Preparation method of sodium cobalt ferrocyanide adsorption film, adsorption film and DGT device

Abstract

The present invention relates to a method for preparing a sodium cobalt ferrocyanide adsorption film, an adsorption film, and a DGT device. The method is applicable to the technical field of environmental monitoring. The technical solution adopted by the present invention is: a method for preparing a sodium cobalt ferrocyanide adsorption film, characterized in that it includes the following steps: S1, dissolving acrylamide, N,N'-methylenebisacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water to obtain an initial solution; S2, then adding N,N,N',N'-tetramethyldiethylamine and potassium persulfate to the initial solution to obtain a mixed solution; S3, injecting the mixed solution into a container and placing it in an oven to react and form a gel; S4, soaking the gel in deionized water to fully expand it; S5, soaking the expanded gel in a cobalt nitrate solution, so that the cobalt ions and the sulfonic acid groups on the gel form corresponding metal complexes, and then transferring the expanded gel to a sodium ferrocyanide solution for soaking, so that the sodium ferrocyanide reacts with the cobalt ions to form a sodium cobalt ferrocyanide adsorption film.

Description

Technical Field

[0001] The present invention relates to a method for preparing a sodium cobalt ferrocyanide adsorption film, the adsorption film and a DGT device, and is applicable to the technical field of environmental monitoring. Background Art

[0002] Excessive ammonia nitrogen can cause eutrophication of water bodies. Under eutrophic conditions, dissolved oxygen levels drop dramatically, leading to hypoxia and even death in aquatic organisms. Ammonia nitrogen in water consists of ammonia molecules and ammonium ions. The balance between ammonium ions and ammonia molecules is related to pH and temperature. In natural waters, the majority of ammonia nitrogen exists as ammonium ions. Therefore, monitoring ammonium ions in aquatic environments is crucial for early warning of eutrophication.

[0003] Diffusive Gradients in Thin-Films (DGT) is a widely used non-equilibrium in-situ passive sampling technique. Based on Fick's first law, it integrates sampling and enrichment, offering in-situ, kinetic sampling, time- and labor-saving methods, and the ability to obtain time-weighted average concentrations of pollutants.

[0004] The core component of DGT technology is the stationary phase, also known as the adsorption membrane. Currently, DGT adsorption membranes used for ammonium ion collection are primarily prepared using a mechanical mixing method. This involves grinding materials such as resin, zeolite, and sodium cobalt ferrocyanide into a powder of a specific particle size and then mixing them with agarose or polyacrylamide to form a gel adsorption membrane. This method of preparing gel adsorption membranes requires a relatively fine particle size of the blended materials, which can lead to uneven dispersion of particles within the gel adsorption membrane. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a method for preparing a sodium cobalt ferrocyanide adsorption film, an adsorption film and a DGT device are provided.

[0006] The technical solution adopted by the present invention is: a method for preparing a sodium cobalt ferrocyanide adsorption film, characterized in that it comprises the following steps:

[0007] S1, dissolving acrylamide, N,N'-methylenebisacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water to obtain an initial solution;

[0008] S2, then adding N,N,N',N'-tetramethyldiethylamine and potassium persulfate to the initial solution to obtain a mixed solution;

[0009] S3, injecting the mixed solution into a container and placing it in an oven to react and form a gel;

[0010] S4, soaking the gel in deionized water to allow it to fully swell;

[0011] S5. Soak the expanded gel in a cobalt nitrate solution, where the cobalt ions form corresponding metal complexes with the sulfonic acid groups on the gel. Then, the gel is transferred to a sodium ferrocyanide solution for immersion, where the sodium ferrocyanide reacts with the cobalt ions to form a sodium cobalt ferrocyanide adsorption film.

[0012] The mass ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid is (0.5-6):1. This process aims to prepare a high-salinity-resistant and high-toughness hydrogel. The preferred mass ratios of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid are 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, and 6:1. The amount of 2-acrylamido-2-methylpropanesulfonic acid added directly determines the ratio of sulfonic acid groups on the gel surface, thereby affecting the ratio of cobalt ion metal complexes and sodium cobalt ferrocyanide formed subsequently.

[0013] The mass ratio of acrylamide to N,N'-methylenebisacrylamide crosslinker is (5-20):1. This process aims to produce high-salinity-resistant, high-toughness hydrogels. The preferred mass ratios of acrylamide to N,N'-methylenebisacrylamide crosslinker are 5:1, 8:1, 10:1, 12:1, 15:1, and 20:1. The amount of N,N'-methylenebisacrylamide crosslinker added directly determines the toughness of the hydrogel. Too low a ratio results in insufficient toughness, while too high a ratio can easily cause cracking when formed on a glass plate.

[0014] In step S2, the volume of N,N,N',N'-tetramethyldiethylamine added is 5-60 μL; the potassium persulfate solution has a concentration of 10%, and the volume added is 0.1-1.0 mL. The volume of N,N,N',N'-tetramethyldiethylamine added is preferably 5, 10, 20, 30, 40, 50, or 60 μL; the volume of potassium persulfate solution added is preferably 0.1, 0.2, 0.4, 0.6, 0.8, or 1.0 mL.

[0015] In step S3, the thickness of the cushion layer of the glass plate is 0.2-1.5 mm, the temperature for reaction to form gel is 25-80° C., and the reaction time is 0.5-5 h.

[0016] The concentration of the cobalt nitrate solution in step S5 is 2%-20%, and the gel is immersed in the cobalt nitrate solution for 2-72 hours.

[0017] The concentration of the sodium ferrocyanide solution in step S5 is 0.1 to 2.0 mol / L -1 The gel is immersed in the sodium ferrocyanide solution for 2 to 96 hours.

[0018] A sodium cobalt ferrocyanide adsorption film is characterized by being prepared by the above-mentioned preparation method.

[0019] A DGT device is characterized by having the sodium cobalt ferrocyanide adsorption membrane.

[0020] A method for capturing ammonium ions in high-salinity water bodies is characterized by using the sodium cobalt ferrocyanide adsorption membrane or the DGT device.

[0021] The beneficial effects of the present invention are as follows: acrylamide, N,N'-methylenebisacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, etc. are dissolved into a mixed solution, and then a cross-linking agent is added and the mixed solution is injected into a container and placed in an oven for reaction to form a gel. The surface of the gel has abundant sulfonic acid groups. The expanded gel is soaked in a cobalt nitrate solution, and the cobalt ions form corresponding metal complexes with the sulfonic acid groups on the gel. The gel is then transferred to a sodium ferrocyanide solution for soaking, and the sodium ferrocyanide reacts with the cobalt ions to form a sodium cobalt ferrocyanide adsorption film. The chemical formula of sodium cobalt ferrocyanide can be expressed as Na y Co[Fe(CN)6] 1-x zH2O, which is a cubic cone-shaped space surrounded by 8 metal points and 12 cyano groups. The sodium ions in it can produce ion exchange with ammonium ions in aqueous solution, thus achieving the capture of ammonium ions in high-salinity water bodies.

[0022] The preparation method of the adsorption film of the present invention is not limited to the particle size of the mixed binding materials, and sodium cobalt ferrocyanide is formed in situ in the gel adsorption film. The method is simple, the adsorption film gel has good toughness, and the particles are evenly dispersed.

[0023] The sodium cobalt ferrocyanide adsorption membrane of the present invention can capture ammonium ions in high-salinity water bodies and accurately and effectively characterize the pollutant concentration of ammonium ions in the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The following are images of the gel prepared in Example 2 (left) and the sodium cobalt ferrocyanide adsorption film (right).

[0025] Figure 2 The following are images of the gel prepared in Example 3 (left) and the sodium cobalt ferrocyanide adsorption film (right).

[0026] Figure 3 This is the SEM image of the sodium cobalt ferrocyanide adsorption film in Example 2.

[0027] Figure 4 This is the capture of ammonium ions in high-salinity water by the sodium cobalt ferrocyanide adsorption membrane in Example 2. DETAILED DESCRIPTION

[0028] Example 1: This example is a sodium cobalt ferrocyanide adsorption film, and its preparation method includes the following steps:

[0029] S1. Dissolve acrylamide, N,N'-methylenebisacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water to obtain an initial solution.

[0030] In this example, the mass ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid is (0.5-6):1; the mass ratio of acrylamide to N,N'-methylenebisacrylamide crosslinker is (5-20):1.

[0031] S2. Then, 5 to 60 μL of N,N,N',N'-tetramethyldiethylamine and 0.1 to 1.0 mL of 10% potassium persulfate solution are added to the initial solution to obtain a mixed solution.

[0032] S3. The mixed solution is injected into a container (having a glass bottom plate, a circle of protrusions formed on the edge of the bottom plate surface, thereby forming a receiving groove in the middle of the glass bottom plate, and a glass cover plate is provided for the corresponding receiving groove) and placed in an oven to react and form a gel.

[0033] In this embodiment, the thickness of the cushion layer of the glass plate is 0.2-1.5 mm, the temperature for forming the gel by reaction is 25-80° C., and the reaction time is 0.5-5 h.

[0034] S4, soaking the gel in deionized water to allow it to fully swell;

[0035] S5. Soak the expanded gel in 2%-20% cobalt nitrate solution for 2-72 hours. The cobalt ions form corresponding metal complexes with the sulfonic acid groups on the gel, and then transfer to 0.1-2.0 mol / L -1 Soak in sodium ferrocyanide solution for 2-96 hours, and sodium ferrocyanide reacts with cobalt ions to form a sodium cobalt ferrocyanide adsorption film.

[0036] This embodiment also provides a DGT device, which contains the sodium cobalt ferrocyanide adsorption membrane of this embodiment.

[0037] This embodiment also provides a method for capturing ammonium ions in high-salinity water, using the sodium cobalt ferrocyanide adsorption membrane or DGT device in this embodiment.

[0038] Example 2: This example is basically the same as Example 1, except that the method for preparing the sodium cobalt ferrocyanide adsorption film in this example includes the following steps:

[0039] S1. Dissolve 4.26 g acrylamide, 0.3 g N,N'-methylenebisacrylamide, and 1.71 g 2-acrylamido-2-methylpropanesulfonic acid in deionized water and stir until completely dissolved.

[0040] S2, then add 20 μL N,N,N',N'-tetramethyldiethylamine and 0.5 mL 10% potassium persulfate solution;

[0041] S3, injecting the mixed solution into a glass plate with a 0.6 mm thick cushion layer and placing it in an oven at 60 degrees Celsius for 2 hours to form a gel;

[0042] S4. Soak the gel in deionized water for 24 hours to allow it to fully swell; then cut the fully swollen gel into discs with a diameter of 2 cm;

[0043] S5. Soak the gel in 5% cobalt nitrate solution for 48 hours, rinse with deionized water, and then transfer to 0.4 mol / L -1 Soak in sodium ferrocyanide solution for 96 hours to form sodium cobalt ferrocyanide adsorption film by in-situ reaction.

[0044] Example 3: This example is basically the same as Example 2, except that after the gel is prepared, it is immersed in 8% cobalt nitrate solution for 72 hours, rinsed with deionized water, and then transferred to 0.8 mol / L -1 Soak in sodium ferrocyanide solution for 120 hours to form sodium cobalt ferrocyanide adsorption film by in-situ reaction.

Claims

1. A method for preparing sodium cobalt ferrocyanide adsorption film, characterized in that: The following steps are involved: S1, dissolving acrylamide, N, N'-methylenebisacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid in deionized water to obtain an initial solution; S2, then adding N,N,N',N'-tetramethyldiethylamine and potassium persulfate to the initial solution to obtain a mixed solution; S3, injecting the mixed solution into a container and placing it in an oven to react and form a gel; S4, soaking the gel in deionized water to allow it to fully swell; S5, soaking the expanded gel in a cobalt nitrate solution, where the cobalt ions form corresponding metal complexes with the sulfonic acid groups on the gel, and then transferring the gel to a sodium ferrocyanide solution for soaking, where the sodium ferrocyanide reacts with the cobalt ions to form a sodium cobalt ferrocyanide adsorption film; The mass ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid is (0.5-6):1; The mass ratio of the acrylamide to the N, N'-methylenebisacrylamide crosslinker is (5-20):

1.

2. The method for preparing sodium cobalt ferrocyanide adsorption film according to claim 1, wherein: In step S2, the volume of N,N,N',N'-tetramethyldiethylamine added is 5-60 μL; the concentration of the potassium persulfate solution is 10%, and the volume added is 0.1-1.0 mL.

3. The method for preparing sodium cobalt ferrocyanide adsorption film according to claim 1, wherein: In step S3, the thickness of the cushion layer of the glass plate is 0.2-1.5 mm, the temperature for forming the gel by reaction is 25-80° C., and the reaction time is 0.5-5 h.

4. The method for preparing sodium cobalt ferrocyanide adsorption film according to claim 1, wherein: The concentration of the cobalt nitrate solution in step S5 is 2%-20%, and the gel is immersed in the cobalt nitrate solution for 2-72 hours.

5. The method for preparing sodium cobalt ferrocyanide adsorption film according to claim 1, wherein: The concentration of the sodium ferrocyanide solution in step S5 is 0.1-2.0 mol L -1 The gel is immersed in the sodium ferrocyanide solution for 2 to 96 hours.

6. A sodium cobalt ferrocyanide adsorption film, characterized in that: The method is prepared according to any one of claims 1 to 5.

7. A DGT device, characterized in that: A sodium cobalt ferrocyanide adsorption film according to claim 6.

8. A method for capturing ammonium ions in high-salinity water, characterized by: The sodium cobalt ferrocyanide adsorption membrane according to claim 6 or the DGT device according to claim 7 is used.

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