Anti-pollution reverse osmosis membrane and preparation method thereof

Abstract

The invention relates to an anti-pollution reverse osmosis membrane and a preparation method thereof.The anti-pollution reverse osmosis membrane comprises a non-woven fabric supporting layer, a surface-patterned polyether sulfone base membrane layer, a polyamide desalination layer and a polyvinyl alcohol protection layer which are sequentially arranged from one side to the other side, the surface-patterned polyethersulfone-based membrane layer is obtained by performing patterning treatment on the surface, close to the side of the polyamide desalination layer, of a polyethersulfone-based membrane, and the polyvinyl alcohol protective layer is an antibacterial polyvinyl alcohol protective layer. According to the invention, the embossed patterned polyethersulfone-based membrane has anti-pollution performance by controlling pattern parameters and embossing parameters on the micro-structure embossing roller, and the anti-pollution performance of the reverse osmosis membrane is realized on the premise of not changing a separation layer and not reducing flux and rejection rate by using the embossed patterned polyethersulfone-based membrane in cooperation with the PVA protection layer of the metal ion antibacterial agent, so that the anti-pollution performance of the reverse osmosis membrane is improved, and the service life of the reverse osmosis membrane is prolonged. Especially, the pollution effect of inorganic substances is resisted.

Description

Technical Field

[0001] The present invention relates to the technical field of reverse osmosis, and specifically relates to an anti-pollution reverse osmosis membrane and a preparation method thereof. Background Art

[0002] Due to the characteristics of being green and efficient, reverse osmosis membranes are widely used in the field of seawater desalination. However, the problems are as follows: There are often some impurities in seawater, such as suspended inorganic substances or organic substances. The long-term accumulation of these impurities will cause the pollution and blockage of the reverse osmosis membrane. At present, the treatment solution for membrane pollution is to graft antibacterial substances on the separation layer. The problems are that it is only effective for bacteria and other microorganisms, but ineffective for other impurities. Moreover, after grafting compounds on the separation layer, it is easy to cause the pores of the reverse osmosis membrane to become smaller, affecting the flux and rejection rate of the reverse osmosis membrane. In addition, it also has the disadvantage that the antibacterial substances are easy to fall off.

[0003] Therefore, it is crucial to develop an anti-pollution reverse osmosis membrane and a preparation method thereof that do not affect the flux and rejection rate of the reverse osmosis membrane and can resist pollution for a long time and stably. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide an anti-pollution reverse osmosis membrane and a preparation method thereof, which improve the anti-pollution effect of the reverse osmosis membrane without changing the flux and rejection rate of the reverse osmosis membrane.

[0005] In order to achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] An anti-pollution reverse osmosis membrane includes a non-woven fabric support layer, a surface-patterned polyethersulfone-based membrane layer, a polyamide desalination layer, and a polyvinyl alcohol protection layer, which are sequentially arranged from one side to the other side. Among them, the surface-patterned polyethersulfone-based membrane layer is obtained by patterning the surface of the polyethersulfone-based membrane on the side close to the polyamide desalination layer, and the polyvinyl alcohol protection layer uses an antibacterial polyvinyl alcohol protection layer.

[0007] As a further technical solution, the patterning treatment includes:

[0008] Using a roll-to-roll nanoimprinting machine, the roll-to-roll nanoimprinting machine includes a flat roll and a printing roll. The polyethersulfone-based membrane layer passes between the flat roll and the printing roll. Among them, the flat roll is in contact with the non-woven fabric support layer, and the printing roll is in contact with the polyethersulfone-based membrane layer to pattern the surface of the polyethersulfone-based membrane layer.

[0009] A preparation method of an anti-pollution reverse osmosis membrane includes the following steps:

[0010] Step 1. Preparation of polyethersulfone-based membrane: The polyethersulfone casting solution is evenly blade-coated on a non-woven fabric (with a thickness of 100 μm) to form a liquid film (with a thickness of 20 - 50 μm), and then it enters a pure water coagulation bath to be solidified into a membrane, obtaining the polyethersulfone-based membrane;

[0011] Step 2. Patterning treatment: Using a roll-to-roll nanoimprinting machine, the polyethersulfone-based membrane is passed between the flat roll and the printing roll of the roll-to-roll nanoimprinting machine. The printing roll contacts the polyethersulfone layer, and a predetermined pattern is pressed on the polyethersulfone-based membrane to obtain a surface-patterned polyethersulfone-based membrane; (The printing roll is made by first electroplating a copper layer with a thickness of 100 - 500 μm on a metal roller, and then using a precision diamond cutter with a special shape to cut out the required pattern structure from head to tail).

[0012] Step 3. Preparation of polyamide desalination layer: First, the surface-patterned polyethersulfone-based membrane is immersed in an aqueous solution containing m-phenylenediamine, then taken out to remove the excess aqueous solution on the surface, and then immersed in an organic phase solution containing trimesoyl chloride for an interfacial polymerization reaction to form a polyamide desalination layer on the surface of the surface-patterned polyethersulfone-based membrane. After the reaction, heat treatment and cleaning are carried out to obtain a polyamide reverse osmosis membrane;

[0013] Step 4. Preparation of polyethylene protective layer: The polyvinyl alcohol protective solution is coated on the surface of the polyamide reverse osmosis membrane, and then dried to form a polyethylene protective layer, obtaining an anti-fouling reverse osmosis membrane.

[0014] As a further technical solution, the printing roll uses a microstructured printing roll; the surface pattern of the microstructured printing roll is a strip-shaped groove pattern, and the strip-shaped groove pattern is a nano-scale pattern; after the surface of the polyethersulfone-based membrane is patterned, its cross-section is wavy, and the peak-to-peak period of the wave is 500 - 1000 nm, the peak height is 400 - 600 nm, and the peak width is 800 - 1000 nm.

[0015] As a further technical solution, the solvent of the polyethersulfone casting solution is one or more of dimethylacetamide (DMAc), dimethylformamide (DMF), and N-methylpyrrolidone (NMP);

[0016] As a further technical solution, in the polyethersulfone casting solution, the mass concentration of polyethersulfone is 14 - 18%;

[0017] As a further technical solution, the polyethersulfone casting solution further contains an additive, and the concentration of the additive is 0.5 - 2%;

[0018] The additive is one or more of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and cellulose.

[0019] As a further technical solution, in the aqueous solution, the concentration of m-phenylenediamine is 1.5 wt%, the concentration of camphorsulfonic acid is 2.2 wt%, the concentration of triethylamine is 1.1 wt%, the concentration of isopropanol is 4 wt%, and the concentration of RO water is 91.2 wt%; in the organic phase solution, the concentration of trimesoyl chloride is 0.2 wt%, and the concentration of Isopar G is 99.8 wt%.

[0020] As a further technical solution, in the polyvinyl alcohol protective solution, the mass concentration of polyvinyl alcohol is 0.5 - 2%;

[0021] As a further technical solution, the polyvinyl alcohol protective solution further contains a metal ion antibacterial agent with a mass concentration of 0.1 - 1%, a crosslinking agent with a mass concentration of 0.5 - 5%, and an acid catalyst with a mass concentration of 0 - 2%.

[0022] As a further technical solution, the metal ion antibacterial agent is one or more of nano silver ions (supported by submicron glass and zirconium phosphate), nano copper ions (supported by submicron glass), and nano zinc ions (supported by submicron glass);

[0023] As a further technical solution, the crosslinking agent is one or more of oxalic acid, glutaraldehyde, maleic anhydride, and succinaldehyde;

[0024] As a further technical solution, the acid catalyst is one or more of nitric acid, sulfuric acid, formic acid, hydrochloric acid, and acetic acid.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0026] 1. Due to the porous ultrafiltration membrane prepared from the glassy polymer polyethersulfone, it has a yield strength of several megapascals at room temperature and can also exhibit an extended plastic deformation plateau under mechanical loads with higher stress until reaching the densification stage. The plasticity of this membrane allows for mechanical patterning of the membrane surface at temperatures far below the glass transition temperature (T g ) or melting temperature (T m ) of the polymer. Therefore, the present invention selects to perform surface patterning on the polyethersulfone substrate membrane, and the periodic nanoscale patterns on the surface of the polyethersulfone substrate membrane enhance the fluid shear on the membrane surface, effectively reducing the concentration polarization and fouling of the reverse osmosis membrane.

[0027] 2. The present invention uses a mechanical roll-to-roll nanoimprinting machine to perform surface patterning on the polyethersulfone substrate membrane. By controlling the pattern parameters and imprinting parameters on the microstructured printing roll, the imprinted patterned polyethersulfone substrate membrane has anti-pollution performance.

[0028] 3. A PVA protective layer with a metal ion antibacterial agent is coated on the separation layer of the present invention. By utilizing the antibacterial and sterilizing activity of the metal ion antibacterial agent, the microbial contamination of the reverse osmosis membrane is further reduced.

[0029] In summary, by controlling the pattern parameters and imprinting parameters on the microstructured nickel imprinting roller, the imprinted patterned polyethersulfone-based membrane of the present invention has anti-pollution performance. In combination with the use of a PVA protective layer with a metal ion antibacterial agent, the effect of anti-inorganic and organic pollution of the reverse osmosis membrane is achieved without changing the separation layer and without reducing the flux and rejection rate. Brief Description of the Drawings

[0030] Figure 1 It is a cross-sectional view of the anti-pollution reverse osmosis membrane in Embodiment 1 of the present invention;

[0031] In the figure, 1: non-woven fabric support layer, 2: polyethersulfone-based membrane layer, 3: surface pattern, 4: polyamide desalination layer, 5: polyvinyl alcohol protective layer. Detailed Description of the Invention

[0032] The present invention will be further described in detail below in conjunction with embodiments.

[0033] The non-woven fabric used for preparing the polysulfone porous support layer is AWAKS-7910, with an air permeability of 1.3 cc / cm 2 / sec and a thickness of 0.1 mm; the polysulfone used: Solvay Udel P-3500LCD MB;

[0034] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0035] Embodiment 1

[0036] An anti-pollution reverse osmosis membrane, comprising a non-woven fabric support layer, a surface-patterned polyethersulfone-based membrane layer, a polyamide desalination layer, and a polyvinyl alcohol protective layer sequentially arranged from one side to the other side. Among them, the surface-patterned polyethersulfone-based membrane layer is obtained by patterning the surface of the polyethersulfone-based membrane close to the polyamide desalination layer side, and the polyvinyl alcohol protective layer adopts an antibacterial polyvinyl alcohol protective layer.

[0037] As an embodiment of an anti-pollution reverse osmosis membrane of the present invention, it comprises a non-woven fabric support layer, a surface-patterned polyethersulfone-based membrane layer, a polyamide desalination layer, and a polyvinyl alcohol protective layer sequentially arranged from one side to the other side. Among them, the surface-patterned polyethersulfone-based membrane layer is obtained by patterning the surface of the polyethersulfone-based membrane close to the polyamide desalination layer side, and the polyvinyl alcohol protective layer adopts an antibacterial polyvinyl alcohol protective layer.

[0038] As an embodiment of the anti-pollution reverse osmosis membrane of the present invention, after the surface of the polyethersulfone-based membrane layer is patterned, a surface pattern is formed.

[0039] As an embodiment of the anti-pollution reverse osmosis membrane of the present invention, the patterning treatment includes:

[0040] Using a roll-to-roll nanoimprinting machine, the roll-to-roll nanoimprinting machine includes a flat roll and a printing roll, and the polyethersulfone-based membrane layer passes between the flat roll and the printing roll. Among them, the flat roll contacts the non-woven fabric support layer, and the printing roll contacts the polyethersulfone-based membrane layer to pattern the surface of the polyethersulfone-based membrane layer.

[0041] As an embodiment of the anti-pollution reverse osmosis membrane of the present invention, the printing roll uses a microstructured printing roll; the surface pattern of the microstructured printing roll is a strip-shaped groove pattern, and the strip-shaped groove pattern is a nano-scale pattern;

[0042] After the surface of the polyethersulfone-based membrane is patterned, its cross-section is wavy, the peak-to-peak period of the wavy shape is 500-1000 nm, the peak height is 400-600 nm, and the peak width is 800-1000 nm.

[0043] Example 2-13

[0044] A method for preparing an anti-pollution reverse osmosis membrane includes the following steps:

[0045] Step 1, preparing a polyethersulfone-based membrane: uniformly scraping a polyethersulfone casting solution on a non-woven fabric with a thickness of 100 μm to form a liquid film with a thickness of 40 μm, and then entering a pure water coagulation bath to solidify into a membrane to obtain a polyethersulfone-based membrane;

[0046] The solvent of the polyethersulfone casting solution is dimethylformamide (DMF);

[0047] In the polyethersulfone casting solution, the mass concentration of polyethersulfone is 16%;

[0048] Polyvinylpyrrolidone (PVP) is also added to the polyethersulfone casting solution, and the concentration of the polyvinylpyrrolidone (PVP) is 0.5%;

[0049] Step 2, patterning treatment: using a roll-to-roll nanoimprinting machine, passing the polyethersulfone-based membrane between the flat roll and the printing roll of the roll-to-roll nanoimprinting machine, and the printing roll contacts the polyethersulfone layer to press a nano-scale predetermined pattern on the polyethersulfone-based membrane to obtain a surface-patterned polyethersulfone-based membrane;

[0050] The nano-scale predetermined pattern is a number of strips, and its cross-section is wavy. The peak-to-peak period of the wavy nano-scale pattern is 500-1000 nm, the peak height is 400-600 nm, and the peak width is 800-1000 nm;

[0051] The printing roller used is a microstructured printing roller; the surface pattern of the microstructured printing roller is a strip groove pattern, and the strip groove pattern is a nanoscale pattern; after the polyethersulfone-based membrane is surface-patterned using the microstructured printing roller, its cross-section is wavy, the peak-to-peak period of the wave is 500 - 1000 nm, the peak valley depth or peak height is 400 - 600 nm, and the peak width is 800 - 1000 nm;

[0052] Step 3: Preparation of the polyamide desalination layer: First, soak the surface-patterned polyethersulfone-based membrane in an aqueous solution containing m-phenylenediamine, then take it out, remove the excess aqueous solution on the surface, and then immerse it in an organic solution containing trimesoyl chloride for interfacial polymerization reaction to form a polyamide desalination layer on the surface of the surface-patterned polyethersulfone-based membrane. After the reaction, perform heat treatment at 70 °C and cleaning to obtain a polyamide reverse osmosis membrane;

[0053] The mass concentration of m-phenylenediamine in the aqueous solution is 1.5 wt%;

[0054] The solvent used in the organic solution is Isopar G; in the organic solution, the mass concentration of trimesoyl chloride is 0.2 wt%;

[0055] Step 4: Preparation of the polyethylene protective layer: Coat the polyvinyl alcohol protective solution on the surface of the polyamide reverse osmosis membrane, and then dry it to form a polyethylene protective layer to obtain an anti-fouling reverse osmosis membrane;

[0056] In the polyvinyl alcohol protective solution, the mass concentration of polyvinyl alcohol is 1%;

[0057] In the polyvinyl alcohol protective solution, it also contains a metal ion antibacterial agent (nano silver ions) with a mass concentration of 0.2%, glutaraldehyde with a mass concentration of 0.05% as a cross-linking agent, and hydrochloric acid with a mass concentration of 0.02% as an acid catalyst;

[0058] The peak-to-peak period, peak height, and peak width in Examples 2 - 13 and Comparative Examples 1 - 2 are shown in Table 1;

[0059] Table 1

[0060] Peak - to - peak period / nm Peak height / nm Peak width / nm Example 2 500 400 800 Example 3 500 400 1000 Example 4 500 600 800 Example 5 500 600 1000 Example 6 800 400 800 Example 7 800 400 1000 Example 8 800 600 800 Example 9 800 600 1000 Example 10 1000 400 800 Example 11 1000 400 1000 Example 12 1000 600 800 Example 13 1000 600 1000 Comparative Example 1 2000 1500 2000 Comparative Example 2 10000 6000 4000

[0061] Comparative Example 3

[0062] A method for preparing an anti-fouling reverse osmosis membrane, including the following steps: the same as Example 2, except that step 2 of patterning treatment is not performed.

[0063] Comparative Example 4

[0064] A method for preparing an anti-fouling reverse osmosis membrane, including the following steps: the same as Example 2, except that no antibacterial agent is added in step 3.

[0065] Effect Example 1: Performance Test

[0066] The reverse osmosis membranes prepared in each example and comparative example were tested for permeation flux, rejection rate, and anti-fouling performance index. The results are shown in Table 2.

[0067] Testing methods for each index:

[0068] Membrane separation performance test: Using a 2000 ppm NaCl solution as the feed solution, the system temperature was maintained at 25.0 ± 0.5 °C. After the membrane was pre-pressed at 1.55 MPa for 30 min, the mass and conductivity of the permeate were measured, and the water flux (J) and solute rejection rate (R) were calculated. Where V is the volume of the permeate; A is the effective filtration area of the membrane cell, and t is the permeation time. C P and C f are the ionic conductivities of the permeate and the feed solution, respectively.

[0069] J = V / (A × Δt)

[0070] R = (1 - C P / C f ) × 100%

[0071] Membrane surface anti-fouling performance test: Using a cross-flow RO system, filter a 2000 ppm NaCl solution at 1.55 MPa and 25.0 ± 0.5 °C for 30 min to obtain the initial flux J0 of the membrane material. Subsequently, add 500 ppm bovine serum albumin (BSA) model contaminants, and then run for 8 h. Test the water flux of the membrane and record it as J t . Finally, rinse the membrane with deionized water at high flow rate and below 3 bar pressure for 30 min. Then, use a 2000 ppm NaCl aqueous solution as the feed solution to test the water flux of the cleaned membrane, denoted as J C . Calculate the initial flux decay rate (FDR) and flux recovery rate (FRR) according to the following formulas, respectively.

[0072] FDR = (1 - J t / J0) × 100%

[0073] FRR = J c / J0 × 100%

[0074] Antibacterial performance test on the membrane surface: Place 0.75 g of the cut membrane sheet into a three-necked flask, and add 70 mL of 0.03 mol / L PBS (phosphate) buffer solution and 5 mL of inoculated bacterial solution (Escherichia coli). Place the three-necked flask on a constant temperature oscillator and oscillate at 24°C ± 1°C and a rotation speed of 150 r / min for 18 h. Take 1 mL of the test solution, add 9 mL of PBS buffer solution, and mix well. Dilute serially by the 10-fold dilution method to an appropriate dilution factor. Pipette 1 mL from each test tube of each dilution factor into a sterilized petri dish, and pour in nutrient agar medium. After solidification, invert and place it in an incubator at 37°C ± 1°C for 48 h. Calculate the number of colonies on the agar plate using the plate counting method, and calculate the sterilization rate based on this.

[0075] Table 2

[0076]

[0077]

[0078] It can be seen from the data in Table 2 that:

[0079] 1) From the flux and rejection results of Examples 2 - 13 and Comparative Example 3, it can be seen that for the RO membrane prepared from the polyethersulfone-based membrane treated by nanoimprint patterning, compared with the RO membrane prepared from the unpatterned polyethersulfone-based membrane, the flux slightly decreases, and the desalination rate has no obvious change. Moreover, in the anti-pollution test of the unpatterned membrane sheet, compared with the patterned membrane sheet, the flux decay is as high as twice, and after cleaning, the flux of the patterned membrane sheet can recover more than 90%, while the flux of the unpatterned membrane sheet can only recover 65.8%.

[0080] 2) From the flux and rejection results of the examples and Comparative Examples 1 - 2, it can be seen that the patterning effect of the polyethersulfone-based membrane should not be too large, otherwise it will seriously affect the flux and rejection of the RO membrane sheet.

[0081] 3) From the results of the initial flux decay rate and flux recovery rate of Examples 2 - 13, it can be seen that the smaller the peak-to-peak period, the higher the peak height, and the wider the peak width, the smaller the flux decay rate and the higher the flux recovery rate of the RO membrane sheet.

[0082] 4) From the sterilization rate results of Examples 2 - 13 and Comparative Example 4, it can be seen that the RO membrane coated with a PVA anti-pollution layer containing a metal ion antibacterial agent (nano silver ions) has an obvious bactericidal effect on Escherichia coli.

[0083] The above-described embodiments are only the preferred embodiments of the present invention and not an exhaustive list of all possible implementations of the present invention. Any obvious modifications made by those of ordinary skill in the art without departing from the principles and spirit of the present invention shall be considered to be included within the scope of the claims of the present invention.

Claims

1. An anti-pollution reverse osmosis membrane, characterized in that, It includes a non-woven fabric support layer, a surface-patterned polyethersulfone-based membrane layer, a polyamide desalination layer, and a polyvinyl alcohol protective layer arranged in sequence from one side to the other side. Among them, the surface-patterned polyethersulfone-based membrane layer is obtained by patterning the surface of the polyethersulfone-based membrane on the side close to the polyamide desalination layer, and the polyvinyl alcohol protective layer is an antibacterial polyvinyl alcohol protective layer.

2. The anti-pollution reverse osmosis membrane according to claim 1, characterized in that, The patterning treatment includes: Using a roll-to-roll nanoimprinting machine, the roll-to-roll nanoimprinting machine includes a flat roll and a printing roll, and the polyethersulfone-based membrane layer passes between the flat roll and the printing roll. Among them, the flat roll contacts the non-woven fabric support layer, and the printing roll contacts the polyethersulfone-based membrane layer to pattern the surface of the polyethersulfone-based membrane layer.

3. A method for preparing an anti-pollution reverse osmosis membrane, characterized in that, It includes the following steps: Step 1, preparing the polyethersulfone-based membrane: uniformly scrape the polyethersulfone casting solution on the non-woven fabric to form a liquid film, and then enter a pure water coagulation bath to solidify into a film to obtain the polyethersulfone-based membrane; Step 2, patterning treatment: using a roll-to-roll nanoimprinting machine, make the polyethersulfone-based membrane pass between the flat roll and the printing roll of the roll-to-roll nanoimprinting machine, the printing roll contacts the polyethersulfone layer, and press a predetermined pattern on the polyethersulfone-based membrane to obtain a surface-patterned polyethersulfone-based membrane; Step 3, preparing the polyamide desalination layer: First, immerse the surface-patterned polyethersulfone-based membrane in an aqueous solution containing m-phenylenediamine, then take it out, remove the excess aqueous solution on the surface, and then immerse it in an organic phase solution containing trimesoyl chloride for interfacial polymerization reaction to form a polyamide desalination layer on the surface of the surface-patterned polyethersulfone-based membrane. After the reaction is completed, perform heat treatment and cleaning to obtain a polyamide reverse osmosis membrane; Step 4, preparing the polyethylene protective layer: coat the polyvinyl alcohol protective solution on the surface of the polyamide reverse osmosis membrane, and then dry it to form a polyethylene protective layer to obtain an anti-pollution reverse osmosis membrane.

4. The preparation method of an anti-pollution reverse osmosis membrane according to claim 3, wherein the printing roll uses a microstructured printing roll; the surface pattern of the microstructured printing roll is a strip-shaped groove pattern, and the strip-shaped groove pattern is a nano-scale pattern; after the surface of the polyethersulfone-based membrane is patterned, its cross-section is wavy, the peak-to-peak period of the wave is 500 - 1000 nm, the peak height is 400 - 600 nm, and the peak width is 800 - 1000 nm.

5. The preparation method of an anti-pollution reverse osmosis membrane according to claim 3, wherein the solvent of the polyethersulfone casting solution is one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone; in the polyethersulfone casting solution, the mass concentration of polyethersulfone is 14 - 18%.

6. The preparation method of an anti-pollution reverse osmosis membrane according to claim 3, wherein, The polyethersulfone casting solution also contains an additive, and the concentration of the additive is 0.5 - 2%; the additive is one or more of polyethylene glycol, polyvinylpyrrolidone, and cellulose.

7. The preparation method of an anti-pollution reverse osmosis membrane according to claim 3, wherein In the aqueous solution, the concentration of m-phenylenediamine is 1.5 wt%, the concentration of camphorsulfonic acid is 2.2 wt%, the concentration of triethylamine is 1.1 wt%, and the concentration of isopropanol is 4 wt%; in the organic phase solution, the concentration of trimesoyl chloride is 0.2 wt%, and the solvent of the organic phase solution is IsoparG.

8. The preparation method of an anti-pollution reverse osmosis membrane according to claim 3, characterized in that in the polyvinyl alcohol protective liquid, the mass concentration of polyvinyl alcohol is 0.5-2%; in the polyvinyl alcohol protective liquid, it also contains a metal ion antibacterial agent with a mass concentration of 0.1-1%, a crosslinking agent with a mass concentration of 0.5-5%, and an acid catalyst with a mass concentration of 0-2%.

9. The preparation method of an anti-pollution reverse osmosis membrane according to claim 8, characterized in that the metal ion antibacterial agent is one or more of nano silver ions, nano copper ions, and nano zinc ions.

10. The preparation method of an anti-pollution reverse osmosis membrane according to claim 8, characterized in that the crosslinking agent is one or more of oxalic acid, glutaraldehyde, maleic anhydride, and succinaldehyde; the acid catalyst is one or more of nitric acid, sulfuric acid, formic acid, hydrochloric acid, and acetic acid.

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