A MOF glass film and its preparation method and application

Abstract

The present invention relates to the field of membrane separation technology, and in particular to a MOF glass membrane and its preparation method and application. The MOF glass membrane uses amorphous ZIF-62 as a matrix and crystalline ZIF-8 as a filler. The crystalline ZIF-8 is uniformly dispersed in the amorphous ZIF-62, and the mass ratio of ZIF-62 to ZIF-8 is 7:3 to 9:1. The results of the separation effect test on different ion pairs show that the MOF glass membrane has different transmission rates for potassium, sodium, and lithium; when the mass ratio of ZIF-62 to ZIF-8 is 7:3 to 9:1, the MOF glass membrane has a certain separation effect on potassium, sodium, and lithium. When the mass ratio is 7:3, the separation effect is the best, and it is expected to be applied to the separation of alkali metal cations in many fields. The MOF glass membrane preparation method provided by the present invention has a simple process route and mild reaction conditions, which is conducive to large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation technology, and in particular to a MOF glass membrane and a preparation method and application thereof. Background Art

[0002] Can metal ion K + 、Na + He Li + Efficient and selective separation is of great significance to many fields.

[0003] Li + As the core material of lithium-ion batteries in the new energy industry, its importance is self-evident. Most of the world's lithium resources exist in salt lakes. However, the composition of salt lake brine is complex, usually accompanied by high concentrations of Na + and K + . Efficiently transfer Li + From Na + , K + Separating lithium from the raw materials is a key step in ensuring the sustainable supply of lithium resources and promoting the stable development of the new energy industry. + and K + The precise separation also plays a decisive role in the fields of nuclear power coolant processing and potash salt mine purification.

[0004] In terms of environmental management and industrial application, if Na is discharged disorderly in industrial wastewater, + , K + He Li + , which will cause soil salinization and cause serious damage to the ecological environment. Take lithium battery production wastewater as an example, which contains Li + If discharged directly without treatment, it will pollute groundwater and cause serious harm to human health.

[0005] In the field of life sciences and medicine, Na + and K + These ions are key ions in maintaining cellular osmotic pressure and nerve conduction, and imbalances in their concentration are closely linked to a variety of conditions, including hypertension and kidney disease. Therefore, technologies that can precisely regulate the separation of these ions play an important role in supporting the development of medical devices such as artificial kidneys.

[0006] However, existing membrane separation technology is not effective in separating K + 、Na + He Li + There are still many problems when using K ions. On the one hand, due to the + 、Na + 、Li +The difference in the hydrated ion radius is extremely small, only at the sub-angstrom level, which makes it difficult for traditional membrane materials to maintain high selectivity while maintaining high flux. For example, the lattice defects of MOF membranes easily lead to non-specific permeation of ions, and although crown ether membranes can improve the selectivity of monovalent ions, they have to sacrifice some transmission rate. On the other hand, organic matter (such as humic acid) and colloidal particles (such as Ca2+) in complex water bodies are 2+ ) is easily adsorbed on the membrane surface, causing membrane fouling and flux reduction. Studies have shown that Ca 2+ Differences in interaction with cation exchange membranes (CEMs) are the primary cause of inorganic scaling. Furthermore, graphene oxide membranes are prone to swelling and delamination over long-term use. Furthermore, the complex and costly synthesis processes of novel membrane materials such as MOFs and COFs make large-scale production difficult.

[0007] Therefore, a method is developed to overcome the defects of the existing technology and realize the metal ion K + 、Na + He Li + The separation of organic matter has urgent practical needs and important application value in many fields such as resource recovery, environmental protection, industrial production and medical treatment. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the first object of the present invention is to provide a MOF glass film; the second object of the present invention is to provide an application of the MOF glass film; and the third object of the present invention is to provide a method for preparing the MOF glass film.

[0009] In order to achieve the first purpose, the technical solution adopted by the present invention is:

[0010] A MOF glass membrane, comprising amorphous ZIF-62 as a matrix and crystalline ZIF-8 as a filler, wherein the crystalline ZIF-8 is uniformly dispersed in the amorphous ZIF-62;

[0011] The mass ratio of ZIF-62 to ZIF-8 is 7:3 to 9:1;

[0012] The unit molecular formula of ZIF-62 is C 28 H 26 N 16 Zn4 is a metal organic framework material composed of zinc atoms and imidazole and benzimidazole ligands. In its structure, zinc atoms are surrounded by sodium imidazole and benzimidazole molecules. Its molecular structure is shown below:

[0013] ;

[0014] ZIF-62 typically exists in a crystalline form, belonging to the Pbca space group and sharing a topological network with phosphate calcite and pyroxenite. Under certain conditions, ZIF-62 undergoes an amorphous transition. For example, at high temperatures, ZIF-62 melts into a viscous liquid, which, upon quenching to room temperature, forms an amorphous glass phase. Mechanical forces can also cause ZIF-62 to amorphize, such as mechanical grinding, which can convert crystalline ZIF-62 into an amorphous state.

[0015] The unit molecular formula of ZIF-8 is C8H 10 N4Zn is composed of zinc ions and 2-methylimidazole ligands, and its molecular structure is shown below:

[0016] .

[0017] In order to achieve the second purpose, the technical solution adopted by the present invention is:

[0018] An application of a MOF glass membrane, such as any one of the MOF glass membranes described above, is used for separating alkali metal cations in a solution.

[0019] Furthermore, the alkali metal cations include Na + , K + He Li + One or more of the .

[0020] Furthermore, the applications include sewage treatment and recovery of lithium ions from waste batteries.

[0021] In order to achieve the third purpose, the technical solution adopted by the present invention is:

[0022] A method for preparing a MOF glass film, for preparing any of the above MOF glass films, comprising the following steps:

[0023] S100, mixing ZIF-62 and ZIF-8, and grinding them uniformly to obtain powder;

[0024] Grinding to a uniform powder size can promote uniform distribution during subsequent tableting and sufficient reaction at high temperature;

[0025] S200, spreading the powder evenly and pressing it into a sheet to form a membrane;

[0026] S300, performing a high-temperature quenching treatment on the membrane to obtain a MOF glass film;

[0027] The high temperature quenching process is as follows:

[0028] The membrane was heated to 435-445° C. at a rate of 1-5° C. / min, kept warm for 15-25 minutes to promote diffusion and mixing of ZIF-62 and ZIF-8, and cooled to 20-25° C. under inert gas conditions to obtain a MOF glass membrane;

[0029] The temperature range is 435-445°C, preferably 440°C, which is higher than the glass transition temperature or eutectic temperature of the ZIF-62 material, so that the crystal structure melts or partially decomposes during heating to form an amorphous glass phase. If the temperature is too low, the crystals are not fully softened and it is difficult to form a uniform glass. If it is too high, it may cause volatilization or side reactions.

[0030] Keeping the temperature for 15 to 25 minutes can ensure that the system reaches thermal equilibrium, promote the full diffusion and mixing of the two metal-organic framework materials ZIF-62 and ZIF-8, and form a uniform molten state;

[0031] Under inert gas conditions, it can prevent metals from being oxidized at high temperatures;

[0032] Cooling to room temperature, preferably slow cooling, which is conducive to the uniform distribution of atoms or ions in the amorphous structure and the formation of a stable glassy structure;

[0033] The preparation method provided by the present invention destroys the lattice structure of the metal crystal at high temperature, rearranges the chemical bonds between atoms, and forms a glassy structure with long-range disorder and short-range order. During the cooling process, the atomic mobility decreases and the structure is finally fixed into an amorphous solid (MOF glass film).

[0034] Furthermore, ZIF-62 was prepared by solvent thermal synthesis.

[0035] Solvothermal synthesis is a synthetic method that uses a liquid solvent as the reaction medium in a sealed container, heated to the critical temperature or near the boiling point, and then undergoes a chemical reaction under high pressure. This method can achieve syntheses under mild conditions that are difficult to achieve with traditional high-temperature solid-phase reactions (such as low-temperature crystallization). The product structure can be precisely controlled by adjusting parameters such as solvent, temperature, pressure, and additives.

[0036] Furthermore, the reaction solvent used to prepare ZIF-62 is selected from dimethylformamide (DMF).

[0037] Furthermore, in step S100, ZIF-8 is prepared by a room temperature synthesis method.

[0038] Furthermore, the reaction solvent used to prepare ZIF-8 is methanol.

[0039] Furthermore, in step S100, the grinding tool selected for grinding is an agate mortar;

[0040] The agate mortar is made of high hardness and strong chemical inertness, which can avoid the introduction of impurities (such as metal ions) during the grinding process and ensure the purity of the raw materials.

[0041] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0042] The MOF glass membrane provided by the present invention uses amorphous ZIF-62 as a matrix and crystalline ZIF-8 as a filler. The crystalline ZIF-8 is uniformly dispersed in the amorphous ZIF-62. The mass ratio of ZIF-62 to ZIF-8 is 7:3 to 9:1. The test results of the separation effect of the MOF glass membrane on binary ion mixtures, ternary ion mixtures and different mass ratios of ZIF-8 show that the MOF glass membrane has a good effect on the separation of K + 、Na + 、Li + The MOF glass film has different transmission rates. When the mass ratio of ZIF-62 to ZIF-8 is 7:3 to 9:1, the MOF glass film has a strong affinity for K + 、Na + 、Li + Both have a certain separation effect. When the mass ratio of ZIF-62 and ZIF-8 is 7:3, the MOF glass membrane has a good effect on K + 、Na + 、Li + Therefore, MOF glass membrane is expected to be used for the separation of alkali metal cations in solution, especially for K + 、Na + 、Li + The separation of the MOF glass membranes of the present invention indicates that the MOF glass membranes provided by the present invention have potential applications in a variety of fields, including resource recovery, environmental protection, industrial production, and medical treatment. Furthermore, the MOF glass membrane preparation method provided by the present invention has a simple process and mild reaction conditions, which is conducive to large-scale production.

[0043] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a provided in Example 1 of the present invention g [(ZIF-62) 0.7 (ZIF-8) 0.3 ]SEM image of glass film.

[0045] Figure 2 It is a schematic diagram of the H-type glass device structure provided in Test Example 1 of the present invention.

[0046] Figure 3 This is the IV curve of the MOF glass film provided in Test Example 1 of the present invention.

[0047] Figure 4 This is a diagram showing the detection results of the MOF glass membrane provided in Detection Example 2 of the present invention for the separation of binary ion mixtures.

[0048] Figure 5 This is a diagram showing the detection results of the MOF glass membrane provided in Detection Example 2 of the present invention for the separation of ternary ion mixtures.

[0049] Figure 6 This is the IV curve of the MOF glass film with different ZIF-62 to ZIF-8 mass ratios provided in Test Example 3 of the present invention.

[0050] Figure 7 This is a graph showing the test results of the separation of three mixed ions by MOF glass membranes with different ZIF-62 to ZIF-8 mass ratios provided in Test Example 3 of the present invention.

[0051] Reference numerals:

[0052] 1.MOF glass film. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0054] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used are all commercially available unless otherwise specified.

[0055] Example 1

[0056] The preparation process of ZIF-62 is as follows:

[0057] Zn(NO3)2·6H2O (6.72 mmol), imidazole (157.69 mmol) and DMF (75 mL) were weighed and added to a screw-top jar and stirred to dissolve completely. Then, benzimidazole (15.89 mmol) was added and heated to 130°C for 48 h to obtain ZIF-62.

[0058] The preparation process of ZIF-8 is as follows:

[0059] ZnCl2 (15.8 mmol) and 2-methylimidazole (262.28 mmol) were dissolved in methanol, respectively. The two solutions were mixed, stirred for 1 h, and allowed to stand at room temperature for 12 h to obtain ZIF-8.

[0060] The MOF glass film was prepared as follows:

[0061] The ZIF-62 (as a matrix) and ZIF-8 (as a filler) prepared above were mixed in different mass ratios (1:0, 9:1, 8:2, 7:3, and 6:4) to obtain a mixture (100 mg). The mixture was placed in an agate mortar and ground clockwise for 60 seconds to obtain a powder of the mixture. The powder of the mixture was transferred to a tablet press, evenly spread, and pressed at a pressure of 15 MPa for 1 minute to obtain a membrane. The membrane was placed on a glass slide and then placed in a tube furnace for high-temperature quenching treatment to obtain MOF glass membranes with different mass ratios of matrix and filler, which were recorded as:

[0062] a g [(ZIF-62)1(ZIF-8)0], a g [(ZIF-62) 0.9 (ZIF-8) 0.1 ]、a g [(ZIF-62) 0.8 (ZIF-8) 0.2 ]、a g [(ZIF-62) 0.7 (ZIF-8) 0.3 ]、a g [(ZIF-62) 0.6 (ZIF-8) 0.4 ];

[0063] Among them, a g [(ZIF-62) 0.7 (ZIF-8) 0.3 ], such as Figure 1 As shown in the figure, the glass film basically covers continuously, and there is no large area of ​​missing film layer, which shows that the MOF glass film was successfully prepared.

[0064] The high temperature quenching process was as follows: the tube furnace was heated to 440°C at a rate of 3°C / min and maintained for 20 min, and then cooled to room temperature under an argon atmosphere.

[0065] Test Example 1 Performance test of MOF glass film.

[0066] Test apparatus: The ion transmembrane transport properties were tested using an H-type glass apparatus and a picoammeter in series.

[0067] The performance test process of MOF glass film is as follows: the MOF glass film prepared above (the mass ratio of ZIF-62 and ZIF-8 is 7:3) is placed between the H-shaped glass devices, such as Figure 2 As shown in the figure, the liquid volume in the glass devices on both sides of the MOF glass membrane 1 is 15 mL. The Ag / AgCl electrode is used as the working electrode. For each measurement, the same salt solution (LiCl, NaCl and KCl) with the same concentration (0.1 mol / L) is added to the glass devices on both sides of the MOF glass membrane, and the current is recorded by scanning from -2V to +2V to obtain the IV curve. The results are shown in the figure. Figure 3 shown.

[0068] Test Example 2: Testing of the separation effect of MOF glass membrane on different ions.

[0069] The test device is as follows: The ion selectivity test uses an H-type glass device for separation, and then uses an inductively coupled plasma emission spectrometer (ICP) to measure the selectivity value.

[0070] The test process of binary ion mixing separation effect is as follows: the MOF glass membrane prepared above (the mass ratio of ZIF-62 and ZIF-8 is 7:3) is placed between H-shaped glass devices. KCl / LiCl, NaCl / LiCl, or KCl / NaCl mixed aqueous solutions with a concentration of 0.1 mol / L are added to the container on one side of the MOF glass membrane, and ultrapure water is added to the container on the other side. After 48 hours of osmotic transmission, the solution on the osmotic side is taken out and the separation effect is tested by ICP. The results are as follows Figure 4 As shown in the figure, it can be seen that the ion selectivity values ​​of MOF glass membrane for three binary ion aqueous solutions are 170, 50 and 12.5 respectively. This result shows that MOF glass membrane has a good selectivity for K + He Li + The highest ion selectivity.

[0071] The test process of ternary ion mixing separation effect is as follows: the MOF glass membrane prepared above (the mass ratio of ZIF-62 and ZIF-8 is 7:3) is placed between the H-shaped glass devices. KCl, LiCl and NaCl / LiCl aqueous solutions with a concentration of 0.1 mol / L are added to the container on one side of the MOF glass membrane, and ultrapure water is added to the container on the other side. After 48 hours of osmotic transmission, the solution on the osmotic side is taken out and the separation effect is tested by ICP. The results are as follows Figure 5 As shown in the figure, it can be seen that MOF glass film has a great influence on K + He Li +The ion selectivity of the ion pair is the highest (ion selectivity is about 400), and the ion selectivity of Na + He Li + The ion selectivity is about 90, for Na + and K + The ion selectivity is about 35.

[0072] Test Example 3

[0073] According to the detection process of detection example 1, the IV curves of MOF glass films with different ZIF-62 and ZIF-8 mass ratios were detected, such as Figure 6 As shown, A~E in the figure are a g [(ZIF-62)1(ZIF-8)0], a g [(ZIF-62) 0.9 (ZIF-8) 0.1 ]、a g [(ZIF-62) 0.8 (ZIF-8) 0.2 ]、a g [(ZIF-62) 0.7 (ZIF-8) 0.3 ]、a g [(ZIF-62) 0.6 (ZIF-8) 0.4 ]IV curve of glass film;

[0074] According to the test process of Test Example 2, the separation of three mixed ions by MOF glass membranes with different ZIF-62 and ZIF-8 mass ratios was tested, such as Figure 7 As shown in the figure, as the mass ratio of ZIF-62 to ZIF-8 decreases from 1:0 to 0.7:0.3, the ion selectivity increases significantly. At a mass ratio of 0.7:0.3, the ion selectivity reaches a maximum value of nearly 400. This result indicates that when the mass ratio of ZIF-62 to ZIF-8 is 7:3, the selectivity of the MOF glass membrane for the ion pair is at a high level.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An application of a MOF glass film, characterized in that: The application is that MOF glass membrane is used for alkali metal cation Na in solution + , K + He Li + separation; The MOF glass film uses amorphous ZIF-62 as a matrix and crystalline ZIF-8 as a filler. The crystalline ZIF-8 is uniformly dispersed in the amorphous ZIF-62, and the mass ratio of ZIF-62 to ZIF-8 is 7:3 to 9:

1. The preparation method of the MOF glass film comprises the following steps: S100, mixing ZIF-62 and ZIF-8, and grinding them uniformly to obtain powder; S200, spreading the powder evenly and pressing it into a sheet to form a membrane; S300, performing a high-temperature quenching treatment on the membrane to obtain a MOF glass film; The high temperature quenching process is as follows: The membrane is heated to 435-445° C. at a rate of 1-5° C. / min, kept warm for 15-25 minutes to promote diffusion and mixing of ZIF-62 and ZIF-8, and cooled to 20-25° C. under inert gas conditions to obtain a MOF glass membrane.

2. The use of the MOF glass film according to claim 1, characterized in that: The applications include wastewater treatment and the recovery of lithium ions from spent batteries.

3. The use of the MOF glass film according to claim 1, characterized in that: In step S100, ZIF-62 is prepared by a solvent thermal synthesis method.

4. The use of the MOF glass film according to claim 1, characterized in that: The reaction solvent used in preparing ZIF-62 is selected from dimethylformamide.

5. The use of the MOF glass film according to claim 1, characterized in that: In step S100, ZIF-8 is prepared by a room temperature synthesis method.

6. The use of the MOF glass film according to claim 1, characterized in that: The reaction solvent used in the preparation of ZIF-8 was methanol.

7. The use of the MOF glass film according to claim 1, characterized in that: In step S100, the grinding tool selected for grinding is an agate mortar.

Images