Preparation method of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine

Abstract

The present invention discloses a preparation method of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine, comprising the following steps: activating silica gel with dilute nitric acid; sequentially adding the activated silica gel and mercury nitrate / bismuth nitrate solution into a three-dimensional mixer for impregnation treatment; placing the impregnated silica gel in a blast drying oven for drying treatment to obtain the mercury and bismuth co-modified silica gel. The mercury and bismuth co-modified silica gel of the present invention has strong iodine adsorption ability, low cost, and simple preparation process, and can be applied to the purification treatment of radioactive gaseous iodine in the nuclear industry system.

Description

Technical Field

[0001] The present invention belongs to the technical fields of nuclear industry and material preparation. More specifically, the present invention relates to a preparation method of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine. Background Art

[0002] As a low-carbon and efficient green energy, actively developing nuclear power has become an important part of China's energy strategy. At present, the number of grid-connected nuclear power units and the total installed capacity in China are second only to those in the United States and France, and it is expected to exceed France in 2024 and climb to the second place in the world. It is worth noting that with the large-scale development of nuclear energy in China, the production of spent nuclear fuel in nuclear power plants is also increasing day by day. Under the relevant policies implemented by the country, it is particularly important to reprocess spent nuclear fuel. China mainly adopts the wet reprocessing technology, and a large amount of radioactive waste gas containing iodine-129 will be generated during this process, mainly including inorganic iodine ( 129 I 2 ) and organic iodine (CH 3 129 I), and it must be purified. At present, silver-based purification materials are mainly used at home and abroad, including silver-coated silica gel, silver-coated zeolite, silver-coated alumina, etc. Although they have excellent performance, they are greatly affected by silver, resulting in high prices. Therefore, it is of great practical significance to design and develop new iodine-129 purification materials. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and / or defects and provide at least the advantages described hereinafter.

[0004] To achieve these objects and other advantages according to the present invention, a preparation method of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine is provided, including the following steps:

[0005] Step 1: Activate the silica gel with dilute nitric acid;

[0006] Step 2: Add the activated silica gel and mercury nitrate / bismuth nitrate solution to a three-dimensional mixer in sequence for impregnation treatment;

[0007] Step 3: Place the impregnated silica gel in a blast drying oven for drying treatment to obtain the mercury and bismuth co-modified silica gel.

[0008] Preferably, in the step 1, the mass concentration of the dilute nitric acid is 3-5%;

[0009] The silica gel is water-resistant silica gel.

[0010] Preferably, in the step 1, the mass-volume ratio of the silica gel to the dilute nitric acid is 1:5-1:10 g / mL.

[0011] Preferably, in the step 1, the specific method of activating the silica gel with dilute nitric acid comprises: placing the silica gel in dilute nitric acid at 80-100° C. and stirring for 2-4 hours.

[0012] Preferably, in the step 2, the mercuric nitrate / bismuth nitrate solution is a dilute nitric acid solution of mercuric nitrate hydrate and bismuth nitrate hydrate, and the volume ratio of nitric acid to water in the dilute nitric acid solution is 1:9 to 1:14;

[0013] The concentration of mercury nitrate in the mercury nitrate / bismuth nitrate solution is 300-360 g / L, and the concentration of bismuth nitrate is 100-120 g / L;

[0014] In the step 2, the volume ratio of the activated silica gel to the mercuric nitrate / bismuth nitrate solution is 0.8 to 1;

[0015] The activated silica gel and mercuric nitrate / bismuth nitrate solution are sequentially added into a three-dimensional mixer for impregnation treatment. The impregnation treatment is carried out for 4 to 8 hours at room temperature, and the room temperature ranges from 15 to 35°C.

[0016] Preferably, in the step 1, after the silica gel is stirred and activated with dilute nitric acid, filtering, washing and drying are further performed, wherein the washing is specifically performed with deionized water for 1 to 3 times;

[0017] The drying is specifically performed at 100-130° C. in an air atmosphere for 24-48 hours;

[0018] In the step three, the impregnated silica gel is placed in a forced air drying oven for drying, and the drying is carried out at 130° C. for 24 hours in an air atmosphere.

[0019] The invention discloses an application of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine. The mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine is applied to purify radioactive gaseous iodine, and the gaseous iodine is single iodine or an iodine compound.

[0020] Preferably, the iodine compound is methyl iodide.

[0021] Preferably, the method of applying the mercury and bismuth co-modified silica gel to statically adsorb radioactive gaseous elemental iodine comprises: weighing elemental iodine, adding it to a quartz crucible at the bottom of a reactor, weighing mercury and bismuth co-modified silica gel, placing it in a porous hanging basket on a sand core partition, covering the upper end of the reactor with a lid and placing the entire reactor in a forced air drying oven for static adsorption at 100°C for 24 hours; wherein the mass ratio of elemental iodine to mercury and bismuth co-modified silica gel is 3:1.

[0022] Preferably, the method for applying the mercury and bismuth co-modified silica gel to statically adsorb radioactive gaseous methyl iodide includes: measuring 3 mL of methyl iodide solution and adding it to the quartz crucible at the bottom of the reactor. Weigh the mercury and bismuth co-modified silica gel and place it in the porous hanging basket on the sand core partition. After covering the upper lid of the reactor, place the whole in a forced air drying oven and statically adsorb at 100 °C for 24 h. Then weigh the mass of the mercury and bismuth co-modified silica gel, and determine its methyl iodide adsorption capacity through the mass difference before and after. The volume-mass ratio of methyl iodide to the mercury and bismuth co-modified silica gel is 3 mL:1 g.

[0023] The method for applying the mercury and bismuth co-modified silica gel to dynamically adsorb radioactive gaseous methyl iodide includes: using 131 I as a tracer source to prepare CH 3 131 I gas; select a 50 mm × 25 mm adsorption bed, load 5 layers, set the gas flow rate of the test system to 24 L / min, and the adsorption temperature to 100 °C. After the temperatures at the inlet and outlet of the adsorption bed are stable, start injecting CH 3 131 I gas. Stop injecting the sample after 1 h, and then continue purging for 1 h. Finally, use a low-background γ spectrometer to measure the total activity of each layer of the adsorption bed, and calculate the removal efficiency of methyl iodide after converting it into a counting rate.

[0024] The present invention has at least the following beneficial effects: The mercury and bismuth co-modified silica gel of the present invention has strong iodine adsorption ability, low cost, and simple preparation process, and can be applied to the purification treatment of radioactive gaseous iodine in the nuclear industry system.

[0025] Other advantages, objectives, and features of the present invention will be partially reflected by the following description, and partially will be understood by those skilled in the art through the research and practice of the present invention. Description of the Drawings

[0026] Figure 1 Powder X-ray diffraction pattern of the mercury and bismuth co-modified silica gel prepared for the example;

[0027] Figure 2 Adsorption isotherm and pore size distribution diagram of the mercury and bismuth co-modified silica gel prepared for the example;

[0028] Figure 3 Appearance photo of the finished product of the mercury and bismuth co-modified silica gel prepared for the example;

[0029] Figure 4 Scanning electron microscope and energy spectrum analysis diagram of the mercury and bismuth co-modified silica gel prepared for the example. Detailed Description of the Invention

[0030] The following further describes the present invention in detail with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0031] It should be understood that terms such as "having", "including", and "comprising" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0032] Example

[0033] This example provides a preparation method of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine, including the following steps:

[0034] Step 1: Place 750 g of silica gel into 1500 mL of dilute nitric acid solution with a mass concentration of 3%, stir at 100 °C in a constant temperature water bath for 2 h, filter, wash repeatedly with deionized water 3 times, and then place it in a blast drying oven and dry at 130 °C in an air atmosphere for 24 h to obtain activated silica gel;

[0035] Step 2: Add 600 g of the activated silica gel prepared in Step 1 and 750 mL of a dilute nitric acid solution containing 325 g / L of mercury hydrate nitrate and 110 g / L of bismuth hydrate nitrate to a three-dimensional mixer in sequence and impregnate for 4 h;

[0036] Step 3: Take out the silica gel after impregnation treatment in Step 2, place it in a blast drying oven, and dry at 130 °C in an air atmosphere for 24 h to obtain mercury and bismuth co-modified silica gel. Figure 1 Powder X-ray diffraction pattern of the prepared mercury and bismuth co-modified silica gel. As can be seen from the figure, mercury in the material mainly exists in the form of Hg(OH)NO 3 and no diffraction peak of bismuth is detected. Figure 2 Adsorption isotherm and pore size distribution diagram of the prepared mercury and bismuth co-modified silica gel. As can be seen from the figure, the specific surface area of the material is 161.60 m 2 / g, the total pore volume is 0.49 cc / g, and the pore size is 9.62 nm. Figure 3 Appearance photo of the finished product of mercury and bismuth co-modified silica gel. Figure 4 Scanning electron microscope and energy spectrum analysis pictures of mercury and bismuth co-modified silica gel. As can be seen from the figure, mercury and bismuth are evenly distributed on the silica gel substrate and no obvious agglomeration phenomenon appears.

[0037] Comparative Example

[0038] This comparative example provides a preparation method of mercury-modified silica gel for purifying radioactive gaseous iodine, including the following steps:

[0039] Step 1: Place 750 g of silica gel into 1500 mL of dilute nitric acid solution with a mass concentration of 3%, stir at 100 °C in a constant temperature water bath for 2 h, filter, wash repeatedly with deionized water 3 times, and then place it in a blast drying oven and dry at 130 °C in an air atmosphere for 24 h to obtain activated silica gel;

[0040] Step 2: Add 600 g of activated silica gel prepared in Step 1 and 750 mL of a dilute nitric acid solution of mercuric nitrate hydrate with a concentration of 325 g / L to a three-dimensional mixer in sequence for impregnation treatment for 4 h;

[0041] Step 3: Take out the silica gel after the impregnation treatment in Step 2, place it in a blast drying oven, and dry it at 130 °C in an air atmosphere for 24 h to obtain mercury-modified silica gel.

[0042] Application Example 1

[0043] Test the static adsorption capacity of the mercury and bismuth co-modified silica gel prepared in the example for simulated radioactive gaseous elemental iodine.

[0044] The experimental process is as follows: Use 127 I to simulate 129 I. Weigh 3 g of elemental iodine and add it to the quartz crucible at the bottom of the reactor. Weigh 1 g of the mercury and bismuth co-modified silica gel prepared in the example (M 1 ), place it in the porous hanging basket on the sintered glass partition, cover the upper lid of the reactor, and then place the whole in a blast drying oven for static adsorption at 100 °C for 24 h. Then weigh the mass of the mercury and bismuth co-modified silica gel (M 2 ), and determine its elemental iodine adsorption capacity through the mass difference before and after, that is:

[0045]

[0046] Experimental result: The calculated static saturated adsorption capacity of the mercury and bismuth co-modified silica gel prepared in the example for elemental iodine is 209.1 ± 1.7 mg / g.

[0047] Application Example 2

[0048] Test the static adsorption capacity of the mercury and bismuth co-modified silica gel prepared in the example for simulated radioactive gaseous methyl iodide.

[0049] The experimental process is as follows: Use 127 I to simulate 129 I. Measure 3 mL of methyl iodide solution and add it to the quartz crucible at the bottom of the reactor. Weigh 1 g of the mercury and bismuth co-modified silica gel prepared in the example (M 1 ), place it in the porous hanging basket on the sintered glass partition, cover the upper lid of the reactor, and then place the whole in a blast drying oven for static adsorption at 100 °C for 24 h. Then weigh the mass of the mercury and bismuth co-modified silica gel (M 2 ), and determine its methyl iodide adsorption capacity through the mass difference before and after, that is:

[0050]

[0051] Experimental results: The static saturated adsorption capacity of the mercury-coated silica gel prepared in the example for methyl iodide was calculated to be 151.0 ± 6.9 mg / g.

[0052] Application Example 3

[0053] The dynamic adsorption capacity of the mercury and bismuth co-modified silica gel prepared in the example for radioactive gaseous methyl iodide was tested.

[0054] The experimental procedure is as follows: Using 131 I as a tracer source, self-prepare CH 3 131 I gas. Select a 50 mm × 25 mm adsorption bed, pack 5 layers, set the gas flow rate of the test system to 24 L / min, and the adsorption temperature to 100 °C. After the inlet and outlet temperatures of the adsorption bed are stable, start injecting CH 3 131 I gas. Stop injecting the sample after 1 h, and continue purging for 1 h. Finally, use a low-background γ spectrometer to measure the total activity of each layer of the adsorption bed, convert it into a counting rate (C), and then calculate the removal efficiency (F), that is:

[0055]

[0056] where n represents the number of layers of the adsorption bed.

[0057] Experimental results: The removal efficiency of the mercury and bismuth co-modified silica gel prepared in the example for methyl iodide was tested as follows: 97.486% for the first layer, 99.866% for the second layer, 99.984% for the third layer, and 99.996% for the fourth layer.

[0058] For the application ratio

[0059] The dynamic adsorption capacity of the mercury-modified silica gel prepared in the comparative example for radioactive gaseous methyl iodide was tested.

[0060] The experimental procedure is as follows: Using 131 I as a tracer source, self-prepare CH 3 131 I gas. Select a 50 mm × 25 mm adsorption bed, pack 5 layers, set the gas flow rate of the test system to 24 L / min, and the adsorption temperature to 100 °C. After the inlet and outlet temperatures of the adsorption bed are stable, start injecting CH 3 131 I gas. Stop injecting the sample after 1 h, and continue purging for 1 h. Finally, use a low-background γ spectrometer to measure the total activity of each layer of the adsorption bed, convert it into a counting rate (C), and then calculate the removal efficiency (F), that is:

[0061]

[0062] Experimental results: The removal efficiency of the mercury-modified silica gel prepared in the comparative example for methyl iodide was tested as follows: 76.192% for the first layer, 96.046% for the second layer, 99.398% for the third layer, and 99.904% for the fourth layer.

[0063] The equipment quantities and treatment scales described herein are used to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0064] Although the embodiments of the present invention have been disclosed above, they are not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to specific details and the illustrated and described examples here.

Claims

1. An application of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine, It is characterized in that The mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine is used to purify radioactive gaseous iodine, and the gaseous iodine is iodine element or iodine compound; The preparation method of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine comprises the following steps: Step 1: Activate silica gel with dilute nitric acid; Step 2: Adding the activated silica gel, mercuric nitrate and bismuth nitrate solution into a three-dimensional mixer in sequence for impregnation treatment; Step 3: placing the impregnated silica gel in a forced air drying oven for drying to obtain the mercury and bismuth co-modified silica gel.

2. The use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that In the step 1, the mass concentration of the dilute nitric acid is 3-5%; The silica gel is water-resistant silica gel.

3. The use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that In the step 1, the mass volume ratio of the silica gel to the dilute nitric acid is 1:5-1:10 g / mL.

4. The use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that In the step 1, the specific method of using dilute nitric acid to activate the silica gel includes: placing the silica gel in dilute nitric acid at 80-100° C. and stirring for 2-4 hours.

5. The use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that In the step 2, the mercuric nitrate and bismuth nitrate solution is a dilute nitric acid solution of mercuric nitrate hydrate and bismuth nitrate hydrate, and the volume ratio of nitric acid to water in the dilute nitric acid solution is 1:9-1:14; The concentration of mercury nitrate in the mercury nitrate and bismuth nitrate solution is 300-360 g / L, and the concentration of bismuth nitrate is 100-120 g / L; In the step 2, the volume ratio of the activated silica gel to the mercuric nitrate and bismuth nitrate solution is 0.8-1; The activated silica gel, mercuric nitrate and bismuth nitrate solutions are sequentially added into a three-dimensional mixer for impregnation treatment. The impregnation treatment is carried out for 4 to 8 hours at room temperature, and the room temperature ranges from 15 to 35°C.

6. The use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that In the step 1, after the silica gel is stirred and activated with dilute nitric acid, filtering, washing and drying are further performed, wherein the washing is specifically performed with deionized water for 1 to 3 times; The drying is specifically performed at 100-130° C. in an air atmosphere for 24-48 hours; In the step three, the impregnated silica gel is placed in a forced air drying oven for drying, and the drying is carried out at 130° C. for 24 hours in an air atmosphere.

7. Use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that The iodine compound is methyl iodide.

8. Use of mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as claimed in claim 1, It is characterized in that The method for applying the mercury and bismuth co-modified silica gel to statically adsorb radioactive gaseous elemental iodine includes: weighing elemental iodine and adding it to the quartz crucible at the bottom of the reactor; weighing the mercury and bismuth co-modified silica gel and placing it in the porous hanging basket on the sand core partition board; covering the upper cover of the reactor and then placing the whole in a forced air drying oven for static adsorption at 100 °C for 24 h; the mass ratio of elemental iodine to the mercury and bismuth co-modified silica gel is 3:

1.

9. The application of the mercury and bismuth co-modified silica gel for purifying radioactive gaseous iodine as described in claim 7, characterized in that the method for applying the mercury and bismuth co-modified silica gel to statically adsorb radioactive gaseous methyl iodide includes: measuring methyl iodide solution and adding it to the quartz crucible at the bottom of the reactor; weighing the mercury and bismuth co-modified silica gel and placing it in the porous hanging basket on the sand core partition board; covering the upper cover of the reactor and then placing the whole in a forced air drying oven for static adsorption at 100 °C for 24 h, and then weighing the mass of the mercury and bismuth co-modified silica gel, and determining its methyl iodide adsorption capacity through the mass difference before and after; the volume-mass ratio of methyl iodide to the mercury and bismuth co-modified silica gel is 3 mL:1 g; The method for applying the mercury and bismuth co-modified silica gel to the dynamic adsorption of radioactive gaseous methyl iodide includes: using 131 I as a tracer source to prepare CH 3 131 I gas; selecting a 50 mm×25 mm adsorption bed, filling it in 5 layers, setting the gas flow rate of the test system to 24 L / min, and the adsorption temperature to 100 °C. After the inlet and outlet temperatures of the adsorption bed are stable, start injecting CH 3 131 I gas, stop sampling after 1 h, and continue purging for 1 h. Finally, use a low-background γ spectrometer to measure the total activity of each layer of the adsorption bed, and calculate the removal efficiency of methyl iodide after converting it into a counting rate.

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