MOF glass film and preparation method and application thereof

Abstract

The invention relates to the technical field of membrane separation, in particular to an MOF glass membrane and a preparation method and application thereof. According to the MOF glass film, amorphous ZIF-62 serves as a matrix, crystalline ZIF-8 serves as filler, the crystalline ZIF-8 is evenly dispersed in the amorphous ZIF-62, and the mass ratio of the ZIF-62 to the ZIF-8 is 7: 3-9: 1. The detection result of the separation effect on different ion pairs shows that the MOF glass film has different transmission rates on potassium, sodium and lithium; when the mass ratio of ZIF-62 to ZIF-8 is 7: 3-9: 1, the MOF glass film has a certain separation effect on potassium, sodium and lithium, when the mass ratio is 7: 3, the separation effect is optimal, and the MOF glass film is expected to be applied to separation of alkali metal positive ions in many fields. The preparation method of the MOF glass film provided by the invention is simple in process route, mild in reaction condition and beneficial to large-scale production.

Description

Technical Field

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

[0002] Whether it is possible to efficiently and selectively separate metal ions K + , Na + and Li + is of great significance in 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 global lithium resources exist in salt lakes. However, the components of salt lake brine are complex and usually accompanied by high concentrations of Na + and K + . Efficiently separating Li + from Na + , K + is the key link to ensure the sustainable supply of lithium resources and promote the stable development of the new energy industry. At the same time, the precise separation of Na + and K + also plays a decisive role in fields such as nuclear power coolant treatment and potassium salt ore purification.

[0004] In terms of environmental governance and industrial applications, if Na + , K + and Li + are discharged disorderly in industrial wastewater, it will cause soil salinization and cause serious damage to the ecological environment. Taking the wastewater from lithium battery production as an example, the Li + contained in it, if directly discharged without treatment, will pollute groundwater and cause serious harm to human health.

[0005] In the fields of life science and medicine, Na + and K + are key ions for maintaining cell osmotic pressure and nerve conduction, and their concentration imbalance is closely related to various diseases such as hypertension and kidney diseases. Therefore, the separation technology that can precisely regulate these ions has an important technical support role for the development of medical devices such as artificial kidneys.

[0006] However, the existing membrane separation technology still has many problems when separating K + , Na + and Li + ions. On the one hand, due to K + , Na + , Li +The difference in the hydrated ion radii is extremely small, only at the sub-ångström level, which makes it difficult for traditional membrane materials to maintain high throughput while ensuring high selectivity. For example, the lattice defects in MOF membranes easily lead to non-specific ion permeation, while crown ether membranes can improve the selectivity of monovalent ions but have to sacrifice some transmission rates. On the other hand, organic substances (such as humic acid) and colloidal particles (such as Ca 2+ ) in complex water bodies are extremely easy to adsorb on the membrane surface, causing membrane fouling and resulting in a decrease in flux. Research shows that the difference in the interaction between Ca 2+ and cation exchange membrane (CEM) is the main cause of inorganic scaling, and membranes such as graphene oxide membranes are also prone to swelling and delamination during long-term use. In addition, the synthesis processes of new membrane materials such as MOF and COF are complex and costly, making it difficult to achieve large-scale production and application.

[0007] Therefore, there is an urgent practical need and important application value in many fields such as resource recovery, environmental protection, industrial production, and medical treatment to develop a method that can overcome the defects of existing technologies and efficiently, stably, and low-costly separate metal ions K + , Na + and Li + . 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 membrane; the second object of the present invention is to provide an application of the MOF glass membrane, and the third object of the present invention is to provide a preparation method of the MOF glass membrane.

[0009] To achieve the first object, the technical solution adopted by the present invention is as follows: A MOF glass membrane, with amorphous ZIF-62 as the matrix and crystalline ZIF-8 as the filler, and 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 unit molecular formula of ZIF-62 is C 28 H 26 N 16 Zn4, which is a metal-organic framework material composed of zinc atoms and imidazole and benzimidazole ligands. In its structure, zinc atoms are surrounded by imidazole sodium and benzimidazole molecules, and its molecular structural formula is shown as follows: ; ZIF-62 usually exists in a crystalline form, belonging to the Pbca space group and having the same topological network as phosphate calcite and metavariscite. ZIF-62 undergoes an amorphous transformation under some special conditions. For example, at high temperatures, ZIF-62 melts into a viscous liquid, and quenching to room temperature can form an amorphous glass phase. In addition, mechanical force can also cause ZIF-62 to become amorphous. For example, through means such as mechanical grinding, crystalline ZIF-62 can be transformed into an amorphous state.

[0010] The unit molecular formula of ZIF-8 is C8H 10 N4Zn, which is composed of zinc ions and 2-methylimidazole ligands, and its molecular structural formula is shown as follows: 。

[0011] To achieve the second object, the technical solution adopted by the present invention is: An application of a MOF glass membrane, such as the MOF glass membrane described in any one of the above, for the separation of alkali metal cations in a solution.

[0012] Further, the alkali metal cations include Na + 、K + and Li + one or more of them.

[0013] Further, the application includes sewage treatment and the recovery of lithium ions in waste batteries.

[0014] To achieve the third object, the technical solution adopted by the present invention is: A preparation method of a MOF glass membrane for preparing the MOF glass membrane described in any one of the above, comprising the following steps: S100. Mix ZIF-62 and ZIF-8 and grind them evenly to obtain a powder; Grinding to a uniform powder particle size can promote uniform distribution during subsequent tablet pressing and sufficient reaction at high temperatures; S200. Spread the powder evenly and form a membrane sheet through tablet pressing; S300. Perform high-temperature quenching treatment on the membrane sheet to obtain a MOF glass membrane; Among them, the high-temperature quenching treatment process is as follows: Heat the membrane sheet at a rate of 1 - 5 °C / min to 435 - 445 °C, then keep it warm for 15 - 25 min to promote the diffusion and mixing of ZIF-62 and ZIF-8, and cool it to 20 - 25 °C under an inert gas condition to obtain a MOF glass membrane; A temperature range of 435 - 445 °C, preferably 440 °C, which is higher than the glass transition temperature or eutectic temperature of the ZIF-62 material, causes the crystal structure to melt or partially decompose during heating to form an amorphous glass phase; if the temperature is too low, the crystal is not sufficiently softened and it is difficult to form a uniform glass; if it is too high, volatilization or side reactions may occur; Insulate for 15 - 25 min, which 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; Under inert gas conditions, it can prevent the metal from being oxidized at high temperatures; Cool to room temperature, preferably by slow cooling. Slow cooling is beneficial for the uniform distribution of atoms or ions in the amorphous structure to form a stable glassy structure; The preparation method provided by the present invention disrupts the lattice structure of metal crystals at high temperatures, 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 finally solidifies into an amorphous solid (MOF glass film).

[0015] Furthermore, ZIF-62 is prepared by a solvothermal synthesis method.

[0016] The solvothermal synthesis method is a synthesis method in a sealed container, using a liquid solvent as the reaction medium, and carrying out chemical reactions under high-pressure conditions by heating to the critical temperature or close to the boiling point. This method can achieve syntheses that are difficult to complete by traditional high-temperature solid-phase reactions under mild conditions (such as low-temperature crystallization), and can precisely control the product structure by adjusting parameters such as solvents, temperature, pressure, and additives.

[0017] Furthermore, the reaction solvent used for preparing ZIF-62 is selected from dimethylformamide (DMF).

[0018] Furthermore, in step S100, ZIF-8 is prepared by a room-temperature synthesis method.

[0019] Furthermore, the reaction solvent used for preparing ZIF-8 is methanol.

[0020] Furthermore, in step S100, the grinding tool selected for grinding is an agate mortar; The agate mortar has a high material hardness and strong chemical inertness, which can avoid introducing impurities (such as metal ions) during the grinding process and ensure the purity of the raw materials.

[0021] One or more of the above technical solutions in the embodiments of the present invention have at least one of the following technical effects: The MOF glass membrane provided by the present invention uses amorphous ZIF-62 as the matrix and crystalline ZIF-8 as the 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 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 different transmission rates for K + , Na + , Li + . 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 K + , Na + , Li + . When the mass ratio of ZIF-62 to ZIF-8 is 7:3, the MOF glass membrane can completely separate K + , Na + , Li + . Therefore, the MOF glass membrane is expected to be applied to the separation of alkali metal cations in solutions, especially suitable for the separation of K + , Na + , Li + . From this, it can be seen that the MOF glass membrane provided by the present invention has potential application value in many fields such as resource recovery, environmental protection, industrial production, and medical treatment. At the same time, the preparation method of the MOF glass membrane provided by the present invention has a simple process route and mild reaction conditions, which is conducive to large-scale production.

[0022] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the SEM image of the a g [(ZIF-62) 0.7 (ZIF-8) 0.3 glass membrane provided in Example 1 of the present invention.

[0024] Figure 2 is the schematic structural diagram of the H-type glass device provided in Test Example 1 of the present invention.

[0025] Figure 3 is the I-V curve diagram of the MOF glass membrane provided in Test Example 1 of the present invention.

[0026] Figure 4 is the test result diagram of the separation of binary ion mixtures by the MOF glass membrane provided in Test Example 2 of the present invention.

[0027] Figure 5It is the test result diagram of the separation of ternary ion mixture by the MOF glass membrane provided in Test Example 2 of the present invention.

[0028] Figure 6 It is the I-V curve of the MOF glass membrane with different mass ratios of ZIF-62 to ZIF-8 provided in Test Example 3 of the present invention.

[0029] Figure 7 It is the test result diagram of the separation of three kinds of mixed ions by the MOF glass membrane with different mass ratios of ZIF-62 to ZIF-8 provided in Test Example 3 of the present invention.

[0030] Reference numerals: 1. MOF glass membrane. Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0032] In the following embodiments, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used are carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. Unless otherwise specified, they can all be obtained from commercial channels.

[0033] Embodiment 1 The preparation of ZIF-62 is as follows: Weigh Zn(NO3)2·6H2O (6.72 mmol), imidazole (157.69 mmol) and DMF (75 mL), add them to a screw-cap jar and stir until completely dissolved, then add benzimidazole (15.89 mmol), heat to 130 °C and react for 48 h to obtain ZIF-62.

[0034] The preparation of ZIF-8 is as follows: Dissolve ZnCl2 (15.8 mmol) and 2-methylimidazole (262.28 mmol) in methanol respectively, mix the two solutions and stir for 1 h, and then stand at room temperature for 12 h to obtain ZIF-8.

[0035] The preparation of the MOF glass membrane is as described below: After mixing the prepared ZIF-62 (as the matrix) and ZIF-8 (as the filler) in different mass ratios (1:0, 9:1, 8:2, 7:3, 6:4), a mixture (100 mg) was obtained. The mixture was put into an agate mortar and ground clockwise for 60 s to obtain the powder of the mixture. The powder of the mixture was transferred to a tablet press, evenly spread, and pressed continuously for 1 min under a pressure of 15 MPa to obtain a membrane. The membrane was placed on a glass slide and then put into a tube furnace for high-temperature quenching treatment to obtain MOF glass membranes with different mass ratios of matrix and filler, which were respectively denoted as: 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 ; Among them, a g [(ZIF-62) 0.7 (ZIF-8) 0.3 of the SEM image is as Figure 1 shown. The glass membrane is basically continuously covered, and no large-area film layer missing area is seen, indicating that the MOF glass membrane is successfully prepared.

[0036] The process of high-temperature quenching treatment is as follows: The tube furnace was heated to 440 °C at a rate of 3 °C / min and held for 20 min, and then cooled to room temperature under an argon atmosphere.

[0037] Test Example 1 Performance test of MOF glass membrane.

[0038] Test device: For the test of ion transmembrane transport properties, an H-type glass device and a picoammeter were connected in series.

[0039] The performance test process of the MOF glass membrane is as follows: The previously prepared MOF glass membrane (the mass ratio of ZIF-62 and ZIF-8 is 7:3) was placed between the H-type glass devices, as Figure 2As shown, the liquid volume in the glass devices on both sides of the MOF glass membrane 1 is 15 mL each. 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 I-V curve is obtained by recording the current through a scan from -2V to +2V. The results are as Figure 3 shown.

[0040] Detection Example 2 Detection of the separation effect of the MOF glass membrane on different ions.

[0041] The test device is as follows: For ion selectivity testing, an H-type glass device is used for separation, and then an Inductively Coupled Plasma Emission Spectrometer (ICP) is used to measure the selectivity value.

[0042] Detection of the separation effect of binary ion mixtures is as follows: The previously prepared MOF glass membrane (mass ratio of ZIF-62 to ZIF-8 is 7:3) is placed between H-type glass devices. A mixed aqueous solution of KCl / LiCl, or NaCl / LiCl, or KCl / NaCl with a concentration of 0.1 mol / L is added to one side container of the MOF glass membrane, and ultrapure water is in the other side container. After 48 hours of permeation and transmission, the solution on the permeation side is taken out, and the separation effect is detected by ICP. The results are as Figure 4 shown. It can be seen from the figure that the ion selectivity values of the MOF glass membrane for the three binary ion aqueous solutions are 170, 50, and 12.5 respectively. This result indicates that the MOF glass membrane has the highest ion selectivity for K + and Li + .

[0043] Detection of the separation effect of ternary ion mixtures is as follows: The previously prepared MOF glass membrane (mass ratio of ZIF-62 to ZIF-8 is 7:3) is placed between H-type glass devices. Aqueous solutions of KCl, LiCl, and NaCl / LiCl with a concentration of 0.1 mol / L are added to one side container of the MOF glass membrane, and ultrapure water is in the other side container. After 48 hours of permeation and transmission, the solution on the permeation side is taken out, and the separation effect is detected by ICP. The results are as Figure 5 shown. It can be seen from the figure that the MOF glass membrane has the highest ion selectivity for the K + and Li + ion pair (ion selectivity is about 400), the ion selectivity for Na + and Li + is about 90, and the ion selectivity for Na + and K + is about 35.

[0044] Detection Example 3 According to the detection process of Detection Example 1, detect the I-V curves of MOF glass membranes with different mass ratios of ZIF-62 to ZIF-8. As Figure 6 shown, in the figure, A to E are respectively 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 I-V curves of the glass membranes; According to the detection process of Detection Example 2, detect the separation of three kinds of mixed ions by MOF glass membranes with different mass ratios of ZIF-62 to ZIF-8. As Figure 7 shown, it can be seen from the figure that as the mass ratio of ZIF - 62 to ZIF - 8 decreases from 1:0 to 0.7:0.3, the ion selectivity increases significantly. When the mass ratio is 0.7:0.3, the ion selectivity reaches the highest value, approaching 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 given ion pairs is at a relatively high level.

[0045] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MOF glass membrane, characterized in that, Using amorphous ZIF-62 as the matrix and crystalline ZIF-8 as the 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.

2. Application of a MOF glass membrane, characterized in that, The MOF glass membrane according to claim 1 is used for the separation of alkali metal cations in solution.

3. The application of the MOF glass film according to claim 2, characterized in that, The alkali metal cations include Na + , K + and Li + or one or more of them.

4. The application of the MOF glass film according to claim 2, characterized in that, The applications include sewage treatment and the recovery of lithium ions in waste batteries.

5. A preparation method of a MOF glass membrane, characterized in that, For the preparation of the MOF glass membrane according to claim 1, the following steps are included: S100: Mix ZIF-62 and ZIF-8 and grind them evenly to obtain a powder; S200: Spread the powder evenly and form a film sheet through tabletting; S300: Perform high-temperature quenching treatment on the film sheet to obtain the MOF glass membrane; Among them, the high-temperature quenching treatment process is as described below: After heating the film sheet to 435-445 °C at a rate of 1-5 °C / min, keep it warm for 15-25 min to promote the diffusion and mixing of ZIF-62 and ZIF-8, and cool it to 20-25 °C under an inert gas condition to obtain the MOF glass membrane.

6. The preparation method of the MOF glass film according to claim 5, characterized in that, In step S100, ZIF-62 is prepared by a solvothermal synthesis method.

7. The preparation method of the MOF glass film according to claim 6, wherein, The reaction solvent used for preparing ZIF-62 is selected from dimethylformamide.

8. The preparation method of the MOF glass film according to claim 5, wherein In step S100, ZIF-8 is prepared by a room-temperature synthesis method.

9. The preparation method of the MOF glass film according to claim 8, wherein, The reaction solvent used for preparing ZIF-8 is methanol.

10. The preparation method of the MOF glass film according to claim 5, characterized in that, In step S100, the grinding tool selected for grinding is an agate mortar.

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