Green Twist in Solvent Extraction and Separation of Metal Species

Topic Information

Dear Colleagues,

The aim of this topic is to provide an original and unique environment for researchers in academia and especially in industry to share and discuss their cutting-edge results of all novel approaches including ionic liquids, covering their in-depth characterization and/or modelling with the respect of the green scope, to their potential applications, not only in the liquid metal extraction and separation chemistry. The global objective is to propose so far unexplored and versatile new strategies: the optimization of the aqueous-biphasic systems composed of water (or not) and an organic phase incorporating “green” extracting moiety/moieties dissolved in different adopted media. Needless to say, these dissimilar “liquid compounds” possess unique chemical properties useful for a wide range of applications in various fields as diverse as solvent extraction, hydrometallurgy, environmental remediation and nuclear sciences, chemical engineering technology, metallurgy and recycling pinpointed the green concept, energy storage, biotechnology, etc. On the other hand, the design of original molecules has a long history in the analytical and solvent extraction chemistry of metal ions, with synthesized multicentre ligands, possessing high extraction efficiency and having a unique chemical structure. In all the presented studies, it is highly appreciated if the environmental gain is clearly outlined.

Dr. Maria Atanassova
Dr. Kojiro Shimojo
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Analytica analytica	-	-	2020	15.6 Days	CHF 1000
Membranes membranes	4.2	4.4	2011	13.6 Days	CHF 2700
Molecules molecules	4.6	6.7	1996	14.6 Days	CHF 2700
Polymers polymers	5.0	6.6	2009	13.7 Days	CHF 2700
Separations separations	2.6	2.5	2014	13.6 Days	CHF 2600

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Published Papers (3 papers)

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All Analytica Membranes Molecules Polymers Separations

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Supplementary material:
Supplementary File 1 (ZIP, 392 KiB)

17 pages, 3326 KiB  

Open AccessArticle

New Sustainable Solvent Extraction Pathways for Rare Earth Metals via Oximes Molecules

by Maria Atanassova, Rositsa Kukeva and Vanya Kurteva

Molecules 2023, 28(22), 7467; https://doi.org/10.3390/molecules28227467 - 07 Nov 2023

Viewed by 807

Abstract

A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid–liquid extraction, commonly applied in the separation science [...] Read more.

A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid–liquid extraction, commonly applied in the separation science of 4f and 5f-ions acidic chelating compounds, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), and 2-thenoyltrifluoroacetone (HTTA) alone and in combination with two synergistic agents, meso-hexamethylpropyleneamine oxime (S2: HM-PAO) and its bis-imine precursor (S1: pre-HM-PAO), are presented. The interaction between the two extractants (acidic/neutral) in deuterochloroform was studied using ¹H, ¹³C, and ¹H-¹H NOESY experiments. Several conclusions are given highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the two synergistic agents for various metal s-, p-, d-, and f-cations in the Periodic table, with almost 25 metal ions. The objective was to optimize a system for 4f-ions solvent extraction based on the new oxime molecules with β-diketone/isoxazolone/pyrazolone partnership. As detailed above, slight enhancements of extraction efficiencies were obtained either by using basic synergistic agents such as HM-PAO and/or using pre-HM-PAO. A competitive solvent extraction test of nearly 18 f-ions by various ligands (HTTA, S1, S2, and HPBI) and the two mixtures HTTA−S1 and HTTA−S2 diluted in ILs or organic diluents was also conducted in order to evaluate the switchable diluent impact. Additionally, electron paramagnetic resonance (EPR) spectroscopy was used to study the established chemical species with Cu²⁺ cations in the obtained organic extracts involving the two synergistic molecules. Full article

(This article belongs to the Topic Green Twist in Solvent Extraction and Separation of Metal Species)

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Supplementary material:
Supplementary File 1 (ZIP, 288 KiB)

12 pages, 1367 KiB  

Open AccessArticle

Mutual Solubilities between Ethylene Glycol and Organic Diluents: Gas Chromatography and NMR

by Maria Atanassova and Vanya Kurteva

Molecules 2023, 28(13), 5121; https://doi.org/10.3390/molecules28135121 - 29 Jun 2023

Cited by 1 | Viewed by 1483

Abstract

In this work, the mutual solubilities of sets of organic diluents (CHCl₃, C₆H₆, C₂H₄Cl₂, CCl₄, C₆H₁₂, and n-hexane) with the organic compound ethylene glycol are [...] Read more.

In this work, the mutual solubilities of sets of organic diluents (CHCl₃, C₆H₆, C₂H₄Cl₂, CCl₄, C₆H₁₂, and n-hexane) with the organic compound ethylene glycol are investigated via gas chromatography (GC). The experimental data measured for these binary organic systems are used to adjust the future nonaqueous systems for the solvent extraction of various metals with ligands. The obtained results showed that the solubility of ethylene glycol decreased in the order CHCl₃ > C₆H₆ > C₂H₄Cl₂ > CCl₄(0%) ≈ C₆H₁₂ ≈ n-hexane. On the other hand, the solubility of the tested traditional organic diluents in ethylene glycol decreased in the following order: C₆H₆ > CHCl₃ > C₂H₄Cl₂ > n-hexane > C₆H₁₂ > CCl₄. ¹H NMR was also used as an analytic method in order to compare the obtained results for the samples showing significant solubility only, including an additional study with 1,2- or 1,3-propanediol. The enhanced solubility of the C₆H₆ compound in ethylene glycol was identified here as critical due to the GC technique, which will be without future consequences in chemical technology. Therefore, it was found that the best molecular diluent for the recovery of metals among the tested ones is C₆H₁₂, with a green protocol as the new paradigm, replacing the aqueous phase with another nonaqueous phase, i.e., a second organic diluent. Full article

(This article belongs to the Topic Green Twist in Solvent Extraction and Separation of Metal Species)

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Supplementary material:
Supplementary File 1 (ZIP, 504 KiB)

19 pages, 4166 KiB  

Open AccessEditor’s ChoiceArticle

Improvement of Gd(III) Solvent Extraction by 4-Benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one: Non-Aqueous Systems

by Maria Atanassova and Rositsa Kukeva

Separations 2023, 10(5), 286; https://doi.org/10.3390/separations10050286 - 03 May 2023

Cited by 1 | Viewed by 1478

Abstract

The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C₁C_nim⁺][Tf₂N⁻], n [...] Read more.

The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C₁C_nim⁺][Tf₂N⁻], n = 4, 10) and CHCl_3, as diluents. Compared to CHCl₃, the ionic liquid offers increased distribution ratios in an aqueous medium. A step forward, enhanced solvent extraction, and improved separation upon the addition of ethylene glycol are demonstrated, i.e., a boost of two immiscible organic phases, compared to traditional aqueous solutions. However, this is noticeable when using CHCl₃, but unfortunately not with ionic liquid combination, [C₁C₁₀im⁺][Tf₂N⁻]. Several conclusions are given, highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the chelating agent HP for various metal s-, p-, d-, and f-cations, i.e., nearly 25 metals. A detailed evaluation of the selectivity between these metals was made when changing both the aqueous phase completely with ethylene glycol or partially with glycerol (1:1). Electron paramagnetic resonance (EPR) spectroscopy has been used to study the established chemical species in the obtained organic extracts, such as Gd³⁺, Fe³⁺, Cu²⁺, and Cr³⁺, with unpaired electrons. Full article

(This article belongs to the Topic Green Twist in Solvent Extraction and Separation of Metal Species)

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