N-oxides of 4-(5-nonyl)pyridine and trioctylamine as extractants for cerium(IV) and its separation from thorium(IV)

Trace level cerium has been oxidized to the quadrivalent state with potassium dichromate and shown to be preferentially extracted from very dilute mineral acid solutions and also from moderate nitric acid media by 0.1M solutions of 4-(5-nonyl)pyridine oxide and trioctylamine oxide dissolved in xylene. The dependence of extraction on the type of N-oxide, acid concentration and the N-oxide concentration has been investigated. The influence of the concentration of salting-out agents is described. Separation factors for a number of metal ions relative to cerium(IV) are reported for 0.1 M 4-(5-nonyl)pyridine oxide/xylene-0.1M sulphuric acid system. The ratio of the D for Ce(IV) to that of Ce(III) is greater than 10⁵, and the D for Ce(IV) is much greater than that for thorium(IV). Separation of cerium(IV) from thorium has been achieved from 0.1M sulphuric acid solutions using 0.1M 4-(5-nonyl)pyridine oxide/xylene as an extractant.     

The extraction of trace amounts of tantalum(V) from different mineral acid solutions by 4-(5-nonyl)pyridine oxide and trioctylamine oxide

Data are presented on the distribution of trace amounts of tantalum (V) between different mineral acid solutions and 0.1M solutions of N-oxides of 4-(5-nonyl)pyridine and trioctylamine. The optimal acidity is 0.01–0.5M, depending on the nature of the acid. Common anions have little effect on extraction. Possible mechanisms of extraction are suggested making use of slope analysis data. Separation factors for a number of metal ions with respect to tantalum are reported for the 0.1M 4-(5-nonyl)pyridine oxide—1M sulphuric acid extraction system. Separation from uranium(VI), thorium(IV) and a number of fission products is suggested. where a part of the work was done.     

Liquid-liquid extraction of zinc from aqueous thiocyanate solutions with 5-(-4-pyridyl)nonane in benzene

5-(4-Pyridyl)nonane dissolved in benzene has been applied to the extraction of zinc, down to very low concentration (< 10(-6)M), from aqueous thiocyanate solutions. The metal can be quantitatively extracted from neutral and acidic thiocyanate solutions (up to 5M HCl, 0.25M HNO(3) or 0.25M H(2)SO(4)) in a single extraction. Equilibration times of 5 min are sufficient for almost complete extraction. The optimum thiocyanate concentration range is 0.05-0.5M. Among the common anions chloride exerts a slight depressing effect on extraction from neutral solution when present in high concentration. The extraction mechanism and the composition of the extracted complexes of zinc are discussed. The metal is predominantly extracted by means of a solvate mechanism. The effect of chloride, nitrate, sulphate, acetate, citrate, oxalate and ascorbate ions on the extraction of zinc is described. Several elements, including those of interest in separation of zinc, have been tested for extraction from O.1M KSCN at the optimal concentrations of the mineral acids, and the separation factors estimated.     

Solvation of thiocyanate complexes of tungsten(VI) by 5-(4-pyridyl) nonane from aqueous hydrochloric acid solutions

5-(4-Pyridyl)nonane has been evaluated as a solvent for trace amounts (<5·10^–5 M) of tungsten(VI) from aqueous chloride-thiocyanate solutions. Remarkable enhancements in metal extractability are observed on the addition of SCN^– to aqueous hydrochloric acid solutions. Extremal partition coefficients are obtained from 0.1 M HCl in 0.2 M KSCN. Diminutions of the metal extractability are produced by relatively high (>0.5 M) SCN^– concentrations and increased concentration of the supporting acid. Slope analysis data, under optimal parameters, indicates the most probable composition of the extractable species as WO₂(SCN)₂·2P_YN. Neutral anions do not have any significant effect on the D values. Behaviour of a number of metal ions has been checked using optimal aqueous conditions of extraction. The investigation shows that the reagent has a great potential for the preconcentration of a number of metal ions including the common toxins.     

The extraction of chromium(VI) from sulphuric acid solutions by 4-(5-nonyl)pyridine and its separation from fission products

4-(5-Nonyl)pyridine, a new liquid anion exchanger, has been studied for the extraction of chromium(VI) from sulphuric acid solutions. The optimal acidity is 0.1–1 M, depending on the concentration of chromium. Common anions have little effect on extraction in concentrations up to 0.1 M. Reducing agents such as ascorbic acid and thiosulphate prevent extraction at concentrations above 0.1 M. Separation of chromium(VI) from fission products was achieved.     

The use of 5-(4-pyridyl)nonane for the separation of chromium(vi) from fission products in hydrochloric acid media

The distribution of chromium(VI) between 5-(4-pyridyl)nonane in benzene and hydrochloric acid media has been studied as a function of the concentration of the acid, extractant, chromium(VI), chloride and a few other ions. The extraction mechanism and the composition of the extracted complexes of Cr(VI) have been proposed. The separation of Cr(VI) from uranium, thorium and fission products in 3M hydrochloric acid has been achieved.     

Development of selective separation method for thorium and rare earth elements from monazite liquor

The present work succeeded to develop new optional procedures to enhance the separation process of thorium and REEs. Selective precipitation of thorium with pyrophosphate was successfully attained for the upscale level in which, complete and efficient thorium separation (99%) was achieved with relatively low co-precipitation of REEs (average 15%) and Fe(III) (2.6%). On the other hand, promising and costless method has been developed to optimize the selective precipitation of REEs by adjusting the ratio of the free acids H₂SO₄ to H₃PO₄ at 5:1. It could be obviously demonstrated that about 65.3% of LREEs could be precipitated with a minor amount of thorium 11.9%. Finally, this proposed method could be successfully applied for production of Th and REEs with relatively high yield and purity in addition to low-cost–benefit.     

Extraction of mercury(II) from aqueous thiocyanate solutions with 5-(4-pyridyl)nonane in benzene, and its subsequent atomic-absorption spectrometric determination

Tracer ( approximately 10(-8)M) mercury(II) can be quantitatively extracted with 5-(4-pyridyl)nonane in benzene from aqueous thiocyanate solutions that are up to 6M in HCl, 1M in H(2)SO(4) or 0.25M in HNO(3), in a single extraction. Optimal conditions for the extraction are given, based on a critical study of the relevant factors such as the effects of the acids, thiocyanate, salting-out and complexing agents and the reagent concentration. The mechanism underlying these extractions is discussed on the basis of the results obtained from partition and slope-analysis data. The extraction of the metal as Hg(PyN)(2)(SCN)(2) is indicated. The extracted mercury can be stripped from the non-aqueous layer with various aqueous solutions, including nitric acid (2M), sodium citrate ( 1M) and sodium thiosulphate (0.1 M). Common salts do not depress the extraction. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain the optimal concentrations of the mineral acids and are in 0.2M in potassium thiocyanate. The data have been applied for the determination of mercury in soil and water samples by atomic-absorption spectrometry.     

Influence of rare earth elements on extraction of actinium with di-(2-ethylhexyl)phosphoric acid from inorganic acid solutions

The extraction of actinium by HDEHP solutions in n-heptane as a function of mineral acids and some lanthanides (Ln) in the aqueous phase has been studied. It was found that the actinium extraction coefficient in the absence of Ln decreased linearly with acid concentration with the slope of –3 in the whole investigated range of its concentration. In the presence of Ln the extraction coefficient decreased with a smaller slope than in the absence of Ln. This slope decreased with the Ln salt concentration. The extraction coefficient of Ac decreased with a slope of –3 at acid concentrations above 0.1N, regardless of the Ln concentration in the extraction system.     

Tc-Mo extraction by tetraphenyl arsonium from different mineral acid solutions

The extraction of SbI₃ by various organic solvents has been investigated as a function of H₂SO₄, KI and organic additive concentrations. At [Sb³⁺]: [I⁻]≈3, extraction increases in the order hexane → cyclohexane → kerosene → CCl₄→CHCl₃ → benzene → toluene → o-xylene → nitrobenzene.     

4-(5-nonyl)pyridine extraction of platinum from different aqueous solutions

The partition of tracer-level (<10^?7 mole/l) platinum between various 4-(5-nonyl)-pyridine phases and aqueous nitric, hydrochloric, and sulphuric acid phases has been studied radiometrically as a function of the amine and acid concentrations. The effects of saltingout agents and some anions on the extraction of the metal are reported. The extraction data is compared with that of gold and conditions are established for the separation of daughter¹⁹⁹Au from neutron irradiated platinum. The distribution coefficients of various metal ions are given for the 4-(5-nonyl)pyridine-10M HCl system and their factors for separation from platinum estimated.     

Extraction of rare earth elements by high molecular weight amines from nitric acid solutions

Extraction of trivalent rare earth elements by a high molecular weight primary amine /decylamine/ from 0.5–3M nitric acid solutions, containing potassium phosphotungstate /K₁₀P₂W₁₇O₆₁/, has been investigated. The effect of nitric acid and potassium phosphotungstate concentration of the organic solvent, and lanthanides ionic radii upon distribution coefficients has been studied. It has been established that decylamine solutions in chloroform can be used for the group isolation of rare earth elements and for their separation.     

Cation-exchange studies of yttrium(III) and its separation from various other elements

Summary Systematic studies are presented on the cation-exchange behaviour of yttrium on Dowex 50W-X8. HCl, HNO₃, H₂SO₄, NH₄Cl, NH₄NO₃, (NH₄)₂SO₄, CH₃COONH₄, NaCl, NaNO₃, malonic acid, tartaric acid and EDTA were used as eluting agents. Y was separated from a large variety of elements by selective elution or selective adsorption. Thus it was possible to separate it from many common ions such as alkalis, alkaline earths, Bi, Hg, V, Cd, U, In, Co, Ga, Zn, Sc, Fe, Al, Ni, and Ce by selective elution. It was separated from Ti, Zr, Hf, and Sb by selective sorption in citrate media and from Cr, Tl, Pb, and Th by gradient elution.     

Extraction of rare earth elements by primary high molecular weight amines from hydrochloric acid solutions

Extraction of trivalent lanthanides: La, Ce, Nd, Eu, Tb, Tm, Yb by primary high molecular weight amines from 0.5–3M hydrochloric acid solutions, containing complex-forming agent potassium phosphotungstate /K₁₀P₂W₁₇O₆₁/ has been investigated. The effect of hydrochloric acid, potassium phosphotungstate and amine concentration, the length of primary amine alkyl chain, organic solvents nature and elements ionic radii on distribution coefficients have been studied. It has been established that the system can be used for group isolation and separation of rare earth elements.     

Search for optimal conditions for the extraction of thiosulfate complexes of Cu(II) by 4-(5-nonyl)pyridine from aqueous mineral acid solutions

Solvent extraction of Cu(II) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiosulfate ions has been studied at room temperature (23±2°C). Mineral acid solutions alone constitute an aqueous phase from which Cu(II) is not extracted. Addition of small amounts of thiosulfate ions augments the extraction to an extent that quantitative recovery is possible. Stoichiometric studies reveal the involvement of ion-pair type complexes (NPy·H)₂·Cu(S₂O₃)₂ which are responsible for extraction. Stability constants lg K_ex for this complex are 7.2±0.2; 9.1±0.2 and 9.5±0.2 for HCl, HNO₃ and H₂SO₄, respectively. The presence of 0.01 mol/l of some complexing ions like ascorbate, acetate, citrate, oxalate, tartrate or iodide does not affect the extraction, thus allowing the recovery of the metal from diverse matrices. Under optimal conditions (0.1M NPy in benzene-0.1M HNO₃ or H₂SO₄+0.01M S₂O ₃ ^?2 or 0.5M HCl+0.05 M S₂O ₃ ^?2 ) a clean separation from some elements, e.g. Cs(I). Co(II), Fe(III), Eu(III), Ce(III), Se(IV) and Cr(VI) can be achieved.     

Determination of total rare earth elements,thorium and chromium with 2-(2-arsenophenylazo)-1,8-dihydroxy-7-(2,6-dibromo-4-fluorophenylazo) naphthalene-3,6-disulphonic acid by reversed-phase ion-pair liquid chromatography

The retention behaviour of the complexes of rare earth elements, thorium and chromium with 2-(2- arsenophenylazo)-1,8-dihydroxy-7-(2,6-dibromo-4-fluorophenylazo)naphthalene-3,6-disulphonic acid was studied. Precolumn derivatization was used. The stationary phase was ODS-bonded silica and the mobile phase was methanol-water-tetrabutylammonium bromide. The detection limits are 2 ng ml^?1 for total rare earths, 2.5 ng ml^?1 for thorium and 10 ng ml^?1 for chromium. The tolerance of foreign ions is very high. The method can be applied satisfactorily to ore samples and rocks.     

4-(5-Nonyl)pyridine as an extractant for cobalt thiocyanate complexes from mineral acid solutions

The partition behaviour of cobalt into 4-(5-nonyl)pyridine (NPy) in benzene from aqueous hydrochloric, nitric and sulfuric acid media containing variable amounts of potassium thiocyanate is described. Cobalt is quantitatively extracted by NPy from 0.1–1M KSCN solutions at 0.01 M concentration of the mineral acids. The extraction mechanism and the possible compositions of the extracted species are discussed. The effects of foreign salts on the extraction of cobalt from three mineral acid solutions are reported. Several elements including those which are of some interest in connection with the separation of cobalt were tested for extraction from 0.01 M solutions of mineral acids 0.3 M with respect to KSCN and their factors for separation from cobalt were estimated.     

Solvent extraction of technetium(VII) by 4-(5-nonyl)pyridine and its separation from uranium and some fission products

The extraction of technetium (VII) by 4-(5-nonyl)pyridine has been investigated from different aqueous solutions. Separation from uranium and some fission products has been achieved in nitrate media. From the results of partition experiments, attempts have been made to deduce the nature of the extracted species.     

Thin-layer chromatographic separation of scandium, yttrium, the rare earths, thorium and uraniuin(VI)

The Chromatographic behaviour of scandium, yttrium, the rare earths, thorium and uranium(VI) in dioxan-hydrochloric acid and dioxan-nitric acid media on a plain cellulose thin layer has been investigated. The following separations are possible: scandium-yttrium-lanthanum, scandium-samarium-thorium, scandium-lanthanum-lutetium, yttrium-lanthanum-thorium, and lutetium-thorium-uranium(VI) with dioxan-12M hydrochloric acid (7:3) and scandium-samarium-thorium, scandium-yttrium-uranium(VI), lutetium-thorium, and scandium-lanthanum-thorium with dioxan-14M nitric acid (7:3). A single chromogenic spray (Arsenazo III) has been used for the detection of all the metal ions studied.     

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.