Uranium extraction composite membrane and preparation method thereof

Abstract

The invention discloses a uranium extraction composite membrane and a preparation method thereof. The uranium extraction composite membrane comprises a PVDF (Polyvinylidene Fluoride) microfiltration membrane, nano-particles formed by polyphenol and organic amine, wherein the nano-particles formed by polyphenol and organic amine are loaded on the surface of the PVDF micro-filtration membrane; the preparation method comprises the following steps: preparing polyphenols, Tris-HCl, CH3CH2OH and CH3CH2OH, performing secondary growth on MOFs crystals, grafting PEI on the MOFs crystals, and then loading the MOFs crystals on nanoparticles formed by the polyphenols and the organic amine, and mixing the polyphenols and the Tris-HCl with the organic amine and the CH3CH2OH to prepare a mixed solution; immersing the pretreated PVDF micro-filtration membrane into the mixed solution to prepare a modified PVDF micro-filtration membrane; adding the MOFs seed crystal into a mixed solution of PEI and NaHCO3 for ultrasonic treatment, and then immersing the modified PVDF microfiltration membrane into the mixed solution; and immersing the obtained PVDF micro-filtration membrane into a precursor solution of MOFs (Metal-Organic Frameworks) to carry out solvothermal reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of uranium extraction, in particular to a uranium extraction composite membrane and a preparation method thereof. Background Art

[0002] During the mining of solid uranium, uranium can easily migrate into groundwater and soil through leaching, causing radioactive contamination and ecosystem damage. Compared with traditional solid uranium mining, extracting uranium from seawater (uranium concentration is approximately 3.3 μg / L) and salt lake brine (uranium concentration can be more than 100 times that of seawater) has two advantages: (1) it can effectively avoid large-scale rock crushing operations, significantly reducing the risk of groundwater pollution and surface ecological damage; (2) the marine environment stores approximately 4.5 billion tons of uranium resources, which is more than a thousand times the proven reserves on land.

[0003] Polyvinylidene fluoride (PVDF), also known as polyvinylidene difluoride, PVDF microfiltration membrane has good chemical resistance, oxidation resistance and mechanical strength and is widely used in the field of water treatment. However, due to the limited active groups, PVDF microfiltration membrane is not suitable for direct use as a membrane-type adsorbent. In addition, the high chemical inertness of PVDF microfiltration membrane makes it difficult to be functionalized. Surface coating method provides an effective strategy to solve the above problems. Tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) coatings with hierarchical structures can be easily coated on various porous membranes. However, the adsorption efficiency and adsorption capacity of functionalized PVDF microfiltration membranes modified with TA and APTES are low, which hinders its adsorption in wastewater, seawater and salt lake brine uranium.

[0004] Nanomaterials are considered to be one of the most promising adsorption materials for extracting uranium from seawater. Using nanomaterials to prepare polymer-based composites is an effective strategy to improve uranium adsorption performance. ZIF-8 is a metal-organic framework material (MOFs) with strong structural adaptability and high porosity. It can effectively create additional active sites and improve adsorption performance, making it a very promising nanofiller. However, in general, the agglomeration of MOFs powders and the poor interfacial compatibility of MOFs polymer-based composites lead to a decrease in the adsorption capacity of MOFs when used as adsorption materials. Therefore, designing MOFs polymer composites with good interfacial compatibility to improve the adsorption performance of adsorbents in natural seawater remains a challenge. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a uranium extraction composite membrane and a preparation method thereof to solve the problem of low adsorption capacity of adsorption materials used for separation and extraction of uranium in the prior art.

[0006] The present invention first provides a uranium extraction composite membrane, which comprises:

[0007] PVDF microfiltration membrane;

[0008] Nanoparticles formed by polyphenols and organic amines, wherein the nanoparticles formed by polyphenols and organic amines are loaded on the surface of the PVDF microfiltration membrane;

[0009] The secondary grown MOFs crystals are grafted with PEI and then loaded on the nanoparticles formed by the polyphenol and the organic amine.

[0010] Preferably, the nanoparticles formed by the polyphenol and the organic amine are nanoparticles formed by the reaction of TA and APTES, and the MOFs crystals are ZIF-8 crystals.

[0011] Preferably, the pore size of the PVDF microfiltration membrane is 0.22 μm to 0.45 μm, the particle size of the nanoparticles is 80 nm to 100 nm; and the particle size of the MOFs crystals is 0.42 μm to 0.54 μm.

[0012] The present invention also provides a method for preparing the above-mentioned uranium extraction composite membrane, which comprises the following steps:

[0013] S1, mixing polyphenols with a Tris-HCl solution to prepare a first mixed solution;

[0014] S2. Mixing the organic amine with the CH3CH2OH solution to prepare a second mixed solution;

[0015] S3, mixing the first mixed solution and the second mixed solution to prepare a third mixed solution;

[0016] S4, immersing the pretreated PVDF microfiltration membrane into the third mixed solution to prepare a modified PVDF microfiltration membrane;

[0017] S5, adding MOFs seed crystals to a mixed solution of PEI and NaHCO3 and performing ultrasonic treatment to prepare a fourth mixed solution;

[0018] S6, immersing the modified PVDF microfiltration membrane in the fourth mixed solution to prepare a PVDF microfiltration membrane coated with MOFs seeds;

[0019] S7. Immersing the PVDF microfiltration membrane prepared in step S6 into the MOFs precursor solution to perform a solvothermal reaction to prepare a uranium extraction composite membrane.

[0020] Preferably, the temperature of the solvent thermal reaction in step S7 is 20° C. to 100° C., and the reaction time is 5 h to 7 h.

[0021] Preferably, the pretreatment of the PVDF microfiltration membrane in step S4 is: cleaning the PVDF microfiltration membrane with CH3CH2OH, and immersing the cleaned PVDF microfiltration membrane in a mixed solution of Tris-HCl and CH3CH2OH.

[0022] Preferably, the volume of the third mixed solution in step S3 is 20 mL to 30 mL, the concentration of polyphenols in the third mixed solution is 1 mg / mL to 3 mg / mL, and the concentration of organic amines is 1 μg / mL to 2 μg / mL.

[0023] Preferably, in step S5, the mass ratio of MOFs seed crystals to PEI is 0.1-0.3:0.1-0.3, and the volume of the NaHCO3 solution is 3 mL-10 mL.

[0024] Preferably, when the MOFs seed crystals in step S7 are ZIF-8 seed crystals, the preparation of the ZIF-8 precursor solution comprises the following steps:

[0025] S10, adding Zn(NO3)2·6H2O and HCOONa to a CH3OH solution and stirring to dissolve them to prepare a fifth mixed solution;

[0026] S20, adding 2-MEIM to the CH3OH solution and stirring to prepare a sixth mixed solution;

[0027] S30, mixing the fifth mixed solution and the sixth mixed solution to prepare a ZIF-8 precursor solution.

[0028] Preferably, the mass ratio of Zn(NO3)2, HCOONa and 2-MEIM in the ZIF-8 precursor solution is 0.4-0.7:0.1-0.3:0.1-0.3.

[0029] The present invention provides a uranium extraction composite membrane and its preparation method. The membrane utilizes a PVDF microfiltration membrane as a base membrane, and the surface of the base membrane is modified with nanoparticles containing polyphenol and organic amine structures, as well as secondary MOF crystals. The introduction of amino groups and MOFs enhances the membrane's uranium adsorption, separation, and extraction capabilities while maintaining its original mechanochemical stability. Furthermore, the membrane possesses strong resistance to biofouling, enabling its application in uranium extraction from seawater and salt lake brine. Furthermore, temperature control and a PEI bridging strategy are employed to prepare the antibacterial uranium extraction composite membrane, enhancing its uranium adsorption capacity. The resulting uranium extraction composite membrane exhibits excellent uranium adsorption and recovery properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of the method for preparing the uranium extraction composite membrane provided by the present invention;

[0031] Figure 2 FT-IR spectrum of the TAPP-ZIF-60 composite membrane provided in Example 1 of the present invention;

[0032] Figure 3 The XRD pattern of the TAPP-ZIF-60 composite membrane provided in Example 1 of the present invention;

[0033] Figure 4 This is a SEM image of the TAPP-ZIF-60 composite membrane provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of this application more clear, the present invention is further described below with reference to the accompanying drawings and examples. Implementation methods of the present invention include, but are not limited to, the following examples. All other embodiments obtained by persons of ordinary skill in the art based on the examples in this application without creative effort are within the scope of protection of this application.

[0035] In this embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0036] In the description and claims of this embodiment, the terms "first" and "second" are used to distinguish different objects rather than to describe a specific order of objects. For example, a first target object and a second target object are used to distinguish different objects rather than to describe a specific order of objects.

[0037] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0038] In the description of the embodiments of this application, unless otherwise specified, "multiple" means two or more. For example, "multiple processing units" means two or more processing units; "multiple systems" means two or more systems.

[0039] The present invention first provides a uranium extraction composite membrane, which includes a PVDF microfiltration membrane; nanoparticles formed by polyphenols and organic amines, which are loaded on the surface of the PVDF microfiltration membrane; and secondary grown MOFs crystals, which are loaded on the nanoparticles formed by the polyphenols and organic amines after being grafted with PEI on the secondary grown MOFs crystals.

[0040] The composite membrane provided by the present invention uses a PVDF microfiltration membrane as its substrate. The PVDF microfiltration membrane has excellent physical and chemical stability and a uniform morphology. The surface of the PVDF microfiltration membrane is modified with nanoparticles with polyphenol and organic amine structures, as well as secondary MOF crystals. The introduction of amino groups and MOFs improves the uranium adsorption, separation and extraction capabilities of the PVDF microfiltration system while maintaining its original mechanochemical stability. It also exhibits strong resistance to biofouling and can be used to extract uranium from seawater, salt lake brine, and wastewater.

[0041] In a preferred embodiment, the nanoparticles formed by the polyphenol and the organic amine are nanoparticles formed by the reaction of TA and APTES.

[0042] The TA is a polyphenol, and the APTES is an organic amine. The TA and APTES coating with a hierarchical structure can be easily coated on a porous PVDF microfiltration membrane.

[0043] In a preferred embodiment, the pore size of the PVDF microfiltration membrane is 0.22 μm to 0.45 μm, the particle size of the nanoparticles is 80 nm to 100 nm; and the particle size of the MOFs crystals is 0.42 μm to 0.54 μm.

[0044] In a preferred embodiment, the MOFs crystal is a ZIF-8 crystal. Wherein, ZIF-8 has an adjustable framework structure, a large specific surface area and antibacterial properties, and is therefore an excellent uranium adsorption material. However, the powder form and dispersibility of ZIF-8 are relatively poor. In the composite membrane of the present invention, PEI (polyethyleneimine) is grafted and modified between ZIF-8 and TAP. One side of the PEI amino group reacts with TA to form a covalent bond, and the other side coordinates with the Zn of ZIF-8, so that ZIF-8 and TAP have good interfacial compatibility. Therefore, the coordination bond between PEI and ZIF-8 and the covalent bond between PEI and TAP can form a stable composite membrane, making the composite membrane an adsorption material with uniform morphology and good adsorption performance for uranium.

[0045] Figure 1 The flow chart of the preparation method of the uranium extraction composite membrane provided by the present invention is shown in FIG. Figure 1The present invention also provides a method for preparing the above-mentioned uranium extraction composite membrane, which comprises the following steps:

[0046] S1. Mixing polyphenols with a Tris-HCl solution to prepare a first mixed solution.

[0047] In a specific embodiment, TA is mixed with a Tris-HCl solution with a pH of 8.5 to prepare a first mixed solution.

[0048] S2. Mixing the organic amine with the CH3CH2OH solution to prepare a second mixed solution;

[0049] In a specific embodiment, APTES is mixed with a CH 3 CH 2 OH solution to prepare a second mixed solution.

[0050] S3. Mix the first mixed solution and the second mixed solution to prepare a third mixed solution.

[0051] The volume of the third mixed solution in step S3 is 20 mL to 30 mL, the concentration of polyphenols in the third mixed solution is 1 mg / mL to 3 mg / mL, and the concentration of organic amines is 1 μg / mL to 2 μg / mL.

[0052] S4. Immersing the pretreated PVDF microfiltration membrane into the third mixed solution to prepare a modified PVDF microfiltration membrane.

[0053] The pretreatment of the PVDF microfiltration membrane in step S4 is as follows: the PVDF microfiltration membrane is cleaned with CH3CH2OH, and the cleaned PVDF microfiltration membrane is immersed in a mixed solution of Tris-HCl and CH3CH2OH for soaking.

[0054] In a specific embodiment, the PVDF microfiltration membrane is washed multiple times with CH3CH2OH and then placed in a mixed solution of Tris-HCl and CH3CH2OH with a volume ratio of 5:1 for 15 minutes to obtain a pretreated PVDF microfiltration membrane.

[0055] S5. Add MOFs seed crystals to a mixed solution of PEI and NaHCO 3 and perform ultrasonic treatment to prepare a fourth mixed solution.

[0056] Wherein, in step S5, the mass ratio of MOFs seed crystals to PEI is 0.1-0.3:0.1-0.3, and the volume of the NaHCO3 solution is 3 mL-10 mL.

[0057] In more specific embodiments, 0.1-0.3 g of ZIF-8 is dissolved in 3-10 mL of NaHCO3 solution, and ultrasonic treatment is performed for 30-40 min.

[0058] In specific embodiments, when the MOFs seed crystal is ZIF-8 seed crystal, the ZIF-8 seed crystal is prepared first, and the prepared ZIF-8 seed crystal is added to the mixed solution of PEI and NaHCO3 for ultrasonic treatment to obtain a fourth mixed solution.

[0059] In the preparation of the ZIF-8 seed crystal, Zn(NO3)2·6H2O is dissolved in CH3OH, and then a CH3OH solution containing 2-MEIM is added, and the reaction is carried out at room temperature to obtain a uniform suspension. Nanocrystals are obtained by centrifugation, washed with CH3OH, and dried at 60°C under vacuum.

[0060] In the preparation of the ZIF-8 seed crystal, the mass ratio of Zn(NO3)2·6H2O to 2-MEIM (2-methylimidazole) is 0.6-0.9:1.5-1.8, and the amount of CH3OH corresponding to 0.6-0.9 g of Zn(NO3)2·6H2O is 80-120 mL.

[0061] S6, the PVDF microfiltration membrane modified in step S4 is immersed in the fourth mixed solution for soaking to obtain a PVDF microfiltration membrane coated with MOFs seed crystals.

[0062] S7, the PVDF microfiltration membrane obtained in step S6 is immersed in the MOFs precursor solution for solvothermal reaction to obtain a uranium extraction composite membrane.

[0063] In step S7, the temperature of the solvothermal reaction is 20-100°C, and the reaction time is 5-7 h.

[0064] In more preferred embodiments, the temperature of the solvothermal reaction is 60°C.

[0065] When the MOFs seed crystal in step S7 is ZIF-8 seed crystal, the preparation of the ZIF-8 precursor solution includes the following steps:

[0066] S10, Zn(NO3)2·6H2O and HCOONa are added to a CH3OH solution for stirring and dissolution to obtain a second mixed solution.

[0067] In this embodiment, 0.4-0.7 g of Zn(NO3)2·6H2O corresponds to a CH3OH amount of 50-80 mL.

[0068] S20, adding 2-MEIM to the CH3OH solution and stirring to prepare a third mixed solution.

[0069] S30, mixing the second mixed solution and the third mixed solution to prepare a ZIF-8 precursor solution.

[0070] The mass ratio of the Zn(NO3)2·6H2O, the HCOONa and the 2-MEIM in the precursor solution of ZIF-8 is 0.4-0.7:0.1-0.3:0.1-0.3.

[0071] The preparation method of the composite membrane of the present invention utilizes the hydrolysis reaction between TA and APTES to form a long-chain molecule with rich amino groups in the condensation of the hydrolyzate. Then, PEI and ZIF-8 seed crystals are introduced into the surface. The introduction of PEI can improve the stability of ZIF-8 in substrate growth. Afterwards, ZIF-8 secondary growth is carried out to grow a ZIF-8 layer with a uniform particle size on the membrane surface, further improving the adsorption capacity of the composite membrane for uranium, and the composite membrane has good stability and recyclability.

[0072] Example 1

[0073] This embodiment 1 provides a uranium extraction composite membrane. The preparation method of the uranium extraction composite membrane is as follows:

[0074] (1) Preparation of ZIF-8 seed crystals

[0075] 0.7333 g of Zn(NO₃)₂·6H₂O was dissolved in 50 mL of CH₃OH, followed by the addition of a 50 mL CH₃OH solution containing 1.6223 g of 2-MEIM. The reaction was allowed to proceed at room temperature for 30 minutes to obtain a homogeneous suspension. Nanocrystals were obtained by centrifugation for 5 minutes, washed three times with CH₃OH, and then dried under vacuum at 60°C for 12 hours to prepare ZIF-8 seed crystals.

[0076] (2) TA-APTES modification

[0077] Pretreatment of PVDF microfiltration membrane: The PVDF microfiltration membrane was washed with CH3CH2OH several times, and then placed in a mixed solution of Tris-HCl and CH3CH2OH with a volume ratio of 5:1 for 15 minutes to obtain a pretreated PVDF microfiltration membrane.

[0078] TA was dissolved in 20 mL of Tris-HCl (pH 8.5) to obtain a 2.5 mg / mL TA solution. 5 mL of CH₃CH₂OH and 0.025 mL of APTES were then added to the 2.5 mg / mL TA solution to obtain a mixed solution. A pretreated PVDF microfiltration membrane was immersed in this mixed solution and incubated at 25°C for 12 hours to prepare TAP. Surface impurities on the TAP were then removed using deionized water.

[0079] (3) PEI grafting and ZIF-8 seed loading

[0080] 0.2 g of PEI was dissolved in 4 mL (50 mmol) of NaHCO3 solution, to which 0.18 g of ZIF-8 seed crystals obtained in step (1) were added, and ultrasonic treatment was performed for 30 min. The TAP obtained in step (2) was immersed in the ultrasonically treated solution for 30 min to achieve seed coating. After seed coating, the membrane was removed and dried at room temperature for 12 h to prepare a PVDF microfiltration membrane (TAPP) after ZIF-8 seed coating.

[0081] (4) Secondary growth of ZIF-8

[0082] 0.6 g of Zn(NO3)2·6H2O and 0.138 g of HCOONa were added to 33 mL of CH3OH and stirred at 25°C for 10 min to obtain solution A. 0.24 g of 2-MEIM was dissolved in 33 mL of CH3OH to obtain solution B. Solution B was then added to solution A to obtain a mixed solution C. The mixed solution C was stirred at 25°C for 10 min. Subsequently, the mixed solution C was transferred to a stainless steel reactor lined with polytetrafluoroethylene. The membrane obtained in step (3) was placed in the above-mentioned mixed solution C and subjected to a solvothermal reaction at 60°C for 6 h. After the reaction was completed, the modified membrane was washed three times with CH3OH and dried to constant weight to prepare a composite membrane of secondary growth of ZIF-8 seeds. According to the preparation temperature, the composite membrane obtained in Example 1 was recorded as TAPP-ZIF-60.

[0083] Example 2

[0084] This Example 2 provides a uranium extraction composite membrane. The preparation of the uranium extraction composite membrane is the same as that of Example 1, wherein the temperature of the solvent thermal reaction in step (4) of Example 2 is adjusted to 20°C. The composite membrane obtained in Example 2 is marked as TAPP-ZIF-20.

[0085] Example 3

[0086] This Example 3 provides a uranium extraction composite membrane. The preparation of the uranium extraction composite membrane is the same as that of Example 1, wherein the temperature of the solvent thermal reaction in step (4) of Example 3 is adjusted to 40°C. The composite membrane obtained in Example 3 is marked as TAPP-ZIF-40.

[0087] Example 4

[0088] This Example 4 provides a uranium extraction composite membrane. The preparation of the uranium extraction composite membrane is the same as that of Example 1, wherein the temperature of the solvent thermal reaction in step (4) of Example 4 is adjusted to 80°C. The composite membrane obtained in Example 4 is marked as TAPP-ZIF-80.

[0089] Example 5

[0090] This Example 5 provides a uranium extraction composite membrane. The preparation of the uranium extraction composite membrane is the same as that of Example 1, wherein the temperature of the solvent thermal reaction in step (4) of Example 4 is adjusted to 100°C. The composite membrane obtained in Example 5 is marked as TAPP-ZIF-100.

[0091] Experiment 1: Structural Representation

[0092] Experiment 1 The TAPP-ZIF-60 composite membrane obtained in Example 1 was subjected to structural identification and characterization, as follows:

[0093] (1) FT-IR test: The FT-IR spectra of ZIF-8 seeds, PVDF, TAP, TAPP and TAPP-ZIF-60 in the TAPP-ZIF-60 composite membrane were detected and compared.

[0094] Figure 2 FT-IR spectrum of the TAPP-ZIF-60 composite membrane provided in Example 1 of the present invention. -1 and 1583cm -1 The peaks at 1184 cm-1 correspond to the out-of-plane stretching vibration of the imidazole ring and the C=N bond stretching vibration. -1 In the FT-IR spectrum of TAP, the -1 、2933cm -1 and 1720cm -1 The peaks at 3219 cm-1 belong to the bending vibrations of Si-O, methylene of APTES and -C=O of TA, respectively, indicating that TA and APTES were successfully introduced into the PVDF microfiltration membrane. -1 -3518cm -1The peak intensity at 1654 cm becomes stronger, which is attributed to the large amount of -NH2 contained in PEI. -1 The increase in the -C=N peak intensity observed at 757 cm indicates that a Schiff base reaction occurred between PEI and TA. -1 and 1583cm -1 The appearance of the peak at indicates that ZIF-8 was successfully introduced into TAP. In TAPP-ZIF-60, the same vibration peaks of ZIF-8 and TAP were observed, indicating that TAPP-ZIF-60 was successfully prepared.

[0095] (2) XRD test: XRD was used to observe and analyze the crystallization of TAPP-ZIF-60, PVDF and ZIF-8.

[0096] Figure 3 This is the XRD pattern of the TAPP-ZIF-60 composite film provided in Example 1 of the present invention. The ZIF-8 and simulated ZIF-8 match well. The diffraction peaks at 7.4°, 10.5°, and 12.8° in TAPP-ZIF-60 correspond to the (110), (200), and (211) crystal planes of ZIF-8, respectively. Furthermore, the diffraction peaks at 18.1°, 20°, and 26.6° correspond to the characteristic crystal planes of PVDF, confirming the successful preparation of TAPP-ZIF-60.

[0097] (3) SEM test: SEM was used to characterize the morphology of TAP, TAPP and TAPP-ZIF-60 composite membranes. Figure 4 This is a SEM image of the TAPP-ZIF-60 composite membrane provided in Example 1 of the present invention, wherein: Figure 4 (a) and (d) show TAP, which forms abundant nanospheres on the PVDF microfiltration membrane due to the hydrolysis of APTES and the oxidation of TA. Figure 4 (b) shows that after the ZIF-8 seeds are loaded onto the membrane through PEI connection, TAPP exhibits an interlaced pore structure. Figure 4 (e) in the figure shows that ZIF-8 nanoparticles were observed on the surface of TAPP. Figure 4 (c) and (f) in the figure show that through the solvothermal reaction at 60°C, more ZIF-8 crystals grow uniformly on the membrane surface and form smaller membrane pores.

[0098] The above structural characterization results show that the present invention forms long-chain molecules containing -OH / -NH2 groups through the hydrolysis reaction between TA and APTES, forming a nanoparticle structure, thereby activating the surface of the PVDF microfiltration membrane. PEI is grafted onto the activated surface and ZIF-8 seeds are loaded. A secondary solvent thermal reaction is then carried out to obtain ZIF-8 crystals with uniform particle size on the membrane surface, thereby changing the surface active groups of the PVDF microfiltration membrane and improving the adsorption capacity for uranium.

[0099] Experiment 2: Performance Verification

[0100] Test 2: The composite films in Examples 1-5 were subjected to relevant performance tests, as follows:

[0101] (1) Adsorption capacity test

[0102] Experimental Method: 0.01 g of each TAP and TAPP-ZIF-60 composite membrane was placed in 20 mL of a 100 mg / L uranyl solution. After 10 hours of adsorption in an Erlenmeyer flask with shaking, the adsorbed solution was collected. The remaining uranyl ion concentration in the aqueous solution was measured by ICP-AES. In this experiment, the pH was adjusted using 0.1 M HCl and 0.1 M NaHCO₃.

[0103] Experimental results showed that the pH of the solution significantly affected the adsorption properties of the composite membranes. With increasing pH, the adsorption capacity of both composite membranes initially increased and then decreased. At pH 5, TAP achieved a maximum adsorption capacity of 124.4 mg / g, while TAPP-ZIF-60 reached 153.68 mg / g at pH 8. The introduction of ZIF-8 significantly enhanced the composite membranes' adsorption capacity for uranyl ions.

[0104] (2) Effect of different solvent thermal temperatures on the adsorption capacity of composite membranes

[0105] Experimental Method: 0.01 g of each of TAPP-ZIF-20, TAPP-ZIF-40, TAPP-ZIF-60, TAPP-ZIF-80, and TAPP-ZIF-100 composite membranes prepared at different solvothermal temperatures were placed in 20 mL of a 100 mg / L uranyl solution. After adsorption in an Erlenmeyer flask for 10 hours, the adsorbed solution was collected. The residual uranyl ion concentration in the aqueous solution was determined by ICP-AES.

[0106] Test results: As the solvothermal temperature increased, the uranium adsorption capacity of the composite membranes first increased and then decreased. The adsorption capacities were 117.56 mg / g, 129.92 mg / g, 153.38 mg / g, 159.48 mg / g, and 130.04 mg / g, respectively. The highest adsorption capacity was achieved at a solvothermal temperature of 80°C, and the uranium adsorption capacity at 60°C was similar to that at 80°C.

[0107] (3) Application in uranium extraction performance verification in natural seawater

[0108] Test Method: Weigh 0.01g of TAPP-ZIF-60 membrane adsorbent and soak it in 50L of natural seawater for a specified period of time. At intervals, 200μL of the solution was sampled and diluted to 8mL with deionized water. Uranyl ion concentration was measured using ICP-MS.

[0109] Test results: As time went on, the adsorption capacity of the material increased steadily. After 30 days, the adsorption capacity of TAPP-ZIF-60 was 5.9 mg / g.

[0110] In summary, the present invention provides a uranium extraction composite membrane and a preparation method thereof, which adopts temperature control and PEI bridging strategy to prepare an antibacterial uranium extraction composite membrane. The introduction of ZIF-8 significantly enhances the adsorption capacity of the composite membrane for uranium. The prepared uranium extraction composite membrane has excellent uranium adsorption capacity and recoverability.

[0111] The above is only a specific implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A composite membrane for uranium extraction, characterized in that: The uranium extraction composite membrane comprises: PVDF microfiltration membrane; Nanoparticles formed by polyphenols and organic amines, wherein the nanoparticles formed by the polyphenols and organic amines are loaded on the surface of the PVDF microfiltration membrane; The secondary grown MOFs crystals are grafted with PEI and then loaded on the nanoparticles formed by the polyphenol and the organic amine.

2. A uranium extraction composite membrane according to claim 1, characterized in that: The nanoparticles formed by the polyphenol and the organic amine are nanoparticles formed by the reaction of TA and APTES, and the MOFs crystals are ZIF-8 crystals.

3. A uranium extraction composite membrane according to claim 1, characterized in that: The pore size of the PVDF microfiltration membrane is 0.22 μm to 0.45 μm, the particle size of the nanoparticles is 80 nm to 100 nm; and the particle size of the MOFs crystals is 0.42 μm to 0.54 μm.

4. A method for preparing a uranium extraction composite membrane according to claim 1, characterized in that: The preparation method comprises the following steps: S1, mixing polyphenols with a Tris-HCl solution to prepare a first mixed solution; S2. Mixing the organic amine with the CH3CH2OH solution to prepare a second mixed solution; S3, mixing the first mixed solution and the second mixed solution to prepare a third mixed solution; S4, immersing the pretreated PVDF microfiltration membrane into the third mixed solution to prepare a modified PVDF microfiltration membrane; S5, adding MOFs seed crystals to a mixed solution of PEI and NaHCO3 and performing ultrasonic treatment to prepare a fourth mixed solution; S6, immersing the modified PVDF microfiltration membrane in the fourth mixed solution to prepare a PVDF microfiltration membrane coated with MOFs seeds; S7. Immersing the PVDF microfiltration membrane prepared in step S6 into the MOFs precursor solution to perform a solvothermal reaction to prepare a uranium extraction composite membrane.

5. The method for preparing a uranium extraction composite membrane according to claim 4, characterized in that: The temperature of the solvent thermal reaction in step S7 is 20° C. to 100° C., and the reaction time is 5 h to 7 h.

6. The method for preparing a uranium extraction composite membrane according to claim 4, characterized in that: The pretreatment of the PVDF microfiltration membrane in step S4 is as follows: the PVDF microfiltration membrane is cleaned with CH3CH2OH, and the cleaned PVDF microfiltration membrane is immersed in a mixed solution of Tris-HCl and CH3CH2OH for soaking.

7. The method for preparing a uranium extraction composite membrane according to claim 4, characterized in that: The volume of the third mixed solution in step S3 is 20 mL to 30 mL, the concentration of polyphenols in the third mixed solution is 1 mg / mL to 3 mg / mL, and the concentration of organic amines is 1 μg / mL to 2 μg / mL.

8. The method for preparing a uranium extraction composite membrane according to claim 4, characterized in that: In step S5, the mass ratio of MOFs seed crystals to PEI is 0.1-0.3:0.1-0.3, and the volume of the NaHCO3 solution is 3 mL-10 mL.

9. The method for preparing a uranium extraction composite membrane according to claim 4, characterized in that: When the MOFs seed crystals in step S7 are ZIF-8 seed crystals, the preparation of the ZIF-8 precursor solution includes the following steps: S10, adding Zn(NO3)2·6H2O and HCOONa to a CH3OH solution and stirring to dissolve them to prepare a fifth mixed solution; S20, adding 2-MEIM to the CH3OH solution and stirring to prepare a sixth mixed solution; S30, mixing the fifth mixed solution and the sixth mixed solution to prepare a ZIF-8 precursor solution.

10. The method for preparing a uranium extraction composite membrane according to claim 9, characterized in that: The mass ratio of Zn(NO3)2, HCOONa and 2-MEIM in the ZIF-8 precursor solution is 0.4-0.7:0.1-0.3:0.1-0.3.

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