A method for preparing a Cr(III) ion imprinted material

Abstract

The application discloses a preparation method of Cr(III) ion imprinted material and belongs to the technical field of adsorbing material preparation. The preparation method of the Cr(III) ion imprinted material comprises the following steps: reacting chitosan and glutaraldehyde to obtain a Schiff base; adding the Schiff base and 2,4-diamino-6-methyl-1,3,5-triazine into acetic acid to react to obtain a functional monomer; then adding the functional monomer into a CrCl3 solution to react, and then adding epichlorohydrin to react at 30-70 DEG C for 4-12 hours to obtain a Cr(III) imprinted polymer; and finally eluting the Cr(III) imprinted polymer to obtain the Cr(III) ion imprinted material. The application does not need to add a substrate carrier, the functional monomer prepared by the reaction of chitosan, glutaraldehyde and 2,4-diamino-6-methyl-1,3,5-triazine can be used as the functional monomer and the solid substrate carrier at the same time in the application. In addition, the polymerization reaction system in the application is carried out in a non-toxic aqueous phase, has the advantages of being green, non-toxic and non-polluting, and the polymerization reaction can be completed without adding an initiator in the system.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material preparation technology, specifically relating to a method for preparing Cr(III) ion imprinted materials. Background Technology

[0002] In recent years, heavy metal pollution in water bodies has attracted increasing public attention. Chromium, an important chemical raw material, is discharged into the environment through industries such as electroplating, dyeing, and metal smelting, posing a serious threat to the health of animals, plants, and humans. Currently, conventional methods for treating chromium-containing wastewater mainly include chemical precipitation, adsorption, ion exchange, and membrane separation. Among these, adsorption is the primary method for water purification and heavy metal ion separation. While it is fast, simple, effective, economical, and environmentally friendly, it also suffers from problems such as complex modification processes and low specificity. Therefore, finding a highly efficient and selective separation method for Cr(III) ions is crucial.

[0003] Ion imprinting, as an important branch of molecular imprinting technology, has significant application potential in treating wastewater containing low concentrations of highly toxic heavy metal ions. Its principle involves using ions as templates to first bind with functional monomers through electrostatic interactions and coordination to form chelates, followed by cross-linking polymerization. The template ions are then eluted to obtain imprinted materials with a three-dimensional void structure. However, traditional ion-imprinted polymers are mostly prepared in organic solvents such as acetonitrile, chloroform, toluene, and ethanol. These organic reagents are not only limited in resources and expensive, but most are also highly toxic, easily causing secondary pollution to the environment. Furthermore, these polymers often exhibit poor adsorption performance in polar solvents where the target pollutants are widely present. Therefore, how to prepare ion-imprinted polymers in green media has become a hot research topic. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides a method for preparing Cr(III) ion-imprinted materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] As a preferred embodiment of the present invention, the method for preparing the alkali-chitosan Cr(III) ion-imprinted material includes the following steps:

[0007] (1) Add water to chitosan and let it stand for 30-40 minutes, then add glutaraldehyde and react at 50°C for 4 hours. Separate, wash and dry to obtain Schiff base;

[0008] (2) Schiff base and 2,4-diamino-6-methyl-1,3,5-triazine were added to acetic acid to react, and then separated, washed and dried to obtain the functional monomer;

[0009] (3) Add the functional monomer to the CrCl3 solution and react for 4 hours, then add epichlorohydrin and react at 30-70℃ for 4-12 hours. After washing and drying, the Cr(III) imprinted polymer is obtained.

[0010] (4) The Cr(III) imprinted polymer was eluted with hydrochloric acid solution to obtain Cr(III) ion imprinted material with stereocavities.

[0011] In a preferred embodiment of the present invention, the degree of deacetylation of the chitosan is 95%.

[0012] In a preferred embodiment of the present invention, in step (3), the mass ratio of the functional monomer, CrCl3, and epichlorohydrin is 0.2:1.33:0.24.

[0013] In a preferred embodiment of the present invention, in step (1), the mass ratio of chitosan to glutaraldehyde is 1:0.25.

[0014] In a preferred embodiment of the present invention, the mass ratio of the Schiff base, 2,4-diamino-6-methyl-1,3,5-triazine and acetic acid is 1:0.5:1.47.

[0015] In a preferred embodiment of the present invention, in step (2), the reaction temperature is 60°C and the time is 6 hours.

[0016] In a preferred embodiment of the present invention, the concentration of the hydrochloric acid solution in step (4) is 0.10 mol / L.

[0017] In a preferred embodiment of the present invention, the elution time in step (4) is 3 hours.

[0018] Compared with existing technologies, the advantages of this invention are as follows: This invention uses chitosan, glutaraldehyde, and 2,4-diamino-6-methyl-1,3,5-triazine to react and prepare a self-made functional monomer, using epichlorohydrin as a crosslinking agent. Through polymerization, a Cr(III) ion-imprinted material with stereochemical vacancies is prepared, exhibiting strong adsorption capacity for Cr(III) ions. This invention requires no additional matrix carrier; the self-made functional monomer can simultaneously serve as both a functional monomer and a solid matrix carrier. Furthermore, the polymerization reaction system of this invention is carried out in a non-toxic aqueous phase, possessing the advantages of being green, non-toxic, and pollution-free. Moreover, the polymerization reaction can be completed without the addition of an initiator. Attached Figure Description

[0019] Figure 1 The image shows the product obtained by the functional monomer preparation method described in Example 1.

[0020] Figure 2 The image shows the product obtained by the method for preparing the functional monomer described in Comparative Example 4.

[0021] Figure 3 This is a comparison diagram of the Cr(III) ion-imprinted materials prepared in Comparative Examples 1-3 and Comparative Example 5. Figure 3 From left to right, the images show the Cr(III) ion-imprinted materials after filtration from Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5. Detailed Implementation

[0022] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Example 1

[0023] A method for preparing a Cr(III) ion-imprinted material includes the following steps:

[0024] (1) Soak 1.0 g of chitosan in water for 30 min, then add 1 mL of 25% ( w / w A glutaraldehyde aqueous solution was reacted at 50°C for 4 hours, followed by washing with ethanol, separation, and drying to obtain a Schiff base; the degree of deacetylation of the chitosan base was 95%.

[0025] (2) Add Schiff base and 4.00 mmol / L 2,4-diamino-6-methyl-1,3,5-triazine to 2% ( v / v The Schiff base was reacted in an aqueous solution of acetic acid at 60°C for 6 h, and then washed, separated, and dried with ethanol to obtain the functional monomer; the mass ratio of the Schiff base: 2,4-diamino-6-methyl-1,3,5-triazine:acetic acid was 1:0.5:1.47.

[0026] (3) Add the functional monomer to a 5.00 mmol / L CrCl3 solution and shake for 4 hours to allow the template ions to fully react with the functional monomer to form a stable chelate. Then add 0.20 mL of epichlorohydrin and react at 30 °C for 6 hours. After washing and drying, the Cr(III) imprinted polymer is obtained.

[0027] (4) The Cr(III) imprinted polymer was shaken at room temperature for 3 h with 0.10 mol / L hydrochloric acid solution to remove template ions. After washing with distilled water until neutral, it was dried to obtain Cr(III) ion imprinted material with three-dimensional vacancies. Example 2

[0028] The only difference between the preparation method of the Cr(III) ion imprinted material in this embodiment and that in Example 1 is that the reaction temperature for adding epichlorohydrin in step (3) is 40°C. Example 3

[0029] The only difference between the preparation method of the Cr(III) ion imprinted material in this embodiment and that in Example 1 is that the reaction temperature for adding epichlorohydrin in step (3) is 50°C. Example 4

[0030] The only difference between the preparation method of the Cr(III) ion imprinted material in this embodiment and that in Example 1 is that the reaction temperature for adding epichlorohydrin in step (3) is 60°C. Example 5

[0031] The only difference between the preparation method of the Cr(III) ion imprinted material in this embodiment and that in Example 1 is that the reaction temperature for adding epichlorohydrin in step (3) is 70°C.

[0032] Comparative Example 1

[0033] A method for preparing a Cr(III) ion-imprinted material includes the following steps:

[0034] (1) Soak 1.0 g of chitosan in water for 30 min, then add 1 mL of 25% ( w / w A glutaraldehyde aqueous solution was reacted at 50°C for 4 hours, followed by washing with ethanol, separation, and drying to obtain a Schiff base; the degree of deacetylation of the chitosan base was 95%.

[0035] (2) Add Schiff base to 5.00 mmol / L CrCl3 solution and shake for 4 hours to allow template ions to fully react with functional monomers to form a stable chelate. Then add 0.20 mL epichlorohydrin and react at 30 °C for 6 hours. After washing and drying, Cr(III) imprinted polymer is obtained.

[0036] (3) The Cr(III) imprinted polymer was shaken at room temperature for 3 h with 0.10 mol / L hydrochloric acid solution to remove template ions. After washing with distilled water until neutral, it was dried to obtain Cr(III) ion imprinted material with three-dimensional vacancies.

[0037] Comparative Example 2

[0038] A method for preparing a Cr(III) ion-imprinted material includes the following steps:

[0039] (1) Soak 1.0 g of chitosan in water for 30 min, then add 1 mL of 25% ( w / w A glutaraldehyde aqueous solution was reacted at 50°C for 4 hours, followed by washing with ethanol, separation, and drying to obtain a Schiff base; the degree of deacetylation of the chitosan base was 95%.

[0040] (2) Add Schiff base and 4.00 mmol of 2,4-diamino-6-methyl-1,3,5-triazine to 2% ( v / v The functional monomer was obtained by reacting the acetic acid aqueous solution in acetic acid at 60°C for 6 h, followed by washing, separation, and drying with ethanol.

[0041] (3) Dissolve 0.5 mol L CrCl3 in 10 ml of pure water, then add 90 ml of ethanol to form a CrCl3 ethanol mixture. Add the functional monomer to 5.00 mol L CrCl3 ethanol mixture and shake for 4 hours to allow the template ions to fully interact with the functional monomer to form a stable chelate. Then add 0.20 mL epichlorohydrin and react at 30 °C for 6 hours. After washing and drying, obtain the Cr(III) imprinted polymer.

[0042] (4) The Cr(III) imprinted polymer was shaken at room temperature for 3 h with 0.10 mol / L hydrochloric acid solution to remove template ions. After washing with distilled water until neutral, it was dried to obtain Cr(III) ion imprinted material with three-dimensional vacancies.

[0043] Comparative Example 3

[0044] A method for preparing a Cr(III) ion-imprinted material includes the following steps:

[0045] (1) Chitosan was added to 5.00 mmol / L CrCl3 solution and shaken for 4 hours to allow the template ions and functional monomers to fully interact and form a stable chelate. Then, 0.20 mL of epichlorohydrin was added and reacted at 30°C for 6 hours. After washing and drying, Cr(III) imprinted polymer was obtained.

[0046] (2) The Cr(III) imprinted polymer was shaken at room temperature for 3 h with 0.10 mol / L hydrochloric acid solution to remove template ions. After washing with distilled water until neutral, it was dried to obtain Cr(III) ion imprinted material with three-dimensional vacancies.

[0047] Comparative Example 4

[0048] A method for preparing a Cr(III) ion-imprinted material includes the following steps:

[0049] (1) Add chitosan and 4.00 mmol of 2,4-diamino-6-methyl-1,3,5-triazine to 2% ( v / v The mixture was reacted in an aqueous acetic acid solution at 60°C for 6 h, followed by washing with ethanol, separation, and drying to obtain the functional monomer; the degree of deacetylation of chitosan was 95%.

[0050] (2) The functional monomer was added to a 5.00 mmol CrCl3 solution and shaken for 4 hours to allow the template ions to fully react with the functional monomer to form a stable chelate. Then, 0.20 mL epichlorohydrin was added and reacted at 30 °C for 6 hours. After washing and drying, the Cr(III) imprinted polymer was obtained.

[0051] (3) The Cr(III) imprinted polymer was shaken at room temperature for 3 h with 0.10 mol / L hydrochloric acid solution to remove template ions. After washing with distilled water until neutral, it was dried to obtain Cr(III) ion imprinted material with three-dimensional vacancies.

[0052] Comparative Example 5

[0053] A method for preparing a Cr(III) ion-imprinted material, the only difference from Example 1 is that in step (3), epichlorohydrin is replaced with trimethylolpropane tris(3-acrylidinylpropionate).

[0054] Example of effect

[0055] 20.00 mg of the Cr(III) ion-imprinted materials prepared in the examples and comparative examples were placed in 2.40 mg / mL CrCl3·6H2O aqueous solution. After adsorption by shaking at room temperature for 12 h, the absorbance of the solution was measured by UV-Vis spectrophotometry, and the corresponding equilibrium adsorption amount was calculated. The results are shown in Table 1.

[0056] Table 1

[0057] sample Adsorption capacity / mg / g Cr(III) ion removal rate / % Example 1 308.99 62.72 Example 2 328.21 63.54 Example 3 321.35 63.34 Example 4 385.89 66.03 Example 5 299.38 62.51 Comparative Example 1 274.65 61.84 Comparative Example 2 270.80 61.54 Comparative Example 3 Unable to prepare Cr(III) ion-imprinted materials none Comparative Example 4 Unable to prepare functional monomers none Comparative Example 5 263.67 61.54

[0058] As can be seen from Examples 1-5, the reaction temperature of epichlorohydrin is crucial to the generation of Cr(III) ion-imprinted materials. Cr(III) ion-imprinted materials cannot be prepared at temperatures below 30°C. Within the temperature range of 30-70°C, the adsorption performance of Cr(III) ion-imprinted materials shows a trend of first increasing and then decreasing. Furthermore, when the temperature is above 70°C, the ring-opening reaction of epichlorohydrin as a crosslinking agent becomes too vigorous at temperatures above 70°C, resulting in a significant decrease in the performance of the obtained Cr(III) ion-imprinted materials.

[0059] As can be seen from Examples 1-5 and Comparative Example 1, the adsorption capacity of the Cr(III) ion-imprinted material finally formed in Comparative Example 1 is much lower than that prepared in Examples 1-5. This is because the modifier 2,4-diamino-6-methyl-1,3,5-triazine is a hard base. After being grafted onto chitosan, it follows the "hard attracts hard" principle, allowing the functional monomer to effectively bind with the hard acid Cr. 3+ Ion chelation.

[0060] According to Examples 1-5 and Comparative Example 2, the Cr(III) ion imprinting material prepared by the medium of water and ethanol used in Comparative Example 2 has poor adsorption capacity for Cr(III) ions. This is because the imprinting material prepared by pure water can eliminate the interference and influence of the medium in which the heavy metal ions are located when adsorbing heavy metal ions in water, and can directly adsorb heavy metal ions.

[0061] As can be seen from Examples 1-5 and Comparative Example 3, Comparative Example 3 directly uses unmodified chitosan as a functional monomer in the polymerization reaction. Because chitosan dissolves or partially dissolves in an acidic environment, no or almost no Cr(III) ion-imprinted material is produced. Examples 1-5 use the modified chitosan product as the functional monomer, which not only has good acid resistance but also eliminates the curing process; the polymerization reaction occurs directly on its surface. Furthermore, the yield of Cr(III) ion-imprinted material obtained in this way is higher than that obtained in the former examples, and it also shows better control over Cr... 3+ Ions also have a specific recognition function.

[0062] As can be seen from Examples 1-5 and Comparative Example 4, Comparative Example 4 lacked glutaraldehyde, resulting in the inability to generate functional monomers. The main reason is that glutaraldehyde plays two roles in the reaction: First, it acts as an adhesive, reacting with chitosan at one end for grafting, and then reacting with 2,4-diamino-6-methyl-1,3,5-triazine at the other end for grafting, thus facilitating the modification of chitosan into functional monomers; second, it enhances the acid stability of chitosan. Glutaraldehyde-modified chitosan does not dissolve in acidic solutions such as acetic acid, which aids in the curing process of the functional monomers. Figure 1-2 It can be seen that, Figure 1 After adding glutaraldehyde, it reacts with 2,4-diamino-6-methyl-1,3,5-triazine in acetic acid to obtain a reddish-brown suspension (the modified chitosan is uniformly dispersed in the solution). After washing, separation, and drying, uniformly sized powdered functional monomers are obtained. The subsequent polymerization medium is water, and the solidified functional monomers can be uniformly dispersed in the solution under stirring, facilitating the subsequent synthesis of Cr(III) ion-imprinted materials on their surface. However, if... Figure 2 Without the addition of glutaraldehyde, chitosan and 2,4-diamino-6-methyl-1,3,5-triazine were reacted directly in acetic acid for 6 hours. Chitosan, with its weak acid stability, dissolved directly in the acid, forming a high-viscosity, transparent solution. However, the subsequent preparation medium for Cr(III) ion-imprinted materials was water. The interaction between water and the viscous solution affected the formation process of the Cr(III) ion-imprinted materials.

[0063] The type of crosslinking agent is very important for the imprinting process. A suitable crosslinking agent is beneficial to the synthesis of polymer network structure. According to Examples 1-5 and Comparative Example 5, epichlorohydrin is more suitable as a crosslinking agent for the preparation method of Cr(III) ion imprinted material of the present invention.

[0064] according to Figure 3 It can be seen that the Cr(III) ion-imprinted materials obtained in Comparative Examples 1, 2, and 5 are all solidified particles, while the product of Comparative Example 3 is significantly less, almost non-existent. This indicates that chitosan, without modification, has low acid resistance. When directly used as a functional monomer, it mainly forms an acidic environment when complexing with Cr(III) ions. After 6 hours of reaction, it dissolves directly in the solution, and no product is obtained in the subsequent filtration process. Therefore, its adsorption capacity and scavenging rate cannot be calculated.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a Cr(III) ion-imprinted material, characterized in that, Includes the following steps: (1) Add water to chitosan and let it stand for 30-40 minutes, then add glutaraldehyde and react at 50°C for 4 hours. Separate, wash and dry to obtain Schiff base; (2) Schiff base and 2,4-diamino-6-methyl-1,3,5-triazine were added to acetic acid to react, and then separated, washed and dried to obtain the functional monomer; (3) Add the functional monomer to the CrCl3 solution and react for 4 hours, then add epichlorohydrin and react at 30-70℃ for 4-12 hours. After washing and drying, the Cr(III) imprinted polymer is obtained. (4) The Cr(III) imprinted polymer was eluted with hydrochloric acid solution to obtain Cr(III) ion imprinted material with stereocavities.

2. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, The degree of deacetylation of the chitosan is 95%.

3. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, In step (1), the mass ratio of chitosan to glutaraldehyde is 1:0.

25.

4. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, The mass ratio of the Schiff base, 2,4-diamino-6-methyl-1,3,5-triazine, and acetic acid is 1:0.5:1.

47.

5. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, In step (3), the mass ratio of the functional monomer, CrCl3, and epichlorohydrin is 0.2:1.33:0.

24.

6. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, In step (2), the reaction temperature is 60°C and the reaction time is 6 hours.

7. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, In step (4), the concentration of the hydrochloric acid solution is 0.10 mol / L.

8. The method for preparing the Cr(III) ion-imprinted material as described in claim 1, characterized in that, In step (4), the elution time is 3 hours.

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