Tracer scale solvent extraction separation of tantalum from niobium using di-(2-ethylhexyl)-phosphoric acid as extractant

A simple solvent extraction procedure for the efficient separation of the radioactive tracers⁹⁵Nb and¹⁸²Ta from each other in a mixture using di-(2-ethylhexyl)phosphoric acid (HDEHP) as extractant is described. Tantalum was found to be quantitatively extracted from an aqueous madium, which is 1.6N in HCl and 10^?2 M in oxalic acid, with a HDEHP solution of 0.1 M concentration. Extractabilities of both niobium and tantalum in mineral acids like HCl, H₂SO₄ and HNO₃ and in some organic acids like oxalic, citric, etc., in HDEHP under the experimental conditions were also studied. The reliability of the separation procedure was verified further by γ-ray spectrometry.     

Extraction of Am(III) from different acid media by di-2-ethyl hexyl phosphoric acid containing phosphorous pentoxide

The extraction of Am(III) from nitric, hydrochloric, oxalic, phosphoric and hydrofluoric acids was studied using 0.4F di-2-ethyl hexyl phosphoric acid (HDEHP) containing 0.1M phosphorous pentoxide (P₂O₅) in dodecane/xylene. The extraction with pure 0.4F HDEHP was found to be negligible from all the media studied. However, the presence of a small amount of P₂O₅ in it increased the extraction substantially. The distribution ratios of Am(III) obtained for HDEHP - P₂O₅ mixture 3M nitric acid containing different concentrations of oxalic acid/phosphoric acid/hydrofluoric acid are in the order of 200-250. The same for 3M hydrochloric acid is very high (800). These distribution ratios are sufficiently high for the quantitative extraction of Am(III) from all the acid media studied. Different reagents such as ammonium oxalate, sodium oxalate, oxalic acid, hydrofluoric acid, sodium carbonate and potassium sulphate were explored for the back extraction of Am(III) from 0.4F HDEHP + 0.1M P₂O₅ in dodecane/xylene. Of these, 0.35M ammonium oxalate and 1M sodium carbonate were found to be most suitable. The back extraction of Am(III) was also attempted with water and 1M H₂SO₄, HNO₃, HClO₄ and HCl solutions after allowing the extracted organics to degrade on its own. It was found that more than 90% of Am could be back extracted with these acids. Using this method more than 90% of Am(III) was recovered from nitric acid solutions containing calcium and fluoride ions.     

Separation of carrier-free166Ho from Dy2O3 targets by partition chromatography and electrophoresis

A partial separation of carrier-free¹⁶⁶Ho from milligram quantities of neutron-irradiated Dy₂O₃ targets was achieved from aqueous acidic solutions with HDEHP or TBP as the chromatographic stationary phase, and with electrophoresis using -HIBA as complexing agent.     

Hochdruck-Flüssigkeits-Chromatographie von Ätherpolycarbonsäuren

Zusammenfassung Es werden zwei HPLC-Methoden vorgestellt, welche die Trennung von zwei-, drei- und vierbasigen Äther-Carbonsäuren in technischen Gemischen erlauben. Die Verfahren funktionieren mit den freien Säuren genause wie mit den Kalium- und Natriumsalzen und basieren auf den folgenden chromatographischen Systemen: (1) ein starker Anionenaustauscher mit einer mobilen Phase, die ein komplexbildendes Mittel enthält: Aminex A 14/Magnesiumacetat + Essigsäure und (2) ein Umkehrphasensystem: -Bondapak-C₁₈/H₂SO₄+Na₂SO₄. Die Trennzeiten betragen 45 bzw. 7 Minuten. Beide Methoden sind viel schneller und wahrscheinlich auch genauer als gas-chromatographische Verfahren, da keine Derivatisierung notwendig ist.

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High-pressure liquid chromatography of ether-polycarboxylic acids

Summary Two HPLC-methods are presented which permit the separation of two-, three-, and fourbasic ether-carboxylic acids in technical mixtures. The procedures work with the free acids as well as with the sodium and potassium salts and are based upon the following chromatographic systems: (1) A strong anion-exchanger with a mobile phase containing a complexing agent: Aminex A 14/magnesium acetate + acetic acid and (2) a reversed phase system: -Bondapak-C₁₈/H₂SO₄+Na₂SO₄. The separation times are 45 and 7 minutes respectively. Both methods are much faster and probably more accurate than gas chromatographic procedures, because no derivatisation is necessary.

     

Separation of europium and thulium from mixed KI−H2SO4 solutions

The extraction of Tm with HDEHP from H₂SO₄, HCl and HBr is inversely proportional to the third power of the hydrogen ion concentration while the extraction is small with HDEHP, LA-2 and TBP from binary mixtures of acids. The extraction of both Eu and Tm with HDEHP from KI solutions decreases in the presence of small concentrations of H₂SO₄. The decrease is sharper in case of Eu leading to high separation factors between Eu and Tm from KI?H₂SO₄ mixtures.     

Separation of hafnium from tungsten by extraction chromatography with TOA in HCl–H<Subscript>2</Subscript>O<Subscript>2</Subscript> mixture

In order to measure ¹⁸²Hf by accelerator mass spectrometry (AMS), a chemical procedure for separation of hafnium from tungsten has been developed by extraction chromatography. The extraction chromatographic behavior of hafnium and tungsten has been studied using tri-n-octylamine (TOA) as the stationary phase, HCl–H₂O₂ mixture and NH₃·H₂O as the mobile phase. The effects of H₂O₂ concentration, column loading and column dimensions are investigated. Hf and W with microgram amounts are successfully separated on a chromatographic column (Ø5 × 196 mm), on which Hf is hardly retained after completely eluted with 6 M HCl–1% H₂O₂ and W strongly adsorbed is then eluted with 3 M NH₃·H₂O. The decontamination factor for tungsten is 3.0 × 10⁵ and the recovery of hafnium is better than 99% using a single column separation.     

Separation of Monovalent and Divalent Cations on a Pure Silica Gel Column with Dilute Oxalic Acid Containing 18-Crown-6 as Mobile Phase

Summary Pure silica gel (Pia Seed 5S-60-SIL) has been investigated as a cation-exchange stationary phase for ion chromatography of common monovalent and divalent cations (Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, and Ca²⁺) with conductimetric detection; dilute oxalic acid (0.05 mm oxalic acid, pH 4.1, to 1 mm oxalic acid, pH 3.0) was used as mobile phase. The Pia Seed 5S-60-SIL silica gel acted as a cation-exchange stationary phase for these cations when 0.2 mm oxalic acid at pH 3.6 was used as the mobile phase. Excellent simultaneous separation and highly sensitive indirect conductimetric detection of these cations were achieved in 20 min on a 150 mm × 4.6 mm i.d. Pia Seed 5S-60-SIL silica gel column with 0.2 mm oxalic acid containing 4 mm 18-crown-6 (1,4,7,10,13,16-hexaoxacycloctadecane), pH 3.7, as mobile phase (detection limits (signal-to-noise ratio, 3, injection volume, 20 L), were 0.15 m for Li⁺, 0.16 m for Na⁺, 0.21 m for NH₄⁺, 1.0 m for K⁺, 0.17 m for Mg²⁺, and 0.25 m for Ca²⁺). The proposed IC–CD method was successfully applied to the separation and detection of major cations (Na⁺, NH₄⁺, K⁺, Mg²⁺, and Ca²⁺) in rain and river water samples.     

Extraction of99Mo-molybdophosphate and99mTc-pertechnetate from various acid solutions by bis/2-ethylhexyl/ phosphoric acid

The extractability of⁹⁹Mo-molybdophosphoric acid H₃/PMo₁₂O₄₀/ and^99mTc-pertechnetic acid /PTcO₄/ in 20% (v/v) bis /2-ethylhexyl/ phosphoric acid /HDEHP/ in benzene has been investigated at different concentrations of HCl, HBr and HNO₃ acids. The effect of extractant concentration and diluent on the extractability of molybdophosphoric and pertechnetic acids with 20% (v/v) HDEHP in benzene from different concentrations of HCl acid has also been studied.⁹⁹Mo-molybdo-phosphoric acid was found to be selectively extracted and separated from^99mTc-pertechnetic acid with 20% HDEHP in benzene at an acidity of about 0.49M HCl, HBr and HNO₃. The extractability of H₃/PMo₁₂O₄₀/ from these acids generally follows the decreasing order HBr>HCl>HNO₃. The separation factors /K_d molybdophosphoric/K_d pertechnetic/ were found to be 12.9×10⁵ and 7.6×10⁵ for HBr and HCl, respectively. The extractability of pertechnetic acid follows the order HCl>HBrHNO₃. Benzene is the diluent due to its radiation stability. A new procedure for the separation of^99mTc from⁹⁹Mo was suggested.     

Synergistic extraction of neodymium and carrier-free promethium by the mixture of HDEHP and PC88A

Carrier free promethium was produced by proton activation in neodymium target. Extraction behavior of both the elements were studied by HDEHP. A pronounced synergism had been observed by the binary mixture of HDEHP and PC88A. Presence of H₂O₂ in aqueous phase also increases the separation factor.     

Formation of super-concentrated hydrochloric acid in the third phase in tertiary amine N235-PtCl 6 2− -HCl system and its influences on the Pt microemulsion extraction

In this paper, we have investigated the formation of the third-phase in tertiary amine (N235)-PtCl ₆ ^2? -HCl system and the microscopic phase structural evolution of platinum-loaded organic phases before and after the occurrence of the third-phase. The third-phase is characterized by various spectroscopic techniques, and the small angle X-ray scattering (SAXS) experiments demonstrate the appearance of nano-aggregates, i.e., water-in-oil reversed micelles, in the third phase. The experimental results indicate that (1) formation of the third phase is related to the aggregation behaviors of nano-reversed micelles in which a super-concentrated hydrochloric acid formed with the H⁺ to H₂O molar ratio being much higher than that of the conventional 37 wt% saturated hydrochloric acid. (2) The occurrence of the super-concentrated HCl results in a great amount of H⁺ and Cl^? ions enriched and confined within the nano-water pools of W/O reversed micelles in third phase. Therefore, the coordination behaviors of platinum complex ions in that super-concentrated hydrochloric acid are very different from their corresponding behaviors in bulk aqueous solutions. It is possible that H⁺ ions participate in the formation of such complexes as H _m PtCl ₆ ^z+ in the super-concentrated hydrochloric acid. (3) The relative contents of various H _m PtCl ₆ ^z+ complexes are different corresponding to the H⁺ ion concentrations in confined nano-water pools. The association ability of the acidified tertiary amine N235 molecules (R₃NH⁺) with various H _m PtCl ₆ ^z+ complexes plays an important role in affecting the platinum extraction behaviors.     

Comparison of the kinetics of cathodic H2 evolution from the unhydrated H3O+ ion and its hydrated form H9O: Frequency factor effects and modes of activation

Experiments are described in which the kinetics of cathodic hydrogen evolution from the unhydrated H₃O⁺ ion in pure CF₃SO H₃O⁺ are compared with those from an aqueous solution of CF₃SO₃H where the proton is mainly in a fully hydrated state as H₉O. From the acid hydrate, which exists mainly as the ionic compound CF₃SOH₃O⁺, rates of H₂ evolution at Ni, Pt, and Hg electrodes, measured at a given overpotential or expressed as exchange current densities, are between about 3.5 and 20 times slower than those from the same electrolyte in dilute (1.0M) aqueous solution. Allowing for the concentration differences in these two types of system and double-layer effects, the rate constants are between about 9.4 and 216 times smaller for the reaction from H₃O⁺ than from H₉O at the above electrodes. The evaluation of apparent heats of activation for H₂ evolution from the two types of proton sources allows ratios of real frequency factors to be calculated for discharge from H₃O⁺ and H₉O. These data have a bearing on the theoretical conclusions regarding proton discharge mechanisms and show that frequency factor effects can be as important as activation energy differences in determining the rates of proton discharge from different proton sources. The results are discussed in terms of current ideas about electron and proton transfer in electrochemical reactions, the state of hydration of H⁺, and the role of discharge from paired CF₃SO and H₃O⁺ ions. In particular, the molecular mechanics of discharge of the proton from the molecular ion H₃O⁺ can be different from that from the fully hydrated H⁺ ion where many more HO- vibrational and librational modes can be involved in the process of activation of the H₉O entity.     

A theoretical study of the H2SO4+H2O → HSO4 −+H3O+ reaction at the surface of aqueous aerosols

The surface region of sulfate aerosols (supercooled aqueous concentrated sulfuric acid solutions) is the likely site of a number of important heterogeneous reactions in various locations in the atmosphere, but the surface region ionic composition is not known. As a first step in exploring this issue, the first acid ionization reaction for sulfuric acid, H₂SO₄ + H₂O HSO₄^– + H₃O⁺, is studied via electronic structure calculations at the Hartree–Fock level on an H₂SO₄ molecule embedded in the surface region of a cluster containing 33 water molecules. An initial H₂SO₄ configuration is selected which could produce H₃O⁺ readily available for heterogeneous reactions, but which involves reduced solvation and is consistent with no dangling OH bonds for H₂SO₄. It is found that at 0 K and with zero-point energy included, the proton transfer is endothermic by 3.4 kcal/mol. This result is discussed in the context of reactions on sulfate aerosol surfaces and, further, more complex calculations.Contribution to the Jacopo Tomasi Honorary Issue     

Extraction of certain actinide and lanthanide elements from different acid media by polyurethane foams loaded with di-(2-ethylhexyl)phosphoric acid (HDEHP)

The effect of added TBP on the extraction of uranium(VI) with a solution of di-(2-ethylhexyl)-phosphoric acid (HDEHP) in o-dichlorobenzene from nitric acid solutions has been investigated at varying concentrations of nitric acid, HDEHP, TBP and uranium(VI). The mechanism of the synergistic effect of TBP is discussed on the basis of the results and can be summarized in the following equation: UO _2(aq) ²⁺ +0.67(HX)_3(o)+2TBP_(o)UO₂X₂·2TBP_(o)+2H _(aq) ⁺ where HX denotes HDEHP and the HDEHP loaded on the foam is trimerized.     

The formation of aryloxenium ion in the reaction of N-nitro-O-(4-nitrophenyl)hydroxylamine with strong acids

The reaction of N-nitro-O-(4-nitrophenyl)hydroxylamine (1) with conc. H₂SO₄ affords 4-nitropyrocatechol and that with conc. sulfonic acids (RSO₃H where R = Me, CF₃) affords 2-hydroxy-5-nitrophenyl-R-sulfonates in yields of 80?C85%. These reactions are assumed to proceed through an intermediate (phenoxy)oxodiazonium ion [NO₂C₆H₄O-N=N=O]⁺, which eliminates the N₂O molecule to form the aryloxenium ion [NO₂C₆H₄O]⁺. The latter reacts with acid anions at the ortho-carbon atom of the phenyl ring. The thermodynamical parameters of the elementary reactions resulting in the formation of the (phenoxy)oxodiazonium ion [NO₂C₆H₄O-N=N=O]⁺ and aryloxenium ion [NO₂C₆H₄O]⁺ were calculated in the B3LYP/6?311+G(d) study of the combined molecular system (nitrohydroxylamine 1 + [H₃SO₄]⁺). The reaction of nitrohydroxylamine 1 with aqueous solutions of strong acids (??70% H₂SO₄, CF₃SO₃H) affords mainly 4-nitrophenol. It appears that the mechanism of this reaction does not involve the formation of the aryloxenium ion.     

Extraction of certain actinide and lanthanide elements from different acid media by polyurethane foams loaded with di(2-ethylhexyl)phosphoric acid (HDEHP)

Except for conditions of low acidity and low ratios of di(2-ethylhexyl)phosphoric acid (HDEHP) to U(VI) the data obtained for the distribution of U(VI) between sulfuric acid solutions and polyurethane foams loaded with solutions of HDEHP in nitrobenzene could be analyzed by the equation: log (4.36 D_u)=log K+1.43 log (C_d–4C_u)/(C_H)^1.4+log f_u where the polymerization number of HDEHP is about 2.8, D_u is the distribution ratio, and f_u=[UO ₂ ²⁺ ]_(aq)/[UO₂]_(aq) indicating that the extraction proceeds via the formation of a 14 UO₂:HDEHP complex. At both low acidity and HDEHP/U(VI) ratio a UO₂-HDEHP polymer is formed.     

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.     

Simultaneous determination of alkali,alkaline earth and transition metal elements in uranium and thorium based nuclear fuel materials by single column ion chromatography

A single-column ion chromatography (SCIC) for the simultaneous determination of alkali, alkaline earth and transition metal elements in UO₂, ThO₂ powders and sintered (Th, U) O₂ pellet is described in this paper. Metrosep cation 1-2 analytical column containing poly butadiene-maleic acid (PBDMA) coated silica has been applied to the ion chromatographic separation of 12 cations (copper, lithium, sodium, ammonium, nickel, potassium, zinc, cobalt, manganese, magnesium, calcium and strontium) using an isocratic elution with tartaric acid and oxalic acid as mobile phase with non-suppressed conductivity detection. Mobile phase composition was optimized to 1 mM tartaric acid and 0.75 mM oxalic acid for the baseline separation of 12 cations. The calibration plots were linear in the range of 0.05–40 mg L⁻¹ with regression coefficients better than 0.998. The relative standard deviations (RSDs) of the retention time, peak area and peak height were less than 1, 2.8 and 3.0%, respectively. The recoveries of the spiked samples for the cations were 94–110%. The method developed was validated by comparison with certified standards of UO₂ and ThO₂ powders.     

Liquid-liquid extraction of trace level zirconium and hafnium with trioctylamine

Extraction behavior of zirconium and hafnium tracers,⁹⁵Zr and^175,181Hf, in HF, HCl, HNO₃ and H₂SO₄ media with the liquid anion exchanger TOA has been studied. Under optimum conditions, TOA was found to be very effective for quantitative extraction of the individual elements at their trace scale concentrations, but due to higher extractibility and almost identical chemical behavior of the radiotracers towards TOA, the reagent was not so effective for mutual separation of the elements when they were present as congeneric pairs in the aqueous solutions. Extents of extraction of the elements at different stages were measured by -ray spectrometry.     

Aripiprazole salts. III. Bis(aripiprazolium) oxalate–oxalic acid (1/1)

The asymmetric unit of the title salt [systematic name: bis(4‐(2,3‐dichlorophenyl)‐1‐{4‐[(2‐oxo‐1,2,3,4‐tetrahydroquinolin‐7‐yl)oxy]butyl}piperazin‐1‐ium) oxalate–oxalic acid (1/1)], 2C₂₃H₂₈Cl₂N₃O₂⁺·C₂O₄²⁻·C₂H₂O₄, consists of one protonated aripiprazole unit (HArip⁺), half an oxalate dianion and half an oxalic acid molecule, the latter two lying on inversion centres. The conformation of the HArip⁺ cation differs from that in other reported salts and resembles more the conformation of neutral Arip units in reported polymorphs and solvates. The intermolecular interaction linking HArip⁺ cations is also similar to those in reported Arip compounds crystallizing in the space group P, with head‐to‐head N—H...O hydrogen bonds generating centrosymmetric dimers, which are further organized into planar ribbons parallel to (01). The oxalate anions and oxalic acid molecules form hydrogen‐bonded chains running along [010], which `pierce' the planar ribbons, interacting with them through a number of stronger N—H...O and weaker C—H...O hydrogen bonds, forming a three‐dimensional network.