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Ionic Liquids and Deep Eutectic Solvents: Greener Approaches for Sustainable Chemistry

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

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 28549

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Special Issue Editors


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Guest Editor
Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia
Interests: analytical methodologies; environmental and biological samples; bioactive compounds; trace and minor elements; spectroscopic and separation techniques; green(er) extractions; chemometrics

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Guest Editor
Faculty of Technology, University of Novi Sad, 21000 Novi Sad, Serbia
Interests: extraction and isolation of bioactive molecules; green extraction solvents; green chemistry; NADES solvents; subcritical water; supercritical carbon dioxide; biological characterization of bioactive molecules
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Guest Editor
Chemistry Department, University of Rome “La Sapienza”, Piazzale Aldo Moro 5, 00185 Rome, Italy
Interests: theoretical chemistry; molecular dynamics; ab-initio calculations; ionic liquids; computational chemistry; computational spectroscopy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Over the last decades, ionic liquids (ILs) and deep eutectic solvents (DES) have been the subject of intense research activities in chemistry and biology due to their biocompatibility and highly tunable physical and chemical properties.

In line with green chemistry principles, the advent of deep eutectic solvents and especially natural deep eutectic solvents (NADES) has opened new avenues for applications in diverse fields, such as the extraction of targeted bioactive compounds from natural sources, catalysis (catalytic and biocatalytic reaction process), production of new media for enzymatic or chemical reactions, biomass processing, dissolution of nonwater soluble pharmaceuticals, food analysis, as well as their use as tailored solvents in energy applications (batteries, hydrogen and oxygen production, cellulosic ethanol, biodiesel, etc.), etc. This intense research activity was hoisted by recent findings on the exceptional recycling/recoveries properties of these greener solvents, on the one hand, and their possible low toxicity and low environmental impact, on the other.

This Special Issue is expected to provide a comprehensive overview on the state-of-the-art of the most recent advancements in the field of sustainable chemical approaches utilizing ionic liquids and deep eutectic solvents. The Special Issue invites researchers to contribute their findings covering all aspects in this field to promote the latest developments in research and innovation through sustainable strategies and characterization.

Prof. Dr. Slavica Ražić
Dr. Aleksandra Cvetanović Kljakić
Prof. Dr. Enrico Bodo
Guest Editors

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Keywords

  • ionic liquids (ILs)
  • deep eutectic solvents (DES)
  • natural deep eutectic solvents (NADES)
  • separation process
  • green sample preparation
  • recycling/recovery of greener solvents

Published Papers (14 papers)

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Research

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17 pages, 5222 KiB  
Article
Deep Eutectic Solvents Based on Carboxylic Acids and Glycerol or Propylene Glycol as Green Media for Extraction of Bioactive Substances from Chamaenerion angustifolium (L.) Scop.
by Alena Koigerova, Alevtina Gosteva, Artemiy Samarov and Nikita Tsvetov
Molecules 2023, 28(19), 6978; https://doi.org/10.3390/molecules28196978 - 8 Oct 2023
Cited by 4 | Viewed by 1409
Abstract
Chamaenerion angustifolium (L.) Scop. is one of the promising sources of biologically active compounds and a valuable industrial crop. Recently, green extraction methods have become more topical. One of them is the application of deep eutectic solvents (DESs). The aim of this work [...] Read more.
Chamaenerion angustifolium (L.) Scop. is one of the promising sources of biologically active compounds and a valuable industrial crop. Recently, green extraction methods have become more topical. One of them is the application of deep eutectic solvents (DESs). The aim of this work was the synthesis and characterization of DES consisting of glycerin or propylene glycol with malonic, malic, or citric acids, evaluation of their effectiveness for extracting useful substances from C. angustifolium during ultrasonic extraction, description of kinetics, and optimization of extraction conditions. DESs were obtained and characterized with FTIR. Their effectiveness in the process of ultrasound-assisted extraction of biologically active substances from C. angustifolium was estimated. Kinetic parameters describing the dependence of the total phenolic, flavonoids, and antioxidant content, free radical scavenging of DPPH, and concentration of flavonoid aglycons (myricetin, quercetin, and kaempferol) via time in the range of 5–60 min at 45 °C are obtained. Extraction conditions were optimized with the Box–Behnken design of experiment. The results of this work make it possible to expand the scope of DES applications and serve the development of C. angustifolium processing methods. Full article
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14 pages, 1376 KiB  
Article
The Formulation and Evaluation of Deep Eutectic Vehicles for the Topical Delivery of Azelaic Acid for Acne Treatment
by Dhari K. Luhaibi, Hiba H. Mohammed Ali, Israa Al-Ani, Naeem Shalan, Faisal Al-Akayleh, Mayyas Al-Remawi, Jehad Nasereddin, Nidal A. Qinna, Isi Al-Adham and Mai Khanfar
Molecules 2023, 28(19), 6927; https://doi.org/10.3390/molecules28196927 - 4 Oct 2023
Cited by 4 | Viewed by 1516
Abstract
The current work was aimed at the development of a topical drug delivery system for azelaic acid (AzA) for acne treatment. The systems tested for this purpose were deep eutectic systems (DESs) prepared from choline chloride (CC), malonic acid (MA), and PEG 400. [...] Read more.
The current work was aimed at the development of a topical drug delivery system for azelaic acid (AzA) for acne treatment. The systems tested for this purpose were deep eutectic systems (DESs) prepared from choline chloride (CC), malonic acid (MA), and PEG 400. Three CC to MA and eight different MA: CC: PEG400 ratios were tested. The physical appearance of the tested formulations ranged from solid and liquid to semisolid. Only those that showed liquid formulations of suitable viscosity were considered for further investigations. A eutectic mixture made from MA: CC: PEG400 1:1:6 (MCP 116) showed the best characteristics in terms of viscosity, contact angle, spreadability, partition coefficient, and in vitro diffusion. Moreover, the MCP116 showed close rheological properties to the commercially available market lead acne treatment product (Skinorin®). In addition, the formula showed synergistic antibacterial activity between the MA moiety of the DES and the AzA. In vitro diffusion studies using polyamide membranes demonstrated superior diffusion of MCP116 over the pure drug and the commercial product. No signs of skin irritation and edema were observed when MCP116 was applied to rabbit skin. Additionally, the MCP116 was found to be, physically and chemically, highly stable at 4, 25, and 40 °C for a one-month stability study. Full article
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13 pages, 2283 KiB  
Article
Folic Acid Ionic-Liquids-Based Separation: Extraction and Modelling
by Alexandra Cristina Blaga, Elena Niculina Dragoi, Alexandra Tucaliuc, Lenuta Kloetzer and Dan Cascaval
Molecules 2023, 28(8), 3339; https://doi.org/10.3390/molecules28083339 - 10 Apr 2023
Cited by 3 | Viewed by 1845
Abstract
Folic acid (vitamin B9) is an essential micronutrient for human health. It can be obtained using different biological pathways as a competitive option for chemical synthesis, but the price of its separation is the key obstacle preventing the implementation of biological methods on [...] Read more.
Folic acid (vitamin B9) is an essential micronutrient for human health. It can be obtained using different biological pathways as a competitive option for chemical synthesis, but the price of its separation is the key obstacle preventing the implementation of biological methods on a broad scale. Published studies have confirmed that ionic liquids can be used to separate organic compounds. In this article, we investigated folic acid separation by analyzing 5 ionic liquids (CYPHOS IL103, CYPHOS IL104, [HMIM][PF6], [BMIM][PF6], [OMIM][PF6]) and 3 organic solvents (heptane, chloroform, and octanol) as the extraction medium. The best obtained results indicated that ionic liquids are potentially valuable for the recovery of vitamin B9 from diluted aqueous solutions as fermentation broths; the efficiency of the process reached 99.56% for 120 g/L CYPHOS IL103 dissolved in heptane and pH 4 of the aqueous folic acid solution. Artificial Neural Networks (ANNs) were combined with Grey Wolf Optimizer (GWO) for modelling the process, considering its characteristics. Full article
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15 pages, 1386 KiB  
Article
Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid–Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils
by Slavica Ražić, Tamara Bakić, Aleksandra Topić, Jelena Lukić and Antonije Onjia
Molecules 2023, 28(5), 2395; https://doi.org/10.3390/molecules28052395 - 5 Mar 2023
Cited by 5 | Viewed by 2358
Abstract
A fast and straightforward reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett–Burman [...] Read more.
A fast and straightforward reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett–Burman design for screening the most influential variables followed by a central composite response surface methodology led to an optimum RP-DLLME setup for a 1 g oil sample: 9 mL hexane as the diluting solvent, vortex extraction with 0.45 mL of DES (choline chloride–urea) at 40 °C, without addition of salt, and centrifugation at 6000 rpm for 4.0 min. The reconstituted extract was directly injected into a high-performance liquid chromatography (HPLC) system working in the diode array mode. At the studied concentration levels, the obtained method detection limits (MDL) was 11 mg/kg, linearity in matrix-matched standards was R2 ≥ 0.997, relative standard deviations (RSD) was 7.8%, and average recovery was 93%. The combined use of the recently developed DES -based RP-DLLME and HPLC provides an innovative, efficient, cost-effective, and more sustainable method for the extraction and quantification of free tryptophan in oily food matrices. The method was employed to analyze cold-pressed oils from nine vegetables (Brazil nut, almond, cashew, hazelnut, peanut, pumpkin, sesame, sunflower, and walnut) for the first time. The results showed that free tryptophan was present in the range of 11–38 mg/100 g. This article is important for its contributions to the field of food analysis, and for its development of a new and efficient method for the determination of free tryptophan in complex matrices, which has the potential to be applied to other analytes and sample types. Full article
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15 pages, 6435 KiB  
Article
Studies on the Prediction and Extraction of Methanol and Dimethyl Carbonate by Hydroxyl Ammonium Ionic Liquids
by Xiaokang Wang, Yuanyuan Cui, Yingying Song, Yifan Liu, Junping Zhang, Songsong Chen, Li Dong and Xiangping Zhang
Molecules 2023, 28(5), 2312; https://doi.org/10.3390/molecules28052312 - 2 Mar 2023
Cited by 3 | Viewed by 1491
Abstract
The separation of dimethyl carbonate (DMC) and methanol is of great significance in industry. In this study, ionic liquids (ILs) were employed as extractants for the efficient separation of methanol from DMC. Using the COSMO-RS model, the extraction performance of ILs consisting of [...] Read more.
The separation of dimethyl carbonate (DMC) and methanol is of great significance in industry. In this study, ionic liquids (ILs) were employed as extractants for the efficient separation of methanol from DMC. Using the COSMO-RS model, the extraction performance of ILs consisting of 22 anions and 15 cations was calculated, and the results showed that the extraction performance of ILs with hydroxylamine as the cation was much better. The extraction mechanism of these functionalized ILs was analyzed by molecular interaction and the σ-profile method. The results showed that the hydrogen bonding energy dominated the interaction force between the IL and methanol, and the molecular interaction between the IL and DMC was mainly Van der Waals force. The molecular interaction changes with the type of anion and cation, which in turn affects the extraction performance of ILs. Five hydroxyl ammonium ILs were screened and synthesized for extraction experiments to verify the reliability of the COSMO-RS model. The results showed that the order of selectivity of ILs predicted by the COSMO-RS model was consistent with the experimental results, and ethanolamine acetate ([MEA][Ac]) had the best extraction performance. After four regeneration and reuse cycles, the extraction performance of [MEA][Ac] was not notably reduced, and it is expected to have industrial applications in the separation of methanol and DMC. Full article
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20 pages, 3682 KiB  
Article
Extraction of Gold Based on Ionic Liquid Immobilized in UiO-66: An Efficient and Reusable Way to Avoid IL Loss Caused by Ion Exchange in Solvent Extraction
by Xinyu Cui, Yani Wang, Yanfeng Wang, Pingping Zhang and Wenjuan Lu
Molecules 2023, 28(5), 2165; https://doi.org/10.3390/molecules28052165 - 25 Feb 2023
Cited by 3 | Viewed by 1630
Abstract
Ionic liquids (ILs) have received considerable attention as a promising green solvent for extracting metal ions from aqueous solutions. However, the recycling of ILs remains difficult and challenging because of the leaching of ILs, which is caused by the ion exchange extraction mechanism [...] Read more.
Ionic liquids (ILs) have received considerable attention as a promising green solvent for extracting metal ions from aqueous solutions. However, the recycling of ILs remains difficult and challenging because of the leaching of ILs, which is caused by the ion exchange extraction mechanism and hydrolysis of ILs in acidic aqueous conditions. In this study, a series of imidazolium-based ILs were confined in a metal–organic framework (MOF) material (UiO-66) to overcome the limitations when used in solvent extraction. The effect of the various anions and cations of the ILs on the adsorption ability of AuCl4 was studied, and 1-hexyl-3-methylimidazole tetrafluoroborate ([HMIm]+[BF4]@UiO-66) was used for the construction of a stable composite. The adsorption properties and mechanism of [HMIm]+[BF4]@UiO-66 for Au(III) adsorption were also studied. The concentrations of tetrafluoroborate ([BF4]) in the aqueous phase after Au(III) adsorption by [HMIm]+[BF4]@UiO-66 and liquid–liquid extraction by [HMIm]+[BF4] IL were 0.122 mg/L and 18040 mg/L, respectively. The results reveal that Au(III) coordinated with the N-containing functional groups, while [BF4] was effectively confined in UiO-66, instead of undergoing anion exchange in liquid–liquid extraction. Electrostatic interactions and the reduction of Au(III) to Au(0) were also important factors determining the adsorption ability of Au(III). [HMIm]+[BF4]@UiO-66 could be easily regenerated and reused for three cycles without any significant drop in the adsorption capacity. Full article
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12 pages, 2097 KiB  
Article
Valorization of Hemp-Based Packaging Waste with One-Pot Ionic Liquid Technology
by Julius Choi, Alberto Rodriguez, Blake A. Simmons and John M. Gladden
Molecules 2023, 28(3), 1427; https://doi.org/10.3390/molecules28031427 - 2 Feb 2023
Cited by 2 | Viewed by 1654
Abstract
The range of applications for industrial hemp has consistently increased in various sectors over the years. For example, hemp hurd can be used as a resource to produce biodegradable packaging materials when incorporated into a fungal mycelium composite, a process that has been [...] Read more.
The range of applications for industrial hemp has consistently increased in various sectors over the years. For example, hemp hurd can be used as a resource to produce biodegradable packaging materials when incorporated into a fungal mycelium composite, a process that has been commercialized. Although these packaging materials can be composted after usage, they may present an opportunity for valorization in a biorefinery setting. Here, we demonstrate the potential of using this type of discarded packaging composite as a feedstock for biofuel production. A one-pot ionic liquid-based biomass deconstruction and conversion process was implemented, and the results from the packaging material were compared with those obtained from untreated hemp hurd. At a 120 °C reaction temperature, 7.5% ionic liquid loading, and 2 h reaction time, the packaging materials showed a higher lignocellulosic sugar yield and sugar concentrations than hemp hurd. Hydrolysates prepared from packaging materials also promoted production of higher titers (1400 mg/L) of the jet-fuel precursor bisabolene when used to cultivate an engineered strain of the yeast Rhodosporidium toruloides. Box–Behnken experiments revealed that pretreatment parameters affected the hemp hurd and packaging materials differently, evidencing different degrees of recalcitrance. This study demonstrated that a hemp hurd-based packaging material can be valorized a second time once it reaches the end of its primary use by supplying it as a feedstock to produce biofuels. Full article
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19 pages, 4318 KiB  
Article
Extraction of Bioactive Compounds from C. vulgaris Biomass Using Deep Eutectic Solvents
by Maria Myrto Dardavila, Sofia Pappou, Maria G. Savvidou, Vasiliki Louli, Petros Katapodis, Haralambos Stamatis, Kostis Magoulas and Epaminondas Voutsas
Molecules 2023, 28(1), 415; https://doi.org/10.3390/molecules28010415 - 3 Jan 2023
Cited by 10 | Viewed by 2452
Abstract
C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio [...] Read more.
C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio were used for that purpose. The extracts’ total carotenoid (TCC) and phenolic contents (TPC), as well as their antioxidant activity (IC50), were determined within the process of identification of the most efficient solvent. This screening procedure revealed ChCl:1,2 butanediol (1:4)/H2O 70/30 w/w as the most compelling solvent; thus, it was employed thereafter for the extraction process optimization. Three extraction parameters, i.e., solvent-to-biomass ratio, temperature, and time were studied regarding their impact on the extract’s TCC, TPC, and IC50. For the experimental design and process optimization, the statistical tool Response Surface Methodology was used. The resulting models’ predictive capacity was confirmed experimentally by carrying out two additional extractions under conditions different from the experimental design. Full article
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20 pages, 4051 KiB  
Article
Tunable Aryl Alkyl Ionic Liquid Supported Synthesis of Platinum Nanoparticles and Their Catalytic Activity in the Hydrogen Evolution Reaction and in Hydrosilylation
by Dennis Woitassek, Till Strothmann, Harry Biller, Swantje Lerch, Henning Schmitz, Yefan Song, Stefan Roitsch, Thomas Strassner and Christoph Janiak
Molecules 2023, 28(1), 405; https://doi.org/10.3390/molecules28010405 - 3 Jan 2023
Cited by 2 | Viewed by 1542
Abstract
Tunable aryl alkyl ionic liquids (TAAILs) are ionic liquids (ILs) with a 1-aryl-3-alkylimidazolium cation having differently substituted aryl groups. Herein, nine TAAILs with the bis(trifluoromethylsulfonyl)imide anion are utilized in combination with and without ethylene glycol (EG) as reaction media for the rapid microwave [...] Read more.
Tunable aryl alkyl ionic liquids (TAAILs) are ionic liquids (ILs) with a 1-aryl-3-alkylimidazolium cation having differently substituted aryl groups. Herein, nine TAAILs with the bis(trifluoromethylsulfonyl)imide anion are utilized in combination with and without ethylene glycol (EG) as reaction media for the rapid microwave synthesis of platinum nanoparticles (Pt-NPs). TAAILs allow the synthesis of small NPs and are efficient solvents for microwave absorption. Transmission electron microscopy (TEM) shows that small primary NPs with sizes of 2 nm to 5 nm are obtained in TAAILs and EG/TAAIL mixtures. The Pt-NPs feature excellent activity as electrocatalysts in the hydrogen evolution reaction (HER) under acidic conditions, with an overpotential at a current density of 10 mA cm−2 as low as 32 mV vs the reversible hydrogen electrode (RHE), which is significantly lower than the standard Pt/C 20% with 42 mV. Pt-NPs obtained in TAAILs also achieved quantitative conversion in the hydrosilylation reaction of phenylacetylene with triethylsilane after just 5 min at 200 °C. Full article
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13 pages, 866 KiB  
Article
Macrocyclic Ionic Liquids with Amino Acid Residues: Synthesis and Influence of Thiacalix[4]arene Conformation on Thermal Stability
by Olga Terenteva, Azamat Bikmukhametov, Alexander Gerasimov, Pavel Padnya and Ivan Stoikov
Molecules 2022, 27(22), 8006; https://doi.org/10.3390/molecules27228006 - 18 Nov 2022
Cited by 3 | Viewed by 1539
Abstract
Novel thiacalix[4]arene based ammonium ionic liquids (ILs) containing amino acid residues (glycine and L-phenylalanine) in cone, partial cone, and 1,3-alternate conformations were synthesized by alkylation of macrocyclic tertiary amines with N-bromoacetyl-amino acids ethyl ester followed by replacing bromide anions [...] Read more.
Novel thiacalix[4]arene based ammonium ionic liquids (ILs) containing amino acid residues (glycine and L-phenylalanine) in cone, partial cone, and 1,3-alternate conformations were synthesized by alkylation of macrocyclic tertiary amines with N-bromoacetyl-amino acids ethyl ester followed by replacing bromide anions with bis(trifluoromethylsulfonyl)imide ions. The melting temperature of the obtained ILs was found in the range of 50–75 °C. The effect of macrocyclic core conformation on the synthesized ILs’ melting points was shown, i.e., the ILs in partial cone conformation have the lowest melting points. Thermal stability of the obtained macrocyclic ILs was determined via thermogravimetry and differential scanning calorimetry. The onset of decomposition of the synthesized compounds was established at 305–327 °C. The compounds with L-phenylalanine residues are less thermally stable by 3–19 °C than the same glycine-containing derivatives. Full article
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16 pages, 4354 KiB  
Article
An Ionic-Liquid-Imprinted Nanocomposite Adsorbent: Simulation, Kinetics and Thermodynamic Studies of Triclosan Endocrine Disturbing Water Contaminant Removal
by Imran Ali, Gunel T. Imanova, Hassan M. Albishri, Wael Hamad Alshitari, Marcello Locatelli, Mohammad Nahid Siddiqui and Ahmed M. Hameed
Molecules 2022, 27(17), 5358; https://doi.org/10.3390/molecules27175358 - 23 Aug 2022
Cited by 11 | Viewed by 1729
Abstract
The presence of triclosan in water is toxic to human beings, hazardous to the environment and creates side effects and problems because this is an endocrine-disturbing water pollutant. Therefore, there is a great need for the separation of this notorious water pollutant at [...] Read more.
The presence of triclosan in water is toxic to human beings, hazardous to the environment and creates side effects and problems because this is an endocrine-disturbing water pollutant. Therefore, there is a great need for the separation of this notorious water pollutant at an effective, economic and eco-friendly level. The interface sorption was achieved on synthesized ionic liquid-based nanocomposites. An N-methyl butyl imidazolium bromide ionic liquid copper oxide nanocomposite was prepared using green methods and characterized by using proper spectroscopic methods. The nanocomposite was used to remove triclosan in water with the best conditions of time 30 min, concentration 100 µg/L, pH 8.0, dose 1.0 g/L and temperature 25 °C, with 90.2 µg/g removal capacity. The results obeyed Langmuir, Temkin and D-Rs isotherms with a first-order kinetic and liquid-film-diffusion kinetic model. The positive entropy value was 0.47 kJ/mol K, while the negative value of enthalpy was −0.11 kJ/mol. The negative values of free energy were −53.18, −74.17 and −76.14 kJ/mol at 20, 25 and 30 °C. These values confirmed exothermic and spontaneous sorption of triclosan. The combined effects of 3D parameters were also discussed. The supramolecular model was developed by simulation and chemical studies and suggested electrovalent bonding between triclosan and N-methyl butyl imidazolium bromide ionic liquid. Finally, this method is assumed as valuable for the elimination of triclosan in water. Full article
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10 pages, 2360 KiB  
Article
A Computational Analysis of the Reaction of SO2 with Amino Acid Anions: Implications for Its Chemisorption in Biobased Ionic Liquids
by Vanessa Piacentini, Andrea Le Donne, Stefano Russo and Enrico Bodo
Molecules 2022, 27(11), 3604; https://doi.org/10.3390/molecules27113604 - 3 Jun 2022
Cited by 1 | Viewed by 2185
Abstract
We report a series of calculations to elucidate one possible mechanism of SO2 chemisorption in amino acid-based ionic liquids. Such systems have been successfully exploited as CO2 absorbents and, since SO2 is also a by-product of fossil fuels’ combustion, their [...] Read more.
We report a series of calculations to elucidate one possible mechanism of SO2 chemisorption in amino acid-based ionic liquids. Such systems have been successfully exploited as CO2 absorbents and, since SO2 is also a by-product of fossil fuels’ combustion, their ability in capturing SO2 has been assessed by recent experiments. This work is exclusively focused on evaluating the efficiency of the chemical trapping of SO2 by analyzing its reaction with the amino group of the amino acid. We have found that, overall, SO2 is less reactive than CO2, and that the specific amino acid side chain (either acid or basic) does not play a relevant role. We noticed that bimolecular absorption processes are quite unlikely to take place, a notable difference with CO2. The barriers along the reaction paths are found to be non-negligible, around 7–11 kcal/mol, and the thermodynamic of the reaction appears, from our models, unfavorable. Full article
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Review

Jump to: Research

17 pages, 3200 KiB  
Review
Deep Eutectic Solvents as Catalysts for Cyclic Carbonates Synthesis from CO2 and Epoxides
by Dorota Mańka and Agnieszka Siewniak
Molecules 2022, 27(24), 9006; https://doi.org/10.3390/molecules27249006 - 17 Dec 2022
Cited by 8 | Viewed by 2903
Abstract
In recent years, the chemical industry has put emphasis on designing or modifying chemical processes that would increasingly meet the requirements of the adopted proecological sustainable development strategy and the principles of green chemistry. The development of cyclic carbonate synthesis from CO2 [...] Read more.
In recent years, the chemical industry has put emphasis on designing or modifying chemical processes that would increasingly meet the requirements of the adopted proecological sustainable development strategy and the principles of green chemistry. The development of cyclic carbonate synthesis from CO2 and epoxides undoubtedly follows this trend. First, it represents a significant improvement over the older glycol phosgenation method. Second, it uses renewable and naturally abundant carbon dioxide as a raw material. Third, the process is most often solvent-free. However, due to the low reactivity of carbon dioxide, the process of synthesising cyclic carbonates requires the use of a catalyst. The efforts of researchers are mainly focused on the search for new, effective catalysts that will enable this reaction to be carried out under mild conditions with high efficiency and selectivity. Recently, deep eutectic solvents (DES) have become the subject of interest as potential effective, cheap, and biodegradable catalysts for this process. The work presents an up-to-date overview of the method of cyclic carbonate synthesis from CO2 and epoxides with the use of DES as catalysts. Full article
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17 pages, 1070 KiB  
Review
Applications of Deep Eutectic Solvents in Sample Preparation and Extraction of Organic Molecules
by Orfeas-Evangelos Plastiras and Victoria Samanidou
Molecules 2022, 27(22), 7699; https://doi.org/10.3390/molecules27227699 - 9 Nov 2022
Cited by 8 | Viewed by 3005
Abstract
The use of deep eutectic solvents (DES) is on the rise worldwide because of the astounding properties they offer, such as simplicity of synthesis and utilization, low-cost, and environmental friendliness, which can, without a doubt, replace conventional solvents used in heaps. In this [...] Read more.
The use of deep eutectic solvents (DES) is on the rise worldwide because of the astounding properties they offer, such as simplicity of synthesis and utilization, low-cost, and environmental friendliness, which can, without a doubt, replace conventional solvents used in heaps. In this review, the focus will be on the usage of DES in extracting a substantial variety of organic compounds from different sample matrices, which not only exhibit great results but surpass the analytical performance of conventional solvents. Moreover, the properties of the most commonly used DES will be summarized. Full article
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