Solvent Extraction Equilibria Research Articles

Incorporation of chloride ion in a copper solvent extraction process: A thermodynamic view

In this study, the impact of chloride content of the seawater on the solvent extraction equilibrium of copper using LIX 984 N was investigated. This effect was studied considering the nonideality of aqueous and organic phases. The presence of chloride ion was shown to increase the extraction tendency toward copper extraction, considering the changes that occur in the ratio of the activity of the dominant copper species to the hydrogen ion (H+). This phenomenon was further confirmed by calculating the equilibrium constant of the copper solvent extraction reaction in presence and absence of the chloride ion. The occurrence of the chloride ion resulted in involvement and dimerization of more organic molecules in the transfer of copper to the organic phase. As a result, a heterogeneous model incorporating the nonideality of the organic and aqueous phases for the solvent extraction of copper was developed and validated by experimental data.

Acidic Chloride Leaching of NMC Cathodes Combined with Solvent Extraction for the Production of Value Metals from Spent Lithium-Ion Battery

Lithium-ion battery is the technology of choice in the development of electric vehicles. This technology is now mature although there are still many challenges to increase their energy density while ensuring an irreproachable safety of use. For this goal, it is necessary to develop new cathodic materials that can be cycled at higher voltages and electrolytes compatible with these materials. But the challenge does not only concern the production of efficient batteries for the electrochemical storage of energy since lithium-ion battery technology relies on the use of critical and/or strategic value resources. It is therefore crucial to include Lithium-ion batteries development in a circular economy approach very early. In particular, optimized recycling and reuse of battery components must both minimize their impact on the environment and limit geopolitical issues related to tensions on the mineral resources necessary for lithium-ion battery production. Although recycling will never replace mining, it reduces resource dependence by ensuring the presence of exploitable resources in the territory, which is particularly important for countries like France where exploited or exploitable resources are limited.This conference addresses the development of a new hydrometallurgical process combining leaching of cathodic material from spent lithium-ion battery in acidic chloride media and solvent extraction process. Most of recycling processes reported in the literature rely on the sulphate route and a few studies investigate the potentialities of the chloride route despite many advantages and the possibility to develop new chemistry, which could get easier the metal separation. The leaching mechanisms and the solvent extraction equilibria will be presented in this conference. Based on the comprehension of the physicochemistry of leaching and solvent extraction, the present study will introduce a new hydrometallurgical process for the production of cobalt, nickel, manganese and lithium from spent cathodic materials.

Insights into non-aqueous solvent extraction of gadolinium and neodymium from ethylene glycol solution using Cyanex 572

Comparison of the separation factors for Gd(III) over Nd(III) extraction from aqueous and non-aqueous ethylene glycol solutions using Cyanex 572 in kerosene. • Addition of water bridges the gap between hydrometallurgy and solvometallurgy. • Extraction of Gd(III) and Nd(III) from non-aqueous solution was compared with aqueous solution. • Gd and Nd extraction increases with increasing Cyanex 572 extractant concentrations. • Temperature had almost no effect on the extraction of both metal ions. • Under certain conditions, maximum separation factor was obtained and reached 22.09. The reprocessing of rare earth elements (REEs) by conventional hydrometallurgical processes remains a challenge because of the difficulties of separation. Solvometallurgy is a new non-aqueous solvent extraction approach including two immiscible organic phases which has been advanced for the extraction of rare earths. The less polar organic phase (LP) was a solution of Cyanex 572 (Cy-572) as an acidic extractant dissolved in kerosene. Whereas, the more polar organic phase (MP) was ethylene glycol with a limited amount of water dissolved in metal nitrate salts and lithium nitrate as a salting-out agent. The extraction of Gd(III) and Nd(III) from ethylene glycol solution was compared with extraction from an aqueous solution. The solvent extraction equilibrium was estimated by slope analysis method, and the composition of the Gd(III) extracted species in the less polar phase was proposed to be Gd(OH) L 2 . 2 HL ¯ . The non-aqueous system performs better separation of rare earths than the corresponding conventional extraction system. Subsequently, 0.1 mol/L HCl is the best stripping agent for both metal ions after two steps from the less polar phase, while a solution composed of 10% HF + 0.05 mol/L HCl is superior for nearly complete separation between the two elements. Eventually, the separation of binary mixtures of Gd(III) and Nd(III) is possible by this new non-aqueous solvent extraction system. A complete flow sheet process including extraction, scrubbing and stripping steps for the separation of Gd(III) and Nd(III) was proposed.

Solvent extraction equilibrium modeling for the separation of ammonia, nickel(II), and copper(II) from the loaded LIX84-I

A novel solvent extraction equilibrium model has been developed to separate nickel and copper from the loaded LIX84-I (active component: 2-hydroxy-5-nonylacetophenone oxime dissolved in a nonpolar diluent, ShellSol D70) formed by the extraction from ammoniacal alkaline solutions. The targeted process consists of the scrubbing of ammonia and subsequent selective stripping of nickel(II) followed by stripping of copper(II), in which sulfuric acid is used in each step. The present model considers the equilibria of extraction of copper, nickel, and ammonia; distribution of metal-extractant complexes; and solution equilibria in aqueous and organic phases and was compared with the experimental results under varying sulfuric acid concentrations and phase ratios. As a result, this model was shown to accurately predict the equilibria after scrubbing and stripping from the initial operational conditions. This model is also applicable to the extraction of copper and nickel from an ammoniacal solution and thus facilitates the design, optimization, and control of the ammoniacal process for the separation of copper and nickel.

Batch flowsheet test for a GANEX-type process: the CHALMEX FS-13 process

ABSTRACT The Chalmers grouped actinide extraction (CHALMEX) process is focused on the co-separation of actinides from all other elements in spent nuclear fuel solution, with the ultimate purpose of transmuting the actinides into shorter-lived and less radiotoxic elements. Based on solvent extraction equilibrium distribution data of actinides and fission products, a preliminary flowsheet was developed and tested in batch mode. The flowsheet consists of one extraction step with the CHALMEX FS-13 solvent (25 mM CyMe4-BTBP in 30% v/v TBP and 70% v/v FS-13), using hydrophilic masking agents (20 mM bimet and 0.2 M mannitol) in the aqueous phase for the complexation of troublesome fission products. Two nitric acid scrub steps (0.5 M HNO3) were efficient in removing co-extracted acid, all molybdenum and the majority of silver. Two stripping stages (0.5 M glycolic acid at pH 4) were efficient in recovery of the actinides from the organic phase. The need for a solvent clean-up stage for the removal of nickel, cadmium, iron and the remaining silver from the organic phase was demonstrated. Based on the distribution data, it was calculated that a 99.9% recovery of americium is possible using only 3 ideal extraction stages, 3 ideal scrubbing stages and 2 ideal stripping stages.

The Effect of Organic Diluent on the Extraction of Eu(III) by HEH[EHP

ABSTRACTBecause there are fewer tools available to probe the interactions therein, the effect of the fundamental chemistry of the organic diluent on solvent extraction equilibria has been under-characterized relative to the aqueous. As a result, diluents for solvent extraction are often selected for an application not for their utility as a medium for reaction, but for other (often equally) important reasons (like low flammability). To begin to improve this imbalance in the science, twenty different diluents have been used in a study of the extraction of radiotracer 152/154Eu3+ from dilute nitric acid solutions using the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]). To increase the utility of the study and to honor the memory of Professor Jan Rydberg, this investigation was conducted by a cadre of comparatively inexperienced separation scientists (who are as a result no longer inexperienced separation scientists) as a radioanalytical chemistry and solvent extraction educational exercise. Slope analysis was used to determine the apparent stoichiometry of the extracted metal complex. The results discussed in the following indicate that, while the pH dependence exhibits the expected three H+ exchanged per metal ion extracted, the extractant dependence suggests that the number of protonated extractant molecules in the extracted complex changes with the organic diluent. The experimentally observed “extractant dependency” ranges from 2.5 to 3.0 dimer equivalent molecules per extracted metal ion. Ironically, in the diluents exhibiting the highest apparent M:(HA)3 stoichiometry, HEH[EHP] extracts Eu3+ less efficiently. Europium luminescence spectroscopy was used to probe for changes in the first coordination sphere of the complex in different diluents. A model and conceptual framework for understanding these observations is described.

Thermodynamic modeling of the solvent extraction equilibrium for the recovery of vanadium (V) from acidic sulfate solutions using Di-(2-ethylhexyl) phosphoric acid

A study of the reaction mechanism and thermodynamic modeling of pentavalent vanadium V(V) extraction from NaVO3-H2SO4-H2O solutions using Di-(2-ethylhexyl) phosphoric acid (D2EHPA or HA) extractant was carried out. The effects of initial pH of the solution, extractant concentration, and temperature on the extraction of V(V) were examined. The stoichiometry of the extraction reaction was determined using the slope analysis method. The extracted species was shown to be VO2A. A thermodynamic modeling approach was proposed for the prediction of equilibrium concentrations and pH of the system based on the known initial concentrations and process temperature. In the presented approach, the non-ideality of both aqueous and organic phases was taken into account. The activity coefficients of all organic components were calculated using UNIQUAC-NRF model, while the Electrolyte-UNIQUAC-NRF model was employed to calculate the activity coefficients of ions in aqueous phase. The equilibrium constant of the extraction reaction and the unknown parameters of the models were adjusted through the regression of experimental data at 25 °C, 35 °C, and 45 °C. Adjusted parameters were used for the prediction of equilibrium vanadium concentration in organic phase and equilibrium pH of the aqueous phase. Both of regressed and predicted values were in very good agreement with the experimental data. Moreover, calculated standard molar enthalpy of the reaction indicated the endothermicity of extraction reaction between VO2+ and D2EHPA.

Comparison of interfacial behavior and silver extraction kinetics with various types calix[4]arene derivatives at heterogeneous liquid-liquid interfaces

Various p-tert-octylcalix[4]arene derivatives as hydrophobic extractants have been prepared to investigate Ag(I) extraction efficiency in a batch-wise process in nitric acid media. The influence of the functional groups of the hydrophobic extractants on the interfacial behavior and Ag(I) extraction efficiency in nitric acid media has been investigated using the drop-volume method. Fitting of the interfacial tension isotherms to the Gibbs and Szyszkowski equations has provided parameters characterizing the interfacial activity of the extractants, in particular the Gibbs free energy of adsorption at the interface, the interface excess on saturation (Г∞) and the average area per the adsorbed extractant molecule (Amin). The amido-type p-tert-octylcalix[4]arene derivatives have strong interfacial activity and fast extraction rates. The interface excess at saturation (Г∞) increased with the type of functional groups in the following order: methyl ketonic < phenyl ketonic < dibenzyl amido < diethyl amido < quinolyl < pyridyl. The relationship between the interfacial activity and the dependence of the Ag(I) extraction efficiency on the different functional groups is discussed. The interfacial behavior of the extractants affected both the solvent extraction equilibrium and the kinetics and the overall results are consistent with a mass transfer mechanism at the heterogeneous liquid-liquid interfaces.

Chemical Model for Solvent Extraction Equilibrium of Mn(II) by Cyanex 272 from Chloride Solutions

Solvent extraction equilibrium of manganese(II) using Cyanex 272 dissolved in kerosene was studied from chloride solutions. Distribution ratio data was collected in order to estimate the extraction equilibrium constant. A slope analysis method was used to verify the solvent extraction reaction. The equilibrium constant for the solvent extraction reaction was estimated by taking into account the complex formation reactions between Mn(II) and chloride ion and mass balance equations. The activity coefficients of species in the aqueous phase were estimated by applying the Bromley equation. A comparison was made between the calculated distribution ratios of Mn(II) and the experimentally measured values. Finally, a chemical model was successfully applied for the estimation of the equilibrium constant. (Received October 1, 2013)

Solvent extraction equilibrium and modeling studies of manganese from sulfate solutions by a mixture of Cyanex 301 and TBP

Studies on solvent extraction equilibrium of Mn(II) from sulfuric acid solutions with a mixture of Cyanex 301 and TBP have been carried out. The extraction of Mn(II) by Cyanex 301 was enhanced significantly by the addition of TBP at a Cyanex 301 mole fraction of 0.6 and the synergistic coefficient calculated was 1.16. Synergistic extraction reaction was identified on the basis of slope analysis and extracted species was proposed to be MnA2·TBP. The solvent extraction equilibrium constant was estimated from the extraction data by considering the formation of complexes and activity coefficients of metal species in the aqueous phase. There was a good agreement between calculated distribution ratios of Mn(II) and experimentally measured values.

Understanding bioavailability and toxicity of sediment‐associated contaminants by combining passive sampling with in vitro bioassays in an urban river catchment

Bioavailable and bioaccessible fractions of sediment-associated contaminants are considered as better dose metrics for sediment-quality assessment than total concentrations. The authors applied exhaustive solvent extraction and nondepletive equilibrium sampling techniques to sediment samples collected along the Brisbane River in South East Queensland, Australia, which range from pristine environments to urban and industry-impacted areas. The wide range of chemicals expected prevents comprehensive chemical analysis, but a battery of cell-based bioassays sheds light on mixture effects of chemicals in relation to various modes of toxic action. Toxic effects were expressed as bioanalytical equivalent concentrations (BEQs) normalized to the organic carbon content of each sediment sample. Bioanalytical equivalent concentrations from exhaustive extraction agreed fairly well with values estimated from polydimethylsiloxane passive sampling extracts via the constant organic carbon to polydimethylsiloxane partition coefficient. Agreement was best for bioassays indicative of photosynthesis inhibition and oxidative stress response and discrepancy within a factor of 3 for the induction of the aryl hydrocarbon receptor. For nonspecific cytotoxicity, BEQ from exhaustive extraction were 1 order of magnitude higher than values from equilibrium sampling, possibly because of coextraction of bioactive natural organic matter that led to an overestimation of toxicity in the exhaustive extracts, which suggests that passive sampling is better suited in combination with bioanalytical assessment than exhaustive extraction.

Solvent Extraction Equilibrium of Zinc from Nitrate Solutions with 2-Ethylhexylphosphonic Acid Mono-2-ethylhexyl Ester

The solvent extraction equilibrium of zinc with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA) in an alkane diluent, Shellsol D70, was studied at a constant ionic strength of 1 mol/L from nitrate solutions considering the correction of the extractant nonideality in the organic phase by Alstad’s method. On the basis of the slope analysis of the obtained data, a molar ratio of 1:2 for the zinc to the EHPNA dimer in the extracted complex was indicated. Apparent extraction equilibrium constants obtained at each temperature from 283 to 323 K showed the endothermic nature of the extraction reaction and gave the apparent standard enthalpy and entropy changes. These two constants enable the calculation of the zinc distribution ratio at each temperature which correlates the experimental data with good accuracy.

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.

RECOVERY OF NI2+ BY DI-(2-ETHYLHEXYL) PHOSPHORIC ACID (HDEHP)

This paper dealts with solvent and bulk liquid membrane extraction of Ni2+ from its chloride solutions by HDEHP in n-heptane. Effects of extraction time, initial pH and Ni2+ concentration in the feed as well as HDEHP concentration in the organic phase were investigated. Solvent extraction equilibrium was established within 10 minutes. Ni2+ showed to be extracted into the organic phase preferentially as Ni(DEHP), complexes. The Ni2+ extraction yield decreased with increasing initial Ni2+ concentration, with decreasing pH and/or HDEHP concentration. The later is not only due to shifting equilibrium of Nils extraction reaction, but also due to concurent extraction of HCI. Results of bulk liquid membrane extraction could be described by the kinetics of interfacial pseudo-first order reactions. Observed rate constants were determined ⁓ 2,30.10-2 ⁒ 2,68.10-2 min-1 for concentration range [Ni2+]0 ⁓ 10-3 ⁒ 10-2 mol/l.

Gadolinium: Central Metal of the Lanthanoids

The physical and chemical properties of gadolinium are compared with those of the other lanthanoids. Some properties are intermediate between those of lanthanum and lutetium; some between those of barium and hafnium; and others (unexpectedly) between those of ytterbium and lutetium. Both the remarkably high molar heat capacity of the metal and the discontinuous expansion of its unit cell parameters on cooling are related to its unusual magnetic properties. The gadolinium break is a real discontinuity observed in many properties: ionic radii, formation constants of complexes, and solvent extraction equilibria. The sawtooth pattern of values of IE3 and ΔHat with atomic number for the lanthanoids is related to the quantum number L of the atomic species. The regular crystal field approach does not apply to the lanthanoid cations. A new arrangement of the lanthanoids in the periodic table places La, Gd, Lu in a column below Y, all having valence electron configuration s2d1.

Artificial neural network simulation of rare earths solvent extraction equilibrium data

Separation of high purity rare earth elements from their mixed oxides, obtained from monazite or xenotime, requires multiple stages of separation by circuits incorporating one or more solvents. The separation factors being small, a large number of counter-current stages become necessary. Process development, analysis, optimization and control of rare earths are a complex task. Computer simulation provides useful tools in this area. Application of artificial neural networks (ANN) for simulation of equilibrium data in solvent extraction of rare earths is described in this paper. The back propagation ANN model has been used. The input neurons correspond to the system state variables such as equilibrium concentration and acidity. The partitioning of the metal ion into the two immiscible phases involved in solvent extraction is measured in terms of distribution ratio D. The model predicts the D value under varying process conditions. Comparison of ANN with conventional models shows that ANN is superior. The average absolute error for ANN model is one-fourth that of the conventional models. The approach has been used, in conjunction with a process simulation model, successfully for industrial process development involving production of high purity neodymium.

Equilibrium and kinetic studies of the extraction of chelated copper(II) anions with Aliquat 336

The equilibrium and kinetics of solvent extraction of Cu2+ from aqueous solutions containing equimolar EDTA with Aliquat 336 in n-decanol and kerosene at 298 K were investigated. The concentrations of Cu2+ (8–50 mol m−3), Cl− (5–60 mol m−3), and Aliquat 336 (20–100 mol m−3) were varied. A semi-empirical model with three parameters was proposed to describe the equilibrium behavior, in which the non-idealities in both aqueous and organic phases were considered. Over the ranges studied, the model agreed reasonably well with the experimental data (standard deviation, 15%). The forward and backward reaction rate constants were determined as (5.31 ± 0.16)×10−6 m9/4 mol−3/4 s−1 and (2.62 ± 0.09)×10−7 s−1, respectively, at 298 K. An interfacial reaction mechanism was proposed, which revealed that the reaction between the chelated anions and trimeric amine molecules at the interface was rate limiting. The derived rate laws were consistent with the experimental results. © 2002 Society of Chemical Industry

Solvent Extraction Equilibrium of Copper(II) with Diisodecylphosphoric Acid in Heptane and Dodecane

Solvent Extraction Equilibrium of Copper(II) with Diisodecylphosphoric Acid in Heptane and Dodecane

Solvent Extraction Equilibrium of Zinc(II) from Ammonium Chloride Medium by CYANEX 923 in Solvesso 100.

The extraction equilibrium of zinc in ammonium chloride medium with CYANEX 923 (phosphine oxides mixture) in Solvesso 100 has been investigated. The distribution coefficient of zinc was independent of the equilibrium pH; this independence being attributable to a solvation extraction mechanism. Slope analysis for the system using dilute zinc solution reveals that two moles of CYANEX 923 react with one mol of zinc. The stoichiometric factor of water in the extraction reaction is found to be 2, whereas experimental data indicated that two chloride ions are involved for each metal extracted. The extraction reaction is exothermic (ΔH° = −42.0 kJ mol-1).

Solvent Extraction Equilibria and Kinetics of Gallium(III) with 2-Thenoyltrifluoroacetone in the Absence and Presence of Trioctylphosphine Oxide in Toluene

Abstract The rate and equilibrium of solvent extraction of gallium(III) from aqueous perchlorate solutions into toluene with 2-thenoyltrifluoroacetone (Htta) was measured in the absence and presence of trioctylphosphine oxide (TOPO). A synergistic enhancement of the extraction was found when TOPO was added. When a correction was made for the association of Htta and TOPO in the organic phase which decreased their concentrations available for the extraction, the extracted adducts was found to be in the form of Ga(tta)3(TOPO)2. The rate of extraction was not high and it was dependent on the second order with respect to Htta and the inverse second order with respect to H+ in both the absence and the presence of TOPO. The rate was accelerated by addition of TOPO; the enhancement of the rate was proportional to the TOPO concentration.