Preparation method of crosslinked chitosan nanosponge adsorbent for efficiently removing cationic and anionic dyes

Abstract

The present invention belongs to the field of environmental functional materials and relates to a preparation method of a cross-linked chitosan nanosponge adsorbent for efficiently removing cationic and anionic dyes. The specific steps are as follows: Dissolve chitosan powder in a 0.5-2% dilute acetic acid solution; Add a 2-5% glutaraldehyde solution according to a volume ratio of 1:(10-20) to the chitosan solution and stir for 0.5-1 h for cross-linking; After the nanosponge fully absorbs the chitosan solution, place it in a refrigerator at 4°C for cross-linking for 4-6 h; Immerse the sponge block in a NaOH solution, allow it to react fully for 5-10 s, and then let it stand at room temperature for 24 h to age the chitosan on the sponge fibers; Wash with ultrapure water until neutral and then dry at a low temperature of 40°C to obtain a cross-linked chitosan nanosponge composite adsorbent. The cross-linked chitosan nanosponge adsorbent prepared by the present invention has excellent removal ability for cationic and anionic dyes in wastewater, and has the advantages of strong acid and alkali resistance, low cost, large adsorption capacity, reusable multiple times, simple and rapid separation, and the dye can be desorbed and recovered, etc., and has good application prospects in the field of wastewater treatment.

Description

Technical Field

[0001] The present invention belongs to the field of environmental functional materials. Specifically, it is a preparation method of a cross-linked chitosan nanosponge adsorbent for efficiently removing anionic and cationic dyes. Background Art

[0002] The development of the dye industry is inseparable from the development of the textile fiber industry. With the growth of the population and the improvement of living standards, the demand for the world's textile fiber industry is increasing continuously, and the dye industry has also developed rapidly accordingly, which has led to a large amount of dye wastewater being discharged into the natural environment. Due to the deep color, high content of organic pollutants, high biological toxicity and difficulty in degradation of dye wastewater, it poses a great threat to the increasingly scarce drinking water sources. Therefore, the research on efficient and environmentally friendly dye wastewater treatment and recycling technologies is of great significance for the sustainable development of the ecological environment.

[0003] At present, physical methods, chemical methods and biological methods are commonly used dye wastewater treatment methods in industry. Among them, the physical adsorption method has become a promising method due to its convenient operation, good reusability, less generation of harmful by-products and low cost and high efficiency. The activated carbon adsorption method is the most commonly used treatment method in industry. However, its large dosage, difficult regeneration and low treatment efficiency. Therefore, there is an urgent need for an efficient and environmentally friendly adsorbent. Chitosan is a natural polymer material with the characteristics of rich resources, low cost and easy availability, and no pollution. There are many hydroxyl and amino functional groups distributed on the macromolecular chain of chitosan, which makes chitosan form a cage-like structure, thus having a stable adsorption capacity for dye molecules. However, chitosan itself also has certain problems such as easy dissolution in acidic conditions and difficulty in separation, which affect its application in the field of dye removal. The ideal state is to load chitosan onto a stable and fluffy carrier, so that the specific surface area of the material increases, more active sites of chitosan are exposed, and at the same time it can be efficiently separated from the treated waste liquid. Nano sponge is a relatively cheap foamed sponge on the market, which can provide a rich porous fiber network and a stable three-dimensional space structure, and can play a role in mechanical stability and support. Therefore, in this patent, nano sponge is used as the skeleton support material, and a new type of cross-linked chitosan nano sponge material is studied as an adsorbent by cross-linking with chitosan. The stability of chitosan is improved by the cross-linking reaction of chitosan and glutaraldehyde, and the high adsorption performance and separation efficiency of the material are realized by loading it on the nano sponge, so that it can be widely used in the treatment of dye wastewater. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art such as poor adsorption performance, low separation efficiency, high cost, etc., and provide a preparation method of a cross-linked chitosan nanosponge adsorbent for efficiently removing anionic and cationic dyes, and apply the adsorbent to the treatment of anionic and cationic dye pollutants in sewage.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A preparation method of a crosslinked chitosan nanosponge adsorbent, the steps of which are as follows: Add an appropriate amount of chitosan powder into a 0.5 - 2% dilute acetic acid solution, stir to dissolve it, and then add a 2 - 5% glutaraldehyde solution according to the volume ratio of 1:(10 - 20) to the chitosan solution, and continue to stir for 0.5 - 1 h for crosslinking; Take a certain amount of pre-cut nanosponges and immerse them in the crosslinked chitosan solution, fish them out after the sponges fully absorb the solution, and place them in the refrigerator at 4 °C for continued crosslinking for 4 - 6 h; Immerse the sponge blocks saturated with crosslinked chitosan in a 0.5 - 1 mol / L NaOH solution, fully react for several seconds, fish them out and place them at room temperature for 24 h to age the chitosan on the grid fibers of the nanosponges; Wash it with ultrapure water until the pH is neutral and then dry it at low temperature in an oven to obtain a crosslinked chitosan nanosponge composite adsorbent material.

[0007] The present invention also provides an application of a crosslinked chitosan nanosponge adsorbent in removing anionic and cationic dyes in wastewater, and the specific steps are as follows:

[0008] 1. Taking Orange II as an example: Weigh a certain mass of the adsorbent, add it to Orange II solutions with different concentrations, adjust the pH value, and gently stir at room temperature to promote the adsorption process; After sufficient reaction, take an appropriate amount of the Orange II solution after adsorption and use a UV-visible spectrophotometer to measure the concentration of the residual dye, and calculate the adsorption capacity of the adsorbent for Orange II after comparison with the concentration before adsorption. The experimental test results show that the adsorbent in the present invention has excellent adsorption performance for Orange II, and rapid separation can be achieved with the nanosponge as the material substrate; In addition, the adsorbent after adsorbing Orange II can be rapidly desorbed and regenerated with a low-concentration NaOH, which is beneficial to the recovery and reuse of the adsorbent and the dye;

[0009] 2. Taking methylene blue as an example: Weigh a certain mass of the adsorbent, add it to methylene blue solutions with different concentrations, adjust the pH value, and gently stir at room temperature to promote the adsorption process; After sufficient reaction, take an appropriate amount of the methylene blue solution after adsorption and use a UV-visible spectrophotometer to measure the concentration of the residual dye, and calculate the adsorption capacity of the adsorbent for methylene blue after comparison with the concentration before adsorption. The experimental test results show that the adsorbent in the present invention has excellent adsorption performance for methylene blue, and rapid separation can be achieved with the nanosponge as the material substrate; In addition, the adsorbent after adsorbing methylene blue can be rapidly desorbed and regenerated with a low-concentration HCl, which is beneficial to the recovery and reuse of the adsorbent and the dye.

[0010] Compared with the prior art, the present invention has the following positive effects:

[0011] The cross-linked chitosan nanosponge adsorbent prepared by the present invention has low cost, excellent adsorption performance, easy separation and recovery, and can be recycled multiple times, showing good application prospects for treating anionic and cationic dye pollutants in sewage. Description of the Drawings

[0012] Figure 1 It is a diagram before and after the cross-linked chitosan nanosponge adsorbent adsorbs Orange II and methylene blue.

[0013] Figure 2 It is an infrared spectrogram before and after the cross-linked chitosan nanosponge adsorbent adsorbs Orange II and methylene blue. Detailed Embodiments

[0014] The following provides a preparation method of a cross-linked chitosan nanosponge adsorbent and specific examples of its application.

[0015] Example 1

[0016] Add 1 g of chitosan powder into a 1% dilute acetic acid solution. After dissolving it into a uniform and stable solution, add a 2.5% glutaraldehyde solution according to the volume ratio of 1:15 to the chitosan solution, and continue stirring for 0.5 h for cross-linking; Immerse the cut nanosponge in the cross-linked chitosan solution. After the sponge fully absorbs the solution, take it out, and continue cross-linking at 4 °C in the refrigerator for 4 h; Immerse the sponge block saturated with cross-linked chitosan in a 1 mol / L NaOH solution, fully react for several seconds, take it out and place it at room temperature for 24 h to age the chitosan on the grid fibers of the nanosponge; Wash it with ultrapure water until the pH is neutral, and then dry it in an infrared dryer to obtain a cross-linked chitosan nanosponge composite adsorbent, with a light yellow sponge appearance.

[0017] Example 2

[0018] Weigh 3 - 4 pieces of adsorbent (about 50 mg), add them into Orange II solutions with initial concentrations of 50, 100, 150, 200, 250, 300 mg / L respectively, adjust the pH value to 3, and gently stir at room temperature to promote the adsorption process; After full reaction, take an appropriate amount of the Orange II solution after adsorption and use a UV-visible spectrophotometer to measure the concentration of the residual dye, and calculate the adsorption capacity of the adsorbent for Orange II.

[0019] Example 3

[0020] Weigh 3 - 4 pieces of adsorbent (about 50 mg) and add them to methylene blue solutions with initial concentrations of 50, 100, 150, 200, 250, and 300 mg / L respectively. Adjust the pH value to 11 and stir gently at room temperature to promote the adsorption process. After sufficient reaction, take an appropriate amount of the adsorbed methylene blue solution and use a UV - visible spectrophotometer to measure the concentration of the residual dye, and calculate the adsorption capacity of the adsorbent for methylene blue.

[0021] Example 4

[0022] Weigh 3 - 4 pieces of adsorbent (about 50 mg) and add them to an orange II solution with an initial concentration of 200 mg / L. Adjust the pH value to 3 and stir gently at room temperature to promote the adsorption process. After sufficient reaction, add 1 mol / L NaOH solution to adjust the solution pH > 12 and shake gently to promote the desorption process. Take an appropriate amount of the desorbed orange II solution and use a UV - visible spectrophotometer to measure the concentration of the desorbed dye, and calculate the desorption rate of the adsorbent for orange II. After washing and drying the desorbed adsorbent material, add it again to an orange II solution with an initial concentration of 200 mg / L. Adjust the pH value to 3 and stir gently at room temperature to promote the adsorption process. After sufficient reaction, take an appropriate amount of the adsorbed orange II solution and use a UV - visible spectrophotometer to measure the concentration of the residual dye, and calculate the adsorption capacity of the recycled adsorbent for orange II.

[0023] Example 5

[0024] Weigh 3 - 4 pieces of adsorbent (about 50 mg) and add them to a methylene blue solution with an initial concentration of 200 mg / L. Adjust the pH value to 11 and stir gently at room temperature to promote the adsorption process. After sufficient reaction, add 1 mol / L HCl solution to adjust the solution pH < 3 and shake gently to promote the desorption process. Take an appropriate amount of the desorbed methylene blue solution and use a UV - visible spectrophotometer to measure the concentration of the desorbed dye, and calculate the desorption rate of the adsorbent for methylene blue. After washing and drying the desorbed adsorbent material, add it again to a methylene blue solution with an initial concentration of 200 mg / L. Adjust the pH value to 11 and stir gently at room temperature to promote the adsorption process. After sufficient reaction, take an appropriate amount of the adsorbed methylene blue solution and use a UV - visible spectrophotometer to measure the concentration of the residual dye, and calculate the adsorption capacity of the recycled adsorbent for methylene blue.

[0025] It can be seen from Figure 1 that the hydroxyl stretching vibration peak of chitosan at 3323 cm -1 shifts to 3423 cm -1 and is located at 1548 cm -1The bending stretching vibration peak of the amino group at [location] redshifts to 1636 cm -1 At this point, the displacements of these characteristic peaks all indicate that both the hydroxyl and amino groups on chitosan are involved in the adsorption process of dye molecules. After adsorbing Orange II, obvious characteristic peaks of Orange II appear between 500 and 1620 cm -1 , proving that Orange II can be effectively adsorbed by the material.

[0026] It can be seen from Figure 2 that the new peaks of chitosan at 1160 cm -1 and 1096 cm -1 can be attributed to the axial stretching vibration of the C-N bond on the aliphatic amine, and its new peaks at 1382 cm -1 and 1322 cm -1 can be attributed to the axial stretching vibration of the C-N bond on the aromatic amine. The displacements of these characteristic peaks all indicate the presence of methylene blue molecules on chitosan, thus proving that methylene blue can be effectively adsorbed by the material.

[0027] The above statements are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the concept of the present invention, several changes, modifications, substitutions, combinations, and simplifications should be regarded as equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. Application of a crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes in removing anionic and cationic dyes from wastewater, characterized in that the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes is an adsorbent material composed of crosslinked chitosan and nanosponge. This material has a sponge-like shape, the molecular weight of chitosan is 50,000 - 500,000, and its content accounts for 20 - 80% of the mass fraction of the composite material; The preparation method of the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes includes the following steps: Add an appropriate amount of chitosan powder into a 0.5 - 2% dilute acetic acid solution, stir to dissolve it, and then add a 2 - 5% glutaraldehyde solution according to the volume ratio of 1:(10 - 20) to the chitosan solution, and continue to stir for 0.5 - 1 h for crosslinking; Take a certain amount of nanosponge and immerse it in the crosslinked chitosan solution. After the sponge fully absorbs the solution, take it out, and place it in the refrigerator at 4°C for continued crosslinking for 4 - 6 h; Immerse the sponge saturated with crosslinked chitosan in a 0.5 - 1 mol / L NaOH solution, react fully for 5 - 10 s, take it out and place it at room temperature for 24 h to age the chitosan on the grid fibers of the nanosponge; Wash it with ultrapure water until the pH is neutral, and then dry it at low temperature in an oven to obtain the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes.

2. The application according to claim 1, wherein The specific steps are as follows: Add the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes into a solution containing anionic and cationic dyes, with a concentration of 10 - 300 mg / L, a temperature of 4 - 40°C, and a solution pH value of 2 - 11. Stir for 24 h, then take out and separate the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes to obtain an anionic and cationic dye solution and the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes that adsorbs anionic and cationic dyes; Add the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes that adsorbs anionic and cationic dyes into an aqueous solution containing a desorbent, stir for several minutes, and then filter to obtain a dye solution and the crosslinked chitosan nanosponge adsorbent for highly efficient removal of anionic and cationic dyes.

3. The application according to claim 2, characterized in that, The removal rate of anionic and cationic dyes is as high as over 99.5%.

4. The application according to claim 2, wherein After adding the desorbent solution, the adsorbed dye molecules can be quickly desorbed, and the dye desorption rate is higher than 99%. The desorbed material can be reused for dye adsorption again.

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