Preparation method and application of polyamide composite nanofiltration membrane containing graphdiyne middle layer

Abstract

The invention discloses a preparation method and application of a polyamide composite nanofiltration membrane containing a graphdiyne middle layer, and belongs to the technical field of membrane separation. Comprising a porous substrate, a graphdiyne middle layer and a polyamide layer. The graphdiyne is selected from graphdiyne, graphdiyne, hydrogen-substituted graphdiyne and other graphdiyne derivatives. The specific preparation method comprises the following steps: carrying out suction filtration on graphdiyne dispersion liquid to a porous substrate, respectively dipping the graphdiyne dispersion liquid in a water phase and an oil phase, carrying out interfacial polymerization to generate a polyamide membrane, and finally, drying the membrane in a constant-temperature and constant-humidity drying oven to obtain the polyamide composite nanofiltration membrane containing the graphdiyne middle layer. The preparation method disclosed by the invention is simple and efficient, and the prepared composite membrane can effectively intercept divalent salt and organic matters in water and has excellent water permeability, ion separation and antibiotic desalination effects.

Description

Technical Field

[0001] The invention belongs to the field of membrane separation and technology, and specifically relates to a preparation method and application of a polyamide composite nanofiltration membrane containing a graphene intermediate layer. Background Art

[0002] Coal-fired power plants, chlor-alkali and pharmaceutical industries produce a large amount of high-concentration saline wastewater. For example, the desulfurization wastewater produced by coal-fired power plants contains a variety of pollutants such as suspended particles, organic matter and inorganic salts, including chlorides and sulfates. Antibiotics are produced by bacterial or fungal fermentation. Wastewater containing inorganic salts will be produced during the antibiotic culture medium and extraction and purification process. Therefore, the effective separation of antibiotics and salts in the pharmaceutical wastewater treatment system is crucial. Traditional water treatment and purification processes often consume a lot of energy. Therefore, in order to reduce energy consumption and reduce environmental impact, it is crucial to develop and use green and efficient technologies to treat saline wastewater and turn it into treasure.

[0003] Membrane separation technology, as an emerging separation technology with high efficiency, low energy consumption and environmental friendliness, has great application potential in the field of water treatment. The pore size of nanofiltration membrane is nanometer-level (usually around 0.5-2nm), which is between ultrafiltration membrane with a pore size of 2-100nm and non-porous reverse osmosis membrane. High flux and high retention rate have always been an important goal in the field of nanofiltration membranes. At present, various materials such as carbon nanotubes, graphene oxide, metal organic frameworks and covalent organic frameworks have been used to construct intermediate layers to prepare high-flux nanofiltration membranes. Guo et al. (Chem. Eng. J., 2024, 481, 148595) used hydroxysodalite / graphene oxide as an intermediate layer to promote a controllable IP process, thereby preparing PA membranes with high water flux and salt retention. The introduction of hydrophilic porous materials in polyamide membranes has been shown to promote the transport of water molecules. For example, embedding TMC-modified UiO-66-(NH2)2 into the PA layer through secondary IP can improve the water flux of PA membranes (Chem. Eng. J., 2024, 497, 154488). However, there are few studies on the use of hydrophobic porous materials to improve water molecule transport for the preparation of PA TFC membranes.

[0004] GDY is formed by inserting acetylene bonds between adjacent benzene rings of graphene. It can be named as Graphyne, Diyne, Triyne, etc. according to the number of acetylene bonds. It can be divided into Graphyne and Hydrogen-substituted Graphyne according to the number of hydrogens replaced on the benzene rings. GDY layers are stacked by van der Waals forces and π-π interactions to form a layered structure (the interlayer spacing is about 0.365nm). Due to the presence of in-plane triangular pores, a structure similar to a three-dimensional channel can be formed after stacking layers, so that GDY has the characteristics of both two-dimensional materials and three-dimensional materials, which is conducive to the transmission of water molecules in its plane and between planes. The hydrophobic channels of Graphyne also reduce the friction between water molecules and the pore wall, promoting the transmission of water molecules, so it is very suitable for introducing polyamide composite nanofiltration membrane as an intermediate layer.

[0005] The present invention uses graphyne as an intermediate layer to prepare a polyamide composite nanofiltration membrane. Polyamide is coated on the surface and pores of the graphyne intermediate layer, which can increase the water mass transfer channel of the nanofiltration membrane, accelerate the transmission of water molecules, and improve the water flux while maintaining a high retention rate, thereby achieving effective treatment of saline wastewater, effectively separating monovalent and divalent salts, and removing salt from antibiotic wastewater. Summary of the invention

[0006] The key technical problem to be solved by the present invention is to provide a method for preparing a polyamide composite nanofiltration membrane containing a graphyne intermediate layer and its application in treating saline wastewater.

[0007] The present invention provides a preparation method and application of a polyamide composite nanofiltration membrane containing a graphyne intermediate layer, characterized in that the separation membrane comprises a porous substrate, a graphyne intermediate layer and a polyamide layer coated on the surface of the graphyne intermediate layer and filling the pores between graphynes.

[0008] The graphyne is selected from graphene monoacetylene, graphene diacetylene, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives.

[0009] The present invention provides a method for preparing the polyamide composite nanofiltration membrane containing the Graphene acetylene intermediate layer, comprising the following steps:

[0010] Step a, washing the surface of the porous substrate with ethanol and water for multiple times to remove organic matter and inorganic dust on the surface;

[0011] Step b, accurately weighing a certain amount of graphyne material, ultrasonically dispersing it in a solvent to obtain a uniform graphyne dispersion, and then filtering a certain volume of the dispersion onto the porous substrate treated in step a to obtain a porous substrate containing a graphyne intermediate layer;

[0012] Step c, immersing the porous substrate containing the graphyne intermediate layer prepared in step b into an aqueous solution of an aqueous phase monomer with a certain mass concentration, taking it out after a certain period of time, drying the surface moisture, and then immersing it in an organic solution of an oil phase monomer with a certain mass concentration to perform an interfacial polymerization reaction to obtain a composite membrane;

[0013] After the composite membrane obtained in step d and step c is subjected to heat treatment for a certain period of time, a polyamide composite nanofiltration membrane containing a graphyne intermediate layer is obtained.

[0014] Specifically, the porous substrate in step a is selected from one or more of polyacrylonitrile membrane, polysulfone membrane, and polyethersulfone membrane, and the average pore size is 0.05-10 μm. The average pore size is 0.05-10 μm;

[0015] Specifically, the graphyne in step b is selected from one or more of graphyne, graphdiyne, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives; the solvent for dispersion is selected from one or more of ethanol, methanol, DMF, and DMAC; the concentration of the graphyne dispersion is 1-10 ppm; when filtering on a porous substrate, the 7 cm 2 The filtration surface area corresponds to a dispersion volume of 0-100 mL and is not 0, and the corresponding porous substrate containing a graphyne intermediate layer is obtained.

[0016] Specifically, the aqueous phase monomer in step c is selected from one or more of piperazine, m-phenylenediamine, and p-phenylenediamine; the aqueous phase monomer concentration is 0.01-3wt%; the immersion time is 5-120s;

[0017] Specifically, the organic phase monomer in step c is selected from one or more of trimesoyl chloride, isophthaloyl chloride, and pyromellitoyl chloride; the organic solution is selected from one or more of n-hexane, cyclohexane, and n-heptane; the oil phase monomer concentration is 0.01-2wt%; and the interfacial polymerization reaction time is 30-120s;

[0018] Specifically, the heat treatment temperature in step d is 30-200°C, preferably 30-80°C; the heat treatment time is 2-120min;

[0019] The polyamide composite nanofiltration membrane containing a graphyne intermediate layer of the present invention is used for sewage purification and saline wastewater treatment, especially for high-concentration salt water treatment, ion separation and antibiotic desalination, such as sodium ion and magnesium ion separation, antibiotic desalination, etc.

[0020] The technical solution provided by the present invention has the following beneficial effects: the polyamide composite nanofiltration membrane containing Graphdye intermediate layer prepared by the present invention comprises a porous substrate and Graphdye loaded on the porous substrate as an intermediate layer, and a porous polyamide layer covering the surface of the Graphdye intermediate layer and filling the pores between Graphdye and Graphdye. Graphdye as an intermediate layer can regulate the growth of polyamide, increase the roughness of the polyamide membrane surface, and enhance the hydrophilicity of the membrane surface; the Graphdye sheet structure can effectively increase the water mass transfer channel of the nanofiltration membrane, and its hydrophobic pore structure is conducive to reducing the friction resistance between water molecules and pores, accelerating the transmission of water molecules, and can increase the water flux without losing the retention rate, thus overcoming the "trade-off" effect of the nanofiltration membrane. Compared with the polyamide membrane without an intermediate layer, the mixed matrix membrane prepared with graphyne intermediate layer has basically unchanged sodium sulfate retention rate, and the water flux can be increased by 1.2-2.0 times, with a more significant improvement effect. The separation factor of sodium ions / magnesium ions is 4-6, and the separation factor of antibiotics / sodium chloride is 20-50. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 .Scanning electron microscope images of the surface (1-1) and cross-section (1-2) of the polyamide composite nanofiltration membrane HsGDY-PA (1-1) containing a hydrogen-substituted graphyne intermediate layer prepared in Example 1 of the present invention.

[0022] Figure 2 .Scanning electron microscope image of the surface of the polyamide composite nanofiltration membrane TPNGDY-PA containing an amine graphyne intermediate layer prepared in Example 3 of the present invention.

[0023] Figure 3 . Scanning electron microscopy images of the surface (3-1) and cross-section (3-2) of the polyamide nanofiltration composite membrane prepared in Comparative Example 1 of the present invention.

[0024] Figure 4 .The water contact angle of the surface of the polyamide composite nanofiltration membrane HsGDY-PA with a hydrogen-substituted graphyne intermediate layer prepared in Example 1 of the present invention and the surface of the polyamide composite nanofiltration membrane PA prepared in Comparative Example 1. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to the following embodiments.

[0026] The invention provides a polyamide composite nanofiltration membrane containing a graphyne intermediate layer, comprising a porous substrate, a graphyne intermediate layer and a polyamide layer coated on the surface of the graphyne intermediate layer and filled in the pores between graphynes.

[0027] The graphyne is selected from graphene monoacetylene, graphene diacetylene, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives.

[0028] The embodiment of the present invention provides a method for preparing the polyamide composite nanofiltration membrane containing the Graphene acetylene intermediate layer, comprising:

[0029] Step 101: Clean the surface of the porous substrate with ethanol and water for multiple times to remove organic matter and inorganic dust on the surface.

[0030] Step 102: accurately weigh a certain amount of graphyne material and disperse it in a solvent to obtain a uniform graphyne dispersion liquid. Then, a certain volume of the dispersion liquid is filtered onto the treated porous substrate to obtain a porous substrate containing a graphyne intermediate layer.

[0031] Step 103, immersing the substrate containing the graphyne intermediate layer porous substrate prepared in step 102 into a water-phase monomer solution of a certain mass concentration, taking it out after a certain period of time, drying the surface moisture, and then immersing it in an organic solution of an oil-phase monomer of a certain mass concentration to perform an interfacial polymerization reaction to obtain a composite membrane;

[0032] Step 104: After the composite membrane is heat treated for a certain period of time, a polyamide composite nanofiltration membrane containing a graphyne intermediate layer is obtained.

[0033] Specifically, the porous substrate in step 101 is selected from and has an average pore size of 0.05-10 μm; wherein the organic polymer membrane can be a polyacrylonitrile membrane, a polysulfone membrane, a polyethersulfone membrane, and preferably a polyacrylonitrile membrane among the organic polymer membranes.

[0034] Specifically, the graphyne in step 102 is selected from one or more of graphene monoacetylene, graphene diacetylene, hydrogen-substituted graphene, amine-type graphene and other graphene derivatives, preferably hydrogen-substituted graphene and amine-type graphene; the dispersion solvent is selected from one or more of water, ethanol, methanol, DMF, and DMAC, preferably ethanol; the concentration of the graphyne dispersion is 1-10ppm, which can be 1ppm, 3ppm, 5ppm, 7ppm; per 7cm 2 The filtration surface area corresponds to a dispersion volume of 0-100 mL and is not 0, but can be 5 mL, 10 mL, 20 mL, 50 mL, 70 mL or 100 mL;

[0035] Specifically, in step 103, the aqueous phase monomer is selected from one or more of piperazine, m-phenylenediamine, and p-phenylenediamine, preferably piperazine; the aqueous phase monomer concentration is 0.01-3wt%; the immersion time is 5-120s;

[0036] Specifically, the organic phase monomer in step 103 is selected from one or more of trimesoyl chloride, isophthaloyl chloride, and pyromellitoyl chloride, preferably trimesoyl chloride; the organic solution is selected from one or more of n-hexane, cyclohexane, and n-heptane, preferably n-hexane; the oil phase monomer concentration is 0.01-2wt%; the interfacial polymerization reaction time is 30-120s;

[0037] Specifically, the heat treatment temperature in step 104 is 30-200° C., preferably 30-80° C.; the heat treatment time is 2-120 min;

[0038] The present invention will be further described below through specific examples.

[0039] In the following specific examples, the operations involved, if the conditions are not specified, are all carried out under conventional conditions or conditions recommended by the manufacturer. The raw materials used, if the manufacturers and specifications are not specified, are all conventional products that can be obtained from the market.

[0040] Example 1

[0041] Step (1) Preparation of Graphene Oxide Interlayer

[0042] The surface of the polyacrylonitrile substrate (average pore size 0.04 μm) was washed with ethanol and water several times to remove the organic matter and inorganic dust on the surface. 5 mg of hydrogen-substituted graphyne material was accurately weighed and dispersed in 1 L of ethanol to obtain a uniform graphyne dispersion. Then 20 ml of the prepared dispersion was filtered onto the treated porous substrate (corresponding to a filtration surface area of ​​7 cm 2 )superior;

[0043] Step (2) first immerses the substrate of the porous substrate of the hydrogen-substituted graphyne intermediate layer prepared in step (1) into an aqueous solution of a water-phase monomer piperazine with a mass concentration of 0.5wt%, takes it out after 30s, wipes off the surface moisture and then immerses it in an n-hexane solution of an oil-phase monomer trimesoyl chloride with a mass concentration of 0.1wt%, and performs interfacial polymerization for 30s; finally, the composite membrane is placed in a heat treatment at 60°C for 3min to obtain a polyamide composite nanofiltration membrane with a hydrogen-substituted graphyne intermediate layer.

[0044] Separation performance tests were conducted on different saline wastewater systems under the following test conditions: the original solution compositions were (1) 1 g / L sodium sulfate aqueous solution, (2) 5 g / L sodium sulfate aqueous solution, (3) 5 g / L sodium sulfate and magnesium sulfate mixed aqueous solution, (4) 5 g / L sodium chloride and sodium sulfate mixed aqueous solution; (5) 0.1 g / L tetracycline solution and 1 g / L sodium chloride mixed aqueous solution; the operating pressure was 0.4 MPa.

[0045] The measured performance of the composite membrane is as follows: (1) The rejection rate is 96.5% and the water flux is 153.9 L m-2 h -1 MPa -1 ; (2) The retention rate is 95.1% and the water flux is 91.3 L m -2 h -1 MPa -1 ; (3) Separation factor 6.1, water flux 119 L m -2 h -1 MPa -1 ; (4) Separation factor is 8.1, flux is 110.9 L m -2 h -1 MPa -1 ; (5) Separation factor is 50.5, and flux is 154.9 L m -2 h -1 MPa -1 .

[0046] Example 2

[0047] Step (1) Wash the surface of the polyacrylonitrile substrate (average pore size 0.04 μm) with ethanol and water several times to remove organic matter and inorganic dust on the surface. Accurately weigh 5 mg of graphyne material and disperse it in 1 L of ethanol to obtain a uniform graphyne dispersion. Then filter 10 ml of the prepared dispersion onto the treated porous substrate (corresponding to a filtration surface area of ​​7 cm 2 );

[0048] Step (2) first immerses the substrate of the porous substrate of the hydrogen-substituted graphyne intermediate layer prepared in step (1) into an aqueous solution of a water-phase monomer piperazine with a mass concentration of 0.5wt%, takes it out after 30s, wipes off the surface moisture and then immerses it in an n-hexane solution of an oil-phase monomer trimesoyl chloride with a mass concentration of 0.1wt%, and performs interfacial polymerization for 30s; finally, the composite membrane is placed in a heat treatment at 60°C for 3min to obtain a polyamide composite nanofiltration membrane with a hydrogen-substituted graphyne intermediate layer.

[0049] For the separation performance test of 1g / L sodium sulfate aqueous solution, the operating pressure was 0.4MPa, the rejection rate was 96.1%, and the water flux was 122.5L m -2 h -1 MPa -1 .

[0050] Example 3

[0051] Step (1) Wash the surface of the polyacrylonitrile substrate (average pore size 0.04 μm) with ethanol and water several times to remove organic matter and inorganic dust on the surface. Accurately weigh 5 mg of amine graphyne material prepared with tri(4-ethynylphenylamine) as a monomer and disperse it in 1 L of ethanol to obtain a uniform graphyne dispersion. Then filter 10 ml of the prepared dispersion onto the treated porous substrate (corresponding to a filtration surface area of ​​7 cm 2 );

[0052] Step (2) first immerses the substrate of the porous substrate containing amine-containing graphyne intermediate layer prepared in step (1) into an aqueous solution of water-phase monomer piperazine with a mass concentration of 0.5wt%, takes it out after 30s, wipes off the surface moisture and then immerses it in an n-hexane solution of oil-phase monomer trimesoyl chloride with a mass concentration of 0.1wt%, and performs interfacial polymerization for 30s; finally, the composite membrane is placed in a heat treatment at 60°C for 3min to obtain a polyamide composite nanofiltration membrane containing an amine-containing graphyne intermediate layer.

[0053] For the separation performance test of 1g / L sodium sulfate aqueous solution, the operating pressure was 0.4MPa, the retention rate was 96.4%, and the water flux was 183.8L m -2 h -1 MPa -1 .

[0054] Comparative Example 1

[0055] Step (1) The surface of the polyacrylonitrile substrate (average pore size of 0.04 μm) is cleaned with ethanol and water for multiple times to remove organic matter and inorganic dust on the surface.

[0056] Step (2) first immerses the porous substrate in an aqueous solution of a water-phase monomer piperazine with a mass concentration of 0.5wt%, takes it out after 30s, wipes off the surface moisture and then immerses it in an organic solution of an oil-phase monomer with a mass concentration of 0.1wt%, and performs interfacial polymerization for 30s; finally, heat-treats the composite membrane at 60°C for 3min to obtain a polyamide-containing composite nanofiltration membrane.

[0057] For the separation performance test of 1g / L sodium sulfate aqueous solution, the operating pressure was 0.4MPa, the retention rate was 97.1%, and the water flux was 101.1L m -2 h -1 MPa -1 .

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A polyamide composite nanofiltration membrane containing a graphene intermediate layer, characterized in that: The composite nanofiltration membrane comprises a porous substrate, a graphyne intermediate layer, and a polyamide layer coated on the surface of the graphyne intermediate layer and filled in the pores between graphyne and graphyne; The graphyne is selected from graphene monoacetylene, graphene diacetylene, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives.

2. The method for preparing the polyamide composite nanofiltration membrane according to claim 1, characterized in that: The following steps are involved: Step a, washing the surface of the porous substrate with ethanol and water for multiple times to remove organic matter and inorganic dust on the surface; Step b, accurately weighing a certain amount of graphyne material, ultrasonically dispersing it in a solvent to obtain a uniform graphyne dispersion, and then filtering a certain volume of the dispersion onto the porous substrate treated in step a to obtain a porous substrate containing a graphyne intermediate layer; Step c, immersing the porous substrate containing the graphyne intermediate layer prepared in step b into an aqueous solution of an aqueous phase monomer with a certain mass concentration, taking it out after a certain period of time, drying the surface moisture, and then immersing it in an organic solution of an oil phase monomer with a certain mass concentration to perform an interfacial polymerization reaction to obtain a composite membrane; After the composite membrane obtained in step d and step c is subjected to heat treatment for a certain period of time, a polyamide composite nanofiltration membrane containing a graphyne intermediate layer is obtained.

3. The method according to claim 2, characterized in that The porous substrate described in step a is selected from one or more of polyacrylonitrile membrane, polysulfone membrane and polyethersulfone membrane, and has an average pore size of 0.05-10 μm.

4. The method according to claim 2, characterized in that In step b, the graphyne is selected from one or more of graphyne, graphdiyne, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives; the solvent for dispersion is selected from one or more of ethanol, methanol, DMF, and DMAC; the concentration of the graphyne dispersion is 1-10ppm.

5. The method according to claim 2, characterized in that When filtering on a porous substrate, every 7 cm 2 The filtration surface area corresponds to a dispersion volume of 0-100 mL and is not 0, and the corresponding porous substrate containing a graphyne intermediate layer is obtained.

6. The method according to claim 2, characterized in that The aqueous phase monomer in step c is selected from one or more of piperazine, m-phenylenediamine, and p-phenylenediamine; the aqueous phase monomer concentration is 0.01-3wt%; and the immersion time is 5-120s.

7. The method according to claim 2, characterized in that The organic phase monomer in step c is selected from one or more of trimesoyl chloride, isophthaloyl chloride, and pyromellitoyl chloride; the organic solution is selected from one or more of n-hexane, cyclohexane, and n-heptane; the oil phase monomer concentration is 0.01-2wt%; and the interfacial polymerization reaction time is 30-120s.

8. The method according to claim 2, characterized in that The heat treatment temperature in step d is 30-200° C., preferably 30-80° C.; the heat treatment time is 2-120 min.

9. Use of the polyamide composite nanofiltration membrane according to claim 1 for sewage purification, saline wastewater treatment, especially for high-concentration salt water treatment, ion separation and antibiotic desalination.

10. The use according to claim 9, for separation of sodium ions and magnesium ions.

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