Solvent extraction of uranium(VI) and thorium(IV) by N,N′-di-p-tolylpyridine-2,6-dicarboxamide from nitric acid solution

Synthesis and characterization of N,N′-di-p-tolylpyridine-2,6-dicarboxamide (DTPDA) was carried out and used for extraction of U(VI) and Th(IV) from nitric acid solutions. The processes of extraction were determined by the slope analysis and by analyzing a function that allows the simultaneous treatment of all the experimental points obtained in different conditions. The different factors affecting the extraction distribution ratio(D) of U(VI) and Th(IV) (extraction concentration, concentrations of nitric acid, salting-out agent NaNO₃ concentration, equilibration time and temperature) were investigated. The results obtained indicated that the extraction species of U(VI) and Th(IV) are mainly extracted as UO₂(NO₃)₂·1.5DTPDA and Th(NO₃)₄·1.5DTPDA. The related thermodynamic functions were calculated. Back-extraction of U(VI) and Th(IV) from organic phases was also studied.     

Extraction behavior of strontium from nitric acid solution with N,N,N′,N′-Tetraisobutyl diglycolamide

The extraction behaviors of strontium from nitric acid solution were investigated with N,N,N′,N′-tetraisobutyl diglycolamide (TiBDGA). Effects of acidity, diluents, concentration of extractant and temperature on the distribution ratio of strontium (D _Sr) were examined. The stoichiometry of the extracted molecule was Sr²⁺:TiBDGA of 1:3. The apparent extraction equilibrium concentration constant logK _ex was 3.25. The enthalpy change ΔH and entropy change ΔS were ?55.6 kJ mol^-1 and ?124 J mol^-1 K^-1, respectively. The extraction is an exothermic process. Through two strip stages, strontium could be stripped effectively by 0.01 M nitric acid solution.     

Synthesis and characterization of N,N,N′,N′-tetraalkyl-4-oxaheptanediamide as extractant for extraction of uranium(VI) and thorium(IV) ions from nitric acid solution

Tridentate ligand N,N,N′,N′-tetraoctyl-4-oxaheptanediamide(TOOHA) and other three analogous diamides have been prepared and characterized by using NMR spectra and element analysis. The extraction of UO₂ ²⁺ and Th⁴⁺ with the present extractants was investigated at 293 ± 1 K from nitric acid solutions. n-Octane was found to be the most suitable diluent in the present study compared with other diluents tested. Extraction distribution ratios (D) of U(VI) and Th(IV) have been studied as a function of aqueous concentrations of HNO₃, extractant concentrations. The results indicated that U(VI) is mainly extracted as UO₂(NO₃)₂·2TOOHA. In the case of Th⁴⁺ ion, the possible compositions of extracted species in organic phase were presumed to be Th(NO₃)₄·2TOOHA and Th(NO₃)₄·3TOOHA. In addition, the influence of concentration of sodium nitrate as salting-out agent on the distribution ratio of U(VI) and Th(IV) with TOOHA was also evaluated.     

N,N,N′,N′-tetrabutylmalonamide as a new extractant for extraction of nitric acid and uranium(VI) in toluene

N,N,N,N-tetrabutylmalonamide (TBMA) was synthesized and used for extraction of uranyl(II) ion from nitric acid media in toluene. The effects of nitric acid concentration, extractant concentration, temperature and salting-out agent (LiNO₃) on distribution coefficients of uranyl(II) ion have been studied. The extraction of nitric acid is also studied. The main adduct of TBMA and HNO₃ is HNO₃. TBMA in 1.0 mol/l nitric acid solution. The 1:2:3 complex of uranyl(II) ion, nitrate ion and TBMA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBMA, and found that the NO ₃ ^– in the extraction species UO₂(NO₃)₂·3TBMA did not participate in coordination of uranyl(II) ion. The values of thermodynamic parameters have also been calculated.     

Solvent extraction of metal ions from aqueous solutions containing N,N,N′,N′-ethylenediaminetetraacetic and related acids—II. La(III) and diethylenetriaminepentaacetic acid

In the absence of a competing anion, [La(DTPA)]²⁻ was extracted from aqueous phases in the pH ranges 1–3 by the perchlorate salt of the primary amine Primene JM-T. The addition of small amounts of SO²⁻₄ to the aqueous phases depressed the extraction of La to near zero. As the SO²⁻₄ concentration was increased further, D_La increased to values greater than that found in the absence of SO²⁻₄; this was caused by a change in the mechanism of extraction and [La(SO₄)₂]⁻ became the extracted species.     

Extraction of U(VI) and Th(IV) from nitric acid solutions with N,N,N′,N′-tetrahexylsuccinylamide

The results of monitoring of⁸⁵Kr volume activity in ground-level air of Prague over the period 1989–1995 are summariyed. Seasonal dependence with a maximum in late spring and summer months and a gradual increase of⁸⁵Kr concentration in the atmosphere were observed. Linear approximation of long-term trend in the period 1983–1995 gives the growth rate of 35 mBq·m^–3 per year. Exponential approximation provides an inter-year growth by 3.7% The measured values were compared to the prognosis of⁸⁵Kr contamination development of the atmosphere from the early 1980s. They were found to be near to the low estimate of the assumed development.     

Solvent extraction of Eu, Th, U and am by N,N′-dimethyl-N,N′-dihexyl-3-thiopentanediamide and thenoyltrifluoroacetone

The diamide, N,N-dimethyl-N,N-dihexyl-3-thiopentanediamide (DMDHTPDA) was synthesized and thested for extraction of Eu(III), Am(III), Th(IV) and U(VI). DMDHTPDA shows a very weak complexation with these metal ions, which can be attributed to the soft base nature of the sulfur atom. None of the cations were extracted into the organic phase when DMDHTPDA alone was present. Synergistic extraction was measured for DMDHTPDA plus thenoyltrifluoroacetone. From the extraction dependencies on pH and extractant concentration, formation of mixed TTA+DMDHTPDA complexes were indicated. Except for the Th(IV) system, the separation and synergistic factors were smaller for the TTA+DMDHTPDA extractant than for the system of TTA+DMDHOPDA (the oxo ether analog of DMDHTPDA).     

Thermodynamic characteristics of protolytic equilibria of hexamethylenediamine-N,N,N′,N′-tetraacetic acid

The heats of dissociation of betaine groups of hexamethylenediamine-N,N,N′,N′-tetraacetic acid (H₄L) at 298.15 K and the ionic strengths of 0.1, 0.5, and 1.0 (KNO₃) were determined by direct calorimetry. The standard thermodynamic characteristics of the ptotolytic equilidria of H₄L were calculated using the results from thermochemical and potentiometric measurements made under identical test conditions.     

Thermodynamic characteristics of the protolytic equilibria of tetramethylenediamine-N,N,N′,N′-tetraacetic acid

The stepwise dissociation constants of tetramethylenediamine-N,N,N′,N′-tetraacetic acid (H₄L) are determined by means of potentiometry at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO₃). The heat effects of the dissociation of the betaine groups of the complexone are measured by direct calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H₄L are calculated via combined use of the results from thermochemical and potentiometric studies performed under identical experimental conditions. Our results are compared with the corresponding data on relative compounds.     

Solvent extraction of uranium from aqueous solutions by α-benzoinoxime

Solvent extraction of uranium with α-benzoinoxime from aqueous solutions has been systematically investigated. The extraction equilibration was very fast and achieved at 60 s for uranium. The extraction of uranium was pH-dependent using α-benzoinoxime as extractant. The effect concentration of uranium and α-benzoinoxime was studied. The uranium loaded in the organic phase can be stripped efficiently with 93 % yield using 0.1 M HCl as the stripping agent in a single stripping step. A good selectivity for uranium was observed through α-benzoinoxime as extractant from aqueous solution with other interfering cation ions. Present study suggested that α-benzoinoxime can be used as a potential extractant for separation of uranium from aqueous solution using centrifugal extractor in industrial application.     

GC-MS determination and optimization of extraction of N,N′-dimethyl-N,N′-diphenylcarbamide from building materials

N,N’-dimethyl-N,N’-diphenylcarbamide (centralite) extracted from building materials was quantitated using ion trap GC-MS detection technique. Both linearity and standard deviation of the calibration curve were dependent on the conditions of the mass spectral detection. The most precise calibration has been achieved by quantification of a mass ion not participating in secondary reactions and which is produced via single fragmentation. The best recovery of centralite was obtained after either 30 min of normal extraction with toluene at 60 °C or 10 min of ultrasonic extraction with chloroform at room temperature. Using the latter method resorption processes might cause decrease in efficiency of the recovery at longer extraction time. Received: 3 July 1998 / Revised: 5 November 1998 / Accepted: 26 January 1999     

The structure effect of N,N,N′,N′-alkylamide in the extraction of uranium and thorium

In this paper, nine N,N,N,N-tetraalkyldiamides have been synthesized and the extracting ability for uranium and thorium under different conditions has been studied. All results were compared with those obtained by using tributyl phosphate (TBP) under exactly the same conditions. The extracting ability of thorium and uranium for different N,N,N,N-tetraalkyldiamides is discussed.     

Physicochemical properties of 4-tert-butylbenzoic acid N′,N′-dialkylhydrazides

Properties of hydrazides of 4-tert-butylbenzoic acid, important for their application in extraction technology, have been studied: solubility, acid-base properties, distribution between immiscible liquids, and hydrolytic stability. pH ranges of existence of different forms of the compounds have been determined. The N′,N′-dialkyl derivatives with alkyl chains longer than C₆ are readily soluble in nonpolar solvents, are not transferred into aqueous phase, and are stable with respect to hydrolysis in acidic and basic media. Linear correlations of the studied physicochemical parameters with the compounds structure and the medium properties have been elucidated.     

Cyclopalladation of N,N,N′,N′-tetramethylisophthalthioamide

Summary N,N,N,N-Tetramethylisophthalthioamide (Hmpt) was cyclopalladated with PdCl₂ in hot dimethylsulphoxide to give [PdCl(mpt)]. The structure was determined by X-ray analysis. The thioamide is metallated at C(2) to act as an S528-01C528-02S tridentate anionic ligand. There is appreciable steric repulsion between the benzene ring H(4, 6) and the dimethylamino groups. The hydrogens and the methyl groups mutually deviate from the coordination plane in opposite directions. The stability of the fused 5,5-membered chelate ring formed by the S528-03C528-04S ligand seems to overcome the steric hindrance. Derivatives were prepared by replacement of the chloride ion with iodide, diethyldithiocarbamate, 4-tert-butylpyridine, or tri-n-butylphosphine, and characterized spectroscopically. The S528-05C528-06S-fused chelate ring was maintained in these derivatives.     

Calorimetric study of the reaction between formic acid and N,N,N′,N′-tetramethylethylenediamine from the aspect of thermal energy storage

The attack by formic acid on the nitrogen electron pairs of N,N,N,N-tetramethylethylenediamine leads to the stoichiometric salt or to many other complexes with different molar fractions. Physical and thermodynamic parameters of two adducts, obtained by calorimetric study, are discussed in terms of their use as potential phase change materials in thermal energy storage because of their large heat of fusion between 288 and 333 K.

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Zusammenfassung Bei der Einwirkung von Ameisensäure auf die Elektronenpaare von N,N,N,N-Tetramethylethylendiamin entsteht ein stöchiometrisches Salz oder mehrere andere Komplexe mit unterschiedlichem Molenbruch. Es werden physikalische und thermodynamische Parameter zweier bei der kalorimetrischen Untersuchung erhaltenen Addukte hinsichtlich ihrer Verwendung als potentielle Phasenwechselsubstanzen bei der thermischen Energiespeicherung diskutiert, da sie im Bereich 288–333 K eine große Schmelz-wärme besitzen.

     

Extraction of molybdenum(VI) from hydrochloric acid solution by N,N’-carbonyl difatty amides

Hydrofluoric acid has been used as a stripping agent for molybdenum(VI) using a mixture of N,N’-carbonyl difatty amides (CDFAs) synthesized from palm oil as a extractant. The CDFAs was characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance technique. In the extraction step, the effects of parameters, such as type of diluent, hydrochloric acid, metal concentration, and temperature, have been studied. The effects of various stripping agents on stripping efficiency have also been investigated. This work presents the development of a low-cost and environmentally friendly extractant to recover molybdenum.