solution was then cooled to room temperature and transferred to a 75 g / m PET nonwoven fabric. A 200 μm thick liquid film was scraped out using a film scraper. The nonwoven fabric and liquid film were then transferred together to a liquid bath at room temperature for a phase inversion reaction. After the film was completely cured, it was transferred to deionized water to remove excess solvent. Finally, the film was stored in 20% glycerol water.

[0131] The Mn-N-TiO2 visible light catalyst obtained in this embodiment is coffee-colored. 0.1g of the catalyst can catalytically degrade 100mL of methyl orange (20mg / L) under simulated sunlight (35W xenon lamp), and the degradation is complete after 640min.

[0132] Using the antifouling ultrafiltration membrane obtained in this embodiment, bovine serum albumin (BSA) aqueous solution was treated, and the pure water flux was measured to reach 416 L / m³. 2 The retention rate of bovine serum albumin reached 96% at h bar.

[0133] After the antifouling ultrafiltration membrane obtained in this embodiment was used to treat humic acid aqueous solution, the flux decreased. After physical cleaning (i.e., backwashing with filtered water), the pure water flux recovery rate was 80%. After simulated sunlight irradiation (using a 35W xenon lamp as a stable light source for 3 hours), the pure water flux recovery rate reached 81%.

[0134] In the wastewater biological treatment system, the antifouling ultrafiltration membrane obtained in this embodiment was used to treat the secondary biological effluent. Compared with the PVC ultrafiltration membrane without the addition of Mn-N-TiO2 visible light catalyst, the adhesion rate of E. coli of the antifouling ultrafiltration membrane was reduced by 20%.

[0135] Results Analysis: The Mn-N-Cu-TiO2 visible light photocatalysts in Examples 1-3 were black; the visible light photocatalysts obtained in Comparative Examples 1-3, lacking one of Mn, N, and Cu respectively, were coffee-colored. Their catalytic degradation efficiency of methyl orange under simulated sunlight was significantly lower than that in Examples 1-3. When used in antifouling ultrafiltration membranes, the flux recovery rate of the contaminated ultrafiltration membranes after sunlight irradiation was significantly lower than that in Examples 1-3. This indicates that the co-doping of TiO2 with Mn, N, and Cu in this invention can improve the catalytic activity of the photocatalyst under visible light, thereby improving the antifouling performance of the ultrafiltration membrane. Cu doping can also enhance the antibacterial properties of the ultrafiltration membrane.

[0136] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An antifouling ultrafiltration membrane, characterized in that, It includes an ultrafiltration membrane base and a Mn-N-Cu-TiO2 visible light catalyst dispersed in the ultrafiltration membrane base; the Mn-N-Cu-TiO2 visible light catalyst is anatase TiO2 doped with Mn, N and Cu.

2. The antifouling ultrafiltration membrane as described in claim 1, characterized in that, The preparation method of the Mn-N-Cu-TiO2 visible light catalyst includes the following steps: dissolving manganese source, copper source and titanium dioxide precursor in solvent I, mixing them evenly to form solution A; dissolving nitrogen source in solvent I, mixing them evenly and adjusting the pH to 1.7~2.5 to form solution B; adding solution B dropwise to solution A under stirring conditions, mixing them evenly, and then carrying out an ultrasonic-low temperature solvothermal reaction; after the reaction is completed, separating the product to obtain the Mn-N-Cu-TiO2 visible light catalyst.

3. The antifouling ultrafiltration membrane as described in claim 2, characterized in that, The molar ratio of the manganese source, nitrogen source and copper source, respectively, is 1.0~1.5:87~95:1, calculated as Mn, N and Cu.

4. The antifouling ultrafiltration membrane as described in claim 2 or 3, characterized in that, The molar ratio of the copper source to the titanium dioxide precursor is 1:20~25, calculated as Cu and Ti respectively.

5. The antifouling ultrafiltration membrane as described in claim 2 or 3, characterized in that, The manganese source is a manganese salt, the nitrogen source is urea, the copper source is a copper salt, and the titanium dioxide precursor is tetrabutyl titanate.

6. The antifouling ultrafiltration membrane as described in claim 2, characterized in that, After dissolving the nitrogen source in solvent I, the mixture was sonicated for 4–8 h, and then the pH was adjusted to 1.7–2.

5.

7. The antifouling ultrafiltration membrane as described in claim 2, characterized in that, The ultrasonic-low temperature solvothermal reaction is carried out at a temperature of 150~300℃ for 5~8 h, with ultrasonication for 2.5~4 h during the reaction, and the ultrasonic frequency is 10000~15000 Hz.

8. The antifouling ultrafiltration membrane as described in claim 2, characterized in that, Solvent I is an organic alcohol.

9. The antifouling ultrafiltration membrane as described in claim 1, characterized in that, The mass ratio of the ultrafiltration membrane base to the Mn-N-Cu-TiO2 visible light catalyst is 1:0.03~0.

08.

10. A method for preparing an antifouling ultrafiltration membrane as described in any one of claims 1 to 9, characterized in that, Includes the following steps: The ultrafiltration membrane base material, pore-forming agent, and Mn-N-Cu-TiO2 visible light catalyst were added to solvent II. After complete dissolution, degassing and aging were performed to obtain a casting solution. The casting solution was transferred to a nonwoven fabric, and a liquid film was scraped out. Then, the nonwoven fabric and the liquid film were transferred together to a liquid bath for a phase inversion reaction. After the membrane was completely solidified, it was transferred to water to remove excess solvent II, thus obtaining an antifouling ultrafiltration membrane.

Images