Super-hydrophilic PTFE nanofiber membrane and preparation method thereof

Abstract

The invention discloses a super-hydrophilic PTFE nanofiber membrane and a preparation method thereof.The preparation method comprises the steps that PTFE dispersion emulsion, a spinning carrier water solution and lithium chloride are mixed to be uniform, a spinning solution is obtained, the spinning solution is subjected to electrostatic spinning, drying and sintering, and the nanofiber membrane is obtained; performing exhaust treatment on the nanofiber membrane; soaking the nanofiber membrane subjected to exhaust treatment in a ferric salt solution containing ferric ions; the super-hydrophilic PTFE nanofiber membrane is characterized in that the PTFE nanofiber membrane is subjected to in-situ mineralization in a pre-mineralization solution, beta-FeOOH is formed on the nanofiber membrane, washing and drying are conducted, the super-hydrophilic PTFE nanofiber membrane is obtained, in-situ mineralization comprises the steps that the PTFE nanofiber membrane is soaked in the pre-mineralization solution at the temperature of 40-80 DEG C under the stirring condition for 6-24 h, the pre-mineralization solution comprises ferric ions and chloride ions, and the pH value of the pre-mineralization solution is 1-4. The super-hydrophilic PTFE nanofiber membrane prepared by the preparation method disclosed by the invention can keep stable hydrophilic performance in a high-concentration alkaline environment, an acid environment and a strong-corrosion environment.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane materials, and particularly relates to a super-hydrophilic PTFE nanofiber membrane and a preparation method thereof. Background Art

[0002] With the advancement of industrialization and urbanization, more and more hazardous wastewater is being generated and discharged. These hazardous wastewaters contain a variety of harmful chemicals, including waste oil, textile dyes, antibiotics or other drugs, and various heavy metal ions, posing a serious threat to the survival of humans, animals, and plants.

[0003] Membrane separation technology is widely used in water purification due to its advantages such as high selectivity, high separation efficiency, strong continuous operation capability and low energy consumption. Among them, polytetrafluoroethylene (PTFE) nanofiber membrane is an ideal candidate material for wastewater treatment under extreme conditions due to its excellent chemical stability, thermal stability and durability in harsh environments such as strong acids, strong bases and oxidants. For example, complex industrial wastewater treatment and seawater desalination. However, due to the low surface energy and high hydrophobicity of PTFE nanofiber membrane, its water contact angle is large, making it difficult to be directly wetted by water, easily causing membrane fouling and significantly reducing water flux, which seriously limits its application in water treatment. Therefore, it is of great significance to prepare a PTFE nanofiber membrane with excellent hydrophilicity. Summary of the Invention

[0004] Aiming at the problems of low surface energy and high hydrophobicity of PTFE nanofiber membranes, the present invention provides a method for preparing a super-hydrophilic PTFE nanofiber membrane.

[0005] To this end, the present invention adopts the following technical solutions.

[0006] A method for preparing a super-hydrophilic PTFE nanofiber membrane comprises the following steps:

[0007] Step 1: uniformly mixing a PTFE dispersed emulsion, a spinning carrier aqueous solution, and lithium chloride to obtain a spinning solution, and subjecting the spinning solution to electrospinning, drying, and sintering to obtain a nanofiber membrane, wherein the nanofiber membrane is a PTFE nanofiber membrane or a PTFE hollow nanofiber membrane;

[0008] Step 2, performing exhaust treatment on the nanofiber membrane prepared in step 1;

[0009] Step 3, immersing the nanofiber membrane after exhaust treatment in an iron salt solution containing trivalent iron ions for 30 to 90 minutes; then performing in-situ mineralization in a pre-mineralization solution to form β-FeOOH on the nanofiber membrane, washing and drying to obtain a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH nanofiber membrane or super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane); wherein:

[0010] The in-situ mineralization comprises: soaking in a pre-mineralization solution at 40-80° C. for 6-24 hours under stirring conditions, wherein the pre-mineralization solution comprises trivalent iron ions and chloride ions, and the pH of the pre-mineralization solution is 1-4.

[0011] In step 3, the concentration of trivalent iron ions in the iron salt solution is 0.1-0.5M.

[0012] In step 1, the electrospinning parameters include: voltage of 20 to 30 kV, distance between spinneret and collector of 10 to 15 cm, and extrusion rate of 0.5 to 0.8 mL / h.

[0013] In step 1, the spinning carrier aqueous solution is a mixture of the spinning carrier and water, the spinning carrier is polyvinyl alcohol (PVA) or polyethylene oxide (PEO), the concentration of the spinning carrier aqueous solution is 10-25wt.%, and the mass fraction of PTFE in the PTFE dispersed emulsion is 60%.

[0014] In step 1, the mass ratio of PTFE in the PTFE dispersed emulsion, the spinning carrier in the spinning carrier aqueous solution, and lithium chloride is (5-30):1:(0.1-0.5).

[0015] In step 1, when preparing the PTFE hollow nanofiber membrane, the collector used in electrospinning is a metal core shaft, and the metal core shaft serves as a support during the sintering process; after the sintering is completed, the metal core shaft is removed to obtain the PTFE hollow nanofiber membrane; the metal core shaft has a diameter of 1 to 5 mm and a length of 15 to 35 cm.

[0016] In step 1, when preparing the PTFE nanofiber membrane, the collector used for electrospinning is a cylinder with a diameter of 10 to 18 cm and a length of 15 to 35 cm.

[0017] In step 1, the sintering temperature is 330-380° C., the sintering time is 4-8 hours, and in step 1, the electrospinning time is 1-10 hours.

[0018] In step 3, the pre-mineralization solution is a mixture of an iron salt solution containing trivalent iron ions and hydrochloric acid, the volume ratio of the iron salt solution to the hydrochloric acid is (2-5):1, the concentration of the trivalent iron ions in the iron salt solution is 0.1-0.5M; the concentration of the hydrochloric acid is 10-30mM.

[0019] In step 2, the exhaust treatment includes: first soaking in anhydrous ethanol for 30 to 40 minutes, and then drying to remove the anhydrous ethanol.

[0020] In the above technical scheme, when the spinning carrier is PVA, the spinning carrier aqueous solution is a PVA aqueous solution, the concentration of PVA in the PVA aqueous solution is 10-25wt.%, and the mass ratio of PTFE in the PTFE dispersed emulsion, PVA and LiCl in the PVA aqueous solution is (5-10):1:(0.1-0.5); when the spinning carrier is PEO, the spinning carrier aqueous solution is a PEO aqueous solution, the concentration of PEO in the PEO aqueous solution is 10-20wt.%, and the mass ratio of PTFE in the PTFE dispersed emulsion, PEO and LiCl in the PEO aqueous solution is (10-30):1:(0.1-0.5).

[0021] In step 1, the PTFE dispersed emulsion, the spinning carrier aqueous solution and lithium chloride (LiCl) are uniformly mixed by stirring at a speed of 200 to 360 r / min and a stirring time of 3 to 6 hours.

[0022] In the above technical solution, the rate of heating to 330-380°C is 2-10°C / min.

[0023] In the above technical solution, the temperature for drying to remove anhydrous ethanol is 60 to 80° C., and the time is 10 to 30 minutes.

[0024] In the above technical solution, the stirring speed of the in-situ mineralization is 300-600 r / min.

[0025] The present invention also provides a super-hydrophilic PTFE nanofiber membrane obtained by the above preparation method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The preparation method of the present invention has simple steps and strong controllability. The obtained super-hydrophilic PTFE nanofiber membrane has excellent hydrophilicity, excellent acid and alkali resistance, and corrosion resistance, and can maintain stable hydrophilicity in high-concentration alkaline environments, acidic environments, and highly corrosive environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1;

[0029] Figure 2 This is a surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2;

[0030] Figure 3 This is a surface electron micrograph of the PTFE nanofiber membrane prepared in Comparative Example 1;

[0031] Figure 4This is a surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 3;

[0032] Figure 5 This is a cross-sectional electron micrograph of the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 4;

[0033] Figure 6 ATR-FTIR spectra of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2 and the PTFE nanofiber membrane obtained in Comparative Example 1;

[0034] Figure 7 This is the water contact angle diagram of the super hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0036] In the following examples, PTFE dispersion emulsion (DF304, the mass fraction of PTFE in the PTFE dispersion emulsion is 60%) was produced by Shandong Dongyue Chemical Co., Ltd.; polyethylene oxide (PEO) was produced by Shanghai MacLean Biochemical Technology Co., Ltd.; hydrochloric acid (HCl) and ferric chloride hexahydrate (FeCl3·6H2O, 99%) were purchased from Tianjin Saichuan Chemical Reagent Technology Co., Ltd.; and lithium chloride (LiCl) was purchased from Tianjin Komeo Chemical Reagent Co., Ltd.

[0037] Example 1

[0038] A method for preparing a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH nanofiber membrane) comprises the following steps:

[0039] Step 1, preparing PTFE nanofiber membrane: PTFE dispersed emulsion, spinning carrier aqueous solution (10wt.% PEO aqueous solution) and lithium chloride (LiCl) are mixed and stirred for 4 hours under 220r / min magnetic stirring until uniform, to obtain spinning solution, the spinning solution is allowed to stand for 60 minutes for degassing and then placed in an electrospinning device for electrospinning; then dried in a 60°C oven for 18 hours to remove the solvent (to prevent the presence of the solvent from causing the membrane to crack during the sintering process), to obtain a PTFE primary nanofiber membrane with a thickness of 60μm, wherein the PTFE in the PTFE dispersed emulsion is The mass ratio of PEO and LiCl in the PEO aqueous solution was 12:1:0.2, and the spinning parameters were set as follows: voltage of 25 kV, distance between spinneret and fiber collector of 12 cm, extrusion rate of 0.6 ml / h, and rotation speed of fiber collector of 300 r / min; the fiber collector used a cylinder with a diameter of 10 cm and a length of 20 cm, and the electrospinning time was 6 h; the PTFE nascent nanofiber membrane was placed in a muffle furnace and sintered at 380 ° C for 6 h to remove the spinning carrier to obtain a PTFE nanofiber membrane, wherein the heating rate to 380 ° C was 5 ° C / min;

[0040] Step 2: Exhaust the PTFE nanofiber membrane to remove air from the membrane pores, specifically, soak the PTFE nanofiber membrane in anhydrous ethanol at room temperature for 30 minutes, and then dry it in an oven at 60°C for 15 minutes;

[0041] Step 3: Preparation of super-hydrophilic PTFE / β-FeOOH nanofiber membrane by in-situ mineralization:

[0042] The PTFE nanofiber membrane after exhaust treatment was immersed in FeCl3·6H2O solution (the concentration of FeCl3·6H2O solution was 0.1M) at room temperature for 30 min to make Fe 3+ It was completely adsorbed in the PTFE nanofiber membrane, and hydrochloric acid was added to the FeCl3·6H2O solution to form a pre-mineralization solution (the volume ratio of FeCl3·6H2O solution and hydrochloric acid (concentration of 10mM) was 3:1). The pH of the pre-mineralization solution was 2. The fiber was immersed in the pre-mineralization solution at 70°C for 6h under stirring (speed of 600r / min) (i.e., the in situ mineralization time was 6h). An in situ mineralization reaction occurred on the surface of the PTFE nanofiber to form β-FeOOH. The fiber was washed alternately with deionized water and ethanol three times and dried at 60°C for 12h to obtain a super hydrophilic PTFE / β-FeOOH nanofiber membrane.

[0043] The test showed that the water flux of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1 was 3013.18 L / h / m 2 / bar, and the water contact angle is 58°.

[0044] Acid, alkali and corrosion resistance test:

[0045] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1 was subjected to three parallel verifications:

[0046] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane was immersed in hydrochloric acid (pH=1, hydrochloric acid concentration: 10 mM) at a temperature of 25° C. for 24 h;

[0047] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane was immersed in a sodium hydroxide aqueous solution (30 wt % NaOH) at a temperature of 25° C. for 24 h;

[0048] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane was immersed in a sodium hypochlorite aqueous solution (2000 ppm NaClO) at a temperature of 25° C. for 24 hours.

[0049] The flux retention rates of the three parallel validations were all >99%. The water flux of the three groups of super-hydrophilic PTFE / β-FeOOH nanofiber membranes after immersion was tested separately, and the water flux values remained at the original level (about 3013.18 L / h / m 2 / bar is 99%), indicating that the super-hydrophilic PTFE / β-FeOOH nanofiber membrane obtained in Example 1 has excellent acid, alkali and corrosion resistance.

[0050] Example 2

[0051] A method for preparing a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH nanofiber membrane) is basically the same as that in Example 1, except that the in-situ mineralization time in Example 2 is 12 hours.

[0052] The test showed that the water flux of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2 was 8286.25 L / h / m 2 / bar, and the water contact angle is 0°.

[0053] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2 was tested for acid, alkali, and corrosion resistance using the same testing methods and conditions as in Example 1. The flux retention rates measured in the three parallel validation runs of Example 2 were all >99%. Water flux measurements were then performed on each of the three groups of super-hydrophilic PTFE / β-FeOOH nanofiber membranes after immersion, and the water flux values remained at the original levels, demonstrating that the super-hydrophilic PTFE / β-FeOOH nanofiber membranes obtained in Example 2 possess excellent acid, alkali, and corrosion resistance.

[0054] Figure 1This is a surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1. Figure 2 This is the surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2. Figure 1 and Figure 2 It can be seen that when the in situ mineralization time is 12 h, β-FeOOH grows more uniformly on the PTFE nanofibers and completely wraps the PTFE nanofibers, resulting in a significant increase in its water flux.

[0055] Figure 7 This is the water contact angle diagram of the super hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2.

[0056] Comparative Example 1

[0057] A method for preparing a PTFE nanofiber membrane is basically the same as that of Example 1, except that the in-situ mineralization of step 4 is not performed in Comparative Example 1.

[0058] After testing, the water flux of the PTFE nanofiber membrane obtained in Comparative Example 1 was 0 L / h / m 2 / bar, and the water contact angle is 138°.

[0059] Figure 2 This is a surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2. Figure 3 The surface electron microscope image of the PTFE nanofiber membrane prepared in Comparative Example 1 is Figure 2 and Figure 3 It can be seen that the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2 is in situ mineralized, so that β-FeOOH grows on the surface of the PTFE nanofiber, while the surface of the PTFE nanofiber membrane of Comparative Example 1 is smooth and does not contain β-FeOOH.

[0060] Figure 6 ATR-FTIR spectra of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2 and the PTFE nanofiber membrane obtained in Comparative Example 1. Figure 6 It can be seen that the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 2 has a high affinity to water at 3250-3600 cm -1 A strong -OH characteristic peak appears, which is due to the deposition of β-FeOOH introducing a large amount of -OH, which in turn gives the PTFE nanofiber membrane hydrophilic properties.

[0061] Example 3

[0062] A preparation method of a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH nanofiber membrane) is basically the same as that of Example 1, except that the in-situ mineralization time in Example 3 is 24 hours.

[0063] The test showed that the water flux of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 3 was 5853.04 L / h / m 2 / bar, and the water contact angle is 0°.

[0064] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 3 was tested for acid, alkali, and corrosion resistance using the same methods as in Example 1. The flux retention rates measured in the three parallel validation runs of Example 3 were all >99%. Water flux measurements were then performed on the super-hydrophilic PTFE / β-FeOOH nanofiber membranes soaked in the three solutions, and the water flux values remained at the original levels, demonstrating that the super-hydrophilic PTFE / β-FeOOH nanofiber membrane obtained in Example 3 possesses excellent acid, alkali, and corrosion resistance.

[0065] Figure 4 This is the surface electron micrograph of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 3. Figure 4 It can be seen that when the in-situ mineralization time is 24 h, β-FeOOH grows too much on the PTFE fibers, thereby reducing the pore size of the PTFE nanofiber membrane and thus causing a decrease in water flux.

[0066] Example 4

[0067] A method for preparing a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane) comprises the following steps:

[0068] Step 1, preparing a PTFE hollow nanofiber membrane: mixing a PTFE dispersed emulsion and a spinning carrier aqueous solution (10 wt.% PEO aqueous solution) and lithium chloride (LiCl) and stirring them under a magnetic stirring of 220 r / min for 4 hours until uniform to obtain a spinning solution, and the spinning solution was allowed to stand for 60 minutes to degas and then placed in an electrospinning device for electrospinning; then dried in an oven at 60°C for 18 hours to obtain a PTFE primary hollow nanofiber membrane with a thickness of 60 μm, wherein the mass ratio of PTFE in the PTFE dispersed emulsion, PEO in the PEO aqueous solution, and LiCl was 12:1:0.2, The spinning parameters were set as follows: voltage of 25 kV, distance between spinneret and collector of 12 cm, extrusion rate of 0.6 ml / h, and collector speed of 600 r / min. The collector used in electrospinning was a metal core shaft, which served as a support during the sintering process. After sintering, the metal core shaft was removed to obtain a PTFE hollow nanofiber membrane. The diameter of the metal core shaft was 2 mm and the length was 20 cm. The spinning time was 6 h. The PTFE nascent hollow nanofiber membrane was placed in a muffle furnace and sintered at 380 °C for 6 h to obtain a PTFE hollow nanofiber membrane. The heating rate to 380 °C was 5 °C / min.

[0069] Step 2: Exhaust the PTFE hollow nanofiber membrane to expel air from the membrane pores, specifically, soak the PTFE hollow nanofiber membrane in anhydrous ethanol at room temperature for 30 minutes and dry it in an oven at 60°C for 15 minutes;

[0070] Step 3, in situ mineralization to prepare PTFE / β-FeOOH hollow nanofiber membrane: the PTFE hollow nanofiber membrane after exhaust treatment is soaked in a FeCl3·6H2O solution (the concentration of FeCl3·6H2O solution is 0.1M) at room temperature for 30 minutes, hydrochloric acid is added to the FeCl3·6H2O solution to form a pre-mineralization solution (the volume ratio of FeCl3·6H2O solution and hydrochloric acid (the concentration of hydrochloric acid is 10mM) is 3:1), the pH of the pre-mineralization solution is 2, and it is immersed in the pre-mineralization solution at 70°C under stirring (speed of 600r / min) for 6 hours (i.e., the in situ mineralization time is 6 hours), and β-FeOOH is in situ mineralized on the surface of the PTFE hollow nanofiber to form PTFE hollow nanofiber. It is washed alternately with deionized water and ethanol 3 times, and dried at 60°C for 12 hours to obtain a super hydrophilic PTFE nanofiber membrane (PTFE / β-FeOOH hollow nanofiber membrane).

[0071] The test showed that the water flux of the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 4 was 1022.96 L / h / m 2 / bar, and the water contact angle is 0°.

[0072] The acid and alkali resistance and corrosion resistance tests of the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 4 were basically the same as the "acid and alkali resistance and corrosion resistance test" in Example 1, with the only difference being that "the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1" was replaced by "the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 4". The flux retention rates measured by the three parallel verifications of Example 4 were all >99%. The water flux tests were performed again on the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membranes soaked in the above three solutions, and the water flux values remained at the original level, indicating that the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane obtained in Example 4 has excellent acid and alkali resistance and corrosion resistance.

[0073] Figure 5 This is an electron microscope image of the cross section of the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 4.

[0074] Example 5

[0075] A preparation method of a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane) is basically the same as that of Example 4, except that the in-situ mineralization time in Example 5 is 12 hours.

[0076] The test showed that the water flux of the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 5 was 3856.04 L / h / m 2 / bar, and the water contact angle is 0°.

[0077] The super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 5 was subjected to acid and alkali resistance and corrosion resistance tests, which were basically the same as the "acid and alkali resistance and corrosion resistance test" in Example 1, with the only difference being that "the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1" was replaced by "the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane prepared in Example 5". The flux retention rates measured by the three parallel verifications of Example 5 were all >99%. The super-hydrophilic PTFE / β-FeOOH hollow nanofiber membranes soaked in the above three solutions were subjected to water flux tests respectively, and the water flux values remained at the original level, indicating that the super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane obtained in Example 5 has excellent acid and alkali resistance and corrosion resistance.

[0078] Example 6

[0079] A preparation method of a super-hydrophilic PTFE nanofiber membrane (super-hydrophilic PTFE / β-FeOOH nanofiber membrane) is basically the same as that in Example 2, except that the electrospinning time in step 1 of Example 6 is 10 hours, and Example 6 obtains a PTFE primary nanofiber membrane with a thickness of 100 μm.

[0080] The test showed that the water flux of the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 6 was 3899.23 L / h / m 2 / bar, and the water contact angle is 0°.

[0081] The super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 6 was subjected to acid and alkali resistance and corrosion resistance tests, which were basically the same as the "acid and alkali resistance and corrosion resistance test" in Example 1, with the only difference being that "the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 1" was replaced by "the super-hydrophilic PTFE / β-FeOOH nanofiber membrane prepared in Example 6". The flux retention rates measured in the three parallel verifications of Example 6 were all >99%. The super-hydrophilic PTFE / β-FeOOH nanofiber membranes soaked in the above three solutions were subjected to water flux tests again, and the water flux values remained at the original levels, indicating that the super-hydrophilic PTFE / β-FeOOH nanofiber membrane obtained in Example 6 has excellent acid and alkali resistance and corrosion resistance.

[0082] By comparing Example 6 with Example 2, it can be seen that although the water contact angles of Example 6 and Example 2 are both 0°, as the electrospinning time increases, the thickness of the PTFE primary nanofiber membrane (base membrane) increases, which leads to a decrease in the water flux of the super hydrophilic PTFE / β-FeOOH nanofiber membrane.

Claims

1. A method for preparing a super-hydrophilic PTFE nanofiber membrane, characterized in that: The following steps are involved: Step 1: uniformly mixing a PTFE dispersed emulsion, a spinning carrier aqueous solution, and lithium chloride to obtain a spinning solution, and subjecting the spinning solution to electrospinning, drying, and sintering to obtain a nanofiber membrane, wherein the nanofiber membrane is a PTFE nanofiber membrane or a PTFE hollow nanofiber membrane; Step 2, performing exhaust treatment on the nanofiber membrane prepared in step 1; Step 3: Soaking the nanofiber membrane after exhaust treatment in an iron salt solution containing trivalent iron ions for 30 to 90 minutes; then performing in-situ mineralization in a pre-mineralization solution to form β-FeOOH on the nanofiber membrane, washing, and drying to obtain a super-hydrophilic PTFE / β-FeOOH nanofiber membrane or a super-hydrophilic PTFE / β-FeOOH hollow nanofiber membrane; wherein: The in-situ mineralization comprises: soaking in a pre-mineralization solution at 40-80° C. for 6-24 hours under stirring conditions, wherein the pre-mineralization solution comprises trivalent iron ions and chloride ions, and the pH of the pre-mineralization solution is 1-4.

2. The preparation method according to claim 1, characterized in that In step 3, the concentration of trivalent iron ions in the iron salt solution is 0.1-0.5M.

3. The preparation method according to claim 1, characterized in that In step 3, the pre-mineralization solution is a mixture of an iron salt solution containing trivalent iron ions and hydrochloric acid, the volume ratio of the iron salt solution to the hydrochloric acid is (2-5):1, the concentration of the trivalent iron ions in the iron salt solution is 0.1-0.5M; the concentration of the hydrochloric acid is 10-30mM.

4. The preparation method according to claim 1, wherein: In step 1, when preparing the PTFE hollow nanofiber membrane, the collector used in electrospinning is a metal core shaft, and the metal core shaft serves as a support during the sintering process; after the sintering is completed, the metal core shaft is removed to obtain the PTFE hollow nanofiber membrane; the diameter of the metal core shaft is 1 to 5 mm and the length is 15 to 35 cm.

5. The preparation method according to claim 1, wherein: In step 1, when preparing the PTFE nanofiber membrane, the collector used for electrospinning is a cylinder with a diameter of 10 to 18 cm and a length of 15 to 35 cm.

6. The preparation method according to claim 1, characterized in that In step 1, the electrospinning parameters include: voltage of 20 to 30 kV, distance between spinneret and collector of 10 to 15 cm, and extrusion rate of 0.5 to 0.8 mL / h.

7. The preparation method according to claim 1, characterized in that In step 1, the spinning carrier aqueous solution is a mixture of the spinning carrier and water, the spinning carrier is polyvinyl alcohol or polyethylene oxide, the concentration of the spinning carrier aqueous solution is 10-25wt.%, and the mass fraction of PTFE in the PTFE dispersed emulsion is 60%.

8. The preparation method according to claim 1, characterized in that In step 1, the mass ratio of PTFE in the PTFE dispersed emulsion, the spinning carrier in the spinning carrier aqueous solution, and lithium chloride is (5-30):1:(0.1-0.5).

9. The preparation method according to claim 1, characterized in that In step 1, the sintering time is 4 to 8 hours, and in step 1, the electrospinning time is 1 to 10 hours; in step 2, the exhaust treatment includes: first soaking in anhydrous ethanol for 30 to 40 minutes, and then drying to remove the anhydrous ethanol.

10. The super-hydrophilic PTFE nanofiber membrane obtained by the preparation method according to any one of claims 1 to 9.

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