A sodium alginate derivative aerogel containing cyclodextrin and a preparation method and application thereof

Abstract

The application belongs to the technical field of gel materials, and provides a sodium alginate derivative aerogel containing cyclodextrin as well as a preparation method and application thereof. The sodium alginate derivative containing cyclodextrin is prepared by an amide reaction of cyclodextrin containing amino groups and sodium alginate. The sodium alginate derivative containing cyclodextrin is further subjected to a gelation reaction and drying to obtain the sodium alginate derivative aerogel containing cyclodextrin. The sodium alginate derivative aerogel containing cyclodextrin has the characteristics of high specific surface area, pore volume and average pore diameter, the specific surface area is not less than 40 m 2 / g, the pore volume is not less than 0.2 cm 3 / g, and the average pore diameter is not less than 15 nm. The sodium alginate derivative aerogel containing cyclodextrin can realize efficient adsorption of hydrophobic organic molecules, the equilibrium removal rate of 2,4,6-trichlorophenol can be as high as 82.52%, the structure is not easy to collapse after use for 250 hours, and the sodium alginate derivative aerogel containing cyclodextrin can be repeatedly used.

Description

Technical Field

[0001] This invention relates to the field of biomaterials technology, and more specifically, to a sodium alginate derivative aerogel containing cyclodextrin, its preparation method, and its application. Background Technology

[0002] Using biomaterials as adsorbents to remove pollutants can significantly reduce costs. Because biomaterials are more environmentally friendly, this adsorption technology is more environmentally friendly. Sodium alginate, an alginate salt, is widely used in the preparation of adsorbents to remove inorganic and organic pollutants from wastewater, such as metal ions, chlorophenols, nitrophenols, and dyes, due to its biodegradability, hydrophilicity, and the presence of functional groups such as carboxyl and hydroxyl groups. Chlorophenols are widely used in industry as intermediates in pharmaceuticals and pesticides; however, industrial wastewater containing chlorophenols can damage the human nervous and respiratory systems and cause environmental pollution. Chlorophenols are hydrophobic, as are similar organic molecules, such as 2,4,6-trichlorophenol (TCP), which are also strongly hydrophobic and unfavorable for adsorption by hydrophilic adsorbent materials. Due to its strong hydrophilicity, sodium alginate's application as an adsorbent in the treatment of wastewater containing hydrophobic organic molecules is severely limited, resulting in low adsorption efficiency.

[0003] Therefore, there is an urgent need to develop a material that can adsorb hydrophobic organic molecules with excellent adsorption performance. Summary of the Invention

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a sodium alginate derivative aerogel containing cyclodextrin, its preparation method, and its application. The sodium alginate derivative aerogel containing cyclodextrin prepared by this invention can adsorb hydrophobic molecules and also has high specific surface area, pore volume, and average pore size, further improving the adsorption efficiency for hydrophobic molecules such as chlorophenols. The equilibrium removal rate for 2,4,6-trichlorophenol can reach 82.52%, and the specific surface area of ​​the aerogel calculated using the Brunauer-Emmett-Teller (BET) method is 51.21 m². 2 / g, pore volume is 0.2550cm³ 3 / g, with an average pore size of 19.92nm; the mesopore surface area (pore size between 2-50nm) of the aerogel was calculated to be 47.79m² using the Barret-Joyner-Halenda (BJH) method. 2 / g, mesopore volume is 0.2542cm³ 3 / g, with an average mesopore diameter of 21.27nm.

[0005] A first aspect of the present invention provides a sodium alginate derivative aerogel containing cyclodextrin.

[0006] Specifically, a method for preparing a sodium alginate derivative aerogel containing cyclodextrin includes the following steps:

[0007] (1) Sodium alginate derivatives containing cyclodextrin were prepared by amide reaction of sodium alginate and amino-containing cyclodextrin.

[0008] (2) Dissolve the sodium alginate derivative containing cyclodextrin obtained in step (1) in a solvent, add a curing agent to carry out a gelation reaction, and obtain sodium alginate derivative gel microspheres containing cyclodextrin.

[0009] (3) The sodium alginate derivative gel microspheres containing cyclodextrin obtained in step (2) are dried to obtain sodium alginate derivative aerogel containing cyclodextrin.

[0010] This invention first utilizes sodium alginate (SA) and amino-containing cyclodextrin (CD) to undergo an amide reaction to obtain a sodium alginate derivative containing cyclodextrin. Then, cyclodextrin is grafted onto sodium alginate through chemical cross-linking, achieving hydrophobic modification of sodium alginate. Simultaneously, the molecular structure of cyclodextrin is conical, possessing hydrophobic inner cavities and hydrophilic outer walls (i.e., containing special hydrophobic cavities). Hydrophobic molecules can partially or completely enter the hydrophobic cavities of cyclodextrin, forming inclusion complexes with hydrophobic molecules through host-guest interactions, thereby improving the adsorption performance for hydrophobic molecules. After gelation and drying, a sodium alginate derivative aerogel containing cyclodextrin (CD-SA aerogel) is obtained. Aerogel is a porous nanomaterial with high specific surface area and low packing density. Using the sodium alginate derivative aerogel containing cyclodextrin obtained in this invention as an adsorbent material, the porous structure of the aerogel can be utilized to further improve the adsorption efficiency for hydrophobic organic molecules such as chlorophenols.

[0011] Preferably, in step (1), the temperature of the amide reaction is 1-5°C and the reaction time is 12-36 hours.

[0012] Preferably, in step (1), the molar ratio of the amino-containing cyclodextrin to the sodium alginate sugar unit is 2:(1-5).

[0013] More preferably, in step (1), the molar ratio of the amino-containing cyclodextrin and the sodium alginate sugar unit is 2:(3-5).

[0014] More preferably, in step (1), the molar ratio of the amino-containing cyclodextrin to the sodium alginate sugar unit is 2:(3-4).

[0015] Preferably, the amino-containing β-cyclodextrin is mono-6-ethylenediamine-β-cyclodextrin.

[0016] Preferably, in step (1), the method for preparing the mono-6-ethylenediamine-β-cyclodextrin includes the following steps:

[0017] First, cyclodextrin is added to an alkaline solution, followed by p-toluenesulfonyl chloride to carry out the first reaction. After filtration, an acid solution is added to the filtrate to neutralize it. After filtration, the residue is washed to obtain mono-6-O-p-methylbenzenesulfonyl-cyclodextrin. Then, ethylenediamine is added to carry out the second reaction. After the reaction is complete, a precipitant is added to the reaction solution to precipitate the precipitate. After filtration and drying, mono-6-ethylenediamine-cyclodextrin is obtained.

[0018] Preferably, the ethylenediamine is anhydrous ethylenediamine.

[0019] Preferably, the alkaline solution is a NaOH solution.

[0020] Preferably, the concentration of the alkaline solution is 0.3-0.5 mol / L.

[0021] Preferably, the cyclodextrin is added to the alkaline solution, stirred at 3-6°C for 3-10 minutes, and then p-toluenesulfonyl chloride is added.

[0022] Preferably, the mass-to-volume ratio (mass concentration, w / v) of the β-cyclodextrin to the NaOH solution is 1:(5-15).

[0023] Preferably, the mass ratio of β-cyclodextrin to p-toluenesulfonyl chloride is (8-12):7.

[0024] Preferably, the p-toluenesulfonyl chloride is added slowly over a period of 10-20 minutes.

[0025] Preferably, the neutralization reaction is carried out at a temperature of 20-30°C for 0.5-2 hours.

[0026] Preferably, the washing is performed 3-5 times.

[0027] Preferably, the drying temperature is 40-60°C and the drying time is 12-24 hours.

[0028] Preferably, the drying is vacuum drying.

[0029] Preferably, the mass-to-volume ratio (mass concentration, w / v) of the mono-6-O-p-methylbenzenesulfonyl-cyclodextrin and ethylenediamine is 1:(0.005-0.007).

[0030] Preferably, the second reaction is carried out in an oil bath.

[0031] Preferably, the temperature of the second reaction is 70-80°C, and the reaction time is 3-5 hours.

[0032] Preferably, the precipitant is acetone.

[0033] Preferably, after precipitating and filtering, the process further includes dissolving the precipitate again in an organic solvent, adding a precipitating agent again, precipitating the precipitate, and filtering. The above-described "dissolving-precipitating" step helps remove unreacted ethylenediamine. This step can be repeated 3-5 times to completely remove unreacted ethylenediamine.

[0034] Preferably, the organic solvent is an aqueous methanol solution.

[0035] Preferably, the volume ratio of water to methanol in the methanol-water solution is (2-4):1.

[0036] Preferably, in step (1), the sodium alginate is first dissolved in a buffer solution containing 2-(N-morpholine) ethanesulfonic acid monohydrate (MES) and sodium chloride (NaCl) to obtain a sodium alginate solution, and then an amide reaction is carried out.

[0037] Preferably, the mass-to-volume ratio (w / v) of the sodium alginate to the buffer solution containing 2-(N-morpholine) ethanesulfonic acid monohydrate (MES) and sodium chloride (NaCl) is (0.005-0.007):1.

[0038] Preferably, in the buffer solution containing 2-(N-morpholine)ethanesulfonic acid monohydrate and sodium chloride, the concentration of 2-(N-morpholine)ethanesulfonic acid monohydrate is 0.05-0.15 mol / L, and the concentration of sodium chloride is 0.4-0.6 mol / L.

[0039] Preferably, step (1) further includes first adding a sodium alginate solution to a solution containing N-hydroxysuccinimide (NHS) and carbodiimide (EDC) for activation, and then using sodium alginate and cyclodextrin containing amino groups through an amide reaction. N-hydroxysuccinimide and carbodiimide can activate the carboxyl groups on sodium alginate.

[0040] Preferably, the molar ratio of the sugar units of the carbodiimide and sodium alginate is 1:(0.5-1.5).

[0041] Preferably, the molar ratio of N-hydroxysuccinimide to carbodiimide is (0.1-1):1.

[0042] Preferably, the activation temperature is 1-5℃ and the activation time is 20-40 minutes.

[0043] Preferably, in step (1), the amino-containing cyclodextrin is dissolved in a buffer solution, and the mass-to-volume ratio (mass concentration, w / v) of the amino-containing cyclodextrin to the buffer solution is (0.01-0.1):1.

[0044] More preferably, in step (1), the amino-containing cyclodextrin is dissolved in a buffer solution, and the mass-to-volume ratio (mass concentration, w / v) of the amino-containing cyclodextrin to the buffer solution is 0.094:1.

[0045] Preferably, in step (1), after the amide reaction, the product is further purified to obtain a sodium alginate derivative containing cyclodextrin.

[0046] Preferably, the purification is performed by dialysis with deionized water.

[0047] Preferably, the dialysis bag used in the dialysis has a molecular weight cutoff of 9000-11000, and the dialysis time is 3-5 days.

[0048] Preferably, in step (2), the solvent is deionized water.

[0049] Preferably, in step (2), the mass-to-volume ratio (mass concentration, w / v) of the sodium alginate derivative containing cyclodextrin to the solvent is (0.03-0.05):1.

[0050] Preferably, in step (2), the curing agent is added using a syringe.

[0051] Preferably, the needle of the syringe is 0.4-0.8 mm.

[0052] Preferably, in step (2), the curing agent is a calcium chloride solution.

[0053] Preferably, the concentration of the calcium chloride solution is 0.5-1 mol / L.

[0054] Preferably, in step (2), the mass-to-volume ratio (mass concentration, w / v) of the sodium alginate derivative containing cyclodextrin to the calcium chloride solution is (0.005-0.015):1.

[0055] More preferably, in step (2), the mass-to-volume ratio (mass concentration, w / v) of the sodium alginate derivative containing cyclodextrin to the calcium chloride solution is (0.01-0.015):1.

[0056] Preferably, in step (2), the curing agent is added by dripping, maintaining a consistent dripping speed and droplet height. Controlling the dripping speed and droplet height during dripping helps to form uniform gel microspheres.

[0057] Preferably, after the curing agent is added, the mixture is kept in the curing agent for 10-20 hours to allow for a gelation reaction. This helps the gelation reaction to proceed more thoroughly, so that during the gradual formation of gel microspheres from the sodium alginate derivative containing cyclodextrin, the gelation reaction occurs not only on the surface of the gel microspheres but also penetrates into the interior of the gel microspheres, ultimately yielding sodium alginate derivative gel microspheres containing cyclodextrin.

[0058] Preferably, after the curing agent is added, the product is stored in the curing agent for 15-20 hours to allow for a gelation reaction.

[0059] Preferably, in step (3), before drying, the sodium alginate derivative gel microspheres containing cyclodextrin are soaked in an aqueous ethanol solution, filtered, and then dried.

[0060] Preferably, the volume fraction of ethanol in the aqueous ethanol solution is 10-100%.

[0061] More preferably, the volume fraction of ethanol in the aqueous ethanol solution is one of 10%, 30%, 50%, 70%, 90%, or 100%.

[0062] Preferably, the soaking time is 10-20 minutes.

[0063] Preferably, in step (3), the drying is supercritical drying and / or subcritical drying.

[0064] More preferably, in step (3), the drying is subcritical CO2 drying.

[0065] Preferably, in step (3), the drying temperature is 30-40°C.

[0066] Preferably, in step (3), the drying pressure is 65-75 bar.

[0067] A second aspect of the present invention provides a sodium alginate derivative aerogel containing cyclodextrin.

[0068] A sodium alginate derivative aerogel containing cyclodextrin, wherein the specific surface area of ​​the sodium alginate derivative aerogel containing cyclodextrin is not less than 40 m². 2 / g, pore volume not less than 0.2cm 3 / g, with an average pore size of not less than 15nm. The pore structure parameters of the aerogel were calculated using the Brunauer-Emmett-Teller (BET) method.

[0069] Preferably, the specific surface area of ​​the sodium alginate derivative aerogel containing cyclodextrin is 50-55 m². 2 / g, pore volume 0.2-0.3cm3 / g, with an average pore size of 15-20nm.

[0070] More preferably, the specific surface area of ​​the sodium alginate derivative aerogel containing cyclodextrin is 51.21 m². 2 / g, pore volume is 0.2550cm³ 3 / g, with an average pore size of 19.92nm.

[0071] Preferably, the surface area of ​​the mesopores in the sodium alginate derivative aerogel containing cyclodextrin is 40-55 m². 2 / g, with a mesopore volume of 0.1-0.35cm³. 3 / g, with an average mesopore diameter of 15-25 nm. The pore structure parameters of the aerogel were calculated using the Barret-Joyner-Halenda (BJH) method.

[0072] More preferably, the surface area of ​​the mesopores in the sodium alginate derivative aerogel containing cyclodextrin is 45-50 m². 2 / g, with a mesopore volume of 0.15-0.3cm³. 3 / g, with an average pore size of 20-25nm for the mesopores.

[0073] More preferably, the surface area of ​​the mesopores in the sodium alginate derivative aerogel containing cyclodextrin is 47.79 m². 2 / g, the pore volume of the mesopore is 0.2542cm³. 3 / g, with an average pore size of 21.27nm for the mesopores.

[0074] A third aspect of the present invention provides an application of a sodium alginate derivative aerogel containing cyclodextrin.

[0075] Application of a sodium alginate derivative aerogel containing cyclodextrin in the preparation of adsorption materials and wastewater treatment.

[0076] Preferably, the adsorbent material adsorbs substances including hydrophobic organic molecules.

[0077] Preferably, the hydrophobic organic molecule is chlorophenol and / or 2,4,6-trichlorophenol.

[0078] Preferably, the concentration of the hydrophobic organic molecule is 10-30 mg / L.

[0079] An adsorbent material comprising the sodium alginate derivative aerogel containing cyclodextrin.

[0080] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0081] (1) This invention utilizes amino-containing cyclodextrin and sodium alginate to prepare a cyclodextrin-containing sodium alginate derivative through chemical cross-linking (amide reaction). Further, through gelation and drying, a cyclodextrin-containing sodium alginate derivative aerogel is obtained with a specific surface area of ​​not less than 40 m². 2 / g, pore volume not less than 0.2cm 3 / g, with an average pore size of not less than 15nm, has the characteristics of high specific surface area, pore volume and average pore size. Combined with the structural characteristics of cyclodextrin, it can achieve efficient adsorption of hydrophobic organic molecules, such as chlorophenol and / or 2,4,6-trichlorophenol. In addition, the present invention uses sodium alginate as the main raw material, which is abundant, renewable and has excellent biosafety and biodegradability, making it more environmentally friendly.

[0082] (2) The present invention uses calcium chloride solution as a curing agent to obtain sodium alginate derivative gel microspheres containing cyclodextrin through cross-linking reaction. The reaction conditions are mild and easy to achieve, and it has application prospects in biomedicine.

[0083] (3) The present invention uses supercritical drying and / or subcritical drying to prepare sodium alginate derivative aerogel containing cyclodextrin, which not only endows the aerogel with a high specific surface area, pore volume and average pore size, but also avoids the shrinkage and collapse of the aerogel. Even after being used in solution for up to 250 hours, it still maintains its special pore structure.

[0084] (4) The sodium alginate derivative aerogel containing cyclodextrin prepared by the present invention can be used to prepare adsorption materials for use in the field of wastewater treatment to achieve efficient adsorption of hydrophobic organic molecules, such as chlorophenol and / or 2,4,6-trichlorophenol. Attached Figure Description

[0085] Figure 1 The 1H NMR spectrum of mono-6-O-p-methylbenzenesulfonyl-β-cyclodextrin prepared in Example 1 of this invention;

[0086] Figure 2 The 1H NMR spectrum of mono-6-ethylenediamine-β-cyclodextrin prepared in Example 1 of this invention;

[0087] Figure 3 The 1H NMR spectrum of the sodium alginate derivative containing cyclodextrin prepared in Example 1 of this invention;

[0088] Figure 4 This is a schematic diagram of the high-pressure Soxhlet extraction vessel used in the subcritical CO2 drying process of this invention.

[0089] Figure 5 This is a scanning electron microscope image of the sodium alginate derivative (CD-SA) containing cyclodextrin prepared in Example 1 of the present invention;

[0090] Figure 6 The nitrogen adsorption-desorption isotherm of the sodium alginate derivative aerogel containing cyclodextrin prepared in Example 1 of this invention.

[0091] Figure 7 The pore size distribution curve of the sodium alginate derivative aerogel containing cyclodextrin prepared in Example 1 of the present invention is shown.

[0092] Figure 8 This is a comparison of the adsorption capacity-time curves of the sodium alginate derivative aerogel containing cyclodextrin prepared in Example 1 of the present invention and sodium alginate.

[0093] Figure 9 This is a comparison chart of the sodium alginate derivative aerogel containing cyclodextrin prepared in Example 1 of the present invention and the sodium alginate removal rate-time curve. Detailed Implementation

[0094] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0095] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0096] Example 1

[0097] A method for preparing a sodium alginate derivative aerogel containing cyclodextrin includes the following steps:

[0098] 1. Preparation of sodium alginate derivatives containing cyclodextrin

[0099] (1) Preparation of β-cyclodextrin containing amino groups:

[0100] (a) Weigh 25 g of β-cyclodextrin and add it to 250 mL of 0.4 mol / L NaOH solution. Stir at 5 °C for 5 minutes until homogeneous, the solution becomes clear and slightly yellow. Slowly add 17.5 g of p-toluenesulfonyl chloride (addition takes 10 minutes), mix and stir for 1 hour. Filter, neutralize the filtrate with hydrochloric acid, stir at room temperature for 1 hour, filter under vacuum, wash the residue three times with water or acetone, and then dry under vacuum at 50 °C for 12 hours to obtain mono-6-O-p-methylbenzenesulfonyl-β-cyclodextrin (6-OTs-β-CD). The 1H NMR spectrum of mono-6-O-p-methylbenzenesulfonyl-β-cyclodextrin (6-OTs-β-CD) is shown below. Figure 1 As shown, the characteristic proton peaks on the benzene ring appeared at 7.38-7.44 ppm and 7.70-7.76 ppm in the 1H NMR spectrum of 6-OTs-β-CD, proving that p-toluenesulfonyl chloride successfully underwent a grafting reaction with cyclodextrin. Figure 1 DMSO in the text is dimethyl sulfoxide.

[0101] (b) Weigh 2g of the mono-6-O-p-methylbenzenesulfonyl-β-cyclodextrin prepared above and add it to 12mL of anhydrous ethylenediamine (EDA). React in an oil bath at 75°C for 4 hours. After cooling to room temperature, add the reaction solution dropwise to a large amount of acetone, and a large amount of precipitate will precipitate. Filter the precipitate. Dissolve the precipitate in water / methanol (volume ratio 3:1) and then add it dropwise to a large amount of acetone to precipitate again. Repeat the above precipitation-dissolution step 3 times to wash away unreacted ethylenediamine. Dry the product under vacuum at 50°C for 24 hours to obtain mono-6-ethylenediamine-β-cyclodextrin (EDA-β-CD).

[0102] The 1H NMR spectrum of the mono-6-ethylenediamine-β-cyclodextrin (EDA-β-CD) prepared above is as follows: Figure 2 As shown in the figure, characteristic proton peaks of amino and imino groups (-NH2, -NH-) appeared at 1.03 ppm and 2.27 ppm; proton peaks of two methylene groups attached to nitrogen appeared at 2.57 ppm and 2.90 ppm; and the characteristic peak at 4.91 ppm was the proton peak of the anolyte carbon on the cyclodextrin sugar ring. These findings demonstrate the successful synthesis of mono-6-ethylenediamine-β-cyclodextrin. Figure 2 In this context, EDA stands for ethylenediamine.

[0103] (2) Preparation of sodium alginate derivatives containing cyclodextrin

[0104] Prepare a buffer solution containing MES (0.1 mol / L) and NaCl (0.5 mol / L); measure 40 mL of the buffer solution and add 0.2376 g of sodium alginate to make the mass-to-volume ratio (w / v) of sodium alginate to the buffer solution 0.006:1. Stir for 3 hours until completely dissolved, then add 69 mg of NHS and 230 mg of sodium alginate. EDC (molar ratio of NHS:EDC:COO- on sodium alginate = 0.5:1:1) was stirred at 4°C for 30 minutes until homogeneous to activate the carboxyl groups on the alginate chain, resulting in a sodium alginate solution. 10 mL of buffer solution was taken, and 0.94 g of the prepared mono-6-ethylenediamine-β-cyclodextrin was added to make the mass-to-volume ratio (w / v) of mono-6-ethylenediamine-β-cyclodextrin to buffer solution 0.094:1. After stirring to dissolve, the solution was added to the sodium alginate solution and reacted at 4°C for 24 hours. The reaction product was then placed in a cellulose dialysis bag with a molecular weight cutoff of 10000 (purchased from Guangzhou Feibo Biotechnology Co., Ltd.), dialyzed with deionized water for 3 days, and finally lyophilized to obtain a sodium alginate derivative containing cyclodextrin (CD-SA).

[0105] The 1H NMR spectrum of the sodium alginate derivative containing cyclodextrin (CD-SA) prepared above is as follows: Figure 3As shown in the figure, characteristic proton peaks on the two methylene groups connecting cyclodextrin and sodium alginate appeared at 2.56 ppm and 2.72 ppm; a proton peak on the 6-carbon of the sugar ring of cyclodextrin participating in the reaction appeared at 3.20 ppm; and the characteristic peak at 4.91 ppm was the proton peak of the anolyte carbon on the cyclodextrin sugar ring. The above proves that mono-6-ethylenediamine-β-cyclodextrin was successfully grafted onto sodium alginate.

[0106] 2. Preparation of sodium alginate derivative gel microspheres containing cyclodextrin

[0107] Weigh 1.4g of the cyclodextrin-containing sodium alginate derivative (CD-SA) prepared above, add 35mL of deionized water, and stir for 2 hours until completely dissolved; add the above aqueous solution of cyclodextrin-containing sodium alginate derivative dropwise to 140mL of 0.5mol / L calcium chloride solution using a syringe (needle diameter 0.6mm), controlling the dropping speed and the height of the droplets to form uniform gel microspheres; after the addition is complete, keep the gel microspheres in the calcium chloride solution for 15 hours so that the gelation process of the cyclodextrin-containing sodium alginate derivative not only takes place on the surface but also penetrates into the interior of the gel microspheres, thus obtaining cyclodextrin-containing sodium alginate derivative gel microspheres.

[0108] 3. Preparation of sodium alginate derivative aerogel containing cyclodextrin

[0109] The cyclodextrin-containing sodium alginate derivative gel microspheres prepared above were soaked in an ethanol aqueous solution (ethanol volume fraction of 10%) for 15 minutes; finally, the solution was filtered off and the microspheres were subjected to subcritical CO2 drying (36℃, 60 bar) using a high-pressure Soxhlet extraction vessel to obtain cyclodextrin-containing sodium alginate derivative aerogel (CD-SA aerogel).

[0110] The above subcritical CO2 drying was carried out using a high-pressure Soxhlet extraction vessel. A schematic diagram of the high-pressure Soxhlet extraction vessel is shown below. Figure 4 As shown, its structure includes a valve 1, a lamp 2, a viewing window 3, a condenser 4, a pressure gauge 5, an upper cup 6, a lower cup 7, an autoclave 8, a contact thermometer 9, a water bath 10, a neckless funnel 11, a heating magnetic stirrer 12, a sample 13, and glass wool 14. This instrument utilizes liquid CO2 for extraction, using evaporation to prepare the liquid. Specifically, the bottom of the autoclave 8 is heated to evaporate the liquid, while the steam condenses on the condenser and drips onto the raw material for extraction. During the experiment, the heating magnetic stirrer is set to approximately 37°C, and the cooling circulating water temperature is approximately 15°C. If the liquid reaches the highest point of the siphon, it will automatically flow out into the lower cup 7, where the liquid is evaporated again, while the extracted product remains in the lower cup 7.

[0111] Examples 2-6

[0112] The difference between Examples 2-6 and Example 1 is that the volume fraction of ethanol in the aqueous ethanol solution in step 3 is replaced with 30%, 50%, 70%, 90%, and 100%, respectively.

[0113] By continuously increasing the proportion of ethanol in the ethanol solution, the water in the pores of the gel microspheres can be effectively replaced step by step, ultimately obtaining sodium alginate derivative gel microspheres containing cyclodextrin with ethanol as the solvent in the pores.

[0114] Comparative Example 1

[0115] The difference from Example 1 is that sodium alginate was replaced with carboxymethyl starch, which prevented cross-linking to obtain gel microspheres.

[0116] Comparative Example 2

[0117] The difference from Example 1 is that the amino-containing cyclodextrin is replaced with amino-containing chitosan or amino-modified hyaluronic acid oligosaccharides. Although a gel can be formed after replacing the cyclodextrin with amino-containing chitosan or amino-modified hyaluronic acid oligosaccharides, the lack of the hydrophobic cavity structure of cyclodextrin actually hinders the adsorption of small molecules.

[0118] Application examples

[0119] The sodium alginate derivative aerogel containing cyclodextrin prepared in Example 1 above was used as an adsorbent material for adsorbing 2,4,6-trichlorophenol, comprising the following steps:

[0120] Prepare a 2,4,6-trichlorophenol solution, adjust the pH to 4 with hydrochloric acid, pipette the solution into a serum bottle, add sodium alginate derivative aerogel containing cyclodextrin, cap the bottle, and shake in a constant temperature water bath to induce adsorption. At regular intervals, take a suitable amount of solution and measure the absorbance at 294 nm using a UV-Vis spectrophotometer (Beijing Purkinje General Instrument Co., Ltd., TU1901 double-beam UV-Vis spectrophotometer). Then, return the solution to the serum bottle to measure the adsorption effect.

[0121] Product effectiveness test

[0122] 1. Microscopic morphology

[0123] The morphology of the aerogel prepared in Example 1 was observed using a scanning electron microscope (SEM) [Quanta400F(FEI / OXFORD / HKL) thermal field emission environment scanning electron microscope-energy dispersive spectroscopy-electron backscatter diffraction system]. The morphology is as follows: Figure 5 As shown, where Figure 5 (a) is a view of the outer surface of the aerogel. Figure 5(b) Figure 5 (c) shows cross-sectional views of the aerogel at different magnifications. The figures show that the outer surface of the aerogel is uneven and porous; the cross-sectional views also reveal pores within the aerogel. This demonstrates that the gelation process of sodium alginate derivatives containing cyclodextrin occurs not only on the surface but also deep within the gel microspheres.

[0124] 2. Distribution of holes

[0125] The cyclodextrin-containing sodium alginate derivative aerogel prepared in Example 1 was analyzed using a Micrometrics ASAP2020 microporous analyzer with N2 as the adsorbate. The nitrogen adsorption-desorption isotherm of the CD-SA aerogel was measured at 77.35 K. The results are as follows: Figure 6 As shown, the aperture size distribution is as follows: Figure 7 As shown, by Figure 6 and Figure 7 It can be seen that the nitrogen adsorption-desorption isotherms of the aerogel are all type IV isotherms, and a significant hysteresis loop is observed, indicating that the aerogel is a mesoporous material. Based on the measured nitrogen adsorption-desorption isotherms, the Brunauer-Emmett-Teller (BET) method was used to calculate the structural parameters of each pore in the aerogel, with the total specific surface area being 51.21 m². 2 / g, total pore volume is 0.2550cm³ 3 / g, with a total average pore size of 19.92nm; the surface area of ​​the mesopores in the aerogel was calculated to be 47.79m² using the Barret-Joyner-Halenda (BJH) method. 2 / g, the pore volume of the mesopore is 0.2542cm³. 3 / g, with an average pore size of 21.27nm for the mesopores.

[0126] 3. Adsorption performance

[0127] A 20 mg / L 2,4,6-trichlorophenol (TCP) solution was prepared, and the pH was adjusted to 4 with hydrochloric acid. 10 mL of the TCP solution was accurately pipetted into a 10 mL serum bottle, and 20 mg of the sodium alginate derivative aerogel containing cyclodextrin prepared in Example 5 was added. The bottle was capped and shaken in a 30°C constant temperature water bath. At regular intervals, a suitable amount of solution was taken out, and the absorbance at 294 nm was measured using a UV-Vis spectrophotometer (Beijing Purkinje General Instrument Co., Ltd., TU1901 double-beam UV-Vis spectrophotometer). The solution was then returned to the serum bottle. The concentration of the solution could be obtained from the absorbance. The adsorption amount qt and removal rate at time t could be calculated using formulas ① and ②, respectively, and adsorption-time curves and removal-time curves were plotted.

[0128] q t =(C o -C t V / m ①

[0129] Removal percentage (%) = 100 × (C) o -C t ) / C o ②

[0130] Where qt is the adsorption amount at time t, in mg / g; Co and Ct are the TCP solution concentrations before adsorption and at time t, respectively, in mg / L; V is the volume of the solution in L; and m is the mass of the adsorbent (aerogel).

[0131] The adsorption-time curves and removal-time curves of SA and CD-SA aerogels for TCP were obtained by calculation, as shown below. Figure 8 and Figure 9 As shown, by Figure 8 and Figure 9 It can be seen that the adsorption capacity of TCP increases continuously with time. The equilibrium removal rates of SA and CD-SA aerogels for 20 mg / L TCP solution are 61.53% and 82.52%, respectively, and the CD-SA aerogel reaches equilibrium at an adsorption capacity of 8.25 mg / g. TCP contains a large number of hydroxyl and chloride ions, while CD-SA aerogel, after grafting with β-CD, contains abundant -COOH and -OH, which can form hydrogen bonds, thereby improving the adsorption capacity of TCP. In addition, β-CD contains hydrophobic cavities with a diameter of 0.8 nm, giving CD-SA aerogel a special structure. Hydrophobic organic molecules containing phenyl groups, such as TCP, can partially or completely enter the hydrophobic cavities to form host-guest complexes, thus further facilitating the adsorption of TCP. As shown in the figure, after 250 hours of use, the pore structure of the aerogel of the present invention remains unchanged, its network structure remains unchanged, and the structure is not easily collapsed, indicating that the gel has reusable properties.

Claims

1. A method for preparing a sodium alginate derivative aerogel containing cyclodextrin, characterized in that, Includes the following steps: (1) Sodium alginate derivatives containing cyclodextrin were prepared by amide reaction of sodium alginate and amino-containing cyclodextrin. (2) Dissolve the sodium alginate derivative containing cyclodextrin obtained in step (1) in a solvent, add a curing agent to carry out a gelation reaction, and obtain sodium alginate derivative gel microspheres containing cyclodextrin. (3) The sodium alginate derivative gel microspheres containing cyclodextrin obtained in step (2) are dried to obtain sodium alginate derivative aerogel containing cyclodextrin. In step (1), the molar ratio of the amino-containing cyclodextrin to the sodium alginate sugar unit is 2:(1-5). The amino-containing cyclodextrin is mono-6-ethylenediamine-β-cyclodextrin; The preparation method of the mono-6-ethylenediamine-β-cyclodextrin includes the following steps: First, cyclodextrin is added to an alkaline solution, followed by p-toluenesulfonyl chloride to carry out the first reaction. After filtration, an acid solution is added to the filtrate to neutralize it. After filtration, the residue is washed to obtain mono-6-O-p-methylbenzenesulfonyl-cyclodextrin. Then, ethylenediamine is added to carry out the second reaction. After the reaction is complete, a precipitant is added to the reaction solution to precipitate the precipitate. After filtration and drying, mono-6-ethylenediamine-β-cyclodextrin is obtained. In step (2), the curing agent is a calcium chloride solution; In step (3), before drying, the sodium alginate derivative gel microspheres containing cyclodextrin are soaked in an ethanol aqueous solution, filtered, and then dried; the drying is supercritical drying and / or subcritical drying.

2. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the amide reaction is 1-5 °C and the reaction time is 12-36 hours.

3. The preparation method according to claim 1, characterized in that, In step (2), the mass-to-volume ratio of the sodium alginate derivative containing cyclodextrin to the calcium chloride solution is (0.005-0.015):

1.

4. The sodium alginate derivative aerogel containing cyclodextrin prepared by the method according to any one of claims 1-2, characterized in that, The specific surface area of ​​the sodium alginate derivative aerogel containing cyclodextrin is not less than 40 m². 2 / g, pore volume not less than 0.2 cm³ 3 / g, with an average pore size of not less than 15 nm.

5. The application of the sodium alginate derivative aerogel containing cyclodextrin as described in claim 4 in the preparation of adsorbent materials or in the field of wastewater treatment.

6. An adsorbent material, characterized in that, It is prepared from the sodium alginate derivative aerogel containing cyclodextrin as described in claim 4.

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