Solvent-resistant hollow fiber nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention relates to a solvent-resistant hollow fiber nanofiltration membrane and a preparation method and application thereof, and belongs to the technical field of membrane separation, the preparation method comprises the following steps: S1, taking an FEP hollow fiber membrane, and carrying out plasma treatment on the FEP hollow fiber membrane; s2, performing PVA modification liquid coating modification on the FEP hollow fiber membrane which is subjected to plasma treatment and prepared in the step S1; s3, carrying out PDMS modification liquid coating modification on the FEP hollow fiber membrane which is prepared in the step S2 and is subjected to PVA modification liquid coating modification; and S4, carrying out interfacial polymerization reaction on the FEP hollow fiber membrane which is prepared in the step S3 and is coated and modified by the PDMS modification liquid, so as to obtain the solvent-resistant hollow fiber nanofiltration membrane. According to the invention, plasma treatment, PVA hydrophilic modification, PDMS coating modification and interfacial polymerization reaction are utilized to prepare the solvent-resistant hollow fiber nanofiltration membrane in the nanofiltration category.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a solvent-resistant hollow fiber nanofiltration membrane and a preparation method and application thereof. Background Art

[0002] Solvent-resistant nanofiltration technology is to intercept molecules in the solvent in an organic solvent system to achieve the purpose of solvent purification. At the same time, hollow fiber membranes are widely used in the field of material separation due to their high packing density, low component cost and strong adaptability.

[0003] At present, commercial hollow fiber membrane materials mainly include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyethersulfone (PES), polyvinyl chloride (PVC), etc. Among them, PTFE has become an extremely attractive membrane material due to its excellent hydrophobic surface, chemical resistance and mechanical strength. However, due to the high temperature required to prepare PTFE hollow fiber membranes and the large pore size, it belongs to the category of microfiltration membranes.

[0004] An existing fluorinated ethylene-propylene copolymer, whose full name is Fluorinated ethylene propylene (FEP), is copolymerized by tetrafluoroethylene and hexafluoropropylene. Compared with PTFE, it has the same excellent chemical resistance, thermal stability, mechanical strength, hydrophobicity and oleophobicity. During the processing, the preparation temperature of FEP is lower, and it is easier to process than PTFE.

[0005] Regarding the above phenomenon, although FEP is easier to process than PTFE, FEP hollow fiber membrane also has the problems of large pore size and low retention efficiency. Therefore, how to improve the nanofiltration level of FEP hollow fiber membrane is an urgent problem to be solved. Summary of the invention

[0006] The purpose of the present invention is to provide a solvent-resistant hollow fiber nanofiltration membrane and a preparation method and application thereof, by hydrophilizing the super-hydrophobic FEP hollow fiber membrane and introducing an interfacial polymerization layer as a selective layer to achieve the purpose of material screening.

[0007] The present invention provides a method for preparing a solvent-resistant hollow fiber nanofiltration membrane, which adopts the following technical scheme:

[0008] A method for preparing a solvent-resistant hollow fiber nanofiltration membrane comprises the following steps:

[0009] S1, taking a FEP hollow fiber membrane and performing plasma treatment on the FEP hollow fiber membrane;

[0010] S2, coating and modifying the plasma-treated FEP hollow fiber membrane obtained in step S1 with a PVA modifying liquid;

[0011] S3, coating and modifying the FEP hollow fiber membrane obtained in step S2 after being coated with the PVA modifying liquid with a PDMS modifying liquid;

[0012] S4, subjecting the FEP hollow fiber membrane obtained in step S3 and modified by coating with the PDMS modifying liquid to interfacial polymerization reaction to obtain a solvent-resistant hollow fiber nanofiltration membrane.

[0013] Preferably, the plasma treatment process of the FEP hollow fiber membrane in step S1 is as follows: the plasma power is 150 W and the treatment time is 0.5-3 min.

[0014] Preferably, the process for coating and modifying the FEP hollow fiber membrane with a PVA modifying liquid in step S2 is to prepare a PVA modifying liquid, and immerse the FEP hollow fiber membrane in the PVA modifying liquid for 0.5-3 hours, take it out and place it in an oven, set the oven temperature to 60-90°C, the time to 10-60 minutes, take out the FEP hollow fiber membrane from the oven and store it in anhydrous ethanol.

[0015] Preferably, the method for preparing the PVA modified liquid in step S2 comprises the following steps:

[0016] S1. Take 1 g of PVA and add it to 100 mL of deionized water, heat it to 95 ° C, stir it for 8 hours, and fully dissolve the PVA. Cool it to room temperature to obtain a PVA solution;

[0017] S2. Add 100 mL of anhydrous ethanol to the PVA solution obtained in step S1, stir for 5 min, then add 2 mL of GA, 5 mL of glacial acetic acid and 5 mL of concentrated sulfuric acid, and continue stirring for 2 h to obtain a PVA modified solution.

[0018] Preferably, the process of coating and modifying the FEP hollow fiber membrane with PDMS modifying liquid in step S3 is to prepare PDMS modifying liquid, immerse the dried FEP hollow fiber membrane in the PDMS modifying liquid for 5-30 seconds, take it out and place it in an oven, set the oven temperature to 40-80°C, and the time to 4-10 hours.

[0019] Preferably, the preparation method of the PDMS modified liquid in step S3 is to take 0.1 g of the curing agent and add it to 9 g of isooctane, then add 2 g of PDMS, and stir for 30 minutes to obtain the PDMS modified liquid.

[0020] Preferably, the process of performing interfacial polymerization reaction on the FEP hollow fiber membrane in step S4 comprises the following steps:

[0021] S1. Take 2 g of MPD and add it into 50 ml of deionized water, stir to prepare MPD solution;

[0022] S2, take 0.1g TMC and dissolve it in 50mL n-hexane solution, stir, and prepare TMC n-hexane solution;

[0023] S3. Soak the dried FEP hollow fiber membrane in the MPD solution obtained in step S1, let it stand for 2 minutes, take it out and wipe it dry, then soak it in the TMC n-hexane solution obtained in step S2, let it stand for 1 minute, take it out and place it in a vacuum oven, set the temperature of the vacuum oven to 95°C and the time to 10 minutes to obtain a solvent-resistant hollow fiber nanofiltration membrane.

[0024] The present invention also provides a solvent-resistant hollow fiber nanofiltration membrane, which is prepared by adopting the above-mentioned method for preparing the solvent-resistant hollow fiber nanofiltration membrane.

[0025] The present invention also provides the use of the solvent-resistant hollow fiber nanofiltration membrane in a solvent-resistant nanofiltration separation process.

[0026] In summary, the present invention includes the following beneficial technical effects:

[0027] 1. The present application uses a device to perform plasma treatment on a FEP hollow fiber membrane to generate oxygen-containing functional groups on its surface, thereby improving the hydrophilicity of the FEP hollow fiber membrane, and then immerses the FEP hollow fiber membrane in a PVA modified liquid, so that the PVA modified liquid is immersed in the membrane pores of the FEP hollow fiber membrane to further improve the hydrophilicity of the FEP hollow fiber membrane, and finally immerses the FEP hollow fiber membrane in a PDMS modified liquid, and obtains a solvent-resistant hollow fiber nanofiltration membrane in the nanofiltration category through an interfacial polymerization reaction. The obtained solvent-resistant hollow fiber nanofiltration membrane has an optimal ethanol permeability of 8L m -2 h -1 bar -1 The optimal dye retention rate is 90.2%.

[0028] 2. The FEP hollow fiber membrane is soaked in a mixed solution of deionized water with ethanol cross-linked with the PVA solution in this application and GA (glutaraldehyde), which can improve the hydrophilicity of the FEP hollow fiber membrane. In the interfacial polymerization reaction, MPD (meta-phenylenediamine) and TMC (1,3,5-trimethylbenzenecarboxylic acid chloride) are prepared, and a polyamide layer (PA) is formed on the membrane filament of the FEP hollow fiber membrane through the interfacial polymerization reaction as a separation selection layer.

[0029] 3. This application reduces the membrane pores of the FEP hollow fiber membrane, improves the nanofiltration level of the FEP hollow fiber membrane, and is easier to process than PTFE, thus having broad market value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic cross-sectional view of a solvent-resistant hollow fiber nanofiltration membrane in the present invention.

[0031] Figure 2 It is an infrared spectra of the solvent-resistant hollow fiber nanofiltration membrane prepared in Example 1 of the present invention and the solvent-resistant hollow fiber membranes of Comparative Examples 1-2.

[0032] Figure 3 It is a surface electron microscope image of the solvent-resistant hollow fiber nanofiltration membrane prepared in Example 1 of the present invention and the solvent-resistant hollow fiber membranes of Comparative Examples 1-2. DETAILED DESCRIPTION

[0033] The following is combined with the embodiments and the attached Figure 1-3 The present invention is described in further detail.

[0034] Example 1

[0035] A method for preparing a solvent-resistant hollow fiber nanofiltration membrane comprises the following steps:

[0036] S1. Take the FEP hollow fiber membrane and perform plasma treatment on the FEP hollow fiber membrane. Set the plasma power to 150W and the treatment time to 0.5-3min.

[0037] S2, take 1g PVA and add it to 100mL deionized water, heat to 95℃, stir for 8h, PVA is fully dissolved, cool to room temperature, obtain PVA solution, add 100mL anhydrous ethanol to the PVA solution, stir for 5min, then add 2mL GA, 5mL glacial acetic acid and 5mL concentrated sulfuric acid, continue stirring for 2h, obtain PVA modified liquid, soak the FEP hollow fiber membrane treated by step S1 in the PVA modified liquid, soak for 0.5-3h, take out and place in an oven, set the oven temperature to 60-90℃, the time is 10-60min, take out the FEP hollow fiber membrane from the oven and store it in anhydrous ethanol for standby use;

[0038] S3, take 0.1g curing agent and add it to 9g isooctane, then add 2g PDMS, stir for 30min to obtain PDMS modified liquid, dry the FEP hollow fiber membrane obtained in step S2 and soak it in the PDMS modified liquid for 5-30s, take it out and place it in an oven, set the oven temperature to 40-80°C, and the time is 4-10h;

[0039] S4, take 2g MPD and add it to 50ml deionized water, stir to obtain MPD solution, dry the FEP hollow fiber membrane obtained by step S3, soak it in MPD solution, and let it stand for 2min; during this period, take 0.1g TMC and dissolve it in 50mL n-hexane solution, stir to obtain TMC n-hexane solution, take out the FEP hollow fiber membrane treated with MPD solution and dry it, then soak it in TMC n-hexane solution, let it stand for 1min, take it out and place it in a vacuum oven, set the temperature of the vacuum oven to 95°C, and the time to 10min to obtain a solvent-resistant hollow fiber nanofiltration membrane.

[0040] Reference Figure 1 The surface of the solvent-resistant hollow fiber nanofiltration membrane prepared in this embodiment is sequentially formed with a PVA modified layer, a PDMS modified layer and a PA layer, and can be applied to the application in the solvent-resistant nanofiltration separation process; Figure 2 and Figure 3 , which is the surface characterization of the solvent-resistant hollow fiber nanofiltration membrane prepared in Example 1.

[0041] Comparative Example

[0042] Comparative Example 1

[0043] A method for preparing a solvent-resistant hollow fiber membrane, which is different from Example 1 in that the FEP hollow fiber membrane is not subjected to the PDMS modification liquid modification treatment and interfacial polymerization reaction treatment in step S3 and step S4 of Example 1, and the remaining steps are the same as those in Example 1; Figure 2 and Figure 3 , which is the surface characterization of the solvent-resistant hollow fiber membrane prepared in Comparative Example 1.

[0044] Comparative Example 2

[0045] A method for preparing a solvent-resistant hollow fiber membrane, which is different from Example 1 in that the interfacial polymerization reaction treatment of step S4 in Example 1 is not performed on the FEP hollow fiber membrane, and the remaining steps are the same as those in Example 1; Figure 2 and Figure 3 , which is the surface characterization of the solvent-resistant hollow fiber membrane prepared in Comparative Example 2.

[0046] Comparative Example 3

[0047] A method for preparing a solvent-resistant hollow fiber membrane is different from Example 1 in that the FEP hollow fiber membrane is not subjected to the PVA modification liquid modification treatment in step S2 of Example 1, and the remaining steps are the same as those in Example 1.

[0048] Comparative Example 4

[0049] A method for preparing a solvent-resistant hollow fiber membrane is different from that in Example 1 in that the FEP hollow fiber membrane is not subjected to the modification treatment with the PDMS modifying liquid in step S3 of Example 1, and the remaining steps are the same as those in Example 1.

[0050] Performance testing

[0051] Detection Methods

[0052] The solvent-resistant hollow fiber nanofiltration membrane sample prepared in Example 1 and the solvent-resistant hollow fiber membrane samples prepared in Comparative Examples 1-4 were respectively placed in a membrane tube equipped with a tee, with one end of the sample in the length direction extending to the liquid outlet of the membrane tube, and the other end of the sample located in the membrane tube; AB glue was poured into both ends of the sample in the length direction for fixation, and the test was carried out after the AB glue was cured.

[0053] Connect the pipeline of the hollow fiber membrane test machine to the raw material tank, add the solvent to be tested into the tank, connect the tee to the test machine and turn on the machine for cross-flow test, adjust the pressure to 0.2MPa and observe whether the flow meter reading is stable, and collect experimental data after it is stable. If the solvent needs to be replaced after the test, the solvent in the pipeline needs to be discharged, and the solution to be tested in the raw material tank needs to be replaced, and the remaining steps are repeated.

[0054] A standard curve of the test dye Brilliant Blue (molecular weight: 792.85) in ethanol solution was drawn using a UV-visible spectrophotometer, and the filtrate collected by cross-flow was measured. The concentration of the dye in the filtrate was calculated using the standard curve. The measurement results are shown in Table 1.

[0055] Table 1 Test results of Example 1 and Comparative Examples 1-4

[0056]

[0057]

[0058] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a solvent-resistant hollow fiber nanofiltration membrane, characterized in that: The following steps are involved: S1, taking a FEP hollow fiber membrane and performing plasma treatment on the FEP hollow fiber membrane; S2, coating and modifying the plasma-treated FEP hollow fiber membrane obtained in step S1 with a PVA modifying liquid; S3, coating and modifying the FEP hollow fiber membrane obtained in step S2 after being coated with the PVA modifying liquid with a PDMS modifying liquid; S4, subjecting the FEP hollow fiber membrane obtained in step S3 and modified by coating with the PDMS modifying liquid to interfacial polymerization reaction to obtain a solvent-resistant hollow fiber nanofiltration membrane.

2. The method for preparing a solvent-resistant hollow fiber nanofiltration membrane according to claim 1, characterized in that: The plasma treatment process of the FEP hollow fiber membrane in step S1 is as follows: the plasma power is 150 W and the treatment time is 0.5-3 min.

3. The method for preparing a solvent-resistant hollow fiber nanofiltration membrane according to claim 1, characterized in that: The process of coating and modifying the FEP hollow fiber membrane with the PVA modifying liquid in step S2 is as follows: preparing the PVA modifying liquid, and immersing the FEP hollow fiber membrane in the PVA modifying liquid for 0.5-3 hours, taking it out and placing it in an oven, setting the oven temperature to 60-90°C, the time to 10-60 minutes, taking out the FEP hollow fiber membrane from the oven and storing it in anhydrous ethanol.

4. The method for preparing a solvent-resistant hollow fiber nanofiltration membrane according to claim 3, characterized in that: The preparation method of the PVA modified liquid in step S2 comprises the following steps: S1. Take 1 g of PVA and add it to 100 mL of deionized water, heat it to 95 ° C, stir it for 8 hours, and fully dissolve the PVA. Cool it to room temperature to obtain a PVA solution; S2. Add 100 mL of anhydrous ethanol to the PVA solution obtained in step S1, stir for 5 min, then add 2 mL of GA, 5 mL of glacial acetic acid and 5 mL of concentrated sulfuric acid, and continue stirring for 2 h to obtain a PVA modified solution.

5. The method for preparing a solvent-resistant hollow fiber nanofiltration membrane according to claim 1, characterized in that: The process of coating and modifying the FEP hollow fiber membrane with PDMS modifying liquid in step S3 is to prepare PDMS modifying liquid, immerse the dried FEP hollow fiber membrane in the PDMS modifying liquid for 5-30 seconds, take it out and place it in an oven, set the oven temperature to 40-80°C, and the time to 4-10 hours.

6. The method for preparing a solvent-resistant hollow fiber nanofiltration membrane according to claim 5, characterized in that: The preparation method of the PDMS modified liquid in step S3 is to take 0.1 g of the curing agent and add it to 9 g of isooctane, then add 2 g of PDMS, and stir for 30 minutes to obtain the PDMS modified liquid.

7. The method for preparing a solvent-resistant hollow fiber nanofiltration membrane according to claim 1, characterized in that: The process of performing interfacial polymerization reaction on the FEP hollow fiber membrane in step S4 comprises the following steps: S1. Take 2 g of MPD and add it into 50 ml of deionized water, stir to prepare MPD solution; S2, take 0.1g TMC and dissolve it in 50mL n-hexane solution, stir, and prepare TMC n-hexane solution; S3. Soak the dried FEP hollow fiber membrane in the MPD solution obtained in step S1, let it stand for 2 minutes, take it out and wipe it dry, then soak it in the TMC n-hexane solution obtained in step S2, let it stand for 1 minute, take it out and place it in a vacuum oven, set the temperature of the vacuum oven to 95°C and the time to 10 minutes to obtain a solvent-resistant hollow fiber nanofiltration membrane.

8. A solvent-resistant hollow fiber nanofiltration membrane obtained according to any one of the preparation methods of claims 1-7.

9. Use of the solvent-resistant hollow fiber nanofiltration membrane according to claim 8 in a solvent-resistant nanofiltration separation process.

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