MOF-808 modified hollow fiber membrane and preparation method thereof

Abstract

The invention provides a preparation method of an MOF-808 modified hollow fiber membrane. The preparation method comprises the following steps: preparing MOF-808 core liquid; preparing a PVDF membrane casting solution, stirring the PVDF membrane casting solution in an oil bath pan, and transferring the PVDF membrane casting solution to a hollow fiber membrane device for secondary defoaming after primary defoaming is completed; setting the initial extrusion rate of the device, extruding the PVDF membrane casting solution from a spinning nozzle of the hollow fiber membrane device, and stopping extruding when the PVDF membrane casting solution is visible in the transparent observation stage; the MOF-808 core liquid is also introduced into the device, the extrusion rate of the membrane casting liquid and the MOF-808 core liquid is adjusted, MOF-808 hollow fiber membrane filaments are obtained, the MOF-808 hollow fiber membrane filaments are placed in deionized water to be subjected to curing treatment, the deionized water is replaced, soaking continues to be conducted, airing is conducted at the room temperature, and the MOF-808 modified hollow fiber membrane is prepared. The invention further provides the MOF-808 modified hollow fiber membrane. The modified membrane provided by the invention is simple in preparation process, good in hydrophilic and oleophobic performance and high in reusability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer membrane separation materials, and particularly relates to a MOF-808 modified hollow fiber membrane and a preparation method thereof. BACKGROUND

[0002] Metal-organic frameworks (MOFs) materials exhibit great potential in gas separation, ion separation and other fields due to their high specific surface area and adjustable pore structure. Mixing MOFs materials with membrane matrix materials to prepare mixed matrix membranes is a current research hotspot. Among them, the hollow fiber membrane form has the advantages of high packing density and good separation efficiency.

[0003] However, the preparation of existing MOFs mixed matrix membranes faces many challenges, including the easy agglomeration of MOFs nanoparticles in the casting solution, which leads to the formation of non-selective defects in the membrane; at high MOFs loading, the viscosity of the casting solution increases sharply, which causes problems such as broken filaments during the preparation of mixed matrix membranes, especially hollow fiber membranes, and reduces the yield of finished products.

[0004] Therefore, there is an urgent need in the art to develop a new MOFs modified hollow fiber membrane formula and process to achieve good dispersion of MOFs particles, improve the spinnability of the spinning solution, and ultimately obtain MOFs hollow fiber membranes with excellent separation performance.

[0005] Chinese patent CN119793218A provides a surface coating in-situ modified hollow fiber membrane material and a preparation method thereof. The preparation method comprises the following steps: step 1, preparing a casting solution; the casting solution is used to prepare a hollow fiber membrane filament precursor through a spinning process; step 2, the hollow fiber membrane filament precursor is sequentially subjected to an air gap, a cooling pool and a solvent exchange pool to obtain a semi-finished product membrane; the cooling liquid in the cooling pool is an ethylene glycol aqueous solution treated by plasma; step 3, the semi-finished product membrane is subjected to surface treatment again by plasma to obtain a hollow fiber membrane containing a surface polyethylene glycol coating structure. The present application fully utilizes the components of the cooling liquid and combines plasma polymerization treatment to in-situ modify the surface of the hollow fiber membrane, and quickly and efficiently form a polyethylene glycol coating on the surface of the hollow fiber membrane; however, the preparation method of the modified membrane is complicated, and the operation cost is high.

[0006] Chinese patent CN120420833A discloses a modified hollow fiber membrane and a preparation method and application thereof. A PVDF (polyvinylidene fluoride) hollow fiber membrane is vertically inserted into a cross-flow device, and PEI solution and sodium lignosulfonate solution are respectively introduced into the cross-flow device for coordination and crosslinking treatment, and the membrane surface is rinsed after crosslinking to realize the modification of the hollow fiber membrane, but the surface modified modification material is easy to fall off, and the membrane pores are easy to be blocked.

[0007] In view of the above, it is necessary to develop a MOFs particle that can achieve good dispersion, improve the spinnability of the spinning solution, and ultimately obtain a MOFs hollow fiber membrane with excellent separation performance.

[0008] In view of the above, it is necessary to develop a MOFs particle that can achieve good dispersion, improve the spinnability of the spinning solution, and ultimately obtain a MOFs hollow fiber membrane with excellent separation performance. SUMMARY

[0009] In view of the above, it is necessary to develop a MOFs particle that can achieve good dispersion, improve the spinnability of the spinning solution, and ultimately obtain a MOFs hollow fiber membrane with excellent separation performance.

[0010] The purpose of the present application is to provide a MOF-808 modified hollow fiber membrane;

[0011] To achieve the above-mentioned purpose and other related purposes, the present application provides a preparation method of a MOF-808 modified hollow fiber membrane, which comprises the following steps:

[0012] a. Disperse MOF-808 powder in ultrapure water, and after ultrasonic treatment, form a uniformly dispersed MOF-808 water dispersion as MOF-808 core liquid;

[0013] b. Prepare a PVDF casting solution, uniformly stir it in an oil bath and complete the first defoaming, then transfer it to a hollow fiber membrane device through siphon action for secondary defoaming;

[0014] c. After the secondary defoaming treatment is completed, set the initial extrusion rate of the hollow fiber membrane device, extrude the PVDF casting solution from the spinneret of the hollow fiber membrane device, and stop extruding when it is visible in the transparent observation stage;

[0015] d. Connect the MOF-808 core liquid to the hollow fiber membrane device through a peristaltic pump, adjust the extrusion rate of the hollow fiber membrane device and the extrusion rate of the peristaltic pump, and continue spinning to obtain a MOF-808 hollow fiber membrane filament with uniform structure;

[0016] e. After the MOF-808 hollow fiber membrane filament is placed in deionized water for solidification treatment, replace the deionized water, continue to soak for 5-40 hours, carefully take out the membrane filament and dry it at room temperature, and obtain the MOF-808 modified hollow fiber membrane.

[0017] Preferably, the mass of MOF-808 powder in step a is 0.1-2.0 g, and the mass of ultrapure water is 100-1000 mL.

[0018] Preferably, in step b, the temperature of the oil bath is set to 25–80°C, the stirring time is 10–35 hours, the first degassing time is 1–6 hours, and the second degassing time is 6–12 hours.

[0019] Preferably, the preparation steps of the PVDF casting solution in step b are as follows: PVDF powder, PVP powder and DMF solution are placed in a three-necked flask and the three-necked flask is placed in an oil bath and stirred, and then pre-degassed.

[0020] Preferably, PVDF accounts for 14-20% of the PVDF casting solution by mass, PVP accounts for 0.5-5% of the PVDF casting solution by mass, and DMF accounts for 75-79.5% of the PVDF casting solution by mass.

[0021] Preferably, the pressure of the siphon effect in step b is -12 to -20 kPa.

[0022] Preferably, the initial extrusion rate in step c is 50–300 mL / min, and the extrusion pressure is 100–200 kPa.

[0023] Preferably, the extrusion rate of the hollow fiber membrane device in step d is 3-15 mL / min, and the extrusion pressure is 100-200 kPa; the extrusion rate of the peristaltic pump is set to 2-8 mL / min.

[0024] Preferably, the curing time in step e is 0.5 to 5 hours.

[0025] A MOF-808 modified hollow fiber membrane prepared according to the above preparation method.

[0026] The MOF-808 modified hollow fiber membrane and its preparation method presented in this case have the following beneficial effects:

[0027] 1) This invention prepares MOF-808 hollow fiber membranes using a unique device. The preparation process is simple and easy to control, with low cost, and the membrane structure is easy to control and uniform.

[0028] 2) In this invention, the deposition of MOF-808 powder with high porosity increases the porosity of the hollow fiber membrane, providing more pathways for water molecules to pass through the membrane, thereby increasing the pure water flux of the membrane to 287 L·m. -2 ·h -1 ·bar -1 ;

[0029] 3) The MOF-808 used in this invention has certain hydrophilicity and high porosity. The hollow fiber membrane prepared by its modification shows improved hydrophilicity and its water contact angle is reduced to 52.3°.

[0030] 4) The MOF-808 hollow fiber membrane prepared by this invention has good retention capacity for different dye molecules in water, and the retention rate of Eriochrome Black T solution can reach more than 90%, while maintaining a high permeation flux of up to 120 L·m -2 ·h -1 ·bar -1 . Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the experimental apparatus used in the embodiments of the present invention;

[0032] Figure 2 These are scanning electron microscope (SEM) comparison images of the MH-0 and MH-2 films in Examples 1 and 3 of this invention.

[0033] Figure 3 This is a diagram showing the pure water flux effect of the MH membrane in Embodiment 1 of the present invention;

[0034] Figure 4 This is a diagram showing the separation effect of the MH-2 membrane on different dye solutions in Example 2 of the present invention. Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0036] This invention provides a method for preparing MOF-808 modified hollow fiber membranes, the preparation steps of which are as follows:

[0037] a. Disperse MOF-808 powder in ultrapure water, and after sonication, form a uniformly dispersed MOF-808 aqueous dispersion as the MOF-808 core liquid.

[0038] b. Prepare the PVDF casting solution, stir it evenly in an oil bath and after the first degassing is completed, transfer it to the hollow fiber membrane device by siphoning for the second degassing.

[0039] c. After the secondary degassing treatment is completed, set the initial extrusion rate of the hollow fiber membrane device, and extrude the PVDF casting liquid from the spinneret of the hollow fiber membrane device. Stop extrusion when it becomes visible in the transparent observation stage.

[0040] d. The MOF-808 core liquid is also introduced into the hollow fiber membrane device through a peristaltic pump. After adjusting the extrusion rate of the hollow fiber membrane device (to the PVDF casting liquid) and the extrusion rate of the peristaltic pump (to the MOF-808 core liquid), the spinning continues to obtain MOF-808 hollow fiber membrane filaments with uniform structure.

[0041] e. After curing the MOF-808 hollow fiber membrane fibers in deionized water, the deionized water is replaced, and the membrane fibers are soaked for another 5–40 hours. The membrane fibers are then carefully removed and air-dried at room temperature to obtain the MOF-808 modified hollow fiber membrane. In step a, the mass of MOF-808 powder is 0.1–2.0 g, and the mass of ultrapure water is 100–1000 mL.

[0042] In step b, the oil bath temperature is set to 25–80°C, the stirring time is 10–35 hours, the first degassing time is 1–6 hours, and the second degassing time is 6–12 hours. The preparation steps for the PVDF casting solution are as follows: PVDF powder, PVP powder, and DMF solution are placed in a three-necked flask, which is then placed in an oil bath and stirred, followed by pre-degassing. PVDF accounts for 14–20% of the mass percentage of the PVDF casting solution, PVP accounts for 0.5–5% of the mass percentage of the PVDF casting solution, and DMF accounts for 75–79.5% of the mass percentage of the PVDF casting solution.

[0043] The pressure of the siphon effect in step b is -12 to -20 kPa; the initial extrusion rate in step c is 50 to 300 mL / min, and the extrusion pressure is 100 to 200 kPa.

[0044] The extrusion rate of the hollow fiber membrane device (for the casting solution) in step d is 3-15 mL / min, and the extrusion pressure is 100-200 kPa; the extrusion rate of the peristaltic pump (for the MOF-808 core solution) is set to 2-8 mL / min.

[0045] The curing time in step e is 0.5 to 5 hours.

[0046] A MOF-808 modified hollow fiber membrane prepared according to the above preparation method.

[0047] Note: The full Chinese name of MOF-808 is Metal-Organic Framework-808, which is a zirconium-based metal-organic framework material. Its name is a direct transliteration of the English abbreviation "MOF" (Metal-Organic Framework) combined with its specific designation "808". In academic and industrial fields, the English abbreviation "MOF-808" or its Chinese transliteration is usually used directly.

[0048] Example 1:

[0049] 1) Take 32g of PVDF (polyvinylidene fluoride) powder, 6g of PVP (polyvinylpyrrolidone) powder and 162g of DMF (N,N-dimethylformamide) solution respectively and put them into a 500mL three-necked flask. Place the three-necked flask in a 60℃ oil bath and stir for 12 hours, then pre-degas for 1 hour.

[0050] 2) The deaerated casting solution is drawn into a Teledyne ISCO 1000D high-pressure, high-precision plunger pump (i.e., hollow fiber membrane device) through a PFA 1 / 4 tube. Figure 1 (As shown below, degas for 6 hours);

[0051] 3) Connect the high-pressure, high-precision plunger pump to the spinneret via a pipeline ( Figure 1 The separate spinneret in the device is installed and then placed on a support for fixation. The Teledyne ISCO 1000D high-pressure, high-precision plunger pump is run, with an initial internal volume reading (obtained from the device surface) of 1015 mL. The initial extrusion rate is set to 350 mL / min to extrude the casting solution into filaments. When the pump volume reading reaches 500 mL, the extrusion rate is changed to 200 mL / min, continuing to extrude the casting solution into filaments. When the volume reading reaches 400 mL, the extrusion rate is adjusted to 150 mL / min. When the volume reading reaches 300 mL, the extrusion rate is adjusted to 20 mL / min. Finally, extrusion is stopped when the casting solution becomes visible during the transparent observation stage.

[0052] 4) Use pure water as the core fluid and connect it to the spinneret of the Teledyne ISCO 1000D high-pressure high-precision plunger pump via a peristaltic pump. Adjust the extrusion rate of the peristaltic pump to an initial value of 3 mL / min. After the core fluid drips out from the middle of the spinneret, continue to run the Teledyne ISCO 1000D high-pressure high-precision plunger pump at a rate of 5 mL / min and start collecting the membrane filaments extruded from the spinneret.

[0053] 5) After spinning, the membrane fibers are soaked in pure water, and the water is changed every hour. After changing the pure water twice, the membrane fibers are soaked overnight. The pure water is changed again the next day. After soaking for 4-5 hours, the membrane fibers are dried to obtain pure PVDF hollow fiber membrane, which is denoted as MH-0.

[0054] Example 2:

[0055] 1) Disperse 0.2g of MOF-808 powder in 200mL of pure water and sonicate for 1 hour to form a uniform MOF-808 aqueous dispersion to obtain MOF-808 core liquid;

[0056] 2) Take 32g of PVDF powder, 6g of PVP powder, and 162g of DMF solution and put them into a 500mL three-necked flask. Place the three-necked flask in a 60℃ oil bath and stir for 12 hours, then pre-degas for 1 hour;

[0057] 3) The above-mentioned deaerated casting solution was drawn into a Teledyne ISCO 1000D high-pressure, high-precision plunger pump through a PFA 1 / 4 tube for deaeration for 6 hours;

[0058] 4) Connect the high-pressure, high-precision plunger pump to the spinneret via a pipeline ( Figure 1 The separate spinneret in the device is installed and then placed on a support for fixation. The Teledyne ISCO 1000D high-pressure, high-precision plunger pump is run, with an initial internal volume reading (obtained from the device surface) of 1015 mL. The initial extrusion rate is set to 350 mL / min to extrude the casting solution into filaments. When the pump volume reading reaches 500 mL, the extrusion rate is changed to 200 mL / min, continuing to extrude the casting solution into filaments. When the volume reading reaches 400 mL, the extrusion rate is adjusted to 150 mL / min. When the volume reading reaches 300 mL, the extrusion rate is adjusted to 20 mL / min. Finally, extrusion is stopped when the casting solution becomes visible during the transparent observation stage.

[0059] 5) Connect the MOF-808 core fluid to the spinneret of the Teledyne ISCO 1000D high-pressure, high-precision plunger pump via a peristaltic pump. Figure 1 (In the separate spinneret), adjust the extrusion rate of the peristaltic pump to an initial setting of 3 mL / min. After the core liquid drips out from the middle of the spinneret, continue to run the Teledyne ISCO 1000D high-pressure, high-precision plunger pump at 5 mL / min and start collecting the membrane filaments extruded from the spinneret.

[0060] 6) After spinning, immerse the membrane fibers in pure water, changing the water every hour. After changing the pure water twice, soak overnight. Change the pure water again the next day, soak for 4-5 hours, and then air dry to obtain MOF-808 modified hollow fiber membrane, denoted as MH-1.

[0061] Example 3

[0062] 1) Disperse 0.4g of MOF-808 powder in 200mL of pure water and sonicate for 1 hour to form a uniform MOF-808 aqueous dispersion to obtain MOF-808 core solution;

[0063] 2) Take 32g of PVDF powder, 6g of PVP powder, and 162g of DMF solution and put them into a 500mL three-necked flask. Place the three-necked flask in a 60℃ oil bath and stir for 12 hours, then pre-degas for 1 hour;

[0064] 3) The above-mentioned deaerated casting solution was drawn into a Teledyne ISCO 1000D high-pressure, high-precision plunger pump through a PFA 1 / 4 tube for deaeration for 6 hours;

[0065] 4) Connect the high-pressure, high-precision plunger pump to the spinneret via a pipeline ( Figure 1 The separate spinneret in the device is installed and then placed on a support for fixation. The Teledyne ISCO 1000D high-pressure, high-precision plunger pump is run, with an initial internal volume reading (obtained from the device surface) of 1015 mL. The initial extrusion rate is set to 350 mL / min to extrude the casting solution into filaments. When the pump volume reading reaches 500 mL, the extrusion rate is changed to 200 mL / min, continuing to extrude the casting solution into filaments. When the volume reading reaches 400 mL, the extrusion rate is adjusted to 150 mL / min. When the volume reading reaches 300 mL, the extrusion rate is adjusted to 20 mL / min. Finally, extrusion is stopped when the casting solution becomes visible during the transparent observation stage.

[0066] 5) Connect the MOF-808 core solution to the spinneret of the Teledyne ISCO 1000D high-pressure high-precision plunger pump via a peristaltic pump. Adjust the extrusion rate of the peristaltic pump to an initial value of 3 mL / min. After the core solution drips out from the middle of the spinneret, continue to run the Teledyne ISCO 1000D high-pressure high-precision plunger pump at a rate of 5 mL / min and begin collecting the membrane filaments extruded from the spinneret.

[0067] 6) After spinning, the membrane fibers are soaked in pure water, and the water is changed every hour. After changing the pure water twice, the membrane is soaked overnight. The pure water is changed again the next day. After soaking for 4-5 hours, the membrane is dried to obtain MOF-808 modified hollow fiber membrane, which is denoted as MH-2.

[0068] 1. Figure 2 Scanning electron microscope (SEM) images of the MOF-808-modified hollow fiber membrane MH-2 prepared according to this invention are presented and compared with the PVDF hollow fiber membrane MH-0. From the surface images (top left 1 and bottom left 1), it can be seen that the MOF-808 particles are successfully and uniformly distributed on the surface of the hollow fiber membrane without obvious agglomeration, forming a well-dispersed composite structure. This uniform distribution not only demonstrates the good compatibility between MOF and the polymer matrix during the modification process, but also provides the membrane with more potential active sites and functionalized surfaces, which are expected to significantly enhance its separation performance, antifouling ability, or catalytic performance. In contrast, the MH-0 membrane surface exhibits a typical polymer porous structure, and no features similar to inorganic particle modification were observed, further highlighting the innovative core of this invention: achieving functionalized membrane structure design through controllable loading of MOF-808.

[0069] 2. To demonstrate the separation capability of the MOF-808 modified hollow fiber membrane in this invention, cross-flow filtration was used to measure the water flux of different membranes MH-0, MH-1, and MH-2. Figure 3 As shown in Table 1, the water flux of the membrane increased due to the introduction of MOF-808.

[0070] Table 1: Pure water flux and water contact angle values ​​of the original PVDF membrane and MOF-808 hollow fiber membrane

[0071] Membrane Water flux Water contact angle MH-0 190 L·m -2 ·h -1 ·bar -1 ]]> 65.2° MH-1 224 L·m -2 ·h -1 ·bar -1 ]]> 60.5° MH-2 287 L·m -2 ·h -1 ·bar -1 ]]> 52.3°

[0072] 3. Different dyes in water were separated using the MH-2 membrane, which has the highest flux. These dyes included: Eriochrome Black T (EBT), Congo Red (CR), Methylene Blue (MB), and Acid Red-66 (AR-66). The dye concentration was 30 mg / L for all dyes. The permeate flux and rejection rate of the MH-2 membrane for filtering different dyes are as follows: Figure 4 As shown.

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a MOF-808 modified hollow fiber membrane, characterized in that, The preparation steps are as follows: a. Disperse MOF-808 powder in ultrapure water, and after sonication, form a uniformly dispersed MOF-808 aqueous dispersion as the MOF-808 core liquid. b. Prepare the PVDF casting solution, stir it evenly in an oil bath and after the first degassing is completed, transfer it to the hollow fiber membrane device by siphoning for the second degassing. c. After the secondary degassing treatment is completed, set the initial extrusion rate of the hollow fiber membrane device, and extrude the PVDF casting liquid from the spinneret of the hollow fiber membrane device. Stop extrusion when it becomes visible in the transparent observation stage. d. The MOF-808 core liquid is also introduced into the hollow fiber membrane device through a peristaltic pump. After adjusting the extrusion rate of the hollow fiber membrane device and the extrusion rate of the peristaltic pump, the filaments are continued to be spun to obtain MOF-808 hollow fiber membrane filaments with uniform structure. e. After the MOF-808 hollow fiber membrane fibers are placed in deionized water for curing treatment, the deionized water is replaced and the membrane fibers are soaked for another 5 to 40 hours. The membrane fibers are then carefully removed and dried at room temperature to obtain the MOF-808 modified hollow fiber membrane.

2. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 1, characterized in that, In step a, the mass of MOF-808 powder is 0.1–2.0 g, and the mass of ultrapure water is 100–1000 mL.

3. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 2, characterized in that, In step b, the temperature of the oil bath is set to 25–80°C, the stirring time is 10–35 hours, the first degassing time is 1–6 hours, and the second degassing time is 6–12 hours.

4. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 3, characterized in that, The preparation steps of PVDF casting solution in step b are as follows: PVDF powder, PVP powder and DMF solution are put into a three-necked flask and the three-necked flask is placed in an oil bath and stirred, and then pre-degassed.

5. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 4, characterized in that, PVDF accounts for 14-20% of the mass of the PVDF casting solution, PVP accounts for 0.5-5% of the mass of the PVDF casting solution, and DMF accounts for 75-79.5% of the mass of the PVDF casting solution.

6. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 5, characterized in that, The pressure of the siphon effect in step b is -12 to -20 kPa.

7. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 6, characterized in that, The initial extrusion rate in step c is 50–300 mL / min, and the extrusion pressure is 100–200 kPa.

8. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 7, characterized in that... The extrusion rate of the hollow fiber membrane device in step d is 3-15 mL / min, and the extrusion pressure is 100-200 kPa; the extrusion rate of the peristaltic pump is set to 2-8 mL / min.

9. The method for preparing the MOF-808 modified hollow fiber membrane according to claim 8, characterized in that, The curing time in step e is 0.5 to 5 hours.

10. A MOF-808 modified hollow fiber membrane, characterized in that, The MOF-808 modified hollow fiber membrane prepared by the preparation method according to any one of claims 1 to 9.

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