Extraction of molybdenum and technetium with diamides of dipicolinic acid from nitric acid solutions

The concentration of molybdenum(VI) in dissolved spent nuclear fuel is comparable with the concentrations of Tc, and the minor actinides (Np, Am). Therefore it is of great interest to understand its behavior under conditions imposed by separation processes. The simultaneous extraction ability of ortho, meta, and para isomers of N,N′-diethyl-N,N′-ditolyl-dipicolinamide (EtTDPA) for molybdenum and technetium were investigated in a large range of nitric and hydrochloric acid conditions. Molybdenum shows no increase in extraction at higher concentrations of nitric acid giving a solvate number n=0 with all isomers of EtTDPA, while Mo shows great extractability from HCl. Technetium distribution ratios decrease with increasing concentrations of nitrate showing indication of ion exchange occurring between TcO₄ ⁻ and NO₃ ⁻ anions. Et(m)TDPA and Et(p)TDPA show the greatest extractability, with 60% of the total technetium extracted into the organic phase at 1M HNO₃.     

Extraction behavior of cerium by tetraoctyldiglycolamide from nitric acid solutions

The diamide N,N,N′,N′-tetraoctyldiglycolamide (TODGA) was synthesized and characterized. The prepared TODGA was applied for extraction of Ce(III) from nitric acid solutions. The equilibrium studies included the dependencies of cerium distribution ratio on nitric acid, TODGA, nitrate ion, hydrogen ion and cerous ion concentrations. Analysis of the results indicates that the main extracted species is Ce(TODGA)₂(NO₃)₃HNO₃. The capacity of Ce loading is approximately 45 mmol/L for 0.1 M solution of TODGA in n-hexane. Finally, the thermodynamic parameters were calculated: K (25 °C) = 3.8 × 10³, ΔH = −36.7 ± 1.0 kJ/mol, ΔS = −54.6 ± 3.0 J/K mol, and ΔG = −20.4 ± 0.1 kJ/mol.     

Extraction of tetravalent berkelium by tributyl phosphate from nitric acid solutions

Extraction of Bk(IV), Ce(IV), Pu(IV) and Zr by tributyl phosphate from 2M to 16M nitric acid solutions has been studied. Using the data on the effect of the extractant, nitric acid and nitrate ion concentrations on the distribution coefficients of Bk(IV) and Ce(IV), the mechanism of Bk(IV) extraction by tributyl phosphate from nitric acid solutions is considered.     

Extraction of strontium from nitric acid solutions by selected crown ethers

The extraction of Sr from nitric acid solutions by the crown ethers, 12-crown-4, 15-crown-5, 18-crown-6 and DB 18-crown-6 dissolved in chloroform has been investigated. Sr is reasonably well extracted by 18-crown-6 compared to other crown ethers from different nitric acid solutions. The extraction is strongly dependent on the concentration of HNO₃ and nitrate salts. Preliminary studies indicate that¹³⁷Cs is also extracted to a limited extent by 18-crown-6 from nitrate medium. Stripping of Sr was achieved by an aqueous solution of low acidity, the crown ether being regenerated for subsequent extraction.     

Extraction of palladium with thiacalix[4]arenes from nitric acid nitrate-nitrite solutions

Calix[4]arene 1, thiacalix[4]arenes 2(LH₄), and calix[4]arenethioether 3 were compared in palladium extraction from nitric acid solutions; D _Pd for 2 was shown to be 2?C3 orders of magnitude larger than for 1 at pH > 3 (comparable with 3) because of cation-exchange and coordination extraction of palladium. It was shown by extraction methods and IR spectroscopy that thiacalixarenes 2 extract complex species [Pd _n L _m H_{4 ? 2n} ] (m = 1, n = 1 and 2) and [(PdA₂) _n L _m H₄] (A = m = 1, n = 1?C4) from nitric acid solutions at pH 3. Extraction constants for these palladium species that satisfactorily describe experimental data were calculated. As distinct from 3, thiacalixarenes 2 are promising for the combined extraction of palladium and silver from alkaline solutions and the selective extraction of fission palladium from nitric acid solutions. Phosphorylated at the upper rim thiacalixarenes 2 can be considered as bifunctional extractants for the separation of fission radionuclides.     

Extraction of actinium with di (2-ethylhexyl) phosphoric acid from hydrochloric and nitric acid solutions

The extraction of actinium with HDEHP from Cl^– and NO ₃ ^– systems has been investigated. It was found that extraction of actinium from HCl solutions is much better than from HNO₃ solutions. Stability constants of the actinium complexes Ac(X^–)²⁺, X^–=Cl^– or NO ₃ ^– , were determined. Our results show that actinium formed less stable complexes with Cl^– than with NO ₃ ^– ligands.     

Extraction of palladium with acyclic analogs of thiacalix[4]arenes from nitric acid solutions

p-tert-Butylcalix[4]arene was compared with its acyclic analogs in palladium extraction from nitric acid solutions as mononuclear and poly(bi)nuclear complexes with participation of protonated molecules of podands and macrocycle. The extraction ability of podands is similar to that of macrocycle because of the same character of complexation (Pd: S = 1: 1) without formation of new chelates and lower than that of monodentate analog owing to formation of a square complex (Pd: S = 1: 2).     

Extraction of uranium/VI/ with octylphenyl acid phosphate from nitric acid solutions and its separation from some trivalent lanthanides

Mössbauer spectra of hexakis/alkylurea/iron/III/ complexes were measured to investigate the paramagnetic relaxation in ionic compounds. The effects of iron-iron distance and temperature on Mössbauer line shape were studied in these compounds, and the results are discussed in comparison with our previous data on tris/\-diketonato/iron/III/.     

Extraction of actinides by dibutyl-N,N-diethylcarbamoylmethylenephosphonate [DBDECMP] from nitric acid solutions

The extraction of Am(III), Pu(IV) and U(VI) as representatives of tri-, tetra- and hexavalent actinides by dibutyl-N,N-diethylcarbamoylmethylenephosphonate (DBDECMP) from nitric acid solution has ben studied with an objective of understanding the extraction mechanism. The dependence of the distribution ratios of the actinide ions was studied as a function of the concentration of H⁺, DBDECMP and NO ₃ ^– . The extraction data revealed that all the three actinide ions are extracted as their neutral nitrate complexes solvated by DBDECMP which behaves as neutral extractant only. The absorption spectra of DBDECMP and TBP extracts of these actinide ions were recorded. From the close similarity of these spectra it is inferred that DBDECMP acts as a monodentate extractant in the present system.     

Extraction of rare earth elements by high molecular weight amines from nitric acid solutions

Extraction of trivalent rare earth elements by a high molecular weight primary amine /decylamine/ from 0.5–3M nitric acid solutions, containing potassium phosphotungstate /K₁₀P₂W₁₇O₆₁/, has been investigated. The effect of nitric acid and potassium phosphotungstate concentration of the organic solvent, and lanthanides ionic radii upon distribution coefficients has been studied. It has been established that decylamine solutions in chloroform can be used for the group isolation of rare earth elements and for their separation.     

Extraction behavior of yttriuí with diisodecylphosphoric acid from nitric acid solution

Extraction of yttrium and some of the lanthanoids by diisodecylphosphoric acid (DIDPA) has been studied as a function of nitric acid concentration in the aqueous phase and concentration of the DIDPA in n-dodecane. The distribution ratio of yttrium was found to increase with the second power of concentration of the extractant and decrease with the third power of concentration of nitric acid. As the concentration of yttrium in the organic phase increased, an amorphous solid was found to precipitate and the composition of the solid was determined to be Y(DIDP)₃. To dissolve Y(DIDP)₃ into n-dodecane, a 14-fold molar excess of DIDPA was required over Y(DIDP)₃. The distribution ratio of yttrium was found to be too high to back-extract this element by nitric acid of medium concentration.     

Extraction of fission products with 1,2-dichloroethane solutions of hexabromo derivative of cobalt dicarbollide from nitric acid medium

The dependence of the distribution of Cs, Sr, Ba, Eu, Ce between nitric acid solutions and 0.06M hexabromo derivative of cobalt dicarbollide (H⁺BBr ₆ ^– ) in dichloroethane has been investigated upon the concentration of the acid, the extractant and the synergistic additive Slovafol 909. The back-extraction due to the presence of propanol, hydrazine, nitric acid and NH₄NO₃ has been studied. The results were similar to those observed in analogous systems using nitrobenzene as the solvent.     

Extraction behavior of moybdenum and zirconium with diisodecylphosphoric acid from nitric acid solution

This study was performed mainly from the viewpoint of consumption of diisodecylphosphoric acid (DIDPA) by the extracted Mo and Zr to estimate extraction capacities. The number of DIDPA molecules consumed per one extracted Mo atom was four when the concentration of Mo in the aqueous phase was less than 10^–3M and it decreased with increasing Mo concentration. Two molecules of DIDPA were consumed per one extracted Zr atom when the Zr concentration was high. Dependencies of the distribution ratio of Mo on the concentrations of Mo, DIDPA and HNO₃ are also described.     

A study of palladium recovery with thiourea from nitric acid solutions

Interaction in the system Pd(II)-HNO₃-SC(NH₂)₂ was studied. It was shown that the precipitates formed, which have various compositions and solubilities, contain palladium(II) and thiourea conversion products. Elemental, X-ray diffraction, and atomic-adsorption analyses and IR and electronic absorption spectroscopies were applied to demonstrate the possibility of virtually quantitative precipitation of palladium(II) under certain conditions in the form of a poorly soluble precipitate Pd₂(CN)₄ · H₂O.     

The sorption of molybdenum from solutions of nitric acid

The sorption of molybdenum(VI) on KU-2 × 8 and AV-17 × 8 ionites from 6 n solutions of nitric acid was studied. The sorption of molybdenum(VI) on the cationite and anionite changed depending on solution composition and nitric acid concentration. The sorption and electromigration data were used to determine the isoelectric point of molybdenum in solutions of nitric acid.     

Extraction of palladium from nitric acid solutions by octyl(phenyl)-N,N-diisobutylcarbamoyl- methylphosphine oxide

Extraction behaviors of Pd(II) in the TRUEX and PUREX solvent extractions were studied by using octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide. The effect of scrubbing in the TRUEX solvent extraction was demonstrated by adding oxalic acid. The distribution ratios of palladium (D _Pd's) in the diluted region of [HNO₃] were found to depend strongly on the fraction of cationic species, Pd(NO₃)⁺, existed in the aqueous phase. The gradual decrease of DPd with the increase of acidity beyond [H⁺] 1 mol·dm^-3 was controlled by the formation of the anionic species Pd(NO₃)₃ ^-.     

Extraction of oxalic acid from solutions of electrolyte mixture

Extraction of oxalic acid with tributyl phosphate and triisoamyl phosphate from solutions of its mixtures with nitric, phosphoric, sulfuric, and hydrochloric acid and with ammonium nitrate and chloride was studied. In the extractability series, oxalic acid occupies the position between nitric and phosphoric acids, with sulfuric and hydrochloric acids acting as strong salting-out agents. Nitric acid salts drastically decrease the distribution ratios of oxalic acid.     

Anion adsorption of lanthanides from aqueous organic nitric acid solutions

Conclusion The equilibrium parameters of the anion exchange of lanthanides in aqueous organic complexing media are related to the acceptor properties of the organic solvents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 924–927, April, 1987.     

Extraction of tri- and tetravalent actinides with dihexyl N,N-diethylcarbamoylmethyl phosphonate (DHDECMP) and TBP from nitric acid solutions

Extraction of trivalent (Pu³⁺, Am³⁺, actinides and Eu³⁺, a representative of lanthanides) and tetravalent (Np⁴⁺ and Pu⁴⁺) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO₃)₃·(3–n) TBP·n DHDECMP (for trivalent ions) and M(NO₃)₄·(2–n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu³⁺ and Am³⁺, a lesser decrease being observed for Pu³⁺ (larger ion).     

Extraction of rhenium(VII) with aliphatic alcohols from acid solutions

Extraction of rhenium(VII) with C₇–C₁₀ aliphatic alcohols from HCl and H₂SO₄ solutions was examined. The rhenium(VII) distribution coefficients were examined in relation to the acidity and temperature. The composition of the extracted complexes and the thermodynamic parameters of extraction were determined. The extraction method of recovery and preconcentration of rhenium(VII) from H₂SO₄ solutions with secondary octyl alcohol was tested in the counterflow mode.