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Separations
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Application of Ionic Liquids in Separation Science
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Application of Ionic Liquids in Separation Science

A special issue of Separations (ISSN 2297-8739).

Deadline for manuscript submissions: closed (10 December 2023) | Viewed by 12001

Special Issue Editors

Dr. Catarina Seiça Neves

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Guest Editor
Department of Chemistry, CICECO, University of Aveiro, Aveiro, Portugal
Interests: ionic liquids; analytical chemistry; green separation processes
Dr. Filipa A. Vicente

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Guest Editor
Department of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
Interests: biopolymers; green downstream processes; alternative solvents; circular economy
Special Issues, Collections and Topics in MDPI journals
Dr. Jorge F. B. Pereira

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Guest Editor
Department of Chemical Engineering, CIEPQPF, University of Coimbra, Coimbra, Portugal
Interests: Ionic liquids; bioprocessing; proteins; enzymes; stability; downstream
Special Issues, Collections and Topics in MDPI journals
Dr. João Henrique Picado Madalena Santos

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Guest Editor
School of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil
Interests: downstream processing; alternative solvents; biopharmaceutical process development; nanobiotechnology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Due to their unique properties, such as low volatility, tunability and relatively easy recyclability, ionic liquids have been deeply studied in the past few years as alternative solvents. They have been used in a wide variety of applications, namely, organic synthesis, electrochemistry, catalysis for clean technology, polymerization processes and separations. The extraction and fractionation of different molecules, from simple solutions up to complex matrices, in gas, liquid and solid state, have been studied more effectively over the last several years. In fact, these methods have led to a higher interest in using these alternative solvents in gas separation membranes and in the selective separation of rare earth elements. Nonetheless, the purification of different types of biomolecules is still of high importance.

Therefore, this Special Issue aims to publish new research in the separation field, using ionic liquids as alternative solvents. Here, researchers are invited to share their original work within the scope of all types of separations with ionic liquids.   

Dr. Catarina Seiça Neves
Dr. Filipa A. Vicente
Dr. Jorge F. B. Pereira
Dr. João Henrique Picado Madalena Santos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Separations is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ionic liquids
  • extraction
  • separation
  • purification
  • liquid phase
  • solid phase
  • gas phase

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Published Papers (6 papers)

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Research

13 pages, 5931 KiB  
Article
Influence of Choline Chloride on the Phase Equilibria and Partition Performance of Polymer/Polymer Aqueous Biphasic Systems
by Mariana B. N. Alves, André M. Lopes, Nathalia A. Santos, Valéria C. Santos-Ebinuma, Filipa A. Vicente and Jorge F. B. Pereira
Separations 2023, 10(10), 528; https://doi.org/10.3390/separations10100528 - 1 Oct 2023
Viewed by 1420
Abstract
A series of polymeric aqueous biphasic systems (ABS) were determined using polyethylene glycol (PEG) and sodium polyacrylate (NaPA) with choline chloride ([Ch]Cl) as an adjuvant. The effect of (i) PEG and NaPA molecular weights, (ii) PEG functionalization, (iii) [Ch]Cl addition (at different concentrations), [...] Read more.
A series of polymeric aqueous biphasic systems (ABS) were determined using polyethylene glycol (PEG) and sodium polyacrylate (NaPA) with choline chloride ([Ch]Cl) as an adjuvant. The effect of (i) PEG and NaPA molecular weights, (ii) PEG functionalization, (iii) [Ch]Cl addition (at different concentrations), and (iv) temperature (25, 37 and 50 °C) was evaluated through their ability to promote the two-phase separation. The results showed that the polymerization degree and functionalization of PEG polymers exhibit a large influence on the ABS formation, with high molecular weight PEG inducing an increase in the biphasic region. Furthermore, the addition of small amount (1–5 wt%) of [Ch]Cl also increased the liquid–liquid demixing. Temperature and the increase in the NaPA molecular weight did not influence the ABS formation ability. Finally, the partition performance of PEG/NaPA + [Ch]Cl ABS was evaluated using caffeine as a model compound. Unlike the ABS formation trend, NaPAs molecular weight significantly influenced the partitioning, which was strengthened when using NaPA-8000. Moreover, the incorporation of [Ch]Cl facilitated an inversion in the partitioning behavior of caffeine, thereby emphasizing the remarkable partitioning tailoring potential exhibited by these systems. Overall, all systems seem to be promising alternatives for the effective extraction, purification and/or concentration of different value-added biomolecules. Full article
(This article belongs to the Special Issue Application of Ionic Liquids in Separation Science)
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15 pages, 2107 KiB  
Article
Enhancing Uranium Extraction Efficiency Using Protonated Amines and Quaternary Ammoniums-Based Ionic Liquids: Mechanistic Insights and Nonlinearities Analysis
by Elise Guerinoni, Sandrine Dourdain, Thomas Dumas, Guilhem Arrachart, Fabrice Giusti, Zijun Lu, Pier-Lorenzo Solari and Stéphane Pellet-Rostaing
Separations 2023, 10(9), 509; https://doi.org/10.3390/separations10090509 - 15 Sep 2023
Cited by 2 | Viewed by 1541
Abstract
This study investigates uranium solvent extraction under AMEX process conditions. The use of pure extractants without diluents or phase modifiers allows us not only to reduce the use of volatile organic compounds but also to provide higher extraction yields without third-phase formation. Pure [...] Read more.
This study investigates uranium solvent extraction under AMEX process conditions. The use of pure extractants without diluents or phase modifiers allows us not only to reduce the use of volatile organic compounds but also to provide higher extraction yields without third-phase formation. Pure extractants are protonated amines or quaternary ammoniums with suitable counter ions, which act at the interface between ion pairs and protic ionic liquids. The mixture of sulphates anion (SO42−) and bis(trifluoromethanesulfonyl)imide anion (NTf2−) revealed unexpected nonlinear extraction behaviors, which appear highly important to rationalize for optimized application. A spectroscopic analysis (NMR, UV-vis, FT-IR, and EXAFS) showed that uranium extraction occurs via a protonated amine and three sulphates. A nonlinear extraction could further be interpreted by considering a water and acid transfer between the two phases: at lower sulphate ratios, the release of acid from the organic phase into the aqueous phase was shown to influence the number of protonated amines in the organic phase, affecting uranium extraction before its enhancement. Furthermore, the extraction loss at higher sulphate ratios was assigned to the destabilization of bidentate uranium–sulphate complexes due to a competition between water and sulphates. Full article
(This article belongs to the Special Issue Application of Ionic Liquids in Separation Science)
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15 pages, 16586 KiB  
Article
Fluorinated Poly(ionic liquid)s Coated Superhydrophobic Functional Materials with Efficient Oil/Water Separation Performance
by Fumin Shen, Xuna Cheng, Shunyang Yao and Yuanchao Pei
Separations 2023, 10(7), 405; https://doi.org/10.3390/separations10070405 - 14 Jul 2023
Cited by 2 | Viewed by 1481
Abstract
There is an urgent need to develop new and improved oil-water separation materials with high stability and reusability for the cleanup of oily environmental pollutants. Here, fluorinated poly(ionic liquid)s were synthesized and their structure and property were characterized by nuclear magnetic resonance spectroscopy, [...] Read more.
There is an urgent need to develop new and improved oil-water separation materials with high stability and reusability for the cleanup of oily environmental pollutants. Here, fluorinated poly(ionic liquid)s were synthesized and their structure and property were characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. These fluorinated poly(ionic liquid)s were proposed as superhydrophobic coating on different metallic substrates through the combination of tethering fluorine groups in the PIL’s cation and anion exchange, and the superhydrophobic coating showed compactly stacked morphology under scanning electron microscope. The results of surface wettability experiments indicated that nearly all the fabricated materials showed a water contact angle larger than 150°, which is devoted to superhydrophobic nature. Moreover, for longer alkyl chain ILs and materials with smaller pore sizes, the water contact angle can be increased. At the same time, the fabricated superhydrophobic material exhibits a relatively high oil phase permeate flux, benefiting from the loose fibrous structure. Take the PIL@SSM300 for instance, the permeate fluxes were reached as high as 374,370 L·m−2·h−1, 337,200 L·m−2·h−1 and 302,013 L·m−2·h−1 for petroleum ether, hexane and cyclohexane, respectively. Instead, water is effectively repelled from the superhydrophobic surface. These virtues make the fabricated superhydrophobic material an effective membrane for oil/water separation under gravity. The separation efficiency and water contact angle are nearly unaffected after at least 20 cycles, confirming the excellent robustness of the coatings. These efficient poly(ionic liquid)s-based superhydrophobic materials possessed the potential to be used for oil/water separation. Full article
(This article belongs to the Special Issue Application of Ionic Liquids in Separation Science)
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14 pages, 2018 KiB  
Article
Experimental and Computational Evaluation of 1,2,4-Triazolium-Based Ionic Liquids for Carbon Dioxide Capture
by Sulafa Abdalmageed Saadaldeen Mohammed, Wan Zaireen Nisa Yahya, Mohamad Azmi Bustam and Md Golam Kibria
Separations 2023, 10(3), 192; https://doi.org/10.3390/separations10030192 - 10 Mar 2023
Cited by 11 | Viewed by 2234
Abstract
Utilization of ionic liquids (ILs) for carbon dioxide (CO2) capture is continuously growing, and further understanding of the factors that influence its solubility (notably for new ILs) is crucial. Herein, CO2 absorption of two 1,2,4-triazolium-based ILs was compared with imidazolium-based [...] Read more.
Utilization of ionic liquids (ILs) for carbon dioxide (CO2) capture is continuously growing, and further understanding of the factors that influence its solubility (notably for new ILs) is crucial. Herein, CO2 absorption of two 1,2,4-triazolium-based ILs was compared with imidazolium-based Ils of different anions, namely bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, and glycinate. The CO2 absorption capacity was determined using an isochoric saturation method and compared with predicted solubility employing COnductor-like Screening Model for Real Solvents (COSMO-RS). To gain an understanding of the effects of cations and anions of the ILs on the CO2 solubility, the molecular orbitals energy levels were calculated using TURBOMOLE. Triazolium-based ILs exhibit higher absorption capacity when compared to imidazolium-based ILs for the same anions. The results also showed that the anions’ energy levels are more determinant towards solubility than the cations’ energy levels, which can be explained by the higher tendency of CO2 to accept electrons than to donate them. Full article
(This article belongs to the Special Issue Application of Ionic Liquids in Separation Science)
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15 pages, 5002 KiB  
Article
β-Diketone-Driven Deep Eutectic Solvent for Ultra-Efficient Natural Stable Lithium-7 Isotope Separation
by Zexing Xie, Meiying Xie, Tingting Tang, Fan Yang, Liyan Xue and Zhengming Jiang
Separations 2023, 10(2), 111; https://doi.org/10.3390/separations10020111 - 4 Feb 2023
Cited by 2 | Viewed by 2295
Abstract
6Li and 7Li are strategic resources. Because Li+ ions have no outermost electrons and the radii of 6Li and 7Li differ by only one neutron, the separation of the naturally stable isotopes of Li, especially by solvent extraction, [...] Read more.
6Li and 7Li are strategic resources. Because Li+ ions have no outermost electrons and the radii of 6Li and 7Li differ by only one neutron, the separation of the naturally stable isotopes of Li, especially by solvent extraction, is recognized as a difficult problem worldwide. Therefore, in this paper, an advanced β-diketone-driven deep eutectic solvent (DES) extraction system containing 2-thenoyltrifluoroacetone (HTTA) and tri-n-octyl phosphine oxide (TOPO) is introduced to the extraction and separation of 6Li+ and 7Li+ ions. Compared with those of reported HTTA extraction systems and crown ether extraction systems, the separation coefficient (β7Li/6Li) of the β-diketone-driven DES extraction system can reach the best value of 1.068, which is now the highest known β-value reported in the extraction system. From the intramolecular hydrogen bond of HTTA to the intermolecular hydrogen bond of DES, the bond energy increases by 47.8%. Because the active site of the proton in DES provides a higher energy barrier for the separation of 7Li, the β7Li/6Li is significantly increased. The extractions were characterized by spectrum, using 1H nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The mechanism was determined on the basis of the reaction kinetics and density functional theory (DFT). The DES extractant shows excellent cycle performance with regard to stripping and reusability. In conclusion, the highly efficient, economical, and stable β-diketone-driven DES extraction system can be used for the separation of naturally stable Li isotopes, which provides good industrial application prospects. Full article
(This article belongs to the Special Issue Application of Ionic Liquids in Separation Science)
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12 pages, 3747 KiB  
Article
Solid Phase Extraction of (+)-Catechin from Cocoa Shell Waste Using Dual Ionic Liquid@ZIF8 Covered Silica
by Xiaoman Li, Ruobing Qiao, Xuyang Jiu and Minglei Tian
Separations 2022, 9(12), 441; https://doi.org/10.3390/separations9120441 - 15 Dec 2022
Cited by 1 | Viewed by 1605
Abstract
(+)-catechin is one category of flavonoids in cocoa shell waste and it has been reported to have many health benefits. In order to isolate it from aqueous extracted solution of cocoa shell waste by solid phase extraction (SPE), a series of dual ionic [...] Read more.
(+)-catechin is one category of flavonoids in cocoa shell waste and it has been reported to have many health benefits. In order to isolate it from aqueous extracted solution of cocoa shell waste by solid phase extraction (SPE), a series of dual ionic liquids@ZIF8-covered silica were prepared as the sorbents. Regarding the operation conditions of SPE and the characteristic structure of (+)-catechin, ZIF8-covered silica was synthesized to establish a stable and porous substrate, and various dual ionic liquids with multiple properties were immobilized on substrate to obtain a high adsorption capacity. Different adsorption conditions were investigated and the highest adsorption capacity (58.0 mg/g) was obtained on Sil@ZIF8@EIM-EIM at 30 °C during 60.0 min. When the sorbent was applied in the SPE process, 96.0% of the total amount of (+)-catechin from cocoa shell waste can be isolated after several washing and elution steps. The satisfactory recoveries of 97.5–100.2% and RSDs of 1.3–3.2% revealed that the SPE process was accurate and precise. The stability of Sil@ZIF8@EIM-EIM was tested in water and the reusability was tested using repeated adsorption/desorption process. The results revealed that Sil@ZIF8@EIM-EIM as an efficient sorbent can isolate (+)-catechin from cocoa shell waste. Full article
(This article belongs to the Special Issue Application of Ionic Liquids in Separation Science)
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