An iron-based MOF material modified ultrafiltration membrane and its preparation method and application

Abstract

The present invention discloses an iron-based MOF material modified ultrafiltration membrane, a preparation method thereof, and an application thereof. The preparation method of the iron-based MOF material modified ultrafiltration membrane comprises the following steps: S1, in the presence of a solvent, crystallizing a mixture of iron salt and 2-aminoterephthalic acid to obtain an iron-based MOF material; wherein the mass ratio of 2-aminoterephthalic acid to iron salt is 3:(3-13); S2, sequentially adding an acrylic monomer and a PVDF membrane to the mixture containing the iron-based MOF material, ultrasonically mixing, and irradiating the mixture to obtain the obtained membrane. The iron-based MOF material modified ultrafiltration membrane of the present invention has excellent flux, pH responsiveness, and anti-pollution properties, and can effectively intercept Ce. 3+ This solves the problem that radioactive wastewater has less complex sites under the conditions of pH and ion concentration, which leads to the ultrafiltration membrane being sensitive to Ce. 3+ It solves the problem of reduced retention rate and shows good filtration performance in the treatment of radioactive wastewater.

Description

Technical Field

[0001] The invention relates to an iron-based MOF material modified ultrafiltration membrane and a preparation method and application thereof. Background Art

[0002] In recent years, with the continuous development of the chemical industry, people have paid more and more attention to the treatment of radioactive wastewater. At present, in the wastewater containing multiple radionuclides, the fragmentation products 141 Ce and 144 Ce is a radioactive nuclide that is widely recognized as having the greatest contribution to human health. 141 Ce and 144 Ce radioactive wastewater must be treated before it can meet discharge standards. Existing radioactive wastewater treatment methods primarily include precipitation, ion exchange, evaporation and concentration, and membrane separation technology. Membrane separation technology, with its low energy consumption, high separation efficiency, zero secondary pollution, and ease of operation, holds great value in radioactive wastewater treatment.

[0003] At present, the ultrafiltration process is used in conjunction with other treatment technologies and is the most widely used in the research and application of radioactive wastewater treatment. However, due to the low hydrophilicity and adaptability of materials such as PVDF and PTFE used to prepare ultrafiltration membranes, ultrafiltration membranes face great difficulties in the treatment of radioactive wastewater. In order to solve this series of technical problems, people have never stopped researching ultrafiltration membranes. Among them, MOF materials have the advantages of high specific surface area and high stability, and are used for the preparation of ultrafiltration membranes. Chinese patent document CN108854569A discloses a method for preparing a metal organic framework material MOF loaded with ZnO scale inhibition ultrafiltration membrane. Metal salts and ligands are used as raw materials to prepare MOF under hydrothermal reaction conditions. The obtained MOF material is loaded with ZnO and then mixed to form a membrane. The hydrophilicity of the MOF material ultrafiltration membrane prepared by this technical patent is improved, the pure water flux is improved to a certain extent, and the retention rate is also improved. However, although the MOF material ultrafiltration membrane has improved the hydrophilicity of the membrane and enhanced the filtration performance to a certain extent, the membrane has weak adaptability under the conditions of pH, ion concentration and other conditions in radioactive wastewater, and the overall removal rate of radioactive ions is low. At present, there is no relevant literature disclosing the use of iron-based MOF materials to prepare ultrafiltration membranes for the removal of cerium nuclides in radioactive wastewater. Summary of the Invention

[0004] The present invention addresses the technical problem of overcoming the existing drawback of ultrafiltration membranes, which suffer from reduced cerium retention due to a limited number of complexing sites in radioactive wastewater under conditions such as pH and ion concentration. The invention provides an iron-based MOF material-modified ultrafiltration membrane, its preparation method, and application. The iron-based MOF material-modified ultrafiltration membrane exhibits excellent flux, pH responsiveness, and anti-fouling properties.

[0005] The present invention solves the above technical problems through the following technical solutions:

[0006] The present invention provides a method for preparing an iron-based MOF material modified ultrafiltration membrane, which comprises the following steps:

[0007] S1. In the presence of a solvent, crystallizing an iron salt and 2-aminoterephthalic acid to prepare an iron-based MOF material; wherein the mass ratio of the 2-aminoterephthalic acid to the iron salt is 3:(3-13);

[0008] S2. Adding acrylic monomers and PVDF membranes sequentially to the mixture containing the iron-based MOF material, performing ultrasonic mixing, and irradiating the mixture to obtain the iron-based MOF material modified ultrafiltration membrane.

[0009] In the present invention, those skilled in the art generally understand that the iron-based MOF material refers to a material based on Fe 3+ A crystalline porous material with a periodic network structure is formed by self-assembly with the organic ligand.

[0010] In step S1, the mass ratio of the 2-aminoterephthalic acid to the iron salt is preferably 3:(7-13), for example, 3:9.

[0011] In step S1, the iron salt may be ferric chloride, ferric nitrate or ferric sulfate.

[0012] In step S1, the solvent may be a conventional solvent in the art, such as N,N-dimethylformamide.

[0013] In step S1, the mass ratio of the solvent to the total amount of the iron salt and 2-aminoterephthalic acid may be (15.5-43.5):1, preferably (15.5-25.6):1, for example, 21.3:1 or 18.1:1. When the mass ratio of the solvent to the total amount of the iron salt and 2-aminoterephthalic acid is (15.5-43.5):1, the yield of the obtained iron-based MOF material is higher.

[0014] In step S1, before the crystallization reaction, a solvent, an iron salt and 2-aminoterephthalic acid are generally stirred and mixed to prepare a mixture.

[0015] The stirring and mixing time can be conventional in the art, and generally the stirring and mixing time is sufficient until the mixture is uniformly mixed. For example, the stirring and mixing time can be 10 minutes.

[0016] In step S1, the crystallization reaction can be carried out by conventional methods in the art. Generally, a mixture of a solvent, an iron salt and 2-aminoterephthalic acid is placed in a reaction kettle and placed in an oven for reaction.

[0017] In step S1, the crystallization reaction time may be 18-30 hours, preferably 22-26 hours, for example 24 hours.

[0018] In step S1, the temperature of the crystallization reaction may be 100-150°C, for example, 120°C.

[0019] In step S1, the crystallization reaction may be followed by cooling, centrifugation, washing and drying.

[0020] The washing may be performed using N,N-dimethylformamide and / or ethanol. Preferably, the washing is performed three times using N,N-dimethylformamide and then three times using ethanol.

[0021] Wherein, the drying may be vacuum drying.

[0022] The drying temperature may be 55-70°C, for example 60°C.

[0023] In step S2, the preparation method of the mixture containing the iron-based MOF material can be conventional in the art, and preferably includes the following steps: ultrasonically mixing the iron-based MOF material and the solvent, and then allowing the mixture to stand.

[0024] The solvent may be a conventional solvent in the art, such as water.

[0025] Wherein, the volume ratio of the iron-based MOF material to the solvent may be 2:1.

[0026] The ultrasonic mixing time may be 30 minutes.

[0027] The standing time may be 10-14 hours, for example 12 hours. The purpose of standing is to degas.

[0028] In step S2, the mass ratio of the iron-based MOF material to the acrylic monomer is preferably 1:15.

[0029] In step S2, the acrylic monomer may be acrylic acid or methacrylic acid, preferably methacrylic acid.

[0030] In step S2, the amount of the PVDF membrane can be 17-19%, for example 17%, where the percentage is the mass percentage of the PVDF membrane to the iron-based MOF material. When the amount of the PVDF membrane is 17%, the yield of the iron-based MOF material-modified ultrafiltration membrane is higher.

[0031] In step S2, the PVDF membrane can be prepared by conventional methods in the art. Preferably, the preparation method of the PVDF membrane comprises the following steps: a casting solution containing PVDF, a porogen and an organic solvent is allowed to stand, subjected to degassing treatment, and subjected to phase separation.

[0032] The porogen can be a conventional porogen in the art, preferably polyvinyl pyrrolidone PVPK30.

[0033] The organic solvent may be a conventional solvent in the art, preferably a non-polar solvent, more preferably one or more of N-methylpyrrolidone NMP, dimethylacetamide DMAc, dimethylformamide DMF, dimethyl sulfoxide DMSO and triethyl phosphate TEP, for example, NMP.

[0034] The amount of the porogen used may be conventional in the art, preferably 20-26%, for example 23.5%, where the percentage is the mass percentage of the porogen to the PVDF.

[0035] The solid content of the casting solution can be conventional in the art, preferably 18-25%, for example 21%. The solid content refers to the mass percentage of the PVDF and the porogen in the casting solution.

[0036] In one embodiment of the present invention, the PVDF membrane is prepared by the following method: a mixture containing PVDF and PVPK30 is stirred in a solvent to form a homogeneous and stable casting solution, and after standing and degassing, a non-solvent-induced phase separation method is used to prepare the PVDF membrane;

[0037] Wherein, the solvent is NMP;

[0038] The mass volume ratio of the PVDF, PVPK30, and NMP is 17 g:4 g:79 mL.

[0039] Among them, the non-solvent induced phase separation method can be carried out according to conventional methods in the field. Generally, an extractant with stronger miscibility with the organic solvent is added to the degassing casting liquid to extract the organic solvent to form a two-phase structure with the PVDF as the continuous phase and the organic solvent as the dispersed phase. The organic solvent is then removed to obtain a PVDF membrane with a certain pore structure.

[0040] In step S2, the ultrasonic mixing operation preferably includes the following steps: adding the acrylic monomer to the mixture containing the iron-based MOF material and ultrasonically mixing for 3 to 8 minutes, for example, 5 minutes, then adding the solvent and ultrasonically mixing for 3 to 8 minutes, for example, 5 minutes, and then adding the PVDF membrane and ultrasonically mixing for 8 to 12 minutes, for example, 10 minutes.

[0041] The added amount of the solvent and the volume-to-mass ratio of the iron-based MOF material are preferably 5 mL:1 mg.

[0042] In step S2, when the order of adding materials in the ultrasonic mixing process is the iron-based MOF material mixture, the acrylic monomer and the PVDF membrane, the yield of the obtained iron-based MOF material modified ultrafiltration membrane is higher.

[0043] In step S2, the irradiation may be performed by ultraviolet light irradiation. The purpose of the irradiation is the grafting reaction. When ultraviolet light irradiation is performed, the intensity of the ultraviolet light is preferably not less than 500w·h / m 2 .

[0044] In step S2, the irradiation time may be 0 to 8 hours, for example, 8 hours.

[0045] In step S2, the irradiation may be followed by filtration.

[0046] The present invention also provides an iron-based MOF material modified ultrafiltration membrane, which is prepared by adopting the preparation method of the iron-based MOF material modified ultrafiltration membrane.

[0047] The present invention also provides an application of an iron-based MOF material modified ultrafiltration membrane in wastewater treatment.

[0048] In the present invention, the wastewater may be radioactive wastewater, for example 141 Ce and / or 144 Ce radioactive wastewater.

[0049] Among them, the 141 Ce and / or 144 Ce in radioactive wastewater, the Ce 3+ The concentration of may be 1-10 mg / L, for example 5 mg / L.

[0050] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0051] The reagents and raw materials used in the present invention are commercially available.

[0052] The positive progress of the present invention is that the iron-based MOF material modified ultrafiltration membrane of the present invention has excellent flux, pH responsiveness and anti-fouling properties, and can effectively intercept Ce 3+ This solves the problem that radioactive wastewater has less complex sites under the conditions of pH and ion concentration, which leads to the ultrafiltration membrane being sensitive to Ce. 3+ It solves the problem of reduced retention rate and shows good filtration performance in the treatment of radioactive wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The relationship between the contact angle of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1 changes over time.

[0054] Figure 2 The iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1 were tested for Ce at different pH values. 3+ The retention rate.

[0055] Figure 3 The relationship between the flux and the operating time of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1.

[0056] Figure 4 The flux attenuation of the fouling and backwashing experiments performed on the iron-based MOF material modified ultrafiltration membrane prepared in Example 4 and the unmodified PVDF membrane prepared in Comparative Example 1 is shown. DETAILED DESCRIPTION

[0057] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0058] In Examples 1 to 6, ferric chloride, N,N-dimethylformamide, 2-aminoterephthalic acid, and methacrylic acid (MAA) were purchased from China Pharmaceutical Group.

[0059] Polyvinylidene fluoride (PVDF) was purchased from Solvay Group, model 6020.

[0060] The PVDF membranes used in Examples 1 to 6 were all pretreated as follows: the PVDF membranes were washed with deionized water, soaked in deionized water for more than one week, during which the water was changed several times, and then dried under vacuum at 70° C. to constant weight.

[0061] The PVDF membranes used in Examples 1 to 6 were prepared by dissolving 17 g PVDF and 4 g PVPK30 in 79 mL of organic solvent NMP, stirring with a magnetic stirrer to form a homogeneous and stable casting solution, allowing the solution to stand and undergo degassing, and then using a non-solvent induced phase separation method to prepare the membranes.

[0062] Example 1

[0063] S1. Add 0.225 g of 2-aminoterephthalic acid and 0.225 g of ferric chloride to 19.55 mL of N,N-dimethylformamide solution. After stirring for 10 minutes, transfer the mixture to a reactor and crystallize in an oven at 120°C for 24 hours. After cooling to room temperature and centrifugation, the resulting product is washed three times with N,N-dimethylformamide solution and three times with ethanol solution. Finally, vacuum dry at 60°C to obtain an iron-based MOF material.

[0064] S2. Take 20 mg of the iron-based MOF material and place it in 10 ml of water for 30 minutes of ultrasonic treatment. After standing for 12 hours, add 300 mg of MAA and continue ultrasonic treatment for 5 minutes. Add 100 mL of water and ultrasonicate again for 5 minutes. Add 17% PVDF membrane and continue ultrasonication for 10 minutes, where the percentage is the percentage of PVDF membrane to the mass of the iron-based MOF material. After ultraviolet light irradiation for 8 hours, filter and obtain an iron-based MOF material modified ultrafiltration membrane.

[0065] Example 2

[0066] In step (1), the amount of ferric chloride is 0.375 g, and the amount of N,N-dimethylformamide is 19.4 mL; in step (2), 19% PVDF membrane is added, and the rest are the same as in Example 1 to obtain an iron-based MOF material modified ultrafiltration membrane.

[0067] Example 3

[0068] In step (1), the amount of ferric chloride is 0.525 g, the amount of N,N-dimethylformamide is 19.25 mL, and the rest are the same as in Example 1, to obtain an iron-based MOF material modified ultrafiltration membrane.

[0069] Example 4

[0070] In step (1), the amount of ferric chloride is 0.825 g, the amount of N,N-dimethylformamide is 19.1 mL, and the rest are the same as in Example 1, to obtain an iron-based MOF material modified ultrafiltration membrane.

[0071] Example 5

[0072] In step (1), the amount of ferric chloride is 0.675 g, the amount of N,N-dimethylformamide is 19.1 mL, and the rest are the same as in Example 1, to obtain an iron-based MOF material modified ultrafiltration membrane.

[0073] Example 6

[0074] In step (1), the amount of ferric chloride is 0.975 g, the amount of N,N-dimethylformamide is 18.8 mL, and the rest are the same as in Example 1, to obtain an iron-based MOF material modified ultrafiltration membrane.

[0075] Comparative Example 1

[0076] 17 g PVDF and 4 g PVPK30 were dissolved in 79 mL organic solvent NMP and magnetically stirred to form a homogeneous and stable casting solution. After standing and degassing, the PVDF membrane was prepared by non-solvent-induced phase separation.

[0077] Effect Example 1

[0078] The contact angles of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1 were measured using a contact angle meter with a 1 μL water droplet. The results are shown in Tables 1 and Figure 1 shown.

[0079] Table 1 Contact angle changes over time of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1

[0080]

[0081] Depend on Figure 1 As can be seen from Table 1, compared with the unmodified PVDF membrane prepared in Comparative Example 1, the hydrophilicity of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 is effectively improved, which provides a guarantee for their use in the treatment of radioactive wastewater.

[0082] Effect Example 2

[0083] In Ce 3+ The membrane filtration experiment was carried out under the conditions of an initial concentration of 5 mg / L and a transmembrane pressure TMP = 0.2 MPa. The effects of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1 on the Ce 3+ The retention rate is shown in Table 2 and Figure 2 As shown, where Ce 3+ The retention rate is calculated using the following formula:

[0084]

[0085] Table 2 Effect of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1 on Ce at different pH values 3+ The retention rate

[0086]

[0087]

[0088] Depend on Figure 2 As shown in Table 2, compared with the unmodified PVDF membrane prepared in Comparative Example 1, the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 showed excellent retention capacity, among which the iron-based MOF material modified ultrafiltration membrane prepared in Example 4 showed the best removal effect. When pH < 4, the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 had a better removal effect on Ce. 3+ The retention rate is 90.5% or less, because the wastewater contains a large amount of H + , H + Will be with Ce3+ Compete with each other for the complexing sites on the complexing agent, resulting in Ce 3+ It is difficult to react with the complexing agent, so the iron-based MOF material modified ultrafiltration membrane has a great influence on Ce 3+ When pH>4, as the pH of the wastewater increases, the iron-based MOF material modified ultrafiltration membrane prepared in Examples 1 to 6 has a lower retention rate for Ce 3+ The rejection rate continued to increase, which proved that the iron-based MOF material modified ultrafiltration membrane has efficient filtration separation and pH response performance.

[0089] Effect Example 3

[0090] In Ce 3+ Under the conditions of concentration of 5 mg / l, pH=4, and transmembrane pressure TMP=0.2 MPa, the net water production was monitored, and the flux (net water production per unit membrane area per unit time) of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1 was tested in relation to the change in operating time. The results are shown in Tables 3 and Figure 3 The flux is calculated using the following formula:

[0091]

[0092] Where F is the flux, the unit is / L / (m 2 h), Q is the liquid permeability, unit is m 3 , A is the area of ​​the membrane, unit is m 2 , t is the time for collecting liquid, in h.

[0093] Table 3 Flux and running time changes of the iron-based MOF material modified ultrafiltration membranes prepared in Examples 1 to 6 and the unmodified PVDF membrane prepared in Comparative Example 1

[0094]

[0095]

[0096] From Table 3 and Figure 3 It can be seen that the flux of the unmodified PVDF membrane prepared in Comparative Example 1 decreased significantly after running for 400 min, while the flux of the iron-based MOF material modified ultrafiltration membrane prepared in Examples 1 to 6 did not decrease significantly even after running for 800 min. This is because the iron-based MOF material in the iron-based MOF material modified ultrafiltration membrane contains metal elements, and its microscopic pores have strong polarity, which can generate a strong force with the adsorbed substance, continuously combining the complexing agent with Ce 3+ The generated complex is blocked outside the membrane, while water molecules can continuously pass through the membrane pores, thereby significantly increasing the clean water output.

[0097] Effect Example 4

[0098] The iron-based MOF material modified ultrafiltration membrane prepared in Example 4 and the unmodified PVDF membrane prepared in Comparative Example 1 were subjected to pollution and backwashing experiments to test their flux attenuation. The pollution experiment was conducted on the membrane at Ce 3+ The membrane was run for 200 min in wastewater with a concentration of 5 mg / l and a pH of 4 at a transmembrane pressure of 0.2 MPa. The cleaning experiment was conducted with the membrane in clean water at a transmembrane pressure of 0.2 MPa for 200 min. The flux of the membrane after fouling and after cleaning was recorded, and the flux decay rate of the membrane was calculated. The specific results are shown in Table 4 and Figure 4 As shown, the flux decay rate is calculated using the following formula:

[0099]

[0100] Table 4 Flux attenuation of the pollution and backwash experiments of the iron-based MOF material modified ultrafiltration membrane prepared in Example 4 and the unmodified PVDF membrane prepared in Comparative Example 1

[0101]

[0102]

[0103] The results showed that after 1400 min of Ce 3+ After the radioactive wastewater pollution and clean water cleaning, the flux of the unmodified PVDF membrane prepared in Comparative Example 1 has dropped to 25% of the original flux. Even after cleaning, its flux only recovered to 39% of the original flux at 1600 min. The iron-based MOF material modified ultrafiltration membrane prepared in Example 4 recovered to 39% of the original flux after 1400 min of Ce-containing 3+ After being contaminated by radioactive wastewater and cleaned with clean water, its flux was reduced to 31% of the original flux, but after being cleaned again, its flux recovered to 95% of the original flux at 1600 minutes, showing excellent anti-pollution performance.

[0104] The above embodiments are preferred implementations of the invention, but the implementation of the present invention is not limited to the above examples. Any other changes, modifications, substitutions, and combination simplifications made without departing from the spirit and principles of the present invention are equivalent.

Claims

1. A method for preparing an iron-based MOF material modified ultrafiltration membrane, characterized in that: It includes the following steps: S1. In the presence of a solvent, crystallizing an iron salt and 2-aminoterephthalic acid to prepare an iron-based MOF material; wherein the mass ratio of the 2-aminoterephthalic acid to the iron salt is 3:(3-13); S2. Adding acrylic monomers and PVDF membranes sequentially to the mixture containing the iron-based MOF material, performing ultrasonic mixing, and irradiating the mixture to obtain the iron-based MOF material modified ultrafiltration membrane.

2. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: In step S1, the mass ratio of the 2-aminoterephthalic acid to the iron salt is 3:(7-13); and / or, the iron salt is ferric chloride, ferric nitrate or ferric sulfate; and / or, the solvent is N,N-dimethylformamide; And / or, the mass ratio of the solvent to "the total amount of the iron salt and 2-aminoterephthalic acid" is (15.5-43.5):

1.

3. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 2, wherein: In step S1, the mass ratio of the 2-aminoterephthalic acid to the iron salt is 3:

9.

4. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 2, wherein: The mass ratio of the solvent to the total amount of the iron salt and 2-aminoterephthalic acid is (15.5-25.6):

1.

5. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 4, wherein: The mass ratio of the solvent to the total amount of the iron salt and 2-aminoterephthalic acid is 21.3:1 or 18.1:

1.

6. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: In step S1, the crystallization reaction time is 18-30 hours; And / or, the temperature of the crystallization reaction is 100-150°C.

7. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 6, wherein: In step S1, the crystallization reaction time is 22 to 26 hours.

8. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 7, wherein: In step S1, the crystallization reaction time is 24 hours.

9. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 6, wherein: The temperature of the crystallization reaction is 120°C.

10. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: The crystallization reaction further includes cooling, centrifugation, washing and drying.

11. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 10, wherein: The washing is performed using N,N-dimethylformamide and / or ethanol; And / or, the drying is vacuum drying; And / or, the drying temperature is 55-70°C.

12. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 11, characterized in that in, The washing step was first washing with N,N-dimethylformamide three times, and then washing with ethanol three times.

13. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 11, wherein: The drying temperature is 60°C.

14. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: In step S2, the method for preparing the mixture containing the iron-based MOF material comprises the following steps: ultrasonically mixing the iron-based MOF material and a solvent, and then allowing the mixture to stand.

15. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 14, wherein: In the method for preparing a mixture containing the iron-based MOF material, the solvent is water; And / or, in the method for preparing a mixture containing the iron-based MOF material, the volume ratio of the iron-based MOF material to the solvent is 2:1; And / or, in the method for preparing a mixture containing the iron-based MOF material, the ultrasonic mixing time is 30 minutes; And / or, in the method for preparing a mixture containing the iron-based MOF material, the standing time is 10-14 hours.

16. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 15, wherein: In the method for preparing the mixture containing the iron-based MOF material, the standing time is 12 hours.

17. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: In step S2, the mass ratio of the iron-based MOF material to the acrylic monomer is 1:15; and / or, the acrylic monomer is acrylic acid or methacrylic acid; And / or, the amount of the PVDF membrane is 17-19%, where the percentage is the mass percentage of the PVDF membrane to the iron-based MOF material; And / or, the preparation method of the PVDF membrane comprises the following steps: a casting solution containing PVDF, a porogen and an organic solvent is allowed to stand, subjected to degassing treatment, and subjected to phase separation to obtain the membrane.

18. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 17, wherein: The acrylic monomer is methacrylic acid.

19. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 17, wherein: The porogen is polyvinyl pyrrolidone PVPK30; And / or, the organic solvent is one or more of N-methylpyrrolidone NMP, dimethylacetamide DMAc, dimethylformamide DMF, dimethyl sulfoxide DMSO and triethyl phosphate TEP; And / or, the amount of the porogen is 20-26%, where the percentage is the mass percentage of the porogen to the PVDF; And / or, the solid content of the casting solution is 18-25%.

20. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 19, wherein: The organic solvent is NMP.

21. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 19, wherein: The amount of the porogen is 23.5%.

22. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 19, wherein: The solid content of the casting solution is 21%.

23. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: In step S2, the ultrasonic mixing operation includes the following steps: adding the acrylic monomer to the mixture containing the iron-based MOF material and ultrasonically mixing for 3 to 8 minutes, then adding the solvent and ultrasonically mixing for 3 to 8 minutes, and then adding the PVDF membrane and ultrasonically mixing for 8 to 12 minutes.

24. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 23, wherein: Adding the acrylic monomer to the mixture containing the iron-based MOF material and then ultrasonically mixing for 5 minutes; and / or, adding a solvent and ultrasonically mixing for 5 minutes; And / or, add PVDF membrane and mix ultrasonically for 10 minutes.

25. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 23, wherein: The volume mass ratio of the added amount of the solvent to the iron-based MOF material is 5 mL:1 mg.

26. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 1, wherein: In step S2, the irradiation is ultraviolet light irradiation; And / or, the irradiation time is 0 to 8 hours; And / or, the irradiation further includes filtration.

27. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 26, wherein: The ultraviolet light intensity of the ultraviolet light irradiation is not less than 500w·h / m 2 .

28. The method for preparing an iron-based MOF material modified ultrafiltration membrane according to claim 26, wherein: The irradiation time is 8 hours.

29. An iron-based MOF material modified ultrafiltration membrane, prepared by the method for preparing an iron-based MOF material modified ultrafiltration membrane according to any one of claims 1 to 28.

30. Use of the iron-based MOF material modified ultrafiltration membrane according to claim 29 in wastewater treatment.

31. Use of the iron-based MOF material modified ultrafiltration membrane in wastewater treatment according to claim 30, characterized in that: The wastewater contains 141 Ce and / or 144 Ce radioactive wastewater.

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