Method for preparing high-purity terbium 161

Abstract

The invention relates to a method for preparing high-purity terbium 161, which comprises the following steps: S1, preparing an acid solution from an irradiated gadolinium target material, and loading the acid solution onto a first separation column filled with terbium separation resin; leaching the first separation column to correspondingly desorb gadolinium and terbium to obtain a first gadolinium desorption solution and a first terbium desorption solution; s2, loading the first terbium desorption solution onto a second separation column, wherein the second separation column is filled with TODGA resin; leaching the second separation column to desorb terbium to obtain a second terbium desorption solution; s3, loading the second terbium desorption solution onto a third separation column, wherein the third separation column is filled with terbium separation resin; leaching the third separation column to desorb terbium, so as to obtain high-purity terbium 161; the terbium separation resin comprises 40 wt%-50 wt% of a first extraction agent, 50 wt%-60 wt% of a first resin matrix and 0.01 wt%-1 wt% of long-chain alcohol based on the total weight of the terbium separation resin, the DGA resin comprises 40 wt% to 50 wt% of a second extractant and 50 wt% to 60 wt% of a second resin matrix based on the total weight of the DGA resin.

Description

Technical Field

[0001] This invention belongs to the field of radioactive isotope preparation, specifically relating to a method for preparing high-purity terbium-161. Background Technology

[0002] Terbium-161 ( 161 Tb is a novel medical isotope with a half-life of 6.89 days, and is a type of β-thionine. - Terbium-161 is a radionuclide that decays at 100%. The decay process emits moderate-energy beta rays, with the main energy at 522 keV (65%). It also emits a significant number of Auger electrons and internal conversion electrons, making it highly suitable for preparing diagnostic and therapeutic radiopharmaceuticals with tumor-targeting capabilities. It is a novel "therapeutic" medical radionuclide. A limited amount of research has been conducted both domestically and internationally on the preparation of terbium-161.

[0003] Therefore, there is a need to develop an efficient method for preparing terbium-161. Summary of the Invention

[0004] In view of this, the present invention establishes a method for preparing high-purity terbium-161. In this method, a highly effective separation resin with fast adsorption kinetics and high selectivity is used to obtain terbium-161 product with high specific activity and generate less radioactive waste liquid. The overall yield of terbium-161 is greater than 95%, and the decontamination factor for gadolinium is greater than 10. 7 It has high industrial application value.

[0005] To achieve the above objectives, the present invention provides a method for preparing high-purity terbium-161, comprising: S1, after preparing an acid solution from the irradiated gadolinium target, it is loaded onto a first separation column, wherein the first separation column is filled with terbium separation resin; then the first separation column is eluted sequentially with 0.4~0.6 mol / L HNO3 and 0.9~1.2 mol / L HNO3 solutions to desorb gadolinium and terbium accordingly, to obtain a first gadolinium desorption solution and a first terbium desorption solution; S2, the first terbium desorption solution is loaded onto the second separation column, wherein the second separation column is filled with TODGA resin; then the second separation column is eluted with 0.05~0.1 mol / L HCl solution to desorb terbium and obtain the second terbium desorption solution; S3, the second terbium desorption solution is loaded onto a third separation column, wherein the third separation column is filled with terbium separation resin; then the third separation column is eluted sequentially with 0.4~0.6 mol / L HNO3 and 0.9~1.2 mol / L HNO3 solutions to elute gadolinium and desorb terbium, thereby obtaining the high-purity terbium-161; The terbium separation resin comprises, based on the total weight of the terbium separation resin, 40 wt% to 50 wt% of a first extractant, 50 wt% to 60 wt% of a first resin matrix, and 0.01 wt% to 1 wt% of a long-chain alcohol.

[0006] The DGA resin comprises: 40 wt% to 50 wt% of a second extractant and 50 wt% to 60 wt% of a second resin matrix, based on the total weight of the DGA resin.

[0007] In some embodiments, the extractant in the terbium separation resin is selected from one or more of the following: di(2-ethylhexyl) phosphate, mono(2-ethylhexyl)-2-ethylhexyl phosphonate, di(2-ethylhexyl)phosphonic acid, di-(2,4,4-trimethylpentyl) phosphate, di(2-ethylhexyl) monothiophosphate, di(2-ethylhexyl) dithiophosphate, mono(2-ethylhexyl)-2-ethylhexyl monothiophosphonate, and mono(2-ethylhexyl)-2-ethylhexyl dithiophosphonate.

[0008] In some embodiments, the long-chain alcohol in the terbium separating resin is selected from one or more of polyvinyl alcohol or polyacryl alcohol.

[0009] In some embodiments, the resin matrix in the terbium separation resin is selected from one or more of polyacrylic acid, polystyrene, and polyethersulfone.

[0010] In some embodiments, the terbium separating resin has a particle size of 50 μm to 100 μm and has mesoporous or macroporous pore sizes.

[0011] In some embodiments, the second extractant in the DGA resin includes, but is not limited to, N,N,N′,N′-tetraoctyl-3-oxopramethylenediamide, N,N,N′,N′-tetraisooctyl-3-oxopramethylenediamide, and N,N,N′,N′-tetramethyl-3-oxa-pentanediamide.

[0012] In some embodiments, the second resin matrix is ​​selected from resins based on polyacrylic acid, polystyrene, or polystyrene-divinylbenzene.

[0013] In some embodiments, the first separation column has an aspect ratio of ≥20 and a column volume of not less than 0.15 mL / mg. V r The mass ratio to gadolinium.

[0014] In some embodiments, the second separation column has an inner diameter of 5 to 10 mm and a height of not less than 5 mm.

[0015] In some embodiments, the method further includes: Before using the first separation column, use no less than 10 V r The first separation column was equilibrated with 0.01~0.05 mol / L HNO3; Before using the second separation column, use no less than 10 V r The second separation column was equilibrated with 1-2 mol / L HNO3; Before using the third separation column, use no less than 10 V r The third separation column was equilibrated with 0.01~0.05 mol / L HNO3.

[0016] Therefore, in the method of the present invention, by employing three separation columns—the first for terbium separation, the second for media conversion, and the third for terbium purification—terbium with a nuclear purity >99.5% can be obtained with a yield of 95%. Furthermore, the method of the present invention has a relatively simple process flow, a short preparation time, and greater industrial application value. Attached Figure Description

[0017] Figure 1 A flowchart of the method of the present invention is shown.

[0018] Figure 2 The product spectrum of terbium-161 obtained by the method of the present invention is shown. Detailed Implementation

[0019] The following detailed description discusses exemplary embodiments. The specific embodiments included herein should not be construed as limiting the invention. Furthermore, while specific language may be used to describe features, actions, and / or structures in the embodiments described herein, the claims are not limited to the described features, actions, and / or structures. Those skilled in the art will understand that other embodiments, including improvements, are within the spirit and scope of the invention.

[0020] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] Terbium-161 has attracted increasing attention due to its excellent radioactivity. Currently, the biggest challenge in producing high-purity terbium-161 lies in its separation process. (General...) 161Tb purification methods mainly include ion-exchange chromatography and lanthanide resin column separation. However, ion-exchange chromatography suffers from low sample loading capacity, making it difficult to carry out large-scale Curie-level production; while lanthanide resin column separation has the advantage of high sample loading capacity, but suffers from high nuclide residue.

[0022] In recent years, Germany has used two-stage cation exchange resins to separate and purify terbium-161. However, the low loading capacity and poor selectivity of the cation exchange resin result in a small amount of terbium-161 produced in a single step, and the decontamination effect is poor. Switzerland used a combination of cation exchange resin and LN3 resin for separation, but the terbium-161 yield was only 80%. Indonesia used two-stage LN resin for separation, achieving better results. Domestically, the China Academy of Engineering Physics and Sichuan Gaotong Pharmaceutical Co., Ltd. have also conducted related research, using cation exchange resin, LN resin, or a combination of both types of resin as separation materials. However, cation exchange resin has a small processing capacity and poor decontamination effect; LN resin is a foreign product, posing a risk of supply and demand. Sichuan Gaotong Pharmaceutical Co., Ltd. used two LN resin columns to separate carrier-free terbium-161 from a large amount of gadolinium after irradiation, but the yield was only about 70%. The separation method used by the China Academy of Engineering Physics achieved a yield of over 95%, but required seven chromatography columns, which limited its industrial application.

[0023] In this application, through detailed research on separation resins, a resin capable of efficiently separating terbium was developed, thus requiring only 3 separation columns to achieve a separation method with nuclear purity and radiochemical purity comparable to the work described above, but with a chemical yield as high as 95%.

[0024] In this application, high-purity terbium-161 refers to terbium-161 with both high nuclear purity and radiochemical purity, such as nuclear purity and radiochemical purity both exceeding 99%, for example, exceeding 99.1%, 99.2%, or 99.3%.

[0025] In this application, based on the total weight of the terbium separating resin, the terbium separating resin comprises 40 wt% to 50 wt%, for example 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, or 50 wt% of a first extractant. For the first extractant that can be used, thiophosphate, phosphate esters, or mixtures thereof may be used in particular. By using this type of extractant, the separation factor can be further increased. For example, the extractants used include one or more of the following: di(2-ethylhexyl) phosphate (P204), mono(2-ethylhexyl)-2-ethylhexyl phosphonate (P507), di(2-ethylhexyl)phosphonic acid (P227), di-(2,4,4-trimethylpentyl) phosphate (C272), di(2-ethylhexyl) monothiophosphate, di(2-ethylhexyl) dithiophosphate, mono(2-ethylhexyl)-2-ethylhexyl monothiophosphonate, and mono(2-ethylhexyl)-2-ethylhexyl dithiophosphonate.

[0026] Supporting matrix: The matrix material is an inert polymer material, including but not limited to polyacrylic acid, polystyrene, and polyethersulfone.

[0027] For this specific terbium separation resin, based on the total weight of the terbium separation resin, the terbium separation resin comprises 50 wt% to 60 wt%, such as 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, or 60 wt% of a resin matrix. There are no particular limitations on the resin matrix that can be used; inert polymeric materials conventionally used in the art can be used. Exemplarily, the resin matrix used includes one or more of polyacrylic acid, polystyrene, and polyethersulfone.

[0028] For this highly effective terbium separation resin, based on the total weight of the terbium separation resin, the terbium separation resin includes 0.01 wt% to 1 wt%, for example, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, or 1.0 wt% of long-chain alcohols. In this application, long-chain alcohols specifically refer to polyvinyl alcohol and polyacryl alcohol. By further adding long-chain alcohols to the separation resin, the resin properties can be further improved, increasing its separation factor for gadolinium and terbium, thereby achieving efficient separation of the two.

[0029] For the terbium separation resin of this application, the extractant mixture is incorporated as a functionalized compound, which is loaded onto the matrix by impregnation or polymerization. Long-chain alcohols are added during the synthesis process to improve resin properties. Compared to currently available resins, the addition of thiophosphate extractant and the use of a mixture of multiple phosphorus extractants can increase the separation factor and improve the resin's separation performance. The addition of long-chain alcohols not only improves the resin's radiation resistance but also further enhances the separation effect. The final resin product can achieve highly efficient separation of gadolinium and terbium.

[0030] In some embodiments, the terbium separation resin described above can be obtained by polymerization. For example, the monomers, initiator, solvent and dispersant are first mixed, and then a particulate matrix is ​​obtained through heterogeneous reaction under stirring; then a certain proportion of extractant and a small amount of long-chain alcohol are added; the above system is heated (60-100°C) and stirred for a certain time (greater than 12 h) to obtain the desired resin.

[0031] There are no particular limitations on the initiators, solvents, and dispersants used in the polymerization process; for example, those commonly used in the art can be used.

[0032] In some embodiments, terbium separation resin can be obtained by impregnation. For example, firstly, the extractant and long-chain alcohol are dissolved in a solvent (including but not limited to solvents such as benzene, cyclohexane, diethyl ether, and carbon tetrachloride). The resin matrix is ​​then added to the above system and thoroughly mixed. The solvent is then slowly evaporated under vacuum or non-vacuum conditions to obtain the desired resin.

[0033] In this application, DGA resin can be synthesized by impregnation using polyacrylic acid resin and polystyrene resin as carriers, respectively.

[0034] For example, a second extractant, such as N,N,N′,N′-tetraoctyl-3-oxopramethylenediamide, N,N,N′,N′-tetraisooctyl-3-oxopramethylenediamide, or N,N,N′,N′-tetramethyl-3-oxa-pentanediamide, is added to a solvent, followed by the addition of a support and the reaction proceeding to the DGA resin. Typically, the amount of the second extractant added is 40 wt% to 50 wt% of the total weight of the DGA resin, for example, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, 48 wt%, 49 wt%, or 50 wt% of the second extractant.

[0035] In one specific embodiment, the method of the present invention includes the following steps: The production of target materials includes adding natural gadolinium or high-abundance gadolinium-160 oxide or nitrate powder into a quartz tube, sealing it, and using it as an irradiation target; or adding natural gadolinium or high-abundance gadolinium-160 solution into a plastic tube, sealing it, and using it as an irradiation target. Reactor irradiation, which includes placing an irradiation target in the reactor for irradiation, with a reactor neutron flux ≥10 12 cm -2 ·s -1 Irradiation time ≥ 1 h; Radiochemical separation involves transferring the irradiated target to the radiochemical laboratory. For solid targets, 2–10 mL of HNO3 with a concentration of at least 2 mol / L is heated to dissolve the target at a hot plate temperature of 60–120°C. After dissolution, the medium is converted to 0.01–0.05 mol / L HNO3. For liquid targets, the medium is directly converted to 0.01–0.05 mol / L HNO3. The radiochemical separation process requires three chromatography columns. The first column has an aspect ratio ≥20 and a column volume of… V r The first column, with a gadolinium mass ratio of not less than 0.15 mL / mg, is filled with the terbium separation resin of this application; the second column, with an inner diameter of 5-10 mm and a height of not less than 5 mm, is filled with the DGA resin or N-type TODGA resin of this application (purchased from Trischem); the third column, with a height-to-diameter ratio ≥20, is filled with the terbium separation resin of this application. Column 1 is used for the coarse separation of terbium and, before use, is prepared with not less than 10... V r A 0.01–0.05 mol / L HNO3 equilibrium chromatography column was used. After loading the sample solution (stored in 0.01–0.05 mol / L HNO3) onto the column, 20–40 μL of solution was used. V r 0.4~0.6mol / L HNO3 and 10~20 V r 0.9~1.2 mol / L HNO3 was used to desorb gadolinium and terbium, respectively. Column-2 was used for media conversion of the terbium-containing desorption solution in Column-1. Before use, it was rinsed with at least 10 mol / L HNO3. V r A 1-2 mol / L HNO3 equilibrium chromatography column. The terbium-containing desorption solution obtained from column-1, i.e., 10-20% of column-1... V r The column is loaded with 1-2 mol / L HNO3 as the desorption buffer, and then terbium is desorbed with 2-8 mL of 0.05-1 mol / L HCl. Column-3 is used for terbium purification and should be used after at least 10 [units of time - missing in original text]. V r A 0.01–0.05 mol / L HNO3 equilibrium chromatography column was used. The terbium desorption solution obtained from column-2, i.e., 2–8 mL of 0.05–1 mol / L HCl desorption solution from column-2, was loaded onto the column, and then subjected to 10–30 mL of HCl solution. V r0.4~0.6mol / L HNO3 eluted gadolinium, 10~20 V r Terbium is desorbed using 0.9~1.2 mol / L HNO3. The desorption solution is the terbium-161 product.

[0036] Terbium-161 product identification. The chemical purity of the terbium-161 product was determined by mass spectrometry, and the nuclear purity of the terbium-161 product was determined by HPGe (γ) spectrometry.

[0037] In this invention, natural gadolinium or high-abundance gadolinium-160 is irradiated in a high-flux reactor through steps including target fabrication, reactor irradiation, chemical separation, and product identification, thereby generating gadolinium-161 and β-gadolinium via a thermal neutron capture reaction. - Terbium-161 is produced by decay. It is separated and purified twice using a self-developed terbium-161 special separation resin to remove lanthanide elements such as gadolinium, alkali metals such as sodium, alkaline earth elements such as calcium, and transition metal impurities such as iron, so as to obtain a high-purity terbium-161 product that meets the requirements for both radionuclear purity and radiochemical purity.

[0038] Compared with other separation methods, the specially formulated separation resin exhibits rapid adsorption kinetics, high selectivity, high specific activity of terbium-161, and low levels of radioactive waste. The entire process achieves a terbium-161 yield greater than 95% and a gadolinium decontamination factor greater than 10. 7 It has high industrial application value.

[0039] The present invention will be described in more detail below through embodiments. It should be understood that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially. The raw materials used in the embodiments are nuclear-grade raw materials.

[0040] Preparation Example 1: Synthesis of Terbium Separating Resin 1) Add 50 g of styrene, 0.5 g of benzoyl peroxide, 40 mL of toluene and 5 g of methylcellulose to 200 g of water.

[0041] 2) Then add 24 g P204, 12 g P507 and 0.1 g polyacrylol.

[0042] 3) Heat the above system to 80°C and stir for a certain time of 15 hours. Wash and dry the synthesized resin with acetone and ethanol to obtain the desired resin.

[0043] Preparation Example 2: Synthesis of Terbium Separating Resin 1) Add 50 g of styrene, 0.5 g of benzoyl peroxide, 40 mL of toluene, and 5 g of methylcellulose to 200 g of water. 2) Then add 12 g P204, 24 g P507 and 0.1 g polyacrylol.

[0044] 3) Heat the above system to 80°C and stir for a certain time of 15 hours. Wash and dry the synthesized resin with acetone and ethanol to obtain the desired resin.

[0045] Preparation Example 3: Synthesis of DGA Resin 1) Add 40 g of TODGA (tetraoctyl diethylene glycol amide) to 500 mL of methanol and stir until homogeneous. Add polyacrylic acid microspheres to the methanol solution and shake for 4 h.

[0046] 2) After filtering, washing, and drying the solution after the reaction, DGA resin is obtained.

[0047] Example 1 10 mg of natural gadolinium oxide powder was added to a quartz tube and sealed. It was then placed in a reactor for irradiation. The reactor neutron flux was 10... 12 cm -2 ·s -1 Irradiation time: 3 hours.

[0048] The irradiation target was transferred to the radiochemistry laboratory and disassembled. 2 mL of 2 mol / L HNO3 was added and heated to dissolve the target, with the hot plate temperature set to 80°C. After dissolution, the solution was evaporated to near dryness on the hot plate, and then 2 mL of 0.05 mol / L HNO3 was added. This process was repeated once to obtain the column loading solution for column 1.

[0049] The loading solution was added to the equilibrated column-1 (chromatographic column with an inner diameter of 4 mm and a height of 120 mm, packed with the terbium separation resin obtained in Preparation Example 1), and then gadolinium and terbium were desorbed sequentially with 45 mL of 0.4 mol / L HNO3 and 17 mL of 1.2 mol / L HNO3.

[0050] The terbium desorption solution from column 1 was added to the equilibrated column 2 (chromatographic column with an inner diameter of 8 mm and a height of 5 mm, packed with the DGA resin obtained in Preparation Example 3), and then the terbium was desorbed with 6 mL of 0.05 mol / L HCl.

[0051] The terbium desorption solution from column 2 was added to the equilibrated column 3 (chromatographic column with an inner diameter of 3 mm and a height of 90 mm, packed with the terbium separation resin obtained in Preparation Example 1). The terbium was then eluted and desorbed using 15 mL of 0.4 mol / L HNO3 and 6 mL of 1.2 mol / L HNO3, respectively. The desorption solution was the terbium-161 product.

[0052] Product identification. The total activity of terbium-161 in the column solution on column 1 was measured to be 2.42 × 10⁻⁶ using an HPGe (γ) spectrometer. 4 After chemical separation, the activity of terbium-161 in the desorption solution of column-3 was measured to be 2.36 × 10⁻⁶ using an HPGe (γ) spectrometer. 4 The chemical separation process yielded 97.5% of terbium-161.

[0053] Mass spectrometry measurements. The terbium concentration in the terbium-161 product is 111 ppb, the concentrations of Gd and Dy are 0.1 ppb, the total amount of other impurities is less than 0.5 ppb, and the chemical purity is greater than 99.4%.

[0054] A quantitative amount of 11.1 mg of terbium-161 product was added dropwise to the measuring pan to obtain a terbium-161 surface source. This source was then placed on a high-purity germanium gamma spectrometer for measurement. The resulting spectrum is shown in the appendix. Figure 2 The specific activity of the terbium-161 product is obtained according to Formula 1.

[0055]

[0056] in, A The specific activity of terbium-161 products is expressed in Bq / g. C η represents the count rate; η is the detection efficiency of the high-purity germanium gamma spectrometer, 2%. Y , where is the branching ratio, 10.2%; m is the sample mass during the preparation of the surface source, in g.

[0057] Figure 2 In the terbium-161 product spectrum, apart from the characteristic peak of terbium-161, no characteristic peaks of gadolinium-161 and dysprosium-159 were found. Based on the background, the nuclear purity of terbium-161 is calculated to be greater than 99.8%.

[0058] Although this disclosure has been described with reference to specific exemplary embodiments thereof, many different variations, modifications, etc. will become apparent to those skilled in the art.

[0059] By studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in the practice of this disclosure.

Claims

1. A method for preparing high-purity terbium-161, comprising: S1, after preparing an acid solution from the irradiated gadolinium target, it is loaded onto a first separation column, wherein the first separation column is filled with terbium separation resin; then the first separation column is eluted sequentially with 0.4~0.6 mol / L HNO3 and 0.9~1.2 mol / L HNO3 solutions to desorb gadolinium and terbium accordingly, to obtain a first gadolinium desorption solution and a first terbium desorption solution; S2, the first terbium desorption solution is loaded onto the second separation column, wherein the second separation column is filled with DGA resin; then the second separation column is eluted with 0.05~0.1 mol / L HCl solution to desorb terbium and obtain the second terbium desorption solution; S3, the second terbium desorption solution is loaded onto a third separation column, wherein the third separation column is filled with terbium separation resin; then the third separation column is eluted sequentially with 0.4~0.6 mol / L HNO3 and 0.9~1.2 mol / L HNO3 solutions to elute gadolinium and desorb terbium, thereby obtaining the high-purity terbium-161; The terbium separation resin comprises, based on the total weight of the terbium separation resin, 40 wt% to 50 wt% of a first extractant, 50 wt% to 60 wt% of a first resin matrix, and 0.01 wt% to 1 wt% of a long-chain alcohol; and The DGA resin comprises: 40 wt% to 50 wt% of a second extractant and 50 wt% to 60 wt% of a second resin matrix, based on the total weight of the DGA resin.

2. The method according to claim 1, wherein, The first extractant in the terbium separation resin is selected from one or more of the following: di(2-ethylhexyl) phosphate, mono(2-ethylhexyl)-2-ethylhexyl phosphonate, di(2-ethylhexyl)phosphonic acid, di-(2,4,4-trimethylpentyl) phosphate, di(2-ethylhexyl) monothiophosphate, di(2-ethylhexyl) dithiophosphate, mono(2-ethylhexyl)-2-ethylhexyl monothiophosphonate, and mono(2-ethylhexyl)-2-ethylhexyl dithiophosphonate.

3. The method according to claim 1 or 2, wherein, The long-chain alcohol in the terbium separation resin is selected from one or more of polyvinyl alcohol or polyacryl alcohol.

4. The method according to any one of claims 1 to 3, wherein, The resin matrix in the terbium separation resin is selected from one or more of polyacrylic acid, polystyrene, and polyethersulfone.

5. The method according to any one of claims 1 to 4, wherein, The terbium separation resin has a particle size of 50 μm to 100 μm and has mesoporous or macroporous pores.

6. The method according to any one of claims 1 to 5, wherein, The second extractant in the DGA resin includes, but is not limited to: N,N,N′,N′-tetraoctyl-3-oxoprandiamide, N,N,N′,N′-tetraisooctyl-3-oxoprandiamide, N,N,N′,N′-tetramethyl-3-oxa-pentandiamide; and / or the second resin matrix is ​​selected from resins based on polyacrylic acid, polystyrene, or polystyrene-divinylbenzene.

7. The method according to any one of claims 1 to 6, wherein, The first separation column has an aspect ratio of ≥20 and a column volume of not less than 0.15 mL / mg. V r The mass ratio to gadolinium.

8. The method according to any one of claims 1 to 7, wherein, The second separation column has an inner diameter of 5 to 10 mm and a height of not less than 5 mm.

9. The method according to any one of claims 1 to 8, wherein, The method further includes: Before using the first separation column, use no less than 10 V r The first separation column was equilibrated with 0.01~0.05 mol / L HNO3; Before using the second separation column, use no less than 10 V r The second separation column was equilibrated with 1-2 mol / L HNO3; Before using the third separation column, use no less than 10 V r The third separation column was equilibrated with 0.01~0.05 mol / L HNO3.

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