Preparation method of high-performance water treatment membrane

Abstract

The invention relates to the technical field of water treatment membrane preparation, in particular to a method for preparing a high-performance polyamide composite membrane by blending amino acid with a polysulfone membrane supporting body. The polyamide water treatment membrane with high water flux and high salt rejection rate is prepared by blending amino acid and polysulfone to enhance binding force and combining metal ion complexing and strong chelating agent dissociation technologies.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment membranes, and in particular to a method for preparing a high-performance polyamide composite membrane through an amino acid blended polysulfone membrane support. Background Art

[0002] As one of the important technologies in the field of modern water treatment, water treatment membrane technology is widely used in many fields such as seawater desalination, brackish water desalination, wastewater treatment and reuse. Among them, polyamide composite membrane has become the mainstream product in the reverse osmosis membrane market due to its excellent separation performance, good chemical stability and mechanical strength. Polyamide composite membrane is usually composed of a porous support layer and a dense polyamide separation layer, and is prepared by interfacial polymerization technology. The porous support layer provides mechanical support and water channels, while the dense polyamide separation layer is responsible for achieving efficient salt retention and water permeation.

[0003] As the problem of water shortage becomes increasingly serious, higher requirements are placed on the water flux of polyamide water treatment membranes. Water flux refers to the amount of water passing through the membrane per unit time, and is one of the important indicators for measuring the performance of polyamide composite membranes. In order to improve the water flux, researchers have tried a variety of methods. On the one hand, the transmission resistance of water in the support layer can be reduced by optimizing the structure and properties of the porous support layer, such as increasing the porosity and increasing the pore size. On the other hand, the water permeability of the polyamide separation layer can be improved by modifying it, such as introducing hydrophilic groups and adjusting the degree of crosslinking. In addition, surface coating, blending modification and other technical means can be used to further improve the performance of the membrane.

[0004] At present, the prior art CN115400603A discloses a method for improving the water flux of polyamide nanofiltration membrane, which adopts plant polyphenol to modify the support layer, and adds metal ions in the aqueous phase to form a support layer loaded with metal complex and aqueous phase monomer. After the polyamide layer is formed by interfacial polymerization, a strong chelating agent is used to dissociate the plant polyphenol metal complex, thereby increasing the water flux of the membrane. However, the inventor found that there are two major technical problems in this method in the study. First, the binding force between plant polyphenol and the support is relatively weak, and the interfacial polymerization process is relatively violent, which easily causes part of the plant polyphenol to detach from the support and form a complex in the polyamide layer. This will form defective holes in the subsequent dissociation process, affecting the separation performance of the membrane. Secondly, in order to improve the efficiency of interfacial polymerization, it is usually necessary to add a surfactant to the aqueous phase monomer to reduce the interfacial tension between the aqueous phase and the organic phase. However, when a surfactant and a metal ion are added simultaneously in the aqueous phase monomer, the metal ion easily interacts with the surfactant to form an ion pair, and is dispersed in the polyamide membrane inside the subsequent interfacial polymerization process. These ion pairs are dissociated in the subsequent strong chelating agent dissociation process, which will reduce the desalination rate of the membrane and affect the application effect of the membrane.

[0005] Therefore, it is necessary to develop a new technical solution to solve the above problems and improve the water flux and separation performance of polyamide water treatment membranes. Summary of the invention

[0006] In view of the above problems, the present invention enhances the binding force by blending amino acids with polysulfone, combines metal ion complexation and strong chelating agent dissociation technology, and prepares a polyamide water treatment membrane with high water flux and high desalination rate. Specifically, a method for preparing a high-performance water treatment membrane includes the following steps:

[0007] (a) mixing a polymer and an amino acid, adding a solvent to form a blend solution, and then preparing an amino acid blend support;

[0008] (b) immersing the amino acid blend support in a solution containing at least one metal ion to form an amino acid-metal ion complex layer;

[0009] (c) washing the support with deionized water to remove excess metal ions on the surface of the amino acid blend support, and drying;

[0010] (d) immersing the support in an aqueous solution containing a polyamine and a surfactant and an organic solution containing a polyacyl chloride in sequence to perform interfacial polymerization to form a polyamide layer;

[0011] (e) treating the polyamide membrane with a strong chelating agent solution to dissociate the amino acid-metal ion complex layer to obtain the high-performance water treatment membrane.

[0012] Preferably, the content of amino acid in the blend solution is 1-3wt%, and the amino acid is selected from one or more of glycine, alanine, valine, leucine, isoleucine, tryptophan, serine, tyrosine, cysteine, aspartic acid, glutamine, threonine, asparagine, lysine, arginine or histidine. Preferably, the content of polymer in the blend solution is 15-45wt%, and the polymer is selected from one of polysulfone, polyethersulfone, polyphenylenesulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyolefin, polysulfoneamide, and polyimide.

[0013] Preferably, the solvent in the blended solution is one or more of N-methylpyrrolidone, dimethylformamide or dimethylacetamide, and the metal ions are selected from one or more of calcium ions, copper ions, zinc ions, iron ions, cobalt ions, nickel ions or manganese ions, derived from the corresponding metal salt solution, with a concentration of 0.01-0.5M.

[0014] Preferably, the amino acid blend support is immersed in the solution containing at least one metal ion for 1-60 minutes.

[0015] Preferably, the polyamine in the aqueous phase solution is selected from one or more of ethylenediamine, hexamethylenediamine, m-phenylenediamine, p-phenylenediamine or triethylenetetramine, and the concentration is 0.5wt% to 5wt%; the surfactant in the aqueous phase solution is selected from one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate and sodium lauryl sulfate, and the concentration is 0.2-1.2wt%.

[0016] Preferably, the polyacyl chloride in the organic phase solution is selected from one or more of trimesoyl chloride, isophthaloyl chloride or terephthaloyl chloride, and the concentration is 0.01 wt % to 0.5 wt %.

[0017] Preferably, the strong chelating agent is selected from one or more of ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid or hydroxyethylethylenediaminetriacetic acid, and the concentration is 0.05-0.5M.

[0018] Preferably, the treatment is soaking or rinsing, the treatment time is 0.5-30 minutes, and the treatment temperature is room temperature-60°C.

[0019] Compared with the prior art, the present invention has the following effects:

[0020] The present invention adopts amino acids to replace plant polyphenols and polymers to prepare a support, which significantly enhances the binding force between the support and the amino acids. As a molecule with good biocompatibility and strong binding ability, the amino acids can effectively form a stable complex structure with the support and the metal ions impregnated subsequently. This enhanced binding force effectively avoids the problem of plant polyphenols detaching from the support during interfacial polymerization, reduces the formation of complexes in the polyamide layer, and further reduces the generation of defective holes in the subsequent dissociation process, thereby improving the desalination rate of the polyamide water treatment membrane.

[0021] The present invention effectively avoids the interaction between metal ions and surfactants by first soaking in deionized water to remove excess metal ions on the surface, and then successively soaking in polyamine and polyacyl chloride to form a polyamide layer. This improvement ensures the normal function of surfactants in the aqueous phase monomer, while avoiding the problem of metal ions and surfactants forming ion pairs and dispersing inside the polyamide membrane, ensuring that the salt rejection rate of the membrane is not affected, and improving the performance of the polyamide water treatment membrane. DETAILED DESCRIPTION

[0022] Example 1

[0023] 1. Preparation of amino acid-polysulfone blend support:

[0024] Dissolve 15wt% polysulfone (PSF) and 2wt% lysine in N-methylpyrrolidone (NMP) and stir until completely dissolved. After the solution is allowed to stand for degassing, it is coated on a glass plate with a scraper to a thickness of 150μm. Immerse the coated glass plate in deionized water for phase inversion to form an amino acid-polysulfone blend support. Take out the support, rinse it thoroughly with deionized water, and dry it for later use.

[0025] 2. Immersing in metal ion solution to form a complex layer:

[0026] Prepare 0.1M CuSO4 solution, immerse the support in the CuSO4 solution, and soak it at room temperature for 30 minutes. Take out the support and soak it in deionized water for 10 minutes to remove the excess Cu on the surface. 2+ . Let dry and set aside.

[0027] 3. Interfacial polymerization to form a polyamide layer:

[0028] Prepare an aqueous solution of 2wt% m-phenylenediamine (MPD) and 0.1wt% sodium dodecyl sulfate (SDS). Prepare a n-hexane solution of 0.1wt% trimesoyl chloride (TMC). Immerse the support in the MPD aqueous solution for 2 minutes. Remove the support and use a rubber roller to remove excess aqueous solution on the surface. Immerse the support in a TMC organic solution and perform an interfacial polymerization reaction for 1 minute. Remove the support and heat treat it at 60°C for 5 minutes.

[0029] 4. Strong chelating agent dissociates the complex layer:

[0030] Prepare 0.15M ethylenediaminetetraacetic acid (EDTA) solution. Immerse the interfacially polymerized membrane in the EDTA solution for 30 minutes at room temperature. Take out the membrane, wash it thoroughly with deionized water, and dry it for later use.

[0031] 5. Test separation performance

[0032] The above polyamide membrane was tested for water treatment performance: the pure water flux was tested using a pure water flux test device at an operating pressure of 15 bar and a temperature of 25°C. Under the same operating conditions, the retention rate was tested using a 2000ppm NaCl solution. The results showed that the pure water flux was 35.4L / m 2 ·h·bar, the retention rate is 98.2%.

[0033] Example 2

[0034] The difference between Example 2 and Example 1 is that aspartic acid is used instead of lysine. The water treatment performance of the polyamide membrane was tested, and the results showed that the pure water flux was 36.1 L / m 2 ·h·bar, the retention rate is 98.0%.

[0035] Comparative Example 1

[0036] The difference between Comparative Example 1 and Example 1 is that the aqueous phase solution does not contain SDS. The water treatment performance of the polyamide membrane was tested, and the results showed that the pure water flux was 28.6 L / m 2 ·h·bar, the retention rate is 90.8%.

[0037] Comparative Example 2

[0038] The difference between Comparative Example 2 and Example 1 is that the metal ions are mixed into the aqueous monomer solution, that is, an aqueous solution of 2wt% MPD, 0.1wt% SDS and 0.1M CuSO4 is prepared, and step 2 in the example is not required. The water treatment performance of the polyamide membrane was tested, and the results showed that the pure water flux was 41.1L / m 2 ·h·bar, the retention rate is 87.8%.

[0039] Comparative Example 3

[0040] The difference between Comparative Example 3 and Example 1 is that step c (deionized water immersion to remove excess metal ions on the surface) is missing. The water treatment performance of the polyamide membrane was tested, and the results showed that the pure water flux was 36.5 L / m 2 ·h·bar, the retention rate is 95.8%.

[0041] Step 1 of Comparative Example 4 is as follows:

[0042] Dissolve 15wt% polysulfone (PSF) in N-methylpyrrolidone (NMP) and stir until completely dissolved. After the solution is allowed to stand for degassing, it is coated on a glass plate with a scraper to a thickness of 150μm. Immerse the coated glass plate in deionized water for phase inversion to form a polysulfone blend support. Take out the support, rinse it thoroughly with deionized water, and dry it. Then immerse the support in a 2wt% lysine aqueous solution, soak it for 30 minutes, dry it and set it aside. The remaining steps are the same as Example 1. The above-mentioned polyamide membrane was tested for water treatment performance, and the results showed that the pure water flux was 39.8L / m 2 ·h·bar, the retention rate is 94.3%.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-performance water treatment membrane, characterized in that: The following steps are involved: (a) mixing a polymer and an amino acid, adding a solvent to form a blend solution, and then preparing an amino acid blend support; (b) immersing the amino acid blend support in a solution containing at least one metal ion to form an amino acid-metal ion complex layer; (c) washing the support with deionized water to remove excess metal ions on the surface of the amino acid blend support, and drying; (d) immersing the support in an aqueous solution containing a polyamine and a surfactant and an organic solution containing a polyacyl chloride to perform interfacial polymerization to form a polyamide layer; (e) treating the polyamide membrane with a strong chelating agent solution to dissociate the amino acid-metal ion complex layer to obtain the high-performance water treatment membrane.

2. The method according to claim 1, characterized in that The content of amino acids in the blended solution is 1-3wt%, and the amino acids are selected from one or more of glycine, alanine, valine, leucine, isoleucine, tryptophan, serine, tyrosine, cysteine, aspartic acid, glutamine, threonine, asparagine, lysine, arginine or histidine.

3. The method according to claim 1, characterized in that The content of the polymer in the blended solution is 15-45wt%, and the polymer is selected from one of polysulfone, polyethersulfone, polyphenylenesulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyolefin, polysulfoneamide, and polyimide.

4. The method according to claim 1, characterized in that: The solvent in the blend solution is one or more of N-methylpyrrolidone, dimethylformamide or dimethylacetamide.

5. The method according to claim 1, characterized in that The metal ions are selected from one or more of calcium ions, copper ions, zinc ions, iron ions, cobalt ions, nickel ions or manganese ions, and are derived from corresponding metal salt solutions with a concentration of 0.01-0.5M.

6. The method according to claim 1, characterized in that The amino acid blend support is immersed in a solution containing at least one metal ion for 1-60 minutes.

7. The method according to claim 1, characterized in that The polyamine in the aqueous phase solution is selected from one or more of ethylenediamine, hexamethylenediamine, m-phenylenediamine, p-phenylenediamine or triethylenetetramine, and the concentration is 0.5wt% to 5wt%; the surfactant in the aqueous phase solution is selected from one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate and sodium lauryl sulfate, and the concentration is 0.2-1.2wt%.

8. The method according to claim 1, characterized in that The polyacyl chloride in the organic phase solution is selected from one or more of trimesoyl chloride, isophthaloyl chloride or terephthaloyl chloride, and the concentration is 0.01 wt % to 0.5 wt %.

9. The method according to claim 1, characterized in that: The strong chelating agent is selected from one or more of ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid or hydroxyethylethylenediaminetriacetic acid, and the concentration is 0.05-0.5M.

10. The method according to claim 1, characterized in that The treatment is immersion or rinsing, the treatment time is 0.5-30 minutes, and the treatment temperature is room temperature-60°C.