A novel high-flux high-selectivity terguride base polyamide acid-resistant nanofiltration membrane and a preparation method thereof

Abstract

The application discloses a novel high-flux high-selectivity terleg base polyamide acid-resistant nanofiltration membrane and a preparation method thereof. Firstly, a self-made novel 3,3'-di(4-aminophenyl)-terleg base (referred to as DAPTB) monomer is added into a polyether sulfone (PES) casting solution, and after uniform stirring and standing and defoaming, the PES supporting bottom membrane rich in the DAPTB on the surface is prepared by non-solvent induced phase inversion, and then the terleg base polyamide acid-resistant nanofiltration membrane is prepared by interfacial polymerization with a multi-acid chloride. Based on the flexibility and hydrophobicity of the biphenyl unit in the DAPTB monomer molecule, and the special rigidity, hydrophilicity and acid-binding property of the terleg base unit, the acid resistance, permeability and separation selectivity of the prepared terleg base nanofiltration membrane are simultaneously improved, the organic matter and inorganic salt can be effectively separated under strong acidic conditions, and the application of the nanofiltration technology in the fields of acid wastewater resource treatment and acid material liquid separation and concentration is expected to be promoted.

Description

Technical Field

[0001] This invention relates to the field of polymer separation membrane technology for water treatment, and specifically to a method for preparing a novel Teleg base polyamide acid-resistant nanofiltration membrane. Background Technology

[0002] Acidic wastewater mainly originates from industries such as electroplating, metallurgy, textile printing and dyeing, and food processing. It contains large amounts of inorganic acids, heavy metal ions, and organic pollutants. Direct discharge can severely disrupt the ecological balance of aquatic bodies and lead to bioaccumulation through the food chain, harming human health. Nanofiltration (NF) is an emerging separation technology between ultrafiltration and reverse osmosis. Through the synergistic effect of size sieving and the Donnan effect, it selectively retains multivalent ions and large organic molecules (molecular weight 200–1000 Da) while allowing monovalent ions and small molecules to pass through, thus achieving the separation of monovalent and multivalent salts, and the separation of salts and organic matter. Compared to traditional chemical precipitation and biological wastewater treatment technologies, as well as traditional concentration technologies such as evaporation, distillation, and extraction, nanofiltration technology has advantages such as high efficiency, energy saving, ease of operation, and easy integration. Therefore, it has been widely used in wastewater resource recovery and clean industrial production processes.

[0003] Currently, the mainstream polypiperazine amide nanofiltration membranes on the market are mainly composed of a porous support layer and an active separation layer. However, the amide bonds (-NH-CO-) in the separation layer are prone to hydrolysis under strong acid conditions, which leads to a sharp decline in the membrane's separation performance and a significant reduction in its service life. This severely limits the application of nanofiltration technology in the field of acidic wastewater treatment. Therefore, it is urgent to develop high-performance acid-resistant nanofiltration membranes. In recent years, Zhang Suojiang et al. (Chemical Engineering Journal, 2022, 450: 137965) prepared an acid-resistant COF layer and a polysulfonamide layer sequentially on a PES support layer through in-situ interfacial polymerization, obtaining an acid-resistant composite nanofiltration membrane; patents (CN202011482126.9, CN202410615519.4, CN202211410595.9) prepared a series of acid-resistant nanofiltration membranes by polymerizing sulfonamide monomers or polyamine monomers with polyacrylamide chloride monomers or polysulfonamide chloride monomers; patent (CN202110880867.0) prepared an acid-resistant high-flux polyaryl ether composite nanofiltration membrane by interfacial polymerization using a non-planar conformation compound with at least two hydroxyl groups and an acid-binding agent as an aqueous solution and a triazine compound as an oil solution. While the above technologies can improve the acid resistance of nanofiltration membranes, they also face some challenges. For example, insufficient interfacial bonding of the COF layer can cause the separation layer of the nanofiltration membrane to peel off. The water flux of polysulfonamide nanofiltration membranes will decrease to a certain extent, while the retention rate of nanofiltration membranes based on non-planar conformations is relatively low. Summary of the Invention

[0004] The purpose of this invention is to overcome the application bottlenecks of conventional commercial polypiperazine amide nanofiltration membranes, such as insufficient acid resistance and low selectivity in organic / inorganic salt separation, and to develop a novel high-flux, high-selectivity telreg base-based polyamide nanofiltration membrane and its preparation method. The nanofiltration membrane is prepared by first adding a self-made 3,3'-di(4-aminophenyl)-telreg base (DAPTB) monomer to a polyethersulfone (PES) casting solution, stirring evenly, allowing it to stand and degas, and then coating it onto a nonwoven fabric to form a liquid film. This liquid film is then placed in a coagulation bath and subjected to a solvent-free, water-induced phase inversion to prepare a DAPTB-rich porous support substrate membrane. This substrate is then subjected to interfacial polymerization in a single-sided contact with an organic phase solution containing acyl chloride monomers. After the reaction is complete, the remaining organic phase solution is removed, and the membrane is air-dried and then heat-treated to obtain the final product. Because the DAPTB molecule contains a telreg base with a unique rigid twisted structure and a long molecular chain, this gives the membrane excellent acid resistance, while simultaneously improving the membrane's water flux and dye / salt separation selectivity.

[0005] This invention proposes to dissolve DAPTB monomer and polyethersulfone together in a polar solution to obtain a casting solution, and then to uniformly enrich DAPTB onto the surface of the polyethersulfone substrate membrane through a non-solvent-induced phase transformation. Finally, a novel Teleg base polyamide nanofiltration membrane is prepared by in-situ interfacial polymerization.

[0006] A novel high-flux, high-selectivity, telage-based polyamide acid-resistant nanofiltration membrane is prepared according to the following method:

[0007] (1) A certain amount of DAPTB monomer is added to the polyethersulfone casting solution and stirred continuously until it is completely homogeneous. Then it is allowed to stand to remove bubbles, and finally a uniform polyethersulfone casting solution containing DAPTB and free of bubbles is obtained.

[0008] (2) The casting solution obtained in step (1) is uniformly coated onto the surface of the nonwoven fabric with a scraper. Then, the nonwoven fabric with the casting solution attached is quickly immersed in the coagulation bath for non-solvent-water induced phase transformation. Then, the membrane surface is rinsed with deionized water to remove impurities and then air-dried to obtain a polyethersulfone support substrate with DAPTB monomers uniformly distributed on the surface.

[0009] (3) The organic phase solution containing polyacrylamide monomers is uniformly poured onto the surface of the polyethersulfone support membrane containing DAPTB monomers that was air-dried in step (2). After reacting for a period of time, the remaining organic phase solution is removed. Then the membrane is heat-treated for a period of time, and then the resulting membrane is immersed and washed in deionized water to finally obtain a high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane;

[0010] Furthermore, in step (1), the stirring temperature is 20-60°C, the stirring time is 10-24h, and the standing degassing time is 10-24h.

[0011] Further, in step (1), the total content of DAPTB monomer in the casting solution is 0.1–3 wt%. Preferably, the weight percentages of DAPTB monomer, polyethersulfone, and polar solvent in the casting solution, calculated as 100% by weight, are as follows:

[0012] DAPTB monomer 0.1–1.5 wt%;

[0013] Polyethersulfone 10-20 wt%;

[0014] Balance of polar solvent.

[0015] Further, the polar solvent in step (1) is one or any combination of two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide or N-methylpyrrolidone; the polyacrylamide monomer in step (3) is one or any combination of two of isophthaloyl chloride, 1,3,5-triazine-2,4,6-triacryl chloride, adipic acid chloride, biphenyltetracarboxylic acid chloride, pyromellitic acid tricarboxylic acid chloride or phthaloyl chloride; the organic solvent in the organic phase solution of the polyacrylamide monomer in step (3) is one or any combination of multiple solvents such as solvent oil Isopar G, cyclohexane, n-hexane or n-heptane.

[0016] Furthermore, in step (2), the coagulation bath is pure water, and the time for the non-solvent-water induced phase transition is 30 to 300 s, preferably 30 to 90 s;

[0017] Furthermore, in step (2), the air-drying time is 10–60 min;

[0018] Further, in step (3), the concentration of polyacryl chloride monomer in the organic phase solution containing polyacryl chloride monomer is 0.01-0.35 wt%, preferably 0.05-0.25 wt%.

[0019] Furthermore, in step (3), the reaction time in the polyacrylamide chloride monomer solution is 30-300 s, preferably 60-120 s;

[0020] Furthermore, in step (3), the heat treatment temperature is 25-40°C and the time is 20-60 min.

[0021] This invention also proposes a novel high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane prepared by the above preparation method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention involves adding a novel, self-made telregane diamine monomer, DAPTB, to a casting solution. DAPTB is introduced into the polyamide separation layer via a coupling method of solvent-inducible phase inversion and in-situ interfacial polymerization, thereby producing a novel high-flux, high-selectivity telregane-based polyamide acid-resistant nanofiltration membrane. Compared to conventional piperazine amide nanofiltration membranes, this membrane, due to the presence of both biphenyl and telregane base structures in the self-made DAPTB monomer, exhibits enhanced acid resistance, permeability, and separation selectivity. Based on the specific flexibility and hydrophobicity of the biphenyl unit, and the unique rigidity, hydrophilicity, and acid-binding properties of the telregane base unit, the membrane's acid resistance, permeability, and separation selectivity are simultaneously improved. It can be effectively used for the efficient separation of organic matter and inorganic salts under strongly acidic conditions, demonstrating broad application prospects. Furthermore, since DAPTB is insoluble in the coagulation bath, it can be directly added to the casting solution to enrich the telegated base phenylenediamine monomer onto the surface of the supporting membrane via a solvent-inducible phase inversion method. This eliminates the need for aqueous phase preparation and dip coating steps, which simplifies the nanofiltration membrane preparation process, improves membrane production efficiency, reduces wastewater generation, lowers membrane production costs, and facilitates industrialization. Attached Figure Description

[0024] Figure 1 This is a chemical structure diagram of the monomer of 3,3'-bis(4-aminophenyl)-teleg base (DAPTB) described in this invention.

[0025] Figure 2 The Fourier attenuated total reflectance infrared (ATR-FTIR) spectra of Teleg base polyamide nanofiltration membranes containing different DAPTB monomer concentrations as described in this invention, including DAPTB4-TMC membranes, DAPTB8-TMC membranes, as well as conventional polypiperazine amide nanofiltration membranes PIP-TMC and blank PES porous support substrates.

[0026] Figure 3 The images are SEM images of the novel Teleg base polyamide acid-resistant nanofiltration membrane (DAPTB4-TMC membrane) and the conventional polypiperazine amide nanofiltration membrane (PIP-TMC) described in this invention after being immersed in 20wt% H2SO4 solution for different times. Detailed Implementation

[0027] The following detailed description, in conjunction with specific embodiments, further clarifies the invention. However, the scope and content of this patent are not limited to the following embodiments. Any variations or implementations that do not depart from the scope and content of this invention should be included within the technical scope of this invention.

[0028] Example 1:

[0029] ① Preparation of casting solution

[0030] 0.4 wt% DAPTB, 16.2 wt% polyethersulfone and dimethyl sulfoxide were added to a round-bottom flask, stirred at 25 °C for 12 h and allowed to stand for 12 h to remove bubbles, resulting in a uniform, bubble-free casting solution.

[0031] ② Non-solvent-induced phase transformation

[0032] The casting solution was poured evenly and quickly onto the nonwoven fabric, and then scraped into a uniform liquid film using a 200μm doctor blade. The nonwoven fabric coated with the liquid film was then immersed in a 2L coagulation bath aqueous solution for a non-solvent-induced phase transformation for 60s to obtain the base film.

[0033] ③ In-situ interface aggregation

[0034] A 0.15 w / v% hexane solution containing 1,3,5-trimethylbenzene chloride was uniformly and rapidly poured onto the surface of an air-dried PES porous support membrane for in-situ interfacial polymerization for 120 s. Excess organic phase solution was removed from the membrane surface, and then the membrane was heat-treated at 30 °C for 30 min to obtain a polyamide nanofiltration membrane containing telage bases, denoted as DAPTB4-TMC membrane.

[0035] Figure 1 This is a chemical structure diagram of the 3,3'-bis(4-aminophenyl)-teleg base (DAPTB) monomer used in the preparation process of this invention. The synthesis method of the 3,3'-bis(4-aminophenyl)-teleg base includes the following steps:

[0036] Step 1: The raw material 4-bromoaniline (1) was dispersed in trifluoroacetic acid and reacted to obtain 3,3'-dibromo-teleg base. Then, it was added to the solvent tetrahydrofuran (THF), and an organolithium reagent was added dropwise to react for a certain period of time. Subsequently, borate ester compounds were added dropwise to further react. After the reaction was completed, ice water was added to quench the reaction, and then dichloromethane was added for extraction. The upper aqueous phase was taken and acidified with hydrochloric acid to produce a white precipitate. After filtration and drying, the intermediate 3,3'-diboron ester-teleg base (2) was obtained.

[0037]

[0038] Step 2: The intermediate 3,3'-diboronate-teleg base obtained in Step 1, p-nitrobenzene compounds, metal catalyst, ligand, base and water are uniformly dispersed in a polar solvent and stirred under inert conditions to obtain intermediate 3,3'-bis(4-nitrophenyl)-teleg base (3).

[0039]

[0040] Step 3: The intermediate 3,3'-bis(4-nitrophenyl)-Tellerg base and palladium on carbon obtained in Step 2 are dispersed in an alcohol reagent, and the mixture is reduced by hydrazine hydrate under heating conditions and then post-treated to obtain the final product 3,3'-bis(4-aminophenyl)-Tellerg base (4), namely the Terlerg base diamine monomer DAPTB.

[0041]

[0042] For details regarding the preparation method of DAPTB monomer, please refer to the Chinese invention patent application number 2025101894495, which will not be elaborated here.

[0043] Example 2:

[0044] The concentration of the diamine monomer DAPTB in step ① was changed from 0.4 wt% to 0.2 wt%, and other operations were the same as in Example 1. The membrane performance data are listed in Table 1.

[0045] Example 3:

[0046] The concentration of the diamine monomer DAPTB in step ① was changed from 0.4 wt% to 0.6 wt%, and other operations were the same as in Example 1. The membrane performance data are listed in Table 1.

[0047] Example 4:

[0048] The concentration of the diamine monomer DAPTB in step ① was changed from 0.4 wt% to 0.8 wt%, and other operations were the same as in Example 1. A nanofiltration membrane was prepared and designated as DAPTB8-TMC membrane. The performance data of the prepared membrane are listed in Table 1.

[0049] Comparative Example 1:

[0050] Replace the diamine monomer DAPTB in step ① with piperazine, and follow the same procedures as in Example 1. The resulting membrane is denoted as PIP-TMC membrane. The membrane was used for comparative testing, and the performance data are listed in Tables 3-5.

[0051] Table 1: Comparison of separation performance of nanofiltration membranes prepared in Examples 1-4

[0052]

[0053] Note: Table 1 refers to the mixed feed solution of Chrome Black T and sodium sulfate.

[0054] Table 2: Comparison of separation performance of nanofiltration membranes prepared in Examples 1-4

[0055]

[0056] Note: Table 2 refers to the mixed feed solution of Congo red and sodium sulfate.

[0057] Table 3: Changes in the rejection rates of Eriochrome Black T and sodium sulfate of the nanofiltration membrane prepared in Example 1 after immersion in strong acid for different times.

[0058] 0 99.8 7.17 3 99.92 6.06 9 99.99 2.91 15 99.99 3.48 30 99.99 5.05 36 99.78 7.16 48 98.95 6.25 60 99.52 5.28

[0059] Note: The strong acid is a 20wt% H2SO4 solution.

[0060] Table 4: Changes in the retention rates of Eriochrome Black T and sodium sulfate of the nanofiltration membrane prepared in Comparative Example 1 after immersion in strong acid for different times.

[0061] 0 99.99 73.29 3 99.99 18.1 9 99.99 5.02 15 99.99 6.12 30 99.72 6.71 36 98.88 6.36 48 98.17 5.42 60 97.53 5.69

[0062] Note: The strong acid is a 20wt% H2SO4 solution.

[0063] Table 5: Water flux (Lm) of nanofiltration membranes prepared in Example 1 and Comparative Example 1 after immersion in strong acid for different times. - 2 .h -1 .bar -1 Changes

[0064] 0 25.15 5.76 3 30.78 10.36 9 28.02 21.36 15 32.92 26.88 30 24.66 21.97 36 24.36 23.85 48 20.01 22.61 60 23.42 24.36.

[0065] Based on the above results, compared with conventional piperazine amide nanofiltration membranes, the Teleg base-based acid-resistant nanofiltration membrane prepared in this invention exhibits higher water flux, excellent dye / divalent salt separation selectivity, and strong acid resistance. After immersion in 20 wt% H₂SO₄ solution for 60 days, the retention of Eriochrome Black T and sodium sulfate in the polypiperazine amide nanofiltration membrane significantly decreased, and the membrane surface was clearly damaged. In contrast, the novel Teleg base-based polyamide nanofiltration membrane prepared based on DAPTB maintained stable retention of Eriochrome Black T and sodium sulfate throughout the 60-day immersion in 20 wt% sulfuric acid solution. The separation selectivity and flux of Eriochrome Black T / sodium sulfate remained stable and excellent, and the membrane structure remained intact. Therefore, the high-flux, high-selectivity Teleg base-based polyamide acid-resistant nanofiltration membrane prepared in this invention has great application potential in the treatment of acidic, high-salt organic wastewater, pharmaceutical separation and concentration, food processing, and other clean production fields.

[0066] Figure 2 The figures show Fourier attenuated total reflectance infrared (ATR-FTIR) spectra of the DAPTB-based polyamide nanofiltration membranes containing different DAPTB monomer concentrations as described in this invention, including DAPTB4-TMC and DAPTB8-TMC membranes, as well as the conventional polypiperazine amide nanofiltration membrane PIP-TMC and a blank PES porous support substrate. The chemical structure of the DAPTB-based nanofiltration (NF) membranes was analyzed using ATR-FTIR, and compared with that of the polyethersulfone support membrane (M... PES ) and conventional polypiperazine amide nanofiltration membranes (M PIP-TMCFor comparison. In the spectrum, 3376cm -1 The absorption peak at this point is attributed to the NH asymmetric stretching vibration of the residual unreacted free amino group (-NH2) in the DAPTB monomer, indicating that M after the interfacial polymerization reaction... DAPTB-TMC Uncrosslinked DAPTB molecules exist on the membrane surface. 1678 cm⁻¹ -1 The absorption peak at 1526 cm⁻¹ corresponds to the amide I band (stretching vibration of C=O) in the separation layer. -1 The absorption peaks at 1526 cm⁻¹ correspond to the amide II band (coupling of NH in-plane bending vibration and CN stretching vibration). The appearance of these characteristic peaks indicates that DAPTB and TMC formed a cross-linked polyamide structure through interfacial polymerization. Furthermore, as the concentration of the aqueous monomer DAPTB increased from 0.4 wt% to 0.8 wt%, the absorption peaks at 1526 cm⁻¹ increased. -1 With 1678cm -1 The intensity of the characteristic peaks increased accordingly, indicating that the degree of crosslinking of the release layer increased with the increase of monomer feed. No amide characteristic peaks were observed in the spectrum of the pure PES support layer, further confirming the existence of the polyamide release layer and its unique chemical structure.

[0067] Figure 3 The images are SEM images of the novel Teleg base polyamide acid-resistant nanofiltration membrane (DAPTB4-TMC) and the conventional polypiperazine amide nanofiltration membrane (PIP-TMC) described in this invention after being immersed in 20wt% H2SO4 solution for different times. Figure 3 M was shown PIP-TMC Membrane and M DAPTB4-TMC The surface morphology of the membrane before and after immersion in sulfuric acid solution. A comparison shows that after immersion in acid for 30 days, the piperazine membrane exhibits obvious nanoscale pores and localized structural collapse. Meanwhile, M... DAPTB4-TMC The membrane maintained a smooth and dense surface morphology under the same conditions (30 days of acid immersion); even after 60 days of immersion, the membrane surface mainly showed an increase in nodule size, but no obvious pores were observed. This phenomenon indicates that the rigid "V"-shaped molecular structure of the DAPTB monomer effectively inhibited the hydrolysis reaction of amide bonds under acidic conditions, inducing only limited swelling, thereby maintaining the integrity of the membrane structure.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a high-flux, high-selectivity, telage base polyamide acid-resistant nanofiltration membrane, characterized in that, Specifically, the steps include the following: (1) Add DAPTB monomer to polyethersulfone casting solution and stir continuously until completely homogeneous. Then let stand to remove bubbles and finally obtain a uniform polyethersulfone casting solution containing DAPTB without bubbles. The DAPTB monomer is 3,3'-bis(4-aminophenyl)-teregol base. (2) The casting solution obtained in step (1) is uniformly coated onto the surface of the nonwoven fabric with a scraper. Then, the nonwoven fabric with the casting solution attached is quickly immersed in the coagulation bath for non-solvent-water induced phase transformation. Then, the membrane surface is rinsed with deionized water to remove impurities. After that, it is air-dried to obtain a polyethersulfone support substrate with DAPTB monomers uniformly distributed on the surface. (3) Pour the organic phase solution containing polyacrylamide monomers evenly onto the surface of the polyethersulfone support substrate membrane containing DAPTB monomers that was air-dried in step (2). After reacting for a period of time, remove the remaining organic phase solution. Then heat-treat the membrane for a period of time. After that, soak and wash the obtained membrane in deionized water to finally obtain a high-flux and high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane. The structural formula of the 3,3'-bis(4-aminophenyl)-teleg base monomer is as follows: ； In step (1), the weight percentages of DAPTB monomer, polyethersulfone, and polar solvent in the casting solution are calculated at 100% by weight as follows: DAPTB monomer 0.1~3wt%; Polyethersulfone 10~20wt%; Balance of polar solvent; In step (3), the polyacryl chloride monomer is one or any combination of two of isophthaloyl chloride, 1,3,5-triazine-2,4,6-triacryl chloride, adipyl chloride, biphenyltetracarboxylic chloride, pyromellitic tricarboxylic chloride or phthaloyl chloride, and the concentration of polyacryl chloride monomer in the organic phase solution containing polyacryl chloride monomer is 0.01~0.35wt%.

2. The method for preparing the high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane as described in claim 1, characterized in that: In step (1), the mixture is stirred at 20-60℃ for 10-24 hours and then allowed to stand for 10-24 hours for degassing treatment.

3. The method for preparing the high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane as described in claim 1, characterized in that: The polar solvent is one or any combination of two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone.

4. The method for preparing the high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane as described in claim 1, characterized in that: In step (2), the coagulation bath is pure water, and the time for the non-solvent-water induced phase transition is 30~300s.

5. The method for preparing the high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane as described in claim 1, characterized in that: In step (2), the time for air drying after phase transformation is 10~60 min.

6. The method for preparing the high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane as described in claim 1, characterized in that: In step (3), the organic solvent in the organic phase solution of the polyacrylamide chloride monomer is one or any combination of Isopar G, cyclohexane, n-hexane or n-heptane.

7. The method for preparing the high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane as described in claim 1, characterized in that: In step (3), the reaction time in the polyacrylamide chloride monomer solution is 30~300s, the heat treatment temperature is 25~40℃, and the time is 20~60min.

8. A high-flux, high-selectivity Teleg base polyamide acid-resistant nanofiltration membrane prepared by the preparation method according to any one of claims 1 to 7.

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