Method for extracting lead-212 and bismuth-212 in thorium-232 decay chain

Abstract

The present application belongs to a kind of medical radioisotope preparation field, specifically related to a kind of method for extracting lead-212 and bismuth-212 in thorium-232 decay chain, solution containing thorium-232 decay chain material is passed through anion exchange resin column, the solution containing thorium-232 decay chain material includes halogen ion, and the concentration of hydrogen ion in the solution containing thorium-232 decay chain material is greater than 0.01mol / L, lead-212 and bismuth-212 are absorbed by anion exchange resin column, and other nuclides directly pass through anion exchange resin column and are not absorbed, lead-212 and bismuth-212 are desorbed from anion exchange resin column by elution reagent, and lead-212 and bismuth-212 are separated and extracted;The present application can extract lead-212 and bismuth-212 simultaneously, and the extraction speed is fast, the purity is high, and the product is not easy to cause organic pollution.

Description

Technical Field

[0001] The invention belongs to the field of preparation of medical radioisotopes, and in particular relates to a method for extracting lead-212 and bismuth-212 from a thorium-232 decay chain. Background Art

[0002] In recent years, the incidence of cancer has been increasing year by year worldwide, posing a serious threat to human life and health. Medical radioisotopes play a crucial role in cancer diagnosis and treatment, and are crucial for ensuring public health and social stability. 212 Pb / 212 Bi is one of the few radioactive isotopes that can be used in "targeted alpha nuclide therapy (TAT)", which has good efficacy in treating malignant tumors such as ovarian cancer, pancreatic cancer, prostate cancer and breast cancer. However, its resources are very scarce, resulting in 212 The development and clinical application of Pb (lead) targeted drugs are severely restricted.

[0003] 212 Pb / 212 Bi is 232 Th decay daughters, separated and extracted from natural thorium 212 Pb / 212 Bi is expected to fundamentally solve the global 212 Pb / 212 The bottleneck problem of insufficient Bi supply is that it does not require a reactor or accelerator, but only relies on 232 The spontaneous decay of Th can produce sufficient 212 Pb / 212 Bi. 232 Th decay chain such as Figure 1 shown.

[0004] Separation and extraction from natural thorium 212 Pb / 212 Bi can be separated into two methods: direct separation and indirect separation. The so-called direct separation method refers to the selective extraction of Bi from natural thorium using highly selective adsorption materials. 212 Pb and 212 Bi is for medical use; and the indirect separation method refers to first 232 Th separation 228 Ra, and then separated step by step 228 Th, 224 Ra, finally with the help of 224 Ra / 212 Pb generator is obtained 212 Pb / 212 Bi. Currently, indirect separation methods are widely reported and the technology is relatively mature. 224 Ra / 212Pb generator for 212 Pb / 212 Bi (half-life = 10.6 h) is more advantageous for large-scale distribution and transportation. However, this method also has its drawbacks, namely, the separation steps are complex and require multiple waiting times to allow the daughters to grow, as well as multiple purification and testing of the separated products. This not only increases the risk of radiation hazards to personnel (especially when short-lived radioactive gases are involved in the process), but also increases the risk of radiation hazards to personnel (especially when short-lived radioactive gases are involved in the process). 220 Rn protection), but also leads to high production costs and long production cycles.

[0005] In comparison, the direct separation method is simple and efficient, and is very suitable for cities, counties, and even provincial administrative regions. 212 Pb / 212 However, the difficulty and key of this method lies in finding suitable separation materials and technologies to make 212 Pb and 212 Bi selectively from 232 Currently, there are reports that the selective separation of thorium from natural thorium can be achieved by using crown ether extractants based on solid phase adsorption (i.e., using Pb resin). 212 Pb targets, but it cannot be extracted at the same time 212 Bi, resulting in a waste of scarce radionuclide resources. In addition, crown ether extractants are very expensive and have a certain degree of water solubility. Further separation and purification may be required to remove the dissolved crown ether before subsequent drug production. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for extracting lead-212 and bismuth-212 from the thorium-232 decay chain, which can simultaneously extract lead-212 and bismuth-212, has a fast extraction speed, high purity, and is not prone to causing organic contamination of the product.

[0007] An embodiment of the present invention provides a method for extracting lead-212 and bismuth-212 from a thorium-232 decay chain. A solution containing thorium-232 decay chain substances is passed through an anion exchange resin column. The solution containing thorium-232 decay chain substances contains halogen ions, and the concentration of hydrogen ions in the solution containing thorium-232 decay chain substances is greater than 0.01 mol / L (preferably, the concentration of hydrogen ions is 0.5-2 mol / L). Lead-212 and bismuth-212 are adsorbed by the anion exchange resin column, while other nuclides such as 228Ra, 228Ac, and 232Th pass directly through the anion exchange resin column without being adsorbed. A washing reagent is introduced to desorb lead-212 and bismuth-212 from the anion exchange resin column, respectively, to separate and extract lead-212 and bismuth-212.

[0008] The thorium-232 decay chain includes the parent232 Th, including its decay daughters at all levels such as 228 Ra, 228 Ac, 228 Th, 212 Pb, 212 Bi, 208 Tl, etc. Figure 1 shown.

[0009] Preferably, the concentration of halogen ions in the solution containing thorium-232 decay chain substances is 0.3-4 mol / L, more preferably 0.5-2 mol / L.

[0010] Preferably, the thorium-232 decay chain substance is a thorium salt or a thorium oxide, more preferably a soluble salt containing thorium-232.

[0011] Preferably, the thorium salt is hydrated thorium nitrate.

[0012] Preferably, the halogen ion exists in the form of Cl - Br - or I - The acid or salt is preferably hydrochloric acid, hydrobromic acid or hydroiodic acid, and the concentration is preferably 0.3 to 4 mol / L, more preferably 0.3 to 2 mol / L. More preferably, it is hydrobromic acid or hydroiodic acid.

[0013] In a solution containing thorium-232 decay chain substances, the anions, in addition to halogen ions, cannot contain other anions that exceed the halogen ion concentration, otherwise competitive adsorption will occur, resulting in a deterioration in the selective adsorption effect of lead and bismuth.

[0014] When hydrochloric acid is used, the concentration of the hydrochloric acid is preferably 0.5 to 3 mol / L, more preferably 1 to 2 mol / L.

[0015] When hydrobromic acid is used, the concentration of the hydrobromic acid is preferably 0.3 to 2 mol / L, more preferably 0.3 to 1 mol / L.

[0016] When hydroiodic acid is used, the concentration of hydroiodic acid is preferably 0.5 to 3 mol / L, more preferably 0.5 to 1 mol / L.

[0017] Preferably, the anion exchange resin is a silica-based anion exchange resin.

[0018] Preferably, the preparation method of the silicon-based anion exchange resin is to carry out an in-situ solution copolymerization reaction between 4-vinylpyridine and divinylbenzene in the presence of an initiator and a diluent in porous SiO2 channels to obtain silicon-based polyvinylpyridine, and then carry out a methylation reaction between silicon-based polyvinylpyridine and dimethyl sulfate to obtain the silicon-based anion exchange resin.

[0019] The initiator is a mixture of azobisisobutyronitrile and 1,1'-azobis(cyclohexanecarbonitrile), the diluent is acetophenone and diethyl phthalate, and the volume ratio of 4-vinylpyridine to divinylbenzene is 15-20:5-7.

[0020] The solvent for the methylation reaction is methanol-water solution, and the mass ratio of methanol to water is 1:1.

[0021] Preferably, the effective particle size of the silica-based anion exchange resin is 37-150 μm, and the BET specific surface area is 50-80 m 2 / g, and the average pore size is 10~50 nm.

[0022] Preferably, when separating lead-212, the elution reagent is an aqueous solution with a salt concentration or acid concentration less than 0.5 mol / L, more preferably ultrapure water; when separating bismuth-212, the elution reagent is a nitric acid solution with a concentration greater than 0.5 mol / L, more preferably 1~2 mol / L HNO3.

[0023] Preferably, before the elution reagent is introduced, a solution containing halogen ions (preferably hydrochloric acid, hydrobromic acid or hydroiodic acid, preferably with a concentration of 0.5-1 mol / L) is introduced to elute out ions other than lead-212 and bismuth-212.

[0024] The beneficial effect of the present invention is that the present invention provides a method for obtaining a 232 Direct, rapid, and simultaneous selective separation of Th 212 Pb and 212 Bi's technical method. The present invention preferably uses a silicon-based anion exchange resin. Compared with conventional all-organic commercial resins, it has the advantages of fast adsorption / desorption speed, low column pressure, and good hydraulic performance. It is particularly suitable for the efficient separation and extraction of radioactive isotopes with short half-lives, such as 212 Pb (half-life 10.64 h) and 212 Bi (half-life of about 1 h). Experiments have shown that it has a 212 Pb and 212 Bi has a high degree of adsorption selectivity and basically does not adsorb 232 Other nuclides in the Th decay chain. Therefore, the separation method using this silica-based anion exchange resin can effectively solve the traditional separation and extraction problems of crown ether materials. 212 The Pb method has many drawbacks. 232 Selective separation and extraction of Th decay chains 212 Pb and 212 Bi, can also be applied to 228 Ra decay chain, 228 Th decay chain and224 Selective separation and extraction of Ra decay chains 212 Pb and 212 Bi can also be used in all other occasions involving the selective extraction of lead and bismuth from complex systems such as thorium, radium, actinium, lanthanum, barium, lead and bismuth.

[0025] The present invention provides a 232 Direct and rapid selective separation of Th from solution 212 Pb and 212 Bi's new method effectively avoids the use of expensive and water-soluble crown ether extractants. The obtained results were confirmed by γ spectrometry. 212 The Pb sample has very high purity and is basically free of impurity nuclides such as Th, Ac and Ra.

[0026] The material used in the present invention is a silicon-based anion exchange resin, which has the advantages of low price, fast adsorption / desorption kinetics, low column pressure, good hydraulic performance, stable chemical properties and not easy to dissolve, and can also achieve 232 Th decay chain 212 Pb and 212 The separation and extraction of Bi ensures the maximum utilization of scarce nuclide resources.

[0027] The present invention uses an acidic solution containing halogen ions, which can make the anion exchange resin absorb the halogen ions simultaneously and quickly. 212 Pb and 212 Bi, but it has little adsorption on other metal elements. 212 Pb and 212 The elution of Bi is achieved 212 Pb and 212 Separation of Bi, the separated product has high purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 for 232 Th and 232 The decay chain of U.

[0029] Figure 2 Comparison of the adsorption kinetics of SiPyR-N4 resin with commercial anion exchange resins IRA900 and PA316 resin.

[0030] Figure 3 The TOC content in SiPyR-N4 suspension changes with time.

[0031] Figure 4 This is the static adsorption behavior of SiPyR-N4 resin for different metal ions in hydrochloric acid medium.

[0032] Figure 5 The static adsorption behavior of SiPyR-N4 resin for different metal ions in hydrobromic acid medium.

[0033] Figure 6 The static adsorption behavior of SiPyR-N4 resin for different metal ions in hydroiodic acid medium.

[0034] Figure 7 The static adsorption behavior of SiPyR-N4 resin for different metal ions in nitric acid medium.

[0035] Figure 8 The static adsorption behavior of commercial IRA900 resin for different metal ions in hydrochloric acid medium.

[0036] Figure 9 This is the static adsorption behavior of commercial PA316 resin for different metal ions in hydrochloric acid medium.

[0037] Figure 10 The figure shows the comparison of the elution effects of different eluents on lead.

[0038] Figure 11 The figure shows the comparison of elution effects of different eluents on bismuth.

[0039] Figure 12 For the separation of Pb, Bi from Th, La and Ba;

[0040] Wherein, I: dead volume; II: mixed metal solution; III: 1.0 M HCl solution; IV: ultrapure water; V: 1.0 M HNO3.

[0041] Figure 13 Solid 232 Th(a) and the separated 212 Pb(b) and 212 Comparison of γ-ray spectra of Bi (c) samples, where (a) is solid 232 γ spectrum of Th, (b) is the separated 212 γ spectrum of Pb solution, (c) is the separated 212 Gamma spectrum of Bi solution. DETAILED DESCRIPTION

[0042] Example 1

[0043] Anion exchange resin is a silica-based anion exchange resin, and its preparation is divided into two steps.

[0044] Step 1: Synthesis of silicon-based polytetravinylpyridine (SiPyR-N3)

[0045] First, add 100 g of porous SiO2 particles to a rotary evaporator flask. Maintain low rotation. Replace the oxygen in the rotary evaporator twice with nitrogen, then evacuate to 20 hPa. Simultaneously, mix 45 mL of ACP (acetophenone), 30 mL of DEP (diethyl phthalate), 17.69 mL of 4-vinylpyridine, 6.41 mL of DVB (divinylbenzene), 0.3215 g of AIBN (azobisisobutyronitrile), and 0.2144 g of V-40 (1,1'-azobis(cyclohexanecarbonitrile)) in that order. Once the initiators AIBN and V-40 are completely dissolved, use a pressure differential to introduce the mixed oil phase into the rotary evaporator flask. Adjust the rotation speed and gently tap the flask to thoroughly mix the oil phase with the SiO2 until no clumping is evident. This indicates that the oil phase has completely entered the SiO2. Nitrogen was then added to restore the pressure to atmospheric pressure, and the polymerization reaction was initiated by increasing the temperature. Heating was performed in an oil bath at 60°C for 1 hour, 70°C for 2 hours, 80°C for 2 hours, and 90°C for 13 hours. After the reaction, the product was washed twice with acetone and then ultrapure water. The product, named SiPyR-N3, was dried in a vacuum drying oven at 40°C for 48 hours before use.

[0046] Step 2: Preparation of silicon-based anion exchange resin SiPyR-N4 using SiPyR-N3 as a precursor

[0047] An appropriate amount of SiPyR-N3 resin and 500 g of methanol / water (1:1 mass ratio) were added sequentially to a dry 250 mL three-necked flask equipped with a stirring paddle and a dropping funnel. The reaction temperature was maintained at approximately 25°C using a water bath. Subsequently, dimethyl sulfate (3 times the molar amount of vinyl pyridine present in the SiPyR-N3 resin) was slowly added to the flask using a dropping funnel. Stirring was continued at low speed, and the pH of the solution was controlled at neutral using 10 M sodium hydroxide solution. Once the pH of the solution stabilized and remained stable, additional dimethyl sulfate (2 times the molar amount of vinyl pyridine present in the SiPyR-N3 resin) was added. The pH was continuously controlled to maintain neutral conditions. After the reaction, the product, designated SiPyR-N4, was rinsed alternately with acetone and ultrapure water twice each. Subsequently, SiPyR-N4 was washed with 5 M NaCl solution and ultrapure water to convert it to the chloroform. Finally, the transformed SiPyR-N4 was placed in a vacuum drying oven and dried at 40°C for 48 hours before use.

[0048] The quaternized strongly basic silica anion exchange resin SiPyR-N4 has a functional group of 1-methylpyridine, an effective particle size of 37-150 μm, an organic component of approximately 25.5%, and a BET specific surface area of ​​approximately 52.2 m 2 / g, and the average pore size is 36.8 nm.

[0049] Example 2

[0050] The adsorption rate comparison experiment of different resins is as follows:

[0051] (1) Dissolve a certain amount of bismuth nitrate in 1.0 M HCl to prepare a mixed working solution containing 1.0 M HCl and 500 mg / L Bi.

[0052] (2) Take several clean 40 mL glass vials and add 0.05 g of the resin from Example 1 to each. Pipette 20 mL of the mixed working solution into each of the vials. Seal the vials with lids and place them in a 25°C water bath shaker, shaking at 120 rpm.

[0053] (3) Set different mixing contact times, and immediately separate the solid and liquid using a microporous filter membrane after the sample reaches the time node.

[0054] (4) The solutions before and after adsorption were diluted with dilute nitric acid to an appropriate concentration, and the Bi concentration in the solution was measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The adsorption efficiency of the resin was determined based on the difference in concentration before and after adsorption, and an adsorption kinetic curve was plotted showing the change in adsorption efficiency over time.

[0055] (5) The adsorption kinetics of commercial strong alkaline anion exchange resins IRA900 and PA316 were evaluated using the methods of steps (1) to (4) above, and the adsorption rates were compared.

[0056] IRA900 resin is a commercial strong alkaline anion exchange resin produced by The Dow Chemical Company in the United States. Its skeleton structure is styrene-divinylbenzene copolymer and its functional group is trimethyl quaternary ammonium salt.

[0057] PA316 resin is a commercial strong alkaline anion exchange resin produced by Mitsubishi Resins Co., Ltd. of Japan. Its skeleton structure and functional groups are consistent with those of IRA900 resin.

[0058] The experimental results are as follows Figure 2 As shown, the resin of Example 1 basically reached adsorption equilibrium within 10 minutes, while IRA900 and PA316 resins required more than 120 minutes to reach adsorption equilibrium. The adsorption rate of the resin of Example 1 was significantly faster than that of commercial anion exchange resins.

[0059] Example 3

[0060] The chemical stability experiment of the resin of Example 1 comprises the following steps:

[0061] (1) Take a batch of clean glass bottles, add 0.1 g of the resin of Example 1 into each glass bottle, then transfer 30 mL of 1.0 M HCl solution to mix with the resin and cover the bottle with a lid.

[0062] (2) Place the batch of glass bottles in a constant temperature water bath shaker at 25°C and oscillate at a frequency of 120 rpm.

[0063] (3) Set different mixing contact times, and immediately use a microporous filter membrane to separate the solid and liquid after the sample reaches the time point.

[0064] (4) A total organic carbon (TOC) analyzer was used to analyze the TOC content in the solution, and a curve of TOC change with contact time was drawn.

[0065] The experimental results are as follows Figure 3 As shown, the TOC content in the solution has basically no significant change with time, which proves that the resin in Example 1 has good chemical stability and is insoluble in water.

[0066] Example 4

[0067] The selective adsorption experiment steps are:

[0068] (1) A certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate, and barium nitrate were weighed and dissolved in HCl media of different concentrations to prepare a mixed solution containing 100 mg / L Th, 90 mg / L Pb, 90 mg / L Bi, 60 mg / L La, and 60 mg / L Ba.

[0069] (2) Take some clean 40 mL glass bottles and add 0.05 g of the resin from Example 1 to each bottle. Transfer 20 mL of the mixed solution to the glass bottle. Cover the bottle with a lid and place it in a 25°C water bath shaker for shaking at a frequency of 120 rpm. Here, the stable 207 Pb is used to simulate 232 Th decay chain 212 Pb; stable 209 Bi is used to simulate 232 Th decay chain 212 Bi; La has similar chemical properties to Ac and is used to simulate 232 Th decay chain 228 Ac; Ba and Ra have similar chemical properties and are used to simulate 232 Th decay chain 224 Ra and 228 Ra.

[0070] (3) After oscillation for 2 h, the sample was separated into solid and liquid using a microporous filter membrane.

[0071] (4) The solutions before and after adsorption were diluted with dilute nitric acid to an appropriate concentration, and the concentrations of the metal elements in the solutions were measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The adsorption efficiency of the resin for different metal elements was determined based on the difference in concentrations of the metal elements before and after adsorption.

[0072] (5) The above steps (1-4) were also used to investigate the adsorption behavior of SiPyR-N4 resin in hydrobromic acid and hydroiodic acid media.

[0073] The experimental results are as follows Figure 4 、 Figure 5 and Figure 6 As shown, the resin of Example 1 exhibits unique adsorption selectivity for Pb and Bi in the three acid media, and does not adsorb Th, Ba and La elements.

[0074] from Figure 4-6 It can be seen that during static adsorption, the anion exchange resin mainly adsorbs Bi in a hydrochloric acid medium, and also adsorbs a small amount of Pb, and basically does not adsorb other ions, such as La, Th, and Ba. In a hydrobromic acid medium, the resin mainly adsorbs Bi and Pb, but the adsorption effect is better in low concentrations of hydrobromic acid than in high concentrations of hydrobromic acid. When the concentration exceeds 3 mol / L, the resin's adsorption effect on Bi and Pb will decrease. The resin also mainly adsorbs Bi and Pb in a hydroiodic acid medium, and the resin's adsorption effect is better in low concentrations of hydroiodic acid than in high concentrations of hydroiodic acid. When the concentration exceeds 2 mol / L, the resin's adsorption of Bi and Pb will decrease.

[0075] Comparative Example 1

[0076] Compared with Example 4, the difference is that step (1) is: weighing a certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate and barium nitrate, and dissolving them in HNO3 media with different concentrations. Other steps are the same as Example 4.

[0077] The experimental results are as follows Figure 7 As shown, the silica-based anion exchange resin does not adsorb any metal ions in the HNO medium, which means that the selective separation of lead and bismuth cannot be achieved. It can be seen that Example 4 is more suitable for the selective separation of lead and bismuth in the solution system than Comparative Example 1.

[0078] Example 5

[0079] Comparative experiment on the adsorption behavior of thorium, lead, bismuth, lanthanum and barium by different anion exchange resins in hydrochloric acid medium. The steps are as follows:

[0080] (1) A certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate, and barium nitrate were weighed and dissolved in HCl media of different concentrations to prepare a mixed solution containing 100 mg / L Th, 90 mg / L Pb, 90 mg / L Bi, 60 mg / L La, and 60 mg / L Ba.

[0081] (2) Take some clean 40 mL glass bottles and add 0.05 g of IRA900 resin to each. Pipette 20 mL of the mixed solution into each bottle. Seal the bottle with a lid and place it in a 25°C water bath shaker for oscillation at 120 rpm.

[0082] (3) After oscillation for 2 h, the sample was separated into solid and liquid using a microporous filter membrane.

[0083] (4) The solutions before and after adsorption were diluted with dilute nitric acid to an appropriate concentration, and the concentrations of the metal elements in the solutions were measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The adsorption efficiency of the resin for different metal elements was determined based on the difference in concentrations of the metal elements before and after adsorption.

[0084] (5) The above steps (1-4) were also used to investigate the adsorption behavior of IRA900 resin and PA316 resin in hydrochloric acid medium, and compared with the adsorption behavior of SiPyR-N4 for the above metal elements.

[0085] The experimental results are as follows Figure 8 and Figure 9 As shown in the figure, the anion exchange resins produced by three different companies all have the same adsorption behavior, that is, they can selectively adsorb lead and bismuth under the experimental conditions, so they can all be used for natural 232 Th decay chain 212 Pb and 212 Selective separation of Bi.

[0086] Example 6

[0087] The steps of the lead elution experiment are as follows:

[0088] (1) Take some SiPyR-N4 resin from Example 1 and fill it into a Fill the glass adsorption column until it is full.

[0089] (2) Using a bottom-up flow mode, first introduce ultrapure water to remove bubbles and adjust the flow rate to 1.0 mL / min.

[0090] (3) Pre-treat the resin column by passing 50 mL of 1.0 M HCl.

[0091] (4) Weigh a certain amount of lead nitrate and dissolve it in 1.0 M HCl to prepare a hydrochloric acid solution containing 90 mg / L Pb.

[0092] (5) About 45 mL of the above lead solution was introduced, followed by 50 mL of ultrapure water. The lead concentration in the effluent was measured by ICP-AES.

[0093] (6) Repeat the above steps (1-4), and replace the ultrapure water in step (5) with 0.1 M HCl and 0.01 M HCl, respectively, and compare the elution effect of ultrapure water and dilute acid solution on lead.

[0094] The experimental results are as follows Figure 10 As shown in the figure, compared with 0.1 M HCl and 0.01 M HCl, ultrapure water can elute lead more easily and achieve a higher enrichment factor.

[0095] Example 7

[0096] The elution experiment of bismuth is as follows:

[0097] (1) Take some SiPyR-N4 resin from Example 1 and fill it into a Fill the glass adsorption column until it is full.

[0098] (2) Using a bottom-up flow mode, first introduce ultrapure water to remove bubbles and adjust the flow rate to 1.0 mL / min.

[0099] (3) Pre-treat the resin column by passing 50 mL of 1.0 M HCl.

[0100] (4) Weigh a certain amount of lead nitrate and dissolve it in 1.0 M HCl to prepare a hydrochloric acid solution containing 90 mg / L Bi.

[0101] (5) About 45 mL of the above Bi solution was introduced, followed by 100 mL of 1.0 M HNO3 solution. The Bi concentration in the effluent was measured by ICP-AES.

[0102] (6) Repeat the above steps (1-4), and replace the ultrapure water in step (5) with 3 M HNO3 and 0.1 M HNO3, respectively, and compare the elution effect of bismuth by 1.0 M HNO3 and other nitric acid solutions.

[0103] The experimental results are as follows Figure 11 As shown in the figure, compared with 3.0 M HNO3 and 0.1 M HNO3, 1.0 M HNO3 can elute Bi more easily and achieve a higher enrichment factor. On the contrary, 0.1 M HNO3 can hardly achieve complete elution of Bi.

[0104] Example 8

[0105] The cold simulated separation experiment steps are:

[0106] (1) Take some of the resin from Example 1 and fill it into a Fill the glass adsorption column until it is full.

[0107] (2) Using a bottom-up flow mode, first introduce ultrapure water to remove bubbles and adjust the flow rate to 1.0 mL / min.

[0108] (3) Pre-treat the resin column by passing 50 mL of 1.0 M HCl.

[0109] (4) Weigh a certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate, and barium nitrate and dissolve them in 1.0 M HCl to prepare a mixed solution containing 100 mg / L Th, 90 mg / L Pb, 90 mg / L Bi, 60 mg / L La, and 60 mg / L Ba.

[0110] (5) About 45 mL of the above mixed solution is introduced. At this time, Pb and Bi are simultaneously fixed on the resin column, while other elements such as thorium, lanthanum, and barium pass directly through the resin column.

[0111] (6) Pass 15 mL of 1.0 M HCl solution to elute the thorium, lanthanum, and barium remaining on the resin column.

[0112] (7) Pass 25 mL of ultrapure water to desorb the Pb adsorbed on the resin column.

[0113] (8) Pass 50 mL of 1.0 M HNO3 solution to desorb the Bi fixed on the resin column.

[0114] (9) The effluent was collected using a fraction collector, with the collection time for each centrifuge tube set to 5 min. The concentration of each metal element in each centrifuge tube was measured using ICP-AES.

[0115] The experimental results are as follows Figure 12 As shown, the resin column of Example 1 can selectively immobilize Pb and Bi in the mixed metal solution, but does not substantially adsorb Th, Ba, and La. Pb and Bi are successfully separated from the Th solution and recovered separately.

[0116] Example 9

[0117] The hot separation experiment steps are:

[0118] (1) Take some of the resin from Example 1 and fill it into a Fill the glass adsorption column until it is full.

[0119] (2) Using a bottom-up flow mode, first introduce ultrapure water to remove bubbles and adjust the flow rate to 1.0 mL / min.

[0120] (3) Pre-treat the resin column by passing 50 mL of 1.0 M HCl.

[0121] (4) Weigh 2.0 g of thorium nitrate hydrate and dissolve it in 45 mL of 1.0 M HCl.

[0122] (5) About 45 mL of the above mixed solution is introduced. At this time, Pb and Bi are simultaneously fixed on the resin column, while other elements such as thorium, actinium, and radium pass directly through the resin column.

[0123] (6) Pass 15 mL of 1.0 M HCl solution to elute the thorium, actinium, and radium remaining on the resin column.

[0124] (7) Pass 25 mL of ultrapure water to remove the adsorbed 212 Pb is desorbed.

[0125] (8) Add 50 mL of 1.0 M HNO3 solution to the resin column. 212 Bi is desorbed.

[0126] (9) Take the collected 212 The Pb samples were analyzed by γ spectrum and compared with 232 Th γ spectrum for comparison. At the same time, ICP-AES analysis 212 Th concentration in Pb samples.

[0127] The experimental results are as follows Figure 13 As shown, with solid 232 Compared with the γ energy spectrum peak of Th, the 212 Pb and 212 Bi sample has fewer nuclide γ spectrum peaks. 232 Trace amounts of Th in the decay chain 224 Ra and 228 Ac was completely removed, and 212 Pb and 212 Bi is basically retained and has a high purity. ICP-AES measurement results show that 212 Pb and 212 The concentration of thorium in the Bi sample solution was 0 mg / L, which was below the instrument detection limit, proving that 232 Th and 228 Th is completely removed. Therefore, combined with Example 4, the experiment successfully proved that this method can be used to directly remove232 Selective extraction from Th decay chains 212 Pb and 212 Bi.

[0128] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0129] The one or more embodiments of this application are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this application should be included in the scope of protection of this application.

Claims

1. A method for extracting lead-212 and bismuth-212 from the thorium-232 decay chain, characterized in that: A solution containing thorium-232 decay chain substances is passed through an anion exchange resin column, wherein the solution containing thorium-232 decay chain substances contains halogen ions, and the concentration of hydrogen ions in the solution containing thorium-232 decay chain substances is greater than 0.01 mol / L, lead-212 and bismuth-212 are adsorbed by the anion exchange resin column, while other nuclides directly pass through the anion exchange resin column without being adsorbed, and a washing reagent is introduced to desorb lead-212 and bismuth-212 from the anion exchange resin column, respectively, to separate and extract lead-212 and bismuth-212.

2. The method according to claim 1, wherein: The concentration of halogen ions is 0.3~4 mol / L.

3. The method according to claim 1, wherein: The thorium-232 decay chain material is a thorium salt or a thorium oxide.

4. The method according to claim 3, wherein: The thorium salt is hydrated thorium nitrate.

5. The method according to claim 1, wherein: Halogen ions exist in the form of Cl - Br - or I - acids or salts.

6. The method according to any one of claims 1 to 5, characterized in that: The anion exchange resin is a silica-based anion exchange resin.

7. The method according to claim 6, wherein: The preparation method of the silicon-based anion exchange resin comprises the following steps: 4-vinylpyridine and divinylbenzene undergo an in-situ solution copolymerization reaction in the presence of an initiator and a diluent in porous SiO2 channels to obtain silicon-based polyvinylpyridine; and the silicon-based polyvinylpyridine undergoes a methylation reaction with dimethyl sulfate to obtain the silicon-based anion exchange resin.

8. The method according to claim 6, wherein: The effective particle size of the silica-based anion exchange resin is 37-150 μm, and the BET specific surface area is 50-80 m 2 / g, and the average pore size is 10~50 nm.

9. The method according to any one of claims 1 to 5, wherein: When separating lead-212, the elution reagent is an aqueous solution with a salt concentration or acid concentration less than 0.5 mol / L; when separating bismuth-212, the elution reagent is a nitric acid solution with a concentration greater than 0.5 mol / L.

10. The method according to claim 9, wherein: When separating lead-212, the eluent is ultrapure water; when separating bismuth-212, the eluent is 1.0 M nitric acid.

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