LIX 84 as an extractant for throium(IV), uranium(VI) and molybdenum(VI)

The extraction order of Th(IV), U(VI) and Mo(VI) based on pH_0.5 values is Mo(VI)>U(VI)>Th(IV). Quantitative extraction has been observed for U(VI) by mixture of 10% (v/v) LIX 84 and 0.1M dibenzoylmethane at pH 4.2 and by mixture of 10% LIX 84 and 0.05M HTTA in the pH range 5.5–7.3 and for Mo(VI) by 10% LIX 84 from chloride media at pH 1.5. The order of extraction of Mo(VI) from 1N acid solutions is HCl>H₂SO₄>HNO₃>HClO₄ and extraction decreases very rapidly with increase in the concentration of HCl as compared to that from H₂SO₄, HNO₃ and HClO₄ acid solutions. The diluents C₆H₆, CCl₄ and CHCl₂ are found to be superior ton-butyl alcohol and isoamyl alcohol for extraction of Mo(VI). Influence of concentration of different anions on the extraction of U(VI) and Mo(VI) has been studied. Very little extraction has been observed in case of Th(IV) by LIX 84 or its mixtures with other chelating extractants or neutral donors.     

Separation of the Oxyanions of Re(VII), Mo(VI), Cr(VI), W(VI), and V(V) from a Multicomponent Solution at pH 6 by foam Fractionation

Abstract

An experimental investigation is presented of the foam separation of the oxyanions of Re(VII), Mo(VI), Cr(VI), W(VI), and V(V). The pH 6.0, multicomponent aqueous solutions are 1.0 × 10 ^?6 M in each metal. The effect of chloride competition with the metal oxyanions for the cationic surfactant is determined with NaCl concentrations up to 0.3 M. With proper NaCl concentration adjustments, V(V) can be separated completely from the other four metals, and Re(VII) and Mo(VI) from the other three. Pulsed surfactant dosage is investigated for 1.0 × 10 ^?6 M Mo(VI) solutions at pH 6.0 and 3.1.     

Chiral monomeric organorhenium(VII) and organomolybdenum(VI) compounds as catalysts for chiral olefin epoxidation reactions

Several attempts have been made to transform the organometallic Re(VII) compound MTO and the (MoO₂)²⁺ moiety to chiral epoxidation catalysts by addition of chiral organic ligands. Being very efficient epoxidation catalysts in achiral reactions, it was hoped that these compounds could be transformed into chiral epoxidation catalysts by adding chiral Lewis base ligands. The major flaw of most of these attempts, however, was the weak coordination of the chiral Lewis base ligands to the metal center, which led either to high ees only at the very beginning of the catalytic reaction (low conversion) or to generally low enantiomeric excesses. The heterogenisation of the Mo(VI) complexes was, at least in some cases, successfully achieved but with the same drawbacks with respect to the ees as in the homogeneous phase. Currently, attempts are being made to synthesize organometallic Re(VII) and Mo(VI) complexes with stronger interactions between the metal containing moiety and the chiral ligand(s).     

Adsorptivity of polyvinylpolypyrrolidone for selective separation of U(VI) from nitric acid media

Adsorptivity of polyvinylpolypyrrolidone (PVPP), a candidate resin with selectivity to U(VI) in HNO₃ media, to various metal ions was examined. It was found that PVPP has a strong adsorptivity to U(VI) in wide concentration range of HNO₃. The Scatchard plot analysis revealed that the adsorption of U(VI) by PVPP occurs at plural binding sites. The infrared spectroscopic analysis suggested that the strong binding site is due to the coordination of the carbonyl oxygen atom and the nitrogen atom in the pyrrolidone ring to UO₂ ²⁺. It was also found that fission product ions except Re(VII) as the simulant of Tc(VII) and Pd(II) are not adsorbed onto PVPP. The adsorptivities to Tc(VII) and Pd(II) species are weak, indicating that U(VI) can be separated from other metal ions by PVPP.     

Solvent Extraction of Rhenium(VII) for Preparation of No-Carrier-Added 186Re Saline Solution with High Specific Volume Activity

By using ¹⁸⁸Re as a radiotracer, the extraction behavior of Re(VII) by a tertiary amine extractant N-235 from HCl and the back-extraction behavior of Re(VII) by HNO₃ and ammonia were studied. A chemical separation procedure, which combined the acid alumina column and solvent extraction was established. The procedure was rapid and efficient for the separation of ¹⁸⁶Re from ¹⁸⁶W irradiated by 16 MeV deuterons. No-carrier-added ¹⁸⁶ReO₄ ^– saline solution with high specific volume activity was obtained. The overall recovery yield of ¹⁸⁶Re was about 85%.     

Selective Separation of Re(VII) and Tc(VII) by Xerogel Microcapsules Enclosing TOA Extractant

Special attention has been given to the separation and recovery of VII-group elements, Tc and Re, in relation to the partitioning of high-level liquid waste (HLLW) generated from the nuclear fuel reprocessing process. In this study, a tertiary amine (tri-n-octylamine, TOA), which is effective for the extraction of oxoanions, was encapsulated in Ca and H-types of alginate xerogel polymers (CaALG, HALG). The uptake behaviors of TcO4^-and ReO4⁻ (substitute of Tc) in the presence of HNO3 were examined by batch method using TOA-xerogel microcapsules (TOA-CaALG, TOA-HALG). The uptake of TcO4- in the presence of 0.1 M HNO3 was readily attained within 5 h, and a relatively large uptake(%) above 90% was obtained. The uptake(%) of Re(VII) for TOA-CaALG in the presence of 0.01∼0.1 M HNO3 was estimated to be about 90%, while gradually decreasing with HNO3 concentration, indicating that the extraction of HNO3 with TOA became dominant in this process: R3NH⁺NO3 (o) + ReO4 (aq) ↔ R3NH⁺ReO4 (o) + NO3 (aq). The order of the uptake(%) for different oxoanions in the presence of 0.01∼5 M HNO3 was Re(VII) > Zr(IV)> Se(VI) > Mo(VI) > Te(VI). The elution study of Tc(VII) revealed 95% and 99% of recovery with 5 M and 7 M HNO3, respectively. The chromatographic separation of Re(VII) from simulated HLLW (28 components of waste solution, SW-11E, JAEA) as well as from mixed solution was accomplished by the stepwise elution techniques using a column packed with TOA-MCs. The Re(VII) ions were effectively eluted with 5 M HNO3, and a relatively large recovery(%) of 98.60% was obtained. Other elements were eluted with H2O and 2 M HNO3. Thus the TOA-xerogel microcapsules are effective for the selective separation of Tc(VII) from HLLW.     

Extraction of rhenium(VII) and molybdenum(VI) with hexabutyltriamide of phosphoric acid from acid media

Extraction of rhenium(VII) and molybdenum(VI) from sulfuric, hydrochloric, and nitric acid solutions with hexabutyltriamide of phosphoric acid was studied. The influence exerted on the extraction of Re(VII) and Mo(VI) by the nature and concentration of an acid in the aqueous phase, temperature, time of contact between phases, and concentration of the extracting agent in the organic phase was analyzed. Isotherms of extraction of rhenium(VII) and molybdenum(VI) with solutions of hexabutyltriamide phosphoric acid in kerosene were obtained, the composition of the complexes being extracted was determined, the enthalpies and entropies were evaluated, and the concentration constants of extraction of the metals were found.     

Thin-Layer Chromatography Method for the Investigations of Re(VII), Mo(VI)

Abstract

The benavicur of Re(VII), Mo(VI) and V(V) ions was studied chromatographically in aliphatic alcohol -HC1 systems on Al ₂O₃ as an adsorbent. Changes in the chromatographic process with the changes of the kind and composition of mobile phase were analysed.

It was also attempted to describe theoretically the results of chromatograpnic separation by using the thermodynamic theory of adsorption from multicomponent solutions.     

Extraction of molybdenum(VI) by 4-(5-nonyl)pyridine in benzene from aqueous mineral acid solutions containing thiocyanate ions

Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO₃, and H₂SO₄) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)₂·[MoO₂(SCN)₄] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C₆H₆–0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.     

Sorption and separation of some elements of nuclear importance using Chelex-100

Chelex-100, in the anionic form has been studied for its ability to perform selective separation and concentration of some metal ions of nuclear importance from mineral acid solutions. The sorption behavior of Zr(IV)–Nb(V), Mo(VI), Tc(VII), Te(IV) and U(VI) from solutions of hydrochloric and sulphuric acids on Chelex-100 has been studied under static and dynamic conditions. Mo(VI) and Tc(VII) have been concentrated on the resin from hydrochloric or sulphuric acid solutions at low acidities probably, as the anions MoO ₄ ^2– and TcO ₄ ^– , respectively. Te(IV) has been isolated from hydrochloric acid solutions of normalities 6 in the form of the anionic chloro complex TeCl ₆ ^2– . Optimum conditions for elution and separation of Mo(VI), Tc(VII), Te(IV) and U(VI) were recommended.     

Reactions between technetium(VII) and some hydrazones and the spectrofluorimetric determination of technetium(VII) with 2,2′-dipyridylketone hydrazone

The reactions between pertechnetate and five hydrazones are described. Of these, the technetium(VII)/2,2′-dipyridylketone hydrazone system was found to be most sensitive, and is studied in detail. Spectrofluorimetric procedures for the determination of technetium(VII) over the range 0.01–12 mg l^?1 are reported. The reaction proceeds most favourably under acidic conditions (1.4 M hydrochloric acid). For 1 mg l^?1 technetium(VII), 100 mg l^?1 levels of U(VI), Re(VII), Mo(VI) or W(VI) do not interfere when the reaction proceeds at room temperature. Sensitivity improves at higher temperatures.     

Liquid-liquid extraction of molybdenum(VI) and uranium(VI) by LIX 622

The order of extraction of Mo(VI) from 1M acid solutions by 5% (v/v) LIX 622 (HL) in benzene is HCl>HNO₃>HClO₄>H₂SO₄, and extraction decreases with increasing concentration of HCl and H₂SO₄, and increases slightly with increasing concentration of HNO₃ and HClO₄. The extracted species is shown to be MoO₂L₂ as established by IR data of organic extracts and the extracted species in the solid form. Extraction is almost quantitative at and above 10% LIX 622, and is found to be independent of [Mo(VI)] in the range of 10^–4 to 10^–3 M. The diluents CCl₄, CHCl₃ and C₆H₆ are found to be superior to solvents of high dielectric constant for extraction of Mo(VI). Extraction of uranium(VI) by 10% (v/v) LIX 622 in benzene was found to increase with increasing equilibrium pH (3.0 to 6.0), and becomes quantitative at pH 5.9. Tributyl phosphate acts as a modifier up to 2% (v/v). Thorium(IV) is almost not extracted by LIX 622 or its mixture. Separation of Mo(VI) and U(VI) is feasible.     

Liquid-liquid extraction of Mo(VI) and V(V) by Primene JMT

The extraction equilibrium of pentavalent vanadium and hexavalent molybdenum with a benzene solution of primary amine Primene JMT sulphate has been investigated. The comparison of the extraction of aqueous solutions containing the salts of the elements and the solutions containing the mixture of Mo(VI) and V(V) was carried out. The attention was directed to the pH 2–6 region in which the heptamolybdates and decavanadates in prevail aqueous phase and to the region ≈1M H₂SO₄ which was suitable for the extraction separation of Mo(VI). The mechanism of extraction is discussed.     

Kinetic Determination of Nanogram Amounts of Mo(VI) in Solution

A new inhibitory reaction is proposed and a kinteic method developed for the determination of ultra‐micro amounts of Mo(VI) on the basis of its inhibitory activity in oxidation of trimethylenediamine ‐N,N,N′,N′‐tetraacetic acid (TDTA) by KMnO₄ in the presence of hydrochloric acid. Under optimal conditions the sensitivity of the method is 0.5 ng/cm³. The probable relative error is 2.9–3.5% for the concentration range 7.5–2.0 ng/cm³ of Mo(VI). The effect of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. The selectivity of the method is relatively good. Kinetic equations were proposed for the investigated process. A method has been applied for determination of Mo(VI) in a certain kind of steel.     

Separation of rhenium from molybdenum and other heavy metals by solvent extraction

Summary Two methods are presented for the extractive separation of rhenium from molybdenum and other heavy metals in hydrochloric acid solution. In the first method, Mo(VI) and Re(VII) are reduced by hydrazine in strong hydrochloric acid solution to Mo(V) and Re(IV). The former is then extracted intoiso-amyl acetate. The Re(IV) remaining in the aqueous phase is oxidised to Re(VII) and determined by known procedures. In the second method, Re(VII) and other ions in 1–1.3N HCl are boiled with hydrazine sulphate for 5 minutes. After adding EDTA to complex Mo(V) and adjusting the solution to 0.33N HCl, rhenium is extracted into chloroform containing 1% tribenzylamine, and is recovered by shaking with water having sufficient ammonia to neutralise the acid and a little hydrogen peroxide.

---

Zusammenfassung Zwei Arbeitsweisen für die extraktive Trennung des Rheniums von Molybdän und anderen Schwermetallen in salzsaurer Lösung wurden angegeben. Bei dem ersten Verfahren werden Mo(VI) und Re(VII) mit Hydrazin in stark salzsaurer Lösung zu Mo(V) und Re(IV) reduziert. Ersteres wird dann mit Isoamylacetat extrahiert. Re(IV) verbleibt in der wäßrigen Phase, wird zu Re(VII) oxydiert und auf bekannte Art bestimmt. Beim zweiten Verfahren werden Re(VII) und die anderen Ionen in 1- bis 1,3-n Salzsäure 5 Minuten mit Hydrazinsulfat gekocht. Nachdem man ÄDTA zur Komplexierung des Mo(V) zugesetzt und die Lösung auf 0,33-n an Salzsäure eingestellt hat, wird Rhenium mit einer 1%igen Lösung von Tribenzylamin in Chloroform extrahiert. Die Rückextraktion erfolgt mit Wasser, worin Ammoniak (zur Neutralisation der Säure) und etwas Wasserstoffperoxid gelöst sind.

     

Spectrophotometric and ESR methods of rhenium determination based on one electron photoreduction of Re(VII)

A possibility of photochemical reduction of Re(VII) to Re(VI) in mixture of concentrated sulfuric and hydrochloric acids has been demonstrated. The reaction mechanisms of Re(VII) photoreduction and Re^VIOCl₅ ^– complex decay have been considered from view point of acids and water content. The optimal conditions of Re^VIOCl₅ ^– stability have been found.Spectrophotometric and ESR methods of rhenium determination based on photochemical production of Re^VIOCl₅ ^– complex with the detection limit of 1g/ml have been proposed. Rhenium concentration in industrial sulfuric acid has been determined.     

Extraction of molybdenum(V) as its ferron complex with trioctylamine in chloroform from a sulphuric acid medium

A simple, rapid, and highly selective method for the separation of molybdenum from a large number of elements of analytical importance has been developed. The method is based on the extraction of a Mo(V)-ferron (7-iodo-8-hydroxyquinoline-5-sulphonic acid) complex into trioctylamine-chloroform in a sulphuric acid medium using ascorbic acid as a reductant. Many elements such as Re(VII), W(VI), U(VI), Th(IV), Cr(III), Cr(VI), V(V), Ce(IV), Ru(III), Co(II), Ni(II), Mn(II), Fe(II), Fe(III), Cd(II), Mg(II), Cu(II), Al(III), Zn(II), Pb(II), Ag(I), and As(V) are not extracted under the conditions proposed and, thus, molybdenum can be easily separated without any interference. Sulphate, chloride, nitrate, phosphate, and oxalate anions have no effect on the extraction of molybdenum. However, zirconium and palladium interfere seriously. The ratio of Mo: ferron: TOA in the extracted species is found to be 1: 1: 3 using Job’s method of continuous variations. This value has been further confirmed by the mole-ratio method. The text was submitted by the authors in English.     

Adsorption Behavior of U(VI) and Re(VII) on Iron Sulfide Nanoparticles Modified with Titanate Nanotubes: Mechanism and Performance Insights

A novel nanocomposite (TNTs-FeS) was developed by anchoring ferrous sulfide (FeS) nanoparticles immobilized on titanate nanotubes (TNTs) by hydrothermal method to remove U(VI) and Re(VII) from aqueous solution, and the removal mechanism and efficiency were examined. The experimental results showed that the TNTs can effectively improve the dispersibility and stability of FeS. The environmental conditions, including initial solution pH, initial concentration, equilibrium time, and dosage, played an important role in the remediation process, which can affect the immobilization efficiency significantly. The maximum quantity removal of U(VI) and Re(VII) was 291.67 and 226.23 mg/g at pH of 6.0 and 12.0. The adsorption kinetics and the equilibrium isotherms of U(VI) and Re(VII) all fitted well with the pseudo-second-order model (R²>0.99) and the Freundlich model (R²>0.99). The main mechanism of removal by TNTs-FeS was electrostatic attraction, chemical reduction, and surface complexation. Thus, TNTs-FeS composites exhibited a high potential to remove U(VI) and Re(VII) heavy metal ions from the surface and groundwater.     

Extraction of rhenium(VII) with aliphatic alcohols from acid solutions

Extraction of rhenium(VII) with C₇–C₁₀ aliphatic alcohols from HCl and H₂SO₄ solutions was examined. The rhenium(VII) distribution coefficients were examined in relation to the acidity and temperature. The composition of the extracted complexes and the thermodynamic parameters of extraction were determined. The extraction method of recovery and preconcentration of rhenium(VII) from H₂SO₄ solutions with secondary octyl alcohol was tested in the counterflow mode.     

Use of amberlite XAD-7HP for the separation of Mn(II) and Mn(VII) in waters

A simple method is proposed for the determination and speciation of Mn(II) and Mn(VII) in waters utilizing a macroporous resin, Amberlite XAD-7HP. The batch method was employed and flame atomic absorption spectrometry was used in all determinations. Amberlite XAD-7HP resin was shown to retain Mn(VII) between pH 4 and 12. If the solution contains only one of the species, either Mn(II) or Mn(VII), the resin behaves selectively depending on the pH of the solution. The elution from the sorbent was realized using K₂C₂O₄ in HNO₃. The efficiency of the method was checked via spike recovery experiments. The proposed method was successfully applied to industrial wastewater samples and quantitative recoveries (≥96.0%) confirmed the accuracy of the method.