Preparation method and application of UIO-66 (Fe) / PAN nanofiber membrane

Abstract

The invention discloses a preparation method and application of a UIO-66 (Fe) / PAN nanofiber membrane, and the preparation method comprises the following steps: (1) adding zircon salt and ferric salt into a solvent, and uniformly mixing to obtain a solution A; (2) adding terephthalic acid into an acid-base regulator, then adding a solvent, and uniformly mixing to obtain a solution B; (3) uniformly mixing the solution A and the solution B, carrying out solvothermal reaction, cooling to room temperature, centrifuging, washing and drying to obtain a UIO-66 (Fe) solid; (4) dissolving polyacrylonitrile in a solvent, and uniformly mixing to obtain a PAN solution; (5) ultrasonically dispersing a UIO-66 (Fe) solid in a solvent to obtain a dispersion liquid, adding the dispersion liquid into the PAN solution, and uniformly stirring and mixing to obtain a spinning solution; and (6) carrying out electrostatic spinning on the spinning solution to obtain the UIO-66 (Fe) / PAN nanofiber membrane. The nanofiber membrane prepared by the method has high adsorption capacity and good selectivity on Se (IV) in a water body.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a preparation method and application of a UIO-66 (Fe) / PAN nanofiber membrane. Background Art

[0002] Selenium is one of the most toxic elements in groundwater and is usually found in nature as selenate (SeO4 2- ), selenite (SeO3 2- ), selenide (Se 2- ) and elemental selenium (Se 0 ) exists in the form of selenide, which is the most toxic compound among all organic substances. However, it is easily oxidized to selenite in the presence of air. Selenium also exists in the form of selenate and selenite in soil and water. There are many factors that cause selenium pollution in groundwater, both natural and human. Sedimentary rocks, volcanic eruptions, rock weathering, mining and smelting of metal ores, nuclear industry, etc. can cause selenium pollution. A one-time intake of high concentrations of selenium (400~800 mg / Kg) can cause headaches, breathing difficulties, muscle cramps, respiratory failure and even death, while long-term intake of higher concentrations of selenium (2400~3000 μg / Kg) can also cause diseases such as hair loss, nail loss, liver and kidney failure. High concentrations of selenium are very toxic, but trace amounts of selenium are also important elements to ensure the normal life activities of the human body. Trace amounts of selenium can reduce the incidence and mortality of cancer, which is particularly significant in the prevention and treatment of prostate cancer, colorectal cancer, and lung cancer. Daily intake of trace amounts of selenium can also improve the body's resistance, relieve joint pain, prevent cataract deterioration, and help resist aging. Therefore, it is particularly important to adopt reasonable methods to adsorb, enrich and transform excess selenium in water to solve the problem of insufficient selenium intake by organisms.

[0003] Metal-organic frameworks (MOFs) have been widely used in catalysis, drug delivery, gas adsorption, and separation-based procedures due to their high specific area, abundant active sites, and easily functionalized surface chemical structures. In addition, MOFs are also considered promising candidates for separating various pollutants from water sources. However, most of the MOFs reported earlier were sensitive to water and their structures and compositions were unstable. Electrospinning is an economical and simple method for the continuous preparation of nanofibers, and it is also the most effective method for preparing polymer nanofibers with simple three-dimensional structures. Electrospun nanofibrous membranes (ENMs) are composed of non-woven fibers with diameters ranging from tens to hundreds of nanometers. They have the advantages of simple preparation, small thickness, large specific surface area, good thermal stability, high porosity, strong tunability, and easy recycling, but electrospun nanofibrous membranes prepared from a single polymer usually have poor separation capabilities.

[0004] At present, most of the research focuses on the modification of traditional MOFs, ignoring the complementary advantages and disadvantages of other methods. How to combine traditional MOFs materials with electrospinning technology to prepare adsorption materials with higher stability and stronger separation ability is a problem that the existing technology needs to solve. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of UIO-66 (Fe) / PAN nanofiber membrane to solve the problems of poor stability and poor separation ability of the above-mentioned adsorption separation material.

[0006] To achieve the above object, the present invention provides a method for preparing a UIO-66 (Fe) / PAN nanofiber membrane, comprising the following steps: (1) adding zirconium salt and iron salt into a solvent and mixing them evenly to obtain solution A; (2) adding terephthalic acid to the acid-base regulator, and then adding the solvent and mixing evenly to obtain solution B; (3) Mixing solution A and solution B evenly, performing a solvothermal reaction, cooling to room temperature, centrifuging, washing and drying to obtain UIO-66(Fe) solid; (4) dissolving polyacrylonitrile in a solvent and mixing the mixture evenly to obtain a PAN solution; (5) Ultrasonic dispersion of UIO-66(Fe) solid in a solvent to obtain a dispersion, adding the dispersion to a PAN solution, stirring and mixing to obtain a spinning solution; (6) The spinning solution is electrospun to obtain UIO-66 (Fe) / PAN nanofiber membrane.

[0007] At present, many MOFs materials are used in water treatment processes to adsorb metal ions in water. However, not only are their adsorption capacity and selectivity poor, but also their adsorption performance varies greatly when facing water environments with different pH values. It is necessary to adjust the pH value of the water environment first, and then adsorb the metal ions. This undoubtedly increases the steps of water treatment and the use of pH adjusters such as acids and alkalis, which increases costs. In response to the above problems, the present invention first obtains zirconium-iron bimetallic MOFs with different molar ratios through a solvent thermal synthesis method, and then mixes it into a polyacrylonitrile (PAN) spinning solution, and combines it with electrospinning technology to prepare UIO-66 (Fe) / PAN electrospinning nanofiber membranes (UFP ENMs). The composite membrane can be used for the recovery of Se (IV) in water. The present invention adopts the above preparation method to first obtain bimetallic MOFs, Fe 3+After the modification of UIO-66, the pore size distribution of the single UIO-66 is improved, and the structural defects inside the MOF are increased, which is beneficial to the adsorption of Se(IV) in the water body. Then, after it is added to the polyacrylonitrile (PAN) spinning solution for electrostatic spinning, the formed UFP ENMs have a high adsorption capacity and good selectivity for Se(IV) in the water body. The membrane material prepared by the present invention has a unique advantage, making it easier to recycle, reducing the secondary pollution of the water body, and solving the problem of the difficulty in recycling the nanoparticle adsorbent. At the same time, the UIO-66(Fe) / PAN nanofiber membrane prepared by the present invention can keep its adsorption capacity for Se(IV) in the water body basically unchanged at different pH values. In actual application, there is no need to adjust the pH value of the water body, and the UIO-66(Fe) / PAN nanofiber membrane can be directly put into the water body, which not only simplifies the steps of water treatment, but also reduces the use of pH regulators and reduces costs.

[0008] Preferably, in step (1), the zirconium salt is ZrCl4, the iron salt is FeCl3·6H2O, the molar ratio of the zirconium salt to the iron salt is (1-2):(1-2), the solvent is DMF, and the molar volume ratio of the zirconium salt to the solvent is 0.001 mol:15-25 mL.

[0009] More preferably, in step (1), the molar ratio of the zirconium salt to the iron salt is 1:1, the solvent is DMF, and the molar volume ratio of the zirconium salt to the solvent is 0.001 mol:20 mL.

[0010] Preferably, in step (2), the solvent is DMF, the acid-base regulator is acetic acid, the molar volume ratio of terephthalic acid to the solvent is 0.001 mol:25-30 mL, and the volume ratio of the solvent to the acid-base regulator is 5-6:30.

[0011] More preferably, in step (2), the molar volume ratio of terephthalic acid to the solvent is 0.001 mol: 30 mL, and the volume ratio of the solvent to the acid-base regulator is 5.8 mL: 30 mL.

[0012] Preferably, in step (3), the molar ratio of the iron salt in solution A to the terephthalic acid in solution B is (1-2):(1-2).

[0013] More preferably, in step (3), the molar ratio of the iron salt in solution A to the terephthalic acid in solution B is 1:1.

[0014] Preferably, in step (3), the temperature of the solvent thermal reaction is 100-140° C. and the time is 12-48 hours.

[0015] More preferably, in step (3), the temperature of the solvent thermal reaction is 120° C. and the time is 24 h.

[0016] Preferably, in step (4), the solvent is DMF, the mass volume ratio of polyacrylonitrile to the solvent is 0.3-0.8 g:1-3 mL, and the mixture is uniformly mixed by stirring at 55-65° C. for 5-8 h.

[0017] More preferably, in step (4), the mass volume ratio of polyacrylonitrile to solvent is 0.5 g:2 mL, and the mixture is uniformly mixed by stirring at 60° C. for 6 h.

[0018] Preferably, in step (5), the mass of UIO-66(Fe) solid is 10-50% of the mass of polyacrylonitrile.

[0019] Preferably, in step (6), the conditions for electrospinning are: voltage of 15-20 kV, injection speed of 0.002-0.003 mm / s, receiving distance of 10-15 cm, and rotating mandrel speed of 40-60 rpm.

[0020] More preferably, in step (6), the conditions for electrospinning are: voltage of 19 kV, injection speed of 0.0026 mm / s, receiving distance of 13 cm, and rotating mandrel speed of 50 rpm.

[0021] The second aspect of the present invention provides a UIO-66 (Fe) / PAN nanofiber membrane, which is prepared by the above preparation method.

[0022] In the present invention, after the electrospinning technology is combined with bimetallic MOFs, MOFs can be dispersed and fixed in situ in the electrospinning nanofiber membrane, which can effectively maintain the adsorption capacity of MOFs while improving its stability, improve the recyclability of MOF, and avoid secondary pollution of water bodies.

[0023] A third aspect of the present invention provides an application of a UIO-66 (Fe) / PAN nanofiber membrane, and an application of the UIO-66 (Fe) / PAN nanofiber membrane in selectively adsorbing oxygen anions in an aqueous solution, wherein the oxygen anions are Se (IV).

[0024] The UIO-66 (Fe) / PAN nanofiber membrane was added to a solution containing Se (IV) for adsorption experiments. The experimental results showed that it had a high adsorption capacity and good selectivity for Se (IV). After six repeated uses, it could still maintain good adsorption performance, laying a solid foundation for its application in actual water bodies. This material is very promising to become a widely used adsorbent.

[0025] Therefore, the preparation method and application of a UIO-66 (Fe) / PAN nanofiber membrane using the above structure in the present invention have the following beneficial effects: (1) Metal-organic frameworks (MOFs) materials have a large specific surface area, abundant metal active sites and high structural adjustability. Zr MOF has better water stability and acid and alkali resistance than other MOFs. Compared with single metal MOF, the bimetallic MOF in the present invention can achieve functional diversification and has more structural defects and adsorption sites.

[0026] (2) The zirconium-iron bimetallic MOF and polyacrylonitrile prepared by the present invention have good adhesion and encapsulation. After the two are co-spun, the zirconium-iron bimetallic MOF is well distributed on the nanofiber membrane, which improves the stability and increases the number of adsorption sites, which is beneficial to adsorption.

[0027] (3) Compared with other adsorbents in the form of fine particles, which are difficult to separate after use in water and may cause secondary pollution, the zirconium-iron bimetallic MOF / polyacrylonitrile (PAN) electrospun nanofiber membrane prepared by the present invention is easy to separate from water after adsorption and is easier to use in real life.

[0028] (4) In the present invention, since each nanofiber is intertwined with each other, the zirconium-iron bimetallic MOF / polyacrylonitrile (PAN) electrospun nanofiber membrane is very stable in water and can be used in more severe environments, thus having broad application prospects.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the infrared spectra of UIO-66(Fe), PAN ENMS, and UFP-5 ENMs; Figure 2 are the XRD patterns of UIO-66, UIO-66(Fe), PAN ENMS, and UFP-5 ENMs; Figure 3 SEM images and EDS images of UIO-66(Fe), PAN ENMs, and UFP-1-5 ENMs, including (a) SEM image of UIO-66(Fe), (b) SEM images of PAN ENMs and (cg) UFP1-5 ENMs, and (h) EDS image of UFP-5 ENMs; Figure 4The adsorption performance of UFP-5 ENMs for Se(IV) under different conditions, including (a) the effect of pH on the adsorption of Se(IV) by UFP-5 ENMs, (b) the adsorption of Se(IV) by UFP-5 ENMs at different concentrations, (c) the adsorption selectivity of Se(IV) by UFP-5 ENMs, (d) the cyclic test of UFP-5 ENMs, (e) the adsorption of Se(IV) by UFP-5 ENMs at different Se(IV) concentrations; Figure 5 This is a graph showing the adsorption capacity of UFP-5 ENMs for Se(IV) in actual water. DETAILED DESCRIPTION

[0031] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0032] Example 1 A method for preparing a UIO-66 (Fe) / PAN nanofiber membrane comprises the following steps: (1) FeCl3·6H2O (2.70 g, 0.001 mol) and ZrCl4 (0.233 g, 0.001 mol) were mixed in 20 mL of DMF to obtain solution A. (2) Add terephthalic acid (0.166 g, 0.001 mol) to 5.8 mL of acetic acid, then add 30 mL of DMF and mix well to obtain solution B; (3) Solution A and solution B were mixed evenly, reacted at 120°C for 24 h in a polytetrafluoroethylene-lined stainless steel autoclave, cooled to room temperature, and centrifuged to obtain a pink solid. The reaction product was washed three times with DMF and methanol, respectively, and purified by immersing in methanol for 12 h. After centrifugation, it was dried at 80°C for 8 h to obtain UIO-66(Fe) solid. (4) Dissolve 0.5 g of polyacrylonitrile in 2 mL of DMF, stir at 60 °C for 6 h, and mix well to obtain a PAN solution; (5) Ultrasonic dispersion of 0.05 g UIO-66(Fe) solid in 3 mL DMF was performed to obtain a dispersion, and the dispersion was added to the PAN solution and stirred for 6 h to obtain a spinning solution. (6) The spinning solution was subjected to electrospinning under the following conditions: voltage of 19 kV, injection speed of 0.0026 mm / s, receiving distance of 13 cm, and rotating mandrel speed of 50 rpm to obtain UIO-66 (Fe) / PAN nanofiber membrane. The loading amount of UIO-66 (Fe) in the above nanofiber membrane was 10 wt%, and was recorded as UFP-1 ENMs.

[0033] Example 2 The difference between this embodiment and embodiment 1 is that the amount of UIO-66(Fe) solid added in step (5) is different. In this embodiment, the amounts of UIO-66(Fe) solid added are 0.1 g, 0.15 g, 0.2 g, and 0.25 g, respectively, and the nanofiber membranes are respectively recorded as UFP-2 ENMs, UFP-3 ENMs, UFP-4 ENMs, and UFP-5 ENMs.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that steps (4) to (6) are omitted, and the UIO-66(Fe) solid material is directly prepared. The specific preparation method of this comparative example is as follows: (1) FeCl3·6H2O (2.70 g, 0.001 mol) and ZrCl4 (0.233 g, 0.001 mol) were mixed in 20 mL of DMF to obtain solution A. (2) Add terephthalic acid (0.166 g, 0.001 mol) to 5.8 mL of acetic acid, then add 30 mL of DMF and mix well to obtain solution B; (3) Solution A and solution B were mixed evenly, reacted in a polytetrafluoroethylene-lined stainless steel autoclave at 120 °C for 24 h, cooled to room temperature, and centrifuged to obtain a pink solid. The reaction product was washed three times with DMF and methanol, respectively, and purified by soaking in methanol for 12 h. After centrifugation, it was dried at 80 °C for 8 h to obtain UIO-66(Fe) solid.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that steps (4) to (6) are omitted, and only zirconium salt is added in step (1) to directly prepare the UIO-66 solid material. The specific preparation method of this comparative example is as follows: (1) ZrCl4 (0.233 g, 0.001 mol) was mixed evenly in 20 mL of DMF to obtain solution A; (2) Add terephthalic acid (0.166 g, 0.001 mol) to 5.8 mL of acetic acid, then add 30 mL of DMF and mix well to obtain solution B; (3) Solution A and solution B were mixed evenly, reacted in a polytetrafluoroethylene-lined stainless steel autoclave at 120°C for 24 h, cooled to room temperature, and centrifuged to obtain a white solid. The reaction product was washed three times with DMF and methanol, respectively, and purified by soaking in methanol for 12 h. After centrifugation, it was dried at 80°C for 8 h to obtain UIO-66 solid.

[0036] Comparative Example 3 The difference between this comparative example and Example 1 is that steps (1) to (3) and step (5) are omitted, and electrospun nanofiber membranes (ENMs) are directly prepared. The specific preparation method of this comparative example is as follows: (1) Dissolve 0.5 g of polyacrylonitrile in 5 mL of DMF and stir at 60 °C for 6 h to obtain a PAN spinning solution. (2) The spinning solution was subjected to electrospinning. The electrospinning conditions were as follows: voltage of 19 kV, injection speed of 0.0026 mm / s, receiving distance of 13 cm, and rotating mandrel speed of 50 rpm to obtain PAN ENMs.

[0037] Test Example 1 (1) The UIO-66(Fe) prepared in Comparative Example 1, the PAN ENMS prepared in Comparative Example 3, and the UFP-5 ENMs prepared in Example 2 were characterized by infrared spectroscopy.

[0038] Infrared spectra such as Figure 1 As shown, UIO-66(Fe) at 3410 cm -1 The infrared absorption peak at 1572 cm -1 The stretching vibration peak corresponding to C=O is at 1402 cm -1 Corresponding to the stretching vibration peaks of CO, 746, 661, and 484 cm -1 The triplet peak at 536 cm -1 The peak at 3441 cm -1 Corresponding to the stretching vibration of the -OH group, 2244 cm -1 The corresponding peak is the stretching vibration peak of the -C≡N group in PAN, 1651 cm -1 Corresponding to the stretching vibration of -C=C group. UIO-66(Fe) and PAN were composited and electrospun to form UFP ENMs, 1579 cm -1 The absorption peak intensity at 746, 661, 484, and 536 cm-1 is weakened, which is attributed to the nanofibers wrapping part of the UIO-66(Fe) particles. -1The retention of Zr-O and Fe-O further proves the successful preparation of UFP ENMs.

[0039] (2) XRD tests were performed on UIO-66 prepared in Comparative Example 2, UIO-66(Fe) prepared in Comparative Example 1, PANENMS prepared in Comparative Example 3, and UFP-5 ENMs prepared in Example 2.

[0040] Figure 2 The X-ray powder diffraction patterns (XRD) of different synthesized materials show that the XRD pattern of UIO-66(Fe) shows obvious characteristic diffraction peaks at 7.4°, 8.5° and 25.8°, corresponding to the (110), (200) and (600) crystal planes of UIO-66, respectively. The results show that the prepared UIO-66(Fe) has a crystal structure similar to that of UIO-66. The film-forming properties of polymer PAN and UIO-66(Fe) were used to form UFP ENMs under electrospinning conditions, and the characteristic peaks of PAN and UIO-66(Fe) were retained. However, some UIO-66(Fe) particles were enclosed in the fibers, which slightly reduced the intensity of their characteristic peaks in UFP ENMs, further proving the successful preparation of the nanofiber membrane.

[0041] (3) SEM and EDS tests were performed on UIO-66(Fe) prepared in Comparative Example 1, PAN ENMs prepared in Comparative Example 3, and UFP-1~5 ENMs prepared in Examples 1 and 2.

[0042] SEM characterization is used to study the morphological changes of different materials, such as Figure 3 As shown in (a), most of the UIO-66(Fe) particles are between 40 and 450 nm, with a smooth surface and a regular octahedral structure. Figure 3 (b) and (g) are SEM images of PAN ENMs and after loading UIO-66(Fe). It can be clearly seen that the fibers of pure PAN nanofiber membrane have a smooth surface with a diameter of about 0.41μm, but with the loading of UIO-66(Fe), the surface of the nanofiber becomes rough, and UIO-66(Fe) particles wrapped inside the fiber or agglomerated on the fiber surface can be observed. In addition, the fiber diameter has also changed significantly. The reduction in the diameter of the nanofibers in the early stage may be due to the increase in the conductivity of the spinning solution after UIO-66(Fe), and the polymer droplets are stretched into thinner fibers due to the enhanced electric field force. When the MOF loading reaches 50%, the diameter of the nanofibers increases suddenly, which may be related to the aggregation of a large number of MOF particles on the fiber. At the same time, EDS also clearly shows the presence of Fe, Zr, N, C, and O, proving the successful preparation of UFP ENMs.

[0043] Test Example 2 (1) Adsorption of Se(IV) by UFP ENMs in ultrapure water The adsorption materials prepared in Examples 1-2 and Comparative Examples 1-5 were added to the prepared simulated Se(IV) water, and the changes in pH value, amount of adsorption material added, anion type and Se(IV) adsorption amount after multiple cycles were tested.

[0044] ① Test the changes in the adsorption capacity of adsorbent materials at different pH values 15 mg of the adsorption materials prepared in Examples 1-2 and Comparative Examples 1-3 were respectively added to the prepared simulated Se(IV) water, the concentration of Se(IV) in the simulated Se(IV) water was 200 mg / L, it did not contain any other anions, and the pH values ​​were 2, 3, 4, 5, 6, 7, 8, 9, and 10, respectively. The adsorption experiment was carried out in a shaker, and the adsorption reaction time was 24 h.

[0045] ② Test the change of adsorption amount by adding different adsorption materials The UFP-5 ENMs adsorption material prepared in Example 2 was added to the prepared simulated Se(IV) water body, the concentration of Se(IV) in the simulated Se(IV) water body was 200 mg / L, it did not contain any other anions, the pH value was 3, and the amount of adsorption material added was 5, 10, 15, 20, 25, 30, and 35 mg / L, respectively. The adsorption experiment was carried out in a shaker, and the adsorption reaction time was 24 h.

[0046] ③ Test the changes in the adsorption capacity of anions 15 mg of the UFP-5 ENMs adsorbent prepared in Example 2 was added to the prepared simulated Se(IV) water, where the concentration of Se(IV) in the simulated Se(IV) water was 200 mg / L, and the anions contained were 200 mg / L of NO 3- , Cl - 、SO4 2- 、HCO3 - 、HPO4 2- , pH value was 3, adsorption experiment was carried out in a shaker, and the adsorption reaction time was 24 h.

[0047] ④ Cycle test 15 mg of the UFP-5 ENMs adsorption material prepared in Example 2 was added to the prepared simulated Se(IV) water body, the concentration of Se(IV) in the simulated Se(IV) water body was 200 mg / L, it did not contain any other anions, and the pH value was 3. The adsorption experiment was carried out in a shaker for 24 h. After the first adsorption was completed, Se(IV) was continuously added to the simulated Se(IV) water body to the initial concentration, followed by a second adsorption until six cycles of adsorption were completed.

[0048] ⑤Test the adsorption performance of adsorption materials at different concentrations The UFP-5 ENMs adsorption material prepared in Example 2 was added to the prepared simulated Se(IV) water body. The mass of the adsorption material was 15 mg. The concentrations of Se(IV) in the simulated Se(IV) water body were 10, 50, 100, 150, 200, 250, and 300 mg / L, respectively. It did not contain any other anions. The pH value was 3. The adsorption experiment was carried out in a shaker. The adsorption reaction time was 24 h.

[0049] The adsorption amounts of the adsorption materials prepared in Examples 1-2 and Comparative Examples 1-3 at different pH values ​​are shown in Table 1.

[0050]

[0051] like Figure 4 As shown in the figure, the test results of UFP-5 ENMs prepared in Example 2 under different test conditions show that UFP-5 ENMs has a high adsorption capacity and good selectivity for Se(IV), and the maximum adsorption amount of Se(IV) solution under acidic conditions can reach 208.5 mg / g. Except for phosphate ions, other anions have almost no effect on the adsorption of Se(IV). After six adsorption-desorption cycles, the adsorption of Se(IV) by UFP-5 ENMs did not decrease significantly.

[0052] (2) Adsorption of Se(IV) by UFP ENMs in actual water The actual water bodies were taken from tap water and Yellow River water, respectively. The concentrations of Se(IV) in the actual water bodies were 20, 100, and 200 mg / L, respectively. The pH value was 7. The adsorption reaction time was 24 h. 15 mg of the UFP-5 ENMs adsorption material prepared in Example 2 was added.

[0053] like Figure 5 As shown in the figure, the synthesized UFP-5 ENMs were actually applied to tap water and Yellow River water, and it was found that the adsorption capacity of UFP-5 ENMs for Se(Ⅳ) reached 142.3 mg / g and 88.6 mg / g, respectively.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a UIO-66 (Fe) / PAN nanofiber membrane, characterized in that: The following steps are involved: (1) adding zirconium salt and iron salt into a solvent and mixing them evenly to obtain solution A; (2) adding terephthalic acid to the acid-base regulator, and then adding the solvent and mixing evenly to obtain solution B; (3) Mixing solution A and solution B evenly, performing a solvothermal reaction, cooling to room temperature, centrifuging, washing and drying to obtain UIO-66(Fe) solid; (4) dissolving polyacrylonitrile in a solvent and mixing uniformly to obtain a PAN solution; (5) Ultrasonic dispersion of UIO-66(Fe) solid in a solvent to obtain a dispersion, adding the dispersion to a PAN solution, stirring and mixing to obtain a spinning solution; (6) The spinning solution is electrospun to obtain UIO-66 (Fe) / PAN nanofiber membrane.

2. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (1), the zirconium salt is ZrCl4, the iron salt is FeCl3·6H2O, the molar ratio of the zirconium salt to the iron salt is (1-2):(1-2), the solvent is DMF, and the molar volume ratio of the zirconium salt to the solvent is 0.001 mol:15-25 mL.

3. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (2), the solvent is DMF, the acid-base regulator is acetic acid, the molar volume ratio of terephthalic acid to the solvent is 0.001 mol: 25-30 mL, and the volume ratio of the solvent to the acid-base regulator is 5-6:

30.

4. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (3), the molar ratio of the iron salt in solution A to the terephthalic acid in solution B is (1-2):(1-2).

5. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (3), the temperature of the solvent thermal reaction is 100-140°C and the time is 12-48 hours.

6. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (4), the solvent is DMF, the mass volume ratio of polyacrylonitrile to the solvent is 0.3-0.8 g:1-3 mL, and the mixture is uniformly mixed by stirring at 55-65° C. for 5-8 h.

7. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (5), the mass of UIO-66(Fe) solid is 10-50% of the mass of polyacrylonitrile.

8. The method for preparing a UIO-66 (Fe) / PAN nanofiber membrane according to claim 1, characterized in that: In step (6), the conditions for electrospinning are: voltage of 15-20 kV, injection speed of 0.002-0.003 mm / s, receiving distance of 10-15 cm, and rotating mandrel speed of 40-60 rpm.

9. A UIO-66 (Fe) / PAN nanofiber membrane, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. The use of a UIO-66 (Fe) / PAN nanofiber membrane according to claim 9, characterized in that: Application of UIO-66 (Fe) / PAN nanofiber membrane for selective adsorption of oxygen anions in aqueous solution, the oxygen anion is Se(IV).

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