A composite photocatalyst modified antifouling reverse osmosis membrane and device thereof

Abstract

The application discloses a composite photocatalyst modified anti-fouling reverse osmosis membrane and a device thereof, a piezoelectric photocatalyst Bi4O5Br2@PTTC with organic-inorganic hybridization and double functions of piezoelectric antibiosis and photodynamic antibiosis is prepared, the catalyst is applied to a modified cellulose acetate reverse osmosis membrane, and an existing reverse osmosis device is simply modified to adapt to the reverse osmosis membrane in the application. The prepared cellulose acetate reverse osmosis membrane not only has excellent antibiosis performance, but also has the function of resisting biofilm. The prepared membrane is very suitable for application in seawater desalination, can reduce and inhibit the growth and reproduction of microorganisms on the membrane surface, and greatly prolongs the service life of the cellulose acetate reverse osmosis membrane.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membrane functionalization technology, specifically relating to a composite photocatalyst-modified antifouling reverse osmosis membrane and its device. Background Technology

[0002] Rapid population growth and industrialization have brought serious problems such as freshwater shortages and environmental pollution. Pollution of freshwater resources and the scarcity of safe drinking water are the main causes of freshwater shortages. Seawater desalination is considered a major solution to alleviate water scarcity in this century. Reverse osmosis technology, due to its advantages of simple process, low energy consumption, high efficiency, and environmental friendliness, has gradually entered industrial applications. Currently, the main components of reverse osmosis membranes are generally polyamide or cellulose acetate. Cellulose acetate, as a widely available and biodegradable environmentally friendly material, has the characteristics of abundant resources, good hydrophilicity, high desalination rate, and good film-forming properties. Importantly, cellulose acetate has excellent chlorine resistance. Cellulose acetate membranes can be stably used in applications with a concentration of 1 mg·L⁻¹ for extended periods. -1 The separation performance of the activated chlorine solution remained largely unchanged. Recent research has yielded cellulose acetate membranes with promising applications in water treatment.

[0003] However, due to the inherent surface structure and physicochemical properties of the membrane, biofouling poses the greatest threat to cellulose acetate reverse osmosis membranes. Various bacteria present in seawater can attach to and multiply on the surface of cellulose acetate membranes, even forming biofilms. Once a biofilm forms, it leads to higher transmembrane pressure (TMP), resulting in increased operating costs and poor membrane performance. Furthermore, the membrane may be degraded and damaged by acidic byproducts from microorganisms in the biofouling layer, shortening its lifespan; and, because the osmosis equipment is high-pressure and sealed, periodic cleaning significantly increases the operating costs of the reverse osmosis membrane. Summary of the Invention

[0004] To address the problem that biofilms easily form on the surface of cellulose acetate reverse osmosis membranes, leading to increased operating costs and poor membrane performance, this invention provides a composite photocatalyst-modified antifouling reverse osmosis membrane and its device. By loading the piezoelectric photocatalyst Bi4O5Br2@PTTC onto the cellulose acetate reverse osmosis membrane, the cellulose acetate reverse osmosis membrane not only possesses excellent antibacterial properties but also has anti-biofilm function.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A composite photocatalyst, specifically Bi4O5Br2@PTTC, wherein the PTTC is: Poly((2Z,3E)-2-((5”-methyl-[2,2':5',2”-terthiophen]-5-yl)methylene)-5-methylenehex-3-enedinitrile).

[0007] The Bi4O5Br2@PTTC was prepared by the following method: 1g Bi4O5Br2, 36.5-219mg 3T-2CHO, and 14-84mg (E)-hex-3-enadionitrile were placed in 20mL of ultra-dry ethanol; 2mL of 20wt% sodium ethoxide ethanol solution was added to the solution using a syringe under nitrogen atmosphere; the solution was refluxed at 60℃ for 48h; after washing and drying, the resulting product was Bi4O5Br2@PTTC.

[0008] The 3T-2CHO was prepared by the following method: 6 mL of ultra-dry N,N-dimethylformamide was injected into a nitrogen-filled flask, and 2 mL of phosphorus oxychloride (POCl3) was slowly added under ice bath conditions, and the mixture was stirred for 1 h; 2 g of 2,2′:5′,2″-trithiophene was weighed, dissolved in 10 mL of anhydrous N,N-dimethylformamide, and slowly added to the flask, and stirred for 1 h; the mixture was transferred to an 80℃ oil bath and refluxed for 12 h; after purification by column chromatography, 2,2′:5′,2″-trithiophene-5,5″-dicarboxaldehyde was obtained, which is 3T-2CHO.

[0009] The Bi4O5Br2 was prepared by the following method:

[0010] 1455.2 mg Bi(NO3)3·5H2O was dissolved in 60 mL of a mixed solution of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 2:1. Then, 546.7 mg CTAB was added and the mixture was stirred for 1 h. After adding 2.5 mL of 3 M NaOH aqueous solution, the suspension was stirred for another 30 min. The mixture was reacted at 160 °C for 24 h. After washing with distilled water and ethanol, Bi4O5Br2 was obtained.

[0011] Application of the composite photocatalyst in resisting reverse osmosis membrane biofouling.

[0012] The reverse osmosis membrane is a cellulose acetate reverse osmosis membrane.

[0013] The cellulose acetate reverse osmosis membrane is loaded with Bi4O5Br2@PTTC.

[0014] The cellulose acetate reverse osmosis membrane loaded with Bi4O5Br2@PTTC was prepared by the following method:

[0015] Mix 1.56g cellulose acetate with 0.576g maleic acid, and dissolve the solid in 10mL of a mixed solvent of 1,4-dioxane, acetone and methanol. Add 0.5g of the composite catalyst Bi4O5Br2@PTTC and stir for 30min. Let stand overnight to obtain the casting solution. Slowly pour the casting solution onto a smooth glass surface and use a film scraper to evenly process it to form a film of a certain thickness. Then immerse and wash in deionized water to remove the solvent.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] (1) After the catalyst is loaded, the permeate flux and salt rejection rate of the reverse osmosis membrane are slightly reduced, but the membrane’s resistance to biofouling is greatly improved. In particular, the membrane is endowed with photosensitive antibacterial and piezoelectric antibacterial properties, which greatly extends the membrane’s service life.

[0018] (2) In addition to its superior antibacterial properties, the composite catalyst also has the ability to eliminate mature biofilms, which greatly enhances the membrane's resistance to biofilm adhesion and indirectly extends its service life.

[0019] (3) Existing devices can achieve efficient decontamination of reverse osmosis membranes without disassembling the machine, simply by making simple modifications.

[0020] Bi4O5Br2 possesses piezoelectric properties, enabling it to convert mechanical energy into chemical energy. Poly((2Z,3E)-2-((5”-methyl-[2,2':5',2”-terthiophen]-5-yl)methylene)-5-methylenehex-3-enedinitrile (PTTC) is an organic semiconductor designed and synthesized in this invention. It plays a role in regulating the energy band and improving light absorption in the overall material, significantly overcoming the weakness of Bi4O5Br2 in visible light absorption and improving the overall light energy conversion efficiency. Under light irradiation or certain pressure, it can generate active oxygen with bactericidal properties; therefore, the catalyst as a whole possesses piezoelectric, photosensitive, and antibacterial characteristics. Attached Figure Description

[0021] Figure 1 This is a simplified diagram of the preparation of Bi4O5Br2@PTTC.

[0022] Figure 2 Here is the synthesis equation for PTTC.

[0023] Figure 3 A schematic diagram of the structure of a device modified to adapt to the reverse osmosis membrane in this invention.

[0024] Figure 4A schematic diagram of the structure of a device modified to adapt to the reverse osmosis membrane in this invention.

[0025] Figure 5 The photodynamic antibacterial effect of reverse osmosis membrane modified with composite catalyst.

[0026] Figure 6 The anti-biofilming ability of reverse osmosis membranes modified with composite catalysts.

[0027] Figure 7 This is a UV-Vis diffuse reflectance spectrum.

[0028] Figure 8 This is a transient photocurrent diagram.

[0029] Figure 9 This is a transient piezoelectric current diagram.

[0030] In the picture, 1 is the water inlet, 2 is the LED light strip, 3 is the transparent water collection pipe, 4 is the outer shell, 5 is the acrylic sheet, and 6 is the water inlet. Detailed Implementation

[0031] To illustrate this invention, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments. This invention utilizes a piezoelectric photocatalyst, Bi4O5Br2@PTTC, loaded onto a cellulose acetate reverse osmosis membrane, thereby enabling the cellulose acetate reverse osmosis membrane to possess not only excellent antibacterial properties but also anti-biofilm formation capabilities. A simplified diagram of the Bi4O5Br2@PTTC preparation process is shown below. Figure 1 As shown, the synthesis equation for PTTC is as follows: Figure 2 As shown.

[0032] Example 1

[0033] This example demonstrates an application of Bi4O5Br2@PTTC preparation. The specific steps are as follows:

[0034] Preparation of 3T-2CHO:

[0035] 6 mL of ultra-dry N,N-dimethylformamide was injected into a nitrogen-filled flask, and 2 mL of phosphorus oxychloride (POCl3) was slowly added under ice bath conditions, with stirring for 1 h. 2 g of 2,2′:5′,2″-trithiophene was weighed, dissolved in 10 mL of anhydrous N,N-dimethylformamide, and slowly added to the flask, with stirring for 1 h. The mixture was then transferred to an 80 °C oil bath and refluxed with stirring for 12 h. After purification by column chromatography, 2,2′:5′,2″-trithiophene-5,5″-dicarboxaldehyde (3T-2CHO) was obtained.

[0036] Preparation of Bi4O5Br2:

[0037] 1455.2 mg Bi(NO3)3·5H2O was dissolved in 60 mL of a mixed solution of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 2:1. Then, 546.7 mg CTAB was added and the mixture was stirred for 1 h. After adding 2.5 mL of 3 M NaOH aqueous solution, the suspension was stirred for another 30 min. The mixture was reacted at 160 °C for 24 h. After washing with distilled water and ethanol, Bi4O5Br2 was obtained.

[0038] Preparation of Bi4O5Br2@PTTC:

[0039] 1 g Bi4O5Br2, 73 mg 3T-2CHO, and 28 mg (E)-hexyl-3-enadionitrile were placed in 20 mL of ultra-dry ethanol. Under nitrogen atmosphere, 2 mL of sodium ethoxide ethanol solution (20 wt%) was added to the solution using a syringe. The solution was refluxed at 60 °C for 48 h. After washing and drying, the resulting composite catalyst was labeled Bi4O5Br2@PTTC-10.

[0040] Preparation of cellulose acetate reverse osmosis membrane:

[0041] Mix 1.56g cellulose acetate with 0.576g maleic acid, and dissolve the solid in 10mL of a mixed solvent of 1,4-dioxane, acetone and methanol. Add 0.5g of the composite catalyst Bi4O5Br2@PTTC and stir for 30min. Let stand overnight to obtain the casting solution. Slowly pour the casting solution onto a smooth glass surface and use a film scraper to evenly process it to form a film of a certain thickness. Then immerse and wash in deionized water to remove the solvent.

[0042] Example 2

[0043] This embodiment is another application example of the preparation of Bi4O5Br2@PTTC. Except for the different components in the preparation of Bi4O5Br2@PTTC compared to Example 1, the other steps are the same as in Example 1.

[0044] Preparation of Bi4O5Br2@PTTC:

[0045] 1 g Bi4O5Br2, 36.5 mg 3T-2CHO, and 14 mg (E)-hexyl-3-enadionitrile were placed in 20 mL of ultra-dry ethanol. Under nitrogen atmosphere, 2 mL of sodium ethoxide ethanol solution (20 wt%) was added to the solution using a syringe. The solution was refluxed at 60 °C for 48 h. After washing and drying, the resulting composite catalyst was labeled Bi4O5Br2@PTTC-5.

[0046] Example 3

[0047] This embodiment is another application example of the preparation of Bi4O5Br2@PTTC. Except for the different components in the preparation of Bi4O5Br2@PTTC compared to Example 1, the other steps are the same as in Example 1.

[0048] Preparation of Bi4O5Br2@PTTC: 1g Bi4O5Br2, 219mg of 3T-2CHO, and 84mg of (E)-hexane-3-enedionitrile were used to obtain the composite catalyst labeled Bi4O5Br2@PTTC-30.

[0049] Example 4

[0050] This embodiment is an application example of preparing Bi4O5Br2 catalyst without PTTC hybridization. The catalyst supported on the reverse osmosis membrane in this embodiment uses Bi4O5Br2, and its preparation steps are the same as in Example 1. The resulting catalyst is labeled as Bi4O5Br2.

[0051] Preparation of cellulose acetate reverse osmosis membrane: 1.56g of cellulose acetate was mixed with 0.576g of maleic acid, and 10mL of a mixed solvent of 1,4-dioxane, acetone and methanol was added to dissolve the solid; 0.5g of catalyst Bi4O5Br2 was added and stirred for 30min; the mixture was allowed to stand overnight to obtain the casting solution; the casting solution was slowly poured onto a smooth glass surface and uniformly treated with a membrane scraper to form a membrane of a certain thickness; then the membrane was immersed in deionized water for coagulation and washed to remove the solvent.

[0052] Example 5

[0053] This example is an example for evaluating antibacterial activity.

[0054] Taking Pseudomonas aeruginosa as an example, the Pseudomonas aeruginosa suspension cultured overnight was diluted to OD. 600 =0.01, the cellulose acetate reverse osmosis membranes from Examples 1, 2, 3, and 4 were mixed with the diluted bacterial solution, and dark and light groups were set up. Both dark and light groups were simultaneously incubated at 37°C for 1 hour. After incubation, the dark group was diluted with PBS buffer. 4 After dilution, the mixture was plated; the light-treated group was irradiated with a xenon lamp for 30 minutes after the culture was completed, and then diluted with PBS buffer. 4 After dilution, the plates were spread on plates. The spread plates were then incubated overnight at 37°C. The antibacterial performance was then determined based on the colony count. Results are as follows: Figure 5 As shown.

[0055] Example 6

[0056] This example is a biofilm resistance assessment example.

[0057] Taking *Pseudomonas aeruginosa* as an example, the effect of an antifouling reverse osmosis membrane on biofilm disruption and bacterial viability of *P. aeruginosa* was studied. *P. aeruginosa* was cultured in TSB medium for 6–8 h and diluted to OD0.05. 600 The initial solution was 0.02. Then, 200 μL of the initial solution was added to each well, and the mixture was incubated at 37°C for 36 h in a constant temperature incubator. Under static conditions, *Pseudomonas aeruginosa* formed a biofilm in 96 wells. After incubation, the biofilm was rinsed with sterile water to remove adhering bacteria. The obtained biofilm was mixed with 200 μL of sterile water and the reverse osmosis membrane with the highest sterilization efficiency in Example 4 (i.e., the reverse osmosis membrane in Example 1), and irradiated for 30 min. After irradiation, the biofilm was rinsed with sterile water and then stained with 4,6-diamino-2-phenylindole (DAPI). The results were observed using a laser confocal scanning microscope (CLSM) at an excitation wavelength of 461 nm. Figure 6 As shown.

[0058] Example 7

[0059] This example demonstrates the UV-Vis diffuse reflectance spectroscopy testing of the prepared catalysts Bi4O5Br2 and Bi4O5Br2@PTTC.

[0060] The UV-Vis diffuse reflectance spectra of the Bi4O5Br2@PTTC catalyst of Example 1 and the Bi4O5Br2 catalyst of Example 4 were measured in a Shimadzu UV3600 UV-Vis diffuse reflectance spectrometer (UV-visDRS). The results are as follows: Figure 7 As shown.

[0061] Example 8

[0062] This embodiment demonstrates the transient photocurrent and transient piezoelectric current testing of the prepared Bi4O5Br2@PTTC cellulose acetate reverse osmosis membrane.

[0063] The reverse osmosis membrane from Example 1 was loaded onto an ITO glass electrode, and transient current intensity was tested in a three-electrode system (counter electrode: platinum electrode; reference electrode: Ag / AgCl; working electrode: ITO). The transient photocurrent was emitted from a xenon lamp, with a 20-second darkness cycle followed by a 20-second illumination cycle, repeated at least four times. The piezoelectric current was simulated using a small ultrasonic generator, with a 20-second off cycle followed by a 20-second on cycle, repeated at least four times. The results are as follows: Figure 8 , Figure 9 As shown.

[0064] To fully utilize the performance of the reverse osmosis membrane with the supported piezoelectric photocatalyst in this invention, existing reverse osmosis devices need to be improved. This will enable low-cost sterilization and decontamination removal of the reverse osmosis membrane, significantly extending its service life. The specific operation is as follows:

[0065] First, the reverse osmosis unit operates in a closed, high-pressure environment, therefore a catalyst with piezoelectric properties was chosen. During the high-pressure water filtration process, mechanical energy is converted into chemical energy, generating highly biotoxic reactive oxygen species. This ensures the membrane's ability to sterilize and remove biofilm even in the dark.

[0066] Secondly, a spiral LED light strip was installed between the device casing and the RO membrane, and encapsulated with acrylic glass to ensure watertightness; simultaneously, the collection tube was replaced with a transparent material, and an LED light strip was installed inside it. The specific structure is as follows: Figure 3 , Figure 4 As shown, 1 is the water collection port, 2 is the LED light strip, 3 is the transparent water collection pipe, 4 is the outer shell, 5 is the acrylic sheet, and 6 is the water inlet. Because the photosensitizer has a short-term, highly effective bactericidal ability, without compromising water purification efficiency, only a short period of light exposure is needed to cause the photosensitizer to remove almost all bacteria and biofilm from the membrane.

[0067] In summary, this invention provides a new improvement route for the preparation of antibacterial and anti-biofilm seawater desalination devices, making up for the shortcomings of commercially available reverse osmosis membranes in preventing biofouling and greatly improving the service life of cellulose acetate membranes.

Claims

1. A composite photocatalyst, characterized in that, Specifically, it is Bi4O5Br2@PTTC, where PTTC is: Poly((2Z,3E)-2-((5''-methyl-[2,2':5',2''-terthiophen]-5-yl)methylene)-5-methylenehex-3-enedinitrile); The Bi4O5Br2@PTTC was prepared by the following method: 1g Bi4O5Br2, 36.5~219mg 3T-2CHO, and 14~84mg (E)-hexane-3-enedionitrile were placed in 20mL of ultra-dry ethanol; 2mL of 20wt% sodium ethoxide ethanol solution was added to the solution using a syringe under nitrogen atmosphere; the solution was refluxed at 60°C for 48h; after washing and drying, the result was Bi4O5Br2@PTTC. The 3T-2CHO was prepared by the following method: 6 mL of ultra-dry N,N-dimethylformamide was injected into a nitrogen-filled flask, and 2 mL of phosphorus oxychloride (POCl3) was slowly added under ice bath conditions, and the mixture was stirred for 1 h; 2 g of 2,2′:5′,2′′-trithiophene was weighed, dissolved in 10 mL of anhydrous N,N-dimethylformamide, and slowly added to the flask, and stirred for 1 h; the mixture was transferred to an 80°C oil bath and refluxed for 12 h; after purification by column chromatography, 2,2':5',2''-trithiophene-5,5''-dicarboxaldehyde was obtained, which is 3T-2CHO.

2. The composite photocatalyst according to claim 1, characterized in that, The Bi4O5Br2 was prepared by the following method: 1455.2 mg Bi(NO3)3∙5H2O was dissolved in 60 mL of a mixed solution of ethylene glycol and water, with a volume ratio of ethylene glycol to water of 2:

1. Then, 546.7 mg CTAB was added and the mixture was stirred for 1 h. After adding 2.5 mL of 3 M NaOH aqueous solution, the suspension was stirred for another 30 min. The mixture was reacted at 160°C for 24 h. After washing with distilled water and ethanol, Bi4O5Br2 was obtained.

3. The application of the composite photocatalyst according to claim 1 on an antifouling reverse osmosis membrane.

4. The application of the composite photocatalyst according to claim 3 on an antifouling reverse osmosis membrane, characterized in that, The reverse osmosis membrane is a cellulose acetate reverse osmosis membrane.

5. The application of the composite photocatalyst according to claim 4 in an antifouling reverse osmosis membrane, characterized in that, The cellulose acetate reverse osmosis membrane is achieved by loading Bi4O5Br2@PTTC.

6. The application of the composite photocatalyst according to claim 5 on an antifouling reverse osmosis membrane, characterized in that, The cellulose acetate reverse osmosis membrane loaded with Bi4O5Br2@PTTC was prepared by the following method: Mix 1.56g cellulose acetate with 0.576g maleic acid, and dissolve the solid in 10mL of a mixed solvent of 1,4-dioxane, acetone and methanol. Add 0.5g of the composite catalyst Bi4O5Br2@PTTC and stir for 30min. Let stand overnight to obtain the casting solution. Slowly pour the casting solution onto a smooth glass surface and use a film scraper to evenly process it to form a film of a certain thickness. Then immerse and wash in deionized water to remove the solvent.

7. A reverse osmosis device, characterized in that, The device uses a cellulose acetate reverse osmosis membrane as described in any one of claims 5-6, loaded with Bi4O5Br2@PTTC, and includes an internal light strip and a transparent water collection pipe.

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