A composite material of polyvinylidene fluoride and metal organic framework and its preparation method and application

Abstract

The present invention relates to a polyvinylidene fluoride and metal organic framework composite material, its preparation method, and application. The preparation method comprises the following synthesis steps: adding PVDF to a reagent bottle containing dimethyl sulfoxide, stirring under heating conditions until the polymer is completely dissolved, to obtain a clear, transparent, viscous solution A; adding MOFs to a centrifuge tube containing dimethyl sulfoxide, ultrasonically mixing, to obtain a mixed solution B; adding solution B to the solution A, stirring evenly to obtain solution C; pouring solution C into a mold and freezing to obtain a solid D; pouring solid D from the mold and placing it in pure water to displace the dimethyl sulfoxide, to obtain a polyvinylidene fluoride and MOF composite material. Compared with the existing technology, the preparation method of the present invention utilizes freeze shaping combined with phase inversion technology to produce a composite material rich in micron-sized pores; it has the characteristics of efficient adsorption, easy recovery, good stability, and environmental friendliness, and can be used for the efficient adsorption and degradation of new pollutants in water.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental functional materials and water pollution control, in particular to a polyvinylidene fluoride and metal organic framework composite material and a preparation method thereof, as well as application of the composite material in adsorbing and catalyzing hydrogen peroxide to degrade new pollutants in water. Background Art

[0002] With the rapid development of industrialization and urbanization, emerging pollutants, such as pharmaceutical residues and personal care product ingredients, are increasingly becoming a serious problem in aquatic environments. These pollutants are highly stable, bioaccumulative, and potentially biotoxic, posing a serious threat to ecosystems and human health. Natural attenuation and conventional treatment processes are unable to effectively remove these emerging pollutants from wastewater, surface water, and drinking water. Therefore, the development of efficient technologies to remove these emerging pollutants is urgently needed.

[0003] In order to meet the challenges of new pollutants, efficient and controllable new pollutant treatment technologies have attracted much attention. The integrated technology of adsorption and advanced oxidation can organically combine adsorption and advanced oxidation methods to achieve effective enrichment and efficient degradation of new pollutants. Metal-organic framework materials are considered to be a highly promising adsorption material due to their high specific surface area, adjustable pore structure and abundant active sites. Metal-organic framework materials can not only efficiently adsorb organic pollutants, but also serve as catalysts or catalyst carriers to promote the progress of advanced oxidation reactions. However, the recycling of powdered metal-organic framework materials is difficult and prone to secondary pollution, which limits their widespread application in water treatment technology. Therefore, the development of immobilization technology for metal-organic framework materials is urgent. Summary of the Invention

[0004] This invention provides a method for preparing a composite material of polyvinylidene fluoride (PVDF) and metal-organic frameworks (MOFs). By immobilizing MOFs within a PVDF matrix, a novel, easily recyclable composite adsorption and catalytic material is prepared. This composite material combines the chemical stability of PVDF with the high adsorption and catalytic properties of MOFs. It not only effectively removes new pollutants from water environments, but also facilitates recovery and reuse in actual water treatment processes.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing a composite material of PVDF and MOFs, comprising the following steps performed under normal pressure:

[0007] S1: Add PVDF to a reagent bottle containing dimethyl sulfoxide and stir with magnetic stirring under heating until the polymer is completely dissolved to obtain a clear, transparent, viscous solution A;

[0008] S2: Add MOFs to a centrifuge tube containing dimethyl sulfoxide and mix by ultrasonication to obtain a mixed solution B;

[0009] S3: adding the mixed solution B to the viscous solution A and stirring the mixture by magnetic stirring to obtain solution C;

[0010] S4: pouring solution C into a mold and then freezing it under low temperature conditions to obtain solid D;

[0011] S5: The frozen solid D is poured out of the mold and placed in pure water to obtain a polyvinylidene fluoride and MOF composite material.

[0012] Furthermore, in S1, the added mass ratio of PVDF to dimethyl sulfoxide is 1:9 to 1:4.

[0013] Further preferably, in S1, the added mass ratio of PVDF to dimethyl sulfoxide is 1.5:9.5.

[0014] Furthermore, in S2, the added mass ratio of the MOFs to dimethyl sulfoxide is not higher than 1:1.

[0015] Further preferably, in S2, the added mass ratio of the MOFs to dimethyl sulfoxide is 1:15.

[0016] Furthermore, in S3, the mass concentration of PVDF in the solution C is not less than 8%.

[0017] Furthermore, in S4, the material and shape of the mold can be any device capable of storing the solution.

[0018] Furthermore, in S4, the low temperature condition is usually below -40°C.

[0019] Furthermore, in S5, the pure water is usually placed for 12-48 hours.

[0020] A second aspect of the present invention provides a PVDF / MOFs composite material prepared by the above method.

[0021] The third aspect of the present invention provides an application of the above-mentioned PVDF / MOFs composite material, wherein the composite material is applied to the Fenton reaction conditions to adsorb and catalyze hydrogen peroxide to degrade pollutants in water, especially new pollutants such as oxytetracycline hydrochloride.

[0022] The main mechanism of the present invention is: using freeze shaping combined with phase inversion technology, by selecting dimethyl sulfoxide as a solvent, to achieve low-temperature rapid freezing and solidification, forming an ice crystal template of a preset shape, and then through phase separation of dimethyl sulfoxide and water, with the help of solvent microcrystals as a natural template, inducing the generation of a porous structure rich in micron-sized pores.

[0023] Compared with the prior art, the present invention has the following technical advantages:

[0024] (1) Efficient adsorption: The high specific surface area and active sites of MOFs provide strong adsorption capacity for pollutants;

[0025] (2) Easy to recycle: The immobilization of PVDF makes the composite material easy to separate and recycle from the aqueous environment;

[0026] (3) Good stability: The chemical stability of PVDF and the structural stability of MOFs ensure the long-term durability of the composite material;

[0027] (4) Environmentally friendly: The preparation method of the present invention is simple, low-cost, and the materials can be recycled, reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : This is a scanning electron microscope photograph of the cross section of the PVDF / MIL-125-Ti composite material in an embodiment of the present invention;

[0029] Figure 2 This is an enlarged scanning electron microscope photograph of the cross section of the PVDF / MIL-125-Ti composite material according to an embodiment of the present invention;

[0030] Figure 3 : is a scanning electron microscope photograph of a cross section of a PVDF / MIL-100-Fe composite material in an embodiment of the present invention;

[0031] Figure 4 This is an enlarged scanning electron microscope photograph of the cross section of the PVDF / MIL-100-Fe composite material in an embodiment of the present invention;

[0032] Figure 5 This is a diagram showing the effect of Fenton-like removal of oxytetracycline hydrochloride by PVDF / MIL-125-Ti composite material and PVDF / MIL-100-Fe composite material in an embodiment of the present invention;

[0033] Figure 6 This is a diagram showing the effect of multiple Fenton-like removal of oxytetracycline hydrochloride by the PVDF / MIL-100-Fe composite material in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Any features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are considered to be common technical features disclosed in the prior art.

[0035] Example 1

[0036] The method for preparing a PVDF / MOFs composite material in this embodiment, wherein the MOFs is MIL-125-Ti, is named a PVDF / MIL-125-Ti composite material. The method comprises the following steps:

[0037] (1) Preparation of metal organic framework material MIL-125-Ti. 6 mL of methanol and 54 mL of dimethylformamide were added to a polytetrafluoroethylene liner and stirred evenly. Then, 3.53 g of terephthalic acid was dissolved in the above mixed solution. After stirring for 20 minutes, 2.1 mL of isopropyl titanate was added as a titanium source, and then stirred for 30 minutes. The evenly mixed solution was transferred to an oven and heated at 150 ° C for 16 hours. After the reaction was completed, the reaction system was cooled to room temperature and crude MIL-125-Ti was obtained by centrifugation. Dimethylformamide was added and ultrasonicated for 1 hour. The precipitate was obtained by centrifugation again and repeated three times. After that, the above operation was repeated with anhydrous ethanol for washing three times, and then washed once with water, and freeze-dried for 48 hours to obtain the final product MIL-125-Ti.

[0038] (2) 1.5 g of PVDF was added to a reagent bottle containing 9.5 g of dimethyl sulfoxide and stirred with magnetic stirring at 60°C until the polymer was completely dissolved to obtain a clear, transparent, viscous solution A;

[0039] (3) Add 0.3 g of MIL-125-Ti to a centrifuge tube containing 4.5 g of dimethyl sulfoxide and mix thoroughly by ultrasonication to obtain a mixed solution B;

[0040] (4) adding the solution B to the solution A and stirring magnetically for 4 hours to obtain solution C;

[0041] (5) Solution C was poured into a 1 mL syringe mold, and then frozen in a -80 °C freezer for 1 hour to obtain solid D;

[0042] (6) The frozen solid D was poured out of the mold and placed in pure water for 48 hours to obtain a polyvinylidene fluoride and MIL-125-Ti composite material.

[0043] like Figure 1 As shown in FIG, there are many micron-sized pores on the cross section of the PVDF / MIL-125-Ti composite column.

[0044] like Figure 2 As shown in the enlarged cross-section of the PVDF / MIL-125-Ti composite column, it can be seen that many MIL-125-Ti material particles are evenly distributed on the surface of the PVDF substrate and are well exposed, which is conducive to the adsorption of contamination by MIL-125-Ti and the exposure of reaction sites.

[0045] Example 2

[0046] The method for preparing a PVDF / MOFs composite material in this embodiment, wherein the MOFs is MIL-100-Fe, and the prepared material is named PVDF / MIL-100-Fe composite material, comprises the following steps:

[0047] (1) Preparation of the metal-organic framework material MIL-100-Fe. 1.676 g of trimesic acid was dissolved in 23.72 g of an aqueous solution containing 1 mol / L NaOH to obtain solution 1. 4.81 g of ferrous sulfate heptahydrate was dissolved in 97.2 g of water to obtain solution 2. Solution 1 was added dropwise to solution 2 with stirring. After further stirring at room temperature for 24 hours, the mixture was centrifuged at 6000 rpm to obtain a crude MIL-100-Fe solid. The solid was then washed three times with water and once with ethanol, and the sample was dried at room temperature.

[0048] (2) 1.5 g of PVDF was added to a reagent bottle containing 9.5 g of dimethyl sulfoxide and stirred with magnetic stirring at 60°C until the polymer was completely dissolved to obtain a clear, transparent, viscous solution A;

[0049] (3) Add 0.3 g of MIL-100-Fe to a centrifuge tube containing 4.5 g of dimethyl sulfoxide and mix by ultrasonication to obtain a mixed solution B;

[0050] (4) adding the solution B to the solution A and stirring magnetically for 4 hours to obtain solution C;

[0051] (5) Solution C was poured into a 1 mL syringe mold and then frozen in a -60 °C cold trap for 2 h to obtain solid D;

[0052] (6) The frozen solid D was poured out of the mold and placed in pure water for 48 hours to obtain a composite material of polyvinylidene fluoride and MIL-100-Fe.

[0053] like Figure 3 As shown in FIG, there are many micron-sized pores on the cross section of the PVDF / MIL-100-Fe composite column.

[0054] like Figure 4 As shown in the enlarged cross-section of the PVDF / MIL-100-Fe composite column, numerous particles of MIL-100-Fe material are evenly and densely distributed on the PVDF substrate, and the outer surfaces of these particles are fully exposed.

[0055] Application Example 1

[0056] This application example demonstrates the efficient adsorption of the Fenton-like antibiotic oxytetracycline hydrochloride in water using PVDF / MIL-100-Fe and PVDF / MIL-125-Ti composite columns. The preparation process for the PVDF / MIL-125-Ti composite column is the same as in Example 1. The preparation process for the PVDF / MIL-100-Fe composite column is the same as in Example 2.

[0057] PVDF / MIL-125-Ti and PVDF / MIL-100-Fe composite solid columns were added to 50 mL of a 50 mg / L oxytetracycline hydrochloride solution, magnetically stirred at 350 rpm, and samples were taken at 260 and 270 minutes. Subsequently, 200 μL of 0.5 M H₂O₂ was added to the solution. At the designated time points, 1 mL of the reaction solution was sampled, filtered through a 0.22 μm polyethersulfone membrane, and analyzed using high-performance liquid chromatography.

[0058] The results are as follows Figure 5 As shown, after adding the PVDF / MIL-125-Ti composite material (prepared in Example 1), the adsorption efficiency of oxytetracycline hydrochloride reached 40%, while the PVDF / MIL-100-Fe composite material (prepared in Example 2) could achieve an adsorption efficiency of 53% for oxytetracycline hydrochloride. After adding hydrogen peroxide, PVDF / MIL-125-Ti could remove more than 85% of oxytetracycline hydrochloride within 90 minutes. The PVDF / MIL-100-Fe composite material, thanks to the excellent adsorption capacity of MIL-100-Fe itself for oxytetracycline hydrochloride, could remove more than 87% of oxytetracycline hydrochloride within 60 minutes.

[0059] Application Example 2

[0060] This application example is the use of PVDF / MIL-100-Fe composite solid columns for multiple recycling to degrade oxytetracycline hydrochloride.

[0061] A PVDF / MIL-100-Fe composite solid column was added to a conical flask containing 50 mL of 50 mg / L oxytetracycline hydrochloride solution. The reaction was stirred at 250 rpm on a magnetic stirrer, and 200 μL of 0.5 mM H₂O₂ was added to the solution. After 12 hours of reaction, 1 mL of the reaction solution was filtered and analyzed for concentration using liquid chromatography. To test the reusability of the material, the reacted material was directly added to a new conical flask containing 50 mL of 50 mg / L oxytetracycline hydrochloride and 2 mM H₂O₂ solution for material recycling experiments. After each five degradation cycles, the PVDF / MIL-100-Fe composite was placed in pure water and allowed to stand for 12 hours before being recycled.

[0062] The columnar PVDF / MIL-100-Fe composite material can be easily separated from the oxytetracycline hydrochloride solution for the next catalytic degradation experiment. Figure 6 Results from 18 cycles of PVDF / MIL-100-Fe composite material. After 18 cycles, the PVDF / MIL-100-Fe composite maintained a removal rate of over 97% for oxytetracycline hydrochloride. Compared to MOF powders, the composite material exhibited superior cycling performance and a higher number of cycles. This is primarily due to the fact that the bulk material effectively avoids material loss during solid-liquid separation or regeneration washing processes during recycling.

[0063] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a composite material of polyvinylidene fluoride and metal organic framework, characterized in that: The following steps are involved: S1: Add polyvinylidene fluoride to a reagent bottle containing dimethyl sulfoxide and stir with magnetic stirring under heating conditions until the polymer is completely dissolved to obtain a clear and transparent viscous solution A; S2: adding the metal organic framework to a centrifuge tube containing dimethyl sulfoxide and mixing by ultrasonication to obtain a mixed solution B; S3: adding the mixed solution B to the viscous solution A and stirring the mixture by magnetic stirring to obtain a precursor solution C; S4: Pour the precursor solution C into a mold and then freeze it under low temperature conditions to obtain solid D; S5: The frozen solid D is poured out of the mold and placed in pure water to displace the dimethyl sulfoxide in the solid D to obtain a PVDF / MOFs composite material.

2. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: In S1, the mass ratio of polyvinylidene fluoride to dimethyl sulfoxide is 1:9~1:

4.

3. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: In S2, the added mass ratio of the MOFs to dimethyl sulfoxide is not higher than 1:

1.

4. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: In S3, the mass concentration of PVDF in the solution C is not less than 8%.

5. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: In S4, the mold is a device capable of storing a solution; In S4, the low temperature condition is a temperature condition lower than -40°C.

6. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: In S5, the pure water is placed for 12-48 hours.

7. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: The metal organic framework is MIL-125-Ti or MIL-100-Fe; The PVDF / MOFs composite material is PVDF / MIL-125-Ti or PVDF / MIL-100-Fe.

8. The method for preparing a composite material of polyvinylidene fluoride and metal organic framework according to claim 1, characterized in that: In S1 to S5, freeze shaping combined with phase transformation technology is used. By selecting dimethyl sulfoxide as a solvent, low-temperature rapid freezing and solidification is achieved to form an ice crystal template of a preset shape. Then, through phase separation of dimethyl sulfoxide and water, the solvent microcrystals are used as a natural template to induce the generation of a PVDF / MOFs composite material with a porous structure rich in micron-sized pores.

9. A PVDF / MOFs composite material prepared by the method according to any one of claims 1 to 8.

10. An application of the PVDF / MOFs composite material as claimed in claim 9, characterized in that: The PVDF / MOFs composite material is applied to the Fenton-like reaction conditions to adsorb and catalyze hydrogen peroxide to degrade new pollutants in water.

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