Efficient separation and recovery of V(V) from Cr(VI) in aqueous solution using new task-specific ionic liquid of [C12H25NH3][Cyanex 272]

An environmentally friendly process for efficient separation and recovery of V(V) from aqueous solution containing Cr(VI) was proposed using the new task-specific ionic liquid of [C₁₂H₂₅NH₃][Cyanex 272]. The separation factor of V(V) from Cr(VI) was about 1.08 × 10³ with the optimum extraction conditions, and the extraction percentage of V(V) was about 99.5 %. The loaded organic phase was stripped using the NH₃·H₂O, and the recovered NH₄VO₃ was obtained with the processes of stripping, filtration, washing, and desiccation. The qualitative analysis of the recovered NH₄VO₃ was made using the X-ray diffraction, and its peaks were good consistent with the standard sample. Morphology of the recovered NH₄VO₃ was also studied using the scanning electron microscope. The extraction mechanism of V(V) using the [C₁₂H₂₅NH₃][Cyanex 272] was investigated using the slope method and infrared spectrum analysis. This new environmentally friendly process can be used for the separation and recovery of V(V) from real leaching solution with the aim of industrial application.     

Extraction of vanadium(V) by N′,N′-dialkylhydrazides of carboxylic acids from acidic solutions

Extraction of vanadium(V) with solutions of 2-ethylhexanoic acid N′,N′-dialkylhydrazides in kerosene from acidic media was studied. The optimal extraction conditions were determined depending on the concentrations of H₂SO₂, HCl, and the extraction agent; the composition of the recovered complexes was proposed. The conditions for back-extraction of vanadium(V) from the organic phase were studied. It was found that benzoic acid N′,N′-diheptylhydrazide did not recover vanadium(V) from acidic media.     

Liquid-liquid extraction of vanadium(V) from sulfate media with diisododecylamine

The liquid-liquid extraction of vanadium(V) from sulfate media with diisododecylamine (DIDA), a new reagent providing an alternative to the well-known trioctylamine-based extractant, has been investigated at 22°C with toluene and kerosene as diluents. DIDA efficiently recovers vanadium(V) from weakly acidic solutions (pH 5–6), yielding a DIDA: V = 1: 2.5 (mol/mol) complex in the organic phase. Vanadium is completely reextractable from the organic phase with an NH₄OH solution (1: 1). IR spectroscopic studies and Karl Fisher determination of the water content of the extracts have demonstrated that vanadium extraction is due an interfacial anion-exchange reaction (log K _ex = 1.6–1.7) yielding amine association species containing inverse micelles.     

Solvent extraction of uranium(VI) and separation of vanadium(V) from sulfate solutions using Alamine 336

The present scientific study on uranium(VI) solvent extraction and vanadium(V) separation from sulfate solutions using Alamine 336 as an extractant diluted in kerosene was established. The preliminary experiments indicating the uranium extraction process will follow the solvation as well as ion-exchange mechanisms. In the present acid region (0.1–1.0 mol dm⁻³ H₂SO₄) it showing the ion-exchange type mechanism. Time (1–120 min) and temperature (25–55 °C) not influencing the present extraction system. Other experimental parameters like loading capacity of Alamine 336, stripping of uranium from loaded organic phase, recycling of Alamine 336 and separation of uranium(VI)/vanadium(V) was studied.     

Speciation of antimony by differential generation of its volatile covalent hydride in aqueous and organic phase

By using the ammonium pyrrolidinedithiocarbamate (APDC) — methylisobutyl ketone (MIBK) extraction system Sb(III) is extracted into the organic phase. Sb(III) is directly determined in this organic phase by hydride generation AAS using NaBH₄/dimethylformamide solution as reducing agent. Sb(V) is determined in the aqueous phase using the same technique.     

Determination of total and extractable hydrogen peroxide in organic and aqueous solutions of uranyl nitrate

The development of a spectrophotometric method for the determination of hydrogen peroxide in uranyl nitrate solutions is reported. The method involves the measurement of the absorbance at 520 nm of a vanadyl peroxide species. This species was formed by the addition of a reagent consisting of vanadium (V) (50 mmol·dm⁻³) in dilute sulphuric acid (2 mol·dm⁻³ H₂SO₄). This reagent, after dilution, was also used as an extractant for organic phase samples. The method is simple and robust and tolerant of nitric acid and U(VI). Specificity and accuracy were improved by the application of solid phase extraction techniques to remove entrained organic solvents and Pu(IV). Reverse phase solid phase extraction was used to clean-up aqueous samples or extracts which were contaminated with entrained solvent. A solid phase extraction system based upon an extraction chromatography system was used to remove Pu(IV). Detection limits of 26 μmol·dm⁻³ (0.88 μg·cm⁻³) or 7 μmol·dm⁻³ (0.24 μg·cm⁻³) for, respectively, a 1 and 4 cm path length cell were obtained. Precisions of RSD=1.4% and 19.5% were obtained at the extremes of the calibration curve (5 mmol·dm⁻³ and 50 μmol·dm⁻³ H₂O₂, 1 cm cell). The introduction of the extraction and clean-up stages had a negligible effect upon the precision of the determination. The stability of an organic phase sample was tested and no loss of analyte could be discerned over a period of at least 5 days. The presence of trace levels of reductants interfered with the determination, e.g., hydrazine (<2 mmol·dm⁻³), but this effect was ameliorated by increasing the concentration of the colormetric reagent.     

Mechanism for Solvent Extraction of Lanthanides from Chloride Media by Basic Extractants

The solvent extraction of lanthanides from chloride media to an organic phase containing an anion exchanger in the chloride form is known to show low extraction percentages and small separation factors. The coordination chemistry of the lanthanides in combination with this kind of extractant is poorly understood. Previous work has mainly used solvent extraction based techniques (slope analysis, fittings of the extraction curves) to derive the extraction mechanism of lanthanides from chloride media. In this paper, EXAFS spectra, luminescence lifetimes, excitation and emission spectra, and organic phase loadings of lanthanides in dry, water-saturated and diluted Aliquat 336 chloride or Cyphos IL 101 have been measured. The data show the formation of the hydrated lanthanide ion [Ln(H₂O)_8–9]³⁺ in undiluted and diluted Aliquat 336 and the complex [LnCl₆]^3? in dry Aliquat 336. The presence of the same species [Ln(H₂O)_8–9]³⁺ in the aqueous and in the organic phase explains the small separation factors and the poor selectivities for the separation of mixtures of lanthanides. Changes in separation factors with increasing chloride concentrations can be explained by changes in stability of the lanthanide chloro complexes in the aqueous phase, in combination with the extraction of the hydrated lanthanide ion to the organic phase. Finally, it is shown that the organic phase can be loaded with 107 g·L^?1 of Nd(III) under the optimal conditions.     

Physicochemical modeling and experimental study of the interaction in the Si-Al-Ca-Mg-Fe-Na-K-V-Cl-H-O system

Physicochemical modeling is used to study the interaction in the SiO₂-Al₂O₃-CaO-MgO-Fe₃O₄-Na₂O-V₂O₃(V₂O₅)-HCl-H₂O system. The regions of formation of calcium (magnesium, iron) vanadates and various vanadium oxides are determined. The conditions for the most complete extraction of vanadium into hydrochloric acid solutions are estimated. The data obtained can be used to develop the procedure a the extraction of vanadium during the leaching of basalt with hydrochloric acid. Original Russian Text ? N.V. Kochetkova, N.P. Dergacheva, S.V. Fomichev, V.A. Krenev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1205–1211.     

Extraction and separation of antimony(III) and (V) by a liquid cation-exchanger HDEHP

A systematic investigation was carried out on the extraction of Sb(III) and (V) with HDEHP from various acidic, neutral and alkaline solutions. Antimony(III) is best extracted from neutral or slightly acidic solutions, and the E values are nearly the same in the forward and backward extractions. Antimony(V) extraction is high only from concentrated HCl and HClO₄, and the E values are much larger in the backward direction. Extraction and separation of Sb(III) and (V) was studied as a function of acidity, alkalinity, anion and water-miscible organic additives in the aqueous phase, as well as the diluent used and HDEHP molarity. Separation factors obtained for Sb(III) and (V) were higher than when using isopropyl ether as solvent, which was hitherto used for this purpose.     

On alkaline opening of columbite and tantalite

Sintering of columbite and tantalite with K₂CO₃·1.5H₂O with subsequent leaching of the sinters with water was studied. The possibility of selective extraction of Nb(V) and Ta(V) into liquid phase was demonstrated.     

Counter current extraction separation of rare earth traces

The discontinuous counter current extraction separation of radioactive traces of rare earth elements from each other was successfully performed by using a 96 stage automatic microscale counter current apparatus. Choice of the optimum composition of the aqueous phase (var. HNO₃ conc.) and organic phase [di-(2-ethylhexyl) phosphoric acid (HDEHP) in toluene] was made on the basis of the results of liquid-liquid extraction measurements. Providing sufficient content of HDEHP in the organic phase, the presence of macroamounts of uranium(VI) did not interfere with the individual separation of rare earth traces. Consequently, uranium was retained in the organic phase, while separated rare earth traces were redistributed into the aqueous phase. The methods of liquid-liquid extraction and extraction chromatography based on the use of HDEHP were compared. The present results confirm that the liquid-liquid extraction has the advantage to be selective for the separation of rare earth traces from each other and from the macroamount of uranium(VI).     

N235萃取HCl体系中TBP消除第三相的作用机理

通过测定萃取有机相的电导率变化研究叔胺N₂₃₅(三烷基胺)萃取盐酸体系中第三相的形成及改性剂消除第三相的作用机理。实验结果表明，无改性剂时萃取体系在各种条件下均出现第三相。第三相组成为R₃NH⁺(H₂O)₃·Cl^-，具有导电性。加改性剂TBP(磷酸三丁酯)后，第三相消失。本文认为改性剂TBP消除第三相的作用机理是TBP能够将萃合物R₃NH+(H₂O)₃·Cl^-拆分为可溶于惰性稀释剂的R₃NH⁺(H₂O)₃·O=P(OC₄H₉)₃大阳离子，Cl^-离子则以抗衡离子分散于稀释剂中。     

Liquid-liquid extraction of protactinium(V) using tri-iso-octylamine

Solvent extraction of protactinium with tri-iso-octyl-amine (TIOA) in xylene, benzene, carbon tetrachloride and chloroform from HCl, HF, HNO₃, HClO₄ and H₂SO₄ media was studied using ²³³Pa as a radiotracer. The extraction efficiencies of protactinium were determined as a function of shaking time, concentrations of mineral acids in aqueous phase, extractant concentrations and diluents in organic phase. The extraction mechanism was discussed. The results show that the extracted species in the organic phase is [(R₃N⁻H)_nPa(OH)_xCl _y ^5−x−y ].     

Physical and chemical properties of N ′, N ′-aliphatic acid dioctylhydrazides and their complexing with copper(II) ions

Some physical and chemical properties of aliphatic acid N′N′-dioctylhydrazides[RC(O)NHN(C₈H₁₇)₂] (DOHs) were studied in comparison to 2-ethylhexanoic acid N′N′-dialkylhydrazides, namely, solubility, acid-base properties, entrainment with an aqueous phase, and partition factors depending on the medium and the acyl radical length. The pH ranges of maximal extraction of copper(II) complexes by DOHs to kerosene and the effect of ammonium salts on copper(II) extraction were determined. The compositions of extracted complexes were determined (Cu(II): DOH = 1: 1 and 1: 2); the extraction constant K _extr was calculated for the CuL₂ complex with butyric acid N′N′-dioctylhydrazide. Original Russian Text ? T.D. Batueva, A.V. Radushev, L.G. Chekanova, V.Yu. Gusev, V.I. Karmanov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 146–150.     

Stability constants of Np(V) complexes with fluoride and sulfate at variable temperatures

Summary A solvent extraction method was used to determine the stability constants of Np(V) complexes with fluoride and sulfate in 1.0M NaClO₄ from 25 to 60 °C. The distribution ratio of Np(V) between the organic and aqueous phases was found to decrease as the concentrations of fluoride and sulfate were increased. Stability constants of the 1 : 1 Np(V)-fluoride complexes and the 1 : 1 Np(V)-sulfate and 1 : 2 Np(V)-sulfate complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of [F^-] and [SO₄^2-] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures by using the Van't Hoff equation.     

Solvent extraction of uranium from lean grade acidic sulfate leach liquor with alamine 336 reagent

This paper describes the solvent extraction studies carried out on an acidic low assay uranium bearing leach liquor generated during sulfuric acid leaching of a refractory uranium ore using alamine 336?Cisodecenol?Ckerosene reagent combine. The leach liquor has a U₃O₈ content of about 270?mg/L, free acidity 2.4?N H₂SO₄ and total dissolved solids concentration of 260?g/L. Process parameteric variation studies indicated strong influence of free acidity of the leach liquor, alamine 336 concentration and aqueous to organic phase ratio on the extraction efficiency of uranium. An extraction efficiency of about 95% was achieved when the free acidity of leach liquor was 1?N H₂SO₄ or lower, using 2% (v/v) alamine 336 at ambient temperature with an aqueous to organic phase ratio of 1:1. The loading capacity under these conditions was 1.2?g/L of U₃O₈. About 98% of the uranium values could be stripped from the loaded organic using 1?N NaCl in 0.2?N H₂SO₄. The solvent extraction studies aided in developing a suitable process flowsheet for treating refractory uranium ores which need high acidity during leaching and relatively lower acidity for purification by solvent extraction.     

Solvent extraction of arsenic(V) with dispersed ultrafine magnetite particles.

The solvent extraction of arsenic(V) was investigated using heptane containing ultrafine magnetite particles and hydrophobic ammonium salt. Arsenic(V) was favorably extracted from aqueous solutions of pH ranging over 2-7, where the distribution ratio (10(3)) was independent of the pH. Although the addition of alkyl ammonium salt improved the phase separation, no notable influence was observed on the extraction of arsenic(V). Oleic acid suppressed the distribution ratio of arsenic(V) when the concentration exceeded 10(-2) M. Sulfate did not interfere with the extraction, while the presence of more than 10(-3) M phosphate decreased the distribution ratio. Metal cations including calcium(II), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and lanthanum(III) did not give any serious interference up to the 10(-4) M level. According to equilibrium and kinetic studies, the extraction of arsenic(V) can be interpreted by the adsorption of H2AsO4- onto the surface of dispersed magnetite particles. The relationship between the amount of arsenic(V) extracted in the organic phase and that remaining in an aqueous phase followed a Langmuir-type equilibrium equation. The maximum uptake capacity was determined to be 4.8 x 10(-4) mol/g-magnetite (36 mg As/g). The arsenic(V) extracted in the organic phase was quantitatively recovered by back-extraction with an alkaline solution.     

Radiochemische Bestimmung der Beständigkeitskonstanten des Komplexes aus Triphenyltetrazoliumchlorid und Antimon(V) in stark salzsaurer Lösung

It is possible to extract Sb(V), even in traces, nearly completely from 6M HCl by 2,3,5-Triphenyltetrazoliumchloride (TTC). The molar ratio of the ion associate in the organic phase is found to be 1∶1. Graphic evaluation of radiometric measurements using¹²⁵Sb as tracer give the following results: extraction constant K_ex=1.65·10⁴, distribution constant K_D=19.95, stability constant of the ion associate β=0.83·10³.     

Radiation stability of benzyldibutylamine and benzyldimethyldodecylammonium nitrate in the extraction of lanthanides and americium

The radiation stability was investigated of organic phases containing tertiary benzyldialkylamines and quaternary benzyltrialkylammonium salts which are sultable for the separation of lanthanides and americium from irradiated nuclear fuel. Attention was paid to changes of the extraction properties in Eu(III) and Am(III) extraction. The influence of the individual components forming the organic phase (extractant, solvent, solubilizer and nitric acid) on the decrease of the extraction capacity of the organic phase after irradiation is discussed. The greatest changes in the distribution coefficients D_Eu and D_Am after irradiation were shown for extraction in the presence of nitric acid. As regards the absorbed dose, these systems can be considered as stable in comparison with organophosphorus extractans.     

Extraction of Arsenic(V) with Hexabutylphosphoric Triamide

The effects of the concentrations of sulfuric acid and arsenic in the aqueous phase, concentration of the extractant in the organic phase, temperature, and time of phase contact on arsenic(V) extraction with hexabutylphosphoric triamide were studied, and the arsenic(V) extraction constant was calculated.