Research

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17 pages, 2530 KiB

Open AccessArticle

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 12 | Viewed by 2938

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

Open AccessArticle

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 - 04 Jan 2020

Cited by 36 | Viewed by 4616

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

Open AccessFeature PaperArticle

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 4364

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

Open AccessFeature PaperArticle

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 35 | Viewed by 4616

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

Open AccessArticle

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 42 | Viewed by 4217

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

Open AccessArticle

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 3252

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

Open AccessArticle

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 - 07 Dec 2018

Cited by 38 | Viewed by 4472

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

Open AccessReview

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 65 | Viewed by 5835

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

Open AccessReview

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 - 06 Nov 2019

Cited by 178 | Viewed by 14836

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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