Preparation method and application of sunflower stem pith foam adsorption material

Abstract

The invention relates to the technical field of adsorbents, and discloses a preparation method and application of a sunflower stem pith foam adsorption material.The preparation method comprises the steps that microfibrillated cellulose, quaternized chitosan and sunflower stem pith powder are put into a beaker to be mixed, a cross-linking agent is added, and stirring cross-linking is conducted; and then cryopreserving and thawing to prepare the composite sunflower stem pith foam adsorption material with the dispersed sunflower stem pith powder wrapped by the chitosan. Chitosan is used as a support to support and disperse sunflower stem pith powder, so that sunflower stem pith agglomeration is avoided, and active adsorption sites are increased. The adsorption capacity of the sunflower stem pith foam adsorption material prepared by the method is greatly increased, the adsorption capacity of Congo red is 9 times that of uncompounded sunflower stem pith, the performance is greatly improved, and the sunflower stem pith foam adsorption material can be applied to adsorption of hydrophobic and anionic azo dyes and has a good application prospect. The adsorbent has the advantages of low cost, simplicity in preparation, no chemical pollution, reproducibility, excellent adsorption performance and the like.

Description

Technical Field

[0001] This invention relates to the field of adsorbent technology, specifically to a method for preparing sunflower stem pith foam adsorbent material and its application. Background Technology

[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.

[0003] Azo dyes, as typical pollutants in industrial wastewater (especially dyeing and printing wastewater), are characterized by stable molecular structure, poor biodegradability, and high toxicity. They also often exhibit hydrophobic and anionic properties—not only do they block light from water bodies and inhibit photosynthesis in aquatic organisms, disrupting the ecological balance, but they also accumulate through the food chain, inducing cell mutations and increasing the risk of cancer in humans. For hydrophobic and anionic azo dyes, hydrophobic adsorbents are particularly effective in their removal. Although progress has been made in the innovation of hydrophobic adsorbent materials in recent years, most materials require complex structural designs and chemical modifications, relying not only on non-renewable petroleum-based resources but also generating non-degradable waste debris. Furthermore, introducing additional cationic functional groups and adsorption sites typically requires harsh processing conditions, complex processes, and excessive use of toxic chemicals and high energy consumption, further exacerbating environmental damage.

[0004] The preparation of adsorbents from agricultural waste aligns with green chemistry and sustainable development principles, making it a current research hotspot. Many agricultural wastes are rich in active components such as lignin and cellulose, possessing significant potential for pollutant removal. However, achieving high adsorption efficiency often relies on complex multi-step modifications involving alkalization, etherification, and amination, resulting in long process chains and demanding conditions. Among these, sunflower pith, an agricultural waste, has attracted considerable attention for its inherent hydrophobicity and honeycomb porous structure, as well as its aromatic components (such as polyphenols and flavonoids) rarely found in other natural materials, particularly in the adsorption of hydrophobic pollutants. Furthermore, studies have demonstrated that unmodified sunflower pith can achieve a 97% removal rate for cationic dyes, and after modification with polyaniline (PANI), its saturated adsorption capacity for Cr(VI) increases to 42.96 mg / g. However, the adsorption capacity of sunflower pith is limited, and the adsorbent is difficult to recover after use. Developing simple, controllable, and environmentally friendly adsorbents with hydrophobic-electrostatic synergistic effects to achieve long-term stable underwater adsorption remains a significant challenge. Summary of the Invention

[0005] The purpose of this invention is to address the problems of insufficient and unstable utilization of the adsorption capacity of sunflower stem pith by providing a method for preparing sunflower stem pith foam adsorption material and its application. This method solves the problems of easy aggregation, strong hydrophobicity, and difficulty in utilization of sunflower stem pith. By using a scaffold material to support and disperse the stem pith powder, the adsorption sites are increased and the adsorption capacity is improved. The adsorption capacity of the sunflower stem pith foam adsorption material is increased by 9 times compared with that of pure sunflower stem pith, realizing the green utilization of agricultural waste.

[0006] The technical solution of the present invention is as follows: The present invention provides a sunflower stem pith foam adsorbent material, comprising a scaffold material and an adsorbent material, wherein the adsorbent material is dispersed between the scaffold material, the scaffold material is prepared from microfibrillated cellulose and quaternized chitosan, and the adsorbent material is sunflower stem pith powder.

[0007] This application mixes sunflower stem pith powder with a scaffold material and separates the powder using physical methods to prevent agglomeration, fully releasing the adsorption sites of the sunflower stem pith and improving its utilization rate. No chemical modification or reagents are required, meeting the requirements of green and environmentally friendly practices.

[0008] Another aspect of the present invention provides a method for preparing sunflower stem pith foam adsorbent material, comprising the following steps: Step S1: Mix microfibrillated cellulose, quaternized chitosan, and sunflower stem pith powder in a beaker, add deionized water, and stir in an electric stirrer for 2-5 hours to completely disperse the solids; then add the crosslinking agent and continue stirring for 0.5-2 hours. Step S2: Transfer the mixed system to a custom mold, freeze it at -10℃ for 10-20 h, and thaw it at room temperature to obtain sunflower stem pith foam adsorbent material.

[0009] The preparation method is simple, uses green materials, fully recycles agricultural waste straw, saves resources, reduces costs, and reduces environmental pressure.

[0010] According to a preferred embodiment, the content of sunflower stem pith powder in the sunflower stem pith foam adsorbent material is 0.25wt%-0.5wt%.

[0011] According to a preferred embodiment, the content of sunflower stem pith powder in the sunflower stem pith foam adsorbent material is 0.5 wt%.

[0012] According to a preferred embodiment, the amount of microfibrillated cellulose and quaternized chitosan added is 25wt%-75wt% and 1wt%-2.5wt%, respectively.

[0013] According to a preferred embodiment, the crosslinking agent is bis(ethylene sulfone)methane, and the amount of the crosslinking agent added is 1wt%-2.5wt%.

[0014] Another aspect of the present invention provides the application of the sunflower stem pith foam adsorbent material as described above in the adsorption of hydrophobic, anionic azo dyes.

[0015] According to a preferred embodiment, the pH of the sunflower stem pith foam adsorbent material is 3-7.

[0016] According to a preferred embodiment, the hydrophobic, anionic azo dye is Congo red, and the initial concentration of Congo red is 100 mg / L-500 mg / L.

[0017] According to a preferred embodiment, the capacity of the sunflower stem pith foam adsorbent material is 727 mg / g.

[0018] Preferably, the prepared sunflower stem pith foam adsorbent material not only has the advantages of low material cost and simple preparation method, but also has high adsorption performance for anionic azo dyes, with an adsorption capacity of 727 mg / g, realizing the efficient utilization of plant materials.

[0019] Compared with existing technologies, the advantages of this invention are: 1. A method for preparing sunflower stem pith foam adsorbent material and its application, which uses renewable natural adsorbent material, is environmentally friendly, and reduces the use of toxic chemicals; the preparation is simple, using a one-pot mixing method, without the need for complex chemical reaction condition control; the preparation cost is low, using agricultural waste sunflower stem pith, recycling waste resources, and the material is renewable; 2. A method for preparing sunflower stem pith foam adsorbent material and its application, comprising assembling quaternized chitosan with sunflower stems to achieve surface charge coverage, thereby avoiding the problem of electrostatic repulsion caused by negatively charged anionic dyes on the original sunflower stem surface; using the inherently hydrophobic sunflower stem as the hydrophobic component of the adsorbent material can fully utilize the significant advantages of hydrophobic adsorbents in removing hydrophobic anionic dyes, improve the hydrophobic performance of hydrophobic adsorbents; and increase the adsorption capacity of Congo red; 3. A method for preparing sunflower stem pith foam adsorbent material and its application. This application prepares sunflower stem pith foam adsorbent material into an integral frozen foam material. The material is columnar in shape, which does not affect the adsorption performance and can improve its recyclability. At the same time, the material also has excellent compression resistance and environmental stability, and can achieve long-term stable underwater adsorption. Attached Figure Description

[0020] Figure 1The water contact angle of the original sunflower stem pith, quaternized chitosan / microfibrillated cellulose substrate, and sunflower stem pith foam adsorbent material; Figure 2 Zeta potential of Congo red and sunflower stem pith foam; Figure 3 (a) is a photograph of the foam material; (b) is a scanning electron microscope image of the foam; (c) shows the effect of sunflower stem pith foam with different percentage contents and raw sunflower stem pith on the adsorption capacity of Congo red; (d) shows the effect of different masses of foam adsorbent on the adsorption capacity of Congo red; (e) shows the effect of different initial concentrations of Congo red solution on the adsorption capacity of Congo red; (f) shows the effect of different pH values ​​on the adsorption capacity of Congo red; and (g) shows the effect of different time conditions on the adsorption capacity of Congo red. Figure 4 Stability testing experiments were conducted on sunflower stem pith foam material under different physicochemical conditions. Detailed Implementation

[0021] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.

[0023] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0024] Example 1: A method for preparing sunflower stem pith foam adsorbent material and its application 10 g of microfibrillated cellulose, 0.6 g of quaternized chitosan, and sunflower stem pith powder of varying masses (2-4 mm) were mixed in a beaker, and 10 mL of deionized water was added. The mixture was stirred in an electric stirrer for 5 hours to ensure complete dispersion of the solids. Then, 0.3 g of the crosslinking agent bis(ethylene sulfone)methane was added, and stirring continued for 2 hours. Finally, the mixture was transferred to a custom mold and frozen at -12°C for 24 hours. After thawing at room temperature, sunflower stem pith foam adsorbent material (SS foam) was obtained.

[0025] Using the same preparation method, but without adding sunflower stem pith powder, a quaternized chitosan / microfibrillated cellulose matrix was obtained.

[0026] The water contact angles of the original sunflower stem pith, quaternized chitosan / microfibrillated cellulose substrate, and sunflower stem pith foam adsorbent material were measured, and the results are as follows: Figure 1 As shown. From Figure 1 It is evident that the original sunflower stem pith is hydrophobic, while the quaternized chitosan / microfibrillated cellulose substrate exhibits hydrophilic properties. The sunflower stem pith foam adsorbent material (SS foam) prepared by assembling the original sunflower stem pith with the substrate retains the hydrophobicity of the sunflower stem pith surface. This material is particularly outstanding in removing hydrophobic and anionic azo dyes.

[0027] The zeta potential of pristine sunflower pith, Congo red, and sunflower pith foam adsorbent material was detected, revealing the inherent negative charge on the surface of pristine sunflower pith. Figure 2 As shown, after the substrate was assembled, the zeta potential of the sunflower stem pith foam surface was +32.5 mV, which formed a strong electrostatic attraction with the negatively charged Congo red molecules (zeta potential approximately -36.16 mV). This electrostatic interaction not only drove the dye molecules to migrate to the foam surface, but also reduced the intermolecular repulsion through charge neutralization, promoting the enrichment of Congo red on the foam surface.

[0028] The morphology of the prepared sunflower stem pith foam adsorbent material (SS foam) is as follows: Figure 3 As shown in figure a. Further analysis of the surface morphology of the foam is as follows: Figure 3 As shown in b, it exhibits a disordered honeycomb-like macroporous structure induced by ice crystal freezing, with a macropore size distribution of 39.05±15.57μm. Figure 3 b).

[0029] To investigate the effect of different amounts of sunflower stem pith added on adsorption capacity, different masses of sunflower stem pith were added during the preparation process: 0 mg (0 wt% SS), 50 mg (0.25 wt% SS), 100 mg (0.5 wt% SS), 200 mg (1 wt% SS), and 300 mg (1.5 wt% SS). Equal masses of 10 mg of sunflower stem pith foam with different percentages of sunflower stem pith were added to 20 ml of a 400 mg / L Congo red solution at pH 7. The adsorption effect of sunflower stem pith foam with different amounts of sunflower stem pith on Congo red was investigated.

[0030] Adsorption experiments on Congo red in raw sunflower stem pith, blank quaternized chitosan / microfibrillated cellulose substrate, and sunflower stem pith foam adsorbent materials with different sunflower stem pith contents showed that the adsorption capacity of raw sunflower stem pith for Congo red was only 90 mg / g, the adsorption capacity of blank quaternized chitosan / microfibrillated cellulose substrate (QCS / MFC blank substrate, 0 wt% ss) for Congo red was 550 mg / g, and the 0.5 wt% sunflower stem pith foam adsorbent material showed the highest adsorption efficiency. Figure 3 c), its adsorption capacity for Congo red reached 727 mg / g, significantly higher than that of foams with other formulations. Notably, the adsorption capacity of 0.5 wt% sunflower stem pith foam adsorbent material for Congo red was nearly 9 times higher than that of natural sunflower stem pith.

[0031] This study investigated the adsorption performance of sunflower stem pith foam (0.5 wt% ss) on 20 ml of Congo red at a concentration of 400 mg / L and pH=7, under different adsorbent masses (sunflower stem pith foam). The effects of different adsorbent addition amounts (m=5 mg, 10 mg, 15 mg, 20 mg, 25 mg) on ​​the adsorption of Congo red by sunflower stem pith foam were explored.

[0032] The study found that the removal efficiency and adsorption capacity of Congo red reached their peak when the adsorbent dosage was 10 mg. Therefore, subsequent experiments all used an adsorbent dosage of 10 mg. Figure 3 d).

[0033] This study investigated the effect of sunflower stem pith foam on the adsorption of Congo red under different pH conditions. Experimental conditions were selected at pH values ​​of 3, 5, 7, 9, and 11. 10 mg of 0.5 wt% SS (equivalent to the percentage of sunflower stem pith) was added to 20 ml of a 400 mg / L Congo red solution to investigate the effect of pH on the adsorption of Congo red by sunflower stem pith foam.

[0034] The experiment on the effect of pH on adsorption performance was conducted in the range of 3-11, with the solution pH adjusted using dilute hydrochloric acid and sodium hydroxide solution. The results showed that the adsorption capacity of the foam decreased with increasing pH. Figure 3 f). Under acidic conditions (pH 3-5), the quaternary ammonium groups on the foam surface are positively charged, generating a strong electrostatic attraction with the negatively charged Congo red molecules, promoting adsorption; as the pH increases to an alkaline environment, OH... - Ions compete with Congo red anions for active sites on the foam surface, leading to a decrease in adsorption capacity. The adsorption capacity of Congo red gradually increases with prolonged contact time, reaching an equilibrium capacity of 727 mg / g after 10 hours. Visual observation shows that the Congo red solution almost completely decolorizes after 10 hours (Figure 3g).

[0035] This study investigated the effect of different initial concentrations of Congo red on the adsorption of Congo red by sunflower stem pith foam. Initial concentrations of Congo red (c0) were selected as 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, and 700 mg / L. 10 mg of a 0.5 wt% ss solution (equivalent to the percentage of sunflower stem pith) was added to 20 ml of Congo red solution to investigate the effect of different initial concentrations of Congo red on the adsorption of Congo red by sunflower stem pith foam.

[0036] In the study on the effect of initial Congo red concentration, the initial concentration was gradually increased from 100 mg / L to 700 mg / L. The experimental results showed that as the concentration increased, the adsorption capacity of the foam gradually increased. When the concentration reached 400 mg / L, the adsorption capacity stabilized at 727 mg / g, and the removal efficiency of Congo red was 90.8%. Figure 3 e).

[0037] The stability of the prepared sunflower stem pith foam material was tested by soaking it in HCl, acetone, ethanol, NaOH, and at a high temperature of 80℃ for one week. Figure 4 As shown, the foam morphology remained intact, verifying its stability under harsh chemical and physical treatments, laying the foundation for long-term stable underwater adsorption.

[0038] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for preparing a sunflower stem pith foam adsorbent material, characterized in that, Includes the following steps: Step S1: Mix microfibrillated cellulose, quaternized chitosan, and sunflower stem pith powder in a beaker, add deionized water, and stir in an electric stirrer for 2-5 hours to completely disperse the solids; then add the crosslinking agent and continue stirring for 0.5-2 hours. Step S2: Transfer the mixed system to a custom mold, freeze it at -10℃ for 10-24 h, and thaw it at room temperature to obtain sunflower stem pith foam adsorbent material.

2. The method for preparing a sunflower stem pith foam adsorbent material according to claim 1, characterized in that, In step S1, the amount of sunflower stem pith powder added is 0.25wt%-0.5wt%.

3. The method for preparing a sunflower stem pith foam adsorbent material according to claim 1, characterized in that, In step S1, the amount of sunflower stem pith powder added is 0.5 wt%.

4. The method for preparing a sunflower stem pith foam adsorbent material according to claim 1, characterized in that, In step S1, the amounts of microfibrillated cellulose and quaternized chitosan added are 25wt%-75wt% and 1wt%-2.5wt%, respectively.

5. The method for preparing a sunflower stem pith foam adsorbent material according to claim 1, characterized in that, In step S1, the crosslinking agent is bis(ethylene sulfone)methane, and the amount of the crosslinking agent added is 1wt%-2.5wt%.

6. A sunflower stem pith foam adsorbent material, characterized in that, It includes a scaffold material and an adsorbent material, wherein the adsorbent material is dispersed between the scaffold material, the scaffold material is prepared from microfibrillated cellulose and quaternized chitosan, and the adsorbent material is sunflower stem pith powder.

7. The application of the sunflower stem pith foam adsorbent material according to claim 6 in the adsorption of hydrophobic, anionic azo dyes.

8. The application according to claim 7, characterized in that, The pH value for the sunflower stem pith foam adsorbent material is 3-7.

9. The application according to claim 7, characterized in that, The hydrophobic, anionic azo dye is Congo Red, and the initial concentration of Congo Red is 100 mg / L-500 mg / L.

10. The application according to claim 9, characterized in that, The capacity of the sunflower stem pith foam adsorbent material is 727 mg / g.

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