Preparation method of ionized covalent organic framework nanofiltration membrane and application of ionized covalent organic framework nanofiltration membrane in dye interception

Abstract

The invention provides a preparation method of an ionized covalent organic framework nanofiltration membrane and application of the ionized covalent organic framework nanofiltration membrane to interception of various dyes. According to the prepared ionized covalent organic framework nanofiltration membrane, an iCOF-PDA membrane can serve as a COF nanofiltration membrane to be used for achieving efficient interception of various dyes. The iCOF-PDA prepared by the invention not only has the advantages of simple preparation method, very mild reaction conditions, simple synthetic route, suitability for large-scale production, high efficiency, simplicity and convenience and the like, but also has good interception performance for various dye solutions, and has important practical significance and application value for environmental restoration, especially for water treatment.

Description

Technical Field

[0001] The invention relates to a method for preparing a novel ionized covalent organic framework material with simple preparation and mild reaction, which is applied to interception of organic pollutants such as dyes and novel pollutants, and belongs to a new material technology in membrane separation. Background Art

[0002] In order to solve the problems of industrial dye pollution, wastewater treatment, screening or extraction of high-value dyes from mixed dyes, etc., membrane separation technology is used to separate water dyes. Compared with conventional water treatment technology, membrane separation technology has the advantages of simple equipment, convenient operation, high removal efficiency, low energy consumption, and environmental friendliness. Therefore, the development of high-performance membranes for water dye removal has become an urgent task.

[0003] Although many commercial membranes have a high water flux for dyes, the retention rate of these membranes for dye separation is not very high. Covalent organic frameworks (COFs) are a new type of periodic porous organic material composed of organic units through covalent bonds. Due to their high specific surface area, high porosity and adjustable pore structure, COFs have shown broad potential in the fields of membrane separation, fluorescence detection, gas separation, electrochemistry, adsorption / separation, catalysis, etc. This patent will focus on designing a new type of porous COFs nanofiltration membrane to achieve efficient removal of water dyes. Therefore, we separate dyes by developing a new type of ionized porous COFs membrane, and scientifically and rationally design porous COFs membranes based on factors such as the specific size structure and functional group characteristics of dye molecules. Specifically, we introduced a modifiable pyridine group into the COFs membrane, and then used iodomethane to ionize and modify the COFs membrane via a nucleophilic substitution reaction, in order to significantly adjust the hydrophilicity, pore size, pore structure and surface properties of the COFs membrane, thereby improving the removal performance of the ionized COFs membrane for water dyes. Therefore, it is reasonable and feasible to obtain an ionized COFs membrane with high retention performance by constructing a pyridine group in the skeleton of the COFs nanofiltration membrane and performing ionization modification. Summary of the invention

[0004] Aiming at the efficient interception of different dyes, the purpose of the present invention is to provide a method for preparing an ionized covalent organic skeleton nanofiltration membrane, wherein the dye is selected from acid fuchsin (AF), Congo red (CR), methylene blue (MLB), methyl blue (MB) and chrome black T (EBT). The present invention can effectively solve the shortcomings of ordinary nanofiltration membranes such as trade-off effect, low water flux, poor interception rate, and difficulty in reuse.

[0005] The technical solution of the present invention is as follows: A method for preparing an ionized covalent organic framework nanofiltration membrane iCOF-PDA membrane is specifically prepared according to the following method: The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which aqueous solutions of amine and acid catalyst and organic solutions containing aldehydes were placed respectively. 2,5-diaminopyridine and acetic acid were placed in the aqueous phase, while a mixed solution of mesitylene, ethyl acetate and mesitylene was placed in the oil phase. The mixture was left to stand at room temperature, and the prepared COF-PDA membrane was taken out, washed with ethanol several times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform several times, and then immersed in CH 3 I and chloroform mixed solution, stand at room temperature for several days, then take out, wash with chloroform, then wash with ethanol, and then soak in ethanol for use.

[0006] The molar ratio of 2,5-diaminopyridine to s-trialdehyde phloroglucinol is 1:0.5-3; The molar concentration of the acetic acid is 0.1-6 mol / L; The volume of the acetic acid is 30-40 ml; The mixing ratio of ethyl acetate to mesitylene is 1:0.5-10; The mixed volume of ethyl acetate and mesitylene is 30-40 ml; The concentration of the 2,5-diaminopyridine in the acetic acid solution is 0.01-0.05 mol / L; The reaction time of the COF-PDA film is 2-7 days; The molar amount of the methyl iodide is 0.1-10 mmol; The volume of the chloroform is 5-20 ml; The reaction time of the iCOF-PDA film is 1-5 days.

[0007] Compared with the prior art, the present invention has the following substantial advantages: (1) The synthetic route is simple and suitable for large-scale production; (2) The preparation method is simple and the preparation conditions are very mild; (3) iCOF-PDA membrane has very good hydrophilicity; (4) The iCOF-PDA membrane has a very good retention rate for both anionic and cationic dyes and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a preparation route map of the COF-PDA film in Example 1 of the present invention; Figure 2Schematic diagram of the preparation of the COF-PDA film in Example 1 of the present invention; Figure 3 is a physical picture of the iCOF-PDA film in Example 1 of the present invention; Figure 4 is a BET schematic diagram of iCOF-PDA in Example 1 of the present invention; Figure 5 is the retention rate of iCOF-PDA for different dyes in Example 1 of the present invention. DETAILED DESCRIPTION

[0009] The present invention is described in detail below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Without departing from the content and scope of the present invention, changes in implementation should be included in the technical scope of the present invention.

[0010] Example 1: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, respectively containing aqueous solutions of amine and acid catalysts and organic solutions containing aldehydes. The aqueous phase contained 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1 M, 35 ml), while the oil phase contained pyrogallol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and mesitylene (ethyl acetate: mesitylene = 1:3, 35 ml). The membrane was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0011] Example 2: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which the aqueous solution of amine and acid catalyst and the organic solution containing aldehyde were placed respectively. The aqueous phase was placed with 2,5-diaminopyridine (0.3 mmol, 34.5 mg) and acetic acid (1 M, 35 ml), while the oil phase was placed with isotrialdehyde phloroglucinol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and isotriene (ethyl acetate: isotriene = 1:3, 35 ml). The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0012] Example 3: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which the aqueous solution of amine and acid catalyst and the organic solution containing aldehyde were placed respectively. The aqueous phase was placed with 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (0.5 M, 35 ml), while the oil phase was placed with s-trialdehyde phloroglucinol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and s-trimethylbenzene (ethyl acetate: s-trimethylbenzene = 1:3, 35 ml). The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0013] Example 4: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which the aqueous solution of amine and acid catalyst and the organic solution containing aldehyde were placed respectively. The aqueous phase was placed with 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1M, 40 ml), while the oil phase was placed with s-trialdehyde phloroglucinol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and s-trimethylbenzene (ethyl acetate: s-trimethylbenzene = 1:3, 35 ml). The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0014] Example 5: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which the aqueous solution of amine and acid catalyst and the organic solution containing aldehyde were placed respectively. The aqueous phase was placed with 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1 M, 35 ml), while the oil phase was placed with isotrialdehyde phloroglucinol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and isotriene (ethyl acetate: isotriene = 1:1, 35 ml). The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0015] Example 6: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which the aqueous solution of amine and acid catalyst and the organic solution containing aldehyde were placed respectively. The aqueous phase was placed with 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1 M, 35 ml), while the oil phase was placed with isotrialdehyde phloroglucinol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and isotriene (ethyl acetate: isotriene = 1:3, 40 ml). The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0016] Example 7: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which the aqueous solution of amine and acid catalyst and the organic solution containing aldehyde were placed respectively. The aqueous phase was placed with 2,5-diaminopyridine (0.7 mmol, 80.6 mg) and acetic acid (1M, 35 ml), while the oil phase was placed with isotrialdehyde phloroglucinol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and isotriene (ethyl acetate: isotriene = 1:3, 35 ml). The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0017] Example 8: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which aqueous solutions of amine and acid catalysts and organic solutions containing aldehydes were placed respectively. 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1M, 35 ml) were placed in the aqueous phase, while pyrogallol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and mesitylene (ethyl acetate: mesitylene = 1:3, 35 ml) were placed in the oil phase. The mixture was left standing at room temperature for 5 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0018] Example 9: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which aqueous solutions of amine and acid catalysts and organic solutions containing aldehydes were placed respectively. 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1M, 35 ml) were placed in the aqueous phase, while pyrogallol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and mesitylene (ethyl acetate: mesitylene = 1:3, 35 ml) were placed in the oil phase. The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (10 mmol, 1413 mg) and chloroform (10 ml), left to stand at room temperature for 2 days, taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0019] Example 10: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which aqueous solutions of amine and acid catalysts and organic solutions containing aldehydes were placed respectively. 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1M, 35 ml) were placed in the aqueous phase, while pyrogallol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and mesitylene (ethyl acetate: mesitylene = 1:3, 35 ml) were placed in the oil phase. The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (20 ml), allowed to stand at room temperature for 2 days, then taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0020] Example 11: Preparation of iCOF-PDA The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which aqueous solutions of amine and acid catalysts and organic solutions containing aldehydes were placed respectively. 2,5-diaminopyridine (0.45 mmol, 51.8 mg) and acetic acid (1M, 35 ml) were placed in the aqueous phase, while pyrogallol (0.3 mmol, 65.8 mg) and a mixed solution of ethyl acetate and mesitylene (ethyl acetate: mesitylene = 1:3, 35 ml) were placed in the oil phase. The mixture was left standing at room temperature for 3 days, and the prepared COF-PDA membrane was taken out, washed with ethanol 3 times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform three times, and then immersed in CH 3 The sample was placed in a mixed solution of I (1 mmol, 141.3 mg) and chloroform (10 ml), left to stand at room temperature for 5 days, then taken out, washed 3 times with chloroform, 3 times with ethanol, and then immersed in ethanol for later use.

[0021] Example 12: Test of dye retention performance of iCOF-PDA A homemade filtration device was used with an effective membrane area of ​​7 cm 2 The retention performance of COF-PDA membrane and iCOF-PDA membrane was determined by nanofiltration under the conditions of t. The membrane was placed in the evaluation tank and a 100 mg / L dye aqueous solution was circulated by a pump. The operating pressure was controlled at 2 bar. Before the measurement, the filtration device was circulated for a period of time until a steady state was reached. The flux (P, L m -2 h -1 bar -1 Then the concentration of the dye solution before interception (C 0 ) and the concentration after interception (C e The calculation formula of dye retention rate (R,%) is: R=(1-C e / C 0 )*100%.

[0022] Through the interception experiment, it can be concluded that the iCOF-PDA membrane has a very good interception rate for various dyes, among which the interception rate for MB and EBT can reach 98%. This patent not only develops a new type of ionic covalent organic skeleton nanofiltration membrane, but also has very good interception performance for various dyes.

[0023] Of course, the above specific embodiments are only detailed explanations of the corresponding technical solutions of the present invention, and are not limited to the above implementation methods. For those skilled in the art, various changes or modifications can still be made on the basis of the above embodiments. All implementation methods are not listed here, and all changes or modifications derived from the above principles or mechanisms are within the protection scope of the present invention.

Claims

1. An ionized covalent organic framework nanofiltration membrane iCOF-PDA, characterized in that: The ionized covalent organic framework nanofiltration membrane is prepared according to the following method: The pretreated PAN membrane was placed vertically in the center of the diffusion cell by interfacial polymerization and divided into two chambers, in which aqueous solutions of amine and acid catalyst and organic solutions containing aldehydes were placed respectively. 2,5-diaminopyridine and acetic acid were placed in the aqueous phase, while a mixed solution of mesitylene, ethyl acetate and mesitylene was placed in the oil phase. The mixture was left to stand at room temperature, and the prepared COF-PDA membrane was taken out, washed with ethanol several times, and stored in ethanol for later use. The prepared COF-PDA membrane was taken out and exchanged with chloroform several times, then immersed in a mixed solution of CH3I and chloroform, left to stand at room temperature for several days, taken out, washed with chloroform, then washed with ethanol, and then immersed in ethanol for use.

2. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The molar ratio of 2,5-diaminopyridine to s-trialdehyde phloroglucinol is 1:0.5-3.

3. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The molar concentration of the acetic acid is 0.1-6 mol / L.

4. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The volume of the acetic acid is 30-40 ml.

5. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The mixing ratio of ethyl acetate to mesitylene is 1:0.5-10.

6. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The mixed volume of the ethyl acetate and mesitylene is 30-40 ml.

7. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The concentration of the 2,5-diaminopyridine in the acetic acid solution is 0.01-0.05 mol / L.

8. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The reaction time of the COF-PDA film is 2-7 days, and the reaction time of the iCOF-PDA film is 1-5 days.

9. The ionized covalent organic framework nanofiltration membrane according to claim 1, characterized in that: The molar amount of the iodomethane is 0.1-10 mmol, and the volume of the chloroform is 5-20 ml.

10. The use of the ionized covalent organic framework nanofiltration membrane as claimed in claim 1 for interception of various dyes, characterized in that: The iCOF-PDA membrane has a very good retention rate for various dyes, and the retention rate for MB and EBT can reach 98%.

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