Extraction of Am(III) and Lanthanides from Nitric Acid Solutions with Polyfunctional Organophosphorus Acids

Extraction of microamounts of Am, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu nitrates from aqueous HNO₃ with solutions of (diphenylphosphinylmethyl)phenylphosphinic, (di-p-tolylphosphinylmethyl)phenylphosphinic, (di-p-anisylphosphinylmethyl)phenylphosphinic, and (dioctylphosphinylmethyl)phenylphosphinic acids and of butyl hydrogen (diphenylphosphinylmethyl)phosphonate in toluene was studied. The metal : extractant ratio in the extractable species was determined.     

Preconcentration of U(VI), Th(IV), and REE(III) from nitric acid solutions using carbon nanotubes modified with bis(dioctylphosphinylmethyl)phosphinic acid

The extraction of microamounts of U(VI) and Th(IV) from HNO₃ solutions in the form of complexes with bis(dioctylphosphinylmethyl)phenylphosphinic acid was studied. The stoichiometry of the extractable complexes was studied, and the influence of the extractant structure on the efficiency and selectivity of the U(VI) and Th(IV) extraction was examined. U(VI), Th(IV), and REE(III) can be preconcentrated from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of bis(dioctylphosphinylmethyl) phosphinic acid on the surface of carbon nanotubes.     

Extraction of U(VI), Th(IV), and REE(III) from nitric acid solutions with (N,N-dialkylcarbamoylmethyl)- and (N-alkylcarbamoylmethyl)phenylphosphinic acids

Extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ solutions with solutions of (N,N-dialkylcarbamoylmethyl)- and (N-alkylcarbamoylmethyl)phenylphosphinic acids in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the influence exerted on the efficiency of the U(VI), Th(IV), and REE(III) recovery into the organic phase by the extractant structure, organic diluent, and aqueous phase composition was examined. The possibility of selective recovery and concentration of U(VI), Th(IV), and REE(III) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of the examined polyfunctional organophosphorus acids on a macroporous polymeric matrix was demonstrated.     

Extraction of Am(III) and Rare-Earth Elements from Nitric Acid Solutions with (Diphenylphosphinylmethyl)phenylphosphinic Acid

Extraction of microamounts of Am, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu nitrates from aqueous HNO₃ with solutions of (diphenylphosphinylmethyl)phenylphosphinic acid in dichloroethane was studied. The stoichiometry of the extractable complexes was determined. Synergistic enhancement of the extraction of rare-earth elements in the presence of tetraphenylmethylenediphosphine dioxide was revealed.     

Extraction of REEs(III), U(VI), and Th(IV) with acidic phosphoryl-containing podands from nitric acid solutions

The extraction of microamounts of REEs(III), U(VI), and Th(IV) from HNO₃ solutions with solutions of acidic phosphoryl-containing podands in 1,2-dichloroethane was studied. The stoichiometry of the extractable complexes was determined. The influence of the extractant structure and aqueous phase composition on the efficiency and selectivity of the recovery of REEs(III), U(VI), and Th(IV) into the organic phase was considered.     

Extraction of Am and Rare-Earth Elements from Nitric Acid Solutions with Ethyl Bis(diphenylphosphinylmethyl)phosphinate

Extraction of HNO₃ and microamounts of Am, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HNO₃ solutions with solutions of ethyl bis(diphenylphosphinylmethyl)phosphinate in dichloroethane was studied. The stoichiometry of the extractable complexes was determined, and the effective extraction constants of HNO₃ and Am were calculated. With increasing number of phosphoryl groups in the extractant molecule, the extraction of Am(III) and rare-earth elements from HNO₃ solutions increases.     

Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with Carbamoylmethylphosphine Oxides in the Presence of Bis[(trifluoromethyl)sulfonyl]imide Ions

Extraction of microamounts of REE(III), U(VI), and Th(IV) with solutions of carbamoylmethylphosphine oxides (CMPOs) in organic diluents from aqueous HNO₃ solutions containing lithium bis[(trifluoromethyl) sulfonyl]imide (LiTf₂N) was studied. The efficiency of the REE(III), U(VI), and Th(IV) extraction from nitric acid solutions with CMPO solutions considerably increases in the presence of Tf₂N^– ions in the aqueous phase. The stoichiometry of the extractable complexes was determined, and the influence of the structure of the CMPO molecule, kind of organic diluent, and aqueous phase composition on the efficiency of the U(VI), Th(IV), and REE(III) extraction into the organic phase was considered.     

Extraction and sorption preconcentration of U(VI), Th(IV), and REE(III) from nitric acid solutions using amine-substituted tetraarylethylenediphosphine dioxides

Extraction of U(VI), Th(IV), and REE(III) from HNO₃ solutions in the form of complexes with amine-substituted tetraarylethylenediphosphine dioxides was studied. The effect of substituents at the P atoms in the extractant molecule on its extraction ability was examined. The stoichiometry of the extractable complexes was determined. The possibility of preconcentration of U(VI), Th(IV), and REE(III) with the complexing sorbent prepared by noncovalent immobilization of the examined extractants on a polymer matrix was demonstrated.     

Extraction and sorption preconcentration of U(VI) and Th(IV) from nitric acid solutions using bis(diphenylphosphorylmethylcarbonylamino)alkanes

Extraction of microamounts of U(VI) and Th(IV) from HNO₃ solutions in the form of complexes with polyfunctional neutral organophosphorus compounds, bis(diphenylphosphorylmethylcarbonylamino)alkanes [Ph₂P(O)CH₂C(O)NH]₂(CH₂) _n (n = 3, 5, 8), was studied. The influence of the extractant structure on the efficiency and selectivity of the extraction of U(VI) and Th(IV) was examined, and the stoichiometry of the extractable complexes was determined. The examined compounds exhibit higher extraction ability and selectivity to metal ions in HNO₃ solutions, compared to the alkylamide Ph₂P(O)CH₂C(O)NHC₉H₁₉. The possibility of selective recovery and preconcentration of U(VI) and Th(IV) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of bis(diphenylphosphorylmethylcarbonylamino)pentane on a macroporous polymeric matrix was demonstrated.     

Extraction of U(VI), Th(IV), and REE(III) from Nitric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine <Emphasis Type="Italic">N</Emphasis>-Oxide

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ solutions in the form of complexes with 2,6-bis(diphenylphosphorylmethyl)pyridine N-oxide (I) was studied in relation to the kind of organic diluent and to the HNO₃ concentration in the equilibrium aqueous phase. The stoichiometry of the extractable complexes was determined. With respect to the ability to extract Th(IV) and REE(III), compound I considerably surpasses tetraphenylmethylenediphosphine dioxide and tetraalkyl-substituted analogs of I.     

Extraction and sorption preconcentration of U(VI), Am(III), and Pu(IV) from nitric acid solutions with alkylenediphosphine dioxides

The extraction of U(VI), Am(III), and Pu(VI) from nitric acid solutions in the form of complexes with alkylenebis(diphenylphosphine) dioxides and their sorption with POLIORGS F-6 sorbent prepared by noncovalent immobilization of methylenebis(diphenylphosphine) dioxide (MDPPD) on a KhAD-7M? polymeric matrix were studied. The preconcentration conditions and distribution coefficients of U(VI), Am(III), and Pu(IV) in their sorption from 3 M HNO₃ were determined. The possibility of concentrating actinides from multicomponent solutions was demonstrated. The composition and nature of complexes of U(VI) with MDPPD were determined from the ³¹P NMR data.     

Reduction of Pu(IV) and Np(VI) with hydroxylamine in solutions of low acidity with high uranium content

Decomposition of hydroxylamine in HNO₃ solutions containing 350 to 920 g l^?1 U(VI) was studied. In the absence of fission and corrosion products (Zr, Pd, Tc, Mo, Fe, etc.), hydroxylamine is stable for no less than 6 h at [HNO₃] < 1 M and 60°C. In the presence of these products, the stability of hydroxylamine appreciably decreases. The reduction of Pu(IV) and Np(VI) with hydroxylamine in aqueous 0.33 and 0.5 M HNO₃ solutions containing 850 g l^?1 U(VI) and fission and corrosion products at 60°C was studied. Np(VI) is rapidly reduced to Np(V), after which Np(V) is partially reduced to Np(IV). The rate of the latter reaction in such solutions is considerably higher than the rate of the Np(V) reduction with hydroxylamine in HNO₃ solutions without U(VI). At [HNO₃] = 0.33 M, the use of hydroxylamine results in the conversion of Pu to Pu(III) and of Np to a Np(IV,V) mixture, whereas at [HNO₃] = 0.5 M the final products are Pu(IV) and Np(V).     

Mechanism and Kinetics of Rh(IV) Radiation-Chemical Reduction in HNO3 Solutions

Reduction of Rh(IV) in -irradiated and nonirradiated solutions of HNO₃ (0.3-3.0 M) was studied. In both systems, Rh(IV) is completely reduced to Rh(III). The reduction rates in nonirradiated solutions amount to 50-90% of rates in irradiated solutions. Reduction of Rh(IV) with water is postulated. The rates of Rh(IV) reduction in both irradiated and nonirradiated solutions increase with [Rh(IV)] growth and decrease with an increase in [HNO₃] from 0.5-1 to 2-3 M. The dependence of the reduction rates on the dose rate is weak. Mathematical simulation was used to reveal the mechanism and kinetics of radiation-chemical reduction of Rh(IV) in HNO₃ solutions. The rate constant of Rh(IV) reduction with water was calculated by fitting to the experimental data.     

Extraction of U(VI), Th(IV), and REE(III) from nitrate solutions with diaryl(dialkylcarbamoylalkyl)phosphine oxides containing a dialkylcarbamoylmethyl substituent in the alkylene bridge

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO₃ and NH₄NO₃ solutions with solutions of diaryl(dialkylcarbamoylalkyl)phosphine oxides containing a dialkylcarbamoylmethyl substituent in the alkylene bridge was studied. The stoichiometry of the complexes extracted from nitric acid solutions with N,N,N',N'-tetrabutyl-2-(di-p-anisylphosphinyl)butanedioic diamide I was determined. The influence of the extractant structure and aqueous phase composition on the efficiency and selectivity of the extraction of U(VI), Th(IV), and REE(III) into the organic phase was examined. Introduction of the–CH₂C(O)NAlk₂ fragment into the methylene bridge of the diaryl(dialkylcarbamoylmethyl)phosphine oxide molecule considerably enhances the extraction of REE(III) from neutral nitrate solutions. Such modification of the extractant molecule only slightly influences the extraction of REE(III) from nitric acid solutions, but leads to a considerable increase in the U(VI) extraction and to a decrease in the Th(IV) extraction. The selectivity of the extraction of U(VI) and REE(III) is thus considerably increased.     

Extraction and sorption preconcentration of U(VI), Th(IV), and REE(III) from nitric acid solutions using bis[2-(diphenylphosphinyl)phenoxymethyl]phosphinic acid

Extraction of microamounts of U(VI) and Th(IV) from HNO₃ solutions in the form of complexes with polyfunctional organophosphorus acids was studied. The influence of the extractant structure on the efficiency and selectivity of the extraction of U(VI) and Th(IV) was examined, and the stoichiometry of the extractable complexes was determined. The possibility of preconcentration of U(VI), Th(IV), and REE(III) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of bis[2-(diphenylphosphinyl) phenoxymethyl]phosphinic acid on a macroporous polymeric matrix was demonstrated.     

Extraction of Am(III) from Nitric Acid Solutions with Bis(diphenylphosphinylmethyl)phosphinic Acid

Extraction of trace quantities of Am(III) from aqueous HNO₃ solutions with solutions of bis(diphenylphosphinylmethyl)phosphinic acid (I), bis[2-(diphenylphosphinyl)phenoxymethyl]phosphinic acid (II), and bis[2-(diphenylphosphinylmethyl)phenoxymethyl]phosphinic acid (III) in dichloroethane was studied. The stoichiometry of the extractable complexes was determined; the effect of organic diluent on the extraction was considered. The extractive power of the reagents toward Am(III) grows in the order III < II < I. Acid I surpasses in the extractive power a neutral bidentate extractant, tetraphenylmethylenediphosphine dioxide (TPMDPD), by three orders of magnitude. A synergistic effect in extraction of Am with mixtures of TPMDPD and acid I was revealed.     

Extraction of U(VI), Th(IV), and rare-earth elements from nitric acid solutions with phosphoryl-and carbonyl-containing podands

The distribution of HNO₃ and microamounts of nitrates of U(VI), Th(IV), La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous solutions of HNO₃ and solutions of N,N′-dimethyl-N,N′-diphenyl-3-oxapentanediamide (I) and 1,3-bis(diphenylphosphinoyl)-2-oxapropane (II) in organic diluents was studied. The stoichiometry of the extractable complexes was determined, and the effect exerted by the extractant structure and by the organic diluent on the efficiency of recovery of rare-earth elements (REE) into the organic phase was examined. In nitric acid solutions, carbonyl-containing podand I surpasses in the extraction ability phosphoryl-containing podand II. The possibility of using a macroporous polymeric sorbent impregnated with compound I for recovering REE from nitric acid solutions was demonstrated. Original Russian Text A.N. Turanov, V.K. Karandashev, V.E. Baulin, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 3, pp. 226–232.     

Extraction properties of polyfunctional P,N-containing podands with diphenylphosphorylacetamide terminal groups in nitric acid solutions

The extraction of HNO₃ and microamounts of U(VI), Th(IV), Sc(III), and REE(III) nitrates from HNO₃ solutions with dichloroethane solutions of phosphorus-containing podands containing two terminal Ph₂P(O)CH₂C(O)NH groups linked by a di-or triethylene glycol chain was studied, and the stoichiometry of the extractable metal complexes was determined. The compounds extract the metal ions from nitric acid solutions more efficiently than does (dibutylcarbamoylmethyl)diphenylphosphine oxide. With increasing length of the polyethylene glycol chain, the extraction of HNO₃ increases, but the degree of recovery of REE(III) ions from HNO₃ solutions of the concentration exceeding 3 M decreases.     

1,3-Bis[(diphenylphosphorylacetamido)methyl]benzene as reagent for extraction and sorption preconcentration of REE(III), U(VI), and Th(IV) from nitric acid solutions

The extraction of microamounts of REE(III), U(VI), and Th(IV) from HNO₃ solutions in the form of complexes with a polyfunctional neutral organophosphorus compound, 1,3-bis[(diphenylphosphorylacetamido)-methyl]benzene, was studied. The influence exerted by the structure of the bridge binding two carbamoylmethyl-phosphine oxide fragments on the efficiency of the extraction of REE(III), U(VI), and Th(IV) and on the stoichiometry of the extractable complexes was analyzed. The possibility of recovering and concentrating REE(III), U(VI), and Th(IV) from nitric acid solutions with a complexing sorbent prepared by noncovalent immobilization of 1,3-bis[(diphenylphosphorylacetamido)methyl]benzene on the surface of carbon nanotubes was examined.     

Sorption recovery of U(VI), Pu(IV), and Am(III) from nitric acid solutions with solid-phase extractants based on Taunit carbon nanotubes and polystyrene supports

Sorption procedures were developed for recovering U(VI), Pu(IV), and Am(III) with solid-phase extractants (SPEs) prepared by impregnation of Taunit carbon nanotubes and polystyrene supports with diphenyl( dibutylcarbamoylmethyl)phosphine oxide (CMPO) and tri-n-octylphosphine oxide (TOPO) The impregnation and actinide recovery were performed in the batch mode and using microcolumns. Procedures for support impregnation and SPE preparation are described. Conditions were found for sorption recovery of U(VI), Pu(IV), and Am(III) from 3 M HNO₃ solutions. The possibility of actinide desorption was demonstrated. The effect of macrocomponents on the degree of actinide recovery was examined.