CS224890B1 - Method of extracting isolation of strontium out of acidic water solutions - Google Patents

Description

The invention relates to an extraction process for the isolation of strontium from acidic aqueous solutions, in particular from solutions after treatment of irradiated nuclear fuel.

Radioactive strontium is one of the major biotoxic nuclides contained in irradiated fuel, and its isolation is therefore desirable in terms of reducing the potential risk in the storage of radioactive waste. In addition, ee strontium 90 is used in thermoelectric power sources and is therefore also a desired technical product.

According to earlier methods, strontium was isolated from high-reactive waste solutions after their preliminary neutralization by extraction with an organic solvent containing dl (2-ethylhexyl) phosphoric acid. In order to prevent precipitation of the hydrolyzable components contained in the high reactive effluents, it was necessary in this process to add complexing agents to the aqueous phase prior to neutralization and extraction, which bound the components to the dissolved complexes.

Due to the disadvantages of this and analogous processes, methods for isolating strontium directly from acidic waste solutions after treatment of irradiated nuclear fuel with tributyl phosphate extraction, i.e. from solutions containing 2.5 to 3.5 moles of HNO 4 / L, have been sought.

224 890

224 890

The process of extraction of strontium by some hydrophobic anions such as metallodicarbolide, polyiodide and molybdophosphoric anion in the presence of C - O - C groups according to the invention of J. Raise, M. Kyrš and S. Heřmánek, č. 153 933. Strontium can be extracted by this process from solutions having an acidity such as a highly reactive solution after treatment with tributylfoephate extraction, i.e. having an HNO2 content of 2.5 to 3.5 moles / ϊ. The disadvantage of this process is the fact that cesium ions also enter the organic phase more efficiently than strontium ions. Thus, for the separation of etronium, it is necessary to use solutions from which cesium has already been separated or to extract both cesium and strontium together and selectively re-extract first separately strontium and cesium from the organic phase. Another disadvantage of the process is that the etronium /

they are too high in the presence of substances containing C - O - C groups, so that reextraction from the organic phase using mineral acids is not sufficiently effective and other substances dissolved in the mineral acid must be used for reextraction which may cause further difficulties from removal from the final product.

These disadvantages are eliminated by the process according to the invention, characterized in that the strontium is extracted into an organic solvent containing a mixture of a two-donor phosphorous reagent with two P = 0 groups or one P = 0 group and one C = O group, preferably dihexyl / ( dlethylcarbamoyl) methyl (phonephonate or dibutyl) (dlethylcarbamoyl) methyl (phosphonate) and a hydrophobic enion selected from the group of metallodicarbol, dipicrylaminate, tetrafenylborate, inorganic polyiodide and inorganic heteropolyacid, and preferably chlorinated dibasic acid cobaltate dicarbolide. Subsequent reextraction is performed with an aqueous solution of a mineral acid such as nitric acid.

The extraction according to the invention does not cause undesirable cesium epoluextraction into the organic phase, the strontium can be reextracted simply by increasing the acidity of the aqueous phase to a relatively small extent, since the dependence of the etronium partition ratio and increasing acidity is relatively very steep. A further disadvantage is that the proposed process significantly increases the partition ratio of both the hydrophobic anion and the two-donor phosphorous reagent compared to the absence of these compounds in the mixture, thereby reducing the loss of reagents to the aqueous phase. Due to the high affinity of the two-donor phosphororganic reagents for the trivalent lanthenides and actinides, the process can be used prospectively for the common isolation of etronium, trivalent lanthanides and trivalent actinides with selective reextraction of the three fractions.

The advantages of the invention are illustrated by the following examples.

224 890

Example 1

An aqueous solution containing 3 moles of HNO ^ / l was extracted at Ronda microdoses of an organic solution containing 0.15 moles of H ⁺ J ^ (C ₂ Cl BglI _g ^) ₂ Co "3/1 and 0.4 moles dlbutyl ^ (diethylenkarbamoyl) methyl phosphonate in a mixture of 60% (v / v) nitrobenzene and 40% (v / v) carbon tetrachloride. The strontium partition ratio between the aqueous and organic phases was 1.4. On subsequent reextraction with an aqueous solution containing 5 moles of HNO 4 / l, the strontium distribution ratio was 0.17.

The cesium partition ratio from the solution of 3 moles of HNO4 / L to the above organic mixture was equal to D _Cg = 0.08 and from the solution of 5 moles of HNO4 / L to the mixture of D _C8 · 0.027.

Example 2

Strontium was extracted from an aqueous solution containing nitric acid of various concentrations below with an organic solution containing 40 g of molybdophosphoric acid / l and 0.1 mol of dibutyl diethylcarbamoyl) methylphosphonate in nitrobenzene.

The following partition ratios were achieved, D _gr = 18.32 (0.5 M HNO 3), 3.51 (1 M HNO ₃ ), 0.46 (2 M HNO ₃ ) and 0.21 (2.5 M HNO ₃ ).

Example 3

The strontium micro-amounts were extracted from 0.5M HNO 4 and 2M HNO 4 with an organic solution containing 0.04 moles / 1 H ⁺ (CgBgHg & PgCoJ 'and 0.06 moles of dibutyl (diethylcarbamoyl) methyl] foaphonate in chloroform or 1,2-dichloromethane, or in diisopropylbenzene. For the two acidities of the aqueous phase, the partition ratios were achieved for chloroform Dgr »2.74 and Dgr = 0.11, for 1,2-dichloromethane Dgr = 7.28 ^{8 D} Sr ^{= 8 for} Diisopropylbenzene Dgr» 30.9 and D _gr - 0.84.

Claims (1)

SUBJECT OF THE INVENTION Extraction process for the isolation of strontium from acidic aqueous solutions, characterized in that the strontium is extracted from the aqueous phase into an organic solvent comprising a mixture of a two-donor phosphorous reagent with two P = 0 groups or one P = 0 group and one C = 0 group, preferably dihexyl [ (diethylcarbamoylmethyl phosphonate or dlbutyl (dlethylcarbamoyl) methyl] phosphonate and hydrophobic anions selected from the group of metalodicarbolide, dipicrylaminate, tetrafenyiborate, inorganic polyiodide and an inorganic heteropolyacid, preferably a chlorinated dicarbolide cobaltoforide acid or re-acid. nitric acid.