JP7567705B2 - Method for refining zirconium - Google Patents

Description

The present invention relates to a method for purifying zirconium.

Conventionally, radioactive zirconium is known to be an effective radioisotope for medical imaging. Therefore, there is a demand for the establishment of a method for producing and purifying radioactive zirconium. A known production method is a method in which a proton beam is irradiated onto an yttrium (Y) target. In a production method using a proton beam, a minute amount of radioactive zirconium of tens to hundreds of nanograms is produced in hundreds of milligrams of yttrium. A method using a chelating resin is known as a purification method for purifying radioactive zirconium from yttrium from which a minute amount of radioactive zirconium has been produced. For example, Non-Patent Document 1 describes a method for purifying radioactive zirconium from yttrium using a chelating resin having a hydroxamic acid group as a functional group (hereinafter, hydroxamic acid resin).

In the method for purifying radioactive zirconium using hydroxamic acid resin described in Non-Patent Document 1, the property of hydroxamic acid resin to form a strong chelate bond with polyvalent metal ions, particularly metal ions with a valence of 4 or more, is utilized. That is, hydroxamic acid resin is used for purifying zirconium ions by utilizing selectivity due to the difference in adsorption power between tetravalent zirconium ions and trivalent yttrium ions. Then, after dissolving the yttrium target in which radioactive zirconium is generated with hydrochloric acid, the obtained solution is passed through the hydroxamic acid resin, whereby the zirconium ions in the solution are selectively adsorbed by the hydroxamic acid resin. When washing water or an acidic solution is passed through the hydroxamic acid resin that has adsorbed and collected zirconium ions, and then an acidic solution such as an aqueous oxalic acid solution ((COOH) ₂ ) is passed through the hydroxamic acid resin, radioactive zirconium is eluted in the aqueous oxalic acid solution, and zirconium ( ⁸⁹ Zr) can be recovered. The hydroxamic acid resin used in Non-Patent Document 1 and the like can be produced by reacting a cation exchange resin having a carboxyl group with tetrafluorophenol or the like in the presence of a carbodiimide to form an active ester, separating the active ester by filtration, and then reacting it with hydroxylamine or the like.

Special table 2017-521645 publication

Jason P.Holland et al. “Standardized methods for the production of high specific-activity zirconium-89”, Nucl. Med. Biol., 2009, 36, 729-739. Lars R. Perk et al. “p-Isothiocyanatobenzyl-desferrioxamine: a new bifunctional chelate for facile radiolabeling of monoclonal antibodies with zirconium-89 for immuno-PET imaging”, European Journal of Nuclear Medicine and Molecular Imaging, 2010, 37, 250- 259.

However, the conventional method for purifying zirconium using a hydroxamic acid resin has a problem in that a large amount of an acid solution such as an aqueous oxalic acid solution is used when eluting radioactive zirconium ( ⁸⁹ Zr). Therefore, there has been a demand for the development of a method for purifying zirconium that can reduce the amount of the acid solution used when eluting radioactive zirconium.

The present invention has been made in view of the above, and its purpose is to provide a method for purifying zirconium that can reduce the amount of acidic solution used when eluting radioactive zirconium.

In order to solve the above-mentioned problems and achieve the object, a method for purifying zirconium according to one embodiment of the present invention includes an adsorption step in which a solution obtained by dissolving yttrium containing zirconium in an acidic dissolution solution is brought into contact with a resin having a cation exchange resin as a base material to selectively adsorb zirconium onto the resin, and a recovery step in which an acidic solution is passed through the resin after the adsorption step to obtain a recovery effluent containing a complex of zirconium ions, and the pore size of the resin is less than 30 nm.

In one aspect of the present invention, in the method for purifying zirconium, the cation exchange resin has a pore size of 10 nm or less.

The method for purifying zirconium according to one embodiment of the present invention includes, in the above invention, a washing step of washing the cation exchange resin after the adsorption step and before the recovery step.

In one embodiment of the method for purifying zirconium according to the present invention, the amount of the resin through which the acidic solution is passed is 10 mg or less.

In the method for purifying zirconium according to one embodiment of the present invention, in the above invention, the cation exchange resin is a hydroxamic acid resin. In this configuration, the method for purifying zirconium according to one embodiment of the present invention includes a reaction step in which a carboxyl group, which is an exchange group of the cation exchange resin, is reacted with hydroxylamine or hydroxylamine hydrochloride in the presence of a carbodiimide to form a hydroxamic acid group, and a separation step in which the cation exchange resin having the hydroxamic acid group and the reaction liquid containing a by-product derived from the carbodiimide are filtered and washed to separate and purify the cation exchange resin having the hydroxamic acid group, and the solvent used in the reaction step is an organic solvent that dissolves the carbodiimide and hydroxylamine or hydroxylamine hydrochloride and does not react with the carboxyl group.

The zirconium purification method of the present invention makes it possible to reduce the amount of acidic solution used when eluting radioactive zirconium.

FIG. 1 is a schematic diagram for explaining a method for purifying zirconium according to one embodiment of the present invention. FIG. 2 is a graph showing the elution rate of radioactive zirconium along a method for purifying zirconium using a hydroxamic acid resin according to one embodiment of the present invention. FIG. 3 is a graph showing the elution rate of radioactive zirconium along a method for purifying zirconium using a hydroxamic acid resin according to one embodiment of the present invention. FIG. 4 is a graph showing the elution rate of radioactive zirconium in accordance with a conventional method for purifying zirconium using a hydroxamic acid resin. FIG. 5 is a graph showing the elution rate of radioactive zirconium in accordance with a conventional method for purifying zirconium using a hydroxamic acid resin.

One embodiment of the present invention will be described below with reference to the drawings. Note that in all drawings of the following embodiment, the same or corresponding parts are given the same reference numerals. Furthermore, the present invention is not limited to the embodiment described below.

(Method for Producing First Hydroxamic Acid Resin)
First, the hydroxamic acid resin (R-C(=O)NHOH, R: resin base material) described in the above-mentioned Non-Patent Document 1 and other publications will be described. The hydroxamic acid resin is synthesized by reacting the carboxyl group of a commercially available weakly acidic ion exchange resin (R-C(=O)OH, R: resin base material) with hydroxylamine (H ₂ N-OH). Specifically, the hydroxamic acid resin can be synthesized by a two-step reaction according to the following reaction formulas (1) and (2).

In the first reaction shown in reaction formula (1), a weakly acidic cation exchange resin is reacted with tetrafluorophenol in an aqueous solution in the presence of a carbodiimide (R1-N=C=N-R2) to convert the carboxyl group of the weakly acidic cation exchange resin into an active ester. The carbodiimide promotes the conversion of the carboxyl group into an active ester.

After the first reaction, the weakly acidic cation exchange resin that has been converted into an active ester is filtered and washed in order to separate the by-product derived from the carbodiimide, and then the second reaction shown in reaction formula (2) is carried out. The second reaction is a reaction in which the weakly acidic cation exchange resin that has been converted into an active ester is reacted with hydroxylamine to form a hydroxamic acid group. After the second reaction, the hydroxamic acid resin is filtered and washed.

In the above-mentioned method for synthesizing the first hydroxamic acid resin, the first and second reactions are carried out in an aqueous solution, in which case the reaction intermediate may react with water and be deactivated, as shown in the following reaction formulas (3) and (4).

(Method for Producing Second Hydroxamic Acid Resin)
Therefore, the present inventors have conducted extensive research to reduce the amount of materials required for the reaction, and have further devised a method for producing hydroxamic acid resins. That is, the method for producing hydroxamic acid resins devised by the present inventors includes a reaction step and a separation step. In the reaction step, a carboxyl group, which is an exchange group of a cation exchange resin, is reacted with hydroxylamine or hydroxylamine hydrochloride in the presence of a carbodiimide to form a hydroxamic acid group. The solvent used in the reaction step is an organic solvent that dissolves carbodiimide and hydroxylamine or hydroxylamine hydrochloride, but does not react with these substances. In the separation step, the reaction solution containing the cation exchange resin having a hydroxamic acid group and a by-product derived from the carbodiimide is filtered and washed to separate and purify the cation exchange resin having a hydroxamic acid group. Here, the cation exchange resin may be any one having a carboxyl group as an exchange group, and either an acrylic acid type or a methacrylic acid type can be used. Specific examples of cation exchange resins that can be used include Accell plus CM (Waters) and CBA resin (GL Sciences).

Any type of carbodiimide (R1-N=C=N-R2) may be used as long as it dissolves in the organic solvent described below. R1 and R2 may be the same or different and are an alkyl group having 1 to 5 carbon atoms, which may have a substituent, a cycloalkyl group having 3 to 8 carbon atoms, which may have a substituent, or an aryl group, which may have a substituent. Examples of such carbodiimides include 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, dicyclohexylcarbodiimide, diisopropylcarbodiimide, N-[3-(dimethylamino)propyl]-N-ethylcarbodiimide, N-tert-butyl-N-ethylcarbodiimide, N-cyclohexyl-N-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate, N,N-di-tert-butylcarbodiimide, and N,N-di-p-tolylcarbodiimide.

The solvent may be any organic solvent that dissolves carbodiimide and hydroxylamine or hydroxylamine hydrochloride and does not react with carboxyl groups. The solvent used is a polar, aprotic solvent that does not have a hydroxyl group, primary amino group, or secondary amino group that reacts with carboxyl groups. Examples of the solvent include N,N-dimethylformamide (DMF), dimethyl sulfoxide, tetrahydrofuran, acetone, and acetonitrile.

The process for producing the hydroxamic acid resin proposed by the present inventors is carried out according to the steps shown in reaction formula (5).

A cation exchange resin having carboxyl groups as exchange groups (weakly acidic cation exchange resin) is added to an organic solvent and suspended. A carbodiimide is added to the solvent in which the cation exchange resin is suspended, and then hydroxylamine or hydroxylamine hydrochloride is added. The mixture is stirred for about an hour to convert the carboxyl groups to hydroxylamids. Even when hydroxylamine hydrochloride is used, it is not necessary to add a base.

In the reaction of the above-mentioned reaction formula (5), it is preferable to add 1.1 to 3 equivalents of carbodiimide and 1.1 to 3 equivalents of hydroxylamine or hydroxylamine hydrochloride per equivalent of carboxyl group of the cation exchange resin. In this embodiment, since water is not used as a solvent, it is not necessary to add excess amounts of carbodiimide and hydroxylamine, and hydroxamic acid resin can be obtained at low cost. In addition, in the above-mentioned reaction formula (5), the cation exchange resin having a carboxyl group can be reacted with hydroxylamine in one step. This reduces the effort required for the reaction, and since the product is a resin, it can be separated from by-products such as by-products derived from carbodiimide by filtration.

The method for producing hydroxamic acid resin devised by the present inventor does not require pH adjustment. The present inventor compared the products produced in a system in which 1 equivalent of N,N-diisopropylethylamine was added to hydroxylamine hydrochloride with those in which it was not added, and found no difference between the two. The hydroxamic acid resin produced by this method does not use metal ions in the production process, so it can adsorb zirconium ions without regeneration treatment, and can separate zirconium ions from a solution containing zirconium ions and yttrium ions.

(Method of refining zirconium)
Next, a method for purifying zirconium according to an embodiment of the present invention will be described. First, in order to facilitate understanding of the present invention, the intensive studies conducted by the present inventors will be described.

According to the findings of the present inventors, the conventional zirconium purification method has a problem in that a large amount of oxalic acid ((COOH) ₂ ) is used as an acidic solution for elution in the elution step of eluting radioactive zirconium. Specifically, in Non-Patent Document 1, the amount of oxalic acid used to elute zirconium-89 (hereinafter, ^89Zr ) was about 3 mL.

On the other hand, when labeling a molecule such as an antibody with ⁸⁹ Zr, the upper limit of the amount of oxalic acid solution containing ⁸⁹ Zr used was about 200 μL per batch. In this case, as described in Non-Patent Document 1, the amount of usable ⁸⁹ Zr in the purified ⁸⁹ Zr was about 1/15 (about 6%) of the total amount (200/3000=). That is, in the conventional zirconium purification method described in Non-Patent Document 1, when labeling a molecule such as an antibody with ⁸⁹ Zr, if the amount of labeled antibody produced is small, only a part of the produced ⁸⁹ Zr, about 1/15 (about 6%), could be used, and the remaining 14/15 (about 94%) of the produced ⁸⁹ Zr had to be discarded.

In order to solve the above-mentioned problems of the prior art, the present inventor has devised a method for reducing the amount of hydroxamic acid resin used in the purification column for purifying zirconium. This makes it possible to elute ⁸⁹ Zr using a smaller amount of oxalic acid than before, and optimizes the purification conditions. The present inventor has conducted experiments and conducted extensive research and found that ⁸⁹ Zr can be sufficiently adsorbed even when the amount of hydroxamic acid resin used is about 10 mg. According to the manufacturer of the purification column, if the amount of hydroxamic acid resin used is less than 10 mg, it becomes difficult to pack the hydroxamic acid resin approximately uniformly in the purification column. Therefore, the amount of hydroxamic acid resin packed or used is about 10 mg, which can be said to be the lower limit at which the hydroxamic acid resin can be approximately uniformly packed in the packed column.

However, the inventors' experiments revealed that even when the purification column is packed with a hydroxamic acid resin having a mass of about 10 mg, the amount of oxalic acid solution used must be about 400 μL in order to achieve a recovery rate of ⁸⁹ Zr of 90% or more. Based on the inventors' studies, it is considered difficult to reduce the amount of elution solution used to elute ⁸⁹ Zr by only optimizing the purification conditions of zirconium as described above.

Therefore, the present inventor further conducted intensive research. The present inventor assumed that in a hydrochloric acid solution, ⁸⁹ Zr has a structure in which it is coordinated with relatively small molecules such as hydroxide ions (OH ^- ) and water molecules (H ₂ O). Based on this assumption, the present inventor considered that ^{89 Zr in a hydrochloric acid solution is adsorbed to a hydroxamic acid resin regardless of the pore size of the resin. The pore size of the resin is the average pore size. On the other hand, when an oxalic acid solution is passed through a purification column, 89 Zr} is desorbed from the hydroxamic acid resin by coordination with oxalic acid and eluted from the purification column. At the same time, a reaction in which ⁸⁹ Zr is adsorbed again to the hydroxamic acid resin is also considered. In this way, it is considered that a larger amount of oxalic acid solution is required in the elution process of ⁸⁹ Zr compared to the hydrochloric acid solution, as ⁸⁹ Zr is adsorbed and desorbed from the purification column repeatedly or in parallel with respect to the purification column.

Now, since oxalic acid ((COOH) ₂ ) is a bulky molecule compared to hydroxide ions (OH ^- ) and water molecules (H ₂ O), it coordinates with zirconium ions by four ions to form [Zr(C ₂ O ₄ ) ₄ ] ^4- . Furthermore, since it is assumed that hydrogen ions (H ⁺ ) and water molecules (H ₂ O) are further coordinated around it to neutralize the charge, it is considered that the molecular size of the zirconium oxalate complex is relatively large. Therefore, when the pore size of the resin used for purification such as hydroxamic acid resin (hereinafter referred to as purification resin) is small, ⁸⁹ Zr in the state of being coordinated with oxalic acid cannot enter the inside of the pores of the resin again and is not re-adsorbed to the purification resin. It is considered that ⁸⁹ Zr can be eluted even with a small amount of oxalic acid solution. In other words, the inventors hypothesized that when a purification resin with a small pore size is used, ⁸⁹ Zr forms a complex with a relatively large molecular size, resulting in an effect similar to size exclusion chromatography, and the ⁸⁹ Zr-oxalate complex is rapidly excluded from the purification resin.

Based on the above-mentioned intensive studies, the present inventor has devised a method for purifying zirconium by using an ion exchange resin having a relatively small pore size as a base material for a purification resin such as a hydroxamic acid resin. In the ion exchange resin, ion exchange is not only performed on the apparent surface, but also inside the pores of the resin. In the prior art, a hydroxamic acid resin is used as a purification resin, which is made of an ion exchange resin having pores with a pore size of about 30 nm as a base material. In contrast, it has been confirmed that by using the purification resin devised by the present inventor, which has a smaller pore size than the conventional one, ⁸⁹ Zr can be recovered at a high recovery rate even with a smaller amount of oxalic acid solution. The present invention has been devised by the present inventor through the above-mentioned intensive studies.

The method for purifying zirconium devised by the inventor described above will now be described. In this embodiment, the second hydroxamic acid resin described above is used as the hydroxamic acid resin used as the purification resin. Figure 1 is a schematic diagram for explaining the method for purifying zirconium according to this embodiment.

As shown in FIG. 1, first, a yttrium target 1 of ⁸⁹ Y in which radioactive zirconium ( ⁸⁹ Zr: hereinafter, zirconium or Zr) (not shown) is generated inside by proton irradiation is prepared. In the dissolution process, the yttrium target 1 in which Zr is generated is dissolved by an acidic dissolution solution 3 in a dissolution tank 2 to prepare a solution. Here, hydrochloric acid (HCl) having a hydrogen ion concentration of, for example, 0.5 mol/L or more and 2.0 mol/L or less is used as the acidic dissolution solution 3. In addition, when using, for example, 0.33 g (330 mg), the yttrium target 1 may be dissolved in about 2 mL of the acidic dissolution solution 3. In addition, in addition to hydrochloric acid, an aqueous solution of nitric acid (HNO ₃ ) or sulfuric acid (H ₂ SO ₄ ) may be used.

In the adsorption process, the solution obtained in the dissolution process is passed through a resin column 5 serving as a chelating resin container filled with the hydroxamic acid resin 4 described above, which is used as a purification column. The hydroxamic acid resin 4 is the second hydroxamic acid resin described above, and the cation exchange resin is a resin having a pore size of less than 30 nm, preferably a resin having a pore size of 10 nm or less, specifically, a CBA resin (manufactured by GL Sciences) having a pore size of 6 nm, for example.

The resin column 5 is configured so that various solutions can be passed through it and then discharged from the drain port 5a. The solution comes into contact with the hydroxamic acid resin 4, and the zirconium ions (Zr ⁴⁺ ) are adsorbed by the hydroxamic acid resin 4, and then discharged from the drain port 5a. The equilibrium distribution coefficient of the zirconium ions (Zr ⁴⁺ ) to the hydroxamic acid resin 4 is larger than that of yttrium (Y), specifically, for example, in 1 mol/L hydrochloric acid, the equilibrium distribution coefficient of zirconium (Zr) is 10 ^4.6 , while that of yttrium (Y) is 10 ^−0.2 . Therefore, the zirconium ions (Zr ⁴⁺ ) are selectively adsorbed to the hydroxamic acid resin 4.

In the washing step, for example, an acidic washing solution is passed through the resin column 5. This washes away impurities such as yttrium and the acidic dissolution solution adhering to the inner walls of the resin column 5 and the hydroxamic acid resin 4, and the solution is discharged as a passing liquid from the drain port 5a. Here, for example, hydrochloric acid with a hydrogen ion concentration of 0.5 mol/L to 2.0 mol/L and water are used as the acidic washing solution. The washing step can be appropriately changed depending on the concentration of the acidic dissolution solution and the acidic washing solution used. Here, in the washing step, it is preferable to wash using an acidic washing solution in a range of 1 to 10 times the amount of the dissolution solution.

In the recovery process, the recovered acidic liquid is passed through the resin column 5 as an acidic solution. As a result, the zirconium ions adsorbed on the hydroxamic acid resin 4 are eluted into the recovered acidic liquid. The recovered acidic liquid containing zirconium is discharged from the drain port 5a. Here, the recovered acidic liquid may be an organic acid aqueous solution having two or more carboxyl groups, specifically, for example, oxalic acid or citric acid. For example, the recovered acidic liquid may be an oxalic acid aqueous solution having a concentration of 0.1 mol/L or more and 1 mol/L or less. In addition, the pH of the recovered acidic liquid is preferably 1 or more and 7 or less.

(Example)
Next, an example based on the above-mentioned embodiment and a comparative example for explaining the effect of the example will be described. The hydroxamic acid resin used in this example is manufactured as follows. That is, 1 g of a cation exchange resin made of a CBA resin (manufactured by GL Sciences) having a pore size of 6 nm and having a carboxyl group as an exchange group is added to 10 mL of dimethylformamide and suspended by stirring. 85 mg of 1-ethyl-3-(3-dimethylamidopropyl)carbodiimide hydrochloride (1.2 equivalents) is added to the solvent in which the cation exchange resin is suspended, and further 31 mg of hydroxylamine hydrochloride (1.2 equivalents) is added, and the mixture is stirred at room temperature for 2 hours. Thereafter, the reaction solution containing the cation exchange resin is filtered with filter paper, washed with 30 mL of pure water, and dried overnight in a desiccator to manufacture a hydroxamic acid resin.

On the other hand, a proton beam was irradiated onto an yttrium target 1 (yttrium foil) having a mass of, for example, about 0.33 g to generate ⁸⁹ Zr, which was then dissolved in hydrochloric acid having a volume of 2 mL and a concentration of 2 mol/L (dissolution step). The solution in which ⁸⁹ Zr was dissolved in hydrochloric acid was passed through a resin column 5 packed with 10 mg of a second hydroxamic acid resin (adsorption step). Here, adsorption of 99% or more of ⁸⁹ Zr was confirmed. The adsorption of ⁸⁹ Zr to the hydroxamic acid resin was calculated from the ratio of radioactivity by measuring the radioactivity of ⁸⁹ Zr dissolved in the liquid phase and ⁸⁹ Zr adsorbed in the resin phase at the stage where the liquid phase and the resin phase reached adsorption equilibrium.

(First embodiment)
In the above manner, with ⁸⁹ Zr adsorbed on the second hydroxamic acid resin packed in the resin column 5, hydrochloric acid with a volume of 10 mL and a concentration of 2.0 mol/L and water with a volume of 10 mL were passed through the resin column 5 in sequence to wash the resin column 5 (washing step). Then, oxalic acid with a volume of 100 μL (0.1 mL) and a concentration of 1 mol/L was passed through at least once, in this embodiment, 10 times, as a recovery acidic liquid, to recover the recovery effluents from which ⁸⁹ Zr had been eluted (recovery step). The ratios of radioactivity of ⁸⁹ Zr contained in the target dissolution solution obtained in the dissolution step, the hydrochloric acid and water obtained in the washing step, and the respective recovery effluents according to the first embodiment are shown in FIG. 2.

2, it can be seen that in the present embodiment, about 90% of ^{the 89} Zr can be recovered at the stage where the recovered acidic solution is passed once through the resin column 5. In other words, it can be seen that about 90% of ^{the 89} Zr can be recovered by using only 100 μL of the recovered acidic solution.

Second Example
The second embodiment is similar to the first embodiment except that the amount of hydroxamic acid resin packed in the resin column 5 was 100 mg. The ratios of the radioactivity of ^89Zr contained in the target dissolution solution obtained in the dissolution step, the hydrochloric acid and water obtained in the washing step, and the respective recovered effluents in the second embodiment are shown in Figure 3.

3, it can be seen that in Example 2, about 90% of ^{the 89} Zr can be recovered at the stage where the recovery acidic solution was passed through seven times. In other words, it can be seen that about 90% of ^{the 89} Zr can be recovered by using 700 μL of the recovery acidic solution.

Comparative Example
Next, a comparative example will be described to explain the effects of the above-mentioned examples. In the comparative example, the first hydroxamic acid resin produced by the method described in Non-Patent Document 1 is used as the hydroxamic acid resin. In addition, Accell plus CM (manufactured by Waters) with a pore size of 30 nm is used as the cation exchange resin serving as the base material.

(First Comparative Example)
In the first comparative example, the resin packed in the resin column 5 was the first hydroxamic acid resin, the amount packed was 10 mg, the same as in Example 1, and the dissolution step, adsorption step, washing step, and recovery step were also the same as in Example 1. The ratio of the radioactivity of ^89Zr contained in the target dissolution solution, hydrochloric acid, and water, and the respective recovered effluents, is shown in Figure 4.

4, it can be seen that in the first comparative example, about 90% of ^{the 89} Zr can be recovered at the stage where the recovered acidic solution was passed through four times. In other words, it can be seen that about 90% of ^{the 89} Zr can be recovered by using 400 μL of the recovered acidic solution.

(Second Comparative Example)
In the second comparative example, the resin packed in the resin column 5 was the first hydroxamic acid resin, the amount packed was 100 mg, the same as in the second embodiment, and the dissolution step, adsorption step, washing step, and recovery step were the same as in the first and second embodiments. The ratios of the radioactivity of ^89Zr contained in the target dissolution solution, hydrochloric acid, and water, and the respective recovered effluents are shown in Figure 5.

5, it can be seen that in the second comparative example, about 90% of ^{the 89} Zr can be recovered at the stage where the recovered acidic solution was passed nine times. In other words, it can be seen that about 90% of ^{the 89} Zr can be recovered by using 900 μL of the recovered acidic solution.

Comparing the first embodiment and the first comparative example, it can be seen that the amount of recovered acidic liquid required to achieve a recovery rate of approximately 90% can be reduced by a factor of four, from 400 μL to 100 μL, in the first embodiment using a hydroxamic acid resin with a pore diameter of 6 nm, compared to the first comparative example using a hydroxamic acid resin with a pore diameter of 30 nm. In other words, it can be seen that the amount of recovered acidic liquid used can be reduced by reducing the pore diameter of the hydroxamic acid resin to 6 nm or less, which is less than 30 nm.

In addition, when comparing the second embodiment with the second comparative example, it can be seen that the amount of recovered acidic liquid required to achieve a recovery rate of approximately 90% can be reduced from 900 μL to 700 μL, or 7/9, in the case of the second embodiment using a hydroxamic acid resin with a pore diameter of 6 nm, compared to the second comparative example using a hydroxamic acid resin with a pore diameter of 30 nm. In other words, it can be seen that the amount of recovered acidic liquid used can be reduced by setting the pore diameter of the hydroxamic acid resin to 6 nm or less, which is less than 30 nm.

Furthermore, comparing the first and second embodiments, it can be seen that in the first embodiment, in which the amount of resin, such as hydroxamic acid resin, packed into the resin column 5 is 100 mg, the amount of recovery acidic liquid required to achieve a recovery rate of approximately 90% can be reduced to 1/7, from 700 μL to 100 μL, in comparison with the second embodiment, in which the amount of resin, such as hydroxamic acid resin, packed into the resin column 5 is 100 mg. In other words, it can be seen that the amount of recovery acidic liquid used can be further reduced by setting the amount of hydroxamic acid resin packed into the resin column 5 to 10 mg, which is less than 100 mg.

According to the embodiment described above, by setting the pore size of the resin that adsorbs zirconium ions to less than 30 nm, 10 nm or less, for example 6 nm or less, the amount of acidic solution such as oxalic acid solution used as the recovery acidic liquid passed through to recover zirconium can be reduced, and the amount of acidic solution used when eluting radioactive zirconium from the resin to which radioactive zirconium has been adsorbed can be reduced. Furthermore, by setting the amount of resin used to 10 mg or less, the amount of acidic solution used as the recovery acidic liquid can also be reduced.

Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical concept of the present invention are possible. For example, the numerical values given in the above-described embodiment are merely examples, and numerical values different from these may be used as necessary, and the present invention is not limited by the description and drawings that form part of the disclosure of the present invention according to this embodiment.

For example, in the embodiment described above, an aqueous solution of oxalic acid is used as the recovery acidic liquid in the recovery process, but this is not necessarily limited to an aqueous solution of oxalic acid. For example, an aqueous solution of an organic acid having two or more carboxyl groups, such as dicarboxylic acid (HOOC-R-COOH, where R is a divalent substituent) or ethylenediaminetetraacetic acid (EDTA), can also be used.

1 Yttrium target 2 Dissolution tank 3 Acid solution for dissolution 4 Hydroxamic acid resin 5 Resin column 5a Drain

Claims (5)

an adsorption step of contacting a solution obtained by dissolving yttrium containing zirconium in an acidic solution with a resin having a cation exchange resin as a base material to selectively adsorb zirconium onto the resin;
and a recovery step of passing an acidic solution through the resin after the adsorption step to obtain a recovery filtrate containing a zirconium ion complex,
The method for purifying zirconium, wherein the cation exchange resin has a pore size of 10 nm or less . The method for purifying zirconium according to claim 1 , further comprising a washing step of washing the cation exchange resin after the adsorption step and before the recovery step. The method for purifying zirconium according to claim 1 or 2 , wherein the amount of the resin through which the acidic solution is passed is 10 mg or less. The method for purifying zirconium according to any one of claims 1 to 3 , wherein the cation exchange resin is a hydroxamic acid resin. The hydroxamic acid resin is
5. The method for purifying zirconium according to claim 4, comprising: a reaction step of reacting a carboxyl group, which is an exchange group of a cation exchange resin, with hydroxylamine or hydroxylamine hydrochloride in a solvent in the presence of a carbodiimide contained in the solvent to form a hydroxamic acid group; and a separation step of filtering and washing the reaction liquid containing the cation exchange resin having the hydroxamic acid group and a by-product derived from the carbodiimide to separate and purify the cation exchange resin having the hydroxamic acid group, wherein the solvent used in the reaction step is an organic solvent that dissolves the carbodiimide and hydroxylamine or hydroxylamine hydrochloride and does not react with the carboxyl group.

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