A method for preparing high permeability polyamide nanofiltration membrane by using crystal template

Abstract

The application belongs to the field of membrane preparation method, and discloses a method for preparing high-permeability polyamide nanofiltration membrane by using a crystal template. First, a mixed aqueous solution of sodium hyaluronate modified by a polysaccharide molecule beta-cyclodextrin, potassium chloride and piperazine monomers is prepared, heat treatment is performed by using an oven to generate a crystal template, then uniform benzene tricarboxylic acid chloride is reacted with the crystal template to form a nascent polyamide nanofiltration membrane, and then heat treatment is performed to obtain a composite polyamide nanofiltration membrane. The composite polyamide nanofiltration membrane prepared by the application has excellent separation performance, the preparation method is simple, and the composite polyamide nanofiltration membrane has a good water treatment application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane preparation method, and particularly relates to a method for preparing high-permeability polyamide nanofiltration membrane by using a crystal template. BACKGROUND

[0002] Membrane separation technology is a separation method with low energy consumption, high precision, high flux and simple operation, and is widely used in the fields of medicine, biology, water treatment, chemical industry and the like, and has great social and economic benefits. The nanofiltration membrane is a novel separation membrane with a pore size between the reverse osmosis membrane and the ultrafiltration membrane, has nanoscale filtration precision, and has the characteristics of large permeation flux, and can greatly improve the membrane separation efficiency.

[0003] Although the ideal nanofiltration membrane has high permeation flux and molecular / ion separation selectivity, the preparation of the nanofiltration membrane still faces a serious trade-off effect between permeability and selectivity. For example, the increase of permeability inevitably leads to the decrease of membrane selectivity, which greatly limits the development and application thereof. Therefore, how to improve the trade-off effect of the membrane and simultaneously improve the permeability and selectivity of the membrane is the key to the preparation of the high-performance nanofiltration membrane.

[0004] Based on the above analysis, the application relates to a polyamide nanofiltration membrane for realizing selective separation of monovalent and divalent anions, which can simultaneously improve the water permeability and ion selectivity of the membrane. The application has simple operation, and the composite polyamide nanofiltration membrane is prepared by the method of supermolecule-induced crystal growth and traditional interfacial polymerization. The optimized functional layer is firm and effective, has a special surface structure and narrow pore size distribution characteristics, effectively improves the permeability and monovalent and divalent ion selectivity of the membrane, and has important significance for the application of the polyamide-based composite nanofiltration membrane in the fields of hard water softening or seawater desalination pretreatment and the like. SUMMARY

[0005] The application is directed to the above technical analysis and the problems existing, and provides a method for preparing high-permeability polyamide nanofiltration membrane by using crystal template, which has the characteristics of large water permeation area, high permeation flux and good separation performance. First, β-cyclodextrin modified sodium hyaluronate (HA-CD) powder is weighed and placed in a conical flask, then deionized water is added to dissolve it to obtain an HA-CD solution; potassium chloride (KCl) powder is weighed and added to the HA-CD solution, and stirred to dissolve it; piperazine monomer (PIP) is dissolved in the above-mentioned mixed solution to obtain a mixed aqueous solution; at the same time, TMC is dissolved in n-hexane solution to obtain an oil phase solution. The polymer base film is immersed in the aqueous solution for a period of time, then drained, and then placed in an oven for heat treatment. After a period of time, the treated polymer base film is taken out and used. Finally, the oil phase solution is poured onto the surface of the base film to perform interfacial polymerization reaction. After a period of time, the residual oil phase solution is removed, and then the base film is placed in an oven for drying treatment. After drying, the deionized water is used for preservation, and the composite polyamide nanofiltration membrane is obtained.

[0006] To achieve the above technical solution, it includes.

[0007] Step one, β-cyclodextrin modified sodium hyaluronate (HA-CD) powder is weighed and placed in a conical flask, then deionized water is added to dissolve it to obtain an HA-CD solution, and the mass concentration fraction of the HA-CD solution is 0-1.0%.

[0008] Step two, potassium chloride (KCl) powder is weighed and added to the HA-CD solution, and stirred to dissolve it, and the mass volume concentration of KCl in the mixed solution is 0-10 g / L.

[0009] Step three, piperazine monomer (PIP) is dissolved in the above-mentioned mixed solution to obtain a mixed aqueous solution, and the mass concentration of PIP is 0.4%.

[0010] Step four, a TMC oil phase solution with a certain mass volume concentration is prepared by using n-hexane solution, and the mass concentration fraction of TMC is 0.1%.

[0011] Step five, the polymer base film is immersed in the mixed aqueous solution, the immersion time is 5 min, and the draining time is 1 min.

[0012] Step six, the base film of the previous step is placed in an oven for heat treatment, the temperature of the oven is set to 40-80℃, and the heat treatment time is 10 min.

[0013] Step seven, the prepared TMC oil phase solution is poured onto the surface of the base film in step six to perform interfacial polymerization reaction. After a period of time, the residual unreacted TMC solution is poured out, and the nascent polyamide nanofiltration membrane is obtained. The reaction time is 2 min.

[0014] Step eight, heat treatment: the nascent polyamide nanofiltration membrane prepared in step seven is placed in an oven for heat treatment, at this time the temperature of the oven is set to 65 DEG C, and the heat treatment time is 15 min, thereby obtaining the composite polyamide nanofiltration membrane.

[0015] Step nine, the composite polyamide nanofiltration membrane is placed in deionized water for storage.

[0016] The polymeric base film material is preferably one of polyether sulfone (PES), polysulfone (PSF), and polyvinylidene fluoride (PVDF); and the composite nanofiltration membrane is a flat sheet membrane.

[0017] The present application has the following prominent technical advantages.

[0018] In the present application, a mixed aqueous solution is prepared, including HA-CD, KCl and PIP. + In this process, the growth of KCl crystals is induced by the coordination interaction between HA-CD and K 2 Cl, and the crystal growth morphology is optimized by adjustable temperature setting, so as to become a template for interfacial polymerization. The composite polyamide nanofiltration membrane prepared on the crystal template can obtain a rough surface structure, which increases the unit water permeation area of the membrane. In addition, the host-guest interaction between HA-CD and PIP molecules helps the functional layer to achieve a narrow pore size distribution, ensuring a high ion selectivity of the polyamide nanofiltration membrane. The composite polyamide nanofiltration membrane has excellent salt rejection rate and permeation flux, wherein the sodium sulfate rejection rate can be more than 98.5%, and the water flux can be more than 14 L / (m ·h·bar). BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a separation performance change graph of the composite polyamide nanofiltration membrane of the present application examples 1-6.

[0020] Figure 2 is a separation performance change graph of the composite polyamide nanofiltration membrane of the present application examples 7-12.

[0021] Figure 3 is a separation performance change graph of the polyamide composite nanofiltration membrane of the present application examples 13-17.

[0022] Figure 4 is a membrane surface roughness change graph of the polyamide composite nanofiltration membrane of the present application examples 13-17.

[0023] Figure 5 is a surface morphology SEM graph of the composite polyamide nanofiltration membrane of the present application example 18.

[0024] Figure 6is a pore size distribution diagram of the composite polyamide nanofiltration membrane in some embodiments of the present application. DETAILED DESCRIPTION

[0025] The present application will be further described in detail in conjunction with specific examples. It should be understood that the specific examples are only used to explain and introduce the present application, and cannot limit the application range of the present application. Any modification and change made to the present application without departing from the purpose and scope of the present application shall fall within the protection scope of the present application.

[0026] Examples 1-6.

[0027] The method for preparing high-permeability polyamide nanofiltration membrane by using crystal template in the present embodiment adopts the following steps:

[0028] Step one, weigh the β-cyclodextrin modified sodium hyaluronate (HA-CD) powder and place it in a conical flask, then add deionized water to dissolve it to obtain a HA-CD solution, and the mass concentration fraction of the HA-CD solution is 0-1.0%.

[0029] Step two, weigh the potassium chloride (KCl) powder and add it to the HA-CD solution, stir to dissolve it, and the mass-volume concentration of KCl in the mixed solution is 6 g / L.

[0030] Step three, weigh the piperazine monomer (PIP) and dissolve it in the above-mentioned mixed solution, that is, the mixed aqueous solution, and the mass concentration of PIP is 0.4%.

[0031] Step four, use n-hexane solution to prepare TMC oil phase solution, and the mass concentration fraction of TMC is 0.1%.

[0032] Step five, immerse the polymer base film in the PIP aqueous solution, the immersion time is 5 min, and the draining time is 1 min.

[0033] Step six, place the base film of the above step in an oven for heat treatment, the temperature of the oven is set to 60℃, and the heat treatment time is 10 min.

[0034] Step seven, use the prepared TMC oil phase solution to pour on the surface of the base film in step six, and carry out interfacial polymerization reaction, after a period of time, pour off the residual unreacted TMC solution, and the nascent polyamide nanofiltration membrane is obtained, and the reaction time is 2 min.

[0035] Step eight, heat treatment: place the nascent polyamide nanofiltration membrane prepared in step seven into an oven for heat treatment, and the temperature of the oven is set to 65℃ at this time, and the heat treatment time is 15 min, and the composite polyamide nanofiltration membrane is obtained.

[0036] Step nine, place the above-mentioned composite polyamide nanofiltration membrane in deionized water for storage.

[0037] The above several main investigation HA-CD concentration changes on the separation performance of composite nanofiltration membrane, the results as shown in the following table: Figure 1

[0038] Examples 7-12.

[0039] Step one, weighing β-cyclodextrin modified sodium hyaluronate (HA-CD) powder placed in a conical flask, then add deionized water to make it dissolved to get HA-CD solution, the mass concentration of HA-CD solution is 0.4%.

[0040] Step two, weighing potassium chloride (KCl) powder into the HA-CD solution, stirring to dissolve, the mass concentration of KCl in the mixed solution is 0-10g / L.

[0041] Step three, weighing piperazine monomer (PIP) dissolved in the above mixed solution, namely the mixed aqueous solution, the mass concentration of PIP is 0.4%.

[0042] Step four, using n-hexane solution to prepare TMC oil phase solution, wherein the mass concentration of TMC is 0.1%.

[0043] Step five, the polymer base film is immersed in the PIP aqueous solution, the immersion time is 5min, and the draining time is 1min.

[0044] Step six, the base film of the above step is placed in an oven for heat treatment, the temperature of the oven is set to 60℃, and the heat treatment time is 10min.

[0045] Step seven, using the prepared TMC oil phase solution is poured on the surface of the base film in step six, and the interfacial polymerization reaction is carried out, after a period of time, the residual unreacted TMC solution is poured off, and the nascent polyamide nanofiltration membrane is obtained, the reaction time is 2min.

[0046] Step eight, heat treatment: the nascent polyamide nanofiltration membrane prepared in step seven is placed in an oven for heat treatment, at this time the temperature of the oven is set to 65℃, and the heat treatment time is 15min, and the composite polyamide nanofiltration membrane is obtained.

[0047] Step nine, the above composite polyamide nanofiltration membrane is placed in deionized water for storage.

[0048] The above several main investigation KCl concentration changes on the separation performance of composite nanofiltration membrane, the results as shown in the following table: Figure 2

[0049] Examples 13-17.

[0050] ​​Step one, take the β-cyclodextrin modified sodium hyaluronate (HA-CD) powder into a conical flask, then add deionized water to dissolve it to obtain a HA-CD solution, the mass concentration fraction of the HA-CD solution is 0.4%.

[0051] Step two, take the potassium chloride (KCl) powder into the HA-CD solution, stir to dissolve it, the mass volume concentration of KCl in the mixed solution is 6 g / L.

[0052] Step three, take the piperazine monomer (PIP) into the above mixed solution, which is the mixed aqueous solution, the mass concentration of PIP is 0.4%.

[0053] Step four, use n-hexane solution to prepare the TMC oil phase solution, the mass concentration fraction of TMC is 0.1%.

[0054] Step five, immerse the polymer base film into the PIP aqueous solution, the immersion time is 5 min, and the draining time is 1 min.

[0055] Step six, place the base film of the above step into an oven for heat treatment, the temperature of the oven is set to 40-80℃, and the heat treatment time is 10 min.

[0056] Step seven, pour the prepared TMC oil phase solution on the surface of the base film in step six to carry out interfacial polymerization reaction, after a period of time, pour away the residual unreacted TMC solution, and the nascent polyamide nanofiltration membrane is obtained, the reaction time is 2 min.

[0057] Step eight, heat treatment: place the nascent polyamide nanofiltration membrane prepared in step seven into an oven for heat treatment, at this time the temperature of the oven is set to 65℃, and the heat treatment time is 15 min, and the composite polyamide nanofiltration membrane is obtained.

[0058] Step nine, place the above composite polyamide nanofiltration membrane in deionized water for storage.

[0059] The above several steps mainly investigate the influence of the change of KCl crystallization temperature on the separation performance of the composite nanofiltration membrane, and the results are shown in the following table. Figure 3

[0060] Example 18.

[0061] Step one, take the β-cyclodextrin modified sodium hyaluronate (HA-CD) powder into a conical flask, then add deionized water to dissolve it to obtain a HA-CD solution, the mass concentration fraction of the HA-CD solution is 0.4%.

[0062] Step two, take the potassium chloride (KCl) powder into the HA-CD solution, stir to dissolve it, the mass volume concentration of KCl in the mixed solution is 6 g / L.​

[0063] Step three, weigh the piperazine monomer (PIP) and dissolve it into the mixed solution above, which is the mixed aqueous solution, and the mass concentration of PIP is 0.4%.

[0064] Step four, prepare the TMC oil phase solution using n-hexane solution, and the mass concentration fraction of TMC is 0.1%.

[0065] Step five, immerse the polymer base film into the PIP aqueous solution, and the immersion time is 5 min and the draining time is 1 min.

[0066] Step six, place the base film of the previous step into the oven for heat treatment, and the temperature of the oven is set to 60℃, and the heat treatment time is 10 min.

[0067] Step seven, pour the prepared TMC oil phase solution onto the surface of the base film in step six to perform the interfacial polymerization reaction, and after a period of time, pour away the residual unreacted TMC solution, and the nascent polyamide nanofiltration membrane is obtained, and the reaction time is 2 min.

[0068] Step eight, heat treatment: place the nascent polyamide nanofiltration membrane prepared in step seven into the oven for heat treatment, and the temperature of the oven is set to 65℃, and the heat treatment time is 15 min, and the composite polyamide nanofiltration membrane is obtained.

[0069] Step nine, place the composite polyamide nanofiltration membrane above into deionized water for storage.

Claims

1. A method for preparing a high-permeability polyamide nanofiltration membrane using a crystal template, characterized in that, Includes the following steps: (1) Dissolve β-cyclodextrin-modified sodium hyaluronate (HA-CD) powder, potassium chloride (KCl) powder and piperazine (PIP) monomer in deionized water to prepare a mixed aqueous solution. In the mixed aqueous solution, the mass concentration fraction of HA-CD is 0.2~1.0%, the mass volume concentration of KCl is 2~10 g / L, and the mass concentration fraction of PIP is 0.4%. (2) Immerse the polymer base film in the mixed aqueous solution obtained in step (1) for 5 min and drain for 1 min. (3) The base film after step (2) is placed in an oven for heat treatment to form a crystal template. The heat treatment temperature is 40~80 ℃ and the time is 10 min. (4) Trimethylbenzene chloride (TMC) is dissolved in n-hexane to prepare an oil phase solution, wherein the mass concentration fraction of TMC in the oil phase solution is 0.1%; (5) Pour the oil phase solution obtained in step (4) onto the crystal template formed in step (3) and carry out interfacial polymerization reaction for 2 min to obtain the nascent polyamide nanofiltration membrane. (6) The nascent polyamide nanofiltration membrane obtained in step (5) is placed in an oven for heat treatment at a temperature of 65°C for 15 min to obtain the composite polyamide nanofiltration membrane.

2. The method according to claim 1, characterized in that, The polymer-based film material is polyethersulfone (PES).

3. The method according to claim 1, characterized in that, The composite polyamide nanofiltration membrane is a flat sheet membrane.

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