Separation of molybdenum(VI) from other elements by solvent extraction with dibenzo-18-crown-6 from hydrochloric acid medium

DB-18-C6 was used for the extractive separation analysis of molybdenum(VI) from a range of other elements. Molybdenum(VI) was quantitatively extracted from 8M hydrochloric acid with 0.01M DB-18-C6 in nitrobenzene. It was stripped from the organic phase with 2M nitric acid and determined spectrophotometrically with Tiron at 390 nm. Molybdenum was separated from a large number of elements in binary mixtures, the tolerance limit for most elements being very high. Selective extraction of molybdenum permits its separation from barium, thorium, cesium, rubidium, strontium, lanthanum, chromium(III) and cerium(III). The method was extended for the analysis of molybdenum in a soil sample.     

Protonation and solvent extraction of N-p-tolylbenzohydroxamic acid in hydrochloric acid medium

the protonation of N-p-tolylbenzohydroxamic acid (p-TBHA) in aqueous hydrochloric acid has been investigated by determination of its distribution between cyclohexane and hydrochloric acid. The pK(a) value found was - 2.30 +/- 0.02 at 30 degrees . The solubility of p-TBHA as a function of hydrochloric acid concentration has also been determined. At lower acid concentrations the solubility decreases owing to a salting-out effect, whereas at higher concentrations it increases because of formation of the more hydrophilic protonated species and a salting-in effect. Intramolecular hydrogen-bonding observed in p-TBHA provides evidence for protonation of the nitrogen atom.     

Separation of molybdenum (VI) by extraction withn-octylaniline from hydrochloric acid medium

n-Octylaniline in bezene was used for the extractive separation of molybdenum (VI) from hydrochloric acid medium. Molybdenum(VI) was extracted quantitatively from 10 ml aqueous solution 1.5M in hydrochloric acid and 10M in lithium chloride into 10 ml of 10%n-octylaninline in benzene. It was stripped from the organic phase with 5% aqueous ammonia solution and estimated spectrophotometrically with thiocyanate at 465 nm. The interference of various ions has been studied in detail and conditions have been established for the determination of molybdenum(VI) in synthetic mixtures and alloy samples.     

Separation of fission and corrosion products from boric acid solutions by solvent extraction

Extractive purification of boric acid from radioactive corrosion and fission products dissolved in aqueous solutions modelling nuclear reactor coolants has been studied. Aliphatic 1,3-diols containing 8 and 9 carbon atoms per molecule were used as extractants fro boric acid. The behaviour of some representative corrosion and fission products as well as various factors affecting their distribution between the organic and aqueous phases have been investigated under the conditions of boric acid extraction. Conditions for the effective separation of boric acid from most of the radioactive contaminants are presented.     

Separation of95Zr and95Nb by means of sorption on silica gel from hydrochloric acid solutions

The adsorption behaviour of zirconium and niobium on silica gel from hydrochloric acid solutions was studied by batch equilibrations and passage through columns. On the basis of this, new methods are suggested for the separation and purification of⁹⁵Zr and⁹⁵Nb in hydrochloric acid and hydrochloric acid—methanol solutions. The methods are comparatively simple and rapid, and both zirconium and niobium can be obtained in a radiochemically pure state.     

Synergistic extraction of americium with MEHPA-DEHPA mixed solvent from nitric acid solution

The synergistic effect of the MEHPA-DEHPA mixed system was examined for the extraction of Am(III) from nitric acid solution. Addition of DEHPA or 2-ethylhexanol in MEHPA results in a deleterious effect at MEHPA concentrations lower than 2·10⁻²M but an enhancing effect at higher concentrations. At DEHPA to MEHPA mole ratios of 2 to 4 in moles, the mixed solvent shows a Df for Am which is 1000 times higher than that of DEHPA.     

Separation of trivalent actinides from lanthanides by solvent extraction

A method is presented for separating the trivalent actinides, mainly Am and Cm, from trivalent lanthanides by the use of only two solvent extractants. The first solvent removes the heavy lanthanides, leaving the Am, Cm and the lighterlanthanides; the second removes the Am and Cm. Because additional complexing agents are not required, waste-disposal and corrosion problems are reduced. Overall separation factors may be as high as several thousand for the separation of Am and Cm from lanthanides in the fission waste products from reactor fuel processing.     

Separation of rhodium from ruthenium and iridium by fast solvent extraction with HDEHP

Solvent extraction of rhodium, ruthenium and iridium with di(2-ethylhexyl)phosphoric acid (HDEHP) has been investigated. Under the conditions [Cl^–1]=0.20M, [(HDEHP)₂]=0.30M, pH 4.05, phase contact time 1 minutes, Rh(III) is extracted 90.7%, Ru(III) and Ir(III) 20.0% and 11.5%, respectively, at phase ratio 11. The distribution ratio of rhodium is proportional to [(HDEHP)₂]³ for a freshly prepared aqueous phase with low chloride concentration but might drop to [(HDEHP)₂]^1to2 for an aqueous phase high in chloride concentration and after standing. The spectroscopic studies indicate that the extracted compound of rhodium is Rh(H₂O)_6–x Cl _x [H(DEHP)₂]_3–x (x=0, 1, 2).     

Separation of thorium from lanthanides by solvent extraction with ionizable crown ethers

Thorium and the lanthanides are extracted by alpha-(sym-dibenzo-16-crown-5-oxy)acetic acid and its analogues in different pH ranges. At pH 4.5, Th is quantitatively extracted by the crown ether carboxylic acids into chloroform whereas the extraction of the lanthanides is negligible. Separation of Th from the lanthanides can be achieved by solvent extraction under this condition. The extraction does not require specific counteranions and is reversible with respect to pH. Trace amounts of Th in water can be quantitatively recovered using this extraction system for neutron activation analysis. The nature of the extracted Th complex and the mechanism of extraction are discussed.     

Separation of strontium from nuclear waste solutions by solvent extraction with crown ethers

The possibilities of strontium separation from medium activity waste (MAW) solutions have been investigated. MAW originates from the PUREX process and contains NaNO₃ and HNO₃ in a large excess. By solvent extraction with the crown ether dicyclohexano-18-crown-6 (DC-18-C-6) in 1,1,2,2-tetrachloroethane, separation is possible. The distribution ratio for Sr²⁺ depends on the concentration of HNO₃, NaNO₃ and Pb(NO₃)₂. The extraction system is employed in a continuous counter-current process. After use, the extraction agent can easily be regenerated by reextraction with pure water.     

Separation of Zr from Hf in acidic chloride solutions by using TOPO and its mixture with other extractants

Liquid–liquid extraction of Zr and Hf from chloride solutions was performed by using TOPO extractant in kerosene. An effective extraction of Zr from Hf was achieved selectively at 2.5–3 M HCl condition. Moreover, a mixture of TOPO with DOS, D2EHPA, Aliquat 336, Alamine 336 and Alamine 308 were tested in order to investigate the extraction behavior of Zr and Hf. The mixture of TOPO and D2EHPA was found to increase the extraction of Zr and Hf. In the extraction by the mixture of TOPO and amine, the extraction percentage of Zr and Hf was decreased with the increase of amine concentration due to the preferential extraction of HCl. Finally, among the mixtures of TOPO and other extractants tested in this study, the TOPO alone system was found to be better for the mutual separation of Zr and Hf in hydrochloric acid media.     

Separation and recovery of heavy metals from hydrometallurgical effluents by solvent extraction

Summary The possibility of separating and recovering heavy metals from hydrometallurgical effluents by successive solvent extractions has been investigated by two different procedures with liquid waste from the Espindesa Zinc process. The waste (pH value near to 1.5) includes significant amounts of Zn (1.35), Cu (0.12), Co (0.32) and Mn (0.6 g/l) in the presence of big concentrations of macro-constituents (sulphate, chloride, Na) and Fe [8.8 g/l, mostly as Fe(II) salts]. As extractants, Amberlite La-2 (a secondary ammine, as chlorohydrate) and DEHPA (di-2-ethylhexyl-phosphoric acid) at 25% volume in kerosene were selected. The first method includes two extraction stages with LA-2 for Zn and Cu separation (the last one with 60 g/l of chloride ions) and three stages with DEHPA at pH values near to 1.5, 2.0 and 3.5 for isolating Fe, Mn and Co. The second method separates firstly Fe (as ferric salts) with DEHPA. Afterwards, one stage with LA-2 isolates Zn and three stages with DEHPA at pH values near to 2.0, 3.0 and 3.5 lead to fractions rich in Mn, Cu and Co. Reextractions from organic layers with water or HCl at different concentrations lead to purer solutions of the isolated metals. With both methods, the liquid waste can be converted into a saline solution with lesser problems for disposal.     

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.

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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.

     

Separation of cesium from intermediate level liquid radioactive waste by solvent extraction with antioxidants

The intermediate level liquid radioactive wastes (RAW) isussed from nuclear power plants have high salt contents ca 200 g·dm^–3, the pH of liquid RAW being 12.5–13.7. A convenient method for separation of cesium under these conditions is solvent extraction with substituted phenols. For this purpose weere tested antioxidants produced in Czechoslovakia: AO 2246 [2,2-methylene-bis-(4-methyl-6-tertbutyl)phenol]; AO 4 [2-tertbutyl-4-(2-phenylpropyl)phenol]; AO 4K [2,6-ditertbuty-4-methylphenol]; AO 301 [2,2-methylene-bis-(4-{2-phenylpropyl}-6-tert-butyl)phenol]; and one antioxidant imporoted from Japan—NOCRAC 2246. This antioxidant is equivalent to AO 2246. After the first experiment it was found that the extraction efficiency for antioxidants AO 4 and Ao 301 is very low and the following experiments were made with AO 2246 (NOCRAC 2246) and AO 4K. Some effects on extracton as, pH of water phase, influence of diluent, influence of concentration of antioxidants, extraction time, were studied. The best results gave antioxidant NOCRAC 2246 in nitrobenzene, the extraction efficiency was 92.3% with pH 13.23.     

Separation of benzene from alkanes by solvent extraction with 1-ethylpyridinium ethylsulfate ionic liquid

The (liquid + liquid) equilibrium (LLE) data for ternary mixtures {alkane + benzene + 1-ethylpyridinium ethylsulfate ([EPy][EtSO₄])} at T = (283.15 and 298.15) K and atmospheric pressure are presented. The alkanes used were hexane and heptane. The cloud point method was used to determinate the binodal curve, and the tie-line compositions were obtained by density measurements. The LLE data obtained were used to calculate distribution coefficients and selectivity values. The consistency of tie-line data was ascertained by applying the Othmer-Tobias and Hand equations. Correlation of the experimental tie-lines was conducted through the use of NRTL equation, which provides good correlation of the experimental data.The results show that [EPy][EtSO₄] can be used as an alternative solvent in liquid extraction processes for the removal of benzene from its mixtures with alkanes.     

Separation of rare earth elements from uranium by solvent extraction and ion exchange

The detection limit of⁹⁹Tc in (,) radio-activation analysis was determined in the presence of molybdenum and compared with that of⁹⁹Tc in pure materials in the previous paper. The isotopic ratio of molybdenum in a⁹⁹Mo–^99mTc generator column could be simultaneously determined by photon activation analysis.     

Rapid extraction of microamounts of protactinium from hydrochloric acid solutions by morin-isoamylol

A new extractant for protactinium has been studied. This paper describes the extraction behaviour of Pa from HCl system by morin-isoamylol. The whole procedure can be completed in 100 sec., yield of extraction is 99.2%.     

Solvent extraction of zirconium from hydrochloric acid solutions by sulphoxides and their mixtures

The solvent extraction of zirconium from HCl solutions by dipentyl sulphoxide (DPSO), dioctyl sulphoxide (DOSO), tributyl phosphate (TBP), and their mixtures in various solvents has been studied. At a given H⁺ strength, the extraction coefficient η of the metal increases with an increase in Cl⁻ activity whereas it is almost independent of H⁺ at constant Cl⁻. Under otherwise identical conditions, η increases with an increase in the extractant concentration but is virtually independent of the metal ion concentration over a wide range. The species extracted are ZrCl₄·DPSO, ZrCl₄·DOSO, and ZrCl₄·2TBP. In the case of mixtures, the slope of the log η−log M extractant plot for one component decreases with an increase in the concentration of the second component, the lines crossing at a common point. Extraction is favoured by solvents of low dielectric constant. It is possible to separate zirconium from thorium and uranium by solvent extraction with sulphoxides.     

The investigation of the solvent extraction of molybdenum from concentrated solution of sulphuric acid

The solvent extraction of molybdenum(VI) from sulphuric acid solutions with di-(2-ethylhexyl)-phosphoric acid (HDEHP) and monododecylphosphoric acid (HDDP) in n-heptane has been studied (a) as a function of the concentration of sulphuric acid, molybdenum and the extractant; (b) in the presence of copper and zinc in the aqueous phase and (c) in the presence of tri-n-butylphosphate (TBP) in the organic phase. The distribution of the sulphuric acid between aqueous and organic phase has also been studied.     

Separation of95Zr and95Nb from each other and from other fission products by adsorption and desorption on silica gel using hydrochloric acid solutions

The silica gel adsorption behaviour of zirconium, niobium, ruthenium and cerium in hydrochloric acid has been investigated by batch and column techniques. A satisfactory radiochemical separation of zirconium and niobium from each other and from other fission products has been achieved by a two column technique. The recommended procedure consists of sorption of all the nuclides on a primary silica gel column. Fifteen per cent of⁹⁵Nb, all of the zirconium and all of the other fission products are eluted first by washing with 5.5 M HCl. A second elution with concentrated hydrochloric acid then recovers the⁹⁵Nb (free from other products). The solution from the first elution after evaporation to 1 ml is then passed through another silica gel column and successively washed with 0.5M HCl, 5.5M HCl and concentrated HCl to obtain three fractions—other fission products—⁹⁵Zr free from other products—⁹⁵Nb free from other products, respectively.