Preparation method and application of pH and light dual-responsive beta-cyclodextrin gel

Abstract

The application relates to a preparation method and application of a pH and light dual-response beta-cyclodextrin gel. The application aims to solve the problems that the existing method consumes high cost, is easy to produce secondary pollution with stronger biochemical persistence and toxicity, cannot be reused, and has poor selective adsorption capacity for hydrophilic / hydrophobic organic matters. The method comprises the following steps: I, preparing beta-cyclodextrin methacrylic acid; II, preparing azobenzene acrylamide; III, preparing the pH and light dual-response beta-cyclodextrin gel. The pH and light dual-response beta-cyclodextrin gel is used for advanced treatment of tail water in a secondary sedimentation tank of a sewage treatment plant, and is used for removing micro-pollutants in the tail water in the secondary sedimentation tank of the sewage treatment plant. The pH and light dual-response beta-cyclodextrin gel prepared by the application can remove 50% to 85% of the micro-pollutants within 120 min.

Description

Technical Field

[0001] This invention relates to a method for preparing a gel and its application. Background Technology

[0002] Pharmaceuticals and personal care products (PPCPs) are a new type of micropollutant characterized by environmental stability, recalcitrant degradation, and bioaccumulation. They are now widely detected in urban water systems, causing damage to the ecological environment and human health. Reclaimed water is the most important source and sink of PPCP pollution in urban aquatic ecosystems (surface water, groundwater, drinking water, landscaping water, agricultural irrigation, industrial water, etc.), accounting for over 80% of PPCP pollution in urban water systems. Given my country's strategy of vigorously promoting the resource-based reuse of wastewater, research on PPCP removal technologies in reclaimed water is of great significance.

[0003] For the removal of PPCPs, ongoing research has been conducted both domestically and internationally on various methods, including coagulation and sedimentation, advanced oxidation (including ozone oxidation, hydrogen peroxide oxidation, Fenton's reagent, ferrates, photocatalysis, etc.), membrane filtration, activated carbon adsorption, and combined processes. Coagulation offers advantages such as low cost and ease of operation, but its removal rate is relatively low (<50%), and it is generally used as a pretreatment unit. Advanced oxidation technologies (AOPs) primarily utilize the strong oxidizing properties of free radicals (mainly OH·) to degrade PPCPs. This technology offers good removal efficiency but consumes a lot of energy, and the oxidation process of PPCPs easily generates secondary pollutants (oxidation byproducts) with stronger biochemical persistence and toxicity. Membrane filtration technologies (ultrafiltration UF, nanofiltration NF, reverse osmosis RO) remove micro-pollutants through the molecular retention of the membrane. NF / RO membrane filtration processes achieve PPCP removal rates of over 99%, but NF / RO systems have very high energy consumption. Activated carbon adsorption for PPCP removal is low-cost, easy to operate, produces no byproducts, and has high removal efficiency; however, the regeneration and effective recovery of the adsorbent remains a significant challenge.

[0004] As the most widely used adsorbent, activated carbon has a rich structure of adsorption sites (mainly external active sites), which can effectively remove hydrophobic PPCPs from reclaimed water. However, the following problems still exist: (1) Activated carbon has a poor removal effect on hydrophilic PPCPs, and the active sites inside the activated carbon cannot be fully utilized. (2) Reclaimed water contains a large amount of organic matter (DOM), and activated carbon has poor selective removal ability for PPCPs in the presence of DOM. (3) Activated carbon has a slow adsorption rate (usually measured in hours) and high regeneration energy consumption (high temperature heating of 500-900℃), and cannot fully restore its activity after regeneration. It can be seen that the adsorption capacity of activated carbon for PPCPs is not only related to the structural properties of the activated carbon itself, but also depends on the physicochemical properties of PPCPs in the reclaimed water (such as hydrophilicity / hydrophobicity, surface charge, etc.) and the presence of organic matter. Developing new adsorbents with faster adsorption rates, strong selective adsorption capacity for hydrophilic / hydrophobic organic matter, and easy activation and regeneration has become a research hotspot in this field. Summary of the Invention

[0005] The purpose of this invention is to address the problems of existing methods for removing PPCPs, such as high energy consumption, easy generation of secondary pollution with stronger biochemical persistence and toxicity, inability to be reused, and poor selective adsorption capacity for hydrophilic / hydrophobic organic matter. The invention provides a method for preparing and applying a pH- and light-responsive β-cyclodextrin gel.

[0006] A method for preparing a pH- and light-responsive β-cyclodextrin gel is specifically carried out according to the following steps:

[0007] I. Preparation of β-cyclodextrin methacrylic acid:

[0008] ① Dissolve β-cyclodextrin in water to obtain a β-cyclodextrin aqueous solution; adjust the pH of the β-cyclodextrin aqueous solution to alkaline, then add methacrylic anhydride to the β-cyclodextrin aqueous solution and stir to obtain a mixture;

[0009] ② Pour the mixture into acetone to precipitate, then pour the precipitate into a dialysis bag and dialyze it in distilled water to obtain the product; place the product in a freeze dryer to freeze dry, and obtain β-cyclodextrin methacrylic acid;

[0010] II. Preparation of azobenzeneacrylamide:

[0011] p-Aminoazobenzene and triethylamine were dissolved in tetrahydrofuran under ice bath conditions to obtain a mixed solution; acryloyl chloride was added to the mixed solution, and the mixture was stirred continuously under ice bath conditions. The mixture was then filtered to remove the precipitate, and the supernatant was concentrated under reduced pressure. Finally, it was recrystallized with dichloromethane to obtain azobenzene acrylamide.

[0012] III. Preparation of pH- and light-responsive β-cyclodextrin gels:

[0013] β-Cyclodextrin methacrylate was added to distilled water, followed by potassium persulfate aqueous solution. Nitrogen gas was introduced under stirring to create an inert gas environment, and the temperature was raised to 80℃–85℃. Hydroxypropyl methacrylate, acrylic acid, and azobenzene acrylamide were then added, and the mixture was stirred to react. Poly(ethylene glycol) diacrylate was then added, and the reaction was continued with stirring until the reaction was complete, yielding the reaction product. The product was washed with methanol solution, then placed in excess acetone overnight, and finally freeze-dried to obtain a pH- and light-responsive β-cyclodextrin gel.

[0014] A pH- and light-responsive β-cyclodextrin gel is used for the advanced treatment of secondary sedimentation tank effluent in wastewater treatment plants to remove micro-pollutants from the effluent.

[0015] Advantages of this invention:

[0016] I. Reversible polymer aggregates that respond to changes in light and pH are particularly promising for water remediation applications because they can capture guest molecules and can be easily separated from aqueous solutions by centrifugation or filtration. The β-cyclodextrin lumen can bind with many organic molecules to form host-guest inclusion complexes, in which contaminants with high molecular configuration and size matching with the cyclodextrin lumen and strong hydrophobicity are more easily included in the cyclodextrin lumen, thereby enabling selective removal of contaminants by cyclodextrin.

[0017] II. The pH and light-responsive β-cyclodextrin gel prepared using this invention can remove 50% to 85% of micro-contaminants within 120 minutes. Attached Figure Description

[0018] Figure 1 The bar charts show the degradation rates of ampicillin, norfloxacin, and tetracycline hydrochloride using the pH- and light-responsive β-cyclodextrin gel prepared in Example 1 in Examples 2-4. Detailed Implementation

[0019] Specific Implementation Method 1: This implementation method describes a method for preparing a pH- and light-responsive β-cyclodextrin gel, which is specifically completed according to the following steps:

[0020] I. Preparation of β-cyclodextrin methacrylic acid:

[0021] ① Dissolve β-cyclodextrin in water to obtain a β-cyclodextrin aqueous solution; adjust the pH of the β-cyclodextrin aqueous solution to alkaline, then add methacrylic anhydride to the β-cyclodextrin aqueous solution and stir to obtain a mixture;

[0022] ② Pour the mixture into acetone to precipitate, then pour the precipitate into a dialysis bag and dialyze it in distilled water to obtain the product; place the product in a freeze dryer to freeze dry, and obtain β-cyclodextrin methacrylic acid;

[0023] II. Preparation of azobenzeneacrylamide:

[0024] p-Aminoazobenzene and triethylamine were dissolved in tetrahydrofuran under ice bath conditions to obtain a mixed solution; acryloyl chloride was added to the mixed solution, and the mixture was stirred continuously under ice bath conditions. The mixture was then filtered to remove the precipitate, and the supernatant was concentrated under reduced pressure. Finally, it was recrystallized with dichloromethane to obtain azobenzene acrylamide.

[0025] III. Preparation of pH- and light-responsive β-cyclodextrin gels:

[0026] β-Cyclodextrin methacrylate was added to distilled water, followed by potassium persulfate aqueous solution. Nitrogen gas was introduced under stirring to create an inert gas environment, and the temperature was raised to 80℃–85℃. Hydroxypropyl methacrylate, acrylic acid, and azobenzene acrylamide were then added, and the mixture was stirred to react. Poly(ethylene glycol) diacrylate was then added, and the reaction was continued with stirring until the reaction was complete, yielding the reaction product. The product was washed with methanol solution, then placed in excess acetone overnight, and finally freeze-dried to obtain a pH- and light-responsive β-cyclodextrin gel.

[0027] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in the following ways: the molar ratio of β-cyclodextrin to methacrylic anhydride in step one ① is (0.6–1):(0.5–0.7); the molar ratio of β-cyclodextrin to water in step one ① is (0.6 mmol–1 mmol):(40 mL–60 mL); the pH of the β-cyclodextrin aqueous solution in step one ① is adjusted to 8–9; and the stirring time in step one ① is 20–24 hours. All other steps are the same as in Specific Implementation Method One.

[0028] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in the following ways: the molecular weight cutoff of the dialysis bag mentioned in step one (②) is 8 kDa to 14 kDa; the dialysis time mentioned in step one (②) is 24 h to 27 h, with distilled water changed every 3 h during this period; the freeze-drying temperature mentioned in step one (②) is -40℃ to -50℃, and the freeze-drying time is 12 h to 24 h. Other steps are the same as in Specific Implementation Method One or Two.

[0029] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in the following ways: the mass ratio of p-aminoazobenzene to acryloyl chloride in step two is (1.5-2.5):(1.2-1.6); the mass ratio of p-aminoazobenzene to triethylamine in step two is (1.5g-2.5g):(1.5mL-2mL); the volume ratio of triethylamine to tetrahydrofuran in step two is (1.5mL-2mL):(75mL-85mL); and the stirring is continuously carried out under ice bath conditions for 4-5 hours in step two. Other steps are the same as in Specific Implementation Methods One to Three.

[0030] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in the following ways: the mass ratio of β-cyclodextrin methacrylate to distilled water in step three is (0.5g~1g):30mL; the volume ratio of potassium persulfate aqueous solution to distilled water in step three is (2mL~4mL):30mL; and the molar ratio of hydroxypropyl methacrylate to distilled water in step three is (28mmol~29mmol):30mL. The other steps are the same as in Specific Implementation Methods One to Four.

[0031] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in the following ways: In step three, the molar ratio of hydroxypropyl methacrylate, acrylic acid, azobenzene acrylamide, and poly(ethylene glycol) diacrylate is (28 mmol–29 mmol):(58 mmol–59 mmol):(3 mmol–4 mmol):(3 mmol–4 mmol); in step three, the molar ratio of potassium persulfate to distilled water in the potassium persulfate aqueous solution is 0.0369 mmol:3 mL; and in step three, the volume ratio of methanol to water in the methanol solution is 70:30. All other steps are the same as in Specific Implementation Methods One to Five.

[0032] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the stirring reaction time in step three is 20-30 minutes, and the continued stirring reaction time is 4-6 hours; the freeze-drying temperature in step three is -40°C to -50°C, and the freeze-drying time is 12-24 hours. Other steps are the same as in Specific Implementation Methods One to Six.

[0033] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: a pH- and light-responsive β-cyclodextrin gel is used for the advanced treatment of effluent from the secondary sedimentation tank of a wastewater treatment plant, removing micro-pollutants from the effluent. Other steps are the same as in Specific Implementation Methods One to Seven.

[0034] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the pollutant is one or a mixture of several of ampicillin, norfloxacin, and tetracycline hydrochloride. The other steps are the same as in Specific Implementation Methods One to Eight.

[0035] Specific Implementation Method Ten: This implementation method utilizes a pH- and light-responsive β-cyclodextrin gel to remove contaminants from water, specifically completed according to the following steps:

[0036] pH and light-responsive β-cyclodextrin gel was added to the effluent of a secondary sedimentation tank containing micro-pollutants with a pH of 6.5–9, and then irradiated under ultraviolet light with a wavelength of 220–365 nm for 60–120 min to obtain water with pollutants removed.

[0037] The dosage of the pH and light-responsive β-cyclodextrin gel is 0.1 g / L to 1 g / L.

[0038] The concentration of micropollutants in the wastewater is 5 mg / L to 50 mg / L.

[0039] The beneficial effects of the present invention are verified using the following embodiments:

[0040] Example 1: A method for preparing a pH and light-responsive β-cyclodextrin gel, specifically completed according to the following steps:

[0041] I. Preparation of β-cyclodextrin methacrylic acid:

[0042] ① Dissolve 0.881 mmol β-cyclodextrin in 50 mL of water to obtain an aqueous solution of β-cyclodextrin; adjust the pH of the aqueous solution of β-cyclodextrin to 8 using 0.1 mol / L NaOH solution, then add 0.6 mmol methacrylic anhydride to the aqueous solution of β-cyclodextrin and stir for 24 h to obtain a mixture;

[0043] ② Pour the mixture into acetone to precipitate, then pour the precipitate into a dialysis bag and dialyze it in distilled water for 24 hours to obtain the product; place the product in a freeze dryer at -40℃ and freeze dry for at least 12 hours to obtain β-cyclodextrin methacrylic acid.

[0044] The molecular weight cutoff of the dialysis bag mentioned in step 1② is 12 kDa;

[0045] As described in step 1②, the distilled water should be changed every 3 hours during dialysis.

[0046] II. Preparation of azobenzeneacrylamide:

[0047] 2.0 g of p-aminoazobenzene and 2 mL of triethylamine were dissolved in 80 mL of tetrahydrofuran under ice bath conditions to obtain a mixed solution; 1.4 g of acryloyl chloride was added to the mixed solution, and the mixture was stirred continuously under ice bath conditions for 4.5 h. The mixture was then filtered to remove the precipitate, and the supernatant was concentrated under reduced pressure. Finally, it was recrystallized from dichloromethane to obtain azobenzene acrylamide.

[0048] III. Preparation of pH- and light-responsive β-cyclodextrin gels:

[0049] 0.5 g of β-cyclodextrin methacrylate was added to 30 mL of distilled water, followed by potassium persulfate solution (0.0369 mmol potassium persulfate dissolved in 3 mL of distilled water). Nitrogen gas was introduced under stirring to create an inert gas environment, and the temperature was raised to 80 °C. Then, 28.4 mmol of hydroxypropyl methacrylate, 58.2 mmol of acrylic acid, and 3.4 mmol of azobenzene acrylamide were added, and the mixture was stirred for 20 min. Then, 3.89 mmol of poly(ethylene glycol) diacrylate was added, and the mixture was stirred for another 5 h. The reaction was then complete, yielding the reaction product. The product was washed with methanol solution, placed in excess acetone overnight, and finally freeze-dried to obtain a pH- and light-responsive β-cyclodextrin gel.

[0050] The volume ratio of methanol to water in the methanol solution described in step three is 70:30.

[0051] The freeze-drying temperature in step three is -40℃, and the freeze-drying time is 12 hours.

[0052] The reaction formula in step three of Example 1 is as follows:

[0053]

[0054] Example 2: The removal of ampicillin from water using a pH- and light-responsive β-cyclodextrin gel was carried out according to the following steps:

[0055] The pH and light-responsive β-cyclodextrin gel prepared in Example 1 was added to the secondary sedimentation tank effluent containing ampicillin with a pH of 7.5, stirred evenly, and the pH of the wastewater was adjusted to 6.5-9. Then, it was irradiated under ultraviolet light with a wavelength of 220 nm for 120 min to obtain water with pollutants removed.

[0056] The mass ratio of the pH and light-responsive β-cyclodextrin gel to the volume of wastewater is 0.05 g: 50 mL.

[0057] The concentration of ampicillin in the wastewater was 5 mg / L.

[0058] Example 3: The removal of norfloxacin from water using a pH- and light-responsive β-cyclodextrin gel was carried out according to the following steps:

[0059] The pH and light-responsive β-cyclodextrin gel prepared in Example 1 was added to the secondary sedimentation tank effluent containing norfloxacin with a pH of 4.5, stirred evenly, and the pH of the wastewater was adjusted to 6.5-9. Then, it was irradiated under ultraviolet light with a wavelength of 278nm for 120min to obtain water with pollutants removed.

[0060] The mass ratio of the pH and light-responsive β-cyclodextrin gel to the volume of wastewater is 0.05 g: 50 mL.

[0061] The concentration of norfloxacin in the wastewater was 5 mg / L.

[0062] Example 4: The removal of tetracycline hydrochloride from water using a pH- and light-responsive β-cyclodextrin gel was carried out according to the following steps:

[0063] The pH and light-responsive β-cyclodextrin gel prepared in Example 1 was added to the effluent of a secondary sedimentation tank containing tetracycline hydrochloride at pH 2.8, stirred evenly, and the pH of the wastewater was adjusted to 6.5-9. Then, it was irradiated under ultraviolet light at a wavelength of 365nm for 120 minutes to obtain water with pollutants removed.

[0064] The mass ratio of the pH and light-responsive β-cyclodextrin gel to the volume of wastewater is 0.05 g: 50 mL.

[0065] The concentration of tetracycline hydrochloride in the wastewater was 5 mg / L.

[0066] Figure 1 The bar chart shows the degradation rates of ampicillin, norfloxacin, and tetracycline hydrochloride using pH- and light-responsive β-cyclodextrin gels in Examples 2-4.

[0067] from Figure 1 It can be seen that the pH and light-responsive β-cyclodextrin gel prepared in Example 1 has a removal efficiency of over 70% for three micro-pollutants with different acidity and alkalinity.

Claims

1. A method for preparing a pH- and light-responsive β-cyclodextrin gel, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of β-cyclodextrin methacrylic acid: ① Dissolve β-cyclodextrin in water to obtain a β-cyclodextrin aqueous solution; adjust the pH of the β-cyclodextrin aqueous solution to alkaline, then add methacrylic anhydride to the β-cyclodextrin aqueous solution and stir to obtain a mixture; The molar ratio of β-cyclodextrin to methacrylic anhydride mentioned in step 1① is (0.6~1):(0.5~0.7); ② Pour the mixture into acetone to precipitate, then pour the precipitate into a dialysis bag and dialyze it in distilled water to obtain the product; place the product in a freeze dryer to freeze dry, and obtain β-cyclodextrin methacrylic acid; II. Preparation of azobenzeneacrylamide: p-Aminoazobenzene and triethylamine were dissolved in tetrahydrofuran under ice bath conditions to obtain a mixed solution; acryloyl chloride was added to the mixed solution, and the mixture was stirred continuously under ice bath conditions. The mixture was then filtered to remove the precipitate, and the supernatant was concentrated under reduced pressure. Finally, it was recrystallized with dichloromethane to obtain azobenzene acrylamide. The mass ratio of p-aminoazobenzene to acryloyl chloride in step two is (1.5~2.5):(1.2~1.6); The mass ratio of p-aminoazobenzene to triethylamine in step two is (1.5g~2.5g):(1.5mL~2mL); III. Preparation of pH- and light-responsive β-cyclodextrin gels: β-Cyclodextrin methacrylate was added to distilled water, followed by potassium persulfate aqueous solution. Nitrogen gas was introduced under stirring to create an inert gas environment, and the temperature was raised to 80℃~85℃. Hydroxypropyl methacrylate, acrylic acid, and azobenzene acrylamide were then added, and the mixture was stirred for 20min~30min. Poly(ethylene glycol) diacrylate was then added, and the reaction was continued for 4h~6h. The reaction was then completed, yielding the reaction product. The product was washed with methanol solution, placed in excess acetone overnight, and finally freeze-dried to obtain a pH- and light-responsive β-cyclodextrin gel. The mass ratio of β-cyclodextrin methacrylate to distilled water in step three is (0.5g~1g):30mL; The molar ratio of hydroxypropyl methacrylate to distilled water in step three is (28 mmol ~ 29 mmol): 30 mL. The molar ratio of hydroxypropyl methacrylate, acrylic acid, azobenzene acrylamide and poly(ethylene glycol) diacrylate in step three is (28 mmol~29 mmol):(58 mmol~59 mmol):(3 mmol~4 mmol):(3 mmol~4 mmol).

2. The method for preparing a pH and light-responsive β-cyclodextrin gel according to claim 1, characterized in that... The volume ratio of β-cyclodextrin to water in step 1① is (0.6 mmol ~ 1 mmol): (40 mL ~ 60 mL); the pH of the β-cyclodextrin aqueous solution in step 1① is adjusted to 8 ~ 9; the stirring time in step 1① is 20 h ~ 24 h.

3. The method for preparing a pH and light-responsive β-cyclodextrin gel according to claim 1, characterized in that... The molecular weight cutoff of the dialysis bag mentioned in step 1② is 8KDa~14KDa; the dialysis time mentioned in step 1② is 24h~27h, during which the distilled water is changed every 3h; the freeze-drying temperature mentioned in step 1② is -40℃~-50℃, and the freeze-drying time is 12h~24h.

4. The method for preparing a pH and light-responsive β-cyclodextrin gel according to claim 1, characterized in that... The volume ratio of triethylamine to tetrahydrofuran in step two is (1.5 mL ~ 2 mL): (75 mL ~ 85 mL); in step two, stirring is continued under ice bath conditions for 4 h ~ 5 h.

5. The method for preparing a pH and light-responsive β-cyclodextrin gel according to claim 1, characterized in that... The volume ratio of potassium persulfate aqueous solution to distilled water in step three is (2 mL ~ 4 mL): 30 mL.

6. The method for preparing a pH and light-responsive β-cyclodextrin gel according to claim 1, characterized in that... In step three, the volume ratio of potassium persulfate to distilled water in the potassium persulfate aqueous solution is 0.0369 mmol:3 mL; in step three, the volume ratio of methanol to water in the methanol solution is 70:

30.

7. The method for preparing a pH and light-responsive β-cyclodextrin gel according to claim 1, characterized in that... The freeze-drying temperature in step three is -40℃ to -50℃, and the freeze-drying time is 12h to 24h.

8. The application of a pH- and light-responsive β-cyclodextrin gel prepared by the method described in claim 1, characterized in that... pH and light-responsive β-cyclodextrin gel is used for advanced treatment of secondary sedimentation tank effluent in wastewater treatment plants to remove micro-pollutants from the effluent; the pollutants are one or a mixture of several of ampicillin, norfloxacin, and tetracycline hydrochloride.

9. The application of a pH- and light-responsive β-cyclodextrin gel prepared by the method according to claim 1, characterized in that... The removal of contaminants from water using pH- and light-responsive β-cyclodextrin gels is accomplished through the following steps: pH and light-responsive β-cyclodextrin gel was added to the effluent of a secondary sedimentation tank containing micro-pollutants with a pH of 2.8-9 and a concentration of micro-pollutants of 5 mg / L-50 mg / L. The effluent was then irradiated with ultraviolet light at a wavelength of 220-365 nm for 60-120 minutes to obtain water with pollutants removed. The dosage of the pH and light-responsive β-cyclodextrin gel is 0.1 g / L to 1 g / L.

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