A method for preparing a core-shell quaternary ammonium ion exchange resin adsorbent

Abstract

The application discloses a preparation method of a core-shell type quaternary ammonium ion exchange resin adsorbent, and comprises the following steps: firstly, modifying a resin base through a polyamine small molecule to increase the amine content of the base resin; and then, through Schiff base reaction, loading the amine-rich PEI and UiO-66-NH2 on the surface of the modified resin successively to increase the content of the adsorption functional groups; finally, adopting glycidyltrimethylammonium chloride to perform quaternary ammonium reaction to increase the positive surface charge of the resin, and further optimizing the comprehensive adsorption capacity of the composite adsorbent. The prepared adsorbent has excellent Cr(VI) removal capacity: 50mL of Cr(VI) with an initial concentration of 130mg / L can be completely removed by using 50mg of the adsorbent, and the adsorbent can be separated from the adsorbed solution through simple filtration, so that the adsorbent can be used for treating Cr(VI) in large-scale industrial wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and heavy metal recovery, and relates to a method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent, and the application of the core-shell type quaternary ammonium ion exchange resin adsorbent prepared by this method in the efficient adsorption of Cr(VI) in wastewater. Background Technology

[0002] Heavy metal pollution from industrial wastewater has become one of the major environmental pollution problems facing the world. These heavy metals can cause serious damage to ecosystems and human health. Among them, Cr(VI) (i.e., hexavalent chromium compounds) is the most toxic. It can enter ecosystems through natural and anthropogenic activities, potentially causing various health problems such as allergic reactions, weakened immune systems, kidney and liver damage, stomach ulcers, rashes, and skin irritation. Cr(VI) easily penetrates cell membranes, thereby damaging cellular and molecular components. In addition, it has potential carcinogenic and mutagenic properties, inducing cancers such as nasopharyngeal carcinoma and lung cancer, seriously threatening human life and health. Therefore, the development of a highly efficient adsorbent for Cr(VI) is of great significance to ecosystems and human health.

[0003] Currently, the main methods for treating Cr(VI) in wastewater include membrane filtration, photocatalysis, electrochemical treatment, and adsorption. However, membrane filtration suffers from numerous problems such as high cost, excessive energy consumption, low flow rate, poor batch wastewater treatment capacity, and susceptibility to membrane pore fouling and clogging. Photocatalysis is limited to small-scale treatment, confined to laboratory settings, and has high technological barriers. Electrochemical treatment has issues such as demanding equipment requirements, high pH dependence, high investment costs, and the need for large amounts of chemical reagents like flocculants, which can cause secondary pollution. Adsorption, due to its simple operation, cost-effectiveness, and ability to treat wastewater on a large scale, is considered one of the best technologies for remediating heavy metal pollution in wastewater. However, traditional adsorbents still have many disadvantages, such as low adsorption capacity, low removal rate, poor selectivity, weak regeneration capacity, and narrow pH range, thus limiting the application scope of adsorption methods.

[0004] In view of the above shortcomings, the present invention uses anion exchange resin as a base and nitrogen-rich cationic polymer PEI and high-adsorption-performance MOF as modifying components to prepare a core-shell structured quaternized high-performance Cr(VI) adsorbent material, which can be used in the field of Cr(VI) treatment of wastewater. Summary of the Invention

[0005] Based on the above analysis, this invention provides a method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent for the efficient removal of heavy metals from wastewater. More specifically, it uses anion exchange resin as a substrate and employs polyamine small molecules and cationic polymers PEI and MOF covalently modified adsorbent materials. The adsorbent prepared by this invention exhibits excellent Cr(VI) removal capacity; 50 mg of adsorbent can completely remove a 50 mL volume of Cr(VI) solution with an initial concentration of 130 mg / L. Furthermore, the subsequent recovery and treatment of the adsorbent is simple, requiring only simple filtration to separate the adsorbent from the adsorbed solution. This method can be used for the treatment of Cr(VI) in large-scale industrial wastewater.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent, comprising the following steps:

[0008] (1) Resin pretreatment: Weigh a certain amount of free amine type basic anion exchange resin, add deionized water and stir repeatedly, repeat the operation three times; add acid solution and stir repeatedly, seal with plastic wrap and let stand for 24 hours; wash the acid-treated ion exchange resin repeatedly with deionized water until neutral, add alkaline solution and stir repeatedly, seal with plastic wrap and let stand for 24 hours; repeat the above acid and alkali treatments three times, then perform acid treatment once, and finally wash repeatedly with deionized water until neutral to obtain pretreated resin for use.

[0009] (2) Polyamine modification of resin: Take a certain amount of dimethylamine in a 250mL three-necked flask, cool it to below 10℃ in an ice-water bath, then add 2g of pretreated resin, and then add epichlorohydrin dropwise with a separatory funnel, controlling the dropwise addition time to 2h and the temperature to 10-20℃. After the dropwise addition is complete, add 1.5g of polyamine molecules, raise the temperature to 60-80℃, and react at a constant temperature for a period of time. Wash the obtained modified resin repeatedly with acetone and ethanol, and dry it thoroughly in a vacuum oven at 50℃. The polyamine modified resin is ready for use.

[0010] (3) PEI loading: Add 1g of polyamine-modified resin to 50mL of polyethyleneimine (PEI) mixed solution, sonicate for 30min, add 40mL of glutaraldehyde crosslinking agent dropwise, react at room temperature with stirring rate of 300rpm for 3h, filter the resin, wash the resin repeatedly with deionized water, and dry in a vacuum oven at 60℃ for 24h to obtain PEI-loaded resin for later use.

[0011] (4) MOF loading: Take 0.1g UiO-66-NH2 and activate it in a vacuum oven at 150℃. Add 20mL of deionized water and 0.8g of PEI-loaded resin. Add 0.2mL of 25wt% crosslinking agent dropwise at a stirring rate of 300rpm. React fully at room temperature for 12h. Filter the resin, wash it repeatedly with acetone and deionized water several times, and dry it in a vacuum oven at 60℃ for 24h to obtain MOF-loaded resin for later use.

[0012] (5) Quaternization reaction: Weigh 10g of glycidyltrimethylammonium chloride into a three-necked flask, add 140ml of a mixed solution of LDM and deionized water, stir thoroughly to dissolve, take 1g of MOF-loaded resin into a three-necked flask, raise the temperature to 60-70℃, reflux for 24h, filter the resin, wash repeatedly with hot water and methanol, wash with deionized water, filter and dry to obtain the core-shell type quaternized ion exchange resin adsorbent.

[0013] Further, in step (1), the free amine type basic anion exchange resin has a particle size of 0.2-1 mm, the acid solution is a hydrochloric acid or nitric acid solution with a concentration of 0.5-3.0 mol / L, and the alkaline solution is a NaOH solution with a concentration of 0.5-3.0 mol / L; the amount of acid solution and alkaline solution used is 3-8 times the volume of the free amine type basic anion exchange resin.

[0014] Further, in step (2), the molar ratio of epichlorohydrin to dimethylamine is 0-2, and the polyamine molecule is any one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0015] Further, the polyethyleneimine (PEI) mixed solution in step (3) is prepared by the following method:

[0016] A certain molecular weight of PEI is added to a solvent and mixed to obtain a polyethyleneimine (PEI) mixed solution.

[0017] Furthermore, the molecular weight of the PEI is any one of 600Da, 1800Da, 3000Da, 25000Da, and 70000Da; the mass concentration of the PEI is 0.1-5wt%; and the solvent is any one of methanol, ethanol, deionized water, and DMF.

[0018] Further, the crosslinking agent in step (3) is a 1-5 wt% glutaraldehyde solution.

[0019] Further, the UiO-66-NH2 in step (4) is prepared by the following method:

[0020] Dissolve 0.102 g of 2-aminoterephthalic acid and 0.1 g of ZrCl4 in 12 mL of DMF, stir well, add 2.2 mL of acid to a beaker and sonicate for several minutes. Transfer the reaction solution to a reaction vessel and place it in an oven at 100-150℃ for 12-24 h. Remove the reaction vessel and allow it to cool naturally to room temperature. Wash the vessel repeatedly with acetone and methanol solutions, centrifuge five times, and dry it thoroughly in a vacuum oven at 80℃ for 24 h to obtain UiO-66-NH2.

[0021] Furthermore, the acid is any one of acetic acid, formic acid, benzoic acid, hydrochloric acid, and nitric acid.

[0022] Further, the crosslinking agent in step (4) is 1-5 wt% glutaraldehyde.

[0023] Further, in step (5), the volume ratio of DMF to deionized water in the mixed solution of DMF and deionized water is 0-10.

[0024] The present invention also discloses a core-shell type quaternary ammonium ion exchange resin adsorbent prepared according to any of the above preparation methods.

[0025] The present invention also discloses an application of the above-mentioned core-shell type quaternary ammonium ion exchange resin adsorbent in the adsorption of Cr(VI) in wastewater.

[0026] The advantages of the technical solution of this invention are:

[0027] This invention utilizes polyamine small molecules to modify and optimize anion exchange resins, further loading amine-rich cationic polymers PEI and MOF onto the modified anion exchange resins. This significantly enriches the resin's adsorption functional groups, enabling the adsorbent surface to carry more positive charges and thus adsorb more heavy metal anions. Furthermore, electron-rich nitrogen can reduce harmful Cr(VI) to Cr(III). In addition, quaternization modification ensures that the resin surface retains a positive charge even at high pH levels. The electrostatic repulsion between resin particles effectively prevents particle aggregation, expanding the adsorbent's operating range and improving its environmental stability. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The above and other objects and / or features of the invention will become clearer from the following description taken in conjunction with the drawings, wherein:

[0029] Figure 1 A flowchart illustrating the preparation method of the core-shell type quaternary ammonium ion exchange resin adsorbent in Exemplary Example 1 of the present invention is shown;

[0030] Figure 2A low-magnification scanning electron microscope image of the MOF in Embodiment 1 of the present invention is shown;

[0031] Figure 3 A high-magnification scanning electron microscope image of the MOF in Embodiment 1 of the present invention is shown;

[0032] Figure 4 A low-magnification scanning electron microscope image of the adsorbent prepared in Example 1 of the present invention is shown;

[0033] Figure 5 A high-magnification scanning electron microscope image of the adsorbent prepared in Example 1 of the present invention is shown;

[0034] Figure 6 The graphs show the Cr(VI) adsorption capacity test results for Examples 1-4 (PEI concentrations of 1-4%).

[0035] Figure 7 The graphs show the Cr(VI) adsorption capacity test results for Examples 1, 5, and 6 (GA concentrations were 1-3% respectively). Detailed Implementation

[0036] The present invention will be described in detail below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Any variations or implementations that do not depart from the content and scope of the present invention should be included within the technical scope of the present invention.

[0037] Example 1

[0038] A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent

[0039] According to the appendix Figure 1 The flowchart in the process of preparing adsorbent

[0040] (1) Resin pretreatment:

[0041] Add 5g of free amine-type basic anion exchange resin with a particle size of 0.2-1mm to deionized water and stir repeatedly. Repeat this process three times. Add 1mol / L HCl solution and stir repeatedly. Seal with plastic wrap and let stand for 24 hours. Wash the acid-treated ion exchange resin repeatedly with deionized water until neutral. Add 1mol / L NaOH solution and stir repeatedly. Seal with plastic wrap and let stand for 24 hours. Repeat the above acid-base treatment process three times, with the last treatment using acid. Then wash repeatedly with deionized water until neutral and dry in a vacuum oven at 50℃ to obtain pretreated resin for later use.

[0042] (2) Polyamine modification of resin:

[0043] 2g of pretreated resin and 15mL of dimethylamine solution were mixed in a three-necked flask and cooled to below 10°C in an ice-water bath. 35mL of epichlorohydrin was added dropwise using a separatory funnel, with the addition time controlled at 2h and the temperature controlled at 10-20°C. After the addition was complete, 1.5g of ethylenediamine was added, the temperature was raised to 70°C, and the reaction was maintained at this temperature for 5h. The resulting modified resin was repeatedly washed with acetone and ethanol and thoroughly dried in a vacuum oven at 50°C. The polyamine-modified resin was then ready for use.

[0044] (3) PEI load:

[0045] Weigh 1g of PEI with a molecular weight of 25000Da into a beaker, add an appropriate amount of methanol to prepare a PEI mixed solution with a mass fraction of 1wt%, stir thoroughly, take 20mL of the PEI mixed solution, add 1g of polyamine-modified resin, sonicate for 30min, add 40mL of 1wt% glutaraldehyde solution dropwise at a stirring speed of 300rpm, react at room temperature for 5h, filter the resin thoroughly, dry in an oven at 50℃ for 24h for later use, and obtain PEI-loaded resin for later use.

[0046] (4) Synthesis of MOFs:

[0047] 0.102 g of 2-aminoterephthalic acid and 0.1 g of ZrCl4 were dissolved in 12 mL of DMF and stirred thoroughly. 2.2 mL of acetic acid was added to the mixture, and the solution was sonicated for 30 min. The reaction solution was then transferred to a reaction vessel and placed in an oven at 120 °C for 24 h. The reaction vessel was then removed and allowed to cool naturally to room temperature. Subsequently, the mixture was repeatedly washed with acetone and methanol solution, centrifuged, and filtered five times. It was then thoroughly dried in a vacuum oven at 150 °C for 24 h to obtain UiO-66-NH2 (i.e., MOF) for later use.

[0048] (5) Loading of MOF:

[0049] Weigh 0.1g MOF into a beaker and add 0.8g PEI-loaded resin, 20mL deionized water, and 0.2mL of 25%wt glutaraldehyde. React at room temperature with a stirring rate of 300rpm for 12h. Filter the resin, wash it repeatedly with acetone and deionized water several times, and dry it in a vacuum oven at 60℃ for 24h for later use to obtain MOF-loaded resin.

[0050] (6) Quaternization reaction:

[0051] Weigh 10g of glycidyltrimethylammonium chloride into a three-necked flask, add 140mL of a mixed solution of DMF and deionized water in a volume ratio of 1:1, stir thoroughly to dissolve, weigh 1g of MOF-loaded resin into a three-necked flask, raise the temperature to 73℃, reflux for 24h, filter the resin, wash repeatedly with hot water and methanol, wash with deionized water, filter and dry to obtain the core-shell type quaternary ammonium ion exchange resin adsorbent.

[0052] according to Figure 2 , 3 It can be seen that the synthesized MOF exhibits a regular octahedral structure of 50-80 nm, indicating the successful synthesis of the MOF. According to... Figure 4 , 5 It can be seen that the surface substrate of the synthesized core-shell quaternized ion exchange resin adsorbent is relatively smooth due to the successful loading of polyamine small molecules and polyethyleneimine, and there are a large number of regular octahedral structures on the surface of the substrate, indicating the successful preparation of the core-shell quaternized ion exchange resin adsorbent.

[0053] Example 2

[0054] A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent

[0055] Compared with Example 1, the mass fraction of the PEI mixed solution in step (3) is 2wt%, and the rest is the same as in Example 1.

[0056] Example 3

[0057] A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent

[0058] Compared with Example 1, the mass fraction of the PEI mixed solution in step (3) is 3 wt%, and the rest is the same as in Example 1.

[0059] Example 4

[0060] A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent

[0061] Compared with Example 1, the mass fraction of the PEI mixed solution in step (3) is 4 wt%, and the rest is the same as in Example 1.

[0062] Example 5

[0063] A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent

[0064] Compared with Example 1, the mass fraction of glutaraldehyde in step (3) is 2wt%, and the rest is the same as in Example 1.

[0065] Example 6

[0066] A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent

[0067] Compared with Example 1, the mass fraction of glutaraldehyde in step (3) is 3 wt%, and the rest is the same as in Example 1.

[0068] Test case

[0069] Take 50 mg of the core-shell type quaternary ammonium ion exchange resin adsorbent prepared in Examples 1-6 respectively, and add it to 50 mL of a solution with an initial Cr(VI) concentration of 130 mg / L. Adjust the pH to 3, place the solution in an air bath constant temperature shaking incubator, set the temperature to 25℃, and the rotation speed to 200 rpm, and allow it to fully adsorb for 12 h to ensure adsorption equilibrium. The parameters are as follows:

[0070] The specific adsorption data are shown in Table 1 below:

[0071] Q e =(C0-C e )×V / m, where Q e C represents the saturated adsorption capacity of the resin when adsorption equilibrium is reached, C0 represents the initial concentration of the Cr(VI) solution, V represents the volume of the Cr(VI) solution, and C e The concentration of Cr(VI) remaining in the solution when adsorption equilibrium is reached is represented by m, where m represents the mass of the adsorbent.

[0072] R = (C0 - C) e ) / C0

[0073] Table 1

[0074] Group <![CDATA[Residual concentration C e (mg / L)]]> Saturated adsorption capacity (mg / g) Removal rate R (%) Example 1 4.19 125.81 96.8 Example 2 5.51 124.49 95.8 Example 3 5.29 124.71 95.9 Example 4 9.06 120.94 93.0 Example 5 0.41 129.59 99.7 Example 6 0 130 100

[0075] From Table 1 and Figure 6 It can be seen that the optimal PEI concentration within the study range is 1 wt%. (From Table 1 and...) Figure 7 It is known that the optimal concentration of glutaraldehyde crosslinking agent within the research scope is 3 wt%.

[0076] The high-adsorption-performance Cr(VI) removal resin prepared by this invention can reduce the Cr(VI) concentration to below 10 mg / L under the adsorption conditions of an initial Cr(VI) concentration of 130 mg / L, pH 3, temperature 25°C, solution volume of 50 mL, and adsorption for 12 h. Among them, Example 6 has the best effect in removing Cr(VI), with a Cr(VI) removal rate of 100%.

[0077] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for preparing a core-shell type quaternary ammonium ion exchange resin adsorbent, comprising: (1) Resin pretreatment: After repeated acid and alkali treatment, the free amine type basic anion exchange resin is washed with deionized water until neutral to obtain pretreated resin for use. (2) Polyamine modification of resin: Dimethylamine is cooled to below 10°C, pretreated resin is added, epichlorohydrin is added dropwise using a separatory funnel, polyamine molecules are added after the reaction is completed, the temperature is raised to 60-80°C, the reaction is kept at a constant temperature, and finally the resin is repeatedly washed with acetone and ethanol and dried in a vacuum oven at 50°C to obtain polyamine modified resin for use. (3) PEI loading: Add polyamine-modified resin to 50 mL of PEI mixed solution, sonicate for 30 min, then add crosslinking agent dropwise, react at room temperature with stirring rate of 300 rpm for 3 h, filter the resin, wash repeatedly with deionized water, and then vacuum dry at 60 °C for 24 h to obtain PEI-loaded resin for use. (4) MOF loading: Take UiO-66-NH2 and activate it in a vacuum oven at 150°C. Add deionized water and PEI-loaded resin. Add crosslinking agent dropwise at 300 rpm. React at room temperature for 12 h. Filter the resin, wash it repeatedly with acetone and deionized water, and dry it in a vacuum oven at 60°C for 24 h to obtain MOF-loaded resin for later use. (5) Quaternization reaction: Add a mixed solution of DMF and deionized water to glycidyltrimethylammonium chloride, stir and dissolve thoroughly, then add MOF-loaded resin, heat to 60-70℃, reflux for 24 hours, filter the resin, wash repeatedly with hot water and methanol, and finally wash with deionized water, filter and dry to obtain core-shell type quaternized ion exchange resin adsorbent.

2. The preparation method according to claim 1, wherein: The free amine-type basic anion exchange resin in step (1) has a particle size of 0.2-1 mm; The acid solution is a hydrochloric acid or nitric acid solution with a concentration of 0.5-3.0 mol / L; The alkaline solution is a NaOH solution with a concentration of 0.5-3.0 mol / L; The acid treatment was performed 4 times, and the alkali treatment was performed 3 times. The amount of acid added is 3-8 times the volume of the free amine-type basic anion exchange resin; The amount of alkali added is 3-8 times the volume of the free amine-type basic anion exchange resin.

3. The preparation method according to claim 1, wherein: The molar ratio of epichlorohydrin to dimethylamine in step (2) is 0-2, and this molar ratio is not 0; The polyamine molecule is any one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

4. The preparation method according to claim 1, wherein: The dripping time for epichlorohydrin in step (2) is 2 hours, and the dripping temperature is 10-20℃.

5. The preparation method according to claim 1, wherein: The polyethyleneimine (PEI) mixed solution in step (3) is prepared by the following method: A certain molecular weight of PEI is taken and a solvent is added to it to obtain a mixed solution of polyethyleneimine (PEI); The crosslinking agent in step (3) is a 1-5 wt% glutaraldehyde solution.

6. The preparation method according to claim 5, wherein: The PEI has a molecular weight of any one of 600Da, 1800Da, 3000Da, 25000Da, and 70000Da; The solvent is any one of methanol, ethanol, deionized water, and DMF.

7. The preparation method according to claim 1, wherein: The UiO-66-NH2 mentioned in step (4) is prepared by the following method: ZrCl4 and 2-aminoterephthalic acid were added to DMF and stirred until homogeneous. A certain amount of acid was then added and the mixture was sonicated. The resulting reaction solution was transferred to a reaction vessel and placed in an oven at 100-150℃ for 12-24 hours. After naturally cooling to room temperature, the solution was washed repeatedly with acetone and methanol solution and centrifuged 5 times. The solution was then dried in a vacuum oven at 80℃ for 24 hours to obtain UiO-66-NH2.

8. The preparation method according to claim 1, wherein: In step (5), the volume ratio of DMF to deionized water in the mixed solution of DMF and deionized water is 0-10, and this volume ratio is not 0.

9. A core-shell type quaternized ion exchange resin adsorbent prepared by any of the preparation methods according to claims 1 to 8.

10. The application of the core-shell type quaternary ammonium ion exchange resin adsorbent according to claim 9 in the adsorption of Cr(VI) in wastewater.

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