A method for preparing a chemical cleaning resistant reverse osmosis membrane

Abstract

The present application relates to the field of reverse osmosis membranes, and specifically discloses a method for preparing a reverse osmosis membrane resistant to chemical cleaning, the preparation method comprising the following steps S1: preparing a casting liquid; S2: coating the casting liquid on a non-woven fabric, allowing it to stand after coating, and placing it in a coagulation liquid after standing to obtain a polysulfone-based membrane; S3: preparing an aqueous phase mixture; S4: coating the aqueous phase mixture on the polysulfone-based membrane obtained in S2, and drying to obtain an aqueous phase-coated base membrane; S5: preparing an oil phase solution; S6: coating the oil phase solution on the aqueous phase-coated base membrane obtained in S4 to carry out an interfacial polymerization reaction, and drying and washing to obtain a composite layer membrane; S7: drying the composite layer membrane, washing the composite layer membrane with pure water, and drying again to obtain a reverse osmosis membrane resistant to chemical cleaning, the casting liquid and the aqueous phase mixture comprising aramid fibers, the aqueous phase mixture further comprising all-silicon molecular sieves, the reverse osmosis membrane of the present application has good resistance to chemical cleaning, especially alkali washing.

Description

Technical Field

[0001] The present application relates to a reverse osmosis membrane, and more particularly to a method for preparing a reverse osmosis membrane resistant to chemical cleaning. Background Art

[0002] There are various reasons for the contamination of the membrane surface during the use of the reverse osmosis membrane, such as hydrated metal oxides, calcium-containing precipitates, organic matter and organisms, etc. These situations will increase the permeation resistance of the reverse osmosis membrane and reduce the separation performance. However, common methods of cleaning the reverse osmosis membrane, such as acid washing, alkali washing, and oxidant cleaning, will cause certain damage to the membrane. In particular, alkali washing will cause the membrane pores to swell, allowing pollutants to enter the membrane pores and produce irreversible membrane pollution. Some researchers use mixtures of ethylene-octene copolymer elastomers, microcrystalline cellulose, polyaspartic acid, polylactic acid, nano zinc oxide, etc. as new membrane materials to improve the chemical cleaning resistance of the reverse osmosis membrane, but the separation performance of the obtained reverse osmosis membrane is low. At present, most polyamide reverse osmosis membranes are still prepared by interfacial polymerization. First, a layer of aqueous solution containing a certain proportion is evenly spread on the surface of the polysulfone membrane as a support layer. After removing the excess aqueous solution, an oil phase solution is poured onto the membrane surface to perform an interfacial polymerization reaction. After a period of reaction, a polyamide reverse osmosis membrane is obtained. The reverse osmosis membrane prepared in this way is relatively simple, has a high filtration efficiency, and still has irreplaceable value. How to provide a polyamide reverse osmosis membrane with good chemical cleaning resistance, especially excellent alkaline cleaning resistance, and membrane pores that are not prone to swelling and deterioration after cleaning is a problem to be solved. Summary of the invention

[0003] In order to solve the problem of reverse osmosis membrane resistance to chemical cleaning, the present application provides a method for preparing a reverse osmosis membrane resistant to chemical cleaning.

[0004] A method for preparing a chemical cleaning resistant reverse osmosis membrane comprises the following steps:

[0005] S1: preparing the casting solution: mixing polysulfone, N,N-dimethylformamide, polyvinyl pyrrolidone and aramid fiber, letting it stand, degassing and filtering for later use;

[0006] S2: coating the casting liquid on the non-woven fabric, allowing it to stand after coating, and placing it in a coagulation liquid after standing to obtain a polysulfone-based membrane;

[0007] S3: preparing a water phase mixture: adding an organic amine monomer, an additive, and a filler into water to obtain a water phase mixture, wherein the filler includes aramid fiber and all-silicon molecular sieve;

[0008] S4: coating the aqueous phase mixture on the polysulfone base membrane obtained in S2, and drying to obtain an aqueous phase coated base membrane;

[0009] S5: preparing an oil phase solution: dissolving an acyl chloride monomer in an oil phase solvent to obtain an oil phase solution;

[0010] S6: coating the oil phase solution on the water phase coating base film prepared in S4 to carry out interfacial polymerization reaction, and performing drying and washing treatment to obtain a composite layer film;

[0011] S7: drying the composite layer membrane, washing the composite layer membrane with pure water, and drying it again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0012] By adopting the above scheme, polysulfone is used as the base membrane, and a polyamide functional layer is obtained on one side of the polysulfone base membrane by interfacial polycondensation of an aqueous phase containing organic amine substances and an oil phase containing acyl chloride substances. The preparation method is simple, and the obtained polyamide functional layer is firmly attached to the polysulfone base membrane, and the desalination rate is high. The main chain of the aramid fiber is composed of an aromatic ring and an amide bond, has high strength and good chemical resistance, and has good compatibility with the reverse osmosis membrane. By adding a certain amount of aramid fiber to the casting liquid and the aqueous phase mixture, the strength and chemical resistance of the reverse osmosis membrane are improved. In the process of coating the aqueous phase mixture on the polysulfone base membrane, the polysulfone base membrane and the aramid fiber in the aqueous phase mixture are entangled to a certain extent, and the functional layer and the polysulfone base membrane layer are more closely combined, and are less likely to swell under chemical cleaning. All-silicon molecular sieve has certain strength and ion exchange performance and uniform molecular size pores, good acid resistance and oxidation resistance. By adding a certain amount of all-silicon molecular sieve to the water phase mixture of the reverse osmosis membrane, after interfacial polymerization, the all-silicon molecular sieve is uniformly deposited on the polyamide functional layer, which does not reduce the flux while further improving the chemical resistance of the reverse osmosis membrane. By adding aramid fiber and all-silicon molecular sieve at the same time, the two work synergistically, and the molecular sieve promotes the stability of the aramid fiber winding structure, further improving the tightness of the functional layer and the polysulfone-based membrane layer, and the reverse osmosis membrane obtained is relatively flexible and not easy to break.

[0013] In a specific embodiment, the components in the casting solution of the method for preparing a chemical cleaning resistant reverse osmosis membrane are as follows: 15-20 parts by weight of polysulfone, 75-85 parts by weight of N,N-dimethylformamide, 1-8 parts by weight of polyvinyl pyrrolidone, and 2-5 parts by weight of aramid fiber.

[0014] By adopting the above scheme, the quality of each component is appropriate, the prepared reverse osmosis membrane has high strength, large flux, high stability, and is not easy to be damaged during the chemical cleaning process.

[0015] In a specific embodiment, the components in the aqueous phase mixture of the method for preparing a chemical cleaning resistant reverse osmosis membrane are as follows: 2-12 parts of organic amine monomers, 2-5 parts of additives, 2-6 parts of fillers, and 75-90 parts of water.

[0016] By adopting the above scheme, the concentration of the water phase mixture is appropriate, the adhesion effect on the polysulfone-based membrane is good, the prepared reverse osmosis membrane has high strength, and is more stable during the chemical reagent flushing process of chemical cleaning.

[0017] In a specific embodiment, the all-silicon molecular sieve is modified with a bisamide silane coupling agent.

[0018] Preferably, the preparation steps of the bisamide silane modified molecular sieve include: adding 23 parts by mass of all-silicon molecular sieve and 1 part by mass of bisamide silane coupling agent to 100 parts by mass of ethanol aqueous solution with a mass concentration of 25%, stirring at 80°C for 2 hours, filtering, washing with distilled water, and drying to obtain the bisamide silane modified molecular sieve.

[0019] By adopting the above scheme, the modified molecular sieve has better compatibility in the reverse osmosis membrane and is more tightly connected. The surface of the modified molecular sieve is rich in amide groups, the activity of the amide bond is higher than that of the aromatic ring, and it is preferentially replaced by chlorine. By adding the modified molecular sieve modified with diamide silane into the reverse osmosis membrane, the reaction activity of aromatic polyamide and active chlorine is effectively reduced, the chlorine resistance is good, and the obtained reverse osmosis membrane has good chemical cleaning resistance.

[0020] Preferably, the preparation step of the bisamide silane coupling agent comprises: mixing 22 parts by mass of xylene and 10 parts by mass of aminoethylaminopropyltrimethoxysilane, stirring evenly at 10-15° C., dropping 11 parts by mass of acetic anhydride, stirring, reacting for 6-7 hours, evaporating and removing excess acetic acid, acetic anhydride and xylene to obtain the bisamide silane coupling agent.

[0021] By adopting the above scheme, the preparation steps of the bisamide silane coupling agent are relatively simple, the prepared bisamide silane coupling agent is relatively stable, has a better modification effect on the molecular sieve, and the prepared modified molecular sieve has abundant amide groups on the surface.

[0022] In a specific embodiment, the aramid fiber in the casting solution and the aqueous phase mixture is para-aramid fiber.

[0023] By adopting the above scheme, the molecular chains of the para-aramid fiber are arranged in a straight line with high strength, and the surface of the obtained reverse osmosis membrane is smoother. During the chemical cleaning process, acid and alkali solutions are not easy to penetrate into the interior to cause swelling that damages the membrane pores.

[0024] In a specific embodiment, the diameter of the aramid fiber in the casting solution and the aqueous phase mixture is 2-5 μm.

[0025] By adopting the above scheme, the aramid fiber is relatively slender and does not significantly increase the hardness of the reverse osmosis membrane. The prepared reverse osmosis membrane is relatively flexible and evenly distributed in the reverse osmosis membrane to provide protection. The prepared reverse osmosis membrane is relatively smooth, chemical reagents are not easy to accumulate, and the chemical cleaning can be quickly cleaned after re-introducing pure water, which causes less damage to the reverse osmosis membrane. The aramid fiber in the polysulfone base membrane and the aramid fiber in the polyamide functional layer have better winding effect and are more tightly attached.

[0026] In a specific embodiment, the mass ratio of aramid fiber to all-silicon molecular sieve in the aqueous phase mixture is (1.1-1.2):0.5.

[0027] By adopting the above scheme, the aramid fiber and the all-silicon molecular sieve are evenly and reasonably distributed in the reverse osmosis membrane, the obtained reverse osmosis membrane will not be too hard to cause cracks during chemical cleaning and flushing, and the flux of the reverse osmosis membrane will not be greatly reduced. The flux and desalination rate of the obtained reverse osmosis membrane will not change significantly after chemical cleaning.

[0028] In a specific possible implementation method, the preparation process of the aramid fiber described in the casting solution and the aqueous phase mixture includes: adding p-phenylenediamine to terephthaloyl chloride, heating to 90-100°C, mixing evenly, and then mixing in a twin-screw extruder under nitrogen protection for 20 minutes to obtain a polymer solution, the mixing temperature is 40°C, spinning the polymer solution under a spinning main machine, coagulation bath, water washing, drying, and heat stretching the raw silk at 300°C for 30 seconds to obtain aramid fiber.

[0029] By adopting the above scheme, the preparation process of aramid fiber is relatively simple, the prepared aramid fiber is relatively slender, and the hardness of the reverse osmosis membrane is not significantly increased. The prepared aramid fiber is para-aramid fiber with high yield and high strength. It is evenly distributed in the base membrane and the functional layer, and has a good strengthening effect on the reverse osmosis membrane.

[0030] In a specific embodiment, the mass ratio of terephthaloyl chloride to p-phenylenediamine in the aramid fiber preparation process in the casting solution and the aqueous phase mixture is 8:5.

[0031] By adopting the above scheme, p-phenylenediamine is excessive in the preparation process of aramid fiber, and the reaction end is amino group. The obtained reverse osmosis membrane does not contain excessive acyl chloride, is more stable and not easy to degrade, and the amino group at the end makes the reverse osmosis membrane more hydrophilic and has a larger flux. It also reduces the reaction activity of aromatic polyamide and is more resistant to chemical reagent cleaning. At the same time, the excess amino group can participate in the polymerization of the polyamide functional layer, further improving the connection strength of the fiber in the reverse osmosis membrane, and the obtained reverse osmosis membrane is more solid and tight.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. This application limits the components and quality of the casting liquid and the aqueous phase mixture, and adds a certain mass of aramid fiber to the casting liquid, and adds a certain mass of aramid fiber and molecular sieve to the aqueous phase mixture, so that the obtained reverse osmosis membrane has good chemical cleaning resistance and high mechanical strength. The aramid fiber winding makes the polyamide functional layer and the polysulfone-based membrane layer more tightly combined and not easy to swell, and has good chemical cleaning resistance. The reverse osmosis membrane obtained by limiting the aramid fiber to para-aramid fiber and limiting the diameter to a certain range, limiting the mass ratio of aramid fiber and molecular sieve, is smoother and more flexible, and the synergistic effect of molecular sieve and aramid fiber further improves the chemical cleaning resistance of the membrane, and is not easy to crack under the impact of chemical cleaning.

[0034] 2. The present application improves the compatibility of the molecular sieve in the reverse osmosis membrane by modifying the all-silica molecular sieve with a bisamide silane coupling agent, and increases the amide bond density on the surface of the all-silica molecular sieve, so as to uniformly introduce more amide bonds into the prepared reverse osmosis membrane, reduce the reaction activity of aromatic polyamide with active chlorine, and improve the chemical cleaning resistance of the reverse osmosis membrane.

[0035] 3. The present application limits the preparation process of aramid fiber and the mass ratio of terephthaloyl chloride to p-phenylenediamine, so that the surface amino density of the obtained reverse osmosis membrane is higher, more hydrophilic, less prone to deterioration, and participates in the polymerization of the polyamide functional layer to improve the firmness. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the experimental reagents in the preparation examples and embodiments are conventional commercial brands or obtained through conventional preparation processes.

[0037] Preparation Example

[0038] Preparation Example 1: Aramid fiber preparation 1:

[0039] 800 g of p-phenylenediamine was added to 500 g of terephthaloyl chloride, the temperature was raised to 90°C, the mixture was evenly mixed, and then the mixture was mixed in a twin-screw extruder under nitrogen protection for 20 minutes to obtain a polymer solution. The mixing temperature was 40°C, and the polymer solution was put into a spinning main machine for spinning, a coagulation bath, water washing, and drying. The raw silk was heat-stretched at 300°C for 30 seconds to obtain a para-aramid fiber with a diameter of 4 μm.

[0040] Preparation Example 2: Aramid fiber preparation 2:

[0041] 600 g of p-phenylenediamine was added to 500 g of terephthaloyl chloride, the temperature was raised to 90°C, the mixture was evenly mixed, and then the mixture was mixed in a twin-screw extruder under nitrogen protection for 20 minutes to obtain a polymer solution. The mixing temperature was 40°C, and the polymer solution was put into a spinning main machine for spinning, a coagulation bath, water washing, and drying. The raw silk was heat-stretched at 300°C for 30 seconds to obtain a para-aramid fiber with a diameter of 4 μm.

[0042] Preparation Example 3: Preparation of bisamide silane coupling agent:

[0043] Mix 220 g of xylene and 100 g of aminoethylaminopropyltrimethoxysilane, stir evenly at 10° C., add 110 g of acetic anhydride dropwise, stir, react for 6 hours, evaporate excess acetic acid, acetic anhydride and xylene to obtain a bisamide silane coupling agent.

[0044] Preparation Example 4: Bisamide silane modified molecular sieve:

[0045] 230 g of all-silicon molecular sieve and 10 g of the bisamide silane coupling agent prepared in Preparation Example 3 were added to 1000 g of 25% ethanol aqueous solution, stirred at 80° C. for 2 hours, filtered, washed with distilled water, and dried to obtain a bisamide silane-modified molecular sieve.

[0046] Preparation Example 5: Aminosilane modified molecular sieve:

[0047] 230g of all-silicon molecular sieve and 10g of aminosilane coupling agent KH-550 were added to 1000g of ethanol aqueous solution with a mass concentration of 25%, stirred at 80°C for 2 hours, filtered, washed with distilled water, and dried to obtain aminosilane-modified molecular sieve.

[0048] Example

[0049] Example 1

[0050] S1: preparing a casting solution: 170 g of polysulfone, 800 g of N,N-dimethylformamide, 30 g of polyvinyl pyrrolidone, and 30 g of the aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1 h at a stirring speed of 50 r / min, and allowed to stand for degassing and filtration for later use;

[0051] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0052] S3: preparing an aqueous phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 34.4 g of the aramid fiber obtained in Preparation Example 1 and 15.6 g of all-silicon molecular sieve into 800 g of water to dissolve, thereby obtaining an aqueous phase mixture; S4: coating the aqueous phase solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50°C to obtain an aqueous phase coated base membrane;

[0053] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0054] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0055] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0056] Example 2

[0057] S1: preparing the casting solution: 150g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 40g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0058] S2: The casting solution is uniformly sprayed on a non-woven fabric (thickness 100 μm, air permeability 2.5 cc / cm2 / s) through a slit coating head, and then allowed to stand after coating. After standing, the non-woven fabric is placed in pure water at 10° C. to solidify to obtain a polysulfone-based membrane;

[0059] S3: preparing a water phase mixture: adding 100 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 20.6 g of the aramid fiber obtained in Preparation Example 1 and 9.4 g of all-silicon molecular sieve into 800 g of water to dissolve, thereby obtaining a water phase mixture; S4: coating the water phase solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain a water phase coated base membrane;

[0060] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0061] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0062] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0063] Example 3

[0064] S1: preparing the casting solution: 200g polysulfone, 850g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 35g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0065] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0066] S3: preparing a water phase mixture: adding 100 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 20.6 g of the aramid fiber obtained in Preparation Example 1 and 9.4 g of all-silicon molecular sieve into 800 g of water to dissolve, thereby obtaining a water phase mixture; S4: coating the water phase solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain a water phase coated base membrane;

[0067] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0068] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0069] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0070] Example 4

[0071] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0072] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0073] S3: preparing an aqueous phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 34.4 g of the aramid fiber obtained in Preparation Example 2 and 15.6 g of all-silicon molecular sieve into 800 g of water to dissolve, thereby obtaining an aqueous phase mixture; S4: coating the aqueous phase solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50°C to obtain an aqueous phase coated base membrane;

[0074] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0075] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0076] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0077] Example 5

[0078] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0079] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0080] S3: preparing an aqueous phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 34.4 g of the aramid fiber prepared in Preparation Example 1 and 15.6 g of the bisamide silane-modified molecular sieve prepared in Preparation Example 4 into 800 g of water and dissolving them to obtain an aqueous phase mixture;

[0081] S4: coating the aqueous solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain an aqueous coated base membrane;

[0082] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0083] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0084] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0085] Example 6

[0086] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0087] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0088] S3: preparing an aqueous phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 34.4 g of the aramid fiber prepared in Preparation Example 1 and 15.6 g of the aminosilane-modified molecular sieve prepared in Preparation Example 5 into 800 g of water and dissolving them to obtain an aqueous phase mixture;

[0089] S4: coating the aqueous solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain an aqueous coated base membrane;

[0090] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0091] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0092] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0093] Example 7

[0094] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0095] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0096] S3: preparing a water phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 33.3 g of the aramid fiber obtained in Preparation Example 1 and 16.7 g of all-silicon molecular sieve into 800 g of water to dissolve, thereby obtaining a water phase mixture; S4: coating the water phase solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50°C to obtain a water phase coated base membrane;

[0097] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0098] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0099] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0100] Comparative Example

[0101] Comparative Example 1

[0102] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0103] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0104] S3: preparing a water phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, and 15.6 g of all-silicon molecular sieve into 800 g of water and dissolving them to obtain a water phase mixture;

[0105] S4: coating the aqueous solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain an aqueous coated base membrane;

[0106] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0107] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0108] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0109] Comparative Example 2

[0110] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0111] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0112] S3: preparing an aqueous phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, 34.4 g of the aramid fiber obtained in Preparation Example 1 and 15.6 g of fumed silica into 800 g of water and dissolving them to obtain an aqueous phase mixture;

[0113] S4: coating the aqueous solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain an aqueous coated base membrane;

[0114] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0115] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0116] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0117] Comparative Example 3:

[0118] S1: preparing the casting solution: 170g polysulfone, 800g N,N-dimethylformamide, 30g polyvinyl pyrrolidone and 30g aramid fiber prepared in Preparation Example 1 were mixed and stirred for 1h at a stirring speed of 50r / min, and allowed to stand for degassing and filtration for later use;

[0119] S2: The casting solution is evenly sprayed on the non-woven fabric (thickness 100μm, air permeability 2.5cc / cm 2 / s), and then allowed to stand after coating, and then placed in pure water at 10°C to coagulate to obtain a polysulfone-based membrane;

[0120] S3: preparing a water phase mixture: adding 50 g of m-phenylenediamine, 25 g of camphorsulfonic acid, 2 g of potassium laurate, 8 g of sodium hydroxide, and 50 g of the aramid fiber obtained in Preparation Example 1 into 800 g of water and dissolving them to obtain a water phase mixture;

[0121] S4: coating the aqueous solution on the polysulfone base membrane obtained in S2, and drying with hot air at 50° C. to obtain an aqueous coated base membrane;

[0122] S5: preparing an oil phase solution: dissolving 10 g of trimesoyl chloride in 900 g of isoparaffin to obtain an oil phase solution;

[0123] S6: coating the oil phase solution on the water phase coating base film in S4 to perform interfacial polymerization reaction, drying with 50° C. hot air after 60 minutes, and then washing with n-hexane and ethanol in sequence to obtain a composite layer film;

[0124] S7: The composite layer membrane is dried with hot air at 100° C.; the composite layer membrane is washed twice with pure water at 50° C., and dried again to obtain a chemical cleaning resistant reverse osmosis membrane.

[0125] Performance test test 1: The reverse osmosis membranes prepared in each embodiment and comparative example were pre-pressed with pure water at 5.0 MPa for 1 hour, and then the flux P1 was tested with pure water, the water temperature was controlled at 25°C, and the pressure was 5.0 MPa. The test results are summarized in Table 1. The calculation method is as follows:

[0126] P=V / (A×t)

[0127] Where P is the permeation flux of the membrane (L / (m 2 h), V is the volume of permeate collected during the test (L), A is the membrane area (m 2 ), t is the permeation time (h). The test results are summarized in Table 1.

[0128] Test 2: Prepare 2000ppm MgSO4 solution as the test solution, adjust the pH value of the solution to 7, control the solution temperature at 25°C, and test the desalination rate R1 of the reverse osmosis membrane prepared in the embodiment and the comparative example under 5.0MPa. The calculation method is as follows:

[0129] R1=(C f -C p ) / C f ×100%

[0130] Among them, C f Feed test solution salt concentration, C p is the salt concentration in the permeate. The test results are summarized in Table 1.

[0131] Test 3: The reverse osmosis membranes prepared in the embodiments and comparative examples were pre-pressed with pure water for 1 hour under 5.0 MPa, and then 2% (W) of ammonium tripolyphosphate and 0.25% (W) of sodium dodecylbenzene sulfonate mixed alkali solution (pH value is 10), and 0.5% (W) of hydrochloric acid solution (pH value is 2.5) were configured. The acid solution and alkali solution were circulated and flushed for 10 hours, and then Test 1 and Test 2 were repeated to test the pure water flux P2 and the desalination rate R2 of the reverse osmosis membrane after chemical cleaning, and the pure water flux decrease and the desalination rate decrease were calculated. The calculation method is as follows:

[0132] Pure water flux decrease = (P1-P2) / P1×100%,

[0133] Desalination rate decrease = (R1-R2) / R1×100%,

[0134] The test results are summarized in Table 1.

[0135] Table 1

[0136]

[0137] In combination with Examples 1 to 3, Example 7, and Comparative Examples 1 to 3, the present application limits the mass ratio of each layer of the membrane, adds a certain mass of aramid fiber to the polysulfone-based membrane, and adds a certain amount of aramid fiber and all-silicon molecular sieve to the polyamide functional layer and limits the mass ratio. The obtained reverse osmosis membrane polysulfone-based membrane and polyamide functional layer have improved connection strength through the winding of aramid fibers. The membrane is flexible, does not easily swell or crack, and has good resistance to chemical cleaning without reducing the desalination rate and water flux.

[0138] In combination with Example 1 and Examples 4-6, the present application modifies the molecular sieve with bisamide silane, and the molecular sieve is evenly distributed in the polyamide functional layer, and the surface has a high density of amide bonds, which reduces the reactivity of the reverse osmosis membrane with active chlorine, and the obtained reverse osmosis membrane has better chemical cleaning resistance. By making the para-phenylenediamine excessive in the process of preparing para-aramid fiber, the amino density on the surface of the reverse osmosis membrane is further increased, the hydrophilicity of the reverse osmosis membrane is increased to increase the flux and protect the reverse osmosis membrane, and the polymerization of the polyamide functional layer is involved to improve the firmness.

[0139] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing a chemical cleaning resistant reverse osmosis membrane, characterized in that: The steps include: S1: preparing the casting solution: mixing polysulfone, N,N-dimethylformamide, polyvinyl pyrrolidone and aramid fiber, letting them stand, degassing and filtering them for later use; S2: coating the casting liquid on the non-woven fabric, allowing it to stand after coating, and placing it in a coagulation liquid after standing to obtain a polysulfone-based membrane; S3: preparing a water phase mixture: adding an organic amine monomer, an additive, and a filler into water to obtain a water phase mixture, wherein the filler includes aramid fiber and all-silicon molecular sieve; S4: coating the aqueous phase mixture on the polysulfone base membrane obtained in S2, and drying to obtain an aqueous phase coated base membrane; S5: preparing an oil phase solution: dissolving an acyl chloride monomer in an oil phase solvent to obtain an oil phase solution; S6: coating the oil phase solution on the water phase coating base film prepared in S4 to carry out interfacial polymerization reaction, and performing drying and washing treatment to obtain a composite layer film; S7: drying the composite layer membrane, washing the composite layer membrane with pure water, and drying it again to obtain a chemical cleaning resistant reverse osmosis membrane; The diameter of the aramid fiber in the casting solution and the aqueous phase mixture is 2-5 μm.

2. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 1, characterized in that The components in the casting solution are as follows: 15-20 parts by weight of polysulfone, 75-85 parts by weight of N,N-dimethylformamide, 1-8 parts by weight of polyvinyl pyrrolidone, and 2-5 parts by weight of aramid fiber.

3. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 1, characterized in that The weight proportions of the components in the aqueous phase mixture are: 2-12 parts of organic amine monomer, 2-5 parts of auxiliary agent, 2-6 parts of filler and 75-90 parts of water.

4. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 1, characterized in that: The all-silica molecular sieve is a bisamide silane modified molecular sieve.

5. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 4, characterized in that The preparation steps of the bisamide silane modified molecular sieve include: adding 23 parts by mass of all-silicon molecular sieve and 1 part by mass of bisamide silane coupling agent to 100 parts by mass of ethanol aqueous solution with a mass concentration of 25%, stirring at 80° C. for 2 hours, filtering, washing with distilled water, and drying to obtain a bisamide silane modified molecular sieve.

6. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 1, characterized in that The aramid fiber described in the casting solution and the aqueous phase mixture is para-aramid fiber.

7. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 1, characterized in that : The mass ratio of aramid fiber and all-silicon molecular sieve in the aqueous phase mixture is (1.1-1.2):0.

5.

8. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 1, characterized in that The preparation process of the aramid fiber described in the casting solution and the aqueous phase mixture includes: adding p-phenylenediamine to terephthaloyl chloride, heating to 90-100°C, mixing evenly, and then mixing in a twin-screw extruder under nitrogen protection for 20 minutes to obtain a polymer solution, the mixing temperature is 40°C, spinning the polymer solution under a spinning main machine, coagulation bath, water washing, drying, and heat stretching the raw silk at 300°C for 30 seconds to obtain aramid fiber.

9. The method for preparing a chemical cleaning resistant reverse osmosis membrane according to claim 8, characterized in that :The mass ratio of terephthaloyl chloride to p-phenylenediamine is 8:5.

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