Synthesis method and application of positive electropositive three-component covalent organic polymer

Abstract

The application relates to a synthesis method of a positive electric three-component covalent organic polymer and application thereof, and belongs to the technical field of sewage treatment. The method is as follows: 1,3,5-benzene triformylhydrazine is dissolved in an organic solvent dimethyl sulfoxide to obtain a solution A; 1,3-diamino guanidine hydrochloride is dissolved in the solution A to obtain a solution B; 2,3,5,6-tetrafluoro-p-xylene dicarboxaldehyde is dissolved in the solution B to obtain a solution C, and the preparation of the solutions is carried out in a constant-temperature oil bath; then, the orange wet gel is obtained by heating at 100 DEG C for 30s; the orange wet gel is placed in a dialysis bag for dialysis, the mixture is taken out for freezing, and then the freezing drying is carried out under vacuum to obtain the positive electric three-component covalent organic polymer. The synthesis method is simple, high in yield and fast in speed, the specific surface area of the positive electric three-component covalent organic polymer is large, the positive electric three-component covalent organic polymer has a hierarchical porous structure and rich reaction active sites, and can be used as a high-efficiency adsorbent to remove perfluorooctanoic acid in water.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a method for synthesizing a positively charged three-component covalent organic polymer and its application. The positively charged three-component covalent organic polymer is named COP-101, where COP is an abbreviation for Covalent Organic Polymers. Background Technology

[0002] The widespread industrial application of perfluorooctanoic acid (PFOA) stems from the thermal stability and chemical inertness conferred by its unique CF bond structure. This structure also makes it extremely difficult to degrade in the natural environment, resulting in strong persistence, long-distance migration, and bioaccumulation. These properties have led to its inclusion in the list of persistent organic pollutants (POPs), and its proven hepatotoxicity, endocrine disruption, and carcinogenic risks further pose a serious threat to ecosystems and human health. To address this increasingly stringent environmental challenge, adsorption methods have become the most promising remediation strategy due to their ease of operation, wide applicability, and suitability for large-scale application. Notably, PFOA typically exists in water in a negatively charged form, and current research confirms that electrostatic attraction and hydrophobic interactions are the two core mechanisms driving its efficient adsorption. Therefore, developing adsorption materials that can synergistically utilize electrostatic attraction and hydrophobic capture effects is of crucial engineering significance for the efficient removal of PFOA from water.

[0003] For perfluorooctanoic acid (PFOA), a novel pollutant, existing adsorbents generally suffer from problems such as small adsorption capacity, low removal efficiency, and difficulty in regeneration, which restricts their application in practical water remediation. In contrast, covalent organic polymers (COPs), with their high porosity, designable pore structure, and tunable surface functional groups, can achieve highly efficient and selective binding of PFOA through multiple synergistic effects such as electrostatics, hydrophobicity, hydrogen bonding, and fluorine-fluorine affinity. They possess both high adsorption performance and excellent recyclability, thus showing great potential for application in the field of PFOA pollution control. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing a positively charged three-component covalent organic polymer.

[0005] Another objective of this invention is the application of positively charged three-component covalent organic polymer powder in the removal of perfluorooctanoic acid from water.

[0006] The mechanism and principle of this invention: The adsorption advantage of COP-101 for perfluorooctanoic acid (PFOA) in this invention stems from the precise matching of its multiple structural features with the molecular characteristics of PFOA. PFOA is composed of a perfluorinated carbon chain and a negatively charged carboxylic acid head group. Its efficient removal requires the use of multiple mechanisms: fluorine-fluorine (FF) interaction, hydrophobic interaction, electrostatic attraction, and hydrogen bonding.

[0007] The COP-101 of this invention perfectly utilizes the above-mentioned mechanism of action: First, the tetrafluoroterephthalaldehyde introduced into the framework provides fluorine atoms, which can selectively recognize and bind to the fluorinated carbon chain of perfluorooctanoic acid (PFOA) through strong FF affinity; then, the rigid framework containing benzene rings endows COP-101 with significant hydrophobic properties, which is conducive to hydrophobic binding with the hydrophobic portion of PFOA; finally, the positively charged groups in COP-101 can efficiently capture the negatively charged carboxylate head group of PFOA through electrostatic attraction, while the -NH2 group in 1,3,5-phenyltricarboxyhydrazide can form hydrogen bonds with the carboxylate head group and fluorine atoms in PFOA; in addition, compared with the traditional two-component system, the three monomers of this material can achieve fine adjustment of pore size, optimize the mass transfer path of PFOA inside the pores, and systematically regulate the hydrophilic-hydrophobic balance of the framework, enhance the hydrophobic reciprocating effect of PFOA, achieve synergistic effect of electrostatic capture and hydrophobic enrichment, and further improve adsorption capacity and kinetic performance. This invention designs and synthesizes a positively charged three-component covalent organic polymer, fully leveraging the synergistic effects of fluorine-fluorine interactions, hydrophobic interactions, electrostatic attraction, and hydrogen bonding. It aims to overcome the structural and functional bottlenecks of traditional COP materials and provide a novel green adsorbent for the efficient and rapid removal of perfluorooctanoic acid (PFOA) from water.

[0008] This invention synthesizes a positively charged three-component covalent organic polymer via a solvothermal method based on Schiff base condensation reaction. Design features: 1. Ternary systems composed of three monomers tend to form porous covalent organic polymers with multiple functions; 2. Since perfluorooctanoic acid (PFOA) mainly exists in aqueous solution as anions, we plan to select a positively charged monomer to synthesize COP with a positively charged skeleton, and adsorb PFOA through electrostatic attraction. 3. Select 1,3,5-benzenetricarboxylhydrazide and 1,3-diaminoguanidine hydrochloride and 2,3,5,6-tetrafluoro-terephthalaldehyde, which are rich in linkage sites and groups. The monomers are rich in benzene rings and fluorine atoms, and can efficiently adsorb perfluorooctanoic acid in water through fluorine-fluorine interactions and hydrophobic interactions. 4. Functional groups such as amide bonds (-CO-NH-), guanidinyl groups (-CN3H4), and amino groups (-NH2) have hydrogen bonding active sites, which can further enhance the material's loading capacity for perfluorooctanoic acid through hydrogen bonding.

[0009] The technical solution of the present invention is as follows: A method for synthesizing a positively charged three-component covalent organic polymer includes the following steps: Step 1: Dissolve 0.25 mmol of 1,3,5-benzenetrihydrazide in 5 mL of the organic solvent dimethyl sulfoxide, and name it solution A; Step 2: Dissolve 0.30 mmol of 1,3-diaminoguanidine hydrochloride in solution A and name it solution B; Step 3: Dissolve 0.60 mmol of 2,3,5,6-tetrafluoro-terephthalaldehyde in solution B and name it solution C; The molar ratio of each component in solution C is: 1,3,5-benzenetricarboxylhydrazide: 1,3-diaminoguanidine hydrochloride: 2,3,5,6-tetrafluoroterephthalaldehyde = 5:6:12; Step 4: Heat solution C at 100℃ for 30 seconds to obtain an orange wet gel; Step 5: Transfer the orange wet gel obtained in Step 4 to a dialysis bag. Use distilled water as the dialysate to remove the organic solvent dimethyl sulfoxide. Dialysis time is 2-3 days. Step 6: Place the product obtained in Step 5 in a beaker and freeze it at -20℃ to -30℃. Then, put the frozen product into a vacuum dryer and dry it at -80℃ to -90℃ to obtain a powdery orange three-component covalent organic polymer. The preparation of solutions A, B, and C is carried out entirely in an electrically heated constant-temperature oil bath.

[0010] The positively charged three-component covalent organic polymer obtained by the method of this invention is used to remove perfluorooctanoic acid from water. The amount of the positively charged three-component covalent organic polymer in the water is 1.0 g / L, and the adsorption temperature is 23℃~27℃.

[0011] The beneficial effects of this invention are as follows: The synthesis method of this invention is simple, has a high synthesis yield and high synthesis efficiency. The obtained positively charged three-component covalent organic polymer has abundant functional groups on its surface, a large specific surface area, a layered porous structure and abundant reactive sites. It has a large adsorption capacity and good adsorption effect for perfluorooctanoic acid (PFOA), and can be used as an adsorbent to remove PFOA from aqueous solutions, which meets the requirements of practical water treatment.

[0012] from Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 It can be concluded that the positively charged three-component covalent organic polymer prepared by this invention has the following advantages: 1. Large specific surface area and many adsorption sites; 2. It has a hierarchical porous structure with abundant reactive sites; 3. It has a fast adsorption rate; after 30 minutes, the adsorption removal rate of perfluorooctanoic acid can reach 78.81%. 4. At 25℃, the saturated adsorption capacity for perfluorooctanoic acid can reach 68.12 mg / g. Attached Figure Description

[0013] Figure 1 These are scanning electron microscope images of the positively charged three-component covalent organic polymer synthesized in this invention; Figure 2 These are the nitrogen adsorption-desorption curves and pore size distribution diagrams of the positively charged three-component covalent organic polymer synthesized in this invention; Figure 3 This is the infrared spectrum of the positively charged three-component covalent organic polymer synthesized in this invention; Figure 4 This is an adsorption kinetic diagram of perfluorooctanoic acid on the positively charged three-component covalent organic polymer synthesized in this invention; Figure 5 This is the adsorption isotherm of perfluorooctanoic acid on the positively charged three-component covalent organic polymer synthesized in this invention. Detailed Implementation

[0014] The raw materials used to synthesize the positively charged three-component covalent organic polymer are all commercially available products.

[0015] A method for synthesizing a positively charged three-component covalent organic polymer includes the following steps: Step 1: Dissolve 0.25 mmol of 1,3,5-benzenetrihydrazide in 5 mL of the organic solvent dimethyl sulfoxide, and name it solution A; Step 2: Dissolve 0.30 mmol of 1,3-diaminoguanidine hydrochloride in solution A and name it solution B; Step 3: Dissolve 0.60 mmol of 2,3,5,6-tetrafluoro-terephthalaldehyde in solution B and name it solution C; The molar ratios of the components in solution C are as follows: 1,3,5-Benzotricarboxylhydrazide: 1,3-Diaminoguanidine hydrochloride: 2,3,5,6-Tetrafluoroterephthalaldehyde = 5:6:12; Step 4: Heat solution C at 100℃ for 30 seconds to obtain an orange wet gel; Step 5: Transfer the orange wet gel obtained in Step 4 to a dialysis bag. Use distilled water as the dialysate to remove the organic solvent dimethyl sulfoxide. Dialysis time is 2-3 days. Step 6: Place the product obtained in Step 5 in a beaker and freeze it at -20℃ to -30℃. Then, put the frozen product into a vacuum dryer and dry it at -80℃ to -90℃ to obtain a powdery orange three-component covalent organic polymer COP-101. The preparation of solutions A, B, and C is carried out entirely in an electrically heated constant-temperature oil bath.

[0016] The positively charged three-component covalent organic polymer obtained by the method of this invention is used to remove perfluorooctanoic acid from water. The amount of the positively charged three-component covalent organic polymer powder in the water is 1.0 g / L, and the adsorption temperature is 23℃~27℃.

[0017] Experiment on the adsorption and removal of perfluorooctanoic acid (PFOA) from water by a positively charged three-component covalent organic polymer: In the adsorption experiment, the adsorption kinetics of perfluorooctanoic acid (PFOA) in water were determined using the following scheme: (1) Prepare a 10 mg / L perfluorooctanoic acid solution; (2) Add 1.0 g / L of COP-101 and immediately place the reactor in a constant temperature shaker at 23℃~27℃. The samples are taken out in batches and filtered using a 0.22 μm membrane filter within a predetermined time interval. (3) The filtrate was transferred to a liquid chromatography vial, and the residual concentration of perfluorooctanoic acid (PFOA) was quantitatively determined using liquid chromatography-tandem mass spectrometry (LC-MS / MS). The final concentration was determined based on an external calibration curve established using a standard PFOA solution prepared with distilled water. The adsorption kinetics are as follows: Figure 4 As shown.

[0018] In the adsorption experiment, the adsorption isotherm of perfluorooctanoic acid (PFOA) in water was determined using the following method: (1) Prepare perfluorooctanoic acid solutions with concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 50 mg / L, 75 mg / L, 100 mg / L, 125 mg / L, 150 mg / L, and 200 mg / L respectively; (2) Add 1.0 g / L of COP-101, place the reactor in a 25°C constant temperature shaker, and take a sample after adsorption equilibrium is reached. Filter the sample using a 0.22 μm membrane filter. (3) The filtrate was transferred to a liquid chromatography bottle, and the residual concentration of perfluorooctanoic acid was quantitatively determined by liquid chromatography-tandem mass spectrometry. The final concentration was determined based on the external calibration curve established by the standard perfluorooctanoic acid solution prepared with distilled water. (4) The maximum adsorption capacity of COP-101 for perfluorooctanoic acid in aqueous solution was calculated to be 68.12 mg / g according to the Langmuir adsorption model. The adsorption isotherm is as follows: Figure 5 As shown.

[0019] Scanning electron microscope images of COP-101 synthesized by the method of this invention are as follows: Figure 1 As shown.

[0020] The nitrogen adsorption-desorption curves and pore size distribution of COP-101 synthesized by the method of this invention are as follows: Figure 2 As shown.

[0021] The infrared spectrum of COP-101 synthesized by the method of this invention is as follows: Figure 3 As shown.

Claims

1. A method for synthesizing a positively charged three-component covalent organic polymer, characterized in that: Includes the following steps: Step 1: Dissolve 0.25 mmol of 1,3,5-benzenetrihydrazide in 5 mL of the organic solvent dimethyl sulfoxide, and name it solution A; Step 2: Dissolve 0.30 mmol of 1,3-diaminoguanidine hydrochloride in solution A and name it solution B; Step 3: Dissolve 0.60 mmol of 2,3,5,6-tetrafluoro-terephthalaldehyde in solution B and name it solution C; The molar ratio of each component in solution C is: 1,3,5-benzotriacyl: 1,3-diaminoguanidine hydrochloride: 2,3,5,6-tetrafluoroterephthalaldehyde = 5:6:12; Step 4: Heat solution C at 100℃ for 30 seconds to obtain an orange wet gel; Step 5: Transfer the orange wet gel obtained in Step 4 to a dialysis bag. Use distilled water as the dialysate to remove the organic solvent dimethyl sulfoxide. Dialysis time is 2-3 days. Step 6: Place the product obtained in Step 5 in a beaker and freeze it at -20℃ to -30℃. Then, put the frozen product into a vacuum dryer and dry it at -80℃ to -90℃ to obtain a powdery orange three-component covalent organic polymer. The preparation of solutions A, B, and C is carried out entirely in an electrically heated constant-temperature oil bath.

2. The application of the positively charged three-component covalent organic polymer synthesized by the method of claim 1 in the removal of perfluorooctanoic acid from water.

3. The application of the positively charged three-component covalent organic polymer according to claim 2 in the removal of perfluorooctanoic acid from water, characterized in that: The positively charged three-component covalent organic polymer is used in water at a concentration of 1.0 g / L, with an adsorption temperature of 23℃~27℃.

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