CS238930B1 - Method of separation of uranium isotopes by controlled distribution method - Google Patents

Abstract

Method of separation of uranium isotopes by controlled distribution method. The essence of the invention is a method of separation of uranium isotopes by controlled distribution method from a solution containing anionic complexes of uranium using anions based on macroreticular spherical crosslinked copolymers of glycidyl methacrylate containing amine groups. An important property of the anion according to the invention is its high mechanical resistance under conditions of use, with a very good senaration effect. The separation method can be used in cases where uranium is contained in aqueous solutions in the form of anionic complexes, as is the case in the large-scale method of obtaining uranium by leaching ores with sulfuric acid.

Description

The invention relates to a method of separating uranium isotopes by a controlled distribution method. The separation of uranium isotopes by the controlled distribution method was elucidated in the patent application (PO 27/81 K. Stamberg, J. Cabicar, Concentration isotope effect in chemical and mass transport processes).

It utilizes the kinetic and equilibrium concentration effect in the distribution of Isotopes in two-phase, ternary and multicomponent systems, such as extraction and sorption systems.

The basic prerequisite for successful separation according to the new principle is a different concentration of isotopes in the mixture to be separated. This condition is met for both natural and flavored uranium compounds for a technically interesting case of the separation of U (uranium) and a (u) uranium isotopes.

The separation itself is due to the unequal transport rate of isotopic components during the transition from one phase to another - under conditions where isotopic exchange is retarded - and with respect to the non-linearity of the equilibrium sorption isotherm.

The controlled distribution method is significantly more efficient than the previously known chemical methods for the separation of uranium isotopes. It is mainly described in MS. No. 214 904 and 214 905.

In the development of a new separation method, the separation effect has been shown to be largely dependent on the sorbent structure. In the development of optimal sorbent types, account has been taken of the extraordinary ability of uranium to produce a large number of species derived from its different valence levels, using various complex bonds and consisting of cationic, anionic and neutral forms.

Particular attention has been paid to hexavalent uranium compounds in a weak or strongly acidic environment. Depending on the composition of the solutions, under these conditions, the uranium may be present in the form of uranyl cations or anionic complexes thereof and accordingly used for the sorption of cation exchangers or anion exchangers.

More attention has been paid to cation exchanges / see above mentioned MS. author's certificate ^ cs. author's certificate No. 225 464 and Czechosl. author's certificate No. 235 645. About the use of anion exchanges is only discussed by MS. author's certificate No 224 844.

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The method of separation of uranium isotopes in the form of anionic complexes is particularly advantageous in that the anionic complexes of uranium are formed very easily and in a high concentration relative to other complex forms and are readily available for the separation process.

For example, it is known that uranium is obtained from natural raw materials by leaching with sulfuric acid, i.e. in the form of anionic complexes, and isolated on anion exchangers. This offers the possibility of some combination of the enrichment process with the recovery of uranium from natural raw materials. '

Attention was paid to finding the optimal structure of anion exchange resin for the separation of uranium isotopes by controlled distribution method. The situation is very difficult for the rational selection of the best structure because the theory of separation process according to the method of controlled distribution is still under development and not yet all the basic relations between the sorbent structure and the achievable separation effect have been known.

Cs. Authentic certificate! No. 224,844 relates to spherical cellulose anion exchangers and gel-based synthetic polymer anion exchangers which have been found to have good separation effects.

The imperfections of the anion exchangers mentioned are their mechanical properties, in particular the softness of the individual grains.

Under operating conditions, i.e. when using large columns with high sorbent layers, such properties are of critical importance. The task was to find a suitable type of anion exchanger with excellent mechanical resistance and very good separation effect.

It has now been found that both properties can be achieved simultaneously according to the invention. Method for the separation of uranium isotopes by a controlled distribution method using in particular a concentration isotopic phenomenon in two-phase systems, wherein one phase is an aqueous or non-aqueous solution of uranium isotopes containing anionic uranium complexes and the other phase is anion exchange according to the invention a spherical crosslinked copolymer of glycidyl methacrylate containing amino groups.

The good mechanical properties of the anion exchanger according to the invention are derived from its rigid macroreticular structure and regular spherical shape. It can be easily packed into columns and the regularly deposited layer does not change its configuration and especially its volume when changing the operating mode and over a long period of use. Under conditions of the separation process, there is practically no abrasion failure of the grains.

The anion exchangers according to the invention are prepared in a known manner. In the first step, they are prepared according to MS. No. 175 112 of the basic copolymer and in the second step into it according to the art. No. 162,535 discloses polymer-analogue conversion of the amino group.

The first step of the preparation is a suspension copolymerization of glycidyl methacrylate and a cross-linking monomer, for example ethylenedimethacrylate, with the addition of an inert component to form a copolymer. the macroreticular dispersion is carried out in an aqueous medium containing a suspension stabilizer.

In the second step, the prepared copolymer is reacted with ammonia or ethylene polyamines. It is an alkylation using oxirane groups in copolymers.

With the anion exchangers according to the invention, very good separation effects have been achieved with the application of the controlled distribution method, as shown in the examples.

Example 1 g of a swollen, centrifuged sample of anion exchanger, in the form of a base, prepared by reaction of copolymers of glycidyl methacrylate and ethylene dimethacrylate with ethylenediamine (i.e. functional group: § COOHCH.CH/OH/CHI.NH.CHj.CH^.NHj/ was contacted with stirring at 298 K with 30 ml of a 0.01 M uranyl sulfate / UO ₂ solution SO ₄ /.

After a given time, stirring was discontinued, the liquid and ion exchange phases were separated and the total uranium concentration / photometric method was determined in the liquid phase.

O □ C J Q of the AZO 1 reagent and the atomic ratio of uranium (U): uranium (U) isotopes on the MICROMASS 30B mass spectrometer.

235

The isotopic composition of the starting solution corresponded to that of natural uranium, ie ♦ uranium (U): ²³⁸ uranium / u / = 0.725.10 ^-2 .

From the results, the value of the separation factor was calculated (the separation factor is defined as 2 35 2 38 as the ratio of isotopic ratio of uranium (U): uranium (U) in the ion exchange phase to the same isotopic ratio in the solution phase).

The results, ie the values of total uranium concentration and separation factors as a function of time, are summarized in the following table:

238930 4 Sas, min 0 2 5 10 Total uranium concentration, M 0.01 0.0066 0.0055 0.0038 Separation factor 1,000 0,986 1,001 1,004

0.0017

1,002

Example 2 g of a swollen, centrifuged sample of anion exchanger, in the form of a base, prepared by reaction of a copolymer of glycidyl methacrylate and ethylene dimethacrylate with ammonia (i.e. with functional group: COO.CH3 CH / OH / CH3 NH3 was contacted with stirring at 298 K with 30 ml of a 0.01 M uranyl sulphate solution (UO2SO4).

After a given time, stirring was discontinued, the liquid and ion exchange phases separated? 75 and in the liquid phase, the total uranium concentration and the isotopic ratio of uranium (U): ²³⁸ uranium (U) was determined.

The further procedure, ie the method of evaluating the results, is described in Example 1. The results, ie the values of total uranium concentration and separation factors as a function of time, are summarized in the following table:

Sas, min

Total uranium concentration, M Separation factor

0.01

1,000

0.0060

0.994

0,0061

0,983

0.0050

0.996

0,0041

0.998

Claims (1)

SUBJECT OF THE INVENTION A method for the separation of uranium isotopes by a controlled distribution method using in particular a concentration isotopic effect in two-phase systems, wherein one phase is an aqueous or non-aqueous solution of uranium isotopes containing anionic uranium complexes and the other phase is an anion exchanger. a spherical crosslinked copolymer of glycidyl methacrylate containing amino groups.