Preparation method of high-flux stable-selection anti-pollution nanofiltration membrane

Abstract

The invention provides a preparation method of a high-flux stable-selection anti-fouling nanofiltration membrane, which comprises the following steps: carrying out amination modification on a nano material by an activation method to prepare a modified nano material; piperazine, an acid absorbent and the modified nano material are added into deionized water to be mixed, and a water phase solution is prepared; the preparation method comprises the following steps: mixing trimesoyl chloride and normal hexane to prepare an organic phase solution; immersing the polyethersulfone-based membrane into the water phase solution, draining, inversely immersing into the organic phase solution, and carrying out interfacial polymerization reaction to generate a polyamide layer to obtain a composite membrane; and then carrying out post-treatment on the composite membrane to obtain the composite membrane. The membrane has high permeability, high selectivity and strong anti-pollution performance.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane separation, and in particular to a method for preparing a high-pass stable selection anti-fouling nanofiltration membrane. Background Art

[0002] In recent years, global climate change and intensified human activities have exacerbated water shortages, making them a pressing issue for countries around the world. In some regions, farmland is severely salinized, freshwater resources are scarce, and brackish water resources are relatively abundant. In these circumstances, efficient brackish water desalination has become a crucial approach to alleviating freshwater shortages. Membrane separation technology, with its advantages of high separation precision, ease of operation, and environmental friendliness, has gained widespread application in the brackish water sector. Common membrane separation technologies include reverse osmosis, nanofiltration, electrodialysis, forward osmosis, and membrane distillation.

[0003] Among them, nanofiltration membrane is a pressure-driven membrane separation technology between ultrafiltration and reverse osmosis. Its working principle combines the pore size screening effect, charge repulsion and dissolution diffusion mechanism, and can selectively separate different substances. In the process of brackish water desalination, nanofiltration membrane has shown unique advantages. It can not only remove hardness ions (such as Ca2+) in water in a targeted manner, but also remove the ions in the water. 2+ Mg 2+ ), heavy metal ions (such as Pb 2+ 、Cu 2+ ) and organic matter (such as humic acid, pesticides), and can also retain monovalent ions (such as Na + 、Cl - ), to avoid excessive desalination.

[0004] From a comprehensive technical and economic perspective, nanofiltration membranes offer significant advantages in brackish water desalination, particularly for sulfate-containing water and small- to medium-sized projects. With continued innovation in materials science and related support, the market share of nanofiltration membranes is expected to gradually expand. However, current nanofiltration membrane technology still faces several challenges. For monovalent and divalent ion separation systems, the development of highly efficient ion / water separation nanofiltration membranes is necessary to achieve high-performance salt separation, thereby optimizing production processes and reducing production costs. Furthermore, high-salinity water treatment and membrane fouling control are currently bottlenecks that require urgent breakthroughs. To address these issues, nanohybrid technology has emerged in recent years. However, existing nanohybrid technologies currently suffer from issues such as poor nanomaterial dispersion uniformity and weak interfacial bonding, which severely limit their industrial application.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The first purpose of the present invention is to provide a method for preparing a high-pass, stable and anti-fouling nanofiltration membrane. The method is simple to operate and realizes the efficient construction of an ultra-thin polyamide layer through the coordinated regulation of the uniform dispersion of amino nanomaterials and inverted interface polymerization technology. At the same time, combined with heat treatment to strengthen the cross-linking structure, the separation performance and anti-fouling ability are significantly improved while ensuring the stability of the membrane.

[0007] The second object of the present invention is to provide a high-pass stable anti-fouling nanofiltration membrane prepared by the above-mentioned preparation method of the high-pass stable anti-fouling nanofiltration membrane, which has high permeability, high selectivity, strong anti-fouling properties and stability.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A method for preparing a high-pass stable and anti-fouling nanofiltration membrane comprises the following steps: The nanomaterial is modified by amino modification through an activation method to prepare a modified nanomaterial; piperazine, an acid absorbent and modified nanomaterials are added into deionized water and mixed to prepare an aqueous solution; Mixing trimesoyl chloride and n-hexane to prepare an organic phase solution; The polyethersulfone-based membrane is immersed in an aqueous solution, drained, and then immersed in an organic solution upside down to perform an interfacial polymerization reaction to generate a polyamide layer to obtain a composite membrane; Then the composite membrane is post-treated to obtain the composite membrane.

[0009] Preferably, as a further embodiment, the nanomaterial is any one of MOFs material and GO.

[0010] Preferably, as a further embodiment, the MOFs material is any one of ZIF-8, HKUST-1, and UiO-66; Preferably, the MOFs material is ZIF-8.

[0011] Preferably, as a further embodiment, the mass ratio of the piperazine, the acid absorbent and the modified nanomaterial is (0.5-1.5): (0.1-1.0): (0.1-1.0).

[0012] Preferably, as a further embodiment, the concentration of trimesoyl chloride in the organic phase solution is 0.1-0.5 wt %.

[0013] Preferably, as a further embodiment, the residence time of the polyethersulfone-based membrane immersed in the aqueous solution is controlled to be 2-3 minutes.

[0014] Preferably, as a further embodiment, the residence time of immersion in the organic phase solution is controlled to be 0.5-1 min.

[0015] Preferably, as a further embodiment, the post-treatment is heating at 60-100° C. for 6-10 minutes.

[0016] Preferably, as a further embodiment, the mixing time for preparing the aqueous phase solution is 28-32 minutes.

[0017] In the present invention, the amino modification of nanomaterials can enhance the MOF S (metal material framework), GO (graphene oxide) nanomaterials in the aqueous phase to prevent agglomeration, while also providing amino sites to promote covalent exchange with piperazine and optimize the network structure of the polyamide layer. S ZIF-8 and other materials are preferred because their porous structure improves membrane water flux, while amino modification further enhances the material's hydrophilicity and interfacial stability. GO's unique two-dimensional lamellar structure allows for the construction of subnanometer-scale water channels within the polyamide layer. Furthermore, the abundant oxygen-containing groups on its surface, after amino modification, significantly enhance hydrophilicity, enabling the introduction of quaternary ammonium antibacterial groups, synergistically achieving both high flux and strong antifouling properties. The mass ratios of the aqueous solution components are controlled within a certain range to synergistically guarantee the performance of interfacial polymerization. Acidic absorbents such as triethylamine neutralize the interfacial polymerization byproduct, HCl, preventing localized pH drops that can lead to reaction stagnation and ensuring polymerization uniformity. Excessive piperazine concentrations can lead to excessively thick polyamide layers, reducing flux, while too low concentrations can result in insufficient crosslinking, impacting selectivity. Modification of the modified nanomaterial enhances the mechanical strength of the polyamide layer through the nanobridge effect. Simultaneously, the microporous structure of MOFs provides molecular-scale water channels, synergistically enhancing flux. The low concentration of trimesoyl chloride in the organic phase is designed to control reaction kinetics. Low concentrations can slow down the rate of interfacial polymerization and promote the formation of an ultra-thin and dense polyamide layer (thickness <50nm), thereby achieving a significant increase in water flux while ensuring a high retention rate, and achieving a balance between high selectivity and low mass transfer resistance. The interfacial polymerization technology uses a polyethersulfone base membrane that is first immersed in the aqueous phase and then inverted and immersed in the organic phase. This avoids the uneven thickness problem caused by the loss of the aqueous phase in the traditional upright method, allowing the aqueous phase to stably adhere to form a more uniform polyamide layer. The residence time of the base membrane immersed in the aqueous phase and the organic phase is controlled to prevent excessive or short time from affecting the performance of the composite membrane. Post-treatment uses heating to promote further cross-linking of unreacted groups, enhance the chemical stability of the polyamide layer to extend its pH range from 2 to 12, and eliminate interfacial defects to improve anti-fouling properties.

[0018] In addition to providing a high-pass, stable, and anti-fouling nanofiltration membrane, the present invention also provides a high-pass, stable, and anti-fouling nanofiltration membrane prepared by the above preparation method, which has high permeability, high selectivity, strong anti-fouling properties, and stability.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a high-flux, stable and anti-fouling nanofiltration membrane. This method breaks through the shackles of "high retention must sacrifice flux" of traditional membranes through the synergistic effect of uniform dispersion of amino-modified nanomaterials, inverted interface polymerization and precise heat treatment process; the post-treatment thermal cross-linking significantly improves the chemical stability of the nanofiltration membrane.

[0020] The present invention provides a high-flux, stable, and anti-fouling nanofiltration membrane prepared by the above-mentioned preparation method. The membrane has a three-dimensional performance breakthrough of "high flux, high selectivity, and strong anti-fouling". The water flux is increased by 50% to 100% compared with traditional nanofiltration membranes, and the mass transfer resistance is significantly reduced; the retention rate of divalent salts is >98%, and the retention rate of monovalent salts is <50%, achieving selective retention of minerals in brackish water; more importantly, the dual anti-fouling mechanism of hydrophilicity and quaternary ammonium salt groups on the surface of the membrane effectively inhibits the contamination of organic matter and microorganisms, maintaining the long-term stability and efficient operation capability of the membrane. Moreover, it can operate for a long time without performance degradation in strong acid and strong alkaline environments, and is particularly suitable for complex systems such as high-salt wastewater and antibiotic wastewater. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0022] Example 1 GO was prepared by the Hummers method, and the obtained GO was subjected to ultrasonic exfoliation treatment, that is, the energy of ultrasound was used in deionized water to separate the graphene oxide layers to obtain single-layer GO nanosheets.

[0023] The obtained GO nanosheets were dispersed in a solution containing EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) and NHS (N-hydroxysuccinimide) to activate the carboxyl groups on the surface of the GO nanosheets; then ethylenediamine was added and the reaction was stirred at room temperature for 24 hours to obtain amino-modified GO.

[0024] Weigh 0.8 g of piperazine, 0.3 g of triethylamine, and 0.3 g of amino GO, dissolve them in deionized water, and stir them thoroughly for 30 min to evenly disperse the components to prepare an aqueous phase solution for later use.

[0025] Trimesoyl chloride (TMC) and n-hexane were mixed to obtain a TMC solution (0.3 wt %), namely, an organic phase solution.

[0026] The polyethersulfone-based membrane was immersed in the prepared aqueous solution for 2 minutes. Subsequently, the polyethersulfone-based membrane was inverted and quickly immersed in the organic phase solution for 0.5 minutes, so that the piperazine in the aqueous phase and the TMC in the organic phase underwent interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0027] The composite membrane is placed in an environment of 80° C. for 8 minutes for heat treatment to obtain the composite membrane.

[0028] Example 2 Zinc acetate and 2-methylimidazole were dissolved in methanol, ultrasonicated for 1 h, and ZIF-8 nanosheets were collected by centrifugation.

[0029] The obtained ZIF-8 nanosheets were dispersed in a solution containing EDC and NHS, and then piperazine solution was added and stirred at room temperature for 12 hours to obtain amino-modified ZIF-8.

[0030] Weigh 1 g of piperazine, 0.5 g of triethylamine, and 0.5 g of amino-ZIF-8, dissolve them in deionized water, stir thoroughly for 30 min to evenly disperse the components, and prepare an aqueous phase solution for later use.

[0031] Trimesoyl chloride (TMC) and n-hexane were mixed to obtain a TMC solution (0.3 wt %), namely, an organic phase solution.

[0032] The polyethersulfone-based membrane was immersed in the prepared aqueous solution for 3 minutes. Subsequently, the polyethersulfone-based membrane was inverted and quickly immersed in the organic phase solution for 1 minute, so that the piperazine in the aqueous phase and the TMC in the organic phase underwent interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0033] The composite membrane is placed in an environment of 80° C. for 10 minutes for heat treatment to obtain the composite membrane.

[0034] Example 3 Zirconium chloride and terephthalic acid were dissolved in N,N-dimethylformamide, ultrasonicated for 1 h, and then UiO-66 nanosheets were collected by centrifugation.

[0035] The obtained UiO-66 nanosheets were dispersed in a solution containing EDC and NHS, and then piperazine solution was added and stirred at room temperature for 12 hours to obtain amino UiO-66.

[0036] Weigh 0.5 g of piperazine, 0.1 g of triethylamine, and 0.1 g of amino UiO-66, dissolve them in deionized water, stir thoroughly for 28 minutes to evenly disperse the components, and prepare an aqueous phase solution for use.

[0037] Trimesoyl chloride (TMC) and n-hexane were mixed to obtain a TMC solution (0.1 wt %), namely, an organic phase solution.

[0038] The polyethersulfone-based membrane was immersed in the prepared aqueous solution for 2.5 minutes. Subsequently, the polyethersulfone-based membrane was inverted and quickly immersed in the organic phase solution for 1 minute, so that the piperazine in the aqueous phase and the TMC in the organic phase underwent interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0039] The composite membrane is placed in an environment of 60° C. for heat treatment for 6 minutes to obtain the composite membrane.

[0040] Example 4 Copper acetate trihydrate and trimesic acid were dissolved in ethanol, sonicated for 1 h, and then the HKUST-1 nanosheets were collected by centrifugation.

[0041] The obtained HKUST-1 nanosheets were dispersed in a solution containing EDC and NHS, and then piperazine solution was added and stirred at room temperature for 12 hours to obtain amino-modified HKUST-1.

[0042] 1.5 g of piperazine, 1 g of triethylamine, and 1 g of amino-HKUST-18 were weighed and dissolved in deionized water. The mixture was stirred for 32 minutes to uniformly disperse the components, and an aqueous phase solution was prepared for use.

[0043] Trimesoyl chloride (TMC) and n-hexane were mixed to obtain a TMC solution (0.5 wt %), namely, an organic phase solution.

[0044] The polyethersulfone-based membrane was immersed in the prepared aqueous solution for 3 minutes. Subsequently, the polyethersulfone-based membrane was inverted and quickly immersed in the organic phase solution for 1 minute, so that the piperazine in the aqueous phase and the TMC in the organic phase underwent interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0045] The composite membrane is placed in an environment of 80° C. for 9 minutes for heat treatment to obtain the composite membrane.

[0046] Example 5 Zinc acetate and 2-methylimidazole were dissolved in methanol, ultrasonicated for 1 h, and ZIF-8 nanosheets were collected by centrifugation.

[0047] The obtained ZIF-8 nanosheets were dispersed in a solution containing EDC and NHS, and then piperazine solution was added and stirred at room temperature for 12 hours to obtain amino-modified ZIF-8.

[0048] Weigh 1.5 g of piperazine, 1 g of triethylamine, and 1 g of amino-ZIF-8, dissolve them in deionized water, stir thoroughly for 30 min to evenly disperse the components, and prepare an aqueous phase solution for later use.

[0049] Trimesoyl chloride (TMC) and n-hexane were mixed to obtain a TMC solution (0.5 wt %), namely, an organic phase solution.

[0050] The polyethersulfone-based membrane was immersed in the prepared aqueous solution for 3 minutes. Subsequently, the polyethersulfone-based membrane was inverted and quickly immersed in the organic phase solution for 1 minute, so that the piperazine in the aqueous phase and the TMC in the organic phase underwent interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0051] The composite membrane is placed in an environment of 80° C. for 10 minutes for heat treatment to obtain the composite membrane.

[0052] Example 6 Specific implementation method: The same as Example 1, only 37g of piperazine, 16g of triethylamine, and 17g of amino ZIF-8 were weighed and dissolved in deionized water, and stirred thoroughly for 30min to uniformly disperse the components to prepare an aqueous solution for use.

[0053] Comparative Example 1 The specific implementation method is consistent with Example 1. Only the polyethersulfone-based membrane is immersed in the prepared aqueous phase solution and maintained for 10 minutes. Subsequently, the polyethersulfone-based membrane is inverted and quickly immersed in the organic phase solution and maintained for 7 minutes, so that the piperazine in the aqueous phase and the TMC in the organic phase undergo interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0054] Comparative Example 2 The specific implementation method is consistent with Example 1. Only the polyethersulfone-based membrane is immersed in the prepared aqueous phase solution and maintained for 10 minutes. Subsequently, the polyethersulfone-based membrane is inverted and quickly immersed in the organic phase solution and maintained for 7 minutes, so that the piperazine in the aqueous phase and the TMC in the organic phase undergo interfacial polymerization reaction on the surface of the polyethersulfone-based membrane to form a polyamide layer to obtain a composite membrane.

[0055] Comparative Example 3 It uses the common polysulfone nanofiltration membrane on the market.

[0056] Experimental Example 1 The nanofiltration membranes prepared in Examples 1-6 and Comparative Examples 1-3 were operated in a brackish water desalination system for 32 days, and relevant performance tests were performed. The test results are shown in Table 1.

[0057] Table 1. Test results

[0058] Based on the above data, we can draw the following conclusions: Compared with the comparative example, the nanofiltration membranes prepared in the present invention under the following preparation conditions were found by optimizing the type of MOFs and finding that ZIF-8 performed best in terms of hydrophilicity and interfacial binding strength, that the membrane performance was best when the nanomaterial concentration was 0.5%, and that the interfacial polymerization time was optimal at 3 minutes. These membranes showed significant advantages in terms of water flux, Na2SO4 retention rate, and BSA anti-fouling rate. Among them, there was also one using GO as the nanomaterial, which effectively reduced the mass transfer resistance. The water flux of the nanofiltration membranes prepared in Examples 1 to 6 was higher than that of the comparative example, with the highest reaching 42 L / (m²·h·bar); the Na2SO4 retention rate was also generally higher, with the lowest being 96.3% and the highest reaching 99.2%; the BSA anti-fouling rate was also significantly better than that of the comparative example, with the highest reaching 95%. In addition, these composite nanofiltration membranes also performed well in terms of operational stability, and were able to operate stably for more than 30 days, far exceeding the number of days of the comparative example. These results demonstrate that by utilizing a nanohybrid design, inverted polymerization, heat treatment, and controlled reaction time, the present invention has produced a high-throughput, stable, and anti-fouling nanofiltration membrane with high flux, high rejection rate, high anti-fouling rate, and good operational stability. This provides a more effective solution for brackish water desalination.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-pass stable and anti-fouling nanofiltration membrane, characterized in that: The following steps are involved: The nanomaterial is modified by amino modification through an activation method to prepare a modified nanomaterial; piperazine, an acid absorbent and modified nanomaterials are added into deionized water and mixed to prepare an aqueous solution; Mixing trimesoyl chloride and n-hexane to prepare an organic phase solution; The polyethersulfone-based membrane is immersed in an aqueous solution, drained, and then immersed in an organic solution upside down to perform an interfacial polymerization reaction to generate a polyamide layer to obtain a composite membrane; Then the composite membrane is post-treated to obtain the composite membrane.

2. The method for preparing a high-pass stable anti-fouling nanofiltration membrane according to claim 1, characterized in that: The nanomaterial is any one of MOFs material and GO.

3. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 2, characterized in that: The MOFs material is any one of ZIF-8, HKUST-1, and UiO-66; Preferably, the MOFs material is ZIF-8.

4. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 1, wherein: The mass ratio of the piperazine, the acid absorbent and the modified nanomaterial is (0.5-1.5): (0.1-1.0): (0.1-1.0).

5. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 1, wherein: The concentration of trimesoyl chloride in the organic phase solution is 0.1-0.5 wt %.

6. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 1, characterized in that: The residence time of the polyethersulfone-based membrane immersed in the aqueous solution is controlled to be 2-3 minutes.

7. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 1, characterized in that: The residence time of immersion in the organic phase solution is controlled to be 0.5-1 min.

8. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 1, characterized in that: The post-treatment is heating at 60-100° C. for 6-10 minutes.

9. The method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to claim 1, characterized in that: The mixing time for preparing the aqueous phase solution was 28-32 minutes.

10. A high-pass stable selection anti-fouling nanofiltration membrane, characterized in that: The membrane is prepared by the method for preparing a high-pass stable and anti-fouling nanofiltration membrane according to any one of claims 1 to 9.

Images