Polyester amide composite nanofiltration membrane and preparation method thereof
By having small molecules of alkanolamines and polyamines participate in the interfacial polymerization reaction, a polyesteramide composite nanofiltration membrane is formed, which solves the problems of chlorine resistance and loose separation layer of polyamide nanofiltration membranes and realizes the preparation of high-performance nanofiltration membranes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEBEI UNIV OF TECH
- Filing Date
- 2024-03-11
- Publication Date
- 2026-07-21
Smart Images
Figure CN118001942B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane separation technology, and in particular relates to a polyesteramide composite nanofiltration membrane and its preparation method. Background Technology
[0002] Nanofiltration membranes, as a member of the membrane family, have a molecular weight cutoff between reverse osmosis and ultrafiltration membranes, approximately 200–500 Da, with pore sizes around 1 nm. Nanofiltration membranes allow water molecules and most monovalent ions to pass through, while retaining most organic molecules, polyvalent ions, and colloidal particles. Since their initial development in 1980, after more than forty years of development, they have found mature applications in pharmaceuticals, biotechnology, the food industry, anhydrous applications, and dye wastewater treatment.
[0003] Interfacial polymerization is a commonly used method for preparing nanofiltration membranes. Since Morgan first proposed the concept of interfacial polymerization in 1965, polyamide composite membranes have experienced unprecedented development. Currently, commonly used aqueous monomers are diamines, such as piperazine and m-phenylenediamine, while commonly used organic monomers are acyl chlorides. Although polyamide composite nanofiltration membranes prepared by interfacial polymerization dominate both the commercial market and laboratory applications, they suffer from problems such as poor chlorine resistance and poor fouling resistance due to the special structure of amide bonds.
[0004] The emergence of polyester and polyesteramide nanofiltration membranes has effectively compensated for the shortcomings of polyamide nanofiltration membranes. However, since the aqueous monomers used to prepare these membranes usually have high polarity, most aqueous monomers have low reactivity, requiring additional technical means to enhance them. Furthermore, the resulting separation layer is relatively loose, which limits their large-scale practical application. Summary of the Invention
[0005] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention proposes a polyesteramide composite nanofiltration membrane and its preparation method. The prepared polyesteramide composite nanofiltration membrane has a dense active layer and good selective separation ability.
[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:
[0007] A polyesteramide composite nanofiltration membrane is provided, comprising a separation layer and a porous support layer. The separation layer is polyesteramide, obtained by interfacial polymerization of an aqueous mixed monomer solution and an organic monomer solution. The aqueous mixed monomer is composed of small amine molecules and polyamines. The organic monomer is a polyacrylamide compound.
[0008] Furthermore, the alkanolamine molecule is at least one of serine, ethanolamine, and diethanolamine.
[0009] Furthermore, the polyamine is at least one of piperazine, m-phenylenediamine, and ethylenediamine.
[0010] Furthermore, the polyacrylamide chloride compound is at least one of pyromellitic chloride, terephthaloyl chloride, and isophthaloyl chloride.
[0011] Furthermore, the porous support layer is a hydrophilic ultrafiltration membrane, preferably a hydrophilic ultrafiltration membrane with a molecular weight cutoff of 80,000 to 100,000 Daltons.
[0012] The preparation method of the above-mentioned polyesteramide composite nanofiltration membrane includes the following steps:
[0013] S1. Dissolve the alkanolamine small molecule and the polyamine together in ultrapure water to obtain an aqueous mixed monomer solution; dissolve the polyacrylamide compound in a nonpolar organic solvent to obtain an organic monomer solution;
[0014] S2. Pour the aqueous mixed monomer solution onto the surface of the porous support layer and wet it, then pour off the excess aqueous mixed monomer solution and remove the residual droplets from the surface of the porous support layer.
[0015] S3. Pour the organic phase monomer solution onto the surface of the porous support layer after operation S2 and wet it, thereby starting the interfacial polymerization reaction, and then pour off the excess organic phase monomer solution.
[0016] S4. The porous support layer surface after S3 is rinsed with a non-polar organic solvent to terminate the interfacial polymerization reaction, and then heat-treated to obtain the polyesteramide composite nanofiltration membrane.
[0017] Furthermore, the concentration of the alkanolamine small molecules is 0.05–0.4 w / v%, that is, 0.05–0.4 g of serine alcohol is added to every 100 mL of ultrapure water and shaken until completely dissolved; more preferably, it is 0.1 w / v%. Since the hydroxyl groups in the alkanolamine small molecules are less reactive than amino groups, too low an alkanolamine concentration results in too few alkanolamine molecules participating in the reaction, which cannot improve the performance of the separation layer; while too high an alkanolamine small molecule concentration will hinder the diffusion of polyamines into the organic phase, resulting in a decrease in the compactness of the separation layer.
[0018] Furthermore, the concentration of the polyamine is 0.01–0.05 w / v%, that is, 0.01–0.05 g of polyamine is added to every 100 mL of ultrapure water and shaken until completely dissolved; the concentration of the polyamine is further preferably 0.01–0.04 w / v%, and even more preferably 0.04 w / v. Due to the high reactivity of polyamine, excessively high polyamine concentrations will cause polyamine to compete for the reaction sites of small alcohol amine molecules, reducing the advantage of small alcohol amine molecules in the preparation of polyesteramide composite nanofiltration membranes.
[0019] Furthermore, the concentration of the polyacrylamide chloride compound is 0.05–0.15 w / v%, that is, 0.05–0.15 g of the polyacrylamide chloride compound is added to every 100 mL of nonpolar organic solvent and shaken until completely dissolved; the concentration of the polyacrylamide chloride compound is further preferably 0.1 w / v%. If the concentration of the polyacrylamide chloride compound is too low, the interfacial polymerization reaction will not be complete, resulting in a defective separation layer; if the concentration is too high, due to the self-limiting effect, it will be impossible to continue to control the separation layer, wasting reagents.
[0020] Furthermore, the nonpolar organic solvent is at least one selected from n-hexane, cyclohexane, n-heptane, and n-octane.
[0021] Further, in step S2, the aqueous mixed monomer solution wets the porous support layer for 2–10 minutes, more preferably 5 minutes. The aqueous mixed monomer solution fully wets the porous support layer, allowing it to fully react with the subsequent polyacrylamide chloride compound. After sufficient wetting, excess aqueous mixed monomer solution is poured off, and residual droplets on the surface of the porous support layer are removed with a rubber scraper.
[0022] Furthermore, in step S3, the interfacial polymerization reaction time is 10-30 seconds, more preferably 20 seconds. If the interfacial polymerization time is too short, the reaction cannot be fully completed; if the time is too long, a self-limiting effect will occur, wasting time.
[0023] Furthermore, in step S3, the required room temperature is: the reaction temperature is 20–30°C; and the relative humidity of the reaction environment is 35–45%.
[0024] Furthermore, in step S4, the heat treatment involves drying in an oven at 40–60°C for 2–5 minutes, with a preferred drying temperature of 50°C and a preferred drying time of 3 minutes. Excessive temperature or prolonged drying time can cause membrane pores to collapse, resulting in loss of separation performance.
[0025] The small molecule alkanolamines and polyamines used in this invention are shown in the following figure:
[0026]
[0027] The alkanolamine small molecules of this invention have amino and hydroxyl groups, and the polyamine is a diamine. Diamines are the most commonly used aqueous monomers in the interfacial polymerization method for preparing polyamide nanofiltration membranes. They have high reactivity, fast diffusion rate, and do not require additional technical means to react with polyacrylamide chloride compounds. Alkanolamine small molecules alone and polyacrylamide chloride compounds can hardly form a dense polyesteramide separation layer without external intervention. However, with the assistance of a small amount of polyamine, a dense polyesteramide separation layer with high desalination rate can be formed. Blending polyamines and alkanolamine small molecules as aqueous monomers can improve the density of the separation layer, thus ensuring the separation efficiency of the nanofiltration membrane. At the same time, the ester bonds formed by the reaction of the hydroxyl groups in the alkanolamine small molecules with the polyacrylamide chloride compounds improve the chlorine resistance of the nanofiltration membrane. In addition, the hydroxyl groups remaining on the surface of the nanofiltration membrane increase hydrophilicity, maintaining considerable permeation efficiency.
[0028] Compared with existing technologies, the polyesteramide composite nanofiltration membrane and its preparation method described in this invention have the following advantages:
[0029] (1) This invention provides a method for preparing a high-performance polyesteramide composite nanofiltration membrane. In the interfacial polymerization reaction, small alcohol amine molecules can be activated by polyamine molecules and undergo interfacial polymerization reaction with polyacrylamide compounds together with polyamines. Compared with simply using small alcohol amine molecules or polyamines as aqueous monomers, the synergy between small alcohol amine molecules and polyamines can generate a denser active layer, which effectively improves the selective separation capability of the polyesteramide composite nanofiltration membrane.
[0030] (2) The present invention can regulate the separation layer thickness and performance of polyester amide composite nanofiltration membrane by adjusting the concentration of small molecule alkanolamine and polyamine. No additional operation is required, the method is simple and the effect is significant.
[0031] (3) The small amine molecules of the present invention have hydroxyl groups, which can form ester bonds by reacting with polyacryl chloride compounds, which can effectively improve the chlorine resistance. At the same time, the unreacted hydroxyl groups can also increase the hydrophilicity of the nanofiltration membrane.
[0032] (4) The polyesteramide composite nanofiltration membrane prepared by the present invention has high density, so it has a considerable pure water flux while maintaining high salt rejection performance, which can effectively alleviate the "trade off" effect.
[0033] (5) The polyesteramide composite nanofiltration membrane prepared by this invention has broad application prospects in the field of water treatment. Attached Figure Description
[0034] Figure 1 Scanning electron microscope images of the nanofiltration membrane prepared with a porous support layer, the nanofiltration membrane prepared in Comparative Example 1, the polyamide nanofiltration membrane prepared in Comparative Example 4, and the polyesteramide composite nanofiltration membrane prepared in Example 1, respectively.
[0035] Figure 2 The infrared spectrum of the polyesteramide composite nanofiltration membrane prepared in Example 1 is shown.
[0036] Figure 3 The image shows the X-ray photoelectron spectrum of the polyesteramide composite nanofiltration membrane prepared in Example 1.
[0037] Figure 4 Water contact angle diagrams of the polyamide nanofiltration membrane prepared in Comparative Example 4 and the polyesteramide composite nanofiltration membrane prepared in Example 1 (Note: the water contact angle is the detection data when the water droplet falls 10 seconds after it falls). Detailed Implementation
[0038] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.
[0039] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.
[0040] Example 1
[0041] Laboratory conditions required: experimental temperature 25±1℃, experimental humidity 40±5%.
[0042] A method for preparing a polyesteramide composite nanofiltration membrane, comprising the following specific steps:
[0043] S1. Prepare an aqueous mixed monomer solution by dissolving serine and piperazine together in ultrapure water, wherein the concentration of serine is 0.1 w / v and the concentration of piperazine is 0.04 w / v%. Prepare an organic monomer solution by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride is 0.1 w / v.
[0044] S2. Pour the aqueous mixed monomer solution from step S1 onto the surface of the porous support layer and wet it for 5 minutes. Then pour off the excess aqueous mixed monomer solution and use a rubber scraper to remove the residual droplets on the surface of the porous support layer.
[0045] S3. Pour the organic phase monomer solution from step S1 onto the surface of the porous support layer after operation S2 and wet it, thereby starting the interfacial polymerization reaction. The interfacial polymerization reaction is carried out for 20 seconds. The ambient temperature during the reaction is 25°C and the relative humidity is 40%. Then, pour off the excess organic phase monomer solution.
[0046] S4. The porous support layer surface after S3 is rinsed with n-hexane solvent to terminate the interfacial polymerization reaction. Finally, the porous support layer is placed in an oven at 50°C for 3 minutes to allow the unreacted monomers to react again, and finally a polyesteramide composite nanofiltration membrane is obtained.
[0047] Example 2
[0048] The only difference between Example 2 and Example 1 is that the aqueous phase monomer of serine alcohol is replaced with aqueous phase monomer of ethanolamine.
[0049] Example 3
[0050] The only difference between Example 3 and Example 1 is that the aqueous phase monomer of serine alcohol is replaced with the aqueous phase monomer of diethanolamine.
[0051] Example 4
[0052] The only difference between Example 4 and Example 1 is that the 0.1 w / v% serine aqueous monomer is replaced with a 0.1 w / v% serine + 0.1 w / v% ethanolamine aqueous mixed monomer.
[0053] Example 5
[0054] The only difference between Example 5 and Example 1 is that the 0.04 w / v% piperazine aqueous monomer is replaced with 0.01 w / v% m-phenylenediamine aqueous monomer (Note: Due to the high reactivity of m-phenylenediamine, its concentration is reduced from 0.04 w / v% to 0.01 w / v%).
[0055] Example 6
[0056] The only difference between Example 6 and Example 1 is that the piperazine aqueous monomer is replaced with ethylenediamine aqueous monomer.
[0057] Example 7
[0058] The only difference between Example 7 and Example 1 is that the 0.04 w / v% piperazine aqueous monomer is replaced with a mixed aqueous monomer of 0.02 w / v% piperazine + 0.02 w / v% ethylenediamine.
[0059] Example 8
[0060] The only difference between Example 8 and Example 1 is that the concentration of serine alcohol is changed to 0.2 w / v.
[0061] Example 9
[0062] The only difference between Example 9 and Example 1 is that the concentration of piperazine is changed to 0.02 w / v.
[0063] Example 10
[0064] The only difference between Example 10 and Example 1 is that the concentration of pyromellitic methyl chloride is changed to 0.15 w / v.
[0065] Comparative Example 1
[0066] The only difference between Comparative Example 1 and Example 1 is that 0.1 w / v% serine alcohol was used alone as an aqueous monomer solution.
[0067] Comparative Example 2
[0068] The only difference between Comparative Example 2 and Example 1 is that 0.1 w / v% ethanolamine was used alone as an aqueous monomer solution.
[0069] Comparative Example 3
[0070] The only difference between Comparative Example 3 and Example 1 is that 0.1 w / v% diethanolamine was used alone as an aqueous monomer solution.
[0071] Comparative Example 4
[0072] The only difference between Comparative Example 4 and Example 1 is that 0.04 w / v% piperazine was used alone as an aqueous monomer solution.
[0073] Comparative Example 5
[0074] The only difference between Comparative Example 5 and Example 1 is that 0.01 w / v% m-phenylenediamine was used alone as an aqueous monomer solution.
[0075] Comparative Example 6
[0076] The only difference between Comparative Example 6 and Example 1 is that 0.04 w / v% ethylenediamine was used alone as an aqueous monomer solution.
[0077] Comparative Example 7
[0078] The only difference between Comparative Example 7 and Example 1 is that the serinel aqueous monomer solution was replaced with a tris(hydroxymethyl)aminomethane aqueous monomer solution.
[0079] Comparative Example 8
[0080] The only difference between Comparative Example 8 and Example 1 is that the concentration of serine alcohol is changed to 0.01 w / v.
[0081] Comparative Example 9
[0082] The only difference between Comparative Example 9 and Example 1 is that the concentration of piperazine was changed to 0.5 w / v.
[0083] Comparative Example 10
[0084] The only difference between Comparative Example 10 and Example 1 is that the concentration of pyromellitic methyl chloride was changed to 0.3 w / v.
[0085] The scanning electron microscope morphologies of the porous support layer, the nanofiltration membrane prepared in Comparative Example 1, the polyamide nanofiltration membrane prepared in Comparative Example 4, and the polyesteramide composite nanofiltration membrane prepared in Example 1 are shown below. Figure 1 As shown, a is a porous support layer, b is the nanofiltration membrane prepared in Comparative Example 1, c is the polyamide nanofiltration membrane prepared in Comparative Example 4, and d is the polyesteramide composite nanofiltration membrane prepared in Example 1.
[0086] Depend on Figure 1 It can be seen that the porous support layer and the nanofiltration membrane prepared in Comparative Example 1 have clearly visible membrane pore structures on their membrane surfaces. This indicates that the serine alcohol aqueous monomer solution has low reactivity and can hardly react with the organic monomer solution to form a separation layer. In contrast, the polyamide nanofiltration membrane prepared in Comparative Example 4 and the polyesteramide composite nanofiltration membrane prepared in Example 1 both formed nanolayers that covered the porous structure on the porous support layer.
[0087] The infrared spectrum and X-ray photoelectron spectrum of the polyesteramide composite nanofiltration membrane prepared in Example 1 are shown below. Figure 2 , Figure 3 As shown. By Figure 2 and Figure 3 The presence of amide and ester bonds indicates that both piperazine and serine successfully participated in the interfacial polymerization reaction, suggesting that the reactivity of serine was activated in the presence of piperazine.
[0088] The water contact angles of the polyamide nanofiltration membrane prepared in Comparative Example 4 and the polyesteramide composite nanofiltration membrane prepared in Example 1 are as follows: Figure 4 As shown. By Figure 4 It is known that the large number of hydroxyl groups remaining in the serine molecule increases the hydrophilicity of the surface of the polyesteramide composite nanofiltration membrane, creating conditions for maintaining a considerable pure water flux.
[0089] The nanofiltration membranes in Examples 1-10 and Comparative Examples 1-10 were subjected to performance and thickness characterization tests.
[0090] The performance testing method was as follows: the temperature was maintained at 25℃, and filtration was carried out using a cross-flow filtration membrane tank device under an operating pressure of 6 bar. After pre-pressurization for 30 minutes, the membrane performance was basically stable. Then, the pure water flux and salt rejection performance of the prepared polyamide nanofiltration membrane and polyesteramide composite nanofiltration membrane were tested under a pressure of 5 bar and a cross-flow velocity of 0.45 m / s. The feed solution Na2SO4 was 2000 ppm.
[0091] The experimental results are shown in Table 1.
[0092] Table 1
[0093]
[0094]
[0095] Examples 1, 4, 7, 8, 9, and 10 show that the separation layer thickness and performance of the polyesteramide composite nanofiltration membrane can be controlled by adjusting the concentrations of small amine molecules, polyamines, and polyacrylamide compounds. For example, increasing the concentration of small amine molecules can increase the separation layer thickness, which also improves the desalination rate; decreasing the concentration of polyamines can decrease the separation layer thickness, which increases the flux but significantly reduces the desalination rate; increasing the concentration of polyacrylamide compounds can increase both the separation layer thickness and the desalination rate, but decreases the water flux.
[0096] Comparative examples 1, 2, and 3 show that when small alkanolamine molecules are polymerized with acyl chloride compounds at the interface, a complete separation layer cannot be formed. Therefore, the retention rate of sodium sulfate is less than 3%. This indicates that small alkanolamine molecules alone can hardly react with organic phase monomer solutions under conventional preparation methods.
[0097] Comparative examples 4, 5, and 6 show that while low concentrations of polyamines can react with organic monomer solutions to form nanomembranes, the resulting active layer is typically porous and thin due to the low concentration, leading to poor salt retention performance in the resulting nanofiltration membrane. However, when polyamines and alkanolamine small molecules are mixed, infrared and X-ray photoelectron spectroscopy reveal that the reactivity of the alkanolamine small molecules is activated by the polyamines, with both participating in the reaction. This results in a denser separation layer, and the thickness of the separation layer can be effectively controlled by adjusting the concentrations of various monomers. Therefore, the performance of polyesteramide composite nanofiltration membranes can be effectively regulated.
[0098] Comparative Example 7 shows that when the small amine molecules are replaced with other similar monomers, the membrane performance is not much different from that of the membrane prepared by the corresponding polyamine alone, indicating that the reactivity of the other similar monomers is not activated by the polyamine.
[0099] Comparative examples 8, 9, and 10 show that if the concentrations of the three reactants are too high or too low, the membrane performance will decrease.
[0100] 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 principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A polyesteramide composite nanofiltration membrane, characterized in that: The polyesteramide composite nanofiltration membrane is composed of a separation layer and a porous support layer; wherein, the separation layer is polyesteramide, which is obtained by interfacial polymerization of an aqueous phase mixed monomer solution and an organic phase monomer solution; the aqueous phase mixed monomer is composed of alkanolamine small molecules and polyamines; the organic phase monomer is a polyacrylamide chloride compound; the alkanolamine small molecules are at least one of serinel, ethanolamine and diethanolamine; The concentration of small alcohol amine molecules in the aqueous mixed monomer solution is 0.05 ~ 0.4 w / v; the concentration of polyamines is 0.01 ~ 0.05 w / v.
2. The polyesteramide composite nanofiltration membrane according to claim 1, characterized in that: The polyamine is at least one of piperazine, m-phenylenediamine, and ethylenediamine.
3. The polyesteramide composite nanofiltration membrane according to claim 1, characterized in that: The polyacryl chloride compound is at least one of pyromellitic chloride, terephthaloyl chloride, and isophthaloyl chloride.
4. The polyesteramide composite nanofiltration membrane according to claim 1, characterized in that: The porous support layer is a hydrophilic ultrafiltration membrane.
5. The method for preparing the polyesteramide composite nanofiltration membrane according to any one of claims 1-4, characterized in that: Includes the following steps: S1. Dissolve the alkanolamine small molecule and the polyamine together in ultrapure water to obtain an aqueous mixed monomer solution; dissolve the polyacrylamide compound in a nonpolar organic solvent to obtain an organic monomer solution; S2. Pour the aqueous mixed monomer solution onto the surface of the porous support layer and wet it, then pour off the excess aqueous mixed monomer solution and remove the residual droplets from the surface of the porous support layer. S3. Pour the organic phase monomer solution onto the surface of the porous support layer after the S2 operation and wet it, thereby starting the interfacial polymerization reaction. After the interfacial polymerization reaction is completed, pour off the excess organic phase monomer solution. S4. The porous support layer surface after S3 is rinsed with a non-polar organic solvent to terminate the interfacial polymerization reaction, and then heat-treated to obtain the polyesteramide composite nanofiltration membrane.
6. The method for preparing the polyesteramide composite nanofiltration membrane according to claim 5, characterized in that: The concentration of small alcohol amine molecules in the aqueous phase mixed monomer solution is 0.05 ~ 0.4 w / v, and the concentration of polyamines is 0.01 ~ 0.05 w / v; the concentration of polyacrylamide compounds in the organic phase monomer solution is 0.05 ~ 0.15 w / v.
7. The method for preparing the polyesteramide composite nanofiltration membrane according to claim 5, characterized in that: In step S4, the nonpolar organic solvent is at least one of n-hexane, cyclohexane, n-heptane, and n-octane.
8. The method for preparing the polyesteramide composite nanofiltration membrane according to claim 5, characterized in that: In step S3, the interfacial polymerization reaction time is 10 to 30 seconds, the reaction temperature is 20 to 30°C, and the relative humidity of the environment during the reaction is 35 to 45%.
9. The method for preparing the polyesteramide composite nanofiltration membrane according to claim 5, characterized in that: In step S4, the heat treatment temperature is 40-60℃ and the heat treatment time is 2-5 minutes.