A preparation method of an organic solvent nanofiltration membrane of a rigid-flexible dual network type IPN

Abstract

A method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN belongs to the field of membrane separation technology. The method includes: 1) dissolving aminated carbon quantum dots or triterpenoid amines containing a twisted structure and aromatic diacyl chlorides to obtain aqueous and oil-phase monomer solutions; using an ultrafiltration membrane as a support, the support is sequentially impregnated with the aqueous and oil-phase monomer solutions to construct a molecular layer with a porous rigid network I structure; 2) preparing organic solutions using an aliphatic amine as the first monomer and an aliphatic acyl chloride as the second monomer; immersing the support containing the porous rigid network I in the first monomer solution, then removing and washing it; then immersing the substrate in the second monomer solution, then removing and washing it, repeating this cycle a certain number of times, followed by heat treatment of the substrate to finally obtain the organic solvent nanofiltration membrane. The above preparation method produces a solvent-resistant nanofiltration membrane with high solvent flux, high separation accuracy, and strong long-term service stability.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically a method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network type IPN. Background Technology

[0002] In industries such as pharmaceuticals and fine chemicals, separation and purification are key links in the entire production process, accounting for 40-60% of total investment and energy consumption (Nature 532(2016)435–437), which is difficult to adapt to the economic development model of synergistic efficiency improvement through pollution reduction and carbon reduction. Compared with traditional thermal separation technologies (such as distillation, etc.), membrane separation technology can save about 60% of energy consumption (Chinese Engineering Science 24(2022)140-152), and has the characteristics of high separation efficiency, low energy consumption, and easy integration design. Coupling membrane separation technology with product separation and purification and solvent recovery processes can promote the optimization and upgrading of the chemical industry structure. Applying membrane separation technology to the separation and purification of materials in organic solvent systems to reduce energy consumption and achieve sustainable development is an inevitable trend. However, unlike water system applications, in organic solvent systems, membrane materials are required to have high permeation separation characteristics, strong solvent resistance, excellent pressure resistance and resistance to physical aging, and long service life. Ultra-thin membrane thickness, highly deformable micro / nano structures, good solvent resistance, uniform pore size, and high porosity are fundamental structural characteristics of membranes used in organic solvent separation systems. These structural features facilitate overcoming the limiting effect between permeability and rejection rate, and also ensure long-term stability under harsh environments. Traditional cross-linked aromatic polyamide (PA) membranes possess good separation accuracy and solvent resistance; however, PA's low glass transition temperature and high molecular chain flexibility result in low solvent flux, unstable pore structure, and poor long-term stability. This makes them unsuitable for current separation applications in the petroleum and chemical, pharmaceutical, and food industries. Summary of the Invention

[0003] To address the aforementioned problems in existing technologies, the present invention aims to design and provide a technical solution for preparing a rigid-flexible dual-network IPN organic solvent nanofiltration membrane. This method utilizes monomers with different rigid molecular cluster structures and flexible structures, employing stepwise interfacial polymerization and liquid-phase molecular layer deposition to construct rigid-flexible dual-network IPN PA membrane materials. It studies and solves key issues in membrane structure control, resulting in a solvent-resistant nanofiltration membrane with high solvent flux, high separation accuracy, and strong long-term service stability. This invention can be widely applied in industries such as petrochemicals, active biological component purification, and food processing, achieving efficient separation of chemical raw materials, extraction of active ingredients, and recovery of organic solvents. This invention helps overcome the limitations of current membrane materials' solvent resistance and stability in organic solvent systems, providing new ideas and options to replace traditional thermal-based separation technologies (such as distillation and evaporation) used in these organic solvent-related industries. Membrane separation technology can be coupled with product synthesis, separation and purification, and solvent recovery processes, promoting the optimization and upgrading of the chemical industry structure.

[0004] The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN is characterized by comprising the following steps:

[0005] 1) At 20-35℃, 0.5-2 wt% of aminated carbon quantum dots or commercially available triterpenoid amine with a twisted structure and 0.05-0.5 wt% of aromatic diacyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, resulting in aqueous monomer solutions and oil monomer solutions. Then, a commercial ultrafiltration membrane was used as the support. The support was impregnated with the aqueous monomer solution for 3-10 min. The aqueous solution was then removed with an air knife. The support was then impregnated with the oil monomer solution for 30-60 s. Excess oil monomer solution was then removed to construct two types of molecular layers with porous rigid network I structures.

[0006] 2) At 30-50℃, using aliphatic amine as the first monomer and aliphatic acyl chloride as the second monomer, prepare 0.5-2wt% organic solutions respectively. Immerse the support containing porous rigid network I in the first monomer solution for 1-3 min, then take it out and wash it 2-3 times in the corresponding solvent. Then immerse the substrate in the second monomer solution for 1-3 min, then take it out and wash it 2-3 times in the corresponding solvent. This is one cycle. Repeat the cycle deposition 6-12 times. Then heat treat the substrate at 50-90℃ for 5-10 min. Activate the prepared rigid-flexible dual-network IPN PA membrane in N,N-dimethylformamide for 15-17 hours, then take it out and exchange it in ethanol for 3-6 hours. Store it at 3-5℃ to obtain the organic solvent nanofiltration membrane.

[0007] The method for preparing an organic solvent nanofiltration membrane of a rigid-flexible dual-network IPN is characterized in that the carbon quantum dots in step 1) are prepared by the following method: using citric acid as a carbon source and aliphatic diamine as an ammonia modifier, graphene quantum dots are prepared by microwave-assisted pyrolysis reaction, wherein the concentration of citric acid is 30wt%-70wt%, the microwave heating power is 400W-750W, the heating time is 1-5min, and the mass fraction of aliphatic diamine added is 3wt%-10wt%.

[0008] The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN is characterized in that, in step 1): the dissolution temperature is 25-32℃, preferably 28-30℃; the mass fraction of carbon quantum dots is 0.8-1.5wt%, preferably 1-1.2wt%; the mass fraction of triptereneamine is 1-1.8wt%, preferably 1.2-1.5wt%; the mass fraction of aromatic diacyl chloride is 0.08-0.35wt%, preferably 0.1-0.25wt%, more preferably 0.15-0.2wt%; the duration of wetting the support with the aqueous monomer solution is 5-7 min, and the duration of wetting the support with the oil monomer solution is 40-50 s.

[0009] The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN is characterized in that, in step 1), the triterpenoid amine containing the twisted structure is at least one of 2,6,14-triaminotriterpenene, 2,7-diaminotriterpenene, and hexaaminotriterpenene.

[0010] The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN is characterized in that, in step 1), the aromatic diacyl chloride is any one of terephthaloyl chloride, 2,6-naphthalenedicarboxyl chloride, azobenzene-4,4'-dicarbonyl chloride, and 4,4'-biphenylacetyl chloride.

[0011] The method for preparing an organic solvent nanofiltration membrane of a rigid-flexible dual-network IPN is characterized in that, in step 2): the organic solution is prepared at a temperature of 35-45℃; the organic solution concentration is 0.8-1.5wt%, preferably 1-1.2wt%; the substrate heat treatment temperature is 60-80℃, preferably 70-75℃; and the heat treatment time is 7-8 min.

[0012] The method for preparing an organic solvent nanofiltration membrane of a rigid-flexible dual-network IPN is characterized in that, in step 2), the solvent used is any one of dioxane, tetrahydrofuran, N,N-dimethylformamide, and mesitylene.

[0013] The method for preparing an organic solvent nanofiltration membrane of a rigid-flexible dual-network IPN is characterized in that, in step 2), the first type of monomer is any one of diethylenetriamine, 1,2,3-propanetriamine, triethylenetetramine, and tris(2-aminoethyl)amine; and the second type of monomer is any one of succinyl chloride, adipyl chloride, octanoyl chloride, and tripropanediol chloride.

[0014] The method for preparing an organic solvent nanofiltration membrane of a rigid-flexible dual-network IPN is characterized in that the aliphatic diamine is at least one of ethylenediamine, propylenediamine, and butanediamine.

[0015] The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN is characterized by a citric acid concentration of 40wt%-60wt%, a microwave heating power of 450W-700W, a heating time of 2min-4min, and an aliphatic diamine feed mass fraction of 4wt%-8wt%; preferably, the citric acid concentration is 45wt%-50wt%, the microwave heating power is 500W-600W, the heating time is 3min-3.5min, and the aliphatic diamine feed mass fraction is 5wt%-6wt%.

[0016] The above-described method for preparing an organic solvent nanofiltration membrane using a rigid-flexible dual-network IPN is an example of a multiphase polymer material composed of two or more polymers intertwined and interconnected (Science 374, (2021) 212–216). The IPN structure organically integrates a rigid network with highly permeable micro-nanopores with a dense flexible network. The rigid network acts as a framework, supporting the overall stability and longitudinal stiffness of the IPN structure, enhancing its resistance to external loads and internal stresses, and ensuring excellent long-term service stability of the membrane material. The flexible network, as a filling phase, is interlocked into the rigid network structure, forming a highly cross-linked and dense structure, ensuring a high retention rate of the membrane material. The twisted 3D structure of the rigid network also hinders the dense stacking of the flexible network, inducing more micro-nanopores and increasing solvent flux. The rigid and flexible networks work synergistically, integrating their advantages to achieve a 1+1 greater than 2 effect, resulting in a solvent-resistant nanofiltration membrane with both excellent long-term service stability and high separation performance. Detailed Implementation

[0017] The present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1

[0019] (1) Graphene quantum dots were prepared by microwave-assisted pyrolysis reaction using citric acid as carbon source and ethylenediamine as ammonia modifier. Graphene quantum dots (with a particle size of 5 nm) were prepared by adjusting the concentration of citric acid (30 wt%), the concentration of ethylenediamine (3 wt%), the microwave heating power (400 W), and the heating time (2 min). The quantum dots were purified by dialysis, concentrated, lyophilized, and stored. The physicochemical structure of the product was characterized and analyzed.

[0020] (2) At 20°C, 0.5 wt% of aminated carbon quantum dots and 0.05 wt% of 2,6-naphthalenedicarbamate chloride were dissolved in deionized water or n-hexane, stirred evenly and allowed to stand to remove bubbles, to obtain aqueous monomer solution and oil monomer solution respectively; then, a commercial ultrafiltration membrane was selected as the support, the support was wetted with the aqueous monomer solution for 3 min, the aqueous solution was removed with an air knife, and then the support was wetted with the oil monomer solution for 30 s, and the excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0021] (3) At 30°C, 0.5 wt% organic solutions were prepared using diethylenetriamine as the first monomer and succinyl chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 1 min, and then taken out and washed 3 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. This process was repeated 8 times. The substrate was then heat-treated at 50°C for 5 min. The prepared rigid-flexible dual-network IPN PA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0022] Example 2

[0023] (1) Graphene quantum dots were prepared by microwave-assisted pyrolysis reaction using citric acid as the carbon source and propylenediamine as the ammonia modifier. Graphene quantum dots (with a particle size of 5 nm) were prepared by adjusting the concentration of citric acid (30 wt%), the concentration of propylenediamine (3 wt%), the microwave heating power (500 W), and the heating time (2 min). The products were purified by dialysis, concentrated, lyophilized, and stored, and their physicochemical structure was characterized and analyzed.

[0024] (2) At 20°C, 0.5 wt% of aminated carbon quantum dots and 0.05 wt% of terephthaloyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 3 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 30 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0025] (3) At 30°C, 0.5 wt% organic solutions were prepared using 1,2,3-propanetriamine as the first monomer and adipic acid chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 3 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. This process was repeated 10 times. The substrate was then heat-treated at 60°C for 5 min. The prepared rigid-flexible dual-network IPNPA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0026] Example 3

[0027] (1) At 20℃, 0.5 wt% of 2,6,14-triaminotriptene (with 1 wt% DMF added for dissolution) and 0.05 wt% of 2,6-naphthalenedicarboxyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 3 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 30 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0028] (2) At 30°C, 0.5 wt% organic solutions were prepared using 1,2,3-propanetriamine as the first monomer and adipic acid chloride as the second monomer. The support containing the porous rigid network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 3 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. This process was repeated 10 times. The substrate was then heat-treated at 70°C for 5 min. The prepared rigid-flexible dual-network IPN PA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0029] Example 4

[0030] (1) At 30°C, 0.5 wt% hexaaminotriptene (with 2 wt% DMF added for solubilization) and 0.1 wt% azobenzene-4,4'-dicarbonyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 3 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 30 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0031] (2) At 30°C, 0.5 wt% organic solutions were prepared using triethylenetetramine as the first monomer and octanoyl chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 5 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 5 times in the corresponding solvent. This process was repeated 8 times. The substrate was then heat-treated at 90°C for 5 min. The prepared rigid-flexible dual-network IPNPA membrane was activated in N,N-dimethylformamide for 15 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0032] Example 5

[0033] (1) Graphene quantum dots were prepared by microwave-assisted pyrolysis reaction using citric acid as the carbon source and ethylenediamine as the ammonia modifier. Graphene quantum dots (particle size of 10 nm) were prepared by controlling the concentration of citric acid (80 wt%), the concentration of ethylenediamine (5 wt%), the microwave heating power (600 W), and the heating time (4 min). The products were purified by dialysis, concentrated, lyophilized, and stored, and their physicochemical structure was characterized and analyzed.

[0034] (2) At 35°C, 1.5 wt% of aminated carbon quantum and 0.4 wt% of 4,4'-biphenylacetyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 10 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 60 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0035] (3) At 50°C, 1 wt% organic solutions were prepared using aliphatic amine as the first monomer and adipic acid chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. This process was repeated 6 times. The substrate was then heat-treated at 90°C for 10 min. The prepared rigid-flexible dual-network IPN PA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0036] Example 6

[0037] (1) Graphene quantum dots were prepared by microwave-assisted pyrolysis reaction using citric acid as the carbon source and propylenediamine as the ammonia modifier. Graphene quantum dots (particle size of 10 nm) were prepared by adjusting the concentration of citric acid (40 wt%), the concentration of propylenediamine (2 wt%), the microwave heating power (600 W), and the heating time (2.5 min). The products were purified by dialysis, concentrated, lyophilized, and stored, and their physicochemical structure was characterized and analyzed.

[0038] (2) At 20°C, 0.4 wt% of aminated carbon quantum dots and 0.15 wt% of terephthaloyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 3 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 30 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0039] (3) At 30°C, 0.7 wt% organic solutions were prepared using tris(2-aminoethyl)amine as the first monomer and succinyl chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 3 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. This process was repeated 10 times. The substrate was then heat-treated at 60°C for 5 min. The prepared rigid-flexible dual-network IPN PA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0040] Example 7

[0041] (1) At 30°C, 0.3 wt% 2,7-diaminotriptene (with 2 wt% DMF added for dissolution) and 0.2 wt% 2,6-naphthalenedicarboxyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 3 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 30 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0042] (2) At 30 °C, 0.5 wt% organic solutions were prepared using triethylenetetramine as the first monomer and trimethylolpropionate chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 4 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 4 times in the corresponding solvent. The deposition cycle was repeated 15 times, and then the substrate was heat-treated at 90 °C for 5 min. The prepared rigid-flexible dual-network IPN PA membrane was activated in N,N-dimethylformamide for 17 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4 °C.

[0043] Example 8

[0044] (1) At 30°C, 1 wt% of 2,6,14-triaminotriptene (with 2 wt% DMF added for dissolution) and 0.15 wt% of 4,4'-biphenylacetyl chloride were dissolved in deionized water or n-hexane, respectively. The mixture was stirred evenly and allowed to stand to remove bubbles, and aqueous monomer solution and oil monomer solution were obtained respectively. Then, a commercial ultrafiltration membrane was selected as the support. The support was wetted with the aqueous monomer solution for 3 min. The aqueous solution was removed with an air knife. Then, the support was wetted with the oil monomer solution for 30 s. The excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0045] (2) At 25°C, 0.5 wt% organic solutions were prepared using tris(2-aminoethyl)amine as the first monomer and octanoyl chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 4 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 4 times in the corresponding solvent. This process was repeated 12 times. The substrate was then heat-treated at 90°C for 5 min. The prepared rigid-flexible dual-network IPNPA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0046] Example 9

[0047] (1) Graphene quantum dots were prepared by microwave-assisted pyrolysis reaction using citric acid as the carbon source and butanediamine as the ammonia modifier. Graphene quantum dots (30 nm in diameter) were prepared by controlling the concentration of citric acid (80 wt%), the concentration of propylenediamine (5 wt%), the microwave heating power (700 W), and the heating time (4.5 min). The products were purified by dialysis, concentrated, lyophilized, and stored. The physicochemical structure of the products was characterized and analyzed.

[0048] (2) At 20°C, 0.05 wt% of aminated carbon quantum dots and 0.05 wt% of terephthaloyl chloride were dissolved in deionized water or n-hexane, stirred evenly and allowed to stand to degas, to obtain aqueous monomer solution and oil monomer solution respectively; then, a commercial ultrafiltration membrane was selected as the support, the support was wetted with the aqueous monomer solution for 3 min, the aqueous solution was removed with an air knife, and then the support was wetted with the oil monomer solution for 30 s, and the excess oil monomer solution was removed to construct two types of molecular layers with porous rigid network I structure.

[0049] (3) At 30°C, 0.5 wt% organic solutions were prepared using tris(2-aminoethyl)amine as the first monomer and succinyl chloride as the second monomer. The support containing porous network I was first immersed in the first monomer solution for 2 min, and then taken out and washed 3 times in the corresponding solvent. The substrate was then immersed in the second monomer solution for 3 min, and then taken out and washed 3 times in the corresponding solvent. This process was repeated 12 times. The substrate was then heat-treated at 60°C for 5 min. The prepared rigid-flexible dual-network IPN PA membrane was activated in N,N-dimethylformamide for 16 hours, then taken out and exchanged in ethanol for 4 hours, and stored in a refrigerator at 4°C.

[0050] The following experimental data further demonstrates the beneficial effects of the present invention.

[0051] Table 1. Performance of the rigid-flexible dual-network IPN organic nanofiltration membrane in Example 1

[0052] Rigid-Flexible Dual-Network IPN Organic Nanofiltration Membrane index film thickness 100 nm Molecular weight cutoff (MWCO) 280 Da methanol flux 15.2 LMH / bar Organic solvent resistance Methanol, ethanol, isopropanol, acetone, and petroleum ether, etc. Long-term service stability Continuous operation for 30 days (methanol) Maximum operating pressure 50 bar

[0053] Table 2 Performance of the rigid-flexible dual-network IPN organic nanofiltration membrane in Example 4

[0054] Rigid-Flexible Dual-Network IPN Organic Nanofiltration Membrane index film thickness 90 nm Molecular weight cutoff (MWCO) 320 Da methanol flux 16.8 LMH / bar Organic solvent resistance Methanol, ethanol, isopropanol, acetone, and petroleum ether, etc. Long-term service stability Continuous operation for 35 days (methanol) Maximum operating pressure 55 bar

[0055] Table 3 Performance of the rigid-flexible dual-network IPN organic nanofiltration membrane in Example 8

[0056] Rigid-Flexible Dual-Network IPN Organic Nanofiltration Membrane index film thickness 130 nm Molecular weight cutoff (MWCO) 250 Da methanol flux 14.1 LMH / bar Organic solvent resistance Methanol, ethanol, isopropanol, acetone, and petroleum ether, etc. Long-term service stability Continuous operation for 40 days (ethanol) Maximum operating pressure 48 bar

[0057] By measuring the membrane thickness, molecular weight cutoff, methanol flux, and solvent resistance of the rigid-flexible dual-network IPN organic nanofiltration membrane, it can be seen that the organic nanofiltration membranes prepared in Examples 1, 4, and 8 of this invention have excellent comprehensive separation performance, as well as high compressive strength and excellent long-term service stability, which meet the requirements of material separation and solvent recovery in industries such as petrochemicals. The organic nanofiltration membranes prepared in other embodiments of this invention can also achieve the technical effects described in this invention after performance testing.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an organic solvent nanofiltration membrane of rigid-soft dual network type IPN, characterized in that Comprise the following steps: 1) Dissolve 0.5-2wt% of amino-functionalized carbon quantum dots or commercially available twisted structure-containing triphenylene amine and 0.05-0.5wt% of aromatic diacid chloride in deionized water or n-hexane respectively at 20-35℃, stir uniformly and stand for defoaming, respectively obtain aqueous monomer solution and oil phase monomer solution; then select a commercial ultrafiltration membrane as a support, immerse the support in the aqueous monomer solution for 3-10min, then remove the aqueous solution with an air knife, then immerse the support in the oil phase monomer solution for 30-60s, and remove the excess oil phase monomer solution to construct two types of porous rigid network I structure molecular layers; The carbon quantum dots are prepared by the following method: using citric acid as a carbon source and aliphatic diamine as an ammonia modifier, graphene quantum dots are prepared by a microwave-assisted pyrolysis reaction, the concentration of citric acid is 30wt%-70wt%, the microwave heating power is 400W-750W, the heating time is 1-5min, and the feeding mass fraction of aliphatic diamine is 3wt%-10wt%. 2) At 30-50℃, prepare 0.5-2wt% of an organic solution using aliphatic amine as a first monomer and aliphatic acid chloride as a second monomer, immerse the support containing the porous rigid network I in the first monomer solution for 1-3min, then take it out and wash it in the corresponding solvent for 2-3times; then immerse the support in the second monomer solution for 1-3min, then take it out and wash it in the corresponding solvent for 2-3times, which is one cycle, and the cycle is repeated for 6-12 times, then heat treat the support at 50-90℃ for 5-10min, place the prepared rigid-flexible double network type IPN PA membrane in N,N-dimethylformamide for activation for 15-17 hours, then take it out and exchange it in ethanol for 3-6 hours, store it at 3-5℃, and an organic solvent nanofiltration membrane is obtained.

2. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... In step 1), the dissolving temperature is 28-30℃, the mass fraction of carbon quantum dots is 1-1.2wt%, the mass fraction of triphenylene amine is 1.2-1.5wt%, the mass fraction of aromatic diacid chloride is 0.1-0.25wt%, the aqueous monomer solution is immersed in the support for 5-7min, and the oil phase monomer solution is immersed in the support for 40-50s.

3. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... In step 1), the twisted structure-containing triphenylene amine is at least one of 2,6,14-triaminotriphenylene, 2,7-diaminotriphenylene and hexaaminotriphenylene.

4. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... In step 1), the aromatic diacid chloride is any one of terephthaloyl chloride, 2,6-naphthalene dicarboxylic chloride, azobenzene-4,4'-dicarbonyl chloride and 4,4'-diphenylacetyl chloride.

5. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... In step 2), the organic solution preparation temperature is 35-45℃, the concentration of the organic solution is 1-1.2wt%, the support heat treatment temperature is 60-80℃, and the heat treatment time is 7-8min.

6. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... In step 2), the solvent used is any one of dioxane, tetrahydrofuran, N,N-dimethylformamide and mesitylene.

7. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... In step 2), the first monomer is any one of diethylenetriamine, 1,2,3-propanetriamine, triethylenetetramine, tris(2-aminoethyl)amine; and the second monomer is any one of succinoyl chloride, adipoyl chloride, suberoyl chloride, propanetrioyl chloride.

8. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that... The aliphatic diamine is at least one of ethylenediamine, propylenediamine, and butylenediamine.

9. The method for preparing an organic solvent nanofiltration membrane with a rigid-flexible dual-network IPN as described in claim 1, characterized in that: The concentration of the citric acid is 45wt%-50wt%, the microwave heating power is 500W-600W, the heating time is 3min-3.5min, and the mass fraction of the aliphatic diamine is 5wt%-6wt%.