Method for separating and extracting lead-212 and bismuth-212 from monazite processing radium slag solution

Abstract

This invention provides a method for separating and extracting lead-212 and bismuth-212 from monazite-processed radium slag dissolution solution, belonging to the field of medical radioisotope preparation technology. The method uses monazite-processed radium slag dissolution solution containing radium-228 decay chain substances as raw material. First, halide ions are added to the raw material and the acidity is adjusted to obtain an acidic radium slag dissolution solution. Then, the solution is pretreated with an anion exchange resin column to remove impurities. After static decay, a decay solution containing lead-212 and bismuth-212 is generated. Utilizing the halogen content and acidic environment of the solution itself, the solution is selectively adsorbed again by an anion exchange resin column. Subsequently, elution is performed using a desorption reagent, and the medium conditions are readjusted for repeated adsorption and desorption, ultimately yielding a high-purity and high-specific-activity lead-212 and bismuth-212 finished desorption solution. This invention can efficiently extract lead-212 and bismuth-212 with fast extraction speed, high recovery rate and purity, and is less likely to cause organic pollution in the product.

Description

Technical Field

[0001] This invention relates to the field of medical radioisotope preparation technology, and in particular to a method for separating and extracting lead-212 and bismuth-212 from radium slag dissolution solution from monazite processing. Background Technology

[0002] In recent years, the global incidence of cancer has been rising year by year, and cancer has become a serious threat to human life and health. Medical radioactive isotopes have important applications in cancer diagnosis and treatment, and are of great significance for ensuring people's health and social stability. 212 Pb and 212 Bi is one of the few radioisotopes that can be used in targeted alpha therapy (TAT), and it has shown good efficacy in treating malignant tumors such as ovarian cancer, pancreatic cancer, prostate cancer, and breast cancer. However, its resources are extremely scarce, and the preparation of high-purity products is difficult, leading to... 212 The development and clinical application of Pb-targeted drugs are severely limited.

[0003] 212 Pb and 212 Bi is 232 The decay daughters of Th, based on 232 The spontaneous decay of Th can produce target nuclides without the need for a reactor or accelerator, which is a solution to... 212 Pb and 212 Effective means to address Bi supply shortages 232 The decay chain of Th is as follows Figure 2 As shown. Currently, thorium is isolated and extracted from natural thorium. 212 Pb separation is mainly divided into direct separation method and indirect separation method, and 212 Bi cannot be extracted using existing technologies. Indirect separation methods are technically mature and have been extensively researched; this method involves a stepwise separation and purification process from a pure thorium nitrate solution. 212 Pb, based on 228 Th- 224 Ra / 212 Pb generators facilitate the large-scale distribution and transport of nuclides; however, the process is complex, requiring multiple periods of static loading to allow daughter nuclei to grow, and repeated purification and testing. This results in a long production cycle, high preparation costs, and potential risks. 220 The risk of Rn radioactive gas leakage poses a significant challenge to personnel radiation protection. Direct separation is a simple process suitable for centralized regional feed supply, but selecting suitable separation materials is difficult; existing crown ether adsorbents can only separate thorium from pure nitrate solutions. 212 Pb cannot be extracted synchronously. 212 Bi has a low utilization rate of radionuclides, and the material is expensive and water-soluble, which increases the difficulty of drug purification.

[0004] At present 212 Pb extraction raw materials are mostly high-purity thorium compounds. The purification process for high-purity thorium is complex and costly, and market production is limited by industry applications and production qualifications, resulting in small-scale production and tight supply. Monazite, on the other hand, is a mineral rich in rare earth elements and thorium, with a thorium dioxide content of 5%–10%. In the hydrometallurgical process of monazite to produce rare earth elements, radioactive radium nuclides can be removed from the feed solution through co-precipitation, producing solid radium slag as a byproduct. Currently, the monazite smelting industry is large-scale, accumulating a large amount of radium slag, most of which is disposed of as radioactive solid waste. This radium slag contains abundant... 228 Ra decay chain substances, naturally occurring byproducts 212 Pb, 212 Bi and other valuable radionuclides. Therefore, it is necessary to provide a method for the efficient separation and extraction of radium from monazite processing slag. 212 Pb and 212 Bi's method. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for separating and extracting lead-212 and bismuth-212 from radium slag dissolution solution from monazite processing. The method utilizes existing radium slag as raw material and selectively adsorbs lead-212 and bismuth-212 by controlling the halogen acidic medium in conjunction with anion exchange resin, thereby achieving the simultaneous recovery of the two nuclides. The method is simple, has a low risk of radiation exposure, and is suitable for large-scale preparation of lead-212 and bismuth-212 products with high nuclide purity and high specific activity.

[0006] To achieve the above objectives, the present invention provides a method for separating and extracting lead-212 and bismuth-212 from radium slag dissolution solution in monazite processing, comprising the following steps: S1. Using monazite slag solution containing radium-228 decay chain substances as raw material, halide ions are added to the raw material and acidic conditions are adjusted to obtain acidic radium slag solution containing halide ions. S2. The obtained acidic radium slag solution is passed through an anion exchange resin column for pretreatment to remove stable lead isotopes and long-lived radioactive lead and bismuth impurity isotopes in the solution, and a purified effluent is obtained. S3. Allow the purified effluent to decay by standing. Based on the spontaneous decay of the parent nuclides in the solution, lead-212 and bismuth-212 are regenerated to obtain the decayed feed solution. S4. Utilizing the halogen ions contained in the decay solution and the acidic environment, the decay solution is directly passed into an anion exchange resin column, so that lead-212 and bismuth-212 are selectively adsorbed, and impurity ions flow out with the solution through the column, thus completing the fixation of the target nuclide. S5. Pass the desorption reagent into the anion exchange resin column loaded with the target nuclide to elute and desorb the lead-212 and bismuth-212 enriched on the resin column to obtain the primary product desorption solution. S6. The concentration and acidity of halide ions in the primary product desorption solution are readjusted, and the adsorption and desorption in steps S4 to S5 are repeated. After enrichment and concentration, the final product desorption solution of lead-212 and bismuth-212 with high nuclide purity and high specific activity is finally obtained.

[0007] Preferably, in step S1, the monazite processing radium slag dissolving solution is a nitric acid dissolving solution, or a hydrohalic acid dissolving solution obtained by converting barium sulfate radium slag into carbonate; in the prepared acidic radium slag dissolving solution, the halide ion concentration is 0.2~4 mol / L and the hydrogen ion concentration is greater than 0.01 mol / L.

[0008] Preferably, the hydrogen ion concentration is 0.5~2 mol / L.

[0009] Preferably, the halide ion is a chloride ion, a bromide ion, or an iodide ion, and the halide ion is added in the form of an acid solution or a soluble salt solution.

[0010] Preferably, in step S2, the isotopes removed during pretreatment are mainly impurity ions in anionic form, including lead-208, lead-206, lead-210 and bismuth-210.

[0011] Preferably, in step S4, the impurity ions flowing out through the column are all in the form of cations, including barium, thorium, uranium, actinium-228, radium-228, and radium-224.

[0012] Preferably, the anion exchange resin is a composite silicon-based anion exchange resin in which an organic anion exchange resin is supported on porous silica carrier particles, the functional group of the composite silicon-based anion exchange resin is polyvinylpyridine, and the effective particle size of the composite silicon-based anion exchange resin is 37~150μm.

[0013] Preferably, in step S5, the desorption reagent is an aqueous solution of a non-hydrogen halide acid with an acid concentration of less than 2.0 mol / L and free of halide ions, or pure water.

[0014] Preferably, the desorption reagent is a perchloric acid solution with a concentration of 0.001~2 mol / L.

[0015] Preferably, in step S6, the halide ion concentration and acidity of the primary product desorption solution are adjusted in the manner of step S1, so that the halide ion concentration reaches 0.2~4 mol / L and the hydrogen ion concentration is greater than 0.01 mol / L.

[0016] Compared with the prior art, the present invention discloses at least the following technical effects: (1) This invention directly uses radium slag from the monazite hydrometallurgical industry as a raw material, making resource-based reuse of industrial radioactive waste. This improves upon the traditional method of relying on high-purity thorium raw materials and solves the problems of strict control, difficulty in procurement, and high preparation costs associated with high-purity thorium. Before formally extracting lead-212 and bismuth-212, this invention performs a pretreatment operation to remove stable lead and long-lived radioactive isotopes lead-210 and bismuth-210 from the feed solution in advance, avoiding harmful impurities remaining in medical products and reducing the risk of internal irradiation during medical use. Gamma spectroscopy and ICP-AES and ICP-MS results show that the lead-212 and bismuth-212 products prepared by this invention have high purity. Impurities such as uranium, actinium, radium, and rare earth elements originally present in the feed solution are basically removed, and the content of barium and thorium impurities is controlled at the ppm level, which meets the standards for the use of medical radioactive isotopes.

[0017] (2) This invention uses a silicon-based composite anion exchange resin as the separation material. Compared with conventional all-organic resins on the market, this resin has a lower column pressure, better thermodynamic stability, and faster adsorption and desorption rates, making it suitable for the rapid separation and preparation of short-half-life radionuclides. At the same time, this resin is inexpensive, chemically stable, and does not easily dissolve to produce organic impurities during use. It solves the problem that crown ether materials are expensive and cannot extract two nuclides at the same time, and can simultaneously recover lead-212Pb and bismuth-212, making reasonable use of scarce radionuclide resources.

[0018] (3) In this invention, halogen ions are added and an acidic environment is controlled during the separation and extraction process. The coordination properties of halogens are used to form complex anions of lead-212 and bismuth-212. The resin can uniquely adsorb the two target nuclides, while most impurity metal ions such as barium, thorium, and uranium are not adsorbed. This separation method is suitable for radium slag solutions with complex compositions, and has good separation selectivity, effectively distinguishing target nuclides from impurity elements. Furthermore, this invention uses a low-concentration perchloric acid solution as the desorption reagent, which is highly safe and can quickly and simultaneously elute the lead-212 and bismuth-212 enriched on the resin. The elution operation is simple and efficient, effectively improving product purity and preparation efficiency.

[0019] In addition, the process of this invention has a wide range of applications. Besides being used for the extraction of lead and bismuth nuclides from the decay chains of radium-228 and radium-224, it can also be applied to the separation of lead and bismuth elements in complex mixed systems such as thorium, uranium, radium, actinium, lanthanum, barium, lead, and bismuth, showing promising prospects for industrial application. For example, the uranium products obtained from the reprocessing of spent nuclear fuel (spent fuel) from nuclear power reactors contain trace amounts of uranium-232 nuclides with a half-life of 68.9 years, and its alpha decay daughter, thorium-228, is also processed according to... Figure 2The decay chain generates radium-224, lead-212, and bismuth-212. The process of this invention can also be applied to the separation and extraction of lead-212 and bismuth-212 from this raw material. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of a method for separating and extracting lead-212 and bismuth-212 from radium slag solution from monazite processing according to the present invention.

[0022] Figure 2 The decay chain of Th-232 provided for existing technology.

[0023] Figure 3 The calculation results of the time-varying curves of Ra-226 parent body and major daughter body production of activity 1 Curie (Ci) provided by the present invention.

[0024] Figure 4 The calculation results of the time-varying curve of the amount of Pb-212 generated by the decay of Th-228 / Ra-224 provided by the present invention.

[0025] Figure 5 The measured results show the changes in the activity of Pb-212 and Bi-212 generated after Pb removal by pre-adsorption of the radium slag solution provided by the present invention over time.

[0026] Figure 6 A comparison of the desorption effects of different desorbents provided by this invention on Pb-212 adsorbed in anion exchange columns.

[0027] Figure 7 A comparison of the desorption effects of different desorbents provided by this invention on Bi-212 adsorbed in anion exchange columns.

[0028] Figure 8 The experimental results of Pb removal by pre-adsorption of radium slag solution using anion exchange column provided by the present invention are shown below; wherein, I: dead volume; II: radium slag solution from monazite processing; III: 0.5M HBr elution solution; IV: 0.1M HClO4 desorption solution.

[0029] Figure 9 The gamma-ray spectrum of the radium slag solution provided by this invention.

[0030] Figure 10The image shows the gamma spectrum of the Pb-212 / Bi-212 product solution obtained by the present invention.

[0031] Figure 11 The experimental results of separating and extracting Pb-212 and Bi-212 using an anion exchange column after 96 hours of decay of the radium slag solution after pre-adsorption and Pb removal provided by the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, the present invention provides a method for separating and extracting lead-212 and bismuth-212 from radium slag solution from monazite processing, comprising the following steps: S1. Using monazite slag solution containing radium-228 decay chain substances as raw material, halide ions are added to the raw material and acidic conditions are adjusted to obtain acidic radium slag solution containing halide ions. S2. The obtained acidic radium slag solution is passed through an anion exchange resin column for pretreatment to remove stable lead isotopes and long-lived radioactive lead and bismuth impurity isotopes in the solution, and a purified effluent is obtained. S3. Allow the purified effluent to decay by standing. Based on the spontaneous decay of the parent nuclides in the solution, lead-212 and bismuth-212 are regenerated to obtain the decayed feed solution. S4. Utilizing the halogen ions contained in the decay solution and the acidic environment, the decay solution is directly passed into an anion exchange resin column, so that lead-212 and bismuth-212 are selectively adsorbed, and impurity ions flow out with the solution through the column, thus completing the fixation of the target nuclide. S5. Pass the desorption reagent into the anion exchange resin column loaded with the target nuclide to elute and desorb the lead-212 and bismuth-212 enriched on the resin column to obtain the primary product desorption solution. S6. The concentration and acidity of halide ions in the primary product desorption solution are readjusted, and the adsorption and desorption in steps S4 to S5 are repeated. After enrichment and concentration, the final product desorption solution of lead-212 and bismuth-212 with high nuclide purity and high specific activity is finally obtained.

[0035] In this invention, the raw material used is barium sulfate radium slag produced from the industrial monazite smelting process. This radium slag is a radioactive waste generated during the rare earth preparation process of monazite hydrometallurgy through the co-precipitation of barium ions and sulfate ions. It has a large domestic reserve and low storage cost. The radium slag is a barium sulfate radium precipitate produced by adding barium ions and sulfate ions to a hydrochloric acid solution after removing a large amount of thorium (mainly thorium-232) from monazite. Typically, the thorium content is already very low. After dissolving the radium slag sample, the activities of the main radionuclides were measured, as shown in Table 1, and the contents of the main elements are shown in Table 2. Figure 2 As shown, the decay chain of natural thorium-232 includes the parent [genome / substrate]. 228 Ra and its decay products at each stage, such as 228 Ac、 228 Th、 224 Ra、 212 Pb, 212 Bi、 208 Tl and lead-stabilized nuclides ( 208 Pb, 206 Pb) and a small amount of residue 232 Furthermore, monazite concentrate typically contains approximately 0.2–0.4% uranium (mainly uranium). 238 Therefore, the radium slag sample also contains a small amount of residue (U). 238 U and its long-lived daughters 226 Ra (half-life 1600 years). 226 Ra further decays to generate its daughter products, mainly including 214 Pb, 214 Bi、 210 Pb, 210 Bi et al., activity 1 Curie (Ci) 226 The theoretical calculation results of the Ra parent body and major daughter body generation amounts over time are as follows: Figure 3 As shown, the longer-lived daughter products are Pb-210 (22 years) and Bi-210 (5 days). However, the actual detection results showed that the activities of the daughter products Pb-214 and Bi-214 in the radium slag sample were very low. It is speculated that during the radium slag dissolution process, most of the first daughter product of Ra-226, Rn-222 (gas, half-life 3.8 days), escaped and did not remain in the solution.

[0036] Specifically, Tables 1 and 2 are shown below: Table 1. Nuclide Activities in Radium Slag

[0037] Table 2. Concentrations of various elements in the solution (ppm)

[0038] In step S1, two dissolution systems can be used for the radium slag stock solution: one is a nitric acid solution with a nitric acid concentration greater than 0.01 mol / L; the other is a hydrohalic acid solution obtained after the barium sulfate radium slag undergoes carbonate conversion treatment. Any one of three types of halide ions—chloride, bromide, or iodide—is added to the stock solution. The halide ions can be added in the form of corresponding acid solutions or soluble salt solutions. The halide ion concentration in the system is controlled at 0.2–4 mol / L, and the hydrogen ion concentration is greater than 0.01 mol / L, preferably controlled at 0.5–2 mol / L. This acidic halogen medium can promote the formation of complex anions of lead-212 and bismuth-212, providing the basic conditions for the selective adsorption of the resin.

[0039] In step S2, the prepared acidic radium slag solution undergoes pretreatment adsorption. This step is mainly used to remove stable lead isotopes (lead-208, lead-206), long-lived radioactive impurity isotopes (lead-210, bismuth-210), and other anionic impurity ions from the solution. These impurity isotopes are highly toxic when exposed to radiation; if they remain in the finished product, they will seriously affect medical safety. Pretreatment can significantly reduce the impurity content, improving the purity of lead-212 and bismuth-212 products from the source.

[0040] In step S3, the pretreated purified effluent is subjected to a static decay treatment for at least 72 hours. More specifically, the static decay treatment of the purified effluent can be carried out in a closed environment to prevent Rn-220 gas from escaping from the solution. 228 After lead removal via adsorption in the radium slag solution of Ra decay chain substances, the residual solution contains... 228 Ra and 224 Ra decays and generates 212 The time-dependent change curve of Pb can be referenced. Figure 4 As shown (theoretical calculation results), Figure 5 The actual radium slag solution obtained from testing, after one adsorption step to remove lead, contains... 212 Pb and 212 Results of the change in Bi formation over time; combined with the results shown in the figure, it can be seen that the solution can reach decay equilibrium again after standing for 72 hours. 212 The Pb formation rate can reach over 90%, meaning that the radium slag solution can be reused repeatedly to extract high purity. 212 Pb and 212 Bi (half-life approximately 1 hour) product. The feed solution after decay is complete requires no additional treatment and can be directly used for the next stage of adsorption separation, enabling multiple cyclic extraction operations.

[0041] In step S4, a composite silicon-based anion exchange resin is selected as the separation medium. This resin uses porous silica as a carrier and is loaded with polyvinylpyridine functional groups. The effective particle size of the resin is controlled within 37~150μm. Compared with conventional organic resins, this resin column has lower pressure and better thermodynamic stability, making it suitable for the rapid separation of short-half-life radionuclides. The decay feed solution is introduced into the resin column due to its own acidity and halide ion conditions. Impurity nuclides such as barium, thorium, uranium, actinium-228, radium-228, and radium-224 are not adsorbed by the resin and directly penetrate the resin column and are discharged. Lead-212 and bismuth-212 are selectively adsorbed by the resin. After adsorption, the resin column is washed with a hydrohalic acid solution with a concentration of 0.2~4mol / L to remove trace impurities entrained in the resin pores, further reducing the amount of impurities entrained in the product.

[0042] In step S5, a non-hydrohalic acid aqueous solution free of halide ions is selected as the desorption reagent. The acid concentration of the desorption reagent is less than 2.0 mol / L, and pure water can be used directly as a simple desorption reagent. This invention preferably uses a perchloric acid solution to complete the desorption operation, with the perchloric acid concentration controlled at 0.001~2 mol / L. This type of desorption reagent can disrupt the adsorption state of lead and bismuth complex anions, rapidly and simultaneously eluting the lead-212 and bismuth-212 enriched on the resin to obtain the primary product desorption solution.

[0043] In step S6, the primary product desorption solution is readjusted according to the preparation standards of step S1, controlling the halide ion concentration to 0.2~4 mol / L and the hydrogen ion concentration to be greater than 0.01 mol / L, replicating the medium environment of the initial adsorption and separation. The adsorption and desorption processes are repeated to complete the enrichment and concentration of the target nuclide, ultimately obtaining lead-212 and bismuth-212 finished desorption solutions with high nuclide purity and high specific activity. Verification by gamma spectroscopy and ICP-AES and ICP-MS shows that the finished desorption solution prepared by this method is essentially free of uranium, actinium, radium, and rare earth impurities, and the barium and thorium content is reduced to below ppm levels. The product purity meets the requirements for use with medical targeted therapy nuclides.

[0044] Furthermore, the adsorption / desorption of the ion exchange column of the present invention is usually operated under normal temperature and pressure conditions. However, the temperature or pressure can be appropriately increased. Higher temperatures (40-90°C) can accelerate the adsorption / desorption rate, and higher pressures (0.1-2 MPa) can increase the liquid flow rate and accelerate the processing time.

[0045] To further illustrate the technical solution of the present invention in detail, the following embodiments are set up in conjunction with specific experimental data. The silicon-based anion exchange resin used in the present invention is SiPyR-N4, which is described in patent ZL202411261811.7. The resin has stable physicochemical properties and is suitable for the radioactive liquid separation system of the present invention.

[0046] Example 1 This embodiment aims to separate and remove Pb and Bi from radium slag solution and perform pre-adsorption treatment to remove harmful impurities such as lead and bismuth isotopes in advance. The specific experimental steps are as follows: Step 1: Take a quantity of uniformly sized silicon-based anion exchange resin SiPyR-N4 and fill it into a glass adsorption column with dimensions φ×H=10mm×200mm until it is full. Step 2: Adopt the bottom-up flow mode, adjust the flow rate to 10 mL / min, and first pass pure water to remove air bubbles in the glass adsorption column; Step 3: Pretreatment of the glass adsorption column resin by introducing 150 mL of 0.5 M HBr in a top-down flow mode; Step 4: Prepare the radium slag solution into a 0.5M HBr medium, and pass the solution through a glass resin adsorption column at a flow rate of 10mL / min for pre-adsorption treatment, so that the resin adsorbs all the lead and bismuth in the solution. Step 6: Then, elute the resin by passing 1M HClO4 at a flow rate of 10mL / min to desorb the stable Pb and other radionuclides of Pb and Bi adsorbed on the resin.

[0047] Combination Figure 3 As shown in Table 2, after approximately 66 days of decay, the activities of Pb-214 and Bi-214 in the radium slag solution reach their peak. However, the actual measured activities of Pb-214 and Bi-214 in the radium slag solution are very low, as shown in Table 1 above. Due to their long half-lives, Pb-210 and Bi-210 regenerate very slowly, far less than the regeneration rate of Pb-212. Therefore, after a single adsorption removal treatment, interference from long-lived impurity nuclides can be effectively avoided, preventing them from adversely affecting the radioactive purity of repeatedly recovered Pb-212 and Bi-212 products.

[0048] Example 2 This embodiment aims to determine the activity trends of Pb-212 and Bi-212 in radium slag solution after pre-adsorption treatment. To further investigate the regeneration pattern of target nuclides in the solution over time after pre-adsorption and impurity removal, the specific experimental steps are as follows: Step 1: The activities of Pb-212 and Bi-212 in the original radium slag solution were determined using a high-purity germanium gamma-ray spectrometer. Step 2: Take 30 mL of radium slag solution and pass it through a SiPyR-N4 silicon-based anion exchange resin column. Then take 10 mL of the effluent and test the activity of Pb-212 and Bi-212 inside the solution to confirm that the anion exchange resin completely adsorbs lead and bismuth elements in the solution. Step 3: Let the radium slag solution after adsorption and impurity removal stand for 1 to 7 days, and test the activities of Pb-212 and Bi-212 in the solution at regular intervals every day; Step 4: Collect all test data and plot the activity curves of Pb-212 and Bi-212 over time.

[0049] Test results as follows Figure 5 As shown, after pre-adsorption treatment, Pb-212 and Bi-212 in the original solution were completely adsorbed by the resin. After the pre-treated solution was allowed to stand for 24 hours, the parent nuclei Ra-228, Ra-224, and Th-228 in the solution underwent spontaneous decay, regenerating daughter nuclei Pb-212 and Bi-212. When the standing time reached 72 hours, the Pb-212 and Bi-212 generated by decay reached their activity peaks, and the solution reached decay equilibrium again.

[0050] Example 3 This embodiment aims to conduct a comparative desorption experiment on Pb-212 / Bi-212 adsorbed from radium slag solution onto resin. To further investigate the elution effect of different types of desorption reagents on the target nuclide and to screen the optimal desorption system, the specific experimental steps are as follows: Step 1: Take a quantity of uniformly sized SiPyR-N4 silicon-based anion exchange resin and fill it into a glass adsorption column with dimensions φ×H=7.8mm×100mm until it is full. Step 2: Adopt the bottom-up flow mode, adjust the flow rate to 10 mL / min, and first pass pure water to remove air bubbles in the glass adsorption column; Step 3: Pretreatment of the glass adsorption column resin by introducing 150 mL of 0.5 M HBr in a top-down flow mode; Step 4: Prepare the radium slag solution into a 0.5M HBr medium, and pass the solution through a glass resin adsorption column at a flow rate of 10 mL / min. Step 5: Then, 100 mL of 0.5 M HBr is passed through for rinsing to remove impurities trapped on the resin surface; Step 6: Adjust the flow rate to 5 mL / min, introduce 1 M HClO4 for desorption and elution, and measure the activities of Pb-212 and Bi-212 in the desorption solution using a high-purity germanium gamma spectrometer.

[0051] Repeat steps one through six above, replacing the 1M HClO4 in step six with 1M HNO3 and pure water, respectively, and compare the elution and desorption effects of the three different desorption solutions on lead and bismuth nuclides. The experimental results are as follows: Figure 6 and Figure 7As shown, compared with 1M HNO3 and pure water, 1M HClO4 has a higher elution efficiency, which can quickly and completely elute Pb-212 and Bi-212 from the resin, while achieving a higher enrichment factor of the target nuclides, making it the optimal desorption reagent.

[0052] Example 4 This embodiment aims to conduct an experiment to separate and remove Pb / Bi from radium slag solution through pre-adsorption treatment, thereby verifying the selective adsorption capacity of the resin for various elements in the complex radium slag system. The specific experimental steps are as follows: Step 1: Take a quantity of uniformly sized SiPyR-N4 silicon-based anion exchange resin and fill it into a glass adsorption column with dimensions φ×H=7.8mm×100mm until it is full. Step 2: Adopt the bottom-up flow mode, adjust the flow rate to 10 mL / min, and first pass pure water to remove air bubbles in the glass adsorption column; Step 3: Pretreatment of the glass adsorption column resin by introducing 150 mL of 0.5 M HBr in a top-down flow mode; Step 4: Prepare the radium slag solution into a 0.5M HBr medium. The specific element concentrations of this solution are: Th 43.6 mg / L, Ba 34000 mg / L, Pb 31.25 mg / L, U 52 mg / L, Fe 1.51 mg / L, Gd 5.8 mg / L, and Ce 337.5 mg / L. Pass the above solution through a glass resin adsorption column at a flow rate of 10 mL / min. At this time, Pb and Bi are simultaneously adsorbed and fixed on the resin column, while impurity elements such as thorium, uranium, and barium pass directly through the resin column. Step 5: Then, 100 mL of 0.5 M HBr is passed through for rinsing to remove trace amounts of thorium, uranium, barium, and other impurities remaining attached to the resin column. Step 6: Elute with 0.1M HClO4 to desorb and elute Pb / Bi (including stable isotopes Pb-208 and Pb-206, as well as all Pb and Bi radionuclides) in the resin column. Step 7: Collect the effluent using a fraction collector. Set the collection time for each centrifuge tube to 2 minutes. Use ICP-AES to measure the concentration of each metal element in each centrifuge tube.

[0053] Experimental results are as follows Figure 8 As shown, this anion exchange resin column has excellent adsorption selectivity, and can selectively adsorb Pb and Bi elements in radium slag solution, while basically not adsorbing metallic impurity elements such as Th, U, and Ba. It can efficiently complete the pre-adsorption separation and removal of Pb and Bi, and has excellent purification effect.

[0054] Example 5 This embodiment aims to conduct an experiment to separate and extract Pb-212 / Bi-212 from the radium slag solution after 96 hours of decay following pre-adsorption and Pb removal, thereby verifying the extraction effect of the target nuclide after feed-liquid regeneration equilibrium and detecting the purity of the finished nuclide. The specific experimental steps are as follows: Step 1: Take a quantity of uniformly sized SiPyR-N4 silicon-based anion exchange resin and fill it into a glass adsorption column with dimensions φ×H=7.8mm×100mm until it is full. Step 2: Adopt the bottom-up flow mode, adjust the flow rate to 10 mL / min, and first pass pure water to remove air bubbles in the glass adsorption column; Step 3: Pretreatment of the glass adsorption column resin by introducing 150 mL of 0.5 M HBr in a top-down flow mode; Step 4: Pass the radium slag solution after pre-adsorption and impurity removal and static decay for 96 hours through a glass resin adsorption column at a flow rate of 10 mL / min. At this time, Pb-212 and Bi-212 are simultaneously adsorbed and fixed on the resin column. Step 5: Then, 100 mL of 0.5 M HBr is passed through for rinsing to remove residual impurities such as thorium, uranium, and barium adhering to the resin column. Step 6: Elute with 0.1M HClO4 at a flow rate of 5mL / min to desorb and elute Pb-212 and Bi-212 from the resin column. Step 7: Collect the eluent using a fraction collector. Set the collection time for each centrifuge tube to 2 minutes. Use a high-purity germanium gamma spectrometer to determine the activities of Pb-212 and Bi-212 in the eluent.

[0055] Test results are as follows Figure 9 , Figure 10 , Figure 11 As shown, compared with the gamma-ray spectral peaks of the original radium slag solution, the Pb-212 and Bi-212 samples prepared by this invention have fewer gamma-ray nuclide peaks. Trace impurities Ra-224 and Ac-228 in the radium slag decay chain are completely removed, and only Pb-212, Bi-212, and their decay product Tl-208 are detected in the samples. Experimental results indicate that the Pb-212 and Bi-212 solutions prepared by this invention have extremely high purity. Combined with Examples 4 and 5, it can be demonstrated that this invention can efficiently and selectively extract target nuclides from radium slag solution, with a high nuclide enrichment rate, making it suitable for batch preparation of high-purity medical Pb-212 and Bi-212 products.

[0056] Therefore, the above-mentioned method for separating and extracting lead-212 and bismuth-212 from radium slag dissolution solution from monazite processing utilizes existing radium slag as raw material. By controlling the halogen acidic medium in conjunction with anion exchange resin to selectively adsorb lead-212 and bismuth-212, the two nuclides can be recovered simultaneously. Moreover, the method is simple, has low radiation exposure risk, and is suitable for large-scale preparation of lead-212 and bismuth-212 products with high specific activity.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0058] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for separating and extracting lead-212 and bismuth-212 from monazite processing radium slag solution, characterized in that, Includes the following steps: S1. Using monazite slag solution containing radium-228 decay chain substances as raw material, halide ions are added to the raw material and acidic conditions are adjusted to obtain acidic radium slag solution containing halide ions. S2. The obtained acidic radium slag solution is passed through an anion exchange resin column for pretreatment to remove stable lead isotopes and long-lived radioactive lead and bismuth impurity isotopes in the solution, and a purified effluent is obtained. S3. Allow the purified effluent to decay by standing. Based on the spontaneous decay of the parent nuclides in the solution, lead-212 and bismuth-212 are regenerated to obtain the decayed feed solution. S4. Utilizing the halogen ions contained in the decay solution and the acidic environment, the decay solution is directly passed into an anion exchange resin column, so that lead-212 and bismuth-212 are selectively adsorbed, and impurity ions flow out with the solution through the column, thus completing the fixation of the target nuclide. S5. Pass the desorption reagent into the anion exchange resin column loaded with the target nuclide to elute and desorb the lead-212 and bismuth-212 enriched on the resin column to obtain the primary product desorption solution. S6. The concentration and acidity of halide ions in the primary product desorption solution are readjusted, and the adsorption and desorption in steps S4 to S5 are repeated. After enrichment and concentration, the final product desorption solution of lead-212 and bismuth-212 with high nuclide purity and high specific activity is finally obtained.

2. The method according to claim 1, characterized in that, In step S1, the monazite processing radium slag dissolving solution is a nitric acid dissolving solution or a hydrohalic acid dissolving solution obtained by converting barium sulfate radium slag into carbonate; in the prepared acidic radium slag dissolving solution, the halide ion concentration is 0.2~4 mol / L and the hydrogen ion concentration is greater than 0.01 mol / L.

3. The method according to claim 2, characterized in that, The hydrogen ion concentration is 0.5~2 mol / L.

4. The method according to claim 2, characterized in that, The halide ion is a chloride ion, a bromide ion, or an iodide ion, and the halide ion is added in the form of an acid solution or a soluble salt solution.

5. The method according to claim 1, characterized in that, In step S2, the isotopes removed during pretreatment are mainly impurity ions in anionic form, including lead-208, lead-206, lead-210 and bismuth-210.

6. The method according to claim 1, characterized in that, In step S4, the impurity ions flowing out through the column are all in the form of cations, including barium, thorium, uranium, actinium-228, radium-228, and radium-224.

7. The method according to claim 1, characterized in that, The anion exchange resin is a composite silicon-based anion exchange resin in which an organic anion exchange resin is supported on porous silica carrier particles. The functional group of the composite silicon-based anion exchange resin is polyvinylpyridine group, and the effective particle size of the composite silicon-based anion exchange resin is 37~150μm.

8. The method according to claim 1, characterized in that, In step S5, the desorption reagent is an aqueous solution of a non-hydrogen halide acid with an acid concentration of less than 2.0 mol / L and free of halide ions, or pure water.

9. The method according to claim 8, characterized in that, The desorption reagent is a perchloric acid solution with a concentration of 0.001~2 mol / L.

10. The method according to claim 1, characterized in that, In step S6, the halide ion concentration and acidity of the primary product desorption solution are adjusted in the manner of step S1, so that the halide ion concentration reaches 0.2~4 mol / L and the hydrogen ion concentration is greater than 0.01 mol / L.

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