G. A. Pribylova

Selective binding of ions of uranium and of transuranium and rare-earth metals with functionally substituted crown ethers

The extraction of uranium and of transuranium and rare-earth elements from nitric acid solutions with solutions of 4,4′(5′)-bis(dialkylphosphoryl)-,-bis(diphenylphosphoryl)-, and-bis[(O-alkyl)phosphoryl]-benzo-n-crown-m ethers (n = 18, m = 6; n = 21, m = 7; n = 24, m = 8) in 1,2-dichloroethane and chloroform was studied. The distribution ratios of U(VI), Pu(IV), Am(III), and Eu(III) in the extraction depend both on the experimental conditions and on the structural features of the ligands. In the range [HNO3] = 0.02–1.0 M, the metal distribution ratios DM depend on the mutual steric orientation of the phosphoryl groups. With the cis (4,4′) isomers, DM is higher than with the trans (4,5′) isomers and with the isomer mixtures. With the compound containing the (n-BuO)2P(O) groups in the cis position as example, it was found that the highest distribution ratios DU = 0.98 were observed in 3 M HNO3; DPu = 5.1, in 0.5 M HNO3; and DAm = 0.007, at pH 2. For the trans conformer under the same conditions, DM of U(VI), Pu(IV), and Am(III) is 0.091, 1.8, and 0.003, respectively. The macroring size (number of carbon atoms n), under other conditions equal, also significantly affect the extraction activity of the reagent. With the extraction of Am(III) from 0.01–3 M HNO3 as example, it was shown that the crown ethers with n = 21 are the most efficient with all the substituents. The maximum of DAm shifts toward higher HNO3 concentrations with increasing n. The coordinating power of phosphoryl-containing ligands based on functionally substituted benzo-21-crown-7 ether in the extraction of Am(III) from 0.01–3 M HNO3 decreases in the order (n-BuO)(OH)P(O)-≫ (n-BuO)2P(O)-> Ph2P(O)-, under other conditions equal. The extraction ability of di(n-BuO)(OH)P(O)-dibenzo-21-crown-7 (DAm = 814 in extraction from 0.1 M HNO3) exceeds that of the other compounds studied by more than two orders of magnitude. Conditions were found for the selective extractive separation of Am(III) and Eu(III) using bis[(O-alkyl)(OH)phosphoryl]dibenzo-21-crown-7, with a separation factor of >90 at [HNO3] = 0.01 M.

Effect of ionic liquids on the extraction of Am from HNO3 solutions with diphenyl(dibutylcarbamoylmethyl)phosphine oxide in dichloroethane

Addition of small (1–5 vol %) amounts of ionic liquids (ILs) increases the Am(III) distribution ratio in the system with diphenyl(dibutylcarbamoylmethyl)phosphine oxide (Ph2Bu2) by more than 2 orders of magnitude. With 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim]+Tf2N−) used as IL, the Am(III) extraction is possible even from 8 M HNO3, which is important in radiochemical analysis of process and environmental samples, because many procedures are based on the transfer of solid samples into 8 M HNO3. The extraction data show that the extractable Am(III) complex contains three Ph2Bu2 ligands, an IL anion, and two NO3− anions.

Extraction of rare-earth elements and americium from acid solutions with alkyl derivatives of dibenzo- and dicyclohexano-18-crown-6

Extraction of rare-earth elements (REEs) and Am(III) from acid solutions with alkyl-substituted crown ethers dibenzo-and dicyclohexano-18-crown-7 in the chloroform-water system was studied. Dicyclo-hexano-18-crown-6 and its alkyl derivatives extract REEs and Am(III) in the presence of trichloroacetic acid (HTCA) considerably better, compared to dibenzo-18-crown-6 and its alkyl derivatives and to the systems containing HNO3 and HC1O4 instead of HTCA. The distribution ratios of the cerium-group REEs are considerably higher than those of the yttrium-group REEs. In all the cases, the metal to crown ether ratio in theextractable complexes is 1:1.

New chelating sorbents based on materials filled with organophosphorus complexing agents

The chelating fibrous “filled” sorbents POLYORGS type with hydrazidine and amidoxime complexing groups (POLYORGS 33) and modified by reagent 3,6-bis-[(2-arsonophenyl)azo]-4,5-dihydroxy-2,7-naphtalen disulphoacid (Arsenazo-III) POLYORGS 33AIII pattern had been synthesized. The sorption ability of these materials were examined in the case of 241Am, 239Pu, 237Np, 233U, and 152Eu pre-concentration from simulated ground water solutions. It was found that all radionuclides above in indicator amounts (~10-5M) under preliminary experiments were recovered almost completely. POLYORGS 33 and POLYORGS 33AIII samples showed as well fast kinetics on the sorption process above. The derivatives of ethers of phosphoric acid, namely O-(2-alkyl)(diéthylcarbamoylmethyl)phenylphosphinates (O2ADECMPP), were synthesized and examined on liquid-liquid extraction of TRlPs, Lantanides and Tc (VII) from nitric acid solutions. A nonlinear increase of distribution coefficients (DM) as the function of the carbon radical extension on radionuclides extraction by O2ADECMPP solutions in meta-nitrobenzotriftoride (Ftoropol-723), or 1,2-dichlorethane had been found. Maximum of a distribution coefficients are found at n = 9 (R = CnH2n+1) for all radionuclides used. However in all further experiments easy available and equally efficient O2EHDECMPP reagent was used. It was shown that maxima of DM for Am(III), and Eu(III) extraction by 02EHDECMPP in 1,2-dichlorethane are at [HNO3]=3M ([R] = 0,1M; DAm = 1,45 and DEu = 1,02). For Pu(IV), and U(VI) extraction the increase of acid concentration in the range [HNO3] from 0.1M to 5M leads to the growth of the distribution coefficients, and at [R]=0,01M values of DPuchanges from 0.48 to 35, and for Du from 0.057 to 4.8. On the contrary, for Tc(VII) extraction by 02EHDECMPP in 1,2-dichlorethane the increase of HNO3 concentration in the solution causes noticeable slowing-down of the distribution coefficients, and DTc in the range [HNO3] from 0.1M to 5M decreases from 9.6 to 0.013 ([R] = 0,1M). Dependencies of the distribution coefficients for TRUs, Lantanides and Tc(VII) on reagent concentration were measured under 3M HNO3. For Am(III), Eu(III), and Tc(VII) it is shown that the increase of reagent concentration in the range [R] from 0.025M to 0.1M leads to the growth of the distribution coefficients for DAm from 0.057 to 1.45, for DEu from 0.055 to 1.02, and for DTc from 0.01 to 0.12. In the logarithm coordinates of DAm and DEu values on [R] dependence slope is close to two, upon which can be considered that extractable complex composition could be as Am.2R and Eu.2R. For Tc(VII) extraction the solvate number in the similar conditions is about 1.5. Probably, in the extraction system two different Tc complexes: mono- and bi-coordinated species were formed. For Pu(IV), and U(VI) it was shown that the increase of reagent concentration in the range [R] from 10-4M to 0.01M leads to the growth of the distribution coefficients for DPu from 0.08 to 11, for DU from 0.02 to 3.2. Values of a solvate number calculated from the slop of these plots above for Pu(IV) and U(VI) are close to one, and we considered that extractable complex composition for these elements could be as MR. For TRUs in comparison with extraction capacity of O2ADECMPP and well known phosphorous containing compounds the ratio has been obtain: DAm(TBP): DAm(Dialkylmethylphoshanates): DAm(02ADECMPP): DAm(Diphenyldibuthyl(carbamoylmethyl)phosphineoxide) = 1: 5.101: 2,5.104: 5.104. For Tc (VII) it was found that the best extractant for this element is O2ADECMPP. On the basis of O2ADECMPP compounds original chelating granulated sorbents were synthesized which were tested to respect of Pu(IV) isolation from nitric acid solutions.