A fixed column preparation method and application for radioactivity detection in seawater

Abstract

The application discloses a fixed column preparation method for seawater radioactive detection and application, and belongs to the technical field of materials for adsorbing radioactive substances. The method for preparing the fixed column for detection is simple in steps, does not need high-temperature treatment, is convenient for production and preparation, and is suitable for the convenient and efficient cesium adsorption fixed column for detecting radionuclides (cesium) in seawater used by a well-type detector of a gamma spectrometer. The fixed column can meet the detection technology of small-volume sampling detection of seawater, prevents the low efficiency of the detection method of marine radioactive pollutants caused by sampling difficulty, and brings great convenience to the monitoring of marine radioactive pollutants.

Description

Technical Field

[0001] This invention belongs to the technical field of materials for the adsorption of radioactive substances, specifically relating to a method for preparing a fixed column for the detection of radionuclides in seawater and its application. Background Technology

[0002] When determining radionuclides (cesium) in seawater using the packed column method, copper ferrocyanide (CuFC) is typically attached to silica gel particles to form an activated adsorption silica gel packed column (HY / T003·8-91) for on-site enrichment of radioactive cesium in seawater. However, this method suffers from drawbacks such as the need for filling the adsorbent material and the need to remove it for measurement after use, as well as low adsorption efficiency (46%). Literature reports the use of granular AMP-PAN resin as an adsorbent for Cs(I) in the determination of radioactive cesium in seawater. AMP-PAN resin granules are used to form a packed column, and a peristaltic pump is used to deliver the sample. After sample processing, the resin is removed and placed in a sample vial for gamma spectroscopy measurement (DOI:10.1007 / S10967-012-2014-5). Particulate adsorbents used in adsorption columns present complex filling and removal operations, with removal potentially posing a risk of radioactive contamination. In contrast, adsorption column methods typically employ copper ferrocyanide (CuFC) columns for on-site enrichment of cesium in seawater on board ships, often using a dual-column configuration where adsorption efficiency is calculated by measuring the activity of both columns (as described in *Practical Guide to Seawater Analysis*, edited by Oliver Wurl). Existing adsorption methods using ferrocyanide (copper, cobalt, nickel, etc.) salts present a trade-off between adsorption efficiency and high flow rates. Due to the colloidal nature of CuFC, the prepared column material exhibits poor pore structure, leading to a significant decrease in adsorption efficiency at high seawater flow rates.

[0003] For example, a Chinese patent discloses a method for preparing a filter element for rapid and efficient adsorption of cesium (publication number CN103357386A). In this technical solution, the ammonium phosphomolybdate adsorption column is formed by melt-blowing and coating the adsorption material on a hollow skeleton material. It has the characteristics of high efficiency and speed and is suitable for large volume water samples. However, this technical solution has problems such as high temperature treatment and complex preparation process. Moreover, it requires various supporting auxiliary devices and is not suitable for use with well-type detectors for small volume low activity environmental samples. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a fixed column for detecting radioactivity in seawater and its application, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a fixed column for radioactivity detection in seawater, comprising the following steps:

[0006] S1. Treatment of matrix materials:

[0007] S1.1, Polypropylene fiber membrane matrix material is selected;

[0008] S1.2. The selected matrix material is treated with ozone oxidation to obtain a polypropylene fiber membrane.

[0009] S2. Forming of the porous skeleton for fixing columns:

[0010] S2.1 Select a fixed column tube of appropriate size and material;

[0011] S2.2. The multilayer polypropylene fiber membrane is placed in layers to maintain a loose pore state, and the multilayer polypropylene fiber membrane is filled into the selected fixed column tube to form a cylindrical porous skeleton, thus obtaining a primary foundation column.

[0012] S3. In-situ generation of adsorbed material on the fixed column skeleton:

[0013] S3.1 Connect the primary foundation column to an external circulation system, wherein the specific steps are as follows: place a glass container with an adjustable speed stirrer on an adjustable temperature heater, insert one end of hose A into the glass container, and connect the other end of hose A to the front section of the primary foundation column through a peristaltic pump, while the rear section of the primary foundation column is connected to one end of another hose B, and the other end of hose B is inserted into the glass container to form a circulation system.

[0014] S3.2. Mix ammonium molybdate, disodium hydrogen phosphate, and ammonium chloride in a certain proportion, dissolve them in a certain amount of deionized water, and place them in a glass container to prepare a mixed solution.

[0015] S3.3 Gradually adjust the pH of the mixed solution with 1-6M hydrochloric acid, decreasing it gradually from high to low, changing the pH of the mixed solution from pH=6 to pH=2, and maintain the cyclic reaction for 1 hour; then, after the turbidity of the mixed solution gradually disappears, continue to adjust the acidity of the mixed solution with hydrochloric acid to pH=1, and maintain it for 30 minutes; ammonium phosphomolybdate microcrystals are generated and fixed on the surface of the polypropylene fiber membrane to form a thin film, and the primary base column gradually turns bright yellow. Stop when the solution becomes clear, and the secondary base column is formed;

[0016] S3.4 The formed secondary foundation column is dried at 60℃-80℃ for 12-24 hours to finally obtain the fixed column.

[0017] In a preferred embodiment, the specific steps of treating the selected matrix material with ozone oxidation in step S1.2 are as follows:

[0018] Use an ozone generator and adjust the ozone generation rate to 5g / h and 100% ozone level. Wrap the polypropylene fiber membrane matrix material in multiple layers around the surface of a general 5-inch filter cartridge, place it in a 5-inch filter housing, and connect it to a circulating water system containing dissolved ozone. The treatment can be completed after circulating for a period of time.

[0019] In a preferred embodiment, in step S1.1, the polypropylene fiber membrane matrix material is selected with a fiber diameter of 5-10 micrometers and a pore size of 5-10 micrometers.

[0020] In a preferred embodiment, in step S2.1, the selected fixed pipe size matches the well-type detector, specifically with an outer diameter of less than 16.0 mm and an inner diameter of 13-14 mm, and the material is either polypropylene or polycarbonate.

[0021] In a preferred embodiment, in step S3, the mixed solution is heated by the adjustable temperature heater and its temperature is controlled within the range of 50°C-90°C.

[0022] In a preferred embodiment, in step S3.2, the weight ratio of ammonium molybdate, disodium hydrogen phosphate, and ammonium chloride dissolved in deionized water is 4:1:6.

[0023] In a preferred embodiment, the ammonium phosphomolybdate loading percentage in the fixed column formed in step S3.4 is 5%-10% by weight, and the thickness of the ammonium phosphomolybdate in the fiber is 5-10 micrometers.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The present invention provides a simple method for preparing a fixed column for detection, which does not require excessive high-temperature treatment and is easy to manufacture. It is a convenient and efficient cesium adsorption fixed column suitable for the detection of radionuclides (cesium) in seawater using gamma spectrometer well-type detectors. It can meet the detection technology requirements for small-volume seawater sampling and detection, and prevent the low efficiency of marine radioactive pollutant detection methods due to sampling difficulties, thus bringing great convenience to the monitoring of marine radioactive pollutants. Attached Figure Description

[0026] Figure 1 A fiber diagram of the structure of the present invention where the fixing column is not generated in situ.

[0027] Figure 2 The fiber diagram shows the in-situ generated post-fixation column of the structure of this invention having a thin film. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments.

[0029] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0030] Example 1

[0031] This invention provides a method for preparing a fixed column for detecting radioactivity in seawater, comprising the following steps:

[0032] S1. Treatment of matrix materials:

[0033] S1.1. Polypropylene fiber membrane matrix material is selected. In this embodiment, the selected polypropylene fiber membrane matrix material has a fiber diameter of 5-10 micrometers and a pore size of 5-10 micrometers.

[0034] S1.2. The selected matrix material is treated with ozone oxidation to obtain a polypropylene fiber membrane.

[0035] The specific steps for treating the selected matrix material using ozone oxidation are as follows:

[0036] S1.2.1 Use an ozone generator and adjust the ozone generation rate of the ozone generator to 5g / h and 100% ozone level.

[0037] S1.2.2. The polypropylene fiber membrane matrix material is wound in multiple layers onto the surface of a general-purpose 5-inch filter cartridge, placed in a 5-inch filter shell, and connected to a circulating water system containing dissolved ozone. The treatment is completed after a period of circulation. In this embodiment, the circulation time is 4 hours. After completion, the polypropylene fiber membrane matrix material is removed, sealed in a plastic bag, and left for 10 minutes to remove natural dripping water. It is then weighed, and the water retention rate is calculated. The highest water retention rate is 398.8%, which is higher than that of traditional chemical oxidation treatment. This is evident from the comparison between neutral and acidic conditions.

[0038] As shown in Table 1 below:

[0039]

[0040] Table 1

[0041] It can be seen that there is no significant difference within 2 hours, but the improvement effect of acidic conditions is better than that of neutral conditions after 4 hours; the filter cartridge with ozone treatment has the highest water retention rate under acidic conditions (pH=3, 4h), indicating that ozone oxidation plays a good role.

[0042] S2. Forming of the porous skeleton for fixing columns:

[0043] S2.1 Select a fixing column tube of suitable size and material. In this embodiment, the fixing column tube is selected with an outer diameter of 16.0 mm and an inner diameter of 13 mm, and the material is polypropylene.

[0044] S2.2. The 4-12 layers of polypropylene fiber membrane (12 layers in this embodiment) are placed in layers to maintain a loose pore state, and the multiple layers of polypropylene fiber membrane are filled into the selected fixed column tube to form a cylindrical porous skeleton, thus obtaining the primary base column. The filling height of the polypropylene fiber membrane matches the depth of the well detector and does not exceed the effective measurement height of the well detector. In this embodiment, the filling height is 25mm, which ensures both effective channels and provides a sufficiently large exchange surface.

[0045] S3. In-situ generation of adsorbed material on the fixed column skeleton:

[0046] S3.1 Connect the primary foundation column to an external circulation system, wherein the specific steps are as follows: place a glass container with an adjustable speed stirrer on an adjustable temperature heater, insert one end of hose A into the glass container, and connect the other end of hose A to the front section of the primary foundation column through a peristaltic pump, while the rear section of the primary foundation column is connected to one end of another hose B, and the other end of hose B is inserted into the glass container to form a circulation system.

[0047] S3.2. Mix ammonium molybdate, disodium hydrogen phosphate, and ammonium chloride in a ratio of 4:1:6 and dissolve them in a certain amount of deionized water (ammonium molybdate weight percentage 2%), and place the mixture in a glass container to obtain a mixed solution.

[0048] S3.3 Gradually adjust the pH of the mixed solution with 1-6M hydrochloric acid, gradually decreasing it from high to low, so that the mixed solution changes from pH=6 to pH=2, and maintain the cyclic reaction for 1 hour; then, after the turbidity of the mixed solution gradually disappears, continue to adjust the acidity of the mixed solution with hydrochloric acid to pH=1, and maintain it for 30 minutes; ammonium phosphomolybdate microcrystals are generated and fixed on the fiber surface of the polypropylene fiber membrane to form a thin film, and the primary base column gradually turns bright yellow. Stop when the solution becomes clear, and the secondary base column is formed.

[0049] S3.4 The formed secondary foundation column is dried at 60℃-80℃ for 12-24 hours to finally obtain the fixed column. In this example, the fiber diagram of the fixed column without in-situ formation and the fiber diagram of the fixed column with a thin film after in-situ formation are respectively... Figure 1 and Figure 2 As shown.

[0050] Example 2

[0051] This embodiment uses the fixed column and well-type detector prepared in Example 1 to test the adsorption efficiency. The specific steps are as follows:

[0052] 99.7 Bq of cesium-137 standard was added to 3 liters of cesium-removed seawater and flowed through the adsorption stationary column prepared in Example 1 at a flow rate of 0.24 ml / s to obtain a cesium-loaded stationary column. Measurements were taken using a high-purity germanium gamma spectrometer (Canberra Company, GCW6023, well-type detector). The filtrate was collected and treated using a conventional precipitation method (HY / T235-2018) to obtain a precipitate. This precipitate was placed in a measuring tube and measured using the same high-purity germanium gamma spectrometer. No effective net count of cesium-137 was found in the filtrate. Under the experimental conditions, the added cesium standard was almost completely adsorbed by the stationary column, and the cesium-137 activity concentration in the filtrate was very low and undetectable. The adsorption efficiency of the stationary column was above 99%.

[0053] Example 3

[0054] This embodiment uses the fixed column and well-type detector obtained in Embodiment 1 to conduct a seawater pollution detection experiment. The specific steps are as follows:

[0055] Using the adsorption stationary column prepared in Example 1, cesium-137 was extracted from nearshore and ocean seawater samples of different volumes (1.5L-21.7L) at different flow rates (dropping - 3.0ml / s), and measured using a high-purity germanium gamma spectrometer (Canberra Company, GCW6023, well-type detector).

[0056] At high flow rates (greater than 1.9 ml / s) (samples 6 and 7), there was no adsorption effect. At low flow rates, adsorption was good, resulting in high activity concentrations. Smaller volumes were more effective; however, seawater volumes that were too small (samples 14 and 15) resulted in too few counts and large errors. Larger volumes (sample 3) led to longer extraction times, significantly lower activity concentrations, and leakage of cesium ions. The sample volume should be controlled between 2-10 L, ideally 3-5 L. (See below.)

[0057] As shown in Table 2:

[0058]

[0059]

[0060] Table 2

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a fixed column for detecting radioactivity in seawater, characterized in that, Includes the following steps: S1. Treatment of matrix materials: S1.1, Polypropylene fiber membrane matrix material is selected; S1.

2. The selected matrix material is treated with ozone oxidation to obtain a polypropylene fiber membrane. S2. Forming of the porous skeleton for fixing columns: S2.1 Select a fixed column tube of appropriate size and material; S2.

2. The multilayer polypropylene fiber membrane is placed in layers to maintain a loose pore state, and the multilayer polypropylene fiber membrane is filled into the selected fixed column tube to form a cylindrical porous skeleton, thus obtaining a primary foundation column. S3. In-situ generation of adsorbed material on the fixed column skeleton: S3.1 Connect the primary foundation column to an external circulation system, wherein the specific steps are as follows: place a glass container with an adjustable speed stirrer on an adjustable temperature heater, set a hose A, and insert one end of the hose A into the glass container. The other end of the hose A is connected to the front section of the primary foundation column through a peristaltic pump, while the rear section of the primary foundation column is connected to one end of another hose B. The other end of the hose B is inserted into the glass container to form a circulation system. S3.

2. Mix ammonium molybdate, disodium hydrogen phosphate, and ammonium chloride in a certain proportion, dissolve them in a certain amount of deionized water, and place them in a glass container to prepare a mixed solution. S3.3 Gradually adjust the pH of the mixed solution with 1-6M hydrochloric acid, decreasing it gradually from high to low, changing the pH of the mixed solution from pH=6 to pH=2, and maintain the cyclic reaction for 1 hour; then, after the turbidity of the mixed solution gradually disappears, continue to adjust the acidity of the mixed solution with hydrochloric acid to pH=1, and maintain it for 30 minutes; ammonium phosphomolybdate microcrystals are generated and fixed on the fiber surface of the polypropylene fiber membrane to form a thin film, and the primary base column gradually turns bright yellow. Stop when the solution becomes clear, and the secondary base column is formed; S3.4 The formed secondary foundation column is dried at 60℃-80℃ for 12-24 hours to finally obtain the fixed column.

2. The method for preparing a fixed column for detecting radioactivity in seawater according to claim 1, characterized in that: In step S1.2, the specific steps for treating the selected matrix material using ozone oxidation are as follows: Use an ozone generator and adjust the ozone generation rate to 5g / h and 100% ozone level. Wrap the polypropylene fiber membrane matrix material in multiple layers around the surface of a general 5-inch filter cartridge, place it in a 5-inch filter housing, and connect it to a circulating water system containing dissolved ozone. The treatment can be completed after circulating for a period of time.

3. The method for preparing a fixed column for detecting radioactivity in seawater according to claim 1, characterized in that: In step S1.1, the polypropylene fiber membrane matrix material selected has a fiber diameter of 5-10 micrometers and a pore size of 5-10 micrometers.

4. The method for preparing a fixed column for detecting radioactivity in seawater according to claim 1, characterized in that: In step S2.1, the selected fixed pipe size matches the well-type detector. Specifically, the outer diameter is less than 16.0 mm, the inner diameter is 13-14 mm, and the material is either polypropylene or polycarbonate.

5. The method for preparing a fixed column for detecting radioactivity in seawater according to claim 1, characterized in that: In step S3, the mixed solution is heated by the adjustable temperature heater and its temperature is controlled within the range of 50℃-90℃.

6. The method for preparing a fixed column for detecting radioactivity in seawater according to claim 1, characterized in that: In step S3.2, the weight ratio of ammonium molybdate, disodium hydrogen phosphate, and ammonium chloride dissolved in deionized water is 4:1:

6.

7. The method for preparing a fixed column for detecting radioactivity in seawater according to claim 1, characterized in that: In step S3.4, the ammonium phosphomolybdate loading percentage in the fixed column is 5%-10%, and the thickness of the ammonium phosphomolybdate in the fiber is 5-10 micrometers.

8. The application of a fixed column prepared by the method for preparing a fixed column for detecting radioactivity in seawater as described in any one of claims 1-7 in the detection of radioactive cesium nuclides in seawater by a gamma spectrometer well-type detector.

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