High-performance composite solvent-resistant nanofiltration membrane with rigid twisted non-planar structure polyamide layer and preparation method of high-performance composite solvent-resistant nanofiltration membrane

Abstract

The invention discloses a high-performance composite solvent-resistant nanofiltration membrane with a rigid twisted non-planar structure polyamide layer and a preparation method of the high-performance composite solvent-resistant nanofiltration membrane. The preparation method comprises the steps of preparation of the rigid twisted non-planar structure polyamide layer and surface modification. A water phase solution containing adamantane diamine and m-phenylenediamine and an organic phase solution containing 1, 3, 5-trimesoyl chloride and acetone are subjected to interfacial polymerization reaction to prepare a polyamide layer with a rigid twisted non-planar structure, and then a polyphenol modifier is used for carrying out hydrophilic modification on the polyamide layer, so that the rigid twisted non-planar structure is obtained. The pure water permeability and retention rate of the solvent-resistant nanofiltration membrane are obviously improved; due to the introduction of adamantane diamine, the interfacial polymerization process and the formation of a polyamide layer are remarkably regulated and controlled, and the separation performance of the solvent-resistant membrane is greatly improved on the premise that the interception performance of the membrane is hardly reduced; the preparation process is simple, and the prepared membrane is excellent in performance and has a good application prospect in the aspect of organic solvent separation.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane separation, and in particular relates to a high-performance composite solvent-resistant nanofiltration membrane with a rigid twisted non-planar structure polyamide layer, a preparation method and an application thereof. Background Art

[0002] Organic solvents are widely used in chemical, pharmaceutical, food and other related industries. At the same time, the separation process of organic solvent systems accounts for about 40% to 70% of the investment and operating costs of chemical and pharmaceutical industries. The volatilization of solvents also causes a lot of resource waste and serious environmental pollution. Therefore, the separation and purification of organic solution systems is an important demand for energy conservation and emission reduction, environmental protection and economic sustainable development, and it is also a major challenge facing the membrane separation field.

[0003] Organic Solvent Nanofiltration (OSN) membrane is an advanced separation technology used in organic solution systems. It can separate organic solvents from solutes with a molecular weight of 200~1000 Daltons (Da). Its energy consumption is only about one-tenth of the energy consumption of traditional distillation. It has great application potential in the separation of organic solvent systems such as catalyst and organic solvent recovery and purification of active pharmaceutical ingredients.

[0004] Since the use environment of solvent-resistant nanofiltration membranes is far more complex and harsh than that of aqueous solution systems, solvent-resistant nanofiltration membranes have a series of problems such as poor separation performance, poor solvent resistance, and poor long-term stability. In order to improve the separation performance of solvent-resistant membranes, researchers will Many researchers have significantly improved the separation performance of solvent-resistant nanofiltration membranes by adding nanomaterials to aqueous or organic phase reaction monomer solutions and then doping the nanomaterials into the separation cortex of the membrane. The most widely used nanomaterials include graphene oxide (GO), metal organic frameworks (MOFs), covalent organic frameworks (COFs), and self-polymerized microporous polymers (PIMs).

[0005] PIMs are polymers with twisted sites and rigid skeletons, with microporous structures and high free volumes. Inspired by PIMs, researchers in recent years have used rigid twisted new reactive monomers as aqueous or organic phase monomers to carry out interfacial polymerization with traditional acyl chloride or diamine monomers to prepare cross-linked PIMs layers, but the retention performance of the solvent-resistant membranes prepared by this method is poor.

[0006] By using adamantane diamine and meta-phenylenediamine with rigid twisted structures as aqueous phase co-monomers, a solvent-resistant nanofiltration membrane with a twisted continuous dense polyamide separation layer and better separation performance and solvent resistance was developed, which has good prospects. Summary of the invention

[0007] The present invention aims to solve the technical problems in the prior art of low flux, poor retention rate, relatively poor solvent resistance and long-term stability of solvent-resistant nanofiltration membranes for organic solvent systems, and proposes a high-performance composite solvent-resistant nanofiltration membrane with a rigid twisted non-planar structure polyamide layer and a preparation method thereof.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows.

[0009] The first aspect of the present invention discloses a high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer, wherein a layer of a rigid twisted non-planar structure polyamide layer is formed on the surface of the base membrane through an interfacial polymerization process, and the polyamide separation layer can also be hydrophilically modified using an organic solution of a polyphenol modifier. Wherein: (1) The polyamide layer having a rigid twisted non-planar structure is prepared by interfacial polymerization of a polyamine monomer aqueous solution containing adamantane diamine and a polyacyl chloride monomer organic solution on the surface of the base film; (2) The surface of the composite solvent-resistant nanofiltration membrane is hydrophilically modified by using a polyphenol modifier.

[0010] Preferably, the composite solvent-resistant nanofiltration membrane further uses a polyphenol modifier to chemically modify the surface of the polyamide separation layer to form a surface modified cortex bonded by covalent bonds.

[0011] Preferably, the average surface roughness (Rq) of the composite solvent-resistant nanofiltration membrane is less than 10 nm.

[0012] Preferably, the average surface roughness (Rq) of the composite solvent-resistant nanofiltration membrane is less than 10 nm.

[0013] The second aspect of the present invention discloses a method for preparing a high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer, comprising the following steps: Step 1: After the surface of the base membrane is fully contacted with an aqueous phase solution containing an ultra-low concentration of an aromatic diamine compound and adamantane diamine monomer for a certain period of time, excess solution on the surface of the base membrane is removed and the base membrane is dried, and then the base membrane is fully contacted with an organic phase monomer solution containing acetone and an aromatic polyacyl chloride compound for a certain period of time, excess solution is removed, and the base membrane is dried to obtain a composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer; Step 2: After the solvent-resistant nanofiltration membrane with a rigid twisted non-planar structure polyamide layer obtained in step 1 is fully contacted with an organic phase monomer solution containing a polyphenol modifier for a certain period of time, the organic phase monomer solution on the membrane surface is removed, and the obtained membrane is immediately placed in anhydrous ethanol to obtain a high-performance composite solvent-resistant nanofiltration membrane with a rigid twisted non-planar structure polyamide layer with a hydrophilic surface modification.

[0014] Preferably, the aromatic diamine compound includes m-phenylenediamine, p-phenylenediamine, other aromatic compounds containing two amine groups, or any combination thereof.

[0015] Preferably, the total mass percentage concentration of amine monomers in the ultra-low concentration aromatic diamine and adamantane diamine monomer solution is in the range of 0.01% to 2%.

[0016] Preferably, the aromatic polybasic acid chloride compound is an aromatic tribasic acid chloride or a combination of different aromatic polybasic acid chlorides; more preferably, the aromatic tribasic acid chloride is 1,3,5-benzenetricarboxylic acid chloride.

[0017] Preferably, the mass percentage concentration range of the aromatic polyacyl chloride compound is 0.05% to 0.2%.

[0018] Preferably, the mass percentage concentration range of acetone is 0.1% to 1.0%.

[0019] Preferably, the organic solution of the polyphenol modifier contains: polyphenol modification monomers and ethanol organic solvent.

[0020] Preferably, the mass percentage concentration range of the polyphenol modifier in the organic phase solution is 0.05% to 1%.

[0021] Preferably, the polyphenol modified monomer includes tannic acid and other polyphenol modified monomers, or a combination of multiple polyphenol modified monomers.

[0022] The third aspect of the present invention discloses a high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer, which is used for separation and purification of organic solvent systems, and is mainly used for separation of organic matter in organic solvent systems.

[0023] The technical solution of the present invention has achieved remarkable technical effects and progress and has substantial characteristics.

[0024] The method for preparing the polyamide layer with a rigid twisted non-planar structure of the present invention introduces adamantane diamine monomer into the aqueous phase monomer and then performs interfacial polymerization, thereby achieving regulation of the interfacial polymerization reaction; then, the modified monomer is used to react with the residual acyl chloride group after the interfacial polymerization, and the surface of the membrane after the interfacial polymerization is further modified. The synergistic effect of the adamantane diamine monomer and the surface modification achieves the purpose of improving the separation performance of the membrane, and a higher performance composite solvent-resistant nanofiltration membrane is obtained, which has a good application prospect.

[0025] A significant technical advantage of the present invention is that an ultra-thin and ultra-smooth polyamide layer can be prepared by using an ultra-low concentration of aqueous amine monomers, while significantly reducing the amount of chemicals used, reducing waste liquid treatment costs and possible environmental pollution.

[0026] The second significant technical advantage of the present invention is that the large volume and rigid cage structure of adamantane diamine have greater diffusion resistance than m-phenylenediamine, which can not only reduce the close stacking of polymer chains, thereby increasing the free volume of the polyamide layer and the permeability of the membrane, but also prevent the polyamide layer from swelling, thereby improving the solvent resistance of the membrane under harsh conditions.

[0027] The third significant technical advantage of the present invention is that the polyphenol modifier contains a large amount of hydroxyl groups, which can react with the residual acyl chloride groups after the interfacial polymerization reaction to produce a surface modified cortex connected by covalent bonds. The appearance of the cortex causes certain changes in the surface structure of the composite solvent-resistant nanofiltration membrane, and the hydrophilicity of the membrane surface is enhanced. When the polyamide layer is modified with a polyphenol modifier, the contact angle is 60.5°, while the contact angle of the polyamide layer modified with a polyphenol modifier is reduced to 53.6°. Under the same operating conditions, a more hydrophilic membrane surface is beneficial to improving the permeability of the membrane to polar solvents.

[0028] Through the above technical innovations, the present invention has achieved remarkable technical achievements and has good application prospects in the separation and purification of organic solvents. DETAILED DESCRIPTION

[0029] The present invention will be further described below through specific comparative examples and embodiments.

[0030] The base membrane is a polyimide ultrafiltration membrane; The interfacial polymerization diamine compound used is a mixture of meta-phenylenediamine and adamantane diamine; The interfacial polymerization organic phase monomer used is a mixture of 1,3,5-trimethylbenzenecarboxylic acid chloride and acetone; The organic phase solvent used for interfacial polymerization was n-hexane; The polyphenolic modifier used was tannic acid; The organic solvent of the modifier used is ethanol.

[0031] At 25 °C and 1.00 MPa transmembrane pressure difference, 100 mg L −1 The ethanol permeability and dye retention rate of the prepared membrane were detected by cross-flow filtration method using Rhodamine B ethanol solution.

[0032] The surface hydrophilicity of the membrane was measured using a contact angle meter.

[0033] Comparative Example 1: The aromatic diamine compound (m-phenylenediamine) is dissolved in deionized water at a mass percent concentration of 0.05% to prepare an aqueous monomer solution.

[0034] The aromatic tribasic acid chloride (1,3,5-benzene trimesoyl chloride) is dissolved in a first organic solvent at a mass percent concentration of 0.15% to prepare an organic phase monomer solution.

[0035] The steps and conditions for preparing the composite solvent-resistant nanofiltration membrane are as follows: After the aqueous monomer solution is immersed in the surface of the base membrane for 8 seconds, the aqueous monomer solution on the surface of the base membrane is removed and the base membrane is naturally dried in the air at room temperature. After the dried base membrane surface is fully contacted with the organic monomer solution for 6 seconds, the organic monomer solution on the membrane surface is removed and the membrane is quickly placed in deionized water to obtain a composite solvent-resistant nanofiltration membrane.

[0036] The prepared composite solvent-resistant nanofiltration membrane can withstand 100 mg L −1 The ethanol permeability and dye retention rate of the prepared membrane were tested by cross-flow filtration of the ethanol solution of Rhodamine B. The retention rate of Rhodamine B was 98.3%, the ethanol permeability was 43.4 LMH / MPa, and the pure water permeability was low, indicating that the free volume of the polyamide layer was small. The surface water contact angle of the membrane was 75.7°, indicating that the hydrophilicity of the membrane was poor. Example

[0037] The diamine compounds (meta-phenylenediamine and adamantane diamine) are dissolved in deionized water with a total mass percentage concentration of 0.05% to prepare an aqueous monomer solution.

[0038] The aromatic tribasic acid chloride (1,3,5-trimethylbenzenecarboxylic acid chloride) and acetone are dissolved in an organic solvent, wherein the mass percentage concentration of 1,3,5-trimethylbenzenecarboxylic acid chloride is 0.15% and the mass percentage concentration of acetone is 0.25%, to prepare an organic phase monomer solution.

[0039] The steps and conditions for preparing the composite solvent-resistant nanofiltration membrane are as follows: After the aqueous monomer solution is immersed in the surface of the base membrane for 8 seconds, the aqueous monomer solution on the surface of the base membrane is removed and the base membrane is naturally dried in the air at room temperature. After the dried base membrane surface is fully contacted with the organic monomer solution for 6 seconds, the organic monomer solution on the membrane surface is removed and the membrane is quickly placed in deionized water to obtain a composite solvent-resistant nanofiltration membrane.

[0040] The test conditions are the same as those of Comparative Example 1.

[0041] Without modifying the surface hydrophilicity, the prepared solvent-resistant nanofiltration membrane has a rejection rate of 98.4% for rhodamine B and an ethanol permeability of 74.0 LMH / MPa. Compared with comparative example 1, the ethanol permeability is greatly improved, while the rhodamine B rejection rate remains basically unchanged, and the surface water contact angle of the membrane is 60.5°, indicating that the introduction of adamantane diamine and acetone in the preparation process of the membrane greatly improves the permeability and surface hydrophilicity of the membrane. Example

[0042] Prepare an aqueous solution with a concentration of 0.04 wt % of m-phenylenediamine and a concentration of 0.01 wt % of adamantane diamine, ultrasonicate for 10 min, and set aside.

[0043] Prepare a n-hexane organic solution with a 1,3,5-trimethylbenzene carboxylic acid chloride concentration of 0.15 wt % and an acetone concentration of 0.25 wt %, ultrasonicate for 10 min, and set aside.

[0044] Prepare an ethanol organic solution with a tannic acid concentration of 0.2 wt%, ultrasonicate for 10 min, and set aside.

[0045] The steps of film making are as follows: Step 1: After the aqueous monomer solution is immersed on the surface of the base membrane for 8 seconds, the aqueous monomer solution on the surface of the base membrane is removed and naturally dried in the air at room temperature. After the dried base membrane surface is fully contacted with the organic monomer solution for 6 seconds, the organic monomer solution on the membrane surface is removed and the membrane is quickly placed in deionized water to obtain a composite solvent-resistant nanofiltration membrane.

[0046] Step 2: After the composite solvent-resistant nanofiltration membrane prepared in step 1 is in contact with the tannic acid ethanol organic solution for 2 minutes, the solution on the membrane surface is removed, and the organic solution on the membrane surface is removed, and the membrane is quickly placed in ethanol.

[0047] The test conditions are the same as those of Comparative Example 1.

[0048] After surface modification, the prepared composite solvent-resistant nanofiltration membrane has a rejection rate of 98.3% for rhodamine B and an ethanol permeability of 76.6 LMH / MPa. Compared with comparative example 1, the ethanol permeability is greatly improved, while the rhodamine B rejection rate remains basically unchanged, and the surface water contact angle of the membrane is 53.6°, indicating that the introduction of adamantane diamine and acetone and the hydrophilic modification step greatly improve the permeability and surface hydrophilicity of the membrane. Example

[0049] The only difference from Example 2 is that the concentration of acetone used is 0.125wt%.

[0050] All other steps are the same as those in Example 2; and the testing conditions are the same as those in Comparative Example 1.

[0051] The prepared composite solvent-resistant nanofiltration membrane has a rejection rate of 98.3% for rhodamine B and an ethanol permeability of 72.6LMH / MPa. Compared with Comparative Example 1, the ethanol permeability is greatly improved, while the rhodamine B rejection rate is slightly improved, indicating that the introduction of adamantane diamine and acetone and the hydrophilic modification step greatly improve the separation performance of the membrane. Compared with Example 2, the ethanol permeability is reduced to a certain extent, indicating that the acetone concentration should be controlled within a certain range during the preparation of the membrane, and an inappropriate concentration of acetone will reduce the permeability of the membrane. Example

[0052] The only difference from Example 2 is that the concentration of adamantane diamine used is 0.2 wt % and the concentration of m-phenylenediamine is 0.3 wt %.

[0053] All other steps are the same as those in Example 2; and the testing conditions are the same as those in Comparative Example 1.

[0054] The prepared composite solvent-resistant nanofiltration membrane has a rejection rate of 98.3% for rhodamine B and an ethanol permeability of 79.4LMH / MPa. Compared with Comparative Example 1, the ethanol permeability is greatly improved, while the rhodamine B rejection rate remains basically unchanged. Compared with Example 2, the ethanol permeability increases and the rejection rate of rhodamine B decreases, indicating that an excessively high proportion of adamantane diamine in the interfacial polymerization aqueous phase monomer reduces the surface crosslinking degree of the membrane, forming an overly loose polyamide layer, which is not conducive to improving the separation performance of the membrane.

[0055] The above examples show that the introduction of adamantane diamine and acetone has a great influence on interfacial polymerization, and the prepared composite solvent-resistant nanofiltration membrane has excellent separation performance. After the surface of the prepared composite solvent-resistant nanofiltration membrane is further modified by using tannic acid solution, the performance of the obtained composite solvent-resistant nanofiltration membrane is further improved, and significant technical effects and progress have been achieved.

[0056] It should be pointed out that the above embodiments are only preferred specific implementations of the present invention and do not constitute limitations to the present invention. Any implementations within the protection scope of the present invention constituted by the features of the claims of the present invention or equivalent features shall infringe the patent rights of the present invention.

Claims

1. A high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer and a preparation method thereof, characterized in that: (1) The polyamide layer having a rigid twisted non-planar structure is prepared by interfacial polymerization of an ultra-low concentration aqueous solution containing adamantane diamine and m-phenylenediamine and an organic solution containing 1,3,5-trimethylbenzene carboxylic acid chloride and acetone; (2) The composite solvent-resistant nanofiltration membrane further comprises a modified layer on the polyamide layer having a rigid twisted non-planar structure, which is hydrophilically modified by a polyphenol modifier; (3) The polyamide layer having a rigid twisted non-planar structure is connected to the modified layer via a covalent bond.

2. A high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer and a preparation method thereof according to claim 1, characterized in that: The high-performance composite solvent-resistant nanofiltration membrane has a good performance in the filtration of 100 mg L −1 The retention rate of Rhodamine B ethanol solution is greater than or equal to 93%, and the ethanol permeability is greater than 70 L m −2 h −1 MPa −1 (abbreviated as LMH / MPa), and has good solvent resistance and long-term stability.

3. A method for preparing a high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer, characterized in that: The following steps are included: Step 1: After the surface of the base membrane is contacted with a monomer solution containing an ultra-low concentration of aromatic diamine and adamantane diamine (i.e., the first aqueous phase monomer solution) for 1 s to 5 min, the excess solution on the surface of the base membrane is removed and the base membrane is dried, and then the base membrane is fully contacted with an organic phase monomer solution containing acetone and aromatic polyacyl chloride (i.e., the first organic phase monomer solution) for 1 s to 2 min, and then the excess solution is removed and dried to obtain a composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer; Step 2: After the solvent-resistant nanofiltration membrane with a rigid twisted non-planar structure polyamide layer obtained in step 1 is fully contacted with an organic phase monomer solution containing a polyphenol modifier (i.e., the second organic phase monomer solution) for 1 s to 10 min, the organic phase monomer solution on the membrane surface is removed, and the obtained membrane is immediately placed in anhydrous ethanol to obtain a high-performance composite reverse osmosis membrane with a rigid twisted non-planar structure polyamide layer modified with a hydrophilic surface.

4. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The mass percentage concentration range of the ultra-low concentration aromatic diamine and adamantane diamine monomer solution is 0.01% to 2%.

5. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The first organic solvent is a non-polar or weakly polar solvent.

6. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The aromatic diamine compound in the first aqueous phase monomer solution includes meta-phenylenediamine and adamantane diamine.

7. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The second organic solvent comprises acetone and aromatic polyacyl chloride, wherein the aromatic polyacyl chloride monomer comprises aromatic ternary acyl chloride or a combination of different aromatic polyacyl chlorides.

8. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The mass percentage concentration of acetone in the first organic phase monomer solution is in the range of 0.1% to 1.0%, and the mass percentage concentration of aromatic polyacyl chloride is in the range of 0.05% to 0.2%.

9. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The mass percentage concentration of the polyphenol modifier in the second organic phase monomer solution is 0.05%-1%.

10. The high-performance composite solvent-resistant nanofiltration membrane having a rigid twisted non-planar structure polyamide layer according to claim 3, characterized in that: The second organic solvent is ethanol or other polar organic solvents.