JP7124685B2 - Zirconium refining method and zirconium refining apparatus - Google Patents

Description

The present invention relates to a zirconium refining method and a zirconium refining apparatus for separating and refining radioactive zirconium produced in yttrium from yttrium.

Radioactive zirconium is conventionally known to be an effective radioisotope for medical imaging. Therefore, establishment of methods for producing and purifying radioactive zirconium is required. As a manufacturing method, a method of irradiating a yttrium (Y) target with a proton beam is known. In the manufacturing method using a proton beam, a minute amount of radioactive zirconium of several tens to several hundred nanograms is generated in several hundred milligrams of yttrium. As a purification method for purifying radioactive zirconium from yttrium in which a trace amount of radioactive zirconium is produced, a method using a chelate resin is known. For example, Non-Patent Document 1 describes a method for purifying radioactive zirconium from yttrium using a chelate resin having a hydroxamic acid group as a functional group (hereinafter referred to as hydroxamic acid resin).

The method for purifying radioactive zirconium using a hydroxamic acid resin described in Non-Patent Document 1 utilizes the property of the hydroxamic acid resin to form a strong chelate bond with tetravalent or higher metal ions. That is, the hydroxamic acid resin collects tetravalent zirconium ions, but hardly collects trivalent yttrium ions. Therefore, after dissolving the yttrium target in which radioactive zirconium is generated with hydrochloric acid, the obtained solution is passed through the hydroxamic acid resin, and the zirconium ions in the solution are adsorbed to the hydroxamic acid resin. When an acidic cleaning solution is passed through hydroxamic acid resin that has adsorbed and collected zirconium ions, and then an aqueous oxalic acid solution ((COOH) ₂ ) is passed through it, zirconium is eluted into the aqueous oxalic acid solution. can be recovered. It is also possible to remove oxalic acid from an oxalic acid solution in which zirconium is dissolved using an anion exchange resin. Furthermore, in Patent Document 1, a compound having a hydroxamic acid group capable of selectively capturing high-valence metal ions having a valence of 3 or more such as zirconium (Zr ⁴⁺ ) even under acidic conditions is introduced into a carrier. A scavenger is disclosed comprising:

Japanese Patent No. 5439691

Jason P. Holland et al. “Standardized methods for the production of high specific-activity zirconium-89”, Nucl. Med. Biol., 2009, Oct, 36, 729-739. Yoshiaki Furusho et al., "Solid Phase Extraction Separating Agents for Inorganic Analysis and Their Applications", Analytical Chemistry, Vol.57, No.12, pp.969-989(2008).

The oxalic acid aqueous solution for recovering zirconium has a low solubility of oxalic acid, which is a solute, in water. Therefore, oxalic acid precipitates due to fluctuations in temperature and pH, and there is a risk of clogging the tubes and valves of the refiner. Since acids other than oxalic acid cannot dissociate and elute silconium from hydroxamic acid, it is necessary to strictly control the concentration of oxalic acid.

On the other hand, as a method for extracting zirconium using a chelate resin other than hydroxamic acid resin, a method using iminodiacetic acid resin is known (see, for example, Non-Patent Document 2). Although it has been shown that the iminodiacetic acid resin forms a complex with zirconium in the range of 9, no investigation has been made on a method for recovering zirconium, that is, a method for eluting zirconium from the iminodiacetic acid resin.

The present invention has been made in view of the above. An object of the present invention is to provide a zirconium refining method and refining apparatus capable of recovering a refining liquid containing pure zirconium.

In order to solve the above-described problems and achieve the object, the method for purifying zirconium according to the present invention includes a dissolving step of dissolving zirconium and yttrium in an acidic solution for dissolution to prepare a solution; An adsorption step of selectively adsorbing zirconium ions (Zr ⁴⁺ ) to the iminodiacetic acid resin by bringing it into contact with the iminodiacetic acid resin, and after the adsorption step, passing an acidic washing solution through the iminodiacetic acid resin. and a recovery step of passing a recovered acidic solution through the iminodiacetic acid resin after the cleaning step to obtain a purified liquid containing the zirconium ions (Zr ⁴⁺ ). do.

The method for purifying zirconium according to the present invention is characterized in that, in the above invention, the acid solution for dissolution has a hydrogen ion concentration of 0.1 mol/L or more and 1 mol/L or less.

The method for purifying zirconium according to the present invention is characterized in that, in the above invention, the recovered acidic solution has a hydrogen ion concentration of 3 mol/L or more and 8 mol/L or less.

The method for purifying zirconium according to the present invention comprises: a dissolution tank for obtaining a solution by dissolving zirconium and yttrium in an acidic solution for dissolution; and an acidic solution storage tank for storing the acidic solution for dissolution. a cleaning acidic solution storage tank for storing the cleaning acidic solution; a recovered acidic solution storage tank for storing the recovered acidic solution; a chelate resin container filled with iminodiacetic acid resin; It is possible to supply an acidic solution for dissolution and to selectively supply the solution, the acidic solution for washing, or the acidic recovery solution to the chelate resin container, and the solution discharged from the chelate resin container, the and a piping system capable of discharging the acidic cleaning solution or the recovered acidic solution.

According to the method and apparatus for purifying zirconium according to the present invention, when zirconium is separated and purified from yttrium, precipitation of solids caused by the recovered acidic solution can be prevented, and the purified zirconium containing high-purity zirconium can be prevented. It becomes possible to recover the liquid.

FIG. 1 is a diagram showing the relationship between the distribution coefficient of zirconium to iminodiacetic acid resin and the concentration of hydrochloric acid according to the embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the zirconium refining method according to the embodiment of the present invention. FIG. 3 is a block diagram for explaining a zirconium refiner according to an embodiment of the present invention. FIG. 4 is a schematic diagram for explaining a method for purifying zirconium using a hydroxamic acid resin according to the prior art. FIG. 5 is a diagram showing the relation between the distribution coefficient of zirconium to hydroxamic acid resin and the concentration of hydrochloric acid according to the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings of the following embodiments, the same reference numerals are given to the same or corresponding parts. Moreover, the present invention is not limited to the embodiments described below.

First, before describing the embodiments of the present invention, experiments and intensive studies conducted by the inventors to solve the above problems will be described in order to facilitate understanding of the present invention.

First, a conventional method for purifying zirconium (see Non-Patent Document 1), which has been the subject of intensive studies by the present inventors, will be described. FIG. 4 is a schematic diagram for explaining a method for purifying zirconium using a hydroxamic acid resin according to the prior art. As shown in FIG. 4, in the conventional method for refining zirconium, a target dissolving step, an adsorption step, a washing step, and a recovery step are sequentially performed.

First, an ⁸⁹ Y yttrium target 100 in which radioactive zirconium ( ⁸⁹ Zr: hereinafter referred to as zirconium or Zr) (not shown) is generated by proton beam irradiation is prepared. Next, in the target dissolving step, the yttrium target 100 is dissolved in the dissolving tank 101 using the acidic solution 102 . Here, the mass of the yttrium target 100 is, for example, 0.33 g (330 mg), and as the acid solution 102, hydrochloric acid (HCl) with a concentration of 6 mol/L and a volume of 2 mL is used.

Next, in a conventional adsorption step, a solution in which the yttrium target 100 in which Zr is generated is dissolved is added to a resin column 104 filled with a chelate resin (hereinafter referred to as hydroxamic acid resin) 103 having a hydroxamic acid group as a functional group. permeate the In the conventional adsorption step, the solution contacts the hydroxamic acid resin 103 and the zirconium in the solution is adsorbed to the hydroxamic acid resin 103 . After zirconium is adsorbed on the hydroxamic acid resin 103, the solution is discharged from the drain port 104a as a passing liquid.

Next, in the conventional washing process, an acidic solution as an acidic solution for washing and pure water are sequentially passed through the resin column 104 . As a result, impurities such as yttrium and acid solution adhering to the inner wall of the resin column 104 and the hydroxamic acid resin 103 are washed and discharged from the discharge port 104a as a passing liquid. Here, as the acid solution, for example, hydrochloric acid with a concentration of 2 mol/L and a volume of 10 mL is used, and the volume of pure water is, for example, 10 mL.

Next, in the conventional recovery process, the recovered acidic solution used as the recovered acidic solution is passed through the resin column 104 . As a result, the zirconium adsorbed on the hydroxamic acid resin 103 is desorbed and eluted into the recovered acidic solution. The recovered acidic solution in which the zirconium has been eluted is discharged from the drainage port 104a as a recovery passing liquid and recovered. Here, as the recovered acidic solution, for example, an oxalic acid aqueous solution ((COOH) ₂ ) having a concentration of 1 mol/L and a volume of 3 mL is used.

In the above recovery step, the solubility in water of oxalic acid used as the recovered acidic solution is 10.2 g/100 cm ³ (102 g/L) at 20° C., and the molar mass of oxalic acid is 90 g. In the 1 mol/L oxalic acid aqueous solution used in the recovery process, oxalic acid precipitates due to changes in temperature and concentration, and there is a risk of clogging tubes and valves in the refining equipment. and strict control of concentration is required. It is conceivable to use acids other than oxalic acid as the recovered acidic solution, but since the bond between hydroxamic acid resin and zirconium is very strong, other acids such as hydrochloric acid can be used at low concentrations ( From 0.01 mol/L) to high concentrations (10 mol/L), zirconium can hardly be eluted from the hydroxamic acid resin because the partition coefficient K _d is much larger than 10 ³ .

Therefore, the present inventor investigated whether it is possible to separate yttrium and zirconium using iminodiacetic acid resin, which is generally used for separating metals. Non-Patent Document 2 discloses that iminodiacetic acid resin forms a complex with zirconium in the pH range of 1 to 9, and yttrium forms a complex in the pH range of 2 to 9, but the complex is difficult to form at pH 1. It is

Therefore, it is presumed that by dissolving yttrium and zirconium in an acidic solution for dissolution of pH 1 and passing this solution through the iminodiacetic acid resin, zirconium can be selectively adsorbed on the iminodiacetic acid resin.

However, Non-Patent Document 2 does not disclose any conditions for decomposing the complex of iminodiacetic acid resin and zirconium. Therefore, the present inventors have made intensive studies on the desorption method of zirconium adsorbed on iminodiacetic acid resin. can be recovered, leading to the completion of the present invention.

Next, an embodiment of the invention will be described. FIG. 1 is a diagram showing the relationship between the distribution coefficient of zirconium to iminodiacetic acid resin and the concentration of hydrochloric acid according to the embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the zirconium refining method according to the embodiment of the present invention.
A method for measuring the partition coefficient _Kd in FIG. 1 will be described. 0.1 g of iminodiacetic acid resin (ME-1, manufactured by GL Sciences) was placed in a 15 mL plastic tube, and 10 mL of a hydrochloric acid solution of a predetermined concentration containing ⁸⁹ Zr was added. Stir with a tube shaker for 1 hour or more, and when adsorption equilibrium was reached between the liquid phase and the resin phase, the radioactivity of ⁸⁹ Zr dissolved in the liquid phase and ⁸⁹ Zr adsorbed to the resin phase was measured. . Then, the partition coefficient _Kd was determined from the radioactivity ratio. This experiment was carried out at different hydrochloric acid concentrations and summarized in FIG.

A method for purifying zirconium according to an embodiment of the present invention comprises a dissolving step of dissolving zirconium and yttrium in an acidic solution for dissolution to prepare a solution; an adsorption step of selectively adsorbing ions (Zr ⁴⁺ ) to the iminodiacetic acid resin; a cleaning step of passing an acidic cleaning solution through the iminodiacetic acid resin after the adsorption step to clean the iminodiacetic acid resin; and a recovery step of passing a recovered acidic solution through the iminodiacetic acid resin to obtain a purified liquid containing the zirconium ions (Zr ⁴⁺ ).

First, an ⁸⁹ Y yttrium target 1 in which radioactive zirconium ( ⁸⁹ Zr: hereinafter referred to as zirconium or Zr) (not shown) is generated by proton beam irradiation is prepared. In the dissolving step, the yttrium target 1 is dissolved by the dissolving acidic solution 3 in the dissolving tank 2 to prepare a solution. Here, as the acidic solution 3 for dissolution, for example, hydrochloric acid having a hydrogen ion concentration of 0.1 mol/L or more and 1.0 mol/L or less is used. When using 0.33 g (330 mg) of the yttrium target 1, for example, it may be dissolved in about 2 mL of the acidic solution 3 for dissolution. In addition to hydrochloric acid, nitric acid and aqueous sulfuric acid can also be used.

In the adsorption step, the solution obtained in the dissolving step is passed through a resin column 5 as a chelate resin container filled with iminodiacetic acid resin 4 . The resin column 5 is configured so that various solutions can be drained from the drain port 5a after being passed therethrough. After the dissolved liquid comes into contact with the iminodiacetic acid resin 4 and the zirconium ions (Zr ⁴⁺ ) are adsorbed on the iminodiacetic acid resin 4 , it is discharged from the drain port 5 a as a passing liquid. As shown in FIG. 1, the partition coefficient K _d of zirconium ions (Zr ⁴⁺ ) with respect to the iminodiacetic acid resin 4 is greater than 10 ³ when the hydrochloric acid concentration is 0.1 mol/L or more and 1.0 mol/L or less. Zirconium ions (Zr ⁴⁺ ) are selectively adsorbed on the resin 4 . As the iminodiacetic acid resin 4, for example, ME-1 (GL Sciences) can be used.

In the washing step, an acidic washing solution is passed through the resin column 5 . As a result, impurities such as yttrium adhering to the inner wall of the resin column 5 and the iminodiacetic acid resin 4 and the acidic solution for dissolution are washed and discharged from the drain port 5a as a passing liquid. Here, as the acidic cleaning solution, for example, hydrochloric acid having a hydrogen ion concentration of 0.1 mol/L or more and 1.0 mol/L or less is used. The washing step may be appropriately changed depending on the concentration of the acidic solution for dissolution and the acid solution for washing, but it is preferable to wash with the acidic solution for washing in an amount 1 to 10 times the volume of the solution. In addition to hydrochloric acid, nitric acid and aqueous sulfuric acid can also be used.

In the recovery step, the recovered acidic solution is passed through the resin column 5 . As a result, the zirconium ions adsorbed on the iminodiacetic acid resin 4 are eluted into the recovered acidic solution. The recovered acidic solution containing zirconium is discharged from the drainage port 5a. Here, as the recovered acidic solution, an acidic aqueous solution such as hydrochloric acid, nitric acid, and sulfuric acid aqueous solution can be used. For the recovered acidic solution, it is preferable to use, for example, an aqueous hydrochloric acid solution having a concentration of 3 mol/L or more and 8 mol/L. As shown in FIG. 1, the partition coefficient K _d of zirconium ions (Zr ⁴⁺ ) with respect to the iminodiacetic acid resin 4 is less than or substantially the same as 10 ⁰ at a hydrochloric acid concentration of 3 mol/L or more and 8 mol/L or less. . Therefore, by using an acidic solution with a hydrogen ion concentration of 3 mol/L or more and 8 mol/L as the recovered acidic solution, zirconium ions can be desorbed from the iminodiacetic acid resin 4 .

The iminodiacetic acid resin 4 and zirconium ions form a complex as shown in formula (1) below. As shown on the right side of equation (1), hydrogen ions are released when zirconium ions are adsorbed on iminodiacetic acid, so the higher the hydrogen ion concentration, the more the equilibrium tilts to the left. This agrees with the trend of the distribution coefficient _Kd on the low hydrogen ion concentration side (4 mol/L or less) in FIG.

However, in FIG. 1, the partition coefficient K _d rises at a hydrogen ion concentration of 4 mol/L. This is probably because chloride ions of zirconium are produced and adsorbed by iminodiacetic acid and ion exchange action, as shown in the following formula (2).

When the hydrogen ion concentration is lower than 3 mol/L, the complex of iminodiacetic acid resin and zirconium ions cannot be decomposed, and when the hydrogen ion concentration is higher than 8 mol/L, the anion adduct of zirconium It was discovered for the first time by the present invention that an ionic bond is formed between the zirconium and the iminodiacetic acid resin, resulting in a low recovery rate of zirconium ions.

Next, experiments conducted by the present inventor on the dissolution process, the adsorption process, the washing process, and the recovery process in the method for refining zirconium according to the above-described embodiment will be described.

A yttrium foil (about 0.33 g) was irradiated with a proton beam to generate zirconium 89 ( ⁸⁹ Zr). This was dissolved in 10 mL of 0.5 mol/L hydrochloric acid. This was passed through an iminodiacetic acid resin (ME-1 (GL Sciences)). Furthermore, it was washed with 10 mL of 0.5 mol/L hydrochloric acid. After that, zirconium 89 was eluted by passing 3 mL of 4 mol/L hydrochloric acid. The recovery of zirconium was 91% and 99.94% of yttrium could be removed.

Next, a zirconium refiner according to an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram for explaining a zirconium refiner according to an embodiment of the invention.

As shown in FIG. 3, the zirconium refining apparatus 10 includes a dissolution tank 2, a resin column 5 filled with iminodiacetic acid resin 4, a collected permeate vial 11, a waste liquid vial 12, a reservoir tank group 13, a valve group 14 and A piping system having a valve group 15 is provided. The reservoir tank group 13 is composed of reservoir tanks 13a, 13b, and 13c, each constituting a storage tank capable of storing various solvents and various solutions.

The dissolution tank 2 is a tank for dissolving the yttrium target in which a minute amount of ⁸⁹ Zr is produced by the proton beam irradiation. The dissolution tank 2 is supplied with an acidic solution for dissolution from a reservoir tank 13a. The reservoir tank 13a stores, for example, a hydrochloric acid aqueous solution having a concentration of 0.5 mol/L as an acidic solution for dissolution. By supplying the dissolving acidic solution from the reservoir tank 13a to the dissolving tank 2, the yttrium target is dissolved. Thereby, a dissolution process is performed and a solution is generated. The supply of the acidic solution for dissolution from the reservoir tank 13a to the dissolving tank 2 is controlled by opening and closing the valve 15a.

The resin column 5 filled with the iminodiacetic acid resin 4 is configured so that the dissolving liquid discharged from the dissolving tank 2 can be supplied. The supply of the solution from the dissolving tank 2 to the resin column 5 is controlled by a valve 2a. By supplying the solution from the dissolution tank 2 to the resin column 5, the adsorption step is executed, and the iminodiacetic acid resin 4 filled therein adsorbs zirconium ions. The resin column 5 is configured so that the acidic cleaning solution and the recovered acidic solution can be supplied from reservoir tanks 13b and 13c, respectively.

A hydrochloric acid aqueous solution having a concentration of 0.5 mol/L, for example, is stored in the reservoir tank 13b. The washing step is performed by supplying the resin column 5 with an acidic washing solution from the reservoir tank 13b. The supply of the acidic cleaning solution from the reservoir tank 13b to the resin column 5 is controlled by opening and closing the valve 15b.

In the adsorption process and the washing process, the passing liquid discharged from the drainage port 5a of the resin column 5 is supplied to the waste liquid vial 12 according to switching of the three-way valve 16b.

A hydrochloric acid aqueous solution having a concentration of 4 mol/L, for example, is stored as the recovered acidic solution in the reservoir tank 13c. The recovery step is performed by supplying the recovered acidic solution to the resin column 5 from the reservoir tank 13c. The supply of the recovered acidic solution from the reservoir tank 13c to the resin column 5 is controlled by opening and closing the valve 15c. In the recovery step, the recovered passing liquid discharged from the drain port 5a of the resin column 5 is supplied to the recovered acidic solution vial 11 in response to switching of the three-way valve 16b.

The zirconium refining apparatus 10 includes a mass flow controller (MFC) 17 as a supply amount control section for supplying inert gas from an inert gas supply source to the dissolving tank 2 and the reservoir tank group 13 . Inert gas is selectively supplied to dissolution tank 2 and reservoir tanks 13a to 13c through MFC 17, respectively. The supply of inert gas to the dissolving tank 2 and the respective reservoir tanks 13a to 13c is controlled by opening and closing valves 2b, 14a, 14b and 14c, respectively. Various solutions can be moved by the pressure of the supplied inert gas. Inert gases used for moving various solutions are preferably helium (He) and nitrogen (N ₂ ), but are not necessarily limited to these gases. Also, the insides of the recovered acidic solution vial 11 and the waste vial 12 communicate with a vacuum pump via a valve 18 . By opening and closing the valve 18, it is possible to reduce the pressure inside the collection acid solution vial 11 and the waste solution vial 12 to facilitate the inflow of various solutions.

In the zirconium refining apparatus 10 configured as described above, by executing the dissolving process, the adsorption process, the washing process, and the recovery process, zirconium with high purity is contained without precipitation of substances caused by the recovered acidic solution. A recovered acidic solution can be obtained. In addition, in the zirconium refining apparatus 10, a control unit that controls each component such as the respective valves 2a, 2b, 14a to 14c, 15a to 15c, 18, the three-way valve 16b, the respective reservoir tanks 13a to 13c, and the MFC 17 is provided. You may prepare. In this case, the above-described copper refining method can be executed by the control unit controlling each component. Furthermore, when the same type and concentration of acidic solutions are used as the acidic solution for dissolution and the acidic solution for washing, the reservoir tank 13a for the acidic solution for dissolution and the reservoir tank 13b for the acidic solution for washing are shared, and one reservoir is used. Acidic solutions may be supplied from the tank as the acidic solution for dissolution and the acidic solution for washing.

1 yttrium target 2 dissolution tank 2a, 2b, 14a, 14b, 14c, 15a, 15b, 15c, 18 valve 3 acid solution for dissolution 4 iminodiacetic acid resin 5 resin column 5a drainage port 10 zirconium refiner 11 recovery acid solution vial 12 waste liquid vial 13 reservoir tank group 13a, 13b, 13c reservoir tank 16b three-way valve 17 mass flow controller (MFC)

Claims (4)

a dissolving step of dissolving zirconium and yttrium in an acidic solution for dissolution to prepare a solution;
an adsorption step of bringing the solution into contact with an iminodiacetic acid resin to selectively adsorb zirconium ions (Zr ⁴⁺ ) to the iminodiacetic acid resin;
After the adsorption step, a washing step of washing by passing an acidic washing solution through the iminodiacetic acid resin;
After the washing step, a recovery step of passing hydrochloric acid, which is a recovered acidic solution, through the iminodiacetic acid resin to obtain a purified liquid containing the zirconium ions (Zr ⁴⁺ );
A method for purifying zirconium, comprising: 2. The method for refining zirconium according to claim 1, wherein the acidic solution for dissolution has a hydrogen ion concentration of 0.1 mol/L or more and 1 mol/L or less. 3. The method for refining zirconium according to claim 1, wherein the recovered acidic solution has a hydrogen ion concentration of 3 mol/L or more and 8 mol/L or less. a dissolution tank for dissolving zirconium and yttrium in an acidic solution for dissolution to obtain a solution;
a dissolving acidic solution storage tank for storing the dissolving acidic solution;
an acidic cleaning solution storage tank for storing an acidic cleaning solution;
a recovered acidic solution storage tank for storing hydrochloric acid , which is the recovered acidic solution;
a chelate resin container filled with iminodiacetic acid resin;
The dissolution acidic solution can be supplied to the dissolution tank, and the dissolution solution, the cleaning acidic solution, or the recovery acidic solution can be selectively supplied to the chelate resin container, and discharged from the chelate resin container. a piping system capable of discharging the dissolving solution, the acidic cleaning solution, or the recovered acidic solution;
A zirconium refiner comprising:

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