Preparation method and application of polyamide composite nanofiltration membrane containing graphdiyne interlayer

Abstract

The application relates to a preparation method of a polyamide composite nanofiltration membrane containing a graphdiyne intermediate layer and application thereof, and belongs to the field of membrane separation and technology. The polyamide composite nanofiltration membrane contains a porous substrate, a graphdiyne intermediate layer and a polyamide layer. The graphdiyne is selected from graphyne, graphdiyne, hydrogen-substituted graphdiyne and other graphdiyne derivatives. The specific preparation method is as follows: a graphdiyne dispersion liquid is suction-filtered onto a porous substrate, is respectively immersed in an aqueous phase and an oil phase, interfacial polymerization is carried out to generate a polyamide membrane, finally, the membrane is dried in a constant-temperature and constant-humidity oven, and a polyamide composite nanofiltration membrane containing a graphdiyne intermediate layer is obtained. The preparation method is simple and efficient, the prepared composite membrane can effectively intercept divalent salts and organic matters in water, and has excellent water permeability, ion separation and antibiotic desalination effect.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation and technology, specifically relating to a method for preparing a polyamide composite nanofiltration membrane containing a graphdiyne interlayer and its application. Background Technology

[0002] Traditional water treatment and purification processes often consume a lot of energy. Therefore, in order to reduce energy consumption and environmental impact, it is crucial to develop and utilize green and efficient technologies to treat saline wastewater and turn it into a valuable resource.

[0003] Membrane separation technology, as a highly efficient, low-energy-consumption, and environmentally friendly emerging separation technology, has great application potential in the field of water treatment. Nanofiltration membranes have pore sizes at the nanometer scale (typically around 0.5-2 nm), falling between ultrafiltration membranes with pore sizes of 2-100 nm and non-porous reverse osmosis membranes. High flux and high rejection rate have always been important goals in the field of nanofiltration membranes. Currently, 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 hydroxysappanite / graphene oxide as an intermediate layer to promote a controllable IP process, thereby preparing a PA membrane with high water flux and salt rejection rate. Introducing hydrophilic porous materials into polyamide membranes has been shown to promote water molecule transport. For example, embedding TMC-modified UiO-66-(NH2)2 into the PA layer via secondary IP can improve the water flux of the PA membrane (Chem. Eng. J., 2024, 497, 154488). However, there is very little research on using hydrophobic porous materials to improve water molecule transport for the preparation of PA TFC membranes.

[0004] Graphdiyne is formed by inserting acetylene bonds between adjacent benzene rings in graphene. It can be named graphodyn, diyne, triyne, etc., based on the number of acetylene bonds, and classified as graphdiyne and hydrogen-substituted graphdiyne based on the number of hydrogen atoms substituted on the benzene rings. GDY layers are stacked to form a layered structure (interlayer spacing approximately 0.365 nm) through van der Waals forces and π-π interactions. Due to the presence of in-plane triangular pores, a three-dimensional channel-like structure can be formed after stacking, giving GDY characteristics of both two-dimensional and three-dimensional materials, which is beneficial for the transport of water molecules both in-plane and between surfaces. The hydrophobic channels of graphdiyne also reduce the friction between water molecules and the pore walls, promoting water molecule transport, making it very suitable as an intermediate layer in polyamide composite nanofiltration membranes.

[0005] This invention uses graphyne as an intermediate layer to prepare a polyamide composite nanofiltration membrane. The polyamide coating on the surface and pores of the graphyne intermediate layer can increase the water mass transfer channels of the nanofiltration membrane, accelerate the transport of water molecules, and increase the water flux while maintaining a high rejection rate, thereby achieving effective treatment of saline wastewater, effectively separating monovalent and divalent salts and removing salts 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 graphdiyne interlayer and its application in the treatment of saline wastewater.

[0007] This invention provides a method for preparing a polyamide composite nanofiltration membrane containing a graphyne interlayer and its application. The membrane is characterized in that it comprises a porous substrate, a graphyne interlayer, and a polyamide layer that coats the surface of the graphyne interlayer and fills the pores between the graphyne layers.

[0008] The graphyne is selected from graphyne mono-, graphyne di-, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives.

[0009] This invention provides a method for preparing the above-mentioned polyamide composite nanofiltration membrane containing a graphdiyne interlayer, comprising the following steps:

[0010] Step a: Clean the porous substrate surface repeatedly with ethanol and water to remove organic matter and inorganic dust.

[0011] Step b: Accurately weigh a certain amount of graphyne material, ultrasonically disperse it in a solvent to obtain a uniform graphyne dispersion, and then filter 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: The porous substrate containing the graphdiyne interlayer prepared in step b is first immersed in an aqueous solution of a certain mass concentration of the monomer. After a certain period of time, it is taken out, the surface moisture is wiped off, and then it is immersed in an organic solution of an oil-phase monomer with a certain mass concentration to carry out an interfacial polymerization reaction to obtain a composite membrane.

[0013] After the composite membranes obtained in steps d and c are heat-treated for a certain period of time, a polyamide composite nanofiltration membrane containing a graphdiyne interlayer is obtained.

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

[0015] Specifically, the graphyne mentioned in step b is selected from one or more of grapho-monyne, graphodyne, hydrogen-substituted graphyne, amine graphyne, and other graphyne derivatives; the dispersion solvent is selected from one or more of ethanol, methanol, DMF, and DMAC; the concentration of the graphyne dispersion is 1-10 ppm; and when filtering on a porous substrate, the dispersion is applied at 7 cm intervals. 2 The filtration surface area corresponds to a dispersion volume of 0-100 mL and is not zero, thus obtaining a porous substrate containing a graphylene intermediate layer.

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

[0017] Specifically, the organic phase monomer in step c is selected from one or more of pyromellitic methyl methacrylate (PMMC), isophthaloyl chloride (IMMR), and pyromellitic tetramethyl methacrylate (PTCM); the organic solution is selected from one or more of n-hexane, cyclohexane, and n-heptane; the concentration of the oil phase monomer is 0.01-2 wt%; and the interfacial polymerization reaction time is 30-120 s.

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

[0019] This invention discloses a polyamide composite nanofiltration membrane with a graphdiyne interlayer, which is applied to wastewater purification and saline wastewater treatment, especially for high-concentration brine treatment, ion separation and antibiotic desalination, such as sodium and magnesium ion separation and antibiotic desalination.

[0020] The beneficial effects of the technical solution provided by this invention are as follows: The polyamide composite nanofiltration membrane with a graphitic diyne interlayer prepared by this invention comprises a porous substrate, a graphitic diyne loaded on the porous substrate as an interlayer, and a porous polyamide layer covering the surface of the graphitic diyne interlayer and filling the gaps between the graphitic diyne layers. The graphitic diyne as an interlayer can regulate the growth of the polyamide, increase the surface roughness of the polyamide membrane, and enhance the hydrophilicity of the membrane surface. The sheet-like structure of graphitic diyne can effectively increase the water mass transfer channels of the nanofiltration membrane. Its hydrophobic pore structure helps to reduce the frictional resistance between water molecules and pores, accelerate the transport of water molecules, and increase the water flux without losing the rejection rate, thus overcoming the "trade-off" effect of nanofiltration membranes. Compared to polyamide membranes without an interlayer, the mixed matrix membranes prepared with graphityne interlayers maintain essentially the same sodium sulfate rejection rate, while increasing water flux by 1.2-2.0 times, showing a significant improvement. The separation factor for sodium ions / magnesium ions is 4-6, and the separation factor for antibiotics / sodium chloride is 20-50. Attached Figure Description

[0021] Figure 1 Scanning electron microscope (SEM) images of the surface and cross section (1-2) of the polyamide composite nanofiltration membrane HsGDY-PA (1-1) with hydrogen-substituted graphyne interlayer prepared in Example 1 of this invention.

[0022] Figure 2 Scanning electron microscope image of the TPNGDY-PA polyamide composite nanofiltration membrane containing an amine-based graphdiyne interlayer prepared in Example 3 of this invention.

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

[0024] Figure 4 The water contact angles of the surface of the HsGDY-PA polyamide composite nanofiltration membrane with hydrogen-substituted graphyne interlayer prepared in Example 1 of the present invention and the surface of the PA polyamide composite nanofiltration membrane prepared in Comparative Example 1 are compared. Detailed Implementation

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

[0026] The present invention provides a polyamide composite nanofiltration membrane containing a graphyne interlayer, comprising a porous substrate, a graphyne interlayer, and a polyamide layer covering the surface of the graphyne interlayer and filling the pores between the graphyne layers.

[0027] The graphyne is selected from graphyne mono-, graphyne di-, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives.

[0028] This invention provides a method for preparing the above-mentioned polyamide composite nanofiltration membrane containing a graphdiyne interlayer, comprising:

[0029] Step 101: Clean the porous substrate surface repeatedly with ethanol and water to remove organic matter and inorganic dust.

[0030] Step 102: Accurately weigh a certain amount of graphyne material and disperse it in a solvent to obtain a uniform graphyne dispersion. Then, filter a certain volume of the dispersion onto a treated porous substrate to obtain a porous substrate containing a graphyne interlayer.

[0031] Step 103: The porous substrate containing graphylene intermediate layer prepared in step 102 is first immersed in an aqueous monomer solution of a certain mass concentration. After a certain time, it is taken out, the surface moisture is wiped off, and then immersed in an organic solution of oil monomer of a certain mass concentration to carry out interfacial polymerization reaction to obtain a composite membrane.

[0032] Step 104: After a certain period of heat treatment, the composite membrane is obtained as a polyamide composite nanofiltration membrane containing a graphdiyne interlayer.

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

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

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

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

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

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

[0039] In the following specific embodiments, operations without specified conditions are performed under standard conditions or conditions recommended by the manufacturer. Raw materials without specified manufacturers and specifications are all commercially available products.

[0040] Example 1

[0041] Step (1) Preparation of the graphyne interlayer

[0042] The surface of the polyacrylonitrile substrate (average pore size 0.04 μm) was repeatedly washed with ethanol and water to remove organic matter and inorganic dust. 5 mg of hydrogen-substituted graphyne material was accurately weighed and dispersed in 1 L of ethanol to obtain a homogeneous graphyne dispersion. Then, 20 ml of the prepared dispersion was filtered through a treated porous substrate (corresponding to a filtration surface area of ​​7 cm²). 2 )superior;

[0043] Step (2) The porous substrate with hydrogen-substituted graphyne interlayer prepared in step (1) is first immersed in an aqueous solution of the monomer piperazine with a mass concentration of 0.5 wt% for 30 s. After wiping off the surface moisture, it is immersed in a hexane solution of the oil-phase monomer trimesoyl chloride with a mass concentration of 0.1 wt% for interfacial polymerization for 30 s. Finally, the composite membrane is heat-treated at 60 ℃ for 3 min to obtain the polyamide composite nanofiltration membrane with hydrogen-substituted graphyne interlayer.

[0044] Separation performance tests were conducted on different saline wastewater systems under the following conditions: the original solution consisted of (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, and (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 performance of the composite membrane was measured as follows: (1) the rejection rate was 96.5% and the water flux was 153.9 L / m. -2 h -1 MPa -1 (2) The retention rate was 95.1%, and the water flux was 91.3 L / m³. -2 h -1 MPa -1 (3) Separation factor 6.1, water flux 119 L m -2 h -1 MPa -1 (4) The separation factor was 8.1 and the flux was 110.9 L m. -2 h -1 MPa -1 (5) The separation factor was 50.5 and the flux was 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) repeatedly with ethanol and water to remove organic matter and inorganic dust. 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 cm²). 2 );

[0048] Step (2) The porous substrate with hydrogen-substituted graphyne interlayer prepared in step (1) is first immersed in an aqueous solution of the monomer piperazine with a mass concentration of 0.5 wt% for 30 s. After wiping off the surface moisture, it is immersed in a hexane solution of the oil-phase monomer trimesoyl chloride with a mass concentration of 0.1 wt% for interfacial polymerization for 30 s. Finally, the composite membrane is heat-treated at 60 ℃ for 3 min to obtain the polyamide composite nanofiltration membrane with hydrogen-substituted graphyne interlayer.

[0049] The separation performance of a 1 g / L sodium sulfate aqueous solution was tested at an operating pressure of 0.4 MPa, with a rejection rate of 96.1% and a water flux of 122.5 L / m³. -2 h -1 MPa -1 .

[0050] Example 3

[0051] Step (1) The surface of the polyacrylonitrile substrate (average pore size 0.04 μm) was washed repeatedly with ethanol and water to remove organic matter and inorganic dust. 5 mg of amine-based graphyne material prepared using tris(4-acetylenephenylamine) as a monomer was accurately weighed and dispersed in 1 L of ethanol to obtain a uniform graphyne dispersion. Then, 10 ml of the prepared dispersion was filtered onto the treated porous substrate (corresponding to a filtration surface area of ​​7 cm²). 2 );

[0052] Step (2) The porous substrate containing amine-based graphdiyne interlayer prepared in step (1) is first immersed in an aqueous solution of the monomer piperazine with a mass concentration of 0.5 wt% for 30 s. After wiping off the surface moisture, it is immersed in a hexane solution of the oil-phase monomer trimesoyl chloride with a mass concentration of 0.1 wt% for interfacial polymerization for 30 s. Finally, the composite membrane is heat-treated at 60℃ for 3 min to obtain a polyamide composite nanofiltration membrane containing amine-based graphdiyne interlayer.

[0053] The separation performance of a 1 g / L sodium sulfate aqueous solution was tested at an operating pressure of 0.4 MPa, with a rejection rate of 96.4% and a water flux of 183.8 L / m³. -2 h -1 MPa -1 .

[0054] Comparative Example 1

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

[0056] Step (2) First, immerse the porous substrate in an aqueous solution of the monomer piperazine with a mass concentration of 0.5 wt% for 30 s. After wiping off the surface moisture, immerse it in an organic solution of the monomer in the oil phase with a mass concentration of 0.1 wt% for interfacial polymerization for 30 s. Finally, place the composite membrane in a heat treatment at 60℃ for 3 min to obtain a polyamide composite nanofiltration membrane.

[0057] The separation performance of a 1 g / L sodium sulfate aqueous solution was tested at an operating pressure of 0.4 MPa, with a rejection rate of 97.1% and a water flux of 101.1 L / m³. -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 within the scope of protection of the present invention.

Claims

1. A method for preparing a polyamide composite nanofiltration membrane containing a graphdiyne interlayer, characterized in that, The composite nanofiltration membrane includes a porous substrate, a graphyne interlayer, and a polyamide layer that coats the surface of the graphyne interlayer and fills the pores between the graphyne layers. The graphyne is selected from graphynyne, graphidyne, hydrogen-substituted graphyne, amine graphyne and other graphyne derivatives. Includes the following steps: Step a: Clean the porous substrate surface repeatedly with ethanol and water to remove organic matter and inorganic dust. Step b: Accurately weigh a certain amount of graphyne material, ultrasonically disperse it in a solvent to obtain a uniform graphyne dispersion, and then filter 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: The porous substrate containing the graphdiyne interlayer prepared in step b is first immersed in an aqueous solution of a certain mass concentration of the monomer. After a certain period of time, it is taken out, the surface moisture is wiped off, and then it is immersed in an organic solution of an oil-phase monomer with a certain mass concentration to carry out an interfacial polymerization reaction to obtain a composite membrane. After the composite membranes obtained in steps d and c are heat-treated for a certain period of time, a polyamide composite nanofiltration membrane containing a graphdiyne interlayer is obtained.

2. The method of claim 1, wherein, The porous substrate mentioned in step a is selected from one or more of polyacrylonitrile membranes, polysulfone membranes, and polyethersulfone membranes, and has an average pore size of 0.05-10 μm.

3. The method of claim 1, wherein, The graphyne mentioned in step b is selected from one or more of grapho-yne, graphidyne, hydrogen-substituted graphyne, amine graphyne, and other graphyne derivatives; the solvent is selected from one or more of ethanol, methanol, DMF, and DMAC; and the concentration of the graphyne dispersion is 1-10 ppm.

4. The method of claim 1, wherein, per 7 cm 2 corresponding to a volume of the dispersed liquid of 0-100 mL and not 0, to obtain a porous substrate containing a graphdiyne interlayer.

5. The method of claim 1, wherein, The aqueous phase monomer mentioned in step c is selected from one or more of piperazine, m-phenylenediamine, and p-phenylenediamine; the concentration of the aqueous phase monomer is 0.01-3 wt%; and the immersion time is 5-120 s.

6. The method of claim 1, wherein, The organic phase monomer in step c is selected from one or more of pyromellitic trimethylolpropionate chloride, isophthaloyl chloride, and pyromellitic tetramethylolpropionate chloride; the organic solution is selected from one or more of n-hexane, cyclohexane, and n-heptane; the concentration of the oil phase monomer is 0.01-2 wt%; and the interfacial polymerization reaction time is 30-120 s.

7. The method of claim 1, wherein, The heat treatment temperature in step d is 30-200℃, and the heat treatment time is 2-120 min.

8. The method of claim 1, wherein, The heat treatment temperature described in step d is 30-80℃.

9. The application of the polyamide composite nanofiltration membrane prepared by the method according to any one of claims 1-8 for brine treatment, ion separation and antibiotic desalination.

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

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