Solvent Extraction of Heavy Lanthanides(III) with 5,7‐Dibromo‐8‐hydroxyquinoline from Aqueous Perchlorate Solution

Abstract

The extraction of Tb(III), Dy(III), Ho(III), Er(III), Tm(III), and Yb(III) with 5,7‐dibromo‐8‐hydroxyquinoline (Hdbq or HA) in chloroform from aqueous perchlorate solutions was investigated. The formation of the LnA₃ species (where Ln = Tb, Dy, Ho, Er, Tm, and Yb) in the organic phase was supported by the data. The parameters of the extraction processes were determined, and the separation factors between two adjacent lanthanides(III) were calculated.     

Extraction of Lanthanides(III) by a Mixture of a Malonamide and a Dialkyl Phosphoric Acid

Several hydrometallurgical processes studied in France for lanthanide/minor actinide separation use a combination of DMDOHEMA and HDEHP as extractants. Although these processes have proved to be reliable, the modeling of their extraction properties remains a difficult task due to a lack of knowledge about the behavior of the mixed DMDOHEMA-HDEHP organic phase. In the present work, it was found that the solvent extraction of Ln(III) ions by a mixture of these extractants exhibits a complex behavior involving a synergistic effect at either 1 M HNO₃ or high metal concentration, and an antagonistic effect on extraction of metal traces at higher pH (> 2). To understand these effects, Ln(III) complexes formed after extraction by DMDOHEMA and/or HDEHP were characterized by several spectroscopic techniques (FT-IR, UV-Vis, ESI-MS, TRLIFS). Results suggested formation of DMDOHEMA-HDEHP adducts and ternary mixed complexes involving both extractants and possibly a nitrate ion.     

SYNERGISTIC EXTRACTION OF LANTHANIDES(III) BY TRIOCTYLMETHYLAMMONIUM NITRATE AND TRIBUTYL PHOSPHATE

ABSTRACT

The synergistic action of tributyl phosphate in the extraction of La(III), Pr(III)Nd(III), Sm(III), Eu(III), Gd(III), Dy(III), Ho(III), Er(III)and Y(III) with trioc-tylmethylammonium nitrate was studied. The synergistic effect is diluent dependent. It is pronounced with a mixed dodecane/xylene diluent, and is weak with mixed heptane/xylene and hexane/xylene diluents as well as with pure xylene diluent. Two or three synergistic complexes are formed simultaneously in the organic phase. Their composition is (A₊)(Ln(N0₃)) ₄),.2B~), (A₊))(Ln(N0₃))J.3B"), and (A₊)) ₂) (Ln(N0₃)) ₅).BJ-) (Ln is a lanthanide(IM), A+ is a trioc-tylmethylammonium cation and B is a tributyl phosphate molecule). The stability of the synergistic complexes generally decreases with increasing atomic number of the lanthanides(III). The synergism enhaces the efficiency of the lanthanide(III) extraction with trioctylmethylammonium nitrate, but deteriorates its selectivity. The separation factors for the Pr(III)-Nd(III) and Eu(III)-Gd(III) pairs are gradually suppressed at increasing concentration of tributyl phosphate.     

EXTRACTIONOFTERVALENTLANTHANIDESWITH ACIDIC ORGANOPHOSPHORUS COMPOUNDS

The equilibrium.extraction behavior for a series of tervalent lanthanide ions (Ln³⁺) using a chloroform solution containing di(2-ethyl-hexyl) phosphoric acid (HDEHP), diphenylphosphinic acid (HDPP), dibutylphosphorothioic acid (HDBPT), di-n-octylphosphorodithoic acid (HDOPDT), or di(2-ethylhexyl)phosphorodithioic acid (HDEHPDT), either alone or combined with adduct forming agents is studied. The extracted species are Ln(DEHP) ₃(HDEHP) ₃, Ln(DPP)₃ (HDPP)₃, Ln(DBPT)₃, and are Ln(DBPT)₃(HDERP)₃ in the presence of o-phen and its analogs (B). Extraction constants for the lanthanides follow the order HDPP > HDEHP > HDBPT » HDOPDT. HDPP was the most selective of all the extractants examined. HDOPDT and HDEHPDT were found to be ineffective lanthanide extractants.     

Extraction of lanthanides(III) from Perchlorate Solutions with Carbamoyl- and Phosphorylmethoxymethylphosphine Oxides and Tetrabutyldiglycolamide

The solvent extraction of Ln(III) ions from perchlorate aqueous solutions into an organic phase containing neutral polyfunctional organophosphorus ligands R₂P(O)CH₂OCH₂C(O)NBu₂ R = Bu (I), R = Ph (II) and R₂P(O)CH₂OCH₂P(O)R¹₂ R = R¹ = Bu (III); R = Bu, R¹ = Ph (IV); R = R¹ = Ph(V) has been studied. Their extraction behavior was compared with that of tetrabutyldiglycolamide (TBDGA), tetrabutylmethylenediphosphine dioxide (VI), P,P-dibutyl-P’P’-diphenylmethylenediphosphine dioxide (VII), tetraphenylmethylenediphosphine dioxide (VIII), dibutyl-N,N-dibutylcarbamoylmethylphosphine oxide (IX) and diphenyl-N,N-dibutylcarbamoylmethylphosphine oxide (X). The extraction equilibrium was investigated, and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted with the studied extractants from perchlorate solutions as LnL₃(ClO₄)₃ complexes. In the NaClO₄ media, TBDGA was found to possess a higher extraction efficiency towards Ln(III) ions than other neutral donor ligands studied. A successive replacement of the C(O)NBu₂ groups in the diglycolamide extractant molecule by phosphoryl ones leads to a decrease in the extraction efficiency of Ln(III) ions. In the NaClO₄ media, compounds II, IV and V with phenyl radicals at the P(O) group demonstrate a lower extraction efficiency towards Ln(III) ions than their butyl-substituted analogs. In contrast, phenyl-substituted diphosphine dioxides VIII, VII and carbamoylmethylphosphine oxide (X) extract Ln(III) ions more effectively than their butyl-substituted analogs VI and IX. The extraction of Ln(III) ions from HClO₄ solutions is accompanied by HClO₄ interaction with neutral donor extractants, which leads to a decrease of the free extractant concentration in the organic phase. By this reason, an increase in the HClO₄ concentration higher than 0.1 M is accompanied by a decrease of the Ln(III) extraction with TBDGA. In the 3 M HClO₄ system, diphosphine dioxide VIII outperforms TBDGA at the Ln(III) extraction.     

Synergistic extraction of rare earths(III) from chloride medium with mixtures of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate

The synergistic effect of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 (HPMBP, HA) and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate (DEHEHP, B) in the extraction of rare earths (RE) from chloride solutions has been investigated. Under the experimental conditions used, there was no detectable extraction when DEHEHP was used as a single extractant while the amount of RE(III) extracted by HPMBP alone was also low. But mixtures of the two extractants at a certain ratio had very high extractability for all the RE(III). For example, the synergistic enhancement coefficient was calculated to be 9.35 for Y³⁺, and taking Yb³⁺ and Y³⁺ as examples, RE³⁺ is extracted as RE(OH)A₂.B. The stoichiometry, extraction constants and thermodynamic functions such as Gibbs free energy change ΔG (?17.06 kJ mol^?1), enthalpy change ΔH (?35.08 kJ mol^?1) and entropy change ΔS (?60.47 J K^?1 mol^?1) for Y³⁺ at 298 K were determined. The separation factors (SF) for adjacent pairs of rare earths were calculated. Studies show that the binary extraction system not only enhances the extraction efficiency of RE(III) but also improves the selectivity, especially between La(III) and the other rare earth elements. Copyright © 2006 Society of Chemical Industry     

Selective removal of magnesium from lithium-rich brine for lithium purification by synergic solvent extraction using β-diketones and Cyanex 923

In the production of battery-grade and high-purity Li₂CO₃, it is essential to remove magnesium impurities. The state-of-the-art solvent extraction (SX) process using Versatic Acid 10 and D2EHPA co-extracts 3.3–5.5% lithium, while removing 86–98% magnesium. Here, we demonstrate that synergic SX systems containing a β-diketone (HPMBP, HTTA or HDBM) and Cyanex 923 are highly selective for magnesium extraction over lithium (separation factor α > 1,000). The extracted magnesium and lithium complexes have the stoichiometry of [Mg∙A₂∙(C923)₂] and [Li∙A _x∙(C923)₂] (x = 1, 2), respectively (A represents deprotonated β-diketone). The three β-diketone synergic SX systems all considerably outperformed the Versatic Acid 10 system for magnesium removal from a synthetic solution containing 24 g L⁻¹ Li and 0.24 g L⁻¹ Mg. In a three-stage batch counter-current extraction, the HPMBP and Cyanex 923 synergic SX system removed 100% magnesium with only 0.6% co-extraction of lithium. This excellent Mg/Li separation is the best result reported so far.     

Mechanistic study of hafnium and zirconium extraction with organophosphorus extractants

Research on the purification of Zr has increased in the last few decades and although effective processes have been developed, little is known about the mechanism of Hf and Zr extraction; particularly, at low acid concentrations. This study’s aim was to determine the influence of alterations in alkyl substituents on the extraction mechanism of Hf and Zr from sulfate media. Seven organophosphorus extractants (Dio-PA, TPPA, DPPA, TPPO, TPPS, D2EHPA and Ionquest 801) were screened with four of them (Dio-PA, DPPA, D2EHPA and Ionquest 801) resulting in promising extraction results. This was attributed to the activity of the acidic hydroxy phosphinyl (=P(O)OH) group which is responsible for the dimerization and cation exchange properties of the extractant. The extractant and hydrogen ion stoichiometries involved in the extraction mechanism were determined for these four extractants by slope analysis from extractant- and acid-variation experiments. It was found that Dio-PA, D2EHPA, and Ionquest 801 extract via a cation-exchange mechanism, according to [M(OH)₂]²⁺ + 2 HA ? M(OH)₂A₂ + 2 H⁺. In contrast, the extraction with DPPA was best described by a solvated cation exchange (SCE) mechanism, according to [M(OH)]³⁺ + 6 HA ? M(OH)A₃.3HA + 3 H⁺. It was concluded that the presence of electron-withdrawing substituents produced softer Lewis base extractants, which favored the extraction of Hf over Zr from acidic sulfate media.     

The Possibility for Separation of Lanthanum by Solid-State Complexes with 2-Ethylhexyl Phosphoric Acids

Abstract

The elemental composition, molecule, and crystal structure of precipitates obtained from an acetone solution of Ln(NO₃)₃ (Ln = Pr + Er or La + Nd) with a mixture of bis- and mono-(2-ethylhexyl) phosphoric acids and their sodium salts were studied. In this study we found enrichment of the precipitate with the heavier lanthanide. The separation factor for the La-Nd couple is much greater than for the Er-Pr couple, and decreases with increasing rare-earth yield in the precipitate. We discuss the significant role of the stability of LnA₃ against HNO₃, especially the formation of La complexes with mono-(2-ethylhexyl) phosphoric acid during enrichment.     

Extraction Behavior of Americium and Curium on Selected Extraction Chromatography Resins from Pure Acidic Matrices

Due to the similar chemical properties between the neighboring trivalent actinide elements americium and curium, their extraction behavior is often perceived as indistinguishable. In this work, the characterization of seven extraction chromatography resins (TEVA, TRU, DGA(N), Actinide, Ln, Ln2, and Ln3) for these trivalent actinides from acidic matrices (HNO₃, HCl, and HBr) has provided some evidence to the contrary. In most cases, Am(III) and Cm(III) exhibit identical extraction properties. However, separation is possible with TRU and DGA(N) resins as demonstrated in this study. The extraction shows a strong dependency on the specific anion in solution that follows the order NO₃^?>Br^?>Cl^?.     

SOLVENT EXTRACTION OF ZINC(II) BY ORGANOPHOSPHORUS ACIDS COMPOUNDS FROM PERCHLORATE SOLUTIONS.

ABSTRACT

The extraction of zinc from perchlorate solutions at 0.1 mol.dm^?3 of ionic strength by di(2-ethylhexyl)phosphoric acid (HDEHP), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and di(n-octyl)phosphinic acid (H[DOP]) dissolved in toluene has been studied at 25 ° C.

The distribution coefficient was determined as a function of pH and HA concentrations and the data were analyzed both graphically and numerically using the computer program LETAGROP-DISTR.

The results showed that the data can be explained assuming the formation of ZnA₂(HA)₂ and ZnA₂HA in organic phase for all the extractants used. A correlation between extracted species and concentration of the various extractants has been found.

The predominance of the different species into the organic phase has been correlated with the difference between their extraction constants.

The anion of the ionic medium is not extracted into the organic phase.     

Solid‐Liquid Extraction of Lanthanum(III), Europium(III), and Lutetium(III) by Acyl‐Hydroxypyrazoles Entrapped in Mesostructured Silica

Abstract

The solid‐liquid extraction of lanthanum(III), europium(III), and lutetium(III) by mesostructured silicas doped with 1‐phenyl‐3‐methyl‐4‐stearoyl‐5‐pyrazolone (HPMSP, bearing one chelating site) or with 1,12‐bis(1′‐phenyl‐3′‐methyl‐5′‐hydroxy‐4′‐pyrazolyl)‐dodecane‐1,12‐dione (HL‐10‐LH, bearing two chelating sites) has been studied and compared to the analogous solvent and micellar extractions in terms of the stoichiometry of the extracted complex and of the extraction efficiency. The solid‐liquid extraction order in the lanthanoid series is La<Eu<Lu; it is the usual liquid‐liquid extraction order obtained with acidic extractants. A theoretical model is used to determine the stoichiometries of the extracted complexes and the extraction yield is measured as a function of the pH, of the extractant/metal ratio (S/M) and of the volume ratio of the two phases (φ). For HPMSP, the extracted complexes involve three ligand molecules for one metal. For HL‐10‐LH, the complex stoichiometries are found to be either Ln(L‐10‐L)(L‐10‐LH) (Ln=La, Eu) or Lu₂(L‐10‐L)₃ for S/M=25, or Eu₂(L‐10‐L)₃ for S/M=5. For the first time, the synergistic solid‐liquid extraction is studied after a successful attempt at simultaneously immobilizing both extractants HL‐10‐LH and 2,4,6‐tri(2‐pyridyl)‐1,3,5‐triazine, “TPTZ”, into silica; the complex extracted in this case differs from the one obtained in solvent extraction.     

Extraction of Lanthanides with N,N′‐Dimethyl‐N,N′‐diphenyl‐malonamide and ‐3,6‐dioxaoctanediamide

Abstract

The extraction properties of the trivalent lanthanides (Ln(III)) with the bidentate N,N′‐dimethyl‐N,N′‐diphenyl‐malonamide (MA) and the tetradentate N,N′‐dimethyl‐N,N′‐diphenyl‐3,6‐dioxaoctanediamide (DOODA) were investigated. These diamides formed by coupling two amide groups with methylene and/or ether groups are bidentate for the MA and tetradentate for the DOODA. By adding a previous data regarding the tridentate N,N′‐dimethyl‐N,N′‐diphenyl‐diglycolamide (DGA), these extraction results enabled us systematically study an effect of number of oxygen donor on its extraction behavior of Ln(III). The change in the distribution ratios (Ds) of Lu(III) with an increase in the HNO₃ concentration is greater than that of La(III) in both the MA and DOODA systems. Therefore, the relationship between the D and atomic number, i.e., the lanthanide pattern, changes with the HNO₃ concentration: the Ds decrease with an increasing atomic number at lower HNO₃ concentrations. The Ds of the lighter Ln(III) are similar to the Ds of the heavier Ln(III) at higher HNO₃ concentrations. The number of the extractant in the extracted species for La(III) and Lu(III) obtained from slope analysis at 4 M HNO₃ in the MA system are about 3, while those in the DOODA system are quite different, i.e., 2 for La(III) and 1.5–3 for Lu(III). The comparison of the extractability of Ln(III) by MA, DOODA, and DGA shows that the magnitude of the Ds is in the sequence of MA < DOODA ? DGA. This suggests the introduction of one ether oxygen atom to the principal chain in the diamides leads to a good extractability for the Ln(III) from HNO₃ solution.     

Modified Diglycolamides for the An(III) + Ln(III) Co-separation: Evaluation by Solvent Extraction and Time-Resolved Laser Fluorescence Spectroscopy

The use of two recently developed diglycolamide-based extractants for the co-separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) is described and compared to the well-known extractant TODGA (N,N,N’,N’-tetraoctyl diglycolamide). The addition of one or two methyl groups to the central methylene carbon atoms of the TODGA molecule leads to a reduction of the extraction efficiency for An(III) and Ln(III). This is attributed to a lower complex formation constant, which was proven by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS). Conditional stability constants were determined by solvent extraction and TRLFS. The reduction in extraction efficiency leads to overall reduced distribution ratios of all tested metal ions, including Sr(II). The reduced Sr(II) extraction is beneficial as a co-extraction in a solvent extraction process could be avoided, while an efficient extraction of the desired An(III) and Ln(III) is still achieved. Furthermore, this might be a benefit, as the stripping behavior might be improved, even at moderate nitric acid concentrations. The slightly higher affinity of the diglycolamides towards Eu(III) over Am(III) is represented by all ligands, although the selectivity is rather low. This results in promising extraction properties of the modified diglycolamides towards the development of continuous solvent extraction processes.     

Solvent extraction of rare earths from chloride medium with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 and sec-octylphenoxyacetic acid

In the present study, the extraction of rare earths with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP, HA) and sec-octylphenoxyacetic acid (CA12, H₂B₂) in benzene has been studied from chloride medium. The synergistic enhancement coefficient decreases with increasing atomic numbers of rare earths. The synergistic extraction of lanthanum and neodymium has been studied with the methods of slope analysis and constant mole. The extracted complexes are determined as LaH₂ClA₂B₂ and NdH₃ClA₃B₂, respectively. The equilibrium constants, formation constants, and the thermodynamic functions are calculated. Furthermore, the different extraction effects on rare earths have been employed to discuss the possibilities for the separation of rare earths.     

Equilibrium and Behavior of Trivalent Metal Ion Extraction with N-p-Octyloxybenzoyl-N-Phenylhydroxylamine

A study of the extraction of the trivalent metal ions Fe, Ga, In and Al, was carried out with benzene solutions containing N-benzoyl-N-phenylhydroxylamine and N-p-octyloxybenzoyl-N-phenylhydroxylamine(HL), respectively. The results demonstrated that the metal ions were extracted as ML₃ for Fe, Ga and In, M(OH)L₂ for Al (where M is metal ion). The extraction constants and separation factors for the two extractants were compared.     

SYNERGISTIC SOLVENT EXTRACTION OF LANTHANIDES WITH MIXTURES OF 1-PHENYL-3-METHYL-4-BENZOYL-PYRAZOL-5-ONE AND ALIQUAT 336

The solvent extraction of Pr(III),Gd(III) and Yb(III) With 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HP) and Aliquat 336(QCl) in CCl₄.C₆H₆ and CHCl₃, has been studied.The composition of the extracted species has been determined as LnP₄ ^?.Q⁺ (Ln=Pr,Gd and Yb).The values of the equilibrium constants have been calculated. The extraction mechanism has been discussed.     

Synergistic Solvent Extraction of Lanthanides (III) with Mixtures of Tetraphenylmethylenediphosphine Dioxide and Picrolonic Acid from HCl Solutions

The solvent extraction of lanthanides(III) from hydrochloric acid solutions into the organic phase containing neutral bidentate extractant tetraphenylmethylenediphosphine dioxide (L) and picrolonic acid (HP) has been studied. A considerable synergistic effect was observed in the presence of HP in the organic phase containing neutral bidentate organophosphorus ligand. The extraction equilibrium was investigated and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted from weak acidic solutions as LnP₃L and LnP₃L₂ complexes. The mixture L–HP offers higher extraction efficiency toward Ln(III) than mixtures of L with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 or picric acid.     

EFFECT OF ALKYL CHAIN LENGTH OF 3-ALKYLPENTANE-2, 4-DIONE ON THE EXTRACTION OF COPPER

The equilibrium and kinetics of the extraction of copper with 3-alkylpentane-2, 4-dione (-H, -C₂H₅, -Ph, and -C₈H₁₇) were studied. It was found that the overall equilibrium constant is related to the proton disscoiation constant and that the ratio of the stability constants of the copper chelate, β₂/β₁ ²was independent of the alkyl chain length of the β-diketone. The rate constants for the reactions between cupric ion and the β-diketones in the aqueous phase were obtained by the relaxation method. The values decreased in the order -H>-Ph>-C₂H₅. The observed extraction rates were explained by a kinetic model using the measured physicochemical properties.