Solvent extraction of Hf(IV) from mixed electrolyte solutions into di-2-ethylhexylphosphoric acid (HDEHP)

Extraction of hafnium(IV) from aqueous sulfuric and sulfuric-nitric acid solutions into di-2-ethylhexylphosphoric acid (HDEHP) in xylene has been investigated. The Hf(IV) species extracted from 5M sulfuric acid was found to be HfY₂(HY₂)₂ where Y and HY₂ represent the anions of monomeric HY and dimeric H₂Y₂ forms of HDEHP, respectively. In the presence of nitrate ion the species extracted are found to be Hf(NO₃)Y(HY₂)₂ and Hf(NO₃)₂)(HY₂)₂. But when the aqueous phase is 3.0M HNO₃+2.5M H₂SO₄ only one species, Hf(NO₃)₂(HY₂)₂ was extrated. No synergism was observed from 5M H₂SO₄ by HDEHP with the addition of thenoyltrifluoracetone (HTTA).     

Solvent extraction of Np(IV) and Pu(IV) with mixtures of TOPO and HTTA

Solutions of HTTA are known to extract tetravalent actinides as M(TTA)₄ species. When TOPO is added to HTTA solutions, the extracting of Np(IV) and Pu(IV) from aqueous perchloric acid was enhanced enormously. The species responsible for the enhanced extraction were identified from the extraction data by the slope ratio method and JOB's method. It was found that the predominant species responsible for enhancement in the extraction, when [HTTA]≫[TOPO], was M(TTA)₄. TOPO for both Np(IV) and Pu(IV). Furthermore, it was established that depending on the relative concentrations of HTTA and TOPO, a number of species with the composition M(TTA)_a(ClO₄)_4-a·b TOPO, with a ranging from 1 to 4 and b having values of 1 or 2, are involved in the extraction. Several equilibrium constant values are given. Fuel Reprocessing Division.     

Some remarks on the extraction of Pu(IV) and Th with tridodecylamine from nitric acid soil leach solutions and the possible existence of a univalent anionic Th-nitrate complex

The extraction of Pu(IV) and Th with tridodecylamine—xylene mixtures from about 6M nitric acid soil leach solutions was studied as a function of the chemical composition of the aqueous phase (iron and calcium concentration, acidity) and the amine concentration in the extractant. No correlation was found between the partition coefficients of Pu(IV) and Th and the composition parameters mentioned above at any of the amine concentrations examined. The slope, in a bilogarithmic plot, of the partition coefficients versus the amine concentrations was found to be close to 2 for Pu(IV) as well as Th in pure 6.5M nitric acid solution, thus indicating the presence of the complexes Pu(NO₃) ₆ ²⁻ and Th(NO₃) ₆ ²⁻ in the extract. When the pure nitric acid solution was replaced by soil leach solutions of similar molarity in HNO₃, the slope remained 2 for Pu(IV), but changed to 1.5 for Th. A possible reason for this slope yielded by Th may be the coexistence of the complexes Th(NO₃) ₆ ²⁻ and Th(NO₃) ₅ ⁻ in the extraction phase. Presented at the 4th SAC Conference on Analytical Chemistry, Birmingham 1977.     

Extraction and thermodynamic behavior of U(VI) and Th(IV) from nitric acid solution with tri-isoamyl phosphate

The extraction behavior of U(VI) and Th(IV) with tri-isoamyl phosphate–kerosene (TiAP–KO) from nitric acid medium was investigated in detail using the batch extraction method as a function of aqueous-phase acidity, TiAP concentration and temperature, then the thermodynamic parameters associated with the extraction were derived by the second-law method. It could be noted that the distribution ratios of U(VI) or Th(IV) increased with increasing HNO₃ concentration until 6 or 5 M from 0.1 M. However, a good separation factor (D _U(VI)/D _Th(IV)) of 88.25 was achieved at 6 M HNO₃, and the stripping of U(VI) from TiAP–KO with deionized water or diluted nitric acid was easier than that of Th(IV). The probable extracted species were deduced by log D-log c plot at different temperatures as UO₂(NO₃)₂·(TiAP)_(1–2) and Th(NO₃)₄·(TiAP)_(2–3), respectively. Additionally, △H, △G and △S for the extraction of U(VI) and Th(IV) revealed that the extraction of U(VI) by TiAP was an exothermic process and was counteracted by entropy change, while the extraction of Th(IV) was an endothermic process and was driven by entropy change.     

Solvent extraction studies of plutonium(IV) and americium(III) in room temperature ionic liquid (RTIL) by di-2-ethyl hexyl phosphoric acid (HDEHP) as extractant

Solvent extraction of Pu(IV) and Am(III) from aqueous nitric acid into room temperature ionic liquid (RTIL) by an acidic extractant HDEHP (di-2-ethyl hexyl phosphoric acid) was carried out. The D values indicated substantial extraction for Pu(IV) and poor extraction for Am(III) at 1M aqueous nitric acid concentration. However at lower aqueous nitric acid concentrations (pH 3), the Am(III) extraction was found to be quantitative. The least squares analysis of the extraction data for both the actinides ascertained the stoichiometry of the extracted species in the RTIL phase for Pu(IV) and Am(III) as [PuH(DEHP)₂]³⁺, AmH(DEHP)²⁺. From the D values at two temperatures, the thermodynamic parameters of the extraction reaction for Pu(IV) was calculated.     

Extraction of uranium (VI), plutonium (IV) and some fission products by tri-iso-amyl phosphate

The extractive properties of tri-isoamyl-phosphate (TAP), an indigenously prepared extractant, and the loading capacity of extraction solvent containing TAP for U(VI) and Pu(IV) ions in nitric solution have been investigated. The dependence of the distribution ratio on the concentration of nitric acid showed that TAP has an ability to extract these actinides, while the fission product contaminants are poorly extracted. The distribution data revealed a quantitative extraction of both U(VI) and Pu(IV) from moderate nitric acidities in the range 2–7 mol · dm^–3. Slope analysis proved predominant formation of the disolvated organic phase complex of the type UO₂(NO₃). 2TAP and Pu(NO₃)₄·2TAP with U(VI) and PU(IV), respectively. On the contrary, the extraction of fission product contaminants such as¹⁴⁴Ce,¹³⁷Cs,⁹Nb.,¹⁴⁷Pr,¹⁰⁶Ru,⁹⁵Zr was almost negligible even at very high nitric acid concentrations in the aqueous phase indicating its potential application in actinide partitioning. The recovery of TAP from the loaded actinides could be easily accomplished by using a dilute sodium carbonate solution or acidified distiled water (0.01 mol · dm^–3 HNO₃) as the strippant for U(VI) and using uranous nitrate or ferrous sulphamate as that for Pu(IV). Radiation stability of TAP was adequate for most of the process applications.     

Synergistic solvent extraction of zirconium(IV)

The extraction of Zr(IV) by 2-thenoyltrifluoroacetone (TTA) in carbon tetrachloride from aqueous hydrochloric acid solutions is a slow process. The addition of a neutral extractant, di-n-pentyl sulfoxide (DPSO) enhances considerably the rate as well as the percentage of extraction. The species extracted appears to be ZrCl₂(TTA)₂·2 DPSO. An increase in temperature results in a further increase in the rate and percentage of extraction. Studies have also been carried out on the extraction of the metal by mixtures of various neutral extractants. Thermodynamic parameters associated with the formation of the synergistic adducts have been evaluated.     

The extraction of iron(III) by dioctylarsinic acid in chloroform

Dioctylarsinic acid, HDOAA, in chloroform solution has been investigated as a reagent for the extraction of iron(III) chloride. The extraction coefficient reaches two maxima, one of 1.5 at 8.5 M hydrochloric acid and another of 7 at pH 2.3. Experiments in the range 4–8 M for sulfuric, nitric and perchloric acids showed no extraction of iron(III) from these solutions for extraction times of 6 h. Evidence for the extraction of H₃FeCl₆ from 4–9 M hydrochloric acid solutions as [(H₂DOAA)⁺]₃FeCl₆^3- is presented. The species extracted from aqueous solutions of pH 1–2.3 is probably a hydroxy complex of the composition [Fe₂(DOAA)₂(HDOAA)X₄(H₂0)₂ ](X = OH and/or Cl).     

Monotonic transfer annealing kinetics associated with an oscillatory phenomenon in51Cr(III)-doped potassium chromate

Infrared absorption spectra of HNO₃ solutions in UO₂(NO₃)₂(TBP)₂ have been taken. The formation of a hydrogen bond between HNO₃ and nitrate or phosphoryl group in UO₂(NO₃)₂(TBP)₂ has been established. On extracting Pu(IV) and Np(IV) by 30% TBP-dodecane, dependence of the distribution coefficients on concentration has been found at UO₂(NO₃)₂ concentrations in the aqueous phase upwards from 0.4M. This dependence appeared in the temperature interval 0–60°C. Such effects may be caused by ordered structure of saturated uranyl nitrate solutions in TBP.     

Uptake of actinides and lanthanides from nitric acid by dihexyl-N,N-diethylcarbamoylmethylphosphonate adsorbed on chromosorb

Batchwise uptake of Am(III), Pm(III), Eu(III), U(VI) and Pu(IV) by dihexyl-N,N-diethylcarbamoylmethylphosphonate (CMP) adsorbed on chromosorb (CAC) at nitric acid concentrations between 0.01 to 6.0M has been studied. The difference between the uptake behavior of Pu(IV) as compared to other actinides and lanthanides is discussed. The Am(III) and U(VI) species taken up on CAC were found to be Am(NO₃)₃·3CMP and UO₂(NO₃)₂·2CMP, respectively. The equilibrium constants for the formation of these species have been evaluated and compared with those of similar species formed in liquid-liquid extraction. Batchwise loading of Pm(III) on CAC from 3.0M HNO₃ has also been studied.     

Plutonium(IV) mononitrate and dinitrate complex formation in acid solutions as a function of ionic strength

Titrations of Pu(IV) with HNO₃ in a series of aqueous HClO₄ solutions ranging in ionic strength from 2 to 19 molal were followed using visible and near-infrared absorption spectrophotometry. The Pu 5f-5f spectra in the visible and near IR range change with complex formation. At each ionic strength, a series of spectra were obtained by varying nitrate concentration. Each series was deconvoluted into spectra of Pu⁴⁺ (aq), Pu(NO₃)³⁻ and Pu(NO₃)₂ ²⁺ complexes, and simultaneously their formation constants were determined. When corrected for the incomplete dissociation of nitric acid, the ionic strength dependence of each formation constant can be described by two parameters, β⁰ and Δε using the formulae of specific ion interaction theory.     

Extraction of Th(IV), La(III), and Y(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate

Extraction of Th(IV), La(III), and Y(III) from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate (Aliquat-336) was studied. The extraction isotherms were analyzed assuming that lanthanides and thorium are extracted with the solid extractant in the form of complexes (R₄N)₂[Ln(NO₃)₅] and (R₄N)₂[Th(NO₃)₆], respectively. The extraction constants were calculated. The joint extraction of Th(IV) and La(III) [Y(III)] with the solid extractant from aqueous salt solutions was studied.     

Synergistic extraction of uranium(VI) and thorium(IV) with mixtures of Cyanex272 and other organophosphorus ligands

The extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been studied using mixtures of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272 or HA), and synergistic extractants (S) such as tri-butylphosphate (TBP), tri-octylphosphine oxide (TOPO) or bis(2,4,4-trimethylpentyl)thiophosphinic acid (Cyanex301). The results showed that these metallic ions are extracted into kerosene as Th(OH)₂(NO₃)A·HA and UO₂(NO₃)A·HA with Cyanex272 alone. In the presence of neutral organophosphorus ligands TBP and TOPO, they are found to be extracted as Th(OH)₂(NO₃)A·HA·S and UO₂(NO₃)A·HA·S. On the other hand, Th(IV), U(VI) are extracted as Th(OH)₂(NO₃)A·HA·2S and UO₂(NO₃)A·HA·S in the presence of Cyanex301. The addition of neutral extractants such as TOPO and TBP to the extraction system enhanced the extraction efficiency of both elements while Cyanex301 as an acidic extractant has improved the selectivity between uranium and thorium. The effect of TOPO on the extraction was higher than other extractants. The equilibrium constants of above species have been estimated by non-linear regression method. The extraction amounts were determined and the results were compared with those of TBP. Also, it was found that the binding to the neutral ligands by the thorium–Cyanex272 complexes follows the neutral ligand basicity sequence.     

Synergistic extraction of U(VI) and Th(IV) from nitric acid with 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (HBMPPT) and tri-n-octylphosphine oxide (TOPO) in toluene

The extractant HBMPPT (4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione) was synthesized from HBMPP. Its m.p. was 106–108°C. The synergistic extraction of U(VI) and Th(IV) from nitric acid solution by HBMPPT and TOPO in toluene was studied. The extraction ability of HBMPPT was not so high as that of its parent (HBMPP), but when a little tri-n-octylphosphine oxide (TOPO) was added the ability to extract U(VI) and Th(IV) was seriously improved. The synergistic extracted complexes may be presented as UO₂NO₃·BMPPT·TOPO and UO₂(BMPPT)₂·TOPO for U(VI), and Th(NO₃)₃·BMPPT·TOPO and Th(NO₃)₂(BMPPT)₂·TOPO for Th(IV) respectively.     

Extraction of thorium(IV), lantanum(III), and yttrium(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylamine

Extraction of Th(IV), La(III), and Y(III) from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylamine (Alamine-336) was studied. The extraction isotherms were analyzed assuming that lanthanides and thorium are extracted with the solid extractant in the form of complexes (R₃HN)₃[Ln(NO₃)₅] and (R₃HN)₂[Th(NO₃)₆], respectively. The extraction constants were calculated. The joint extraction of Th(IV) and La(III) [Y(III)] with the solid extractant from aqueous salt solutions was studied.     

Extractive separation and photometric determination of neptunium(IV) and plutonium(IV) from their mixtures

A rapid and sensitive method for the photometric determination of trace amounts of neptunium and plutonium from their mixtures is described. Np(IV) is selectively extracted from about 1 M HNO₃ medium with TTA in xylene retaining Pu in the nonextractable trivalent state in the aq. phase with ferrous sulfamate. Plutonium in the aqueous phase is subsequently oxidized with NaNO₂ to the highly extractable tetravalent state and extracted with TTA. Np(IV) as well as Pu(IV) thus extracted are finally estimated in the organic phase itself spectrophotometrically employing xylenol orange as the chromogenic reagent. Their molar absorptivities are in the 5 × 10⁴ range. Beer's law is valid up to 2.4 ppm Np and 3.5 ppm Pu. The color of the solutions is stable for at least 48 hr. The method tolerates large excess of several common contaminants encountered during spent fuel reprocessing. Cerium(IV) and phosphoric acid, however, interfere with the final estimation.     

Synthese und Kristallstruktur von Y(HSO4)3-I und Y(HSO4)3 · H2O

Syntheses and Crystal Structures of Y(HSO₄)₃-I and Y(HSO₄)₃ · H₂O Lath shaped crystals of Y(HSO₄)-I are obtained by treatment of Y₂O₃ with conc. sulfuric acid at 200 °C. Y(HSO₄)₃-I crystallizes orthorhombic (Pbca, Z = 8, a = 1201.5(1), b = 953.76(8), c = 1650.4(1) pm, R_all = 0.0388). In the crystal structure Y³⁺ is coordinated by eight monodentate HSO₄^– groups. Colorless, plate like single crystals of Y(HSO₄)₃ · H₂O grew from a solution of Y₂O₃ in 85% sulfuric acid upon cooling. In the crystal structure of the triclinic compound (P1, Z = 2, a = 679.8(1), b = 802.8(2), c = 965.9(2) pm, α = 79.99(2)°, β = 77.32(2)°, γ = 77.50(2)°, R_all = 0.0264) Y³⁺ is surrounded by seven HSO₄^– groups and one molecule of water.     

Solvent extraction of neptunium(IV) from nitric acid solutions by sulphoxides and their mixtures

Studies have been performed on the liquid-liquid extraction of neptunium from nitric acid solutions by di-n-hexylsulphoxide (DHSO) di-no-octylsulphoxide (DOSO) and di-iso-amylsulphoxide (DISO) and their mixtures over a wide range of conditions. At a given strength of the extractant, extraction of Np(IV) increases initially rapidly with increase in the acid concentration; at high acidities, above 8M HNO₃, the extraction decreases. Under otherwise identical conditions, extraction increases with an increase in the extractant concentration. The species extracted would appear to be Np(NO₃)₄·2(R₂SO). A mixture of two extractants extracts more than the sum of the extractions due to the individual components at concentrations corresponding to those of the mixture. After loading the organic phase with uranium(VI), extractability of Np(IV) becomes considerably lower. The diminution in extraction with increase in temperature is small. A comparison of the extraction behaviour of Np(IV) with those of Pu(IV), U(VI) and some associated fission products has been made.     

Solvent extraction of Pu(IV) with TODGA in C6mimTf2N

Studies on the solvent extraction of Plutonium(Pu(IV)) from aqueous nitric acid by N,N,N′,N′-tetraoctyl-diglycolamide (TODGA) in 1-hexyl-3-methylimidazolium-bis(trifluoromethylsulfonyl) imide (C₆mimTf₂N) room temperature ionic liquid (RTIL) were carried out. It was found that Pu(IV) is extracted into RTIL phase as [Pu(NO₃)(TODGA)]³⁺ through cation exchange mechanism. Extraction reaction equation is obtained by the influence of acidity and extractant concentration, and the parameters of thermodynamic equilibrium constant was calculated.     

Extraction of uranium (VI) from sulfuric acid solution with TOPO

The extraction of uranium(VI) from sulfuric acid medium with tri-octylphosphine oxide (TOPO) in n-heptane was studied. Accompanied with the increase in the concentration of H₂SO₄, the distribution coefficient of uranium(VI) increased in the region of dilute sulfuric acid. When the concentration of H₂SO₄ surpassed 3.5 mol·dm⁻³, the distribution coefficient of uranium(VI) was at maximum. This result was due to the competition extraction between uranium(VI) and H₂SO₄. From the data, the composition of extracted species and the equilibrium constant of extraction reaction have been evaluated, which were (TOPOH)₂UO₂(SO₄)₂ (TOPO) and 10^7.6±0.15, respectively.