A magnetic bio-based adsorbent, and a preparation method and application thereof

Abstract

The application discloses a novel selective adsorption of primary amino-containing dye magnetic bio-based adsorbent, and a preparation method thereof, which comprises the following steps: reacting sodium lignosulfonate, carboxylated chitosan, sodium alginate, magnetic particles, epichlorohydrin and polyethylene imine. The raw material containing rich carboxyl, sulfonic acid group and imine group is added to facilitate the coordination of metal ions, more active sites are added, the new design idea of adding the pore-forming agent polyethylene glycol to increase the specific surface area of the adsorbent microspheres, and the composite preparation of carboxylated chitosan (CCS), sodium lignosulfonate (LS), sodium alginate (SA) and magnetic particles (Fe3O4) and the modification of polyethylene imine (PEI) are realized through the one-pot method, so as to obtain a magnetic bio-based adsorbent which can selectively adsorb primary amine-containing dyes. The removal rate of the adsorbent SA-CCS-LS@Fe3O4 to the primary amine-containing dyes reaches more than 98%, and the adsorbent can be recycled.

Description

Technical Field

[0001] This invention relates to the fields of materials technology and chemistry, specifically to a magnetic bio-based adsorbent, its preparation method, and its application in the adsorption of primary amino dyes. Background Technology

[0002] In recent years, organic dyes have been widely used in textile printing and dyeing, leather printing and dyeing, inks, pharmaceuticals, cosmetics, papermaking, and other fields. Most of these dyes are toxic, persistent, and potentially carcinogenic. Currently, mature technologies for dye removal from wastewater include biological treatment, electrochemical treatment, membrane separation, photocatalytic degradation, and adsorption. Adsorption is considered the most promising method for removing dye pollutants due to its high efficiency, simple operation, and economic feasibility. However, traditional adsorbents such as activated carbon have poor selectivity, are expensive, and difficult to regenerate; zeolites and molecular sieves have low saturation adsorption capacity and poor selective adsorption effects. However, dye wastewater systems are complex and require selective separation of dyes of the same type. Therefore, developing novel adsorbents is of significant practical importance.

[0003] Sodium alginate (SA) is a non-toxic, biocompatible, renewable, and low-cost polysaccharide derived from seaweed. It contains abundant carboxylate groups (COOH), which can chelate with metal ions to form complex "egg-box" structures, and can be used as an adsorbent to remove dyes from aquatic environments. Furthermore, sodium alginate can form hydrogels under the action of calcium ions, which facilitates the recovery of the adsorbent from aqueous solutions. However, its mechanical properties are poor, and it is brittle. Therefore, preparing spherical sodium alginate magnetic particles is of significance, as it can impart a certain strength to the product and facilitate subsequent recycling and reuse.

[0004] Sodium lignosulfonate (LS) is an unavoidable byproduct of the papermaking industry, possessing environmental friendliness, low cost, and abundant functional groups (hydroxyl and sulfonic acids). These properties make it a potential candidate for high-performance absorbents capable of removing dyes.

[0005] Carboxylated chitosan (CCS) is a derivative of chitosan with good biocompatibility, lipid-lowering, antibacterial, and non-toxic properties. CCS side chains contain polar groups such as amino and carboxyl groups. Furthermore, CCS is an effective chelating agent for metals such as silver, zinc, and copper, facilitating coordination and chelation with metal ions. Therefore, CCS can be used in agriculture, medical devices, cosmetics, textiles, and wastewater purification. Unlike chitosan, CCS is easily dispersed in water because it is rich in hydrophilic functional groups such as hydroxyl, amino, and carboxyl groups. However, the high solubility of CCS in water hinders its application in water pollution control.

[0006] Polyethyleneimine (PEI) is a polyamine containing multiple amino groups. Due to its strong ability to chelate heavy metal ions, it has been widely used in adsorbent modification. Its abundant imino groups provide more adsorption sites, which is beneficial for enhancing adsorption efficiency.

[0007] However, the adsorption materials currently being developed are difficult to recycle, cannot selectively recycle dyes containing primary amines, are easily broken, and can easily cause secondary pollution of water bodies. Therefore, the preparation of a magnetic hydrogel microsphere that can be easily recycled is of great practical significance. Summary of the Invention

[0008] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a novel magnetic bio-based adsorbent for selectively adsorbing primary amino dyes, its preparation method, and its application.

[0009] To address the aforementioned technical problems, this invention discloses a method for preparing a magnetic bio-based adsorbent, comprising the following steps:

[0010] (1) Mix carboxylated chitosan, sodium lignosulfonate, magnetic particles, polyethylene glycol and sodium alginate in water to obtain a mixture.

[0011] (2) The mixture is reacted with polyethyleneimine and a crosslinking agent to obtain a viscous solution.

[0012] (3) The viscous solution is added to the calcium ion solution to obtain the magnetic bio-based adsorbent SA-CCS-LS@Fe3O4.

[0013] In step (1), the magnetic particles are Fe3O4; in step (2), the crosslinking agent is epichlorohydrin. Preferably, the magnetic particles are Fe3O4 powder, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0014] The carboxylated chitosan has a number-average molecular weight range of 1400–1600; the sodium lignosulfonate has a number-average molecular weight range of 400–600; the polyethylene glycol has a number-average molecular weight range of 3900–4100; and in step (2), the polyethyleneimine has a number-average molecular weight range of 700–900. Preferably, the carboxylated chitosan has a number-average molecular weight of 1500, the sodium lignosulfonate has a number-average molecular weight of 534, the sodium alginate has a molecular weight of 200, the polyethyleneimine has a number-average molecular weight of 800, and the polyethylene glycol has a number-average molecular weight of 4000.

[0015] In step (1), the mixing is a "one-pot" mixing.

[0016] The concentration of sodium alginate in the mixture is 0.001–0.05 g / mL, preferably 0.005–0.03 g / mL, more preferably 0.008–0.025 g / mL, and even more preferably 0.015 g / mL; the concentration of polyethylene glycol in the mixture is 0.001–0.01 g / mL, preferably 0.002–0.008 g / mL, more preferably 0.004–0.008 g / mL, and even more preferably 0.006 g / mL.

[0017] In step (1), the mass ratio of carboxylated chitosan, sodium lignosulfonate, magnetic particles and sodium alginate is 1:1:1~2:0.1~3.5, preferably 1:1:1:0.5~3, more preferably 1:1:1:0.5~2.5, and even more preferably 1:1:1:1.5~1.7.

[0018] In step (1), the mixing is carried out at 20-30°C for 4-8 hours, preferably at 25°C and 120 rpm for 4-6 hours.

[0019] In step (2), the added mass of polyethyleneimine is based on a mass ratio of sodium alginate to polyethyleneimine of 1 to 3: 2 to 9, preferably 1: 1 to 8, more preferably 1: 1.5 to 5.5, and even more preferably 1: 2 to 3.

[0020] In step (2), the volume of the crosslinking agent added is calculated as 2% to 10% of the volume of water and the volume of the crosslinking agent in step (1), preferably 4% to 8%, and more preferably 6%.

[0021] In step (2), the reaction is carried out at 20-30°C for 3-6 hours with stirring, preferably at 25°C and 300 rpm for 4-6 hours.

[0022] In step (2), the reaction solution obtained from the reaction is filtered to obtain a viscous solution.

[0023] In step (3), the viscous solution is converted into beads; preferably, into microspheres.

[0024] In step (3), the calcium ion solution is a 0.1–3M calcium chloride aqueous solution, preferably a 1M calcium chloride aqueous solution; the amount of calcium ion solution added is based on a volume ratio of 10%–20% of the water volume in step (1), preferably 10%. The viscous solution is added by flow addition or drop addition, preferably by a peristaltic pump at a rate of 0.5–4 mL / min. More preferably, the viscous solution is added as a drop at a rate of 2.5 mL / min.

[0025] In step (3), the viscous solution is added to the calcium ion aqueous solution to precipitate SA-CCS-LS@Fe3O4 microspheres. The SA-CCS-LS@Fe3O4 microspheres after the reaction are scooped out with a 60-mesh sieve, washed with deionized water to remove salt, and freeze-dried for 72 hours to obtain the magnetic bio-based adsorbent SA-CCS-LS@Fe3O4.

[0026] A second aspect of the present invention is that it also provides a magnetic bio-based adsorbent SA-CCS-LS@Fe3O4 prepared by the above method.

[0027] A third aspect of the present invention is that it provides the application of the above-mentioned magnetic bio-based adsorbent SA-CCS-LS@Fe3O4 in the adsorption of primary amino dyes.

[0028] A fourth aspect of the present invention is the application of the aforementioned magnetic bio-based adsorbent SA-CCS-LS@Fe3O4 in the removal of primary amino dyes from wastewater. Preferably, the primary amino dyes include any one or more combinations of Neutral Red, Congo Red, or Reactive Black-5.

[0029] Beneficial effects:

[0030] This invention utilizes a novel design approach that incorporates raw materials containing numerous carboxyl and sulfonic acid groups to facilitate the coordination of metal ions and increase the number of active sites. It also incorporates polyethylene glycol as a pore-forming agent to increase the specific surface area of ​​the adsorbent microspheres. Furthermore, it innovatively achieves the composite preparation of carboxylated chitosan (CCS), sodium lignosulfonate (LS), sodium alginate (SA), and magnetic particles via a "one-pot method," along with modification with polyethyleneimine (PEI), to obtain a selective adsorption dye containing primary amines.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. This invention provides a novel bio-based adsorbent for selectively adsorbing primary amino dyes. It exhibits good adsorption performance and regenerability for primary amino dyes in dyeing and printing wastewater. Specifically, the adsorbent SA-CCS-LS@Fe3O4-1.5 achieves a removal rate of over 98% for neutral red dye and can be recycled.

[0033] 2. The SA-CCS-LS@Fe3O4 microspheres provided by this invention have the following advantages: the addition of sodium alginate facilitates the drop formation into microspheres; sodium lignosulfonate, carboxylated chitosan, and polyethyleneimine provide more active sites; and the addition of magnetic particles makes them easier to recycle. The "one-pot" reaction of carboxylated chitosan, PEI, Fe3O4, sodium lignosulfonate, and sodium alginate can achieve good selectivity for dyes containing primary amines and is more environmentally friendly. Attached Figure Description

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0035] Figure 1 The FTIR spectra of each raw material and SA-CCS-LS@Fe3O4 are shown.

[0036] Figure 2 The graph shows the removal rates of different dyes by SA-CCS-LS@Fe3O4 adsorbent with varying amounts of sodium alginate. NR, CR, RB-5, MB, MV, MO, E102, and RhB represent aqueous solutions of Neutral Red, Congo Red, Reactive Black-5, Methylene Blue, Methyl Violet, Methyl Orange, Tartrazine, and Rhodamine B, respectively.

[0037] Figure 3 The graph shows the removal rates of different dyes by SA-CCS-LS@Fe3O4 adsorbent with different amounts of polyethylene glycol.

[0038] Figure 4 The relative removal rate is shown for repeated use of SA-CCS-LS@Fe3O4-1.5-0.6. Detailed Implementation

[0039] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0040] In the following embodiments, the magnetic particle powder is Fe3O4. The Fe3O4 powder was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0041] In the following examples, the number-average molecular weight of the carboxylated chitosan is 1500, the number-average molecular weight of the sodium lignosulfonate is 534, the molecular weight of the sodium alginate is 200, the number-average molecular weight of the polyethyleneimine is 800, and the number-average molecular weight of the polyethylene glycol is 4000.

[0042] In the following embodiments, the removal rate Re% is calculated using the following formula:

[0043]

[0044] Where C0 is the initial concentration of the dye, C e This represents the concentration of the dye after adsorption equilibrium.

[0045] Example 1: Preparation of SA-CCS-LS@Fe3O4 microsphere adsorbent

[0046] Three microsphere adsorbents, SA-CCS-LS@Fe3O4-1, SA-CCS-LS@Fe3O4-1.5, and SA-CCS-LS@Fe3O4-2, were prepared by adding different amounts (0.8g, 1.5g, and 2.2g) of sodium alginate.

[0047] The specific steps are as follows:

[0048] (1) Take 0.8g, 1.5g, 2.2g of sodium alginate, 0.9g of carboxylated chitosan, 0.9g of sodium lignosulfonate, 0.9g of magnetic particle powder and 0.4g of polyethylene glycol into a beaker containing 100mL of deionized water, stir at 25℃ and 120rpm for 5h to obtain a mixture.

[0049] (2) Add 6 mL of epichlorohydrin and 4.3 g of polyethyleneimine to the mixture described in step (1), react at 25 °C and 300 rpm for 5 h, filter, and obtain a viscous solution.

[0050] (3) Convert the viscous solution obtained in step (2) into beads: inject the viscous solution obtained in step (2) as drops into an aqueous solution containing 1L of 1M calcium chloride at a rate of 2.5mL / min, and SA-CCS-LS@Fe3O4 microspheres will precipitate.

[0051] (4) Use a 60-mesh sieve to remove the SA-CCS-LS@Fe3O4 microspheres after the reaction, wash off the salt with deionized water, and freeze-dry for 72 hours.

[0052] The FTIR spectra of each raw material and SA-CCS-LS@Fe3O4-1, SA-CCS-LS@Fe3O4-1.5 and SA-CCS-LS@Fe3O4-2 are as follows: Figure 1 As shown. The Fe3O4 spectrum at 590 cm⁻¹ -1 Fe-O peaks appeared. In the SA spectrum, the peak was at 3390 cm⁻¹. -1 A stretching vibration with a blunt peak representing -OH was observed, and the peak value of the symmetric stretching vibration of the carboxylate was at 1421 cm⁻¹. -1 The infrared spectrum of LS is shown at 3460 cm⁻¹. -1 The broad peak at 1607 cm⁻¹ is due to the stretching vibration of the -OH group. -1 1514cm -1 The characteristic peak is due to the stretching vibration of the aromatic ring. 1045 cm⁻¹ -1 This is attributed to the stretching vibrations of the sulfonic acid group. The CCS infrared spectrum shows that the symmetric stretching vibration peak of the carboxylate is at 1421 cm⁻¹. -1 Furthermore, for SA-CCS-LS@Fe3O4-1, the peak value of CO tensile vibration derived from sodium lignosulfonate (1145 cm⁻¹) was... -1The phenolic hydroxyl groups of primary alcohols on the carboxylated chitosan branches disappear, while at 1573 cm⁻¹... -1 A new CN vibration peak appears at 1421 cm⁻¹. This indicates that sodium lignosulfonate, sodium alginate, and carboxylated chitosan all undergo cross-linking reactions with epichlorohydrin to modify the amino groups. The carboxyl groups in sodium alginate and carboxylated chitosan show a peak at 1421 cm⁻¹. -1 Migrating to 1409cm -1 The sulfonic acid group in sodium lignosulfonate starts from 1045 cm⁻¹ -1 Migrate to 1021cm -1 After the reaction, it was shown that the carboxylic acid group and the sulfonic acid group participated in the reaction with Ca. 2+ Crosslinking, at 567cm -1 The appearance of a blunt peak may be due to Ca 2+ Crosslinking with sodium lignosulfonate, sodium alginate, and carboxylated chitosan. These conclusions indicate that sodium lignosulfonate, carboxylated chitosan, and sodium alginate were successfully modified with polyethylene polyamine and simultaneously hybridized through crosslinking with divalent calcium ions.

[0053] Example 2: Adsorption experiment of adsorbent SA-CCS-LS@Fe3O4-1

[0054] (1) At room temperature, prepare a series of aqueous solutions of neutral red, Congo red, reactive black-5, methylene blue, methyl violet, methyl orange, tartrazine and rhodamine B dyes with a concentration of 100 mg / L.

[0055] (2) 0.01g of SA-CCS-LS@Fe3O4-1 adsorbent was weighed and dispersed in 5mL of 100mg / L aqueous solutions of neutral red (522nm), Congo red (498nm), Reactive Black-5 (600nm), methylene blue (644nm), methyl violet (584nm), methyl orange (465nm), tartrazine (427nm), and rhodamine B (535nm). The solutions were placed in a shaking incubator and the adsorption experiment was carried out at 25℃ and 120rpm.

[0056] (3) Once adsorption equilibrium is reached, i.e., the adsorption amount tends to be the same, samples are taken and their concentrations are measured using a UV-Vis spectrophotometer at the maximum absorption wavelength of each dye. The removal rate of each dye is then calculated as follows: Figure 2 .

[0057] Example 3: Adsorption experiment of adsorbent SA-CCS-LS@Fe3O4-1.5

[0058] (1) At room temperature, prepare a series of aqueous solutions of neutral red, Congo red, reactive black-5, methylene blue, methyl violet, methyl orange, tartrazine and rhodamine B dyes with a concentration of 100 mg / L.

[0059] (2) 0.01g of SA-CCS-LS@Fe3O4-1.5 adsorbent was weighed and dispersed in 5mL of 100mg / L aqueous solutions of neutral red (522nm), Congo red (498nm), Reactive Black-5 (600nm), methylene blue (644nm), methyl violet (584nm), methyl orange (465nm), tartrazine (427nm), and rhodamine B (535nm). The solutions were placed in a shaking incubator and the adsorption experiment was carried out at 25℃ and 120rpm.

[0060] (3) Once adsorption equilibrium is reached, samples are taken and their concentrations are measured using a UV-Vis spectrophotometer at the maximum absorption wavelength of each dye. The removal rate of each dye is then calculated. Figure 2 .

[0061] Example 4: Adsorption experiment of adsorbent SA-CCS-LS@Fe3O4-2

[0062] (1) At room temperature, prepare a series of aqueous solutions of neutral red, Congo red, reactive black-5, methylene blue, methyl violet, methyl orange, tartrazine and rhodamine B dyes with a concentration of 100 mg / L.

[0063] (2) Weigh 0.01g of SA-CCS-LS@Fe3O4-2 adsorbent and disperse it in 5mL of 100mg / L aqueous solutions of neutral red (522nm), Congo red (498nm), Reactive Black-5 (600nm), methylene blue (644nm), methyl violet (584nm), methyl orange (465nm), tartrazine (427nm), and rhodamine B (535nm). Place the solution in a shaking incubator and conduct the adsorption experiment at 25℃ and 120rpm.

[0064] (3) Once adsorption equilibrium is reached, samples are taken and their concentrations are measured using a UV-Vis spectrophotometer at the maximum absorption wavelength of each dye. The removal rate of each dye is then calculated. Figure 2 .

[0065] from Figure 2 It can be seen that for dyes containing primary amine groups, such as Neutral Red, Reactive Black-5, and Congo Red, the removal rates of the three adsorbents all reached over 85%, while the removal rates for other types of dyes were less than 50%. Furthermore, the adsorbent SA-CCS-LS@Fe3O4-1.5 achieved a removal rate of over 95% for dyes containing primary amine groups, demonstrating even better adsorption performance.

[0066] Example 5: Optimization of the amount of porogen polyethylene glycol added

[0067] Based on the SA-CCS-LS@Fe3O4-1.5 material prepared in Example 1, the pore-forming agent was optimized, and adsorbents with the addition of 0.4g polyethylene glycol (as described in Example 1), 0.6g polyethylene glycol, and 0.8g polyethylene glycol were prepared respectively. The preparation method was the same as in Example 1, and the prepared adsorbents were named SA-CCS-LS@Fe3O4-1.5-0.4, SA-CCS-LS@Fe3O4-1.5-0.6, and SA-CCS-LS@Fe3O4-1.5-0.8 respectively.

[0068] Example 6: Adsorption experiment of adsorbent SA-CCS-LS@Fe3O4-1.5-0.4

[0069] The experimental method described is the same as that described in Example 2, except that the adsorbent SA-CCS-LS@Fe3O4-1 is replaced with SA-CCS-LS@Fe3O4-1.5-0.4 adsorbent. The removal rate is as follows: Figure 3 .

[0070] Example 7: Adsorption experiment of adsorbent SA-CCS-LS@Fe3O4-1.5-0.6

[0071] The experimental method described is the same as that described in Example 2, except that the adsorbent SA-CCS-LS@Fe3O4-1 is replaced with SA-CCS-LS@Fe3O4-1.5-0.6 adsorbent. The removal rate is as follows: Figure 3 .

[0072] Example 8: Adsorption experiment of adsorbent SA-CCS-LS@Fe3O4-1.5-0.8

[0073] The experimental method described is the same as that described in Example 2, except that the adsorbent SA-CCS-LS@Fe3O4-1 is replaced with SA-CCS-LS@Fe3O4-1.5-0.8 adsorbent, and the removal rate is as follows: Figure 3 .

[0074] from Figure 3It can be seen that adsorbent SA-CCS-LS@Fe3O4-1.5-0.6 has a better adsorption effect, and the removal rate of dyes containing primary amines is improved compared with adsorbents SA-CCS-LS@Fe3O4-1.5-0.4 and SA-CCS-LS@Fe3O4-1.5-0.8. Adsorbent SA-CCS-LS@Fe3O4-1.5-0.6 achieved a removal rate of 98.82% for Neutral Red, 97.54% for Congo Red, and 95.77% for Reactive Black-5. Furthermore, by optimizing the amount of porogen added, the removal rate of other dyes such as methylene blue, methyl violet, methyl orange, tartrazine, and rhodamine B by adsorbent SA-CCS-LS@Fe3O4-1.5-0.6 was also significantly increased.

[0075] Example 9: Reusable Adsorption Experiment

[0076] 0.01 g of SA-CCS-LS@Fe3O4-1.5-0.6 was placed in 5 mL of 100 mg / L neutral red aqueous solution and 5 mL of 100 mg / L Congo red aqueous solution, respectively. The solutions were placed in a shaking incubator at 25 °C and 120 rpm for adsorption experiments. After adsorption equilibrium was reached and the adsorption capacity was measured, the solutions were placed in 5 mL of 0.1 M sodium hydroxide and then freeze-dried for 72 h for the next cycle. After 5 cycles, as shown... Figure 4 As shown, with the adsorption level of the adsorbent during its first use as 100% removal rate, the removal rate of each subsequent cycle is relative to the removal level of the first use. Figure 4 It can be seen that after the adsorbent was recycled 5 times, the actual relative removal rate of neutral red decreased from 100% to 98.82%, and the actual relative removal rate of Congo red decreased from 100% to 98.19%, indicating that SA-CCS-LS@Fe3O4 hydrogel microspheres can be used for actual wastewater treatment at low cost.

[0077] This invention provides a magnetic bio-based adsorbent, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. The application of the magnetic bio-based adsorbent SA-CCS-LS@Fe3O4 in the adsorption of primary amino dyes, characterized in that, The primary amino dyes include Neutral Red or Reactive Black-5; the preparation method of the magnetic bio-based adsorbent SA-CCS-LS@Fe3O4 includes the following steps: (1) Mix carboxylated chitosan, sodium lignosulfonate, magnetic particles, polyethylene glycol and sodium alginate in water to obtain a mixture; (2) The mixture is reacted with polyethyleneimine and a crosslinking agent to obtain a viscous solution; (3) The viscous solution is added to the calcium ion solution to obtain the magnetic bio-based adsorbent SA-CCS-LS@Fe3O4; In step (1), the magnetic particles are Fe3O4; in step (2), the crosslinking agent is epichlorohydrin. In step (1), the concentration of sodium alginate in the mixture is 0.005-0.03 g / mL; the concentration of polyethylene glycol in the mixture is 0.002-0.008 g / mL.

2. The application according to claim 1, characterized in that, In step (1), the carboxylated chitosan has a number average molecular weight of 1400-1600; the sodium lignosulfonate has a number average molecular weight of 400-600; the polyethylene glycol has a number average molecular weight of 3900-4100; and in step (2), the polyethyleneimine has a number average molecular weight of 700-900.

3. The application according to claim 1, characterized in that, In step (1), the mass ratio of carboxylated chitosan, sodium lignosulfonate, magnetic particles and sodium alginate is 1:1:1~2:0.1~3.5; the mixing is carried out at 20~30℃ for 4~8h.

4. The application according to claim 1, characterized in that, In step (2), the added mass of polyethyleneimine is based on a mass ratio of sodium alginate to polyethyleneimine of 1-3:2-9; the added volume of crosslinking agent is based on a volume ratio of water to crosslinking agent of 2%-10% in step (1); the reaction is carried out at 20-30°C with stirring for 3-6 hours.

5. The application according to claim 1, characterized in that, In step (3), the calcium ion solution is a 0.1-3M calcium chloride aqueous solution; the amount of calcium ion solution added is calculated based on the volume ratio of water to calcium ion solution in step (1) being 10%-20%; the viscous solution is added by flow addition or drop addition.

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