Preparation method and application of novel adsorption material

Abstract

The invention belongs to the technical field of adsorption materials, and particularly relates to a preparation method and application of a novel adsorption material. The preparation process of the novel adsorption material provided by the invention comprises the following steps: dissolving chitosan in an acetic acid solution to prepare a chitosan-acetic acid solution, then adding the chitosan-acetic acid solution into a sodium hydroxide solution to form gel beads, and further pre-crosslinking the formed gel beads in a formaldehyde solution, and crosslinking in a sodium tripolyphosphate solution. The novel adsorption material provided by the invention is low in cost, can be used for treating heavy metal-containing pollutants such as RR24 in a water body, has double adsorption effects of physical adsorption and chemical adsorption, and has the advantages of large adsorption capacity, high material strength, strong stability and the like, and the obtained product is a gel bead, is convenient to recover and is suitable for industrial production. The method has a good application prospect in the field of water environment treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adsorption materials, and particularly relates to a preparation method and application of a novel adsorption material. BACKGROUND

[0002] With the rapid evolution of the global industrial pattern, the ecological environment is facing a serious challenge of wastewater pollution. Pollutants such as heavy metal ion wastewater and azo dye wastewater generated in the industrial production process have the characteristics of being difficult to biodegrade, and the heavy metal ions and azo dyes contained therein can be enriched in living organisms through the food chain, which not only causes human poisoning and damages the body function, interferes with normal life activities, but also poses a serious threat to the health of living organisms and the balance of the ecological environment.

[0003] The molecular formula of Reactive Red 24 (RR24) is C 26 H 17 O 10 N7S3Na3Cl, which is a typical reactive azo dye and has a wide application in the textile, printing and dyeing industries. Its chemical structure is very stable. After being discharged into water, it is extremely difficult to be degraded or biodegraded, and thus it will exist stably in living organisms for a long time. The unique molecular structure and chemical composition of Reactive Red determine its great harm to living organisms, such as carcinogenicity, teratogenicity and genetic mutation, and excessive Reactive Red dye entering the human body will cause dizziness, vomiting, anemia, and even blindness in more serious cases. Therefore, green, safe and efficient methods are needed to remove and decolorize the Reactive Red RR24 dye discharged into water by industrial dyes and control its concentration in water.

[0004] Existing RR24 treatment methods include coagulation and flocculation, oxidation-reduction, electrochemical methods, membrane separation, and adsorption. Among these, adsorption is the simplest and most economical method, capable of quickly and conveniently removing soluble dyes from water. It is also the most widely used physical treatment method, offering advantages such as low cost, simple operation, and high efficiency. Common adsorption materials include activated carbon (fruit shell / wood / durian peel base), biochar, magnesium oxide nanoparticles, zeolite, and clay minerals, each with drawbacks such as poor selectivity, susceptibility to interference from inorganic salts and organic matter, high cost, small adsorption capacity, low adsorption efficiency, difficulty in recovery, easy agglomeration, and fragility. Chitosan (CS) is an environmentally friendly, inexpensive, and highly absorbent renewable material. However, pure chitosan has weak chemical stability, poor mechanical properties, and is difficult to recycle. Sodium tripolyphosphate (TPP), as an ionic crosslinking agent, is widely used in the chemical modification of chitosan. Compared to other crosslinking agents, sodium tripolyphosphate is more environmentally friendly and less expensive. However, sodium tripolyphosphate crosslinked chitosan beads prepared under acidic conditions are very fragile, while alkaline environments cannot achieve the molding and effective crosslinking of chitosan beads.

[0005] Chinese patent CN111482163A discloses a method for preparing an enhanced chitosan-based aerogel for adsorbing heavy metal ions, using a sol-gel method. By employing gelation and freeze-drying techniques, and with the aid of post-chemical modification methods, a low-density, high-porosity reinforced chitosan-based aerogel adsorbent material was prepared. This material remains suspended on the liquid surface throughout the adsorption process, facilitating adsorbent recovery. However, its floating nature limits its application to surface water treatment, restricting its applicability.

[0006] Therefore, it is necessary to invent a new type of adsorbent material that is environmentally friendly, inexpensive, has excellent adsorption performance, and can be recycled, in order to solve the problem of treating pollutants such as RR24 in water bodies. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a novel method for preparing and applying an adsorbent material, which features high adsorption capacity, strong acid resistance, excellent strength, resistance to breakage, easy recycling, and low cost.

[0008] This invention provides a method for preparing a novel adsorbent material, specifically comprising the following steps: S1. Dissolve chitosan in an organic acid solution to prepare a chitosan-acid solution; S2. Transfer the chitosan-acid solution mixture from step S1 to an alkaline solution to form gel beads; S3. Pre-crosslink the gel beads described in step S2 in an aldehyde crosslinking agent solution; S4. The cross-linked gel beads from step S3 are subjected to a second cross-linking process in a sodium tripolyphosphate solution to obtain the final product.

[0009] Preferably, the chitosan-acid solution in step S1 contains 1% to 5% chitosan by mass.

[0010] Preferably, the organic acid solution in step S1 is an aqueous acetic acid solution, wherein the volume fraction of acetic acid in the aqueous acetic acid solution is 1-3%.

[0011] Preferably, after the chitosan-acetic acid solution in step S1 is prepared, it is left to stand overnight to defoam.

[0012] Preferably, the alkaline solution in step S2 has a pH ≥ 12 at room temperature and a concentration of 0.1–1.0 M.

[0013] More preferably, the alkaline solution is a 0.5 M sodium hydroxide solution.

[0014] Preferably, step S2 is performed at room temperature.

[0015] Preferably, the transfer method in step S2 is dropwise addition.

[0016] More preferably, the dripping is performed by slowly dripping the solution into the syringe at a rate of 1 to 2 drops per second.

[0017] Preferably, the gel beads formed in step S2 are left to stand for 12–36 hours.

[0018] Preferably, the aldehyde crosslinking agent in step S3 is a formaldehyde solution with a concentration of 0.5% to 1.0%.

[0019] Preferably, the pre-crosslinking temperature in step S3 is 50℃~70℃, and the duration is 20~40 min.

[0020] Preferably, the concentration of sodium tripolyphosphate in step S4 is 1% to 16%.

[0021] Preferably, the crosslinking temperature in step S4 is room temperature, and the duration is 2-6 hours.

[0022] Preferably, the preparation method further includes: step S5, washing, and preservation.

[0023] Preferably, step S5 is washing with distilled water, and the storage temperature is 2~8℃.

[0024] In another aspect, this invention provides a novel adsorbent material prepared by the aforementioned preparation method.

[0025] Preferably, the novel adsorbent material has a three-dimensional network structure formed by double cross-linking of chitosan, wherein the double cross-linking includes aldehyde pre-cross-linking and sodium tripolyphosphate secondary cross-linking.

[0026] Preferably, the novel adsorbent material is a gel bead with a particle size of 1–5 mm.

[0027] In another aspect, the present invention provides the application of the novel adsorbent material in water treatment.

[0028] Preferably, the water treatment includes removing azo dyes and / or heavy metal ions from the water.

[0029] Preferably, the azo dye comprises Reactive Red RR24.

[0030] Optionally, the application involves using the adsorbent material in a fixed bed or stirred batch manner for industrial wastewater treatment, wherein the pH range of the industrial wastewater is 4–8 and the treatment temperature is 20–40°C.

[0031] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a dual crosslinking mechanism, using formaldehyde pre-crosslinking and sodium tripolyphosphate secondary crosslinking to enhance the structural stability and mechanical strength of the material, thus solving the problem of difficult molding and easy breakage of a single crosslinking agent under acid / alkali conditions.

[0032] (2) The present invention selects to form under alkaline conditions, forming gel beads in alkaline solution, which provides a stable carrier for subsequent cross-linking and avoids the brittleness of materials caused by direct cross-linking under acidic conditions.

[0033] (3) The material prepared by the present invention is in the form of gel microspheres, which is easy to recycle and reuse, and is suitable for continuous or batch water treatment systems.

[0034] (4) This invention uses biodegradable and inexpensive raw materials such as chitosan and sodium tripolyphosphate, which are both environmentally friendly and low-cost, and conform to the principles of green chemistry. Attached Figure Description

[0035] Figure 1 This is the novel adsorbent material prepared in Example 1. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments. It should be noted that the following embodiments are only intended to enable those skilled in the art to better understand the present invention, and are not intended to limit the present invention. For those skilled in the art, any improvements and modifications made to the present invention without departing from the basic idea of ​​the present invention should also be considered within the scope of protection of the present invention.

[0037] Unless otherwise specified, all reagents and equipment mentioned below are commercially available. Unless otherwise specified, all percentages below are by mass.

[0038] Example 1: A novel adsorbent material The specific preparation steps are as follows: S1. Dissolve 1.0 g of chitosan (CS) powder in 50 mL of 2% acetic acid solution, let the mixed solution stand overnight to defoam, and obtain chitosan-acid solution; S2. Using a 10 mL syringe (needle orifice diameter of 0.7 mm), slowly drip the chitosan-acid solution obtained in step S1 into 100 mL of 0.5 M NaOH solution at a rate of 1~2 drops / second. After the gel beads are solidified in the NaOH aqueous solution for 24 h, wash them with distilled water until neutral (final washing solution pH=7). S3. Pre-crosslink the gel beads in 0.7% formaldehyde solution for 30 minutes (60℃, 150rpm).

[0039] S4. Then, react the chitosan beads in a 1% sodium tripolyphosphate solution for 4 hours. Finally, wash the cross-linked chitosan beads with distilled water until neutral and store them at 4°C.

[0040] The gel beads prepared using Example 1 are as follows Figure 1 As shown, its diameter ranges from 1 to 5 mm.

[0041] Example 2 A novel adsorbent material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that step S4 uses a 5% sodium tripolyphosphate solution for the reaction.

[0042] Example 3 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that step S4 uses a 10% sodium tripolyphosphate solution for the reaction.

[0043] Example 4 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that step S4 uses a 16% sodium tripolyphosphate solution for the reaction.

[0044] Example 5 A novel adsorbent material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that in step S3 the gel beads are pre-crosslinked in 0.5% formaldehyde solution for 40 minutes (50°C, 150 rpm).

[0045] Example 6 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that in step S3 the gel beads are pre-crosslinked in 1.0% formaldehyde solution for 20 minutes (70°C, 150 rpm).

[0046] Example 7 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that the volume fraction of acetic acid in step S1 is 1%.

[0047] Example 8 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that the volume fraction of acetic acid in step S1 is 3%.

[0048] Example 9 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that the mass fraction of chitosan in step S1 is 1%, that is, 0.5g is added.

[0049] Example 10 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that the mass fraction of chitosan in step S1 is 5%, that is, 2.5g is added.

[0050] Example 11 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that the crosslinking conditions in step S4 are changed to 20°C and 6h.

[0051] Example 12 A Novel Adsorbent Material The specific preparation steps are as follows: The preparation method is basically the same as that in Example 1, except that the crosslinking conditions in step S4 are changed to 30°C and 2h.

[0052] Comparative Example 1: An Adsorbent Material Material source: Commercially available wood-based activated carbon (granular activated carbon from Yujia Environmental Protection Materials Co., Ltd. with a specific surface area of ​​550 m² / g), pulverized and screened to form particles with a diameter of 1~5 mm, consistent with the particle size of the material in the invention, and dried at 105℃ for 2 hours for later use.

[0053] Comparative Example 2: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, except that the pre-crosslinking temperature in step S3 is 40°C.

[0054] Comparative Example 3: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, except that the formaldehyde pre-crosslinking step S3 is omitted.

[0055] Comparative Example 4: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, except that the formaldehyde solution in step S3 is replaced with a 0.7% glutaraldehyde solution.

[0056] Comparative Example 5: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, the only difference being that step S4 is not performed, that is, only formaldehyde single pre-crosslinking is performed, and sodium tripolyphosphate secondary crosslinking is not performed.

[0057] Comparative Example 6: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, except that in step S2, sodium hydroxide is replaced with 0.5M acetic acid solution.

[0058] Comparative Example 7: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, the only difference being that chitosan is replaced with an equal amount of gelatin.

[0059] Comparative Example 8: An Adsorbent Material The specific preparation steps are basically the same as in Example 1, except that the crosslinking time in step S4 is shortened to 1 hour.

[0060] Table 1. Information on the dosage of sodium tripolyphosphate and chitosan in Examples 1-12 and Comparative Examples 2-8

[0061] Experimental Example 1: Adsorption Capacity Test (1) Test method The adsorption performance of all adsorbents was tested at 150 rpm. 0.10 g of lightly dried gel beads (CS or gelatin content approximately 0.005 g dry weight; Comparative Example 1 used 0.10 g activated carbon) were weighed and placed in 50 mL of an RR24 dye aqueous solution (Sinopharm Chemical Reagent Co., Ltd., CAS: 70210-20-7, catalog number: XW017021020702). The solution was shaken and adsorbed in a 30℃ constant temperature water bath shaker. Every 1 hour, a certain amount of solution was taken out to measure its absorbance. The concentration of the RR24 dye solution was calculated, and the solution was poured back into the original adsorption system for continued shaking and adsorption.

[0062] (2) Calculation method The formulas for calculating the amount and removal rate of RR24 dye removed are shown in Table 2.

[0063] Table 2. Calculation Formulas for the Amount and Removal Rate of RR24 Dye

[0064] Q: The amount of dye removed per unit mass of chitosan, in mg / g.

[0065] E: Removal rate of RR24 dye, %.

[0066] C0: is the initial concentration of the dye, in mg / L.

[0067] C: Final or equilibrium concentration of the dye, mg / L.

[0068] V: Volume of the dye solution, in liters (L).

[0069] W: is the weight of the hydrogel beads, in grams.

[0070] (3) Test results As shown in Table 3.

[0071] Table 3 Adsorption equilibrium capacity results of Examples 1-12 and Comparative Examples 1-8

[0072] As shown in the table above, Examples 1-12 adopted a double cross-linking process combined with alkaline molding, which enabled chitosan to form a three-dimensional network structure with stable structure and uniform pore distribution. This not only ensured sufficient exposure of adsorption sites and improved the adsorption performance of active azo dyes, but also improved the mechanical stability of the material. Furthermore, the adsorption capacity gradually increased with the increase of sodium tripolyphosphate concentration, from 151.54 mg / g to 175.82 mg / g, and was not lower than 150 mg / g.

[0073] Comparative Example 1 uses commercially available wood-based activated carbon, which relies solely on physical adsorption. It lacks specific adsorption sites for reactive azo dyes like Reactive Red RR24, exhibiting poor selectivity and a limited number of effective adsorption sites, resulting in the lowest adsorption capacity of only 118.50 mg / g. Comparative Example 2 uses formaldehyde pre-crosslinking at 40℃, leading to incomplete covalent crosslinking between formaldehyde and chitosan. This results in insufficient density of the three-dimensional network structure, inadequate exposure of adsorption sites, and an adsorption capacity of only 134.80 mg / g. Comparative Example 3 omits the formaldehyde pre-crosslinking step, lacking the structural support of covalent crosslinking. The chitosan gel beads have a loose and easily deformable structure, leading to easy loss of adsorption sites during the adsorption process. Comparative Example 4 replaces the formaldehyde pre-crosslinking agent with glutaraldehyde. The crosslinking reaction efficiency with chitosan is lower than with formaldehyde, resulting in uneven pore distribution in the three-dimensional network of the gel beads, reduced effective adsorption sites, and an adsorption capacity of 141.60 mg / g. Comparative Example 5, which underwent single-linking with formaldehyde, only formed physical adsorption sites through covalent cross-linking, lacking chemical adsorption sites resulting from ionic cross-linking. Therefore, Comparative Example 5 exhibited a single adsorption type and insufficient number of sites, with an adsorption capacity of 140.23 mg / g, lower than Examples 1-12. Comparative Example 6, prepared in an acidic environment, failed to form stable chitosan gel beads. The beads after sodium tripolyphosphate cross-linking were highly brittle, and the material structure damage during adsorption led to a significant loss of adsorption sites. Comparative Example 7 replaced the chitosan substrate with gelatin. Gelatin has a lower amino content than chitosan, resulting in fewer effective adsorption sites and an adsorption capacity of 129.70 mg / g. Comparative Example 8 shortened the secondary cross-linking time of sodium tripolyphosphate to 1 hour. The ionic cross-linking reaction between sodium tripolyphosphate and chitosan was incomplete, resulting in insufficient density of the gel bead structure and the masking of some adsorption sites, thus leading to a slightly lower adsorption capacity of 147.80 mg / g.

[0074] Experimental Example 2: Effect of Different Initial Concentrations on Adsorption Equilibrium Capacity (1) Test method The test method was the same as that used in Example 1. The difference was that 50 mL of RR24 dye solutions of different concentrations (18-66 mg / L) were used.

[0075] (2) Calculation method The calculation method used is the same as that used in Experimental Example 1.

[0076] (3) Test results As shown in Table 4.

[0077] Table 4. Effect of different initial concentrations of RR24 dye on adsorption equilibrium capacity (Example 4)

[0078] As shown in the table above, in Example 4, within an initial RR24 concentration range of 18~66 mg / L, the adsorption equilibrium capacity increased from 175.71 mg / g to 626.26 mg / g, with no signs of adsorption saturation. This indicates that the present invention still possesses excellent adsorption capacity in high-concentration RR24 dye wastewater and can be used in dye wastewater treatment scenarios of different concentrations.

[0079] Experimental Example 3: Effect of different pH values ​​on adsorption equilibrium capacity (1) Test method The test method was basically the same as that used in Example 1. The difference was that 50 mL of 18 mg / L RR24 dye solution was used for testing at different pH values, the pH was adjusted to 4-8 using an acetate / sodium acetate buffer solution, and the estimated adsorption time was reduced to 24 h.

[0080] (2) Calculation method The calculation method used is the same as that used in Experimental Example 1.

[0081] (3) Test results As shown in Table 5.

[0082] Table 5. Effect of initial pH on different RR24 dyes (Example 4): Adsorption equilibrium capacity results

[0083] As shown in the table above, in Example 4, the adsorption equilibrium capacity of RR24 reached a peak of 175.71 mg / g at pH 7 when pH=4~8. It also maintained a high adsorption capacity in the weak acid and weak base range of pH=6~8, which is suitable for the common treatment range of pH=4~8 for industrial wastewater and has good practicality.

[0084] Test Example 4: Recycling Performance Test of Adsorbent Materials (1) Test method Weigh 0.10 g of the gel beads (after gently drying) and place them in 50 mL of an RR24 dye aqueous solution (18 mg / L, Sinopharm Chemical Reagent Co., Ltd., CAS: 70210-20-7, Catalog No.: XW017021020702). After adsorption for 24 h in a 30℃ constant temperature water bath shaker, measure the absorbance of the solution. Remove the gel beads (prepared using the method in Example 4), gently rinse with deionized water, and place them in 50 mL of 0.1 M NaOH solution. Desorb the gel beads by shaking at 30℃ and 150 rpm for 2 hours. Wash the desorbed gel beads with deionized water until neutral and observe their morphology. Repeat the above adsorption experiment with the regenerated gel beads under identical adsorption conditions (50 mL, 18 mg / L RR24), and calculate the second adsorption capacities Q2, Q3, Q4, and Q5 sequentially.

[0085] (2) Calculation method The calculation method used is the same as that used in Experimental Example 1.

[0086] (3) Test results After cycling, the gel beads prepared in Example 4 exhibited good integrity, with no obvious breakage or swelling, and the capacity retention rate is shown in Table 6.

[0087] Table 6. Capacity retention rate after 5 cycles (Example 1)

[0088] As shown in the table above, the capacity retention rate of this invention is over 80% after 5 cycles, demonstrating good recyclability and cycle stability.

[0089] It should be noted that the above-described embodiments should be understood as illustrative, not as limiting the scope of protection of this invention. The scope of protection of this invention is defined by the claims. For those skilled in the art, some non-essential improvements and adjustments made to this invention without departing from the essence and scope of this invention still fall within the scope of protection of this invention.

Claims

1. A method for preparing a novel adsorbent material, characterized by, Specifically comprising the following steps: S1, dissolving chitosan in an organic acid solution to prepare a chitosan-acid solution; S2, transferring the chitosan-acid solution of step S1 to an alkaline solution to form gel beads; S3, pre-crosslinking the gel beads of step S2 in an aldehyde crosslinking agent solution; S4, secondary crosslinking the pre-crosslinked gel beads of step S3 in a sodium tripolyphosphate solution, thereby obtaining the new adsorbent material.

2. The method of claim 1, wherein the novel adsorbent material is prepared by the steps of: The organic acid solution of step S1 is an acetic acid aqueous solution, and the volume fraction of acetic acid in the acetic acid aqueous solution is 1-3%, and the mass fraction of chitosan in the chitosan-acid solution is 1-5%.

3. The method of claim 1, wherein the novel adsorbent material is prepared by the steps of: The alkaline solution of step S2 is a sodium hydroxide solution with a concentration of 0.1-1.0 M; the gel beads formed in step S2 are allowed to stand for 12-36 h.

4. The method of claim 1, wherein the novel adsorbent material is prepared by the steps of: The aldehyde crosslinking agent of step S3 is formaldehyde with a concentration of 0.5-1.0% (w / v); the concentration of sodium tripolyphosphate is 1-16%.

5. The production method according to claim 1, characterized by, The pre-crosslinking temperature in step S3 is 50-70℃, and the time is 20-40 min; the secondary crosslinking temperature in step S4 is 20-30℃, and the time is 2-6 h.

6. The method of claim 1, wherein the novel adsorbent material is prepared by the steps of: It also includes step S5: washing and storage; the washing uses pure water, and the storage temperature is 2-8℃.

7. A novel adsorbent material characterized in that, The new adsorbent material is prepared by the preparation method of any one of claims 1-6, and has a three-dimensional network structure formed by double crosslinking of chitosan, wherein the double crosslinking includes aldehyde pre-crosslinking and secondary crosslinking of sodium tripolyphosphate.

8. The novel adsorbent material as claimed in claim 7, wherein, The new adsorbent material is a gel bead with a particle size of 1-5 mm.

9. The application of the new adsorbent material of claim 7 in water treatment.

10. Use according to claim 8, characterized in that, The water treatment includes removing azo dyes and / or heavy metal ions in water bodies, and the azo dyes include reactive red RR24.

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