Equilibrium studies of the extraction of zirconium(IV) from sulfuric acid solutions with Di(2-ethylhexyl)phosphoric acid

Equilibrium studies were made at 25°C in the extraction of zirconium(IV) from sulfuric acid solutions with di(2-ethylhexyl)phosphoric acid (D2EHPA, HR) dissolved in kerosene. The reaction stoichiometry was numerically determined and the compositions of the extracted species were found to be ZrR₄ and ZrR₄(HR) at low loading ratios of D2EHPA (α < 0.09), but became ZrR₄ and ZrR₄(HR)₃ at relatively higher loading ratios (0.10 < α < 0.32). The equilibrium constants for the formation of these species were also obtained. Furthermore, numerical treatment of the experimental data excluded the existence of polynuclear complexes under the conditions studied (α < 0.32).     

Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions with CMPO-Functionalized Ionic Liquid in Molecular Diluents

The extraction of microquantities of U(VI), Th(IV), and lanthanides(III) from nitric acid solutions with CMPO-functionalized ionic liquid 1-[3[[(diphenylphosphinyl)acetyl]amino]propyl]-3-tetradecyl-1H-imidazol-3-ium hexafluorophosphate, CMPO-FIL(I) in molecular organic diluents has been studied. The effect of HNO₃ concentration in the aqueous phase and that of extractant concentration in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes was determined. CMPO-FIL(I) demonstrates greater extraction ability towards Ln(III) than its neutral CMPO analog, diphenylphosphorylacetic acid N-nonylamide. This inner synergistic effect increases with a decreasing organic diluent polarity. The partition of CMPO-FIL(I) between the equilibrium organic and aqueous phases is the dominant factor governing the extractability of Ln(III) ions in the extraction system.     

Extraction and separation of Pr(III)/Ce(III) from chloride medium by 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester in the presence of two complexing agents

Extraction and separation of Pr(III)/Ce(III) from a chloride medium using 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester in the presence of two water-soluble complexing agents, lactic acid and citric acid, were experimentally studied. By adding the complexing agents into an aqueous chloride medium, the extraction capacity and separation factor were as high as 30.97 g/L and 10.48, respectively, which were much higher than those in conventional solvent extraction systems. The cation-exchange mechanism was also verified by IR spectra. Thus, it was demonstrated that this complexing method can be used as an effective method for improving extraction efficiency and increasing selectivity of adjacent rare earth metals.     

Solvent Extraction and Separation of Gallium(III) using Hexaacetato Calix(6)Arene

Gallium(III) was extracted at pH 3.5 by equilibrating eight min with 10 mL of 0.0001 M acetyl derivative of calix(6)arene in xylene. Gallium(III) was stripped quantitatively with 0.1 N hydrochloric acid and determined spectrophotometrically with 0.01% PAR at 510 nm. The nature of the extracted species was determined from the log-log plots and its stoichiometry was confirmed by numerical treatment to experimental data. The IR analysis of Ga(III) loaded organic phase was also studied. The conformational change of reagent during complex formation was studied from the ¹H NMR treatment. The temperature dependence of the extraction equilibrium and metal loading capacity of the reagent was also evaluated. The proposed method was successfully applied for the extraction and separation of multicomponent mixtures, synthetic mixtures, and binary and ternary separation of gallium from the associated elements. The results obtained were reproducible and accurate.     

Selective removal of iron(III) from highly salted chloride acidic solutions by solvent extraction using di(2-ethylhexyl) phosphate

Metal ions including Fe³⁺, Ca²⁺, Mg²⁺, Ni²⁺, Co²⁺ and Cu²⁺ are commonly found in the leaching solution of laterite-nickel ores, and the pre-removal of Fe³⁺ is extremely important for the recovery of nickel and cobalt. Di(2-ethylhexyl)phosphate acid (D2EHPA) showed high extraction rate and selectivity of Fe³⁺ over other metal ions. The acidity of the aqueous solution is crucial to the extraction of Fe³⁺, and the stoichiometry ratio between Fe³⁺ and the extractant is 0.86:1.54. The enthalpy for the extraction of Fe³⁺ using D2EHPA was 19.50 kJ/mol. The extraction of Fe³⁺ was ≥99% under the optimized conditions after a three-stage solvent extraction process. The iron stripping effects of different reagents showed an order of H₂C₂O₄>NH₄HCO₃>HCl>NaCl>NaHCO₃>Na₂SO₃. The stripping of Fe was ≥99% under the optimized conditions using H₂C₂O₄ as a stripping reagent.     

Solvent Extraction Investigations on Pu(IV) and Th(IV) Complexes with Hydrophilic SO3-Ph-BTP and SO3-Ph-BTBP Ligands

ABSTRACT

Complexation of Pu(IV) and Th(IV) cations by the title ligands – hydrophilic sulfophenyl triazinyl derivatives of bis-triazinyl-pyridine and -bipyridine – was studied in solvent extraction systems containing a TODGA extractant and one of these hydrophilic ligands. Stoichiometries and stability constants of the complexes formed in an acidic (HNO₃) aqueous phase have been determined. The Pu(IV) complexes are significantly stronger than their Th(IV) analogues. Only two complexes of each metal with SO₃-Ph-BTP (1:1 and 1:2) have been detected, and only one (1:1) with SO₃-Ph-BTBP; both numbers being less than expected based on the coordination numbers of the metal ions and on the denticities of the ligands. Possible reasons of this discrepancy are discussed.     

Extraction and separation of Pt(IV)/Rh(III) from acidic chloride solutions using Aliquat 336

Extraction and separation of Pt(IV)/Rh(III) from chloride solutions using Aliquat 336 (Quaternary ammonium salt made by the methylation of mixed tri octyl/decyl amine) diluted in kerosene as an extractant/synergist alone and mixed with organophosphorous extractants as synergists/extractants were carried out from an aqueous feed containing 0.0005 mol L⁻¹ Pt(IV)/Rh(III).Variation of hydrochloric acid concentration of aqueous phase from 0.005 to 10.0 mol L⁻¹ increased the percentage extraction of platinum up to 5.0 mol L⁻¹ there after it decreases. Whereas in the case of rhodium, from 0.005 to 1.0 mol L⁻¹ acid range the percentage extraction was decreased from 1.0 to 10.0 mol L⁻¹ acid range is favorable for extraction. Platinum(IV)/rhodium(III) separation factor of 279.2 was obtained at 1.0 mol L⁻¹ HCl concentration with 0.005 mol L⁻¹ Aliquat 336 and separation factor of 612.3 was obtained at 3.0 mol L⁻¹ HCl concentration with 0.01 mol L⁻¹ Aliquat 336. The present study optimized the various experimental parameters like phase contact time, effect of extractant, salts, temperature, loading capacity of extractant, stripping studies with various mineral acids/bases, recycling and reusing capacity of extractant up to ten cycles.     

Synergistic Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions Using Mixtures of TODGA and Dinonylnaphthalene Sulfonic Acid

The extraction of U(VI), Th(IV), and lanthanides(III) from aqueous nitric acid solutions with mixtures of N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA) and dinonylnaphtalene sulfonic acid (HDNNS) in n-decane has been investigated. The extraction efficiency of U(VI), Th(IV), and Ln(III) ions is greatly enhanced by addition of HDNNS to an organic phase containing TODGA. The synergistic effect arises from the higher hydrophobicity of U(VI), Th(IV), and Ln(III) extracted species formed by TODGA and DNNS^? anions as compared to those formed by TODGA and NO₃^? ions as counter anions. The synergistic effect for U(VI), Th(IV), and Ln(III) extraction from aqueous nitric acid solutions with mixtures of TODGA and HDNNS becomes weaker when the acidity of the aqueous phase increases. A high synergistic enhancement is accompanied with a high selectivity of Ln(III) extraction from nitric acid solutions.     

Extraction of Uranium(VI) and Plutonium(IV) with Tetra-Alkylcarbamides

ABSTRACT

The use of tetra-alkylcarbamides as novel extractants for the separation of uranium(VI) and plutonium(IV) by solvent extraction from spent nuclear fuels is investigated in this study. Batch extraction experiments show that tetra-alkylcarbamides strongly extract U(VI) with high distribution ratios. Plutonium(IV) can be co-extracted with U(VI) at high nitric acid concentration, while high U(VI)/Pu(IV) selectivities can be reached at lower acidity. Loading capacity experiments with high uranium concentrations show that alkyl chains longer than butyl are necessary to avoid third phase formation. Nevertheless, the viscosity of uranium-loaded solvents gets too high with alkyl chains longer than pentyl. Overall, this study shows that with TPU extractant (with four pentyl chains), an efficient co-extraction of uranium and plutonium can be reached (D_U,Pu > 1) for a concentration of nitric acid higher than 4 mol?L^?1, while the partition between uranium(VI) and plutonium(IV) could be operated even at 2 mol?L^?1 nitric acid without redox chemistry.     

Solvent extraction modeling of Ce/Eu/Y from chloride media using D2EHPA

End-of-life fluorescent lamps are becoming essential in the rare earths (REEs) field and suppose a feasible secondary source for getting them, reducing thus their supply risk. Considering the proved viability of the cationic extractants, the present study aims at establishing a solvent extraction model using di-(2-ethylhexyl)phosphoric acid (D2EHPA) not only based on the individual Ce, Eu, and Y behavior in chloride media, but also bearing in mind the competitive extraction of these metals in Ce/Eu/Y mixtures, depending on the media variables. Furthermore, the model allow determining the optimal REEs separation conditions. The results disclose that Y could be separated from the mixture using 0.1 mol/L D2EHPA, acidity above of 3 mol/L of protons and chloride concentrations higher than 4 mol/L.     

Separation of rhodium(III) and iridium(IV) chlorido complexes using polymer microspheres functionalized with quaternary diammonium groups

Merrifield resin functionalized with different quaternary diammonium groups derived from ethylenediamine (EDA), tetramethylenediamine (TMDA), hexamethylenediamine (HMDA), 1,8-diaminooctane (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) were investigated for the separation of [RhCl₅(H₂O)]^2? and [IrCl₆]^2?. Selective loading of [IrCl₆]^2? in 6 M HCl medium onto the column was achieved in the presence of [RhCl₅(H₂O)]^2? by the synthesized sorbents. The iridium loading capacities were 3.80, 6.49, 13.07, 19.29, 27.09 and 4.36 mg/g for EDA, TMDA, HMDA, OMDA, DMDA and DDMDA-functionalized microspheres, respectively. The materials showed great potential for application in separating rhodium and iridium from aqueous HCl solutions.     

Extraction of Lanthanides(III), U(VI), and Th(IV) from Nitric Acid Solutions with 1,5-N,N'-Bis[(diphenylphosphoryl)acetylamino]pentanes

Novel polyfunctional neutral organophosphorus ligands, namely 1,5-N,N'-bis[(diphenylphosphoryl)acetyl(alkyl)amino]pentanes [Ph₂P(O)CH₂C(O)NR]₂(CH₂)₅ (Ia, R = C₆H₁₃; Ib, R = CH₃), were studied as extractants for Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, and U from nitric acid solutions. The effect of both HNO₃ concentration in the aqueous phase and that of the extractant in the organic phase on the extraction of metal ions is considered. The stoichiometry of the extracted complexes was determined by the slope analysis method. Compared with the related bisaminopentane [Ph2P(O)CH₂C(O)NH]₂(CH₂)₅ (Ic), the replacement of hydrogen atoms at the amide nitrogens by alkyl radicals (compounds Ia,b) leads to an increase of metal ions extraction. Bis-CMPO ligands Ia-c were found to possess higher extraction efficiency towards U(VI), Th(IV), and Ln(III) than their monophosphorylated analogue Ph₂P(O)CH₂C(O)N(C₄H₉)₂.     

Behavior of a synergistic system in the extraction of Pr(III) from chloride medium using di-2-ethylhexyl phosphoric acid and 2-ethylhexylphosphonic mono-2-ethylhexyl ester

This paper will investigate the synergistic solvent extraction of extracted Pr from a chloride medium, using a mixture of two acidic extractants, namely 2-ethylhexylphosphonic mono-2-ethylhexyl ester (P507, HA) and di-2-ethylhexyl phosphoric acid (P204, HB) in kerosene. The stoichiometry of the extracted species was characterized by a classical lg–lg plot analysis. The composition of the extracted complexes has been determined as Pr(HA₂)(HB₂)₂. Moreover, the differences of the extraction behavior from sulfuric and chloride medium were discussed in detail. The values of equilibrium constant and thermodynamic parameters such as △G, △H, and △S were also calculated. A cation-exchange mechanism was proposed and further clarified by slope analysis and IR spectra.     

Extraction Equilibria of 4-Hydroxypyridine using Di (2-ethylhexyl) Phosphoric Acid

Extractions of 4-Hydroxpyridine (4HP) from aqueous solutions using Di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant in 1-octanol and kerosene were studied. The factors that affected the distribution coefficient (D), such as equilibrium pH, the concentration of D2EHPA, and the type of diluents were discussed. The interaction mechanism between 4HP and D2EHPA was validated by infrared spectroscopic analysis. D increased with the increase of the concentration of D2EHPA and peak values appeared at equilibrium pH = 3.6–5.0. D in the polar diluent (1-octanol) was much higher than those in the non-polar diluent (kerosene). The extraction reaction was found to be a proton-transfer process and D2EHPA mainly reacted through its –OH with –N– of 4HP. The apparent reactive extraction equilibrium constants K ₁₁ and K ₁₂ were obtained by fitting the experimental data of extraction equilibrium. By comparing calculated D values from the proposed model with the experimental ones, the accuracy of the proposed model was examined.     

Separation of Electrochemically Generated Ce(IV) from Rare Earths(III) in Nitric Acid Media by TBP Impregnated Resin

Abstract

Electro‐oxidation of Ce(III) to Ce(IV) in nitric acid media at different anode materials with high oxygen evolution overpotential was carried out. Ce(IV) nitrato complexes were adsorbed on a novel resin, based on porous silica beads with immobilized polystyrene/DVB copolymer, that was impregnated with tri‐n‐butyl phosphate (TBP). Under the studied conditions, Ce(IV) sorption increased with increasing nitric acid concentration (0.5–6 mol · dm^?3). Oxidation of sorbent by adsorbed Ce(IV) species resulting in Ce(III) release to the solution was observed and thoroughly evaluated. In spite of problems with TBP leakage (12%), column separation of pure Ce(IV) from Y(III) and La(III) was achieved in 6 mol · dm^?3 HNO₃ at 288 K. Ce(IV) breakthrough capacity was 0.48 mol · kg^?1‐TBP. Column regeneration with 0.1 mol · dm^?3 nitric acid yielded Ce solution with purity higher than 99.99 wt.% with respect to La and Y impurities.     

Solvent extraction separation of titanium(IV), vanadium(V) and iron(III) from simulated waste chloride liquors of titanium minerals processing industry by the trialkylphosphine oxide Cyanex 923

The solvent extraction of magnesium(II), aluminium(III), titanium(IV), vanadium(V), chromium(III), manganese(II) and iron(III) from hydrochloric acid solutions has been investigated using the trialkylphosphine oxide Cyanex 923 (TRPO) in kerosene as extractant. The results demonstrate that titanium(IV), vanadium(V) and iron(III) are extracted into kerosene as TiOCl₂·2TRPO, VO₂Cl·TRPO and HFeCl₄·2TRPO, respectively. On the other hand magnesium(II), aluminium(III), chromium(III) and manganese(II) are not extracted with TRPO from hydrochloric acid solutions (1.0–4.0 mol dm^?3) under the experimental conditions. IR spectral studies of the extracted complexes were further used to clarify the nature of the extracted complexes. The effect of the diluent on the extraction of titanium(IV), vanadium(V) and iron(III) has been studied and correlated with the dielectric constant. The loading capacity of the TRPO system has been evaluated and the potential for the separation and recovery of titanium(IV), vanadium(V) and iron(III) from simulated waste chloride liquors of the titanium minerals processing industry has been assessed. Copyright © 2004 Society of Chemical Industry     

Extraction Behavior of Am(III) and Eu(III) from Nitric Acid Medium in Tetraoctyldiglycolamide-Bis(2-Ethylhexyl)Phosphoric Acid Solution

The extraction behavior of Am(III) and Eu(III) in a solution of tetra-octyldiglycolamide (TODGA), bis(2-ethylhexyl)phosphoric acid (HDEHP), and n-dodecane (n-DD) was studied to understand the role of TODGA and HDEHP in the combined solvent system. The extraction behavior of these metal ions was compared with those observed in TODGA/n-DD and HDEHP/n-DD. The effect of various parameters such as concentrations of HNO₃, TODGA, and HDEHP on the distribution ratio of Am(III) and Eu(III) was studied. Synergistic extraction of both the metal ions observed at lower acidities (<2.0 M) was attributed to the involvement of TODGA and HDEHP for extraction. However, the extraction of Am(III) and Eu(III) in the combined solvent was comparable with that observed in TODGA at higher acidities. The slope analysis of the extraction data confirmed the involvement of both the extractants at all acidities investigated in the present study.     

Separation of U(VI) and Th(IV) from Nd(III) by Cross-Current Solvent Extraction Mode Using Tri-iso-amyl Phosphate as the Extractant

Separation of U(VI) and Th(IV) from Nd(III) in nitric acid media with solutions of tri-iso-amyl phosphate (TiAP) in n-dodecane has been studied by batch extraction in cross-current mode to evaluate the feasibility of employing TiAP as an alternate extractant to tri-n-butyl phosphate (TBP) for monazite ore processing. The interference of U(VI), Th(IV), and Nd(III) in the presence of each other during their analyses by titrations has also been validated in the present study. The extraction studies substantiate that the high solvent loading conditions can be achieved without organic phase splitting in the extraction from concentrated feed solutions with TiAP based solvents, whereas TBP forms third phase under such conditions. The separation factor for Th(IV) with respect to Nd(III) can be improved with TiAP as the extractant and by carrying out the extraction with feed solution in 8 M HNO₃. Solvent extraction studies conducted with solutions of U(VI), Th(IV), and Nd(III) in nitric acid media by TBP and TiAP revealed the identical extraction, scrubbing, and stripping behavior of both the extractants with respect to U(VI), Th(IV), and Nd(III). The results insinuate that TiAP can be used as an alternate extractant to TBP for the separation of U(VI) and Th(IV) from monazite ores. The data generated in the present study can be exploited for the development of flow sheets using TiAP based solvents to separate U(VI) and Th(IV) from rare earths for the processing of monazite leach solutions.