Preparation method of high-temperature-resistant reverse osmosis membrane and high-temperature-resistant reverse osmosis membrane

Abstract

The application discloses a preparation method of a high-temperature-resistant reverse osmosis membrane and the high-temperature-resistant reverse osmosis membrane. The preparation method comprises the following steps: (1) adding polyarylene ether nitrile into an organic solvent under heating and stirring, stirring for a period of time after the feeding is completed, and obtaining a mixed solution; (2) continuing to add a pore former after the mixed solution is cooled, stirring for a period of time after the feeding is completed, and obtaining a precursor solution; (3) performing vacuum defoaming treatment on the precursor solution, and obtaining a casting solution; (4) loading the casting solution on a carrier, and then performing gel bath treatment, and obtaining a base film; (5) sequentially immersing the base film in a first aqueous solution, a second aqueous solution and an organic phase solution for polyamide treatment, and obtaining the high-temperature-resistant reverse osmosis membrane; wherein the first aqueous solution comprises benzalkonium chloride; the second aqueous solution comprises polyethyleneimine; and the organic phase solution comprises trimesoyl chloride. The application has the advantages of simple process and significantly improved heat resistance of the obtained reverse osmosis membrane.

Description

Technical Field

[0001] This invention relates to the technical field of reverse osmosis membranes, and more specifically, to a method for preparing a high-temperature resistant reverse osmosis membrane and the high-temperature resistant reverse osmosis membrane itself. Background Technology

[0002] Reverse osmosis membranes are a key membrane separation technology that uses high pressure to separate water or other solutions from a solution, thereby purifying or concentrating substances. They are widely used in water treatment, wastewater treatment, and seawater desalination. In reverse osmosis membranes, the base membrane is the crucial component supporting the entire membrane structure, determining its mechanical properties, chemical stability, and separation efficiency. Currently, polysulfone is the primary substrate for reverse osmosis membranes. Polysulfone possesses excellent chemical stability, high-temperature resistance, and mechanical strength, making it widely used in reverse osmosis membrane fabrication. However, traditional polysulfone-based membranes have some shortcomings, such as uneven pore structure, limited separation efficiency, and insufficient elastic modulus, all of which can lead to membrane compaction and failure under high pressure.

[0003] The applicant of this application has filed Chinese invention patent CN119258820A, which discloses a method for preparing a reverse osmosis membrane and the reverse osmosis membrane itself. By introducing polyethersulfone and polymerizing it at the interface, the membrane's heat resistance, chemical stability, mechanical strength, hydrophilicity, biocompatibility, and solute rejection rate are significantly improved compared to traditional polysulfone-based membranes. However, in many industries, contaminated process water must undergo membrane separation treatment at high temperatures to achieve sustainable and energy-efficient water recycling. For example, in the food industry, treatment is carried out at temperatures above 80°C to reduce microbial growth. In such high-temperature applications, existing membranes exhibit poor heat resistance, and long-term use may lead to chain segment relaxation or degradation. Summary of the Invention

[0004] To further improve heat resistance while ensuring separation efficiency, this invention provides a method for preparing a high-temperature resistant reverse osmosis membrane and the membrane itself. The technical solution is as follows:

[0005] A method for preparing a high-temperature resistant reverse osmosis membrane, characterized by comprising the following steps:

[0006] (1) Polyarylene ether nitrile is added to an organic solvent under heating and stirring conditions. After the addition is completed, the mixture is stirred for a period of time to obtain a mixture.

[0007] (2) After cooling the mixture, continue to add the pore-forming agent. After the addition is complete, stir for a period of time to obtain the precursor solution;

[0008] (3) Vacuum degassing treatment is performed on the precursor solution to obtain the casting solution;

[0009] (4) Load the casting solution onto the carrier and then perform a gel bath treatment to obtain the base film;

[0010] (5) The base membrane is sequentially immersed in a first aqueous solution, a second aqueous solution and an organic solution for polyamide treatment to obtain a high-temperature resistant reverse osmosis membrane; wherein the first aqueous solution includes benzyl chloride; the second aqueous solution includes polyethyleneimine; and the organic solution includes trimesoyl chloride.

[0011] The advantages of the preparation method of the present invention are: (1) The glass transition temperature of polyarylene ether nitrile is above 250℃, which is significantly higher than that of polysulfone and polyethersulfone. At the same time, the rigid aromatic ring skeleton and cyano polar groups of polyarylene ether nitrile enhance the thermal oxidation stability of the membrane, making the polyarylene ether nitrile-based membrane more stable in high temperature environment and preventing performance degradation caused by chain segment relaxation or degradation, making it suitable for long-term high-temperature operation. (2) The rigid molecular chain of polyarylene ether nitrile gives it higher tensile strength and elastic modulus, making it more resistant to creep in high-pressure reverse osmosis operation, reducing the risk of membrane structure collapse and extending service life. (3) In the polyamidation process, benzyl chloride is used as a cationic surfactant to effectively reduce the interfacial tension between oil and water, thereby accelerating the diffusion rate of the aqueous monomer to the organic phase. The benzyl chloride benzene ring structure can undergo π-π stacking with the benzene ring of trimesoyl chloride, which helps to form a more regular and ordered monomer arrangement at the oil-water interface, thereby inducing the formation of a polyamide network with fewer defects and a more uniform structure, indirectly promoting the improvement of effective crosslinking degree. At the same time, its quaternary ammonium salt structure enhances the hydrophilicity of the membrane surface. (4) Polyethyleneimine is a highly branched polymer containing primary, secondary and tertiary amine groups. Its polyamine structure can form a polyamide layer with higher crosslinking degree with acyl chloride monomer, effectively improving the high temperature resistance of the composite membrane.

[0012] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membrane: in step (1), the organic solvent is N,N-dimethylacetamide; when the temperature reaches 50-80℃, polyarylene ether nitrile is added, and the mixture is stirred for 12-18 hours after the addition is completed.

[0013] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membrane: in step (2), the mixture is cooled to 15-35°C and then the pore-forming agent is added. After the addition is completed, the mixture is stirred for 10-15 hours. The pore-forming agent is polyvinylpyrrolidone-K30. The mass ratio of organic solvent, polyarylene ether nitrile and pore-forming agent is (80-90):(10-20):(1-10).

[0014] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membranes:

[0015] In step (3), the precursor solution is degassed under vacuum at 60°C for 10 to 12 hours;

[0016] In step (4), nonwoven fabric is used as a carrier, and casting solution at a temperature of 20-50°C is loaded onto the nonwoven fabric and subjected to a gel bath treatment in pure water at 10-40°C for 20-50 minutes.

[0017] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membranes: step (5) includes the following steps performed sequentially:

[0018] The base membrane was immersed in the first aqueous solution. After immersion, it was removed and the surface of the base membrane was swept with compressed air.

[0019] Then the base membrane is immersed in the second aqueous solution. After immersion, it is removed and the surface of the base membrane is swept with compressed air.

[0020] The base membrane is then immersed in an organic phase solution. After immersion, it is removed and the surface of the base membrane is rinsed with deionized water.

[0021] The base membrane is then immersed in a densification solution for heat treatment. After the heat treatment is completed, the base membrane is removed and rinsed with deionized water to obtain a high-temperature resistant reverse osmosis membrane. The molecular weight of the solute in the densification solution is less than that of pyromellitic acid chloride.

[0022] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membrane: the first aqueous solution is a benzyl chloride solution with a mass fraction of 0.1-1 wt%; the base membrane is immersed in the first aqueous solution for 1-5 minutes.

[0023] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membranes: the second aqueous solution is a mixture of polyethyleneimine and glutaraldehyde, with polyethyleneimine having a mass fraction of 0.5–3 wt% and glutaraldehyde having a mass fraction of 0.05–0.3 wt%; the base membrane is immersed in the second aqueous solution for 3–5 minutes. Thus, the trace amounts and mild glutaraldehyde in the second aqueous solution allow for slight pre-crosslinking within or between the polyethyleneimine molecular chains, transforming them into nanogel particles with a certain degree of rigidity, which can then be more tightly packed on the surface of the base membrane.

[0024] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membrane: the organic phase solution is a pyromellitic trimethylol chloride solution with a mass fraction of 0.1-1 wt%; the base membrane is immersed in the organic phase solution for 40-60 seconds.

[0025] As a further improvement to the above-mentioned method for preparing high-temperature resistant reverse osmosis membranes: the densification solution is a 0.05–0.2 wt% solution of 1,4-butanediol diglycidyl ether; the base membrane is immersed in the densification solution at 40–60°C for 30–60 minutes. Thus, a polyamide pre-network rich in polyamine groups is first formed through interfacial polymerization, providing a large number of active sites for the second reaction step. Then, small-molecule 1,4-butanediol diglycidyl ether permeates into the nanopores of the pre-network and reacts with the residual amine groups, thereby significantly reducing the free volume of the entire separation layer and making the pore size distribution narrower and more concentrated. Simultaneously, the mild heat treatment process also helps the polyamide network undergo thermal rearrangement and relaxation, eliminating some of the internal stress formed during rapid interfacial polymerization, causing the network structure to tend towards a lower-energy dense state, which synergistically enhances the separation performance of the membrane with the chemical crosslinking effect.

[0026] The high-temperature resistant reverse osmosis membrane is prepared by the above-described method for preparing high-temperature resistant reverse osmosis membranes.

[0027] In summary, the preparation method of the high-temperature resistant reverse osmosis membrane of the present invention is simple in process and low in material cost. The resulting high-temperature resistant reverse osmosis membrane not only has good separation effect and mechanical properties, but also significantly improved heat resistance. It can operate stably at a high flux under high temperature conditions, has a wider range of applications, and is highly practical.

[0028] The present invention will be further described below through specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0029] The present invention will now be clearly and completely described. Those skilled in the art will be able to implement the present invention based on this description. Before describing the present invention, it should be particularly noted that:

[0030] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0031] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0032] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0033] Example 1

[0034] The method for preparing the high-temperature resistant reverse osmosis membrane in this embodiment includes the following steps:

[0035] (1) Add N,N-dimethylacetamide to a three-necked flask, place the three-necked flask in an electric heating mantle and heat it while stirring. When the temperature reaches 60°C, add polyarylene ether nitrile to N,N-dimethylacetamide. After the addition is complete, stir for 18 hours to obtain a mixture.

[0036] (2) When the temperature of the mixture is lowered to 15°C, polyvinylpyrrolidone-K30 is added and the mixture is stirred for 12 hours to obtain the precursor solution; wherein, the mass ratio of N,N-dimethylacetamide, polyarylene ether nitrile and polyvinylpyrrolidone-K30 is 80:20:10.

[0037] (3) The precursor solution was degassed under vacuum at 60°C for 12 hours to obtain the casting solution.

[0038] (4) Using a doctor blade with a blade spacing of 150 μm and a moving speed of 10 m / min, the casting solution at a temperature of 40 °C is loaded onto the nonwoven fabric. Then, a gel bath treatment is performed in pure water at 15 °C for 10 minutes to allow N,N-dimethylacetamide and pure water to exchange and solidify into a film, thus obtaining the base film.

[0039] (5) Polyamidation treatment of the base film, specifically:

[0040] First, the base membrane is immersed in the first aqueous solution for 3 minutes. After immersion, it is removed and the surface of the base membrane is blown away with a compressed air knife. The first aqueous solution is a benzyl chloride solution with a mass fraction of 1 wt%.

[0041] The base film was then immersed in the second aqueous solution for 4 minutes. After immersion, it was removed and the surface of the base film was swept with a compressed air knife. The second aqueous solution was a polyethyleneimine solution with a mass fraction of 3 wt%.

[0042] The base membrane was then immersed in the organic phase solution for 50 seconds. After immersion, it was removed and the surface of the base membrane was rinsed with deionized water to obtain a high-temperature resistant reverse osmosis membrane. The organic phase solution was a 1 wt% trimesoyl chloride solution (the solvent was n-hexane, the same below).

[0043] The high-temperature resistant reverse osmosis membrane flux was tested to be 32 L / (m²). 2After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 96.51%.

[0044] Example 2

[0045] Compared with Example 1, the difference in the preparation method of the high-temperature resistant reverse osmosis membrane in this example is that the second aqueous solution is a mixture of polyethyleneimine and glutaraldehyde, with a mass fraction of 3 wt% for polyethyleneimine and 0.3 wt% for glutaraldehyde.

[0046] The high-temperature resistant reverse osmosis membrane flux was tested to be 33 L / (m²). 2 After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 96.49%.

[0047] Example 3

[0048] Compared with Example 2, the preparation method of the high-temperature resistant reverse osmosis membrane in this example is different in that: step (5) further includes immersing the base membrane in a densification solution at 60°C for 30 minutes after wetting the organic phase solution, taking it out after heat treatment and rinsing the surface of the base membrane with deionized water to obtain the high-temperature resistant reverse osmosis membrane; wherein, the densification solution is a 1,4-butanediol diglycidyl ether solution with a mass fraction of 0.05wt%.

[0049] The high-temperature resistant reverse osmosis membrane flux was tested to be 36 L / (m²). 2 After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 99.18%.

[0050] Example 4

[0051] Compared with Example 3, the difference in the preparation method of the high-temperature resistant reverse osmosis membrane in this example is that the mass ratio of N,N-dimethylacetamide, polyarylene ether nitrile, and polyvinylpyrrolidone-K30 is 90:10:1.

[0052] The high-temperature resistant reverse osmosis membrane flux was tested to be 34 L / (m²). 2 After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 98.69%.

[0053] Example 5

[0054] Compared with Example 3, the difference in the preparation method of the high-temperature resistant reverse osmosis membrane in this example is that the first aqueous phase solution is a benzyl chloride solution with a mass fraction of 0.1 wt%.

[0055] The high-temperature resistant reverse osmosis membrane flux was tested to be 35 L / (m²). 2After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 98.78%.

[0056] Example 6

[0057] Compared with Example 3, the difference in the preparation method of the high temperature resistant reverse osmosis membrane in this example is that the second aqueous solution is a mixture of polyethyleneimine and glutaraldehyde, with a mass fraction of 0.5 wt% for polyethyleneimine and 0.05 wt% for glutaraldehyde.

[0058] The high-temperature resistant reverse osmosis membrane flux was tested to be 34 L / (m²). 2 After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 98.61%.

[0059] Example 7

[0060] Compared with Example 3, the difference in the preparation method of the high-temperature resistant reverse osmosis membrane in this example is that the base membrane is immersed in a densification solution at 40°C for 60 minutes, wherein the densification solution is a 0.2wt% solution of 1,4-butanediol diglycidyl ether.

[0061] The flux of the high-temperature resistant reverse osmosis membrane was measured to be 36 L / (m²). 2 After running continuously for 24 hours at 80℃ and 50bar, the sodium chloride desalination rate was 99.06%.

[0062] Comparison Example

[0063] Compared with Example 1, the difference in the preparation method of the reverse osmosis membrane in this comparative example is that the organic material is polyethersulfone.

[0064] The test yielded a reverse osmosis membrane flux of 28 L / (m²). 2 After running continuously for 24 hours at 80℃ and 50 bar, the sodium chloride desalination rate was 94.53%.

[0065] The flux (pure water) and sodium chloride desalination rate of the reverse osmosis membranes in the above examples and control examples were tested according to the "Test Methods for Reverse Osmosis Membranes" (GB / T 32373-2015), as follows:

[0066] 1. Take several (no fewer than 4) samples. The samples should be free of obvious defects such as wrinkles and damage. The size of the samples should meet the requirements of completely covering the sealing ring of the evaluation cell. The effective membrane area of ​​the samples in the evaluation cell should not be less than 2.5 × 10⁻⁶. -3 m 2 Prepare a sodium chloride solution with a concentration of 32000 ppm and adjust the pH to 7.5 ± 0.5.

[0067] 2. Immerse the sample in deionized water or distilled water for 30 minutes;

[0068] 3. Flux test: Take a sample and put it into the evaluation cell. Turn on the water supply pump and slowly adjust the operating pressure to 50 bar for cross-flow filtration. Maintain the temperature at 25℃±0.5℃. After running stably for 30 minutes, collect the permeate produced after passing through the sample with a measuring cup (no less than 30 ml for a single sample) and use a stopwatch to calculate the required time.

[0069] Sodium chloride desalination rate test: Another sample was placed in the evaluation cell, the booster pump was turned on, the operating pressure was adjusted to 50 bar, and the temperature was adjusted to 80℃±0.5℃; after running stably under constant pressure for 24 hours, the total dissolved solids (TDS) of the original solution (sodium chloride solution) and the permeate were determined according to GB / T 5750.4.

[0070] 4. After the test is completed, slowly reduce the operating pressure to below 0.05MPa and turn off the booster pump or water supply pump.

[0071] Flux is calculated using the following formula:

[0072]

[0073] In the formula, J represents flux, with units of L / (m²). 2 ﹒ h); V is the volume of the graduated cylinder sample, in L; T is the sampling time, in h; A is the effective area of ​​the sample, in m². 2 .

[0074] The sodium chloride desalination rate is calculated using the following formula:

[0075]

[0076] In the formula, R is the sodium chloride desalination rate, in units of %; C P The total dissolved solids (TDS) of the permeate is expressed in mg / L; C f The TDS of the stock solution is expressed in mg / L.

[0077] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant reverse osmosis membrane, characterized in that: Includes the following steps: (1) Add polyarylene ether nitrile to an organic solvent under heating and stirring conditions, and stir for a period of time after the addition is completed to obtain a mixture; wherein, the organic solvent is N,N-dimethylacetamide; add polyarylene ether nitrile when the temperature reaches 50-80℃, and stir for 12-18 hours after the addition is completed; (2) After cooling the mixture, continue to add the pore-forming agent. After the addition is complete, stir for a period of time to obtain the precursor solution; (3) Vacuum degassing treatment is performed on the precursor solution to obtain the casting solution; (4) Load the casting solution onto the carrier and then perform a gel bath treatment to obtain the base film; (5) The base membrane is sequentially immersed in a first aqueous solution, a second aqueous solution, and an organic solution for polyamidation treatment to obtain a high-temperature resistant reverse osmosis membrane; wherein, the first aqueous solution includes benzyl chloride; the second aqueous solution includes polyethyleneimine; and the organic solution includes trimesoyl chloride; Step (5) includes the following steps performed sequentially: The base membrane is immersed in the first aqueous solution. After immersion, it is removed and the surface of the base membrane is swept with compressed air. The first aqueous solution is a benzyl chloride solution with a mass fraction of 0.1-1 wt%. The base membrane is immersed in the first aqueous solution for 1-5 minutes. The base membrane is then immersed in the second aqueous solution. After immersion, it is removed and the surface of the base membrane is swept with compressed air. The second aqueous solution is a mixture of polyethyleneimine and glutaraldehyde, with a mass fraction of 0.5-3 wt% for polyethyleneimine and 0.05-0.3 wt% for glutaraldehyde. The base membrane is immersed in the second aqueous solution for 3-5 minutes. The base membrane is then immersed in the organic phase solution. After immersion, it is removed and the surface of the base membrane is rinsed with deionized water. The organic phase solution is a 0.1-1 wt% trimesoyl chloride solution. The base membrane is immersed in the organic phase solution for 40-60 seconds. The base membrane is then immersed in a densification solution for heat treatment. After heat treatment, it is removed and the surface of the base membrane is rinsed with deionized water to obtain a high-temperature resistant reverse osmosis membrane. The molecular weight of the solute in the densification solution is less than that of trimesoyl chloride. The densification solution is a 1,4-butanediol diglycidyl ether solution with a mass fraction of 0.05-0.2 wt%. The base membrane is immersed in the densification solution at 40-60°C for 30-60 minutes.

2. The method for preparing the high-temperature resistant reverse osmosis membrane as described in claim 1, characterized in that: In step (2), the mixture is cooled to 15-35°C before the porogen is added, and the mixture is stirred for 10-15 hours after the addition is completed. The porogen is polyvinylpyrrolidone-K30. The mass ratio of organic solvent, polyarylene ether nitrile and porogen is (80-90):(10-20):(1-10).

3. The method for preparing the high-temperature resistant reverse osmosis membrane as described in claim 1, characterized in that: In step (3), the precursor solution is degassed under vacuum at 60°C for 10 to 12 hours; In step (4), nonwoven fabric is used as a carrier, and casting solution at a temperature of 20-50°C is loaded onto the nonwoven fabric and subjected to a gel bath treatment in pure water at 10-40°C for 20-50 minutes.

4. A high-temperature resistant reverse osmosis membrane, characterized in that: It is prepared by the method for preparing high-temperature resistant reverse osmosis membrane according to any one of claims 1-3.

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