Preparation method of polyamide membrane for separating dye and inorganic salt

Abstract

The invention relates to a preparation method of a polyamide membrane for separating dye and inorganic salt, which comprises the following steps of: soaking a polyamide membrane support layer by using an aqueous phase solution and an oil phase solution in sequence to generate a polyamide active layer on the surface of the polyamide membrane support layer, and finally heating and cross-linking to obtain the polyamide membrane, the aqueous phase solution is a solution obtained by dissolving 2, 4, 6-triaminopyrimidine in an alkaline solution, and the oil phase solution is a solution obtained by dissolving 2, 4, 6-triaminopyrimidine in an alkaline solution. The polyamide membrane prepared by the method is high in flux, can realize good separation of dye and salt, has good chlorine resistance and organic pollution resistance, is good in repeatability, enables polyamide membrane formation to be more stable, and can be produced on a large scale.

Description

Technical Field

[0001] The invention relates to the technical field of separation of printing and dyeing wastewater, in particular to a method for preparing a polyamide membrane for separating dyes and inorganic salts. Background Art

[0002] There is printing and dyeing wastewater with high salt concentration in the dye industry production process. If it is directly discharged, it will seriously pollute the environment. The separation of dyes and salts in dye wastewater can not only realize the recycling of high value-added organic matter in dye wastewater, but also reduce the environmental pollution caused by wastewater discharge. Membrane separation technology has become one of the most promising technologies for printing and dyeing wastewater treatment, industrial product purification, etc. due to its high separation efficiency, low energy consumption, and environmental friendliness. However, the traditional polyamide nanofiltration membrane has a high retention rate for inorganic salts, a small flux during use, and requires high pressure to promote filtration, which leads to greater energy consumption and difficulty in achieving effective separation of dyes and inorganic salts in dye wastewater. How to achieve high flux, anti-oxidation, and selective separation of salts and dyes has always been a problem faced by researchers in this field.

[0003] In view of the above problems, Chinese patent CN111921378B discloses a polyamide membrane that can be used for dye and salt separation and its preparation method, wherein hydrolyzed polyacrylonitrile is used as a support layer, 3,5-diamino-1,2,4-triazole is used as an aqueous phase solution, and reacted with an oil phase monomer 1,3,5-triphenylamine chloride, and after sufficient reaction, a heat treatment is performed to obtain a polyamide membrane with high flux and good separation of dye and salt. However, the aqueous phase solution in the method is 3,5-diamino-1,2,4-triazole, and the polyamide membrane prepared using the aqueous phase solution has poor repeatability. Summary of the invention

[0004] The present invention aims to provide a method for preparing a polyamide membrane for separating dyes and inorganic salts, which can form a polyamide membrane with high flux and good separation effect, good repeatability and high film-forming stability.

[0005] In order to achieve the above-mentioned purpose, the specific scheme adopted by the present invention is: a method for preparing a polyamide membrane for separating dyes and inorganic salts, wherein a polyamide membrane support layer is soaked in an aqueous solution and an oil phase solution in sequence to generate a polyamide active layer on its surface, and finally a polyamide membrane is obtained by heating and cross-linking, wherein the aqueous phase solution is a solution obtained by dissolving 2,4,6-triaminopyrimidine in an alkaline solution.

[0006] As an optimization scheme of the above-mentioned polyamide membrane preparation method for separating dyes and inorganic salts: the polyacrylonitrile ultrafiltration membrane is immersed in a sodium dodecylbenzene sulfonate solution for 24 hours to obtain a treated polyacrylonitrile ultrafiltration membrane, which is used as a polyamide membrane support layer.

[0007] As another optimization scheme of the above-mentioned method for preparing a polyamide membrane for separating dyes and inorganic salts: the mass fraction of sodium dodecylbenzene sulfonate in the sodium dodecylbenzene sulfonate solution is 0.1-0.3%.

[0008] As another optimization scheme of the above-mentioned method for preparing a polyamide membrane for separating dyes and inorganic salts: the mass fraction of 2,4,6-triaminopyrimidine in the aqueous phase solution is 0.1-1wt%.

[0009] As another optimized solution of the above-mentioned method for preparing a polyamide membrane for separating dyes and inorganic salts: the oil phase solution is a solution obtained by dissolving 1,3,5-benzenetricarboxylic acid chloride in n-hexane solvent.

[0010] As another optimization scheme of the above-mentioned method for preparing a polyamide membrane for separating dyes and inorganic salts: the mass fraction of 1,3,5-trimethylbenzenecarboxylic acid chloride in the oil phase solution is 0.1-0.3wt%.

[0011] As another optimization scheme of the above-mentioned method for preparing a polyamide membrane for separating dyes and inorganic salts: the alkaline solution is an aqueous solution of Na2CO3, and its concentration is 0.01-0.03wt%.

[0012] As another optimization scheme of the above-mentioned polyamide membrane preparation method for separating dyes and inorganic salts: the polyamide membrane support layer is soaked in an aqueous solution for 1-15 minutes and dried at room temperature; then the polyamide membrane is soaked in an oil solution for 1-15 minutes.

[0013] As another optimization scheme of the above-mentioned method for preparing a polyamide membrane for separating dyes and inorganic salts: the heating cross-linking temperature is 60-80° C. and the time is 15 minutes.

[0014] A polyamide membrane for separating dyes and inorganic salts is obtained by adopting the preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention provides a method for preparing a polyamide membrane for separating dyes and inorganic salts. First, a polyamide membrane support layer is soaked in a 2,4,6-triaminopyrimidine aqueous solution, and then, an oil phase solution is soaked in the polyamide membrane support layer to generate a polyamide active layer on its surface. Finally, the polyamide membrane is obtained by heating and cross-linking. The polyamide membrane prepared by the method not only has a high flux and can achieve good separation of dyes and salts, but also has good chlorine resistance. At the same time, the polyamide membrane has good repeatability, so that the polyamide membrane formation is more stable and can be mass-produced.

[0017] 2. In the present invention, 2,4,6-triaminopyrimidine aqueous phase monomer and oil phase solution are used to directly form a polyamide membrane. In the prior art, 2,4,6-triaminopyrimidine is also used as an aqueous phase solution to prepare a polyamide membrane. However, 2,4,6-triaminopyrimidine needs to be mixed with m-phenylenediamine to regulate the degree of crosslinking of the polyamide functional layer. In the present invention, 2,4,6-triaminopyrimidine alone reacts with the acyl chloride group in 1,3,5-triphenylene carboxylic acid chloride to form a polyamide membrane with good repeatability, greater stability, and excellent anti-pollution performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the pure water flux and dye rejection of the polyamide membrane prepared in Examples 1-5;

[0019] Figure 2 is the salt rejection of the polyamide membrane prepared in Examples 1-5;

[0020] Figure 3 is the flux and dye retention rate of the polyamide membrane prepared in Example 3 after being soaked in NaClO;

[0021] Figure 4 is the normalized flux of the polyamide membrane prepared in Example 3 after being contaminated with bovine serum albumin;

[0022] Figure 5 This is a surface SEM image of the polyamide membrane prepared in Example 3. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts of the present invention that are not described and disclosed in detail in the following embodiments should be understood as existing technologies known or should be known to those skilled in the art, such as the structure of metal containers.

[0024] A method for preparing a polyamide membrane for separating dyes and inorganic salts comprises soaking a polyamide membrane support layer with an aqueous solution and an oily solution in sequence to form a polyamide active layer on its surface, and finally heating and cross-linking to obtain a polyamide membrane, wherein the aqueous solution is a solution obtained by dissolving 2,4,6-triaminopyrimidine in an alkaline solution. Specifically, the method comprises the following steps:

[0025] Preparation of a polyamide membrane support layer: soaking a polyacrylonitrile ultrafiltration membrane in a sodium dodecylbenzene sulfonate solution for 24 hours to obtain a treated polyacrylonitrile ultrafiltration membrane, which is used as a polyamide membrane support layer, wherein the mass fraction of sodium dodecylbenzene sulfonate in the sodium dodecylbenzene sulfonate solution is 0.1-0.3%. Soaking the polyacrylonitrile ultrafiltration membrane in the sodium dodecylbenzene sulfonate solution can remove oil stains on its surface and improve its surface hydrophilicity.

[0026] Prepare an aqueous phase solution: dissolve 2,4,6-triaminopyrimidine in an alkaline solution to obtain an aqueous phase solution, wherein the mass fraction of 2,4,6-triaminopyrimidine in the aqueous phase solution is 0.1-1%, and the alkaline solution is a Na2CO3 aqueous solution with a concentration of 0.01-0.03wt%. The Na2CO3 aqueous solution is introduced into the aqueous phase solution to promote the interfacial polymerization reaction between 2,4,6-triaminopyrimidine and the oil phase, so that the two eventually form a loose polyamide membrane, thereby improving the flux of the polyamide membrane;

[0027] Prepare an oil phase solution: dissolve 1,3,5-trimethylbenzene carboxylic acid chloride in n-hexane solvent to obtain an oil phase solution, wherein the mass fraction of 1,3,5-trimethylbenzene carboxylic acid chloride in the oil phase solution is 0.1-0.3wt%;

[0028] The prepared polyamide membrane support layer is fixed in a metal container, and the surface of the polyamide membrane support layer is blown dry, and the aqueous phase solution prepared above is introduced into the metal container, and the aqueous phase solution covers the polyamide membrane support layer, and after standing at room temperature for 1-15 minutes, the aqueous phase solution in the metal container is poured out, and the soaked polyamide membrane support layer is naturally dried in the shade;

[0029] Slowly pour the oil phase solution prepared in the above step into a metal container, and the oil phase solution covers the polyamide membrane support layer soaked in the water phase solution, soak at room temperature for 1-15 minutes to form a polyamide active layer on the surface of the polyamide membrane support layer, pour out the oil phase solution in the metal container, and rinse with n-hexane solution to remove the unreacted oil phase solution on the surface;

[0030] The polyamide film is obtained by heating and cross-linking, and the heating and cross-linking temperature is 60-80° C. and the time is 15 minutes.

[0031] The polyamide membrane prepared by this method not only has a high flux and can achieve good separation of dyes and salts, but also has good repeatability, making the polyamide membrane formation more stable and capable of large-scale production.

[0032] Example 1

[0033] A method for preparing a polyamide membrane for separating dyes and inorganic salts, specifically comprising the following steps:

[0034] The polyacrylonitrile ultrafiltration membrane of 8×8 cm was immersed in a 0.2% sodium dodecylbenzene sulfonate aqueous solution for 24 hours to obtain a polyamide membrane support layer;

[0035] Weigh 10 mg of 2,4,6-triaminopyrimidine, 2 mg of Na2CO3, and 9.988 g of water, mix the three and dissolve them by ultrasonication to prepare a 0.1 wt% 2,4,6-triaminopyrimidine aqueous solution;

[0036] Weigh 20 mg of 1,3,5-trimethylbenzenecarboxylic acid chloride and 9.98 g of n-hexane, dissolve them by ultrasonication, and prepare an oil phase solution with a concentration of 0.2 wt%;

[0037] Fix the polyamide membrane support layer in a metal container, blow dry the deionized water on its surface with an air gun, pour 5 mL of the aqueous solution into the metal container, let it stand at room temperature for 15 minutes, then pour out the aqueous solution and dry it naturally in the shade;

[0038] Then slowly pour 5 mL of the oil phase solution into the metal container, react at room temperature for 10 min, pour out the oil phase solution in the metal container, and rinse with n-hexane solution to remove the unreacted oil phase solution on the surface;

[0039] The polyamide membrane support layer after the reaction was placed in an oven at 70° C. to crosslink it for 15 minutes, thereby obtaining a polyamide membrane, which was marked as M-0.1 and immersed in deionized water for later testing.

[0040] The polyamide membrane prepared in this example was used to perform a pure water flux test. The test results are shown in FIG. Figure 1 As shown, the pure water flux is 136.3Lm -2 h -1 bar -1 .

[0041] The polyamide membrane prepared in this example was used to perform a dye interception test. The test results are shown in FIG. Figure 1 And as shown in Table 1.

[0042] The polyamide membrane prepared in this example was used to perform a salt retention test. The test results are shown in FIG. Figure 2 And as shown in Table 1.

[0043] Example 2

[0044] A method for preparing a polyamide membrane for separating dyes and inorganic salts, specifically comprising the following steps:

[0045] The polyacrylonitrile ultrafiltration membrane of 8×8 cm was immersed in a 0.2% sodium dodecylbenzene sulfonate aqueous solution for 24 hours to obtain a polyamide membrane support layer;

[0046] Weigh 25 mg of 2,4,6-triaminopyrimidine, 2 mg of Na2CO3, and 9.973 g of water, mix the three and dissolve them by ultrasonication to prepare a 0.25 wt% 2,4,6-triaminopyrimidine aqueous solution;

[0047] Weigh 20 mg of 1,3,5-trimethylbenzenecarboxylic acid chloride and 9.98 g of n-hexane, dissolve them by ultrasonication, and prepare an oil phase solution with a concentration of 0.2 wt%;

[0048] Fix the polyamide membrane support layer in a metal container, blow dry the deionized water on its surface with an air gun, pour 5 mL of the aqueous solution into the metal container, let it stand at room temperature for 15 minutes, then pour out the aqueous solution and dry it naturally in the shade;

[0049] Then slowly pour 5 mL of the oil phase solution into the metal container, react at room temperature for 10 min, pour out the oil phase solution in the metal container, and rinse with n-hexane solution to remove the unreacted oil phase solution on the surface;

[0050] The polyamide membrane support layer after the reaction was placed in an oven at 70° C. to be cross-linked for 15 minutes to obtain a polyamide membrane, which was marked as M-0.25 and immersed in deionized water for later testing.

[0051] The polyamide membrane prepared in this example was used to perform a pure water flux test. The test results are shown in FIG. Figure 1 As shown, the pure water flux is 108.2Lm -2 h -1 bar -1 .

[0052] The polyamide membrane prepared in this example was used to perform a dye interception test. The test results are shown in FIG. Figure 1 And as shown in Table 1.

[0053] The polyamide membrane prepared in this example was used to perform a salt retention test. The test results are shown in FIG. Figure 2 And as shown in Table 1.

[0054] Example 3

[0055] A method for preparing a polyamide membrane for separating dyes and inorganic salts, specifically comprising the following steps:

[0056] The polyacrylonitrile ultrafiltration membrane of 8×8 cm was immersed in a 0.2% sodium dodecylbenzene sulfonate aqueous solution for 24 hours to obtain a polyamide membrane support layer;

[0057] Weigh 50 mg of 2,4,6-triaminopyrimidine, 2 mg of Na2CO3, and 9.948 g of water, mix the three and dissolve them by ultrasonication to prepare a 0.5 wt% 2,4,6-triaminopyrimidine aqueous solution;

[0058] Weigh 20 mg of 1,3,5-trimethylbenzenecarboxylic acid chloride and 9.98 g of n-hexane, dissolve them by ultrasonication, and prepare an oil phase solution with a concentration of 0.2 wt%;

[0059] Fix the polyamide membrane support layer in a metal container, blow dry the deionized water on its surface with an air gun, pour 5 mL of the aqueous solution into the metal container, let it stand at room temperature for 15 minutes, then pour out the aqueous solution and dry it naturally in the shade;

[0060] Then slowly pour 5 mL of the oil phase solution into the metal container, react at room temperature for 10 min, pour out the oil phase solution in the metal container, and rinse with n-hexane solution to remove the unreacted oil phase solution on the surface;

[0061] The polyamide membrane support layer after the reaction was placed in an oven at 70° C. to crosslink it for 15 minutes, thereby obtaining a polyamide membrane, which was marked as M-0.5 and immersed in deionized water for later testing.

[0062] The polyamide membrane prepared in this example was used to perform a pure water flux test. The test results are shown in FIG. Figure 1 As shown, the pure water flux is 80.6Lm -2 h -1 bar -1 .

[0063] The polyamide membrane prepared in this example was used to perform a dye interception test. The test results are shown in FIG. Figure 1 And as shown in Table 1.

[0064] The polyamide membrane prepared in this example was used to perform a salt retention test. The test results are shown in FIG. Figure 2 And as shown in Table 1.

[0065] Example 4

[0066] A method for preparing a polyamide membrane for separating dyes and inorganic salts, specifically comprising the following steps:

[0067] The polyacrylonitrile ultrafiltration membrane of 8×8 cm was immersed in a 0.2% sodium dodecylbenzene sulfonate aqueous solution for 24 hours to obtain a polyamide membrane support layer;

[0068] Weigh 75 mg of 2,4,6-triaminopyrimidine, 2 mg of Na2CO3, and 9.923 g of water, mix the three and dissolve them by ultrasonication to prepare a 0.75 wt% 2,4,6-triaminopyrimidine aqueous solution;

[0069] Weigh 20 mg of 1,3,5-trimethylbenzenecarboxylic acid chloride and 9.98 g of n-hexane, dissolve them by ultrasonication, and prepare an oil phase solution with a concentration of 0.2 wt%;

[0070] Fix the polyamide membrane support layer in a metal container, blow dry the deionized water on its surface with an air gun, pour 5 mL of the aqueous solution into the metal container, let it stand at room temperature for 15 minutes, then pour out the aqueous solution and dry it naturally in the shade;

[0071] Then slowly pour 5 mL of the oil phase solution into the metal container, react at room temperature for 10 min, pour out the oil phase solution in the metal container, and rinse with n-hexane solution to remove the unreacted oil phase solution on the surface;

[0072] The polyamide membrane support layer after the reaction was placed in a 70° C. oven to be cross-linked for 15 minutes to obtain a polyamide membrane, which was marked as M-0.75 and immersed in deionized water for later testing.

[0073] The polyamide membrane prepared in this example was used to perform a pure water flux test. The test results are shown in FIG. Figure 1 As shown, the pure water flux is 75.9 L m -2 h -1 bar -1 .

[0074] The polyamide membrane prepared in this example was used to perform a dye interception test. The test results are shown in FIG. Figure 1 And as shown in Table 1.

[0075] The polyamide membrane prepared in this example was used to perform a salt retention test. The test results are shown in FIG. Figure 2 And as shown in Table 1.

[0076] Example 5

[0077] A method for preparing a polyamide membrane for separating dyes and inorganic salts, specifically comprising the following steps:

[0078] The polyacrylonitrile ultrafiltration membrane of 8×8 cm was immersed in a 0.2% sodium dodecylbenzene sulfonate aqueous solution for 24 hours to obtain a polyamide membrane support layer;

[0079] Weigh 100 mg of 2,4,6-triaminopyrimidine, 2 mg of Na2CO3, and 9.898 g of water, mix the three and dissolve them by ultrasonication to prepare a 2,4,6-triaminopyrimidine aqueous solution with a concentration of 1 wt%;

[0080] Weigh 20 mg of 1,3,5-trimethylbenzenecarboxylic acid chloride and 9.98 g of n-hexane, dissolve them by ultrasonication, and prepare an oil phase solution with a concentration of 0.2 wt%;

[0081] Fix the polyamide membrane support layer in a metal container, blow dry the deionized water on its surface with an air gun, pour 5 mL of the aqueous solution into the metal container, let it stand at room temperature for 15 minutes, then pour out the aqueous solution and dry it naturally in the shade;

[0082] Then slowly pour 5 mL of the oil phase solution into the metal container, react at room temperature for 10 min, pour out the oil phase solution in the metal container, and rinse with n-hexane solution to remove the unreacted oil phase solution on the surface;

[0083] The polyamide membrane support layer after the reaction was placed in an oven at 70° C. to be cross-linked for 15 minutes to obtain a polyamide membrane, which was marked as M-1 and immersed in deionized water for later testing.

[0084] The polyamide membrane prepared in this example was used to perform a pure water flux test. The test results are shown in FIG. Figure 1 As shown, the pure water flux is 65.3Lm -2 h -1 bar -1 .

[0085] The polyamide membrane prepared in this example was used to perform a dye interception test. The test results are shown in FIG. Figure 1 And as shown in Table 1.

[0086] The polyamide membrane prepared in this example was used to perform a salt retention test. The test results are shown in FIG. Figure 2 And as shown in Table 1.

[0087] The dye interception test in the above-mentioned Examples 1 to 5 uses a dye with a concentration of 0.2 g / L, and the salt interception test uses a salt with a concentration of 1 g / L.

[0088] The polyamide membrane prepared in Example 3 was immersed in 5000 ppm NaClO for 6-36 h, and the water flux and direct red dye interception rate remained basically unchanged (eg Figure 3 The prepared polyamide membrane has good chlorine resistance.

[0089] The polyamide membrane prepared in Example 3 was subjected to a dynamic filtration pollution experiment. A 1000 ppm bovine serum albumin solution was used as the protein pollutant. After three cycles of pollution-backwashing, the normalized flux of the membrane fluctuated within a very small range (e.g. Figure 4 As shown), it shows that the prepared polyamide membrane has excellent anti-fouling performance.

[0090] Table 1 Interception rate of dyes and salts

[0091] Example 6

[0092] The method for preparing the polyamide membrane in this example is the same as that in Example 3, and 10 groups of polyamide membranes are prepared. The dye interception test and the salt interception test are respectively performed on the 10 groups of polyamide membranes, and the test results are shown in Table 2. The results show that the dye and salt interception performance of the 10 parallel membranes prepared fluctuate within a very small range and remain basically unchanged.

[0093] Table 2 Interception rate of dyes and salts

[0094] Comparative Example

[0095] Ten groups of polyamide membranes were prepared using a polyamide membrane for separating dyes and salts and a preparation method thereof disclosed in Chinese patent CN111921378B, and dye interception tests and salt interception tests were performed on the ten groups of polyamide membranes, respectively, and the test results are shown in Table 3. The results show that the interception performance of dyes and salts of the ten parallel membranes prepared in Chinese patent CN111921378B fluctuates within a large range, indicating that the stability is general.

[0096] Table 3 Interception rate of dyes and salts

[0097] Compared with the comparative example, the polyamide membrane prepared in Example 6 of the present invention is more stable.

[0098] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a polyamide membrane for separating dyes and inorganic salts, wherein a polyamide membrane support layer is soaked in an aqueous solution and an oily solution in sequence to form a polyamide active layer on its surface, and finally a polyamide membrane is obtained by heating and cross-linking, wherein: The aqueous phase solution is a solution obtained by dissolving 2,4,6-triaminopyrimidine in an alkaline solution.

2. The method for preparing a polyamide membrane for separating dyes and inorganic salts according to claim 1, characterized in that: The polyacrylonitrile ultrafiltration membrane was immersed in a sodium dodecylbenzene sulfonate solution for 24 hours to obtain a treated polyacrylonitrile ultrafiltration membrane, which was used as a polyamide membrane support layer.

3. A method for preparing a polyamide membrane for separating dyes and inorganic salts as claimed in claim 2, characterized in that: The mass fraction of sodium dodecylbenzene sulfonate in the sodium dodecylbenzene sulfonate solution is 0.1-0.3%.

4. The method for preparing a polyamide membrane for separating dyes and inorganic salts according to claim 1, characterized in that: The mass fraction of 2,4,6-triaminopyrimidine in the aqueous phase solution is 0.1-1 wt %.

5. The method for preparing a polyamide membrane for separating dyes and inorganic salts according to claim 1, characterized in that: The oil phase solution is a solution obtained by dissolving 1,3,5-trimethylbenzenecarboxylic acid chloride in n-hexane solvent.

6. A method for preparing a polyamide membrane for separating dyes and inorganic salts as claimed in claim 5, characterized in that: The mass fraction of 1,3,5-trimethylbenzenecarboxylic acid chloride in the oil phase solution is 0.1-0.3 wt %.

7. The method for preparing a polyamide membrane for separating dyes and inorganic salts according to claim 1, characterized in that: The alkaline solution is an aqueous solution of Na2CO3, and its concentration is 0.01-0.03wt%.

8. The method for preparing a polyamide membrane for separating dyes and inorganic salts according to claim 1, characterized in that: The polyamide membrane support layer is soaked in an aqueous solution for 1-15 minutes and dried at room temperature; then, the polyamide membrane is soaked in an oily solution for 1-15 minutes.

9. The method for preparing a polyamide membrane for separating dyes and inorganic salts according to claim 1, characterized in that: The cross-linking temperature is 60-80°C and the time is 15 minutes.

10. A polyamide membrane for separating dyes and inorganic salts, characterized in that: The method is obtained by any one of claims 1 to 9.

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