Self-cleaning GO / CPU / PAA / TiO2 composite film and preparation method thereof
By preparing a self-cleaning GO/CPU/PAA/TiO2 composite membrane, the problems of low permeation flux and easy fouling of graphene oxide membranes were solved, achieving efficient dye separation and wastewater treatment, and exhibiting good self-cleaning and reusability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-28
- Publication Date
- 2026-03-27
AI Technical Summary
Existing graphene oxide membranes have low permeation flux and are easily fouled in water purification, which limits their application in dye separation and wastewater treatment.
A self-cleaning GO/CPU/PAA/TiO2 composite membrane was prepared by vacuum filtration self-assembly method to create a composite membrane with a unique intercalation structure. The core-shell structure of CPU microspheres is cross-linked with TiO2 to form nanochannels, which improves separation efficiency by combining hydrogen bonds and van der Waals forces, and achieves self-cleaning effect through photocatalysis.
It significantly improved the membrane's separation flux and rejection rate, enhanced its self-cleaning ability and reusability, and demonstrated excellent performance in dye separation and wastewater treatment.
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Figure CN116422160B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of membrane separation, and particularly relates to a self-cleaning GO / CPU / PAA / TiO2 composite membrane and a preparation method thereof. BACKGROUND
[0002] Dyes are usually applied to color textiles, leather, paper, food, etc. The large demand for dyes leads to an increase in industrial dye wastewater discharge. Almost all dyes have the characteristics of complex composition, toxicity, harm and almost non-biodegradability. Therefore, the large discharge of dye wastewater not only causes environmental pollution, but also affects human health and ecological balance. Membrane separation technology is widely concerned due to its high efficiency, low energy consumption and simple operation. Among them, graphene oxide (GO) has become the most widely used two-dimensional nanomaterial in membrane separation due to its rich surface oxygen-containing functional groups, adjustable interlayer spacing and good mechanical stability. However, the low permeation flux, easy pollution of membrane pores and membrane surface and other shortcomings limit the application of GO membranes in water purification. In order to solve these problems, photocatalytic nanomaterials are added to GO membranes, which can not only improve the permeability and separation efficiency of GO membranes, but also effectively resist membrane pollution and prolong the service life of the membranes. Therefore, developing a self-cleaning graphene oxide / photocatalytic material composite membrane has far-reaching significance for dye separation and wastewater treatment. SUMMARY
[0003] In view of the above problems, the application aims to provide a self-cleaning GO / CPU / PAA / TiO2 composite membrane and a preparation method thereof.
[0004] The technical scheme adopted by the application is as follows:
[0005] S1, preparation of carbon nanometer support ball CNS: taking a glucose solution, high-pressure hydrothermal reaction is carried out at a temperature of 180 DEG C for 24 hours, and after the reaction is completed, the product is collected by centrifugation and drying to obtain the carbon nanometer support ball CNS;
[0006] S2, preparation of CPU microspheres with shell-core structure: dispersing CNS in deionized water, adding a certain amount of Tris hydrochloride, adjusting pH to 8.5 with NaOH, and then adding hydrochloric acid dopamine, and stirring magnetically for 16 hours; after the reaction is completed, centrifugation and drying are carried out to obtain CNS / PDA balls coated with a layer of polydopamine on the surface; then the CNS / PDA balls are added into a DMF solution containing a proper amount of deionized water and stirred uniformly, and then ZrCl4 and 2-amino terephthalic acid are added and stirred for 30 minutes, respectively, and then placed in a hydrothermal kettle and heated at 120 DEG C for 48 hours; after the reaction is completed, centrifugation and drying are carried out with DMF and methanol for 24 hours to obtain CPU microspheres with shell-core structure with a layer of UiO-66-NH2 nano particles grown on the surface;
[0007] S3, Preparation of TiO2: Prepared by a simple solvothermal method; first, a proper amount of HF solution was gradually added into the n-butyll titanate solution, stirring for 30 min; then, solvothermal reaction was carried out at 180℃ for 24 h; then, white solid was collected and centrifuged several times by ethanol and deionized water; the obtained sample was dried at 60℃ overnight and vacuum treated at 120℃; finally, calcination in a muffle furnace was carried out to obtain the final sample;
[0008] S4, Preparation of CPU / PAA / TiO2 dispersion: CPU microspheres were mixed with deionized water for 20 min to obtain a CPU dispersion, then PAA solution was added and ultrasonic treatment was continued for 20 min to make it fully crosslinked to obtain a CPU / PAA dispersion; TiO2 was ultrasonically pretreated for 15 min to avoid nanoparticle agglomeration; the ultrasonically treated TiO2 was added to the above CPU / PAA dispersion and ultrasonic treatment was continued for 20 min; under the crosslinking action of PAA, TiO2 and CPU microspheres were successfully assembled to obtain a uniform CPU / PAA / TiO2 dispersion;
[0009] S5, Preparation of graphene oxide GO dispersion: GO powder was ultrasonically dispersed in deionized water to obtain a GO dispersion;
[0010] S6, The GO dispersion obtained in step S5 was mixed with deionized water and ultrasonically treated for 20 min, then the CPU / PAA / TiO2 dispersion obtained in step S4 was added and ultrasonic treatment was continued for 20 min to form a uniformly dispersed film-forming solution; under a pressure of 0.09 MPa, a self-cleaning GO / CPU / PAA / TiO2 composite membrane was prepared on the surface of a base film using a vacuum filtration device.
[0011] As a preferred, the glucose concentration in step S1 is 1M.
[0012] As a preferred, the CNS, Tris hydrochloride, and dopamine hydrochloride in step S2 are used in a mass ratio of 0.6:0.32:2.0, and saturated NaOH solution is used to adjust the pH.
[0013] As a preferred, the CNS / PDA balls, deionized water, DMF solution, ZrCl4, and 2-amino terephthalic acid in step S2 are used in an amount of 0.6 g, 5 mL, 50 mL, 0.233 g, and 0.181 g, respectively.
[0014] As a preferred, the amount of HF used in step S3 is 3 mL, and the amount of n-butyll titanate used is 30 mL.
[0015] As a preferred, the calcination temperature of TiO2 in step S3 is 300-550℃, the heating rate is 5℃ / min, and the calcination time is 2-4h.
[0016] As preferred, the centrifugal treatment method in steps S1, S2 and S3 is centrifuged 3-5 times, the centrifugal speed is 3500-6500 rpm, and each time is 5-10 min; drying is performed at 60 DEG C by using an oven.
[0017] As preferred, the CPU dispersion liquid concentration in step S4 is 0.2 mg / mL, the concentration ratio of CPU microspheres and TiO2 in the CPU / PAA / TiO2 dispersion liquid is 2:1, and the PAA usage amount is 0.5 mL; the GO dispersion liquid concentration in step S5 is 0.05 mg / mL.
[0018] As preferred, the self-cleaning GO / CPU / PAA / TiO2 composite film in step S6 has a GO mass and a CPU / PAA / TiO2 mass of 0-0.3 mg and 0-0.3 mg respectively loaded on each film, and the deionized water usage amount is 90-100 mL; the base film includes one or more of CA film, polyvinylidene fluoride film, nylon film, polyacrylonitrile film, polyether sulfone film and polysulfone film.
[0019] On the other hand, a self-cleaning GO / CPU / PAA / TiO2 composite film is provided, which is prepared by the preparation method in any one of the above.
[0020] Compared with other prior arts, the present application has the following advantages:
[0021] The present application adopts a simple vacuum filtration self-assembly method to prepare a self-cleaning GO / CPU / PAA / TiO2 composite film with a unique intercalation structure. The CPU with a shell-core structure prepared by a template method has a larger specific surface area and adsorption site, and the CPU, after cross-linking with TiO2 and PAA, acts as a filler to support the GO interlayer spacing to form a water channel. The strategy of constructing a nanochannel by hydrogen bond and van der Waals force greatly improves the separation flux and rejection rate of the film. In addition, the synergistic effect of CPU / PAA / TiO2 as an interlayer filler shows good photocatalytic self-cleaning effect and excellent reusability, and has excellent application prospect in dye separation and wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS
[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.
[0023] Figure 1A schematic diagram of a scanning electron microscope observation result of a cross section of a film prepared in Example 1 and Example 2 of the present application.
[0024] Figure 2 A schematic diagram of a three-dye separation cycle test result of a film prepared in Example 1 of the present application.
[0025] Figure 3 A schematic diagram of a cyclic test result of photocatalytic degradation of methylene blue of a film prepared in Example 1 of the present application. DETAILED DESCRIPTION
[0026] The present application will be described in detail below with specific examples, and the present application will be further illustrated below with the aid of the accompanying drawings and examples, comparative examples, and experimental examples.
[0027] Example 1
[0028] A self-cleaning GO / CPU / PAA / TiO2 composite film and a preparation method thereof, comprising the following steps:
[0029] S1: A glucose solution with a concentration of 1M was prepared, and after being stirred uniformly, a 24h high-pressure hydrothermal reaction was carried out at a temperature of 180℃; after the reaction was completed, the product was collected, and was centrifuged 5 times with deionized water and ethanol, respectively, at a centrifugal speed of 5000rpm for 5min each time, and was then dried in an oven at 60℃ to obtain carbon nanosphere support balls CNS.
[0030] S2: 0.6g of CNS and 0.32g of Tris buffer were sequentially added to 200mL of deionized water, and were mixed uniformly by magnetic stirring; then, the pH of the mixed solution was adjusted to 8.5 by saturated NaOH; subsequently, 2.0g of dopamine hydrochloride was added, and was magnetically stirred for 16h; after being centrifuged 4 times with deionized water and ethanol, CNS / PDA balls were obtained, and were vacuum treated at 80℃ for 24h; 5mL of deionized water was added to a beaker containing 50mL of DMF, and 0.6g of CNS / PDA was dissolved in the mixed solution; then, 0.233g of ZrCl4 and 0.181g of 2-amino terephthalic acid were sequentially added to the solution, and were stirred for 30min; next, a hydrothermal reaction was carried out at 120℃ for 48h; the product was washed with DMF and methanol; and then, the product CPU was obtained after being dried in an oven at 60℃ for 24h;
[0031] S3: 3mL of HF(40%) was gradually added to 30mL of n-butyl titanate, and was stirred for 30min; subsequently, a solvothermal reaction was carried out at 180℃ for 24h; then, white solids were collected and were centrifuged 5 times with ethanol and deionized water; the obtained sample was dried at 60℃ overnight; finally, the required sample was obtained after being calcined at 350℃ in a muffle furnace for 4h;
[0032] S4: the CPU microspheres were mixed with deionized water under ultrasonic for 20 min to obtain a CPU dispersion liquid with a concentration of 0.2 mg / mL; then 0.5 mL of PAA solution was added, and ultrasonic was continued for 20 min to make it fully crosslinked to prepare a CPU / PAA dispersion liquid; TiO2 was pretreated by ultrasonic for 15 min to avoid agglomeration of the nanoparticles; the TiO2 treated by ultrasonic was added into the above CPU / PAA dispersion liquid and ultrasonic was continued for 20 min, under the crosslinking action of PAA, TiO2 was assembled with the CPU microspheres, and a uniform CPU / PAA / TiO2 dispersion liquid was prepared, and the concentration ratio of the CPU microspheres to TiO2 was 2:1.
[0033] S5: the GO powder was ultrasonically dispersed in deionized water to obtain a GO dispersion liquid with a concentration of 0.05 mg / mL;
[0034] S6: the GO dispersion liquid obtained in step S5 was mixed with deionized water under ultrasonic for 20 min, then the CPU / PAA / TiO2 dispersion liquid obtained in step S4 was added and ultrasonic was continued for 20 min to form a dispersion liquid for film preparation; under the pressure condition of 0.09 MPa, a composite membrane was prepared on the surface of the CA base membrane of the porous support layer by using a vacuum filtration device, wherein the mass of GO and the mass of CPU / PAA / TiO2 loaded on the composite membrane were 0.3 mg and 0.3 mg respectively, and the amount of deionized water used was 95 mL, that is, a self-cleaning GO / CPU / PAA / TiO2 membrane.
[0035] Example 2
[0036] Different from example 1, in step S6 of the present example, the mass of GO and the mass of CPU / PAA / TiO2 loaded on the composite membrane were 0.3 mg and 0 respectively, and the amount of deionized water used was 95 mL, that is, a GO membrane.
[0037] Comparative Example 1
[0038] Different from example 1, in step S6 of the present comparative example, the mass of GO, the mass of CPU / PAA / TiO2 and the amount of deionized water loaded on the composite membrane were all 0, that is, a CA membrane base membrane.
[0039] Experimental Example 1
[0040] The cross-sections of the composite membranes obtained in example 1 and example 2 were observed by scanning electron microscopy, and the results are shown in Figure 1 Fig. 1(a) is a cross-sectional morphology diagram of the GO membrane obtained in example 2; Fig. 1(b) is a cross-sectional morphology diagram of the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in example 1; from Figure 1It can be seen that the self-cleaning GO / CPU / PAA / TiO2 film prepared in Example 1 exhibits a clear structure of CPU / PAA / TiO2 filler intercalated between the graphene oxide layers compared to the GO film prepared in Example 2, which has a close interlayer spacing. The successful construction of the intercalated structure not only provides more adsorption sites, but also forms water channels with a certain width, which improves the flux while ensuring high retention rate.
[0041] Experimental Example 2
[0042] The surface hydrophilicity of the self-cleaning GO / CPU / PAA / TiO2 film obtained in Example 1 and the GO film obtained in Example 2 was analyzed using a contact angle tester.
[0043] The water contact angle of the GO film obtained in Example 2 was 43.6°, and the water contact angle of the self-cleaning GO / CPU / PAA / TiO2 film obtained in Example 1 was 35.3°. Therefore, with the construction of the CPU / PAA / TiO2 intercalated GO interlayer structure, the water contact angle of the self-cleaning composite film decreases, and the hydrophilicity increases. The increase in hydrophilicity is beneficial to attracting water molecules into the water transport channel, which can effectively improve the membrane separation flux.
[0044] Experimental Example 3
[0045] The separation performance of the membranes was evaluated using a vacuum filtration device. The separation effect of the self-cleaning GO / CPU / PAA / TiO2 film obtained in Example 1 and the GO film obtained in Example 2 on 20 mL of pure water and 20 mL of three dyes, Congo red, methylene blue, and crystal violet, with a concentration of 20 mg / mL, was analyzed.
[0046] The water flux of the self-cleaning GO / CPU / PAA / TiO2 film obtained in Example 1 was significantly increased compared to the GO film obtained in Example 2. Due to the close stacking of GO, the pure water flux of the GO film obtained in Example 2 was very low, at 5.42 L·m -2 ·h -1 ·bar -1 . The pure water flux of the self-cleaning GO / CPU / PAA / TiO2 film obtained in Example 1 was 256.56 L·m -2 ·h -1 ·bar -1 ·bar -2 ·h -1 ·bar -1 , 4.59 L·m -2 ·h -1 ·bar-1 5.13 L·m -2 ·h -1 ·bar -1 The self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 achieved a separation flux of over 220 L·m for all three dyes. -2 ·h -1 ·bar -1 The separation flux was approximately 44 times that of the GO membrane obtained in Example 2. Furthermore, the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 exhibited rejection rates of 99.58%, 99.91%, and 99.86% for Congo red, methylene blue, and crystal violet, respectively, demonstrating superior dye separation performance compared to the GO membrane obtained in Example 2 (approximately 97%).
[0047] Experiment Example 4
[0048] The reusability of the membrane was evaluated using a vacuum filtration system. The membrane surface was rinsed three times with deionized water and ethanol before each cycle to remove any dye adhering to the membrane surface from the previous cycle. Figure 2 As shown, after 10 dye separation cycles, the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 exhibited retention rates of 98.16%, 98.65%, and 97.92% for Congo Red, Methylene Blue, and Crystal Violet, respectively. While the dye flux decreased slightly, it still reached 209.92 L·m⁻¹. -2 ·h -1 ·bar -1 209.25 L·m -2 ·h -1 ·bar -1 and 209.13 L·m -2 ·h -1 ·bar -1 Therefore, it can be considered that the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 has excellent reusability in practical applications.
[0049] Experimental Example 5
[0050] The photocatalytic effects of the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1, the GO membrane obtained in Example 2, and the CA membrane obtained in Comparative Example 1 were evaluated using a long-arc xenon lamp to simulate a visible light environment. The prepared membranes were placed face up in a jacketed beaker containing 50 mL of methylene blue solution (concentration 20 mg / mL), and circulating water was introduced to maintain the experimental temperature at approximately 20°C. Before photocatalysis, the beaker was placed in the dark for 60 min to reach adsorption equilibrium. Then, a 120 min methylene blue degradation experiment was conducted under visible light irradiation (500 W, long-arc xenon lamp, with the reaction temperature maintained at approximately 20°C by circulating water).
[0051] Tests showed that after 60 minutes under initial dark conditions, the concentration of methylene blue in the solution decreased over time as it was adsorbed onto the membrane. The self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 had an adsorption rate of 31.77%, while the GO membrane obtained in Example 2 had an adsorption rate of 13.26%, and the CA membrane obtained in Comparative Example 1 had an adsorption rate of only 3.23% (the CA membrane obtained in Comparative Example 1 was intended to eliminate the influence of the substrate membrane on methylene blue adsorption). The difference in adsorption rate also indicates that the GO / CPU / PAA / TiO2 membrane has a stronger adsorption efficiency for dyes than the GO and CA membranes, which is one of the reasons for the high dye rejection rate of the GO / CPU / PAA / TiO2 membrane. Compared with the methylene blue degradation rates of the CA membrane obtained in Comparative Example 1 and the GO membrane obtained in Example 2 (30.16% and 46.56%, respectively), the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 showed a higher methylene blue degradation rate (94.21%) due to the introduction of the high-performance photocatalyst CPU / PAA / TiO2. Therefore, it can be considered that the self-cleaning GO / CPU / PAA / TiO2 film obtained in Example 1 has excellent self-cleaning effect under visible light irradiation, which is of great significance for practical applications.
[0052] Experimental Example 6
[0053] The photodegradation cycling capability of the membrane was evaluated through a four-cycle repeated degradation experiment. After each cycle, the membrane was removed from the jacketed beaker and washed three times with deionized water before being added to the next cycle. Figure 3 As shown, the degradation rate of methylene blue by the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 showed a slight decreasing trend after 4 cycles. After the 4th cycle, the degradation rate of methylene blue remained at 90.50%. Therefore, it can be considered that the self-cleaning GO / CPU / PAA / TiO2 membrane obtained in Example 1 has excellent self-cleaning effect under visible light irradiation, and the membrane photocatalytic performance is stable, allowing for multiple recycling.
[0054] In summary, this invention utilizes a simple vacuum filtration self-assembly method to prepare a self-cleaning GO / CPU / PAA / TiO2 membrane with a unique intercalation structure. The layered structure of GO and the water channels formed by the photocatalytic nanofiller CPU / PAA / TiO2 coexist within the composite membrane. The cross-linking modification of CPU / PAA / TiO2 endows the composite membrane with excellent water flux, dye separation performance, and photocatalytic activity. Furthermore, the self-cleaning GO / CPU / PAA / TiO2 membrane exhibits excellent reusability in terms of dye separation and photocatalytic performance.
[0055] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art, without departing from the technical solution of the present application, can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, as long as it does not deviate from the technical solution of the present application, still belongs to the scope of the technical solution of the present application.
Claims
1. A method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane, characterized in that, Includes the following steps: S1. Preparation of carbon nanotube supported spheres (CNS): Glucose solution was subjected to high-pressure hydrothermal reaction at 180℃ for 24 hours. After the reaction was completed, the product was collected by centrifugation and drying to obtain carbon nanotube supported spheres (CNS). S2. Preparation of core-shell structured CPU microspheres: CNS was dispersed in deionized water, a certain amount of Tris hydrochloric acid was added, the pH was adjusted to 8.5 with NaOH, and then dopamine hydrochloride was added. The mixture was magnetically stirred for 16 h. After the reaction, the mixture was centrifuged and dried to obtain CNS / PDA spheres with a polydopamine coating on the surface. Subsequently, the CNS / PDA spheres were added to a DMF solution containing an appropriate amount of deionized water and stirred evenly. Then, ZrCl4 and 2-aminoterephthalic acid were added sequentially and stirred for 30 min. The mixture was then placed in a hydrothermal reactor and heated at 120℃ for 48 h. After the reaction, the mixture was centrifuged with DMF and methanol and dried for 24 h to obtain core-shell structured CPU microspheres with a UiO-66-NH2 nanoparticle layer on the surface. Preparation of S3 and TiO2: S3 and TiO2 were prepared via a simple solvothermal method. First, an appropriate amount of HF solution was gradually added dropwise to a tetrabutyl titanate solution and stirred for 30 min. Then, a solvothermal reaction was carried out at 180 °C for 24 h. Subsequently, the white solid was collected and centrifuged several times with ethanol and deionized water. The obtained sample was dried overnight at 60 °C and then vacuum-treated at 120 °C. Finally, it was calcined in a muffle furnace to obtain the final sample. S4. Preparation of CPU / PAA / TiO2 dispersion: CPU microspheres were mixed with deionized water and sonicated for 20 min to obtain CPU dispersion. PAA solution was then added and sonicated for another 20 min to fully crosslink the mixture and obtain CPU / PAA dispersion. TiO2 was sonicated for 15 min to prevent nanoparticles from agglomerating. The sonicated TiO2 was added to the above CPU / PAA dispersion and sonicated for another 20 min. Under the crosslinking effect of PAA, TiO2 and CPU microspheres were successfully assembled, and a uniform CPU / PAA / TiO2 dispersion was obtained. S5. Preparation of graphene oxide (GO) dispersion: GO powder was ultrasonically dispersed in deionized water and mixed evenly to obtain GO dispersion. S6. After mixing the GO dispersion obtained in step S5 with deionized water and sonicating for 20 min, add the CPU / PAA / TiO2 dispersion obtained in step S4 and continue sonicating for 20 min to form a uniformly dispersed film-forming solution. Under a pressure of 0.09 MPa, a self-cleaning GO / CPU / PAA / TiO2 composite membrane is formed on the surface of the bottom membrane using a vacuum filtration device.
2. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: The concentration of the glucose solution in step S1 is 1M.
3. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: In step S2, the ratio of CNS to Tris hydrochloric acid to dopamine hydrochloride is 0.6:0.32:2.0 by mass, and the pH is adjusted using saturated NaOH solution.
4. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: In step S2, the amounts of CNS / PDA spheres, deionized water, DMF solution, ZrCl4, and 2-aminoterephthalic acid used are 0.6 g, 5 mL, 50 mL, 0.233 g, and 0.181 g, respectively.
5. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: In step S3, the amount of HF solution used is 3 mL, and the amount of tetrabutyl titanate solution used is 30 mL.
6. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: The calcination temperature in step S3 is 300–450℃, the heating rate is 5℃ / min, and the calcination time is 2–4h.
7. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: In steps S1, S2 and S3, the centrifugation treatment method is to centrifuge 3 to 5 times, with a centrifugation speed of 3500 to 6500 rpm, for 5 to 10 minutes each time, and then dry it in an oven at 60°C.
8. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: In step S4, the concentration of the CPU dispersion is 0.2 mg / mL, the concentration ratio of CPU microspheres to TiO2 in the CPU / PAA / TiO2 dispersion is 2:1, and the amount of PAA solution used is 0.5 mL; in step S5, the concentration of the GO dispersion is 0.05 mg / mL.
9. The method for preparing a self-cleaning GO / CPU / PAA / TiO2 composite membrane according to claim 1, characterized in that: In the self-cleaning GO / CPU / PAA / TiO2 composite membrane described in step S6, the mass of GO and the mass of CPU / PAA / TiO2 loaded on each membrane are 0-0.3 mg and 0-0.3 mg, respectively, and the amount of deionized water used is 90-100 mL; the bottom membrane includes one or more of CA membrane, polyvinylidene fluoride membrane, nylon membrane, polyacrylonitrile membrane, polyethersulfone membrane, and polysulfone membrane.
10. A self-cleaning GO / CPU / PAA / TiO2 composite membrane, characterized in that: The self-cleaning GO / CPU / PAA / TiO2 composite membrane is prepared by the preparation method described in any one of claims 1 to 9.