Comparative Study on Reactive Extraction of Picolinic Acid with Six Different Extractants (Phosphoric and Aminic) in Two Different Diluents (Benzene and Decan-1-ol)

The equilibrium study on reactive extraction of picolinic acid by six different extractants (phosphoric and aminic) dissolved in two different diluents (benzene and decane-1-ol) is carried out to evaluate the performance of extractants and diluents. The extraction ability in terms of the distribution coefficient (K _D) is found to be in the order of tri-n-octylamine (TOA) ≥ tri-n-dodecylamine (TDDA) > di-2-ehylhexyl phosphoric acid (D2EHPA) > tri-n-butyl phosphate (TBP) > tri-octyl methyl ammonium chloride (Aliquat 336) > tri-n-octyl phosphine oxide (TOPO) with both diluents. Decan-1-ol is found to be the better solvating medium for the acid-extractant complexes. A mathematical model based on mass action law is employed to estimate the values of partition coefficient (P) and dimerization constant (D) in physical extraction, and equilibrium extraction constants (K _E) in chemical extraction. The values of loading ratios (Z) less than 0.5 imply the formation of (1:1) acid:extractant solvates in the organic phase. Decan-1-ol with TOA is the most effective solvation medium with K _{D, max} = 9 at 0.01 kmol · m^?3 of picolinic acid and K _E = 19.448 m³ · kmol^?1.     

SEPARATION OF PALLADIUM(II) FROM PLATINUM(II), IRIDIUM(III), AND RHODIUM(III) USING CENTRIFUGAL PARTITION CHROMATOGRAPHY

The separation of Pd(II) from Pt(II), Ir(III) and Rh(III) with trioctylphosphine oxide (TOPO) in heptane using centrifugal partition chromatography (CPC) has been investigated for the first time. The extraction of Pd(II) has been studied by CPC and batch solvent extraction. The distribution ratios for Pd(II) determined by both methods agree well. In low HCl concentrations (<0.1 M), the extracted species was PdCl₂.(TOPO)₂, irrespective of the chloride concentration, while at acid concentrations above 0.1 M, the Pd was extracted as the ion pair, 2(TOPO.H⁺).PdCl₄ ^2-. Base line separation of Pd(II) and Pt(II) in CPC was obtained under a variety of chloride and HCl concentration with the average number of theoretical plates being 390 ± 40 at a flow rate of 0.47 ± 0.05 mL/min.     

SOLVENT EXTRACTION OF METALS WITH 4-DINITROBENZOYL-2, 4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-ONE (DMPP)

ABSTRACT

The mechanism of the extraction of copper (II), nickel (II), cobalt (II) and thorium (IV) from aqueous buffer media with 4-dinitrobenzoyl1-2, 4-dihydro-5-methyl-2-phenyl-311-pyrazol-3-one (DMPP) in benzene has been investigated. The values of log K^*where K^*refers to the extraction equilibrium Mn⁺+-nHL ? MD_n+ nH⁺are Cu(II)& lpar; + 0.3), Co(II) (?6.65), Ni(II) (?5.04) and Th(IV) ( + 6.1). Solid complexes synthesized have the composition CuL₂· 2H₂O, NiL₂· 2H₂O and ThL₄respectively (L = anion of the ligand). DMPP seems to be superior to the corresponding 4-benzoyland 4-nitrobenzoyl derivatives of 2,4-dihydro-5-methyl-2-phenyl1-3 H-pyrazol1-3-one (MPP) and also better than thenoyltrifluoroacetone, the popularly employed fluorinated β-dike tone in the system investigated.     

SOLVENT EXTRACTION OF COPPER(II) WITH THE ACTIVE COMPONENT OF LIX 54. SYNERGIC EFFECT IN THE PRESENCE OF TRI-n-OCTYLPHOSPHINE OXIDE.

The extraction of Cu(II) from nitrate medium of ionic strength 1.0 mol.dm^-3 by l-phenyl-l,3-decanedione (HR) and by the mixture 1-phenyl-l,3-decanedione and tri-n-octylphosphine oxide (TOPO), dissolved in toluene, has been studied by distribution methods. The experimental data treated both graphical and numerically can be explained assuming the formation in the organic phase of the species CuR₂ and Cu(NO₃)R. The synergic effect found in the presence of TOPO has been explained by the formation of the complex CuR₂(TOPO). Equilibrium extraction constants for the species are given.     

REACTIVE EXTRACTION OF LEVULINIC ACID FROM AQUEOUS SOLUTIONS WITH TRI-n-OCTYLAMINE (TOA) IN 1-OCTANOL: EQUILIBRIA,KINETICS, AND MODEL DEVELOPMENT

Levulinic acid, a carboxylic acid containing a ketone structure, can be used as an acidulant in foods and beverages. Reactive extraction is a promising alternative for the recovery of carboxylic acids from aqueous streams. The design of an amine extraction process requires kinetic data for the acid-amine + solvent system used. In this study, equilibrium and kinetic data on the extraction of levulinic acid from aqueous solutions using tri-n-octylamine (TOA) in 1-octanol have been determined. The mass transfer coefficients of levulinic acid, TOA, and 2:1 levulinic acid-amine complex in 1-octanol were calculated from the acetic acid mass transfer coefficient, which was determined by measuring its fluxes of simple diffusion from kerosene to water. Based on the Hatta number and the criterion given by Doraiswamy and Sharma, the reaction regime has been found to be instantaneous reaction regime occurring at the interface on the organic phase side. An extraction model comprising equilibrium complexation constant w.r.t 2:1 levulinic acid-TOA complex formation, K_E2i (14.794 (m³ kmol^?1)²), and complex mass transfer coefficient, k_B2A (2.193 × 10^?6 m s^?1), has been developed.     

KINETIC STUDIES OF THE SOLVENT EXTRACTION OF PLATINUM(II) WITH DIPHENYLTHIOUREA

The race of extraction of plaCinum(II) wich diphenylthiourea (DPTU) into chloroform has been evaluated as a function of [DPTU]₀, [Cl] and the solution pH at 25° C. The homogeneous chemical reaction:

PtCl^? ₃ + DPTU → PtC1₃(DPTU)^?

is considered to be the rate determining step with a rate constant of 17.2 M^-1s^-1 The role of tetraheptylammonium chloride (THA^?,C1), thiourea (TU), thiocyanate, and iodide in catalyzing the extraction is examined.     

Extraction of Platinum(IV) with Trioctylamine and its Application to Liquid Membrane Transport

Abstract

The extraction and stripping behavior of platinum(IV) between trioctylamine (TOA) in kerosene and different aqueous media has been investigated. Perchlorate anion was found to be most effective for the stripping of platinum under acidic and neutral conditions. The transport of platinum was performed through a supported liquid membrane (SLM) impregnated with TOA as a mobile carrier. Platinum was almost quantitatively transported from the hydrochloric acid solution to the stripping solutions containing perchlorate anion against its large concentration gradient without accumulation in the liquid membrane layer. The transport behavior of platinum was greatly improved by the addition of 1-octanol in SLM, and the permeation rate was mainly controlled by diffusion in the aqueous boundary layer.     

Solvent-Extraction Behavior of Cobalt(II), Nickel(II), Copper(II), and Palladium(II) with Tri-n-butylphosphate

Abstract

A systematic study of the extraction behavior of cobalt(II), nickel(II), copper(II), and palladium(II) with TBP from thiocyanate system in various ranges of acid concentrations has been performed. The thiocyanate medium leads to enhanced extractions in all these cases compared to those in the previously used chloride medium. For palladium, the chloride and nitrate systems have been critically examined. Sixty-two per cent extraction occurs from 4 M hydrochloric acid using 100% TBP in a single run and the extraction becomes quantitative (>99%) after four successive equilibrations. A simpler method has been proposed for rapid extraction of palladium(II) as the thiocyanate complex. Quantitative extraction occurs in the presence of 1.2% thiocyanate solution from 0.5 to 2 M hydrochloric acid (initial) up to pH 8.0. The extractable species of cobalt(II), nickel(II), copper(II), and palladium(II) from thiocyanate medium are probably similar and of the type [M(CNS)₄]^2? [K·TBP·3H₂O]₂ ⁺ (buffer solution) and [M(CNS)₄]^2? [H·TBP·3H₂O]⁺ ₂ (acid solution). A simple extraction scheme has been worked out for the separation of palladium(II) from iron(III), cobalt(II), nickel, manganese(II), copper(II), and platinum.     

Methods for correction of selectivity of N-(2-sulfoethyl)chitosan-based materials towards platinum(IV) and palladium(II) ions

In this paper, we report methods for correction of selectivity of sorbents based on N-(2-sulfoethyl)chitosan towards platinum(IV) and palladium(II) in HCl solutions. The common method for correction of selectivity of the sorbents is variation of their modification degree with complexing groups. An increase in the degree of sulfoethylation of the chitosan leads to the significant increase in selectivity of sorption of palladium(II) over platinum(IV). Application of the N-(2-sulfoethyl)chitosan with the highest degree of sulfoethylation allows for selective separation palladium(II) from platinum(IV) (рН = 5.0). Palladium is quantitatively desorbed from the surface of the N-(2-sulfoethyl)chitosans by 3.5 mol/dm³ solution of HCl.     

Extraction relationship of Li+ and H+ using tributyl phosphate in the presence of Fe(III)

ABSTRACT

During the extraction of lithium from high Mg-containing salt lake brines by tributyl phosphate (TBP) in the presence of Fe(III), H⁺ is used to stabilize Fe(III). However, the distribution ratio of H⁺ (D_H) is 4–6 times higher than that of Li⁺ (D_Li), which affects the extraction of Li⁺ significantly. In this study, the competition mechanism between H⁺ and Li⁺ was investigated by spectral analysis and thermodynamic equilibrium. The extracted species are determined as HFeCl₄ · 2TBP and LiFeCl₄ · 2TBP for H⁺ and Li⁺, respectively. The apparent equilibrium constants are K_H = 799.8 and K_Li = 120.6, respectively. Both equilibrium constants and the distribution ratios for H⁺ and Li⁺ extraction show that extraction of H⁺ is stronger than Li⁺.     

Extraction of iridium(III) by ion-pair formation with 2-octylaminopyridine in weak organic acid media

To extract iridium(III), various physicochemical parameters were studied. 2-Octylaminopyridine was used for the extraction of iridium(III) from acetate medium at 8.5 pH. Quantitative extraction of iridium(III) was achieved via ion-pair formation of cation [2-OAPH⁺] and anion [Ir(CH₃COO)₄]^?. The stripping of iridium(III)-laden organic phase was carried out 2 M HCl (3 × 10 mL) . The stoichiometry of the extracted ion–pair complex was found to be 1:4:1 (metal: acetate: extractant). The extracted species [2-OAPH⁺. Ir(CH₃COO)₄^?] is assumed to be an ion association product of [Ir(CH₃COO)₄] ^? and [2-OAPH]⁺. The proposed method was successfully used in the separation of iridium(III) from binary and ternary mixtures. Analysis of various alloy samples was also carried out.     

Synergistic Extraction of Plutonium (IV) from Nitric Acid Medium by Mixtures of TOPO and HTTA

Abstract

Synergistic solvent extraction of Pu(IV) from nitric acid medium by mixtures of thenoyltrifluoroacetone (HTTA) and tri-n-octylphosphine oxide (TOPO) in benzene was investigated by a method developed for such studies. The species involved in the extraction were identified as Pu(NO₃)₄ · 2TOPO, Pu-(N0₃)₃(TTA) · 2TOPO, Pu(NO₃)₂(TTA)₂ · TOPO, and Pu(NO₃)(TTA)₃ · TOPO. The concentration equilibrium constants for the extraction of all the suggested species from 1.0 M nitric acid were calculated from the data obtained, and the concentration equilibrium constants for their formation in the organic phase were estimated.     

PARAFFIN WAX - TOPO,AN EXTRACT ANT FOR ACTINIDES AND LANTHANIDES

ABSTRACT

Paraffin wax - TOPO has been used for the extraction of Eu³⁺, Pu⁴⁺, and U0₂ ²⁺ from HN0₃ solutions at 65^° C. The extraction of Eu³⁺ increased with increasing TOPO percent in the wax phase but it decreased with increasing HNO₃ or Eu³⁺ carrier concentrations. The extraction of Pu4+ at tracer and U022+ between 2 to 10 mg (U)/ml from 0.5 to 1.0 M HN0₃ was almost quantitative while using 10 or 15% TOPO/wax at an aqueous to wax phase ratio of 1:1. In presence of uranyl ion, the extraction of Eu³⁺ decreased under all conditions. The best possible condition has been established and a scheme has been proposed for the separation of trivalent actinides and lanthanides, Pu⁴⁺ and U0₂ ²⁺ from their mixtures in laboratory wastes by using non-preequilibrated 15% TOPO/wax. The metal ions were individually stripped using various reagents. The easy phase separation from use of paraffin wax as the diluent makes the separation technique very simple.     

Extraction equilibria of chromium(VI) from sulfuric acid solutions with tri-n-octylphosphine oxide

The extraction equilibria of chromium(VI) from sulfuric acid solutions with tri-n-octylphosphine oxide (TOPO) dissolved in kerosene at 25°C have been studied. The possible complexes of chromium(VI) with TOPO in organic phase and extraction constants were determined by best fitting the distribution coefficient expression of Cr(VI) with experimental data using the Rosenbrock method. The extraction reactions, including the equilibria among seven species in aqueous phase (H₂CrO₄, HCrO₄⁻, HCr₂O₇⁻, Cr₂O₇²⁻, CrSO₇²⁻, HSO₄⁻ and SO₄²⁻) and five possible complexes in organic phase (H₂CrO₄·(TOPO), H₂Cr₂O₇·(TOPO)₃, H₂CrSO₇·(TOPO)₃, H₂SO₄·(TOPO)₂ and (H₂SO₄)₂·(TOPO)₂) were proposed. The influence of initial sulfuric acid concentration on the fraction of extracted complexes and on the distribution coefficients of Cr(VI) is discussed. This result was helpful for the clarification of the extraction reactions of Cr(VI). © 1998 Society of Chemical Industry     

Kinetics of Solvent Extraction of Iron(III) from Sulfate Medium by Purified Cyanex 272 using a Lewis Cell

Abstract

The kinetics of the forward and backward extraction of the title process have been investigated using a Lewis cell operated at 3 Hz and flux or (F) – method of data treatment. The dependences of (F) in the forward extraction on [Fe³⁺], [H₂A₂]_(o), pH, and [HSO₄ ^?] are 1, 0.5, 1, and ?1, respectively. The value of the forward extraction rate constant (k _f ) has been estimated to be 10^?7.37 kmol^3/2 m^?7/2 s^?1. The analysis of the experimentally found flux equation gives the following simple equation: F _f =10^0.13 [FeHSO₄ ²⁺] [A^?], on considering the monomeric model of BTMPPA and the stability constants of Fe(III)‐HSO₄ ^? complexes. This indicates the following elementary reaction occurring in the aqueous film of the interface as rate determining: [FeHSO₄]²⁺+A^?→[FeHSO₄.A]⁺. The very high activation energy of 91 kJ mol^?1 supports this chemical reaction step as rate-determining. The negative value of the entropy change of activation (?94 J mol^?1 K^?1) indicates that the slow chemical reaction step occurs via the S_N2 mechanism.

The backward extraction rate can be expressed by the equation: F _b =10^?5.13 [[FeHSO₄A₂]]_(o) [H⁺] [H₂A₂]_(o) ^?0.5. An analysis of this equation leads to the following chemical reaction step as rate-determining: [FeHSO₄A₂]_(int)→[FeHSO₄A]+A_(i) ^?. However, the activation energy of 24 kJ mol^?1 suggests that the backward extraction process is intermediate controlled with greater contribution of the diffusion of one or the other species as a slow process. The equilibrium constant obtained from the rate study matches well with that obtained from the equilibrium study.     

SOLVENT EXTRACTION EQUILIBRIA OF LEAD(II) WITH ACIDIC ORGANOPHOSPHATE AND PHOSPHONATE

Distribution equilibria of lead(II) in the extraction with di(2-ethylhexyl)phosphoric acid and 2-ethylhexyl 2-ethylhexylphosphonic acid in toluene from aqueous ammonium nitrate solutions were measured at 303 K to elucidate the concentration dependencies of the reactant species on the distribution ratio. It was found that lead(II) is extracted as the mononuclear complex, PbR₂2HR, with the former extrac-tant while it is extracted not only as the complex, PbR₂2HR, but also as the complex, Pb(NO₃)R;HR, accompanied by simultaneous transfer of nitrate anion with the latter ex-tractant. The extraction equilibrium constants of these complexes were evaluated as well as the stability constants of lead(II) -nitrato complexes, Pb(NO₃)⁺, Pb(NO₃)₂and Pb(NO₃)^? ₃.     

Studies on the Separation and Recovery of Uranium from Phosphoric Acid Medium Using a Synergistic Mixture of (2-Ethylhexyl)phosphonic Acid Mono 2-Ethyl Hexyl Ester (PC-88A) and Tri-n-octylphosphine Oxide (TOPO)

This paper deals with studies on the extraction of uranium(VI) from phosphoric acid medium using (2-ethylhexyl)phosphonic acid mono 2-ethylhexyl ester and tri-n-octylphosphine oxide individually as well as from their synergistic mixture. Different extraction parameters were investigated. With an increase in phosphoric acid concentration in the aqueous phase, the distribution ratio (Du) was found to decrease in all the cases. Synergism was observed when a mixture of PC-88A and TOPO was used. The synergistic mixture in the mole ratio of 4:1 (1.80 M PC-88A: 0.45 M TOPO) in xylene was found to be most suitable for uranium extraction. Among the various strip liquors used, 5% (w/v) solution of (NH₄)₂CO₃ was found to be the most suitable. Using a mixture of 1.8 M PC-88A and 0.45 M TOPO as the extractant system and 0.5 M ammonium carbonate as the stripping agent, uranium recovery was found to be better than 97% ± 3% in multiple contacts, (n = 2) from actual Davies Gray Waste while in case of wet phosphoric acid more than 52% ± 3% (n = 3) only could be recovered where n is the number of contacts.     

The Development of Palladium(II)-Specific Amine-Functionalized Silica-Based Microparticles: Adsorption and Column Separation Studies

The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl₆]^2? and [PdCl₄]^2?) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl₆^2? and PdCl₄]^2?. The adsorption model for both [PtCl₆]^2? and [PdCl₄]^2? on the different sorbent materials fitted the Freundlich isotherm with R² values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl₆]^2? with 0.5 M of NaClO₄ in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources.     

SPECTROSCOPIC STUDY OF THE EXTRACTION OF NICKEL BY 2-HYDROXY-5-NONYLBENZOPHENONE OXIME (LIX 65N) AND 5,8-DIETHYL-7-HYDROXYDODECANE-6-ONE OXIME (LIX 63).

ABSTRACT

A novel method for determination of solvent extraction equilibria and kinetics using Infrared attenuated total reflectance spectroscopy (ATR) is described. The method allows complete, quantitative kinetic studies using a total of one gram of extractant. Solvent extraction of aqueous Ni²⁺ into 0.5 - 1.0 μm films of Apiezon M (ApM, aliphatic hydrocarbon) containing the title reagents was examined. In contrast with LIX 65N extraction which proceeds solely through the LIX 65N anion, extraction of Ni²⁺ by LIX 63 proceeds through both neutral and anionic forms of LIX 63. This results in a kinetic rate law having two terms, each exhibiting first order dependence on both [Ni²⁺] and [LIX 63]₀. For mixtures of LIX 65N and LIX 63 (LIX 63:LIX 65N ≤ 0.12) In the ApH films, the rate law has only one term, of orders [LIX 65N]₀ ¹, [LIX 63] ₀ ¹, [Ni²⁺]¹, and [H⁺]^?1. While the equilibrium constants favor Ni(LIX 65N)₂, the relatively large rate of reaction of the neutral LIX 63 leads to a catalysis of the overall LIX 65N extraction.     

One unexpected mixed-valence Cu(I,II)-cyanide coordination polymer in situ originating from the cleavage of acetonitrile

Solvothermal reaction of CuCl₂·2H₂O and 2-(4-pyridyl)benzimidazole (PyHBIm) in a acetonitrile-water mixed solvent afforded a mixture of [Cu^I₂Cu^II(CN)₂(PyHBIm)₂Cl₂]_n (1) and [Cu^II(PyH₂BIm)₂Cl₄] (2). Complex 1 is a mixed-valence 1D ribbon Cu(I,II)-cyanide coordination polymer. One Cu(II) center linearly links two Cu(I) ions via two μ₂-CN bridges. XPS spectrum and bond valence sum (BVS) analysis have confirmed the mixed-valence characteristics. Cu(II) ion adopts a centrosymmetric square-planar geometry surrounded by two cyanides and two pyridyl groups. Cu(I) ions adopt a trigonal geometry coordinated by cyanide, imidazole group and Cl⁻ anion. The cyanide ligand is in situ generated from the cleavage of acetonitrile solvent, which indicates that acetonitrile is an environmentally friend cyanating agent. The mechanism of acetonitrile in situ cleavage under solvothermal condition is explained. Complex 2 is a centrosymmetric mononuclear Cu(II) compound. Four equivalent Cl⁻ anions lie on the equatorial plane. The protonated PyH₂BIm⁺ cation as a monodentate ligand coordinates to Cu(II) center via pyridyl terminal.