A resin for separating and detecting uranium and a preparation method thereof

Abstract

The present invention discloses a resin for separating and detecting uranium and a preparation method thereof. The resin of the present invention is in the form of spherical particles with a particle size ranging from several micrometers to hundreds of micrometers, and its components include a matrix material, a scintillating substance, a wavelength shifter, and a functional group. The matrix material is polymerized from an unsaturated matrix monomer containing active groups. The wavelength shifter is any one of 1,4-bis(5-phenyloxazole)benzene or -bis-(σ-methylstyryl)benzene. The scintillating substance is 2,5-diphenyloxazole or bis(2-methylstyryl)benzene. The functional group is an adsorbent material capable of selectively adsorbing and enriching uranium. The plastic scintillating resin of the present invention has very good physical and chemical stability, the ability to be stored for a long time, is non-toxic and easy to process, has the advantages of a simple and convenient synthesis method and good stability, and is a new material with separation and detection performance. It can not only perform uranium separation and enrichment but also can be used for on-line detection.

Description

Technical Field

[0001] The present invention relates to a resin, in particular to a resin for separating and detecting uranium and a preparation method thereof. Background Art

[0002] Nuclear energy, as a clean energy with high efficiency and high energy density, is an effective means to address climate warming and achieve carbon peak. However, during the entire nuclear fuel cycle (i.e., uranium mining, uranium purification and conversion, nuclear power plant fuel assembly manufacturing and decommissioning, etc.), a large amount of uranium waste liquid is generated, posing a potential threat to the ecological environment. Therefore, the uranium waste liquid needs to be treated before being discharged into the environment. However, during the treatment of a large number of uranium-containing waste liquids, uranium will form aerosols in the air, directly causing harm to the operators. Therefore, in order to ensure the personal safety of relevant staff and ultimately achieve the effective protection of the ecological environment, it is very necessary to establish an online and rapid measurement method for the uranium concentration in the operating environment.

[0003] Currently, the main methods for separating radionuclides include ion exchange method, solvent extraction method, extraction chromatography method, adsorption method, etc. The main analysis methods include alpha spectrometry, inductively coupled plasma emission spectrometry, inductively coupled plasma mass spectrometry, liquid scintillation counting method, etc.

[0004] Due to its advantages such as high selectivity, simple operation, low pollution, and no waste, the ion exchange method is widely used for the separation and enrichment of uranium. For example, during the uranium ore mining process, the uranium solution obtained by the acid leaching method can first use strongly basic anion exchange resin to separate uranium, and then be eluted with a suitable eluent to obtain a high-purity uranium solution. Chen Mumei et al. [Chen Mumei, Li Zheng, He Shuhua, Zhang Lan. Extraction of trace uranium from a large amount of thorium by ion exchange method. Journal of Nuclear Chemistry and Radiochemistry, 2016, 38(03):159-165] dissolved uranium oxide and thorium oxide with concentrated hydrochloric acid, and then used Dowex1×8 anion exchange resin and Dowex50×8 cation exchange resin as ion exchangers. By using different types and concentrations of eluents, trace uranium was successfully separated from grams per liter of Th and other fission product elements by the ion exchange method, with the recovery rate of uranium greater than 98% and the content of other elements less than 0.05 μg / L. However, the commercial resins used in the ion exchange method generally have a small specific surface area, are prone to water absorption and swelling leading to fragmentation, poor mechanical strength, and poor radiation resistance, with many limitations. The solvent extraction method is one of the most widely used methods in industry. The Purex process widely used in nuclear fuel reprocessing currently uses the solvent extraction method, with tributyl phosphate (TBP) as the extractant. Through several extractions and back-extractions, different elements can be successfully extracted from the spent fuel solution. Currently, other extractants such as ionic liquids also have good extraction effects. Wu Kaige et al. [Wu Kaige, Shen Xinghai. Assembly of UO2(CMPO)3(NO3)2 in ionic liquid and mechanism of CMPO extraction of uranium. Journal of Nuclear Chemistry and Radiochemistry, 2021, 43(02): 136-141] studied the mechanism of the extractant octyloctylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) extracting uranyl ions in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimNTf2), providing an important reference for the principle of uranium extraction by ionic liquids in this system. However, most of the organic solvents used in the solvent extraction method have disadvantages such as easy volatility, toxicity, and harmfulness, and the extraction method is limited by the solvent extraction rate and will produce a large amount of toxic organic radioactive waste liquid. The adsorption method refers to the method of transferring the radionuclide to be enriched from one phase to another phase. The adsorption method has advantages such as convenience, high efficiency, and good selectivity. Chen Rui et al. [Chen Rui, Cui Anxi, Zheng Bowen, Xu Wei. Study on the adsorption performance of zirconium divinyltriamine pentamethylene phosphonate for uranium. New Chemical Materials, 2021, 49(03):126-130] used diethylenetriamine pentamethylene phosphonic acid as the phosphorus source and zirconium oxychloride as the zirconium source to synthesize a new type of organic porous hybrid material, and experimentally proved that this new material can efficiently remove uranium(VI) from aqueous solution.

[0005] Among the common analytical methods, the alpha spectrometry method is a method that uses an alpha spectrometer to measure the alpha particles emitted by a sample during the decay process to identify and quantify radionuclides. Xiongxin Dai [Isotopic uranium analysis in urine samples by alpha spectrometry. J Radioanal Nucl Chem., 2011, 289: 595-600] established an analytical method for measuring the uranium form and content in urine samples using an alpha spectrometer. However, the measurement using the alpha spectrometry method has requirements for the form of the sample source. When using this analytical method for measurement, enrichment and concentration, separation and purification, or spiking treatment are often required, and the operation process is rather troublesome. The inductively coupled plasma optical emission spectrometer is an instrument that is widely used in various analytical fields and can perform qualitative and quantitative analysis on more than seventy elements, including the measurement of uranium in samples. Offer Zeiri et al. [Offer Zeiri, Noa Fruchter, Eyal Elish, Haim Gizbar, Dror Shamir, Itzhak Sedgi. Determination of Uranium Isotopic Ratio by ICP-OES Using Optimal Sensitivity Position Analysis. Anal. Chem. 2021, 93, 12: 5123–5128] analyzed the most sensitive position of uranium isotopes in the sample using an inductively coupled plasma optical emission spectrometer and achieved the determination of 235 U and 238Separate quantitative analysis of U. C. Derrick Quarles et al. [C. Derrick Quarles, Benjamin T. Manard, E. Miller Wylie, Ning Xu. Trace elemental analysis of bulk uranium materials using an inline automated sample preparation technique for ICP-OES. Talanta, 2018, 190: 460-465] successfully analyzed 21 different elements in water samples using U-TEVA resin enrichment and ICP-OES analysis, with a detection limit for uranium of 326 ng / mL. The main difference between inductively coupled plasma mass spectrometry and emission spectrometry is that mass spectrometry is mainly used to analyze a large number of trace elements, with a greatly reduced detection limit, but sample preparation is cumbersome and the operation is relatively complex. Liquid scintillation counting is one of the most commonly used methods in radiochemical analysis. Feng Xiaogui et al. [Feng Xiaogui, He Qiange, Chen Zhonggong, Wang Zhaoyang, Guo Jianfeng. Absolute measurement of uranium content in uranium solution by liquid scintillation α spectrometry. Atomic Energy Science and Technology, 2010, 44(S1): 63-68] used a liquid scintillation spectrometer with α / β discrimination function to directly resolve the activities of three isotopes in natural uranium from the α spectrum, and the relative error was only 3.5%, realizing the absolute measurement of α nuclides by the liquid scintillation counter. However, traditional liquid scintillation measurement produces radioactive organic waste, which is extremely difficult to dispose of.

[0006] Traditional separation and analysis methods are independent of each other, which greatly prolongs the time for enrichment separation and sample preparation analysis. At the same time, the radiation exposure of operators will also increase. To shorten the operation time, it is very necessary to establish a new type of integrated separation and analysis method. Flow injection separation is one of the mainstream automated separation techniques. This method is simple to operate, easy for continuous automatic analysis, and has a fast analysis speed and high precision. Wang Chang et al. [Wang Chang, Xie Wenbing, Liu Jie, Liu Jiantong. Determination of bioavailable Cr(VI) and Cr(III) in sediment by flow injection separation-atomic absorption spectrometry. Chinese Journal of Analytical Chemistry, 2007, (03):451-454] used the combination of flow injection separation technology and atomic absorption spectrometry to achieve the simultaneous on-line separation and measurement of Cr(VI) and Cr(III) in sediment. The detection limits and maximum relative standard deviations of Cr(VI) and Cr(III) were 0.9 μg / L, 6.4% and 2.7 μg / L, 3.5% respectively. For the automated separation and analysis of radionuclides, an injection pump and a chromatographic column can also be used to separate plutonium, uranium, or neptunium [1. J. Qiao, X. Hou, P. Roos, M. Miro. (2011). High-throughput sequential injection method for simultaneous determination of plutonium and neptunium in environmental solids using macroporous anion-exchange chromatography, followed by inductively coupled plasma mass spectrometric detection. Analytical Chemistry, 2011, 83(1):374-81; 2. J. X. Qiao, X. L. Hou, P. Roos, J. Lacher, M. Christl, Y. H. Xu. Sequential injection approach for simultaneous determination of ultratrace Plutonium and Neptunium in urine with Accelerator Mass Spectrometry. Analytical Chemistry, 2013a, 85(18):8826-8833], and then combined with ICP-MS to achieve the full-automatic on-line separation and analysis of radionuclides.

[0007] At present, although there have been some explorations on automated and integrated separation and analysis equipment, there is a lack of integrated analysis systems for radionuclides. Since traditional liquid scintillation analysis cannot analyze high-salinity samples, cannot perform continuous measurements, and the analysis process will generate organic radioactive waste liquid, which makes the subsequent waste treatment difficult. Therefore, it is very important to study a new material for integrated separation, enrichment and measurement for liquid scintillation counters. Summary of the Invention

[0008] The present invention provides a scintillator resin that can solve the deficiencies of the prior art and replace the scintillation liquid, a scintillator resin that can separate and enrich uranium and can be directly measured in a liquid scintillation counter, a preparation method thereof, and a specific application.

[0009] A resin for separating and detecting uranium according to the present invention, wherein the resin is in the form of spherical particles with a particle size of several micrometers to several hundred micrometers, and its components include a matrix material, a scintillating substance, a wavelength shifter, and a functional group. The matrix material is polymerized from an unsaturated matrix monomer containing an active group. The wavelength shifter is any one of 1,4-bis(5-phenyloxazole)benzene or -bis-(σ-methylstyryl)benzene. The scintillating substance is 2,5-diphenyloxazole or bis(2-methylstyryl)benzene. The functional group is an adsorbent material that can selectively adsorb and enrich uranium.

[0010] Preferably, the matrix monomer in the resin of the present invention is styrene or / and divinylbenzene, the scintillating substance is 2,5-diphenyloxazole, and the functional group is bis-(2-ethylhexyl) phosphate.

[0011] Preferably, the mass ratio of styrene to divinylbenzene in the matrix monomer is 3:1 to 1:3.

[0012] The preparation method of the resin of the present invention is as follows: add 2,5-diphenyloxazole with a mass ratio of 0.50%-3.00%, 1,4-bis(5-phenyloxazole)benzene with a mass ratio of 0.01%-0.03% or an equal amount of p-bis-(σ-methylstyryl)benzene to a mixed solution of styrene or / and divinylbenzene, and then add azobisisobutyronitrile with a mass ratio of 0.5%-1.5%, dissolve and shake well for standby; prepare a 20 g / L gelatin solution, a 1.7 g / L CaCO3 solution, and a 0.9 g / L sodium dodecylsulfonate solution; take 5 mL-20 mL of the above-prepared mixed solution, add 1200-195 mL of deionized water, stir and heat to 60°C, add 1 mL-20 mL of styrene solution, then slowly raise the temperature to 70°C-80°C, continue the reaction, and after stopping the reaction, wash the product with warm water and dry it to obtain the product.

[0013] In the preparation method of the present invention, resins with different particle sizes, different separation effects can be obtained by controlling factors such as reaction temperature, reaction time, stirring speed, relative proportion of water to organic phase in raw materials, ratio of dispersants such as gelatin / calcium carbonate / sodium dodecyl sulfonate, and adsorbent content.

[0014] The resin of the present invention can be used for separating uranium and also for detecting uranium, especially for realizing on-line uranium detection.

[0015] Due to its advantages of low price and simple processing, the plastic scintillator resin of the present invention has become an excellent material among many different types of scintillators. When a solution containing the radionuclide uranium contacts the scintillation resin, uranium is intercepted into the resin by selectively binding with functional groups, while other nuclides flow out through the resin bed. When the rays emitted by natural uranium enter the plastic scintillator matrix, the first luminescent substance is excited by the electrons it emits to emit light. At the same time, the wavelength shifter enables the final emission wavelength of light to match that of the photomultiplier tube, converting the optical signal into an electrical signal for detection, thus achieving the purpose of integration of enrichment and detection.

[0016] The plastic scintillator resin of the present invention is similar in composition to liquid scintillators. It is a white solid micro-spherical granular material formed by adding a first scintillation substance, a wavelength shifter, and an adsorbent to a plastic monomer and then polymerizing. It has very good physical and chemical stability, the ability to be stored for a long time, is non-toxic and easy to process, and has the advantages of simple and convenient synthesis method and good stability.

[0017] The resin synthesized by the present invention is a new material with separation and detection performance. Connecting the column system with the detection system, after the resin is packed into the column to separate and enrich uranium, it can be detected on-line with the detection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a microscope photo of the plastic scintillator resin prepared by the present invention. The left figure is without adding the extractant P204, and the right figure is the scintillation resin prepared by the present invention.

[0019] Figure 2 It is an electron microscope photo of the plastic scintillator resin prepared by the present invention.

[0020] Figure 3 It is an infrared characterization of the plastic scintillator resin prepared by the present invention.

[0021] Figure 4 It is the fluorescence emission spectrum of the plastic scintillator resin of the present invention.

[0022] Figure 5 is the static adsorption experimental data of the plastic scintillator resin prepared by the present invention.

[0023] Figure 6Liquid scintillation analysis data of the plastic scintillator resin prepared by the present invention. Detailed implementation manners

[0024] The following are several preferred embodiments of the present invention.

[0025] (I) Resin preparation Embodiment

[0026] Take 1 L of deionized water, add 20 g of gelatin, 1.7 g of CaCO3, and 0.9 g of sodium dodecyl sulfonate, stir and dissolve for standby.

[0027] Take 150 mL of styrene solution and 50 mL of divinylbenzene solution, add 1.00% of PPO, 0.02% of POPOP, 2.0% of azobisisobutyronitrile, and a certain amount of P204 solution, dissolve and shake well, and store in the refrigerator for standby.

[0028] Take 20 mL of the aqueous solution, add 140 mL of deionized water, add 20 mL of the styrene and divinylbenzene solution, slowly heat up to 75 °C, and react for 5 h. Pour the product into a 500 mL beaker, wash it several times with warm water, filter, and dry to obtain the product.

[0029] Embodiment 2

[0030] Take 1 L of deionized water, add 20 g of gelatin, 1.7 g of CaCO3, and 0.9 g of sodium dodecyl sulfonate, stir and dissolve for standby.

[0031] Take 50 mL of styrene solution and 50 mL of divinylbenzene solution, add 1.00% of PPO, 0.02% of POPOP, 2.0% of azobisisobutyronitrile, and 14% of P204 solution, dissolve and shake well, and store in the refrigerator for standby.

[0032] Take 20 mL of the aqueous solution, add 140 mL of deionized water, add 20 mL of the styrene and divinylbenzene solution, slowly heat up to 75 °C, and react for 5 h. Pour the product into a 500 mL beaker, wash it several times with warm water, filter, and dry to obtain the product.

[0033] Embodiment 3

[0034] Take 1 L of deionized water, add 20 g of gelatin, 1.7 g of CaCO3, and 0.9 g of sodium dodecyl sulfonate, stir and dissolve for standby.

[0035] Take 50 mL of styrene solution and 50 mL of divinylbenzene solution, add 1.00% of PPO, 0.02% of POPOP, 1.0% of azobisisobutyronitrile, and 10% of P204 solution, dissolve and shake well, and store in the refrigerator for standby.

[0036] Take 20 mL of the aqueous solution, add 140 mL of deionized water, add 20 mL of the styrene and divinylbenzene solution, slowly heat up to 75 °C, and react for 5 h. Pour the product into a 500 mL beaker, wash it several times with warm water, filter, and dry to obtain the product.

[0037] (II) The characterizations of the products obtained in the above examples and the related test results are as follows:

[0038] (1) Characterization of the scintillator resin

[0039] Figure 1 The microscopic photos of the scintillator microspheres (left) and the scintillator resin (right). As can be seen from the figure, the surface of the scintillator microspheres without the adsorbent P204 is smooth, and obvious concavities and convexities can be seen on the surface of the scintillator resin synthesized according to the synthesis method established in the present invention, indicating the successful grafting of the adsorbent. At the same time, it can be found from the microscope that the synthesized scintillator resin still has good transparency and can transmit different rays to support scintillation measurement.

[0040] (2) Electron microscopic characterization of the scintillator resin

[0041] Figure 2 In a and b are the scintillator microspheres without P204, and c and d are the graft-modified scintillator resins. It can be seen that obvious wrinkles and voids appear on the resin surface after adding the extractant P204, which is beneficial to the enrichment of uranium.

[0042] (3) Infrared characterization of the scintillator resin

[0043] From Figure 3 it can be known that taking the material synthesized without the extractant as the control group, it can be judged that the O-H bond peak of the extractant P204 appears at 3200 - 3500 cm-1, and the P=O bond peak appears at 1250 - 1350 cm-1, indicating that the extractant P204 is successfully grafted into the scintillator resin.

[0044] (4) Fluorescence of the scintillator resin

[0045] From Figure 4 it can be known that when the scintillator resin is excited at 300 nm, the fluorescence spectrum of the material can be obtained. From the figure, it can be seen that the spherical material without the scintillator does not have excitation at 400 - 420 nm, but the scintillator synthesized in the present invention has the maximum excitation at 410 nm, which conforms to the best detection range of the photomultiplier tube.

[0046] (III) Static adsorption results of the resin of the present invention

[0047] As can be seen from Figure 5, from the relationship between the adsorption pH and the adsorption capacity in Figure 5(b), it can be obtained that as the pH of the system increases, the adsorption rate continuously increases and stabilizes at 5.0. This is because as the pH increases, the concentration of H + in the solution decreases, and the competition with uranyl ions in the solution weakens. The research results show that the best adsorption effect is achieved when the pH reaches 5.0.

[0048] Figure 5(c) shows that the material reaches the adsorption equilibrium after 36 h of adsorption, but can reach 85% of the maximum equilibrium adsorption capacity at 3 h, which provides a guarantee for rapid separation and measurement. At the same time, the kinetic model of the material conforms to the pseudo-second-order kinetic model (R 2 = 0.999).

[0049] Figure 5(d) shows the relationship between the temperature change and the adsorption rate of the material. It can be seen from the figure that as the temperature increases, the adsorption rate of the material also increases. This indicates that the adsorption reaction is an endothermic reaction, and increasing the temperature is beneficial to the forward progress of the adsorption reaction. Thermodynamic fitting shows that the thermodynamic adsorption model of the scintillation resin conforms to the Freundlich model.

[0050] Figure 5(e) shows the selectivity of the scintillation resin for metal ions with the same concentration. It can be seen from the figure that the scintillation resin has the best selectivity for uranyl ions, has a certain adsorption effect on zinc ions, but has a very poor adsorption effect on the remaining divalent metal ions, laying a foundation for its selective separation and measurement in a mixed metal ion solution.

[0051] (IV) Scintillator resin liquid scintillation measurement results

[0052] As Figure 6 can be seen, liquid scintillation measurements were performed on chromatographic resins enriched with different masses of natural uranium, and the relationship between the uranium mass and the scintillation count was obtained. It can be found that as the uranium mass enriched in the same mass of resin increases, its counting rate increases linearly. Therefore, the concentration of an unknown sample can be obtained from the liquid scintillation count. It is proved that the synthesized scintillation resin of the present invention can achieve the effect of integrating enrichment and detection.

Claims

1. A method for preparing a resin for separating and detecting uranium, characterized in that: In a mixed solution of styrene and / or divinylbenzene, add 2,5-diphenyloxazole with a mass ratio of 0.50% - 3.00%, 1,4-bis(5-phenyloxazole)benzene with a mass ratio of 0.01% - 0.03% or an equal amount of p-bis(σ-methylstyryl)benzene, then add azobisisobutyronitrile with a mass ratio of 0.5% - 1.5%, and bis(2-ethylhexyl) phosphate (P204), dissolve and shake well for standby; prepare a 20 g / L gelatin solution, a 1.7 g / L CaCO3 solution, and a 0.9 g / L sodium dodecyl sulfate solution; take 5 mL - 20 mL of the above-prepared mixed solution, add 1200 - 195 mL of deionized water, stir and heat to 60°C, add 1 mL - 20 mL of styrene solution, then slowly raise the temperature to 70°C - 80°C and continue the reaction. After the reaction stops, wash the product with warm water and dry it to obtain the product.

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