Fundamentals of Solvent Extraction of Metal Ions

Narbutt, Jerzy

doi:10.1016/b978-0-12-816911-7.00004-9

Cited by 8 publications

(4 citation statements)

References 66 publications

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“…We also noticed that the minimum required salt amount varies, which is positively proportional to the size of solvent molecules (i.e., EC < DMC < EMC < DEC). This can be rationally related to the fact that long-chain molecules are more hydrophobic, thus making it more difficult for them to be dispersed in water . For the hybrid electrolytes involving PC and EC, the smaller amounts of salt for PC should be ascribed to the fact that the PC with higher polarity can be originally dissolved in polar water with a maximum concentration of 16.7 vol %.…”

Section: Resultsmentioning

confidence: 99%

Co-Solvent Electrolyte Engineering for Stable Anode-Free Zinc Metal Batteries

et al. 2022

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Anode-free metal batteries can in principle offer higher energy density, but this requires them to have extraordinary Coulombic efficiency (>99.7%). Although Zn-based metal batteries are promising for stationary storage, the parasitic side reactions make anode-free batteries difficult to achieve in practice. In this work, a salting-in-effect-induced hybrid electrolyte is proposed as an effective strategy that enables both a highly reversible Zn anode and good stability and compatibility toward various cathodes. The as-prepared electrolyte can also work well under a wide temperature range (i.e., from −20 to 50 °C). It is demonstrated that in the presence of propylene carbonate, triflate anions are involved in the Zn2+ solvation sheath structure, even at a low salt concentration (2.14 M). The unique solvation structure results in the reduction of anions, thus forming a hydrophobic solid electrolyte interphase. The waterproof interphase along with the decreased water activity in the hybrid electrolyte effectively prevents side reactions, thus ensuring a stable Zn anode with an unprecedented Coulombic efficiency (99.93% over 500 cycles at 1 mA cm–2). More importantly, we design an anode-free Zn metal battery that exhibits excellent cycling stability (80% capacity retention after 275 cycles at 0.5 mA cm–2). This work provides a universal strategy to design co-solvent electrolytes for anode-free Zn metal batteries.

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Section: Resultsmentioning

confidence: 99%

Co-Solvent Electrolyte Engineering for Stable Anode-Free Zinc Metal Batteries

et al. 2022

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“…Although the effects of metal complexation on solvent extraction of metals are rather well understood, the underlying principles governing the salting effects on solvent extractions are not completely clear yet. ,, Some studies have already been performed, predicting salting effects on the extraction of metal ions from nitrate media by solvating extractants. , These studies link salt activity coefficients to the extraction efficiency of a metal ion by a solvating extractant. However, they are unable to explain the observed effects when nitrate salts of di- and trivalent cations are used or when the ionic strength is higher than 5 molal .…”

Section: Introductionmentioning

confidence: 99%

Cation Effect of Chloride Salting Agents on Transition Metal Ion Hydration and Solvent Extraction by the Basic Extractant Methyltrioctylammonium Chloride

2020

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The addition of a nonextractable salt has an important influence on the solvent extraction of metal ions, but the underlying principles are not completely understood yet. However, relating solute hydration mechanisms to solvent extraction equilibria is key to understanding the mechanism of solvent extraction of metal ions as a whole. We have studied the speciation of Co(II), Zn(II), and Cu(II) in aqueous solutions containing different chloride salts to understand their extraction to the basic extractant methyltrioctylammonium chloride (TOMAC). This includes the first speciation profile of Zn(II) in chloride media with the three Zn(II) species [Zn(H 2 O) 6 ] 2+ , [ZnCl 3 H 2 O] − , and [ZnCl 4 ] 2– . The observed differences in extraction efficiency for a given transition metal ion can be explained by transition metal ion hydration due to ion–solvent interactions, rather than by ion–solute interactions or by differences in speciation. Chloride salting agents bearing a cation with a larger hydration Gibbs free energy reduce the free water content more, resulting in a lower hydration for the transition metal ion. This destabilizes the transition metal chloro complex in the aqueous phase and increases the extraction efficiency. Salting agents with di- and trivalent cations reduce the transition metal chloro complex hydration less than expected, resulting in a lower extraction efficiency. The cations of these salting agents have a very large hydration Gibbs free energy, but the overall hydration of these salts is reduced due to significant salt ion pair formation. The general order of salting-out strength for the extraction of metal ions from chloride salt solutions is Cs + < Rb + < NH 4 + ≈ K + < Al 3+ ≈ Mg 2+ ≈ Ca 2+ ≈ Na + < Li + . These findings can help in predicting the optimal conditions for metal separation by solvent extraction and also contribute to a broader understanding of the effects of dissolved salts on solutes.

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“…Previous studies showed that the extraction of transition-metal ions to basic extractants for a given extractant and its concentration is mainly determined by the metal ion hydration. − These studies focused mainly on the effects of a changing aqueous phase composition on the aqueous phase itself. However, it seems logical to assume that the organic phase is also influenced by changes in the aqueous phase.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic Modeling of Salting Effects in Solvent Extraction of Cobalt(II) from Chloride Media by the Basic Extractant Methyltrioctylammonium Chloride

Lommelen

Binnemans

2021

ACS Omega

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The design and optimization of solvent extraction processes for metal separations are challenging tasks due to the large number of adjustable parameters. A quantitative predictive solvent extraction model could help to determine the optimal parameters for solvent extraction flow sheets, but such predictive models are not available yet. The main difficulties for such models are the large deviations from ideal thermodynamic behavior in both the aqueous and organic phases due to high solute concentrations. We constructed a molecular thermodynamic model for the extraction of CoCl 2 from different chloride salts by 0.2 mol L –1 trioctylmethylammonium chloride in toluene using the OLI mixed-solvent electrolyte (OLI-MSE) framework. This was accomplished by analyzing the water and hydrochloric acid content of the organic phase, measuring the water activity of the system, and using metal complex speciation and solvent extraction data. The full extractant concentration range cannot be modeled by the OLI-MSE framework as this framework lacks a description for reversed micelle formation. Nevertheless, salting effects and the behavior of hydrochloric acid can be accurately described with the presented extraction model, without determining specific Co(II)–salt cation interaction parameters. The resulting model shows that the salting effects originate from indirect salt cation–solvent interactions that influence the availability of water in the aqueous and organic phases.

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Fundamentals of Solvent Extraction of Metal Ions

Cited by 8 publications

References 66 publications

Co-Solvent Electrolyte Engineering for Stable Anode-Free Zinc Metal Batteries

Co-Solvent Electrolyte Engineering for Stable Anode-Free Zinc Metal Batteries

Cation Effect of Chloride Salting Agents on Transition Metal Ion Hydration and Solvent Extraction by the Basic Extractant Methyltrioctylammonium Chloride

Thermodynamic Modeling of Salting Effects in Solvent Extraction of Cobalt(II) from Chloride Media by the Basic Extractant Methyltrioctylammonium Chloride

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