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Ionic Liquids: Green Solvents for the Future

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Molecular Liquids".

Deadline for manuscript submissions: closed (1 July 2023) | Viewed by 10371

Special Issue Editors


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Guest Editor
Centro de Química Estrutural, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
Interests: molecular dynamics; nucleation; polymorphism; active pharmaceutical ingredients; crystallization; calorimetry; instrumentation; ionic liquids

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Guest Editor
Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
Interests: ionic liquid; high pressure; vibrational spectroscopy; IR

Special Issue Information

Dear Colleagues,

By the end of the 21 century, ionic liquids (ILs) had started to attract significant interest from the scientific community due to their potential applications and as alternatives to organic solvents. These substances are normally composed of organic cations and anions, so that just by swapping the ions that compose the substance it is possible to change the physical properties of the IL. As a result, this ability makes these substances extremely versatile, as it makes it possible to tune the properties of the ILs with an application in mind. Additionally, because ILs often exhibit extremely low vapor pressures, are high-temperature resistant, and can be recycled, the title of “green solvents” started to be associated with these substances. This classification has been challenged because of the toxicity of some of the cations and anions used in their preparation, among other reasons. However, their employment in the development of new environmentally friendly applications (e.g., CO2 capture or the development of more efficient batteries) is reinforcing the role of ILs as green solvents.

The current Special Issue aims to provide a view of the most recent advances in the development and employment of ionic liquids. The topics of interest include but are not limited to the synthesis of these substances, their physical and chemical characterization, and their application.

Dr. Carlos Eduardo Sabino Bernardes
Prof. Dr. Hai-Chou Chang
Guest Editors

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Keywords

  • Ionic liquids
  • Deep eutectic solvents
  • Energy storage
  • Electrodeposition
  • Environment
  • Carbon nanomaterials
  • CO2 capture

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Published Papers (5 papers)

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Research

12 pages, 3000 KiB  
Article
Benzothiophene Adsorptive Desulfurization onto trihexYl(tetradecyl)phosphonium Dicyanamide Ionic-Liquid-Modified Renewable Carbon: Kinetic, Equilibrium and UV Spectroscopy Investigations
by Mohamed A. Habila, Zied A. ALOthman, Monerah R. ALOthman and Mohammed Salah El-Din Hassouna
Molecules 2023, 28(1), 298; https://doi.org/10.3390/molecules28010298 - 30 Dec 2022
Cited by 4 | Viewed by 1691
Abstract
The negative environmental and industrial impacts of the presence of sulfur compounds such as benzothiophene in fuels have led to a greater interest in desulfurization research. In this work, carbon from palm waste sources was modified with trihexYl(tetradecyl)phosphonium dicyanamide-ionic liquid and characterized by [...] Read more.
The negative environmental and industrial impacts of the presence of sulfur compounds such as benzothiophene in fuels have led to a greater interest in desulfurization research. In this work, carbon from palm waste sources was modified with trihexYl(tetradecyl)phosphonium dicyanamide-ionic liquid and characterized by SEM, EDS, XRD and FTIR to assess surface properties. Then, the prepared carbon and carbon modified with ionic liquid were evaluated for the adsorption of benzothiophene by investigating the effects of time. The equilibrium occurred after 120 min, recording adsorption capacities of 192 and 238 mg/g for carbon and carbon modified with ionic liquid, respectively. The effect of the adsorbent dose on the adsorption of benzothiophene was evaluated, indicating that the maximum adsorption capacities were obtained using a dose of 1 g/L for both carbon and carbon modified with ionic liquid. The kinetic investigation for the adsorption of benzothiophene onto carbon and carbon modified with ionic liquid indicated that the second-order kinetic model is well fitted with the adsorption data rather than the first-order kinetic model. The equilibrium investigations for the adsorption of benzothiophene onto carbon and carbon modified with ionic liquid with Langmuir and Freundlich isotherm models reveals that the Freundlich model is the most suitable for describing the adsorption process, suggesting a multilayer adsorption mechanism. The desulfurization process showed a high impact on environmental safety due to the possibility of regenerating and reusing the prepared adsorbents with promising results up to five cycles. Full article
(This article belongs to the Special Issue Ionic Liquids: Green Solvents for the Future)
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16 pages, 3835 KiB  
Article
Confinement Effects on the Magnetic Ionic Liquid 1-Ethyl-3-methylimidazolium Tetrachloroferrate(III)
by Christopher M. Burba and Hai-Chou Chang
Molecules 2022, 27(17), 5591; https://doi.org/10.3390/molecules27175591 - 30 Aug 2022
Cited by 5 | Viewed by 1625
Abstract
Confinement effects for the magnetoresponsive ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate(III), [C2mim]FeCl4, are explored from thermal, spectroscopic, and magnetic points of view. Placing the ionic liquid inside SBA-15 mesoporous silica produces a significant impact on the material’s response to temperature, pressure, [...] Read more.
Confinement effects for the magnetoresponsive ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate(III), [C2mim]FeCl4, are explored from thermal, spectroscopic, and magnetic points of view. Placing the ionic liquid inside SBA-15 mesoporous silica produces a significant impact on the material’s response to temperature, pressure, and magnetic fields. Isobaric thermal experiments show melting point reductions that depend on the pore diameter of the mesopores. The confinement-induced reductions in phase transition temperature follow the Gibbs–Thomson equation if a 1.60 nm non-freezable interfacial layer is postulated to exist along the pore wall. Isothermal pressure-dependent infrared spectroscopy reveals a similar modification to phase transition pressures, with the confined ionic liquid requiring higher pressures to trigger phase transformation than the unconfined system. Confinement also impedes ion transport as activation energies are elevated when the ionic liquid is placed inside the mesopores. Finally, the antiferromagnetic ordering that characterizes unconfined [C2mim]FeCl4 is suppressed when the ionic liquid is confined in 5.39-nm pores. Thus, confinement provides another avenue for manipulating the magnetic properties of this compound. Full article
(This article belongs to the Special Issue Ionic Liquids: Green Solvents for the Future)
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12 pages, 1323 KiB  
Article
Single-Stage Extraction and Separation of Co2+ from Ni2+ Using Ionic Liquid of [C4H9NH3][Cyanex 272]
by Xiaohua Jing, Zhumei Sun, Dandan Zhao, Huimin Sun and Jie Ren
Molecules 2022, 27(15), 4806; https://doi.org/10.3390/molecules27154806 - 27 Jul 2022
Cited by 3 | Viewed by 1968
Abstract
The purpose of this study was to optimize the extraction conditions for separating Co2+ from Ni2+ using N-butylamine phosphinate ionic liquid of [C4H9NH3][Cyanex 272]. A Box–Behnken design of response surface methodology was used to analyze [...] Read more.
The purpose of this study was to optimize the extraction conditions for separating Co2+ from Ni2+ using N-butylamine phosphinate ionic liquid of [C4H9NH3][Cyanex 272]. A Box–Behnken design of response surface methodology was used to analyze the effects of the initial pH, extraction time, and extraction temperature on the separation factor of Co2+ from sulfuric acid solution containing Ni2+. The concentrations of Co2+ and Ni2+ in an aqueous solution were determined using inductively coupled plasma-optical emission spectrometry. The optimized extraction conditions were as follows: an initial pH of 3.7, an extraction time of 55.8 min, and an extraction temperature of 330.4 K. The separation factor of Co2+ from Ni2+ under optimized extraction conditions was 66.1, which was very close to the predicted value of 67.2, and the error was 1.7%. The equation for single-stage extraction with high reliability can be used for optimizing the multi-stage extraction process of Co2+ from Ni2+. The stoichiometry of chemical reaction for ion-exchange extraction was also investigated using the slope method. Full article
(This article belongs to the Special Issue Ionic Liquids: Green Solvents for the Future)
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14 pages, 1131 KiB  
Article
Aprotic Ionic Liquids: A Framework for Predicting Vaporization Thermodynamics
by Sergey P. Verevkin, Dzmitry H. Zaitsau and Ralf Ludwig
Molecules 2022, 27(7), 2321; https://doi.org/10.3390/molecules27072321 - 3 Apr 2022
Cited by 5 | Viewed by 2145
Abstract
Ionic liquids (ILs) are recognized as an environmentally friendly alternative to replacing volatile molecular solvents. Knowledge of vaporization thermodynamics is crucial for practical applications. The vaporization thermodynamics of five ionic liquids containing a pyridinium cation and the [NTf2] anion were studied [...] Read more.
Ionic liquids (ILs) are recognized as an environmentally friendly alternative to replacing volatile molecular solvents. Knowledge of vaporization thermodynamics is crucial for practical applications. The vaporization thermodynamics of five ionic liquids containing a pyridinium cation and the [NTf2] anion were studied using a quartz crystal microbalance. Vapor pressure-temperature dependences were used to derive the enthalpies of vaporization of these ionic liquids. Vaporization enthalpies of the pyridinium-based ionic liquids available in the literature were collected and uniformly adjusted to the reference temperature T = 298.15 K. The consistent sets of evaluated vaporization enthalpies were used to develop the “centerpiece”-based group-additivity method for predicting enthalpies of vaporization of ionic compounds. The general transferability of the contributions to the enthalpy of vaporization from the molecular liquids to the ionic liquids was established. A small, but not negligible correction term was supposed to reconcile the estimated results with the experiment. The corrected “centerpiece” approach was recommended to predict the vaporization enthalpies of ILs. Full article
(This article belongs to the Special Issue Ionic Liquids: Green Solvents for the Future)
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14 pages, 11406 KiB  
Article
Structural Engineering and Optimization of Zwitterionic Salts for Expeditious Discovery of Thermoresponsive Materials
by Yen-Ho Chu, Chien-Yuan Chen and Jin-Syuan Chen
Molecules 2022, 27(1), 257; https://doi.org/10.3390/molecules27010257 - 31 Dec 2021
Cited by 2 | Viewed by 1787
Abstract
This work reported the discovery of N-triflimide (NTf)-based zwitter-ionic liquids (ZILs) that exhibit UCST-type phase transitions in water, and their further structural optimization in fine-tuning polarity to ultimately afford newfangled thermosensitive materials carrying attractive and biocompatible Tc values that clearly demonstrated [...] Read more.
This work reported the discovery of N-triflimide (NTf)-based zwitter-ionic liquids (ZILs) that exhibit UCST-type phase transitions in water, and their further structural optimization in fine-tuning polarity to ultimately afford newfangled thermosensitive materials carrying attractive and biocompatible Tc values that clearly demonstrated the true value of the tunability of ZIL structure. This research established that with non-aromatic, acyclic ZILs as small-molecule thermoresponsive materials, their mixing and de-mixing with water triggered by temperatures are entirely reversible. Full article
(This article belongs to the Special Issue Ionic Liquids: Green Solvents for the Future)
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