Isotope exchange between U/III/ and U/IV/ in the HCl-TBP extraction system

The measurement of the isotope-exchange reaction between U/IV/ in the organic phase and U/III/ in the aqueous phase in the extraction systems: 7-8M HCl—5–40% TBP /aromatic diluent or CCL₄/ were made. The high rate of exchange with the rate constant >10²M^–1min^–1 was observed.     

Kinetics of iron(III) chloride extraction with n-tributyl phosphate

The equilibrium and rate of solvent extraction of FeCl₃ complexes from HCl solutions into benzene solutions of tributyl phosphate (TBP) has been studied. The extracted species was found to be FeCl₃·3TBP. The results show that the extraction is first order in both Fe(III) and TBP. The rate constant of adduct formation equals ～1.24M min^?1. The reaction order is zero for the aqueous phase acidity. The rate-controlling steps are discussed in the light of the results.     

Extraction of Am(III) by mixture of dihexyl N,N-diethylcarbamoylmethyl phosphonate and tributyl phosphate in benzene from nitric acid solutions

Extraction of Am(III) by dihexyl N,N-diethylcarbamoylmethyl phosphonate (CMP) in benzene from nitric acid solutions (pH 2.0 to 6.0M) has been studied. High extraction of Am(III) by CMP from 2–3M HNO₃ was observed. The species extracted was found to be Am(NO₃)₃·3CMP. The extraction was also done with mixtures of CMP+TBP and CMP+TOPO, where mixed species were extracted in the organic phase. The back-extraction experiments gave an efficient back-extraction of Am(III) by pH 2.0 (HNO₃) from the loaded CMP+TBP phase but a poor back-extraction from the loaded CMP+TOPO phase. The loading of Nd(III) by mixture of CMP and TBP was 50% of the CMP concentrations at a total Nd(III) concentration of 0.182M. The thermodynamic parameters of Am(III) extraction by a mixture of CMP and TBP were evaluated by temperature variation method, which suggests that the two-phase reaction is stabilized by enthalpy and opposed by entropy.     

Equilibrium and kinetics of Zn(II) bromide extraction with Amberlite LA-2 and methyl isobutyl ketone

The rates of extraction of Zn(II) from hydrobromic acid solutions into benzene solutions of the liquid anion exchanger Amberlite LA-2 and those into methyl isobutyl ketone (MIBK) have been investigated. The distribution equilibria of this system have been also studied. Under the used experimental conditions the extracted species of Zn(II) have been proposed. The kinetic data indicated a first order reaction with respect to Zn(II) in both systems, nearly one with respect to HBr and from 0–0.38 for LA-2. In case of extraction of Zn(II) with methyl isobutyl ketone, MIBK, the reaction order with respect to MIBK was found to be 4 and with respect to HBr inverse first order. The rate constants of these extraction processes were determined and the rate determining steps were discussed in the light of the obtained results.     

Kinetic studies on the extraction of U(IV) by TBP in kerosene from nitrate medium

The kinetics of extraction of U(IV) by TBP in kerosene was investigated using a stirred Lewis cell. The effect of the different parameters affecting the extraction rate as well as temperature were separately investigated. The rate equation deduced from the experimental results show that the extraction of U(IV) is first order dependent on TBP concentration while it is of zero order with respect to U(IV), H⁺, NO ₃ ^– and HNO₃ concentrations. The data obtained show that the extraction process is governed by chemical reactions taking place at teh interface.     

Method of separating uranium from iron and thorium

Acid leaching of uranium deposits is not a selective process. Sulfuric acid solubilizes iron(III) and half or more of the thorium depending on the mineralog of this element. In uranium recovery by solvent extraction process, uranium is separated from iron by an organic phase consisting of 10 vol% tributylphosphate(TBP) in kerosine diluent. Provided that the aqueous phase is saturated with ammonium nitrate or made 4–5 M in nitric acid prior to extraction. Nitric acid or ammonium nitrate is added to the leach solution in order to obtain a uranyl nitrate product. Leach solutions containing thorium(IV) besides iron are treated in an analogous fashion. Uranium can be extracted away from thorium using 10 vol% TBP in kerosine diluent. The aqueous phase should be saturated with ammonium nitrate and the pH of the solution lowered to 0.5 with sufficient amount of sulfuric acid. In other words, the separation of uranium and thorium depends on the way the relative distributions of the two materials between aqueous solutions and TBP vary with sulfuric acid concentration. Thorium is later recovered from the waste leach liquor, after removal of sulfate ions. Uranium can be stripped from the organic phase by distilled water, and precipitated as ammonium diuranate.     

Synergic liquid-liquid extraction studies of neodymium and praseodymium with mixtures of tributyl phosphate and Aliquat-336 in nitrate media

Extraction studies of neodymium and praseodymium with mixtures of tributyl phosphate and Aliquat-336 in xylene have been carried out. From 3.0M aqueous ammonium nitrate solutions, negatively charged complexes of neodymium and praseodymium were extracted with Aliquat-336 in the presence of tributyl phosphate into the organic phase. The synergic extracted species observed was M(NO₃) ₄ ^– L⁺·TBP. The synergic extraction of lanthanide elements in nitrate media increases from lanthanum to lutetium.     

Extraction of polyvanadates by means of amines

The present paper is aimed at obtaining quantitative information on the extraction of polyvanadates from aqueous solutions with benzene solutions of tri-n-octylamine and Primene JMT with respect to initial pH value of aqueous solution and the ratio of volumes of the organic and aqueous phase. The predominant species in acidic solutions at concentrations in excess of 0.01 M are decavanadates. The extraction equilibria were studied within the range of pH 2–4. At this concentration of sulfuric acid the species V₁₀O₂₆(OH)^4– and V₁₀O₂₇(OH)^5– prevail. Supposing that the nonideality of the aqueous phase does not play an important role and that the activity coefficient of the amine sulfate remains constant, the nonideal behavior of the extraction system can be explained by the hydration of complexes in the organic phase. On the basis of suggested reactions and mass balance equations the comparison of experimental and calculated equilibrium data was done.     

Extraction of rare earth elements with organophosphorus extractants as carriers in supported liquid membranes

The membrane extraction of Y, Ce, Eu, Tm and their binary mixtures Ce–Y, Ce–Eu, Ce–Tm with supported liquid membranes containing TBP and HDEHP as carriers in decanedodecane hydrocarbon solvent, has been studied. Upon extraction with TBP aqueous nitrate solutions of rare earth elements (REE) were used as feed phase. In some cases they also contained EDTA or DCTA. In most cases, the receiving phase was an aqueous solution of EDTA. Extraction with HDEHP was performed from nitrate and chloride solutions and the receiving phase was the corresponding dilute acid. Pertraction of an element through a membrane was studied as a function of time and of initial composition of phases. The results are presented in the following forms: flux of metal through membrane, coefficients of permeability, separation factors and effective diffusion coefficients.     

Kinetics of the radiation chemical reactions of tervalent and quadrivalent actinides and lanthanides in carbonate solutions

The reactions of the ions of tervalent and quadrivalent actinides and lanthanides with hydrated electrons e_aq ^– and CO₃ ^– radicals in concentrated carbonate solutions have been studied by microsecond pulse radiolysis, using spectrophotometric recording of short-lived particles. It is shown that the rate of the reactions of e_aq ^– with carbonato complexes of Ce(IV), Pu(IV), and Np(IV) is controlled by diffusion. The carbonato complex of Eu(III) reacts with e_aq ^–appreciably more slowly. A linear relationship is obtained between the logarithm of the rate constant for the reactions of CO₃ ^– with the carbonato complexes of Am(III), Ce(III), and Pu(III) and the redox potential of the complexes. The rate of the reaction of CO₃ ^– with Np(III) in carbonate solutions is controlled by diffusion.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 28–32, January, 1990.     

Radiation induced depolymerization of hyaluronic acid (HA) in aqueous solutions at pH 7.4

The separation of the trivalent metal ions Am(III) and Eu(III) by extraction chromatography employing TBP impregnated macroporous XAD-4 resin as the stationary phase was examined; some parameters affecting the distribution ratio (K_d) and the column resolution (R_s) of Am(III) and Eu(III) were investigated. These parameters are the effect of TBP loading, aqueous nitrate concentrations, and flow rate. Both K_d andR_s increase with the TBP loading.     

Extraction of indium(III) from sulfate solutions with organophosphorus acids

Extraction of indium(III) from sulfuric acid solutions with di-2-ethylhexyl hydrogen phosphate and isododecylphosphethanic and diisooctylphosphinic acids was studied. The effect of H₂SO₄ and In(III) concentrations in the aqueous phase, type and concentration of the extractant in the organic phase, temperature, and time of phase contact on the extraction of In(III) and impurity metal ions was considered. The In(III) extraction constants were estimated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1625–1629.Original Russian Text Copyright © 2004 by Travkin, Kubasov, Glubokov, Busygina, Kazanbaev, Kozlov.     

Solvent extraction of yttrium(III) by TBP from acidic organic-aqueous solutions

Extraction by benzene solutions of TBP of carrier-free⁹⁰Y(III) from mixed aqueous-organic nitrate and perchlorate solutions was studied with special respect to the S-shaped D_Y versus acid concentration plots observed in aqueous systems. The presence of organic solvents in the aqueous phase enhanced the extraction of Y(III) and also influenced the shape of the D_Y vs. acid concentration plots in that the minimum was shifted towards lower acid concentration, became less pronounced, and eventually vanished completely.     

Solvent extraction of uranium(VI) and molybdenium(VI) by Alamine 310 and its mixtures from aqueous H3PO4 solution

Liquid-liquid extraction of uranium (VI) from aqueous phosphoric acid solution by triisodecylamine (Alamine 310), tri-n-butyl phosphate (TBP), di-n-pentyl sulfoxide (DPSO) and their mixtures in benzene in the range 1–10M aqueous H₃PO₄ shows that extraction is maximum (80%) in the higher acidity range 6–8 M. Extraction of this metal ion by bis(2,4,4-trimethylpentyl)phosphinicacid (Cyanex 301) and its mixtures studied in the range 0.2–1.0M aqueous H₃PO₄ is far from being quantitative. Antagonism in extraction by mixtures of extractants is observed in most of the cases. Extraction of molybdenum(VI) under identical conditions shows that it is quantitative in the lower acidity range upto 2M H₃PO₄. Separation of uranium(VI) from molybdenum(VI) is feasible by Alamine 310, TBP and DPSO, the order of efficiency being TBP>DPSO>Alamine 310.     

Radioanalytical investigation on rhodium extraction behaviour with tri-N-butylphosphate from iodide solutions

Radioanalytical techniques are used in this work to investigate the extraction behaviour with TBP of rhodium (III) chloride solutions to which a large excess of iodide is added. Extraction yields and distribution coefficients are determined as a function of HClO₄ or H₂SO₄ content in the aqueous phase. Rhodium-stripping from the organic phase with ammonia solutions is also tested.     

Extraction of metal ions with a primary amine

This paper describes some experimental results obtained at the extraction of sulfate solutions of U(VI), Mo(VI), V(V), Ce(IV), Zr(IV), Fe(III), Al(III) with a benzene solution of Primene JMT. The aqueous solutions consist of metal sulfates (or other metal salts) in the presence of sulfuric acid with a concentration range of 0–2.1 mol·dm^–3, the concentration of amine in the organic phase being 0.1–0.3 mol·dm^–3. The presence of various species of metal ions in the aqueous phase is considered and the equilibrium concentration of substances extracted in the organic phase is determined. On the basis of the results of chemical analysis (concentration of metals and sulfate ions) the composition of the prevailing complexes in the organic phase is proposed.     

Extraction and extraction chromatographic separation of minor actinides from sulphate bearing high level waste solutions using CMPO

Bench-Scale studies on the partitioning and recovery of minoractinides from the actual and synthetic sulphate-bearing high level waste (SBHLW) solutions have been carried out by giving two contacts with 30% TBP to deplete uranium content followed by four contacts with 0.2M CMPO+1.2M TBP in dodecane. The acidity of the SBHLW solutions was about 0.3M. In the case of actual SBHLW, the final raffinate contained about 0.4% -activity originally present in the HLW, whereas with synthetic SBHLW the -activity was reduced to the background level.¹⁴⁴Ce is extracted almost quantitative in the CMPO phase,¹⁰⁶Ru about 12% and¹³⁷Cs is practically not extracted at all. The extraction chromatographic column studies with synthetic SBHLW (aftertwo TBP contacts) has shown that large volume of waste solutions could be passed through the column without break-through of actinide metal ions. Using 0.04M HNO₃>99% Am(III) and rare earths could be eluted/stripped. Similarly >99% Pu(IV) and U(VI) could be eluted.stripped using 0.01M oxalic acid and 0.25M sodium carbonate, respectively. In the presence of 0.16M SO ₄ ^2– (in the SBHLW) the complex ions AmSO ₄ ⁺ , UO₂SO₄, PuSO ₄ ²⁺ and Pu(SO₄)₂ were formed in the aqueous phase but the species extracted into the organic phase (CMPO+TBP) were only the nitrato complexes Am(NO₃)₃·3CMPO, UO₂(NO₃)₂·2CMPO and Pu(NO₃)₄·2CMPO. A scheme for the recovery of minor actinides from SBHLW solution with two contacts of 30% TBP followed by either solvent extraction or extraction chromatographic techniques has been proposed.     

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.     

Determination of the formation rate constant of carrier-free111In(III) with EDTA

The kinetics of reaction of indium(III)ion with EDTA (H₄ edta) has been studied in aqueous acidic solutions using carrier-free¹¹¹In and low concentrations of EDTA. The reaction takes place predominatly between indium(III) and H₃ edta. The rate constant k₃ is determined to be k₃=(1.3±0.1)·10⁵ dm³ mol^–1 s^–1 (25 °C).     

Chemical oxidation of the components of extraction solutions and critical parameters of heat explosion

Thermochemical interaction of TBP with nitric acid in single-phase organic systems has been studied at the concentrations of HNO₃ 1.4 to 5.6M, in temperature range of 110–140 °C. The termochemical oxidation of TBP includes a number of consecutive and concurrent reactions, such as acid hydrolysis, the oxidation of the TBP hydrolysis products, and TBP destructive oxidation. Some of these reactions can proceed with heat explosion. The limiting temperature (120–130 °C) and acid concentration (2.5 mol/l) at which the oxidation reactions are able to transform to heat explosion have been estimated. The rate constants and activation energies were determined for the reactions presenting a potential hazard.