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Recent Advances in Ionic Liquids and Their Applications

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

Deadline for manuscript submissions: closed (30 September 2024) | Viewed by 10346

Special Issue Editor


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Guest Editor
School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
Interests: ionic liquids; polyhalides; organometallic chemistry; chloride hydrates

Special Issue Information

Dear Colleagues,

Ionic liquids (ILs), due to their distinctive properties, have attracted the interest of researchers for over 30 years. Ionic liquids have gone from being a curiosity to being one of the most fruitful fields of science.

The main aim of this Special Issue is to publish original research articles on the current state and future trends in the field of ionic liquids, ensuring coverage of both the scientific fundaments and industrial applications. Review articles by experts in the field are also welcomed if they contribute to defining the direction in which research and new applications will evolve.

Dr. Owen Curnow
Guest Editor

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Keywords

  • ionic liquids
  • deep eutectic solvents
  • applications

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Published Papers (7 papers)

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Research

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19 pages, 2922 KiB  
Article
Ionic Liquids toward Enhanced Carotenoid Extraction from Bacterial Biomass
by Tiago P. Silva, Luís Alves, Francisco Salgado, José C. Roseiro, Rafał M. Łukasik and Susana M. Paixão
Molecules 2024, 29(17), 4132; https://doi.org/10.3390/molecules29174132 - 30 Aug 2024
Cited by 1 | Viewed by 845
Abstract
Carotenoids are high added-value products primarily known for their intense coloration and high antioxidant activity. They can be extracted from a variety of natural sources, such as plants, animals, microalgae, yeasts, and bacteria. Gordonia alkanivorans strain 1B is a bacterium recognized as a [...] Read more.
Carotenoids are high added-value products primarily known for their intense coloration and high antioxidant activity. They can be extracted from a variety of natural sources, such as plants, animals, microalgae, yeasts, and bacteria. Gordonia alkanivorans strain 1B is a bacterium recognized as a hyper-pigment producer. However, due to its adaptations to its natural habitat, hydrocarbon-contaminated soils, strain 1B is resistant to different organic solvents, making carotenoid extraction through conventional methods more laborious and inefficient. Ionic liquids (ILs) have been abundantly shown to increase carotenoid extraction in plants, microalgae, and yeast; however, there is limited information regarding bacterial carotenoid extraction, especially for the Gordonia genus. Therefore, the main goal of this study was to evaluate the potential of ILs to mediate bacterial carotenoid extraction and develop a method to achieve higher yields with fewer pre-processing steps. In this context, an initial screening was performed with biomass of strain 1B and nineteen different ILs in various conditions, revealing that tributyl(ethyl)phosphonium diethyl phosphate (IL#18), combined with ethyl acetate (EAc) as a co-solvent, presented the highest level of carotenoid extraction. Afterward, to better understand the process and optimize the extraction results, two experimental designs were performed, varying the amounts of IL#18 and EAc used. These allowed the establishment of 50 µL of IL#18 with 1125 µL of EAc, for 400 µL of biomass (cell suspension with about 36 g/L), as the ideal conditions to achieve maximal carotenoid extraction. Compared to the conventional extraction method using DMSO, this novel procedure eliminates the need for biomass drying, reduces extraction temperatures from 50 °C to 22 ± 2 °C, and increases carotenoid extraction by 264%, allowing a near-complete recovery of carotenoids contained in the biomass. These results highlight the great potential of ILs for bacterial carotenoid extraction, increasing the process efficiency, while potentially reducing energy consumption, related costs, and emissions. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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13 pages, 3869 KiB  
Article
Comparison of Eco-Friendly Ionic Liquids and Commercial Bio-Derived Lubricant Additives in Terms of Tribological Performance and Aquatic Toxicity
by Xin He, Louise M. Stevenson, Chanaka Kumara, Teresa J. Mathews, Huimin Luo and Jun Qu
Molecules 2024, 29(16), 3851; https://doi.org/10.3390/molecules29163851 - 14 Aug 2024
Cited by 2 | Viewed by 1032
Abstract
Approximately half of the lubricants sold globally find their way into the environment. The need for Environmentally Acceptable Lubricants (EALs) is gaining increased recognition. A lubricant is composed of a base oil and multiple functional additives. The literature has been focused on EAL [...] Read more.
Approximately half of the lubricants sold globally find their way into the environment. The need for Environmentally Acceptable Lubricants (EALs) is gaining increased recognition. A lubricant is composed of a base oil and multiple functional additives. The literature has been focused on EAL base oils, with much less attention given to eco-friendly additives. This study presents the tribological performance and aquatic toxicity of four short-chain phosphonium-phosphate and ammonium-phosphate ionic liquids (ILs) as candidate anti-wear and friction-reducing additives for EALs. The results are benchmarked against those of four commercial bio-derived additives. The four ILs, at a mere 0.5 wt% concentration in a synthetic ester, demonstrated a 30–40% friction reduction and >99% wear reduction, superior to the commercial baselines. More impressively, all four ILs showed significantly lower toxicity than the bio-derived products. In an EPA-standard chronic aquatic toxicity test, the sensitive model organism, Ceriodaphnia dubia, had 90–100% survival when exposed to the ILs but 0% survival in exposure to the bio-derived products at the same concentration. This study offers scientific insights for the future development of eco-friendly ILs as lubricant additives. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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10 pages, 1966 KiB  
Article
Multi-Component Syntheses of Spiro[furan-2,3′-indoline]-3-carboxylate Derivatives Using Ionic Liquid Catalysts
by Mehdi Khalaj, Maryam Zarandi, Malihe Samadi Kazemi, Seyed Mahmoud Musavi, Johannes Hohnsen and Axel Klein
Molecules 2024, 29(6), 1223; https://doi.org/10.3390/molecules29061223 - 8 Mar 2024
Cited by 1 | Viewed by 1274
Abstract
Two previously described Brønsted acidic ionic liquids, 3,3′-(1,6-hexanediyl)bis(1-methyl)-1H-imidazolium hydrogen sulfate (Cat1) and 1,1′-(1,6-hexanediyl)bis(pyridinium) hydrogen sulfate (Cat2), were used as catalysts for the preparation of spiro[furan-2,3′-indoline]-3-carboxylate derivatives via a three-component reaction of anilines, isatins (N-alkyl-indoline-2,3-diones), and [...] Read more.
Two previously described Brønsted acidic ionic liquids, 3,3′-(1,6-hexanediyl)bis(1-methyl)-1H-imidazolium hydrogen sulfate (Cat1) and 1,1′-(1,6-hexanediyl)bis(pyridinium) hydrogen sulfate (Cat2), were used as catalysts for the preparation of spiro[furan-2,3′-indoline]-3-carboxylate derivatives via a three-component reaction of anilines, isatins (N-alkyl-indoline-2,3-diones), and diethyl acetylenedicarboxylate, in high yields. The use of ultrasonic (US) irradiation led to the targeted products (1a15a) in high yields ranging from 80% to 98%. Under the same conditions, the use of sulfuric acid and acetic acid as a Brønstedt catalyst did not yield the desired benchmark product 1a. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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21 pages, 3332 KiB  
Article
Extraction of Pyrrole from Its Mixture with n-Hexadecane Using Ionic Liquids and Their Binary Mixtures
by Sorfina Amran, Muhammad Zulhaziman Mat Salleh, Hanee F. Hizaddin, Abdullah Amru Indera Luthfi, Ahmad Alhadid and Mohamed Kamel Hadj-Kali
Molecules 2023, 28(24), 8129; https://doi.org/10.3390/molecules28248129 - 16 Dec 2023
Cited by 3 | Viewed by 1525
Abstract
The conventional hydrodenitrogenation method is expensive and involves the use of catalysts and harsh procedures. In the last few years, ionic liquids (ILs) have gained attention as a promising alternative solvent for fuel oil extractive denitrogenation. In this work, the Conductor-like Screening Model [...] Read more.
The conventional hydrodenitrogenation method is expensive and involves the use of catalysts and harsh procedures. In the last few years, ionic liquids (ILs) have gained attention as a promising alternative solvent for fuel oil extractive denitrogenation. In this work, the Conductor-like Screening Model for Real Solvents (COSMO-RS) was used to screen 173 potential ILs as solvents for fuel oil. Two ILs (1-ethyl-3-methylimidazolium dicyanamide ([EMIM][N(CN)2]) and 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO3])) were selected for experimental investigation. The experimental liquid–liquid extraction of pyrrole (taken as the model nitrogen compound) from n-hexadecane (the model fuel) was conducted at 298 K and 1 atm with feed concentrations of pyrrole ranging from 10 to 50 wt%, using either the two pure ILs or their mixtures with dimethylformamide or ethylene glycol. Moreover, the NRTL model was effectively used to correlate the experimental tie lines. This work shows that the use of a binary mixture of ILs with a conventional solvent results in good selectivity, but has a low capacity for extracting pyrrole compounds. On the other hand, using an IL-IL mixture exhibits good results for both capacity and selectivity. All the ternary systems tested showed positive slopes, indicating that the nitrogen compounds had a higher affinity for the IL and binary mixture extract phase. In fact, the extraction efficiency for all the systems shows promising results. This characteristic is advantageous, as it requires less solvent to remove nitrogen compounds. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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15 pages, 1687 KiB  
Article
Lignin-Derivative Ionic Liquids as Corrosion Inhibitors
by Sharon Monaci, Daniela Minudri, Lorenzo Guazzelli, Andrea Mezzetta, David Mecerreyes, Maria Forsyth and Anthony Somers
Molecules 2023, 28(14), 5568; https://doi.org/10.3390/molecules28145568 - 21 Jul 2023
Cited by 5 | Viewed by 1764
Abstract
Corrosion is a significant problem that negatively affects a wide range of structures and buildings, resulting in their premature failure, which causes safety hazards and significant economic loss. For this reason, various approaches have been developed to prevent or minimize the effects of [...] Read more.
Corrosion is a significant problem that negatively affects a wide range of structures and buildings, resulting in their premature failure, which causes safety hazards and significant economic loss. For this reason, various approaches have been developed to prevent or minimize the effects of corrosion, including corrosion inhibitors. Recently, biobased inhibitors have gained a certain interest thanks to their unique properties, eco-friendliness, and availability. Among all the green precursors, lignin is of particular interest, being a natural polymer that can be obtained from different sources including agricultural residues. Corrosion inhibitors based on ionic liquids (ILs) also present interesting advantages, such as low volatility and high tunability. If combined, it may be possible to obtain new lignin-based ILs that present interesting corrosion inhibitor properties. In this work, the inhibition properties of new biobased lignin ILs and the influence of anions and cations on the corrosion of mild steel in an aqueous solution of 0.01 M NaCl were investigated by Potentiostatic Electrochemical Impedance Spectroscopy (PEIS) and Cyclic Potentiodynamic Polarization (CPP). Moreover, the surface was characterized using SEM, EDS, and optical profilometry. The IL choline syringate showed promising performance, reducing the corrosion current after 24 h immersion in 0.01 M sodium chloride, from 1.66 µA/cm2 for the control to 0.066 µA/cm2 with 10 mM of the IL present. In addition to its performance as a corrosion inhibitor, both components of this IL also meet or exceed the current additional desired properties of such compounds, being readily available, and well tolerated in organisms and the environment. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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17 pages, 5437 KiB  
Article
Sustainable Phenylalanine-Derived SAILs for Solubilization of Polycyclic Aromatic Hydrocarbons
by Illia V. Kapitanov, Surya M. Sudheer, Toshikee Yadav, Kallol K. Ghosh, Nicholas Gathergood, Vijai K. Gupta and Yevgen Karpichev
Molecules 2023, 28(10), 4185; https://doi.org/10.3390/molecules28104185 - 19 May 2023
Cited by 3 | Viewed by 1795
Abstract
The solubilization capacity of a series of sustainable phenylalanine-derived surface-active ionic liquids (SAILs) was evaluated towards polycyclic aromatic hydrocarbons—naphthalene, anthracene and pyrene. The key physico-chemical parameters of the studied systems (critical micelle concentration, spectral properties, solubilization parameters) were determined, analyzed and compared with [...] Read more.
The solubilization capacity of a series of sustainable phenylalanine-derived surface-active ionic liquids (SAILs) was evaluated towards polycyclic aromatic hydrocarbons—naphthalene, anthracene and pyrene. The key physico-chemical parameters of the studied systems (critical micelle concentration, spectral properties, solubilization parameters) were determined, analyzed and compared with conventional cationic surfactant, CTABr. For all studied PAH solubilization capacity increases with extension of alkyl chain length of PyPheOCn SAILs reaching the values comparable to CTABr for SAILs with n = 10–12. A remarkable advantage of the phenylalanine-derived SAILs PyPheOCn and PyPheNHCn is a possibility to cleave enzymatically ester and/or amide bonds under mild conditions, to separate polycyclic aromatic hydrocarbons in situ. A series of immobilized enzymes was tested to determine the most suitable candidates for tunable decomposition of SAILs. The decomposition pathway could be adjusted depending on the choice of the enzyme system, reaction conditions, and selection of SAILs type. The evaluated systems can provide selective cleavage of the ester and amide bond and help to choose the optimal decomposition method of SAILs for enzymatic recycling of SAILs transformation products or as a pretreatment towards biological mineralization. The concept of a possible practical application of studied systems for PAHs solubilization/separation was also discussed focusing on sustainability and a green chemistry approach. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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Review

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41 pages, 5796 KiB  
Review
A New 2-Aminospiropyrazolylammonium Cation with Possible Uses in the Topical Areas of Ionic Liquids
by Lyudmila Kayukova and Anna Vologzhanina
Molecules 2024, 29(10), 2326; https://doi.org/10.3390/molecules29102326 - 15 May 2024
Viewed by 1222
Abstract
Based on the fact that 2-aminospiropyrazolinium compounds and structurally related azoniaspiro compounds belong, in a broad sense, to the class of ionic liquids, we have reviewed them and studied their practical applications. To search for possible uses of a new 2-aminospiropyrazolinium compounds, it [...] Read more.
Based on the fact that 2-aminospiropyrazolinium compounds and structurally related azoniaspiro compounds belong, in a broad sense, to the class of ionic liquids, we have reviewed them and studied their practical applications. To search for possible uses of a new 2-aminospiropyrazolinium compounds, it is necessary to undertake a comparison with the related class of azoniaspiro compounds based on available information. The structures of the well-studied class of azoniaspiro compounds and the related but little-studied class of 2-aminospiropyrazolinium have rigid frameworks, limited conformational freedom, and a salt nature. These properties give them the ability to organize the nearby molecular space and enable the structure-forming ability of azoniaspiro compounds in the synthesis of zeolites, as well as the ability to act as phase-transfer catalysts and have selective biological effects. Additionally, these characteristics enable their ability to act as electrolytes and serve as materials for anion exchange membranes in fuel cells and water electrolyzers. Thus, the well-studied properties of azoniaspiro compounds as phase-transfer catalysts, structure-directing agents, electrolytes, and materials for membranes in power sources would encourage the study of the similar properties of 2-aminospiropyrazolinium compounds, which we have studied in relation to in vitro antitubercular, antidiabetic, and antimicrobial activities. Full article
(This article belongs to the Special Issue Recent Advances in Ionic Liquids and Their Applications)
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