Preparation method of reverse osmosis membrane and reverse osmosis membrane

Abstract

The invention discloses a preparation method of a reverse osmosis membrane and the reverse osmosis membrane. The preparation method comprises the following steps: (1) adding polyethersulfone into N, N-dimethylacetamide in a heating and stirring state, and stirring for a period of time after charging is completed, so as to obtain a mixed solution; (2) cooling the mixed solution, continuing to add a pore-foaming agent, and stirring for a period of time after charging is completed to obtain a precursor solution; (3) performing vacuum defoaming treatment on the precursor solution to obtain a membrane casting solution; (4) loading the membrane casting solution on a carrier, and then carrying out gel bath treatment to obtain a base membrane; and (5) performing polyamide treatment on the surface of the base membrane to obtain the reverse osmosis membrane. The preparation method disclosed by the invention is simple in process and low in material cost, and the obtained reverse osmosis membrane has more uniform and more through-type pore structures, higher separation efficiency, more excellent chemical stability and better mechanical properties, can adapt to higher operation pressure, and can continuously and stably operate at higher flux under high pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of reverse osmosis membranes, and in particular to a method for preparing a reverse osmosis membrane and a reverse osmosis membrane. Background Art

[0002] Reverse osmosis membrane is a key membrane separation technology. It separates water or other solutions from solutions under high pressure to purify or concentrate substances. Since the 1950s, it has been widely used in water treatment, wastewater treatment, seawater desalination and other fields. In reverse osmosis membrane, the base membrane is the key part that supports the entire membrane structure and determines the mechanical properties, chemical stability and separation efficiency of the membrane.

[0003] At present, the base membrane of reverse osmosis membrane mainly uses polysulfone as the substrate. Polysulfone has excellent chemical stability, high temperature resistance and mechanical strength, so it is widely used in the preparation of reverse osmosis membrane. However, the traditional polysulfone-based membrane has some shortcomings in some aspects, such as its pore structure is not uniform, the separation efficiency is limited, and the elastic modulus strength is not enough, which will cause the membrane to fail due to compression under high pressure operation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a reverse osmosis membrane and a reverse osmosis membrane having a more uniform and more penetrating pore structure, a higher separation efficiency and better mechanical properties.

[0005] In order to achieve the above object, the present invention first provides a method for preparing a reverse osmosis membrane, and the technical scheme is as follows:

[0006] The method for preparing a reverse osmosis membrane comprises the following steps:

[0007] (1) adding polyethersulfone to N,N-dimethylacetamide under heating and stirring, stirring for a period of time after the addition is completed to obtain a mixed solution;

[0008] (2) After the mixed solution is cooled, the porogen is continuously added, and after the addition is completed, the mixture is stirred for a period of time to obtain a precursor solution;

[0009] (3) performing vacuum degassing on the precursor solution to obtain a film casting solution;

[0010] (4) loading the casting solution onto a carrier, and then performing a gel bath treatment to obtain a base film;

[0011] (5) The surface of the base membrane is subjected to polyamide treatment to obtain a reverse osmosis membrane.

[0012] As a further improvement to the above-mentioned method for preparing the reverse osmosis membrane: in step (1), polyethersulfone is added when the temperature reaches 50 to 80°C, and after the addition is completed, stirring is performed for 24 to 36 hours.

[0013] As a further improvement of the above-mentioned method for preparing the reverse osmosis membrane: in step (2), the porogen is added when the mixed solution is cooled to 20-40° C., and stirred for 12-24 hours after the addition is completed.

[0014] As a further improvement of the above-mentioned method for preparing the reverse osmosis membrane: in step (2), the porogen is polyvinyl pyrrolidone-K30, and the mass ratio of N,N-dimethylacetamide, polyether sulfone and polyvinyl pyrrolidone-K30 is (75-82):(16-22):(1-3).

[0015] As a further improvement of the above-mentioned method for preparing the reverse osmosis membrane: in step (3), the precursor solution is vacuum degassed at 50° C. for 6 to 12 hours.

[0016] As a further improvement of the above-mentioned method for preparing the reverse osmosis membrane: in step (4), a non-woven fabric is used as a carrier, a casting solution at a temperature of 30 to 60° C. is loaded onto the non-woven fabric, and a gel bath treatment is performed in pure water for 2 to 150 minutes.

[0017] As a further improvement of the above-mentioned method for preparing the reverse osmosis membrane: in step (5), the polyamidation treatment is to sequentially use a m-phenylenediamine solution and a trimesoyl chloride oil phase solution to infiltrate the base membrane.

[0018] As a further improvement of the above-mentioned method for preparing a reverse osmosis membrane: in step (5),

[0019] First, the basement membrane is soaked in a m-phenylenediamine solution;

[0020] Then use a compressed air knife to blow the surface of the base film;

[0021] The basement membrane is then immersed in a trimesoyl chloride oil phase solution;

[0022] Finally, the surface of the base membrane is rinsed with deionized water to obtain a reverse osmosis membrane.

[0023] As a further improvement of the above reverse osmosis membrane preparation method: the base membrane is immersed in a 0.5-3% by mass m-phenylenediamine solution for 1-5 minutes; the base membrane is immersed in a 0.1-1% by mass trimesoyl chloride oil phase solution for 5-60 seconds.

[0024] In order to achieve the above object, the present invention secondly provides a reverse osmosis membrane, and the technical scheme is as follows:

[0025] The reverse osmosis membrane is prepared by the reverse osmosis membrane preparation method described in the first aspect above.

[0026] The method for preparing the reverse osmosis membrane and the reverse osmosis membrane of the present invention have the following advantages:

[0027] First, compared with the traditional polysulfone substrate, the polyethersulfone substrate introduced in the present invention has the following advantages: (1) Higher heat resistance: The glass transition temperature (Tg) of polyethersulfone is about 220°C, which is higher than the Tg of polysulfone (about 190°C), which means that polyethersulfone can maintain better mechanical strength and stability at high temperatures and is suitable for the preparation of reverse osmosis membranes that require higher heat resistance. (2) Better chemical stability: Polyethersulfone exhibits better chemical stability in acids, alkalis, oxidants and most organic solvents, which makes it more corrosion-resistant and durable in various chemical environments and more reliable when handling corrosive or chemically complex liquids. (3) Higher antioxidant performance: The molecular structure of polyethersulfone contains ether bonds (-O-), which gives it strong antioxidant properties and can reduce the performance degradation of membrane materials caused by oxidation during long-term use. (4) Better mechanical strength: Polyethersulfone has higher mechanical strength and toughness, can withstand greater pressure and mechanical stress, and is not easy to break or deform, which is particularly important for the use of reverse osmosis membranes in high-pressure filtration and separation processes. (5) Better hydrophilicity: The hydrophilicity of polyethersulfone is better than that of polysulfone, which makes it easier for polyethersulfone to form a uniform pore structure during membrane preparation, which helps to improve the flux and anti-pollution ability of the membrane and reduce the accumulation of pollutants on the membrane surface. (6) Higher biocompatibility: Polyethersulfone has good biocompatibility and is often used in the production of medical devices and biological products. It can reduce bacterial attachment and membrane biofouling during water treatment.

[0028] Secondly, the present invention performs polyamide treatment on the surface of the base membrane and forms a polyamide layer through interfacial polymerization reaction, which has the following advantages: (1) Improved solute retention rate: The polyamide layer has a dense molecular structure and can effectively intercept solute molecules to achieve efficient separation. (2) Resistance to chemical corrosion and pollution: The polyamide layer has excellent chemical stability and can resist corrosion from a variety of chemical substances, thereby extending the service life of the membrane. (3) Improved hydrophilicity: The polyamide layer can improve the hydrophilicity of the reverse osmosis membrane surface, which helps to reduce the adsorption of pollutants and reduce the risk of membrane pollution; and the enhanced hydrophilicity helps to improve the water / salt selectivity, thereby improving the desalination efficiency and water permeability of the membrane.

[0029] In summary, the preparation method of the reverse osmosis membrane of the present invention has a simple process and low material cost. The obtained reverse osmosis membrane has a more uniform and more penetrating pore structure, higher separation efficiency and better mechanical properties, can adapt to higher operating pressures, and can continuously and stably operate at a higher flux under high pressure. It has a wider range of application scenarios and strong practicality.

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of the present invention are used to assist in understanding the present invention. The contents provided in the drawings and their related descriptions in the present invention can be used to explain the present invention, but do not constitute improper limitations on the present invention. In the drawings:

[0032] Figure 1 This is a cross-sectional SEM photograph of the reverse osmosis membrane of Example 1 of the present invention before use.

[0033] Figure 2 This is a cross-sectional SEM photograph of the reverse osmosis membrane of Example 1 of the present invention after continuous operation at a high pressure of 120 bar for 72 hours. DETAILED DESCRIPTION

[0034] The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0035] The technical solutions and technical features provided in each part of the present invention, including the following description, may be combined with each other if there is no conflict.

[0036] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] About the terms and units in the present invention: The terms "include", "have" and any variations thereof in the description and claims of the present invention and related parts are intended to cover non-exclusive inclusions.

[0038] Example 1

[0039] The method for preparing a reverse osmosis membrane comprises the following steps:

[0040] (1) Add N,N-dimethylacetamide to a three-necked flask, place the three-necked flask in an electric heating mantle, heat and stir, and when the temperature reaches 60° C., add polyethersulfone to the N,N-dimethylacetamide. After the addition is completed, stir for 30 hours to obtain a mixed solution.

[0041] (2) When the temperature of the mixed solution is cooled to 30° C., polyvinyl pyrrolidone-K30 is continuously added. 18 hours after the addition is completed, a precursor solution is obtained; the mass ratio of N,N-dimethylacetamide, polyether sulfone and polyvinyl pyrrolidone-K30 is 75:22:3.

[0042] (3) The precursor solution was vacuum degassed at 50°C for 9 hours to obtain a casting solution.

[0043] (4) Using a scraper with a blade spacing of 150 μm and a moving speed of 10 m / min, a casting solution at a temperature of 40°C is loaded onto the nonwoven fabric, and then a gel bath treatment is performed in pure water for 10 minutes to allow N,N-dimethylacetamide and pure water to exchange and solidify into a film, thereby obtaining a base film.

[0044] (5) performing polyamide treatment on the surface of the base membrane to obtain a reverse osmosis membrane;

[0045] The polyamidation treatment is to sequentially use a m-phenylenediamine solution and a trimesoyl chloride oil phase solution to wet the base film, specifically:

[0046] First, the base film was immersed in a 1% by mass m-phenylenediamine solution for 2 minutes;

[0047] Then use a compressed air knife to blow the surface of the base film;

[0048] Then, the base film was immersed in a 0.1% by mass fraction of trimesoyl chloride oil phase solution for 15 seconds;

[0049] Finally, the surface of the base membrane is rinsed with deionized water to obtain a reverse osmosis membrane.

[0050] The reverse osmosis membrane flux was tested to be 31L / (m 2 ·h), the sodium chloride desalination rate is 99.65%.

[0051] Example 2

[0052] Compared with Example 1, the method for preparing the reverse osmosis membrane of this embodiment has the following difference: the mass ratio of N,N-dimethylacetamide, polyethersulfone and polyvinylpyrrolidone-K30 is 77:20:3.

[0053] The reverse osmosis membrane flux was tested to be 32L / (m 2 ·h), the sodium chloride desalination rate is 99.78%.

[0054] Example 3

[0055] Compared with Example 1, the method for preparing the reverse osmosis membrane of this embodiment has the following difference: the mass ratio of N,N-dimethylacetamide, polyethersulfone and polyvinylpyrrolidone-K30 is 80:18:2.

[0056] The reverse osmosis membrane flux was tested to be 28L / (m 2 ·h), the sodium chloride desalination rate is 99.65%.

[0057] Example 4

[0058] Compared with Example 1, the method for preparing the reverse osmosis membrane of this embodiment has the following difference: the mass ratio of N,N-dimethylacetamide, polyethersulfone and polyvinylpyrrolidone-K30 is 80:19:1.

[0059] The reverse osmosis membrane flux was tested to be 26L / (m 2 ·h), the sodium chloride desalination rate is 99.70%.

[0060] Example 5

[0061] Compared with Example 1, the method for preparing the reverse osmosis membrane of this embodiment has the following difference: the mass ratio of N,N-dimethylacetamide, polyethersulfone and polyvinylpyrrolidone-K30 is 82:16:2.

[0062] The reverse osmosis membrane flux was tested to be 29L / (m 2 ·h), the sodium chloride desalination rate is 99.65%.

[0063] Comparative Example 1

[0064] Compared with Example 1, the preparation method of the reverse osmosis membrane of this comparative example has the following difference: the mass ratio of N,N-dimethylacetamide, polyethersulfone and polyvinylpyrrolidone-K30 is 73:22:3.

[0065] The reverse osmosis membrane flux was tested to be 28L / (m 2 ·h), the sodium chloride desalination rate is 99.69%.

[0066] Comparative Example 2

[0067] Compared with Example 5, the preparation method of the reverse osmosis membrane of this comparative example has the following difference: the mass ratio of N,N-dimethylacetamide, polyethersulfone and polyvinylpyrrolidone-K30 is 84:16:2.

[0068] The reverse osmosis membrane flux was tested to be 29L / (m 2 ·h), the sodium chloride desalination rate is 99.54%.

[0069] Example 6

[0070] Compared with Example 1, the preparation method of the reverse osmosis membrane of this embodiment has the following differences: the mass fraction of the m-phenylenediamine solution is 0.5%, and the mass fraction of the trimesoyl chloride oil phase solution is 0.1%.

[0071] The reverse osmosis membrane flux was tested to be 28L / (m 2 ·h), the sodium chloride desalination rate is 99.71%.

[0072] Example 7

[0073] Compared with Example 1, the preparation method of the reverse osmosis membrane of this embodiment has the following differences: the mass fraction of the m-phenylenediamine solution is 3%, and the mass fraction of the trimesoyl chloride oil phase solution is 0.1%.

[0074] The reverse osmosis membrane flux was tested to be 32L / (m 2 ·h), the sodium chloride desalination rate is 99.56%.

[0075] Example 8

[0076] Compared with Example 1, the preparation method of the reverse osmosis membrane of this embodiment has the following differences: the mass fraction of the m-phenylenediamine solution is 1%, and the mass fraction of the trimesoyl chloride oil phase solution is 0.5%.

[0077] The reverse osmosis membrane flux was tested to be 33L / (m 2 ·h), the sodium chloride desalination rate is 99.62%.

[0078] Example 9

[0079] Compared with Example 1, the preparation method of the reverse osmosis membrane of this embodiment has the following differences: the mass fraction of the m-phenylenediamine solution is 1%, and the mass fraction of the trimesoyl chloride oil phase solution is 1%.

[0080] The reverse osmosis membrane flux was tested to be 34L / (m 2 ·h), the sodium chloride desalination rate is 99.45%.

[0081] Comparative Example 3

[0082] Compared with Example 1, the preparation method of the reverse osmosis membrane of this comparative example has the following difference: the mass fraction of the trimesoyl chloride oil phase solution is 0.06%.

[0083] The test results show that the reverse osmosis membrane flux is 25L / (m 2 ·h), the sodium chloride desalination rate is 99.78%.

[0084] Comparative Example 4

[0085] Compared with Example 7, the preparation method of the reverse osmosis membrane of this comparative example has the following difference: the mass fraction of the m-phenylenediamine solution is 3.2%.

[0086] The reverse osmosis membrane flux was tested to be 29L / (m 2 ·h), the sodium chloride desalination rate is 99.63%.

[0087] Comparative Example 5

[0088] Compared with Example 1, the preparation method of the reverse osmosis membrane of this comparative example is different in that polysulfone is used instead of polyethersulfone.

[0089] The flux of the reverse osmosis membrane of comparative example 5 is only 19L / (m 2 ·h), and after 72 hours of continuous operation at 120 bar high pressure, the flux dropped to 12 L / (m 2 ·h). The initial flux of the reverse osmosis membrane of Example 1 of the present invention is 31L / (m 2 ·h), the flux is still as high as 28L / (m 2 h), indicating that the reverse osmosis membrane of Example 1 has more through-hole structures, so that the membrane material can still maintain a high flux after long-term use under high pressure.

[0090] Figure 1 This is a cross-sectional SEM photograph of the reverse osmosis membrane of Example 1 of the present invention before use. Figure 2 This is a cross-sectional SEM photograph of the reverse osmosis membrane of Example 1 of the present invention after continuous operation at a high pressure of 120 bar for 72 hours.

[0091] from Figure 1 It can be seen that the pores of the reverse osmosis membrane are very developed and uniform, and have a large number of through-hole structures. Figure 1 and Figure 2 It can be seen that after continuous operation at 120 bar high pressure for 72 hours in the disc-tube reverse osmosis equipment, the reverse osmosis membrane shrinks less.

[0092] The flux (pure water) and sodium chloride rejection rate of the reverse osmosis membrane in the above embodiment and the control example were tested according to the "Reverse Osmosis Membrane Test Method" (GB / T 32373-2015), as follows:

[0093] 1. Take several (not less than 4) samples. The samples should be free of obvious defects such as wrinkles and damages. The size of the samples should meet the requirements of the sealing ring that completely covers the evaluation pool. The effective membrane area of ​​the samples in the evaluation pool should not be less than 2.5×10 -3 m 2 ; Prepare sodium chloride solution and adjust the pH to 7.5±0.5.

[0094] 2. Soak the sample in deionized water or distilled water for 30 minutes;

[0095] 3. Sodium chloride desalination rate test: Load the sample into the evaluation tank, start the booster pump, and adjust the operating pressure to 800psi; after stable operation at constant pressure for 30 minutes, use a measuring cylinder to collect a certain amount of stock solution (sodium chloride solution, no less than 30 ml for a single sample) passing through the sample to produce the permeate, use a stopwatch to calculate the required time, and determine the total dissolved solids (TDS) content of the stock solution and the permeate respectively in accordance with the provisions of GB / T 5750.4.

[0096] Flux test: Take another sample and put it into the evaluation tank, turn on the water supply pump, slowly adjust the operating pressure to 800psi for cross-flow filtration, maintain the temperature at 25℃±0.5℃, and after stable operation for 30 minutes, use a measuring cup to collect the water produced after passing through the sample (a single sample is not less than 30 ml), and use a stopwatch to calculate the time required.

[0097] 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.

[0098] The flux was calculated using the following formula:

[0099]

[0100] Where J is the flux, the unit is L / (m 2 ﹒ h); V is the sampling volume of the measuring cylinder, in L; T is the sampling time, in h; A is the effective area of ​​the sample, in m 2 .

[0101] The sodium chloride rejection rate was calculated using the following formula:

[0102]

[0103] Where, R is the sodium chloride desalination rate, in %; C P is the TDS of the permeate, in mg / L; C f It is the TDS of the original solution, in mg / L.

[0104] The above is a description of the relevant contents of the present invention. A person skilled in the art will be able to implement the present invention based on these descriptions. Based on the above contents of the present invention, all other embodiments obtained by a person skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a reverse osmosis membrane, characterized in that: The following steps are involved: (1) adding polyethersulfone to N,N-dimethylacetamide under heating and stirring, stirring for a period of time after the addition is completed to obtain a mixed solution; (2) After the mixed solution is cooled, the porogen is continuously added, and after the addition is completed, the mixture is stirred for a period of time to obtain a precursor solution; (3) performing vacuum degassing on the precursor solution to obtain a film casting solution; (4) loading the casting solution onto a carrier, and then performing a gel bath treatment to obtain a base film; (5) The surface of the base membrane is subjected to polyamide treatment to obtain a reverse osmosis membrane.

2. The method for preparing a reverse osmosis membrane according to claim 1, wherein: In step (1), polyethersulfone is added when the temperature reaches 50 to 80°C, and stirred for 24 to 36 hours after the addition is completed.

3. The method for preparing a reverse osmosis membrane according to claim 1, wherein: In step (2), the mixed solution is cooled to 20-40° C. before adding the porogen, and the mixture is stirred for 12-24 hours after the addition is completed.

4. The method for preparing a reverse osmosis membrane according to claim 1, wherein: In step (2), the porogen is polyvinyl pyrrolidone-K30, and the mass ratio of N,N-dimethylacetamide, polyether sulfone and polyvinyl pyrrolidone-K30 is (75-82):(16-22):(1-3).

5. The method for preparing a reverse osmosis membrane according to claim 1, wherein: In step (3), the precursor solution is vacuum degassed at 50° C. for 6 to 12 hours.

6. The method for preparing a reverse osmosis membrane according to claim 1, wherein: In step (4), a non-woven fabric is used as a carrier, a casting solution at a temperature of 30 to 60° C. is loaded onto the non-woven fabric, and a gel bath treatment is performed in pure water for 2 to 150 minutes.

7. The method for preparing a reverse osmosis membrane according to claim 1, wherein: In step (5), the polyamidation treatment is to sequentially use a m-phenylenediamine solution and a trimesoyl chloride oil phase solution to infiltrate the base film.

8. The method for preparing a reverse osmosis membrane according to claim 7, wherein: In step (5), First, the basement membrane is soaked in a m-phenylenediamine solution; Then use a compressed air knife to blow the surface of the base film; The basement membrane is then immersed in a trimesoyl chloride oil phase solution; Finally, the surface of the base membrane is rinsed with deionized water to obtain a reverse osmosis membrane.

9. The method for preparing a reverse osmosis membrane according to claim 8, wherein: The base film is immersed in a m-phenylenediamine solution with a mass fraction of 0.5-3% for 1-5 minutes; and the base film is immersed in a trimesoyl chloride oil phase solution with a mass fraction of 0.1-1% for 5-60 seconds.

10. A reverse osmosis membrane, characterized in that: The reverse osmosis membrane is prepared by the method for preparing the reverse osmosis membrane according to any one of claims 1 to 9.

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