Extraction Equilibrium Constants Research Articles

Extraction Equilibria of Palladium(II) and Platinum(IV) with N,N-Di(2-ethylhexyl)aminomethylquinoline from Hydrochloric Acid

N,N-Di(2-ethylhexyl)aminomethylquinoline (DEQ) has been newly synthesized to develop selective extractants for precious metals. DEQ is designed so as to exhibit high selectivity for precious metals through the electrostatic force and coordination ability of the tertiary amine and quinoline moieties, respectively. DEQ in toluene exhibits a high selectivity for gold(III), palladium(II) and platinum(IV) over base metals such as copper(II), nickel(II) and cobalt(II) from hydrochloric acid. This is attributed to the strong basicity of the tertiary amine and high coordination ability of quinoline for precious metals. Palladium(II) and platinum(IV) extraction is significantly dependent on the concentration of hydrochloric acid, while gold(III) is quantitatively extracted over the whole concentration region of hydrochloric acid examined. We have quantitatively discussed the extraction equilibria of palladium(II) and platinum(IV) with DEQ in toluene from hydrochloric acid. It is observed that palladium(II) was extracted by the anion exchange mechanism, while platinum(IV) was extracted through the anion exchange and solvation mechanisms. Palladium(II) was extracted as a 1 : 1 complex formed by ion pair formation and coordination bonding, and its extraction equilibrium constant was determined as 1.28 × 107 [-]. Platinum(IV) was extracted as a 1 : 1 complex and a 1 : 2 complex at low and high concentrations of hydrochloric acid, respectively. These extraction equilibrium constants were determined as 4.15 × 102 [mol dm−3] and 3.46 × 104 [-], respectively.

Kinetics of Au (III) extraction by DBC from hydrochloric solution using Lewis cell

The kinetics of forward extraction [AuCl4]− from aqua regia medium by diethylene glycol dibutyl ether (DBC) have been investigated by the Lewis cell (LC) technique. At first gold extraction has been carried out under different experimental conditions for achieving the stoichiometry coefficients and the value of the extraction equilibrium constant (K=0.1). For kinetic data treatment, flux ‘F’ method has been applied. Reaction order with respect to DBC, pH and [AuCl4]− was determined and then the rate constant was calculated. The rate of gold extraction from 2M chloride medium can be expressed as F=100.88[AuCl4−]1.25 [DBC]0.4 [H+]−0.22. Kinetics data were treated by EVIEWS software and coefficients were obtained. The comparison of manual and software results indicated that the results had good conformity. Influence of temperature was studied and then activation energy, Ea, (11.17kJ/mol), activation enthalpy (11.66kJ/mol) and entropy (−187J/molK) were calculated by using Arrhenius and activation complex theory respectively. Ea value (<20.9kJ/mol) indicates that, the extraction of gold (III) in the investigated system is controlled by diffusion process.

The effective recovery of praseodymium from mixed rare earths via a hollow fiber supported liquid membrane and its mass transfer related

The recovery of praseodymium from mixed rare earths via a hollow fiber supported liquid membrane (HFSLM) was examined. Bis(2,4,4-trimethylpentyl) phosphinic acid – known as Cyanex 272 – was used as an extractant carrier. The stripping solution was hydrochloric acid solution. The experiments examined in functions of the concentrations of the carrier in liquid membrane, the (initial) pH's of initial feed solution within the acidic-pH range, the concentrations of hydrochloric acid, the flow rates of feed and stripping solution, and the operation mode of runs through the hollow fiber module. In addition, the influence of circulation of the stripping solution at various numbers of runs through the HFSLM on the outlet concentration of praseodymium ions in the stripping solution was observed. Mass transfer mechanism in the system was investigated. Extraction equilibrium constant ( K ex), distribution ratio ( D), permeability ( P) and mass transfer coefficients were determined. The aqueous-phase mass-transfer coefficient ( k i) and organic-phase mass-transfer coefficient ( k m) were reported to 0.0103 and 0.788 cm s −1, respectively, in which k m is much higher than the k i. Thus it suggests the rate-controlling step is the diffusion of praseodymium ions through the film layer between the feed solution and the liquid membrane. Model prediction of the dimensionless concentrations and separation factors were also put on trial in this paper. The results showed promising agreement with the experimental data.

Mathematical modeling of cadmium(II) solvent extraction from neutral and acidic chloride media using Cyanex 923 extractant as a metal carrier

This paper describes experimental work and the mathematical modeling of solvent extraction of cadmium(II) from neutral and acidic aqueous chloride media with a Cyanex 923 extractant in Exxol D-100. Solvent extraction experiments were carried out to analyze the influence of variations in the composition of the aqueous and organic phases on the efficiency of cadmium(II) extraction. In neutral and acidic chloride conditions, the extraction of cadmium(II) by the organophosphorous extractant Cyanex 923 (L) is based on the solvation mechanism of neutral H n CdCl (2+ n) species and the formation of H n CdCl (2+ n) L q complexes in the organic phase, where n = 0, 1, 2 and q = 1, 2. The mathematical model of cadmium(II) extraction was derived from the mass balances and chemical equilibria involved in the separation system. The model was computed with the Matlab software. The equilibrium parameters for metal extraction, i.e. the stability constants of the aqueous Cd–Cl complexes, the formation constants of the acidic Cd–Cl species and the metal equilibrium extraction constants, were proposed. The optimized constants were appropriate, as there was good agreement when the model was fitted to the experimental data for each of the experiments.

Solvent extraction equilibrium of dysprosium(III) from nitric acid solutions with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester

Abstract In view of the importance of solvent extraction of rare earth metals with the acidic organophosphorous reagent, the development of a chemically based model applicable to high concentration is desired. In the present study, the equilibrium distribution of dysprosium(III) between an aqueous nitric acid solution and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A) was measured in the range of an initial aqueous dysprosium(III) concentration from 1.0×10 −3 to 1.0×10 −1 kmol/m 3 and PC88A concentration from 0.16 to 0.65 kmol/m 3 in Shellsol D70 as the diluent. The obtained data were analyzed using the chemically based model in order to correlate the equilibrium distribution ratios. In this model, dysprosium(III) was assumed to be extracted with the PC88A dimer as a 1:3 complex, the activities were considered for the aqueous species, and the effective concentration of the PC88A dimer was calculated using Alstad's empirical equation. As a result, the apparent extraction equilibrium constant was determined to be 253 (kmol·m −3) −2 with an excellent correlation between the experiment and calculation results in the wide range of the logarithm of the distribution ratio from −2 to 3.5. In conclusion, the methodology in this model would be effective for quantitative description of solvent extraction behavior of general rare earth elements as well as dysprosium.

Solvent extraction equilibrium study of manganese(II) with Cyanex 302 in kerosene

Abstract The single-stage extraction of manganese(II) sulphate with Cyanex 302 in kerosene (O:A = 1:1) has been studied. The pH50 values are 5.75, 5.35, 5.20 and 4.15 for 0.025, 0.05, 0.07 and 0.1 M Cyanex 302, respectively. The mechanism of extraction and stoichiometries of metal-containing extracted species has been established on the basis of slope analysis and the distribution data has been used to calculate the extraction equilibrium constant. From the slope analysis data, the composition of the extracted species in the organic phase is proposed to be MnR2(RH)4. The temperature variation studies show that the extraction process is exothermic which is confirmed from the negative value of ∆H. The negative value of ∆S indicates strong complexation between Mn(II) and Cyanex 302.

Liquid-liquid extraction and recovery of gallium(III) from acid media with 2-octylaminopyridine in chloroform: Analysis of bauxite ore

The liquid-liquid extraction of gallium(III) from hydrochloric acid solution using 2-octylaminopyridine (2-OAP) in chloroform was investigated. The extraction of gallium(III) from 6.0-9.0 mol dm-3 hydrochloric acid was found to be quantitative using 0.033 mol dm-3 2-OAP in chloroform. The effect of the reagent concentration and other parameters on the extraction of gallium(III) was also studied. The stoichiometry of the extracted species of gallium(III) was determined based on the slope analysis method. The extraction reaction proceeded via the anion exchange mechanism from hydrochloric acid and the extracted species was [RR?NH2+GaCl4-]org. The extraction of gallium(III) was performed in the presence of various ions to ascertain the tolerance limit to individual ions. The temperature dependence of the extraction equilibrium constants was examined to estimate the apparent thermodynamic functions (?H, ?S and ?G) for the extraction reaction. Gallium(III) was successfully separated from commonly associated metal ions, such as Zn(II), Pb(II), Cd(II), Hg(II), Bi(III), Al(III), Se(IV), Sb(III), Sn(IV), In(III), Tl(I) and Tl(III). However, gallium(III) was separated from Fe(III) from weak organic acid media. The procedure was also extended to the determination of gallium(III) in bauxite ore by the standard addition method.

Extraction chromatographic method of preconcentration and separation of lead (II) with high molecular mass liquid cation exchanger

A selective method has been developed for the extraction chromatographic separation of lead (II) with Versatic 911 (liquid cation exchanger) coated on silanised silica gel. Lead (II) has been extracted from 0.1 M acetate buffer at the range of pH 4.5–6.5. The effects of pH, flow-rate, stripping agents on extraction and elution have been investigated. Exchange capacity of the prepared exchanger at different temperatures with respect to lead (II) has been determined. The extraction equilibrium constant ( K ex) and different standard thermodynamic parameters have also been calculated by temperature variation method. The effect of pH on R f values in ion exchange paper chromatography has been investigated. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. Lead (II) has been separated from synthetic binary and multi-component mixtures containing various metal ions associated with it in ores and alloy samples. The method effectively permits sequential separation of lead (II) from synthetic quaternary mixture containing its congeners Cu (II), Sn (II), Hg (II) and Cu (II), Cd (II), Bi (III) of the same analytical group. The method was found effective for removal and recovery of lead (II) from industrial waste and standard alloy samples following its preconcentration on the column. A plausible mechanism for the extraction of lead (II) has been suggested.

Allosteric coextraction of sodium and metal ions with calix[4]arene derivatives 1

Solvent extraction of three alkali metal ions with p-t-octylcalix[6]arene hexacarboxylic acid, p-t-octylcalix[4]arene tetracarboxylic acid, corresponding linear trimeric and monomeric analogs was investigated. Cyclic tetramer selectively extracts sodium ion among alkali ions at extremely low pH, while the corresponding cyclic hexamer, the trimer, and the monomer exhibited only poor extraction ability for all alkali metals examined. The detailed extractive investigation of sodium ions with the cyclic tetramer was carried out. It was found that two sodium ions are simultaneously extracted by a single molecule of calix[4]arene derivative and that the second sodium extraction is facilitated by the uptake of the first sodium. The self-coextraction mechanism of sodium ions proposed in the present paper also strongly supports allosteric coextraction of sodium and other metal ions. In the competitive extraction of four alkali metal ions, potassium ion was slightly extracted as the second ion at low pH region, whereas it was hardly extracted in the individual extraction system. The result also supports the coextraction mechanism and role of the first-extracted sodium ion as an allosteric trigger. The extraction equilibrium constants of the cyclic tetramer and two sodium ions, Kex1 and Kex2, were estimated.

Reactive extraction of diols with phenyl boronic acid and trioctylmethylammonium chloride as coextractants and quantitative structure–property relationship of their extraction behaviors

AbstractBACKGROUND: Diols that can be produced biologically have attracted much attention because of the increased cost of producing them chemically. The cost of separating the diols from the broth forms a major part of the total cost of microbial production. Reactive extraction using organoboronate is one promising method for recovering diols from the dilute aqueous solution.RESULTS: A basic investigation of solvent extraction of diols was conducted at 303 K employing phenylboronic acid and trioctylmethylammonium chloride as coextractants in the mixed solvent. Both the tetrahedral boronate anion complex and trigonal boronate neutral complex were extracted. 1,3‐diols and vicinal diols were extracted, but 1,4‐diol was not extracted. Extraction equilibrium constants were correlated with the enthalpies of formation of the complexes, which were calculated by molecular modeling with semi‐empirical molecular orbital calculations considering the solvent effect.CONCLUSION: The complex extraction behaviour of diols with phenylboronic acid and quaternary ammonium salt can be predicted by using the quantitative structure–property relationship (QSPR). Copyright © 2009 Society of Chemical Industry

Investigation of phase equilibria of levulinic acid distribution between aqueous phase to organic phase by Aliquat 336 in different modifiers

The extraction of levulinic acid by tricaprylmethylammonium chloride (Aliquat 336) dissolved in five alcohols solvents (isoamyl alcohol, hexan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol) and five esters solvents (dimethyl phthalate, dimethyl adipate, dimethyl succinate, dimethyl glutarate, diethyl carbonate), two ketones (diisobutyl ketone (DIBK), methyl isobutyl ketone (MIBK)) were investigated to understand effect of modifier on levulinic acid extraction. In addition to these Aliquat 336 + modifier system, the experiments were done also with single solvents. All measurements were carried out T = 298.15 K. Organic solutions of Aliquat 336 are being used increasingly to separate organic acids from aqueous mixture solutions by reactive extraction. The extent to which the organic phase may be loaded with levulinic acid is explained as a loading ratio, Z Z , extraction efficiency E and, distribution coefficients K D were calculated. The maximum extraction efficiency was obtained value of 72.1 for isoamyl alcohol. The extraction equilibrium constant, K E, has been calculated for each modifier. Furthermore, Freundlich, Langmuir, and LSER model equations have been obtained for experimental data of alcohols.

Extraction of Pyridine-3-carboxylic Acid Using 1-Dioctylphosphoryloctane (TOPO) with Different Diluents: Equilibrium Studies

Pyridine-3-carboxylic acid (also known as nicotinic acid) is widely used in food, pharmaceutical, and biochemical industries. The production of acid can be intensified by enzymatic conversion of 3-cyanopyridine or biosynthesis and by reactive extraction used as a separation step from a dilute fermentation broth. The extraction of pyridine-3-carboxylic acid by 1-dioctylphosphoryloctane, also known as tri-n-octylphosphine oxide (TOPO), with five different diluents (n-octane, methylbenzene, 4-methyl-2-pentanone (MIBK), decan-1-ol, and dichloromethane) is studied. The equilibrium experiments are carried out to investigate the effects of diluent, extractant (TOPO) composition, and initial acid concentration on extraction efficiency. The extraction efficiency is found to increase with increasing TOPO composition concentration, (0.10 to 0.60) mol·m−3, and found to decrease with increasing initial acid concentration, (0.02 to 0.12) mol·m−3. The number of TOPO molecules in the acid:TOPO complex is estimated through a proposed mathematical model using graphical methods as well as through an optimization route using the differential evolution algorithm and found to be 1:1 complexes in most of the cases. The extraction equilibrium constants are also determined. In all the tested diluents, methylbenzene containing the benzene ring in the structure is the best solvating agents for acid−TOPO complexation giving KE1 = 5.04.

Temperature effect on the solvent extraction of copper(II), cobalt(II) and nickel(II) with salicylideneaniline from sulphate media

The temperature effect on the solvent extraction of copper(II), cobalt(II) and nickel(II) by Schiff base salicylideneaniline (SAN) in chloroform from sulfate aqueous medium of constant ionic strength was studied. The temperature dependence of the extraction equilibrium constants were investigated to estimate the variation of enthalpy (ΔH) and entropy (ΔS). These thermodynamic functions were, as a result, calculated and discussed in conjunction with the structure of the extracted species. It was found that the extraction of each metal increased with increase in temperature. Besides ΔH and ΔS have been discussed in connection with the nature of bonding and also the symmetry of the metal complexes. It was established through this study that the types of bonding in the complexes formed in the aqueous solution are clearly reflected by the values of ΔH and ΔS for the complex formation reaction.

Solvent extraction of trivalent indium from succinate solution by 2-octylaminopyridine in chloroform

Extraction processes of indium(III) with 2-octylaminopyridine (2-OAP) from media of various complexing ability, succinate and salicylate, in chloroform have been elucidated. The ion-pair complex has also quantitative extraction in xylene and 1,2-dichloroethane. Indium(III) from organic phase was stripped with 1.0 M hydrochloric acid and determined complexometrically with EDTA. The stoichiometry of the extracted species was found out on the basis of slope analysis. The extraction of indium(III) proceeds by an anion exchange mechanism and the extracted species is [RR′NH2+In(succinate)2-](org). Temperature dependence of the extraction equilibrium constant was also examined to estimate the apparent thermodynamic functions (ΔH, ΔG and ΔS) for extraction reaction. It is possible to separate indium(III) from Zn(II), Cd(II), Pb(II), Hg(II), Bi(III), Tl(I), Tl(III), Ga(III), Al(III), Te(IV), Se(IV), Sb(III), Fe(III) and Sn(IV). The method is simple, rapid and reproducible and can be used to determine the indium from samples like alloys.

Equilibrium study on reactive extraction of propionic acid with N1923 in different diluents

The equilibrium for the propionic acid extraction by N1923 in three diluents, represented as proton-donator (n-octanol), polar (butyl acetate), inert (hexane) types, have been studied. The diluents had a significant influence on the equilibrium. The loading ratio, Z, was employed to investigate the effect of diluents on the extraction efficiency. When Z exp was lower than 1, N1923 extraction followed the order: n-octanol > butyl acetate > hexane. When the loading ratio Z exp was higher than 1, the order changed to: butyl acetate > hexane > n-octanol. Equilibrium complex constants K 11, K 21, K 31 have been estimated. The results showed that K 11 was much higher than K 21 and K 31, demonstrated K 11 as the dominant factor in the extraction process. Comparing the values of K 11 of all the three diluents, the following order was observed: n-octanol > butyl acetate > hexane. The influence of amine concentration on the extraction equilibrium constant in different diluents was also investigated. The extraction equilibrium constant K 11 decreased with the increase of amine concentration in n-octanol. When hexane and butyl acetate were used as diluent, the extraction equilibrium constant K 11 increased slightly with the increase of amine concentration.

Extraction chromatographic method of preconcentration and separation of fluoride with high molecular mass liquid anion exchanger, Aliquat-336

A selective method has been developed for the extraction chromatographic separation of fluoride with Aliquat-336 (liquid cation exchanger) coated on silanised silica gel. Its quantitative extraction has been achieved in HCl medium at 0.1-0.3 M range. The effects of acid with different concentrations, flow-rate, stripping agents on extraction and elution have been investigated. Exchange capacity and break-through capacity of the prepared exchanger at different temperatures with respect to fluoride have been determined. The extraction equilibrium constant (K ex ) and different standard thermodynamic parameters have also been calculated by temperature variation method. Effect of influent concentration and influent volume on preconcentration factor (PF) has been investigated. Fluoride has been separated from synthetic binary and multi-component mixtures containing various anions associated with it in environmental samples. The method effectively permits sequential separation of fluoride from synthetic mixture containing its congeners, chloride, bromide and iodide of analytical group. The method was found effective for removal and recovery of fluoride from industrial waste and environmental samples following its preconcentration on the column. A plausible mechanism for the extraction of fluoride has been suggested.

Two‐Phase Calorimetry. I. Studies on the Thermodynamics of Lanthanide Extraction by Bis(2‐EthylHexyl) Phosphoric Acid

Enthalpies of extraction of lanthanide ions by bis(2‐ethylhexyl) phosphoric acid (HDEHP) from aqueous nitrate solutions have been determined using isothermal titration microcalorimetry. This solvent extraction system was chosen as a model for developing a direct method of calorimetric investigation of thermochemistry of liquid‐liquid distribution reactions because it has been well‐studied and is predictable. To provide a quantitative validation for a two‐phase calorimetric technique, the enthalpy of extraction of europium(III) by HDEHP also was determined applying the more conventional method of van't Hoff analysis of temperature dependent extraction equilibrium constants. Within the accuracy of the measurements, the determination of thermodynamic parameters by the complementary techniques agreed. The extraction enthalpies determined in this study have been correlated with reported free energies of extraction of the lanthanides to reveal the patterns of extraction entropies observed across the lanthanide series. Challenges and opportunities for application of two‐phase calorimetry as a new analytical method for routine analyses of the thermochemistry of solvent extraction reactions are discussed.

Synergistic extraction of rare earth by mixtures of 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester and di-(2-ethylhexyl) phosphoric acid from sulfuric acid medium

The extraction of Nd 3+ and Sm 3+, including the extraction and stripping capability as well as the separation effect of Nd 3+ or Sm 3+, from a sulfuric acid medium, by mixtures of di-(2-ethylhexyl) phosphoric acid (HDEHP, H 2A 2(0)) and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (HEH/EHP, H 2L 2(0)) were studied. The distribution ratios and synergistic coefficients of Nd 3+ and Sm 3+ in different acidities were also determined. A synergistic extractive effect was found when HDEHP and HEH/EHP were used as mixed extractants for Sm 3+ or Nd 3+. The chemical compositions of the extracted complex were determined as Nd · (HA 2) 2 · HL 2 and Sm · (HA 2) 2 · HL 2. The extraction equilibrium constants, enthalpy change, and entropy change of the extraction reaction were also determined.

Rapid liquid-liquid extraction of thallium(III) from succinate media with 2-octylaminopyridine in chloroform as the extractant

A simple solvent extraction study of thallium(III) was conducted. Selective and quantitative extraction of thallium(III) by 2-octylaminopyridine (2-OAP) in chloroform occurred from aqueous sodium succinate medium (0.0075 M) at pH 3.0. Thallium(III) was back extracted with acetate buffer (pH 4.63). The effect of the concentration of succinate and 2-OAP, the role of various diluents, stripping agents, loading capacity of 2-OAP, equilibrium time and aqueous:organic volume ratio on the extraction of thallium(III) was studied. The stoichiometry of the extracted species was determined based on the slope analysis method and found to be 1: 2: 1 (metal:acid:extractant). The temperature dependence of the extraction equilibrium constant was also examined to estimate the apparent thermodynamic functions ?H, ?G and ?S for the extraction reaction. The method is free from interference of a large number of cations and anions. The method was used for the selective extraction of thallium(III) from its binary mixture with Zn(II), Cd(II), Hg(II), Bi(III), Pb(II), Se(IV), Te(IV), Sb(III), Ga(III), In(III), Al(III), Tl(I) and Fe(III). The proposed method was applied to the synthetic mixtures and alloys. It is simple, selective, rapid and eco-friendly.

Synthesis, Characterization and Extraction Properties of Four Unsymmetricall vic‐Dioximes and their Complexes with Nickel (II), Cobalt (II) and Copper (II)

Four new unsymmetrical vic‐dioximes: [L 1 H 2 ] N‐(4‐acetanilidyl)amino‐amphi‐glyoxime, [L 2 H 2 ] N‐(4‐acetanilidyl)amino‐anti‐glyoxime, [L 3 H 2 ] N‐(2‐thiazolyl)amino‐amphi‐glyoxime and [L 4 H 2 ] N‐(2‐thiazolyl)amino‐anti‐glyoxime were prepared by the reaction of amphi‐chloroglyoxime and anti‐chloroglyoxime with 4‐aminoacetanilide and 2‐aminothiazol in absolute ethanol. The preparation Ni(II), Co(II), and Cu(II) complexes of the amphi‐and anti‐isomers of these ligands are described.The ligands and their complexes were characterized by elemental analyses, IR, mass, H1 and 13C NMR spectra and magnetic susceptibility measurements. Ligands complexing properties were studied by the liquid‐liquid extraction of selected alkali (Li+, Na+, K+, Cs+) and transition metals (Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+). It has been observed that all ligands show a high affinity to Cu2+ and Hg2+ ions, where as almost no affinity to alkali metals. The extraction equilibrium constants (K ex) for complexes of ligands with Cu2+ and Hg2+ metal picrates between dichloromethane and water have been determined at 25°C.