Membrane for filtering metal ions in water bodies, and method for preparing the same

Abstract

The present application belongs to the technical field of water treatment membranes, and in particular to a preparation method of a diaphragm capable of filtering metal ions in water, characterized in that the method comprises: a modification step of mixing a MOF-808, a chelating agent, and water to react, so as to obtain a solid substance, and then cleaning the solid substance with a first cleaning solution, and then drying to obtain a modified metal organic framework material; a melt forming step of uniformly mixing the modified metal organic framework material, polyethylene, and paraffin oil at a melting temperature to form a melt; and a hot pressing step of hot pressing and cooling the melt to obtain a diaphragm.

Description

Technical Field

[0001] This invention relates to a water treatment membrane, and more particularly to a membrane capable of removing metal ions from water, and its preparation method. Background Technology

[0002] Industrial wastewater is often discharged during the production and processing of traditional manufacturing industries or high-tech products. This wastewater contains a large amount of heavy metal ions. If it is discharged into rivers or the sea without treatment, it can easily pollute drinking water or the food chain, which can harm people's health. In addition, if wastewater containing heavy metal ions is used to irrigate land or crops, it may cause irreversible damage. Therefore, in order to avoid the above situations, it is necessary to remove the heavy metal ions contained in industrial wastewater.

[0003] Because heavy metal ions are uniformly distributed in wastewater, their settling rate is slow. Waiting for natural sedimentation and separation is impractical. Therefore, current water quality improvement technologies involve adding chemical agents to wastewater to accelerate the precipitation of heavy metal ions. However, this method has drawbacks: the reaction of chemical agents with heavy metal ions produces a large amount of precipitated waste residue, inevitably causing significant secondary pollution. Furthermore, it requires additional resources to separate the waste residue from the water, making it uneconomical. Therefore, providing a substance that can efficiently filter heavy metal ions from water without causing secondary pollution is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a membrane that can adsorb metal ions contained in water without causing secondary pollution to the water, and a method for preparing the membrane.

[0005] To achieve the above objectives, the present invention provides a method for preparing a membrane capable of filtering metal ions in water, characterized by comprising: a modification step, wherein a MOF-808, a chelating agent, and water are mixed and reacted to obtain a solid substance, and the solid substance is washed with a first cleaning solution and then dried to obtain a modified metal-organic framework material; a melt formation step, wherein the modified metal-organic framework material, polyethylene, and paraffin oil are uniformly mixed at a melting temperature to form a melt; and a hot pressing step, wherein the melt is hot-pressed and cooled to obtain a membrane.

[0006] More preferably, in the melt formation step, the modified metal-organic framework material, the polyethylene, and the paraffin oil are stirred and mixed at a melting temperature of 110 to 130°C and a rotation speed of 80 to 120 rpm for 30 to 60 minutes.

[0007] More preferably, in the hot pressing step, the melt is poured into a container and hot-pressed at a temperature of 60 to 120°C and a pressure of 1 to 20 MPa.

[0008] Preferably, the container is a stainless steel frame with a length of 10cm, a width of 10cm, and a height of 1 to 2mm.

[0009] More preferably, it further includes a stretching step, stretching the length and width of the diaphragm by a factor of 10.

[0010] More preferably, in the stretching step, the diaphragm is stretched at a temperature of 100 to 130°C and at a rate of 2 to 10 mm / s.

[0011] More preferably, it further includes an extraction step, which is performed after the stretching step, by extracting the membrane with an extraction solution.

[0012] Preferably, the extraction solution contains dichloromethane.

[0013] More preferably, it further includes a heat-setting step, wherein the membrane is heat-set at a temperature of 100 to 120°C after the extraction step to obtain a mixed matrix membrane.

[0014] More preferably, the thickness of the hybrid matrix membrane is 10 to 20 μm.

[0015] More preferably, the chelating agent is diethyltriaminepentaacetic acid (DPTA), and the modified metal-organic framework material is MOF-808-DPTA; the chelating agent is aminotriacetic acid (NTA), and the modified metal-organic framework material is MOF-808-NTA; the chelating agent is ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), and the modified metal-organic framework material is MOF-808-EGTA; or the chelating agent is sodium ethylenediaminetetramethylenephosphonate (EDTMPS), and the modified metal-organic framework material is MOF-808-EDTMPS.

[0016] More preferably, the mass ratio of the modified metal-organic framework material to the polyethylene is 1:1 to 2; the mass ratio of the total mass of the modified metal-organic framework material and the polyethylene to the mass ratio of the paraffin oil is 1:2 to 4; the molecular weight of the polyethylene is 500,000 to 900,000; the chelating agent comprises: diethyltriaminepentaacetic acid (DPTA), aminotriacetic acid (NTA), sodium citrate, ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), or sodium ethylenediaminetetramethylenephosphonate (EDTMPS); the mass ratio of MOF-808, the chelating agent, and the water is 1:10 to 50:200; or the first cleaning solution comprises: water and ethanol.

[0017] More preferably, the method for preparing MOF-808 comprises: a mixing step, wherein N,N-dimethylformamide, a monobasic acid, trimesic acid, and zirconium oxychloride octahydrate are mixed to obtain a mixture; a filtration step, wherein the mixture is reacted at 130°C for 2 days, and then the mixture is centrifuged and filtered to obtain a white precipitate; and a drying step, wherein the white precipitate is washed with a second washing solution and dried to obtain MOF-808.

[0018] More preferably, the volume ratio of N,N-dimethylformamide to the monocarboxylic acid is 1:1; the mass ratio of trimesic acid to zirconium chloride octahydrate is 3:1; the mass ratio of the total mass of N,N-dimethylformamide and the monocarboxylic acid to the total mass of trimesic acid and zirconium chloride octahydrate is 10:1; the monocarboxylic acid comprises: formic acid, acetic acid, or hydrochloric acid; or the second cleaning solution comprises: N,N-dimethylformamide, water, and acetone.

[0019] The present invention also provides a membrane capable of filtering metal ions in water, characterized in that its preparation method comprises: a modification step, wherein a MOF-808, a chelating agent, and water are mixed and reacted to obtain a solid substance, and the solid substance is washed with a first cleaning solution and then dried to obtain a modified metal-organic framework material; a melt formation step, wherein the modified metal-organic framework material, polyethylene, and paraffin oil are uniformly mixed at a melting temperature to form a melt; and a hot pressing step, wherein the melt is hot-pressed and cooled to obtain a membrane.

[0020] More preferably, in the melt formation step, the modified metal-organic framework material, the polyethylene, and the paraffin oil are stirred and mixed at a melting temperature of 110 to 130°C and a rotation speed of 80 to 120 rpm for 30 to 60 minutes.

[0021] More preferably, in the hot pressing step, the melt is poured into a container and hot-pressed at a temperature of 60 to 120°C and a pressure of 1 to 20 MPa.

[0022] Preferably, the container is a stainless steel frame with a length of 10cm, a width of 10cm, and a height of 1 to 2mm.

[0023] More preferably, it further includes a stretching step, stretching the length and width of the diaphragm by a factor of 10.

[0024] More preferably, in the stretching step, the diaphragm is stretched at a temperature of 100 to 130°C and at a rate of 2 to 10 mm / s.

[0025] More preferably, it further includes an extraction step, which is performed after the stretching step, by extracting the membrane with an extraction solution.

[0026] Preferably, the extraction solution contains dichloromethane.

[0027] More preferably, it further includes a heat-setting step, wherein the membrane is heat-set at a temperature of 100 to 120°C after the extraction step to obtain a mixed matrix membrane.

[0028] More preferably, the thickness of the hybrid matrix membrane is 10 to 20 μm.

[0029] More preferably, the chelating agent is diethyltriaminepentaacetic acid (DPTA), and the modified metal-organic framework material is MOF-808-DPTA; the chelating agent is aminotriacetic acid (NTA), and the modified metal-organic framework material is MOF-808-NTA; the chelating agent is ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), and the modified metal-organic framework material is MOF-808-EGTA; or the chelating agent is sodium ethylenediaminetetramethylenephosphonate (EDTMPS), and the modified metal-organic framework material is MOF-808-EDTMPS.

[0030] More preferably, the mass ratio of the modified metal-organic framework material to the polyethylene is 1:1 to 2; the mass ratio of the total mass of the modified metal-organic framework material and the polyethylene to the mass ratio of the paraffin oil is 1:2 to 4; the molecular weight of the polyethylene is 500,000 to 900,000; the chelating agent comprises: diethyltriaminepentaacetic acid (DPTA), aminotriacetic acid (NTA), sodium citrate, ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), or sodium ethylenediaminetetramethylenephosphonate (EDTMPS); the mass ratio of MOF-808, the chelating agent, and the water is 1:10 to 50:200; or the first cleaning solution comprises: water and ethanol.

[0031] More preferably, the method for preparing MOF-808 comprises: a mixing step, wherein N,N-dimethylformamide, a monobasic acid, trimesic acid, and zirconium oxychloride octahydrate are mixed to obtain a mixture; a filtration step, wherein the mixture is reacted at 130°C for 2 days, and then the mixture is centrifuged and filtered to obtain a white precipitate; and a drying step, wherein the white precipitate is washed with a second washing solution and dried to obtain MOF-808.

[0032] More preferably, the volume ratio of N,N-dimethylformamide to the monocarboxylic acid is 1:1; the mass ratio of trimesic acid to zirconium chloride octahydrate is 3:1; the mass ratio of the total mass of N,N-dimethylformamide and the monocarboxylic acid to the total mass of trimesic acid and zirconium chloride octahydrate is 10:1; the monocarboxylic acid comprises: formic acid, acetic acid, or hydrochloric acid; or the second cleaning solution comprises: N,N-dimethylformamide, water, and acetone.

[0033] In summary, the advantages of this invention over prior art lie in the following: This invention modifies the structure of MOF-808 by using various non-coordinating synthesized monocarboxylic acids and by using various non-coordinating synthesized chelating agents to obtain a modified metal-organic framework material. This modified material exhibits a three-dimensional porous framework structure and, through its high specific surface area, high active sites, and adsorption performance with chelating agents, can generate synergistic adsorption to adsorb various types of metal ions. Specifically, the modified metal-organic framework material of this invention can adsorb metal ions contained in water to achieve water purification, and it does not produce additional residues or precipitates in the water, thus improving the efficiency and quality of water purification.

[0034] Furthermore, due to the low cost, good chemical corrosion resistance, high porosity, and adjustable pore size of polyethylene membranes, the difficulty in recovering metal ions in water treatment can be overcome by combining modified metal-organic framework materials with polyethylene membranes. In addition, because polyethylene membranes are highly hydrophobic while modified metal-organic framework materials are highly hydrophilic, combining them with polyethylene membranes can improve the hydrophilicity of the polyethylene membrane and increase its water flux, thereby significantly enhancing its efficiency in adsorbing metal ions.

[0035] Furthermore, the hybrid matrix membrane of the present invention is prepared using a thermally induced phase separation (TIPS) method. Specifically, in the hot pressing step, after the membrane is hot-pressed, it is cooled to melt the paraffin oil into a liquid state, while the polyethylene and modified metal-organic framework material remain solid. Then, in the extraction step, the paraffin oil in the membrane is removed with an extraction solution to form a hybrid matrix membrane with a porous structure. Since the preparation method of the hybrid matrix membrane provided by the present invention is simple, the porosity or stretching ratio can be adjusted to control the water flux of the hybrid matrix membrane, and it has excellent metal ion adsorption capacity, it can filter out more than 99% of metal ions in water, and it does not produce additional residues or industrial waste that would cause secondary pollution, it is understood that the present invention can purify water more efficiently and cost-effectively compared to prior art. Attached Figure Description

[0036] Figures 1A to 1D A series of block flowcharts are used to illustrate the preparation process of the hybrid matrix membrane;

[0037] Figure 2 This is a block flowchart used to illustrate the preparation process of MOF-808;

[0038] Figure 3 This is an XRD pattern used to illustrate the structural features of MOF-808-DPFA;

[0039] Figure 4 This is a SEM image used to illustrate the particle size of MOF-808-DPFA;

[0040] Figure 5 This is a nitrogen adsorption-desorption curve to illustrate the specific surface area of ​​MOF-808-DPFA.

[0041] Figure 6 The graph is a histogram used to compare and illustrate the adsorption performance of MOF-808-DPFA, MOF-808-NTA, and MOF-808 for metal ions.

[0042] Figure 7This is a cross-sectional view used to illustrate the structural features of the hybrid matrix membrane;

[0043] Figure 8 This is a line graph used to illustrate the narrow pore size of the hybrid matrix membrane. Detailed Implementation

[0044] To make the above and / or other objects, effects, and features of the present invention more apparent and understandable, preferred embodiments are described in detail below:

[0045] The purpose of this invention is to provide a method for preparing a membrane capable of filtering metal ions from water, characterized in that, as... Figure 1A As shown, the process includes: a modification step S1, in which a MOF-808, a chelating agent, and water are mixed and reacted to obtain a solid substance, which is then washed with a first cleaning solution and dried to obtain a modified metal-organic framework material; a melt formation step S2, in which the modified metal-organic framework material, polyethylene, and paraffin oil are uniformly mixed at a melting temperature to form a melt; and a hot pressing step S3, in which the melt is hot-pressed and cooled to obtain a film. In a preferred embodiment, in order to obtain a mixed and uniformly melted melt, in the melt formation step S2, the mixture of the modified metal-organic framework material, the polyethylene, and the paraffin oil is stirred and mixed at a melting temperature of 110 to 130°C and a rotation speed of 80 to 120 rpm for 30 to 60 minutes. In another preferred embodiment, to obtain a flat and uniformly thick membrane, in the hot-pressing step S3, the melt is poured into a container and hot-pressed at a temperature of 60 to 120°C and a pressure of 1 to 20 MPa. In yet another preferred embodiment, the container is a stainless steel frame with a length of 10 cm, a width of 10 cm, and a height of 1 to 2 mm, but not limited thereto. In yet another preferred embodiment, the purpose of cooling after hot-pressing in the hot-pressing step S3 is to maintain the paraffin oil contained in the membrane in a liquid phase and to cool the modified metal-organic framework material and polyethylene into a solid phase, so that the paraffin oil flows out from the microporous structure on the membrane.

[0046] Preferably, such as Figure 1B As shown, to control the thickness of the diaphragm, it further includes a stretching step S4, in which the length and width of the diaphragm are each stretched by a factor of 10. In a preferred embodiment, in the stretching step S4, the diaphragm is stretched at a temperature of 100 to 130°C at a rate of 2 to 10 mm / s, but is not limited thereto. In another preferred embodiment, as... Figure 1CAs shown, it further includes: an extraction step S5, which is performed after the stretching step S4, by extracting the membrane with an extraction solution. In another preferred embodiment, the extraction solution contains dichloromethane. It is understood that the extraction step S5 is to remove liquid paraffin oil from the membrane to prevent clogging of the membrane's pore structure. In yet another preferred embodiment, as... Figure 1D As shown, in order to shape the membrane after its thickness is determined to prevent it from expanding or contracting due to external forces or environmental factors, the method further includes a heat-setting step S6, which involves heat-setting the membrane at a temperature of 100 to 120°C after the extraction step S5 to obtain a mixed matrix membrane. In another preferred embodiment, the thickness of the mixed matrix membrane is 10 to 20 μm, but is not limited thereto.

[0047] Preferably, in order to adsorb metal ions in water, MOF-808 needs to be modified. Specifically, the modification methods may include the following: the chelating agent is diethyltriaminepentaacetic acid (DPTA), and the modified metal-organic framework material is MOF-808-DPTA; the chelating agent is aminotriacetic acid (NTA), and the modified metal-organic framework material is MOF-808-NTA; the chelating agent is ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), and the modified metal-organic framework material is MOF-808-EGTA; or the chelating agent is sodium ethylenediaminetetramethylenephosphonate (EDTMPS), and the modified metal-organic framework material is MOF-808-EDTMPS, but not limited thereto. In a preferred embodiment, the mass ratio of the modified metal-organic framework material to the polyethylene is 1:1 to 2; the mass ratio of the total mass of the modified metal-organic framework material and the polyethylene to the mass ratio of the paraffin oil is 1:2 to 4; the molecular weight of the polyethylene is 500,000 to 900,000; the chelating agent comprises: diethyltriaminepentaacetic acid (DPTA), aminotriacetic acid (NTA), sodium citrate, ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), or sodium ethylenediaminetetramethylenephosphonate (EDTMPS); the mass ratio of MOF-808, the chelating agent, and the water is 1:10 to 50:200; or the first cleaning solution comprises: water and ethanol, but is not limited thereto.

[0048] Preferably, such as Figure 2As shown, in order to enable MOF-808 to contain unsaturated metal sites so that the modified metal-organic framework material obtained after modification with a chelating agent can adsorb metal ions, the preparation method of MOF-808 includes: a mixing step S7, in which N,N-dimethylformamide, a monobasic acid, trimesic acid, and zirconium oxychloride octahydrate are mixed to obtain a mixture; a filtration step S8, in which the mixture is reacted at a temperature of 130°C for 2 days, and then the mixture is centrifuged and filtered to obtain a white precipitate; and a drying step S9, in which the white precipitate is washed with a second washing solution and dried to obtain MOF-808. In a preferred embodiment, the volume ratio of N,N-dimethylformamide to the monocarboxylic acid is 1:1; the mass ratio of trimesic acid to zirconium chloride octahydrate is 3:1; the mass ratio of the total mass of N,N-dimethylformamide and the monocarboxylic acid to the total mass of trimesic acid and zirconium chloride octahydrate is 10:1; the monocarboxylic acid comprises formic acid, acetic acid, or hydrochloric acid; or the second cleaning solution comprises N,N-dimethylformamide, water, and acetone, but is not limited thereto. The working principle and advantages of the present invention are explained in detail below: When formic acid is used as a non-coordinated organic framework to prepare MOF-808, the formic acid is easily removed after obtaining MOF-808 to expose the active metal sites on MOF-808. Therefore, MOF-808 can be subsequently modified by grafting EDTA onto it using solvent-assisted ligand exchange to obtain MOF-808-EDTA with high specific surface area and good hydrophilicity. Furthermore, by combining MOF-808-EDTA with a low-cost and corrosion-resistant polyolefin membrane, the resulting membrane can improve water flux and achieve high efficiency in removing metal ions from water by leveraging the high specific surface area of ​​MOF-808, the enrichment effect of the porous material itself, and the properties of the grafted EDTA carboxylic acid functional groups.

[0049] Preferably, the present invention also provides a "membrane capable of filtering metal ions in water". Since its preparation method is the same as the above-mentioned "preparation method of membrane capable of filtering metal ions in water", it will not be described in detail here.

[0050] Examples 1 to 4 and Comparative Examples 1 to 2 of the "hybrid matrix membrane" are provided below, and the effects of different preparation processes on the water flux and metal ion adsorption performance of the prepared hybrid matrix membrane are explained.

[0051] Example 1 is provided below to illustrate the first embodiment of the "hybrid matrix membrane" of the present invention. Its preparation method sequentially includes the following steps: a mixing step S7, in which 250 ml of N,N-dimethylformamide and 250 ml of formic acid are mixed to obtain a mixed solvent, and 2 g of trimesic acid and 6 g of zirconium chloride octahydrate are ultrasonically dissolved in the mixed solvent to obtain a mixture; a filtration step S8, in which the mixture is first placed in a high-pressure reactor and reacted at 130°C for 2 days, and then the mixture is centrifuged and filtered. A white precipitate was obtained; in a drying step S9, the white precipitate was washed several times with N,N-dimethylformamide, water, and acetone, and then vacuum dried to obtain MOF-808, wherein the MOF-808 contains unsaturated metal sites; in a modification step S1, 2g of the MOF-808 was added to 200ml of an aqueous solution containing 20g of diethylenetriaminepentaacetic acid (DPTA), reacted at 60°C for 18 hours, washed several times with water and ethanol, and then vacuum dried to obtain The process involves: a MOF-808-DPTA mixture; a melt formation step S2, in which 100g of the MOF-808-DPTA, 100g of polyethylene with a molecular weight of 500,000, and 400g of paraffin oil are mixed in a rheometer mixing chamber at 120°C and a roller speed of 100 rpm for 45 minutes to ensure uniform mixing and form a melt; and a hot pressing step S3, in which the melt is poured into a stainless steel frame with dimensions of 10cm (length), 10cm (width), and 2mm (height), and pressed at 90°C and 5... The melt is hot-pressed under a pressure of MPa and then cooled to obtain a white sheet-like film; a stretching step S4 is performed, in which the film is stretched at a stretching temperature of 100°C and a stretching rate of 4 mm / s to stretch the length and width of the film to 10 times their original size; an extraction step S5 is performed, in which the film is extracted with dichloromethane; and a heat setting step S6 is performed, in which the film is heat-set at a temperature of 120°C to obtain a mixed matrix film, wherein the thickness of the mixed matrix film is 20 μm.

[0052] Example 2 is provided below to illustrate a second embodiment of the "hybrid matrix membrane" of the present invention. Specifically, it differs from Example 1 in that, in the modification step S1, 2g of the MOF-808 is added to a 300ml aqueous solution containing 30g of aminotriacetic acid (NTA), reacted at 60°C for 18 hours, washed several times with water and ethanol, and then vacuum dried to obtain MOF-808-NTA. Since the other steps and corresponding processes of Example 2 are the same as those of Example 1, they will not be described in detail here.

[0053] Example 3 is provided below to illustrate a third embodiment of the "mixed matrix membrane" of the present invention. Specifically, it differs from Example 1 in that, in the melt formation step S2, 50g of the MOF-808-DPTA, 100g of polyethylene with a molecular weight of 900,000, and 500g of paraffin oil are stirred at 100 rpm for 45 minutes in a rheometer mixing chamber at a temperature of 130°C to ensure uniform mixing and form a melt. Since the other steps and corresponding processes in Example 3 are the same as in Example 1, they will not be described in detail here.

[0054] Example 4 is provided below to illustrate a fourth embodiment of the "hybrid matrix membrane" of the present invention. Specifically, it differs from Example 1 in that, in the stretching step S4, the membrane is stretched at a stretching temperature of 120°C and a stretching rate of 10 mm / s, so that the length and width of the membrane are stretched to 15 times their original values, and the final thickness of the hybrid matrix membrane is 9 μm. Since the other steps and corresponding processes of Example 4 are the same as those of Example 1, they will not be described in detail here.

[0055] The following Comparative Example 1 illustrates a fifth embodiment of the "hybrid matrix membrane" of the present invention. Specifically, it differs from Example 1 in that, in the modification step S1, 2g of the MOF-808 is added to 200ml of water. Therefore, it can be understood that Comparative Example 1 does not modify MOF-808 with a chelating agent. Since the other steps and corresponding processes of Comparative Example 1 are the same as those of Example 1, they will not be described in detail here.

[0056] The following Comparative Example 2 illustrates a sixth embodiment of the "mixed matrix membrane" of the present invention. Specifically, it differs from Example 1 in that, in the melt formation step S2, 100g of polyethylene with a molecular weight of 500,000 and 400g of paraffin oil are stirred at 100 rpm for 45 minutes at a temperature of 120°C in a rheometer mixing chamber to achieve uniform mixing and form a melt. Therefore, it can be understood that the mixed matrix membrane prepared in Comparative Example 2 is simply a microporous polyethylene membrane. Since the other steps and corresponding processes of Comparative Example 2 are the same as those in Example 1, they will not be described in detail here.

[0057] Preferably, the structure and morphology of the MOF-808-DPTA prepared in "Example 1" are further analyzed below, such as... Figure 3 The image shown is the result of X-ray diffraction (XRD) analysis of MOF-808-DPTA, in which the structural features of MOF-808-DPTA can be clearly observed; as shown... Figure 4The image shown is an image obtained after scanning electron microscopy (SEM) analysis of MOF-808-DPTA. It can be observed that the particle size of the synthesized MOF-808-DPTA is approximately 50 nm; and as shown... Figure 5 The image shows the results of nitrogen adsorption-desorption spectral analysis of MOF-808-DPTA. It can be observed that MOF-808-DPTA has a high specific surface area of ​​1060 m². 2 / g.

[0058] Preferably, the metal ion adsorption performance of the mixed matrix membranes of Example 1, Example 2, and Comparative Example 1 were tested respectively. First, mercury, copper, cobalt, cadmium, or lead ions were added to water to prepare an initial metal ion concentration of 10 mg / L. Then, 10 mg of powder was added to the water, and after standing for 30 minutes, the supernatant was taken for inductively coupled plasma optical emission spectrometry (ICP-OES) testing. The results are as follows: Figure 6 As shown, it can be found that: Comparative Example 1 did not add a chelating agent to modify MOF-808, so the adsorption performance of the mixed matrix membrane made therefore was less than 5% for various metal ions in water; while in Example 1 and Example 2, MOF-808 was modified into MOF-808-DPTA and MOF-808-NTA, respectively, so both of them had superior adsorption performance for metal ions in water, both exceeding 99%, but in terms of metal adsorption performance, Example 1 was better than Example 2.

[0059] Preferably, the morphology of the mixed matrix membrane in Example 1 is analyzed, wherein, for example... Figure 7 The image shown is a cross-sectional analysis of the hybrid matrix membrane, revealing that MOF-808-DPTA was successfully doped into the polyethylene separator. Further, narrow-pore size analysis was performed on the hybrid matrix membrane from Example 1, and the results are as follows... Figure 8 As shown, it can be found that the median pore size of the hybrid matrix membrane is 23 nm.

[0060] Preferably, the water flux of the mixed matrix membranes of Example 1, Example 2, and Comparative Example 2 was tested, and the results are shown in Table 1 below. It can be seen that: the mixed matrix membrane of Comparative Example 2 did not contain MOF-808-DPFA in its raw materials, and its water flux was 160 lm⁻²h⁻¹ / bar; while the mixed matrix membranes of Example 1 and Example 2 contained MOF-808-DPFA and MOF-808-NTA, respectively, thus increasing their water flux to 250 lm⁻²h⁻¹ / bar, 220 lm⁻²h⁻¹ / bar, and 220 lm⁻²h⁻¹ / bar, respectively. It is understood that, compared to a simple polyethylene separator, adding a hydrophilic modified metal-organic framework material to the mixed matrix membrane can significantly improve the water flux of the mixed matrix membrane.

[0061] Table 1

[0062]

[0063] Preferably, the mixed matrix membranes prepared in Examples 1 and 2, and the mixed matrix membrane in Comparative Example 2, were subjected to experiments on their metal ion adsorption performance. The results are shown in Table 2. It can be found that the adsorption performance of the pure polyethylene membrane for various metal ions is less than 0.5%; while the mixed matrix membranes prepared by adding MOF-808-DPFA and MOF-808-NTA to the mixed matrix membrane raw materials, respectively, both showed adsorption performance for various metal ions better than 99%. Therefore, it can be understood that the mixed matrix membrane prepared by adding modified metal-organic framework materials can realize the deviceization of multifunctional powders and improve the recycling efficiency of metal ions.

[0064] Table 2

[0065]

[0066] In summary, the advantages of this invention over prior art lie in the following: This invention modifies the structure of MOF-808 by using various non-coordinating synthesized monocarboxylic acids and by using various non-coordinating synthesized chelating agents to obtain a modified metal-organic framework material. This modified material exhibits a three-dimensional porous framework structure and, through its high specific surface area, high active sites, and adsorption performance with chelating agents, can generate synergistic adsorption to adsorb various types of metal ions. Specifically, the modified metal-organic framework material of this invention can adsorb metal ions contained in water to achieve water purification, and it does not produce additional residues or precipitates in the water, thus improving the efficiency and quality of water purification.

[0067] Furthermore, due to the low cost, good chemical corrosion resistance, high porosity, and adjustable pore size of polyethylene membranes, the difficulty in recovering metal ions in water treatment can be overcome by combining modified metal-organic framework materials with polyethylene membranes. In addition, because polyethylene membranes are highly hydrophobic while modified metal-organic framework materials are highly hydrophilic, combining them with polyethylene membranes can improve the hydrophilicity of the polyethylene membrane and increase its water flux, thereby significantly enhancing its efficiency in adsorbing metal ions.

[0068] Furthermore, the hybrid matrix membrane of the present invention is prepared using a thermally induced phase separation (TIPS) method. Specifically, in the hot pressing step S3, after the membrane is hot-pressed, it is cooled to melt the paraffin oil into a liquid state, while the polyethylene and modified metal-organic framework material remain solid. Then, in the extraction step S5, the paraffin oil in the membrane is removed with an extraction solution to form a hybrid matrix membrane with a porous structure. Since the preparation method of the hybrid matrix membrane provided by the present invention is simple, the porosity or stretching ratio can be adjusted to control the amount of water flux of the hybrid matrix membrane, and it has excellent metal ion adsorption capacity, it can filter out more than 99% of metal ions in water, and it does not produce additional residues or industrial waste that would cause secondary pollution, it is understood that the present invention can purify water more efficiently and cost-effectively compared to prior art.

[0069] However, the above description is only a preferred embodiment of the present invention, and should not be construed as limiting the scope of patent protection of the present invention. Therefore, any simple equivalent changes and modifications made in accordance with the scope of patent protection and the contents of the specification of the present invention shall still fall within the scope of patent protection of the present invention.

Claims

1. A method for preparing a separator membrane capable of filtering metal ions in water, characterized by, Include: A modification step involves reacting a MOF-808, a chelating agent, and water to obtain a solid substance, washing the solid substance with a first cleaning solution, and then drying it to obtain a modified metal-organic framework material. A melt formation step involves uniformly mixing the modified metal-organic framework material, a polyethylene, and a paraffin oil at a melting temperature to form a melt; and A hot pressing step involves hot pressing and cooling the melt to obtain a film; The mass ratio of the modified metal-organic framework material to the polyethylene is 1:1 to 2. The total mass ratio of the modified metal-organic framework material and the polyethylene to the paraffin oil is 1:2 to 4. The molecular weight of the polyethylene is between 500,000 and 900,000; The chelating agent comprises: diethyltriaminepentaacetic acid (DPTA), aminotriacetic acid (NTA), sodium citrate, ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), or sodium ethylenediaminetetramethylenephosphonate (EDTMPS); The mass ratio of MOF-808, the chelating agent, and the water is 1:10 to 50:200; or The first cleaning solution contains water and ethanol.

2. The method according to claim 1, characterized in that In the melt formation step, the modified metal-organic framework material, the polyethylene, and the paraffin oil are stirred and mixed at a melting temperature of 110 to 130°C and a rotation speed of 80 to 120 rpm for 30 to 60 minutes.

3. The method of claim 1, wherein In the hot pressing step, the melt is poured into a container and hot-pressed at a temperature of 60 to 120°C and a pressure of 1 to 20 MPa.

4. The method according to claim 3, characterized in that The container is a stainless steel frame with a length of 10cm, a width of 10cm, and a height of 1 to 2mm.

5. The method of claim 1, wherein, It further includes a stretching step, in which the length and width of the diaphragm are each stretched by 10 times.

6. The method according to claim 5, characterized by In the stretching step, the membrane is stretched at a temperature of 100 to 130°C and at a rate of 2 to 10 mm / s.

7. The method according to claim 5, characterized by It further includes an extraction step, which involves extracting the membrane with an extraction solution after the stretching step.

8. The method according to claim 7, characterized in that, The extraction solution contains dichloromethane.

9. The method according to claim 7, characterized in that, It further includes a heat-setting step, which involves heat-setting the membrane at a temperature of 100 to 120°C after the extraction step to obtain a mixed matrix membrane.

10. The method according to claim 9, characterized in that, The thickness of the hybrid matrix membrane is 10 to 20 μm.

11. The method according to claim 1, characterized in that: The chelating agent is diethyltriaminepentaacetic acid (DPTA), and the modified metal-organic framework material is MOF-808-DPTA; The chelating agent is aminotriacetic acid (NTA), and the modified metal-organic framework material is MOF-808-NTA; The chelating agent is ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), and the modified metal-organic framework material is MOF-808-EGTA; or The chelating agent is sodium ethylenediaminetetramethylenephosphonate (EDTMPS), and the modified metal-organic framework material is MOF-808-EDTMPS.

12. The method according to claim 1, characterized in that, The method for preparing MOF-808 includes: A mixing step involves mixing N,N-dimethylformamide, a monobasic acid, pyromellitic acid, and zirconium chloride octahydrate to obtain a mixture. In the first filtration step, the mixture is reacted at 130°C for 2 days, and then centrifuged and filtered to obtain a white precipitate. as well as A drying step involves washing the white precipitate with a second cleaning solution and drying the white precipitate to obtain the MOF-808.

13. The method according to claim 12, characterized in that: The volume ratio of the N,N-dimethylformamide to the monobasic acid is 1:1; The mass ratio of the pyromellitic acid to the zirconium oxychloride octahydrate is 3:

1. The mass ratio of the total mass of N,N-dimethylformamide and the monocarboxylic acid to the total mass of pyromellitic acid and the zirconium chloride octahydrate is 10:

1. The monocarboxylic acid includes: formic acid, acetic acid, or hydrochloric acid; or The second cleaning solution comprises: N,N-dimethylformamide, water, and acetone.

14. A membrane for filtering metal ions in water, characterized in that, Its preparation method includes: A modification step involves reacting a MOF-808, a chelating agent, and water to obtain a solid substance, washing the solid substance with a first cleaning solution, and then drying it to obtain a modified metal-organic framework material. A melt formation step involves uniformly mixing the modified metal-organic framework material, a polyethylene, and a paraffin oil at a melting temperature to form a melt; and A hot pressing step involves hot pressing and cooling the melt to obtain a film; The mass ratio of the modified metal-organic framework material to the polyethylene is 1:1 to 2. The total mass ratio of the modified metal-organic framework material and the polyethylene to the paraffin oil is 1:2 to 4. The molecular weight of the polyethylene is between 500,000 and 900,000; The chelating agent comprises: diethyltriaminepentaacetic acid (DPTA), aminotriacetic acid (NTA), sodium citrate, ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), or sodium ethylenediaminetetramethylenephosphonate (EDTMPS); The mass ratio of MOF-808, the chelating agent, and the water is 1:10 to 50:200; or The first cleaning solution contains water and ethanol.

15. The membrane for filtering metal ions in water according to claim 14, characterized in that, In the melt formation step, the modified metal-organic framework material, the polyethylene, and the paraffin oil are stirred and mixed at a melting temperature of 110 to 130°C and a rotation speed of 80 to 120 rpm for 30 to 60 minutes.

16. The membrane for filtering metal ions in water according to claim 14, characterized in that, In the hot pressing step, the melt is poured into a container and hot-pressed at a temperature of 60 to 120°C and a pressure of 1 to 20 MPa.

17. The membrane for filtering metal ions in water according to claim 16, characterized in that, The container is a stainless steel frame with a length of 10cm, a width of 10cm, and a height of 1 to 2mm.

18. The membrane for filtering metal ions in water according to claim 14, characterized in that, It further includes a stretching step, in which the length and width of the diaphragm are each stretched by 10 times.

19. The membrane for filtering metal ions in water according to claim 18, characterized in that, In the stretching step, the membrane is stretched at a temperature of 100 to 130°C and at a rate of 2 to 10 mm / s.

20. The membrane for filtering metal ions in water according to claim 18, characterized in that, It further includes an extraction step, which involves extracting the membrane with an extraction solution after the stretching step.

21. The membrane for filtering metal ions in water according to claim 20, characterized in that, The extraction solution contains dichloromethane.

22. The membrane for filtering metal ions in water according to claim 20, characterized in that, It further includes a heat-setting step, which involves heat-setting the membrane at a temperature of 100 to 120°C after the extraction step to obtain a mixed matrix membrane.

23. The membrane for filtering metal ions in water according to claim 22, characterized in that, The thickness of the hybrid matrix membrane is 10 to 20 μm.

24. The membrane for filtering metal ions in water according to claim 14, characterized in that: The chelating agent is diethyltriaminepentaacetic acid (DPTA), and the modified metal-organic framework material is MOF-808-DPTA; The chelating agent is aminotriacetic acid (NTA), and the modified metal-organic framework material is MOF-808-NTA; The chelating agent is ethylene glycol-bis-(2-aminoethyl)tetraacetic acid (EGTA), and the modified metal-organic framework material is MOF-808-EGTA; or The chelating agent is sodium ethylenediaminetetramethylenephosphonate (EDTMPS), and the modified metal-organic framework material is MOF-808-EDTMPS.

25. The membrane for filtering metal ions in water according to claim 14, characterized in that, The method for preparing MOF-808 includes: A mixing step involves mixing N,N-dimethylformamide, a monobasic acid, pyromellitic acid, and zirconium chloride octahydrate to obtain a mixture. In the first filtration step, the mixture is reacted at 130°C for 2 days, and then centrifuged and filtered to obtain a white precipitate. as well as A drying step involves washing the white precipitate with a second cleaning solution and drying the white precipitate to obtain the MOF-808.

26. The membrane for filtering metal ions in water according to claim 25, characterized in that: The volume ratio of the N,N-dimethylformamide to the monobasic acid is 1:1; The mass ratio of the pyromellitic acid to the zirconium oxychloride octahydrate is 3:

1. The mass ratio of the total mass of N,N-dimethylformamide and the monocarboxylic acid to the total mass of pyromellitic acid and the zirconium chloride octahydrate is 10:

1. The monocarboxylic acid includes: formic acid, acetic acid, or hydrochloric acid; or The second cleaning solution comprises: N,N-dimethylformamide, water, and acetone.

Images