Preparation method of magnetic adsorbent based on nitrogen-doped graphene aerogel

Abstract

The invention discloses a preparation method of a magnetic adsorbent based on nitrogen-doped graphene aerogel, which comprises the following steps: (1) ferroferric oxide nanoparticles are prepared by a solvothermal method: ferric trichloride hydrate is dissolved in ethanol, and sodium acetate and PEG-2000 are added; and (2) preparation of the magnetic nitrogen-doped graphene aerogel: adjusting the pH value, and carrying out a reaction on graphene oxide, p-phenylenediamine and the ferroferric oxide nanoparticle suspension. According to the preparation method, a nitrogen source such as p-phenylenediamine is introduced into a hydrothermal reaction system, so that the p-phenylenediamine is adsorbed to the surface of graphene oxide, the stacking force between graphene oxide layers is overcome, the self-assembly reaction is smoothly carried out, and an environment-friendly and effective nitrogen source induced hydrothermal self-assembly method is developed for preparing the magnetic nitrogen-doped graphene aerogel. In addition, nitrogen is doped in the 3D-graphene aerogel, so that the adsorption selectivity of the 3D-graphene aerogel is improved, and the application range of the 3D-graphene aerogel as a magnetic adsorbent in the field of pretreatment of food and environmental samples is widened.

Description

Technical Field

[0001] The invention relates to the preparation of magnetic adsorption materials, and in particular to a method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel. Background Art

[0002] Magnetic graphene composites have become a rising star in the field of magnetic solid phase extraction because they combine the excellent adsorption properties of graphene and the ability of magnetic materials to facilitate separation in an external magnetic field. They are widely used as magnetic adsorbents in the pretreatment of food and environmental samples. However, the irreversible aggregation of graphene caused by the π-π interaction between graphene layers will reduce the specific surface area of ​​graphene, reduce its adsorption performance, and increase the difficulty of synthesizing magnetic graphene composites.

[0003] In order to solve the irreversible agglomeration problem of graphene, three-dimensional (3D)-graphene aerogel came into being. The porous and interconnected structure of 3D-graphene aerogel provides it with a larger specific surface area. However, when preparing 3D-graphene aerogel by traditional hydrothermal synthesis, graphene oxide is easy to accumulate in the reaction aqueous solution, making the self-assembly reaction difficult to proceed, and thus causing the synthesized graphene aerogel to collapse easily. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel. The present invention proposes a method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel, and the steps are as follows: (1) Ferroferric oxide nanoparticles were prepared by a solvothermal method: hydrated ferric chloride was dissolved in ethanol, and sodium acetate and PEG-2000 were added to react to obtain the nanoparticles. (2) Preparation of magnetic nitrogen-doped graphene aerogel: The aerogel is prepared by reacting graphene oxide, p-phenylenediamine and a suspension of ferroferric oxide nanoparticles by adjusting the pH.

[0005] Furthermore, the masses of hydrated ferric chloride, sodium acetate and PEG-2000 in step (1) are 7.02 g, 8.537 g and 2.6 g respectively.

[0006] Furthermore, the reaction temperature of step (1) is 200° C. and the reaction time is 24 h.

[0007] Furthermore, the pH in step (2) is 10.6.

[0008] Furthermore, in step (2), the masses of graphene oxide, p-phenylenediamine and ferrosoferric oxide nanoparticles are 120 mg, 0.06 g and 60 mg respectively.

[0009] Furthermore, in step (2), the reaction temperature is 180° C. and the reaction time is 12 h.

[0010] Furthermore, in step (2), graphene oxide and p-phenylenediamine are added to water adjusted to pH value, ultrasonicated, and then the ferrosoferric oxide nanoparticle suspension is added to react.

[0011] The specific steps of step (1) are as follows: accurately weigh 7.02 g of hydrated ferric chloride and dissolve it in 130 mL of ethylene glycol to form a clear yellow solution, accurately weigh 8.537 g of sodium acetate and 2.6 g of PEG-2000 in the above solution, and ultrasonicate until uniformly dispersed; transfer to a 200 mL reaction kettle, put it in a 200°C oven, and react at high temperature for 24 h; after cooling to room temperature, repeatedly wash the black powder with ethanol until it is neutral, vacuum dry it at 60°C for 12 h, and then store it for future use.

[0012] The specific steps of step (2) are as follows: 60 mL of ultrapure water was measured and the pH was adjusted to 10.6 with ammonia water (10%); 120 mg of graphene oxide (GO) and 0.06 g of p-phenylenediamine (PPD) were accurately weighed in the above solution and ultrasonicated for 2 h until uniformly dispersed; 60 mg of Fe3O4 nanoparticles were added and stirred vigorously for 10 min until a uniform suspension was obtained; the mixture was transferred to a 100 mL reactor and placed in a 180°C oven for reaction for 12 h; after cooling to room temperature, the magnetic nitrogen-doped graphene hydrogel generated by the reaction was washed with ultrapure water until neutral. The washed magnetic nitrogen-doped graphene hydrogel was pre-frozen in a -80°C refrigerator overnight, and the magnetic nitrogen-doped graphene aerogel obtained after vacuum freeze drying (20 Pa, -50°C, 8 h) was ground until uniform and ready for use.

[0013] Beneficial effects: The present invention introduces a nitrogen source such as p-phenylenediamine into a hydrothermal reaction system, thereby allowing p-phenylenediamine to be adsorbed onto the surface of graphene oxide, thereby overcoming the stacking force between graphene oxide layers and allowing the self-assembly reaction to proceed smoothly, thereby developing an environmentally friendly and effective nitrogen source-induced hydrothermal self-assembly method for preparing magnetic nitrogen-doped graphene aerogels. In addition, nitrogen doping in 3D-graphene aerogels can further change the energy band structure of 3D-graphene aerogels, improve the mechanical strength of 3D-graphene aerogels, stabilize the three-dimensional structure of 3D-graphene aerogels, increase the free carrier density of 3D-graphene aerogels, enhance the interaction between 3D-graphene aerogels and target analytes, improve the adsorption selectivity of 3D-graphene aerogels, and broaden their application range as magnetic adsorbents in the field of food and environmental sample pretreatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The schematic diagram of the preparation and synthesis of magnetic nitrogen-doped graphene aerogel and the finished product display diagram; Figure 2 This is a scanning electron microscope image of magnetic nitrogen-doped graphene aerogel; Figure 3 is the XRD diffraction pattern of magnetic nitrogen-doped graphene aerogel; Figure 4 This is the XPS image of magnetic nitrogen-doped graphene aerogel; Figure 5 VSM curve of magnetic nitrogen-doped graphene aerogel. DETAILED DESCRIPTION

[0015] The present invention will be further explained below in conjunction with specific embodiments.

[0016] Example 1 Preparation method of magnetic 3D-nitrogen-doped graphene aerogel Ferroferric oxide nanoparticles (Fe3O4) were prepared by solvothermal method. Accurately weigh 7.02 g of hydrated ferric chloride and dissolve it in 130 mL of ethylene glycol to form a clear yellow solution. Accurately weigh 8.537 g of sodium acetate and 2.6 g of PEG-2000 in the above solution and ultrasonicate until uniformly dispersed. Transfer to a 200 mL reactor, place in a 200°C oven, and react at high temperature for 24 h. After cooling to room temperature, wash the black powder repeatedly with ethanol until it is neutral, vacuum dry at 60°C for 12 h, and store for later use.

[0017] The preparation of magnetic nitrogen-doped graphene aerogel was completed using nitrogen source induced hydrothermal self-assembly method and freeze-drying technology. Measure 60 mL of ultrapure water and adjust the pH to 10.6 with ammonia water (10%). Accurately weigh 120 mg of graphene oxide (GO) and 0.06 g of p-phenylenediamine (PPD) in the above solution and ultrasonicate for 2 h until uniformly dispersed. Add 60 mg of Fe3O4 nanoparticles and stir vigorously for 10 min to a uniform suspension. Transfer to a 100 mL reactor and place in a 180°C oven to react for 12 h. After cooling to room temperature, use ultrapure water to wash the magnetic nitrogen-doped graphene hydrogel generated by the reaction until neutral. The washed magnetic nitrogen-doped graphene hydrogel was placed in a -80°C refrigerator for pre-freezing overnight. The magnetic nitrogen-doped graphene aerogel obtained after vacuum freeze drying (20 Pa, -50°C, 8 h) was ground until uniform and ready for use. The preparation schematic diagram and product are as follows Figure 1 shown.

[0018] Example 2 Material Characterization Diagram Figure 2 SEM images of magnetic nitrogen-doped graphene aerogels are shown. Figure 2 a Shows the classic aerogel 3D structure formed by magnetic nitrogen-doped graphene aerogel after freeze-drying. Figure 2b shows that Fe3O4 nanoparticles are scattered between the grid structures in magnetic nitrogen-doped graphene aerogel. Figure 2 c shows Fe3O4 encapsulated by single-layer graphene in magnetic nitrogen-doped graphene aerogel. Figure 2 d shows the classic lattice defects appearing in the magnetic nitrogen-doped graphene aerogel structure due to the doping of nitrogen atoms.

[0019] from Figure 3 The XRD diffraction pattern of magnetic nitrogen-doped graphene aerogel shows that the decrease in the reflection value at 2θ = 11.68° is the disappearance of the diffraction peak after the reduction of the classic graphene oxide. The diffraction peak at 2θ = 25.76° corresponds to the 002 crystal plane of graphene, proving that the magnetic nitrogen-doped graphene aerogel contains a single-layer graphene sheet structure.

[0020] Figure 4 a shows that the magnetic nitrogen-doped graphene aerogel contains four elements, namely C, N, O, and Fe. Figure 4 b C 1s fitting results show that the peaks of C-containing groups are at 283.75 ev (C=C / CC), 285 ev (CN), and 287.1 ev (C=O / CO). Figure 4 The high-resolution N 1s spectrum shown in c can be fitted with three peaks, namely 398.35 ev (pyridine N), 399.35 ev (pyrrole N) and 400.45 ev (graphite N), which can prove the successful doping of N. In addition Figure 4 The high-resolution O 1s spectrum shown in d can be deconvoluted into two peaks at 530.85 ev (C=O) and 532.25 ev (CO).

[0021] Depend on Figure 5 As shown in Figure 2, the saturation magnetization of magnetic nitrogen-doped graphene aerogel (N-GAM) is 24.9 emu g -1 , greater than 16.8 emu g -1 , indicating that it can be used as a magnetic adsorbent, that is, it can be separated from the solution simply by magnetic attraction without the need for filtration or other physical separation means.

Claims

1. A method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel, characterized in that: The following steps are involved: (1) Ferroferric oxide nanoparticles were prepared by a solvothermal method: hydrated ferric chloride was dissolved in ethanol, and sodium acetate and PEG-2000 were added to react to obtain the nanoparticles. (2) Preparation of magnetic nitrogen-doped graphene aerogel: The pH value is adjusted to react graphene oxide, p-phenylenediamine and a suspension of ferroferric oxide nanoparticles to obtain the aerogel.

2. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1, characterized in that: In step (2), graphene oxide and p-phenylenediamine are added to water adjusted to pH value, ultrasonicated, and then a suspension of ferrosoferric oxide nanoparticles is added for reaction.

3. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1 or 2, characterized in that: The masses of hydrated ferric chloride, sodium acetate and PEG-2000 in step (1) are 7.02 g, 8.537 g and 2.6 g respectively.

4. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1 or 2, characterized in that: The reaction temperature of step (1) is 200°C and the reaction time is 24h.

5. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1 or 2, characterized in that: The pH in step (2) was 10.

6.

6. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1 or 2, characterized in that: In step (2), the masses of graphene oxide, p-phenylenediamine and ferrosoferric oxide nanoparticles are 120 mg, 0.06 g and 60 mg respectively.

7. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1 or 2, characterized in that: In step (2), the reaction temperature is 180°C and the reaction time is 12 h.

8. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1, characterized in that: The specific steps of step (1) are as follows: accurately weigh 7.02 g of hydrated ferric chloride and dissolve it in 130 mL of ethylene glycol to form a clear yellow solution, accurately weigh 8.537 g of sodium acetate and 2.6 g of PEG-2000 in the above solution, and ultrasonicate until uniformly dispersed; transfer to a 200 mL reaction kettle, put it in a 200°C oven, and react at high temperature for 24 h; after cooling to room temperature, repeatedly wash the black powder with ethanol until it is neutral, and vacuum dry it at 60°C for 12 h.

9. The method for preparing a magnetic adsorbent based on nitrogen-doped graphene aerogel according to claim 1, characterized in that: The specific steps of step (2) are as follows: measure 60 mL of ultrapure water and adjust the pH to 10.6 with ammonia water; accurately weigh 120 mg of graphene oxide and 0.06 g of p-phenylenediamine in the above solution, and ultrasonicate for 2 h until uniform dispersion; add 60 mg of Fe3O4 nanoparticles and stir vigorously for 10 min until a uniform suspension is obtained; transfer to a 100 mL reactor and place in a 180°C oven for reaction for 12 h; after cooling to room temperature, use ultrapure water to wash the magnetic nitrogen-doped graphene hydrogel generated by the reaction until it is neutral; put the washed magnetic nitrogen-doped graphene hydrogel into a -80°C refrigerator for pre-freezing overnight, and vacuum freeze-drying at 20 Pa, -50°C, for 8 h to obtain the magnetic nitrogen-doped graphene aerogel.

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