Combined supramolecular and mesoscale modelling of liquid–liquid extraction of rare earth salts

Karmakar, Anwesa; Duvail, Magali; Bley, Michael; Zemb, Thomas; Dufrêche, Jean‐François

doi:10.1016/j.colsurfa.2018.07.013

Cited by 23 publications

(28 citation statements)

References 45 publications

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“…36,37 Note that such considerations are only able to provide a qualitative description of the extraction trends, but they fail completely in quantitative assessment. 38…”

Section: Introductionmentioning

confidence: 99%

“…44 The predictive power of this decomposition has been illustrated successfully in three cases with a focus on the simple case of one uncharged complexing extractant without any synergy. 38,45,46 An explicit parametric study has shown in the case of uncharged extractant that this ienaic approach is able to link quantitatively the observed free energy of transfer controlling the yield of the process to the complexation free energy that is determined in supramolecular chemistry. 39 This ienaic approach, evaluating the various relevant interactions is extended here to the common case of acidic extractants.…”

Section: Introductionmentioning

confidence: 99%

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Colloidal Model for the Prediction of the Extraction of Rare Earths Assisted by the Acidic Extractant

et al. 2019

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We propose the statistical thermodynamic model for the prediction of the liquid–liquid extraction efficiency in the case of rare-earth metal cations using the common bis(2-ethyl-hexyl)phosphoric acid (HDEHP) extractant. In this soft matter-based approach, the solutes are modeled as colloids. The leading terms in free-energy representation account for: the complexation, the formation of a highly curved extractant film, lateral interactions between the different extractant head groups in the film, configurational entropy of ions and water molecules, the dimerization, and the acidity of the HDEHP extractant. We provided a full framework for the multicomponent study of extraction systems. By taking into account these different contributions, we are able to establish the relation between the extraction and general complexation at any pH in the system. This further allowed us to rationalize the well-defined optimum in the extraction engineering design. Calculations show that there are multiple extraction regimes even in the case of lanthanide/acid system only. Each of these regimes is controlled by the formation of different species in the solvent phase, ranging from multiple metal cation-filled aggregates (at the low acid concentrations in the aqueous phase), to the pure acid-filled aggregates (at the high acid concentrations in the aqueous phase). These results are contrary to a long-standing opinion that liquid–liquid extraction can be modeled with only a few species. Therefore, a traditional multiple equilibria approach is abandoned in favor of polydisperse spherical aggregate formations, which are in dynamic equilibrium.

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“…36,37 Note that such considerations are only able to provide a qualitative description of the extraction trends, but they fail completely in quantitative assessment. 38…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Colloidal Model for the Prediction of the Extraction of Rare Earths Assisted by the Acidic Extractant

et al. 2019

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“…However, a quantitative evaluation requires to abandon the concept of average stoichiometry and consider a Boltzmann distribution of complexing aggregates in dynamic equilibrium [47]. Since, the selectivity also depends on pH, it also shows the impact of interfacial curvature frustration that depends on the total volume of all the hydrophilic extracted species in each aggregate [48,49].…”

Section: Resultsmentioning

confidence: 99%

Effects of porous media on extraction kinetics: Is the membrane really a limiting factor?

Theisen

Penisson

Rey

et al. 2019

Journal of Membrane Science

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Porous media in extraction and especially pertraction are often suspected to add unnecessary diffusive resistance and considerably slow down extraction kinetics. This work presents a miniaturized pertraction device and simulation of diffusive and reactive solute transport. Kinetics are experimentally observed and numerically fitted. Reaction rates-or solute transfer rates-are estimated via this fit on a numerical basis. The work shows that the diffusive resistance created by a porous medium is prevalent only at low distribution coefficients. At high distribution coefficients as is the case of quasi all industrial processes, the porous membrane does not interfere with overall kinetics. Instead, the diffusive resistance is shared between the feed and extraction phases, and the interface transfer, depending on the value of the transfer rate. Overall, this work can be generalize as enabling the measurement of solute transfer rates at the liquid-liquid interface, a key parameter in pertraction and membrane separation which is difficult to measure using classic methods of extraction.

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“…Previously reported values of adjusted κ* for reverse aggregates were 2.5 k B T per DMDOHEMA molecule. 25 , 26 Recently, a molecular dynamics study done by our group provided a value of 16 k B T per extractant molecule in heptane solvent. 27 This value points to very high curvature toward water (in the reverse micelles) and was attributed to the strong interactions of Eu 3+ and DMDOHEMA molecules.…”

Section: Resultsmentioning

confidence: 99%

“…The term − k B T ln D Eu 3+ is often referred to as the apparent energy of the extraction. 26 In Figure 9 , the assumption complexation = extraction (a green dashed line) is plotted for purpose of easier understanding of the context. Figures 9 a−b show the − k B T ln D Eu 3+ / k B T for a system = 0.1 mol dm –3 and = 1 mol dm –3 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Multicomponent Model for the Prediction of Nuclear Waste/Rare-Earth Extraction Processes

et al. 2018

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We develop a minimal model for the prediction of solvent extraction. We consider a rare earth extraction system for which the solvent phase is similar to water-poor microemulsions. All physical molecular quantities used in the calculation can be measured separately. The model takes into account competition complexation, mixing entropy of complexed species, differences of salt concentrations between the two phases, and the surfactant nature of extractant molecules. We consider the practical case where rare earths are extracted from iron nitrates in the presence of acids with a common neutral complexing extractant. The solvent wetting of the reverse aggregates is taken into account via the spontaneous packing. All the water-in-oil reverse aggregates are supposed to be spherical on average. The minimal model captures several features observed in practice: reverse aggregates with different water and extractant content coexist dynamically with monomeric extractant molecules at and above a critical aggregate concentration (CAC). The CAC decreases upon the addition of electrolytes in the aqueous phase. The free energy of transfer of an ion to the organic phase is lower than the driving complexation. The commonly observed log–log relation used to determine the apparent stoichiometry of complexation is valid as a guideline but should be used with care. The results point to the fact that stoichiometry, as well as the probabilities of a particular aggregate, is dependent on the composition of the entire system, namely the extractant and the target solutes’ concentrations. Moreover, the experimentally observed dependence of the extraction efficiency on branching of the extractant chains in a given solvent can be quantified. The evolution of the distribution coefficient of particular rare earth, acid, or other different metallic cations can be studied as a function of initial extractant concentration through the whole region that is typically used by chemical engineers. For every chemical species involved in the calculation, the model is able to predict the exact equilibrium concentration in both the aqueous and the solvent phases at a given thermodynamic temperature.

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Combined supramolecular and mesoscale modelling of liquid–liquid extraction of rare earth salts

Cited by 23 publications

References 45 publications

Colloidal Model for the Prediction of the Extraction of Rare Earths Assisted by the Acidic Extractant

Colloidal Model for the Prediction of the Extraction of Rare Earths Assisted by the Acidic Extractant

Effects of porous media on extraction kinetics: Is the membrane really a limiting factor?

Multicomponent Model for the Prediction of Nuclear Waste/Rare-Earth Extraction Processes

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