JP2018123373A - Selective separation method of metal element and separation unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently separating a specific metal element from an acidic solution containing various metal elements by using an impregnated adsorbent having an extraction agent impregnated.SOLUTION: Provided is a method for selectively separating a specific metal element from an acidic solution, comprising the steps of: preparing an impregnated adsorbent where there is prepared an impregnated adsorbent by impregnating particles having the surface coated with a polymer with 2 or more kinds of extraction agents; and having the metal element adsorbed by the impregnated adsorbent by contacting the acidic solution containing the specific metal element with the impregnation adsorbent.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for separating a metal element present in an acidic solution using an extraction chromatography method.

Japan, which has few resources in its own country and relies on foreign imports, collects rare metal elements from used products. As a rare metal element, rare earths are abundant in spent nuclear fuel from municipal mines and nuclear reactors such as waste electrical appliance substrates and liquid crystals.
There are various methods for recovering rare earth from a solution obtained by dissolving these products in acid. Among them, the recovery method using an impregnated adsorbent impregnated with an extractant is said to have a low environmental load because it uses less organic solvent than other recovery methods.

For example, rare earth recovery using an impregnated adsorbent includes recovery of trivalent lanthanoid (Ln (III)) from spent nuclear fuel. The solution after dissolving the spent nuclear fuel with acid and separating and recovering uranium and plutonium is called high-level radioactive liquid waste (HLLW). This acidic solution contains Ln (III), trivalent minor actinoids (MA (III): Am (III) and Cm (III)), and fission products (FP).
Conventionally, since Ln (III) is very similar in chemical behavior to MA (III), it has been difficult to separate and recover Ln (III) and MA (III).
According to Non-Patent Document 1, as a processing method for separating and recovering these nuclides, a two-stage column processing process by an extraction chromatography method using an impregnated adsorbent is being studied.
However, in the method of Non-Patent Document 1, since the separation and recovery of Ln (III) is performed by a two-stage column, the processing steps are complicated, the apparatus length is increased, and the amount of adsorbent required is increased.

S. Watanabe, I. Goto, K. Nomura, Y. Sano, Y. Koma, “Extraction chromatography experiments on repeated operation using engineering scale column system”, Energy Procedia, 7, p.449-453, (2011) Y. Wei, A. Zhang, M. Kumagai, M. Watanabe, N. Hayashi, “Development of the MAREC Process for HLLW Partitioning Using a Novel Silica-Based CMPO Extraction Resin”, J. Nucl. Sci., 41, 315 -322, (2004)

  The present invention has been made in view of these circumstances, and it is an object to improve the efficiency of separating and recovering a specific metal element using an impregnated adsorbent impregnated with an extractant from an acidic solution containing various metal elements. To do. Another object is to separate the adsorbed metal element from the impregnated adsorbent in order to reuse the impregnated adsorbent.

In order to solve the above problems, in the present invention, an impregnated adsorbent prepared by mixing and impregnating two kinds of extractants usually used in a two-stage column processing step is prepared, and a specific metal element is obtained from an acidic solution by the following process. Is separated and recovered. That is, a method for selectively separating a specific metal element according to an embodiment of the present invention is as follows.
A step of preparing an impregnated adsorbent prepared by impregnating two or more kinds of extractants into particles whose surfaces are coated with a polymer, contacting an acidic solution containing a specific metal element with the impregnated adsorbent, A method for selectively separating a specific metal element from an acidic solution, comprising an adsorption step of adsorbing the metal element on the impregnated adsorbent.

According to the present invention, an impregnated adsorbent impregnated with two or more kinds of extractants is used in place of the column treatment process in which two kinds of extractants are impregnated in two stages. Processing can be performed in stages. Accordingly, the processing apparatus can be reduced and the amount of adsorbent required for column packing can be reduced as compared with the case of two stages. Therefore, the separation and recovery process for a specific metal element can be performed efficiently.
Moreover, the adsorbed metal element can be separated from the impregnated adsorbent and reused.
Further, by utilizing the present invention, MA (III) can be separated and recovered simultaneously with the recovery of Ln (III) from the high-level radioactive liquid waste (HLLW), so the radioactive waste can be reduced by reducing the volume of the high-level radioactive waste. A technology for improving safety, reliability, efficiency, and the like can be provided.

Schematic diagram of an adsorbent impregnated with CMPO-HDEHP used in a metal element separation method according to an embodiment of the present invention. Schematic diagram showing the separation process of Ln (III) and MA (III) according to an embodiment of the present invention. The graph which shows the nitric acid concentration dependence of the adsorption partition coefficient with respect to neodymium (Nd (III)) of each adsorbent which changed extractant molar ratio. The graph which shows the adsorption distribution coefficient of Ln (III) of each adsorbent which changed the extractant molar ratio in 1 mol / L nitric acid solution The graph which shows the adsorption distribution coefficient of Eu and ²⁴¹ Am with respect to each adsorbent which changed extractant molar ratio. The graph which shows the elution rate of Eu and ²⁴¹ Am from each adsorbent which changed the extractant molar ratio at the time of using a DTPA solution

The process of the metal element separation method according to the present invention will be described with reference to the drawings.
(First embodiment)
The specific metal element separation method according to the present invention includes an impregnated adsorbent preparation step in which an impregnated adsorbent prepared by impregnating particles coated with a polymer with two or more kinds of extractants, and a specific metal element A method of selectively separating a specific metal element from the acidic solution, comprising an adsorption step of contacting the impregnated adsorbent with an acidic solution containing the metal element and adsorbing the metal element onto the impregnated adsorbent.

  The specific metal element to be separated is not particularly limited as long as it can form a metal complex with the extractant. Specifically, for example, actinide elements (An) including uranium (U), plutonium (Pu) and americium (Am), curium (Cm), and other superuranium elements (An), lanthanum (La), neodymium (Nd), europium. Lanthanoid elements (Ln) such as (Eu), lutetium (Lu), platinum group elements such as rhodium (Rh), palladium (Pd), ruthenium (Ru), cesium (Cs), strontium (Sr), technetium (Tc) , Tin (Sn), zirconium (Zr) and the like. One or more of the above metal elements can be included in the acidic solution that contacts the impregnated adsorbent.

The extractant is capable of forming a metal complex and impregnating particles described later.
The selective separation of the metal element is performed by appropriately selecting the extractant impregnated in the adsorbent.
Specifically, for example, when selectively separating Ln elements such as La, Nd, Eu, and Lu and Am and Cm from various metal elements contained in the solution, CMPO (n-octyl (phenyl) is used as an extractant. ) -N, N′-diisobutylcarbamoylmethylphosphine oxide), TODGA (N, N, N ′, N′-tetraoctyl diglycolamide) can be selected. When the Ln element and the An element contained in the solution are selectively separated, HDEHP (di-2-ethylhexyl phosphate), R-BTP (2,6-bis- (5,6-) is used as an extractant. Dialkyl-1,2,4-triazin-3-yl) pyridine) and TPEN (N, N, N, N-tetrakis (2-pyridylmethyl) ethylenediamine) can be selected. Moreover, when selectively separating U and Pu which are tetravalent or hexavalent An elements, TBP (tributyl phosphate) can be selected as an extractant. Two or more kinds of extractants can be selected from those listed above.
In order to selectively separate Ln elements such as La, Nd, Eu, and Lu, and Am and Cm, the present inventors use a mixture of CMPO and HDEHP as an extractant, thereby providing a cooperative extraction effect. Was found to express. What is the cooperative extraction effect? In the solvent extraction method, when other extraction agents are added to an organic solvent containing an extraction agent and metal ions are extracted in a system containing two or more extraction agents, the respective distribution ratios are added together. This is a phenomenon that expresses more extraction performance.

  A schematic diagram of a preferred impregnated adsorbent packed in a column is shown in FIG. The impregnated adsorbent is obtained by impregnating two or more kinds of extractants on one particle coated with a polymer.

The particles are not particularly limited as long as they can be coated with a polymer. Specifically, porous silica particles, porous alumina particles, polymer beads and the like can be used. Among these, porous silica particles are preferable because of their high chemical stability and radiation resistance and excellent mechanical strength.
The number average particle size measured with a particle size distribution meter of these particles is usually 10 to 100 μm, preferably 30 to 50 μm. The size of the pores of the particles is usually 50 to 800 nm, preferably 400 to 600 nm. If the size of the pores is within the above range, it is preferable because the solution can be easily brought into contact with the inside of the adsorbent. Moreover, the shape includes a true sphere, an elliptical sphere (egg), a columnar shape, a prismatic shape, a flat shape, and the like. As particles satisfying these physical properties, there are silica particles manufactured by Asahi Kasei Corporation, silica particles manufactured by Fuji Silysia Chemical, and the like.

Examples of the polymer include styrene-divinylbenzene copolymer.
The method for coating the particles with the polymer is not particularly limited, and may be performed according to a conventional method. For example, polymerization by a crosslinking reaction on the particles can be used. The adhesion rate on the particle surface of the polymer is determined from the amount of thermal decomposition measured by thermogravimetry, and is usually 10 to 25%, preferably 15 to 20%. It is preferable that the adhesion rate of the polymer particles is within the above range because the extractant can be impregnated efficiently.

After impregnating such particles with a solution obtained by mixing and diluting two or more kinds of extractants with an organic solvent, the impregnated adsorbent of the present invention is prepared by removing the organic solvent. In this impregnated adsorbent, the same particles are impregnated with two or more kinds of extractants.
Examples of the organic solvent include acetone, dichloromethane, methanol, and ethanol, which are appropriately selected depending on the type of extractant to be mixed and diluted.
When CMPO and HDEHP are used as the extractant, those having various mixing ratios can be used. Usually, CMPO: HDEHP is in a molar ratio of 1: 1 to 8: 1, preferably 2: 1 to 4: 1. is there.
When the mixing ratio of CMPO and HDEHP is within the above range, the adsorption efficiency of the impregnated adsorbent impregnated in the particles and the elution efficiency in the elution step described later can be improved.

  In the adsorption step of the present embodiment, an acidic solution containing a specific metal element is brought into contact with the impregnated adsorbent prepared as described above, and the metal element is adsorbed on the impregnated adsorbent.

Furthermore, in the method for separating a specific metal element according to the present invention, when the eluent is brought into contact with the impregnated adsorbent after the adsorption step, further metal element can be selectively separated.
When selectively eluting An elements such as Am and Cm, DTPA can be selected as the eluent. The concentration of the DTPA is usually 10 to 100 mmol / L, preferably 25 to 50 mmol / L, and the pH is usually 1 to 4, preferably 2 to 3. It is preferable that each physical property is within the above range since elution efficiency is increased.
Further, when selectively eluting Ln elements such as La, Nd, Eu, and Lu, lactic acid, oxalic acid, ammonium acetate, and citric acid can be selected as an eluent. Among these, citric acid is preferable because of its high elution rate. The eluent of Ln element has a concentration of usually 0.01 to 1 mol / L, preferably 0.5 to 1 mol / L, and a pH of usually 3 to 7, preferably 5 to 7. It is preferable that each physical property is within the above range since elution efficiency is increased.
Two or more of these eluents may be sequentially used, such as an An eluent as the first eluent and an Ln eluent as the second eluent. In addition, the impregnated adsorbent can be reused by eluting the metal element adsorbed from the impregnated adsorbent using the eluent. From the viewpoint of reusing the impregnated adsorbent, the elution rate of the adsorbed metal element in the impregnated adsorbent is preferably 98% or more.

The acidic solution is not particularly limited as long as a specific metal element can be adsorbed in the adsorption step. For example, sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), hydrochloric acid (HCl), and the like can be given.
The acid concentration of the acidic solution is usually 0.1 to 6N, preferably 1 to 3N. When CMPO and HDEHP are used as the extractant, the acid concentration of the acidic solution is preferably 1 to 3N.

(Second Embodiment)
In the second embodiment of the present invention, a column filled with an impregnated adsorbent obtained by impregnating particles coated with a polymer with two or more kinds of extractants, and connected to the column, the column is specified. And a sample supply unit that supplies an acidic solution containing the metal element, and an eluent supply unit that is connected to the column and supplies an eluent to the column.

By using this separation device, it is possible to separate a specific metal element from an acidic solution (sample) containing various metal elements.
The impregnated adsorbent is the same impregnated adsorbent as described in detail in the first embodiment. The impregnated adsorbent is packed in a column and installed in a separation device. The sample supply unit is connected to the column, and a specific metal element contained in the sample is adsorbed to the impregnated adsorbent by passing the sample through the column. Metal elements that are not adsorbed flow out of the column. The eluent supply unit is connected to the column, and elutes the specific metal element adsorbed on the impregnated adsorbent from the impregnated adsorbent by passing an eluent specific to the specific metal element through the column. It can be included in the effluent. The eluent supply section can connect a plurality of eluent supply sections such as a first eluent supply section and a second eluent supply section to the column according to the number of types of specific metal elements to be eluted.

This separation device may have a simple configuration capable of connecting a sample or eluent supply unit to a column packed with an impregnated adsorbent. The sample or eluent supply unit may be constituted by a tube or the like. The separation apparatus may include an introduction liquid switching unit that switches between the sample supply unit and the plurality of eluent supply units.
The separation device may include an introduction liquid container configured to accommodate a sample or an eluent, and controls a suction pump for introducing the sample or the eluent into the column and a flow rate of the sample or the eluent. An introduction liquid flow rate control unit may be included. Further, the separation device may include a container for receiving the effluent from the column.

  A column in which particles coated with styrene-divinylbenzene polymer on the surface are filled with an adsorbent impregnated with CMPO and HDEHP as an extractant, and as an acidic solution supplied to the column, spent nuclear fuel is dissolved in nitric acid, and uranium and Fig. 2 shows a schematic diagram of the process for separating Ln (III), trivalent minor actinoids (MA (III)), and fission products (FP) using high-level radioactive liquid waste (HLLW) after separating and recovering plutonium. Show. The high-level radioactive liquid waste that is a nitric acid solution contains Ln (III), trivalent minor actinoids (MA (III)), and fission products (FP).

  When a high-level radioactive waste liquid (HLLW) whose concentration is adjusted to 1 to 3 mol / L nitric acid is passed through a column packed with the impregnated adsorbent, Ln (III) and MA (III) are adsorbed by the impregnated adsorbent. On the other hand, the fission product (FP) is discharged without being adsorbed, and the fission product (FP) is washed away by passing 1 to 3 mol / L nitric acid. By supplying DTPA as a MA (III) eluent to the column, MA (III) is eluted from the impregnated adsorbent and discharged. Subsequently, citric acid is supplied to the column as an Ln (III) eluent, so that lanthanoids (Ln (III): La, Nd, Eu, Lu, etc.) are eluted from the impregnated adsorbent and discharged. This completes the separation and recovery of MA (III), Ln (III), and FP.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely with reference to an Example, this invention is not limited only to these Examples.
<Preparation of particles impregnated with extractant>
Spherical silica particles (SiO ₂ ) having a diameter of 40-60 μm and a pore diameter of 600 nm were placed in a glass flask and set on a rotary evaporator, and the flask was decompressed with a vacuum pump. Monomer (m / p-formylstyrene and m / p-divinylbenzene), polymerization initiator (α, α-azobisisobutyronitrile and 1,1′-azobiscyclohexane-1-carbonitrile), and diluent A mixture of (1,2,3-trichloropropane and m-xylene) was sucked through the rubber tube into the flask. The flask was continuously rotated so that the mixture completely penetrated the pores of the silica particles, and then the flask was filled with nitrogen gas. The flask was heated to 90 ° C. in a silicone oil bath and held for 20 hours. The grafted material (SiO ₂ —P) was washed with acetone and hot water and then dried at 50 ° C. overnight. The adhesion rate of the copolymer (formylstyrene-divinylbenzene) to the SiO ₂ -P particles measured by thermogravimetric analysis was 17.6 wt%.

<Preparation of impregnated adsorbent impregnated with extractant and packing in column>
First, silica particles (SiO ₂ —P) coated with styrene-divinylbenzene were washed three times with methanol and dried at 60 ° C. overnight. 5 g of 98.3% pure CMPO and 2 g of 95.0% HDEHP in a conical flask were dissolved in 60 cm ³ of dichloromethane and diluted, followed by 10 g of dry particles (SiO ₂ —P). The addition mixture was spun vigorously at 25 ° C. for 2 hours. Thereafter, the diluent was removed by reducing the pressure at 50 ° C. using a rotary evaporator. The residue was dried overnight at 50 ° C. to obtain CMPO-HDEHP / SiO ₂ —P, which is an impregnated adsorbent based on silica. Since there was no loss of CMPO and HDEHP in the impregnation step, the impregnated adsorbent contained 0.5 g CMPO, 0.2 g HDEHP and 1.0 g SiO ₂ —P.
The impregnated adsorbent thus obtained was packed in a column as necessary to prepare for the adsorption step.

<Separation of metal elements>
[Example 1]
Examination of the adsorption behavior of the column packing material CMPO-HDEHP impregnated adsorbent was carried out by a batch type adsorption test method. After putting a 4 cm ³ metal solution in which Nd (III) is dissolved in 0.2 g adsorbent and 1 mol / L nitric acid solution into a glass vial and shaking for 3 hours, the concentration of metal ions in the solution before and after is measured, The adsorption partition coefficient was calculated. In this test, the adsorbent was prepared by changing the mass of HDEHP while keeping the mass of CMPO constant, and the adsorption distribution coefficients were compared using adsorbents having different CMPO: HDEHP molar ratios as described below. The types of adsorbents are CMPO adsorbent, HDEHP adsorbent, adsorbent with a CMPO: HDEHP molar ratio of 1.5: 1, 2: 1 adsorbent, 4: 1 adsorbent, 8: 1 adsorbent, A 15: 1 adsorbent was used. The adsorption distribution coefficient of Nd (III) for each adsorbent is shown in FIG. The following formula shows the calculation formula for the adsorption distribution coefficient Kd.
Kd = (C ₀ −C _S ) / C _S × V / W
Here, _{C 0} metal density before the test aqueous phase [mmol / L], _{C S} is the metal concentration in the aqueous phase after the test [mmol / L], V the volume of the metal solution ^[cm 3], W Indicates the dry weight [g] of the resin.

  From FIG. 3, it is confirmed that each CMPO-HDEHP adsorbent has an increase in the adsorption distribution coefficient at any nitric acid concentration compared to the CMPO adsorbent, and particularly in the low concentration nitric acid region, the adsorption distribution coefficient increases with the increase in HDEHP addition amount. The increase was significant. On the other hand, an increase in the adsorption partition coefficient was confirmed even in a 1 mol / L nitric acid solution in which HDEHP is non-adsorbed with respect to Nd (III). That is, at a nitric acid concentration of 1 mol / L, the adsorption partition coefficient increases due to the cooperative extraction effect. At a nitric acid concentration of 1 mol / L, an increase in the Nd (III) adsorption distribution coefficient of the 2: 1 adsorbent is remarkable among the CMPO-HDEHP adsorbents.

[Example 2]
The adsorption behavior of the CMPO-HDEHP adsorbent which is the column packing material in the present invention was examined by a batch type adsorption test method. After putting a 4 cm ³ metal solution having Ln (III) dissolved in a 0.2 g adsorbent and a 1 mol / L nitric acid solution into a glass vial and shaking for 3 hours, the concentration of metal ions in the solution before and after was measured. The adsorption partition coefficient was calculated. In this test, the CMPO adsorbent of Example 1 and a 2: 1 adsorbent were used.
As can be seen from FIG. 4, both adsorbents showed an increase in the adsorption partition coefficient as the nitric acid concentration increased for both elements, and the adsorption partition coefficient increased as the atomic number increased and decreased at the middle rare earth element. confirmed. That is, it was suggested that any adsorbent tends to be adsorbed in the order of medium rare earth elements, light rare earth elements, and heavy rare earth elements. Compared with the CMPO adsorbent, the adsorbent distribution coefficient was higher in the 2: 1 adsorbent, particularly in heavy rare earth elements. Accordingly, it was confirmed that the selectivity of Ln (III) was improved by the expression of the cooperative extraction effect, and in particular, the selectivity of heavy rare earth elements was improved.

[Example 3]
The saturation adsorption amount of the CMPO-HDEHP adsorbent which is the column filler in the present invention was examined by a column test method. A metal solution in which Ln (III) was dissolved in a 1 mol / L nitric acid solution was passed through a 1 cm diameter column packed with each 7.85 cm ³ adsorbent, and the effluent was fractionated. Thereafter, Ln (I) is obtained from the breakthrough curve obtained by measuring the metal ion concentration in each solution.
The saturated adsorption amount of II) was calculated. Table 1 shows the saturated adsorption amount of Ln (III) of each adsorbent. In this test, the CMPO adsorbent of Example 1 and 2: 1 adsorbent were used.
From Table 1, it was confirmed that the 2: 1 adsorbent increased in the saturated adsorption amount of each element due to the cooperative extraction effect and the overall saturated adsorption amount as compared with the CMPO adsorbent.

[Example 4]
The adsorption behavior of the CMPO-HDEHP adsorbent which is the column packing material in the present invention was examined by a batch type adsorption test method. 4 cm ³ each of Eu and ²⁴¹ Am dissolved in 0.2 g adsorbent and 1 mol / L nitric acid solution were placed in a glass vial and shaken for 3 hours, and then the metal ion concentration in the solution before and after was measured. The adsorption partition coefficient was calculated. In this test, the CMPO adsorbent of Example 1, 2: 1 adsorbent, and 1: 1 adsorbent were used. FIG. 5 shows the adsorption distribution coefficients of Eu and ²⁴¹ Am for each adsorbent.
From FIG. 5, Eu and ²⁴¹ Am both showed high adsorption distribution coefficients in any adsorbent. From this, it was confirmed that the CMPO-HDEHP adsorbent has a high adsorption performance for Ln (III) and MA (III).

[Example 5]
The elution behavior of the CMPO-HDEHP adsorbent which is a column packing material in the present invention was examined by a batch type elution test method. Glass vials together with 4 cm ³ of 50 mmol / L DTPA solution with Eu and ²⁴¹ Am adsorbed on 0.2 g adsorbent, diluted with 0.1 mol / L nitric acid solution as the first eluent and pH adjusted to 2.3 After putting in a bottle and shaking for 1 hour, the metal ion concentration in the solution before and after was measured, and the elution rate was calculated. In this test, the CMPO adsorbent of Example 1, 2: 1 adsorbent, and 1: 1 adsorbent were used. FIG. 6 shows the elution rates of Eu and ²⁴¹ Am from each CMPO-HDEHP adsorbent when a DTPA solution is used as the eluent.
From FIG. 6, in the case of the CMPO adsorbent, elution of both adsorbed elements was confirmed by the DTPA solution. On the other hand, in the case of the CMPO-HDEHP adsorbent, elution of adsorbed Eu was not confirmed by the DTPA solution, but elution of ²⁴¹ Am was confirmed. From this, it was confirmed that MA (III) can be selectively eluted by using a DTPA solution.

[Example 6]
Put a 4cm ³ second eluent with 0.2g adsorbent adsorbing Nd (III) into a glass vial and shake for 1 hour, then measure the metal ion concentration in the solution before and after, and calculate the elution rate did. When a 1 mol / L ammonium acetate solution diluted with pure water was used as the second eluent, the elution rate was 20%. When 0.5 mol / L citric acid diluted with pure water was used as the second eluent, the elution rate was 98.5%.

Claims (11)

A step of preparing an impregnated adsorbent for preparing an impregnated adsorbent obtained by impregnating two or more kinds of extractants into particles whose surfaces are coated with a polymer;
An adsorption step in which an acidic solution containing a specific metal element is brought into contact with the impregnated adsorbent, and the metal element is adsorbed on the impregnated adsorbent;
A method for selectively separating a specific metal element from an acidic solution.   The method of claim 1, wherein the extractant is CMPO and HDEHP. The particles are porous silica particles;
The method according to claim 1 or 2, wherein the polymer is a styrene-divinylbenzene copolymer.   The method according to any one of claims 1 to 3, wherein the specific metal element is one or more selected from the group consisting of an actinoid element, a lanthanoid element, and a platinum group element. An elution step of eluting the metal element using an eluent from the impregnated adsorbent adsorbing the specific metal element after the adsorption step;
The method according to claim 1, further comprising:   The method according to claim 5, wherein the eluent is one or more selected from the group consisting of DTPA, oxalic acid, lactic acid, ammonium acetate and citric acid.   The method according to claim 5 or 6, wherein the elution step includes a first elution step, a first elution step of selectively eluting the metal element using a second eluent, and a second elution step.   8. The method of claim 7, wherein the elution step includes a first elution step of eluting the actinide element using DTPA and a second elution step of eluting the lanthanoid element using ammonium acetate or citric acid. A column packed with an impregnated adsorbent formed by impregnating two or more kinds of extractants into particles whose surfaces are coated with a polymer;
A sample supply unit connected to the column and supplying an acidic solution containing a specific metal element to the column;
A separation apparatus comprising: an eluent supply unit connected to the column and supplying an eluent to the column.   The separation device according to claim 9, wherein the eluent is at least one selected from the group consisting of DTPA, oxalic acid, lactic acid, ammonium acetate, and citric acid.   The eluent supply unit supplies DTPA to the column to elute actinoid elements, and the second eluent supply to supply ammonium acetate or citric acid to the column to elute lanthanoid elements. The separation device according to claim 9 or 10, comprising a section.