Cleaning-resistant anti-pollution reverse osmosis composite membrane and preparation method thereof

Abstract

The invention relates to the technical field of reverse osmosis composite membranes, and provides a cleaning-resistant and anti-pollution reverse osmosis composite membrane and a preparation method thereof.The prepared reverse osmosis composite membrane has good cleaning resistance and solvent resistance and has good pollution resistance to insoluble inorganic pollutants. The preparation method comprises the following steps: (1) providing a supporting base membrane; (2) preparing a polyamide functional layer on the supporting base membrane to obtain a composite membrane containing the polyamide functional layer; and (3) immersing the composite membrane containing the polyamide functional layer into a modification layer reaction solution for reaction, and then carrying out water washing and first heat treatment to obtain the reverse osmosis composite membrane, wherein the modification layer reaction solution comprises an activating agent and a pH response polymer.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis composite membrane technology, specifically to a cleaning-resistant and fouling-resistant reverse osmosis composite membrane and its preparation method. Background Technology

[0002] Reverse osmosis membrane technology, a commonly used water treatment process, has been widely applied in brackish water desalination, seawater desalination, industrial wastewater treatment, and municipal wastewater treatment. However, during long-term operation, the membrane surface inevitably becomes fouled by colloids, microorganisms, impurities, and insoluble salts, leading to a decline in membrane performance. This is especially true for insoluble inorganic pollutants such as barium sulfate, calcium sulfate, and silica scale, where inorganic scale deposition on the reverse osmosis membrane surface is more severe. Currently, the removal of large amounts of pollutants deposited on the membrane surface mainly relies on membrane cleaning. However, frequent cleaning can cause the membrane coating to peel off or form defects, thus also degrading membrane performance. Therefore, there is an urgent need to develop clean-resistant and fouling-resistant reverse osmosis membranes with stronger cleaning resistance, stronger anti-fouling capabilities, and wider applications.

[0003] Patent CN114053876B discloses a method for preparing an antifouling reverse osmosis membrane, comprising the following steps: 1) Preparing the reverse osmosis membrane: using interfacial polymerization, a polysulfone-based membrane is successively contacted with an aqueous solution and an oil solution to undergo an interfacial polymerization reaction, forming a polyamide separation layer on the surface of the base membrane to obtain the reverse osmosis membrane; 2) Preparing the coating solution: dissolving polyvinylpyrrolidone, hydroxypiperazine derivatives, and polyvinyl alcohol in hot water at 70-90℃, stirring for 3-5 hours, and then cooling to room temperature for degassing; separately preparing a mixed solution of hexamethylenetetramine and methanesulfonic acid, and mixing the two solutions evenly to obtain the coating solution; 3) Modifying the reverse osmosis membrane: uniformly coating the surface of the reverse osmosis membrane with the coating solution prepared in step 2), and treating it to obtain an antifouling reverse osmosis membrane. This invention can prepare an antifouling reverse osmosis membrane with excellent antibacterial and permeation properties. However, the antifouling coating modified by physical coating in this method is unstable and easily peels off during use, thereby reducing the antifouling properties of the reverse osmosis membrane.

[0004] Patent CN112827368B provides an antifouling reverse osmosis membrane and its preparation method. The reverse osmosis membrane includes a support layer and a polyamide desalination layer formed on the support layer. The surface of the polyamide desalination layer is modified with a fluorinated amine and a guanidine-containing compound. The reverse osmosis membrane of this invention is prepared by first heat-treating the polyamide desalination layer and then reacting it with the modifying material. The modification process occurs on the outer surface of the membrane and does not affect the performance of the separation membrane itself. The fluorinated surface of the membrane reduces the adhesion of contaminants. After contaminant deposition, the presence of guanidine groups on the membrane surface kills microorganisms deposited thereon, reducing the rate of membrane fouling. The fluorinated or guanidine-containing compounds introduced in this method primarily resist microbial or organic fouling, but are not effective against inorganic fouling, especially silica fouling. Summary of the Invention

[0005] This invention provides a cleaning-resistant and anti-fouling reverse osmosis composite membrane and its preparation method. The cleaning-resistant and anti-fouling reverse osmosis composite membrane prepared by the method of this invention has good cleaning resistance and solvent resistance, and good anti-fouling properties against insoluble inorganic pollutants. Moreover, the preparation process is simple.

[0006] To achieve its objective, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a wash-resistant and fouling-resistant reverse osmosis composite membrane, the method comprising the following steps:

[0008] (1) Provide a supporting base film;

[0009] (2) A polyamide functional layer is prepared on the supporting base film to obtain a composite film containing a polyamide functional layer;

[0010] (3) The composite membrane containing the polyamide functional layer is immersed in the modification layer reaction solution for reaction, and then washed with water and subjected to a first heat treatment to obtain the reverse osmosis composite membrane; wherein, the modification layer reaction solution includes an activator and a pH-responsive polymer;

[0011] The activator comprises a first component and a second component, wherein the first component is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and the second component is N-hydroxysuccinimide and / or N-hydroxythiosuccinimide;

[0012] The pH-responsive polymer is selected from one or more of the following: polyethyleneamine, polyethyleneimine, polyvinylpyridine, alkyl salts of polyethyleneimine, branched polyethyleneimine-polyethylene glycol, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinylphosphonic acid, carboxyl-polyethylene glycol-sulfonic acid, and polyacrylamide.

[0013] A second aspect of the present invention provides a cleaning-resistant and fouling-resistant reverse osmosis composite membrane, wherein the cleaning-resistant and fouling-resistant reverse osmosis composite membrane is prepared by the preparation method described above.

[0014] The technical solution provided by this invention has the following beneficial effects:

[0015] This invention first prepares a polyamide functional layer on a supporting base membrane, then places the composite membrane containing the polyamide functional layer in a modification layer reaction solution, and uses a one-step method to bring the composite membrane containing the polyamide functional layer into contact with an activator and a pH-responsive polymer for reaction. This method can obtain a reverse osmosis membrane with high rejection rate and strong anti-fouling properties, especially strong resistance to inorganic silica fouling, while also exhibiting good cleaning and solvent resistance. Detailed Implementation

[0016] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" as used herein may include any and all combinations of one or more of the associated listed items. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0019] This invention provides a method for preparing a wash-resistant and fouling-resistant reverse osmosis composite membrane, the method comprising the following steps:

[0020] (1) Provide a supporting base film;

[0021] (2) A polyamide functional layer is prepared on the supporting base film to obtain a composite film containing a polyamide functional layer;

[0022] (3) The composite membrane containing the polyamide functional layer is immersed in the modification layer reaction solution for reaction, and then washed with water and subjected to a first heat treatment to obtain the reverse osmosis composite membrane; wherein, the modification layer reaction solution includes an activator and a pH-responsive polymer;

[0023] The activator comprises a first component and a second component, wherein the first component is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and the second component is N-hydroxysuccinimide (NHS) and / or N-hydroxythiosuccinimide.

[0024] The pH-responsive polymer is selected from one or more of polyethyleneamine, polyethyleneimine, polyvinylpyridine, alkyl salts of polyethyleneimine, branched polyethyleneimine-polyethylene glycol, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinylphosphonic acid, carboxyl-polyethylene glycol-sulfonic acid, and polyacrylamide. Among these, carboxyl-polyethylene glycol-sulfonic acid includes, but is not limited to, one or more of carboxyl-diethylene glycol-sulfonic acid, carboxyl-triethylene glycol-sulfonic acid, and carboxyl-pentaethylene glycol-sulfonic acid.

[0025] This invention first prepares a polyamide functional layer on a supporting base membrane, then places the composite membrane containing the polyamide functional layer in a modification layer reaction solution, and uses a one-step method to bring the composite membrane containing the polyamide functional layer into contact with an activator and a pH-responsive polymer for reaction. The reverse osmosis membrane obtained by this method is a composite membrane composed of a supporting base membrane, a polyamide functional layer, and a modification layer. This method can obtain a reverse osmosis membrane with high rejection rate and strong antifouling properties, while also exhibiting good cleaning resistance and solvent resistance.

[0026] In a preferred embodiment, in step (3), the mass ratio of the first component to the second component in the activator is 1:0.3-1:1.5, for example, 1:0.3, 1:0.5, 1:0.9, 1:1.2, 1:1.5, etc., such as 1:0.3-1:0.9. Using this preferred mass ratio helps to improve reaction efficiency and promotes the interaction between the modified layer and the film surface.

[0027] In some preferred embodiments, in step (3), the mass concentration of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in the modification layer reaction solution is 0.3%-3%, for example 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, etc., for example 0.3%-2%, etc.; using a preferred mass concentration is beneficial to improving reaction efficiency and promoting the interaction between the modification layer and the membrane surface. In some preferred embodiments, in step (3), the mass concentration of the pH-responsive polymer in the modification layer reaction solution is 0.3%-5%, for example 0.3%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc., for example 0.5%-2%, etc.; using a preferred mass concentration is beneficial to improving reaction efficiency and promoting the interaction between the modification layer and the membrane surface. More preferably, in the modified layer reaction solution of step (3), the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to the pH-responsive polymer is 0.4:1-1.2:1. Using the preferred mass ratio is beneficial to obtaining a reverse osmosis composite membrane with better performance.

[0028] In this invention, the pH-responsive polymer is one or more of the following: polyethyleneamine, polyethyleneimine, polyvinylpyridine, alkyl polyvinylimine salt, branched polyethyleneimine-polyethylene glycol, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinylphosphonic acid, carboxyl-polyethylene glycol-sulfonic acid, and polyacrylamide; all of the above pH-responsive polymers can be commercially available polymers of the corresponding type. Preferably, in step (3), the pH-responsive polymer is preferably one or more of polyethyleneamine, polyethyleneimine, and polyacrylic acid. The inventors have found that by using the preferred pH-responsive polymer to prepare the reverse osmosis membrane using the method of this invention, the inorganic fouling resistance, solvent resistance, and cleaning resistance of the composite membrane can be further improved.

[0029] Preferably, in step (3), the second component of the activator is N-hydroxythiosuccinimide. The inventors have found that by using the preferred second activator component in the preparation of the reverse osmosis membrane by the method of the present invention, the reaction efficiency can be further improved, and the composite membrane's resistance to inorganic fouling, solvents, and cleaning can be further improved.

[0030] In a preferred embodiment, in step (3), the pH-responsive polymer is one or more of polyethyleneamine, polyethyleneimine, and polyacrylic acid, and the second component in the activator is N-hydroxythiosuccinimide. By using this preferred method to prepare the reverse osmosis composite membrane of the present invention, a reverse osmosis composite membrane with better solvent resistance, cleaning resistance and inorganic fouling resistance can be obtained.

[0031] Preferably, in step (3), the reaction is carried out at 15-40°C, for example 15°C, 25°C, 30°C, 40°C, etc., for example 25-40°C, and the reaction time is for example 0.5h-12h, for example 1-6h;

[0032] Preferably, in step (3), the temperature of the first heat treatment is 60-80°C, for example 60°C, 70°C, 80°C, etc., and the time is, for example, 30s-10min, for example 1-5min. Performing the first heat treatment at the preferred temperature is beneficial to promote a more complete reaction.

[0033] Furthermore, the polymer in the supporting base film includes one or more of the first polymer and the second polymer;

[0034] The first polymer is selected from one or more of polyimide and polyetherimide;

[0035] The second polymer is selected from one or more of polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyvinylidene fluoride, and polyacrylonitrile.

[0036] Both the first and second polymers can be commercially available polymers, such as polyimide, but not limited to, commercially available Matrimid 5218, P84, etc.

[0037] Preferably, the polymer in the supporting substrate membrane includes at least the first polymer; more preferably, the second polymer is 0-200% of the mass of the first polymer. The inventors have discovered that preparing a reverse osmosis membrane using the method of the present invention, in conjunction with a preferred supporting substrate membrane, is beneficial for further improving the cleaning resistance, solvent resistance, and inorganic fouling resistance of the resulting reverse osmosis membrane.

[0038] In a more preferred embodiment, the polymer in the supporting base membrane includes at least the first polymer; more preferably, the second polymer is 0-200% of the mass of the first polymer, for example, 0%, 20%, 50%, 80%, 100%, 150%, 200%, etc.; and the second component in the activator is N-hydroxythiosuccinimide, and / or, in step (3), the pH-responsive polymer is one or more of polyethyleneamine, polyethyleneimine, and polyacrylic acid. The reverse osmosis composite membrane prepared by this preferred method in the method of the present invention has further improved solvent resistance, cleaning resistance, and inorganic fouling resistance. More preferably, the polymer in the supporting base membrane is the first polymer, the second component in the activator is N-hydroxythiosuccinimide, and, in step (3), the pH-responsive polymer is one or more of polyethyleneamine, polyethyleneimine, and polyacrylic acid; by preparing the reverse osmosis composite membrane of the present invention by the above more preferred method, a reverse osmosis composite membrane with superior solvent resistance, cleaning resistance, and inorganic fouling resistance can be obtained.

[0039] The support base membrane can be prepared using conventional processes in the art. In some specific embodiments, the support base membrane is prepared by the following steps: dissolving the polymer in a polar solvent to form a casting solution and degassing it, then applying (e.g., coating) the casting solution onto a nonwoven fabric, followed by immersion in deionized water (e.g., at room temperature) for a duration of 30 min to 5 h, and then rinsing the fabric to obtain the support base membrane.

[0040] Preferably, the polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide;

[0041] Preferably, the mass concentration of the polymer in the casting solution is 12-30%, such as 12%, 15%, 20%, 25%, 30%, etc., such as 15-25%.

[0042] In some specific embodiments, in step (2), the polyamide functional layer is prepared on the supporting substrate film by interfacial polymerization;

[0043] Preferably, the supporting substrate film is first immersed in an aqueous solution for an immersion time of, for example, 20s-3min, at a temperature of, for example, 20-40℃; after drying, it is then immersed in an oil solution for an immersion time of, for example, 20s-3min, at a temperature of, for example, 20-40℃; followed by a second heat treatment to obtain the composite film containing the polyamide functional layer; preferably, the temperature of the second heat treatment is 60-80℃, for example, 70-80℃, and the time is, for example, 30s-10min, for example, 30s-2min.

[0044] Preferably, the aqueous phase solution is an aqueous solution of a polyamine; the polyamine is preferably selected from one or more of piperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, ethylenediamine, 1,3,6-phenyltriamine, diethylenetriamine, triethylenetetramine, and polyethyleneimine; preferably, the mass concentration of the aqueous phase solution is 0.5%-5%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0045] Preferably, the oil phase solution is a solution of a polyfunctional acyl chloride in an organic solvent; preferably, the polyfunctional acyl chloride is selected from one or more of isophthaloyl chloride, terephthaloyl chloride, phthaloyl chloride, trimesoyl chloride, biphenyltetramethyl chloride, trimesoyl chloride, cyanuric chloride, dansyl chloride, and benzenesulfonyl chloride; the organic solvent is selected, for example, from one or more of toluene, xylene, chloroform, ISOPAR, n-butane, n-heptane, n-hexane, cyclohexane, and ethylcyclohexane; wherein, ISOPAR can be any one or more of the ISOPAR series, such as ISOPAR C, ISOPAR, ISOPAR G, ISOPAR H, ISOPAR L, ISOPAR M, etc. Preferably, the mass concentration of the polyfunctional acyl chloride in the oil phase solution is 0.05%-0.5%, for example, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0046] The present invention also provides a cleaning-resistant and fouling-resistant reverse osmosis composite membrane, which is prepared by the preparation method described above.

[0047] The present invention will be further illustrated by the following examples, but should not be construed as limiting the invention to these embodiments. In the following examples, unless otherwise specified, all raw materials used are commercially available.

[0048] In the following examples and comparative examples, the membrane separation performance was mainly evaluated by flux and rejection rate.

[0049] Flux refers to the volume of permeate passing through a unit effective membrane area per unit time. Flux F can be calculated using the following formula:

[0050]

[0051] In the formula, F—membrane flux, L·m -2 ·h -1 V—Volume of permeate, L; A—Effective area of ​​membrane, m² 2 t—test time, h;

[0052] Retention rate refers to the percentage of the concentration of the retained substance relative to the concentration of the feed liquid. The retention rate R can be calculated using the following formula:

[0053]

[0054] In the formula, R is the retention rate (%); C is the retention rate (%). P —Osmium concentration, g·L -1 C f —Feed concentration, g·L -1 .

[0055] Unless otherwise specified, all materials or reagents used in the following examples or comparative examples are commercially available.

[0056] The following descriptions of some of the raw materials used in the examples or comparative examples are as follows:

[0057] Polyimide: Evonik, P84;

[0058] Polyetherimide: SABIC Ultem 1000E;

[0059] Polysulfone: BASF Ultrason US 6010NAT;

[0060] Polymethacrylic acid: weight average molecular weight is 40,000 g / mol;

[0061] Polyvinylamine: weight-average molecular weight is 110,000 g / mol;

[0062] Polyacrylic acid: weight average molecular weight is 100,000 g / mol.

[0063] Example 1:

[0064] (1) Polyimide P84 particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 65°C for 5 hours to form a casting solution (in which the mass percentage of polyimide was 24wt%). After standing for 12 hours to remove bubbles, the casting solution was scraped onto a nonwoven fabric and then immersed in deionized water for 2 hours. After being taken out and rinsed with deionized water, the supporting base film was obtained.

[0065] (2) The above-mentioned supporting base film is first immersed in an aqueous solution (containing 2.2 wt% m-phenylenediamine) and reacted at 25°C for 2 min. After drying at room temperature, it is then immersed in an oil solution (containing 0.1 wt% pyromellitic chloride in n-heptane) and reacted at 25°C for 1 min. Subsequently, it is heat-treated at 80°C for 2 min to obtain a composite film containing a polyamide functional layer.

[0066] (3) The composite membrane containing the polyamide functional layer was then immersed in a mixed aqueous solution of EDC·HCl, NHS, and polymethyl methacrylate for 5 hours. The mass concentration of EDC·HCl in the mixed aqueous solution was 0.8%, the mass ratio of EDC·HCl to NHS was 1:0.4, the mass concentration of polymethyl methacrylate was 2%, and the reaction temperature was 28°C. After rinsing with clean water, the membrane was heat-treated at 70°C for 1 minute to obtain a reverse osmosis membrane. The performance of the obtained reverse osmosis membrane was then tested. The tested performance included initial performance, performance after 12 alternating acid and alkali cleanings, and performance after 24 hours of fouling. The results are shown in Tables 1 and 2 below.

[0067] Example 2

[0068] The procedure was carried out in accordance with Example 1, except that in step (3), polyvinylamine was used instead of polymethacrylic acid.

[0069] Example 3

[0070] The procedure was carried out in accordance with Example 2, except that in step (3), N-hydroxythiosuccinimide was used instead of NHS.

[0071] Example 4

[0072] The procedure was carried out in accordance with Example 1, except that in step (3), polyacrylic acid was used instead of polymethacrylic acid.

[0073] Example 5

[0074] The procedure was carried out in accordance with Example 1, except that in step (1), polysulfone particles were used instead of polyimide particles.

[0075] Example 6

[0076] The process was carried out in accordance with Example 5, except that in step (1), polysulfone particles and polyetherimide particles were used to prepare the casting solution, wherein the ratio of polysulfone particles to polyetherimide particles was 30% (by mass).

[0077] Example 7

[0078] The procedure is the same as in Example 1, except that:

[0079] In step (1), the mass concentration of polyimide P84 in the casting solution is 12%, and the polar solvent is N,N-dimethylformamide.

[0080] In step (2), the mass concentration of m-phenylenediamine in the aqueous solution is 0.5%, the mass concentration of trimesoyl chloride in the oil solution is 0.05%, and the heat treatment is carried out at a temperature of 60°C for 30 seconds.

[0081] In step (3), the reaction time is 0.5 h, the mass concentration of EDC·HCl in the mixed aqueous solution is 0.3%, the mass ratio of EDC·HCl to NHS is 1:0.3, the mass concentration of polymethyl methacrylate is 0.5%, the reaction temperature is 15 °C, the heat treatment temperature is 60 °C, and the heat treatment time is 30 s.

[0082] Example 8

[0083] The procedure is the same as in Example 1, except that:

[0084] In step (1), the mass concentration of polyimide P84 in the casting solution is 30%, and the polar solvent is N-methylpyrrolidone.

[0085] In step (2), the mass concentration of m-phenylenediamine in the aqueous solution is 5%, the mass concentration of pyromellitic chloride in the oil solution is 0.2%, and the heat treatment is carried out at a temperature of 60°C for 10 min.

[0086] In step (3), the reaction time is 12h, the mass concentration of EDC·HCl in the mixed aqueous solution is 3%, the mass ratio of EDC·HCl to NHS is 1:1, the mass concentration of polymethyl methacrylate is 2.5%, the reaction temperature is 40℃, the heat treatment temperature is 80℃, and the heat treatment time is 1min.

[0087] Example 9

[0088] The procedure is the same as in Example 1, except that:

[0089] In step (2), the mass concentration of pyromellitic chloride in the oil phase solution is 0.5%, and the heat treatment is carried out at 70°C for 2 minutes.

[0090] In step (3), the mass concentration of EDC·HCl in the mixed aqueous solution is 3%, the mass ratio of EDC·HCl to NHS in the mixed aqueous solution is 1:1.5, the mass concentration of polymethyl methacrylate is 5%, the heat treatment temperature is 60℃, and the heat treatment time is 10min.

[0091] Example 10

[0092] The procedure was carried out in accordance with Example 1, except that in step (3), the mass concentration of EDC·HCl in the mixed aqueous solution was 1% and the mass concentration of polymethyl methacrylate was 5%.

[0093] Example 11

[0094] The procedure was carried out in accordance with Example 1, except that in step (3), the mass concentration of EDC·HCl in the mixed aqueous solution was 1% and the mass concentration of polymethacrylic acid was 0.8%.

[0095] Comparative Example 1: (No modification layer was prepared compared to Example 1)

[0096] (1) Polyimide P84 particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 65°C for 5 hours to form a casting solution (in which the mass percentage of polyimide P84 was 24wt%). After standing for 12 hours to remove bubbles, the casting solution was scraped onto a nonwoven fabric and then immersed in deionized water for 2 hours. After being taken out and rinsed with deionized water, the supporting base film was obtained.

[0097] (2) The above-mentioned supporting substrate membrane was first immersed in an aqueous solution (containing 2.2 wt% m-phenylenediamine) and reacted at 25°C for 2 min. After drying at room temperature, it was then immersed in an oil solution (containing 0.1 wt% trimesoyl chloride in n-heptane) and reacted at 25°C for 1 min. Subsequently, it was heat-treated at 80°C for 2 min to obtain a composite membrane containing a polyamide functional layer. The performance of the obtained composite membrane was tested and is shown in Tables 1 and 2 below.

[0098] Comparative Example 2 (Traditional Reverse Osmosis Membrane):

[0099] (1) Polysulfone particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 65°C for 5 hours to form a casting solution (in which the mass percentage of polysulfone was 24wt%). After standing for 12 hours to remove bubbles, the casting solution was scraped onto a nonwoven fabric and then immersed in deionized water for 2 hours. After being taken out and rinsed with deionized water, a supporting base film was obtained.

[0100] (2) The above-mentioned supporting base film is first immersed in an aqueous solution (containing 2.2 wt% m-phenylenediamine) and reacted at 25°C for 2 min. After drying at room temperature, it is then immersed in an oil solution (containing 0.1 wt% pyromellitic chloride in n-heptane) and reacted at 25°C for 1 min. Subsequently, it is heat-treated at 80°C for 2 min to obtain a polyamide functional layer composite film.

[0101] The performance of the obtained composite membrane is shown in Tables 1 and 2 below.

[0102] Comparative Example 3

[0103] The procedure is the same as in Example 1, except that:

[0104] The operation of immersing the composite membrane in a mixed aqueous solution containing EDC·HCl, NHS, and polymethyl methacrylate in step (3) of Example 1 is replaced by the following operation: the composite membrane containing the polyamide functional layer is first immersed in a mixed aqueous solution of EDC·HCl and NHS (where the mass concentration of EDC·HCl is 0.8% and the mass ratio of EDC·HCl to NHS is 1:0.4) and reacted at 28°C for 20 min, and then immersed in an aqueous solution of polymethyl methacrylate (mass concentration of 2%) and reacted at 28°C for 5 h. All other operations are performed in accordance with Example 1.

[0105] In the performance tests of the above embodiments and comparative examples, the flux and rejection rate of the reverse osmosis membrane were tested at 1.6 MPa in an aqueous solution containing 2000 ppm NaCl at a test temperature of 25°C. The cleaning resistance test conditions of the reverse osmosis membrane were as follows: alternating cleaning with sodium hydroxide aqueous solution at pH 12 and HCl aqueous solution at pH 2 for 2 hours each, and after 12 alternating cleaning cycles, the flux and rejection rate of the membrane were measured (corresponding to the results in "After 12 alternating acid and alkali cleaning cycles" in Table 1). The antifouling test conditions of the reverse osmosis membrane were as follows: at 1.6 MPa in an aqueous solution containing 1000 ppm Na2SiO3 and 2000 ppm NaCl, the flux and rejection rate of the membrane were measured after 24 hours of fouling (corresponding to the results in "After 24 hours of fouling" in Table 2).

[0106] Table 1

[0107]

[0108]

[0109] Table 2

[0110]

[0111]

[0112] As can be seen from the comparison of the examples and Comparative Example 2, the reverse osmosis membrane prepared by the method of the present invention has significant advantages over the traditional reverse osmosis membrane in terms of cleaning resistance, solvent resistance and resistance to silica fouling, and has a relatively low flux decline rate.

[0113] A comparison of Example 1 and Comparative Example 1 shows that, under essentially the same conditions, the composite film with the modified layer prepared by step (3) has better cleaning resistance, solvent resistance and anti-silicone fouling properties than the comparative example.

[0114] As can be seen from the comparison between Example 1 and Comparative Example 3, the composite film obtained by using the one-step method of the present invention to prepare the modified layer in step (3) has better cleaning resistance, solvent resistance and anti-silicone fouling properties.

[0115] A comparison of Examples 1 and 5 and 6 shows that the reverse osmosis composite membrane prepared by the method of the present invention, with the use of a preferred polymer in the supporting base membrane, can further significantly improve the cleaning resistance, solvent resistance and anti-silicone fouling performance of the obtained composite membrane.

[0116] A comparison of Examples 2-4 and Example 1 shows that, under otherwise essentially the same conditions, using preferred activator components and / or preferred pH-responsive polymers is beneficial for achieving a better balance between solvent resistance, washability, and resistance to silicone fouling.

[0117] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a wash-resistant and fouling-resistant reverse osmosis composite membrane, characterized in that, The preparation method includes the following steps: (1) Provide a supporting base film; (2) A polyamide functional layer is prepared on the supporting base film to obtain a composite film containing a polyamide functional layer; (3) The composite membrane containing the polyamide functional layer is immersed in the modification layer reaction solution for reaction, and then washed with water and subjected to a first heat treatment to obtain the reverse osmosis composite membrane; wherein, the modification layer reaction solution includes an activator and a pH-responsive polymer; The activator comprises a first component and a second component, wherein the first component is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, and the second component is N-hydroxysuccinimide and / or N-hydroxythiosuccinimide; The pH-responsive polymer is selected from one or more of the following: polyethyleneamine, polyethyleneimine, polyvinylpyridine, alkyl salts of polyethyleneimine, branched polyethyleneimine-polyethylene glycol, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinylphosphonic acid, carboxyl-polyethylene glycol-sulfonic acid, and polyacrylamide.

2. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of the first component and the second component in the activator is 1:0.3-1:1.

5.

3. The preparation method according to claim 2, characterized in that, In the modified layer reaction solution of step (3), the mass concentration of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is preferably 0.3%-3%; In the modified layer reaction solution of step (3), the mass concentration of the pH-responsive polymer is preferably 0.3%-5%; More preferably, in the modified layer reaction solution of step (3), the mass ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to the pH-responsive polymer is 0.4:1-1.2:

1.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (3), the pH-responsive polymer is preferably one or more of polyethyleneamine, polyethyleneimine, and polyacrylic acid.

5. The preparation method according to any one of claims 1-3, characterized in that, In step (3), the second component in the activator is preferably N-hydroxythiosuccinimide; Preferably, in step (3), the pH-responsive polymer is one or more of polyethyleneamine, polyethyleneimine, and polyacrylic acid.

6. The preparation method according to any one of claims 1-3, characterized in that, In step (3), the reaction is carried out at 15-40°C for a time of, for example, 0.5-12 h. And / or, in step (3), the temperature of the first heat treatment is 60-80°C and the time is, for example, 30s-10min.

7. The preparation method according to any one of claims 1-3, characterized in that, The polymer in the supporting base film includes one or more of the first polymer and the second polymer; The first polymer is selected from one or more of polyimide and polyetherimide; The second polymer is selected from one or more of polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyvinylidene fluoride, and polyacrylonitrile; Preferably, the polymer in the supporting base film includes at least the first polymer; more preferably, the second polymer is 0-200% of the mass of the first polymer; even more preferably, the second component in the activator is N-hydroxythiosuccinimide, and / or, in step (3), the pH-responsive polymer is one or more of polyethyleneimine, polyethyleneimine, and polyacrylic acid.

8. The preparation method according to claim 7, characterized in that, The supporting base membrane is prepared by the following steps: The polymer is dissolved in a polar solvent to form a casting solution and degassed. The casting solution is then applied to a nonwoven fabric and then immersed in deionized water for a time of, for example, 30 min to 5 h. After rinsing, the supporting base film is obtained. Preferably, the polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; Preferably, the mass concentration of the polymer in the casting solution is 12-30%.

9. The preparation method according to any one of claims 1-3, characterized in that, In step (2), the polyamide functional layer is prepared on the supporting substrate film by interfacial polymerization; Preferably, the supporting substrate film is first immersed in an aqueous solution for, for example, 20 seconds to 3 minutes, at a temperature of, for example, 20 to 40 degrees Celsius; after drying, it is then immersed in an oil solution for, for example, 20 seconds to 3 minutes, at a temperature of, for example, 20 to 40 degrees Celsius; followed by a second heat treatment to obtain the composite film containing the polyamide functional layer; preferably, the temperature of the second heat treatment is 60 to 80 degrees Celsius, and the time is, for example, 30 seconds to 10 minutes. Preferably, the aqueous phase solution is an aqueous solution of a polyamine; the polyamine is preferably selected from one or more of piperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, ethylenediamine, 1,3,6-phenyltriamine, diethylenetriamine, triethylenetetramine, and polyethyleneimine; preferably, the mass concentration of the aqueous phase solution is 0.5%-5%. Preferably, the oil phase solution is a solution of a polyfunctional acyl chloride in an organic solvent; preferably, the polyfunctional acyl chloride is selected from one or more of isophthaloyl chloride, terephthaloyl chloride, phthaloyl chloride, trimesoyl chloride, biphenyltetramethyl chloride, trimesoyl chloride, cyanuric chloride, dansyl chloride, and benzenesulfonyl chloride; the organic solvent is selected, for example, from one or more of toluene, xylene, chloroform, ISOPAR, n-butane, n-heptane, n-hexane, cyclohexane, and ethylcyclohexane; preferably, the mass concentration of the polyfunctional acyl chloride in the oil phase solution is 0.05%-0.5%.

10. A washable and fouling-resistant reverse osmosis composite membrane, characterized in that, The wash-resistant and anti-fouling reverse osmosis composite membrane is prepared by the preparation method described in any one of claims 1-9.

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