Preparation method of functionalized graphene oxide for trapping radioactive gaseous iodine

Abstract

The invention provides a preparation method of functionalized graphene oxide for trapping radioactive gaseous iodine. The functionalized graphene prepared by the method provided by the invention has a rich pore structure, is lamellar, has a large number of wrinkles on the surface, has a specific surface area of 1058 m < 2 > / g, a surface defect concentration ID / IG of 1.97 and an adsorption capacity of 1217 mg / g on gaseous iodine.

Description

Technical Field

[0001] The present invention relates to the technical field of radioactive waste treatment and environmental protection, and more specifically, to a method for preparing functionalized graphene oxide for capturing radioactive gaseous iodine and the functionalized graphene oxide obtained according to the method. Background Art

[0002] Safe and proper handling and disposal of radioactive waste is the only way for the sustainable development of nuclear energy. Radioactive 129I accounts for 76.5% of iodine isotopes in spent fuel. It has a long half-life, high content, high toxicity, high mobility and high volatility, posing a serious threat to human health and the environment. Therefore, it is urgent to develop high-performance adsorption materials for capturing radioactive gaseous iodine.

[0003] Graphene is a two-dimensional material composed of carbon atoms arranged in a honeycomb structure. It has the advantages of ultra-thin structure, high strength, good thermal stability, high conductivity, etc. However, it is easily damaged by oxidation, which affects its performance. Graphene oxide is an oxidized graphene that is more stable, has rich oxygen-containing functional groups, and its conductivity can be adjusted by controlling the degree of oxidation. Studies have shown that the oxygen-containing functional groups such as carbonyl, carboxyl, and hydroxyl in carbon-based materials can enhance the interaction between iodine and materials through electrostatic attraction and hydrogen bonding. However, due to the reduction of surface energy and the presence of impurities, agglomeration is prone to occur during the impregnation modification process, and its application is limited by the agglomeration problem. Moreover, the prepared graphene samples usually need to be exposed to high temperature for annealing to eliminate their internal stress and defects and optimize their crystal structure and performance. Summary of the invention

[0004] The present invention aims to provide a novel method for preparing functionalized graphene oxide for radioactive iodine capture and the functionalized graphene oxide prepared thereby, so as to overcome the shortcomings of the prior art.

[0005] The inventors of the present invention use graphene oxide dispersion with better dispersibility and higher cost performance as the matrix, and based on the interaction between rich oxygen-containing functional groups and iodine, synthesize high-performance functionalized graphene oxide iodine adsorbent in one step through a solution blending method, avoiding agglomeration during the impregnation modification of graphene oxide, and simultaneously solving the problem of low material adsorption capacity. Moreover, the inventors unexpectedly found that the graphene prepared according to the method can have excellent adsorption performance without annealing.

[0006] According to a first aspect of the present invention, a method for preparing functionalized graphene oxide for radioactive iodine capture is provided, characterized in that: a graphene oxide dispersion is used as a matrix, a bismuth nitrate solution is used as a bismuth source, a solution blending method is used to synthesize functionalized graphene oxide in one step, and the prepared functionalized graphene oxide is dried at a low temperature. The prepared functionalized graphene oxide does not need to be annealed, and the preparation process is simple.

[0007] Furthermore, the preparation method comprises the following steps:

[0008] Step 1: Preparation of bismuth nitrate solution: Specifically, a proper amount of bismuth nitrate is dissolved in a proper solvent (preferably ethanol or ethylene glycol), and magnetic stirring is performed until the bismuth nitrate is fully dissolved to obtain a bismuth nitrate solution, wherein the bismuth ion concentration is 1 to 2M, preferably 1.5M.

[0009] Step 2: Evenly mix the graphene oxide dispersion with the bismuth nitrate solution. Specifically, take a certain amount of graphene oxide dispersion (self-made, concentration 10 mg / g, solvent is deionized water) in a beaker, and mix it with the bismuth nitrate solution in a volume ratio (10-5): 1, preferably 10: 1, and then, ultrasonically disperse to make the solution evenly mixed.

[0010] Step 3: Dry the mixed solution to obtain a film-shaped functionalized graphene oxide. Specifically, place the uniformly mixed solution in an oven and bake it at normal pressure and a temperature of 30-40° C. (preferably 35° C.) for 24-48 hours, preferably 36 hours, to obtain a film-shaped functionalized graphene oxide.

[0011] Furthermore, the method does not include an annealing step for the functionalized graphene oxide.

[0012] According to a second aspect of the present invention, a functionalized graphene oxide prepared according to the above method is provided, wherein the functionalized graphene oxide has a rich pore structure, is in a lamellar shape, has a large number of wrinkles on the surface, and has a specific surface area of ​​up to 1058 m 2 / g, surface defect concentration I D / I G It reaches 1.97, and the adsorption capacity for gaseous iodine reaches 1217 mg / g.

[0013] Beneficial Effects

[0014] The present invention provides a method for avoiding agglomeration of graphene oxide during impregnation modification and simultaneously improving the adsorption capacity of an iodine adsorbent: a solution blending method is adopted to uniformly mix a graphene oxide dispersion and a bismuth nitrate solution, and a high-performance functionalized graphene oxide iodine adsorbent is synthesized in one step, thereby avoiding the problem of agglomeration of graphene oxide during impregnation modification, and the obtained functionalized graphene oxide does not need to be annealed.

[0015] The active component bismuth is evenly and dispersedly distributed on the surface of graphene oxide, which can enhance the thermodynamic and kinetic characteristics of the reaction with gaseous iodine and significantly improve the adsorption capacity. At the same time, the large specific surface area and abundant surface defects of graphene oxide can provide a large number of adsorption sites. The abundant functional groups significantly improve the affinity with gaseous iodine through electrostatic attraction, hydrogen bonding and π-bond stacking, solving the problem of low material adsorption capacity. It is expected to significantly reduce the frequency of iodine adsorbent replacement and minimize radioactive waste.

[0016] The method for preparing functionalized graphene oxide of the present invention has simple process and low cost, and is expected to be used for removing radioactive gaseous iodine in nuclear facilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a scanning electron microscope photograph of the functionalized graphene oxide prepared according to Example 1 of the present invention.

[0018] Figure 2 This is a scanning electron microscope photograph of the functionalized graphene oxide after annealing prepared according to Comparative Example 2 of the present invention.

[0019] Figure 3 This is the Raman spectrum of the functionalized graphene oxide prepared according to Example 1 of the present invention.

[0020] Figure 4 : This is the Raman spectrum of the functionalized graphene oxide after annealing prepared according to Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are exemplary embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application.

[0022] (I) Preparation of functionalized graphene oxide

[0023] Embodiment 1:

[0024] Step 1: Dissolve 23.7 g of bismuth nitrate in 40 mL of ethylene glycol and stir magnetically for 1 hour to fully dissolve to obtain a bismuth nitrate solution, wherein the bismuth ion concentration in the obtained bismuth nitrate solution is 1.5 M.

[0025] Step 2: Take 400 mL of graphene oxide dispersion (concentration 10 mg / g) in a beaker and mix it with 40 mL of bismuth nitrate solution, then ultrasonically disperse it for 1 hour.

[0026] Step 3: Place the uniformly mixed solution in an oven and dry it at normal pressure and 35° C. for 36 hours to obtain a film-like functionalized graphene oxide.

[0027] Comparative Example 2:

[0028] Step 1: Dissolve 23.7 g of bismuth nitrate in 40 mL of ethylene glycol and stir magnetically for 1 hour to fully dissolve to obtain a bismuth nitrate solution, wherein the bismuth ion concentration in the obtained bismuth nitrate solution is 1.5 M.

[0029] Step 2: Take 400 mL of graphene oxide dispersion (concentration 10 mg / g) in a beaker and mix it with 40 mL of bismuth nitrate solution, then ultrasonically disperse it for 1 hour.

[0030] Step 3: Place the uniformly mixed solution in an oven, dry it at normal pressure and 35° C. for 36 hours, and then heat treat it at 550° C. for 2.5 hours to obtain annealed functionalized graphene oxide.

[0031] Drying at low temperature can keep the functionalized graphene oxide with a large specific surface area and defect concentration, while high temperature annealing will cause the functionalized graphene oxide to transform from an "amorphous" state to a "graphitized" state, resulting in a decrease in specific surface area and defect concentration, and a decrease in adsorption performance.

[0032] (II) Adsorption capacity test

[0033] The adsorption capacity of the obtained functionalized graphene oxide for gaseous iodine was tested.

[0034] First, weigh 0.75g of elemental iodine and place it at the bottom of a glass bottle. Then, weigh m0 adsorbent and seal the bottle mouth. Finally, place the glass bottle in an oven (the oven temperature is set at 100-200°C), measure and record the weight of the adsorbent, and stop the experiment until the weight remains unchanged (m1). Calculate its adsorption capacity for gaseous iodine by mass change, that is: C (mg / g) = (m1-m0) / m0. The adsorption capacity of gaseous iodine for the functionalized graphene oxide synthesized according to Example 1 reaches 1217mg / g, and the adsorption capacity of gaseous iodine for the functionalized graphene oxide after annealing according to Comparative Example 2 is 831mg / g.

[0035] (III) Scanning electron microscopy analysis

[0036] Electron microscope photographs of the functionalized graphene oxide obtained in Example 1 and Comparative Example 2 were taken.

[0037] The surface microstructure of the material was characterized by a scanning electron microscope (SEM), model: German ZEISS Sigma 360. The material was dispersed on a conductive adhesive and a layer of gold was sprayed. The electron beam energy of the test was 30 keV, and the image collection time was 100 s.

[0038] like Figure 1 As shown in electron microscope photos, functionalized graphene has a rich porous structure, is in the form of layers, and has a large number of wrinkles on the surface. Figure 2 It can be seen from the electron microscope photos that after annealing, the surface morphology of the functionalized graphene changes significantly, presenting a flaky structure and the wrinkles disappear.

[0039] (IV) Specific surface area measurement

[0040] The specific surface area of ​​the prepared functionalized graphene oxide was tested using a fully automatic specific surface and porosity analyzer (BET), analyzer model: American Micromeritics ASAP 2460, test conditions: 77K, nitrogen.

[0041] Test principle: In the BET test, the material is usually in the form of a solid powder or film, and the gas is usually nitrogen. In the test, the material is first placed in a vacuum to remove moisture and other impurities from the surface and pores of the material. Then, nitrogen is slowly introduced into the material until the nitrogen reaches a state of equilibrium with the surface and pores of the material. In this equilibrium state, the nitrogen has been completely adsorbed on the surface and pores of the material, forming a certain adsorption amount. Then, the specific surface area and pore structure of the material can be calculated based on the amount of nitrogen added and the shape of the adsorption isotherm.

[0042] Test steps:

[0043] 1. Sample preparation: Prepare the sample to be tested into a uniform powder.

[0044] 2. Vacuum treatment: Place the sample in vacuum at 150°C to remove gas and moisture adsorbed on the surface.

[0045] 3. Adsorption isotherm measurement: Place the sample in the adsorption instrument, set the liquid nitrogen temperature to 77K, and measure the adsorption isotherm by gradually increasing the nitrogen pressure. Under low pressure, gas molecules will adsorb on the sample surface to form a monolayer.

[0046] 4. BET fitting: According to the adsorption isotherm data, the BET equation is used for fitting to obtain the slope and intercept of the adsorption isotherm.

[0047] 5. Calculation of specific surface area: Calculate the specific surface area of ​​the sample based on the parameters in the BET equation.

[0048] The BET specific surface area of ​​the functionalized graphene oxide according to Example 1 of the present invention is as high as 1058 m 2 / g, while the BET specific surface area of ​​the functionalized graphene oxide after annealing according to Comparative Example 2 is 527 m 2 / g.

[0049] (V) Surface defect concentration measurement

[0050] Test principle: Raman is a scattering spectrum. The Raman effect originates from molecular vibration, lattice vibration and rotation. Therefore, the relevant information of molecular vibration energy level, lattice vibration energy level and rotation energy level structure can be obtained from the Raman spectrum.

[0051] Test steps:

[0052] 1. Place the sample on a glass slide, move it under the test lens, and perform optical focusing;

[0053] 2. Perform secondary laser focusing to form good photon collection;

[0054] 3. Select the laser and switch the laser, change the laser power to test, set the integration time and grating size according to the test results;

[0055] 4. Click test to export the test results;

[0056] 5. Perform peak fitting on the D peak and the G peak, and the surface defect concentration I D / I G =Area of ​​D peak / Area of ​​G peak.

[0057] The surface defect concentration (I D / I G ) is 1.97, while the surface defect concentration (I D / I G ) is 1.64.

[0058] (VI) Comparison of measurement results

[0059] The following table shows the comparison of the measurement results of various parameters (specific surface area, surface defect concentration, iodine adsorption capacity) of the functionalized graphene oxide according to Example 1 and the annealed functionalized graphene oxide according to Comparative Example 2.

[0060]

[0061] It can be seen that the specific surface area and surface defect concentration of the material after annealing are reduced, resulting in a decrease in iodine adsorption capacity. Therefore, the functionalized graphene oxide without annealing according to Example 1 of the present invention is more suitable as an adsorbent for adsorbing radioactive gaseous iodine.

Claims

1. A method for preparing functionalized graphene oxide for radioactive iodine capture, the method comprising the following steps: Step 1: Preparation of bismuth nitrate solution; Step 2: uniformly mixing the graphene oxide dispersion and the bismuth nitrate solution; Step 3: Dry the mixed solution to obtain a film-like functionalized graphene oxide.

2. The method according to claim 1, characterized in that The method does not include an annealing step for the functionalized graphene oxide.

3. The method according to claim 1 or 2, characterized in that: The step 1 comprises: dissolving bismuth nitrate in a solvent, and magnetically stirring until the bismuth nitrate is fully dissolved to obtain a bismuth nitrate solution, wherein the bismuth ion concentration is 1-2M.

4. The method according to claim 3, characterized in that The solvent is ethanol or ethylene glycol, and the ion concentration of bismuth is 1.5M.

5. The method according to claim 1 or 2, characterized in that: The second step comprises: placing the graphene oxide dispersion in a beaker, and mixing it with the bismuth nitrate solution in a volume ratio of (10-5):1, and then ultrasonically dispersing the solution to make it uniform.

6. The method according to claim 5, characterized in that The graphene oxide dispersion is a dispersion of graphene oxide in deionized water with a concentration of 10 mg / g. The graphene oxide dispersion is mixed with a bismuth nitrate solution at a volume ratio of 10:

1.

7. The method according to claim 1 or 2, characterized in that: The step three comprises: placing the uniformly mixed solution in an oven, and drying it at normal pressure and a temperature of 30-40° C. for 24-48 hours to obtain a film-shaped functionalized graphene oxide.

8. The method according to claim 7, characterized in that The temperature of the oven was set to 35°C and the drying time was set to 36 hours.

9. Functionalized graphene oxide for radioactive iodine capture obtained by the method according to any one of claims 1 to 8, characterized in that: Functionalized graphene has a rich pore structure, is lamellar, has a large number of wrinkles on the surface, and has a specific surface area of ​​up to 1058m 2 / g, surface defect concentration I D / I G It reaches 1.97, and the adsorption capacity for gaseous iodine reaches 1217 mg / g.

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