Method for separating and purifying 212Pb from thorium solution

Abstract

The invention belongs to the field of medical isotope separation and preparation, and particularly relates to a method for separating and purifying < 212 > Pb from a thorium solution, which comprises the following steps: 1) leacheate is introduced into a Pb selective adsorption column to pretreat the Pb selective adsorption column, and then < 232 > Th salt solution and leacheate are introduced in sequence; 2) continuously introducing a desorption solution into the Pb selective adsorption column, enabling the desorption solution passing through the Pb selective adsorption column to flow into the Th selective adsorption column, and collecting the outflowing desorption solution; a desorption solution only containing 212Pb is obtained; according to the method, the 212Pb in the high-concentration thorium solution can be separated and purified at the same time. While < 232 > Th impurity entrainment and pollution in a < 212 > Pb product are remarkably reduced, compared with a single-column process, the separation time is basically not increased. The separated 212Pb product has high radionuclide purity and chemical purity at the same time, and can meet related pharmaceutical requirements.

Description

A method for separating and purifying thorium from solution 212 Pb method Technical Field

[0001] This invention belongs to the field of medical isotope separation and preparation, specifically relating to a method for separating and purifying thorium from a solution. 212 Pb's method. Background Technology

[0002] 212 Pb is an important medical radioactive isotope with promising applications in the treatment of malignant tumors such as prostate cancer, breast cancer, and pancreatic cancer; however, its resources are extremely scarce. 232 Direct separation and extraction from the Th decay chain 212 Pb holds promise for fundamentally solving the current problem. 212 The bottleneck problem of insufficient Pb supply.

[0003] exist 232 In the Th decay chain, the Pb / Th mass ratio reaches more than 10 orders of magnitude, and various other radionuclides are present. 232 Th impurities have long half-lives, so reducing the content of Th and improving the purity of Pb is crucial.

[0004] For from 232 Direct extraction from Th salt solution 212 Currently, thorium (Pb) is mainly extracted using two methods. The first method utilizes the supramolecular recognition effect of crown ether materials to selectively extract it directly from thorium nitrate / nitric acid solutions. 212 While this method is effective, its drawbacks include the difficulty and high cost of obtaining crown ether materials, and the tendency for these materials to be lost during adsorption or extraction due to their water solubility. The second method is our pioneering anion exchange process (authorization announcement number CN119120899 B), which utilizes… 232 The differences in chemical seed states of Pb and other key nuclides in the Th decay chain within a halogenated medium were investigated using anion exchange resin for selective extraction. 212 Pb. Compared to crown ether-based methods, this process offers advantages such as readily available separation materials, avoids the problem of water solubility loss, and boasts higher separation efficiency. However, both crown ether-based and anion exchange resin-based methods face challenges in applications involving high concentrations. 232 Direct extraction from Th salt solution 212 When Pb is separated, the obtained 212 Pb samples inevitably contain a small amount of Pb. 232 Th impurities, whose chemical purity is difficult to meet pharmaceutical requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for separating and purifying thorium from a solution. 212 Pb methods to improve 212 The purity of Pb.

[0006] This invention provides a method for separating and purifying thorium from a solution. 212 The method for treating Pb includes the following steps: 1) Pre-treating the Pb selective adsorption column by passing the eluent through it, and then sequentially passing the eluent through the column. 232 Th salt solution and eluent; the eluent is an aqueous solution of hydrogen halide, the... 232 The Th salt solution is an aqueous solution of hydrogen halide containing thorium nitrate, and the packing material of the Pb selective adsorption column is an anion exchange resin; in step 1) 232 The Th salt solution and eluent are only passed into the Pb-selective adsorption column and do not flow into the Th-selective adsorption column. 232 Th salt solution 212 Pb is captured and immobilized by a Pb selective adsorption column.

[0007] 2) Continuously pass the desorption solution into the Pb-selective adsorption column, and allow the desorption solution after passing through the Pb-selective adsorption column to flow into the Th-selective adsorption column (the desorption solution contains entrained ions). 232 Th impurities are captured and fixed by a Th-selective adsorption column, and the eluent is collected; the product contains only Th impurities. 212 The desorption solution for Pb is an aqueous nitric acid solution. The packing material for the Th selective adsorption column is APA resin. The APA resin is prepared by bonding aminophosphonic acid groups to the primary amine groups via the Mannich reaction using a weakly basic anion exchange resin carrying primary amine groups as a carrier. The preparation method of the APA resin includes the following steps: mixing the weakly basic anion exchange resin carrying primary amine groups, phosphorous acid, and concentrated hydrochloric acid evenly, then adding formaldehyde, refluxing, filtering, washing, and drying to obtain the APA resin.

[0008] Preferably, after the weakly basic anion exchange resin carrying primary amine groups, phosphorous acid, and concentrated hydrochloric acid are mixed evenly, the mixture is heated to 80-90°C (preferably 85°C) before formaldehyde is added.

[0009] Preferably, phosphorous acid exists in the form of an aqueous solution of phosphorous acid with a mass concentration of 10-15 g / mL. Formaldehyde exists in the form of an aqueous solution of formaldehyde with a mass fraction of 35-40%.

[0010] Preferably, the hydrogen halide is hydrogen bromide.

[0011] This invention does not place particular requirements on the adsorption capacity of the anion exchange resin for Pb, only requiring it to have a certain adsorption capacity. Its main function is to enrich Pb so that after the desorption solution flows through the anion exchange resin, it can be purified by a Th-selective adsorption column to obtain purified Pb. Of course, the higher the Pb adsorption capacity of the anion exchange resin, the better, as this results in a higher degree of Pb enrichment. Preferably, the anion exchange resin is prepared by in-situ solution copolymerization of 4-vinylpyridine and divinylbenzene in the presence of an initiator and a diluent within porous SiO2 channels to obtain silicon-based polyvinylpyridine, followed by methylation reaction of the silicon-based polyvinylpyridine with dimethyl sulfate to obtain the anion exchange resin.

[0012] Preferably, the concentration of the aqueous solution of hydrogen halide is 0.3-1 mol / L, and the concentration of the aqueous solution of nitric acid is 0.3-1 mol / L.

[0013] Preferred, 232 The flow rate of Th salt solution and eluent into the Pb selective adsorption column was 1-3 mL / min.

[0014] Preferably, a three-way valve is connected between the Pb selective adsorption column and the Th selective adsorption column.

[0015] The beneficial effect of this invention is that, compared with the single-column process using anion exchange columns, the integrated dual-column method provided by this invention can achieve high-concentration thorium solutions... 212 Simultaneous separation and purification of Pb. Significantly reduced... 212 Pb products 232 While reducing impurity entrainment and contamination, the separation time is essentially no longer compared to single-column processes. The separated... 212 Pb products possess both high radionuclide purity and chemical purity, meeting relevant pharmaceutical requirements.

[0016] This invention discovers that by bonding aminophosphonic acid groups (-NH-CH2-PO(OH)2) to the primary amine groups on a weakly basic anion exchange resin via the Mannich reaction, a stable C-P bond structure is formed. The APA resin obtained in this way only adsorbs thorium and not lead. Therefore, thorium and lead can be separated very well. Compared with other conventional resins that also contain phosphate groups (such as HDEHP extraction resin with phosphate groups, TBP extraction resin containing P, and P507 extraction resin), its analytical effect is significantly better, resulting in higher Pb purity.

[0017] This invention is a dual-column process. 232The Th salt solution is first passed through a Pb-selective adsorption column, where Pb is adsorbed. However, a small amount of Th is also present in the solution. Then, Pb and Th are washed out using an eluent and passed into an APA resin column (i.e., a Th-selective adsorption column). Th is selectively adsorbed, and the eluent contains only Pb. This dual-column process significantly reduces the amount of Th adsorbed in the APA resin column, extending the resin's lifespan. Furthermore, this method involves simultaneous separation and purification, minimizing the time required for each step and reducing degradation. 212 Pb decay loss. Attached Figure Description

[0018] Figure 1 shows the adsorption behavior of APA resin and ZGA452 resin for Th and Pb in nitric acid medium.

[0019] Figure 2 shows the separation and purification from the high-concentration thorium salt solution. 212 A flowchart of the Pb process.

[0020] Figure 3 shows the desorption solution in the dual-column system. 212 Pb activity and Th concentration.

[0021] Figure 4 shows the gamma spectrum of the sixth desorption sample in the dual-column system.

[0022] Figure 5 shows the adsorption behavior of APA resin on Th and Pb in HBr medium.

[0023] Figure 6 shows a comparison of the Th / Pb separation performance of various materials.

[0024] Figure 7 shows the desorption solution in a single-column system. 212 The activity of Pb and the concentration of Th.

[0025] Figure 8 shows the gamma spectrum of the first desorption sample in the single-column system. Detailed Implementation

[0026] Example 1: A method for preparing an APA resin, comprising 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Example 2 Study on the separation performance of APA resin 1) Prepare a mixed working solution containing 400 mg / L Th and 100 mg / L Pb, with the solution medium being 0.05 M, 0.1 M, 0.5 M, 0.75 M, 1 M, 3 M, 5 M and 7 M HNO3 respectively.

[0031] 2) Take a batch of 40 mL clean glass bottles and add 0.05 g of the dried APA resin or ZGA452 resin from Example 1 to each bottle. At the same time, add 20 mL of the prepared mixed working solution to each bottle using a pipette.

[0032] 3) After sealing the glass bottle, place it in a 25°C water bath shaker and shake for 24 h, then use a 0.45 μm filter membrane for solid-liquid separation.

[0033] 4) After dilution, the concentrations of Th and Pb in the solution were detected by ICP-AES, and the corresponding adsorption efficiency was calculated based on the changes in the concentrations of each metal ion before and after adsorption.

[0034] As shown in Figure 1, ZGA452 resin did not adsorb either Th or Pb before modification. However, after modification into APA resin, it exhibited high adsorption selectivity for Th and did not adsorb Pb from the solution. APA resin showed good adsorption performance for Th at nitric acid concentrations above 0.5 M, but still retained selective adsorption capacity for Th under low acid conditions.

[0035] Example 3: A method for separating and purifying thorium from a solution 212 The method for Pb purification is shown in Figure 2. The separation and purification apparatus includes components connected via pipelines. 232 Th salt solution container, rinsing solution container, 212 The Pb desorption container and the Pb selective adsorption column and Th selective adsorption column located in the radiation protection device; a three-way valve 1 is provided between the Pb selective adsorption column and the Th selective adsorption column (therefore, the solution can be introduced into the Pb selective adsorption column only, or into the Pb selective adsorption column and the Th selective adsorption column in sequence).

[0036] 232 Th salt solution container, eluent container and 212 Three-way valves are installed between the Pb desorption solution containers, namely the eluent container and the... 212 A three-way valve 3 is installed between the Pb desorption solution containers. 232 A three-way valve 2 is installed between the Th salt solution container and the eluent container, therefore... 232 Th salt solution, rinsing fluid and 212 Pb desorption solution can be introduced into Pb selective adsorption columns and Th selective adsorption columns independently, sequentially, or simultaneously.

[0037] The steps include: 1) Take a piece of a certain specification A glass column was filled with SiPyR-N4 anion exchange resin (Example 1 disclosed in CN119120899 B, whose functional group is N-methylpyridine) to serve as a Pb selective adsorption column; another column of a specific size was taken. A glass column was filled with the APA resin of Example 1 to serve as a Th-selective adsorption column.

[0038] 2) Connect the two adsorption columns using a three-way valve 1, and then use a peristaltic pump to introduce sufficient ultrapure water to remove air bubbles from the adsorption columns.

[0039] 3) Dissolve 40 g of thorium nitrate hydrate in 100 mL of 0.5 M HBr to prepare the Th solution. 232 Th decay occurs 212 Pb), that is 232 Th salt solution.

[0040] 4) Adjust the three-way valve 1 to isolate the two columns, then pre-treat the SiPyR-N4 resin column by introducing 100 mL of 0.5 M HBr solution (i.e., eluent) at a flow rate of 2.0 mL / min. Then, sequentially introduce 100 mL of pre-prepared Th feed solution (i.e.,...) at the same flow rate. 232 Th salt solution) and 30 mL 0.5 M HBr solution (i.e., rinsing solution).

[0041] 5) Continuously pass 100 mL of 0.5 M HNO3 solution (i.e., ...) at a flow rate of 2.0 mL / min. 212 After the dead volume of the Pb desorption solution was largely eliminated, the three-way valve 1 was opened to connect the two columns, and the desorption solution flowing out from the APA resin column (i.e., the Th selective adsorption column) was collected using a fraction collector. The collection time for each centrifuge tube was set to 5 min, and the samples were named sequentially as No. 1, No. 2, No. 3... No. 10.

[0042] 6) The concentration of gamma-ray spectroscopy was measured in each centrifuge tube using a gamma-ray spectrometer.212 The total activity of Pb was determined by ICP-AES, which measured the concentration of Th in each centrifuge tube.

[0043] The results are shown in Figures 3 and 4. After separation by the dual-column system... 212 Pb is mainly concentrated in centrifuge tubes 6, 7, and 8. 212 The chemical recovery rate of Pb was 93.3%. The concentration of Th in each centrifuge tube was 0, and except for... 212 Pb and its progeny were not found in vitro. 224 Ra and 228 The peaks of impurity nuclides such as Ac indicate that the sample obtained by separation using a two-column system... 212 Pb possesses both high radionuclide purity and high chemical purity.

[0044] Comparative Example 1: Adsorption behavior of APA resin for Th and Pb in HBr. The difference between Comparative Example 1 and Example 2 is that the working solution medium was changed from HNO3 to HBr. Everything else was the same as in Example 2.

[0045] As shown in Figure 5, the APA resin adsorbs both Th and Pb in the HBr medium. Therefore, the APA resin cannot be used for the selective removal of Th and the selective retention of Pb in the HBr system.

[0046] Comparative Example 2: Comparison of the adsorption and separation performance of various materials for Th / Pb 1) Prepare a mixed working solution containing 200 mg / L Th, 100 mg / L Pb and 0.5 M HNO3.

[0047] 2) Weigh 0.2 g of the APA resin from Example 1 and place it in a 40 mL glass bottle, and add 20 mL of the mixed working solution from step 1) to mix with the APA resin.

[0048] 3) After sealing the glass bottle, place it in a 25°C water bath shaker and shake for 24 h, then use a 0.45 μm membrane filter for solid-liquid separation.

[0049] 4) After dilution, the concentrations of Th and Pb in the filtrate were measured using ICP-AES. The adsorption efficiency was calculated based on the changes in Th and Pb concentrations before and after adsorption.

[0050] 5) Using the same steps as 1) to 4), compare the extraction resin loaded with HDEHP (HDEHP / SiO2-P, prepared in the laboratory, see the paper He X, Liao L, Tang J, et al. Preparation and characterization of a mesoporous silica-based copolymer loaded with bis (2-ethylhexyl) phosphate for the efficient separation of trace radium from natural thorium[J]. Journal of Radioanalytical and Nuclear Chemistry, 2024, 333(11): 5721-5733) and the extraction resin loaded with P507 (P507 / SiO2-P, prepared in the laboratory, see the paper Huang M, Ning S, Liu J, et al. Study on the efficient preparation of low radioactivity ultra-high purity lanthanum oxide (≥ 6 N) by a single chromatographic column using aphosphonic acid functional resin[J]. Journal of Materials Chemistry A, 2025,13(45): 39315-39329), TBP-loaded extraction resin (TBP / SiO2-P, prepared in the laboratory, see the paper Meng J J, He CL, Zhou J, et al. Recovery of gallium by silica‐based polymer TBP / SiO2‐P obtained from hydrochloric acid solution[J]. Journal of Applied Polymer Science, 2021, 138(4): 49732), commercial anion exchange resin (model IRA900, purchased from Shanghai Maclean Biochemical Reagent Co., Ltd.), and silicon-based cation exchange resin (named A1, prepared in the laboratory, see the paper Tang J, Liao L, He X, et al.)The study compared the efficient separation of radium from natural thorium using a mesoporous silica-supported composite resin with sulfonic acid groups for the acquisition of targeted α-nuclides 212Pb[J]. Chemical Engineering Journal, 2024, 485: 150022, with the separation performance of a commercial cation exchange resin (TapTec™ SR1L Na-QP, purchased from DuPont Resin, abbreviated as Na-QP) for Th and Pb under the same conditions.

[0051] As shown in Figure 6, A1 resin, HDEHP-loaded extraction resin, P507-loaded extraction resin, and commercial cation exchange resin Na-QP all adsorbed some Pb while adsorbing Th. However, commercial anion exchange resin IRA900 and TBP-loaded extraction resin did not adsorb Th under these conditions. Only APA resin, under the same conditions, achieved selective removal of Th and complete retention of Pb, perfectly matching the dual-column process and technology proposed in this invention.

[0052] The single-column separation process of Comparative Example 3 is basically the same as that of Example 3. The difference is that the three-way valve 1 is kept in a state of isolating the two columns throughout the experiment, and all solutions flow only through the single column packed with SiPyR-N4 resin (lead selective adsorption column).

[0053] The separation results are shown in Figures 7 and 8. Separation based on single-column process. 212 Pb was mainly concentrated in the first centrifuge tube. (Collected) 212 Although the Pb samples had high radionuclide purity, their chemical purity was relatively low. Trace amounts of Th impurities were present in all desorption samples, with the highest concentration reaching approximately 12 mg / L.

[0054] 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.

[0055] 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 separating and purifying thorium from a solution 212 The Pb method is characterized by, The steps include: 1) Pre-treating the Pb selective adsorption column by passing the eluent through it, and then sequentially passing the eluent through the column. 232 Th salt solution and eluent; the eluent is an aqueous solution of hydrogen halide, the... 232 The Th salt solution is an aqueous solution of hydrogen halide containing thorium nitrate, and the packing material of the Pb selective adsorption column is an anion exchange resin; 2) The desorption solution is continuously passed into the Pb selective adsorption column, and the desorption solution after passing through the Pb selective adsorption column flows into the Th selective adsorption column, and the outflowing desorption solution is collected; to obtain a solution containing only thorium nitrate. 212 The desorption solution for Pb is an aqueous nitric acid solution. The packing material for the Th selective adsorption column is APA resin. The APA resin is prepared by bonding aminophosphonic acid groups to the primary amine groups via the Mannich reaction using a weakly basic anion exchange resin carrying primary amine groups as a carrier. The preparation method of the APA resin includes the following steps: mixing the weakly basic anion exchange resin carrying primary amine groups, phosphorous acid, and concentrated hydrochloric acid evenly, then adding formaldehyde, refluxing, filtering, washing, and drying to obtain the APA resin.

2. The method as described in claim 1, characterized in that, After the weakly basic anion exchange resin carrying primary amine groups, phosphorous acid, and concentrated hydrochloric acid are mixed evenly, the mixture is heated to 80-90℃, and then formaldehyde is added.

3. The method as described in claim 2, characterized in that, After heating to 85℃, formaldehyde is added.

4. The method as described in claim 1, characterized in that, Phosphorous acid exists in the form of an aqueous solution of phosphorous acid with a mass concentration of 10-15 g / mL.

5. The method as described in claim 1, characterized in that, Formaldehyde exists in the form of an aqueous solution with a mass fraction of 35-40%.

6. The method as described in claim 1, characterized in that, The hydrogen halide is hydrogen bromide.

7. The method as described in claim 1, characterized in that, The anion exchange resin is prepared by in-situ solution copolymerization of 4-vinylpyridine and divinylbenzene in the presence of an initiator and a diluent within porous SiO2 channels to obtain silicon-based polyvinylpyridine. The silicon-based polyvinylpyridine is then methylated with dimethyl sulfate to obtain the anion exchange resin.

8. The method as described in claim 1, characterized in that, The concentration of the aqueous solution of hydrogen halide is 0.3-1 mol / L, and the concentration of the aqueous solution of nitric acid is 0.3-1 mol / L.

9. The method as described in claim 1, characterized in that, 232 The flow rate of Th salt solution and eluent into the Pb selective adsorption column was 1-3 mL / min.

10. The method as described in claim 1, characterized in that, A three-way valve connects the Pb-selective adsorption column and the Th-selective adsorption column.

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