Porous molecular imprinting hydrogel membrane for detecting glyphosate in water body

Abstract

The invention relates to a porous molecular imprinting hydrogel membrane for detecting glyphosate in a water body. According to the molecularly imprinted hydrogel membrane, polyvinyl alcohol (PVA) serves as a matrix, polyvinylpyrrolidone (PVP) serves as a pore-forming agent, thiolated cyclodextrin (beta-CD) serves as a reaction site, a gel framework is obtained through a circulating freezing and unfreezing method, a porous structure of the hydrogel membrane is obtained by dissolving out the pore-forming agent PVP in water, and glyphosate (GLY) serves as a template molecule. Wherein a functional monomer acrylamide (AA) and a cross-linking agent ethylene glycol dimethacrylate (EGDMA) are subjected to addition polymerization with reaction sites on a gel framework to obtain a molecularly imprinted polymer, and then an imprinting cavity is obtained by eluting template molecules. The molecularly imprinted hydrogel membrane is simple in preparation process, uniform in pore structure, stable in imprinted polymer and obvious in trace detection result, has hydrophilicity of PVA, is environment-friendly due to PVA, and is a candidate material for water body detection application.

Description

Technical Field

[0001] The invention relates to the technical field of environmental monitoring, in particular to a porous molecular imprinting hydrogel membrane for detecting glyphosate in water. Background Art

[0002] As a matrix material in the field of environmental testing, molecular imprinted membranes have overcome the problems of previous direct detection of nanopowders that are not recyclable. The porous structure exhibits the properties of high specific surface area, high flux and low selectivity. The porous membrane can increase the contact between water entering the membrane matrix and the detection particles. However, the traditional method of mixing and dispersing molecular imprinted polymers reduces the stability of its recycling application, and often encounters dispersion aggregation that affects the mechanical properties of the membrane. Currently, the most studied method is to fix the imprinted polymer on the membrane material to achieve recycling.

[0003] PVA is an ideal green polymer with extremely strong hydrophilicity. If a polymer can be designed that can not only mix well with the PVA matrix but also induce cross-linking polymerization of the imprinted polymer, then this material will achieve the stability of the imprinted membrane and will be widely used in the field of environmental water testing. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the shortcomings of the prior art, the present invention provides a porous molecular imprinted hydrogel membrane for detecting glyphosate in water. The composite membrane has a simple preparation process, uniform pore structure, and good detection effect in water, thus solving the problems raised in the above-mentioned background technology.

[0006] (II) Technical solution

[0007] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions:

[0008] A porous molecular imprinted hydrogel membrane for glyphosate detection in water, firstly synthesizing a modified cyclodextrin, obtaining thiolated cyclodextrin (HS-β-CD) by esterification reaction between mercaptopropionic acid and cyclodextrin, then uniformly mixing HS-β-CD and pore formers PVP and PVA by solution blending, then preparing gel membrane by freeze-thaw method, and forming a uniform pore structure film by immersing the membrane in water through dissolution of the pore former. Finally, the functional monomer and crosslinking agent of the imprinted polymer are polymerized by the thiol group of HS-β-CD on the gel frame, thereby obtaining a stable molecular imprinted hydrogel membrane.

[0009] The structure of the thiolated cyclodextrin is as follows:

[0010]

[0011] (III) Beneficial effects

[0012] Compared with the prior art, the present invention provides a porous molecular imprinted hydrogel membrane for detecting glyphosate in water, which has the following beneficial effects:

[0013] The invention uses polyvinyl alcohol (PVA) as a matrix, polyvinyl pyrrolidone (PVP) as a pore-forming agent, thiolated cyclodextrin (β-CD) as a reaction site, adopts a cyclic freezing and thawing method to obtain a gel frame, the porous structure of a hydrogel membrane is obtained by dissolving the pore-forming agent PVP in water, glyphosate (GLY) is used as a template molecule, functional monomer acrylamide (AA) and cross-linking agent ethylene glycol dimethacrylate (EGDMA) are added and polymerized with the reaction sites on the gel frame to obtain a molecular imprinting polymer, and then the template molecule is eluted to obtain an imprinting cavity. The molecular imprinting hydrogel membrane has a simple preparation process, a uniform pore structure, a stable imprinting polymer, obvious trace detection results, has the hydrophilicity of PVA, is environmentally friendly to PVA, and is a candidate material for water body detection application. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the H NMR spectrum of thiolated cyclodextrin;

[0015] In the H-NMR spectrum, the characteristic peaks in the 3-5ppm range are attributed to the protons of cyclodextrin, the peaks in the 2.5-3ppm range correspond to the -CH2- protons in mercaptopropionic acid, and the peaks in the 5.7ppm range correspond to the -SH protons in mercaptopropionic acid. The results of the H-NMR spectrum indicate that the thiolated cyclodextrin has been successfully synthesized.

[0016] Figure 2 SEM images of gel films, A is pure PVA gel, B is PVA porous gel, C is HS-β-CD / PVA porous gel, and D is MIP / HS-β-CD / PVA porous gel;

[0017] Figure 3 To analyze the element content of gel film samples;

[0018] Figure 4 Raman spectra of different gel-blotted membrane samples, a is NIP / HS-β-CD / PVA, b is MIP / HS-β-CD / PVA. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example

[0021] A porous molecular imprinting hydrogel membrane for glyphosate detection in water, synthesizing thiolated cyclodextrin (HS-β-CD). First, β-cyclodextrin (5.0 g, 4.4 mmol), 3-mercaptopropionic acid (3.3 g, 31.0 mmol) and N, N-dimethylformamide (50 mL) solvent were added to a 250 mL round-bottom flask and stirred under N2 atmosphere. Then, concentrated sulfuric acid (H2SO4) solution (4 wt%) was slowly added dropwise and stirred at 60°C for about 24 hours. After cooling to room temperature, the reaction mixture was poured into 100 mL of acetone, the precipitated product was collected by filtration, thoroughly washed with acetone (usually 3×100 mL) (to remove residual DMF), and dried under vacuum at room temperature for 12 hours to obtain the product.

[0022] A porous PVA hydrogel film (HS-β-CD / PVA) was prepared. A uniform polyvinyl alcohol solution was obtained by dissolving 2 g of PVA in 20 mL of deionized water at 95 °C for 3 hours. After cooling to room temperature, 1 g of polyvinyl pyrrolidone and 0.4 g of mercaptocyclodextrin were added to the solution and stirred until completely dissolved. After defoaming for 20 minutes at room temperature (RT), the mixed solution was poured into the template. Finally, the template was placed in a refrigerator at -20 °C for 20 hours, thawed for 3 hours, and the freezing and thawing was repeated 3 times. The obtained hydrogel was soaked in deionized water for 12 hours to remove the PVP contained in the pores, obtain a porous gel, and soaked in anhydrous ethanol to replace the deionized water for use.

[0023] Grafting molecular imprinting polymer (MIP / HS-β-CD / PVA) on porous gel framework. 8.45×10-3g GLY (0.05mmol) was dissolved in a mixture of 10mL chloroform and methanol (v chloroform: v methanol = 4:1) in a 50mL flask, 0.1895g AA was added, and the mixture was shaken for 4h. The composite porous hydrogel prepared in the previous step, 3.76mL EGDMA and 30mg azobisisobutylnitrile (AIBN) were added. The solution was purged with nitrogen for 15 minutes and polymerized at 60°C for 24 hours. In order to eliminate traces of templates and unreacted monomers from the imprinted polymers, they were washed with a 1:9 (v / v) mixture of acetic acid and methanol, and the purity of the washing solvent was detected by UV spectrophotometry until no traces of GLY were detected in the eluent. Then, the porous molecular imprinting gel membrane was freeze-dried until constant weight. Non-imprinted porous gel membranes were also synthesized following exactly the same procedure, but excluding the template GLY(NIP / HS-β-CD / PVA).

[0024] Different molecular imprinting gel membrane samples were placed in 30 mL of glyphosate solution (1 mg / mL). After 1 hour, the membranes were taken out and freeze-dried to test the detection effect of Raman spectrum characterization.

[0025] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A porous molecular imprinted hydrogel membrane for detecting glyphosate in water, characterized in that: Thiolated cyclodextrin is added to the gel matrix, a porous framework structure is produced by dissolving the pore-forming agent, and the imprinted polymer is fixed on the porous gel framework by thiol chemistry; The structure of the thiolated cyclodextrin is as follows:

Images