Polyurethane modified poly (arylene ether nitrile oxime) photocatalytic oil-water separation membrane and preparation method thereof

Abstract

The invention relates to a polyurethane modified poly (arylene ether nitrile oxime) photocatalytic oil-water separation membrane and a preparation method thereof, and belongs to the technical field of polymer separation membrane materials. Comprising the following steps: 1) adding TiO2 / MCD hybrid particles and amphiphilic polyurethane into N, N-dimethylacetamide to obtain a homogeneous solution; 2) dissolving polyarylene ether nitrile oxime and LiCl in N, N-dimethylacetamide, and then adding the solution prepared in the previous step to obtain a membrane casting solution; and (3) blade-coating a glass plate with the membrane casting solution, and carrying out phase separation in deionized water to obtain the separation membrane. According to the invention, amphiphilic polyurethane and TiO2 / modified carbon dot hybrid particles are used as a PEN-Ao membrane modifier, and the modified membrane is endowed with photocatalytic performance. The obtained composite membrane is excellent in oil-water separation performance and photocatalytic capacity, has good stability and reusability when being used for treating complex dye oil-containing aqueous emulsion, and provides a new thought for development and utilization of polymeric membrane substrates and preparation of hydrophilic photocatalytic membranes.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer separation membrane materials, and particularly relates to a polyurethane-modified polyarylether nitrile oxime photocatalytic oil-water separation membrane and a preparation method thereof. Background Art

[0002] With the continuous increase in the discharge of industrial and textile wastewater, oil-containing wastewater that is difficult to degrade under natural conditions has had a profound negative impact on human health and the ecological environment. At present, traditional pollutant treatment methods, such as centrifugal separation, chemical coagulation, and redox methods, are restricted by many factors in implementation. Most of these methods require a large amount of energy or chemical reagent input to achieve, making them inapplicable to large-scale industrial production in terms of cost, operability, and environmental safety factors. Therefore, low-energy and high-efficiency water pollution treatment technologies are a hot topic of global concern today. Compared with traditional pollution treatment methods, membrane separation technology has gradually become an important technology in the field of wastewater treatment due to its advantages of simple operation, high efficiency, and low energy consumption. According to membrane materials, separation membranes can be divided into inorganic separation membranes and polymer separation membranes. Polymer separation membranes (such as polyvinylidene fluoride, polysulfone, polyacrylonitrile, and polyarylether nitrile) have been widely used in the treatment of oil-containing wastewater due to their simple production process, excellent flexibility, ease of modification, and easy industrial production.

[0003] However, actual oily sewage often presents a complex multiphase system, especially oil-water emulsions containing surfactants and dyes, which makes it difficult for single-functional oil-water separation membranes to meet the multiple requirements in wastewater treatment. Therefore, developing membrane materials with multiple functions to achieve efficient removal of oils and other pollutants has become an urgent challenge in the field of wastewater treatment.

[0004] As a novel multifunctional material, photocatalytic separation membranes exhibit remarkable advantages in oil-water separation, pollutant degradation, self-cleaning, etc. Photocatalytic separation membranes can effectively degrade organic pollutants and convert them into harmless substances (such as CO2 and H2O), demonstrating excellent environmental protection performance. However, due to the hydrophobicity of the membrane matrix, these photocatalytic membranes usually face the problem of poor anti-pollution ability, and the surface is easily contaminated by oil, resulting in a significant decrease in their separation efficiency over time. To solve this problem, researchers have developed various hydrophilic photocatalytic membranes in recent years. Generally, these membranes are hydrophilically modified by grafting polymers onto the membrane surface or by compounding hydrophilic nanoparticles or polymer matrices. Although these hydrophilic photocatalytic membranes have improved the hydrophilicity of the membranes to a certain extent, they still face problems such as complex modification processes and weak binding forces between hydrophilic fillers and hydrophobic substrates in practical applications, leading to filler shedding and uneven dispersion, thus affecting the hydrophilic modification effect of the membranes. In addition, the poor interaction between hydrophilic photocatalysts and hydrophobic polymer substrates is also prone to cause self-aggregation of photocatalysts, thereby limiting their photocatalytic performance. Therefore, how to develop a new type of multifunctional composite membrane with enhanced hydrophilicity and photocatalytic performance through a simple process has become an urgent and important topic in the current research of membrane separation technology. Summary of the Invention

[0005] The object of the present invention is to propose a polyurethane (PU)-modified polyarylether nitrile oxime (PEN-Ao) photocatalytic oil-water separation membrane and a preparation method thereof with a simple process and excellent stability in view of the problems existing in the background technology. The present invention introduces TiO2 / MCD hybrids, which not only improve the hydrophilicity of the composite membrane but also endow the separation membrane with excellent photocatalytic performance; the amphiphilic PU forms hydrogen bonds with PEN-Ao rich in functional groups, ensuring permanent hydrophilic modification while promoting the uniform dispersion of TiO2 / MCD hybrids and improving their light utilization rate, resulting in enhanced photocatalytic performance.

[0006] To achieve the above object, the technical scheme adopted by the present invention is as follows:

[0007] A preparation method of a polyurethane-modified polyarylether nitrile oxime photocatalytic oil-water separation membrane, comprising the following steps:

[0008] Step 1. Add 0.03 - 0.07 parts by mass of TiO2 / MCD hybrid particles and 0.1 - 0.3 parts by mass of amphiphilic polyurethane (PU) to 1 - 3 parts by mass of N,N-dimethylacetamide (DMAc) solvent, and stir and dissolve at 30°C to obtain a red TiO2 / MCD-PU-DMAc homogeneous solution;

[0009] Step 2. Dissolve 0.2 - 0.4 parts by mass of polyarylether nitrile oxime (PEN-Ao) and 0.04 - 0.08 parts by mass of LiCl in 1 - 3 parts by mass of N,N-dimethylacetamide (DMAc) solvent. Then add the TiO2 / MCD-PU-DMAc homogeneous solution prepared in Step 1 thereto, and stir and dissolve at 25 - 50 °C to obtain a homogeneous and bubble-free casting solution;

[0010] Step 3. At room temperature, scrape the homogeneous and bubble-free casting solution obtained in Step 2 onto a clean glass plate. After exposing it to the air for 10 - 30 s, put it into a container filled with 400 - 800 mL of deionized water and soak for 12 - 24 h for phase separation to obtain the photocatalytic oil-water separation membrane.

[0011] Furthermore, the synthesis route of the amphiphilic polyurethane (PU) described in Step 1 is as follows:

[0012]

[0013] Furthermore, the structural formula of the amphiphilic polyurethane (PU) described in Step 1 is:

[0014]

[0015] Furthermore, the amphiphilic polyurethane (PU) described in Step 1 is obtained by reacting a diisocyanate and a polyol at 50 - 80 °C to form a prepolymer, and then adding a chain extender to continue growing the molecular chain of the prepolymer. Among them, the diisocyanate is two of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate or lysine diisocyanate, and the molar ratio of the two is 1:1; the polyol is a mixture of a hydrophilic polyol and a hydrophobic polyol with a mass ratio of 2:1. The hydrophilic polyol is two or more of polycaprolactone diol with a molecular weight of 600 - 2000, polyethylene glycol, and polypropylene glycol. The hydrophobic polyol is two or more of polytetrahydrofuran diol with a molecular weight of 1000 - 4000, polybutylene adipate, and polycarbonate diol; the chain extender is two or more of 1,4-butanediol, ethylene glycol, 2,2-dihydroxymethylpropionic acid, and p-hydroxyanisole.

[0016] More specifically, the preparation process of the amphiphilic polyurethane (PU) described in Step 1 is as follows:

[0017] (1) Mix the diisocyanate and the polyol (molar ratio m NCO :m OH = 2:1 - 3:1), and react at 50 - 80 °C for 2 - 4 h to form a prepolymer;

[0018] (2) Dilute the prepolymer with an organic solvent (acetone), and add a chain extender to continue growing the molecular chain of the prepolymer and increase the molecular weight. When the NCO content in the system is less than 5% (test the NCO in the system by the dibutylamine titration method), the reaction ends (the part marked in red in the figure is the chain extender).

[0019] Furthermore, the TiO2 / MCD hybrid particles described in step 1 are hydrophilic nanoparticles obtained by a two-step hydrothermal reaction, composed of TiO2 and modified carbon dots (CQs), and the modified carbon dots (CQs) account for 5-10 wt% of the mass of the TiO2 / MCD hybrid particles.

[0020] Furthermore, in step 1, the stirring is carried out in a magnetic stirrer for 30-60 min at a rotation speed of 500-1000 rpm. After stirring, ultrasonicate for 10-30 min to obtain a red TiO2 / MCD-PU-DMAc homogeneous solution.

[0021] Furthermore, the polyarylether nitrile oxime (PEN-Ao) described in step 2 is a polyarylether nitrile with amidoxime groups, carboxyl groups and nitrile groups, and the structural formula is:

[0022]

[0023] Furthermore, in step 2, the stirring is carried out in a magnetic stirrer for 12-24 h at a rotation speed of 500-1000 rpm. After stirring, ultrasonicate for 10-30 min, and then stand for 1-3 h to defoam to obtain a homogeneous and bubble-free casting solution.

[0024] Furthermore, in step 3 during soaking, replace the deionized water every 8 h to make the membrane fully formed.

[0025] A preparation method of a polyurethane-modified polyarylether nitrile oxime photocatalytic oil-water separation membrane provided by the present invention uses amphiphilic polyurethane (PU) and photocatalytically active TiO2 / modified carbon dots (MCD) hybrid particles as PEN-Ao membrane modifiers. By directly mixing PU and TiO2 / MCD hybrids with the PEN-Ao casting solution, a composite photocatalytic membrane is prepared in one step by the non-solvent induced phase separation (NIPS) method. Among them, the polymer PEN-Ao material with active groups is used as the membrane matrix, which can increase the compatibility and interaction with the hydrophilic modifier, effectively avoiding the problems of the hydrophilic modifier detaching from the membrane surface or insufficient modification effect caused by the weak adhesion between the hydrophilic modifier and the hydrophobic matrix; during the process of the hydrophilic segment of the amphiphilic polyurethane (PU) modifier migrating to the surface, the pore size on the membrane surface will be enlarged, the number of cavity-shaped pores will be increased, the porosity and average pore size of the membrane will be improved, enabling the water permeability of the membrane to accelerate, and the compatibility between polyurethane and PEN-Ao will be enhanced, significantly improving the hydrophilicity of the membrane matrix; at the same time, the amphiphilic polyurethane (PU) modifier can also form hydrogen bonds with the TiO2 / modified carbon dots (MCD) hybrid particles of the modifier, hindering the aggregation between the TiO2 / MCD hybrid particles, enabling them to be evenly dispersed on the membrane surface, maximizing the development and utilization of the surface area of the hybrid particles with photocatalytic functions, and the increase in roughness can also cause incident light to be reflected multiple times on its surface, effectively improving the light utilization rate of the TiO2 / MCD hybrid particles, further facilitating the photocatalytic degradation of oil and dye pollutants by the photocatalytic membrane.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. A preparation method of a polyurethane-modified polyarylether nitrile oxime photocatalytic oil-water separation membrane provided by the present invention uses amphiphilic polyurethane (PU) and photocatalytically active TiO2 / modified carbon dots (MCD) hybrid particles as PEN-Ao membrane modifiers, and endows the membrane with photocatalytic ability. The obtained PEN-Ao-PU-T / M composite membrane exhibits excellent performance in oil-water separation performance and photocatalytic ability, and has good stability and reusability when treating complex dye-containing oil-water emulsions, providing new ideas for the development and utilization of polymer membrane substrates and the preparation of hydrophilic photocatalytic membranes.

[0028] 2. The photocatalytic oil-water separation membrane of the present invention has excellent hydrophilicity (the water contact angle in air is 18°) and permeability (the flux of pure water is 985 L·m -2 ·h -1 ), enabling it to achieve efficient separation of oil-water emulsions. The flux of the oil-water emulsion is 285 L·m -2 ·h -1 , and the separation efficiency is as high as over 98.9%. It has high anti-fouling property, and its flux recovery rate is 94.1%.

[0029] 3. The photocatalytic oil-water separation membrane of the present invention has excellent photocatalytic function. Under the irradiation of an ultraviolet lamp, the photocatalytic degradation efficiency of the photocatalytic membrane for methylene blue dye is 94.2% (UV light irradiation for 60 min), and the photocatalytic degradation efficiency for rhodamine B dye is 99.1% (UV light irradiation for 40 min).

[0030] 4. The photocatalytic oil-water separation membrane of the present invention has an efficient self-cleaning function driven by light. When the membrane is contaminated by oil and dye pollutants, after being irradiated by an ultraviolet lamp with an intensity of 300 W for 20 - 40 min, the pollutants on the membrane are almost completely degraded, and its hydrophilicity and separation performance are restored as before, thus realizing efficient photocatalytic self-cleaning.

[0031] 5. The photocatalytic oil-water separation membrane of the present invention has high separation and photocatalytic degradation capabilities for the oil-water mixture containing rhodamine B, which enables the separation of oil-water mixed pollutants containing dyes. Description of the Drawings

[0032] Figure 1 It is a comparison chart of the porosity and average pore diameter of the photocatalytic oil-water separation membranes of Comparative Example 1 and Examples 1 - 3;

[0033] Figure 2 It is a comparison chart of the water contact angles of the photocatalytic oil-water separation membranes of Comparative Example 1 and Examples 1 - 3;

[0034] Figure 3 It is a comparison chart of the separation flux and separation efficiency of the photocatalytic oil-water separation membranes of Comparative Example 1 and Examples 1 - 3 for the oil-in-water emulsion;

[0035] Figure 4 It is a comparison chart of the photocatalytic degradation of methylene blue dye by the photocatalytic oil-water separation membranes of Comparative Example 1 and Examples 1 - 3;

[0036] Figure 5 It is a comparison chart of the photocatalytic degradation of rhodamine B dye by the photocatalytic oil-water separation membranes of Comparative Example 1 and Examples 1 - 3;

[0037] Figure 6 It is a separation characteristic chart of the photocatalytic oil-water separation membrane prepared in Example 1 for separating the oil-water mixture containing dyes under multiple cyclic alternating tests;

[0038] Figure 7 It is a separation characteristic chart of the photocatalytic oil-water separation membrane prepared in Comparative Example 1 for separating the oil-water mixture containing dyes under multiple cyclic alternating tests. Detailed Embodiments

[0039] The present invention will be further described below through specific embodiments. However, this is not a limitation of the present invention. Those skilled in the art can make various modifications or variations based on the basic idea of the present invention. As long as they do not depart from the basic idea of the present invention, they are within the scope of the present invention.

[0040] Example 1

[0041] Step 1. Add 0.015 g of TiO2 / MCD hybrid particles and 0.05 g of amphiphilic polyurethane (PU) into 0.9 g of N,N-dimethylacetamide (DMAc) solvent. Stir in a magnetic stirrer at 30 °C for 30 min at a rotation speed of 600 rpm. After stirring, ultrasonicate for 30 min to obtain a red TiO2 / MCD-PU-DMAc homogeneous solution.

[0042] Step 2. Dissolve 0.2 g of polyarylether nitrile oxime (PEN-Ao) and 0.02 g of LiCl in 0.9 g of N,N-dimethylacetamide (DMAc) solvent. Then add the TiO2 / MCD-PU-DMAc homogeneous solution prepared in Step 1. Stir in a magnetic stirrer at 30 °C for 12 h at a rotation speed of 600 rpm. After stirring, ultrasonicate for 30 min and let it stand to defoam for 1 h to obtain a homogeneous and bubble-free casting solution.

[0043] Step 3. At room temperature, pour the homogeneous and bubble-free casting solution obtained in Step 2 onto a clean glass plate. After exposing it to the air for 20 s, place it in a container filled with 500 mL of deionized water and soak for 24 h, replacing the deionized water every 8 h during this period to completely form the membrane, obtaining the photocatalytic oil-water separation membrane PEN-Ao-PU-3TiO2 / MCD.

[0044] Example 2

[0045] Compared with Example 1, the difference in this example is that the mass of TiO2 / MCD hybrid particles in Step 1 is 0.025 g; the remaining steps are the same as those in Example 1, obtaining the photocatalytic oil-water separation membrane PEN-Ao-PU-5TiO2 / MCD.

[0046] Example 3

[0047] Compared with Example 1, the difference in this example is that the mass of TiO2 / MCD hybrid particles in Step 1 is 0.035 g; the remaining steps are the same as those in Example 1, obtaining the photocatalytic oil-water separation membrane PEN-Ao-PU-7TiO2 / MCD.

[0048] Comparative Example 1

[0049] Step 1. Add 0.015 g of TiO2 / MCD hybrid particles into 0.9 g of N,N-dimethylacetamide (DMAc) solvent, stir in a magnetic stirrer at 30 °C for 30 min at a rotation speed of 600 rpm. After stirring, ultrasonicate for 30 min to obtain a homogeneous TiO2 / MCD-DMAc solution;

[0050] Step 2. Dissolve 0.2 g of polyarylether nitrile oxime (PEN-Ao) and 0.02 g of LiCl in 0.9 g of N,N-dimethylacetamide (DMAc) solvent, then add the TiO2 / MCD-DMAc homogeneous solution prepared in Step 1 thereto. Stir in a magnetic stirrer at 30 °C for 12 h at a rotation speed of 600 rpm. After stirring, ultrasonicate for 30 min and let it stand for 1 h to defoam, obtaining a homogeneous and bubble-free casting solution;

[0051] Step 3. At room temperature, scrape the homogeneous and bubble-free casting solution obtained in Step 2 onto a clean glass plate. After exposing to air for 20 s, place it in a container filled with 500 mL of deionized water and soak for 24 h for phase separation. Replace the deionized water every 8 h during this period to make the membrane fully formed, obtaining the photocatalytic oil-water separation membrane PEN-Ao-3TiO2 / MCD.

[0052] (I) Testing the oil-water separation characteristics of the photocatalytic oil-water separation membrane:

[0053] (1) Testing the porosity and average pore size of the photocatalytic oil-water separation membrane:

[0054] Use the classical gravimetric method to measure the porosity (ε) and average pore size (r m ) of the photocatalytic oil-water separation membranes prepared in Example 1, Example 2, Example 3 and Comparative Example 1 to measure the permeability of the membrane. After soaking circular wafers with a diameter of 3 cm in pure water for 12 h, wipe off the water on the membrane surface with filter paper and then weigh. Take the average value of three samples for each group. The calculation formula is as follows:

[0055]

[0056] Among them, w1 and w2 represent the weights of the wet membrane and dry membrane (kg) respectively; A represents the area of the circular membrane sheet (m 2 ); ρ is the density of water (998 kg / m 2 ); l represents the thickness of the membrane (m). The calculation formula for the average pore size is as follows:

[0057]

[0058] Among them, η is the viscosity of water (Pa·s); Q is the volume of pure water permeated per unit time (m 3 / s); ΔP is the operating pressure (0.1 MPa). The results are asFigure 1 As shown, Example 1 has the highest porosity and the largest average pore size. It is proved that the oil-water separation membrane has a porous structure. The larger the porosity, the more paths water can pass through the membrane, which is beneficial to the penetration of water, and its porosity exceeds 86%.

[0059] (2) Contact angle test of the photocatalytic oil-water separation membrane:

[0060] After drying the photocatalytic oil-water separation membranes prepared in Example 1, Example 2, Example 3 and Comparative Example 1, they were flatly attached to a glass slide with double-sided tape and placed on a contact angle measuring instrument. The injection needle was controlled to slowly drop 2 μL of water droplets on the surfaces of different membranes, and the water contact angle in the air was measured and recorded by the measuring instrument, and recorded again after 20 s. The results are as Figure 2 shown. The photocatalytic oil-water separation membrane of Example 1 has the lowest water contact angle of 18°, which proves that the membrane has excellent hydrophilicity.

[0061] (3) Oil-water separation property test of the photocatalytic oil-water separation membrane:

[0062] Water, isooctane and sodium dodecyl sulfate were configured into an oil-in-water emulsion (the volume ratio of water to isooctane is 99:1), and then pure water and the oil-water emulsion were respectively passed through the photocatalytic oil-water separation membranes prepared in Example 1, Example 2, Example 3 and Comparative Example 1. An oil-water separation experiment was carried out using a dead-end filtration device. When the membrane surface came into contact with the oil-water emulsion, the oil phase could not penetrate and could only stay on the surface of the hydrophilic separation membrane, while the water phase could pass through the membrane and enter the collection device at the back end to achieve oil-water separation. The results are as Figure 3 shown. It can be seen from the figure that the photocatalytic oil-water separation membrane prepared in Example 1 has a good oil-water separation flux of 285 L·m -2 ·h -1 and excellent separation efficiency of 98.9%.

[0063] (2) Photodegradation property test of the photocatalytic oil-water separation membrane for organic dyes:

[0064] Methylene blue (MB) and rhodamine B (Rh B) powders were configured into a dye solution with a concentration of 20 mg / L, and then photocatalytic degradation tests were carried out through the photocatalytic oil-water separation membranes prepared in Example 1, Example 2, Example 3 and Comparative Example 1. Soak for 30 min under dark conditions to reach adsorption-desorption equilibrium, and then turn on a 300 W mercury lamp for irradiation. Take samples of different solutions every 10 min to test their concentrations. Figure 4 It is a comparison chart of the concentration ratio (C / C0) of the photocatalytic degradation of MB by four photocatalytic oil-water separation membranes. Figure 5It is a comparison graph of the concentration ratio (C / C0) of the photocatalytic degradation of Rh B by four photocatalytic oil-water separation membranes. As can be seen from the graph, the photocatalytic oil-water separation membranes prepared in Example 1, Example 2, and Example 3 all showed excellent photocatalytic degradation ability for dyes. However, since the amount of TiO2 / MCD photocatalyst in Example 3 was the largest, its membrane also had the best photocatalytic performance. The specific photocatalytic degradation of dyes by the photocatalytic oil-water separation membranes prepared in Example 1, Example 2, and Example 3 is as follows: After 60 minutes of ultraviolet light irradiation, the C / C0 values of MB were 0.127, 0.112, and 0.058 respectively, and their photocatalytic degradation efficiencies were 87.3%, 88.8%, and 94.2% respectively; after 40 minutes of ultraviolet light irradiation, the C / C0 values of Rh B were 0.038, 0.020, and 0.009 respectively, and their photocatalytic degradation efficiencies were 96.2%, 98.0%, and 99.1% respectively. This shows that the polyarylether nitrile oxime photocatalytic oil-water separation membranes prepared in Example 1, Example 2, and Example 3 can all efficiently degrade MB and Rh B organic dyes, realizing pollution-free treatment of organic dyes in wastewater.

[0065] (III) Separation characteristic test of the photocatalytic oil-water separation membrane under multiple alternating experiments of oil-water separation containing dyes:

[0066] Using a dead-end filtration device and a 300W ultraviolet lamp, the self-cleaning and separation characteristics of the polyarylether nitrile oxime photocatalytic oil-water separation membrane prepared in Example 1 were tested. A dye-containing oil-water mixture was prepared by mixing rhodamine B (Rh B), isooctane, and pure water. First, the dye-containing oil-water mixture was separated, then pure water was filtered, and then the mixture was filtered for multiple alternating cycle experiments. Figure 6 It is a separation characteristic graph of the dye-containing oil-water mixture separated under multiple cyclic alternation tests of the photocatalytic self-cleaning oil-water separation membrane prepared in Example 1. As can be seen from the figure, in the first 7 cycles of separation, the separation performance of the membrane basically remained at a high level, and the fluxes of pure water and the dye-containing oil-water mixture basically remained at about 805 L·m -2 ·h -1 and 280 L·m -2 ·h -1 respectively. After the separation performance of the membrane decreased significantly later, after irradiating the membrane with ultraviolet light for 20 - 40 minutes, the separation fluxes of pure water and the dye-containing oil-water mixture recovered to about 790 L·m -2 ·h -1 and 260 L·m -2 ·h -1 respectively, and had a certain stability. This shows that under light irradiation, the oil and dyes on the membrane can be effectively photocatalytically degraded, and the pollutants on the membrane can be accurately degraded without damaging the structure of the polymer separation membrane, realizing the self-cleaning function.

[0067] Figure 7Separation characteristic diagram of an oil-water mixture containing dyes under multiple cyclic alternation tests of the photocatalytic self-cleaning oil-water separation membrane prepared in Comparative Example 1. As can be seen from the figure, the separation performance, anti-fouling property, and stability of the photocatalytic oil-water separation membrane prepared in Comparative Example 1 are far inferior to those of the membrane prepared in Example 1. Under the same experimental operations and conditions, the performance of the sample membrane in Comparative Example 1 decreased significantly after 4 alternating cyclic experiments. After irradiating with an ultraviolet lamp for 20 - 40 min, the separation fluxes of the membrane for pure water and the oil-water mixture containing dyes only recovered to about 446 L·m -2 ·h -1 and 125 L·m -2 ·h -1 respectively, and the comprehensive performance of the membrane was unstable. This shows that the lack of amphiphilic polyurethane will not only seriously affect the separation, anti-fouling, stability, and photocatalytic properties of the membrane, but also lead to the lack of self-cleaning ability of the membrane and reduce its service life.

Claims

1. A method for preparing a polyurethane-modified polyarylether nitrile oxime photocatalytic oil-water separation membrane, characterized in that: The following steps are involved: Step 1. Add 0.03-0.07 parts by mass of TiO2 / MCD hybrid particles and 0.1-0.3 parts by mass of amphiphilic polyurethane into 1-3 parts by mass of N,N-dimethylacetamide solvent, and stir to obtain a TiO2 / MCD-PU-DMAc homogeneous solution; Step 2. Dissolve 0.2-0.4 parts by mass of polyarylether nitrile oxime and 0.04-0.08 parts by mass of LiCl in 1-3 parts by mass of N,N-dimethylacetamide solvent, and then add the TiO2 / MCD-PU-DMAc homogeneous solution prepared in step 1, stir, and obtain a homogeneous, bubble-free casting solution; Step 3. At room temperature, the homogeneous and bubble-free casting solution obtained in step 2 is scraped onto a glass plate, exposed to air for 10 to 30 seconds, and then placed in a vessel filled with deionized water and immersed for 12 to 24 hours to obtain the photocatalytic oil-water separation membrane.

2. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: The structural formula of the amphiphilic polyurethane in step 1 is:

3. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: The amphiphilic polyurethane in step 1 is a block copolymer obtained by reacting diisocyanate and polyol at 50-80° C. to generate a prepolymer, and then adding a chain extender to further extend the prepolymer.

4. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 3, characterized in that: The diisocyanate is two of toluene diisocyanate, hexamethyl diisocyanate, isophorone diisocyanate or lysine diisocyanate, wherein the molar ratio of the two is 1:1; the polyol is a mixture of a hydrophilic polyol and a hydrophobic polyol in a mass ratio of 2:1, wherein the hydrophilic polyol is two or more of polycaprolactone diol, polyethylene glycol and polyoxypropylene diol with a molecular weight of 600 to 2000, and the hydrophobic polyol is two or more of polytetrahydrofuran diol, polybutylene adipate and polycarbonate diol with a molecular weight of 1000 to 4000; and the chain extender is two or more of 1,4-butanediol, ethylene glycol, 2,2-dihydroxymethylpropionic acid and p-hydroxyanisole.

5. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: Step 1: The TiO2 / MCD hybrid particles are hydrophilic nanoparticles obtained by a two-step hydrothermal reaction, and are composed of TiO2 and modified carbon dots, wherein the modified carbon dots account for 5 to 10 wt% of the mass of the TiO2 / MCD hybrid particles.

6. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: In step 1, the stirring is carried out in a magnetic stirrer for 30 to 60 minutes at a rotation speed of 500 to 1000 rpm. After the stirring is completed, ultrasonication is performed for 10 to 30 minutes to obtain a TiO2 / MCD-PU-DMAc homogeneous solution.

7. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: The polyarylether nitrile oxime in step 2 is a polyarylether nitrile having amidoxime group, carboxyl group and nitrile group, and has the structural formula:

8. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: In step 2, the stirring is carried out in a magnetic stirrer for 12 to 24 hours at a rotation speed of 500 to 1000 rpm. After the stirring is completed, ultrasonication is performed for 10 to 30 minutes, and the mixture is allowed to stand for defoaming for 1 to 3 hours to obtain a homogeneous and bubble-free casting solution.

9. The method for preparing the polyurethane modified polyarylether nitrile oxime photocatalytic oil-water separation membrane according to claim 1, characterized in that: During the soaking step 3, the deionized water was replaced every 8 hours to allow the membrane to be fully formed.

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