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.     

Extraction of Uranium(VI) with N,N′-Dilauroylpiperazine in Carbon Tetrachloride

A novel extractant, N,N-dilauroylpiperazine (DLPEZ), was synthesized for the first time. The extraction of uranium(VI) with the novel extractant in carbon tetrachloride from aqueous nitric acid media has been studied. The dependence of extraction distribution ratio on the concentration of aqueous nitric acid, extractant, salting-out agent and temperature was investigated and the enthalpy of the extraction was determined.     

Thermodynamic Approach of Uranium(VI) Extraction by N,N-(2–ethylhexyl)Isobutyramide

The study of extraction of U(VI) from LiNO3 media by N,N-(2-ethylhexyl)isobutyramide (DEHiBA) in dodecane has been performed at 25.00 °C using isothermal titration microcalorimetry. The raw heat measured is a sum of contributions. To obtain the net extraction enthalpy variation, different heats have to be evaluated as the dilution of amide into dodecane phase which has been measured and subtracted. The microcalorimetric extraction results are then compared to data obtained by Van’t Hoff classical method. The extraction enthalpies obtained by both methods are similar. This first study allowed to define the experimental calorimetric conditions and will be followed by determination with other actinides and amides.     

Extraction and Mutual Separation of Actinide(III), (IV), (V) and (VI) Ions by N,N′-Dimethyl-N,N′-Dihexyl-3-Oxapentanediamide and Thenoyltrifluoroacetone

Actinide(III), (IV), (V) and (VI) ions were extracted by N,N-dimethyl-N,N-dihexyl-3-oxapentanediamide (DMDHOPDA) and thenoyltrifluoroacetone (HTTA). The extraction behaviors suggested the possibility of the mutual separation, and the convenient separation method of actinide ions (III), (IV), (V) and (VI) without reducing and oxidizing agents was studied. Th(IV) was extracted from the aqueous phase by HTTA (5 mM in toluene) in the first step. The Am(III) and U(VI) ions can be extracted by 1 and 20 mM DMDHOPDA in toluene, and the Np(V) ion can be extracted into nitrobenzene with 100 mM DMDHOPDA in the last step. The residual activities in the aqueous phase were much lower than the initial activities. These activities in the fractions were confirmed by the gamma- and the alpha-spectrometry. The one-through and rough separation is advanced, and in case of the fine isolation of actinide elements, each fraction should be purified in more detail.     

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.     

Extraction and separation performance of rhenium(VII) and uranium(VI) from nitric acid medium using N,N′-dimethyl-N,N′-dioctyldiglycolamide

Journal of Radioanalytical and Nuclear Chemistry - The extraction behavior and separation performance of Re(VII) and U(VI) from the nitric acid medium were studied respectively, in which an...     

Extraction of U(VI) with N,N′-dimethyl-N,N′-dioctylmalonamide from nitrate media

The extraction of uranyl nitrate with the novel extractant N,N′-dimethyl-N,N′-dioctylmalonamide (DMDOMA) from aqueous sodium nitrate (and nitric acid) was investigated. The extraction mechanism was established and the stoichiometry of the main extracted species confirms to UO₂(NO₃)₂ · DMDOMA. The IR spectral study was also made of the extracted species. Methyl substituent improves the extraction ability of malonamide for U(VI) compared with that of N,N,N′,N′-tertrabutylmalonamide (TBMA).     

Extraction of actinides by long-chain amines—I: Extraction of Np(IV), Np(V), Np(VI), Pu(VI) and U(VI) by TLA and Aliquat-336

The extraction of Np(IV) into tricaprylmethyl ammonium nitrate (Aliquat-336) and Np(V), Np(VI), Pu(VI) and U(VI) into TLA and Aliquat-336 from nitric acid medium was investigated. The absorption spectra of Aliquat-336 extracts containing Np(IV), Pu(IV), Np(VI) and Pu(VI) were obtained to know the species of these ions present in the amine.     

Extraction of microamounts of europium and americium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of N,N′-dibutyl-N,N′-dimethyl-2-(2-dodecyloxyethyl)-malonamide

Extraction of microamounts of europium and americium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻¹) in the presence of N,N′-dibutyl-N,N′-dimethyl-2-(2-dodecyloxyethyl)-malonamide (DBDMDDOEMA, L) has been investigated. The equilibrium data have been explained assuming that the cations HL₂⁺, ML₂³⁺ and ML₃³⁺ (M³⁺ = Eu³⁺, Am³⁺) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It has been found that the stability constants of the corresponding complexes EuL _n ³⁺ and AmL _n ³⁺, where n = 2,3 and L is DBDMDDOEMA, in water saturated nitrobenzene are comparable.     

Dioxomolybdenum(VI) complex with N,N′- ethylenebis(salicylideneimine)

The interaction of N,N′-ethylenebis(salicylideneimine), H₂salen, with ammonium molybdate yielded the molybdenum(VI) complex MoO₂(salen) with the cis-dioxostructure as inferred from IR spectral studies. The ¹H NMR chemical shifts of azomethine protons in the free ligand and the complex are 8.14 and 8.39 δ, respectively, suggesting the bonding of the azomethine nitrogen to MoO₂ group. The thermal decomposition behaviour of the complex is discussed.     

Extraction of americium(III) and europium(III) using a gamma pre-irradiated solution of N,N′-dimethyl-N,N′-dibutyltetradecyl malonamide in n-dodecane modified with N,N′-dihexyloctanamide

The extraction of Am(III) and Eu(III) using a γ-pre-irradiated N,N′-dimethyl-N,N′-dibutyltetradecyl malonamide (DMDBTDMA) modified with N,N′-dihexyloctanamide (DHOA) in n-dodecane (NDD) at 4.5M HNO₃ has been studied as a function of the absorbed dose up to 2×10⁶ Gray. The distribution ratios of Am(III) and Eu(III) were almost constant until a dose of 1×10⁵ Gray and then they decreased gradually up to a dose of 2×10⁶ Gray. The decrease of the distribution ratios of Am(III) and Eu(III) are due to the decreasing concentration of the DMDBTDMA by a γ-pre-irradiation and these results were supported by a determination of the DMDBTDMA concentration with a gas chromatography method. The distribution ratios of Am(III), Eu(III), Ce, Nd and Y with γ-pre-irradiated (DMDBTDMA-DHOA)/NDD have also been studied as a function of the nitric acid concentration and the extraction temperature.     

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.     

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).     

Extraction of cobalt(Ⅱ) from aqueous solution by N,N'-carbonyl difatty amides

The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal.In this study,solvent extraction of Co(Ⅱ) from aqueous solution using a mixture of N,N’-carbonyl difatty amides(CDFAs) synthesised from palm oil as the extractant was carried out.The effects of various parameters such as acid,contact time,extractant concentration,metal ion concentration and stripping agent and the separation of Co(Ⅱ) from other metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ) were investigated.It was found that the extraction of Co(Ⅱ) into the organic phase involved the formation of 1:1 complexes.Co(Ⅱ) was successfully separated from commonly associated metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ).Co(Ⅱ) stripping from the loaded organic phase was studied in aqueous solution.These results are useful to recover Co(Ⅱ) from aqueous solution utilising(CDFAs) as an extractant.     

Recovery of tungsten(VI) and molybdenum(VI) with N′,N′-dialkylhydrazides of aliphatic carboxylic acids from acid solutions

Russian Journal of Applied Chemistry - Recovery of tungsten(VI) with solutions of N′,N′-dialkylhydrazides of 2-ethylhexanoic and octanoic acids in kerosene from sulfuric acid and...     

Extraction of copper(II) with N-(para-tert-butylbenzoyl)-N′,N′-dialkylhydrazines

Extraction of Cu(II), Co(II), Ni(II), and Zn(II) with N-(para-tert-butylbenzoyl)-N??,N??-dialkylhydrazines was studied. In contrast to other listed elements, copper(II) is extracted with these reagents in a wide pH range and NH₃ concentrations, which provides its selective separation. Effect of chain length of the N??,N??-alkyl groups and solvent nature on copper extraction and its stripping conditions were determined. Extraction constants were calculated. Ammonium salts decrease the extraction degree of copper(II). The studied reagents are superior to the known industrial reagent of ??-diketone class, LIX 54, in terms of copper(II) extraction efficiency from ammonia media.     

Study on the Mechanism of the Radiation-Induced Chain Oxidation of N,N,N,N-Tetramethyl-4,4′-diaminodiphenylmethane by Tetrabromomethane in Poly(vinyl chloride) Films

Kinetics and mechanism of the radiation-induced chain oxidation of N,N,N,N-tetramethyl-4,4-diaminodiphenylmethane (Am) by tetrabromomethane in poly(vinyl chloride) (PVC) films were studied by ESR and optical spectroscopy. The quantitative analysis of the ESR spectra of PVC films containing Am and CBr₄ irradiated with -rays at 77 K was performed. The nature of radical species involved in the chain process was established. It was shown that the heating of the films after their irradiation at 77 K resulted in the formation of free radicals Am^·, which initiated the chain oxidation of amine with a chain length of 100. The kinetic features of the chain oxidation–reduction reactions occurring in vacuum and in the presence of oxygen were compared.     

Kinetics and mechanism of the oxidation of L-ascorbic acid by the N,N′-ethylenebis(salicylideneiminato)manganese(III) complex in aqueous solution

Summary The kinetics of oxidation of l-ascorbic acid by the N,N-ethylenebis(salicylideneiminato) manganese(III) complex have been studied over the 4.5–9.3 pH range. An intermediate ascorbate complex was formed which had an inhibiting effect on the rate of the redox reaction. The rapid formation of this intermediate was followed using the stopped-flow technique, whereas its slow decomposition was monitored using a conventional spectrophotometer. The formation of this intermediate was strongly pH dependent. Addition of sodium perchlorate and sodium dodecyl sulphate (anionic surfactant) affected the reaction rate. A probable mechanism comprising both the intermediate formation and the overall redox reaction is discussed.