Spectrophotometric determination of thorium with arsenazo III in the organic phase after extraction with di-(2-ethylhexyl)orthophosphoric acid

A simple, direct colorimetric determination of thorium extracted from chloride solution with di-(2-ethylhexyl)orthophosphoric acid is described; the colour is developed in the organic phase by adding arsenazo III and then isopropanol. Two different procedures are outlined for different thorium levels; maximum absorbance occurs at 660 nm and Beer's law is obeyed within limited ranges. Molar extinction coefficients for the two methods are 4.93 · 10⁴ and 8.77 · 10⁴ respectively. With the more sensitive method, 0.696 μg Th/ml was determined with 0.0028 as standard deviation. The effects of the various parameters were studied. Among 69 foreign cations tested, serious interferences are U(VI), Se (IV), Ti(IV), Y and the rare earths. Of the common anions, only large amounts of sulpliate slightly interfered. Several ways of overcoming interferences are suggested, with particular-reference to uranium.Several extensions of the method are outlined; 2 p.p.b. Th in aqueous media can be determined by modifying the extraction step. The procedure also appears to be extremely sensitive for the light rare-earth elements.     

Tracer scale solvent extraction separation of tantalum from niobium using di-(2-ethylhexyl)-phosphoric acid as extractant

A simple solvent extraction procedure for the efficient separation of the radioactive tracers⁹⁵Nb and¹⁸²Ta from each other in a mixture using di-(2-ethylhexyl)phosphoric acid (HDEHP) as extractant is described. Tantalum was found to be quantitatively extracted from an aqueous madium, which is 1.6N in HCl and 10^?2 M in oxalic acid, with a HDEHP solution of 0.1 M concentration. Extractabilities of both niobium and tantalum in mineral acids like HCl, H₂SO₄ and HNO₃ and in some organic acids like oxalic, citric, etc., in HDEHP under the experimental conditions were also studied. The reliability of the separation procedure was verified further by γ-ray spectrometry.     

Atomic absorption determination of indium after extraction with di-(2-ethylhexyl)phosphoric acid

The equilibrium data show that indium can be quickly extracted from acidic aqueous solutions by di-(2-ethylhexyl)phosphoric acid in methyl isobutyl ketone. In this polar solvent the species ML₃·HL is extracted. The overall extraction constant is higher than that for other tervalent metals. The extraction process can be combined with AAS determination of the indium. The method is fast because stripping is not necessary, and the organic phase can be analysed directly by AAS. Use of a 51 v/v aqueous: organic phase ratio increases the sensitivity. In the pH-range used the method has good selectivity.     

Solvent extraction of neodymium,europium and thulium by di-(2-ethylhexyl)phosphoric acid

The extraction of Na³⁺, Eu³⁺ and Tm³⁺ by di-(2-ethylhexyl)phosphoric acid, HDEHP has been studied from various aqueous acidic solutions. The extraction of these elements is inversely proportional to the third power of the hydrogen ion concentration. Antagonistic effects were observed when the extraction was studied by mixtures of HDEHP and tributyl phosphate, TBP, or trioctylphosphine oxide, TOPO. The presence of water-miscible alcohols and acetone generally increases the extraction of these three elements from HCl solutions. Reaction mechanisms have been suggested and discussed in the light of the data obtained.     

Solvent extraction of Fe(III) by di-(2-ethylhexyl)phosphoric acid from phosphoric acid solutions

The extraction of iron(III) from aqueous phosphoric acid was studied using di-(2-ethylhexyl)phosphoric acid and trioctylphosphine oxide in nonaromatic hydrocarbon diluent. Distribution ratios have been investigated as a function of concentration of iron(III), phosphoric acid concentration, extractant concentration and extraction temperature. The apparent enthalpy change for the extraction reaction has been calculated from the temperature dependence data. It was found that the extractant dependency for iron(III) is first power indicating hydrolysis of iron(III) in the aqueous phase.     

Studies on the solvent extraction behaviour of Pu(IV) from sulfuric acid medium into di-2-ethylhexyl phosphoric acid (HDEHP)

Extraction of plutonium(IV) from aqueous sulfuric and sulfuric-nitric acid into di-2-ethylhexyl phosphoric acid (HY) in the diluents n-dodecane, toluene or chloroform has been investigated. The composition of the Pu(IV) species extracted from H₂SO₄ was found to be PuH₂Y₆, which changed to Pu(NO₃)H₂Y₅ and Pu(NO₃)₂H₂Y₄ with increasing concentration of nitrate ion in the aqueous medium. These three species can be represented as PuY₂(HY₂)₂, Pu(NO₃)Y(HY₂)₂ and Pu(NO₃)₂(HY₂)₂, respectively, where Y represents the anion of monomeric HY, and HY₂ the anion of dimeric H₂Y₂. Synergism in the extraction of Pu(IV) by the addition of thenoyltrifluoroacetone (HTTA) to HY was also investigated and attributed to extraction of the additional species, Pu(TTA)Y(HY₂)₂ and Pu(TTA)₂(HY₂)₂. The addition of the neutral extractant tri-n-octylphosphine oxide (TOPO) to HY did not result in synergism in the extraction of Pu(IV) from aqueous sulfuric acid. With aqueous nitric acid under similar conditions, however, synergism was observed. The possible equilibria in these systems were identified and the corresponding equilibrium constants were determined.     

The extraction of vanadium(IV) from hydrochloric acid solutions by di-(2-ethylhexyl)-phosphoric acid

The distribution of vanadium(IV) between hydrochloric acid solutions and solutions of di-(2-ethylhexyl)-phosphoric acid (DEHPA; HX) in organic solvent has been investigated under different conditions. Both the aqueous and organic phases have been examined spectrophotometrically. IR and electron spin resonance spectroscopies have been applied to the organic extracts. The mechanism of extraction is discussed on the basis of the results obtained.     

Determination of radiocerium in fission products by extraction chromatography using di-(2-ethylhexyl)phosphoric acid

An extraction chromatographic method is described for the determination of cerium in a fission product mixture. Cerium(IV) is separated on a column of siliconized kieselguhr saturated with di-(2-ethylhexyl)phosphoric acid (HDEHPA). After washing the column with a mixture of sodium bromate and nitric acid, cerium is eluted by a mixture of 5M HNO₃ and 0.1M ascorbic acid. The optimum conditions for the quantitative sorption and elution of cerium were found, and the reproducibility of the yield was verified. The influence of other fission and corrosion products (Mg, Fe, Al, U) on the sorption and elution of cerium was studied. The method has been successfully applied for the determination of cerium in artificial and natural mixtures of fission products.     

New cyclen derivative ligand for thorium(IV) separation by solvent extraction

A new N-containing ligand, 1,4,7,10-tetra-(4-nitrobenzyl)-1,4,7,10-tetraazacyclo-dodecane (L), was synthesized, and its structure was determined by ¹H NMR, high resolution mass spectrometry and X-ray diffraction. L crystallized in the monoclinic system (P2₁/n space group; a = 7.7895(2) Å, b = 22.9592(5) Å, c = 9.9204(2) Å; α = 90.00°, β = 105.481(3)°, γ = 90.00°; Z = 2). Slope analysis and the continuous variation method demonstrated that 1:2 complexes between Th(IV) and L are formed; furthermore, the XPS analysis suggested that two oxygen atoms might be provided by two water molecules and that eight nitrogen atoms might be provided by two L molecules to form a ten-coordinate compound with Th(IV). The extraction equilibrium constant for the complex formation between Th(IV) and L was logK _ex = 6.95 ± 0.15 (25 °C), and the Gibbs free energy, ΔG ^o (25 °C), of the 1:2 Th–L complex in dichloromethane was ?39.56 kJ/mol. The L ligand in dichloromethane only slightly extracted Th(IV) from HNO₃ solution at pH = 1–3; however, an extraction efficiency of E = 94.9 ± 0.3 % was observed at pH = 4.63. The selectivity of L for the Th(IV) cation over other cations (i.e., Cs(I), Sr(II), Y(III), La(III), Sm(III), Eu(III), U(VI), and ²⁴¹Am(III)) was evaluated. Furthermore, the stripping experiments showed that the stripping agent (0.5 mol/L Na₂CO₃ + 0.1 mol/L EDTA) could provide an optimal condition for stripping thorium, and thorium recovery was up to 91.6 ± 0.1 %.     

Effect of radiolysis products of di-(2-ethylhexyl)phosphoric acid upon the extraction of lanthanides

In order to clarify the influence of radiation degradation of DEHPA upon the extraction of lanthanides, the extraction of neodymium(III) was studied using DEHPA, MEHPA, 2-ethylhexanol and γ-ray irradiated DEHPA. The most significant effect of DEHPA radiolysis on the extraction was found to be the enhacement of extraction capability mainly due to the primary radiolysis product MEHPA. 2-Ethylhexanol, another radiolysis product, showed a depressant effect on DEHPA-Nd(III) extraction. However, the mixture of MEHPA and 2-ethylhexanol improved the extraction. The mixed solvent DEHPA-MEHPA was found to be more effective than the individual components for lanthanide extraction.     

Liquid-liquid distribution studies of thorium salicylate with tris-(2-ethylhexyl)phosphate

A method is proposed for the extraction of thorium(IV) from salicylate media using tris-(2-ethylhexyl)phosphate dissolved in toluene as an extractant. The optimum conditions were evaluated from a critical study of pH, salicylate concentration, extractant concentration, period of equilibration and diluent. The method permits the separation of thorium from the associated elements and is applicable to the analysis of monazite sand. The method is precise, accurate, fast and selective.     

In situ electro-oxidation and liquid-liquid extraction of cerium(IV) from nitric acid medium using tributyl phosphate and 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate

The process of in situ electro-oxidation of Ce(III) to Ce(IV) followed by its extraction into the organic phase has been investigated for its applicability in the separation of Ce from nitrate medium. Solvent extraction of cerium from nitric acid after its electro-oxidation to fourth valency state was carried out using tributyl phosphate (TBP) and 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (KSM-17, equivalent to PC-88A). The efficiency of the extractants at different aqueous phase nitric acid concentrations and different electrode potentials were determined. Various reducing agents such as hydroxylamine hydrochloride, sodium nitrite, ferrous sulphate as well as complexing agents like EDTA, oxalic acid etc, were studied as strippants for the back extraction of cerium from the loaded organic phase. The method developed for the extraction of cerium was further extended to the partitioning of cerium from Ce-Am mixture obtained during the KSM-17 based extraction chromatographic elemental fractionation of PUREX High Activity Waste (HAW) solutions. Recovery of Ce obtained in the extraction experiments by batch as well as by continuous flow organic phase was >95% with good radiochemical purity.     

2-乙基己基膦酸单2-乙基己基酯与钕的萃合物在正己烷溶液中的结构研究

2-乙基己基膦酸单2-乙基己基酯[HEH(EHP)]是一种良好的萃取剂, 已被广泛地应用于稀土和钴和镍的分离[1,2]。对于它的萃取性能和机理已作过大量的研究。本文针对用HEH(EHP)萃取分离稀土时必须保证萃取剂与有机相稀土含量的摩尔比大于6, 否则即发生乳化现象, 利用蒸气压渗透法及红外光谱为手段, 研究了HEH(EHP)与钕所生成的萃合物在溶液中的存在形式及结构, 阐明发生乳化及破乳过程的实质。     

Separation of thorium from lanthanides by solvent extraction with ionizable crown ethers

Thorium and the lanthanides are extracted by alpha-(sym-dibenzo-16-crown-5-oxy)acetic acid and its analogues in different pH ranges. At pH 4.5, Th is quantitatively extracted by the crown ether carboxylic acids into chloroform whereas the extraction of the lanthanides is negligible. Separation of Th from the lanthanides can be achieved by solvent extraction under this condition. The extraction does not require specific counteranions and is reversible with respect to pH. Trace amounts of Th in water can be quantitatively recovered using this extraction system for neutron activation analysis. The nature of the extracted Th complex and the mechanism of extraction are discussed.     

Influence of rare earth elements on extraction of actinium with di-(2-ethylhexyl)phosphoric acid from inorganic acid solutions

The extraction of actinium by HDEHP solutions in n-heptane as a function of mineral acids and some lanthanides (Ln) in the aqueous phase has been studied. It was found that the actinium extraction coefficient in the absence of Ln decreased linearly with acid concentration with the slope of –3 in the whole investigated range of its concentration. In the presence of Ln the extraction coefficient decreased with a smaller slope than in the absence of Ln. This slope decreased with the Ln salt concentration. The extraction coefficient of Ac decreased with a slope of –3 at acid concentrations above 0.1N, regardless of the Ln concentration in the extraction system.     

Activity Coefficients of di-(2-ethylhexyl) Phosphoric Acid in Select Diluents

This work characterizes the non-ideal behavior of the solvent extraction agent di-(2-ethylhexyl) phosphoric acid (HDEHP), constituting one piece of an effort to develop increasingly accurate models of advanced fuel separation processes such as TALSPEAK. Robust models are particularly important for processing high-level radioactive material in order to minimize the generation of secondary waste and to ensure reliable process control. Here, vapor pressure osmometry (VPO) data on binary solutions of HDEHP in toluene, dodecane, or cyclooctane yields the activity coefficients for each component after analysis. Initially, diluent activity data is obtained using the VPO results and then modeled using Scatchard-Hildebrand theory to provide the activity coefficients for HDEHP.     

Synthesis of gold nanoparticles stabilized with di-(2-ethylhexyl)dithiophosphoric acid and tris(2-aminoethyl)amine

Methods for preparing gold nanoparticles (NPs) surface-stabilized with di-(2-ethylhexyl)dithiophosphoric acid (DTPA) and tris(2-aminoethyl)amine (TAEA), which endow the nanoparticles with hydrophobic and hydrophilic properties, are described. In the case of DTPA, Au-NPs are first synthesized with surfactant shells by means of reducing [AuCl₄]^? with hydrazine in inverted micelles of oxyethylated Triton N-42 in a low-polarity medium of decane; then, the micelles are destroyed by polar chloroform in the presence of DTPA, which has a great affinity to gold due to its sulfur donor atoms and substitutes for the surfactant on the surface of the nanoparticles. In preparing hydrophilic nanoparticles, [AuCl₄]^? is reduced with solid NaBH₄ directly in a nonaqueous solution of TAEA based on an ethanol and 2-propanol (3: 10) mixture. The nanoparticles are characterized by elemental analysis (for Au, C, H, N, and Na), X-ray powder diffraction, electronic absorption spectra, IR spectra, photon-correlation spectra, and transmission electron microscopy (TEM).     

Solvent extraction separation of tin (IV) with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A)

Solvent extraction of tin(IV) from hydrochloric acid media was carried out with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in toluene. Tin(IV) was quantitatively extracted with 2.5x10(-2) M PC-88A in toluene from 0.1-0.3 M HCl when equilibrated for 5 min. Tin(IV) from the organic phase was stripped with 4 M HCl and determined spectrophotometrically by both the morin and pyrocatechol violet method. The nature of the extracted species was determined from the log-log plots. Various other diluents such as xylene, hexane and cyclohexane also gave quantitative extraction of tin. The metal loading capacity of the reagent was found to be 0-15 ppm of tin(IV). The extraction of tin(IV) was carried out in the presence of various ions to ascertain the tolerance limit of individual ions. Tin(IV) was successfully separated from commonly associated metal ions such as antimony(III), bismuth(III), lead(II), thallium(I), copper(II), nickel(II), etc. The method was extended for determination of tin in real samples.