Species In Organic Phase Research Articles

Comment to the Bigeleisen's Theory of Isotope Chemistry of the Heavy Elements

The recent Bigeleisens Theory of isotope chemistry of the heavy elements is discussed in terms of nuclear charge size and shape variations, mass formula, even-odd and odd-odd effects, magic numbers, nuclear field shift versus resulting contraction or expansion of the s, p, d, and f shells, and corresponding variations of the isotope ionic radii and isotope ionization potentials. The effects of even-odd, odd-odd, magic and doubly magic nuclei, as accompanied by a decrease of the nuclear charge size, are of the same sign at the same orbitals of the outermost electrons. Therefore, these effects alter the chemical equilibria of the isotope exchange in the same direction. An expansion of the nuclear charge distribution, usually associated with the addition of neutrons to a nucleus, causes all the s orbitals, and to a lesser extent all the p½ orbitals, to expand, resulting in a less effective screening of the nucleus. In consequence, the outer d and all the f orbitals become less diffuse, i.e. they contract. The emphasis is given to the uranium isotope chemistry. It is indicated that the uranium ions involved in the Chemex and Asahi technologies must have the outermost electrons on the s or p orbitals in the respective organic or resin phase complexes, and on the f orbitals in the uranium species of the aqueous phase: U3+ - [Rn]5f3 versus U4+ -[Rn]6d17s15f0 for the Chemex cascade solvent extraction, and U4+ - [Rn]5f2 versus O≡U≡O2+-6p6II4 gII4 u[sgrave]2 g[sgrave]2 u5f06d07s0 for the Asahi process, where the complexes adsorbed by the anion exchange resin correspond to the organic phase species. We conlude that the isotope ions of the heavy elements that have the outermost electrons on the d5/2 or f7/2 and f5/2 subshells in the organic phase species and on the s or P½ orbitals in the aqueous phase complexes should display the inverse chemical isotopic effect in comparison with that reported for the chemical uranium enrichment.

Effect of temperature on the extraction of octahedral and tetrahedral cobalt(II) by 8-hydroxyquinoline and/or dibenzo-18-crown-6 or dibenzylamine

The extraction behavior of octahedral and tetrahedral cobalt(II) complexes from aqueous nitrate medium was studied in the system 8-hydroxyquinoline (HOX) and dibenzo-18-crown-6 (Db 18C6) or dibenzylamine (DBA) in chloroform at different temperatures to evaluate the thermodynamic functions as well as the equilibrium constants of each reaction. The stoichiometry of the extracted organic phase species were established to be Co(OX)2·Db18C6 for the octahedral cobalt and Co(OX)2·DBA for the tetrahedral cobalt.

ω-THIOCAPROLACTAM AS AN EXTRACTING REAGENT FOR Hg(II) FROM CHLORIDE, NITRATE, AND PERCHLORATE MEDIA.

ABSTRACT Solvent extraction of Hg(II) from chloride, nitrate, and perchlorate media using ω-thiocaprolactam (R) dissolved in chloroform was studied. In all media the extraction equilibria are reached very fast, less than a 5 minute period of shaking time is needed. At high metal: extractant ratio (1:10) the percent of extraction of Hg(II) decreases in the order chloride > nitrate = perchlorate and in the pH range studied ( 0-3 ) is independent of this variable. At low metahextractant ratios (1:50, 1:100) the percent of extraction does not depend on the media used. In the latter case a dependence with the acidity in the chloride media is observed. The dimerization constant of the extractant in CHCI3 was determined to be 109±15 by UV measurements. Graphical and numerical analysis of the data with the LETAGROP-DISTR program allowed to propose the extraction reactions involved and evaluate their equilibrium constants. Organic phase species of the type HgX2R and HgX2R2 ( where X = CI, NO3, or CIO4) were found to explain better the experimental results obtained. However, in concentrated HCI the extraction of Hg(II) is explained by the formation of HgCI3RH and HgCI4(RH)2 species.

Extraction of ternary complexes of thorium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone and neutral donors from nitric acid medium

The extraction behaviour of thorium(IV) from aqueous nitric acid employing 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in the presence of tri- n-octyl phosphine oxide (TOPO) as well as tri- n-butyl phosphate (TBP) in xylene medium was investigated. The extraction constant (log k ex) for the binary organic phase species Th(PBI) 4 was determined to be 8.26 which is by far the largest amongst the corresponding values known for other β-diketones. The overall extraction constant (log K) for the ternary species Th(PBI) 4 TBP and Th(PBI) 4·2TOPO were estimated to be 14.96 and 20.96 respectively. An inverse correlation of the adduct formation constant (log K s) with the p K a of the β-diketones, 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and HPBI, was observed. The steric as well as the electronic effects of adduct formation have been discussed. Analytical application of HPBI for the separation of 234Th radiotracer from natural uranium (99.3% 238U) has been suggested.

DIPHASIC ACIDO-BASIC PROPERTIES OF DI(OCTYLPHENYL)PHOSPHORIC ACID (DOPPA)

ABSTRACT In the first part of this work, the diphasic acido-basic constant (pka*) of di(octylphenyl)phosphoric acid, denoted hereafter DOPPA or HL, is determined from its experimental diphasic neutralization curve. The pka* value of DOPPA appears to be equal to 2.6 in the presence of 1 mol/dm3 sodium salt. Such a value is significantly lower than that previously determined for di(2-ethylhexyl) phosphoric acid (DEHPA, pka* = 5.2), 2-ethylhexylphosphonic acid, mono-2-ethylhexyl ester (PC88A®, pka* = 7.1) and di(2,4,4-trimethylpentyl)phosphinic acid (CYANEX® 272, pka* = 8.7). DOPPA (HL) is definitely more acidic than the other organophosphorus acids because its acidic proton can be easily exchanged with sodium cation to form Na+;HL2- species in organic phase. In the second and final part of the work, molecular modelling is used to model the dimers of various organophosphorus acids. A structure-activity relationship is obtained between the association energies of modelled dimers and their diphasic acido-basic...

EXTRACTION OF Pm(III) AND Gd(III) BY 8-HYDROXYQUINOLINE AND SOHE RELATED AMINES IN CHLOROFORM FROM NITRATE MEDIUM

The extraction of the trivalent radioactive lanthanides (Ln), Pm and Gd from nitrate aqueous medium by 8-hydroxyquinoline (HOX) and/or trilaurylamine (TLA), trioctylamine (TOA), tributylamine (TBA), tripropylamine (TPA) or triallylamine (TAA),L, in chloroform was investigated. The chemical formulae of the extracted organic phase species for both lanthanides were found Ln.NO{sub 3}.(OX){sub 2} for the chelate and Ln.NO{sub 3}(OX){sub 2}.L for the adduct. The respective extraction and formation constants were evaluated. The synergic extraction of Pm and Gd by HOX-amine was investigated as a function of temperature. The thermodynamic parameters, free energy change, enthalpy change and entropy change were evaluated. The stoichiometry of the extracted organic phase species was established and the different data obtained were discussed. 15 refs., 8 figs., 2 tabs.

Solvent extraction of lanthanum(III) and cerium(III) with dialkyldithiophosphoric acids. Separation from thorium(IV)

The extraction of lanthanum(III) and cerium(III) with dialkyldithiophosphoric acids, Hdtp, into different polar and nonpolar solvents (cyclohexane, benzene, carbon tetrachloride, chloroform, diethyl ether, dibutyl ether, n-butanol and cyclohexanone) from aqueous solutions containing perchlorate, nitrate and chloride anions has been investigated. The effect of various factors, such as nature of the solvent, pH, metal concentration and foreign anions present in the aqueous phase was investigated in order to establish the mechanism of extraction process. The data obtained suggest an ion-exchange mechanism. The anions present in the aqueous phase do not participate in the extraction process and do not influence significantly the magnitude of the extraction ratios either. The extracted species in the organic phase is a 1∶2 complex of lanthanide with Hdtp. The extraction efficiency (E%) is calculated and the possibility of Th-rare earths separation is discussed.

THE SYNERGISTIC SOLVENT EXTRACTION OF RADIUM FROM ALKALINE NITRATE MEDIA BY DICYCLOHEXANO-21-CROWN-7 COMBINED WITH 2-METHYL-2-HEPTYL NONANOIC ACID EQUtUBRIUM REACTIONS AND METAL ION COMPETITION∗

ABSTRACT The equilibria in the solvent extraction of radium from aqueous sodium nitrate/sodium hydroxide solutions by toluene solutions of dicyclohexano-21-crown-7 (DC21C7). 2-methyl-2-heptylnonanioc acid (HMHN). and mixtures of the two reagents are examined. The mixed reagents are synergistic in the extraction of radium and selective for radium over other alkali and alkaline earth elements. The dependencies of the extraction on pH and reagent concentration were utilized in computer modeling to estimate the stochiometry of the extracted complexes and equilibria involved the extraction. Three organic-phase species were identified in the extraction under basic (pH 11-13) conditions. With A = MHN−. B = DC21C7 and assuming NaA is a 10-fold aggregate they are. RaA2B.NaA. Log K = 3.57: RaA NaA. Log K = 0.99: and B 2NaA. Log K = − 0.41. The effect of the presence of various concentrations of sodium

A Thermodynamic Model of Nitric Acid Extraction by Tri-n-Butyl Phosphate

A thermodynamic model is presented for nitric acid extraction by tri-n-butyl phosphate (TBP). This model is based on the formation of the organic phase species: TBP · HNO3 and (TBP)2 · HNO3. The mo...

Permeation rate and selectivity in the separation of cobalt and nickel by supported liquid membranes.

The transport of cobalt and nickel from nitrate solutions through supported liquid membranes (SLM) containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester dissolved in n-dodecanc as a carrier was studied. High selectivity in the separation of cobalt and nickel was obtained when the diffusional resistance in the liquid membrane was dominant. Experiments on the extraction of cobalt and/or nickel were also carried out over a wide range of metal loading ratio, and empirical correlations representing the concentrations of the aggregated species in organic phase were presented. Using a permeation model in which the formation of aggregates of metal-carrier complexes was considered, the fluxes in single and simultaneous permeations were quantitatively explained.

The solvent extraction of metal ions from aqueous solutions containing NNN′N′-Ethylenediaminetetraacetic and related ccids. Part 1. Uranium(IV)

The uranium(IV) complexes [U(EDTA)(H 2O) 2], [U(HOEDTA)] +, and [U(DTPA)] − are well-formed in the pH fange 2–3 ([DTPA] 5- = diethylenetriaminepentaacetate; [HOEDTA] 3-  N-(2-hydroxyethyl)ethylenediaminetriacetate). Of these, only [U(DTPA)]- is extracted from an aqueous phase at pH 2 by the perchlorate salt of the primary amine, Primene JM-T. As the aqueous phase pH was raised, extraction occurred in all three cases and hydrolysed species may be extracted from EDTA and HOEDTA solutions but [U(DTPA)] − resists hydrolysis. The addition of sulphate had a marked effect on the extraction of U(IV) from EDTA and HOEDTA through the formation of [U(EDTA)(SO 4)(H 2O)] 2- and [U(HOEDTA)(SO 4)(H 2O) n] −. The equilibrium constant, log β 1, for: [(U(EDTA)(H 2O) 2] † [SO 4] 2− ⇌ [U(EDTA)(SO 4)(H 2O)] 2- † H 2O was found to be 2.43 ± 0.04 (I = 1 mol dm −3, NaClO 4; pH 2.0; 20 °C) from spectrophotometric data. With tri-n-octylphosphine oxide (TOPO) electronic spectroscopy showed that the same U(IV) complex was extracted at pH 2 for Cs 2UCl 6, U(IV)/ HOEDTA, and U(IV)/DTPA and the aminepoly- carboxylates were aqueous phase masking agents but with [U(EDTA)(H 2O) 2] oxidation gave a uranyl(VI) organic phase species. Uranium(IV) is strongly extracted from aqueous solutions of HOEDTA at pH 2 or 3 by bis(2-ethyl- hexyl)phosphoric acid (HBEHP) but less so from EDTA and DTPA. Since U(IV) is completely extracted from Cs 2UCl 6 it could be that the amine- polycarboxylates were aqueous phase masking agents although spectral evidence did not support this.

Formation of mixed-ligand complexes of zinc(II) with chloride and substituted pyridines in 1,2-dichloroethane as solvent

The formation of mixed-ligand complexes of zinc(II) chloride with pyridine (py) and substituted pyridines R-py [R-py = 4-methyl-(4Me-py), 3-methyl-(3Me-py), 2-methyl-(2Me-py), 2-ethyl-(2Et-py), 4-acetyl-(4MeCO-py), and 4-cyano-pyridine (4CN-py)] in 1,2-dichloroethane has been investigated at 25.0 °C by means of solvent extraction. The extraction equilibrium of zinc(II) between the NaCl aqueous phase and the NBut4Cl–1,2-dichloroethane phase is given by equation (I), where the Zn2++ 2 Cl–+ 2 NBut4Cl (org) [graphic omitted] (NBut4)2ZnCI4(org)(i), thermodyanamic extraction constant log Kex,0= 5.61 ± 0.03 and ‘org’ denotes the species in the organic phase. The addition of substituted pyridines in this extraction system gives rise to the equilibria (ii) and (iii). (NBut4)2ZnCI4(org)+ R-py (org) [graphic omitted] (NBut4)ZnCl3(R-py)(org)+ NBut4Cl (org)(ii), (NBut4)ZnCl3(R-py)(org)+ R-py (org) [graphic omitted] ZnCl2(R-py)2(org)+ NBut4Cl (org)(iii), The successive formation constants, K1 and K2, were determined as log K1= 0.45, 0.25, –0.07, –0.47, 0.07, 0.13, and –0.48 ± 0.03, and log K2=–1.09, –1.34, –3.21, –3.33, –1.70, –3.56, and –4.86 ± 0.03 for the 4Me-py, 3Me-py, 2Me-py, 2Et-py, py, 4MeCO-py, and 4CN-py complexes, respectively. Except for the 2Me-py and 2Et-py complexes, the values of log K1 and log K2 show linear correlations with the pKa of the conjugate acid of the substituted pyridines.

Extraction of nickel and cobalt with 2-ethylhexyl-phosphonic acid mono-2-ethylhexyl ester.

Extraction equilibrium formulations were established for the distribution of nickel, cobalt and sodium between n-heptane and xylene containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester ((LH)2) and 5 × 102 mol/m3 (Na, H)NO3. The composition of the organic phase species is NiL22(LH)2, CoL2(LH)2 and NaL(3/2)(LH)2, over a range of loading ratio, [M]1/[(LH)2]feed, less than 0.08 for cobalt and 0.008 for nickel. The ratio of the extraction constant for the commonly used di-(2-ethylhexyl)phosphoric acid to that using the present reagent is of the order of 10 for cobalt, copper and sodium, but increases to the order of 100 for nickel. With increase in loading ratio, successively larger aggregated species such as (NiL2(LH)2)n(LH)2 and (CoL2)n(LH)2 (n=l, 2, 3, ...) appear. Identification of these species has been established on the assumption that the extraction constants are independent of the number of metal atoms, n, in the species.

Equilibrium studies of the extraction of divalent metals from nitrate media with di-(2ethylhexyl) phosphoric acid

Using the distribution data for di-(2ethylhexyl)phosphoric acid (= HDEHP = RH) between n-heptane and 0.1 mol/dm3 (Na, H)NO3, the equilibrium constants of HDEHP such as the dimerization, the distribution and the acid dissociation constant were determined, respectively, as K2 = 3.13 × 104 dm3/mol, Kd = 1.6 × 103(−) and Ka = 3.10 × 10−2 dm3/mol. The extraction equilibrium formulations were established for the distribution of cobalt, copper and nickel between n-heptane, benzene and toluene containing HDEHP and 0.5 mol/dm3 (Na, H)NO3. The composition of the organic phase species is CoR2(RH)2, CuR2(RH)2 and NiR22(RH)2. These single species exist in the range of less than 24% of the extractant being converted to the complex. A considerable improvement of the extraction constants, especially for nickel, was brought about by changing the diluent from an aromatic to an aliphatic nature. An addition of less than 0.3 mol/dm3 buffer solution, CH3COOHCH3COONa, instead of 0.5 mol/dm3 (Na, H)NO3, did not change the extraction equilibrium formulation, except for a small increase in the empirical extraction constant for each metal-diluent system.

Organic phase species in the extraction of molybdenum(VI) by aliquat 336 from chloride media

The extraction of molybdenum(VI) from hydrochloric acid medium at relatively low aqueous acid concentration, with a long-chain quaternary ammonium hydrochloride, Aliquat 336, in various organic diluents, is described. The optimum extraction occurs at approximately pH 2. Both chemical and spectroscopic methods have been used to study the extracted species present in the organic phase which is an oxocomplex of Mo(VI) containing no chloride and with a ratio ammonium salt: Mo(VI) = 1:2.

Mass transfer rate in liquid anion exchange processes—I: Kinetic of the two-phase acid-base reaction in the system trilaurylamine-toluene-HCl-water

By using a stirred cell with a constant interfacial area the rate of the two phase acid-base reaction between aqueous HCl and trilaurylamine (TLA) dissolved in toluene has been studied. A reaction mechanism, where interfacial chemical reactions are the main rate determining processes, has been hypothized on the basis of both kinetic experiments as well through the knowledge of the interfacial properties of the system. The reactions are the following: H + + ( TLA) i⇌( TLAH +) i slow Cl − + ( TLAH +) i⇌( TLAHCl) i fast ( TLAHCl) i+ TLA ⇌ TLAHCl +(TLA) i slow where i and the bar indicate interfacial and organic phase species respectively. An expression for the overall rate of reaction has been derived and the rate constants evaluated. By means of an approximate model, coupling diffusion and chemical reactions together, it has been shown that a possible diffusional contribution to the overall rate can affect the numerical values of the rate constants while the type of dependence of the rate of extraction on the concentrations is the same. The proposed reaction mechanism has been shown to hold up to equilibrium.

Organic phase species in the extraction of hydrochloric acid by triisooctylamine in various organic diluents

Organic phase species in the extraction of hydrochloric acid by triisooctylamine in various organic diluents

Equilibria in the system: Di(2-ethylhexyl)-phosphoric acid-benzene-water-alkali (hydroxide, nitrate)

The extraction of the alkali metals from 3M alkali metal nitrate by di(2-ethylhexyl)phosphoric acid (HDEHP or HA) in benzene is examined as a function of HDEHP concentration and of aqueous phase pH. The dependence of extraction on reagent concentration over a wide range of reagent loading ( M A HA ) was interpreted using average degree of aggregation of the 0·1 M reagent in benzene measured in this and earlier work. A single metal organic phase species, MA·3HA, was found to exist up to 25 per cent MA in all cases except Cs (Fr not tested). The cesium system gave evidence of the presence of at least some CsA·4HA or CsA·5HA. At higher fractions of MA, the acid-coordinated species disappears and large aggregates of MA appear. At 100 per cent MA the order of extraction of the alkali metals is: Li > Na > K > Rb > Cs. However, the extractabilities of K, Rb, and Cs are very close together and Cs becomes more extractable than K and Rb at low fractions of MA.

The meaning of slope analysis in solvent extraction chemistry: The case of zinc extraction by trilaurylammonium chloride

By using suitable equations, which are derived by treating the extraction of a metal complex in the general form pMY n + q RY ⇌ (RY) q(MY n) p (with MY n extractable species, RY extracting agent, (RY) q(MY n) p complex formed by the extraction reaction, with the bar indicating organic phase species), the physical meaning obtained by the slope analysis of extraction data (logarithmic plot of distribution coefficient vs. extractant concentration) has been discussed. The experimental case of distribution data obtained by extracting ZnCl 2 with a benzene solution of trilaurylammonium chloride in a wide range of metal and extractant concentration has been treated.

Extraction en milieu nitrique du thorium, du neptunium, du plutonium, par les solutions de phosphate de tributyle chargees en uranium

Partition coefficients of Th(NO 3) 4, Np(NO 3) 4, NpO 2(NO 3) 2, Pu(NO 3) 4 and PuO 2(NO 3) 2 have been determined in the system TBP 30%, Dodecane: UO 2(NO 3) 2HNO 3H 2O. The relative variations of the partition coefficients are attributed to the varying degree of activity coefficients of the species both in aqueous and organic phase. In the acidity range investigated, (HNO 3) aq. ≤ 4·5 N. our results show a striking similarity in the variation of activity coefficients corresponding to hexavalent elements; the tetravalent elements exhibit a rather intricate behaviour and so makes it difficult to draw any systematic conclusion.