JPS6260136B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating isotopes by chromatography, in which a platform (equivalent to the isotope in the initially supplied solution) is maintained inside the chromatogram; Thus, a desired isotope concentrate can be produced more effectively.

According to the invention, from lithium 7 to lithium 6
, boron-10 from boron-11, and other isotopes, such as uranium-235 from uranium-238.

The present invention relates to a method that makes the overall operation simpler and improves the efficiency of liquid or gas chromatographic separations for producing isotopic concentrates.

The chromatographic method for producing isotopic concentrates according to the invention includes the following two steps.

(1) Initial Concentration Step (Start-up) (2) Manufacturing Process The initial concentration step is the start-up of a chromatographic operation in which the atomic fraction of the desired isotope is placed at the front or rear of the chromatogram without removing any product fluid. This process is continued until the desired level is achieved.

The next manufacturing step is semi-continuously or continuously removing the product of the desired atomic fraction from the front or rear of the chromatogram.

The separation efficiency of isotope separation by conventional chromatography has tended to decrease because the enriched and depleted regions overlap and isotope mixing occurs.

In the present invention, the chromatography is carried out in such a way that a substitution front is formed at the front and/or the rear of the chromatogram and the sum of the concentrations of the two isotopes remains constant.

The chromatographic bands are sufficiently broad that the enriched and depleted regions are always separated from each other and there is no overlap between them.

The salient features of the method according to the invention are as follows.

(1) Mixing of isotopes can be prevented, and a platform (equivalent to the isotope in the feed solution) is maintained between the rich region and the depleted region.

(2) Expansion of enriched and depleted areas caused by changes in total concentration can be prevented.

(3) New supply solution can be added to the center of the chromatogram without interrupting operation.

As a result of the method of the present invention, concentrates of desired isotopes can be produced more effectively.

Specific examples of the method of the present invention carried out using liquid phase chromatography will be described in more detail, but these specific examples are for illustrating the present invention and are not intended to limit the present invention.

Example 1 Production of Lithium 6 Natural lithium has two isotopes: lithium 6 (7.2%) and lithium 7 (92.8%)
It becomes.

A set of column apparatus such as the one shown in Figure 1 (each column is 22 mm in diameter and 1300 mm in length) was packed with ion exchange resin Dowex 50W to a height of 1200 mm, and this resin was converted to the acid form R-H. . The chromatographic operation was performed by feeding a 0.3M aqueous solution of lithium acetate (CH ₃ COOLi) to this column to form an absorption band, and then eluting this absorption band with a 0.3M aqueous solution of sodium acetate (CH ₃ COONa). I did it.

By operating in this way, the front part was enriched with lithium 7 and the rear part of the absorption band was enriched with lithium 6.

In the case of isotope platform retention, a 6 m wide lithium absorption band was formed and displaced within the column. After traveling a total length of 202 m, the atomic fraction of lithium-6 at the rear of the band is
It increased from 7.2% to 15.0%.

In this way, by feeding natural lithium into the central region of the chromatogram, a 15% concentration of lithium 6 can be produced at a rate of 2.9 mmol per cm ² and per day. At the front of the band,
As shown in Figure 2, the atomic fraction of lithium-6 decreased from 7.2% to 2.9% after traveling a distance of 202 m.

Without retention of isotope platform A 3 m wide lithium column was formed and displaced within the column apparatus. In order to concentrate the atomic fraction of lithium-6 from 7.2% to 15.0% at the front of the band, it was necessary to displace the band by 450 m.

At this point, a concentration of 15% lithium 6 could be produced at a rate of 1.4 mmol per cm ² and per day.

However, it was difficult to replenish the center of the band with fresh feed solution without destroying the chromatogram, thus slowing down the production rate as shown in FIG.

Example 2 Preparation of Boron-10 Natural boron consists of two isotopes: boron-10 (19.8%) and boron-11 (80.2%).

As shown in Figure 4, a column device with a diameter of 22 mm and a height of 4100 mm was used with an anion exchange resin and a weak base Diaion.
WA21 (free base form) was filled to a height of 4000 mm and the resin was converted to the base form R-OH and washed with pure water.

Next, this column was filled with an aqueous solution of boric acid to form an absorption band, and chromatography was performed by eluting the boron band with water.

By doing so, boron 11 was concentrated in the front part of the band, and boron 10 was concentrated in the rear part.

In the case of isotopic platform retention A 4 m ion exchange resin column was packed with 5.0 liters of a 0.1 M boric acid aqueous solution.

The front of the absorption band decreased and no boron-11 concentrate could be recovered.

Chromatography is performed by eluting the absorption band with water, and the boron-10
was concentrated from 19.8% to 33.3%. The width of the rich area was 34 cm as shown in Figure 5.

When not retaining the isotope platform When first filling the column with 2.0 liters of 0.1M boric acid solution, it was impossible to perform displacement chromatography, and it was also impossible to retain the isotope platform in the chromatogram. It was hot.

After moving over a distance of 4 m, the elemental fraction of boron 10 reached only 25.8% at the rear of the band, and the width of the enriched zone was 96 cm as shown in Figure 6.

Example 3 Production of 90% Boron 10 In order to produce Boron 10 at a concentration of 90%, the same procedure as in Example 2 was carried out.

A set of column apparatus such as that shown in FIG. 7 (each column having a diameter of 21 mm and a length of 1100 mm) was filled with resin to a height of 1000 mm and the resin was processed as in Example 2. Each column was first filled with 2.0 l of 0.1M boron solution.

Excess solution was fed to each column, and the region depleted of boron-10 was removed, leaving a resin bath in chemical and isotopic equivalents to that fed in solution.

The columns were then connected in series with vinyl chloride pipes with an internal diameter of 0.8 mm, and chromatography was carried out by supplying water to the first column of the column apparatus and displacing boric acid into the remaining columns.
The width of the absorption band was wide enough to maintain the platform (equivalent to isotope in the feed solution) during operation.

After the boric acid was completely eluted from the first column, the column was removed from the column apparatus, refilled with feed solution and connected to the end of the column apparatus in the same flow direction.

In this way, the absorption band can be easily displaced over long distances without interrupting operation. After the band has traveled a total length of 250 m, the atomic fraction of boron-10 at the back of the band is
It is concentrated to 90%, and as shown in Figure 8, 1
90% boron 10 could be produced at a rate of 0.09 mmol per hour per cm ² .

As is clear from these examples, isotope enrichments can be produced more effectively if the isotope platform is retained within the separating chromatogram.

FIG. 1 is a schematic diagram showing the arrangement of a column apparatus used in the production of lithium-6, and reference number 1 is shown in the figure.
indicates the lithium acetate solution used to form the lithium absorption band. 2 is a sodium acetate solution as an eluent, and 3 is an acetic acid solution for regenerating the resin. The hatched areas in the column are lithium absorption bands. The spotted areas indicate the eluted resin 5 in the sodium form R-Na or the resin 6 in the acid form R-H.

FIG. 2 shows a chromatogram of lithium with retention of a 6 m long isotopic platform resulting from the migration of the absorption band over a total length of 202 m. In the figure, elution curve 1 shows the concentration of lithium (expressed in mol/l) plotted on the left vertical axis as a function of the position of the chromatogram (expressed in m) plotted on the horizontal axis. The atomic fraction 2 (the ratio of the number of atoms present as an element to the total number of atoms) is the ratio of the atomic fraction of lithium 6 plotted on the right vertical axis as a function of the position (m) of the chromatogram plotted on the horizontal axis. %). Dotted line 3 shows the initial atomic fraction of lithium 6 (7.2%).

FIG. 3 shows a chromatogram similar to FIG. 2, but without retaining the isotope platform. The reference numbers have the same meaning as in FIG.

FIG. 4 shows a single column apparatus used for enriching boron-10. In the figure, reference number 1 indicates the boric acid solution used for absorption, and 2 is the eluent water. The hatched area 4 in the column indicates the resin that has already been eluted.

FIG. 5 shows a chromatogram of boron containing an isotopic platform corresponding to the initial atomic fraction of boron-10 (19.8%). Elution curve 1 shows the boric acid concentration (mol/) plotted on the left vertical axis as a function of the position (m) of the chromatogram plotted on the horizontal axis.

FIG. 6 shows a chromatogram similar to FIG. 5, but without retaining the isotope platform. Reference numbers have the same meaning as in FIG.

FIG. 7 is a schematic diagram showing the arrangement of a column apparatus for producing boron-10 enriched boric acid. The reference numbers have the same meaning as in FIG.

FIG. 8 shows a chromatogram of boron with retention of isotopic platforms in the production of 90% boron 10, and the reference numbers have the same meanings as in FIG.

The length of the chromatogram, 250 m, is found to correspond to a band of boron 10 with a concentration of 90% at the rear of the band.

The present invention has been described in detail with respect to specific examples thereof, but
It goes without saying that the invention is not limited to this particular embodiment, and that many changes and modifications may be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the column apparatus used in the present invention, Figure 2 is a graph showing a chromatogram of lithium when the method of the present invention is used to produce lithium 6, and Figure 3 is a graph showing no isotope platform. A graph showing the chromatogram of lithium in the case of
Figure 4 is a schematic diagram of a column apparatus used in another specific example of the method of the present invention, Figure 5 is a graph showing a chromatogram of boron when the method of the present invention is used, and Figure 6 is an isotope platform holding. 7 is a schematic diagram of a column apparatus used in yet another embodiment of the present invention, and FIG. 8 is a chromatogram of boron when the method of the present invention is used. It is a graph.

Claims (1)

[Claims] 1. Effective separation of isotopes by liquid chromatography or gas chromatography, which consists of maintaining an isotope platform equivalent to that originally supplied as a solution inside the chromatogram. isotopic enrichment by forming very broad absorption bands in which the enriched and depleted regions formed at the front and rear of the chromatogram are always separated from each other in the column. and an isotope separation method characterized by preserving an isotope platform. 2 Maintaining an isotopic platform equivalent to that originally supplied in solution prevents isotope mixing and expansion of enriched and depleted regions, and allows for new addition to the center of the chromatogram without interruption of operation. 2. A method according to claim 1, wherein replenishment of the feed solution is possible. 3. An initial start-up step consisting of maintaining the platform until the atomic fraction of the desired isotope reaches the desired concentration at the front or rear of the chromatogram without removing any products, followed by or semi-continuously or continuously removing the product of the desired atomic fraction from the rear.