High-performance polyamide composite reverse osmosis membrane and preparation method thereof

Abstract

The invention belongs to the technical field of reverse osmosis membranes, and discloses a high-performance polyamide composite reverse osmosis membrane and a preparation method thereof.The preparation method specifically comprises the following steps that 1, a nascent state polyamide reverse osmosis membrane is prepared on a supporting base membrane through an interfacial polymerization reaction; and 2, immersing the nascent state polyamide reverse osmosis membrane prepared in the step 1 into a post-treatment solution containing an acylation catalyst and polyether amine for treatment, and rinsing with water to obtain the polyamide reverse osmosis membrane. According to the preparation method of the reverse osmosis membrane provided by the invention, the flux of the reverse osmosis membrane can be remarkably improved on the premise of keeping a relatively high desalting rate, the flux stability is remarkably improved within a relatively long operation time, and the reverse osmosis membrane can be widely applied to the fields of ultra-low pressure, household water purification and the like.

Description

Technical Field

[0001] This invention relates to the technical field of reverse osmosis membranes, and specifically to a high-performance polyamide composite reverse osmosis membrane and its preparation method. Background Technology

[0002] Reverse osmosis membranes can be used for various fluid separations. Currently, the most widely used aromatic polyamide reverse osmosis membrane is prepared by interfacial polymerization of m-phenylenediamine and trimesoyl chloride. The resulting polyamide layer is crucial influencing water permeability and salt rejection. With the rapid development of reverse osmosis membrane technology and the widespread use of membrane elements, the development and preparation of high-flux reverse osmosis membranes has gradually become a research focus. High flux means lower energy consumption for processing the same volume of liquid, effectively saving investment and equipment operating costs, and improving treatment efficiency. Numerous patents and documents have been published introducing high-flux reverse osmosis membranes; examples are given below.

[0003] Patent CN111545065A discloses a method for preparing a high-flux, high-desalination reverse osmosis membrane. The method involves activating an interfacial polymerized reverse osmosis membrane with an organic solvent and then immersing it in nitrous acid to obtain a reverse osmosis membrane with good flux and desalination rate. This post-treatment method improves permeability by swelling polyamide with an organic solvent, altering the polyamide structure, and synergistically using a nitration process to increase the degree of polyamide crosslinking, thereby improving the desalination rate. In a specific embodiment, a polyolefin composite membrane is treated with a 1:4 volume ratio dimethylformamide / isopropanol mixed solvent, combined with nitration. This increases the flux from 27.9 GFD to 59.8 GFD, and the corresponding desalination rate from 99.01% to 99.26%. The flux is significantly improved without sacrificing the desalination rate. However, this method requires the use of a polar solvent, which presents numerous problems such as operational difficulties and significant safety risks during production.

[0004] Patent CN115055064A discloses a method for preparing a high-performance polyamide composite reverse osmosis membrane. This invention involves adding pure water dropwise to a pyromellitic chloride liquid, causing one or more -COCl groups of the pyromellitic chloride to hydrolyze into -COOH groups. This creates voids in the polyamide layer structure during the polymerization reaction, increasing flux. The -COOH groups introduced onto the polyamide surface also increase the charge repulsion of the polyamide layer, thereby improving the desalination rate of the reverse osmosis membrane. In a specific embodiment, this membrane preparation method can increase the flux from 19 GFD to 24.3 GFD, corresponding to a desalination rate increase from 98.3% to 98.6%. While this method is simple to operate, it cannot confirm the degree of hydrolysis of a single acyl chloride monomer, and therefore cannot ensure the repeatability and stability of the production process.

[0005] Patent CN118649565B discloses a method for preparing a high-pressure reverse osmosis membrane. This invention patent improves the permeation performance by precisely constructing a polyamide network structure by adding ε-caprolactam to an aqueous solution. In a specific embodiment, this membrane preparation method can increase the flux from 45.17 LMH to 60 LMH, with a slight loss in desalination rate.

[0006] It can be seen that although some methods for improving the flux and desalination rate of reverse osmosis membranes have been developed in the existing technology, these solutions only mention the initial performance improvement and do not mention the flux stability after the improvement over a long operating period. Therefore, this invention conducts research on this issue. Summary of the Invention

[0007] The purpose of this invention is to provide a high-performance polyamide reverse osmosis membrane and its preparation method, wherein the obtained polyamide reverse osmosis membrane can improve performance and maintain good flux stability.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a high-performance polyamide composite reverse osmosis membrane specifically includes the following steps:

[0010] Step 1: Prepare a nascent polyamide reverse osmosis membrane on a supporting substrate membrane via interfacial polymerization.

[0011] Step 2: Immerse the nascent polyamide reverse osmosis membrane prepared in Step 1 into a post-treatment solution containing an acylation catalyst and polyetheramine. After treatment, rinse with water to obtain the polyamide reverse osmosis membrane.

[0012] In a preferred embodiment of the present invention, in step one, the nascent polyamide reverse osmosis membrane is prepared by forming a polyamide layer on a supporting base membrane through an interfacial polymerization reaction of polyamines and polyacrylamide chlorides.

[0013] Specifically, the supporting base film includes at least one of polysulfone, polyethersulfone, polyaryl ether, polyvinylidene fluoride, polytetrafluoroethylene and polyaryl ether ketone, preferably a polysulfone supporting base film.

[0014] As a specific method for interfacial polymerization, any known operating procedure can be adopted. For example, the supporting substrate film can be first brought into contact with an aqueous phase containing polyamines and kept for a certain period of time to remove the residual aqueous phase on the surface. Then, it can be brought into contact with an organic phase containing polyacrylamide chlorides to carry out an interfacial polymerization reaction to obtain a polyamide layer. The specific conditions for the interfacial polymerization reaction can be referred to in the prior art such as CN114053876B and CN119015899B. This invention does not impose any special limitations on these conditions.

[0015] As a preferred embodiment of the present invention, after the polymerization reaction yields the polyamide layer, the nascent polyamide reverse osmosis membrane is dried, such as at 60-90°C.

[0016] In a preferred embodiment of the present invention, in step two, the acylation catalyst refers to a catalyst that promotes the hydrolysis reaction of acyl chloride and increases the amount of carboxyl group generated, including but not limited to one or more of δ-valeramide, ε-caprolactam, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolium ketone, and N,N-dimethylpropenylurea.

[0017] In a preferred embodiment of the present invention, in step two, the functionality of the polyetheramine can be selected from at least one of monoamine, diamine, and triamine; the number average molecular weight range is preferably 100 to 2000.

[0018] Preferably, the post-treatment solution is an aqueous solution, wherein the mass concentration of the acylation catalyst is 10-30%, the mass concentration of the polyetheramine is 0.01-0.5%, the post-treatment temperature is 60-90°C, and the post-treatment time is 1-5 minutes.

[0019] As a preferred embodiment of the present invention, the polyamide reverse osmosis membrane after post-treatment is rinsed with water to obtain the polyamide reverse osmosis membrane. Specifically, the rinsing temperature is 70-90°C and the treatment time is 1-3 minutes.

[0020] This invention employs an acylation catalyst and polyetheramine to treat nascent polyamide reverse osmosis membranes. The working principles of the acylation catalyst and polyetheramine during the treatment process are as follows: First, the acylation catalyst, acting as a nucleophilic catalyst, reacts with residual acyl chlorides on the membrane surface, promoting acyl chloride hydrolysis to generate more carboxyl-rich polyamide segments, improving membrane hydrophilicity and increasing membrane flux. Simultaneously, the polyetheramine also reacts with residual acyl chlorides, grafting the polyetheramine onto the polyamide segments, providing skeletal support and improving segment stability to maintain flux stability. Furthermore, the polyetheramine grafted onto the polyamide segments exhibits a certain steric hindrance effect, which to some extent improves the membrane's desalination rate.

[0021] The reverse osmosis membrane preparation method provided by this invention is simple and easy to implement, and easy to scale up. Moreover, the polyamide reverse osmosis membrane prepared by this method can significantly improve water flux and flux stability while maintaining a high desalination rate. Detailed Implementation

[0022] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0023] Unless otherwise specified, the raw materials used in the following examples or comparative examples are all commercially available conventional raw materials. The main raw material information is shown in Table 1 below.

[0024] Table 1. Information on Main Raw Materials

[0025]

[0026]

[0027] The following describes the methods used or that may be used in the embodiments or comparative examples of the present invention:

[0028] 1. Evaluation of desalination rate and permeability flux

[0029] Desalination rate and permeate flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. This invention evaluates the separation performance of reverse osmosis membranes according to GB / T32373-2015 "Test Methods for Reverse Osmosis Membranes".

[0030] Desalination rate (R) is defined as: under certain operating conditions, the salt concentration (C) of the feed solution... f ) and the salt concentration in the permeate (C p The difference between the two is then divided by the feed solution salt concentration (C). f ), as in formula (1).

[0031]

[0032] Permeation flux is defined as the volume of water that permeates through a unit membrane area per unit time under certain operating conditions, and its unit is L·m. -2 ·h -1 .

[0033] The operating conditions used for the reverse osmosis membrane performance determination in this invention are as follows: the feed solution is a 500 ppm sodium chloride aqueous solution, the solution pH is 7.5 ± 0.5, the operating pressure is 75 psi, and the operating temperature is 25 ± 1℃.

[0034] 2. Changes in permeation flux after 72 hours of continuous operation

[0035] The structural stability of the membrane is characterized by testing the rate of change in membrane flux both initially and after 72 hours of continuous operation. The main steps are as follows: First, the initial flux of the membrane is evaluated according to GB / T32373-2015 "Test Methods for Reverse Osmosis Membranes". The initial flux is denoted as J0. The test conditions are kept constant, and the membrane is run continuously for 72 hours. The membrane flux is then measured after 72 hours and denoted as J. t The formula for the rate of change of flux is as follows:

[0036] Flux change rate = 100% × (J) t / J0-1)

[0037] Example 1

[0038] The preparation process of nascent polyamide reverse osmosis membranes via interfacial polymerization is as follows:

[0039] An aqueous solution containing 2.0% m-phenylenediamine and 2% triethylamine was prepared. The polysulfone membrane was immersed in the aqueous solution for 30 seconds. Then, it was removed and the excess aqueous phase on the surface was gently squeezed with a pressure roller. After that, the front side of the polysulfone membrane that had been in contact with the aqueous phase was brought into contact with a 0.12% pyromellitic acid chloride solution at 25°C for 30 seconds. The excess decane solution was poured off, and the membrane was evenly swept with an air knife until there was no residual solvent on the membrane surface. The membrane was then placed in a 90°C oven and dried for 3 minutes to prepare a nascent reverse osmosis membrane.

[0040] Post-processing is as follows:

[0041] The nascent polyamide reverse osmosis membrane was immersed in a solution containing an acylation catalyst and polyetheramine for treatment. The post-treatment solution consisted of 10% (w / w) ε-caprolactam and 0.05% (w / w) polyetheramine. The polyamide reverse osmosis membrane was treated with an aqueous solution of M-2070 at a temperature of 80°C for 1 minute. Then, the treated polyamide reverse osmosis membrane was immersed in a pure water washing tank at 80°C for 2 minutes. The rinsed reverse osmosis membrane is the prepared high-performance polyamide composite reverse osmosis membrane.

[0042] Example 2

[0043] Nascent polyamide reverse osmosis membranes were prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution and the pure water rinsing process. The post-treatment solution consisted of 30% ε-caprolactam and 0.5% polyetheramine. The M-600 aqueous solution was treated at a temperature of 75℃ for 3 minutes, and then rinsed with pure water at a temperature of 85℃ for 2 minutes. The resulting reverse osmosis membrane was the high-performance polyamide composite reverse osmosis membrane.

[0044] Example 3

[0045] Nascent polyamide reverse osmosis membranes were prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution and the pure water rinsing process. The post-treatment solution consisted of 20% δ-valeramide and 0.1% polyetheramine. The D-2000 aqueous solution was treated at a temperature of 90°C for 1 minute. The treated polyamide reverse osmosis membrane was then immersed in a pure water washing tank at 70°C for 3 minutes. The rinsed reverse osmosis membrane is the prepared high-performance polyamide composite reverse osmosis membrane.

[0046] Example 4

[0047] Nascent polyamide reverse osmosis membranes were prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution and the pure water rinsing process. The post-treatment solution consisted of 25% N-methylpyrrolidone and 0.4% polyetheramine. The D-400 aqueous solution was treated at a temperature of 75°C for 4 minutes. The treated polyamide reverse osmosis membrane was then immersed in a pure water washing tank at 80°C for 2 minutes. The rinsed reverse osmosis membrane is the prepared high-performance polyamide composite reverse osmosis membrane.

[0048] Example 5

[0049] Nascent polyamide reverse osmosis membranes were prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution and the pure water rinsing process. The post-treatment solution consisted of 15% (w / w) 1,3-dimethyl-2-imidazolium ketone and 0.01% (w / w) polyetheramine. The T-403 aqueous solution was treated at a temperature of 60°C for 5 minutes. The treated polyamide reverse osmosis membrane was then immersed in a 90°C pure water washing tank for 1 minute. The rinsed reverse osmosis membrane is the prepared high-performance polyamide composite reverse osmosis membrane.

[0050] Example 6

[0051] Nascent polyamide reverse osmosis membranes were prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution and the pure water rinsing process. The post-treatment solution consisted of 30% N,N-dimethylpropylene urea and 0.3% polyetheramine. The ED-2003 aqueous solution was treated at a temperature of 90°C for 2 minutes. The treated polyamide reverse osmosis membrane was then immersed in a pure water washing tank at 70°C for 2 minutes. The rinsed reverse osmosis membrane is the prepared high-performance polyamide composite reverse osmosis membrane.

[0052] Example 7

[0053] Nascent polyamide reverse osmosis membranes were prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution and the pure water rinsing process. The post-treatment solution consisted of 20% N-methylpyrrolidone and 0.2% polyetheramine. An aqueous solution of ED-600 was used for treatment at 85°C for 1 minute. The treated polyamide reverse osmosis membrane was then immersed in a pure water washing tank at 80°C for 1 minute. The rinsed reverse osmosis membrane is the prepared high-performance polyamide composite reverse osmosis membrane.

[0054] Comparative Example 1

[0055] The nascent polyamide reverse osmosis membrane was prepared using the same interfacial polymerization method as in Example 1. The difference was in the composition of the post-treatment solution, which was only a 10% (w / w) ε-caprolactam aqueous solution. The subsequent rinsing process was the same as in Example 1.

[0056] Comparative Example 2

[0057] A nascent polyamide reverse osmosis membrane was prepared using the same interfacial polymerization method as in Example 1, the difference being the composition of the post-treatment solution, which consisted only of 0.05% polyetheramine by mass. The aqueous solution of M-2070 was followed by the same rinsing process as in Example 1.

[0058] Comparative Example 3

[0059] The nascent polyamide reverse osmosis membrane was prepared using the same interfacial polymerization method as in Example 1. The difference was in the composition of the post-treatment solution, which contained no acylation catalyst or polyetheramine and was treated with pure water. The subsequent rinsing process was the same as in Example 1.

[0060] Comparative Example 4

[0061] The nascent polyamide reverse osmosis membrane was prepared using the same interfacial polymerization method as in Example 1. The difference was in the composition of the post-treatment solution, which consisted of only 10% citric acid aqueous solution. The treatment temperature was 80°C and the treatment time was 1 minute. The subsequent rinsing process was the same as in Example 1.

[0062] Comparative Example 5

[0063] A nascent polyamide reverse osmosis membrane was prepared using the same interfacial polymerization method as in Example 1, except that a solution of 2.0% m-phenylenediamine, 2% triethylamine, and 1% ε-caprolactam was used instead of the aqueous phase solution in Example 1, and the post-treatment solution was only 0.05% polyetheramine. The aqueous solution of M-2070 was used, and the subsequent rinsing process was the same as in Example 1. Basic performance and continuous operation for 72 hours were tested on the examples and comparative examples, and the flux change rate was calculated. The performance is summarized in Table 2 below.

[0064] Table 2. Test Results of Examples and Comparative Examples

[0065]

[0066] As shown in Table 2, the high-performance polyamide composite reverse osmosis membrane prepared by this invention, through the use of an acylation catalyst and polyetheramine to treat the nascent polyamide membrane and optimizing the post-treatment process, combined with subsequent pure water rinsing, exhibits improved flux and desalination rate compared to the method using pure water rinsing (Comparative Example 3). If only the acylation catalyst (Comparative Example 1) or polyetheramine (Comparative Example 2) is used, only a single performance improvement in flux and desalination rate can be achieved. Furthermore, compared to the traditional acid washing process, the post-treatment process of this invention is superior in performance. Regarding flux stability, the embodiments of this invention show significantly improved flux stability compared to the comparative examples, demonstrating greater advantages in practical applications.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high performance polyamide composite reverse osmosis membrane, characterized in that, The method comprises the following steps: treating the nascent polyamide reverse osmosis membrane by immersing it in a post-treatment solution containing an acylation catalyst and a polyetheramine, and then rinsing it with water to obtain the polyamide reverse osmosis membrane. The nascent polyamide reverse osmosis membrane is prepared by forming a polyamide layer on a support base film through interfacial polymerization of a polyamine and a polyacyl chloride.

2. The production method according to claim 1, characterized by, The acylation catalyst comprises one or more of δ-valerolactam, ε-caprolactam, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, and N,N-dimethylacryl urea. The functionality of the polyetheramine comprises at least one of monoamine, diamine, and triamine, preferably having a number average molecular weight ranging from 100 to 2000.

3. The production method according to claim 1 or 2, characterized by, The post-treatment solution is an aqueous solution, wherein the mass concentration of the acylation catalyst is 10-30%, and the mass concentration of the polyetheramine is 0.01-0.5%.

4. The production method according to any one of claims 1 to 3, characterized by, The post-treatment temperature is 60-90°C, and the treatment time is 1-5 minutes.

5. The preparation method according to claim 1, characterized in that, The water rinsing temperature is 70-90°C, and the treatment time is 1-3 minutes.

6. A high-performance polyamide composite reverse osmosis membrane prepared by the method according to any one of claims 1-5.

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