Preparation method of pectin-based anionic adsorbent

Abstract

The invention relates to a preparation method of a pectin-based anionic adsorbent, and belongs to the field of adsorbent preparation. According to the preparation method, pectin is taken as a matrix, N, N '-methylenebisacrylamide is taken as a cross-linking agent, and the pectin-based cryogel particle medium is successfully prepared by adopting a freezing casting method and an airflow cutting drop-making technology. Then, the prepared pectin-based cryogel medium reacts with an ammonia water solution for amidation and then reacts with maleic anhydride, and finally the pectin-based anionic adsorbent is obtained. The pectin-based anionic adsorbent prepared by the preparation method disclosed by the invention takes polysaccharide as a matrix, has biodegradability, is environment-friendly, has relatively large adsorption capacity and relatively high adsorption rate, and shows a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of adsorbent preparation, and particularly relates to a preparation method of a pectin-based anionic adsorbent. Background Art

[0002] With the rapid development of the textile printing and dyeing and biopharmaceutical industries, the demand for the treatment of wastewater containing cationic dyes and the separation and purification of bioactive substances is increasing day by day. Cationic dyes are widely used in textile dyeing due to their bright colors and strong color fastness. However, their wastewater has complex components, high chromaticity and is difficult to degrade. Traditional treatment methods such as activated carbon adsorption and chemical flocculation have problems such as low adsorption capacity and secondary pollution. In the field of biomedicine, as important bioactive substances, cationic proteins often face bottlenecks such as complex operations and high material costs in existing separation technologies. Developing new and efficient adsorption materials has become an urgent need in the industry.

[0003] In recent years, the pollution of cationic dyes in textile printing and dyeing wastewater and the high-efficiency enrichment demand of active proteins in biopharmaceuticals have put forward higher requirements for adsorption materials. Traditional gel-like adsorbents (such as chitosan gel and sodium alginate hydrogel) have certain adsorption capacities, but problems such as high swelling degree and unstable pore structure lead to poor reusability. Especially in the dynamic adsorption process, the gel material is prone to structural collapse, resulting in a large loss of effective adsorption sites. Cryogel adsorbents have attracted much attention due to their unique three-dimensional interconnected macroporous structure and rigid framework characteristics. Different from ordinary gels, the structure obtained by low-temperature polymerization of cryogel materials can not only maintain high porosity but also effectively resist swelling deformation. It is worth noting that the research on cryogel adsorbents based on pectin is still blank at present. Most existing pectin-based materials remain in the gel state, and their soft network structure is difficult to meet the requirements of both high mechanical strength and fast mass transfer.

[0004] Therefore, developing a pectin-based anionic adsorbent and modifying functional groups directionally have important value for solving problems such as large mass transfer resistance and poor environmental tolerance of traditional adsorbents. Summary of the Invention

[0005] The present invention is mainly used to solve problems such as high water solubility and low mechanical strength of current gel-like adsorbents, and provides a preparation method of a pectin-based anionic adsorbent.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is a preparation method of a pectin-based anionic adsorbent, which is characterized in that the specific preparation steps are as follows:

[0007] (1) Dissolve pectin and N,N'-methylenebisacrylamide in water, and stir at 35 °C until completely dissolved to obtain mixed solution 1;

[0008] (2) Ammonium persulfate and tetramethylethylenediamine solution were respectively and sequentially added to the mixed solution 1, and mixed evenly to obtain a pectin-based crystalline gel precursor solution;

[0009] (3) The above-mentioned pectin-based crystalline gel precursor solution was placed in an air flow cutting and droplet-forming device to obtain pectin-based crystalline gel particle media with different particle sizes;

[0010] (4) The pectin-based crystalline gel particle media and ammonia water solution were reacted at 20-40 °C for 1-3 h. The obtained product was cross-washed with hydrochloric acid and deionized water to obtain amidated pectin-based crystalline gel particle media;

[0011] (5) The amidated pectin-based crystalline gel particle media and maleic anhydride-acetone solution were reacted at 20-60 °C for 1-3 h. The obtained product was cross-washed with 20% wt acetone solution and deionized water to obtain a pectin-based anionic adsorbent.

[0012] Further, in the step (1), the mass fraction of pectin is 2-3%, and the molar ratio of pectin to N,N'-methylenebisacrylamide is 1-4:1; the complete dissolution is carried out by ultrasonic treatment to remove bubbles.

[0013] Further, in the step (2), the mass ratio of ammonium persulfate to pectin in the mixed solution 1 is 1:10-1:100, and the mass ratio of tetramethylethylenediamine to pectin is 1:10-1:100.

[0014] Further, in the step (3), the process parameters of the air flow cutting and droplet-forming device are that the liquid flow rate is 0.02-0.2 mL / min, and the gas flow rate is 0-12 L / min; the average particle size of the obtained pectin-based crystalline gel particle media is 200-1600 μm.

[0015] Further, in the step (4), the concentration of the ammonia water solution is 2-4 mol / L; the concentration of the hydrochloric acid solution is 1 mol / L.

[0016] Further, in the step (5), the concentration of the maleic anhydride-acetone solution is 0.2-0.5 mol / L.

[0017] The present invention also provides a pectin-based anionic adsorbent prepared by the above preparation method, which has good mechanical strength, high permeability, large adsorption capacity and fast adsorption rate.

[0018] The present invention also provides the use of the aforementioned anionic adsorbent in adsorbing cationic dyes or enriching cationic proteins.

[0019] The present invention also provides a method for adsorbing cationic dyes or enriching cationic proteins, which is to add the aforementioned anionic adsorbent to the target water body or solution.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. On the basis of retaining the inherent active sites such as -COOH and -OH of pectin molecules, the pectin-based anionic adsorbent prepared by the present invention introduces a large number of -COOH functional groups through functionalization modification technology, thereby providing more binding sites for cationic proteins and cationic dyes, forming a synergistic effect of multiple functional groups, and effectively improving the adsorption capacity of the adsorbent.

[0022] 2. The crystal-gel framework structure of the pectin-based anionic adsorbent prepared by the present invention exhibits high porosity, good permeability and strong mechanical strength. This structure not only overcomes the disadvantages of traditional gel adsorbents with high water solubility and low mechanical strength, but also effectively strengthens the mass transfer during the adsorption process.

[0023] 3. The pectin-based anionic adsorbent prepared by the present invention has a high adsorption capacity, a fast adsorption rate, is simple and convenient to operate, is easy to biodegradable, and is environmentally friendly. Therefore, it has broad application prospects in the fields of cationic dye removal and cationic protein purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a scanning electron micrograph of 30 times that of the anionic adsorbent of the present invention.

[0025] Figure 2 It is a scanning electron micrograph of 500 times that of the anionic adsorbent of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] In order to further elaborate on the preparation method of the pectin-based anionic adsorbent of the present invention and achieve the intended invention purpose, the following is a detailed description of the preparation method, specific implementation manner, structure, characteristics and effects of a pectin-based anionic adsorbent proposed according to the present invention with reference to preferred embodiments. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0027] The following will further introduce in detail the preparation method of a pectin-based anionic adsorbent of the present invention with reference to specific embodiments. The technical solution of the present invention is as follows:

[0028] Using pectin as the matrix and N,N'-methylenebisacrylamide as the crosslinking agent, a pectin-based crystal-gel particle medium was successfully prepared by the freeze-casting method and the gas-flow cutting and droplet-forming technology. Subsequently, the obtained pectin-based crystal-gel medium was reacted with an ammonia water solution for amidation, and then reacted with maleic anhydride to finally obtain the pectin-based anionic adsorbent.

[0029] Preferably, the preparation method includes the following steps:

[0030] (1) Dissolve pectin and N,N'-methylenebisacrylamide in water, and stir at 35°C until completely dissolved to obtain mixed solution 1;

[0031] (2) Sequentially add ammonium persulfate and tetramethylethylenediamine solution to mixed solution 1, mix evenly to obtain a pectin-based crystalline gel precursor solution;

[0032] (3) Place the above-mentioned pectin-based crystalline gel precursor solution in an air flow cutting and droplet-forming device to obtain pectin-based crystalline gel particle media with different particle sizes;

[0033] (4) React the pectin-based crystalline gel particle media with ammonia water solution at 20-40°C for 1-3 h. After cross-washing the obtained product with hydrochloric acid and deionized water, obtain amidated pectin-based crystalline gel particle media;

[0034] (5) React the amidated pectin-based crystalline gel particle media with maleic anhydride-acetone solution at 20-60°C for 1-3 h. Wash the obtained product with 20% wt acetone solution and deionized water crosswise to obtain a pectin-based anionic adsorbent.

[0035] Preferably, in step (1), the mass fraction of pectin is 2-3%, and the molar ratio of pectin to N,N'-methylenebisacrylamide is 1:1-4:1; the complete dissolution is achieved by ultrasonic treatment to remove bubbles.

[0036] Preferably, in step (2), the mass ratio of ammonium persulfate to pectin in mixed solution 1 is 1:10-1:100, and the mass ratio of tetramethylethylenediamine to pectin is 1:10-1:100.

[0037] Preferably, in step (3), the process parameters of the air flow cutting and droplet-forming device are: liquid flow rate 0.02-0.2 mL / min, gas flow rate 0-12 L / min; the average particle size of the obtained pectin-based crystalline gel particle media is 200-1600 μm.

[0038] Preferably, in step (4), the concentration of the ammonia water solution is 2-4 mol / L; the concentration of the hydrochloric acid solution is 1 mol / L.

[0039] Preferably, in step (5), the concentration of the maleic anhydride-acetone solution is 0.2-0.5 mol / L.

[0040] The present invention is prepared by the above preparation method. The product prepared by the above preparation method has good mechanical strength, high permeability, large adsorption capacity and fast adsorption rate.

[0041] Example 1:

[0042] The specific operation steps are as follows:

[0043] (1) Dissolve pectin and N,N'-methylenebisacrylamide in water, and stir at 35 °C until completely dissolved to obtain a mixed solution 1 with a mass fraction of 2-3%. The molar ratio of pectin to N,N'-methylenebisacrylamide is 1:1 to 4:1.

[0044] (2) Dissolve ammonium persulfate and tetramethylethylenediamine in the mixed solution 1, stir for 1 min, and mix evenly to obtain a pectin-based crystalline gel precursor solution; the mass ratio of ammonium persulfate to pectin is 1:10 to 1:100, and the mass ratio of tetramethylethylenediamine to pectin is 1:10 to 1:100.

[0045] (3) Pump the pectin-based crystalline gel precursor solution into an air-flow cutting droplet-forming device at a liquid flow rate of 0.02-0.2 mL / min, and at the same time blow it with a gas flow rate of 0-12 L / min to obtain droplets, and collect the obtained droplets with liquid nitrogen to obtain solid particles.

[0046] (4) Fish out the solid particle medium, pour it into a petri dish with a diameter of 7-15 cm, freeze it at -20 °C for 24-48 h, and then place it in deionized water at room temperature and thaw it for 10-30 min to obtain a wet pectin-based crystalline gel particle medium.

[0047] (5) Immerse the pectin-based crystalline gel particle medium in deionized water for 3-6 h, and then rinse it repeatedly with deionized water for 3-5 times to remove unreacted substances; place the washed wet pectin-based crystalline gel particle medium in a suction flask and perform vacuum suction filtration to remove excess water.

[0048] (6) React the suction-filtered pectin-based crystalline gel particle medium with 2-4 mol / L ammonia water at 20-40 °C for 1-3 h. After the reaction, cross-wash the product with 1 mol / L hydrochloric acid and deionized water for 3-5 times to obtain an amidated pectin-based crystalline gel particle medium; place the amidated pectin-based crystalline gel particle medium in a suction flask and perform vacuum suction filtration to remove excess water.

[0049] (7) React the suction-filtered amidated pectin-based crystalline gel particle medium with a 0.2-0.5 mol / L maleic anhydride-acetone solution at 20-60 °C for 1-3 h. After the reaction, cross-wash the product with a 20% wt acetone solution and deionized water for 3-5 times to obtain a pectin-based anionic adsorbent.

[0050] Example 2:

[0051] The specific operation steps are as follows:

[0052] (1) Dissolve 0.4 g of pectin and 0.1 g of N,N'-methylenebisacrylamide in 20 mL of water, and stir at 35 °C until completely dissolved to obtain a mixed solution 1 with a mass fraction of 2%.

[0053] (2) Dissolve 0.016 g of ammonium persulfate and 0.08 g of tetramethylethylenediamine in the mixed solution 1, stir for 1 min, and mix evenly to obtain a pectin-based crystalline gel precursor solution.

[0054] (3) Pump the pectin-based crystalline gel precursor solution into an air flow cutting droplet-forming device at a liquid flow rate of 0.02 mL / min, and at the same time purge with a gas flow rate of 0 L / min to obtain droplets, and collect the obtained droplets with liquid nitrogen to obtain solid particles.

[0055] (4) Fish out the solid particle medium, pour it into a petri dish with a diameter of 10 cm, freeze it at -20 °C for 24 h, and then thaw it in deionized water at room temperature to obtain a wet pectin-based crystalline gel particle medium.

[0056] (5) Soak the pectin-based crystalline gel particle medium with deionized water for 3 - 6 h, and then rinse it repeatedly with deionized water for 3 - 5 times to remove unreacted substances; place the washed wet pectin-based crystalline gel particle medium in a suction flask and perform vacuum filtration to remove excess water.

[0057] (6) React the suction-filtered pectin-based crystalline gel particle medium with 2 mol / L ammonia water at 25 °C for 1 h. After the reaction, cross-wash the product with 1 mol / L hydrochloric acid and deionized water for 3 - 5 times to obtain an amidated pectin-based crystalline gel particle medium; place the amidated pectin-based crystalline gel particle medium in a suction flask and perform vacuum filtration to remove excess water.

[0058] (7) React the suction-filtered amidated pectin-based crystalline gel particle medium with a 0.2 mol / L maleic anhydride-acetone solution at 25 °C for 1 h. After the reaction, cross-wash the product with a 20% wt acetone solution and deionized water for 3 - 5 times to obtain a pectin-based anionic adsorbent A.

[0059] The pectin-based anionic adsorbent A described in Example 2 has good mechanical strength and high permeability. Its average particle size is 1500 μm, and its average pore size is 38 μm; the permeability is 1.9×10 -11 .

[0060] Example 3:

[0061] The specific operation steps are as follows:

[0062] (1) Dissolve 0.6 g of pectin and 0.6 g of N,N'-methylenebisacrylamide in 20 mL of water, and stir at 35 °C until completely dissolved to obtain a mixed solution 1 with a mass fraction of 3%.

[0063] (2) Dissolve 0.06 g of ammonium persulfate and 0.03 g of tetramethylethylenediamine in mixed solution 1, stir for 1 min to mix evenly, and obtain a pectin-based crystalline gel precursor solution.

[0064] (3) Pump the pectin-based crystalline gel precursor solution into an air-flow cutting droplet-forming device at a liquid flow rate of 0.2 mL / min, and at the same time purge with a gas flow rate of 9 L / min to obtain droplets, and collect the obtained droplets with liquid nitrogen to obtain solid particles.

[0065] (4) Fish out the solid particle medium, pour it into a petri dish with a diameter of 10 cm, freeze it at -20 °C for 24 h, and then thaw it in deionized water at room temperature to obtain a wet pectin-based crystalline gel particle medium.

[0066] (5) Immerse the pectin-based crystalline gel particle medium in deionized water for 3 - 6 h, then rinse it with deionized water 3 - 5 times repeatedly to remove unreacted substances; place the washed wet pectin-based crystalline gel particle medium in a suction flask and perform vacuum suction filtration to remove excess moisture.

[0067] (6) React the suction-filtered pectin-based crystalline gel particle medium with 2 mol / L ammonia water at 25 °C for 2 h. After the reaction, cross-wash the product 3 - 5 times with 1 mol / L hydrochloric acid and deionized water to obtain an amidated pectin-based crystalline gel particle medium; place the amidated pectin-based crystalline gel particle medium in a suction flask and perform vacuum suction filtration to remove excess moisture.

[0068] (7) React the suction-filtered amidated pectin-based crystalline gel particle medium with a 0.2 mol / L maleic anhydride-acetone solution at 25 °C for 2 h. After the reaction, cross-wash the product 3 - 5 times with a 20% wt acetone solution and deionized water to obtain a pectin-based anionic adsorbent B.

[0069] The pectin-based anionic adsorbent B described in Example 3 has good mechanical strength and high permeability. Its average particle size is 560 μm, and its average pore size is 9 μm; the permeability is 3.12×10 -12 .

[0070] Example 4:

[0071] The specific operation steps are as follows:

[0072] (1) Dissolve 0.6 g of pectin and 0.3 g of N,N'-methylenebisacrylamide in 20 mL of water, and stir at 35 °C until completely dissolved to obtain a 3% by mass mixed solution 1.

[0073] (2) Dissolve 0.048 g of ammonium persulfate and 0.05 g of tetramethylethylenediamine in mixed solution 1, stir for 1 min to mix evenly, and obtain a pectin-based crystalline gel precursor solution.

[0074] (3) Pump the pectin-based crystalline hydrogel precursor solution into the gas-stream cutting droplet-forming device at a liquid flow rate of 0.2 mL / min, and simultaneously purge with a gas flow rate of 9 L / min to obtain droplets. Collect the obtained droplets with liquid nitrogen to obtain solid particles with a diameter of 560 μm.

[0075] (4) Fish out the solid particle medium, pour it into a petri dish with a diameter of 10 cm, freeze it at -20 °C for 24 h, and then thaw it in deionized water at room temperature to obtain a wet pectin-based crystalline hydrogel particle medium.

[0076] (5) Soak the pectin-based crystalline hydrogel particle medium with deionized water for 3 - 6 h, and then rinse it repeatedly with deionized water for 3 - 5 times to remove unreacted substances; place the washed wet pectin-based crystalline hydrogel particle medium in a suction flask and perform vacuum filtration to remove excess water.

[0077] (6) React the suction-filtered pectin-based crystalline hydrogel particle medium with 2 mol / L ammonia water at 25 °C for 1 h. After the reaction, cross-wash the product with 1 mol / L hydrochloric acid and deionized water for 3 - 5 times to obtain an amidated pectin-based crystalline hydrogel particle medium; place the amidated pectin-based crystalline hydrogel particle medium in a suction flask and perform vacuum filtration to remove excess water.

[0078] (7) React the suction-filtered amidated pectin-based crystalline hydrogel particle medium with 0.2 mol / L maleic anhydride-acetone solution at 25 °C for 1 h. After the reaction, cross-wash the product with 20% wt acetone solution and deionized water for 3 - 5 times to obtain pectin-based anionic adsorbent C.

[0079] Use the pectin-based anionic adsorbent C obtained in Example 4 for the adsorption of methylene blue and the enrichment of lysozyme in two target solutions respectively at a feed ratio of 1:8 (mass ratio, g / g). Through the determination of adsorption isotherms and dynamic curves, the results show that the maximum adsorption capacities of the pectin-based anionic adsorbent for methylene blue and lysozyme in the two target solutions are 408 mg / g dry basis and 1717 mg / g dry basis respectively. In addition, the adsorption of methylene blue and lysozyme reaches the adsorption equilibrium within 20 min.

Claims

1. A preparation method of a pectin-based anionic adsorbent, characterized in that The specific preparation steps are as follows: (1) Dissolve pectin and N,N'-methylenebisacrylamide in water, and stir at 35 °C until completely dissolved to obtain mixed solution 1; (2) Add ammonium persulfate and tetramethylethylenediamine solution to mixed solution 1 in sequence, mix evenly to obtain a pectin-based crystal gel precursor solution; (3) Place the above-mentioned pectin-based crystal gel precursor solution in an air flow cutting and droplet-forming device to obtain pectin-based crystal gel particle media with different particle sizes; (4) React the pectin-based crystal gel particle media with ammonia water solution at 20-40 °C for 1-3 h. After cross-washing the obtained product with hydrochloric acid and deionized water, an amidated pectin-based crystal gel particle media is obtained; (5) React the amidated pectin-based crystal gel particle media with maleic anhydride-acetone solution at 20-60 °C for 1-3 h. Wash the obtained product with 20% wt acetone solution and deionized water crosswise to obtain a pectin-based anionic adsorbent.

2. The preparation method according to claim 1, wherein in step (1), the mass fraction of pectin is 2-3%, and the molar ratio of pectin to N,N'-methylenebisacrylamide is 1:1-4:1; the complete dissolution is carried out by ultrasonic treatment to remove bubbles.

3. The preparation method according to claim 1, wherein in step (2), the mass ratio of ammonium persulfate to pectin in mixed solution 1 is 1:10-1:100, and the mass ratio of tetramethylethylenediamine to pectin is 1:10-1:

100.

4. The preparation method according to claim 1, wherein in step (3), the process parameters of the air flow cutting and droplet-forming device are that the liquid flow rate is 0.02-0.2 ml / min and the gas flow rate is 0-12 L / min; the average particle size of the obtained pectin-based crystal gel particle media is 200-1600 μm.

5. The preparation method according to claim 1, wherein in step (4), the concentration of the ammonia water solution is 2-4 mol / L; the concentration of the hydrochloric acid solution is 1 mol / L.

6. The preparation method according to claim 1, wherein in step (5), the concentration of the maleic anhydride-acetone solution is 0.2-0.5 mol / L.

7. A pectin-based anionic adsorbent, characterized in that, The anionic pectin-based adsorbent is prepared by the preparation method according to any one of claims 1-6.

8. The pectin-based anionic adsorbent according to claim 7, wherein The pectin-based anionic adsorbent has the advantages of large adsorption capacity and fast adsorption rate, and can be used for the adsorption of cationic dyes or the enrichment of cationic proteins.

9. A method for a pectin-based anionic adsorbent, characterized in that The method is to add the pectin-based anionic adsorbent according to claim 7 to the target water body or solution.

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