Extraction of Ternary Beta‐Diketonates of Uranyl Ion Using Some Substituted Monoamides

Abstract

The extraction behavior of uranyl ion from dilute nitric acid medium employing 1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone (HPMBP)/2‐thenoyl‐ trifluoroacetone (HTTA) in toluene and their mixture with several structurally modified monoamides viz. di‐2‐ethylhexyl acetamide (D2EHAA), di‐2‐ethylhexyl propanamide (D2EHPrA), di‐2‐ethylhexyl isobutyramide (D2EHiBA), and di‐2‐ethylhexyl pivalamide (D2EHPvA) was investigated. The species of the type UO₂(A)₂ and UO₂(A)₂·B were extracted for the binary and ternary extraction systems respectively where A = PMBP/TTA and B = D2EHAA, D2EHPrA, D2EHiBA, or D2EHPvA. The extraction constants (log K _ex) for the binary species UO₂(A)₂ were determined to be ?2.32 ± 0.03 for HTTA and 0.21 ± 0.02 for HPMBP, which was an inverse function of their pK _a value. The overall extraction constants (log K) for the ternary species UO₂(A)₂·B were determined as 4.70, 4.22, 4.00, 3.61, 2.65, 2.39, 2.32, and 1.76 for UO₂(PMBP)₂·D2EHAA, UO₂(PMBP)₂·D2EHPrA, UO₂(PMBP)₂·D2EHiBA, UO₂(PMBP)₂·D2EHPvA, UO₂(TTA)₂·D2EHAA, UO₂ (TTA)₂·D2EHPrA, UO₂(TTA)₂·D2EHiBA, and UO₂(TTA)₂·D2EHPvA, respectively. A linear correlation was observed between the basicity of the amide and the corresponding adduct's formation constants.     

Equilibrium Studies on the Synergic Liquid‐Liquid Extraction Process of Copper(II) from Sulphate Media with Mixtures of some Bidentate Mono‐Schiff Bases and Acyclic Polyether Non‐ionic Surfactant in Chloroform

The liquid‐liquid extraction of copper(II) with bidentate mono‐Schiff base extractants(HL), namely, N‐salicylideneaniline (SA), N‐(2‐hydroxy‐1‐naphthalidene)aniline (HNA), N‐salicylidene‐1‐naphthylamine (SN), and N‐(2‐hydroxy‐1‐naphthalidene)‐1‐naphthylamine (HNN), from a weakly acidic sulphate media into chloroform was studied in both the absence and the presence of acyclic polyether non‐ionic surfactant (S). In the absence of the non‐ionic surfactant, the extractability of copper(II) was 92.6% with SA, 89% with HNA, 81% with SN, and 80% with HNN. The estimated extraction constants, (log K_ex) of the four extractants revealed that the extraction efficiency increased in the order HNN< SN< HNA<SA. Besides, it was found that copper(II) was extracted as CuL₂ (HL) with SA and HNA, and as CuL₂ with SN and HNN. The extraction of copper(II) was significantly enhanced with HL into chloroform upon the addition of a non‐ionic surfactant. An extractability of 100% was reached. The stoichiometry of the extracted complexes was CuL₂S. The synergic extraction ability of extractants changed in the order SA>HNA>SN～HNN, whereas, the synergic effect fell in the order HNN>SN>HNA～SA.     

Temperature‐induced surfactant‐ mediated pre‐concentration of uranium assisted by complexation

Cloud‐point extraction (CPE) was used with lipophilic chelating agent to extract uranium(VI) from aqueous solutions. The methodology used is based on the formation of metal complexes soluble in a micellar phase of a non‐ionic surfactant, Triton X‐114. The metal ions complexes are then extracted into the surfactant‐rich phase at a temperature above the cloud‐point temperature. The influence of surfactant concentration on extraction efficiency was studied and the advantage of adding 8‐hydroxyquinoline (8HQ) as lipophilic chelating agent was evidenced. High extraction efficiency was observed, indicating the feasibility of extracting U(VI) using CPE. This study describes a four‐step process—(1) extraction, (2) thermo‐induced phase splitting, (3) back‐extraction and (4) second phase splitting—for the recovery of uranium from water. In our conditions, the extraction yield is quantitative and the concentration factor obtained is superior to 100. After stripping with a diluted nitric acid solution (pH < 1), the system can be recycled through a new four‐step cycle. Copyright © 2006 Society of Chemical Industry     

Equilibrium and kinetic studies on the extraction of gadolinium(III) from nitrate medium by di‐2‐ethylhexylphosphoric acid in kerosene using a single drop technique

The liquid–liquid extraction of Gd(III) from aqueous nitrate medium was studied using di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene. On the basis of the slope analysis data, the composition of the extracted species was found to be [Gd A₃(HA)] with the extraction equilibrium constant (K_ex) = (1.48 ± 0.042) × 10^?12 mol dm^?3. The results of the effect of temperature on the value of the equilibrium extraction constant indicated the endothermic character of the extraction system. The kinetics of the forward extraction of Gd³⁺ from nitrate medium by HDEHP in kerosene was investigated using the single drop column technique. The rate of flux (mass transfer per unit area) was found to be proportional to [Gd(III)], [H₂A₂]_(o), [NO₃^?], and [H⁺]^?1 in the liquid drop organic phase. The forward extraction rate constant, k_f, was 2.24 × 10^?3 m s^?1 using the equation: Copyright © 2005 Society of Chemical Industry     

Influence of Solvent Polarity on the Mechanism and Efficiency of Formic Acid Reactive Extraction with Tri‐n‐Octylamine from Aqueous Solutions

The reactive extractions of formic acid with tri‐n‐octylamine (TOA) dissolved in three solvents with different dielectric constants (dichloromethane, butyl acetate, n‐heptane) without and with 1‐octanol as phase modifier were comparatively analyzed. The results indicated that the mechanism of the interfacial reaction between acid and extractant (Q) is controlled by the organic phase polarity. In the absence of 1‐octanol, the structures of the extracted complexes are (HA)₂Q₂ for dichloromethane and butyl acetate, and (HA)₂Q₄ for n‐heptane. These structures are modified by adding 1‐octanol and become (HA)₂Q for extraction in dichloromethane or butyl acetate, and (HA)₂Q₂ for extraction in n‐heptane. Although the presence of 1‐octanol improves the extraction efficiency, it leads to a reduction of the extraction constants for all considered solvents, an influence that is more significant for n‐heptane.     

Chemical Properties of 2‐Bromodecanoic Acid

Abstract

Some chemical equilibrium constants for 2‐bromodecanoic acid were investigated. The dimerization constant of 2‐bromodecanoic acid, k₂ =278 M^?1, in tert‐butylbenzene was first derived from IR spectroscopy measurements. Secondly, the distribution coefficient, k _d =799, was found by combining the value of k₂ with distribution data obtained from solvent extraction experiments evaluated with the aid of neutron activation analysis. Finally the dissociation constant, k _a =3.18 ?10^?3 M, was estimated from two‐phase titrations. A theoretical calculation was made based on the obtained constants and this calculation was validated by a second solvent extraction experiment that gave a good correspondence between calculated and experimental values.     

Liquid Emulsion Membrane (LEM) Process for Vanadium (IV) Enrichment: Process Intensification

Abstract

A liquid emulsion membrane (LEM) system for vanadium (IV) transport has been designed using di‐2‐ethylhexyl phosphoric acid (D2EHPA), dissolved in n‐dodecane as carrier. The selection of extractant, D2EHPA, was made on the basis of conventional liquid‐liquid extraction studies. The work has been undertaken by first carrying out liquid‐liquid extraction studies for vanadium (IV) to get stoichiometric constant (n), and equilibrium constant (K_ex), which are important for process design.

Transport experiments were carried out at low vanadium (IV) concentration (ppm level). The studies on liquid emulsion membrane included i) the influence of process parameters i.e. feed phase pH, speed of agitation, treat ratio, residence time and ii) emulsion preparation study i.e., organic solvent, extractant concentration, surfactant concentration, internal strip phase concentration. When the strip phase concentration was 2 mol/dm³ (H₂SO₄) and feed phase pH 3 better extraction of vanadium was obtained. Higher V_m/V₁ gave higher extraction of vanadium (IV). A simplified, design engineer friendly model was developed.     

New Heavy Metal Ion‐Selective Macrocyclic Ligands with Nitrogen and Sulfur Donor Atoms and their Extractant Properties

Abstract

Two new macrocyclic ligands, containing nitrogen and sulfur donor atoms were designed and synthesized in a multi‐step reaction sequence. The macrocycles with amide group were used in solvent extraction of picrates of metals such as Ag⁺, Hg²⁺, Cd²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Co²⁺ and Pb²⁺ from aqueous phase to the organic phase. The metal picrate extractions were investigated at 25±0.1°C by using UV‐visible spectrometry. The extractability and selectivity of the mentioned metal picrates were evaluated according to the organic solvents. The values of the extraction constants (log K_ex) and the complex compositions were determined for the extracted complexes.     

Synergistic Solvent Extraction and Separation of Lanthanide(III) Ions with 4‐Benzoyl‐3‐Phenyl‐5‐Isoxazolone and the Quaternary Ammonium Salt

The solvent extraction of the lanthanide(III) ions (without Pm) with a 4‐benzoyl‐3‐phenyl‐5‐isoxazolone(HPBI) alone and in the presence of the quaternary ammonium salt Aliquat 336 in perchlorate form (QClO₄) in C₆H₆ was investigated by the slope analysis method. The composition of the extracted species was determined as Ln(PBI)₃ and Q[Ln(PBI)₄] (Q⁺ is the quaternary ammonium salt cation). The values of the equilibrium constant were calculated. Synergistic effects were found for all lanthanide metals when they were extracted with a binary mixture of HPBI and QClO₄. The influence of the synergistic agent on the extraction process has been discussed. The parameters of the extraction process were determined. The separation factors between adjacent metals were evaluated.     

Interpretation of Third Phase Formation in the Th(IV)–HNO3, TBP–n‐Octane System with Baxter's “Sticky Spheres” Model

Abstract

Small‐angle neutron scattering (SANS) data for the tri‐n‐butylphosphate (TBP)–n‐octane, HNO₃–Th(NO₃)₄ solvent extraction system, obtained under a variety of experimental conditions, have been interpreted using two different models. The particle growth model led to unrealistic results. The Baxter model for hard‐spheres with surface adhesion, on the other hand, was more successful. According to this model, the increase in scattering intensity in the low Q range observed when increasing amounts of Th(NO₃)₄ are extracted into the organic phase, has been interpreted as arising from interactions between small reverse micelles containing three TBP molecules. Upon extraction of Th(NO₃)₄, the micelles interact through attractive forces between their polar cores with a potential energy of up to about 2 k_BT. The intermicellar attraction, under suitable conditions, leads to third phase formation. Upon phase splitting, most of the solutes of the original organic phase separate in a continuous phase containing interspersed layers of n‐octane.     

Liquid‐Liquid Extraction of Tetravalent Hafnium from Acidic Chloride Solutions using Bis(2,4,4‐trimethylpentyl) Dithiophosphinic Acid (Cyanex 301)

Abstract

Liquid‐liquid extraction studies of tetravalent hafnium from acidic chloride solutions have been carried out with bis(2,4,4‐trimethylpentyl) dithiophosphinic acid (Cyanex 301) as an extractant diluted in kerosene. Increase of acid concentration decreases the percentage extraction of metal. Plot of log D vs. log [HCl] gave a straight line with a negative slope of 2±0.1 indicating the exchange of two moles of hydrogen ions for every mole of Hf(IV) extractacted into the organic phase. Extraction of Hf(IV) increases with increase of extractant concentration. The plot of log D vs. log [HA] is linear with slope 2±0.1, indicating the association of two moles of extractant with the extracted metal species. The addition of sodium salts enhanced the percentage extraction of metal, and followed the order NaSCN>Na₂SO₄> NaNO₃>NaCl. Stripping of metal from the loaded organic (LO) with HCl and H₂SO₄ indicated sulphuric acid as the best stripping agent. Increase of temperature increases the percentage extraction of metal indicating the process is endothermic. Regeneration and recycling capacity of Cyanex 301, extraction behavior of associated elements such as Zr(IV), Ti(IV), Al(III), Fe(III), and IR spectra of the Hf(IV)‐Cyanex 301 complex was studied.     

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 Benzene and Naphthalene Carboxylic Acids Using Quaternary Ammonium Salts As a Model Study for the Separation of Coal Oxidation Products

Abstract

The ion‐pair solvent extraction of benzene‐ and naphthalene‐carboxylic acids has been investigated as a model study for the separation of coal oxidation products, which are formed by treatment with alkaline solutions at high temperatures. It was possible that benzene‐ and naphthalene‐dicarboxylic acids are extracted into several types of organic solvents with quaternary ammonium ions. The extraction equilibrium constants (K_ex) for benzoic acid, 1,2‐benzenedicarboxylic acid, 1,3‐benzenedicarboxylic acid, 1‐naphthoic acid, 2‐naphthoic acid, 2,3‐naphthalenedicarboxylic acid, and 2,6‐naphthalenedicarboxylic acid into chloroform were determined at 20°C. The difference of K_ex among the aromatic acids was sufficiently large for designing a separation method for these aromatic acids. It was unexpected that the extraction of dicarboxylic acids was slower than that of monocarboxylic acids, although the ion‐pair formation of aromatic carboxylate ion with quaternary ammonium ion is normally considered as a diffusion control reaction in aqueous phase. Thus, this fact suggests that the phase transfer of the ion‐pair from aqueous to organic phase is the rate‐determining step. Liner‐free‐energy relationship was observed for the monocarboxylic acids using different quaternary ammonium salts while that was ambiguous for the dicarboxylic acids. This is due to the steric influence of the counter ions for the magnitude of K_ex.     

Solvent Extraction of Uranium (VI) from Chloride Solutions using Cyphos IL-101

The solvent extraction of uranium (VI) from chloride solutions by Cyphos IL-101 in xylene has been studied. Distribution coefficients were found to increase with aqueous chloride concentration and extractant concentration. The enthalpy of extraction is endothermic with ΔH = +24 ± 2 kJ·mol^?1. Based upon slope analysis, an anion exchange extraction mechanism is proposed, with formation of a UO₂Cl₄ ^2- complex in association with 4 Cyphos IL-101 ligands. The extraction kinetics were fast, with complete equilibration occurring within 30 seconds. An isotherm for uranium extraction from 1.0 mol·L^?1 chloride solution by 0.1 mol·L^?1 Cyphos IL-101 in xylene shows that 45 mmol·L^?1 uranium can be loaded into the organic phase in equilibrium with 2.1 mmol·L^?1 in the aqueous phase. The absorption spectrum of the uranium loaded solvent between 350 and 550 nm is indicative of the UO₂Cl₄ ^2- complex with only chlorides present in the inner coordination sphere, unlike the more strongly hydrogen bonded Alamine 336 extracted uranium complex. Subject to the same experimental conditions, distribution coefficients for Cyphos IL-101 were significantly greater than for Alamine 336 or Aliquat 336.     

Extraction of Uranyl Ion Using 2-Thenoyltrifluoro Acetone (HTTA) in Room Temperature Ionic Liquids

The extraction of UO₂²⁺ ion was studied using six different solvent systems containing 2-thenoyltrifluoroacetone (HTTA) in room temperature ionic liquids such as [C_nmim][X] (where, n = 4, 6, or 8 and X^? = PF₆^? or NTf₂^?) from low to moderate pH solutions for the first time. The extraction kinetics studies indicated rather slow attainment of equilibrium which in some cases improved if the solutions were pre-equilibrated with the aqueous phase prior to the actual experiments. The D_U values were found to increase with increasing pH and leading to a plateau like profile at higher pH values. The D values were quite high as compared to that obtained with molecular diluents. The nature of the extracted species was ascertained by slope analysis method which suggested species of the type: UO₂(TTA)⁺_IL, UO₂(TTA)_2,IL, and UO₂(TTA)₂(HTTA)_IL in different ionic liquid based solvents. Temperature variation studies on UO₂²⁺ ion extraction were also carried out and the thermodynamic parameters were calculated which indicated high endothermicity of the reactions with large positive entropy values.     

From supercritical carbon dioxide to gas expanded liquids in extraction and chromatography of lipids

Analytical‐scale extraction and chromatography of oils, fats and other liposoluble compounds can be achieved by using supercritical carbon dioxide as a solvent. Since the 90's when supercritical fluid chromatography (SFC) was a hot topic, this technology has developed into a robust, modern analytical technique that uses any proportions of compressed CO₂ mixed with an organic solvent. Supercritical fluid extraction (SFE) on the other hand is only recently starting to reform in a similar way, towards the use of more robust extraction system and enabling mixing of compressed CO₂ with larger proportions of organic solvents. In this Feature article, the development of SFC and SFE into what options we have today is described, including the latest trend of using CO₂‐expanded liquid (CXL) as extraction solvent for lipids.     

Highly efficient extraction of tetra- and hexavalent plutonium using DGA functionalized pillar[5]arene in RTIL: Understanding speciation,thermodynamics and radiolytic stability

DGA functionalized pillar[5]arene (P5DGA) in ionic liquid was demonstrated as highly efficient system for the extraction of plutonium from acidic aqueous solution in tetravalent and hexavalent oxidation state. The extraction followed ‘cation-exchange’ mechanism via [Pu.P5DGA]⁴⁺ and [PuO₂.P5DGA]²⁺, as extracted species for Pu⁴⁺ and PuO₂²⁺, respectively. Evaluation of thermodynamic parameters (ΔG, ΔH and ΔS) showed the feasibility and spontaneity of the extraction process. The process was exothermic and primarily ‘enthalpy driven’, since entropy change was found negative. P5DGA-RTIL solvent system showed good radiolytic stability even at 1000 kGy of gamma dose.     

Removal of Copper(II) from a Concentrated Sulphate Medium by Cloud Point Extraction Using an N,N′-Bis(salicylaldehyde)Ethylenediimine Di-Schiff Base Chelating Ligand

Various chelating ligands have been investigated for the cloud point extraction of several metal ions. However, limited studies on the use of the Schiff base ligands have been reported. In this work, cloud point extraction behavior of copper(II) with N,N′‐bis(salicylaldehyde)Ethylenediimine Schiff base chelating ligand, (H₂SALEN), was investigated in aqueous concentrated sulphate medium. The extraction process used is based on the formation of hydrophobic H₂SALEN–copper(II) complexes that are solubilized in the micellar phase of a non‐ionic surfactant, i.e. ethoxylated (9.5EO) tert‐butylphenol. The copper(II) complexes are then extracted into the surfactant‐rich phase above cloud point temperature. Different parameters affecting the extraction process of Cu(II), such as equilibrium pH, extractant concentration, and non‐ionic surfactant concentration were explored. The extraction of Cu(II) was studied in the pH range of 2–11. The results obtained showed that it was profoundly influenced by the pH of the aqueous medium. The concentration factor, C_f, of about 17 with extraction efficiency of E % ≈100 was achieved. The stoichiometry of the extracted complex of copper(II) was ascertained by the Yoe–Jones method to give a composition of 1:1 (Cu:H₂L). The optimum conditions of the extraction‐removal have been established as the following: (1) 1.86 × 10^?3 mol/L ligand; (2) 3 wt% surfactant; (3) pH of 8 (4) 0.5 mol/L Na₂SO₄ and (5) temperature of 60 °C.     

Liquid–liquid extraction of Hg(II) from acidic chloride solutions using bis‐2‐ethylhexyl sulfoxide

The liquid–liquid extraction of Hg(II) from acidic chloride solutions has been studied using bis‐2‐ethylhexyl sulfoxide (B2EHSO) as an extractant. For comparison, extraction studies have also been carried out using di‐n‐octyl sulfoxide (DOSO) and diphenyl sulfoxide (DPhSO). The extraction data have been analysed by both graphical and theoretical methods taking into account aqueous phase speciation and all plausible complexes extracted into the organic phase. These results demonstrate that Hg(II) is extracted into xylene as HgCl₂.3R₂SO (where R₂SO represents the sulfoxide). The equilibrium constant of the extracted complex has been deduced by non‐linear regression analysis. The developed liquid–liquid extraction procedure has been applied for the recovery of mercury from the brine‐sludge of a Chlor‐Alkali plant. © 2001 Society of Chemical Industry     

Solvent Extraction of U(VI) by Calix[6]arenes

Abstract

This paper focuses on the solvent extraction of U(VI) traces by 1,3,5‐OMe‐2,4,6‐OCH₂CONHOH‐p‐tert‐butylcalix[6]arene (LH₃). The global extraction equation of U(VI) has been established. The complex formed in the organic phase is (UO₂)(LH) with an apparent extraction constant equal to 7.1×10^?5 M (I=0.04 M). Distribution data show that LH₃ efficiently extracts U(VI) from NaNO₃ media at pH 5 and that the stripping of U(VI) can be achieved in nitric acid solutions. Finally a comparison with previous results obtained with the 1,3,5‐OMe‐2,4,6‐OCH₂COOH‐p‐tert‐butylcalix[6]arene (L′H₃) shows that the hydroxamate groups are as efficient as the carboxylate ones for uranyl extraction.