JP5953548B2 - Molybdenum cycle system and method for regenerating molybdenum adsorbent used in the cycle system - Google Patents

Description

  The present invention relates to a molybdenum cycle system implemented when applying a technetium 99m generator for medical diagnostic imaging, and a method for regenerating a molybdenum adsorbent used in the cycle system.

Technetium 99m generators, reactors molybdenum ⁹⁹ to produce natural molybdenum by neutron irradiation of ^{(99 Mo) PZC (Poly-} Zirconium Compound: Polymer zirconium compound) or titanium, zirconium, a metal alkoxide such as silicon hydrolytic condensation It is a generator for producing technetium 99m for nuclear medicine diagnosis, which is adsorbed with an adsorbent made of materials and used for image diagnosis of cancer, myocardial infarction, and the like.

In image diagnosis of diseases such as cancer and myocardial infarction, technetium 99m ( ^99m Tc), which is a radioisotope, is used. ^In order to obtain ^99m Tc, a ⁹⁹ Mo- ^99m Tc generator (hereinafter simply referred to as a technetium 99m generator) using ⁹⁹ Mo having a half-life of about 66 hours decays to ^99m Tc is used.

⁹⁹ Mo is the parent nuclide of ^99m Tc is produced by causing fission of enriched uranium (n, f) method, and was ⁹⁸ Mo target (n, gamma) method ^{{98 Mo (n, γ)} 99 Mo} The The (n, f) method uses ⁹⁹ Mo with a high specific activity of about 10 ⁵ Ci / g to reduce the size and weight of the generator, and has been commercialized. However, in order to use the ²³⁵ U fission reaction, ⁹⁹ Mo must be extracted from various fission products through a complicated process, and in addition, a large amount of radioactive waste is generated. On the other hand, in the (n, γ) method, a solid containing natural molybdenum (such as molybdenum trioxide pellets) is irradiated with neutrons in a nuclear reactor as a target, and ⁹⁸ Mo neutron capture ( ⁹⁸ Mo (n, γ) ⁹⁹ This is a method for producing ⁹⁹ Mo by Mo reaction.

The (n, γ) method is advantageous not only in solving the above-mentioned problems of the (n, f) method, but also in reducing the manufacturing cost. However, since the natural abundance ratio of ⁹⁸ Mo is as low as 24.1%, the specific activity of ⁹⁹ Mo obtained is as low as around 2 Ci / g, and in order to obtain about 500 mCi of ⁹⁹ Mo necessary as a generator, the Mo adsorption capacity High adsorbent is required. Patent Documents 1 to 3 propose an inorganic polymer zirconium compound (PZC) as an adsorbent having a high Mo adsorption capacity. Further, the present inventors have proposed a hydrolysis condensate of metal alkoxides such as titanium, zirconium or silicon (Japanese Patent Application No. 2010-263801) for compounds other than the PZC.

An adsorbent having excellent performance in ⁹⁹ Mo adsorption characteristics and ^99m Tc elution rate is expected as a technetium 99m generator. The technetium 99m generator is discarded as radioactive waste after ^99m Tc is taken out by using physiological saline in a hospital for imaging diagnosis of a patient's disease.

As mentioned ^above, natural abundance of 98 Mo in order 24.1% and low, (n, gamma) in the ^process, in order to increase the abundance ratio of 98 ^Mo, 98 Mo concentration and reuse like Is being considered. For example, Patent Document 4 proposes an extraction and reuse technique of ⁹⁸ Mo that has been disposed of as radioactive waste. This technology focuses on the fact that the adsorbent of the used technetium 99m generator adsorbs not only ⁹⁹ Mo produced by the (n, γ) reaction but also unreacted ⁹⁸ Mo, etc. From the viewpoint of effective utilization of Mo resources, used Mo can be efficiently recovered to reduce the volume of radioactive waste. Further, Patent Document 4 discloses a cycle system that can reuse a used PZC adsorbent. Further, it is described that an adsorbent such as PZC that has adsorbed Mo can be used again as an adsorbent for ⁹⁹ Mo after desorption of Mo.

JP-A-8-309182 Japanese Patent Laid-Open No. 10-30027 Japanese Patent Laid-Open No. 2004-150977 JP 2012-13617 A

As described above, in the (n, γ) method, it is necessary not only to efficiently recover Mo and reuse the used adsorbent, but also to establish a method for regenerating the adsorbent such as PZC. In particular, if a regeneration method capable of reusing ⁹⁹ Mo adsorbent more than once can be established, the manufacturing cost of the Mo adsorbent can be greatly reduced, and efficient recovery of Mo can be achieved at low cost. Molybdenum cycle system can be constructed. However, the above-mentioned Patent Document 4 only describes that the adsorbent after desorbing Mo can be used again as a ⁹⁹ Mo adsorbent. It is not disclosed, and it is completely unknown whether or not an adsorption amount equivalent to the initial value can be stably secured even if regeneration is performed twice or more.

Further, the Patent Document 4, by using an adsorbent after desorption of Mo, again, for the best method and conditions for adsorbing ^{99 Mo,} only an example in the third embodiment have been described The details are unknown. In addition, the amount of Mo adsorption on the PZC adsorbent described in Example 3 of Patent Document 4 (Mo adsorption amount of 148 mg with respect to 1 g of PZC adsorbent) is generally used in the adsorbent used in the (n, γ) method. However, it does not reach 150 mg or more, which is the desired Mo adsorption amount, and further improvement is necessary.

The present invention has been made to solve such a problem. When ⁹⁹ Mo adsorbent such as PZC or a hydrolysis condensate of metal alkoxide is regenerated, ⁹⁹ Mo adsorption and desorption characteristics and ^99m Tc elution are obtained. The efficiency of Mo is improved by establishing a regeneration method that can maintain excellent performance such as a rate substantially equal to the initial value and optimizing the re-adsorption conditions of ⁹⁹ Mo to the regenerated ⁹⁹ Mo adsorbent. It is an object of the present invention to provide a molybdenum cycle system capable of performing efficient recovery at a low cost and a method for regenerating a molybdenum adsorbent used in the cycle system.

The present inventors, after desorption of ^{99m Tc} from the adsorbent of ^{99 Mo,} in reproducing, as clarified functional groups to be ^{99 Mo} adsorption site to form a structure having the functional group ⁹⁹ Focusing on establishing a method for regenerating Mo adsorbent and re-adsorbing ⁹⁹ Mo on the regenerated adsorbent, the pH of the solution containing ⁹⁹ Mo is a major factor in determining resorption performance. Thus, the present inventors have found that the above-mentioned problems can be solved by optimizing the pH of the solution.

［Ｍ_１はジルコニウムであり、Ｒ_１及びＲ_２は塩素、アルコキシ基、水酸基又はＯ_1/2から選ばれる何れか一つであり、Ｒ_１及びＲ_２は同じ基であってもよい。］

［Ｍ_２はチタン、ジルコニウム及びシリコンの少なくとも何れか１種であり、Ｒ_３及びＲ_４はアルコキシ基、１分子中に水酸基とカルボキシル基とを有する有機配位子、水酸基又はＯ_1/2から選ばれる何れか一つであり、Ｒ_３及びＲ_４は同じ基であってもよい。］

［Ｍ_３はアルミニウムであり、Ｒ_５はアルコキシ基、１分子中に水酸基とカルボキシル基とを有する炭化水素基、水酸基及びＯ_1/2から選ばれる何れか１つである。］
［２］本発明は、前記［１］に記載のサイクルシステムにおいて、前記の再吸着工程で使用されるモリブデン吸着剤は、前記の化７で表される繰返し単位を含有する骨格構造を有することを特徴とするモリブデンのサイクルシステムを提供する。
［３］本発明は、前記［１］に記載のサイクルシステムにおいて、前記の再吸着工程で使用されるモリブデン吸着剤は、前記の化８若しくは前記の化９で表される繰返し単位を含有する骨格構造、又は前記の化８及び前記の化９で表される繰返し単位を含有する骨格構造、を有することを特徴とするモリブデンのリサイクルシステムを提供する。
［４］本発明は、前記［１］又は［３］に記載のモリブデンのサイクルシステムにおいて、前記のアルコキシ基及び１分子中に水酸基とカルボキシル基とを有する有機配位子は、１〜８の炭素数を有するものであることを特徴とするモリブデンのサイクルシステムを提供する。
［５］本発明は、前記［１］〜［４］の何れかに記載のモリブデンのサイクルシステムにおいて、前記の再吸着工程で使用されるモリブデン吸着剤は、前記の再吸着工程が開始されるまで水中又はアルコールを含む水中で保存されることを特徴とするモリブデンのサイクルシステムを提供する。
［６］本発明は、前記［１］〜［５］の何れかに記載のモリブデンのサイクルシステムにおいて、前記の再吸着工程は、ｐＨが６以下に調整されたモリブデン９９を含有する溶液を用いて行われることを特徴とするモリブデンのサイクルシステムを提供する。
［７］本発明は、前記［６］に記載のモリブデンのサイクルシステムにおいて、前記のモリブデン９９を含有する溶液はｐＨが１〜５に調整されることを特徴とするモリブデンのサイクルシステムを提供する。
［８］本発明は、前記［１］〜［７］の何れかに記載のモリブデンのサイクルシステムにおいて、前記のモリブデン吸着量は、前記のモリブデン吸着剤の１ｇに対して２００ｍｇ以上であることを特徴とするモリブデンのサイクルシステムを提供する。
［９］本発明は、モリブデン又は三酸化モリブデンペレットに中性子照射して得られるモリブデン９９を含有するモリブデン又は三酸化モリブデンを溶解してモリブデン吸着剤に吸着する工程（吸着工程）、前記のモリブデン吸着剤から成るジェネレータからテクネチウム９９ｍを抽出した後の使用済みモリブデン吸着剤を用いて、該使用済みモリブデン吸着剤からモリブデンを脱着する工程（脱着工程）、前記モリブデン脱着後のモリブデン吸着剤にモリブデン９９含有のモリブデンを再吸着する工程（再吸着工程）、及び前記の脱着工程によって回収される三酸化モリブデンを前記のペレットとして再利用する工程を含み、前記の脱着工程及び際吸着工程が１回以上繰り返されるモリブデンのサイクルシステムにおいて使用されるモリブデン吸着剤の再生方法であって、前記の再吸着工程で使用されるモリブデン吸着剤は、下記の化１０、化１１、及び化１２で表される繰返し単位の少なくとも何れか１つを含有する骨格構造と、再吸着されるモリブデン吸着量が前記のモリブデン吸着剤の１ｇに対して１５０ｍｇ以上となるように高濃度の水酸基とを有するものに再生することを特徴とするモリブデン吸着剤の再生方法を提供する。

［Ｍ_１はジルコニウムであり、Ｒ_１及びＲ_２は塩素、アルコキシ基、水酸基又はＯ_1/2から選ばれる何れか一つであり、Ｒ_１及びＲ_２は同じ基であってもよい。］

［Ｍ_２はチタン、ジルコニウム及びシリコンの少なくとも何れか１種であり、Ｒ_３及びＲ_４はアルコキシ基、１分子中に水酸基とカルボキシル基とを有する有機配位子、水酸基又はＯ_1/2から選ばれる何れか一つであり、Ｒ_３及びＲ_４は同じ基であってもよい。］

［Ｍ_３はアルミニウムであり、Ｒ_５はアルコキシ基、１分子中に水酸基とカルボキシル基とを有する炭化水素基、水酸基及びＯ_1/2から選ばれる何れか１つである。］
［１０］本発明は、前記の再吸着工程で使用されるモリブデン吸着剤が、前記の化１０で表される繰返し単位を含有する骨格構造を有することを特徴とする前記［９］に記載のモリブデン吸着剤の再生方法を提供する。
［１１］本発明は、前記の再吸着工程で使用されるモリブデン吸着剤が、前記の化１１若しくは前記の化１２で表される繰返し単位を含有する骨格構造、又は前記の化１１及び前記の化１２で表される繰返し単位を含有する骨格構造、を有することを特徴とする前記［９］に記載のモリブデン吸着剤の再生方法を提供する。
［１２］本発明は、前記のアルコキシ基及び１分子中に水酸基とカルボキシル基とを有する有機配位子は、１〜８の炭素数を有するものであることを特徴とする前記［９］又は［１１］に記載のモリブデン吸着剤の再生方法を提供する。
［１３］本発明は、前記の再吸着工程で使用されるモリブデン吸着剤は、前記の再吸着工程が開始されるまで水中又はアルコールを含む水中で保存されることを特徴とする前記［９］〜［１２］の何れかに記載のモリブデン吸着剤の再生方法を提供する。
［１４］本発明は、前記のモリブデン吸着量が、前記のモリブデン吸着剤の１ｇに対して２００ｍｇ以上であるように再生することを特徴とする前記［９］〜［１３］の何れかに記載のモリブデン吸着剤の再生方法を提供する。
［発明の効果］ That is, the configuration of the present invention is as follows.
[1] The present invention includes a step of adsorbing molybdenum or molybdenum trioxide containing molybdenum 99 obtained by neutron irradiation to molybdenum or molybdenum trioxide pellets and adsorbing it on a molybdenum adsorbent (adsorption step). A step of desorbing molybdenum from the used molybdenum adsorbent (desorption step) using the used molybdenum adsorbent after extracting technetium 99m from the generator comprising the agent, and the molybdenum adsorbent after the molybdenum desorption contains molybdenum 99 A molybdenum cycle system comprising a step of re-adsorbing molybdenum (re-adsorption step), and a step of reusing molybdenum trioxide recovered by the desorption step as the pellets. The molybdenum adsorbent used is the following chemical formula 7, chemical formula 8, A skeleton structure containing at least one of repeating units represented by the beauty of 9, a high concentration as molybdenum adsorbed amount of re-adsorption is more 150mg respect 1g of the molybdenum adsorbent hydroxyl And the desorption process and the resorption process are repeated one or more times.

[M ₁ is zirconium , R ₁ and R ₂ are any one selected from chlorine, an alkoxy group, a hydroxyl group or O _1/2 , and R ₁ and R ₂ may be the same group. ]

[M ₂ is at least one of titanium, zirconium and silicon , R ₃ and R ₄ are alkoxy groups, organic ligands having hydroxyl and carboxyl groups in one molecule, hydroxyl groups or O _1/2 Any one selected, and R ₃ and R ₄ may be the same group. ]

[M ₃ is aluminum , and R ₅ is any one selected from an alkoxy group, a hydrocarbon group having a hydroxyl group and a carboxyl group in one molecule, a hydroxyl group, and O _1/2 . ]
[ 2 ] In the cycle system according to [1] , the molybdenum adsorbent used in the re-adsorption step has a skeleton structure containing the repeating unit represented by the chemical formula 7 above. A molybdenum cycle system is provided.
[ 3 ] In the cycle system according to [1] , the molybdenum adsorbent used in the re-adsorption step includes a repeating unit represented by the chemical formula 8 or the chemical formula 9 described above. There is provided a molybdenum recycling system characterized by having a skeletal structure or a skeletal structure containing a repeating unit represented by Chemical Formula 8 and Chemical Formula 9 above.
[ 4 ] The present invention provides the molybdenum cycle system according to [1] or [3] , wherein the alkoxy ligand and the organic ligand having a hydroxyl group and a carboxyl group in one molecule are 1-8. Provided is a molybdenum cycle system characterized by having a carbon number.
[ 5 ] The present invention is the molybdenum cycle system according to any one of [1] to [4] , wherein the molybdenum adsorbent used in the re-adsorption step starts the re-adsorption step. The molybdenum cycle system is characterized by being stored in water or in water containing alcohol.
[ 6 ] The present invention provides the molybdenum cycle system according to any one of [1] to [5] , wherein the re-adsorption step uses a solution containing molybdenum 99 having a pH adjusted to 6 or less. A molybdenum cycle system is provided.
[ 7 ] The present invention provides the molybdenum cycle system according to the above [6] , wherein the solution containing the molybdenum 99 has a pH adjusted to 1 to 5. .
[ 8 ] The present invention provides the molybdenum cycle system according to any one of [1] to [7] , wherein the molybdenum adsorption amount is 200 mg or more per 1 g of the molybdenum adsorbent. A feature molybdenum cycle system is provided.
[ 9 ] The present invention relates to a step of adsorbing molybdenum or molybdenum trioxide containing molybdenum 99 obtained by neutron irradiation to molybdenum or molybdenum trioxide pellets and adsorbing it on a molybdenum adsorbent (adsorption step). A step of desorbing molybdenum from the used molybdenum adsorbent (desorption step) using the used molybdenum adsorbent after extracting technetium 99m from the generator comprising the agent, and the molybdenum adsorbent after the molybdenum desorption contains molybdenum 99 A step of re-adsorbing molybdenum (re-adsorption step), and a step of reusing molybdenum trioxide recovered by the desorption step as the pellet, wherein the desorption step and the adsorption step are repeated one or more times. Molybdenum used in the molybdenum cycle system A method for regenerating a den adsorbent, wherein the molybdenum adsorbent used in the re-adsorption step contains at least one of repeating units represented by the following chemical formulas (10), (11), and (12): A method for regenerating a molybdenum adsorbent comprising regenerating a skeleton structure and one having a high concentration of hydroxyl groups so that the amount of molybdenum adsorbed again is 150 mg or more per 1 g of the molybdenum adsorbent. I will provide a.

[M ₁ is zirconium , R ₁ and R ₂ are any one selected from chlorine, an alkoxy group, a hydroxyl group or O _1/2 , and R ₁ and R ₂ may be the same group. ]

[M ₂ is at least one of titanium, zirconium and silicon , R ₃ and R ₄ are alkoxy groups, organic ligands having hydroxyl and carboxyl groups in one molecule, hydroxyl groups or O _1/2 Any one selected, and R ₃ and R ₄ may be the same group. ]

[M ₃ is aluminum , and R ₅ is any one selected from an alkoxy group, a hydrocarbon group having a hydroxyl group and a carboxyl group in one molecule, a hydroxyl group, and O _1/2 . ]
[10] The present invention is molybdenum adsorbents used in the re-adsorption step, according to [9], which has a skeleton structure containing a repeating unit represented by the formula 10 A method for regenerating a molybdenum adsorbent is provided.
[ 11 ] In the present invention, the molybdenum adsorbent used in the re-adsorption step includes a skeletal structure containing a repeating unit represented by the chemical formula 11 or the chemical formula 12, or the chemical formula 11 and the chemical formula The method for regenerating a molybdenum adsorbent according to [9] above, which has a skeleton structure containing a repeating unit represented by Chemical formula 12:
[ 12 ] The above [9] or [9] , wherein the alkoxy group and the organic ligand having a hydroxyl group and a carboxyl group in one molecule have 1 to 8 carbon atoms . [11] A method for regenerating a molybdenum adsorbent according to [11] is provided.
[ 13 ] The present invention is characterized in that the molybdenum adsorbent used in the resorption step is stored in water or water containing alcohol until the resorption step is started. [9] A method for regenerating a molybdenum adsorbent according to any one of to [12] is provided.
[ 14 ] The invention according to any one of [9] to [13], wherein the regeneration is performed so that the molybdenum adsorption amount is 200 mg or more per 1 g of the molybdenum adsorbent. A method for regenerating a molybdenum adsorbent is provided.
[Effect of the invention]

According to the present invention, since the regenerated Mo adsorbent has at least one OH group functioning as an adsorption site for ⁹⁹ Mo in the structure of the repeating unit, the adsorption and desorption characteristics of ⁹⁹ Mo and the elution rate of ^99m Tc The excellent performance such as the above is maintained substantially equal to the initial value and is stably maintained. The positive introduction of OH groups into the Mo adsorbent has the effect that the amount of ⁹⁹ Mo adsorbed can be greatly improved as compared to the conventional case. Further, since the Mo adsorbent is regenerated so as to contain at least one OH group in the structure of the repeating unit every time it is regenerated, the number of regeneration is not limited to one time, and more than two times, It can be increased to 10 times or more. In addition, the method for regenerating the Mo adsorbent so as to contain at least one OH group in the structure of the structural unit is performed in water or water containing alcohol until the re-adsorption step after desorption of the Mo adsorbent is started. It can be performed by a simple method of storage.

According to the present invention, when ⁹⁹ Mo is re-adsorbed on the regenerated Mo adsorbent, ⁹⁹ Mo adsorption and desorption characteristics and ^{99 m} are obtained by optimizing the pH of the solution containing ⁹⁹ Mo in a neutral to acidic range. Performances such as the elution rate of Tc can be greatly improved. Accordingly, the regeneration of ⁹⁹ Mo adsorbent is not limited to one time, and the adsorbent used in the (n, γ) method with respect to 1 g of the above-mentioned adsorbent even if it is performed twice or more. In general, it is possible to achieve 150 mg or more, preferably 200 mg or more, which is generally desired. The adsorption amount can be maintained even during a plurality of regenerations.

Furthermore, the regeneration method of the molybdenum ( ⁹⁹ Mo) adsorbent of the present invention is applied to hydrolysis condensates of PZC or metal alkoxides such as titanium, zirconium and silicon, which are expected to be widely used as Mo adsorbents in the future. Is possible and the application range is extremely wide. Thus, according to the present invention, it is possible to significantly reduce the manufacturing cost of the adsorbent and to construct a molybdenum cycle system that can efficiently recover molybdenum at a low cost.

1 is a schematic flow diagram of a molybdenum cycle system according to the present invention. FIG. It is a figure which shows the presumed mechanism of adsorption | suction and desorption of Mo about the reproduced | regenerated PZC type Mo adsorbent of this invention. It is a figure which shows the relationship between pH of Mo solution at the time of re-adsorption, and the re-adsorption amount of Mo to the PZC type Mo adsorbent by this invention. It is a figure which shows the relationship between pH of Mo solution at the time of re-adsorption, and the desorption amount of Mo from the PZC type Mo adsorbent by this invention. It is a figure which shows the desorption rate of Mo from Mo re-adsorption PZC type Mo adsorption agent. It is a figure which shows the infrared absorption spectrum of the reproduced | regenerated PZC type Mo adsorbent of this invention. It is a figure which shows the infrared absorption spectrum of the regenerated PTC-type Mo adsorbent of this invention. It is a figure which shows the adsorption | suction estimation mechanism of Mo about the PTC-type Mo adsorbent of this invention.

A molybdenum cycle system according to the present invention will be described with reference to FIG. In the schematic flow diagram of the molybdenum cycle system of the present invention shown in FIG. 1, first, in step S1, molybdenum (Mo) or molybdenum trioxide (MoO ₃ ) powder is baked and solidified into a pellet. In step S2, Mo or MoO ₃ -containing pellets are irradiated in a nuclear reactor, and ⁹⁹ Mo is obtained from a neutron capture reaction of ⁹⁸ Mo in the pellets {(n, γ) method}. Next, in step S3, the irradiated Mo or MoO ₃ -containing pellets are dissolved with a sodium hydroxide solution to obtain a molybdenum solution containing ⁹⁹ Mo / Mo. Subsequently, in the step of S4, the addition of Mo adsorbent molybdenum solution containing the ^{99 Mo,} is adsorbed to 99 Mo / Mo. This produces a technetium 99m generator.

The technetium 99m generator thus produced is transported in a special solution, and ^99m Tc is taken out by flowing physiological saline in a hospital or the like. The extracted ^99m Tc is mixed with other chemicals and then sent into the patient's body, for example, with a syringe, and used for image diagnosis of diseases such as cancer and myocardial infarction.

The process of S5 shown in FIG. 1 is a process of collecting the Mo adsorbent that has been used in a hospital or the like in a regeneration processing facility. The used Mo adsorbent recovered in the step S5 is processed using an elution method or the like in the step S6, and Mo is desorbed and extracted. In the step of S6, Mo contained in the Mo adsorbent is eluted and recovered as molybdate anions in an alkaline solution, and this solution is treated with an acid such as hydrochloric acid to be recovered as molybdic acid in solid form. This Molybdic acid solid can be heated and oxidized to obtain MoO ₃ for use in pellet production performed in the step S1.

On the other hand, the Mo adsorbent after Mo is desorbed and extracted in the step S6 is moved to the regeneration step S7. The Mo adsorbent regenerated in the step S7 is reused, and ⁹⁹ Mo / Mo is re-adsorbed through the same step as S4. Here, the regeneration performed in the step S7 is performed by storing the used Mo adsorbent in water, in water containing alcohol, or in a steam atmosphere until the re-adsorption step is started. The present invention has a characteristic structure possessed by the Mo adsorbent regenerated in the process of S7, and this structure has a great influence on performance such as ⁹⁹ Mo adsorption and desorption characteristics and ^99m Tc elution rate during reuse. It was made by finding to give. That is, it is a feature of the present invention to form a structure having an OH group that becomes a ⁹⁹ Mo adsorption site as a constituent unit of the Mo adsorbent. Details of the structure of the Mo adsorbent of the present invention will be described later.

In FIG. 1, the processes that characterize the present invention include ⁹⁹ Mo / Mo adsorption step S4 to Mo adsorbent, S5 step of obtaining used Mo adsorbent after extracting ^99m Tc, and Mo from the used Mo adsorbent. Desorption and extraction step S6, and Mo adsorbent regeneration step S7 after Mo is desorbed and extracted. The steps S4 to S7 in the present invention are repeated one or more times in the reuse of the Mo adsorbent. In the present invention, even when reuse is performed 4 times or more, and further 10 times or more, a decrease in performance as an adsorbent is hardly seen compared to the initial stage.

The Mo adsorbent that has been repeatedly regenerated and reused in the steps S4 to S7 in FIG. 1 and finally determined to be unrecyclable is transferred to another processing flow, and processed using a sublimation method or the like in the step S8. Is done. In the step of S8, Mo contained in the Mo adsorbent becomes MoO ₃ by heating in the atmosphere. This MoO ₃ is sublimated by heating to a high temperature of 900 ° C. or higher. The sublimated Mo or MoO ₃ is extracted and recovered at a low temperature part in the same system in the step S9, and used for pellet production in the step S1 in FIG. On the other hand, the Mo adsorbent heated at a high temperature is reduced in volume as a metal oxide such as Zr, Ti, Si or Al.

  Next, the Mo adsorbent used in the present invention will be described.

As the Mo adsorbent of the present invention, an adsorbent having excellent performance in ⁹⁹ Mo adsorption and desorption characteristics, ^99m Tc elution rate and the like is used. As the Mo adsorbent having a high Mo adsorption capacity, for example, PZC systems disclosed in JP-A-8-309182 and JP-A-10-30027 can be used. Specifically, it is a Mo adsorbent having a skeleton structure mainly composed of repeating units represented by the following chemical formula 13.

ここで、Ｘ_１は塩素、１個から８個までの炭素原子を有するアルコキシ基の何れかで、１０％以上のＸ_１が塩素であり、Ｒは１個から８個までの炭素原子を有するアルキレン、ポリメチレンあるいは不飽和結合を有する炭素鎖であり、繰り返し単位（Ｄ）は繰り返し（Ａ）、（Ｂ）、（Ｃ）の何れかに結合し、繰返し単位（Ａ）、（Ｂ）、（Ｃ）の含有量により分岐構造が制御される。

Here, X ₁ is any of chlorine, an alkoxy group having 1 to 8 carbon atoms, 10% or more of X ₁ is chlorine, and R has 1 to 8 carbon atoms It is an alkylene, polymethylene or carbon chain having an unsaturated bond, and the repeating unit (D) is bonded to any one of the repeating units (A), (B) and (C), and the repeating unit (A), (B), ( The branched structure is controlled by the content of C).

（式中、Ｘ_２は塩素、アルコキシ基及び水酸基から成る群より選ばれる１種で、１０％以上のＸ_２が塩素を示す）で表される繰返し単位から主としてなる骨格構造を有し、繰返し単位（Ｅ）、（Ｆ）、（Ｇ）の含有量により分岐構造が制御されたブロック（Ｉ）と、次の化１５；

（式中Ｍ_４はシリコン又はチタン、Ｙ_１は塩素、アルコキシ基及び水酸基から成る群より選ばれる１種を示す）で表される繰返し単位から主として骨格構造を有するメタシロキサンブロック（ＩＩ）から成るＭｏ吸着剤である。 In addition, the following chemical formula 14;

(Wherein X ₂ is one selected from the group consisting of chlorine, an alkoxy group and a hydroxyl group, and 10% or more of X ₂ represents chlorine), and has a skeleton structure mainly composed of repeating units represented by The block (I) in which the branch structure is controlled by the content of the units (E), (F), (G), and the following chemical formula 15;

(Wherein M ₄ represents silicon or titanium, and Y ₁ represents one selected from the group consisting of chlorine, alkoxy group and hydroxyl group) and consists of a metasiloxane block (II) mainly having a skeleton structure. Mo adsorbent.

Alkoxy group is described as _X 1, _{X 2} and _{Y 1} in the above formula 13, formula 14 and Formula 15 is preferably the number of carbon atoms is in the 1-8 range. When the number of carbon atoms is 9 or more, the hydrophobicity increases, so that not only the immersion in the aqueous solution or the penetration of the aqueous Mo solution into the particles of the Mo adsorbent becomes difficult, but also the alcohol removal becomes difficult, and the hydrolysis reaction Can not control. In the present invention, among alkoxy groups having 1 to 8 carbon atoms, alkoxy groups having 2 to 6 carbon atoms are more preferable from the viewpoint of permeability of aqueous Mo solution and control of hydrolysis reaction, specifically, An ethoxy group, a butoxy group, an isopropoxy group, and a hexyloxy group are mentioned.

  Furthermore, in the present invention, it is possible to use a Mo adsorbent composed of a hydrolytic condensate of an alkoxide containing a tetravalent metal, preferably an alkoxide of titanium, zirconium or silicon. These Mo adsorbents are superior in handling properties to the Mo adsorbents having a skeleton structure mainly composed of the repeating units represented by Chemical Formula 13 or Chemical Formula 14 and Chemical Formula 15 above in that they contain no chlorine. It is an adsorbent that is gentle to the environment. Specifically, an Mo adsorbent having a skeleton structure mainly composed of repeating units represented by the following chemical formulas (L), (M) and (N) can be used.

［Ｍ_５が４価の金属、好ましくはチタン、ジルコニウム及びシリコンの少なくとも何れか１種であり、Ｘ_３が炭素数１〜８のアルコキシ基又は１分子中に水酸基とカルボキシ基を有する炭素数１〜８の有機配位子の何れかである。］

[M ₅ is a tetravalent metal, preferably at least one of titanium, zirconium and silicon, and X ₃ is an alkoxy group having 1 to 8 carbon atoms or a carbon number of 1 having a hydroxyl group and a carboxy group in one molecule. Any of ˜8 organic ligands. ]

In the present invention, in addition to the above, an Mo adsorbent composed of a hydrolysis condensate of an alkoxide containing a trivalent metal, preferably an aluminum alkoxide, can be used. Specifically, it is a Mo adsorbent having a skeleton structure mainly composed of repeating units represented by (O), (P) and (Q) shown in the following chemical formula 17.

［Ｍ_６が３価の金属、好ましくはアルミニウムであり、Ｘ_４が炭素数１〜８のアルコキシ基又は１分子中に水酸基とカルボキシ基を有する炭素数１〜８の有機配位子の何れかである。］

[M ₆ is a trivalent metal, preferably aluminum, and X ₄ is either an alkoxy group having 1 to 8 carbon atoms or an organic ligand having 1 to 8 carbon atoms having a hydroxyl group and a carboxy group in one molecule. It is. ]

X ₃ shown in Chemical formula 16 or X ₄ shown in Chemical formula 17 is either an alkoxy group having 1 to 8 carbon atoms or an organic ligand having 1 to 8 carbon atoms having a hydroxyl group and a carboxy group in one molecule. It is preferable that When the number of carbon atoms is 9 or more, the hydrophobicity increases, and it becomes difficult to immerse the Mo aqueous solution in the aqueous solution or into the particles of the Mo adsorbent. Moreover, in the case of an alkoxy group, removal of alcohol becomes difficult and the hydrolysis reaction cannot be controlled. In the alkoxy group having 1 to 8 carbon atoms, the alkoxy group having 2 to 6 carbon atoms is more preferable from the viewpoint of the permeability of the aqueous Mo solution and the control of the hydrolysis reaction, specifically, an ethoxy group. , Butoxy group, isopropoxy group and hexyloxy group. As the organic ligand having 1 to 8 carbon atoms having a hydroxyl group and a carboxy group, for example, ethyl 3-oxobutanoate is more preferably used.

  In the present invention, the block (III) having a skeleton structure mainly composed of the repeating unit represented by the chemical formula 16 and having a branched structure controlled by the content of the repeating units (L), (M), and (N). And a block (IV) having a skeletal structure mainly composed of the repeating unit represented by the chemical formula 17 and having a branched structure controlled by the content of the repeating units (O), (P) and (Q). You may use the comprised hydrolysis-condensation product as Mo adsorption agent.

  Next, the structure of the Mo adsorbent regenerated in the step S7 shown in FIG. 1 will be described.

In the present invention, the used Mo adsorbent obtained in the step S5 contains water or alcohol in the step S7 until the desorption step is started after the desorption and extraction of Mo in the step S6. It is regenerated by storing it in water or in a steam atmosphere. It was found that the Mo adsorbent regenerated by the method has high Mo adsorption performance, and performance such as ⁹⁹ Mo adsorption and desorption characteristics and ^99m Tc elution rate can be maintained substantially the same as the initial performance. In addition, it was found that even when the processing was performed not only once but also two or more times, there was almost no decline in performance that was a concern during reuse, and the quality was stable.

On the other hand, when the used Mo adsorbent is stored as it is in the air or in a dry state, in the reuse of the Mo adsorbent, performance such as ⁹⁹ Mo adsorption and desorption characteristics and ^99m Tc elution rate are obtained. Declined. In addition, there was a large variation in the performance of each production lot, and the produced technetium 99m generator had a problem that the quality was not stable. For example, PZC having a skeletal structure represented by the above chemical formula 13 or chemical formula 14 and chemical formula 15 as a Mo adsorbent is disclosed in JP-A-8-309182, JP-A-10-30027 and JP-A-2004-150977. As described in the publication, the Mo adsorbent site is a Zr-Cl bond, and when PZC is completely hydrolyzed, the amount of adsorption of Mo becomes small. For this reason, even if the adsorbent is regenerated, the concentration of the Zr—Cl bond in the Mo adsorbent can only be considered to be lower than that in the initial stage, and the regeneration is expected to be difficult. Further, it is a condensate by hydrolysis of the alkoxide containing the above tetravalent or trivalent metal, and also in the Mo adsorbent having the skeleton structure represented by the above chemical formula 16 or chemical formula 17, the Mo at the time of reuse The adsorption site could not be clearly identified, and it was completely unknown whether or not regeneration was possible.

Therefore, the structure of the Mo adsorbent regenerated by the present invention was analyzed by Fourier transform infrared spectroscopy (FT-IR). The measurement conditions were a wave number of 400 to 4000 cm ⁻¹ and a cumulative number of 300 times, and were performed by transmission measurement. As a result, the Mo adsorbent regeneration, peak due to OH groups in the 1650～1750Cm ^-1 and 3000～3500Cm ^-1 is found to be larger than those of the previous play. That is, in the Mo adsorbent regenerated by the present invention, it was confirmed that the Mo adsorption site is an OH group. Therefore, in the present invention, it is essential that the Mo adsorbent reused by regeneration has at least one OH group in the repeating unit. Specifically, it is a configuration having a skeleton structure containing at least one of the repeating units represented by the following chemical formula 18, chemical formula 19 and chemical formula 20, and the objects and effects of the present invention are achieved by this configuration. can do.

［Ｍ_１は４価の金属であり、Ｒ_１及びＲ_２は塩素、アルコキシ基、水酸基又はＯ_1/2から選ばれる何れか一つであり、Ｒ_１及びＲ_２は同じ基であってもよい。］

[M ₁ is a tetravalent metal, R ₁ and R ₂ are any one selected from chlorine, an alkoxy group, a hydroxyl group or O _1/2 , and R ₁ and R ₂ may be the same group. Good. ]

［Ｍ_２は４価の金属であり、Ｒ_３及びＲ_４はアルコキシ基、１分子中に水酸基とカルボキシル基とを有する有機配位子、水酸基又はＯ_1/2から選ばれる何れか一つであり、Ｒ_３及びＲ_４は同じ基であってもよい。］

[M ₂ is a tetravalent metal, R ₃ and R ₄ are any one selected from an alkoxy group, an organic ligand having a hydroxyl group and a carboxyl group in one molecule, a hydroxyl group, or O _1/2. Yes, R ₃ and R ₄ may be the same group. ]

［Ｍ_３は３価の金属であり、Ｒ_５はアルコキシ基、１分子中に水酸基とカルボキシル基とを有する炭化水素基、水酸基及びＯ_1/2から選ばれる何れか１つである。］

[M ₃ is a trivalent metal, and R ₅ is any one selected from an alkoxy group, a hydrocarbon group having a hydroxyl group and a carboxyl group in one molecule, a hydroxyl group, and O _1/2 . ]

The repeating unit represented by the chemical formula 18, the chemical formula 19 or the chemical formula 20 is different in the unit to be introduced depending on the type of the Mo adsorbent. The Mo adsorbent having a skeleton structure containing a repeating unit represented by Chemical Formula 13 or Chemical Formula 14 and Chemical Formula 15 is a skeleton containing the repeating unit represented by Chemical Formula 18 in the step S7 shown in FIG. Played into the structure. Further, the Mo adsorbent having a skeleton structure containing the repeating unit represented by the chemical formula 16 and / or the chemical formula 17 is the repeating unit represented by the chemical formula 19 and / or the chemical formula 20 in the step S7. Regenerated to contain skeleton structure. In addition, as the Mo adsorbent used in the present invention, in addition to the repeating unit represented by the chemical formula 18, chemical formula 19, or chemical formula 20, for example, M (-O1 _{/ 2} ) ₄ or the like (where, M includes a repeating unit of M ₁ , M ₂ or M ₃ described above.

  In the present invention, the number of OH groups contained in the repeating units represented by the above chemical formulas 18, 19 and 20 is a factor governing the Mo adsorption performance. If the number of OH groups contained in the repeating unit increases and the concentration of OH groups in the Mo adsorbent increases, the Mo adsorption performance increases. The OH concentration in the Mo adsorbent can be adjusted by storage temperature, storage time, or water vapor pressure in storage in water or water containing alcohol or in a water vapor atmosphere. These conditions can be optimized and determined by calibrating the OH concentration using, for example, the FT-IR method using the regenerated Mo adsorbent. Thereby, the Mo adsorbent regenerated to the desired performance and characteristics can be obtained.

  In the present invention, when the used Mo adsorbent after the desorption and extraction of Mo is stored in water until the re-adsorption process is started, not only water alone but also water containing alcohol is used. be able to. The regeneration method of the present invention is not limited to storage in water, water containing alcohol, or in a steam atmosphere as long as it can be stored in a Mo adsorbent without reducing M-OH after adsorbing Mo. However, in order to perform the regeneration step shown in S7 of FIG. 1 simply and at low cost and to perform reliable regeneration, it is preferable to perform in water or water containing alcohol or in a steam atmosphere (including a saturated steam atmosphere). It is. Among them, the method of storing in a water vapor atmosphere is preferably in a saturated water vapor atmosphere, but it is difficult to control the water vapor pressure, and when the humidity is low, it tends to reduce the amount of OH groups, which is not preferred. Therefore, the reproduction | regeneration of this invention has a more preferable method stored in water or the water containing alcohol.

FIG. 2 shows an estimated mechanism of ⁹⁹ Mo adsorption and desorption for the regenerated PZC-based Mo adsorbent according to the present invention. As shown in FIG. 2, the PZC-based Mo adsorbent in which Zr—Cl bonds are converted to Zr—OH bonds, Mo is adsorbed to Zr—OH by immersion in an alkaline aqueous solution in which Mo is dissolved. The Mo adsorbed on the Mo adsorbent in this manner is desorbed in an alkaline solution and eluted and recovered as molybdate anions. On the other hand, the Mo adsorbent by the hydrolysis condensate of metal alkoxide is the same as that shown in FIG. 2 except that the M-OR bond is converted into an M-OH bond instead of the Zr-Cl bond. It is thought that adsorption and desorption of Mo are performed by a simple mechanism.

Next, re-adsorption conditions when Mo re-adsorption is performed by the same process as the step S4 using the Mo adsorbent regenerated in the step S7 shown in FIG. 1 will be described. In the present invention, not only the Mo adsorbent regeneration method described above but also the Mo resorption conditions are optimized to provide excellent performance such as ⁹⁹ Mo adsorption and desorption characteristics and ^99m Tc elution rate. It is possible to establish a reproduction method that can be maintained substantially the same as that of the reproduction method and that has a reduced performance and less variation even after being reused many times.

Mo re-adsorption is performed by immersing the regenerated Mo adsorbent in an alkaline solution in which ⁹⁹ Mo / Mo is dissolved. At this ^time, 99 Factors affecting the re-adsorption of Mo / ^Mo, 99 concentrations of the solution containing the Mo / Mo, temperature, not only the immersion time, and pH, particle diameter or Mo adsorbent such as stirring conditions Various things are possible. However, in the molybdenum recovery method described in the aforementioned Japanese Patent Application Laid-Open No. 2012-13617, in Example 3, it is only described that Mo re-adsorption is immersed in a thermostatic bath at 50 ° C. for 3 hours. There is no description or suggestion about the optimum conditions for adsorption, and the prior art has hardly been studied. Among these conditions, the present invention finds that the pH of a solution containing ⁹⁹ Mo / Mo is a main factor that governs the amount of Mo resorption, and adjusts the pH to an acidic to neutral range. The object and the effect of the present invention can be achieved by optimizing between the two.

  In addition, the reduction in the amount of Mo re-adsorption also affects the Mo desorption performance. Although details are unknown, when a continuous decrease in the Mo adsorption amount is observed according to the number of re-adsorptions, the Mo desorption ability also tends to decrease. Therefore, the Mo re-adsorption condition affects not only the Mo re-adsorption performance but also the Mo desorption performance as a result.

In the present invention, Mo re-adsorption increases the amount of Mo re-adsorption and desorption due to desorption when the pH of the solution containing ⁹⁹ Mo / Mo is 6 or less, and the amount increases as the pH decreases. . In this pH range, even if the Mo adsorbent is regenerated two or more times, almost no performance degradation is observed. When the pH of the solution exceeds 6, the amount of Mo resorbed and the amount desorbed by desorption are greatly reduced, and even if the Mo adsorbent regenerated in the step shown in S7 of FIG. It is difficult to achieve the purpose and effect. In the present invention, when the pH of the solution is 5 or less, the amount of Mo resorption and the amount of desorption due to desorption are greatly increased. The amount of Mo adsorbent used can be 150 mg or more, which is generally desired, and further 200 mg or more. However, when the pH of the solution becomes less than 1, the solution turns blue after the Mo adsorbent is added, which has some adverse effects not only on the performance of the Mo adsorbent but also on the molybdenum cycle system. There is a risk of giving. Therefore, in this invention, it is more preferable to adjust pH to 1-5 for the solution containing ⁹⁹ Mo / Mo.

  The present invention will be described with reference to examples, but the scope of the present invention is not limited to these examples.

[Example 1]
In the schematic flow diagram of the molybdenum cycle system shown in FIG. 1, the Mo adsorbent regeneration technology is examined according to the steps S4 to S7 characteristic of the present invention.

<Synthesis of PZC-based Mo adsorbent>
The synthesis is performed using a rotary evaporator into which nitrogen gas is introduced. First, in the first step, a mixed solution of 48 g of di-n-butyl ether and 62.4 g of 2-propanol was added to 120 g of ZrCl ₄ at room temperature from the middle of the gas introduction tube over 20 to 30 minutes. Next, the mixture was heated to 50 ° C. with an oil bath and reacted for 1 hour. In the second step, a mixed solution of 24 g of di-n-butyl ether and 9.1 g of water was added from the middle of the gas introduction pipe in 5 to 10 minutes. After completion of the addition, each was reacted at 50, 70, 90, 110, 130, and 150 ° C. for 1 hour. Thereafter, the remaining solvent was removed by reducing the pressure at 150 ° C. Finally, in the third step, Mo adsorbent (hereinafter abbreviated as PZC-based Mo adsorbent) was synthesized by heat treatment for 0.5 to 2 hours in a temperature range of 150 to 160 ° C. in a nitrogen atmosphere.

<Mo adsorption>
Na ₂ was dissolved MoO ₄ · 2H ₂ O in distilled water, to prepare a Mo-15 mg / ml solution. The Mo solution was adjusted to a neutral region of pH 7. 0.5 g of the PZC-based Mo adsorbent prepared above is added to 10 ml of this Mo solution and heated for 1 hour at 90 ° C. with occasional light stirring. After cooling, the adsorbent and the solution were separated into solid and liquid by decantation to adsorb Mo.

<Mo desorption>
After separating the adsorbent and the solution by decantation, 10 ml of 1M NaOH is added to the PZC-based Mo adsorbent that has already been adsorbed with Mo. went.

<Regeneration of Mo adsorbent>
A regenerated PZC-based Mo adsorbent after desorption of Mo was obtained by storing in water at room temperature for 2 days.

<Mo re-adsorption>
Mo was adsorbed again on the regenerated PZC Mo adsorbent from which Mo was desorbed. For re-adsorption, 10 ml of a 15 mg-Mo / ml Mo solution adjusted in the pH range of 1 to 9 was added and heated at 90 ° C. for 3 hours. Desorption and re-adsorption were repeated 4 times. The desorption was carried out by adding 1M NaOH and heating at 90 ° C. for 1 hour in the same manner as the initial conditions described above. In addition, the regenerated Mo adsorbent was stored in water at room temperature for 2 days, respectively. Mo adsorption characteristics were evaluated by determining the amount of Mo adsorption by the method described below. FIG. 3 shows the relationship between the pH of the Mo solution during re-adsorption and the amount of Mo re-adsorbed on the PZC-based Mo adsorbent of this example. FIG. 4 shows the relationship between the pH of the Mo solution during re-adsorption and the amount of Mo desorbed from the PZC-based Mo adsorbent of this example.

<Evaluation of Mo adsorption amount>
The separated PZC-based Mo adsorbent was washed with a predetermined amount of purified water, dried and dried at 90 ° C., and its mass was measured. The amount of Mo adsorption was evaluated based on the mass increase compared with the sample for mass change evaluation. The amount of Mo adsorption in the used Mo solution was measured by measuring the amount of Mo in the adsorption solution and the cleaning solution using an inductively coupled plasma issuance analyzer (ICP-AES), and adsorbing Mo on the Mo adsorbent. The amount was estimated.

  As shown in FIG. 3, when the pH of the Mo solution becomes 6 or less, the re-adsorption amount starts to increase. When the pH is 5 or less, the re-adsorption amount is 100 mg or more per 1 g of the Mo adsorbent. When the Mo solution has a pH of 2 or less, the re-adsorption amount is 200 mg or more, which is close to the initial adsorption amount (205 mg). Not only the initial Mo solution but also the pH of the solution when it is actually re-adsorbed is acidic, and the lower the solution pH, the greater the amount of Mo re-adsorption. In addition, it was confirmed that the PZC-based Mo adsorbent of this example had almost the same Mo re-adsorption amount as the first time even when desorption and re-adsorption were repeated four times. It has been confirmed that the PZC-based Mo adsorbent of this example hardly shows a decrease in the Mo re-adsorption amount even when desorption and re-adsorption are repeated 10 times. When the pH of the above solution is less than 1, the amount of Mo resorption increases, but the solution changed to blue after the addition of the Mo adsorbent to the solution, so there is a concern that the Mo resorption treatment becomes non-uniform.

  As for the amount of Mo desorbed from the regenerated PZC-based Mo adsorbent of this example, as shown in FIG. 4, when the pH of the Mo solution becomes 6 or less, the amount of desorption begins to increase, and the pH is 5 In the following, the desorption amount is 100 mg or more per 1 g of Mo adsorbent. The relationship shown in FIG. 4 shows almost the same tendency as the relationship shown in FIG. 3, and the Mo re-adsorption condition is not only for Mo re-adsorption performance, but also for Mo desorption performance as a result. You can see that it has an impact.

  FIG. 5 shows the desorption rate obtained from the results shown in FIGS. As shown in FIG. 5, 80% or more of the Mo solution used for re-adsorption is desorbed under a pH of 5 or less, and high-efficiency and stable adsorption / desorption treatment should be performed in this pH range. Can do.

  From the above evaluation results, the regenerated PZC-based Mo adsorbent of this example is not limited to being reused once, and the amount of Mo re-adsorption is reduced even when reused two or more times. In addition, since it has a high liberation rate, an excellent molybdenum cycle system can be constructed. In addition, in order to stably and repeatedly perform Mo re-adsorption on the regenerated PZC-based Mo adsorbent of this example, the Mo solution preferably has a pH of 6 or less, and further the pH is in the range of 1 to 5. It is more preferable to prescribe | regulate.

[Example 2]
Desorption and re-adsorption were carried out by the same method as in Example 1 except that the storage in water containing 10% by volume of ethanol was used instead of the method of storing in water adopted as the Mo adsorbent regeneration step in Example 1. The test was performed four times, and the amount of Mo re-adsorption and desorption were evaluated at each number of times. The obtained evaluation results showed almost the same relationship and tendency as those shown in FIGS. Thus, in the reproduction | regeneration process of Mo adsorption agent of this invention, the reproduction | regeneration method by the preservation | save in the water containing not only the water storage but the alcohol is also employable.

[Comparative Example 1]
In the regeneration process of the Mo adsorbent of Example 1, instead of storing the PZC-based Mo adsorbent in water, after leaving it in the atmosphere of 50% humidity for 2 days, Mo was re-adsorbed, and Example 1 Similarly, desorption and re-adsorption were repeated four times. Mo re-adsorption and desorption were performed under the same conditions as in Example 1. However, regeneration of the Mo adsorbent was performed by leaving it in the atmosphere of 50% humidity for 2 days for 4 times. The amount of Mo re-adsorption when the pH of the Mo solution was 2 was determined in the same manner as in Example 1. As a result, the Mo re-adsorption amount became 100 mg or less with respect to 1 g of the Mo adsorbent at the first time, and a decrease in the Mo re-adsorption amount was observed each time the desorption and re-adsorption were repeated sequentially. Finally, in the fourth treatment, the re-adsorption amount of Mo was less than 50 mg.

[Reference Example 1]
<Mo adsorption mechanism of PZC-based Mo adsorbent>
In Example 1, Fourier transform infrared spectroscopy (FT-IR) was performed using sample 1 which was naturally dried from the PZC-based Mo adsorbent regenerated first time and sample 2 after this sample 1 was further dried at 110 ° C. ) Structural analysis was performed by the method. The measurement conditions were a wave number of 400 to 4000 cm ⁻¹ and a cumulative number of 300 times, and were performed by transmission measurement. The infrared spectrum measured by the FT-IR method is shown in FIG. In FIG. 6, the solid line is the infrared absorption spectrum of sample 1, and the broken line is the infrared absorption spectrum of sample 2.

As shown in Figure 6, the sample 1 is PZC based Mo adsorbent regenerated in Example 1, a peak attributed to the OH group in 1650～1750Cm ^-1 and 3000～3500Cm ^-1 are observed. Further, when comparing the solid line (sample 1) and the broken line (sample 2) shown in FIG. 6, when compared with the relative peak intensity ratio with respect to the absorption peak intensity at a wave number of 500 cm ⁻¹ , it is attributed to the OH group. The peak (3000 to 3500 cm ⁻¹ ) is larger in the solid line, and the amount of the OH group that is a functional group is overwhelming in the sample 1 which is the regenerated PZC-based Mo adsorbent compared to the sample 2 dried at 110 ° C. Many. Therefore, it can be seen that in the regenerated PZC-based Mo adsorbent, the Mo adsorption site is an OH group.

  From the above, the Mo adsorption mechanism shown in FIG. 2 is estimated, and the regenerated PZC-based Mo adsorbent of Example 1 has a skeleton structure containing the repeating unit represented by the chemical formula 18 above. Easy to understand. Therefore, in order to achieve the objects and effects of the present invention, it is essential that the Mo adsorbent has a skeleton structure containing a repeating unit having at least one OH group bonded as a substituent.

In addition, in the infrared absorption spectrum indicated by the broken line in FIG. 6, the shoulder of the absorption peak is observed at two locations indicated by arrows (↓), though very slightly. Peak observed in 2600-2800Cm ^-1 to C-H, also, since the peak observed in 1050-1250Cm ^-1 is C-O, the C-H, is caused respectively, the arrow (↓ It is considered that the absorption peak at the position indicated by) is due to a part of the alkoxy group bonded in the PZC-based Mo adsorbent. It is presumed that trace amounts of alkoxy groups contained in the structure can be relatively observed during the measurement of the infrared absorption spectrum by drying the regenerated PZC-based Mo adsorbent. This indicates that in the repeating unit represented by the above formula 18, at least _one of the substituents R ₁ and R ₂ may contain an alkoxy group.

[Example 3]
<Synthesis of PTC-based Mo adsorbent>
First, in the first step, 1.8 moles of butanol is added to 1 mole of titanium tetraisopropoxide using titanium tetraisopropoxide as a raw material to replace at least one isopropoxy group with a butyl group. In the next second step, 2.1 mol of water (H ₂ O) was added, and the remaining isoproxy group or substituted butoxy group was preferentially hydrolytically condensed to synthesize a polymer. Specifically, a chain polymer was preferentially synthesized while selectively hydrolyzing easily hydrolyzable organic groups little by little. At this time, in order to prevent rapid hydrolysis, it was diluted with 2-propanol more than twice and added. In this step, 0.1 to 0.01 mol of hydrochloric acid was further added to control and slow the rate of hydrolysis. In the final third step, the solvent was removed while promoting condensation. Specifically, condensation was promoted along with removal of the solvent while heating under reduced pressure using an evaporator at a temperature of 45 ° C. Thereafter, sieving was performed to obtain a titanium-based Mo adsorbent (hereinafter abbreviated as PTC-based Mo adsorbent).

  Using the PTC-based Mo adsorbent thus synthesized, Mo was adsorbed by the same method as in Example 1. As a result, the Mo adsorption amount was 207 mg with respect to 1 g of the PTC-Mo adsorbent.

  Further, the steps of Mo desorption, Mo adsorption and Mo resorption are performed in the same manner as in Example 1 except that the pH of the Mo solution used in the Mo adsorption step is adjusted to 4 instead of 7, and desorption and resorption are performed. Was repeated four times. The Mo re-adsorption process was performed by adjusting the pH of the solution to pH 2 using a 15 mg-Mo / ml Mo solution at any number of treatments. The Mo re-adsorption amount for each number of times was determined by the same method as in Example 1.

  The Mo re-adsorption amount was 204 mg with respect to 1 g of the PTC-based Mo adsorbent at the first time, and even when the desorption and re-adsorption were repeated up to 4 times, a decrease in the Mo re-adsorption amount was hardly observed. Finally, in the fourth treatment, the re-adsorption amount of Mo exceeded 200 mg. In this example, desorption and re-adsorption were further performed up to 10 times. However, even after the 10th treatment, the amount of Mo re-adsorption exceeded 200 mg, and it was confirmed that it had excellent Mo adsorption characteristics. .

[Reference Example 2]
<Mo adsorption mechanism of PTC-based Mo adsorbent>
In order to clarify the Mo adsorption mechanism of the PTC-based Mo adsorbent, FT-IR measurement was performed under the same conditions as in Reference Example 1 using a sample obtained by naturally drying the PTC-based Mo adsorbent of Example 3. The measured infrared absorption spectrum is shown in FIG.

As shown in FIG. 7, the PZC based Mo adsorbent regenerated in Example 3, are observed peaks due to OH groups in the 1650～1750Cm ^-1 and 3000～3500Cm ^-1, Example 1 PZC It can be seen that the adsorption site of Mo is an OH group as in the case of the system Mo adsorbent.

  From this result, as shown in FIG. 8A, in the PTC-based Mo adsorbent, an OH group generated by hydrolysis becomes a Mo adsorption site, and an adsorption mechanism for chemically adsorbing Mo can be estimated. Therefore, the regenerated PTC-based Mo adsorbent of Example 3 has a skeleton structure containing a repeating unit represented by the above chemical formula 19 and / or chemical formula 20, and achieves the objects and effects of the present invention. It is essential to have a skeletal structure containing a repeating unit bonded with at least one OH group as a substituent.

  When the regenerated PTC-based Mo adsorbent is stored in a dry atmosphere or heated at a high temperature, as shown in (b) or (c) of FIG. 8, it is caused by a hydrolysis reaction between OH groups or between OH groups and alkoxy groups. The formation of —O— bonds facilitates the formation of a strong three-dimensional structure, with the result that the amount of Mo adsorption tends to decrease. In order to suppress these reactions and leave a predetermined amount of OH groups in the structure, the regeneration method of the present invention in which the Mo adsorbent is stored in water or water containing alcohol is extremely effective.

[Examples 4 to 6]
<Synthesis of other metal-based Mo adsorbents using the production method of PTC-based Mo adsorbents>
The Mo adsorbent containing zirconium (Zr), silicon (Si) and aluminum (Al) was synthesized using the same method as the method for synthesizing the PTC-based Mo adsorbent in Example 3, and Mo desorption and resorption were performed. Every time it was repeated four times, the amount of Mo re-adsorption was measured for each regenerated Mo adsorbent. The conditions for Mo desorption and re-adsorption and the measurement method and conditions for the amount of Mo re-adsorption are the same as in Example 3.

  The Zr-based Mo adsorbent was synthesized by leaving a butoxy group in the side chain using zirconium tetrabutoxide and hydrolyzing the remainder (hereinafter abbreviated as PZCBu-based Mo adsorbent). The Si-based Mo adsorbent was synthesized by leaving an ethoxy group in the side chain using tetraethoxysilane and hydrolyzing the remainder (hereinafter abbreviated as PSiC-based Mo adsorbent). The Al-based Mo adsorbent was synthesized by leaving ethyl acetoacetate (ethyl 3-oxobutanoate) in the side chain and hydrolyzing the remainder (hereinafter abbreviated as PAlC-based Mo adsorbent). The synthesis conditions are shown in Table 1 below.

  Mo was adsorbed by the same method as in Example 3 using various metal-based Mo adsorbents synthesized as described above. The results are shown in Table 1 below. Table 1 shows the measurement results of the Mo re-adsorption amount when Mo is re-adsorbed to the various metal-based Mo adsorbents before the regeneration and the Mo re-adsorption amount after the fourth regeneration process. It also shows.

  As shown in Table 1, although the Mo adsorbents of Examples 4 to 6 have a smaller Mo adsorption amount than the PTC-based Mo adsorbent of Example 3, even if desorption and resorption are repeated up to 4 times, Almost no decrease in the amount of resorbed Mo was observed. Thus, it can be seen that the method for regenerating Mo adsorbent in the present invention has the effect of hardly reducing the Mo adsorption characteristics.

[Examples 7 to 9]
<Synthesis of Mo adsorbent hybridized with multiple metals>
When using a hydrolysis condensate of a metal alkoxide as a Mo adsorbent, it is possible to improve the mechanical strength and durability of the Mo adsorbent by a method of hybridization with a plurality of metals. Therefore, in the PTC-based Mo adsorbent of Example 3, hybridization of Ti and a metal other than Ti was examined.

  In the synthesis method of the PTC-based Mo adsorbent of Example 3, 0.1 to 0.01 mol of hydrochloric acid was added to control the rate of hydrolysis, but in this example, the hybrid was added without adding hydrochloric acid. The synthesized Mo adsorbent was synthesized. During the synthesis, 1-butanol was added to the side chain of Ti. In hybridization with Al, aluminum ethyl acetoacetate diisopropylate is used as a raw material. This compound has isopropoxy groups in two of the trivalent side chains and one ethyl acetoacetate (ethyl 3-oxobutanoate). The molecular design was carried out in such a way that a propoxide group of Al and a propoxy group of Ti formed a chain structure, and the remaining ethyl acetoacetate was used as a Mo adsorption site (the synthesized product is hereinafter abbreviated as PTC: Al). In the hybridization with Si, silicon tetraethoxide was used as a raw material. This compound has an ethoxy group in each of the tetravalent side chains. The ethoxy group of Si and the propoxy group of Ti were hydrolyzed and condensed in a form that forms a chain structure, and the remainder was used as a Mo adsorption site (the synthesized product is hereinafter abbreviated as PTC: Si). Moreover, in the hybridization with Zr, zirconium tetraisobutoxide was used as a raw material. This compound has a butoxy group in each of the tetravalent side chains. The butoxy group of Zr and the propoxy group of Ti were hydrolyzed and condensed to form a chain structure, and the rest was used as Mo adsorption sites (the synthesized product is hereinafter abbreviated as PTC: Zr). Since only the Mo adsorbent hybridized with Zr needed to control the hydrolysis reaction slowly in the synthesis, water mixed with 0.01 mol of hydrochloric acid was used. The synthesis conditions are shown in Table 2 below.

  Mo was adsorbed by the same method as in Example 3 using a system Mo adsorbent obtained by hybridizing Ti thus synthesized with various metals. The results are shown in Table 2 below. Table 2 also shows the measurement results of the Mo re-adsorption amount when Mo is re-adsorbed to the hybrid Mo adsorbent before regeneration and the Mo re-adsorption amount after the fourth regeneration process. It shows.

  As shown in Table 2, the Mo adsorbents of Examples 7 to 9 differ depending on the type of metal hybridized with Ti, but in Examples 7 and 9, the amount of Mo resorbed before regeneration was PTC-based. It became 200 mg or more with respect to 1 g of Mo adsorbents. Moreover, even if Mo adsorption agent shown in Table 2 repeated desorption and re-adsorption up to 4 times, the fall of Mo re-adsorption amount was hardly seen. Furthermore, in Examples 7 and 9, the Mo resorption amount is 150 mg or more even after four treatments, and in particular, Example 9 can ensure 200 mg or more. In Example 9, desorption and re-adsorption were further performed up to 10 times, but it was confirmed that the amount of Mo re-adsorption exceeded 200 mg even after the 10th treatment. Thus, it can be seen that the Mo adsorbent regeneration method of the present invention not only exhibits excellent Mo adsorption characteristics, but also has the effect of hardly reducing the Mo adsorption characteristics.

[Comparative Example 2]
In the regeneration process of the Mo adsorbent of Example 3, instead of storing the PTC-based Mo adsorbent in water, after leaving it in the atmosphere of 50% humidity for 2 days, Mo was re-adsorbed, and Example 3 and Similarly, desorption and re-adsorption were repeated four times. Mo resorption and desorption were carried out under the same conditions as in Example 3, but regeneration of the Mo adsorbent was carried out by leaving it in the atmosphere of 50% humidity for 2 days for 4 times. The amount of Mo re-adsorption when the pH of the Mo solution was 2 was determined in the same manner as in Example 3. As a result, the Mo re-adsorption amount was about 130 mg or less with respect to 1 g of the Mo adsorbent at the first time, and a decrease in the Mo re-adsorption amount was observed each time the desorption and re-adsorption were repeated sequentially. Finally, after the fourth treatment, the re-adsorption amount of Mo was less than 80 mg.

  As described above, the regeneration method of the molybdenum adsorbent according to the present invention can be performed by a simple method of storing in water or water containing alcohol, and positively has a structure having at least one OH group in the repeating unit. In this case, the Mo re-adsorption and desorption operations are not limited to one time, and the Mo re-adsorption amount and the desorption amount due to the desorption are less than the initial value even if the operation is performed four times or more, and further ten times or more. It is maintained at almost the same value, and performance degradation of the regenerated Mo adsorbent can be prevented. Furthermore, when re-adsorbing Mo on the regenerated Mo adsorbent, the re-adsorption characteristics of Mo can be greatly improved by optimizing the pH of the solution containing Mo in the acidic region. Thereby, the Mo re-adsorption amount per 1 g of Mo adsorbent can be set to 150 mg or more, further 200 mg or more desired as a high-performance Mo adsorbent used in the (n, γ) method. Therefore, by applying the method for regenerating a molybdenum adsorbent according to the present invention, it is possible to construct a molybdenum cycle system capable of efficiently recovering Mo at a low cost.

Claims (14)

A step of dissolving molybdenum or molybdenum trioxide obtained by neutron irradiation on molybdenum or molybdenum trioxide pellets and adsorbing the molybdenum adsorbent on a molybdenum adsorbent (adsorption step), and a technetium 99m from a generator comprising the molybdenum adsorbent Step of desorbing molybdenum from the used molybdenum adsorbent (desorption step) using the used molybdenum adsorbent after extraction of the catalyst, and re-adsorbing molybdenum 99-containing molybdenum to the molybdenum adsorbent after the molybdenum desorption (Re-adsorption step), and a molybdenum cycle system including a step of reusing molybdenum trioxide recovered by the desorption step as the pellet,
The molybdenum adsorbent used in the re-adsorption step is a skeleton structure containing at least one of the repeating units represented by the following chemical formula 1, chemical formula 2, and chemical formula 3, and molybdenum adsorption to be re-adsorbed. It has a high concentration of hydroxyl groups so that the amount is 150 mg or more per 1 g of the molybdenum adsorbent , and the desorption step and the resorption step are repeated one or more times. Cycle system.

[M ₁ is zirconium , R ₁ and R ₂ are any one selected from chlorine, an alkoxy group, a hydroxyl group or O _1/2 , and R ₁ and R ₂ may be the same group. ]

[M ₂ is at least one of titanium, zirconium and silicon , R ₃ and R ₄ are alkoxy groups, organic ligands having hydroxyl and carboxyl groups in one molecule, hydroxyl groups or O _1/2 Any one selected, and R ₃ and R ₄ may be the same group. ]

[M ₃ is aluminum , and R ₅ is any one selected from an alkoxy group, a hydrocarbon group having a hydroxyl group and a carboxyl group in one molecule, a hydroxyl group, and O _1/2 . ] 2. The cycle system according to claim 1 , wherein the molybdenum adsorbent used in the re-adsorption step has a skeleton structure containing a repeating unit represented by the chemical formula ( 1 ). . 2. The cycle system according to claim 1 , wherein the molybdenum adsorbent used in the re-adsorption step is a skeleton structure containing a repeating unit represented by the chemical formula 2 or the chemical formula 3 or the chemical formula 2 and molybdenum recycling system characterized by have a skeleton structure containing a repeating unit represented by the chemical formula 3. 4. The molybdenum cycle system according to claim 1 , wherein the alkoxy ligand and the organic ligand having a hydroxyl group and a carboxyl group in one molecule have 1 to 8 carbon atoms. 5. Molybdenum cycle system. The molybdenum cycle system according to any one of claims 1 to 4 , wherein the molybdenum adsorbent used in the resorption process is stored in water or water containing alcohol until the resorption process is started. Molybdenum cycle system characterized by that. In the cycle system molybdenum according to any one of claims 1 to 5, wherein the re-adsorption process, molybdenum, characterized in that it is carried out using a solution containing a molybdenum 99 pH is adjusted to 6 or less Cycle system. The molybdenum cycle system according to claim 6 , wherein the solution containing molybdenum 99 is adjusted to have a pH of 1 to 5. The molybdenum cycle system according to any one of claims 1 to 7 , wherein the molybdenum adsorption amount is 200 mg or more per 1 g of the molybdenum adsorbent. A step of dissolving molybdenum or molybdenum trioxide obtained by neutron irradiation on molybdenum or molybdenum trioxide pellets and adsorbing the molybdenum adsorbent on a molybdenum adsorbent (adsorption step), and a technetium 99m from a generator comprising the molybdenum adsorbent Step of desorbing molybdenum from the used molybdenum adsorbent (desorption step) using the used molybdenum adsorbent after extraction of the catalyst, and re-adsorbing molybdenum 99-containing molybdenum to the molybdenum adsorbent after the molybdenum desorption (Re-adsorption step) and a step of reusing molybdenum trioxide recovered by the desorption step as the pellet, and used in a molybdenum cycle system in which the desorption step and the adsorption step are repeated one or more times. Of molybdenum adsorbent used A law,
Molybdenum adsorbent used in the re-adsorption step, and skeletal structure containing at least one of repeating units represented by Formula 4, Formula 5, and Formula 6 below, molybdenum adsorption being re-adsorbed A method for regenerating a molybdenum adsorbent, comprising regenerating to a high concentration hydroxyl group so that the amount is 150 mg or more per 1 g of the molybdenum adsorbent.

[M ₁ is zirconium , R ₁ and R ₂ are any one selected from chlorine, an alkoxy group, a hydroxyl group or O _1/2 , and R ₁ and R ₂ may be the same group. ]

[M ₂ is at least one of titanium, zirconium and silicon , R ₃ and R ₄ are alkoxy groups, organic ligands having hydroxyl and carboxyl groups in one molecule, hydroxyl groups or O _1/2 Any one selected, and R ₃ and R ₄ may be the same group. ]

[M ₃ is aluminum , and R ₅ is any one selected from an alkoxy group, a hydrocarbon group having a hydroxyl group and a carboxyl group in one molecule, a hydroxyl group, and O _1/2 . ] 10. The method for regenerating a molybdenum adsorbent according to claim 9 , wherein the molybdenum adsorbent used in the re-adsorption step has a skeleton structure containing a repeating unit represented by the chemical formula 4 below. The molybdenum adsorbent used in the re-adsorption step is a skeleton structure containing a repeating unit represented by Chemical Formula 5 or Chemical Formula 6 or a repeating structure represented by Chemical Formula 5 and Chemical Formula 6 above. The method for regenerating a molybdenum adsorbent according to claim 9 , comprising a skeleton structure containing a unit. The molybdenum adsorbent according to claim 9 or 11 , wherein the alkoxy group and the organic ligand having a hydroxyl group and a carboxyl group in one molecule have 1 to 8 carbon atoms. Playback method. Molybdenum adsorbent used in the re-adsorption step, according to any of claims 9-12, wherein the re-adsorption step is stored in water with water or alcohol until the start Regeneration method of molybdenum adsorbent. The regeneration method for a molybdenum adsorbent according to any one of claims 9 to 13 , wherein the regeneration is performed so that the molybdenum adsorption amount is 200 mg or more per 1 g of the molybdenum adsorbent.

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