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Deep Eutectic Solvents

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

Deadline for manuscript submissions: closed (15 October 2019) | Viewed by 54242

Special Issue Editors


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Guest Editor
Chemical and Paper Engineering Department, Western Michigan University, 1903 W Michigan Ave, Kalamazoo, MI 49008-5462, USA
Interests: deep eutectic solvents; ionic liquids; CO2 capture; thermodynamics; molecular modeling
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Chemistry and ICCRAM, University of Burgos, 09001 Burgos, Spain
Interests: multiscale materials modeling; thermodynamics; in silico toxicology; safe and sustainable by design; deep eutectic solvents; CO2 capture; nanomaterials; phase equilibrium; physical chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Deep eutectic solvents (DES), being cost-effective solvents, have attracted increasing attention in both academia and industry in recent years. Bringing together mixtures of hydrogen-bond donor(s) and hydrogen-bond acceptor(s), DESs are formed and such mixtures show substantially high melting-point depression upon mixing.

Due to their task-specific character, DES have recently been considered as alternatives to current industry benchmark solvents since DES maintain most of their relevant properties and at the same DESs time avoid some of their economic and environmental issues. DES are produced from low cost and natural sources, together with their almost null toxicity and high biodegradability make them solvents as a suitable for wide range of applications such as organic synthesis, catalysis, biocatalysis, biodiesel transformation, electrochemistry, batteries and capacitors, (nano)materials, pharmaceutical ingredient delivery vehicles and gas separation technologies.

The purpose of this Special Issue on DES in Molecules is to bring experts from the fields of chemistry, chemical engineering and materials science backgrounds and highlight recent advancements in above-mentioned areas for these innovative solvents and their applications. We welcome both experimental and theoretical approaches in order to diversify this special issue and give broader perspective on the subject to the readers.

We hope this Special Issue will catalyze the ongoing research activities on DES and inspire many others in both academia and industry to consider promising novel solvents, DES, as one of the most state-of-the-art mediums for sustainable chemical process applications.

Prof. Mert Atilhan
Prof. Santiago Aparicio
Guest Editors

Manuscript Submission Information

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Keywords

  • Deep Eutectic Solvents
  • Ionic Liquids
  • Organic Acids
  • Gas Solubility
  • Gas Separation
  • Natural Deep Eutectic Solvents
  • Density Functional Theory
  • Molecular Dynamics
  • Organic Synthesis
  • Catalysis
  • Biocatalysis
  • Biodiesel Transformation
  • Electrochemistry
  • Batteries and Capacitors
  • Nano-materials
  • Drug Delivery

Published Papers (9 papers)

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Research

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17 pages, 2530 KiB  
Article
Feedforward Artificial Neural Network-Based Model for Predicting the Removal of Phenolic Compounds from Water by Using Deep Eutectic Solvent-Functionalized CNTs
by Rusul Khaleel Ibrahim, Seef Saadi Fiyadh, Mohammed Abdulhakim AlSaadi, Lai Sai Hin, Nuruol Syuhadaa Mohd, Shaliza Ibrahim, Haitham Abdulmohsin Afan, Chow Ming Fai, Ali Najah Ahmed and Ahmed Elshafie
Molecules 2020, 25(7), 1511; https://doi.org/10.3390/molecules25071511 - 26 Mar 2020
Cited by 13 | Viewed by 3125
Abstract
In the recent decade, deep eutectic solvents (DESs) have occupied a strategic place in green chemistry research. This paper discusses the application of DESs as functionalization agents for multi-walled carbon nanotubes (CNTs) to produce novel adsorbents for the removal of 2,4-dichlorophenol (2,4-DCP) from [...] Read more.
In the recent decade, deep eutectic solvents (DESs) have occupied a strategic place in green chemistry research. This paper discusses the application of DESs as functionalization agents for multi-walled carbon nanotubes (CNTs) to produce novel adsorbents for the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solution. Also, it focuses on the application of the feedforward backpropagation neural network (FBPNN) technique to predict the adsorption capacity of DES-functionalized CNTs. The optimum adsorption conditions that are required for the maximum removal of 2,4-DCP were determined by studying the impact of the operational parameters (i.e., the solution pH, adsorbent dosage, and contact time) on the adsorption capacity of the produced adsorbents. Two kinetic models were applied to describe the adsorption rate and mechanism. Based on the correlation coefficient (R2) value, the adsorption kinetic data were well defined by the pseudo second-order model. The precision and efficiency of the FBPNN model was approved by calculating four statistical indicators, with the smallest value of the mean square error being 5.01 × 10−5. Moreover, further accuracy checking was implemented through the sensitivity study of the experimental parameters. The competence of the model for prediction of 2,4-DCP removal was confirmed with an R2 of 0.99. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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11 pages, 1396 KiB  
Article
Extraction of High Value Triterpenic Acids from Eucalyptus globulus Biomass Using Hydrophobic Deep Eutectic Solvents
by Nuno H. C. S. Silva, Eduarda S. Morais, Carmen S. R. Freire, Mara G. Freire and Armando J. D. Silvestre
Molecules 2020, 25(1), 210; https://doi.org/10.3390/molecules25010210 - 4 Jan 2020
Cited by 37 | Viewed by 4896
Abstract
Triterpenic acids (TTAs), known for their promising biological properties, can be found in different biomass sources and related by-products, such as Eucalyptus globulus bark, and have been extracted using organic volatile solvents such as dichloromethane. Recently, deep eutectic solvents (DES) have been identified [...] Read more.
Triterpenic acids (TTAs), known for their promising biological properties, can be found in different biomass sources and related by-products, such as Eucalyptus globulus bark, and have been extracted using organic volatile solvents such as dichloromethane. Recently, deep eutectic solvents (DES) have been identified as promising alternatives for the extraction of value-added compounds from biomass. In the present work, several hydrophobic DES were tested for the extraction of TTAs from E. globulus bark. Initial solubility studies revealed that DES based on menthol and thymol as the most promising solvents for these compounds given the highest solubilities obtained for ursolic acid (UA) at temperatures ranging from room temperature up to 90 °C. Accordingly, an eutectic mixture of menthol:thymol (1:2) was confirmed as the best candidate for the TTAs extraction from E. globulus outer bark, leading to extraction yields (weight of TTA per weight of biomass) at room temperature of 1.8 wt% for ursolic acid, 0.84 wt% for oleanolic acid and 0.30 wt% for betulinic acid. These values are significantly higher than those obtained with conventional organic solvents under similar conditions. The results obtained using these DES are promising for the recovery of TTAs for nutraceutical and pharmacological applications, while reinforcing the potential of DES as promising solvents to be applied in biorefinery processes. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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15 pages, 2719 KiB  
Article
The Role of Charge Transfer in the Formation of Type I Deep Eutectic Solvent-Analogous Ionic Liquid Mixtures
by Dinis O. Abranches, Nicolas Schaeffer, Liliana P. Silva, Mónia A. R. Martins, Simão P. Pinho and João A. P. Coutinho
Molecules 2019, 24(20), 3687; https://doi.org/10.3390/molecules24203687 - 14 Oct 2019
Cited by 21 | Viewed by 4650
Abstract
It was recently shown that tetramethylammonium chloride presented negative deviations to ideality when mixed with tetraethylammonium chloride or tetrapropylammonium chloride, leading to a strong decrease of the melting points of these salt mixtures, in a behavior akin to that observed in the formation [...] Read more.
It was recently shown that tetramethylammonium chloride presented negative deviations to ideality when mixed with tetraethylammonium chloride or tetrapropylammonium chloride, leading to a strong decrease of the melting points of these salt mixtures, in a behavior akin to that observed in the formation of deep eutectic solvents. To better rationalize this unexpected melting point depression between two structurally similar compounds devoid of dominant hydrogen bonding capability, new solid–liquid equilibria data for tetramethylammonium-based systems were measured and analyzed in this work. Molecular dynamics was used to show that the strong negative deviations from ideality presented by these systems arise from a synergetic share of the chloride ions. A transfer of chloride ions seems to occur from the bigger cation in the mixture (which possesses a more disperse charge) to the smaller cation (tetramethylammonium), resembling the formation of metal–chloride complexes in type I deep eutectic solvents. This rearrangement of the charged species leads to an energetic stabilization of both components in the mixture, inducing the negative deviations to the ideality observed. The conclusions presented herein emphasize the often-neglected contribution of charge delocalization in deep eutectic solvents formation and its applicability toward the design of new ionic liquid mixtures. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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18 pages, 8077 KiB  
Article
Quantum Chemistry Insight into the Interactions Between Deep Eutectic Solvents and SO2
by Mert Atilhan, Tausif Altamash and Santiago Aparicio
Molecules 2019, 24(16), 2963; https://doi.org/10.3390/molecules24162963 - 15 Aug 2019
Cited by 39 | Viewed by 4871
Abstract
A systematic research work on the rational design of task specific Deep Eutectic Solvents (DES) has been carried out via density functional theory (DFT) in order to increase knowledge on the key interaction parameters related to efficient SO2 capture by DES at [...] Read more.
A systematic research work on the rational design of task specific Deep Eutectic Solvents (DES) has been carried out via density functional theory (DFT) in order to increase knowledge on the key interaction parameters related to efficient SO2 capture by DES at a molecular level. A total of 11 different DES structures, for which high SO2 affinity and solubility is expected, have been selected in this work. SO2 interactions in selected DES were investigated in detail through DFT simulations and this work has generated a valuable set of information about required factors at the molecular level to provide high SO2 solubility in DES, which is crucial for enhancing the current efficiency of the SO2 capture process and replacing the current state of the art with environmentally friendly solvents and eventually implementing these materials in the chemical industry. Results that were obtained from DFT calculations were used to deduce the details of the type and the intensity of the interaction between DES and SO2 molecules at various interaction sites as well as to quantify short-range interactions by using various methods such as quantum theory of atoms in a molecule (QTAIM), electrostatic potentials (ESP) and reduced density gradients (RDG). Systematic research on the molecular interaction characterization between DES structures and SO2 molecule increases our knowledge on the rational design of task-specific DES. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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19 pages, 6393 KiB  
Article
Modeling of Solid–Liquid Equilibria in Deep Eutectic Solvents: A Parameter Study
by Ahmad Alhadid, Liudmila Mokrushina and Mirjana Minceva
Molecules 2019, 24(12), 2334; https://doi.org/10.3390/molecules24122334 - 25 Jun 2019
Cited by 43 | Viewed by 4513
Abstract
Deep eutectic solvents (DESs) are potential alternatives to many conventional solvents in process applications. Knowledge and understanding of solid–liquid equilibria (SLE) are essential to characterize, design, and select a DES for a specific application. The present study highlights the main aspects that should [...] Read more.
Deep eutectic solvents (DESs) are potential alternatives to many conventional solvents in process applications. Knowledge and understanding of solid–liquid equilibria (SLE) are essential to characterize, design, and select a DES for a specific application. The present study highlights the main aspects that should be taken into account to yield better modeling, prediction, and understanding of SLE in DESs. The work is a comprehensive study of the parameters required for thermodynamic modeling of SLE—i.e., the melting properties of pure DES constituents and their activity coefficients in the liquid phase. The study is carried out for a hypothetical binary mixture as well as for selected real DESs. It was found that the deepest eutectic temperature is possible for components with low melting enthalpies and strong negative deviations from ideality in the liquid phase. In fact, changing the melting enthalpy value of a component means a change in the difference between solid and liquid reference state chemical potentials which results in different values of activity coefficients, leading to different interpretations and even misinterpretations of interactions in the liquid phase. Therefore, along with reliable modeling of liquid phase non-ideality in DESs, accurate estimation of the melting properties of their pure constituents is of clear significance in understanding their SLE behavior and for designing new DES systems. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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9 pages, 1194 KiB  
Article
Permeabilities of CO2, H2S and CH4 through Choline-Based Ionic Liquids: Atomistic-Scale Simulations
by Abdukarem Amhamed, Mert Atilhan and Golibjon Berdiyorov
Molecules 2019, 24(10), 2014; https://doi.org/10.3390/molecules24102014 - 27 May 2019
Cited by 17 | Viewed by 3399
Abstract
Molecular dynamics simulations are used to study the transport of CO 2 , H 2 S and CH 4 molecules across environmentally friendly choline-benzoate and choline-lactate ionic liquids (ILs). The permeability coefficients of the considered molecules are calculated using the free energy and [...] Read more.
Molecular dynamics simulations are used to study the transport of CO 2 , H 2 S and CH 4 molecules across environmentally friendly choline-benzoate and choline-lactate ionic liquids (ILs). The permeability coefficients of the considered molecules are calculated using the free energy and diffusion rate profiles. Both systems show the largest resistance to CH 4 , whereas more than 5 orders of magnitude larger permeability coefficients are obtained for the other two gas molecules. The CO 2 /CH 4 and H 2 S/CH 4 selectivity was estimated to be more than 10 4 and 10 5 , respectively. These results indicate the great potential of the considered ILs for greenhouse gas control. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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12 pages, 1410 KiB  
Article
Deep Eutectic Solvent-Based Ultrahigh Pressure Extraction of Baicalin from Scutellaria baicalensis Georgi
by Hui Wang, Xiaodi Ma, Qibin Cheng, Li Wang and Liwei Zhang
Molecules 2018, 23(12), 3233; https://doi.org/10.3390/molecules23123233 - 7 Dec 2018
Cited by 45 | Viewed by 4694
Abstract
Deep eutectic solvents (DESs), promising green solvents, and ultrahigh pressure extraction (UPE) as an effective auxiliary extraction method, have attracted wide attention. In this study, DES was coupled with UPE to efficiently extract baicalin from Scutellaria baicalensis Georgi. First, choline chloride: lactic acid [...] Read more.
Deep eutectic solvents (DESs), promising green solvents, and ultrahigh pressure extraction (UPE) as an effective auxiliary extraction method, have attracted wide attention. In this study, DES was coupled with UPE to efficiently extract baicalin from Scutellaria baicalensis Georgi. First, choline chloride: lactic acid (ChCl-LA, molar ratio 1:1) was selected as the most appropriate DES by comparing the extraction yield of different DESs. Second, the extraction protocol was optimized by response surface methodology (RSM) considering the impacts of ChCl-LA concentration, extraction pressure, extraction time and liquid-solid ratio on the extraction yield. Under the optimal condition (40 vol% water content, extraction pressure of 400 MPa, extraction time of 4 min and a liquid-solid ratio of 110 mL/g), a maximum yield of 116.8 mg/g was achieved, higher than that obtained by the traditional extraction method. The microstructure of the raw and extracted Scutellaria baicalensis Georgi samples according to scanning electron microscope (SEM) images revealed that the dissolution of chemical components was enhanced from the disrupted root tissues after DESs-UPE. DESs coupled with UPE could effectively extract the baicalin from Scutellaria baicalensis Georgi as a rapid and efficient extraction method. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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Review

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12 pages, 803 KiB  
Review
Application of Deep Eutectic Solvents in Food Analysis: A Review
by Jingnan Chen, Yun Li, Xiaoping Wang and Wei Liu
Molecules 2019, 24(24), 4594; https://doi.org/10.3390/molecules24244594 - 16 Dec 2019
Cited by 73 | Viewed by 6212
Abstract
Deep eutectic solvents (DESs) have emerged recently as new and green solvents. DESs can be used for extraction and separation of both inorganic metallic components and organic compounds such as phenolic compounds, flavonoids, sugars, and aromatic amines from food samples. DESs possess a [...] Read more.
Deep eutectic solvents (DESs) have emerged recently as new and green solvents. DESs can be used for extraction and separation of both inorganic metallic components and organic compounds such as phenolic compounds, flavonoids, sugars, and aromatic amines from food samples. DESs possess a tunable property simply by adjusting the ratio of hydrogen bond acceptors to the hydrogen bond donors. As a green extraction medium, DESs have various applications in the pretreatment process and improve the efficiency of different food analyses. This review summarizes the findings of recent studies on the development, production, application, and efficacy of DESs in the pretreatment process of various food analyses. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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37 pages, 5973 KiB  
Review
Deep Eutectic Solvents for Pretreatment, Extraction, and Catalysis of Biomass and Food Waste
by Payam Kalhor and Khashayar Ghandi
Molecules 2019, 24(22), 4012; https://doi.org/10.3390/molecules24224012 - 6 Nov 2019
Cited by 187 | Viewed by 15664
Abstract
Valorization of lignocellulosic biomass and food residues to obtain valuable chemicals is essential to the establishment of a sustainable and biobased economy in the modern world. The latest and greenest generation of ionic liquids (ILs) are deep eutectic solvents (DESs) and natural deep [...] Read more.
Valorization of lignocellulosic biomass and food residues to obtain valuable chemicals is essential to the establishment of a sustainable and biobased economy in the modern world. The latest and greenest generation of ionic liquids (ILs) are deep eutectic solvents (DESs) and natural deep eutectic solvents (NADESs); these have shown great promise for various applications and have attracted considerable attention from researchers who seek versatile solvents with pretreatment, extraction, and catalysis capabilities in biomass- and biowaste-to-bioenergy conversion processes. The present work aimed to review the use of DESs and NADESs in the valorization of biomass and biowaste as pretreatment or extraction solvents or catalysis agents. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents)
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