Extraction of lanthanide nitrates with trioctylmethylammonium di(2,4,4-trimethylpentyl)phosphinate

A binary extractant based on trioctylmethylammonium di(2,4,4-trimethylpentyl)phosphinate R₄NA was prepared. The extraction of lanthanide (Gd-Lu) nitrates from aqueous solutions with 0.6 M toluene solutions of R₄NA and trioctylmethylammonium nitrate was studied. The extraction isotherms of lanthanide nitrates with these extractants were obtained and physicochemical and mathematical models of extraction of lanthanides were developed. The extraction isotherms with the binary extractant were analyzed assuming that the Ln(III) extractable complexes LnA₃, (R₄N)₂[Ln(NO₃)₅], (R₄N)₃[Ln(NO₃)₆], (R₄N)₂[Ln(NO₃)₃A₂], and (R₄N)[Ln(NO₃)₃A] [A is di(2,4,4-trimethylpentyl)phosphinate anion] are formed in the organic phase. The extraction constants were calculated.     

Extraction of Lanthanide(III) and Y(III) Nitrates with Trialkylbenzylammonium Nitrate in Toluene

Extraction of lanthanides(III) [La(III)-Lu(III), including also yttrium(III)] from their aqueous solutions with 0.55 M toluene solution of trialkylbenzylammonium nitrate (TABAN) was studied at 298 K. The extraction isotherms were analyzed assuming formation the following extractable complexes: (R₄N)₃·[Ln(NO₃)₆] and (R₄N)[Ln(NO₃N))₇N)] for La(III) and Ce(III), (R₄N)₂[Ln(NO₃)₅] and (R₄N)₃[Ln(NO₃)₆] for Pr(III)-Gd(III), and (R₄N)N)₂N)[Ln(NO₃N))₅N)] for Tb(III)-Lu(III) and Y(III). The extraction constants of Y(III) and Yb(III) are close. The TABAN concentration in the organic phase does not noticeably influence the composition of the extractable complexes and the extraction constants.     

Mutual Influence of Lanthanides(III) in Their Joint Extraction from Aqueous Multicomponent Solutions with a Toluene Solution of Trialkylbenzylammonium Naphthenate

Extraction of lanthanides(III) [Sm(III)-Lu(III), including also yttrium(III)] from their aqueous multicomponent solutions with a toluene solution of trialkylbenzylammonium naphthenate was studied at 298 K and pH 3. Physicochemical and mathematical models describing distribution and mutual influence of lanthanides(III) [Ln(III)] in their joint extraction from multicomponent aqueous solutions were developed. Distribution of Ln(III) was studied as a function of the total concentration and composition of Ln(III) mixture in the aqueous phase taking into account that the Ln(III) extractable complexes (R₄N)₂[Ln(NO₃)₃A₂] (A is naphthenate anion) are formed in the organic phase.     

Extraction of REE(III) Nitrates with Polymer-Supported Tributyl Phosphate

Extraction of La, Ce, Pr, Nd, Sm, and Y(III) nitrates with polymer-supported TBP in the presence of 1-5 M NaNO₃ in the aqueous phase is studied. The extraction isotherms are described taking into account formation of [Ln(NO₃)₃(TBP) _j ](o) (j = 3, 4) in the extractant phase. The extraction constants corrected for the TBP concentration in the extractant phase are considerably higher than in the cases of extraction with neat TBP or TBP supported on a porous material (Teflon).     

Extraction of Lanthanide(III) Nitrates from Aqueous Solutions with Mixtures n-Octanol-Decane, Tri-n-butyl Phosphate-n-Octanol, and Diisoamyl Methylphosphonate-n-Octanol

Extraction of lanthanide(III) (La-Eu) nitrates from aqueous solutions with 3.15 M solution of octanol (ROH) in n-decane (extractant 1), 2.02 M solution of diisoamyl methylphosphonate (S = DIAMP) in n-octanol (extractant 2), and 1.83 M solution of tri-n-butyl phosphate (S = TBP) in n-octanol (extractant 3) was studied at T = 298.15 K. The extraction of lanthanide(III) nitrates with extractant 1 at C(aq) > 0.6 M is described by the equation of the heterogeneous reaction Ln³⁺(aq) + 3NO ₃ ⁻ (aq) + 4ROH(o) = [Ln(NO₃)₃ ⋅ (ROH)₄](o). The extraction of Ln(III) nitrates with extractants 2 and 3 involves the reaction described above in combination with the heterogeneous reaction Ln³⁺(aq) + 3NO ₃ ⁻ (aq) + 3S(o) = [Ln(NO₃)₃(S)₃](o) and the homogeneous reaction ROH(o) + S(o) = [ROH ⋅ S](o), where S is DIAMP or TBP. The electronic absorption and IR spectra of Nd(III) and Pr(III) nitrates in n-octanol and n-octanol-TBP mixtures were analyzed.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 245–251.Original Russian Text Copyright © 2005 by Kudrova, Keskinov, Pyartman.     

Phase equilibria at various temperatures in ternary liquid systems consisting of thorium(IV) and lanthanide(III) nitrate solvates with tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate and of isooctane

The phase diagrams of ternary liquid systems (TLSs) [Th(NO₃)₄(TBP)₂]-[Ln(NO₃)₃(TBP)₃] (Ln = Nd, Gd, Ho; TBP = tri-n-butyl phosphate)-isooctane at 298.15–333.15 K were studied. The TLSs are characterized by the fields of homogeneous solutions and of two-phase liquid systems (systems with phase separation) in which one of the phases (I) is enriched in [Th(NO₃)₄(TBP)₂] and [Ln(NO₃)₃(TBP)₃], and the other phase (II), in isooctane. The temperature (298.15–333.15 K) does not noticeably affect the mutual solubility of [Th(NO₃)₄(TBP)₂] and isooctane but decreases the field of phase separation in ternary systems. In two-phase systems, [Ln(NO₃)₃(TBP)₃] is predominantly distributed into phase I, despite the fact that binary systems [Ln(NO₃)₃(TBP)₃]-isooctane are single-phase at all the examined temperatures. The distribution of [Ln(NO₃)₃(TBP)₃] into phase I results in the redistribution of [Th(NO₃)₄(TBP)₂] into phase II and of isooctane into phase I. The critical composition points of the TLSs at various temperatures were determined; they depend on particular lanthanide(III).     

Extraction of uranyl,La(III), and Y(III) nitrates with a composite solid extractant based on a polymeric support impregnated with trialkylamine

Extraction of uranyl, La(III), and Y(III) nitrates from aqueous solutions containing 0–4 M sodium nitrate with a composite solid extractant based on a polymeric support impregnated with trialkylamine (C₇-C₉) was studied. The extraction isotherms were analyzed assuming that La(III), Y(III), and uranyl nitrates are extracted with the solid extractant in the form of complexes (R₃NH)₃[Ln(NO₃)₆] and (R₃NH)₂[UO₂(NO₃)₄], respectively. The extraction constants were calculated. The joint extraction of uranyl and La(III) [Y(III)] nitrates with the solid extractant from aqueous salt solutions was studied. The composite solid extractant based on a polymeric support impregnated with trialkylamine can be used for purification of aqueous solutions of rare-earth metal nitrates to remove uranium impurities.     

Phase Separation in Ternary Liquid Systems Tetradecane-n-Octanol (or Cyclohexanone)-Lanthanide(III) Nitrate Solvates with Tri-n-Butyl Phosphate

The phase diagrams of ternary liquid systems tetradecane-n-octanol (or cyclohexanone)-lanthanide(III) nitrate solvates with tri-n-butyl phosphate [Ln(NO₃)₃(TBP)₃, Ln = La, Ce, Pr, or Sm] at T = 298.15 K were studied. These diagrams contain areas of homogeneous solutions and an area of separation into two liquid phases (I, II). Phases I and II are enriched in tetradecane and Ln(NO₃)₃(TBP)₃, respectively. n-Octanol and cyclohexanone mainly pass into phase II.     

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

Extraction of uranyl, La(III), and Y(III) nitrates 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 uranyl, La(III), and Y(III) nitrates are extracted with the solid extractant in the form of complexes (R₄N)₂[Ln(NO₃)₅] and (R₄N)₂[UO₂(NO₃)₄], respectively. The calculated extraction constants decrease in the order La³⁺ > UO ₂ ²⁺ > Y³⁺. The joint extraction of uranyl, La(III), and Y(III) nitrates with the solid extractant from aqueous salt solutions was studied. The La/U separation factor increases with increasing total concentration of uranyl and La(III) nitrates in aqueous phase. Original Russian Text A.K. Pyartman, V.A. Keskinov, V.V. Lishchuk, A.V. Konstantinova, V.V. Belova. 2007, published in Radiokhimiya, 2007, Vol. 49, No. 3, pp. 237–240.     

Influence of Temperature on the Mutual Solubility of Components in the Binary Systems Tetradecane—Rare-Earth Metal (Nd,Sm, Gd,Y, Lu) Nitrate Solvate with TBP

The phase diagrams of binary liquid systems tetradecane—rare-earth metal (Nd, Sm, Gd, Y, Lu) nitrate solvate with TBP were studied in the temperature range 273.15–373.15 K. These diagrams contain the fields of homogeneous solutions and the field of separation into two liquid phases (I, II). Phases I and II are enriched, respectively, in tetradecane and Ln(NO₃)₃(TBP)₃ (Ln = Nd, Sm, Gd, Y, and Lu). With increasing temperature, the fields of separation into two liquid phases contract. The upper critical solution temperatures are dependent on the kind of rare-earth metal(III).     

Extraction of REE(III) Nitrates with Polymer-Supported Trialkylmethylammonium Nitrate

Extraction of La, Ce, Pr, Nd, Sm, and Y(III) nitrates with polymer-supported trialkylmethylammonium nitrate (Aliquat-336) in the presence 1-5 M NaNO₃ in the aqueous phase is studied. The extraction isotherms are described taking into account formation of (R₄N)₂[Ln(NO₃)₅] in the extractant phase. The extraction constants decrease from La to Sm. The extraction constant of Y(III) is considerably lower than those of La(III)-Sm(III).     

Extraction of Lanthanide(III) and Yttrium(III) Nitrates with a Toluene Solution of Trialkylbenzylammonium Salts of Higher α,α'-Branched Carboxylic Acids

Extraction of lanthanide(III) [La(III)-Lu(III), including also yttrium(III)] nitrates with a toluene solution of trialkylbenzylamonium salts of higher ,'-branched carboxylic acids (A) was studied at 298 K. The extraction isotherms were described taking into account that the Ln(III) extractable complexes (R₄N)₂[Ln(NO₃)₃A₂] and (R₄N)₃[Ln(NO₃)₃A₃] (A is carboxylate anion) are formed in the organic phase. The extraction constants decrease in going from La(Ce)(III) to Lu(III). The extraction constant of Y(III) is less than that of La(III)-Lu(III). The IR spectra of extractable complexes were studied.     

Extraction of REE(III) Nitrates with Polymer-Supported Trialkylamine

Extraction of HNO₃ and La, Ce, Pr, Nd, and Sm nitrates with polymer-supported trialkylamine C₇-C₉ from 0.5 M HNO₃ containing 1-5 M NaNO₃ is studied. The extraction isotherms are described taking into account formation of (R₃NH)₃[Ln(NO₃)₆] in the extractant phase. The extraction constants decrease in the series La(III)-Sm(III).     

Linear alkylbenzene (LAB) as diluent for extractants. Extraction of rare-earth elements with solutions of neutral organophosphorus compounds in LAB

Extraction of REE with solutions of neutral organophosphorus compounds (TBP, TIAP, DIOMP) in a new diluent, linear alkylbenzene (LAB), was studied. LAB exhibits significant advantages over known diluents: high flash point (+147°C), nontoxicity, absence of odor, low cost, availability, and good compatibility with polymeric structural materials. LAB is well compatible with TBP, TIAP, and DIOMP. Extraction of HNO₃ and REE nitrates is not accompanied by precipitation of extractable complexes or by formation of a second organic phase in a wide concentration range, up to saturation of the extractant. The major extractable complex in extraction of REE nitrates is Ln(NO₃)₃·3NOPC, where NOPC = TBP, TIAP. The main parameters of extraction systems (distribution ratios, separation factors) with LAB are similar to those of the related systems with paraffin hydrocarbons as diluents. Experiments on group separation of REEs on a 56-step extraction installation gave results agreeing with the calculation data.     

Influence of temperature on phase separation in the binary system tetradecane-Nd(III) nitrate solvate with tri-n-butyl phosphate and ternary system tetradecane-tri-n-butyl phosphate-Nd(III) nitrate solvate with tri-n-butyl phosphate

The phase diagrams of the liquid binary system tetradecane-Nd(III) nitrate solvate with tri-n-butyl phosphate [Nd(NO₃)₃ (TBP)₃] and ternary liquid system tetradecane-tri-n-butyl phosphate-Nd(III) nitrate solvate with tri-n-butyl phosphate were studied in the temperature range 298.15–344.85 K. The phase diagrams of the binary and ternary systems contain an area of homogeneous solutions and an area of separation into two liquid phases (I, II). Phases I and II are enriched in tetradecane and Nd(NO₃)₃ (TBP)₃, respectively. With increasing temperature, the areas of separation into two liquid phases in the binary and ternary systems contract. The compositions of the binary and ternary systems in the critical points at different temperatures and their upper critical solution temperatures were determined.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 433–435.Original Russian Text Copyright © 2004 by Pyartman, Kudrova, Keskinov.     

Uranium(IV) Complexes Formed in Extraction with Tributyl Phosphate from Nitric Acid Solutions

Speciation of U(IV) in tributyl phosphate (TBP) solutions prepared by extraction of U(IV) from 2 M HNO₃ was studied. The electronic spectra showed that in the solutions containing from 3 to 60% TBP a mixture of disolvate U(NO₃)₄(TBP)₂ and hydrates with hypothetical formula (TBP) _m ...[U(NO₃) _k · (H₂O) _n ]^(4-k)+ (k = 3 or 4) is formed. Within the 70-100% concentration range, the hexanitrate complex (TBP) _n ...2H₅O₂(H₂O) _p ⁺...[U(NO₃)₆]^{2 -} also appears. In undiluted TBP, as the concentration of uranyl nitrate increases, first the hexanitrate complex and then hydrated complexes of U(IV) gradually disappear. At uranium concentration more than 300 g l^-1, only U(IV) tetranitrate disolvate exists in the organic phase.     

Kinetics of REE separation by nonequilibrium extraction at oscillating temperature

The effect of periodic oscillations of temperature on the extraction and backwashing in the extraction systems 6 M NaNO₃-Nd(NO₃)₃-Pr(NO₃)₃-TBP-kerosene and [Nd(NO₃)₃ · 3TBP]-[Pr(NO₃)₃ · 3TBP]-kerosene-0.1 M HNO₃ was studied. Application of periodic temperature oscillations to the extraction system NaNO₃-Nd(NO₃)₃-Pr(NO₃)₃-TBP-kerosene-0.1 M HNO₃ increased the REE separation factor in a unit consiting of a continuous liquid membrane between two extractors. A mathematical model of nonstationary membrane extraction supplemented by the block of the temperature dependences of the extraction rate constants was developed. The activation energies of the forward and reverse reactions of the extraction and backwashing of Pr and Nd were calculated. For the extraction process of REE separation with a liquid membrane under the effect of periodic temperature oscillations, the following parameters were optimized: frequency and amplitude of temperature oscillations, distribution of the total volume of the organic phase between the extractors, and flow rate of the liquid membrane. Original Russian Text A.A. Kopyrin, A.A. Fomichev, M.A. Afonin, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 3, pp. 244–247.     

Phase diagrams of the ternary liquid systems [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2] and [Ce(NO3)3(TBP)3]-C10H22-[Th(NO3)4(TBP)2] and of the quaternary liquid system [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2]-[Th(NO3)4(TBP)2]

The phase diagrams of the ternary liquid systems [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂] and [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] and of the quaternary liquid system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂]-[Th(NO₃)₄(TBP)₂] at T = 298.15 K are constructed. The phase diagrams are characterized by areas of homogeneous solutions and of two-phase liquid systems (systems with phase separation), with one phase (I) enriched in [Ce(NO₃)₃(TBP)₃], [Th(NO₃)₄(TBP)₂], and [UO₂(NO₃)₂(TBP)₂], and the other phase (II), in C₁₀H₂₂. Using the data on the mutual solubility of the components in the systems under consideration and equations of the NRTL model, the parameters of intermolecular interactions and the excess Gibbs energies (G ^ex) were calculated for the binary, ternary, and quaternary systems. Passing from the ternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] to the quaternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂ (TBP)₂]-[Th(NO₃)₄(TBP)₂] does not appreciably affect the distribution of C₁₀H₂₂ between phases I and II, but leads to the redistribution of [Ce(NO₃)₃(TBP)₃] into phase II and of [Th(NO₃)₄(TBP)₂] into phase I.     

Phase equilibria in the liquid ternary system [Th(NO3)4(TBP)2]-[UO2(NO3)2(TBP)2]-Isooctane at different temperatures

The phase diagrams of the ternary systems [Th(NO₃)₄(TBP)₂]-[UO₂(NO₃)₂(TBP)₂]-isooctane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂(TBP)₂], and phase II is enriched in isooctane. With increasing temperature from 298.25 to 333.15 K, the mutual solubility of Th(NO₃)₄(TBP)₂ and isooctane does not change noticeably, but the two-phase fields somewhat contract. In the two-phase systems [UO₂(NO₃)₂(TBP)₂] is preferentially distributed in phase I, although the binary system [UO₂(NO₃)₂(TBP)₂]-isooctane is single-phase over the entire temperature range examined. The preferential accumulation of [UO₂(NO₃)₂(TBP)₂] in phase I causes the redistribution of [Th(NO₃)₄(TBP)₂] and isooctane into phases II and I, respectively. The compositions of the ternary systems in the critical points at different temperatures were determined. The electronic absorption spectra of uranyl nitrate solvate with TBP in the homogeneous and two-phase systems were recorded and analyzed. Original Russian Text ? A.K. Pyartman, V.A. Keskinov, V.V. Lishchuk, Ya.A. Reshetko, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 420–422.     

Phase equilibria in the liquid ternary system [Y(NO3)3(TBP)3]-[UO2(NO3)2(TBP)2]-C14H30 at different temperatures

The phase diagrams of the ternary system [Y(NO₃)₃(TBP)₃]-[UO₂(NO₃)₂(TBP)₂]-tetradecane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Y(NO₃)₃(TBP)₃] and [UO₂(NO₃)₂(TBP)₂], and phase II is enriched in tetradecane. With increasing temperature, the two-phase fields contract. The critical points of the ternary liquid systems depend on temperature. In the two-phase systems, [UO₂(NO₃)₂(TBP)₂] is preferentially distributed in phase I, although the binary system [UO₂(NO₃)₂(TBP)₂] tetradecane is homogeneous over the entire temperature range. Original Russian Text ? V.A. Keskinov, V.V. Lishchuk, A.K. Pyartman, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 417–419.