A method for extracting high-quality thorium salts 212 Pb Systems and Methods

Abstract

The present application relates to a kind of from high quality 212 Pb extraction system and method, comprising first resin column, filled with silicon-based anion exchange resin, for selective adsorption 212 Pb from thorium salt feed solution 212 Pb;Second resin column, filled with amine-based phosphoric acid chelating resin, for selective adsorption Th;Third resin column, filled with silicon-based cation exchange resin, for adsorption and enrichment 212 Pb;First conveying device is connected with the inlet of the first resin column, for pumping thorium salt feed solution, eluent and desorbent into the first resin column;Second conveying device is connected with the inlet of the third resin column, for pumping enrichment desorbent into the third resin column, and the enrichment desorbent is hydrochloric acid solution;Valve assembly is arranged between each resin column and outlet, for controlling the communication state of flow path;The present application quickly and efficiently extracts 212 Pb, improves radionuclide purity and specific activity, and reduces impurity content.

Description

Technical Field

[0001] This invention belongs to the field of medical isotope separation and preparation, specifically relating to a method for extracting high-quality thorium salts. 212 Systems and methods for Pb. Background Technology

[0002] 212 Pb is a medical radionuclide with important applications, which can be obtained from natural thorium (Pb is a radioactive nuclide with significant potential applications). 232 It can be directly obtained from the decay chain of Th, and has broad application prospects in biomedical fields such as targeted α-nucleoside therapy.

[0003] However, direct extraction from natural thorium 212 Pb faces two key challenges: First, in natural thorium... 212 The mass content of Pb is extremely low, and it also contains 228 Ac、 228 Th、 228 How to selectively extract trace amounts of various impurity nuclides such as Ra from a large thorium matrix and its decay products? 212 Pb is the primary challenge; secondly, due to 212 Pb has a short half-life, so it must be highly enriched in a short time to avoid significant decay losses during processing. 232 After Th salt dissolves to form a high-concentration thorium solution, in which... 212 The specific activity of Pb is typically only several hundred to several thousand Bq / mL, far from meeting the requirements for drug labeling and clinical research. Therefore, the rapid and efficient extraction of Pb from large quantities of thorium matrix and its decay products is a key challenge. 212 The key technical challenge in this field is to obtain Pb and simultaneously achieve high radionuclide purity, low impurity content, and high specific activity in the resulting product.

[0004] Currently, the international standard for direct extraction from high-concentration thorium salt solutions is... 212 Pb mainly exists in the following ways: 1) Separation method for crown ether materials This method relies on the supramolecular recognition properties of crown ether materials to achieve recognition in thorium nitrate media. 212 Selective separation of Pb. However, such methods have significant drawbacks: crown ether materials are expensive to obtain and have high solubility in water, which can easily lead to problems. 212 Pb products pose a potential organic pollution risk, impacting the safety of subsequent medical applications.

[0005] 2) Combined process of seed state regulation and anion exchange This method utilizes Pb(II) and 232The differences in the chemical forms of other impurity elements (such as Th(IV), Ac(III), and Ra(II)) in the Th decay chain in halogen media make... 212 Pb is selectively adsorbed and separated by anion exchange resin columns. Because a solid-phase resin is used as the separation medium, this method fundamentally avoids the problem of material loss due to water solubility, while simultaneously possessing both high selectivity and high separation efficiency, particularly effective for thorium. 212 The chemical recovery rate of Pb reached 88.3%, the highest reported to date. However, regardless of the process used, the separation of trace amounts from high-concentration thorium salt solutions remains challenging. 212 When processing Pb, the presence of trace amounts of thorium impurities is unavoidable, which poses a significant challenge. 212 The subsequent labeling and use of Pb have a significant impact.

[0006] 3) Dual-column separation and purification system To address the issue of residual trace amounts of thorium impurities, Chinese Patent Publication No. CN 121944786 A discloses a method for separating and purifying thorium from a solution. 212 The method for Pb involves an integrated dual-column system composed of a silicon-based anion exchange resin SiPyR-N4 column and an aminophosphate chelating resin APA column connected in series. The SiPyR-N4 column achieves... 212 Selective separation of Pb is achieved using APA resin columns. 212 Purification of Pb products. This system allows for the direct extraction of radionuclides with high purity and low impurity content from natural thorium solutions. 212 Pb sample, 232 Th and 228 Th can be completely removed. However, what is obtained through this system 212 The specific activity of Pb products is still very low, making it difficult to meet the requirements for drug labeling.

[0007] Besides the aforementioned separation and purification techniques, existing methods for nuclide enrichment mainly include evaporation and chemical methods. Evaporation methods have significant drawbacks when applied to the enrichment of short-lived nuclides: high energy consumption, long processing time, and significant decay loss of the nuclide. Chemical methods (such as ion exchange or extraction) are limited by the properties of the functional materials: traditional ion exchange or extraction materials have slow adsorption / desorption or extraction / back-extraction kinetics and long operation times, also suffering from significant decay loss of short-lived nuclides, and cannot simultaneously achieve high enrichment rates and high chemical recovery rates. Summary of the Invention

[0008] The technical problem to be solved by this invention is to provide a method for extracting high-quality thorium salts. 212 Systems and methods for the rapid and efficient extraction of Pb. 212 Pb improves the purity and specific activity of radionuclides and reduces impurity content.

[0009] This invention provides a method for extracting high-quality thorium salts. 212 Pb's systems include: The first resin column is filled with silicon-based anion exchange resin, used to extract from... 212 Selective adsorption of Pb in thorium salt solution 212 Pb; The second resin column is filled with aminophosphate chelating resin for selective adsorption of Th. The third resin column is filled with silicon-based cation exchange resin for adsorption and enrichment. 212 Pb; A first conveying device is connected to the inlet of the first resin column and is used to pump thorium salt solution, leaching agent and desorbent into the first resin column; The second conveying device is connected to the inlet of the third resin column and is used to pump the enrichment desorbent into the third resin column. The enrichment desorbent is a hydrochloric acid solution. Valve assemblies, located between resin columns and at the outlet, are used to control the flow path connectivity, ensuring that: During the adsorption and leaching stages, the first, second, and third resin columns are not connected. The thorium salt solution and leaching agent pass only through the first resin column. 212 Pb is adsorbed and fixed by the first resin column; During the desorption stage, the first resin column, the second resin column, and the third resin column are connected in series, and the desorbent flows sequentially through the first resin column, the second resin column, and the third resin column, causing... 212 After Pb is desorbed from the first resin column, it passes through the second resin column with the desorbent to remove Th impurities, and is then adsorbed and fixed by the third resin column. During the enrichment stage, the third resin column is not connected to the second resin column, and the enrichment desorbent passes through the third resin column. 212 Pb was eluted and enriched.

[0010] Preferably, the silicon-based anion exchange resin is a silicon-based anion exchange resin with N-methylpyridine as the functional group; The preparation method of the silicon-based anion exchange resin with N-methylpyridine as the functional group is as follows: 4-vinylpyridine and divinylbenzene undergo an in-situ solution copolymerization reaction in the presence of an initiator and a diluent within porous SiO2 channels to obtain silicon-based polyvinylpyridine. The silicon-based polyvinylpyridine then undergoes a methylation reaction with dimethyl sulfate to obtain the silicon-based anion exchange resin. The effective particle size of the silicon-based anion exchange resin is 37~150 μm, and the BET specific surface area is 50~80 m². 2 / g, with an average pore size of 10~50 nm.

[0011] Preferably, the aminophosphate chelating resin is a chelating resin with aminophosphate functional groups; The chelating resin with aminophospho groups as functional groups is a weakly basic anion exchange resin carrying primary amine groups as a carrier, and aminophosphonic acid groups are bonded to the primary amine groups through the Mannich reaction. The preparation method of the chelating resin with the functional group being an aminophosphate group includes the following steps: a weakly basic anion exchange resin carrying a primary amine group, phosphorous acid and concentrated hydrochloric acid are mixed evenly, then formaldehyde is added, the mixture is refluxed, filtered, washed, and dried to obtain the final product.

[0012] Preferably, the silicon-based cation exchange resin is a silicon-based cation exchange resin with sulfonic acid functional groups.

[0013] Preferably, the preparation method of the silicon-based cation exchange resin with sulfonic acid functional groups is as follows: silicon-based polystyrene, sulfonation reaction catalyst (preferably silver sulfate) and solvent (preferably dichloroethane) are mixed, heated (preferably 70-90℃) and concentrated sulfuric acid is added dropwise to carry out the sulfonation reaction. After the reaction is completed, the mixture is washed and dried to obtain the silicon-based cation exchange resin with sulfonic acid functional groups.

[0014] The method for preparing the silicon-based polystyrene involves mixing a mixture containing monomers, an initiator, and a diluent with porous silica under vacuum conditions, followed by polymerization at a controlled temperature under an inert atmosphere. The reaction product is then washed and dried to obtain silicon-based polystyrene. The monomers are divinylbenzene and styrene, the initiator is azobisisobutyronitrile, and the diluent is acetophenone and diethyl phthalate.

[0015] The polymerization is carried out under normal pressure at the following temperatures: 60℃±5℃ for 0.5-2 hours, 70℃±5℃ for 1-3 hours, 80℃±5℃ for 2-4 hours, and 90℃±5℃ for 10-15 hours. Washing is performed using alternating acetone and ultrapure water; drying is carried out at 100℃-110℃.

[0016] Preferably, the thorium salt solution is a hydrobromic acid solution containing thorium nitrate (the concentration of hydrobromic acid is preferably 0.2-1 mol / L), the leaching agent is a hydrobromic acid solution (the concentration of hydrobromic acid is preferably 0.2-1 mol / L), and the desorbent is a nitric acid solution (the concentration of nitric acid is preferably 0.2-1 mol / L).

[0017] Preferably, the valve assembly includes a switching valve disposed before the inlet of the first resin column, a first three-way valve disposed at the outlet of the first resin column, a third three-way valve disposed between the second resin column and the third resin column, and a fourth three-way valve disposed at the outlet of the third resin column.

[0018] This invention provides a method for extracting high-quality thorium salts. 212 Pb's method includes the following steps: 1) The thorium salt solution and eluent are passed through a first resin column filled with silica-based anion exchange resin, so that... 212 Pb is selectively adsorbed and fixed; 2) A desorbent is introduced into the first resin column to desorb the adsorbed resin. 212 Pb and Th impurities are eluted and sequentially passed through a second resin column filled with aminophosphate chelating resin and a third resin column filled with silicon-based cation exchange resin; Th impurities are selectively adsorbed and removed by the second resin column. 212 Pb is adsorbed and fixed by the third resin column; 3) An enrichment and desorption agent, which is a hydrochloric acid solution, is introduced into the third resin column. 212 Pb was eluted and enriched to obtain a product containing high-quality Pb. 212 Pb 212 Pb enrichment solution.

[0019] Preferably, the concentration of the hydrochloric acid solution is 0.5-5 mol / L; more preferably, it is 0.5-3 mol / L.

[0020] The thorium salt solution is a hydrobromic acid solution containing dissolved thorium nitrate, the leaching agent is a hydrobromic acid solution, and the desorbent is a nitric acid solution.

[0021] Preferably, the thorium salt solution is pre-passed through an anion exchange resin column before passing through a first resin column filled with silicon-based anion exchange resin, in order to remove impurities therein. 208 Pb, 210 Pb, 212 Pb and 214 Pb nuclide, the solution after column chromatography is sealed and stored for later use. 212 After Pb is generated, it passes through a first resin column filled with silicon-based anion exchange resin.

[0022] The beneficial effects of this invention are: 1) This invention achieves the integration of separation, purification, and enrichment. This invention is the first to design a three-column system (consisting of a SiPyR-N4 column, an APA resin column, and a silicon-based cation exchange resin A1 column coupled in series), simultaneously completing the selective separation of ²¹²Pb, the deep removal of Th impurities, and the high enrichment of ²¹²Pb in a single process. This overcomes the shortcomings of existing dual-column systems, which can only perform separation and purification, resulting in products with extremely low specific activity that cannot meet the requirements for drug labeling.

[0023] 2) This invention significantly improves the specific activity of ²¹²Pb products. Hot radioactivity experiments show that the ²¹²Pb product obtained using the system and process of this invention has a specific activity of 8.84 μCi / mL, nearly 900 times higher than the untreated sample (0.010 μCi / mL). It can be directly used for subsequent drug labeling and small animal experiments, solving the long-standing key bottleneck of insufficient specific activity in ²¹²Pb products directly extracted from high-concentration thorium salts.

[0024] 3) This invention combines high radionuclide purity with low impurity content. The obtained ²¹²Pb product has a radionuclide purity exceeding 99.9%, and no ²¹²Pb or its daughter bodies were found in the enrichment solution. 8 Th、²² 8 Ac and 22 4 Ra and other impurity nuclides that emit gamma radiation; ICP-OES analysis showed that the contents of U, Th and Mg were all below the instrument detection limit, and Th impurities were completely removed, meeting the high-quality requirements for medical nuclides.

[0025] 4) This invention achieves both high chemical recovery rate and high enrichment factor. The chemical recovery rate of Pb in this invention reaches 88.2%, and the enrichment factor reaches more than 884 times (more than 1000 times in cold state experiments), overcoming the technical limitations of traditional evaporation, extraction or conventional ion exchange methods that cannot achieve both high recovery rate and high enrichment factor.

[0026] 5) This invention minimizes the decay loss of short-lived nuclides. The entire separation-purification-enrichment process can be controlled within 3.3 hours, which is very close to the time required for single-column separation based on SiPyR-N4. Due to the extremely fast adsorption kinetics of A1 resin (adsorption equilibrium is reached within about 10 minutes, which is 3 to 9 times faster than commercial resins) and sharp desorption peak (no tailing, only about 4 mL is needed for complete elution), the operation time is greatly shortened, effectively avoiding the large decay loss of ²¹²Pb during the processing due to its short half-life (10.6 h).

[0027] 6) This invention avoids the risks of organic pollution and material loss. The invention uses solid-phase resin as the separation medium throughout the process, fundamentally overcoming the potential organic pollution problem caused by the high water solubility of crown ether materials, while also preventing water loss of the material.

[0028] 7) The device of this invention is compact, low-cost, and controllable in operation. All materials used in this invention are low-cost resin materials. The device is simple and compact, and automatic switching of flow paths at different process stages can be achieved through valve assemblies, making it easy to scale up and operate continuously.

[0029] 8) This invention provides a promising technical solution for the direct separation and extraction of high-quality²¹²Pb from natural thorium, which is of great significance for ensuring the independent production and long-term stable supply of important medical isotopes in my country. Attached Figure Description

[0030] Figure 1 The present invention provides a method for extracting high-quality thorium salts. 212 A schematic diagram of the structure of the Pb system.

[0031] Figure 2 The adsorption and desorption of Pb, Th, La and Ba in a three-column system (I: dead volume; II: working solution; III: eluent; IV: desorbent 1; V: desorbent 2).

[0032] Figure 3 The solution flowing out of the A1 resin column after the introduction of desorbent 2 212 Pb activity distribution (each sample represents a 5 mL volume, collected sequentially).

[0033] Figure 4 The image shows the gamma spectrum of the third desorption sample (measured after a 1250-fold dilution). Figure 4 (b) is Figure 4 (a) is a magnified view of a portion of the image.

[0034] Figure 5 A comparison of the adsorption rates of Pb by different resins in 0.3 M HNO3 medium.

[0035] Figure 6 A comparison of the desorption effects of different desorbents on Pb on an A1 resin column.

[0036] Figure 7 The dynamic desorption curves of Pb by different resins under 2 M HCl conditions are shown.

[0037] Figure 8 The adsorption and desorption of Pb, Th, La and Ba in a two-column system (I: dead volume; II: working solution; III: eluent; IV: desorbent 1). Detailed Implementation

[0038] Example 1 The preparation method of silicon-based cation exchange resin A1 includes the following steps: 1) Preparation of silicon-based polystyrene First, 100 g of SiO2 particles were placed in a glass flask of a rotary evaporator, and the evaporator was evacuated for approximately 30 minutes. Simultaneously, 7.48 mL of DVB (divinylbenzene, monomer), 20.87 mL of styrene (monomer), 0.354 g of AIBN (azobisisobutyronitrile, initiator), 42.42 mL of acetophenone (diluent), and 28.28 mL of diethyl phthalate (diluent) were uniformly mixed. The mixture was drawn into the glass flask under vacuum and continuously rotated to ensure complete penetration of the organic phase into the pores of the SiO2. Then, nitrogen gas was purged to atmospheric pressure, and the temperature was increased. The reaction was carried out at 60°C for 1 hour, 70°C for 2 hours, 80°C for 3 hours, and 90°C for 13 hours. After the reaction was complete, the product was washed alternately with acetone and ultrapure water (UPW), and then dried in a drying oven at 105°C for later use. The obtained product was silicon-based polystyrene, named SiPS.

[0039] 2) Grafting of sulfonic acid groups 20 g SiPS, 0.2 g Ag₂SO₄, and 60 mL dichloroethane were added to a three-necked glass flask connected to a stirrer, condenser, and dropping funnel. The stirring speed was controlled at 90 rpm. The flask was heated to 80 °C in an oil bath, and 80 mL of concentrated sulfuric acid was added dropwise over 30 minutes, with the reaction continuing for 3 hours. Afterward, the product was first washed with sulfuric acid of different concentrations to prevent breakage of the composite resin, and then washed with ethanol and deionized water. The wet product was vacuum dried at 40 °C for 48 h, finally yielding a pale yellow powder, named Al.

[0040] The preparation method of silicon-based anion exchange resin SiPyR-N4 includes the following steps: Step 1: Synthesis of silicon-based polytetravinylpyridine (SiPyR-N3) First, 100g of porous SiO2 particles were added to the flask of a rotary evaporator. The flask was kept rotating at a low speed. The oxygen in the rotary evaporator was replaced twice with nitrogen, followed by evacuation to 20 hPa. Simultaneously, 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(cyclohexanecarbonyl)) were mixed sequentially. After the initiators AIBN and V-40 were completely dissolved, the mixed oil phase was introduced into the rotary evaporator flask using a pressure difference. The rotation speed was adjusted and the flask walls were gently tapped to ensure thorough mixing of the oil phase with the SiO2 until no obvious clumps formed. At this point, the oil phase was considered to have completely penetrated the SiO2. Nitrogen gas was introduced to restore atmospheric pressure, and then the polymerization reaction was initiated by heating. An oil bath was used for heating, maintaining 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 alternately with acetone and ultrapure water. The product was named SiPyR-N3 and dried in a vacuum drying oven at 40°C for 48 hours before use.

[0041] Step 2: Preparation of silicon-based anion exchange resin SiPyR-N4 using SiPyR-N3 as a precursor. An appropriate amount of SiPyR-N3 resin and 500g of methanol / water (mass ratio 1:1) were added sequentially to a dry 250mL three-necked flask equipped with a stirrer and a dropping funnel. The reaction was heated in a water bath, maintaining the reaction temperature at approximately 25°C. Then, three times the molar amount of dimethyl sulfate (the same as the amount of vinylpyridine in the SiPyR-N3 resin in the flask) was measured and slowly added to the flask using a dropping funnel, controlling the flow rate. The mixture was stirred at low speed, and the pH of the solution was maintained at neutral using a 10M sodium hydroxide solution. Once the pH stabilized and remained unchanged, two more times the molar amount of dimethyl sulfate (the same as the amount of vinylpyridine in the SiPyR-N3 resin in the flask) was added. The pH was maintained at neutral conditions. After the reaction was complete, the product was named SiPyR-N4 and washed twice each with alternating acetone and ultrapure water. Subsequently, it was washed again with 5M NaCl solution and ultrapure water to convert SiPyR-N4 to its chloride form. Finally, the transformed SiPyR-N4 was placed in a vacuum drying oven and dried at 40°C for 48 hours before use.

[0042] The quaternized strong-base silica-based anion exchange resin SiPyR-N4 has a 1-methylpyridine functional group, an effective particle size of 37–150 μm, an organic content of approximately 25.5%, and a BET specific surface area of ​​approximately 52.2 m². 2 / g, with an average pore size of 36.8nm.

[0043] A method for preparing an APA resin includes the following steps: 1) Measure 80 mL of a weakly basic anion exchange resin (code: ZGA452, from Zhejiang Zhengguang Industrial Co., Ltd.) carrying primary amine groups and add it to a three-necked flask.

[0044] 2) Weigh 11.9 g of phosphorous acid (99% by mass), dissolve it in about 106 mL of ultrapure water, then add 23.8 mL of concentrated hydrochloric acid (36.0~38.0% by mass) and stir well. Then add it to a three-necked flask.

[0045] 3) Connect the three-necked flask to the stirrer, condenser, and dropping funnel, and control the stirring speed at 150 rpm. Start heating, and after the temperature rises to 85℃, add 11.4 mL of formaldehyde aqueous solution (mass fraction of 37%) dropwise to the three-necked flask over 1 hour to react with the resin.

[0046] 4) After the addition is complete, the reaction is continuously refluxed for 16 h. The product is filtered through a sintered glass funnel and washed with sufficient ultrapure water until neutral. Finally, the washed product is dried in a vacuum drying oven at 60 °C for 48 h to obtain the dried APA resin.

[0047] Example 2 A method for extracting high-quality thorium salts 212 Pb systems, such as Figure 1 As shown, it includes: The first resin column (i.e.) Figure 1 of 212 A Pb-selective adsorption column, filled with silicon-based anion exchange resin SiPyR-N4, is used to adsorb Pb from Pb-containing... 212 Selective adsorption of Pb in thorium salt solution 212 Pb; The second resin column (i.e.) Figure 1 A Th-selective adsorption column is filled with aminophosphate chelating resin (APA) for selective adsorption of Th. The third resin column (i.e.) Figure 1 of 212 Pb enrichment column), packed with silicon-based cation exchange resin A1, for adsorption and enrichment. 212 Pb; First conveying device (i.e. Figure 1 Pump 1) is connected to the inlet of the first resin column and is used to pump thorium salt solution, eluent and desorbent into the first resin column; Second conveying device (i.e.) Figure 1 Pump 2), connected to the inlet of the third resin column, is used to pump the enriched desorbent (i.e., Figure 12) The desorbent 2) is pumped into the third resin column, wherein the enriching desorbent is a hydrochloric acid solution; Valve assemblies, located between resin columns and at the outlet, are used to control the flow path connectivity, ensuring that: During the adsorption and leaching stages, the first, second, and third resin columns are not connected. The thorium salt solution and leaching agent pass only through the first resin column. 212 Pb is adsorbed and fixed by the first resin column; During the desorption stage, the first resin column, the second resin column, and the third resin column are connected in series, and the desorbent flows sequentially through the first resin column, the second resin column, and the third resin column, causing... 212 After Pb is desorbed from the first resin column, it passes through the second resin column with the desorbent to remove Th impurities, and is then adsorbed and fixed by the third resin column. During the enrichment stage, the third resin column is not connected to the second resin column, and the enrichment desorbent passes through the third resin column. 212 Pb was eluted and enriched.

[0048] The thorium salt solution is a hydrobromic acid solution containing dissolved thorium nitrate (i.e., Figure 1 The content 212 Pb 232 The Th solution), the rinsing agent is hydrobromic acid solution, and the desorbent is nitric acid solution (i.e., Th solution). Figure 1 Desorbent 1).

[0049] The valve assembly includes a switching valve disposed before the inlet of the first resin column (i.e. Figure 1 The system includes an automatic switching valve, a first three-way valve (i.e., three-way valve 1) located at the outlet of the first resin column, a third three-way valve (i.e., three-way valve 3) located between the second and third resin columns, and a fourth three-way valve (i.e., three-way valve 4) located at the outlet of the third resin column.

[0050] A method for extracting high-quality thorium salts 212 Pb's method includes the following steps: 1) The thorium salt solution and eluent are passed through a first resin column filled with silica-based anion exchange resin, so that... 212 Pb is selectively adsorbed and fixed; 2) A desorbent is introduced into the first resin column to desorb the adsorbed resin. 212 Pb and Th impurities are eluted and sequentially passed through a second resin column filled with aminophosphate chelating resin and a third resin column filled with silicon-based cation exchange resin; Th impurities are selectively adsorbed and removed by the second resin column. 212 Pb is adsorbed and fixed by the third resin column; 3) An enrichment and desorption agent, which is a hydrochloric acid solution, is introduced into the third resin column. 212 Pb was eluted and enriched to obtain a product containing high-quality Pb. 212 Pb 212 Pb enrichment solution.

[0051] The concentration of the hydrochloric acid solution is 0.5-5 mol / L; The thorium salt solution is a hydrobromic acid solution containing dissolved thorium nitrate, the leaching agent is a hydrobromic acid solution, and the desorbent is a nitric acid solution.

[0052] The thorium salt solution is pre-passed through an anion exchange resin column before passing through a first resin column filled with silicon-based anion exchange resin, in order to remove impurities in advance. 208 Pb, 210 Pb, 212 Pb and 214 Pb nuclide, the solution after column chromatography is sealed and stored for later use. 212 After Pb is generated, it passes through a first resin column filled with silicon-based anion exchange resin.

[0053] Specifically, it includes the following steps: 1) A certain amount of Th(NO3)4· x H2O was dissolved in 0.5 M HBr medium to prepare a solution for extraction. 212 Pb 232 Th salt solution, i.e., thorium salt solution; simultaneously, appropriate leaching agents and 212 Pb desorbents. In the figure, the eluent is a 0.5 M HBr solution; desorbent 1 is a 0.3 M HNO3 solution; and desorbent 2 is a 2 M HCl solution.

[0054] 2) Pass the thorium salt solution through an anion exchange column to remove impurities beforehand. 208 Pb, 210 Pb, 212 Pb and 214 Pb nuclide. The solution after column chromatography is sealed and stored for several days, pending new... 212 Pb generation.

[0055] 3) Building such Figure 1 The separation device shown uses SiPyR-N4 silica-based anion exchange resin as the packing material for the Pb selective adsorption column and APA chelating resin as the packing material for the Th selective adsorption column. 212 The packing material for the Pb enrichment column is silicon-based cation exchange resin A1.

[0056] 4) Adjust the three-way valve 1 to pump in sequentially through pump 1 at a certain flow rate. 232The feed solution and eluent are used to ensure that the above solution passes through the SiPyR-N4 column but not the APA column. At this point, 232 Th liquid 212 Pb is captured and immobilized by the SiPyR-N4 resin column. After passing through the column... 232 The feed liquid and the rinsing agent are collected separately by adjusting the three-way valve 2.

[0057] 5) Pump the desorbent 1 into the column at a certain flow rate using pump 1. After the residual eluent in the column is discharged, adjust the three-way valve 1 and the three-way valve 3 to connect the SiPyR-N4 resin column, the APA resin column and the A1 resin column.

[0058] 6) Desorbent 1 is continuously introduced through pump 1. At this time, the desorbent 1 is fixed on the SiPyR-N4 resin column. 212 Pb and Th impurities were eluted and entrained by desorbent 1 and subsequently entered the APA and A1 columns; the Th impurities in desorbent 1 were selectively removed by the APA column, while... 212 Pb is refixed by the A1 resin column; the desorbent 1 flowing through the A1 resin column is collected separately by adjusting the three-way valve 4, becoming free of Pb. 212 Pb desorbent 1; 7) Adjust three-way valves 3 and 4 to pump desorbent 2 into the A1 resin column at a certain flow rate via pump 2. The desorbent 2 is then fixed by the A1 resin column. 212 Pb was eluted and enriched, ultimately yielding 212 Pb enrichment solution.

[0059] Example 3 Extracting Pb from a simulated thorium solution includes the following steps: (1) Configure with stable Pb (simulation) 212 Pb), Th, La (simulation) 228 Ac), Ba (simulation) 228,224 The working solution of Ra was prepared in 0.5 M HBr medium, with each metal ion having a concentration of 1.0 mg / L; 0.5 M HBr was prepared as the eluent; 0.3 M HNO3 was prepared as desorbent 1; and 2 M HCl was prepared as desorbent 2.

[0060] (2) Building such Figure 1 The three-column separation system shown. Among them... 212 A Pb selective adsorption column is filled with SiPyR-N4 resin, and the column specifications are as follows: The Th selective adsorption column is filled with APA resin, and the column specifications are as follows: ; 212 The Pb enrichment column is filled with A1 resin, column specifications .

[0061] (3) Pass in enough ultrapure water in advance to remove air bubbles in the resin column; then pass in 500 mL of 0.5 M HBr solution at a flow rate of 10 mL / min to pretreat the SiPyR-N4 resin column, and adjust the three-way valve 1 to prevent the HBr solution from entering the APA column.

[0062] (4) Pump 5000 mL of simulated thorium solution into the column using pump 1 at a flow rate of 50 mL / min, and pump 500 mL of eluent into the column using a flow rate of 20 mL / min. Ensure that the solution passes through the SiPyR-N4 resin column but does not enter the APA resin column. The solution after column chromatography... 232 The feed solution and eluent were collected separately by adjusting three-way valve 2. The concentration of each metal in the effluent at different times was analyzed by ICP-OES.

[0063] (5) Continue pumping 900 mL of desorbent 1 through pump 1 at a flow rate of 20 mL / min. After the remaining eluent in the column has been discharged (approximately 200 mL), adjust three-way valves 1 and 3 to connect the SiPyR-N4 resin column, APA resin column, and A1 resin column. Then, continue pumping 500 mL of desorbent 1 through pump 1 at a flow rate of 10 mL / min. Collect the eluent from the A1 resin column containing no eluent by adjusting three-way valve 4. 212 Pb desorbent 1.

[0064] (6) Turn off pump 1 and pump 50 mL of desorbent 2 at a flow rate of 2.0 mL / min using pump 2. Adjust the three-way valve 3 to ensure that the above solution flows through the A1 resin column but does not flow into the APA resin column. At the same time, adjust the three-way valve 4 to collect the desorbent 2 flowing out of the A1 resin column separately. Analyze the concentrations of Th, Ba, Pb, and La in every 5 mL collected using ICP-OES.

[0065] The results are as follows Figure 2 As shown, the SiPyR-N4 resin column selectively captures Pb from the simulated thorium feed solution without immobilizing Th, Ba, and La. Using 0.3 M HNO3 as the desorbent, all Pb immobilized on the SiPyR-N4 resin column can be eluted. The APA resin column selectively removes Th from the 0.3 M HNO3 medium, while the A1 resin column effectively captures and immobilizes Pb in the 0.3 M HNO3 medium. Using 2.0 M HCl as the desorbent, the Pb immobilized by the A1 resin column can be completely eluted and enriched. Lead mainly accumulates in approximately 5 mL of the enrichment solution, with a lead concentration 1009 times that in the simulated thorium feed solution, and a chemical recovery rate close to 100%. The concentrations of Th, Ba, and La in this enrichment solution are below the ICP-OES detection limits.

[0066] Example 4 Direct extraction from high-concentration Th feed solution 212 Pb Example 4 is basically the same as Example 3 in terms of steps, the only difference being the use of a high concentration of... 232 The actual thorium feed solution replaced the simulated thorium feed solution. Its preparation method was as follows: 2 kg of thorium nitrate hydrate was dissolved in 5000 mL of 0.5 M HBr solution, stirred until homogeneous, and filtered to remove insoluble impurities. This solution was pre-filtered through a SiPyR-N4 resin column (…). Remove from it 208,210,212,214 Pb nuclide, then sealed and waited for 4 days 212 Pb regenerates and reaches long-term equilibrium. Gamma-ray spectroscopy analysis indicates that the thorium feed solution contains... 212 The total Pb activity was 1.88 MBq, or 50.7 μCi; the specific activity was 375 Bq / mL, or 0.010 μCi / mL.

[0067] The results are as follows Figure 3 and Figure 4 As shown. Thorium feed liquid 212 Pb was successfully isolated. 212 Pb mainly accumulated in 5.08 mL of enrichment solution, with a total activity of 1.66 MBq (44.9 μCi) and a specific activity of 0.327 MBq / mL (8.84 μCi / mL). The enrichment solution contained, except for... 212 Pb and its progeny were not found in vitro. 228 Th、 228 Ac and 224 Ra and other impurity nuclides that can emit gamma radiation; ICP-OES analysis showed that the contents of U, Th and Mg were below the instrument detection limit. 212 The chemical recovery rate of Pb reached 88.2%, and the enrichment factor (the ratio of the Pb concentration after enrichment to the Pb concentration before enrichment) reached 884 times.

[0068] Comparative Example 1 Adsorption rates of Pb by A1 resin and commercial resin (1) Prepare a working solution containing 100 mg / L Pb in 0.3 M HNO3 medium.

[0069] (2) Weigh 0.05g of A1 resin, D001 resin (purchased from Shanghai McLean Biochemical Technology Co., Ltd.), Na-QP (purchased from DuPont) and 732 resin (purchased from Shanghai McLean Biochemical Technology Co., Ltd.) into 40 mL glass bottles respectively, and add 20 mL of Pb working solution to mix with the resin.

[0070] (3) After sealing the glass bottle, place it in a 25°C water bath shaker and shake it at a frequency of 120 rpm for 1, 3, 5, 8, 10, 15, 30, 45, 60, 90 or 120 min.

[0071] (4) After the oscillation is completed, a 0.45 μm membrane filter is used for solid-liquid separation.

[0072] (5) The concentration of Pb in the diluted filtrate was measured by ICP-OES. The amount of adsorption was calculated based on the change in Pb concentration before and after adsorption.

[0073] The results are as follows Figure 5 As shown in the figure, the experimental results indicate that there are significant differences in the adsorption rates of Pb by the four resins in 0.3 M HNO3 medium. The A1 resin shows a rapid increase in Pb adsorption capacity in the initial stage of adsorption, reaching adsorption equilibrium within approximately 10 minutes, after which the adsorption capacity remains relatively stable. In contrast, the D001, Na-QP, and 732 resins require longer times to reach adsorption equilibrium, with equilibrium times of 90 min, 30 min, and 60 min, respectively. In terms of adsorption rate, the A1 resin is 3–9 times faster than commercially available resins. This extremely rapid adsorption rate is highly advantageous for the adsorption and separation of short-lived nuclides, reducing decay losses during the adsorption and separation process.

[0074] Comparative Example 2 Comparison of desorbent elution effects (1) Fill the A1 resin into the container with a specification of Inside the glass column.

[0075] (2) Prepare a working solution containing Pb (concentration of 100 mg / L) in 0.3 M HNO3 medium; and prepare 1.0 M HCl, 1.0 M HNO3 and 2.0 M HCl as desorbents.

[0076] (3) Use a peristaltic pump to pass in enough ultrapure water to remove air bubbles from the resin column.

[0077] (4) Pass 10 mL of working solution containing Pb and 30 mL of desorbent sequentially at a flow rate of 1.0 mL / min.

[0078] (5) The eluent was collected using an automatic fraction collector, with 2 mL collected each time for subsequent ICP-OES analysis.

[0079] (6) Plot the desorption curve of Pb with the outflow volume as the vertical axis and the ratio of the desorbent Pb concentration to the working liquid Pb concentration (C / C0) as the horizontal axis.

[0080] The results are as follows Figure 6As shown, using 2 M HCl as the desorbent, the elution peak of Pb is very sharp, and only about 4 mL is needed to completely elute Pb from the resin column, which is very beneficial for Pb enrichment. Although 1.0 M HCl can also elute Pb, the elution effect is not as good as 2.0 M HCl, and the elution peak is relatively flat. Using 1.0 M HNO3 as the desorbent, almost no lead is eluted from the resin within a 30 mL volume. These results indicate that compared with 1.0 M HNO3 and 1.0 M HCl, 2.0 M HCl is more suitable for eluting and enriching Pb from A1 resin columns.

[0081] Comparative Example 3 Comparison of dynamic desorption performance of Pb between A1 resin and commercial resin (1) Equal volumes of A1 resin, 732 resin, Na-Qp resin and D001 resin were respectively filled into containers with a specification of [specification missing]. A glass column.

[0082] (2) Prepare 30 mL of working solution containing Pb (concentration of 100 mg / L) in 0.3 M HNO3 medium; and prepare 2 M HCl as Pb desorption agent.

[0083] (3) Use a peristaltic pump to pass in enough ultrapure water to remove air bubbles from the resin column.

[0084] (4) Pretreatment of the resin column was performed by passing 20 mL of 0.3 M HNO3 solution through the column at a flow rate of 2.0 mL / min, followed by sequential passing of 30 mL of prepared Pb working solution and 100 mL of desorbent at the same flow rate.

[0085] (5) The eluent was collected using an automatic fraction collector, with 2 mL collected each time for subsequent ICP-OES analysis.

[0086] (6) Plot the desorption curve of Pb with the outflow volume as the vertical axis and the ratio of the desorbent Pb concentration to the working liquid Pb concentration (C / C0) as the horizontal axis.

[0087] The results are as follows Figure 7 As shown in the figure, for A1 resin, the desorption curve of Pb is very sharp with no tailing phenomenon, and the enrichment effect of lead is very obvious, with the highest C / C0 reaching 11.5; while for 732 resin, Na-QP resin, and D001 resin, the desorption curve of Pb is relatively diffuse, with the highest C / C0 only reaching about 4.2, and obvious tailing phenomenon exists. These results indicate that A1 resin is more suitable for the enrichment of trace nuclides than commercial resins, and can achieve a higher enrichment factor than commercial resins, while meeting the dual requirements of high chemical recovery rate and high enrichment factor.

[0088] Comparative Example 4 Comparative Example 4 and Example 3 are identical in steps (1) to (4), except that in step (5), the A1 column and the APA column are disconnected by adjusting the three-way valve 3, thus changing the three-column system containing the SiPyR-N4 column, the APA column, and the A1 column into a two-column system containing only the SiPyR-N4 column and the APA column. The solution flowing out of the APA column is directly collected and sent for analysis. In addition, Comparative Example 4 does not include step (6).

[0089] The results are as follows Figure 8 As shown, a dual-column system comprising a SiPyR-N4 column and an APA column can achieve selective separation of Pb and removal of Th, La, and Ba impurities. However, its maximum enrichment factor for Pb is only 40, and the concentration distribution is relatively diffuse, making it impossible to simultaneously achieve high enrichment factor and high chemical recovery rate; in contrast, a three-column system ( Figure 2 The three-column system achieves a maximum enrichment factor of 1009 times for Pb, with a highly concentrated concentration distribution, effectively balancing high enrichment factor and high chemical recovery rate. Under the same experimental conditions and without considering chemical recovery rate, the maximum enrichment factor of Pb by the three-column system is more than 25 times that of the two-column system.

[0090] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0091] One or more embodiments in this application are intended to cover 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 in this application should be included within the protection scope of this application.

Claims

1. A method for extracting high-quality thorium salts 212 The Pb system is characterized by... include: The first resin column is filled with silicon-based anion exchange resin, used to extract from... 212 Selective adsorption of Pb in thorium salt solution 212 Pb; The second resin column is filled with aminophosphate chelating resin for selective adsorption of Th. The third resin column is filled with silicon-based cation exchange resin for adsorption and enrichment. 212 Pb; A first conveying device is connected to the inlet of the first resin column and is used to pump thorium salt solution, leaching agent and desorbent into the first resin column; The second conveying device is connected to the inlet of the third resin column and is used to pump the enrichment desorbent into the third resin column. The enrichment desorbent is a hydrochloric acid solution. Valve assemblies, located between resin columns and at the outlet, are used to control the flow path connectivity, ensuring that: During the adsorption and leaching stages, the first, second, and third resin columns are not connected; the thorium salt solution and leaching agent pass only through the first resin column. 212 Pb is adsorbed and fixed by the first resin column; During the desorption stage, the first resin column, the second resin column, and the third resin column are connected in series, and the desorbent flows sequentially through the first resin column, the second resin column, and the third resin column, causing... 212 After Pb is desorbed from the first resin column, it passes through the second resin column with the desorbent to remove Th impurities, and is then adsorbed and fixed by the third resin column. During the enrichment stage, the third resin column is not connected to the second resin column, and the enrichment desorbent passes through the third resin column. 212 Pb was eluted and enriched.

2. The extraction of high-quality thorium salts according to claim 1 212 The Pb system is characterized by... The silicon-based anion exchange resin is a silicon-based anion exchange resin with N-methylpyridine as the functional group.

3. The extraction of high-quality thorium salts according to claim 1 212 The Pb system is characterized by... The aminophosphate chelating resin is a chelating resin with aminophosphate functional groups.

4. The extraction of high-quality thorium salts according to claim 1 212 The Pb system is characterized by... The silicon-based cation exchange resin is a silicon-based cation exchange resin with sulfonic acid functional groups.

5. The extraction of high-quality thorium salts according to claim 4 212 The Pb system is characterized by... The method for preparing the silicon-based cation exchange resin with sulfonic acid functional groups is as follows: silicon-based polystyrene, sulfonation reaction catalyst and solvent are mixed, heated and then concentrated sulfuric acid is added dropwise to carry out the sulfonation reaction. After the reaction is completed, the mixture is washed and dried to obtain the silicon-based cation exchange resin with sulfonic acid functional groups.

6. The extraction of high-quality thorium salts according to claim 1 212 The Pb system is characterized by... The thorium salt solution is a hydrobromic acid solution containing dissolved thorium nitrate, the leaching agent is a hydrobromic acid solution, and the desorbent is a nitric acid solution.

7. The extraction of high-quality thorium salts according to any one of claims 1-6 212 The Pb system is characterized by... The valve assembly includes a switching valve disposed before the inlet of the first resin column, a first three-way valve disposed at the outlet of the first resin column, a third three-way valve disposed between the second resin column and the third resin column, and a fourth three-way valve disposed at the outlet of the third resin column.

8. A method for extracting high-quality thorium salts 212 The method of Pb is characterized by, Includes the following steps: 1) The thorium salt solution and eluent are passed through a first resin column filled with silica-based anion exchange resin, so that... 212 Pb is selectively adsorbed and fixed; 2) A desorbent is introduced into the first resin column to desorb the adsorbed resin. 212 Pb and Th impurities are eluted and sequentially passed through a second resin column filled with aminophosphate chelating resin and a third resin column filled with silicon-based cation exchange resin; Th impurities are selectively adsorbed and removed by the second resin column. 212 Pb is adsorbed and fixed by the third resin column; 3) An enrichment and desorption agent, which is a hydrochloric acid solution, is introduced into the third resin column. 212 Pb was eluted and enriched to obtain a product containing high-quality Pb. 212 Pb 212 Pb enrichment solution.

9. The extraction of high-quality thorium salts according to claim 8 212 The method of Pb is characterized by, The concentration of the hydrochloric acid solution is 0.5-5 mol / L; The thorium salt solution is a hydrobromic acid solution containing dissolved thorium nitrate, the leaching agent is a hydrobromic acid solution, and the desorbent is a nitric acid solution.

10. The extraction of high-quality thorium salts according to claim 8 212 The method of Pb is characterized by, The thorium salt solution is pre-passed through an anion exchange resin column before passing through a first resin column filled with silicon-based anion exchange resin, in order to remove impurities in advance. 208 Pb, 210 Pb, 212 Pb and 214 Pb nuclide, the solution after column chromatography is sealed and stored for later use. 212 After Pb is generated, it passes through a first resin column filled with silicon-based anion exchange resin.

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