A fouling-resistant and washable reverse osmosis membrane and its preparation method

Abstract

This invention belongs to the field of separation membranes, and particularly relates to an antifouling and washable reverse osmosis membrane and its preparation method. The reverse osmosis membrane provided by this invention is prepared according to the following steps: a nascent polyamide reverse osmosis membrane is immersed in a first treatment solution, removed and washed, then immersed in a second treatment solution, removed and drained to obtain an antifouling and washable reverse osmosis membrane; the nascent polyamide reverse osmosis membrane comprises a nonwoven fabric layer, a porous support layer, and a polyamide separation layer in sequential contact; the first treatment solution contains bi-amino-terminated polyethylene glycol and triethylamine; the second treatment solution contains polyvinyl alcohol and α-aldehyde-ω-carboxyl polyethylene glycol. Experimental results show that the reverse osmosis membrane provided by this invention has high antifouling ability, high desalination rate, and resistance to acid and alkali washing.

Description

Technical Field

[0001] This invention belongs to the field of separation membranes, and particularly relates to a fouling-resistant and washable reverse osmosis membrane and its preparation method. Background Technology

[0002] Reverse osmosis technology is a state-of-the-art and energy-efficient separation technology. Its principle is based on the separation of solutes and solvents in a solution by using a semi-permeable membrane—which allows only water to pass through and not other substances—under pressure higher than the osmotic pressure of the solution. Utilizing the separation characteristics of reverse osmosis membranes, dissolved salts, colloids, organic matter, bacteria, microorganisms, and other impurities in water can be effectively removed. It has advantages such as low energy consumption, no pollution, advanced technology, and simple operation and maintenance. Among these, polyamide composite reverse osmosis membranes have received widespread attention and use due to their excellent physicochemical stability.

[0003] However, since the advent of reverse osmosis technology, fouling and performance degradation after acid and alkali cleaning of polyamide composite reverse osmosis membranes have been bottlenecks restricting the promotion and development of this technology. The adsorption and deposition of pollutants on the membrane surface and within the pores cause the pore size to decrease and become clogged. Furthermore, once pollutants adhere to the membrane surface, cleaning is difficult, and even after cleaning, the membrane flux still decreases significantly. Simultaneously, the amide bonds in the polyamide layer hydrolyze under strong acid or alkaline conditions, leading to a decrease in the degree of cross-linking of the polyamide layer. Since the cleaning of reverse osmosis membrane modules typically involves acid and alkali washing steps, this can cause an irreversible decrease in the desalination rate of the reverse osmosis membrane.

[0004] To address these issues, existing technologies employ methods such as post-treatment of the reverse osmosis membrane to form a protective surface layer. Polyvinyl alcohol (PVA), due to its abundant hydroxyl groups in its molecular structure, exhibits strong hydrophilicity. Coating it onto the polyamide layer increases the hydrophilicity of the membrane surface, thereby enhancing its antifouling ability. It is one of the most common polyamide surface coating protective layers for reverse osmosis membranes. However, because PVA has relatively weak adhesion to the reverse osmosis membrane surface, the PVA layer gradually detaches during the operation of the reverse osmosis membrane, leading to a gradual loss of its antifouling performance. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a fouling-resistant and washable reverse osmosis membrane and its preparation method. The reverse osmosis membrane prepared by the method of the present invention has high anti-fouling ability, desalination rate and acid and alkali cleaning resistance.

[0006] This invention provides a method for preparing a fouling-resistant and washable reverse osmosis membrane, comprising the following steps:

[0007] The nascent polyamide reverse osmosis membrane was immersed in the first treatment solution, removed and cleaned, then immersed in the second treatment solution, removed and drained to obtain a fouling-resistant and washable reverse osmosis membrane.

[0008] The nascent polyamide reverse osmosis membrane comprises a nonwoven fabric layer, a porous support layer, and a polyamide separation layer in sequential contact.

[0009] The first treatment solution contains bi-amino-terminated polyethylene glycol and triethylamine;

[0010] The second treatment solution contains polyvinyl alcohol and α-aldehyde-ω-carboxyl polyethylene glycol.

[0011] Preferably, the nascent polyamide reverse osmosis membrane is prepared according to the following steps:

[0012] a) The casting solution is coated onto one side of the nonwoven fabric layer, then phase-inversion curing is performed in water, followed by rinsing, thermal curing and dehydration to obtain the base film; the front side of the base film is a porous support layer and the back side is a nonwoven fabric layer.

[0013] b) Coat the front side of the base film with an aqueous solution containing a polyamine monomer; then dry until the aqueous phase of the base film is surface dry;

[0014] c) Coat the front side of the aqueous-phase surface-dried base membrane with an oil phase solution containing polyacrylamide chloride monomers; then perform a drying process to form a polyamide separation layer, thereby obtaining a nascent polyamide reverse osmosis membrane.

[0015] Preferably, the polyamine monomer is one or more selected from m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, N-(2-hydroxyethyl)ethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, diethylenetriamine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, mesitylenetriamine, piperazine, and 4-aminomethylpiperazine;

[0016] The polyacryl chloride monomer is one or more of the following: pyromellitic methyl chloride, terephthaloyl chloride, orthophthaloyl chloride, isophthaloyl chloride, biphenyl methyl chloride, and benzene disulfonyl chloride.

[0017] Preferably, the diamino-terminated polyethylene glycol is α,ω-diamino polyethylene glycol; the number-average molecular weight of the diamino-terminated polyethylene glycol is 600~5000.

[0018] Preferably, the content of the diamino-terminated polyethylene glycol in the first treatment solution is 200~500 g / L; and the content of the triethylamine in the first treatment solution is 5~50 g / L.

[0019] Preferably, the immersion temperature in the first treatment solution is 1~10℃ and the time is 1~5min.

[0020] Preferably, the polyvinyl alcohol is one or more of PVA-17-99, PVA-20-99, PVA-17-88, PVA-17-92, PVA-117, PVA-105, PVA-124, PVA-217, PVA-205, and PVA-224; and the number average molecular weight of the α-aldehyde-ω-carboxyl polyethylene glycol is 1000~4000.

[0021] Preferably, the content of polyvinyl alcohol in the second treatment solution is 5~80 g / L; the content of α-aldehyde-ω-carboxyl polyethylene glycol in the second treatment solution is 1~30 g / L.

[0022] Preferably, the immersion temperature in the second treatment solution is 10~40℃ and the time is 1~5min.

[0023] This invention provides a fouling-resistant and washable reverse osmosis membrane, which is prepared according to the preparation method described in the above technical solution.

[0024] Compared with existing technologies, this invention provides an antifouling and washable reverse osmosis membrane and its preparation method. The reverse osmosis membrane provided by this invention is prepared according to the following steps: a nascent polyamide reverse osmosis membrane is immersed in a first treatment solution, removed and cleaned, then immersed in a second treatment solution, removed and drained to obtain an antifouling and washable reverse osmosis membrane; the nascent polyamide reverse osmosis membrane comprises a nonwoven fabric layer, a porous support layer, and a polyamide separation layer in sequential contact; the first treatment solution contains bi-amino-terminated polyethylene glycol and triethylamine; the second treatment solution contains polyvinyl alcohol and α-aldehyde-ω-carboxyl polyethylene glycol. This invention first uses bi-amino-terminated polyethylene glycol to react with a large number of acyl chloride groups on the surface of the nascent reverse osmosis membrane under the promotion of triethylamine, to achieve the purpose of increasing the crosslinking degree of the polyamide layer and increasing the surface amino groups; then, α-aldehyde-ω-carboxyl polyethylene glycol is used as a bridging compound to graft polyvinyl alcohol onto the surface of the reverse osmosis membrane through chemical bonds. Experimental results show that the reverse osmosis membrane provided by this invention has high antifouling ability, desalination rate, and acid and alkali washing resistance. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a method for preparing a fouling-resistant and washable reverse osmosis membrane, comprising the following steps:

[0027] The nascent polyamide reverse osmosis membrane was immersed in the first treatment solution, removed and cleaned, then immersed in the second treatment solution, removed and drained to obtain a fouling-resistant and washable reverse osmosis membrane.

[0028] The nascent polyamide reverse osmosis membrane comprises a nonwoven fabric layer, a porous support layer, and a polyamide separation layer in sequential contact.

[0029] The first treatment solution contains bi-amino-terminated polyethylene glycol and triethylamine;

[0030] The second treatment solution contains polyvinyl alcohol (PVA) and α-aldehyde-ω-carboxyl polyethylene glycol.

[0031] In the preparation method provided by the present invention, the nascent polyamide reverse osmosis membrane is preferably prepared according to the following steps:

[0032] a) The casting solution is coated onto one side of the nonwoven fabric layer, then phase-inversion curing is performed in water, followed by rinsing, thermal curing and dehydration to obtain the base film; the front side of the base film is a porous support layer and the back side is a nonwoven fabric layer.

[0033] b) Coat the front side of the base film with an aqueous solution containing a polyamine monomer; then dry until the aqueous phase of the base film is surface dry;

[0034] c) Coat the front side of the aqueous-phase surface-dried base membrane with an oil phase solution containing polyacrylamide chloride monomers; then perform a drying process to form a polyamide separation layer, thereby obtaining a nascent polyamide reverse osmosis membrane.

[0035] In the preparation method provided by this invention, in step a), the thickness of the nonwoven fabric layer is preferably 70~150μm, specifically 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm or 150μm; the air permeability of the nonwoven fabric layer is preferably 1~3cm. 3 / cm 2 / s, specifically 1cm 3 / cm 2 / s, 1.2cm 3 / cm 2 / s, 1.5cm 3 / cm 2 / s, 1.7cm 3 / cm 2 / s、2cm 3 / cm 2 / s, 2.3cm 3 / cm 2 / s, 2.5cm 3 / cm 2 / s, 2.7cm 3 / cm 2 / s or 3cm 3 / cm 2 / s.

[0036] In the preparation method provided by this invention, in step a), the casting solution preferably comprises sulfonated polysulfone and an organic solvent. The sulfonated polysulfone is preferably of the grade S2010G6, which is supplied by BASF, Germany. The organic solvent includes, but is not limited to, N,N-dimethylformamide. The concentration of the sulfonated polysulfone in the casting solution is preferably 10-20 wt%, specifically 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%.

[0037] In the preparation method provided by the present invention, in step a), the phase transformation curing temperature is preferably 10~25℃, specifically 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃ or 25℃; the phase transformation curing time is preferably 1~5min, specifically 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min.

[0038] In the preparation method provided by the present invention, in step a), after the phase transformation and curing are completed, it is preferable to clean the obtained base film.

[0039] In the preparation method provided by this invention, in step b), the aqueous solution contains a polyamine monomer and water. The polyamine monomer is preferably one or more of the following: m-phenylenediamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, N-(2-hydroxyethyl)ethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, diethylenetriamine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, mesopranitaryltriamine, piperazine, and 4-aminomethylpiperazine. The content of the polyamine monomer in the aqueous solution is preferably 0.5-5 wt%, specifically 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.3 wt%, 2.5 wt%, 2.8 wt%, 3 wt%, 3.2 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0040] In the preparation method provided by the present invention, in step b), the aqueous solution preferably also contains a surfactant and / or a non-aqueous polar solvent. The surfactant is preferably sodium dodecylbenzenesulfonate and / or sodium lauryl sulfate; the surfactant content in the aqueous solution is preferably 0.5-2 wt%, specifically 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2 wt%; the non-aqueous polar solvent is preferably dimethyl sulfoxide and / or N-methylpyrrolidone; the non-aqueous polar solvent content in the aqueous solution is preferably 3-10 wt%, specifically 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%.

[0041] In the preparation method provided by the present invention, in step b), the pH value of the aqueous solution is preferably 7 to 9, and the pH value of the aqueous solution can be adjusted by adding sodium hydroxide.

[0042] In the preparation method provided by the present invention, the specific process of step b) preferably includes: coating the front side of the base film with an aqueous solution, then removing excess solution from the surface and air drying.

[0043] In the preparation method provided by this invention, in step c), the oil phase solution contains a polyacrylamide chloride monomer and a solvent oil. The polyacrylamide chloride monomer is preferably one or more of pyromellitic trimethylbenzene chloride, terephthaloyl chloride, phthaloyl chloride, isophthaloyl chloride, biphenyl dimethylbenzene chloride, and benzene disulfonyl chloride; the content of the polyacrylamide chloride monomer in the oil phase solution is preferably 0.05~0.3wt%, specifically 0.05wt%, 0.07wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.17wt%, 0.2wt%, 0.23wt%, 0.25wt%, 0.27wt%, or 0.3wt%; the solvent oil includes, but is not limited to, one or more of aliphatic hydrocarbons, cyclic aliphatic hydrocarbons, and aromatic hydrocarbons, preferably one or more of Isopar G, Isopar L, and n-hexane.

[0044] In the preparation method provided by the present invention, in step c), after the base film is coated with oil phase solution, it is preferable to remove excess solvent from the surface first, and then perform drying treatment.

[0045] In the preparation method provided by the present invention, in step c), the drying temperature is preferably 60~80℃, specifically 60℃, 65℃, 70℃, 75℃ or 80℃; the drying time is preferably 2~5min, specifically 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min; during the drying process, the aqueous solution and the oil solution undergo interfacial polymerization reaction on the porous support layer to form a polyamide separation layer.

[0046] In the preparation method provided by this invention, the first treatment solution contains biamino-terminated polyethylene glycol, triethylamine, and water. The biamino-terminated polyethylene glycol is preferably α,ω-diamino polyethylene glycol; the number-average molecular weight of the biamino-terminated polyethylene glycol is preferably 600-5000, specifically 600, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, or 5000; the content of the biamino-terminated polyethylene glycol in the first treatment solution is preferably 200-500 g / L. Specifically, the concentration can be 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L, or 500 g / L; the content of triethylamine in the first treatment solution is preferably 5~50 g / L, specifically 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, or 50 g / L.

[0047] In the preparation method provided by the present invention, the immersion in the first treatment solution is preferably carried out under ultrasonic conditions; the immersion temperature is preferably 1~10℃, specifically 1℃, 2℃, 3℃, 4℃, 5℃, 6℃, 7℃, 8℃, 9℃ or 10℃; the immersion time is preferably 1~5min, specifically 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min.

[0048] In the preparation method provided by this invention, the second treatment solution contains polyvinyl alcohol, α-aldehyde-ω-carboxyl polyethylene glycol, and water. Preferably, the polyvinyl alcohol is one or more of PVA-17-99, PVA-20-99, PVA-17-88, PVA-17-92, PVA-117, PVA-105, PVA-124, PVA-217, PVA-205, and PVA-224; the number average molecular weight of the α-aldehyde-ω-carboxyl polyethylene glycol is preferably 1000-4000, specifically 1000, 1200, 1500, 1700, 200, 2300, 2500, 2700, 3000, 3200, 3500, 3700, or 4000; the polyvinyl alcohol in the second treatment solution contains... The preferred concentration is 5~80 g / L, specifically 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L or 80 g / L; the preferred concentration of α-aldehyde-ω-carboxyl polyethylene glycol in the second treatment solution is 1~30 g / L, specifically 1 g / L, 3 g / L, 5 g / L, 7 g / L, 10 g / L, 12 g / L, 15 g / L, 17 g / L, 20 g / L, 23 g / L, 25 g / L, 27 g / L or 30 g / L.

[0049] In the preparation method provided by the present invention, the membrane material taken out from the first treatment solution is preferably cleaned by ultrasonic cleaning; the cleaning temperature is preferably 40~60℃, specifically 40℃, 45℃, 50℃, 55℃ or 60℃; the cleaning time is preferably 5~20min, specifically 5min, 10min, 15min or 20min; the number of cleaning cycles is preferably 1~5 times, specifically 1 time, 2 times, 3 times, 4 times or 5 times.

[0050] In the preparation method provided by the present invention, the soaking temperature in the second treatment solution is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃ (room temperature), 30℃, 35℃ or 40℃; the soaking time is preferably 1~5min, specifically 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min.

[0051] The present invention also provides a fouling-resistant and washable reverse osmosis membrane, which is prepared according to the preparation method described in the above technical solution.

[0052] The technical solution provided by this invention has at least the following innovative aspects:

[0053] (1) In this invention, under the promotion of triethylamine, bi-amino-terminated polyethylene glycol reacts with the residual acyl chloride groups on the surface of the nascent polyamide reverse osmosis membrane. Triethylamine can consume the HCl generated in the reaction, thereby promoting the reaction. Both ends of the bi-amino-terminated polyethylene glycol can react with acyl chloride groups, which can significantly increase the crosslinking degree of the polyamide layer of the reverse osmosis membrane, thereby increasing the desalination rate of the membrane. In addition, since polyethylene glycol has good hydrophilicity, its composite on the surface of the polyamide layer can also increase the hydrophilicity of the reverse osmosis membrane surface, reduce the resistance of water passing through the reverse osmosis membrane, and thus increase the water flux of the reverse osmosis membrane. Furthermore, the increase in the hydrophilicity of the reverse osmosis membrane surface can also reduce the adhesion of hydrophobic pollutants, thereby improving the antifouling ability of the reverse osmosis membrane. In addition, the increase in the crosslinking degree of the polyamide layer of the reverse osmosis membrane can reduce the reactivity of amide bonds under strong acid and strong alkali conditions, and the chemical bond crosslinking is also more stable under strong acid and strong alkali conditions, thereby improving the acid and alkali cleaning resistance of the reverse osmosis membrane.

[0054] (2) Using α-aldehyde-ω-carboxyl polyethylene glycol as a bridging agent, the aldehyde group at one end of the polymer can react with the hydroxyl group in PVA, and the carboxyl group at the other end can react with the amino group on the polyamide layer. Since the reverse osmosis membrane surface treated with double-amino polyethylene glycol has a higher amino content, the introduction of the above-mentioned bridging agent can enable PVA to be connected to the polyamide layer more through chemical bonds. PVA forms a protective layer on the surface of the polyamide layer that is not easy to fall off, which can greatly improve the antifouling ability and acid and alkali washing ability of the polyamide reverse osmosis membrane.

[0055] The technical solution provided by this invention has at least the following advantages:

[0056] (1) In this invention, under the promotion of triethylamine, the reaction of bi-amino-terminated polyethylene glycol with the residual acyl chloride groups on the surface of the nascent polyamide reverse osmosis membrane can not only improve the surface crosslinking degree of the reverse osmosis membrane, but also increase the amino content on the surface, providing more reaction sites for PVA grafting.

[0057] (2) By increasing the degree of crosslinking of the polyamide layer, the present invention improves the desalination rate of the reverse osmosis membrane and also improves the acid and alkali resistance of the reverse osmosis membrane.

[0058] (3) The present invention can make the surface of the reverse osmosis membrane have a large amount of polyethylene glycol, thereby making the reverse osmosis membrane more hydrophilic. The improvement of hydrophilicity will improve the flux and antifouling properties of the reverse osmosis membrane.

[0059] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0060] Comparative Example 1

[0061] A reverse osmosis membrane is produced by the following method:

[0062] (1) Preparation of casting solution: The composition includes 16wt% sulfonated polysulfone (BASF, Germany, S2010G6) and the balance is N,N-dimethylformamide.

[0063] (2) Preparation of the support layer: The casting solution was coated onto the nonwoven fabric (thickness 140 μm, air permeability 1.5 cm). 3 / cm 2 The nonwoven fabric is formed by immersing a single-sided surface of the nonwoven fabric in ionized water for phase transformation, followed by cleaning, to obtain a porous support layer on the surface of the nonwoven fabric; wherein the phase transformation temperature is 17°C and the phase transformation time is 2 min.

[0064] (3) Preparation of aqueous solution: Add 30g m-phenylenediamine, 3g sodium dodecylbenzenesulfonate and 20g N-methylpyrrolidone to 947g water, adjust the pH value to 8.5~9 with sodium hydroxide, and stir evenly to obtain aqueous solution.

[0065] (4) Preparation of oil phase solution: Dissolve 3g of trimesoyl chloride in 997g of Isopar G and stir until homogeneous to obtain oil phase solution.

[0066] (5) Preparation of nascent polyamide reverse osmosis membrane: Aqueous solution is coated on the support layer, excess solution is removed from the surface and air-dried, then oil solution is coated on it, excess solution is removed from the surface, and then it is dried in a 70°C oven for 3 minutes to form a polyamide separation layer and obtain nascent polyamide reverse osmosis membrane.

[0067] Comparative Example 2

[0068] A reverse osmosis membrane is produced by the following method:

[0069] (1) Preparation of casting solution: Same as comparative example 1.

[0070] (2) Preparation of the support layer: Same as Comparative Example 1.

[0071] (3) Preparation of aqueous phase: Same as comparative example 1.

[0072] (4) Preparation of oil phase solution: Same as comparative example 1.

[0073] (5) Preparation of nascent polyamide reverse osmosis membrane: same as comparative example 1.

[0074] (6) Preparation of post-treatment solution: PVA-205 was added to water at a concentration of 15 g / L, heated to dissolve at 80°C, then cooled to -10°C, and then heated to dissolve again at 80°C. After cooling to room temperature, 3 g / L of α-aldehyde-ω-carboxylated polyethylene glycol with a number average molecular weight of 2000 was added to obtain the post-treatment solution.

[0075] (7) Post-treatment of nascent polyamide reverse osmosis membrane: Immerse the nascent polyamide reverse osmosis membrane in a post-treatment solution at 40°C, sonicate for 60 min, remove and remove excess post-treatment solution, drain, and obtain the treated polyamide reverse osmosis membrane.

[0076] Comparative Example 3

[0077] A reverse osmosis membrane is produced by the following method:

[0078] (1) Preparation of casting solution: Same as comparative example 1.

[0079] (2) Preparation of the support layer: Same as Comparative Example 1.

[0080] (3) Preparation of aqueous solution: Add 30g m-phenylenediamine, 3g sodium dodecylbenzenesulfonate, 10g polyethylene glycol with dual amino terminals, and 20g N-methylpyrrolidone to 937g water. Adjust the pH value to 8.5~9 with sodium hydroxide and stir evenly to obtain an aqueous solution.

[0081] (4) Preparation of oil phase solution: Same as comparative example 1.

[0082] (5) Preparation of nascent polyamide reverse osmosis membrane: Aqueous solution is coated on the support layer, excess solution is removed from the surface and air-dried, then oil solution is coated on it, excess solution is removed from the surface, and then it is dried in a 70°C oven for 3 minutes to form a polyamide separation layer and obtain nascent polyamide reverse osmosis membrane.

[0083] (6) Preparation of post-treatment solution: Dissolve PVA-205 in water at a concentration of 30 g / L, and then add 3 g / L of α-aldehyde-ω-carboxylated polyethylene glycol with a number average molecular weight of 2000 to obtain the post-treatment solution.

[0084] (7) Post-treatment of nascent polyamide reverse osmosis membrane: Clean the nascent polyamide reverse osmosis membrane, then immerse the reverse osmosis membrane in the post-treatment solution at room temperature for 3 minutes, take it out and drain it to obtain the treated polyamide reverse osmosis membrane.

[0085] Example 1

[0086] A fouling-resistant, high-desalination polyamide reverse osmosis membrane is produced by the following method:

[0087] (1) Preparation of casting solution: Same as comparative example 1.

[0088] (2) Preparation of the support layer: Same as Comparative Example 1.

[0089] (3) Preparation of aqueous phase: Same as comparative example 1.

[0090] (4) Preparation of oil phase solution: Same as comparative example 1.

[0091] (5) Preparation of nascent polyamide reverse osmosis membrane: same as comparative example 1.

[0092] (6) Preparation of post-treatment solution 1: Dissolve the diamino-terminated polyethylene glycol with a number average molecular weight of 2500 in water at a concentration of 200 g / L, and then add 20 g / L of triethylamine to obtain post-treatment solution 1.

[0093] (7) Preparation of post-treatment solution 2: Dissolve PVA-205 in water at a concentration of 30 g / L, and then add 3 g / L of α-aldehyde-ω-carboxylated polyethylene glycol with a number average molecular weight of 2000 to obtain the post-treatment solution.

[0094] (8) Post-treatment of nascent polyamide reverse osmosis membrane: Immerse the nascent polyamide reverse osmosis membrane in treatment solution 1 at 5°C and react under ultrasonic conditions for 3 min. After removal, clean it with an ultrasonic cleaner at 50°C for 10 min. Repeat the cleaning 3 times. After cleaning, immerse the reverse osmosis membrane in post-treatment solution 2 at room temperature for 3 min. Remove and drain to obtain a fouling-resistant and highly desalinated polyamide reverse osmosis membrane.

[0095] Example 2

[0096] A fouling-resistant, high-desalination polyamide reverse osmosis membrane, referring to Example 1, differs only in that the concentration of double-terminated amino polyethylene glycol in posttreatment solution 1 is 250 g / L.

[0097] Example 3

[0098] A fouling-resistant, high-desalination polyamide reverse osmosis membrane, referring to Example 1, differs only in that the concentration of double-terminated amino polyethylene glycol in posttreatment solution 1 is 300 g / L.

[0099] Performance Evaluation

[0100] The antifouling performance and acid / alkali cleaning resistance of the reverse osmosis membranes prepared in Comparative Examples 1-3 and Examples 1-3 were tested, as follows:

[0101] The initial flux and desalination rate of the antifouling and wash-resistant reverse osmosis membrane were tested by filtering a 2000 ppm sodium chloride aqueous solution for 30 min at 1.55 MPa, 25 °C, and a membrane flow rate of 1.1 L / min. Under the same operating conditions, the test aqueous solution was replaced with a 1000 ppm bovine serum albumin solution and a lysozyme solution, respectively. The bovine serum albumin solution was filtered for 150 min, followed by the lysozyme solution for 90 min, for a total of 240 min. Then, the test solution was replaced with a 2000 ppm sodium chloride aqueous solution, and the 2000 ppm sodium chloride aqueous solution was filtered for 30 min at 1.55 MPa, 25 °C, and a membrane flow rate of 1.1 L / min. The flux and desalination rate of the reverse osmosis membrane after fouling were tested. All test results are shown in Table 1. Under the same operating conditions, another antifouling and washable reverse osmosis membrane sample was filtered sequentially with hydrochloric acid solution at pH 2 for 150 min and sodium hydroxide solution at pH 12 for 150 min, for a total of 300 min. Then, the test solution was replaced with a 2000 ppm sodium chloride aqueous solution, and the 2000 ppm sodium chloride aqueous solution was filtered for 30 min at 1.55 MPa, 25 °C and a membrane flow rate of 1.1 L / min. The flux and desalination rate of the reverse osmosis membrane after acid and alkali cleaning were tested. All test results are shown in Table 2.

[0102] Table 1. Test data on the antifouling performance of polyamide reverse osmosis membranes

[0103]

[0104] Table 2 Test data on the acid and alkali resistance of polyamide reverse osmosis membranes

[0105]

[0106] As can be seen from Tables 1 and 2, compared with Comparative Example 1, the reverse osmosis membrane provided in the examples has a higher desalination rate, significantly better antifouling ability, and acid and alkali cleaning resistance; compared with Comparative Example 2, the reverse osmosis membrane provided in the examples has significantly better acid and alkali cleaning resistance; compared with Comparative Example 3, the reverse osmosis membrane provided in the examples has a better initial desalination rate, better antifouling ability, and significantly better acid and alkali cleaning resistance. Therefore, the technical solution provided in this application enables the reverse osmosis membrane to simultaneously possess high antifouling ability, desalination rate, and acid and alkali cleaning resistance.

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a fouling-resistant and washable reverse osmosis membrane, characterized in that, Includes the following steps: The nascent polyamide reverse osmosis membrane was immersed in the first treatment solution, removed and cleaned, then immersed in the second treatment solution, removed and drained to obtain a fouling-resistant and washable reverse osmosis membrane. The nascent polyamide reverse osmosis membrane comprises a nonwoven fabric layer, a porous support layer, and a polyamide separation layer in sequential contact. The nascent polyamide reverse osmosis membrane is prepared according to the following steps: a) The casting solution is coated onto one side of the nonwoven fabric layer, then phase-inversion curing is performed in water, followed by rinsing, thermal curing and dehydration to obtain the base film; the front side of the base film is a porous support layer and the back side is a nonwoven fabric layer. b) Coat the front side of the base film with an aqueous solution containing a polyamine monomer; then dry until the aqueous phase of the base film is surface dry; c) Coat the front side of the aqueous-phase surface-dried base membrane with an oil phase solution containing polyacrylamide chloride monomers; then perform drying treatment to form a polyamide separation layer, thereby obtaining a nascent polyamide reverse osmosis membrane; The first treatment solution contains bi-amino-terminated polyethylene glycol and triethylamine; the content of bi-amino-terminated polyethylene glycol in the first treatment solution is 200~500 g / L; the content of triethylamine in the first treatment solution is 5~50 g / L. The second treatment solution contains polyvinyl alcohol and α-aldehyde-ω-carboxyl polyethylene glycol; the content of polyvinyl alcohol in the second treatment solution is 5~80 g / L; the content of α-aldehyde-ω-carboxyl polyethylene glycol in the second treatment solution is 1~30 g / L.

2. The preparation method according to claim 1, characterized in that, The polyamine monomer is one or more selected from ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, N-(2-hydroxyethyl)ethylenediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, diethylenetriamine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, mesitylenetriamine, piperazine, and 4-aminomethylpiperazine. The polyacryl chloride monomer is one or more of the following: pyromellitic methyl chloride, terephthaloyl chloride, orthophthaloyl chloride, isophthaloyl chloride, biphenyl methyl chloride, and benzene disulfonyl chloride.

3. The preparation method according to claim 1, characterized in that, The diamino-terminated polyethylene glycol is α,ω-diamino polyethylene glycol; the number-average molecular weight of the diamino-terminated polyethylene glycol is 600~5000.

4. The preparation method according to claim 1, characterized in that, The immersion temperature in the first treatment solution is 1~10℃, and the time is 1~5min.

5. The preparation method according to claim 1, characterized in that, The polyvinyl alcohol is one or more of PVA-17-99, PVA-20-99, PVA-17-88, PVA-17-92, PVA-117, PVA-105, PVA-124, PVA-217, PVA-205, and PVA-224; the number average molecular weight of the α-aldehyde-ω-carboxyl polyethylene glycol is 1000~4000.

6. The preparation method according to claim 1, characterized in that, The immersion temperature in the second treatment solution is 10~40℃, and the time is 1~5min.

7. A fouling-resistant and washable reverse osmosis membrane, characterized in that, Prepared according to the preparation method according to any one of claims 1 to 6.

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