RU2400845C1 - Extraction mixture for separating transuranic and rare-earth elements from acidic and saline media - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: mixture contains substituted bis-aryl-tetrazolyl-pyridine, having formula:

, where R₁ and R₂ denote hydrogen, halogen (CI, Br, F, I), alkyl, alkoxy. The solvent used is organic liquids with permittivity greater than 4. Components of the mixture are in the following ratio, mol/l: heterocyclic compound 0.001-0.2; organoboron complex compound 0.001-0.2, solvent - the rest.

EFFECT: efficient separation of a pair of transuranic and rare-earth elements during extraction from acidic and saline media.

Description

The invention relates to the field of radiochemical technology, in particular to the processing of radioactive waste in the handling of spent nuclear fuel (SNF), and can also be used in the extraction of non-ferrous metals.

Plutonium and minor actinides (neptunium, americium) have been the main contributors to the radiotoxicity of highly active waste (HLW) for over 10 ⁵ years. To comply with environmental safety standards, it is required that these elements be isolated and converted into forms that impede their distribution into the environment during storage.

Preliminary extraction of minor actinides can significantly simplify the process of vitrification and disposal of HLW. Isolated minor actinides can be immobilized into particularly strong mineral-like matrices and buried, or transmuted into short-lived radionuclides in a nuclear reactor. Neptunium can be separated from spent nuclear fuel together with uranium and plutonium in the PUREX process; extracting americium and other transplutonium elements (TPE) is a difficult task. TPEs are almost complete chemical analogues of rare-earth elements (REE), which are present in large quantities in HLW. The amount of REE in HLW is 2-3 orders of magnitude higher than the amount of TPE. Therefore, it is more expedient to carry out the extraction of TPE, and to leave the REE in the raffinate.

To separate Am (III) and Cm (III) ions from REE, N- or S-containing compounds are used, for example: 2,4,6-tri (2-pyridyl) -1,3,5-triazine (TPT), 2 , 6-bis (5,6-alkyl-1,2,4-triazin-3-yl) pyridine (R-BTP) and di (isobutyl) dithiophosphoric acid (DID, trade name Cyanex 301).

From "C. Musikas, Proc. Int. Symp. Actinide / Lantanide Sepps., Honolulu, Hawai, 16. - 12.22.1984, World Scientific, Singapore (1985), S.19", it is known that the Am (III) and Cm (III) from lanthanides can be produced using TPT from relatively acidic solutions (pH 1-2). The values of the separation factor for the pair Am / Eu = 10-20. Using sulfur compounds such as Cyanex 301/302, separation factors of more than 10,000 can be achieved at pH 3-4 (Yongyun Zhu, Jing Chen und Rongzhou Jiao, Solvent Extr. Ion Exch. 14, 61 (1996); WO 99/14386 A1, 03/25/1999). Tridentant extractants exhibit high efficiency and selectivity: 2,6-bis (5-n-alkyl-1,2,4-triazol-5-yl) pyridine (BTZP) and 2,6-bis (5,6-di-n -alkyl-1,2,4-triazin-3-yl) pyridine (R-BTP) (Kolarik, Z; Műllich, U .; Gassner, F. Selective extraction of Am (III) over Eu (III) by 2, 6-ditriazolyl- and 2,6-ditriazinylpyridines. Solvent Extr. Ion. Exch. 1999, 17 (1), 23-32; DE 19810895 C1, 05/11/2000). Separation factor 150 was obtained by extraction from 0.1 M HNO ₃ +0.1 M NH ₄ NO ₃ .

The disadvantages of all the above methods for the separation of TPE from REE include the very low acidity of the medium from which the separation occurs and the low resistance of the compounds used to hydrolysis and radiolysis.

Closest to the claimed extraction mixture by extraction properties is a system based on diethylmi-BTP (6- (5,6-diethyl-1,2,4-triazin-3-yl) -2,2'-bipyridine, di (benzyloxyphenyl) hemi-BTP (6- [5,6-di (benzyloxyphenyl) -1,2,4-triazin-3-yl] -2,2'-bipyridine

where R is -C ₂ H ₅ - diethylmi-BTP;

- ди(бензилоксифенил)hemi-BTP,

- di (benzyloxyphenyl) hemi-BTP,

synergistic supplement and organic solvent (Krejzler, J .; Narbutt, J .; Foreman, MR St J .; Hudson, MJ; Casensky, B .; Madic, C. Solvent extraction of Am (III) and Eu (III) from nitrate solution using synergistic mixtures of N-tridentate heterocycles and chlorinated cobalt dicarbollide. Czechoslovak Journal of Physics, 2006, (56), suppl. D, 459-467), selected as a prototype.

This mixture is capable of selectively extracting a pair of americium (III) / europium (III) from slightly acidic solutions with a separation factor of 40-60 when 1-octanol or nitrobenzene is used as a solvent.

The disadvantage of the prototype is the need for extraction from slightly acidic media pH> 2, which complicates the use of these systems in the processing of HLW. The significant solubility of hemi-BTP in acid solutions can lead to an increase in the cost of replenishing the extractant.

An object of the present invention is to efficiently separate a pair of TUE (transuranic elements) (III) / REE (III) upon extraction from acidic and saline media.

The problem is solved using a mixture that includes substituted bis-aryl-tetrazolyl-pyridine having the formula:

where R ₁ , R ₂ is hydrogen, halogen (Cl, Br, F, I), alkyl, alkoxyl,

a synergistic additive (e.g., chlorinated cobalt dicarbolide) and an organic solvent immiscible with water.

Organic solvents with a dielectric constant greater than 4 are used as a solvent, for example: dichloroethane, nitrobenzene, meta-nitrobenzotrifluoride, phenyl trifluoromethyl sulfone, etc.

with the ratio of components in the mixture:

Heterocyclic compound 0.001-0.2 Organoboron complex compound 0.001-0.2 Solvent Rest.

Example 1

A solution containing 0.001 M of 2,6-bis (1- (4-butylphenyl) -1H-tetrazol-5-yl) pyridine, 0.08 M of chlorinated cobalt dicarbolide (CDA) in meta-nitrobenzotrifluoride was contacted with 0.1 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 57.4 8.6 7

Example 2

A solution containing 0.2 M 2,6-bis (1- (4-butylphenyl) -1H-tetrazol-5-yl) pyridine, 0.2 M chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 3 M nitric acid, containing 0.16 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 56.8 0.89 64

Example 3

A solution containing 0.02 M of 2,6-bis (1-phenyl-1H-tetrazol-5-yl) pyridine, of 0.02 M of chlorinated cobalt dicarbolide in methionitrobenzotrifluoride was contacted with 0.5 M perchloric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 25.6 0.32 80

Example 4

A solution containing 0.2 M 2,6-bis (1- (4-butylphenyl) -1H-tetrazol-5-yl) pyridine, 0.2 M chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 2 N sulfuric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 1090 57 19

Example 5

A solution containing 0.01 M 2,6-bis (1-phenyl-1H-tetrazol-5-yl) pyridine, 0.01 M chlorinated cobalt dicarbolide in phenyl trifluoromethyl sulfone was contacted with 0.1 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 min. The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 2.5 0,03 83

Example 6

A solution containing 0.05 M 2,6-bis (1- (4-methylphenyl) -tetrazol-5-yl) pyridine, 0.05 M chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 6 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the extraction (K _M ) and separation (KP) ratios was used.

K _am K _eu KP = K _Am / K _Eu 1.4 0.14 10

Example 7

A solution containing 0.02 M of 2,6-bis (1- (4-methylphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 1 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 60 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 1.96 0.05 40

Example 8

A solution containing 0.02 M of 2,6-bis (1- (4-methylphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 0.3 M hydrochloric acid, containing 2 M lithium nitrate and 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 34,4 0.47 73

Example 9

A solution containing 0.02 M of 2,6-bis (1- (4-ethoxyphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 1 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 177.0 3.2 55

Example 10

A solution containing 0.02 M of 2,6-bis (1-phenyl-tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 0.5 M nitric acid containing 0.05 M of chromium (III) nitrate and 10 ^-5 M of europium nitrate labeled with a radioisotope at 23 ° C for 5 min. The standard radiometric distribution coefficient determination procedure (D _Am ) was used. The distribution coefficient was 0.63 for americium (III).

D _am D _eu KP = D _Am / D _Eu 97.8 1.4 70

Example 11

A solution containing 0.01 M 2,6-bis (1- (1- (3,4-dichlorophenyl) -tetrazol-5-yl) pyridine, 0.01 M chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 0, 05 M nitric acid containing 10 ^-5 M europium nitrate, labeled with a radioisotope, at 23 ° C for 5 minutes, the Standard procedure for radiometric determination of distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 8.07 7.17 1,1

Example 12

A solution containing 0.02 M of 2,6-bis (1- (4-methylphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 1 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The ratio of organic to aqueous phases was 3: 1. The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 4.09 0.16 26

Example 13

A solution containing 0.02 M of 2,6-bis (1- (4-ethylphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 1 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 4 hours. The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _am D _eu KP = D _Am / D _Eu 4.87 0,091 54

Example 14

A solution containing 0.02 M of 2,6-bis (1- (4-methylphenyl) -1H-tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 0.3 M nitric acid containing 10 ^-4 M REE nitrates at 23 ° C for 5 minutes Distribution coefficients (D _M ) were determined by a standard procedure using data determined by atomic mass spectrometry.

D _la D _sm D _lu D _am 0.015 1,2 4.4 > 1000

Example 15

A solution containing 0.02 M of 2,6-bis (1- (4-methylphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 0.5 M nitric acid, containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination of distribution coefficients (D _{Pu (III)} ) was used.

D _{Pu (III)} = 16.5

Example 16

A solution containing 0.015 M of 2,6-bis (1- (4-methylphenyl) -tetrazol-5-yl) pyridine, 0.02 M of chlorinated cobalt dicarbolide in meta-nitrobenzotrifluoride was contacted with 1.5 M nitric acid containing 10 ^-5 M europium nitrate labeled with a radioisotope at 23 ° C for 5 minutes The standard radiometric determination procedure for the distribution coefficients (D _M ) and separation (KP) was used.

D _cm D _eu KP = D _Cm / D _Eu 2.2 0,039 56

The above examples indicate that the use of the proposed extraction mixture allows you to effectively separate a pair of TUE / REE, during extraction from acidic and saline solutions.

When comparing the proposed extraction mixture with the prototype, it can be noted that the extraction of TUE and REE of the claimed extraction mixture can be carried out from much more acidic environments than in the case of the prototype.

The properties of the extraction mixture meet the requirements of radiochemical technology.

Claims (1)

An extraction mixture for the separation of transuranic and rare-earth elements from acidic and saline media, containing a heterocyclic compound based on bisubstituted pyridine, a synergistic additive - an organoboron complex compound and an organic solvent, characterized in that it contains bistetrazolyl-pyridine derivatives of the general formula

where R ₁ , R ₂ is hydrogen, halogen, alkyl, alkoxyl,
as a solvent - organic liquids with a dielectric constant of more than 4, with the following ratio of components, mol / l:
heterocyclic compound 0.001-0.2 organoboron complex compound 0.001-0.2 solvent rest