Cyclodextrin-based adsorbing hydrogel, its preparation method and application

Abstract

This invention provides a cyclodextrin-based adsorbent hydrogel, its preparation method, and its application, belonging to the field of adsorption material technology. The preparation method of the cyclodextrin-based adsorbent hydrogel includes the following steps: mixing acrylic acid with a neutralizing agent and then performing a neutralization reaction; subsequently, adding α-cyclodextrin, carboxymethyl chitosan, sodium 4-styrene sulfonate, a crosslinking agent, and an initiator to the reaction system, and carrying out a free radical polymerization reaction to obtain the cyclodextrin-based adsorbent hydrogel. The cyclodextrin-based adsorbent hydrogel prepared by this invention has a maximum adsorption capacity of over 800 mg / g for low concentrations of norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions, and copper ions. Within 3 hours, the removal rate of norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions, and copper ions can reach over 85%. Compared with commonly available multifunctional adsorbent materials, it not only has extremely high adsorption performance and removal efficiency but also a faster adsorption rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorption materials, in particular to a cyclodextrin-based adsorption hydrogel and a preparation method and application thereof. BACKGROUND

[0002] Environmental pollution has become a major challenge to the ecosystem, mainly due to the large amount of discharge of domestic sewage and industrial wastewater, leading to the continuous accumulation of pollutants in the soil and rivers. Common pollutants in the environment include heavy metals, dyes and organic pollutants, which not only enrich in plants, but also circulate through the food chain, directly or indirectly into the human body, posing a potential threat to human health. In order to address this problem, a variety of pollutant treatment technologies have been studied, including advanced oxidation processes, membrane technology, coagulation sedimentation method, and adsorption method. However, most of these methods have limitations such as high cost, difficult operation, and poor biodegradability, compared with the adsorption method which is widely concerned due to its simple operation, high efficiency and superior economy. However, the current adsorption materials generally have small adsorption capacity, which makes it difficult to achieve effective removal of pollutants. SUMMARY

[0003] Therefore, the present application aims to provide a cyclodextrin-based adsorption hydrogel and a preparation method and application thereof.

[0004] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] One of the technical solutions of the present application is a preparation method of a cyclodextrin-based adsorption hydrogel, comprising the following steps:

[0006] After mixing the acrylic acid and the neutralizing agent, a neutralization reaction is carried out, and then the reaction system is added with alpha-cyclodextrin, carboxymethyl chitosan, sodium 4-styrene sulfonate, a crosslinking agent and an initiator to carry out a free radical polymerization reaction, thereby obtaining the cyclodextrin-based adsorption hydrogel.

[0007] The second technical solution of the present application is a cyclodextrin-based adsorption hydrogel prepared by the above-mentioned preparation method.

[0008] The third technical solution of the present application is the application of the above-mentioned cyclodextrin-based adsorption hydrogel in adsorbing wastewater pollutants; the pollutants are antibiotics, dyes or heavy metals.

[0009] The present application discloses the following technical effects:

[0010] The prepared cyclodextrin-based adsorption hydrogel adsorbent has a maximum adsorption capacity of 800mg / g or more for norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions and copper ions at a low concentration, and has a high removal rate for norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions and copper ions within 3h, compared with common multifunctional adsorbents on the market, and has extremely high adsorption performance and removal efficiency, and a fast adsorption rate. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0012] Figure 1 Preparation schematic diagram of cyclodextrin adsorption hydrogel;

[0013] Figure 2 Infrared spectrum of cyclodextrin-based adsorption hydrogel obtained in Example 1;

[0014] Figure 3 XRD diagram of cyclodextrin-based adsorption hydrogel obtained in Example 1;

[0015] Figure 4 Scanning electron microscope diagram of cyclodextrin-based adsorption hydrogel obtained in Example 1. DETAILED DESCRIPTION

[0016] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0017] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the range, and any other stated value or intermediate value in the range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict, the content of the present specification will control.

[0019] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0020] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more other elements can be added or otherwise included.

[0021] Cyclodextrin (CD) is a cyclic oligosaccharide obtained by amylase degradation. The hydrophobic cavity structure of cyclodextrin enables it to match molecules of appropriate size and polarity and form host-guest interactions, especially showing significant adsorption capacity for aromatic organic pollutants. The rich hydroxyl groups on its surface can also form coordination complexes and electrostatic attraction with heavy metal ions, which can explain the potential of cyclodextrin-based adsorbents in achieving efficient adsorption of organic pollutants and heavy metals.

[0022] Carboxymethyl chitosan (CMS) is a chemical modified derivative of chitosan. Its active functional groups (amine, hydroxyl, carboxyl) can interact with heavy metal ions and organic pollutants through chelation, electrostatic attraction and hydrogen bonding, thereby improving adsorption efficiency.

[0023] The present application introduces alpha-CD into CMS to compensate for the shortcomings of CMS in organic pollutant adsorption. The cyclodextrin-based composite hydrogel has application potential in the field of simultaneous adsorption of multiple pollutants.

[0024] The present application provides a preparation method of a cyclodextrin-based adsorption hydrogel, comprising the following steps:

[0025] After mixing acrylic acid (AA) with a neutralizing agent and performing a neutralization reaction, alpha-cyclodextrin (alpha-CD), carboxymethyl chitosan (CMS), sodium 4-styrene sulfonate (SS), a crosslinking agent and an initiator are added to the reaction system to perform a free radical polymerization reaction, thereby obtaining the cyclodextrin-based adsorption hydrogel.

[0026] In a preferred embodiment of the present invention, the neutralizing agent is sodium hydroxide; the amount of the neutralizing agent is added according to the degree of neutralization of acrylic acid being 5-30%.

[0027] In a preferred embodiment of the present invention, the neutralizing agent is added in an amount of 5-20% based on the degree of neutralization of acrylic acid.

[0028] In a preferred embodiment of the present invention, the neutralizing agent is added in an amount equal to 10% of the degree of neutralization of acrylic acid.

[0029] In this invention, if the degree of neutralization of acrylic acid exceeds the above parameter range, the adsorption performance of the resulting cyclodextrin-based adsorption hydrogel will be significantly reduced.

[0030] In a preferred embodiment of the present invention, the molar ratio of acrylic acid and sodium 4-styrenesulfonate is 1:1 to 13:1.

[0031] In a preferred embodiment of the present invention, the molar ratio of acrylic acid and sodium 4-styrenesulfonate is 7:1 to 10:1.

[0032] In a preferred embodiment of the present invention, the molar ratio of acrylic acid and sodium 4-styrenesulfonate is 8:1.

[0033] In this invention, if the molar ratio of acrylic acid and sodium 4-styrenesulfonate exceeds the above range, the adsorption performance of the resulting cyclodextrin-based adsorption hydrogel for norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions and copper ions will be significantly reduced.

[0034] In a preferred embodiment of the present invention, the amount of α-cyclodextrin used is 0.1% to 1.2% of the total molar amount of acrylic acid and sodium 4-styrenesulfonate.

[0035] In a preferred embodiment of the present invention, the amount of α-cyclodextrin used is 0.6% to 0.8% of the total molar amount of acrylic acid and sodium 4-styrenesulfonate.

[0036] In a preferred embodiment of the present invention, the molar ratio of α-cyclodextrin to carboxymethyl chitosan is 3:1 to 4:1. In this invention, the prepared cyclodextrin-based adsorption hydrogel primarily targets the selective adsorption of small-molecule organic pollutants. Since the cavity of α-cyclodextrin is well-matched with the aromatic groups of small molecules, α-cyclodextrin is selected in this invention. Carboxymethyl chitosan is soluble in water and has more adsorption sites than regular chitosan; therefore, carboxymethyl chitosan is chosen in this invention.

[0037] In a preferred embodiment of the present invention, the crosslinking agent is N,N'-methylenebisacrylamide; the initiator is potassium persulfate; the crosslinking agent is 0.05% to 0.5% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate; and the initiator is 0.1% to 0.8% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate.

[0038] In a preferred embodiment of the present invention, the crosslinking agent is 0.2% to 0.3% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate; and the initiator is 0.6% to 0.7% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate.

[0039] In this invention, if the amount of crosslinking agent exceeds the above parameter range, the adsorption performance of the obtained cyclodextrin-based adsorption hydrogel on pollutants will be reduced.

[0040] If the amount of initiator is higher than the above parameters, the polymerization reaction will be too fast, thereby reducing the adsorption capacity of the resulting cyclodextrin-based adsorption hydrogel for norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions and copper ions.

[0041] In a preferred embodiment of the present invention, the temperature of the free radical polymerization reaction is 70-80°C and the time is 30-40 min.

[0042] A second aspect of the present invention provides a cyclodextrin-based adsorbed hydrogel prepared by the above preparation method.

[0043] The adsorbent prepared by this invention contains a large number of hydroxyl, carboxyl and sulfonic acid groups, which generate hydrogen bonds and electrostatic interactions with pollutant molecules, while α-cyclodextrin can form host-guest inclusion interactions with antibiotic and dye molecules.

[0044] A third aspect of the present invention provides an application of the above-mentioned cyclodextrin-based adsorption hydrogel in the adsorption of pollutants in wastewater; the pollutants are antibiotics, dyes, or heavy metals.

[0045] In a preferred embodiment of the present invention, the antibiotic is at least one of norfloxacin, tetracycline hydrochloride, and procaine; the dye is methylene blue; and the heavy metal is manganese ions and / or copper ions.

[0046] In a preferred embodiment of the present invention, the amount of cyclodextrin-based adsorbent hydrogel used is: 20-25 mg of cyclodextrin-based adsorbent hydrogel is added to every 20 ml of wastewater.

[0047] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0048] In the examples, the removal rate (%) and adsorption capacity (Qe) (mg / g) were calculated using the following formulas:

[0049]

[0050] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] 0.3501 g of sodium hydroxide was dissolved in 3 mL of deionized water and mixed thoroughly with 6 mL of AA for neutralization (degree of neutralization 10%). Then, 2.2552 g of sodium 4-styrene sulfonate (molar ratio of AA to sodium 4-styrene sulfonate was 8:1), 0.01 g of carboxymethyl chitosan, and 0.1158 g of α-cyclodextrin were added to the reaction system. The resulting solution was placed in a three-necked flask and stirred. Nitrogen gas was introduced into the system, and when the temperature reached 75 °C, 0.044 g of N,N'-methylenebisacrylamide was added and stirred for 10 min. Finally, 0.1597 g of potassium persulfate was added, and the polymerization reaction was carried out for 20 min. After the reaction was completed, the product was washed with anhydrous ethanol, dried at 60 °C, and pulverized to obtain adsorbent particles (i.e., cyclodextrin-based adsorbent hydrogel).

[0053] like Figure 2 , 3 As shown in the infrared spectrum, XRD spectrum, and scanning electron microscope image of α-cyclodextrin, the characteristic peaks of α-cyclodextrin are obvious, proving that the material was successfully synthesized.

[0054] Adsorption performance test: Under pH 5 conditions, 20 mg of adsorbent was added to 20 ml solutions of norfloxacin (10 mg / ml), tetracycline hydrochloride (2.5 mg / ml), procaine (10 mg / ml), methylene blue (500 mg / ml), manganese ions (10 mg / ml), and copper ions (25 mg / ml) for adsorption performance testing. After 3 hours, the adsorption of each pollutant by the adsorbent reached a basic stable state, and the pollutant removal rate was measured at this point. The results showed that within 3 hours, the removal rates of 10 mg / L norfloxacin, 2.5 mg / L tetracycline hydrochloride, 10 mg / L procaine, 500 mg / L methylene blue, 10 mg / L manganese ions, and 25 mg / L copper ions were 99.6%, 84.8%, 97.1%, 99.6%, 97.6%, and 99.2%, respectively. For pollutants with an initial concentration of 2000 mg / L, the maximum adsorption capacities of this adsorption hydrogel for norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions, and copper ions can reach 861.48, 924.94, 829.84, 1667.52, 1054.87, and 1226.00 mg / g, respectively.

[0055] Example 2

[0056] The only difference from Example 1 is that the molar ratio of AA and sodium 4-styrenesulfonate is adjusted from "8:1" to "10:1". All other steps and parameters are the same as in Example 1.

[0057] The adsorption performance of the hydrogel obtained in this embodiment was tested in the same way as in Example 1. The results showed that the adsorption hydrogel removed norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions and copper ions from the solution within 3 hours. The removal rates were 92.4%, 33.9%, 38.4%, 94.7%, 89.5% and 95.8%, respectively.

[0058] Example 3

[0059] The only difference from Example 1 is that the mass of N,N'-methylenebisacrylamide is adjusted from "0.044g" to "0.0379g". All other steps and parameters are the same as in Example 1.

[0060] The adsorption hydrogel obtained in this embodiment was subjected to the same adsorption performance test as in Example 1. The results showed that the adsorption hydrogel exhibited the following adsorption performance: within 3 hours, the removal rates of norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions, and copper ions were 95.9%, 76.6%, 78.1%, 99.6%, 93.0%, and 96.3%, respectively.

[0061] Example 4

[0062] The only difference from Example 1 is that the mass of potassium persulfate is adjusted from "0.1597g" to "0.1331g".

[0063] The adsorption hydrogel obtained in this embodiment was subjected to the same adsorption performance test as in Example 1. The results showed that the adsorption hydrogel of the obtained embodiment exhibited the following adsorption performance: within 3 hours, the removal rates of norfloxacin, tetracycline hydrochloride, procaine, methylene blue, manganese ions, and copper ions were 96.9%, 72.7%, 75.8%, 96.5%, 92.4%, and 93.5%, respectively.

[0064] As can be seen from the above examples, the adsorbent hydrogel prepared by the present invention has high adsorption performance and fast adsorption rate, and has broad application prospects.

[0065] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cyclodextrin-based adsorbed hydrogel, characterized in that, Includes the following steps: Acrylic acid was mixed with a neutralizing agent and then neutralized. α-Cyclodextrin, carboxymethyl chitosan, sodium 4-styrene sulfonate, a crosslinking agent, and an initiator were then added to the reaction system to carry out a free radical polymerization reaction, resulting in the cyclodextrin-based adsorbed hydrogel. The molar ratio of acrylic acid to sodium 4-styrene sulfonate is 1:1 to 13:1; the amount of α-cyclodextrin is 0.1% to 1.2% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate; and the molar ratio of α-cyclodextrin to carboxymethyl chitosan is 3:1 to 4:

1.

2. The preparation method according to claim 1, characterized in that, The neutralizing agent is sodium hydroxide; the amount of the neutralizing agent is added according to the degree of neutralization of acrylic acid of 5-30%.

3. The preparation method according to claim 1, characterized in that, The crosslinking agent is N,N'-methylenebisacrylamide; the initiator is potassium persulfate; the crosslinking agent is 0.05% to 0.5% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate; the initiator is 0.1% to 0.8% of the total molar amount of acrylic acid and sodium 4-styrene sulfonate.

4. The preparation method according to claim 1, characterized in that, The free radical polymerization reaction is carried out at a temperature of 70-80℃ for 30-40 minutes.

5. A cyclodextrin-based adsorbed hydrogel prepared by the preparation method according to any one of claims 1-4.

6. The application of the cyclodextrin-based adsorption hydrogel of claim 5 in the adsorption of pollutants in wastewater; wherein the pollutants are antibiotics, dyes, or heavy metals.

7. The application according to claim 6, characterized in that, The antibiotic is at least one of norfloxacin, tetracycline hydrochloride, and procaine; the dye is methylene blue; and the heavy metal is manganese ions and / or copper ions.

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