An effective process for the separation of U(VI), Th(IV) from rare earth elements by using ionic liquid Cyphos IL 104

Separation and recovery of U(VI) and Th(IV) from rare earth minerals is a very challenging work in rare earth industrial production. In the present study, a homemade membrane emulsification circulation (MEC) extractor was used to separate U(VI) and Th(IV) from rare earth elements by using Cyphos IL 104 as an extractant. Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104 could reach the extraction equilibrium within 30 min for all the three elements, i.e., U(VI), Th(IV), and Eu(III). Besides, the MEC extractor possessed a strong phase separation ability. The extraction efficiencies of U(VI), Th(IV), La(III), Eu(III) and Yb (III) increased with the increase of pH. La(III), Eu(III) and Yb(III) were hardly extracted when pH ≤ 1.50, which was beneficial for effectively separating U(VI) and Th(IV) from La(III), Eu(III) and Yb(III). In the multi-stages stripping experiments, when the stripping stage number was 3, the effective separation could be achieved by using HCl and H₂SO₄, since the stripping efficiency reached 80.0% and 100.0% for Th(IV) and U(VI), respectively. Slope method and FT-IR spectra showed that Cyphos IL 104 reacted with U(VI) and Th(IV) by chelation mechanism. The extraction of multi-elements indicated that U(VI) and Th(IV) could be well separated from the solution which contains all rare earth elements, and the extraction efficiencies of U(VI) and Th(IV) both were close to 100.0%. Based on the above experimental results, a flowchart for efficient separation of U(VI) and Th(IV) from rare earth elements was proposed.     

Studies on the extraction behavior of Zr(IV), Ce(III), Th(IV) and U(VI) from aqueous solutions of Arsenazo-I with HDEHP,HTTA, TDA and TCMA

The extraction behavior of Zr(IV), Ce(III), Th(IV) and U(VI) from aqueous solutions containing Arsenazo-I with the organic solvents tridodecylamine (TDA), 1-[thenoyl-(2)]-3-3-3-trifluoroacetone (HTTA), di(2-ethylhexyl) phosphoric acid (HDEHP) and tricaprylmethylammonium chloride (TCMA) in xylene has been investigated. Effect of hydrogen ion concentration in the aqueous phase, Arsenazo-I concentration, as well as the effect of solvent concentration on the extraction was studied. Some alternatives for separation of the elements studied were recommended enabling the spectrophotometric determination of these elements using Arsenazo-I without interference.     

The effect of previous gamma-irradiation on the extraction of U(VI), Th(IV), Zr(IV), Eu(III) and Am(III) by various amides

The extraction behavior of U(VI), Th(IV), Zr(IV), Eu(III) and Am(III) from 3.5M nitric acid with a series of gamma-pre-irradiated symmetrical and unsymmetrical monoamides in benzene has been investigated up to a dose of 100 Mrad. The results indicated that the radiolytic stability is influenced by the structure of amides. Symmetrical monoamides seem to be less affected by radiation compared with unsymmetrical monoamides. Infrared studies identify the final products of radiolysis as the respective carboxylic acids and amines. The radiolytic degradation of the investigated monoamides has been estimated by quantitative IR spectroscopy. Extraction data obtained under similar experimental conditions for U(VI), Th(IV) and Zr(IV) with the TBP/benzene system have also been compared. This revised version was published online in August 2006 with corrections to the Cover Date.     

Carbonate extraction-based refining of uranium. Separation of U(VI), Ce(IV), and Ln(III) from aqueous carbonate solutions with methyltrioctylammonium carbonate

The extraction of U(VI), Ce(IV), La(III), Nd(III), Sm(III), and Y(III) from an aqueous solution of Na₂CO₃ (0.25 mol/L) resulting from oxidative dissolution of U(IV) in the presence of H₂O₂ into a solution of methyltrioctylammonium carbonate (0.25 mol/L) in toluene. It was found that β_{U(VI)/Ln(III)} values vary from ~8 to 3290 as the O : W ratio changes from 2 : 1 to 10 : 1, while β_U(VI)/Ce(IV) varies from ~1.5 to 10, which allows for the extraction separation of U(VI) from Ce(IV) in a 8- to 10-stage counter-current extraction cascade and from Ln(III) in 2- to 3-stage cascade under the same conditions.     

Solvent extraction of lanthanum(III), europium(III) and lutetium(III) with fluorinated 1-phenyl-3-methyl-4-benzoyl-5-pyrazolones into chloroform

A series of chelating reagents, 1-phenyl-3-methyl-4-(2-fluorobenzoyl)-5-pyrazolone, 1-phenyl-3-methyl-4-(3-fluorobenzoyl)-5-pyrazolone and 1-phenyl-3-methyl-4-(4-fluorobenzoyl)-5-pyrazolone, has been synthesized. The extraction of Ln(III), (Ln = La, Eu and Lu) into chloroform with these reagents at 30 +/- 1 degrees has been studied. The composition of the complexes extracted has been determined by the slope method, and the extraction constants K(ex), were measured. The presence of the fluorine atom in the reagents does not make the K(ex), values much different from those obtained with the parent pyrazolone.     

Studies on the liquid-liquid extraction of iron(III) and titanium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone

The extraction behaviour of iron(III) and titanium(IV) from acidic chloride solutions has been investigated using 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in xylene as an extractant. The results demonstrate that these metal ions are extracted into xylene as Fe(PBI)(3) and TiO(PBI)(2). The equilibrium constants of the extracted complexes have been deduced by non-linear regression analysis by taking into account complexation of metal ion with inorganic ligands in the aqueous phase and all plausible complexes extracted into the organic phase. IR and proton NMR ((1)H NMR) spectra were used to further clarify the nature of complexes extracted into organic phase. The effect of the nature of the diluent on the extraction of iron(III) and titanium(IV) has been studied and correlated with dielectric constants. The extraction behaviour of titanium(IV) has also been compared with that of other metal ions, viz. magnesium(II), vanadium(V), chromium(VI), iron(III), manganese(II), zinc(II) and zirconium(IV), which are associated with the titanium in waste chloride liquors of the titanium-mineral-processing industry.     

The synergistic extraction of thorium(IV) and uranium(VI) with mixtures of 3-phenyl-4-benzoyl-5-isoxazolone and crown ethers

The extraction of thorium(IV) and uranium(VI) from nitric acid solutions has been studied using mixtures of 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) and dicyclohexano-18-crown-6, benzo-18-crown-6, dibenzo-18-crown-6 or benzo-15-crown-5. The results demonstrate that these metal ions are extracted into chloroform as Th(PBI)(4) and UO(2)(PBI)(2) with HPBI alone and as Th(PBI)(4) . CE and UO(2)(PBI)(2) . CE in the presence of crown ethers (CE). The equilibrium constants of the above species have been deduced by non-linear regression analysis. The addition of a CE to the metal chelate system enhances the extraction efficiency and also improves the selectivities between thorium and uranium. IR spectral data of the extracted complexes were used to further clarify the nature of the complexes. The binding to the CEs by Th(PBI)(4) and UO(2)(PBI)(2) follows the CE basicity sequence but with DC18C6 and DB18C6, steric effects become more important.     

Sorption behaviour of lanthanum(III), neodymium(III), terbium(III), thorium(IV) and uranium(VI) on Amberlite XAD-4 resin functionalized with bicine ligands

The complexing properties (capacity, pH effect, breakthrough curve) of a chelating resin, containing bicine ligands, were investigated for La(III), Nd(III), Tb(III), Th(IV) and U(VI). Trace amounts of these metal ions were quantitatively retained on the resin and recovered by eluting with 1 M hydrochloric acid. The capacity of the resin for La(III), Nd(III), Tb(III), Th(IV) and U(VI) was found to be 0.35, 0.40, 0.42, 0.25 and 0.38 mmol g(-1), respectively. Separation of U(VI) and Th(IV) from Ni(II), Zn(II), Co(II) and Cu(II) in a synthetic solution was carried out.     

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 beta-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 pK(a) of the beta-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 (234)Th radiotracer from natural uranium (99.3% (238)U) has been suggested.     

Mixed-ligand chelate extraction of trivalent lanthanides and actinides with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 and dihexyl-N,N-diethylcarbamoylmethyl phosphonate

Mixed-ligand chelate extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am into xylene with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and dihexyl-N,N-diethylcarbamoylmethylphosphonate (CMP) has been studied by tracertechniques. These trivalent metal ions are found to be extracted from 0.01 mol/dm³ chloroacetate buffer solutions as M(PMBP)₃·HPMBP type self adducts with HPMBP alone and in the presence of CMP as M(PMBP)₃·CMP (where M=La, Eu, Lu and Am) into the organic phase. The equilibrium constants of the above species are deduced by non-linear regression analysis. The synergistic constants of trivalent lanthanides do not increase monotonically with atomic number but have a maximum at Eu and that of Am was found to lie between that of La and Eu.     

Extraction of Th(IV), La(III), and Y(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate

Extraction of Th(IV), La(III), and Y(III) from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylmethylammonium nitrate (Aliquat-336) was studied. The extraction isotherms were analyzed assuming that lanthanides and thorium are extracted with the solid extractant in the form of complexes (R₄N)₂[Ln(NO₃)₅] and (R₄N)₂[Th(NO₃)₆], respectively. The extraction constants were calculated. The joint extraction of Th(IV) and La(III) [Y(III)] with the solid extractant from aqueous salt solutions was studied.     

Extraction of thorium(IV), lantanum(III), and yttrium(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylamine

Extraction of Th(IV), La(III), and Y(III) from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylamine (Alamine-336) was studied. The extraction isotherms were analyzed assuming that lanthanides and thorium are extracted with the solid extractant in the form of complexes (R₃HN)₃[Ln(NO₃)₅] and (R₃HN)₂[Th(NO₃)₆], respectively. The extraction constants were calculated. The joint extraction of Th(IV) and La(III) [Y(III)] with the solid extractant from aqueous salt solutions was studied.     

Ion exchange separation of Eu(III), Th(IV), U(VI) and Pu(IV) ions on Amberlyst A-15 in non-aqueous solutions

Distribution ratios of europium(III), thorium(IV), uranium(VI) and plutonium(IV) ions on Amberlyst A-15, a macroreticular polystyrene sulfonate resin, after extraction in HTTA-TBP-Shell Sol-T and HTTA-TOPO-benzene solutions have been determined as a function of the aqueous acidity. The affinity orders were EuPu>Th>U and Eu>Th>Pu>U in the former and the latter solutions, respectively. Separation factors were computed from the observed K_d values. A procedure for the separation of a mixture of Eu(III), Th(IV), and U(VI) ions in HTTA-TOPO-benzene solution in an ion-exchange column is described.     

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.     

Synergistic extraction of lanthanum(III) from chloride medium by mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 and triisobutylphosphine sulphide

The synergistic effect of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP) and triisobutylphosphine sulphide (TIBPS, B) is investigated in the extraction of lanthanum(III) from chloride solution. Lanthanum(III) is extracted by the mixture as LaCl₂·PMBP·B_0.5 instead of La(PMBP)₃·(HPMBP) which is extracted by HPMBP alone. The equilibrium constants and thermodynamic functions such as ΔG, ΔH and ΔS are determined. The extraction of other rare earth ions by mixtures of HPMBP and TIBPS is also studied and the possibility of separating rare earth ions is discussed.     

Aqueous complexation of thorium(IV), uranium(IV), neptunium(IV), plutonium(III/IV), and cerium(III/IV) with DTPA

Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log β(101) = 20.01 ± 0.02, log β(111) = 22.0 ± 0.2, and log β(101) = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log β(101) = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log β(101) = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal.     

Synergistic extraction of Ce(III), Eu(III) and Tm(III) with a mixture of picrolonic acid and benzo-15-crown-5 in chloroform

Summary The synergistic mixture comprising picrolonic acid (HPA) and benzo-15-crown-5 (B15C5) in chloroform has been used for the extraction of Ce(III), Eu(III) and Tm(III) as representatives of lanthanide(III) ions from pH 1-2 solutions having ionic strength of 0.1 mol^. dm^-3(K⁺/H⁺, Cl^-). The composition of the extracted species has been determined as M(PA)₃^. nB15C5 where M is Ce, Eu and Tm and n=1 or 2. The influence of various anions and cations on the extraction of these ions has also been studied and only oxalate, cyanide and tartrate have some deleterious effect. The extraction equilibrium constants have been evaluated and discussed.     

铀的三元协萃规律研究-HTTA-HPMBA-(C8H5)4AsCl三元协萃高氯酸铀酰的机理

本文研究α-噻吩甲酰三氟丙酮(HTTA),1-苯基-3-甲基-4-苯甲酰基-5吡唑啉酮(HPMBP)与四苯基砷氯(C5H5)4AsCl的氯仿溶液从高氯酸中萃取U(VI).该体系属螯合,离子缔合AAC类,测定了其二元及三元协同萃取体系平衡常数.用亚甲基蓝光度法测定了萃合物中ClO4^-的存在,用斜率法确定二元协萃物组成为(C6H5)4As^+[UO2(ClO4)(TTA)2]^-和C6H5)4As^+[UO2(ClO4)(PMBP)2]^-三元协萃配合物为(C6H5)4As^+[UO2(ClO4)(TTA)(PMBP)]^-.     

Sorption study of U(VI), Th(IV) and Ce(III) on poly[dibenzo-18-crown-6] in <Emphasis Type="SmallCaps">l</Emphasis>-arginine to develop sequential column chromatographic separation method

A simple and efficient column chromatographic method has been developed for the sequential separation of U(VI), Th(IV) and Ce(III) using poly[dibenzo-18-crown-6] as stationary phase and l-arginine as a counter ion. The different elution patterns with various eluting agents were observed for individual element. The capacity of poly[dibenzo-18-crown-6] for U(VI), Th(IV) and for Ce(III) was found to be 0.96, 0.86 and 1.49 (±0.01) mmol/g of crown polymer, respectively. The method is efficient to separate the elements in multicomponent mixtures and has good recovery. The method is extended to determine the U(VI), Th(IV) and Ce(III) from monazite sand. The method is simple, rapid and selective having good reproducibility (~±2%).