A β-cyclodextrin-polyacrylamide hydrogel based on a covalent organic skeleton and its preparation method and application

Abstract

The present invention discloses a β-cyclodextrin-polyacrylamide hydrogel based on a covalent organic skeleton and its preparation method and application, and belongs to the technical field of organic pollutant treatment. The preparation of the β-cyclodextrin-polyacrylamide / covalent organic skeleton hydrogel in the present invention is to use COF TFPB-BD and acrylamide as raw materials, and under the action of β-CD-MA cross-linking agent, ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED), vortex mixing to obtain a prepolymer solution; then the prepolymer solution is dripped into a culture plate, and the polymerization reaction is allowed to stand; then the culture plate is soaked and demoulded to obtain a yellow β-CD-PAAM / TFPB-BD hydrogel; the hydrogel has a high selectivity and removal rate for triazole pesticides, and has good salt resistance, acid resistance, alkali resistance, and is easy to recycle, and has application potential in sewage treatment in extreme environments.

Description

Technical Field

[0001] The present invention relates to a β-cyclodextrin-polyacrylamide hydrogel based on covalent organic framework, a preparation method thereof and an application thereof, and belongs to the technical field of organic pollutant treatment. Background Art

[0002] Triazole pesticides are a series of organic heterocyclic compounds, which have been used to prevent various plant diseases, especially powdery mildew, scab and rust, since the 1970s. At present, due to the excessive and unreasonable use of pesticides, they have become an influential water pollution source. And triazole pesticides have a stable structure and rarely undergo photodegradation under environmental conditions, which will cause serious environmental problems.

[0003] Existing studies have shown that wastewater, surface water and aquatic organisms have been polluted by various triazole pesticides. If humans are exposed to these environments for a long time, it will cause reproductive toxicity, hepatotoxicity and developmental toxicity, etc. Therefore, a simple, rapid and efficient method for removing triazole pesticides from water samples is crucial for controlling environmental safety and protecting human health.

[0004] So far, the commonly used methods for treating pesticide residues in sewage in the prior art include photocatalysis, biodegradation and adsorption, etc. Among these methods, photocatalysis and biodegradation have high costs, complex mechanisms, and are likely to degrade the target into another product with unknown toxicity, presenting potential risks. Adsorption is basically a mass transfer process, in which the target is transported from the mobile phase to the solid surface and adheres to the solid surface through physicochemical interactions. This technology is simple, economical, sustainable, energy-saving and environmentally friendly.

[0005] In the existing adsorption methods, most adsorbents adopt powder preparations, such as graphene oxide composites, molecularly imprinted materials, activated carbon materials, etc. Although these materials have a certain adsorption effect, they are difficult to recycle in practical applications. Currently, adsorbents based on magnetic materials such as magnetic metal organic frameworks and magnetic covalent organic frameworks have been proposed. However, although their recyclability, rapidity and high adsorption capacity are recognized in laboratory tests, it is difficult and energy-consuming to provide a corresponding strong magnetic field in large-scale sewage treatment.

[0006] Hydrogel is a three-dimensional cross-linked polymer network formed by hydrophilic polymer chains through physical or chemical interactions. In recent years, hydrogel-based adsorbents have received extensive attention due to their convenient collection, good hydrophilicity and relatively simple preparation process, and have high attractiveness and cost-effectiveness. Common hydrogels used for water treatment are those based on carboxyl or chitosan structures, but their selectivity and adsorption capacity are usually poor. Summary of the Invention

[0007] [Technical Problem]

[0008] In the prior art, there are problems such as poor selectivity for triazole pesticides and poor adsorption and removal effect of hydrogels.

[0009] [Technical Solution]

[0010] In view of the above technical problems, the present invention provides a method for synthesizing β-cyclodextrin-polyacrylamide (β-CD-PAAM / TFPB-BD) hydrogel based on covalent organic framework at room temperature, and uses the prepared hydrogel as an adsorbent for the adsorption and removal of triazole pesticides in water. This hydrogel has high selectivity and removal rate for triazole pesticides, and at the same time shows good salt tolerance, acid and alkali resistance, and is easy to recycle, and has application potential in the sewage treatment of extreme environments.

[0011] The first object of the present invention is to provide a method for preparing β-CD-PAAM / TFPB-BD hydrogel based on covalent organic framework, and the method includes the following steps:

[0012] (1) Synthesis of COF TFPB-BD

[0013] Dissolve 1,3,5-tris(4-formylphenyl)benzene (TFPB) and benzidine (BD) in a mixed solution of mesitylene and 1,4-dioxane, sonicate, seal, and let stand at room temperature for reaction. After the reaction, centrifuge and collect the precipitate, and then wash the precipitate with tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and acetone in sequence, and dry to obtain yellow powder of COF TFPB-BD;

[0014] (2) Synthesis of β-CD-MA

[0015] Dissolve β-cyclodextrin in an organic solvent, add triethylamine (TEA), then stir it in an ice bath and cool it to 0-4 °C, and dropwise add a mixed solution of methacryloyl chloride and DMF while stirring; then slowly raise the temperature to room temperature; React at room temperature, filter after the reaction, precipitate the filtrate in acetone, collect the precipitate, dry and grind to obtain β-CD-MA powder;

[0016] (3) Synthesis of β-CD-PAAM / TFPB-BD hydrogel

[0017] Dissolve the COF TFPB-BD prepared in step (1) and acrylamide (AAM) in dimethyl sulfoxide / water (DMSO / H 2In the solution of O), mix well by ultrasonic, and then add the β-CD-MA prepared in step (2) as a cross-linking agent into the solution, dissolve it by shaking, and then immediately add ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED), mix well by vortex to obtain a prepolymerization solution; drop the prepolymerization solution into a 48-well cell culture plate, and let it stand for polymerization reaction; then soak the culture plate and demold to obtain a yellow β-CD-PAAM / TFPB-BD hydrogel.

[0018] In one embodiment, the room temperature standing reaction time in step (1) is 2 to 4 days.

[0019] In one embodiment, the drying in step (1) is carried out under vacuum at 50 to 60 °C for 8 to 12 h.

[0020] In one embodiment, the volume ratio of methacryloyl chloride to DMF in step (2) is 1 to 2:1.5.

[0021] In one embodiment, the reaction time at room temperature in step (2) is 4 to 6 h.

[0022] In one embodiment, the organic solvent in step (2) is N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA).

[0023] In one embodiment, the mass ratio of acrylamide to β-CD-MA in step (3) is 1:2.5 to 10; preferably 1:10.

[0024] In one embodiment, the mass ratio of COF TFPB-BD to β-CD-MA in step (3) is 1 to 4:100.

[0025] In one embodiment, the mass ratio of COF TFPB-BD to β-CD-MA in step (3) is 1 to 2:100; preferably 1:50.

[0026] In one embodiment, the mass fraction of ammonium persulfate in step (3) is 10 to 15%.

[0027] The second object of the present invention is to provide a β-CD-PAAM / TFPB-BD hydrogel prepared by the above-mentioned method.

[0028] In one embodiment, the β-cyclodextrin-polyacrylamide hydrogel can tolerate pH 4 to 10.

[0029] In one embodiment, the β-cyclodextrin-polyacrylamide hydrogel can tolerate organic solvents.

[0030] In one embodiment, the organic solvent includes one or more of acetone, methanol, and ethanol.

[0031] In one embodiment, the β-CD-PAAM / TFPB-BD hydrogel can be reused 5 to 10 times.

[0032] The third object of the present invention is to provide an application of the β-CD-PAAM / TFPB-BD hydrogel described above in the technical field of organic pollutant treatment.

[0033] The fourth object of the present invention is to provide a method for removing triazole pesticides in sewage, which is to adsorb triazole pesticides in sewage by using the β-CD-PAAM / TFPB-BD hydrogel described above.

[0034] In one embodiment, the triazole pesticides include one or several of paclobutrazol, hexaconazole, flusilazole, propiconazole, and tebuconazole.

[0035] In one embodiment, the adsorption treatment time is 30 to 60 min.

[0036] In one embodiment, the concentration of the triazole pesticides is 20 to 50 mg / L.

[0037] The fifth object of the present invention is to provide a method for removing triazole pesticides in high-salt sewage, which is to adsorb triazole pesticides in high-salt sewage by using the β-CD-PAAM / TFPB-BD hydrogel described above.

[0038] In one embodiment, the high salt is NaCl and / or Na 2 SO 4 .

[0039] In one embodiment, the mass concentration of the salt in the high-salt wastewater is 0.5 to 2.0%.

[0040] [Beneficial effects]

[0041] The present invention provides a method for synthesizing a β-CD-PAAM / TFPB-BD hydrogel. The synthesis conditions are mild, and the size of the gel can be freely controlled by changing the size of the mold. The synthesized gel is easy to recycle, and the powdered COF material is connected to the gel network structure, which is not easy to cause material loss. In addition, the hydrogel has a fast adsorption time, good reusability, and a wide pH tolerance range. The adsorption efficiency is basically not affected by the acidity and alkalinity, and it has broad application prospects in the treatment of sewage in extreme environments. Description of the drawings

[0042] Figure 1Schematic diagram of the synthesis process of β-CD-PAAM / TFPB-BD hydrogel in Example 1 of the present invention; (a) Schematic diagram of the synthesis of COF TFPB-BD; (b) Schematic diagram of the synthesis of β-CD-PAAM / TFPB-BD hydrogel;

[0043] Figure 2 Appearance diagram of β-CD-PAAM / TFPB-BD hydrogel prepared by adjusting the amount of cross-linking agent β-CD-MA in Example 2 of the present invention;

[0044] Figure 3 Appearance diagram of β-CD-PAAM / TFPB-BD hydrogel prepared by adjusting the amount of COF TFPB-BD in Example 3 of the present invention;

[0045] Figure 4 (a) Scanning electron micrograph and (b) physical picture of the COF TFPB-BD powder prepared in Example 1 of the present invention;

[0046] Figure 5 Cross-sectional scanning electron micrographs of 4 hydrogels prepared in Example 1 of the present invention and Comparative Examples 1 to 3; (a) PAAM gel; (b) PAAM / TFPB-BD gel (1000×); (c) PAAM / TFPB-BD gel (4000×); (d) β-CD-PAAM gel; (e) β-CD-PAAM / TFPB-BD gel (300×); (f) β-CD-PAAM / TFPB-BD gel (3000×);

[0047] Figure 6 FT-IR diagram of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention;

[0048] Figure 7 Adsorption schematic diagram of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention for triazole pesticides;

[0049] Figure 8 Comparison data diagram of the removal rates of triazole pesticides by 4 hydrogels prepared in Example 1 and Comparative Examples 1 to 3;

[0050] Figure 9 XPS full-scan spectra of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention (a) before adsorption and (b) after adsorption;

[0051] Figure 10 Effect diagram of salt concentration on the removal of β-CD-PAAM / TFPB-BD hydrogel in Example 5 of the present invention;

[0052] Figure 11Data graph of the acid and alkali resistance performance of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention;

[0053] Figure 12 Data graph of the organic solvent resistance performance of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention; (a) Data graph of the influence of soaking in different organic solvents on the adsorption efficiency of the β-CD-PAAM / TFPB-BD hydrogel; (b) Physical diagram of the β-CD-PAAM / TFPB-BD hydrogel after soaking in different organic solvents;

[0054] Figure 13 Data graph of the cycling performance of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention;

[0055] Figure 14 Chromatograms of the simulated removal of triazole pesticides from actual (a) lake water and (b) wastewater samples by the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 of the present invention. Detailed implementation manners

[0056] The present invention will be further described in detail below in conjunction with specific embodiments.

[0057] Example 1

[0058] A preparation method of a covalent organic framework-based β-cyclodextrin-polyacrylamide (β-CD-PAAM / TFPB-BD) hydrogel (the process flow is as Figure 1 shown), the method includes the following steps:

[0059] (1) Dissolve 62.5 mg, 0.16 mmol of 1,3,5-tris(4-formylphenyl)benzene (TFPB) and 44.2 mg, 0.24 mmol of benzidine (BD) in 6 mL of a mixed solution of mesitylene and 1,4-dioxane (volume ratio 1:1), ultrasonically disperse for 10 min, then slowly add 0.6 mL of 6 mol / L acetic acid solution, then seal, and react at room temperature for 3 days; then centrifuge to collect the yellow precipitate, wash successively with tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and acetone, and collect the powder and vacuum dry at 60 °C for 12 h to obtain yellow COF TFPB-BD powder;

[0060] (2) Vacuum dry β-cyclodextrin (β-CD) at 80 °C for one day. Take the dried β-CD (3.9 g, 3.4 mmol) and dissolve it in 30 mL of DMF. Then add triethylamine (TEA) (3.4 mL, 24.4 mmol). Stir the reaction mixture in an ice bath and cool it to 0 °C. While stirring, dropwise add methacryloyl chloride (2.0 mL, 20.5 mmol) and DMF (1.5 mL). Then slowly raise the temperature to room temperature and stir the reaction for 4 h. Filter the mixture, precipitate the filtrate in 200 mL of acetone, filter and collect the precipitate, and vacuum dry it at 60 °C. Then grind the dried solid, redissolve it in 5 mL of DMF, and precipitate it again in 50 mL of acetone. Filter and collect the precipitate, vacuum dry it at 60 °C, and then grind the dried solid to obtain β-CD-MA powder.

[0061] (3) Take 20 mg of the COF TFPB-BD prepared in step (1) and 0.1 g of acrylamide (AAM) and dissolve them in 1 mL of DMSO / H 2 O (v / v = 1 / 1) solution (the mass fraction of COF TFPB-BD is 2%, w / v%). Ultrasonic for 3 min to fully dissolve and disperse it. Then add 1.0 g of the β-CD-MA prepared in step (2) as a crosslinking agent and shake to dissolve for 1 min. Immediately add 25 μL of ammonium persulfate (APS) (mass fraction = 10%) and 5 μL of N,N,N',N'-tetramethylethylenediamine (TEMED), vortex and mix well to form a prepolymerization solution. Then take 200 μL of the prepolymerization solution and drop it into a 48-well cell culture plate respectively, and let it stand and polymerize for 30 min. Finally, soak the well plate in deionized water for 1 day, then demold the hydrogel and soak it in deionized water for 2 days to fully wash away the residual unreacted monomers, and finally obtain a yellow β-CD-PAAM / TFPB-BD hydrogel.

[0062] Example 2 Optimization of the amount of crosslinking agent β-CD-MA

[0063] The difference from Example 1 is only that the addition amount of β-CD-MA in step (3) is adjusted to 0.25 g, 0.5 g, and 0.75 g respectively, and other conditions are the same as those in Example 1; prepare β-CD-PAAM / TFPB-BD hydrogel.

[0064] The results are as Figure 2 shown: As the addition amount of β-CD-MA gradually increases, the structure of the hydrogel gradually changes from soft and collapsed to stable. When the mass of β-CD-MA reaches 1.0 g (i.e., w AAM : w β-CD-MA = 1:10), the synthesized hydrogel has a round appearance, good water retention, and is not easy to collapse in a dry environment.

[0065] Example 3 Optimization of the Usage Amount of COF TFPB-BD

[0066] The difference from Example 1 is only that the addition amounts of COF TFPB-BD in step (3) are adjusted to be 10 mg (1%), 30 mg (3%), and 40 mg (4%) respectively, and other conditions are the same as those in Example 1; β-CD-PAAM / TFPB-BD hydrogel is prepared.

[0067] The results are as Figure 3 shown: when the amount of COF TFPB-BD gradually increases, the color of the gel gradually changes from light yellow to dark yellow; when the amount of COF TFPB-BD exceeds 2% (w / v%) (20 mg), the gel structure begins to collapse, and there is more COF powder residue on the mold after demolding, indicating that the β-CD-PAAM / TFPB-BD hydrogel can carry a maximum amount of COF TFPB-BD of about 2%.

[0068] Comparative Example 1 Preparation of PAAM Hydrogel

[0069] Dissolve 0.1 g of acrylamide (AAM) in 1 mL of DMSO / H 2 O (v / v = 1 / 1) solution, ultrasonicate for 3 min to fully dissolve and disperse it; then add 5.6 mg of commercially available N,N'-methylenebisacrylamide (MBA) as a crosslinking agent and shake to dissolve for 1 min; immediately add 25 μL of ammonium persulfate (APS) (mass fraction = 10%) and 5 μL of N,N,N',N'-tetramethylethylenediamine (TEMED), vortex and mix well to form a prepolymerization solution; then take 200 μL of the prepolymerization solution and drop it into a 48-well cell culture plate respectively, and let it stand and polymerize for 30 min; finally, soak the well plate in deionized water for 1 day, then demold the hydrogel and soak it in deionized water for 2 days to fully wash away the residual unreacted monomers, and finally obtain a transparent PAAM hydrogel.

[0070] Comparative Example 2 Preparation of PAAM / TFPB-BD Hydrogel

[0071] Take 20 mg of COF TFPB-BD prepared in step (1) and 0.1 g of acrylamide (AAM) and dissolve them in 1 mL of DMSO / H 2In an O(v / v = 1 / 1) solution (the mass fraction of COF TFPB-BD is 2%, w / v%), ultrasonicate for 3 min to fully dissolve and disperse it; then add 5.6 mg of commercially available N,N'-methylenebisacrylamide (MBA) as a crosslinking agent and shake to dissolve for 1 min; immediately add 25 μL of ammonium persulfate (APS) (mass fraction = 10%) and 5 μL of N,N,N',N'-tetramethylethylenediamine (TEMED), vortex to mix evenly to form a pre-polymerization solution; then take 200 μL of the pre-polymerization solution and drop it into a 48-well cell culture plate respectively, and let it stand for polymerization for 30 min; finally, soak the well plate in deionized water for 1 day, then demold the hydrogel and soak it in deionized water for 2 days to fully wash away the residual unreacted monomers, and finally obtain a yellow PAAM / TFPB-BD hydrogel.

[0072] Preparation of β-CD-PAAM hydrogel in Comparative Example 3

[0073] Dissolve 0.1 g of acrylamide (AAM) in 1 mL of DMSO / H 2 O(v / v = 1 / 1) solution, ultrasonicate for 3 min to fully dissolve and disperse it; then add 1.0 g of β-CD-MA prepared in step (2) as a crosslinking agent and shake to dissolve for 1 min; immediately add 25 μL of ammonium persulfate (APS) (mass fraction = 10%) and 5 μL of N,N,N',N'-tetramethylethylenediamine (TEMED), vortex to mix evenly to form a pre-polymerization solution; then take 200 μL of the pre-polymerization solution and drop it into a 48-well cell culture plate respectively, and let it stand for polymerization for 30 min; finally, soak the well plate in deionized water for 1 day, then demold the hydrogel and soak it in deionized water for 2 days to fully wash away the residual unreacted monomers, and finally obtain a transparent β-CD-PAAM hydrogel

[0074] Material characterization

[0075] Take the COF TFPB-BD material synthesized in step (1) of Example 1 for scanning electron microscope (SEM) characterization. As Figure 4 shown in a, the microscopic morphology of the COF TFPB-BD material is spherical with a diameter of about 2 μm, indicating the successful synthesis of the material; the appearance of the COF TFPB-BD material is yellow powder ([[]] Figure 4 b).

[0076] Perform SEM characterization on the internal morphology of the hydrogels prepared in Example 1 and Comparative Examples 1 - 3; the results are as Figure 5 shown:

[0077] The pore size of the β-CD-PAAM (Comparative Example 3) gel with β-CD-MA as the crosslinking agent ( Figure 5 d) is significantly larger than that of the PAAM gel (Figure 5 a), indicating that the addition of β-CD-MA enlarges the pores of the gel, promotes the flow of water, and increases the contact area between the target substance and the adsorbent. In the local magnification Figure 5 c and 5f, spherical materials with a diameter of about 2 μm were observed, which were consistent with the morphology of COF TFPB-BD( Figure 4 a), indicating that COF TFPB-BD had been successfully incorporated.

[0078] The chemical composition and structural information of the β-CD-PAAM / TFPB-BD gel were characterized by FT-IR, and the results were as Figure 6 shown. The N-H stretching vibration peak of the hydrogel material at 3300 - 3400 cm -1 corresponded to the amino group in the hydrogel monomer AAM, and the C=N stretching vibration peak at 1618 cm -1 corresponded to COF TFPB-BD. The C=O stretching vibration peak at 1686 cm -1 corresponded to the hydrogel monomer AAM and COF TFPB-BD, and the α-(1→4) glucosyl ring at 942 cm -1 corresponded to β-CD. Multiple characteristic peaks indicated the successful synthesis of the composite material.

[0079] Example 4

[0080] Application of the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 in the adsorption and removal of triazole pesticides

[0081] One hydrogel prepared in Example 1 and those prepared in Comparative Examples 1 - 3 were respectively put into 10 mL of sample solutions of paclobutrazol, hexaconazole, flusilazole, propiconazole, and tebuconazole with a concentration of 20 mg / L, and statically adsorbed for 50 min. After adsorption, the remaining water samples were taken, dried with nitrogen, redissolved with methanol, filtered through a 0.22 μm nylon filter membrane to obtain sample solutions, and the concentrations of pesticides in the sample solutions were measured to calculate the removal rate.

[0082] The flow chart of the specific adsorption treatment was as Figure 7 shown. The removal effects of PAAM hydrogel, PAAM / TFPB-BD hydrogel, β-CD-PAAM hydrogel, and β-CD-PAAM / TFPB-BD hydrogel as adsorbents on triazole pesticides in water; the results were as Figure 8As shown in Table 1, the removal rate of triazole pesticides by PAAM hydrogel is relatively low. After compounding with COF TFPB-BD or using β-CD-MA as a cross-linking agent, the removal rate of triazole pesticides has increased significantly. The reason may be that COF TFPB-BD can adsorb triazole pesticides through π-π interactions, hydrogen bonds, etc., and β-CD can adsorb triazole pesticides through host-guest interactions, both of which enhance the hydrogel adsorption ability of PAAM to varying degrees. When β-CD and COF TFPB-BD are combined, the adsorption rate of the synthesized β-CD-PAAM / TFPB-BD hydrogel for triazole pesticides is further improved. The reason may be that on the one hand, COF TFPB-BD and β-CD can co-adsorb triazole pesticides, and on the other hand, the pore size of the hydrogel synthesized with β-CD-MA as a cross-linking agent becomes larger, promoting the flow of water, thereby increasing the contact area between the adsorbent and the target, enhancing the adsorption effect.

[0083] Table 1 Comparison of the removal rates of triazole pesticides by 4 hydrogels

[0084]

[0085] To prove the successful adsorption of triazole pesticides, XPS elemental analysis was performed on the β-CD-PAAM / TFPB-BD gel before and after adsorption; as Figure 9 shown, the proportions of C and N elements in the β-CD-PAAM / TFPB-BD gel after adsorption increased significantly, indicating that triazole pesticides have been successfully adsorbed.

[0086] Example 5

[0087] Removal of triazole pesticides by the β-CD-PAAM / TFPB-BD hydrogel prepared in Example 1 in high-salt solutions.

[0088] Prepare 20 mg / L triazole pesticide solutions containing 0.0% - 2.0% (by mass) of NaCl respectively; then take one hydrogel from Example 1 and put it into 10 mL of the sample solution respectively, and perform static adsorption for 50 min; after adsorption, take the remaining water sample, dry it with nitrogen, re-dissolve it with methanol, filter it through a 0.22 μm nylon filter membrane to obtain the sample solution, measure the concentration of pesticides in the sample solution, and calculate the removal rate.

[0089] The results are as Figure 10 shown, the removal rate of triazole pesticides first increases and then decreases with the increase of salt concentration. When the salt concentration is 1%, the removal efficiency for 5 triazole pesticides is better. The reason may be that on the one hand, the increase in salt concentration will reduce the solubility of the target through the salting-out effect, which is beneficial to adsorption; on the other hand, when the salt concentration further increases, the viscosity of the solution will also increase, thus restricting the mass transfer of the target. In addition, with the increase of salt concentration, Na+ It may also occupy more adsorption sites, resulting in a decrease in the removal rate.

[0090] Performance determination of β-CD-PAAM / TFPB-BD hydrogel

[0091] 1. Acid and alkali resistance performance determination

[0092] Take triazole pesticides with a concentration of 20 mg / L respectively, then adjust the pH to 4 - 10. Then take one hydrogel from Example 1 and put it into 10 mL of the sample solution respectively, and perform static adsorption for 50 min; after adsorption, take the remaining water sample, dry it with nitrogen, redissolve it with methanol, filter it through a 0.22 μm nylon filter membrane to obtain the sample solution, measure the concentration of pesticides in the sample solution, and calculate the removal rate.

[0093] The results are as Figure 11 shown. In the range of pH 4 - 10, pH has almost no effect on the removal rate of triazole pesticides. It shows that this hydrogel has good acid and alkali resistance and has the potential to be used in sewage treatment under extreme conditions.

[0094] 2. Organic solvent tolerance performance determination

[0095] To further explore the potential of β-CD-PAAM / TFPB-BD hydrogel in applications under extreme environments, the solvent tolerance was tested. The β-CD-PAAM / TFPB-BD hydrogel was soaked in common organic reagents acetone, methanol, and ethanol overnight, and then rehydrated with deionized water for 24 h before being used to remove triazole pesticides.

[0096] Take the rehydrated hydrogels and put them into 10 mL of 20 mg / L triazole pesticide sample solutions respectively, and perform static adsorption for 50 min; after adsorption, take the remaining water sample, dry it with nitrogen, redissolve it with methanol, filter it through a 0.22 μm nylon filter membrane to obtain the sample solution, measure the concentration of pesticides in the sample solution, and calculate the removal rate.

[0097] The results are as Figure 12 shown; the β-CD-PAAM / TFPB-BD hydrogel shrinks to varying degrees after being soaked in organic solvents ( Figure 12 b), because organic solvents will compete for the water in the hydrogel, causing it to dehydrate and become smaller; and when the dehydrated hydrogel is put into water again, its morphology can be rehydrated and restored, and it can also be used to remove triazole pesticides. The results are shown in Figure 12 a. The removal rate of triazole pesticides by the β-CD-PAAM / TFPB-BD hydrogel after being soaked in organic solvents does not change significantly, indicating that it has good organic solvent tolerance.

[0098] 3. Reusability

[0099] The β-CD-PAAM / TFPB-BD hydrogel was soaked in a methanol solution overnight and then immersed in deionized water for two days for rehydration regeneration. The regenerated β-CD-PAAM / TFPB-BD hydrogel was put into a 10 mL 20 mg / L triazole pesticide sample solution and statically adsorbed for 50 min. After adsorption, the remaining water sample was taken, dried with nitrogen, redissolved in methanol, filtered through a 0.22 μm nylon filter membrane to obtain a sample solution, and the concentration of the pesticide in the sample solution was measured to calculate the removal rate.

[0100] As Figure 13 shown, after 5 adsorption-desorption cycles, the removal efficiency of the β-CD-PAAM / TFPB-BD hydrogel for triazole pesticides did not change significantly, indicating its good reusability.

[0101] 4. Influence of actual sample matrix effect

[0102] Lake water and wastewater in the environment were taken as experimental water samples to simulate the actual feasibility of removing triazole pesticides. The concentrations of all target substances in the actual lake water and wastewater were lower than the LOD value of this detection method; further, 10 mg / mL -1 and 20 mg / mL -1 of triazole pesticides were spiked into the lake water and wastewater respectively, and each sample was repeated 3 times; a simulated removal experiment was carried out to explore the influence of the matrix effect; after one removal, the removal rates of the 5 triazole pesticides were: lake water: 72.3%-86.2%, wastewater: 74.2%-83.9% ( Figure 14 , Table 2); on this basis, the spiked water samples were removed for a second time, and the removal rates were: lake water: 80.8%-99.0%, wastewater: 79.4%-99.0% ( Figure 14 , Table 3).

[0103] The results show that the matrix effect of the actual sample has no significant influence on the adsorption capacity of the β-CD-PAAM / TFPB-BD hydrogel, and most triazole pesticides can be reliably removed from the actual sample, and the removal rate can be close to 100% after multiple removals.

[0104] Table 2 Simulated removal rate of triazole pesticides by β-CD-PAAM / TFPB-BD hydrogel in actual water samples (first time)

[0105]

[0106] Table 3 Simulated removal rate of triazole pesticides by β-CD-PAAM / TFPB-BD hydrogel in actual water samples (second time)

[0107]

[0108] > 99.0 1 : The actual detected amount is less than the detection limit and is calculated as equal to the detection limit, and the removal rate is 99.0%

[0109] > 98.4 2 : The actual detected amount is less than the quantification limit and is calculated as equal to the quantification limit, and the removal rate is 98.4%

[0110] Although the present invention has been disclosed above in a preferred embodiment, it is not intended to limit the present invention. Any person familiar with this technology can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims

1. A method for preparing β-CD-PAAM / TFPB-BD hydrogel based on a covalent organic skeleton, characterized in that: The method comprises the following steps: (1) Synthesis of COF TFPB-BD 1,3,5-tri(4-formylphenyl)benzene TFPB and benzidine BD were dissolved in a mixed solution of mesitylene and 1,4-dioxane, ultrasonicated, sealed, and allowed to stand at room temperature for reaction. After the reaction, centrifuged, the precipitate was collected, and then washed with tetrahydrofuran THF, N,N-dimethylformamide DMF and acetone in sequence, and dried to obtain COF TFPB-BD yellow powder. (2) Synthesis of β-CD-MA Dissolve β-cyclodextrin in an organic solvent, add triethylamine TEA, then stir in an ice bath and cool to 0-4°C, add a mixed solution of methacryloyl chloride and DMF dropwise while stirring; then slowly raise the temperature to room temperature; react at room temperature, filter after the reaction, precipitate the filtrate in acetone, collect the precipitate, dry, and grind to obtain β-CD-MA powder; (3) Synthesis of β-CD-PAAM / TFPB-BD hydrogel The COF TFPB-BD and acrylamide AAM prepared in step (1) are dissolved in a dimethyl sulfoxide / water solution, and ultrasonically mixed. Then, the β-CD-MA prepared in step (2) is added to the solution as a crosslinking agent, and the mixture is shaken to dissolve. Then, ammonium persulfate APS and N,N,N',N'-tetramethylethylenediamine TEMED are immediately added, and the mixture is vortexed to mix, thereby obtaining a prepolymer solution. The prepolymer solution was dropped into a 48-well cell culture plate, and the polymerization reaction was allowed to stand; the culture plate was then immersed and demolded to obtain a yellow β-CD-PAAM / TFPB-BD hydrogel; the mass ratio of acrylamide to β-CD-MA was 1:2.5-10; the mass ratio of COF TFPB-BD to β-CD-MA was 1-2:

100.

2. The method according to claim 1, characterized in that The organic solvent in step (2) is N,N-dimethylformamide or N,N-dimethylacetamide.

3. β-CD-PAAM / TFPB-BD hydrogel prepared by the method described in any one of claims 1 or 2.

4. Use of the β-CD-PAAM / TFPB-BD hydrogel according to claim 3 in the treatment of organic pollutants.

5. A method for removing triazole pesticides from sewage, characterized in that: The method comprises using the β-CD-PAAM / TFPB-BD hydrogel described in claim 3 to adsorb triazole pesticides in sewage.

6. The method for removing triazole pesticides from sewage according to claim 5, characterized in that: The triazole pesticides include one or more of paclobutrazol, hexaconazole, flusilazole, propiconazole and tebuconazole.

7. A method for removing triazole pesticides from high-salinity wastewater, characterized in that: The method comprises using the β-CD-PAAM / TFPB-BD hydrogel described in claim 3 to adsorb triazole pesticides in high-salt wastewater.

8. The method for removing triazole pesticides from high-salinity sewage according to claim 7, characterized in that: The mass concentration of salt in the high-salt wastewater is 0.5-2.0%.

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