Anti-pollution reverse osmosis composite membrane and preparation method thereof

Abstract

The invention provides an anti-pollution reverse osmosis composite membrane and a preparation method thereof. The reverse osmosis composite membrane prepared by the method has good cleaning resistance and solvent resistance, and has better anti-pollution performance. The preparation method comprises the following steps: (1) providing a supporting base membrane; (2) preparing a polyamide functional layer on the supporting base membrane through interfacial polymerization to obtain a composite membrane containing the polyamide functional layer; a water phase solution used for preparing the polyamide functional layer is a water solution of polyamine and polyacid electrolyte, and an oil phase solution used for preparing the polyamide functional layer is a solution formed by polyfunctional group acyl chloride in an organic solvent; and (3) immersing the composite membrane obtained in the step (2) 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, the modification layer reaction liquid is an aqueous solution containing a polyacid electrolyte.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis composite membrane technology, specifically to an anti-fouling 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 antifouling reverse osmosis membranes with stronger cleaning resistance, stronger antifouling 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: polyvinylpyrrolidone, hydroxypiperazine derivatives, and polyvinyl alcohol are dissolved in hot water at 70-90℃ and stirred for 3-5 hours, then cooled to room temperature for degassing; a mixed solution of hexamethylenetetramine and methanesulfonic acid is prepared separately, and the two solutions are mixed evenly to obtain the coating solution; 3) Modifying the reverse osmosis membrane: the coating solution prepared in step 2) is uniformly coated onto the surface of the reverse osmosis membrane 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 modified coating in this method is a physical coating on the polyamide membrane surface, and the antifouling coating is unstable and easily peels off during use, thus 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 fluorinated amines and guanidine-containing compounds. 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 subsequent contaminant deposition, the presence of guanidine groups on the membrane surface kills microorganisms deposited thereon, reducing the rate of membrane fouling. This method utilizes the reaction of residual acyl chloride groups on the surface after interfacial polymerization with the amino groups on the antifouling compound. The introduced fluorinated or guanidine-containing compounds primarily resist microbial or organic fouling but are not effective against inorganic fouling, especially silica fouling. Summary of the Invention

[0005] This invention provides an antifouling reverse osmosis composite membrane and its preparation method. The reverse osmosis composite membrane prepared by the method of this invention has good cleaning and solvent resistance, and excellent antifouling performance.

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

[0007] This invention provides a method for preparing an anti-fouling 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 by interfacial polymerization to obtain a composite film containing a polyamide functional layer; and the aqueous solution used to prepare the polyamide functional layer is an aqueous solution of polyamine and polyacid electrolyte, and the oil solution used to prepare the polyamide functional layer is a solution formed by polyfunctional acyl chloride in an organic solvent.

[0010] (3) The composite membrane obtained in step (2) 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; the modification layer reaction solution is an aqueous solution containing polyacid electrolytes;

[0011] The polyacid electrolytes in steps (2) and (3) are each independently selected from one or more of polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl phosphate, carboxyl-polyethylene glycol-sulfonic acid, and ammonium polyacrylate, preferably selected from one or more of polyacrylic acid, polymethacrylic acid, and polystyrene sulfonic acid.

[0012] A second aspect of the present invention provides an antifouling reverse osmosis composite membrane, which is prepared by the preparation method described above.

[0013] The technical solution provided by this invention has the following beneficial effects:

[0014] The reverse osmosis composite membrane prepared by the method of the present invention firstly prepares a polyamide functional layer on a supporting base membrane, and introduces a polyacid electrolyte during the preparation of the polyamide functional layer to obtain a polyamide functional layer containing a polyacid electrolyte. On this basis, it continues to react with a modification layer reaction solution containing a polyacid electrolyte to obtain a composite membrane layer with a specific membrane structure. The composite membrane prepared by the method of the present invention has good cleaning resistance and solvent resistance, and has better antifouling performance. Detailed Implementation

[0015] 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.

[0016] 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," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0017] 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.

[0018] This invention provides a method for preparing an antifouling reverse osmosis composite membrane, the method comprising the following steps:

[0019] (1) Provide a supporting base film

[0020] (2) A polyamide functional layer is prepared on the supporting base film by interfacial polymerization to obtain a composite film containing a polyamide functional layer; and the aqueous solution used to prepare the polyamide functional layer is an aqueous solution of polyamine and polyacid electrolyte, and the oil solution used to prepare the polyamide functional layer is a solution formed by polyfunctional acyl chloride in an organic solvent.

[0021] (3) The composite membrane obtained in step (2) 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; the modification layer reaction solution is an aqueous solution containing polyacid electrolytes;

[0022] The polyacid electrolytes in steps (2) and (3) are each independently selected from one or more of polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl phosphate, carboxyl-polyethylene glycol-sulfonic acid, and ammonium polyacrylate.

[0023] The method of this invention prepares a reverse osmosis composite membrane. First, a polyamide functional layer is prepared on a supporting substrate membrane. During the preparation of the polyamide functional layer, a polyacid electrolyte is introduced to obtain a polyamide functional layer containing the polyacid electrolyte. This layer is then reacted with a modification layer reaction solution containing the polyacid electrolyte to obtain a composite membrane structure consisting of a supporting substrate membrane, a polyamide functional layer (intermediate layer) containing the polyacid electrolyte, and a polyacid electrolyte modification layer. During the preparation process, the polyacid electrolyte first reacts in an aqueous phase, and then directly reacts with the remaining acyl chloride after the interfacial polymerization reaction, introducing the polyacid layer twice. The resulting membrane exhibits reduced surface charge and increased hydrophilicity. The composite membrane prepared by this method has good cleaning and solvent resistance, and excellent antifouling performance, resisting fouling by insoluble inorganic pollutants such as barium sulfate, calcium sulfate, and silica scale.

[0024] Preferably, the polyacid electrolyte is selected from one or more of polyacrylic acid, polymethacrylic acid, and polystyrene sulfonic acid. Using a preferred polyacid electrolyte is beneficial for further improving the membrane's antifouling performance.

[0025] Preferably, in step (2), the mass ratio of the polyacid electrolyte and the polyamine in the aqueous solution is 0.1:1-1.4:1, for example, 0.1:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.4:1, etc., preferably 0.35:1-0.5:1. Using the preferred mass ratio is beneficial to further improving the membrane's antifouling performance.

[0026] In some embodiments, the mass concentration of the polyamine in the aqueous solution is 0.5-5%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0027] In some embodiments, the polyamine is selected from one or more of piperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, ethylenediamine, 1,3,6-phenyltriamine, diethylenetriamine, and triethylenetetramine.

[0028] In some embodiments, in step (2), the polyfunctional acyl chloride is selected from one or more of isophthaloyl chloride, terephthaloyl chloride, o-phthaloyl chloride, pyromellitic acyl chloride, biphenyl tetramethyl chloride, pyromellitic acyl chloride, cyanuric chloride, dansyl chloride, and benzenesulfonyl chloride.

[0029] In some embodiments, the organic solvent in the oil phase solution is selected from one or more of toluene, xylene, chloroform, ISOPAR, n-butane, n-heptane, n-hexane, cyclohexane, and ethylcyclohexane. ISOPAR can be any one or more of the ISOPAR series, such as ISOPAR C, ISOPAR E, ISOPAR G, ISOPAR H, ISOPAR L, ISOPAR M, etc.

[0030] In some embodiments, 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.

[0031] Preferably, in step (2), the supporting base film is first immersed in the aqueous solution for reaction, for example, 20s-10min, and at a temperature of 15-40℃; after drying, it is then immersed in the oil solution for example, 20s-10min, and at a temperature of 15-40℃, and then subjected to a second heat treatment to obtain the composite film containing the polyamide functional layer.

[0032] Preferably, the temperature of the second heat treatment is 60-80°C, and the time of the second heat treatment is 30s-10min.

[0033] Preferably, in step (3), the mass concentration of the polyacid electrolyte in the modified layer reaction solution is 0.2-8%, for example, 0.2%, 0.5%, 1%, 3%, 5%, 8%, etc., preferably 3-5%.

[0034] In some embodiments, in step (3), the reaction is carried out at a temperature of 15-40°C for a reaction time of, for example, 30s-1h.

[0035] In some embodiments, in step (3), the temperature of the first heat treatment is 60-80°C and the time is, for example, 30s-10min.

[0036] In some embodiments, in step (1), the supporting base film is obtained by applying a casting solution to a nonwoven fabric, wherein the casting solution is a polymer solution;

[0037] The polymer in the casting solution includes one or more of a first polymer and a second polymer;

[0038] The first polymer is selected from one or more of polyimide and polyetherimide;

[0039] The second polymer is selected from one or more of polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyvinylidene fluoride, and polyacrylonitrile;

[0040] Preferably, the mass concentration of the polymer in the casting solution is 12-30%.

[0041] Preferably, the polymer includes at least the first polymer; more preferably, the second polymer is 0-200% of the mass of the first polymer, for example, 0%, 30%, 50%, 80%, 100%, 150%, 200%, etc. The inventors have found that, in the method of the present invention, the reverse osmosis membrane prepared based on the preferred polymer has further improved washability and solvent resistance.

[0042] In this invention, the polyacid electrolyte used can be a commercially available polymer, and the polymer used to prepare the supporting base membrane can also be a commercially available polymer.

[0043] The supporting base membrane can be prepared using conventional preparation processes in the art. In some embodiments, the preparation steps of the supporting base membrane specifically include: 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 for solvent exchange, for example, for 30 min to 5 h, and then rinsing with water to obtain the supporting base membrane.

[0044] The polar solvent used to prepare the casting solution is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0045] In some preferred embodiments, in step (2), the mass ratio of the polyacid electrolyte to the polyamine in the aqueous solution is 0.35:1-0.5:1; and in step (3), the mass concentration of the polyacid electrolyte in the modified layer reaction solution is 3-5%. Using this preferred method to prepare a reverse osmosis composite membrane, under essentially the same conditions, a composite membrane that balances good initial performance with excellent cleaning and antifouling properties can be obtained.

[0046] The present invention also provides an anti-fouling 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] Description of some of the raw materials used in the examples and comparative examples:

[0057] Polyvinylphosphoric acid: weight average molecular weight is 20,000 g / mol;

[0058] Ammonium polyacrylate: weight average molecular weight 10,000 g / mol

[0059] Polyacrylic acid: weight average molecular weight is 100,000 g / mol;

[0060] Polyimide: Evonik, P84;

[0061] Polyetherimide: SABIC Ultem 1000E;

[0062] Polysulfone: BASF Ultrason S 6010NAT.

[0063] Example 1:

[0064] (1) The polyetherimide particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 60°C for 6 hours to form a casting solution (the concentration of polyetherimide was 23wt%). 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 rinsing with deionized water, the supporting base film was obtained.

[0065] (2) The above-mentioned supporting base film is first immersed in an aqueous solution (i.e., aqueous phase solution) containing 1.6 wt% m-phenylenediamine and 0.6 wt% polyacrylic acid and reacted at 25°C for 2 min. After drying at room temperature, it is then immersed in a heptane solution (i.e., oil phase solution) containing 0.1 wt% terephthaloyl chloride 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 obtained in step (2) is then immersed in an aqueous solution containing 5 wt% polyacrylic acid and reacted at 30°C for 2 min. After rinsing with clean water, it is heat-treated at 70°C for 1 min. The performance of the obtained composite membrane is tested, as shown in Table 1 below.

[0067] Example 2

[0068] The procedure was carried out in accordance with Example 1, except that in step (1), the polyetherimide particles in the casting solution were replaced with polysulfone particles.

[0069] Example 3

[0070] The process was carried out in accordance with Example 2, except that in step (1), the polysulfone particles in the casting solution were replaced with polysulfone particles and polyetherimide particles, wherein the mass of the polysulfone particles was 30% of the mass of the polyetherimide particles.

[0071] Example 4

[0072] The procedure was carried out in accordance with Example 1, except that in steps (2) and (3), polyacrylic acid was replaced with polyvinyl phosphate.

[0073] Example 5

[0074] The procedure was carried out in accordance with Example 1, except that in steps (2) and (3), polyacrylic acid was replaced with ammonium polyacrylate.

[0075] Example 6

[0076] The procedure is the same as in Example 1, except that:

[0077] In step (1), the concentration of polyetherimide in the casting solution is 12 wt%.

[0078] In step (2), the mass concentration of intermediate phenylenediamine in the aqueous phase solution is 0.5 wt%, the mass concentration of polyacrylic acid is 0.5 wt%, the reaction temperature is 15℃, and the reaction time is 10 min; the mass concentration of terephthaloyl chloride in the oil phase solution is 0.05 wt%, the reaction temperature is 15℃, and the reaction time is 10 min; the heat treatment is carried out at a temperature of 70℃ for 30 s.

[0079] In step (3), the mass concentration of polyacrylic acid is 0.5%, the reaction temperature is 40℃, the reaction time is 30s, and the heat treatment is carried out at a temperature of 60℃ for 10min.

[0080] Example 7

[0081] The procedure is the same as in Example 1, except that:

[0082] In step (1), the concentration of polyetherimide in the casting solution is 30 wt%.

[0083] In step (2), the mass concentration of intermediate phenylenediamine in the aqueous phase solution is 5 wt%, the mass concentration of polyacrylic acid is 1.5 wt%, the reaction temperature is 40℃, and the reaction time is 1 min; the mass concentration of terephthaloyl chloride in the oil phase solution is 0.5 wt%, the reaction temperature is 40℃, and the reaction time is 1 min; the heat treatment is carried out at a temperature of 60℃ for 10 min.

[0084] In step (3), the mass concentration of polyacrylic acid is 2%, the reaction temperature is 15℃, the reaction time is 1h, and the heat treatment is carried out at 80℃ for 30s.

[0085] Example 8

[0086] The procedure was carried out in accordance with Example 1, except that in step (2), the concentration of intermediate phenylenediamine in the aqueous solution was 0.3 wt% and the concentration of polyacrylic acid was 0.03 wt%.

[0087] In step (3), the concentration of the polyacrylic acid aqueous solution used is 0.2 wt%.

[0088] Example 9

[0089] The procedure was carried out in accordance with Example 1, except that in step (2), the concentration of intermediate phenylenediamine in the aqueous solution was 6 wt% and the concentration of polyacrylic acid was 8 wt%.

[0090] In step (3), the concentration of the polyacrylic acid aqueous solution used is 8 wt%.

[0091] Comparative Example 1: (Compared to Example 1, step (3) was not performed)

[0092] (1) The polyetherimide particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 60°C for 6 hours to form a casting solution (the concentration of polyetherimide was 23wt%). 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 rinsing with deionized water, the supporting base film was obtained.

[0093] (2) The above-mentioned supporting base film was first immersed in an aqueous solution (i.e., aqueous phase solution) containing 1.6 wt% m-phenylenediamine and 0.6 wt% polyacrylic acid at 25°C for 2 min, dried at room temperature, and then immersed in a heptane solution (i.e., oil phase solution) containing 0.1 wt% terephthaloyl chloride at 25°C for 1 min, followed by heat treatment at 80°C for 2 min to obtain a composite film containing a polyamide functional layer. The performance of the obtained composite film is shown in Table 1 below.

[0094] Comparative Example 2 (Traditional Reverse Osmosis Membrane):

[0095] (1) Polysulfone particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 60°C for 6 hours to form a casting solution (the concentration of polysulfone was 23wt%). 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.

[0096] (2) The above-mentioned supporting base film was first immersed in an aqueous solution containing 2.2 wt% m-phenylenediamine (i.e., aqueous phase solution) and reacted at 25°C for 2 min. After drying at room temperature, it was then immersed in a heptane solution containing 0.1 wt% terephthaloyl chloride (i.e., oil phase solution) and reacted at 25°C for 2 min. Subsequently, it was heat-treated at 80°C for 2 min to obtain a composite film containing a polyamide functional layer. Its performance was tested and is shown in Table 1 below.

[0097] Comparative Example 3 (compared to Example 1, step (2) did not introduce polyacid electrolytes)

[0098] (1) The polyetherimide particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 60°C for 6 hours to form a casting solution (the concentration of polyetherimide was 23wt%). 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 rinsing with deionized water, the supporting base film was obtained.

[0099] (2) The above-mentioned supporting base film is first immersed in an aqueous solution containing 2wt% m-phenylenediamine (i.e., aqueous phase solution) and reacted at 25°C for 2 min. After drying at room temperature, it is then immersed in a heptane solution containing 0.1wt% terephthaloyl chloride (i.e., oil phase solution) 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.

[0100] (3) The composite membrane obtained in step (2) is then immersed in an aqueous solution containing 5 wt% polyacrylic acid and reacted at 30°C for 2 min. After rinsing with clean water, it is heat-treated at 70°C for 1 min. The performance of the obtained composite membrane is tested, as shown in Table 1 below.

[0101] Comparative Example 4 (different from Example 1, step (3))

[0102] (1) The polyetherimide particles were mechanically stirred in the polar solvent N,N-dimethylacetamide at 60°C for 6 hours to form a casting solution (the concentration of polyetherimide was 23wt%). 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 rinsing with deionized water, the supporting base film was obtained.

[0103] (2) The above-mentioned supporting base film is first immersed in an aqueous solution (i.e., aqueous phase solution) containing 1.6 wt% m-phenylenediamine and 0.6 wt% polyacrylic acid and reacted at 25°C for 2 min. After drying at room temperature, it is then immersed in a heptane solution (i.e., oil phase solution) containing 0.1 wt% terephthaloyl chloride 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.

[0104] (3) The above composite membrane was then immersed in a mixed solution of EDC·HCl, NHS and polyacrylic acid in water and reacted at 25°C for 5 hours. The mass concentration of EDC·HCl in the mixed solution was 1%, EDC·HCl:NHS = 1:0.5 (mass ratio), and the mass concentration of polyacrylic acid was 5%. After rinsing with clean water, the membrane was heat-treated at 70°C for 1 minute. The performance of the obtained composite membrane was then tested, as shown in Table 1 below.

[0105] In the above embodiments and comparative examples, the performance tests of the final obtained reverse osmosis membranes included initial separation performance, separation performance after 12 alternating acid-base cleanings, and separation performance after 24 hours of fouling. The flux and rejection rate of the obtained reverse osmosis membranes 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 for the reverse osmosis membranes were alternating cleaning in NaOH aqueous solution at pH 12 and HCl aqueous solution at pH 2 for 2 hours each, followed by 12 alternating cleanings, after which the membrane flux and rejection rate were measured (corresponding to the results in Table 1 under "After 12 Alternating Acid-Base Cleanings"). The fouling resistance test conditions for the reverse osmosis membranes were tested at 1.6 MPa in an aqueous solution containing 1000 ppm Na2SiO3 and 2000 ppm NaCl, after 24 hours of fouling, and the membrane flux and rejection rate were measured (corresponding to the results in Table 2 under "After 24 hours of Fouling").

[0106] Table 1

[0107]

[0108]

[0109] Table 2

[0110]

[0111]

[0112] As can be seen from the above experimental results, the reverse osmosis composite membrane prepared by the method of the present invention can take into account good initial performance, fouling resistance, cleaning resistance and inorganic fouling resistance (e.g., resistance to silica fouling).

[0113] A comparison of Examples 1 and Examples 2-5 shows that, in the method of the present invention, under essentially the same conditions, the use of a preferred supporting substrate membrane and / or a preferred polyacid electrolyte is beneficial for further improving the solvent resistance, cleaning resistance, and inorganic fouling resistance (e.g., resistance to silica fouling) of the obtained reverse osmosis composite membrane.

[0114] 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 an anti-fouling 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 by interfacial polymerization to obtain a composite film containing a polyamide functional layer; and the aqueous solution used to prepare the polyamide functional layer is an aqueous solution of polyamine and polyacid electrolyte, and the oil solution used to prepare the polyamide functional layer is a solution formed by polyfunctional acyl chloride in an organic solvent. (3) The composite membrane obtained in step (2) 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; the modification layer reaction solution is an aqueous solution containing polyacid electrolytes; The polyacid electrolytes in steps (2) and (3) are each independently selected from one or more of polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl phosphate, carboxyl-polyethylene glycol-sulfonic acid, and ammonium polyacrylate, preferably selected from one or more of polyacrylic acid, polymethacrylic acid, and polystyrene sulfonic acid.

2. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the polyacid electrolyte to the polyamine in the aqueous solution is 0.1:1-1.4:1, preferably 0.35:1-0.5:1; Preferably, the mass concentration of the polyamine in the aqueous solution is 0.5-5%; Preferably, the polyamine is selected from one or more of piperazine, m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, ethylenediamine, 1,3,6-phenyltriamine, diethylenetriamine, and triethylenetetramine.

3. The preparation method according to claim 1, characterized in that, In step (2), the polyfunctional acyl chloride is selected from one or more of isophthaloyl chloride, terephthaloyl chloride, orthophthaloyl chloride, pyromellitic methyl methacrylate chloride, biphenyl tetramethyl methacrylate chloride, pyromellitic methyl methacrylate chloride, cyanuric chloride, dansyl chloride and benzenesulfonyl chloride; Preferably, the organic solvent in the oil phase solution is selected 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%.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (2), the supporting base film is first immersed in the aqueous solution for reaction, dried, and then immersed in the oil solution for reaction. Then, a second heat treatment is performed to obtain the composite film containing the polyamide functional layer. Preferably, the reaction in the aqueous solution is carried out at a temperature of 15-40°C for a reaction time of, for example, 20 s-10 min; Preferably, the reaction in the oil phase solution is carried out at a temperature of 15-40°C for a reaction time of, for example, 20 s-10 min; Preferably, the temperature of the second heat treatment is 60-80°C, and the time of the second heat treatment is 30s-10min.

5. The preparation method according to any one of claims 1-3, characterized in that, In step (3), the mass concentration of the polyacid electrolyte in the modified layer reaction solution is 0.2-8%, preferably 3-5%.

6. The preparation method according to any one of claims 1-3, characterized in that, In step (3), the reaction is carried out at a temperature of 15-40°C for a time of, for example, 30s-1h; 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, In step (1), the supporting base film is obtained by applying a casting solution to a nonwoven fabric, wherein the casting solution is a polymer solution; The polymer in the casting solution includes one or more of a first polymer and a 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 mass concentration of the polymer in the casting solution is 12-30%.

8. The preparation method according to claim 7, characterized in that, The polymer includes at least the first polymer; Preferably, the second polymer is 0-200% of the mass of the first polymer.

9. The preparation method according to claim 7, characterized in that, The preparation steps of the supporting base film specifically include: dissolving the polymer in a polar solvent to form a casting solution and degassing it, then applying the casting solution to a nonwoven fabric, and then immersing it in deionized water for a time of, for example, 30 min to 5 h, and then rinsing it with water to obtain the supporting base film. Preferably, the polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

10. A fouling-resistant reverse osmosis composite membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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