Preparation method and application of metal organic framework surface modified flat sheet membrane
By loading a PFS-MMOFs layer onto a flat sheet membrane substrate, the problem of insufficient removal capacity of traditional flat sheet membranes for new pollutants is solved, achieving efficient and low-cost water treatment and expanding the application fields.
Patent Information
- Application Number
- CN202511687500.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-01-27
AI Technical Summary
In existing technologies, traditional flat sheet membranes have limited ability to remove new pollutants, and the modification process of MOF materials is complex and costly, resulting in low adsorption performance and stability.
MMOF nanoparticles were prepared by solvothermal and hydrothermal methods. The flat sheet membrane substrate was modified with a coupling agent to firmly load the MMOF nanoparticles, forming a PFS-MMOFs layer, which improved the adsorption performance and stability of the membrane.
The prepared metal-organic framework surface-modified flat sheet membrane has excellent adsorption capacity for heavy metals and new pollutants, which improves water treatment efficiency, reduces costs and extends service life, and is suitable for seawater desalination, sewage treatment and new energy fields.
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Figure CN121401882A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane materials technology, specifically to a method for preparing and applying a metal-organic framework surface-modified flat sheet membrane. Background Technology
[0002] With rapid industrial development and improved living standards, heavy metals and various new pollutants are constantly emerging and entering aquatic environments. These new pollutants include, but are not limited to, antibiotics, endocrine disruptors, pesticide residues, and microplastics. They pose potential ecological risks and health hazards, and conventional water treatment technologies are difficult to remove them effectively.
[0003] Membrane technology, as a highly efficient water treatment separation technology, has advantages such as no phase change, low energy consumption, high separation efficiency, and small footprint, and has been widely used in the field of water treatment. However, traditional flat sheet membranes can only remove suspended particles and macromolecules in water through physical sieving, and their ability to remove new pollutants is limited. In addition, the surface of polyvinyl alcohol (PVA) flat sheet membranes is prone to oxidation, which affects their performance with long-term use.
[0004] MOF (Metal-Organic Facility) materials are a class of crystalline porous materials with periodic network structures formed by the self-assembly of metal ions or clusters and organic ligands. MOF materials possess high specific surface area, abundant pore structure, tunable pore size, and diverse chemical functions, showing great application potential in adsorption, separation, and catalysis. MOFs are also a current research hotspot in porous materials and are gradually becoming a potential alternative to overcome the technical limitations of traditional porous and nanomaterials in environmental applications. The coordination mode, coordination environment, and structural differences between the inorganic central metal and the organic ligand ultimately affect the structural properties of synthesized MOFs. Selecting specific modification synthesis methods to functionalize the central metal element, organic ligands, and pre-synthesized MOFs can prepare MOF materials with desired properties. Therefore, MOFs are widely used in drug carriers, sensors, catalysts, hydrogen storage materials, and new energy fields, showing promising application prospects. They are also receiving increasing attention in the field of water treatment, with further optimization designs to enhance their application value. The development of the water treatment industry is inseparable from technological and material innovation. MOFs, as a novel porous material with low density, high adsorption capacity, and high specific surface area, have broad development prospects in the water treatment industry. Combining MOF materials with current water treatment technologies can effectively improve the removal efficiency of pollutants in the water environment. MOF materials are increasingly being used to modify membranes and improve membrane filtration performance. However, at present, there is relatively little research on using MOF materials to modify membranes for new pollutants.
[0005] Current research on MOF surface-modified flat sheet films faces challenges such as complex MOF material modification processes, high costs, and the need for further improvement in adsorption performance and stability. Therefore, developing a simple, efficient, low-cost, and high-performance method for preparing metal-organic framework surface-modified flat sheet films is of significant practical importance. Summary of the Invention
[0006] This invention provides a method for preparing and applying a metal-organic framework (MMOF) surface-modified flat sheet membrane. MMOF nanoparticles are prepared using common methods such as solvothermal and hydrothermal methods. The flat sheet membrane substrate is modified by a coupling agent, enabling the MMOF nanoparticles to be firmly loaded onto the surface of the flat sheet membrane substrate. This solves the problems of complex modification, high cost, and low adsorption performance and stability mentioned in the background art.
[0007] This invention provides the following technical solution:
[0008] A method for preparing and applying a metal-organic framework (MMOF) surface-modified sheet film includes the following steps: Step 1: Preparing MMOF nanoparticles. Metal oxide and polycarboxylic acid ligands are taken in a predetermined mass ratio, dissolved in deionized water, and refluxed at an effective temperature for a first predetermined time. The mixture is then filtered to obtain a gel solid. The gel solid is redispersed in deionized water, refluxed again for a second predetermined time, and treated under inert gas protection to obtain MMOF nanoparticles. Step 2: Preparing liquid PFS. Ferrous salt is taken in a predetermined ratio, acidified with concentrated sulfuric acid, and stirred until a paste is formed. An oxidant solution is added for oxidation. After the solution turns yellow-brown, deionized water is added, and the mixture is heated in a water bath at an effective temperature with stirring for a third predetermined time. After cooling, the mixture is allowed to mature for a third predetermined time. Step 4: Obtain liquid PFS after four preset times; Step 3: Prepare PFS-MMOFs dispersion by compounding the MMOF nanoparticles obtained in step S1 into the liquid PFS obtained in step 2 at a preset ratio and aging for a fifth preset time to obtain PFS-MMOFs dispersion; Step 4: Surface modification of materials by immersing the sheet film substrate in a mixed solution containing coupling agent and amination crosslinking agent and reacting at an effective temperature for a sixth preset time, then rinsing with deionized water; Step 5: Post-treatment of material surface by immersing the pretreated sheet film substrate in the PFS-MMOFs dispersion obtained in step 3 for a seventh preset time, then rinsing with deionized water and drying to obtain PFS-MMOFs modified sheet film.
[0009] As a preferred embodiment of the present invention, in step one, the metal oxide is iron(II,III) oxide, the polycarboxylic acid ligand is pyromellitic acid, and the mass ratio of the metal oxide, the polycarboxylic acid ligand and the deionized water is 2-4:4-8:50-80.
[0010] As a preferred technical solution of the present invention, in step one, the effective temperature is 80℃-100℃, the first preset time is 24 hours, the second preset time is 16 hours, and the inert gas is nitrogen.
[0011] As a preferred technical solution of the present invention, in step two, the ferrous salt is ferrous sulfate heptahydrate, the oxidant is sodium chlorate, the mass ratio of the ferrous salt, concentrated sulfuric acid, oxidant solution and deionized water is 20-50:5:10:10-20, the effective temperature is 40℃, the third preset time is 30min, and the fourth preset time is 24 hours.
[0012] As a preferred embodiment of the present invention, in step three, the mass ratio of MMOF nanoparticles to liquid PFS is 1-5:100, the fifth preset time is 24-48 hours, and the solid content of the PFS-MMOFs dispersion is 5%-15%.
[0013] As a preferred embodiment of the present invention, in step four, the coupling agent is an amino-type silane coupling agent, the amination crosslinking agent is a small molecule amino compound, the solvent of the mixed solution is a mixture of anhydrous ethanol and deionized water, the volume ratio of anhydrous ethanol to deionized water is 6-8:2-4, the volume fraction of the coupling agent in the mixed solution is 1%-3%, and the volume fraction of the amination crosslinking agent in the mixed solution is 0.5%-2%.
[0014] As a preferred technical solution of the present invention, in step four, the effective temperature is 25℃-60℃, and the sixth preset time is 1-4 hours.
[0015] As a preferred technical solution of the present invention, in step five, the seventh preset time is 0.5-2 hours, the drying treatment is vacuum drying, the vacuum drying temperature is 40℃-60℃, and the drying time is 2-6 hours.
[0016] The metal-organic framework surface-modified flat sheet film prepared by the above method.
[0017] The above-mentioned metal-organic framework surface-modified flat sheet membranes are used in the field of water purification for heavy metals and new pollutants.
[0018] Compared with the prior art, the present invention provides a method for preparing and applying a metal-organic framework surface-modified flat sheet film, which has the following beneficial effects:
[0019] 1. In the preparation method of the metal-organic framework surface-modified flat sheet membrane, by loading a PFS-MMOFs layer on the surface of the flat sheet membrane substrate, the flat sheet membrane not only has good filtration performance, but also has excellent adsorption capacity for heavy metals and new pollutants. It can effectively remove heavy metals, antibiotics, endocrine disruptors, pesticide residues, microplastics and other new pollutants from water, improve the treatment effect of the flat sheet membrane on complex water quality, and can also be used for the enrichment and extraction of special raw material metals in the field of new energy applications.
[0020] 2. The preparation method of the metal-organic framework surface-modified flat sheet film is simple, easy to implement and low in cost. Common methods such as solvothermal and hydrothermal methods are used to prepare MMOF nanoparticles. The flat sheet film substrate is modified by coupling agent so that the MMOF nanoparticles can be firmly loaded on the surface of the flat sheet film substrate, thereby improving the stability and service life of the modified flat sheet film.
[0021] 3. The preparation method of the metal-organic framework surface-modified flat sheet membrane has broad application prospects in the field of water treatment. It can be used in seawater desalination, sewage treatment, new energy and other fields, and can effectively solve the pollution problem of new pollutants in water bodies, and protect the safety of the aquatic ecological environment and human health. Attached Figure Description
[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, the elements or parts are not necessarily drawn to actual scale.
[0023] Figure 1 This is a schematic diagram of the process of the present invention;
[0024] Figure 2 SEM images of different materials for this invention Figure 1 ;
[0025] Figure 3 SEM images of different materials for this invention Figure 2 ;
[0026] Figure 4 The image shows the XRD pattern of the PFS-MMOFs of this invention.
[0027] Figure 5 This is a graph showing the trend of Zeta potential changes of PFS and PFS-MMOFs under different dosages according to the present invention;
[0028] Figure 6 The graph shows the removal efficiency of various membranes of this invention for new pollutants.
[0029] Figure 7 The graph shows the removal efficiency of various membranes of the present invention for humic acid.
[0030] Figure 8 This is a schematic diagram of the metal-organic framework surface-modified flat sheet film of the present invention. Detailed Implementation
[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0032] Example 1:
[0033] Reference Figures 1-8 A method for preparing a metal-organic framework surface-modified flat sheet film includes the following steps:
[0034] Step 1: Prepare MMOF nanoparticles. Take metal oxide and polycarboxylic acid ligands according to a preset mass ratio, dissolve them in deionized water, and reflux at an effective temperature for a first preset time. Filter to obtain a gel solid. Redisperse the gel solid in deionized water and reflux a second time for a second preset time. Treat under inert gas protection to obtain MMOF nanoparticles. The obtained MMOF particles are full of micropores and have an extremely large specific surface area (equivalent to the adsorption area of a football field for one small particle). They can firmly "grab" pollutants in water (such as heavy metals and small molecule organic matter). Nitrogen protection can prevent the particles from being oxidized and maintain their adsorption activity. The second reflux makes the particle purity higher and the subsequent binding with PFS more stable.
[0035] Step 2: Prepare liquid PFS. Take ferrous salt according to a preset ratio, add concentrated sulfuric acid for acidification and stir until a paste is formed. Add oxidant solution to carry out the oxidation reaction. After the solution turns yellow-brown, add deionized water and heat in a water bath at an effective temperature for a third preset time. After cooling, mature for a fourth preset time to obtain liquid PFS.
[0036] Concentrated sulfuric acid acidification: inhibits premature agglomeration of iron ions and provides a suitable environment for the oxidation reaction, making the oxidation of sodium chlorate more efficient;
[0037] Sodium chlorate oxidation: It turns the "ferrous iron" (which has little flocculation effect) in ferrous sulfate into "ferric iron" (flocculation nuclei), and the yellow-brown color is a characteristic of the polymerization of ferric iron.
[0038] Step 3: Prepare PFS-MMOFs dispersion. The MMOF nanoparticles obtained in step S1 are compounded in liquid PFS obtained in step 2 according to a preset ratio and aged for a preset time to obtain PFS-MMOFs dispersion. The synergistic effect makes PFS positively charged, which can flocculate large particulate impurities, and MMOF is porous, which can adsorb small molecule pollutants. The combination of the two can "capture both large and small" pollutants, doubling the purification capacity.
[0039] Step 4: Material surface modification. Here, the flat sheet membrane substrate is one of PVA flat sheet membrane, PVDF flat sheet membrane, or PES flat sheet membrane. The flat sheet membrane substrate is immersed in a mixed solution containing coupling agent and amination crosslinking agent, and reacted at an effective temperature for a preset time. After removal, it is rinsed with deionized water, thereby breaking the "inertia" of the blank membrane, making the surface of the PVA membrane itself smooth and difficult to adhere to other materials. The "active groups" formed after pretreatment can chemically react with PFS-MMOFs to form a "layer-by-layer stacked structure", making the membrane surface rougher, increasing the adhesion area of subsequent functional materials, and improving the bonding strength, thus preventing the modified layer from falling off during use.
[0040] Step 5: Post-treatment of material surface. Immerse the pretreated flat sheet membrane substrate in the PFS-MMOFs dispersion obtained in Step 3. After soaking for a preset time of seven hours, remove it, rinse with deionized water, and dry it to obtain the PFS-MMOFs modified flat sheet membrane. Through the integration of three functions, the membrane can both flocculate large particulate impurities through PFS, adsorb small molecule pollutants through MMOF, and retain remaining impurities through its own filter pores. The purification effect is far superior to traditional membranes. The improved antifouling properties are due to the positive charge of PFS, which reduces the adsorption of negatively charged pollutants on the membrane surface. The porous structure of MMOF reduces membrane pore clogging, making the filtration flux (effluent velocity) more stable and extending the service life. Because the modified layer is firmly bonded and not easy to fall off, and has strong antifouling ability, the membrane does not need to be cleaned frequently, and its service life is more than 30% longer than that of a simple MOF modified membrane.
[0041] In step one, the metal oxide is iron(III) oxide, the polycarboxylic acid ligand is pyromellitic acid, and the mass ratio of the metal oxide, polycarboxylic acid ligand and deionized water is 2-4:4-8:50-80.
[0042] In step one, the effective temperature is 80℃-100℃, the first preset time is 24 hours, the second preset time is 16 hours, and the inert gas is nitrogen.
[0043] In step two, the ferrous salt is ferrous sulfate heptahydrate, and the oxidant is sodium chlorate. The oxidant can also be replaced by potassium permanganate or hydrogen peroxide. The mass ratio of ferrous salt, concentrated sulfuric acid, oxidant solution, and deionized water is 20-50:5:10:10-20. The effective temperature is 40℃. The third preset time is 30 minutes, and the fourth preset time is 24 hours. Through a 40℃ water bath and aging for 24 hours, ferric iron forms stable "flocculation macromolecules," which can quickly aggregate suspended solids and colloids in the water into large particles for easy filtration.
[0044] In step three, the mass ratio of MMOF nanoparticles to liquid PFS is 1-5:100, the fifth preset time is 24-48 hours, and the solid content of the PFS-MMOF dispersion is 5%-15%. By aging for 24 hours, the two are more firmly bonded, and they will not easily fall off after being loaded onto the membrane, thus ensuring the long-term performance of the membrane.
[0045] In step four, the coupling agent is an amino-type silane coupling agent, and the amination crosslinking agent is a small molecule amino compound. Here, the amino-type silane coupling agent is at least one of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-540), or N-β-aminoethyl-γ-aminopropyltrimethoxysilane (KH-792); the small molecule amino compound is at least one of ethylenediamine, propylenediamine, and melamine.
[0046] The solvent for the mixed solution is a mixture of anhydrous ethanol and deionized water, with a volume ratio of anhydrous ethanol to deionized water of 6-8:2-4. The volume fraction of the coupling agent in the mixed solution is 1%-3%, and the volume fraction of the amination crosslinking agent in the mixed solution is 0.5%-2%.
[0047] In step four, the effective temperature is 25℃-60℃, and the preset time in step six is 1-4 hours.
[0048] In step five, the seventh preset time is 0.5-2 hours, the drying process is vacuum drying, the vacuum drying temperature is 40℃-60℃, and the drying time is 2-6 hours.
[0049] The metal-organic framework surface-modified flat sheet membrane prepared by the above method has a water flux of 80-150 L·m. -2 ·h -1 The removal rate of COD is ≥85%, and the removal rate of turbidity is ≥95%.
[0050] Applications of metal-organic framework surface-modified flat sheet membranes in the purification of water containing heavy metals and new pollutants, as well as their applicability in wastewater treatment, seawater desalination, and new energy fields.
[0051] Example 2:
[0052] Reference Figures 1-8 A method for preparing a metal-organic framework surface-modified flat sheet film includes the following:
[0053] The preparation process of MMOF nanoparticles is as follows: 2 parts of iron(III) oxide and 4 parts of pyromellitic terephthalic acid (BTEC) were accurately weighed and dissolved in 50 parts of deionized water. The mixture was stirred thoroughly and heated under reflux at 80°C for 24 hours. After the reaction was completed, the white gel was filtered out and repeatedly washed with deionized water to remove unreacted organic ligands and central metal ions. The collected white gel solid was redispersed in deionized water and refluxed for another 16 hours. Finally, the obtained white solid was centrifuged (5000 r / min) for 5 minutes, washed several times with anhydrous ethanol and deionized water, and dried under vacuum at 70°C for 24 hours. MMOFs were then synthesized under nitrogen protection according to the above method.
[0054] The preparation process of PFS is as follows: Weigh 20 parts of ferrous sulfate, add 5 parts of concentrated sulfuric acid to fully acidify, and continue stirring until a paste is formed. Add 10 parts of sodium chlorate solution to fully oxidize, and the solution will turn yellow-brown. After fully stirring and dissolving, add 10 parts of deionized water to allow PFS to undergo hydrolysis and polymerization. Heat and stir in a water bath at 40°C for 30 minutes. While adjusting the alkalinity, maintain the original water temperature and speed until the powder is completely dissolved. Remove the powder and use an electric heating mantle to heat the synthesized PFS to accelerate its maturation. When bubbles are generated at the edge of the coagulant and there is a slight boiling phenomenon, stop heating and place it at room temperature. After cooling, bottle and store for 24 hours to obtain liquid PFS. Measure the iron content of PFS and calculate the effective iron mass contained in a certain volume. According to the ratio of MMOF mass to PFS effective iron mass, weigh the corresponding mass of MMOFs and compound it into the above certain volume of PFS. Mature for 24 hours to obtain PFS-MMOFs.
[0055] Modified flat sheet membrane substrate: The flat sheet membrane substrate is immersed in a solution containing coupling agent and amination crosslinking agent, and reacted at a certain temperature for a certain time, so that the coupling agent and amination crosslinking agent form an active group on the surface of the flat sheet membrane substrate and form a stacked structure. During the modification process, a protective film is formed, which slows down the aging of PVA membrane in subsequent use. The flat sheet membrane substrate is then removed and rinsed clean with deionized water.
[0056] Loading PFS-MMOFs: The modified PVA sheet film substrate was immersed in a dispersion containing PFS-MMOF nanoparticles and stirred at a certain temperature for a certain time, so that the PFS-MMOF nanoparticles were loaded onto the surface of the sheet film substrate through chemical bonding and charge attraction. The sheet film substrate was removed, rinsed with deionized water, and then dried under vacuum to obtain a PFS-MMOF surface-modified PVA sheet film.
[0057] Example 3:
[0058] Reference Figures 1-7 A method for preparing a metal-organic framework surface-modified flat sheet film includes the following:
[0059] The preparation process of MMOF nanoparticles is as follows: 3 parts of iron(III) oxide and 6 parts of pyromellitic terephthalic acid (BTEC) were accurately weighed and dissolved in 70 parts of deionized water. The mixture was stirred thoroughly and heated under reflux at 90°C for 24 hours. After the reaction was completed, the white gel was filtered out and repeatedly washed with deionized water to remove unreacted organic ligands and central metal ions. The collected white gel solid was redispersed in deionized water and refluxed for another 16 hours. Finally, the obtained white solid was centrifuged (5000 r / min) for 5-10 minutes, washed several times with anhydrous ethanol and deionized water, and dried under vacuum at 70°C for 24 hours. MMOFs were then synthesized under nitrogen protection according to the above method.
[0060] The preparation process of PFS is as follows: Weigh 30 parts of ferrous sulfate, add 5 parts of concentrated sulfuric acid for thorough acidification, and stir continuously until a paste is formed. Add 10 parts of sodium chlorate solution for thorough oxidation, and the solution will turn yellowish-brown. After thorough stirring and dissolution, add 10-20 parts of deionized water to allow PFS to undergo hydrolysis and polymerization. Heat and stir in a water bath at 40°C for 30 minutes. While adjusting the alkalinity, maintain the original water temperature and rotation speed until the powder is completely dissolved. Remove the PFS and use an electric heating mantle to accelerate its maturation. When bubbles are generated at the edge of the coagulant and a slight boiling phenomenon occurs, stop heating and place it at room temperature. After cooling, bottle and store for 24 hours to obtain liquid PFS. Measure the iron content of PFS and calculate the effective iron mass contained in a certain volume. According to the ratio of MMOF mass to PFS effective iron mass, weigh the corresponding mass of MMOFs and compound it into the above certain volume of PFS. Mature for 24 hours to obtain PFS-MMOFs.
[0061] Modified flat sheet membrane substrate: The flat sheet membrane substrate is immersed in a solution containing coupling agent and amination crosslinking agent, and reacted at a certain temperature for a certain time, so that the coupling agent and amination crosslinking agent form a layer of active groups on the surface of the flat sheet membrane substrate and form a layer-by-layer stacked structure. During the modification process, a protective film is formed, which slows down the aging of PVA membrane in subsequent use. The flat sheet membrane substrate is then removed and rinsed clean with deionized water.
[0062] Loading PFS-MMOFs: The modified PVA sheet film substrate was immersed in a dispersion containing PFS-MMOF nanoparticles and stirred at a certain temperature for a certain time, so that the PFS-MMOF nanoparticles were loaded onto the surface of the sheet film substrate through chemical bonding and charge attraction. The sheet film substrate was removed, rinsed with deionized water, and then dried under vacuum to obtain a PFS-MMOF surface-modified PVA sheet film.
[0063] Example 4:
[0064] Reference Figures 1-7 A method for preparing a metal-organic framework surface-modified flat sheet film includes the following:
[0065] MMOF nanoparticles were prepared as follows: 4 parts of iron(III) oxide and 8 parts of pyromellitic acid (BTEC) were accurately weighed and dissolved in 80 parts of deionized water. The mixture was stirred thoroughly and refluxed at 100°C for 24 hours. After the reaction, the white gel was filtered out and repeatedly washed with deionized water to remove unreacted organic ligands and central metal ions. The collected white gel solid was redispersed in deionized water and refluxed for another 16 hours. Finally, the obtained white solid was centrifuged (5000 r / min) for 10 minutes. After washing several times with anhydrous ethanol and deionized water, the solid was vacuum dried at 70°C for 24 hours. MMOFs were then synthesized under nitrogen protection using the method described above.
[0066] The preparation process of PFS is as follows: Weigh 50 parts of ferrous sulfate, add 5 parts of concentrated sulfuric acid to fully acidify, and continue stirring until a paste is formed. Add 10 parts of sodium chlorate solution to fully oxidize, and the solution will turn yellow-brown. After fully stirring and dissolving, add 20 parts of deionized water to allow PFS to undergo hydrolysis and polymerization. Heat and stir in a water bath at 40°C for 30 minutes. While adjusting the alkalinity, maintain the original water temperature and speed until the powder is completely dissolved. Remove the powder and use an electric heating mantle to heat the synthesized PFS to accelerate its maturation. When bubbles are generated at the edge of the coagulant and there is a slight boiling phenomenon, stop heating and place it at room temperature. After cooling, bottle it and store it for 24 hours to obtain liquid PFS. Measure the iron content of PFS and calculate the effective iron mass contained in a certain volume. According to the ratio of MMOF mass to PFS effective iron mass, weigh the corresponding mass of MMOFs and compound it into the above certain volume of PFS. Mature for 24 hours to obtain PFS-MMOFs.
[0067] Modified flat sheet membrane substrate: The flat sheet membrane substrate is immersed in a solution containing coupling agent and amination crosslinking agent, and reacted at a certain temperature for a certain time, so that the coupling agent and amination crosslinking agent form a layer of active groups on the surface of the flat sheet membrane substrate and form a layer-by-layer stacked structure. During the modification process, a protective film is formed, which slows down the aging of PVA membrane in subsequent use. The flat sheet membrane substrate is then removed and rinsed clean with deionized water.
[0068] Loading PFS-MMOFs: The modified PVA sheet film substrate was immersed in a dispersion containing PFS-MMOF nanoparticles and stirred at a certain temperature for a certain time, so that the PFS-MMOF nanoparticles were loaded onto the surface of the sheet film substrate through chemical bonding and charge attraction. The sheet film substrate was removed, rinsed with deionized water, and then dried under vacuum to obtain a PFS-MMOF surface-modified PVA sheet film.
[0069] In this invention, Figure 2 Results a show that the core-shelled iron oxide particles are nearly spherical, with no particle agglomeration, and their surface is rough with small particle protrusions; results b show that UiO-66-2COOH is attached and grown on and around the surface of the core-shelled iron oxide, and some MOFs and MNPs are aggregated together; results c show that the laboratory-made MOFs and Figure 2 The commercial MOFs purchased by d have the same structure, all being sheet-like structures.
[0070] Figure 3 In this study, PFS has a smooth surface and exhibits a large, blocky, amorphous granular structure with few pores. The introduction of MNPs, MOFs, and MOFs has a profound impact on its morphological characteristics. PFS-MOFs with added MOFs have a surface that is a mixture of rod-shaped and sheet-like structures, presenting an overall coral cluster-like structure with a relatively large surface area. PFS-MNPs with added MNPs are granular and layered with an irregular structure, and their surface area is smaller than that of PFS-MOFs. The structure of PFS-MMOFs with added MMOFs is basically between that of PFS-MOFs and PFS-MNPs, exhibiting a porous, layered, thin-sheet structure. This indicates that the structure of PFS-MNPs is influenced by both MNPs and MOFs.
[0071] Figure 4In the process of loading crystalline MMOFs into the PFS system, their crystal structure undergoes a significant change, transforming from a crystalline structure to an amorphous structure. The XRD patterns of the synthesized PFS-MMOFs differ from those of PFS. Comparing the peak shapes of PFS and PFS-MMOFs between 2θ = 25 and 35, it can be seen that the narrow peaks of PFS change into the broad peaks of PFS-MMOFs. This indicates that the addition of MMOFs transforms the low-polymerization inorganic polymer material into a high-polymerization polymer material, suggesting that MMOFs and PFS undergo a polymerization reaction and combine together.
[0072] Figure 5 In this study, the effect of dosage on the zeta potential of water was investigated. The original water pH was 7.64. After adjusting the original water pH to 6, 7, 8, 9, and 10, 18 mg / L of nanoparticles were added. The zeta potential changes of PFS and PFS-MMOFs at different pH values were measured as follows: Figure 5 As shown in Figure a, after adjusting the raw water to pH = 9, nanoparticles of 10, 14, 18, and 22 mg / L were added respectively. The zeta potential changes of PFS and PFS-MMOFs under different dosages were measured as follows: Figure 5 As shown in b.
[0073] Figure 6 The study demonstrated the removal efficiency of PVA membranes, modified MMOF-5 membranes (5 parts MMOF), MMOF-10 membranes (10 parts MMOF), and PSF-MMOFs-10 membranes (10 parts PSF-MMOFs) for the novel pollutant atenolol. The study also showcased the removal performance of metal-organic framework-modified and unmodified PVA membranes for atenolol. Prepared as described in Example 4, the modified MMOF-5, MMOF-10, and PSF-MMOFs-10 membranes showed a significant improvement in the removal performance of the novel pollutant compared to the unmodified membrane. This improvement was primarily due to the adsorption performance of the metal-organic framework for the novel pollutant, which significantly enhanced the removal performance of the modified membrane.
[0074] Figure 7 The paper demonstrates the removal efficiency of humic acid by PVA membranes, modified MMOF-5 membranes (5 parts MMOF), MMOF-10 membranes (10 parts MMOF), and PSF-MMOFs-10 membranes (10 parts PSF-MMOFs). It also showcases the humic acid removal performance of metal-organic framework-modified and unmodified PVA membranes, prepared as described in Example 2. The modified MMOF-5, MMOF-10, PSF-MMOFs-10 membranes, and the unmodified membrane all exhibit good humic acid removal performance, with the modified membrane showing a certain improvement in humic acid removal rate.
[0075] Components not described in detail in this article are existing technologies.
[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a metal-organic framework surface-modified flat sheet film, characterized in that, Includes the following steps: Step 1: Prepare MMOF nanoparticles. Take metal oxide and polycarboxylic acid ligands according to a preset mass ratio. Here, the polycarboxylic acid ligands can also be replaced by one of pyromellitic acid and terephthalic acid. Dissolve them in deionized water, reflux and heat at an effective temperature for a first preset time, filter to obtain gel solid, redisperse the gel solid in deionized water, reflux and heat again for a second preset time, and treat under inert gas protection to obtain MMOF nanoparticles. Step 2: Prepare liquid PFS. Take ferrous salt according to the preset ratio, add concentrated sulfuric acid to acidify and stir until it becomes a paste. Add oxidant solution to carry out the oxidation reaction. After the solution turns yellow-brown, add deionized water and heat and stir in a water bath at an effective temperature for a third preset time. After cooling, mature for a fourth preset time to obtain liquid PFS. Step 3: Prepare PFS-MMOFs dispersion. The MMOF nanoparticles obtained in step S1 are compounded in liquid PFS obtained in step 2 according to a preset ratio and aged for a fifth preset time to obtain PFS-MMOFs dispersion. Step 4: Surface modification of the material. The flat sheet film substrate is immersed in a mixed solution containing coupling agent and amination crosslinking agent, and reacted at the effective temperature for a preset time. After removal, it is rinsed with deionized water. Step 5: Post-treatment of material surface. The pretreated flat sheet membrane substrate is immersed in the PFS-MMOFs dispersion obtained in Step 3. After immersion for a preset time, it is taken out, rinsed with deionized water, and dried to obtain the PFS-MMOFs modified flat sheet membrane.
2. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step one, the metal oxide is iron(III) oxide, the polycarboxylic acid ligand is pyromellitic acid, and the mass ratio of the metal oxide, polycarboxylic acid ligand and deionized water is 2-4:4-8:50-80.
3. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step one, the effective temperature is 80℃-100℃, the first preset time is 24 hours, the second preset time is 16 hours, and the inert gas is nitrogen.
4. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step two, the ferrous salt is ferrous sulfate heptahydrate, the oxidant is sodium chlorate, and the mass ratio of the ferrous salt, concentrated sulfuric acid, oxidant solution, and deionized water is 20-50:5:10:10-20. The effective temperature is 40℃, the third preset time is 30 minutes, and the fourth preset time is 24 hours.
5. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step three, the mass ratio of MMOF nanoparticles to liquid PFS is 1-5:100, the fifth preset time is 24-48 hours, and the solid content of the PFS-MMOFs dispersion is 5%-15%.
6. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step four, the coupling agent is an amino-type silane coupling agent, the amination crosslinking agent is a small molecule amino compound, the solvent of the mixed solution is a mixture of anhydrous ethanol and deionized water, the volume ratio of anhydrous ethanol to deionized water is 6-8:2-4, the volume fraction of the coupling agent in the mixed solution is 1%-3%, and the volume fraction of the amination crosslinking agent in the mixed solution is 0.5%-2%.
7. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step four, the effective temperature is 25℃-60℃, and the preset time in step six is 1-4 hours.
8. The method for preparing a metal-organic framework surface-modified flat sheet film according to claim 1, characterized in that, In step five, the seventh preset time is 0.5-2 hours, the drying process is vacuum drying, the vacuum drying temperature is 40℃-60℃, and the drying time is 2-6 hours.
9. The metal-organic framework surface-modified flat sheet film prepared by any of the methods described in claims 1-8.
10. The application of the metal-organic framework surface-modified flat sheet membrane according to claim 9 in the field of water purification of heavy metals and new pollutants.