A covalent organic framework material for removing nanoplastics from water, its preparation method and application

Abstract

This invention belongs to the field of pollutant removal, providing a covalent organic framework material for removing nanoplastics from water, its preparation method, and its application. The preparation method uses 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde as monomers, and prepares the covalent organic framework material TAPB-TPA COF under ambient temperature and pressure conditions via ultrasonic synthesis. The COF prepared by this invention exhibits good adsorption effects on polystyrene nanoplastics in water, achieving a removal rate of 99% within 2 hours, with a maximum adsorption capacity approaching 180 mg / g. After three cycles, the adsorption efficiency of the COF material still reaches over 80%, demonstrating good recyclability. The removal efficiency of PSNPs in seawater can reach 97.96%, showing good application potential in the remediation of water bodies contaminated by nanoplastics.

Description

Technical Field

[0001] This invention belongs to the field of environmental water pollution control technology, and relates to a covalent organic framework material for removing nanoplastics from water, its preparation method, and its application. Background Technology

[0002] Plastic products, with their advantages of high cost-effectiveness, lightweight, and high plasticity, are widely used in all aspects of life. However, most plastic waste is incinerated, landfilled, or directly released into the environment. Under the influence of mechanical wear, solar radiation, natural weathering, and microbial degradation, these widely distributed plastics are broken down into tiny particles, resulting in microplastics (MPs, 1μm–5mm) and nanoplastics (NPs, <1μm). Due to their unique physicochemical properties and chemical stability, micro and nanoplastics accumulate in soil, sediments, oceans, freshwater, and the atmosphere. Nanoplastics have a larger specific surface area and hydrophobicity than microplastics, potentially posing a greater environmental risk. Persistent organic pollutants and heavy metals readily adsorb and bind to nanoplastics, increasing their toxicity and accumulating up the food chain, thus harming human health. Once nanoplastics enter the body, they interfere with metabolic pathways, causing metabolic disorders in organs such as the liver, pancreas, kidneys, and intestines, leading to metabolic dysfunction (S. Haldar, Y. Muralidaran, D. Miguez, et al., Eco-toxicity of nano-plastics and its implication on human metabolism: Current and future perspective, Science of the Total Environment 861(2023)12.). Therefore, nanoplastic pollution has become a global environmental concern, and removing nanoplastics from water bodies has become an urgent task to ensure aquatic ecological security.

[0003] As a highly efficient, simple, and convenient removal technology, the selection of efficient adsorption materials is the most crucial issue. Adsorbents need to possess high adsorption capacity, excellent chemical stability, selectivity, and reusability. In recent years, polymeric materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have stood out from numerous materials due to their ease of functionalization, tunable pore size, and high specific surface area. However, research has found that MOFs, being porous materials linked by ionic and coordinate bonds, exhibit poor stability in aqueous solutions and are prone to structural collapse, potentially leading to metal leakage during operation. The Fenton reaction triggered by the release of metal ions generates reactive oxygen species, exhibiting varying degrees of cytotoxicity both in vitro and in vivo (QXLiu, SMKhor, Emerging absorption-based techniques for removing microplastics and nanoplastics from actual water bodies, TrAC Trends in Analytical Chemistry 170(2024)117465.). Therefore, in order to study adsorbents with high removal efficiency and high stability of nanoplastics, a method for preparing COF materials for removing nanoplastics from water and their application are proposed. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a covalent organic framework material for removing nanoplastics from water, its preparation method, and its application. The TAPB-TPACOF material, which is simple to prepare, has excellent adsorption performance, and is reusable, is obtained through ultrasonic synthesis, thus overcoming the shortcomings of existing adsorbents in the removal of nanoplastics.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a covalent organic framework material for removing nanoplastics from water is disclosed. The method uses 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde as monomers, and prepares the covalent organic framework material TAPB-TPA COF under ambient temperature and pressure conditions via ultrasonic synthesis. The specific steps include:

[0007] Step (1): Disperse 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde in an organic solvent and stir to obtain a uniform mixture.

[0008] Furthermore, in step (1), the molar ratio of terephthalaldehyde and 1,3,5-tris(4-aminophenyl)benzene is 3:2 to 3:4, and the mass concentration of 1,3,5-tris(4-aminophenyl)benzene in the mixture is 3.3 to 6.6 mg / mL.

[0009] Furthermore, in step (1), the organic solvent includes dimethyl sulfoxide solution, acetonitrile, and dichloromethane.

[0010] Furthermore, in step (1), the stirring time is 10 to 30 minutes.

[0011] Step (2): Under ultrasonic conditions, acetic acid is slowly added to the mixture obtained in step (1) until a yellow solid product appears, and stirring is continued. The yellow solid product is washed with detergent and then vacuum dried to obtain the TAPB-TPA COF material.

[0012] Furthermore, in step (2), 1-3 mL of acetic acid is added to every 32 mL of the mixture. The sonication time is 10-30 min, and the stirring time is 30 min-12 h.

[0013] Furthermore, in step (2), the detergent is tetrahydrofuran and methanol, and the yellow solid product is washed with tetrahydrofuran and methanol in sequence.

[0014] Furthermore, in step (2), the vacuum drying temperature is 55-75°C and the vacuum drying time is 12-24 hours.

[0015] This invention uses Fourier transform infrared spectroscopy and field emission scanning electron microscopy to characterize TAPB-TPA COF materials.

[0016] Furthermore, in step (2), the structural formula of the TAPB-TPA COF material is as follows:

[0017]

[0018] An application of a covalent organic framework material for removing nanoplastics from water is disclosed. Using this covalent organic framework material, the removal rate of nanoplastic PSNPs in water can reach 99%. Specifically:

[0019] Step (1): Add covalent organic framework material to water containing nanoplastics and shake. The dosage of TAPB-TPACOF is 0.1-0.5 g / L, the concentration of nanoplastics is 5-20 mg / L, and the adsorption time is 0.5-6 h. Add interfering ions at a concentration of 5-50 mM.

[0020] Furthermore, the interfering ion is Na. + K + , Ca 2+ NO3 - HCO3 - SO4 2- and PO4 2- .

[0021] Furthermore, the nanoplastic is polystyrene, and the particle size of the nanoplastic is 70-110 nm.

[0022] Step (2): Centrifuge to separate the used TAPB-TPA COF material, add detergent to wash and decompose the nanoplastic, and vacuum dry to complete the regeneration. Repeat 1 to 3 times.

[0023] Furthermore, the detergents are anhydrous ethanol, methanol, and NaOH solution.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The reaction principle and innovation of this invention are as follows: The synthesis of TAPB-TPA COF is mainly based on the Schiff base reaction, that is, through the condensation reaction between aldehyde and amino groups; The innovation is that the TAPB-TPA COF material prepared by this invention solves the problem of metal leakage in existing adsorbents. There are no reports on its application in the removal of nanoplastics in water, and it has good application potential.

[0026] (2) The present invention uses ultrasonic synthesis to obtain a stable covalent organic framework structure at room temperature. The operation is simple and the preparation time is short. It also has the advantages of fast adsorption rate and reusability for nanoplastics. The removal rate of PSNPs in nanoplastics can reach 99%. Attached Figure Description

[0027] Figure 1 Fourier transform infrared (FTIR) spectra of the TAPB-TPA COF-1 material and the reactive ligands TAPB and TPA prepared in Example 1 of this invention.

[0028] Figure 2 The images show scanning electron microscope (SEM) images of the TAPB-TPA COF-1 material prepared in Example 1 of this invention before and after adsorption of PSNPs.

[0029] Figure 3 The removal rate of PSNPs by different doses of TAPB-TPA COF-1 prepared in Example 1 of this invention.

[0030] Figure 4 The effect of TAPB-TPACOF-1 prepared in Example 1 of this invention on the removal of PSNPs when interfering ions are present.

[0031] Figure 5 This refers to the reusability of TAPB-TPACOF-1 prepared in Example 1 of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be noted that the following embodiments are only for describing the content of this invention and are not intended to limit the scope of this invention in any way. Other examples obtained by those skilled in the art based on the embodiments of this invention without departing from the theory of this invention are all within the protection scope of this invention.

[0033] Example 1

[0034] A method for preparing a covalent organic framework material for removing nanoplastics from water, comprising the following steps:

[0035] (1) Under normal temperature and pressure conditions, add 32 mL of dimethyl sulfoxide solution to an Erlenmeyer flask. Weigh 106 mg of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and disperse it in the solution. Then weigh 60 mg of terephthalaldehyde (TPA) and add it to the Erlenmeyer flask. Stir for 10 min, wherein the molar ratio of TPA to TAPB is 3:2.

[0036] (2) Under ultrasonic conditions (ultrasonication for 10 min), slowly add 1 mL of acetic acid (99.5%) to the above solution until a yellow precipitate appears, and continue stirring for 30 min.

[0037] (3) The yellow solid product was washed sequentially with tetrahydrofuran and methanol (filter membrane pore size 0.22 μm), and then vacuum dried at 55 °C for 12 h. The resulting material was named TAPB-TPACOF-1. The solid adsorbent with a size of less than 700 μm was obtained by sieving through a 26-mesh sieve.

[0038] Structural characterization of TAPB-TPACOF-1 material:

[0039] The surface structure and morphology of TAPB-TPA COF-1 prepared in Example 1 were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy, respectively. Figure 1 These are the FTIR analysis chromatograms of the reaction ligands TAPB and TPA, as well as the TAPB-TPA COF-1 material in Example 1. It can be seen that the TPA monomer at 1694 cm⁻¹... -1 The characteristic peak at 3433 cm⁻¹ originates from the stretching vibration of C=O; the TAPB monomer at 3433 cm⁻¹... -1 3353cm- 1and 3208cm -1 The characteristic peak at 1515 cm⁻¹ is the stretching vibration peak of NH. TAPB at 1515 cm⁻¹ -1 The absorption peak at 1499 cm⁻¹ and the TPA at 1499 cm⁻¹ -1 The absorption peaks at 1621 cm⁻¹ are all C=C stretching vibration peaks. With the significant weakening of the C=O stretching vibration peak of TPA and the NH characteristic peak of TAPB, the absorption peak of TAPB-TPACOF⁻¹ at 1621 cm⁻¹... -1 The appearance of a new characteristic peak belonging to the C=N stretching vibration indicates that the amino group of TAPB and the aldehyde group of TPA successfully underwent a Schiff base reaction to generate an imine bond, confirming that the present invention successfully prepared TAPB-TPA COF-1 material.

[0040] The microstructure of the TAPB-TPA COF material prepared in Example 1 was observed by SEM, such as... Figure 2 As shown in Figure a, the TAPB-TPA COF-1 materials aggregate together to form irregularly shaped and porous macropolymers. This irregular and rough surface may provide a large number of adsorption sites for the removal of PSNPs.

[0041] Example 2

[0042] A method for preparing a covalent organic framework material for removing nanoplastics from water, comprising the following steps:

[0043] (1) Under normal temperature and pressure conditions, add 32 mL of acetonitrile solution to an Erlenmeyer flask. Weigh 159 mg of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and disperse it in the solution. Then weigh 60 mg of terephthalaldehyde (TPA) and add it to the Erlenmeyer flask. Stir for 20 min, wherein the molar ratio of TPA to TAPB is 3:3.

[0044] (2) Under ultrasonic conditions (ultrasonication for 20 min), slowly add 2 mL of acetic acid (99.5%) to the above solution until a yellow precipitate appears, and continue stirring for 3 h.

[0045] (3) The yellow solid product was washed sequentially with tetrahydrofuran and methanol (filter membrane pore size 0.22 μm), and then vacuum dried at 65 °C for 18 h. The resulting material was named TAPB-TPA COF-2 material. It was sieved through a 26-mesh sieve to obtain a solid adsorbent with a size less than 700 μm.

[0046] Structural characterization of TAPB-TPACOF-2 material:

[0047] The surface structure of TAPB-TPA COF-2 prepared in Example 2 was analyzed using Fourier transform infrared spectroscopy. The TPA monomer was observed at 1694 cm⁻¹. -1The characteristic peak at 3433 cm⁻¹ originates from the stretching vibration of C=O; the TAPB monomer at 3433 cm⁻¹... -1 3353cm- 1 and 3208cm -1 The characteristic peak at 1515 cm⁻¹ is the stretching vibration peak of NH. TAPB at 1515 cm⁻¹ -1 The absorption peak at 1499 cm⁻¹ and the TPA at 1499 cm⁻¹ -1 The absorption peaks at 1621 cm⁻¹ are all C=C stretching vibration peaks. With the significant weakening of the C=O stretching vibration peak of TPA and the NH characteristic peak of TAPB, the absorption peak of TAPB-TPACOF₂ at 1621 cm⁻¹... -1 The appearance of a new characteristic peak belonging to the C=N stretching vibration indicates that the amino group of TAPB and the aldehyde group of TPA successfully underwent a Schiff base reaction to generate an imine bond, confirming that the present invention successfully prepared TAPB-TPA COF-2 material.

[0048] Example 3

[0049] A method for preparing a covalent organic framework material for removing nanoplastics from water, comprising the following steps:

[0050] (1) Under normal temperature and pressure conditions, add 32 mL of dichloromethane solution to an Erlenmeyer flask. Weigh 212 mg of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and disperse it in the solution. Then weigh 60 mg of terephthalaldehyde (TPA) and add it to the Erlenmeyer flask. Stir for 30 min, wherein the molar ratio of TPA to TAPB is 3:4.

[0051] (2) Under ultrasonic conditions (ultrasonication for 30 min), slowly add 3 mL of acetic acid (99.5%) to the above solution until a yellow precipitate appears, and continue stirring for 6 h.

[0052] (3) The yellow solid product was washed sequentially with tetrahydrofuran and methanol (filter membrane pore size 0.22 μm), and then vacuum dried at 75 °C for 24 h. The resulting material was named TAPB-TPACOF-3. The solid adsorbent with a size less than 700 μm was obtained by sieving through a 26-mesh sieve.

[0053] Structural characterization of TAPB-TPA COF-3 material:

[0054] The surface structure and morphology of TAPB-TPACOF-3 prepared in Example 3 were characterized using Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The TPA monomer was analyzed at 1694 cm⁻¹. -1 The characteristic peak at 3433 cm⁻¹ originates from the stretching vibration of C=O; the TAPB monomer at 3433 cm⁻¹... -1 3353cm- 1 and 3208cm -1The characteristic peak at 1515 cm⁻¹ is the stretching vibration peak of NH. TAPB at 1515 cm⁻¹ -1 The absorption peak at 1499 cm⁻¹ and the TPA at 1499 cm⁻¹ -1 The absorption peaks at 1621 cm⁻¹ are all C=C stretching vibration peaks. With the significant weakening of the C=O stretching vibration peak of TPA and the NH characteristic peak of TAPB, the absorption peak of TAPB-TPACOF⁻³ at 1621 cm⁻¹ is [missing value]. -1 The appearance of a new characteristic peak belonging to the C=N stretching vibration indicates that the amino group of TAPB and the aldehyde group of TPA successfully underwent a Schiff base reaction to generate an imine bond, confirming that the TAPB-TPACOF-3 material was successfully prepared by this invention.

[0055] Example 4

[0056] An application of a covalent organic framework material for removing nanoplastics from water:

[0057] The following steps utilize TAPB-TPACOF-1 prepared in Example 1 as an adsorbent to study the removal performance of the material of the present invention on nanoplastics.

[0058] (1) Determine the optimal dosage of the adsorbent

[0059] The dosages of TAPB-TPA COF-1 selected were 0.1 g / L, 0.3 g / L, and 0.5 g / L, respectively. The concentration of nanoplastics in the water to be treated was 10 mg / L. The removal efficiencies of different dosages of TAPB-TPA COF-1 on PSNPs were as follows: Figure 3 As shown, the higher the dosage, the shorter the time to reach adsorption equilibrium, which may be because more TAPB-TPA COF-1 material can provide more adsorption sites. At a TAPB-TPA COF-1 dosage of 0.1 g / L, the adsorption process is slow with increasing time, requiring 6 hours to reach adsorption equilibrium. At TAPB-TPA COF-1 dosages of 0.3 and 0.5 g / L, the adsorption rate significantly increases, reaching over 90% within 1 hour. After 1 hour, the adsorption performance of 3 mg and 5 mg COF is similar. Therefore, the optimal dosage of TAPB-TPA COF-1 is 0.3 g / L.

[0060] In addition, the SEM image after adding PSNPs is as follows: Figure 2 As shown in b, regularly shaped PSNPs are attached to the surface of TAPB-TPACOF-1, proving that TAPB-TPACOF-1 successfully adsorbs PSNPs.

[0061] (2) Effects of interfering ions

[0062] To investigate the removal effect of the adsorbent on nanoplastics in the presence of other ions in the solution, TAPB-TPACOF-1 was added to solutions containing Na+. + K + , Ca 2+ NO3 - HCO3 - SO4 2- and PO4 2- In PSNPs solution.

[0063] like Figure 4 The figure shows the removal rate of PSNPs after adding different ions. When Na+ is present in the solution... + K + , Ca 2+ Cl - and SO4 2- When NaNO3 is present, the removal efficiency of PSNPs is almost unaffected, and the removal rate can still reach 99%. In NaNO3 solution, the PSNP removal rate decreases slightly. However, after adding 5 mM NaHCO3 to the solution, the removal efficiency rapidly decreases to 9.5%; when 5 mM Na3PO4 is present in the solution, the removal efficiency of TAPB-TPACOF-1 for PSNPs is only 21%, indicating that HCO3... - and PO4 3- TAPB-TPACOF-1 has a significant inhibitory effect on the removal of PSNPs.

[0064] (3) The impact of environmental samples

[0065] To evaluate the adsorption capacity of TAPB-TPA COF-1 for PSNPs in real environmental samples, river water, sewage, and seawater were selected as environmental samples. The three water samples were filtered using a 0.22 μm filter membrane to remove impurities. A 10 mg / L PSNP solution was prepared using the pretreated water sample for adsorption experiments. In seawater, the PSNP removal rate reached 97.96%. In river water and sewage, the removal rate decreased slightly but still reached 85%. Compared to river water and sewage, seawater has higher salinity and total dissolved solids, making PSNPs more prone to destabilization and aggregation, which is beneficial for adsorption. These results indicate that TAPB-TPA COF-1 has the ability to remediate environmental samples.

[0066] Example 5

[0067] An application of a covalent organic framework material for removing nanoplastics from water:

[0068] The following steps utilize TAPB-TPA COF-1 prepared in Example 1 as an adsorbent to investigate the reusability of the material of the present invention for nanoplastics:

[0069] Centrifuge the used TAPB-TPA COF-1 material, add anhydrous ethanol solution, wash and decompose the nanoplastics, and vacuum dry to complete the regeneration. Repeat the cycle 1 to 3 times.

[0070] like Figure 5 As shown, TAPB-TPA COF-1 still achieves a removal rate of 99% after one cycle. After three cycles, the TAPB-TPACOF-1 material maintains a high removal efficiency, capable of removing more than 80% of PSNPs from the solution. Furthermore, FTIR analysis revealed that the molecular structure of the adsorbent remained almost unchanged after each washing with anhydrous ethanol, indicating its excellent regeneration capability.

[0071] Example 6

[0072] An application of a covalent organic framework material for removing nanoplastics from water:

[0073] The following steps utilize TAPB-TPA COF-1 prepared in Example 1 as an adsorbent to investigate the reusability of the material of the present invention for nanoplastics:

[0074] The used TAPB-TPACOF-1 material was separated by centrifugation, methanol solution was added, the nanoplastics were washed and desorbed, and vacuum drying was performed to complete regeneration. The cycle was repeated 1 to 3 times.

[0075] Example 7

[0076] An application of a covalent organic framework material for removing nanoplastics from water:

[0077] The following steps utilize TAPB-TPA COF-1 prepared in Example 1 as an adsorbent to investigate the reusability of the material of the present invention for nanoplastics:

[0078] The used TAPB-TPA COF-1 material was separated by centrifugation, NaOH solution was added, the nanoplastics were washed and desorbed, and vacuum drying was performed to complete regeneration. The cycle was repeated 1 to 3 times.

[0079] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An application of a covalent organic framework material for removing nanoplastics from water, characterized in that, The covalent organic framework material described above is used to remove nanoplastics from water. The covalent organic framework material is a TAPB-TPA COF material, and its structural formula is shown below: It is prepared using the following method: The covalent organic framework material was prepared by using 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde as monomers, and synthesizing the covalent organic framework material TAPB-TPA COF under ambient temperature and pressure conditions using an ultrasonic synthesis method; specifically... Includes the following steps: The first step involves dispersing 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde in an organic solvent and stirring to obtain a homogeneous mixture. In the second step, under ultrasonic conditions, acetic acid is slowly added to the mixture obtained in step (1) until a yellow solid product appears, and stirring is continued; the yellow solid product is washed with detergent and then vacuum dried to obtain TAPB-TPACOF material.

2. The application of the covalent organic framework material for removing nanoplastics from water according to claim 1, characterized in that, When applied, the removal rate of PSNPs in nanoplastics can reach 99%. The specific application process is as follows: Step (1): Add covalent organic framework material to water containing nanoplastics and shake. The dosage of TAPB-TPA COF is 0.1~0.5 g / L, the concentration of nanoplastics is 5~20 mg / L, and the adsorption time is 0.5~6 h. Add interfering ions at a concentration of 5~50 mM. Step (2): Centrifuge to separate the used TAPB-TPA COF material, add detergent to wash and decompose the nanoplastic, and vacuum dry to complete the regeneration. Repeat 1 to 3 times.

3. The application of the covalent organic framework material for removing nanoplastics from water as described in claim 2, characterized in that, In step (1): the interfering ion is Na + K + , Ca 2+ NO3 - HCO3 - SO4 2- and PO4 2- The nanoplastic is polystyrene, and the particle size of the nanoplastic is 70~110 nm.

4. The application of the covalent organic framework material for removing nanoplastics from water as described in claim 2, characterized in that, In step (2), the detergent is anhydrous ethanol, methanol or NaOH solution.

5. The application of the covalent organic framework material for removing nanoplastics from water according to claim 1, characterized in that, In the first step of the preparation method of the covalent organic framework material: the molar ratio of terephthalaldehyde and 1,3,5-tris(4-aminophenyl)benzene is 3:2 to 3:4; the mass concentration of 1,3,5-tris(4-aminophenyl)benzene in the mixture is 3.3 to 6.6 mg / mL.

6. The application of the covalent organic framework material for removing nanoplastics from water according to claim 1, characterized in that, In the first step of the method for preparing the covalent organic framework material: the organic solvent includes dimethyl sulfoxide solution, acetonitrile, or dichloromethane; the stirring time is 10-30 min.

7. The application of the covalent organic framework material for removing nanoplastics from water according to claim 1, characterized in that, In the second step of the preparation method of the covalent organic framework material: 1~3 mL of acetic acid is added to every 32 mL of mixture; the ultrasonic time is 10~30 min, and the stirring time is 30 min~12 h.

8. The application of the covalent organic framework material for removing nanoplastics from water according to claim 1, characterized in that, In the second step of the preparation method of the covalent organic framework material: the detergent is tetrahydrofuran and methanol, and the yellow solid product is washed with tetrahydrofuran and methanol in sequence; the vacuum drying temperature is 55~75 ℃, and the vacuum drying time is 12~24 h.

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