Special Issue "Alternative Solvents for Green Chemistry"

A special issue of Sustainable Chemistry (ISSN 2673-4079).

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Dr. Ana B. Pereiro
E-Mail Website
Guest Editor
LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: ionic liquids; chemical engineering; thermodynamic study; phase equilibria; separation processes
Special Issues and Collections in MDPI journals
Dr. João M. M. Araújo
E-Mail Website
Guest Editor
LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: separation/purification processes; aqueous biphasic systems; solubilisation and aggregation mechanisms; biomass valorisation
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Sustainable or green chemistry aims to design products or processes that eliminate or minimize the use and production of hazardous compounds. Nowadays, an emerging research field of interest is the use of alternative solvents such as ionic liquids (ILs) and deep eutectic solvents (DES). ILs have become one of the increasingly popular “green” media for engineers, not only due to their remarkable properties but also for their recyclability. Additionally, ILs can be tailored for specific applications by accurately selecting the cation and/or the anion. More recently, DES are evolving as a new class of task-specific solvents that can overcome the major handicaps of some ILs, namely nonbiodegradability, complex synthesis and purification processes, and high cost.

Dr. Ana B. Pereiro
Dr. João M. M. Araújo
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainable Chemistry is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Green solvents
  • Ionic liquids
  • Deep eutectic solvents
  • Sustainability

Published Papers (9 papers)

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Research

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Article
Alkali Iodide Deep Eutectic Solvents as Alternative Electrolytes for Dye Sensitized Solar Cells
Sustain. Chem. 2021, 2(2), 222-236; https://doi.org/10.3390/suschem2020013 - 06 Apr 2021
Viewed by 557
Abstract
Different alkali deep eutectic solvents (DES), such as LiI:nEG, NaI:nEG, and KI:nEG, have been tested as electrolytes for dye sensitized solar cells (DSSCs). These DSSCs were prepared using pure DES or, alternatively, DES combined with different amounts of iodine (I2). The [...] Read more.
Different alkali deep eutectic solvents (DES), such as LiI:nEG, NaI:nEG, and KI:nEG, have been tested as electrolytes for dye sensitized solar cells (DSSCs). These DSSCs were prepared using pure DES or, alternatively, DES combined with different amounts of iodine (I2). The most important parameters, such as open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and the overall conversion efficiency (η), were evaluated. Some DES seem to be promising candidates for DSSC applications, since they present higher VOC (up to 140 mV), similar FF values but less current density values, when compared with a reference electrolyte in the same experimental conditions. Additionally, electrochemical impedance spectroscopy (EIS) has been performed to elucidate the charge transfer and transport processes that occur in DSSCs. The values of different resistance (Ω·cm2) phenomena and recombination/relaxation time (s) for each process have been calculated. The best-performance was obtained for DES-based electrolyte, KI:EG (containing 0.5 mol% I2) showing an efficiency of 2.3%. The efficiency of this DES-based electrolyte is comparable to other literature systems, but the device stability is higher (only after seven months the performance of the device drop to 60%). Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Article
Unveiling the Influence of Non-Toxic Fluorinated Ionic Liquids Aqueous Solutions in the Encapsulation and Stability of Lysozyme
Sustain. Chem. 2021, 2(1), 149-166; https://doi.org/10.3390/suschem2010010 - 04 Mar 2021
Viewed by 527
Abstract
Proteins are bioactive compounds with high potential to be applied in the biopharmaceutical industry, food science and as biocatalysts. However, protein stability is very difficult to maintain outside of the native environment, which hinders their applications. Fluorinated ionic liquids (FILs) are a promising [...] Read more.
Proteins are bioactive compounds with high potential to be applied in the biopharmaceutical industry, food science and as biocatalysts. However, protein stability is very difficult to maintain outside of the native environment, which hinders their applications. Fluorinated ionic liquids (FILs) are a promising family of surface-active ionic liquids (SAILs) that have an amphiphilic behavior and the ability to self-aggregate in aqueous solutions by the formation of colloidal systems. In this work, the protein lysozyme was selected to infer on the influence of FILs in its stability and activity. Then, the cytotoxicity of FILs was determined to evaluate their biocompatibility, concluding that the selected compounds have neglected cytotoxicity. Therefore, UV–visible spectroscopy was used to infer the FIL-lysozyme interactions, concluding that the predominant interaction is the encapsulation of the lysozyme by FILs. The encapsulation efficiency was also tested, which highly depends on the concentration and anion of FIL. Finally, the bioactivity and thermal stability of lysozyme were evaluated, and the encapsulated lysozyme keeps its activity and thermal stability, concluding that FILs can be a potential stabilizer to be used in protein-based delivery systems. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Article
Ecotoxicity and Hemolytic Activity of Fluorinated Ionic Liquids
Sustain. Chem. 2021, 2(1), 115-126; https://doi.org/10.3390/suschem2010008 - 02 Mar 2021
Viewed by 609
Abstract
The task-specific design of ionic liquids (ILs) has emerged in several industrial and pharmaceutical applications. The family of ILs with fluorine tags equal to or longer than four carbon atoms, the fluorinated ionic liquids (FILs), combine the best properties of ILs with the [...] Read more.
The task-specific design of ionic liquids (ILs) has emerged in several industrial and pharmaceutical applications. The family of ILs with fluorine tags equal to or longer than four carbon atoms, the fluorinated ionic liquids (FILs), combine the best properties of ILs with the ones of perfluorinated compounds, and are being designed for several specific purposes. In the pharmaceutical field, there is an urgency to search for novel antibacterial agents to overcome problems associated to antimicrobial resistances. Then, the main purpose of this work is to evaluate the environmental impact and the ability of FILs to be used as antibacterial agents against Pseudomonas stutzeri bacteria. Beyond its rare pathogenicity, these bacteria are also used as a bioremediation agent to treat several contamination sites. Then, it is important to determine which FILs have antibacterial properties, and which do not impact the bacterial growth. The biocompatibility of FILs was also evaluated through their hemolytic activity and represent a step forward the application of FILs in pharmaceutical applications. The results proved that high concentrations of FILs can have a reduced ecotoxicity and a high biocompatibility. [C8C1Im][CF3SO3] was identified as the most promising compound to be used as an antibacterial agent since it prevents the growth of bacteria at concentrations compatible with the red blood cells’ viability. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Article
On the Dissolution of Metals in Ionic Liquids 1. Iron, Cobalt, Nickel, Copper, and Zinc
Sustain. Chem. 2021, 2(1), 63-73; https://doi.org/10.3390/suschem2010005 - 07 Feb 2021
Viewed by 670
Abstract
Ionic liquids are critical reagents for science and technical processes nowadays. Metals are the most used reagents in the industry. It is crucial to have a deeper understanding of how ionic liquids and metals could interact. In this article the interaction of those [...] Read more.
Ionic liquids are critical reagents for science and technical processes nowadays. Metals are the most used reagents in the industry. It is crucial to have a deeper understanding of how ionic liquids and metals could interact. In this article the interaction of those two families of compounds is accessed. The dissolution (reaction) of metals with ionic liquids is studied, namely the influence of temperature, redox potential, and availability of an oxidant in the process. The final state achieved by the iron metal samples was also addressed by Mössbauer spectroscopy. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Communication
Biocatalyzed Sulfoxidation in Presence of Deep Eutectic Solvents
Sustain. Chem. 2020, 1(3), 290-297; https://doi.org/10.3390/suschem1030019 - 12 Nov 2020
Cited by 1 | Viewed by 775
Abstract
The flavin-containing monooxygenase from Methylophaga sp. strain SK1 (mFMO) is a valuable biocatalyst for the preparation of optically active sulfoxides, among other valuable compounds. In this study, we explored to benefits of using Natural Deep Eutectic Solvents (NADESs) when doing oxidation [...] Read more.
The flavin-containing monooxygenase from Methylophaga sp. strain SK1 (mFMO) is a valuable biocatalyst for the preparation of optically active sulfoxides, among other valuable compounds. In this study, we explored to benefits of using Natural Deep Eutectic Solvents (NADESs) when doing oxidation with this biocatalyst, fused to phosphite dehydrogenase for cofactor regeneration (PTDH-mFMO). It was found that optically active sulfoxides could be obtained with slightly higher conversions in 10% v/v NADES when working at substrate concentrations of 50–200 mM, whereas there was no loss in the enantioselectivity. With these results, it is demonstrated for the first time that flavin-containing monooxygenases can be employed as biocatalysts in presence of NADESs. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Article
Phenol Recovery from Aromatic Solvents by Formation of Eutectic Liquids with Trialkyl-2,3-dihydroxypropylammonium Chloride Salts
Sustain. Chem. 2020, 1(1), 49-61; https://doi.org/10.3390/suschem1010004 - 09 Jun 2020
Cited by 2 | Viewed by 968
Abstract
Trialkyl-2,3-dihydroxypropylammonium chloride salts have been investigated as liquid eutectic-forming salts for the extraction of phenol from aromatic-rich model oil (toluene), demonstrating how the increased partitioning of phenol from oil-phases can be combined with reduced co-miscibility of the salt with aromatic hydrocarbons through the [...] Read more.
Trialkyl-2,3-dihydroxypropylammonium chloride salts have been investigated as liquid eutectic-forming salts for the extraction of phenol from aromatic-rich model oil (toluene), demonstrating how the increased partitioning of phenol from oil-phases can be combined with reduced co-miscibility of the salt with aromatic hydrocarbons through the introduction of the dihydroxypropyl-function. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Review

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Review
Green Chemistry Approach for Fabrication of Polymer Composites
Sustain. Chem. 2021, 2(2), 254-270; https://doi.org/10.3390/suschem2020015 - 09 Apr 2021
Viewed by 629
Abstract
Solvents are an inevitable part of industries. They are widely used in manufacturing and processing industries. Despite the numerous controlling measures taken, solvents contaminate our environment to a vast extent. Green and sustainable solvents have been a matter of growing interest within the [...] Read more.
Solvents are an inevitable part of industries. They are widely used in manufacturing and processing industries. Despite the numerous controlling measures taken, solvents contaminate our environment to a vast extent. Green and sustainable solvents have been a matter of growing interest within the research community over the past few years due to the increasing environmental concerns. Solvents are categorized as “green” based on their nonvolatility, nonflammability, availability, biodegradability and so on. The use of ionic liquids, super critical carbon dioxide and aqueous solvents for the fabrication of polymer composites is discussed in this review. The progress of utilizing solvent-free approaches for polymer composite preparation and efforts to produce new biobased solvents are also summarized. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Review
Review on Hydrometallurgical Recovery of Metals with Deep Eutectic Solvents
Sustain. Chem. 2020, 1(3), 238-255; https://doi.org/10.3390/suschem1030016 - 03 Oct 2020
Cited by 4 | Viewed by 1200
Abstract
Deep eutectic solvents (DESs) appeared recently as a new class of green designer solvents. The recovery of metals using hydrometallurgy is of major importance with the growth in metal demand. Several authors used these solvents for the hydrometallurgical recovery of metals from primary [...] Read more.
Deep eutectic solvents (DESs) appeared recently as a new class of green designer solvents. The recovery of metals using hydrometallurgy is of major importance with the growth in metal demand. Several authors used these solvents for the hydrometallurgical recovery of metals from primary and secondary resources, and these studies are reviewed in the present work. Hydrophilic DESs can be used for the leaching of metals and have great potential to replace mineral acids, and even to reduce water consumption. Efficient and selective leaching of metals from minerals or wastes is feasible by using DESs. However, the kinetics of leaching as well as the physicochemical properties of DESs are still limiting their large-scale application. Electrochemical recovery from DES is also possible but deserves further investigation. Finally, the recovery of metals from aqueous solutions using hydrophobic DESs was studied in several works. For the solvent extraction of metals, hydrophobic DESs constitute credible alternative ionic liquids. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Review
Recent Trends in Processing of Proteins and DNA in Alternative Solvents: A Sustainable Approach
Sustain. Chem. 2020, 1(2), 116-137; https://doi.org/10.3390/suschem1020010 - 25 Aug 2020
Cited by 6 | Viewed by 1340
Abstract
Throughout numerous research works on biomacromolecules, several breakthrough innovations have occurred in the field of biomacromolecule processing. Remarkable improvements have been made so far to address the problems associated with biomacromolecule processing technologies in terms of enhancing the efficiency of the processes. Green [...] Read more.
Throughout numerous research works on biomacromolecules, several breakthrough innovations have occurred in the field of biomacromolecule processing. Remarkable improvements have been made so far to address the problems associated with biomacromolecule processing technologies in terms of enhancing the efficiency of the processes. Green technology broadly focuses on the search for new techno-economic systems to replace the conventional systems which exhibit pernicious consequences for the environment and the health of organisms. The strategy practiced popularly is the use of alternate solvent systems, replacing the conventional toxic, volatile, and harsh organic solvents to prevent denaturation, biotransformation, enzyme activity loss, and degradation of biomacromolecules. Ionic liquids (ILs) and deep eutectic solvents (DESs) are emerging as greener alternatives over the past two decades and there has been an exponential increase in reports in the literature. The utility of neoteric solvents in biomacromolecule treatment may be envisaged for industrial processes in the near future. The current state of the art regarding the recent developments made over the past few years using neoteric solvents has been reviewed in this article. The recent scientific developments regarding the use of these neoteric solvents, especially ILs and DESs, for processes such as solubilization, extraction, and functionalization of biomacromolecules, especially proteins and DNA, have been addressed in this article. This review may be beneficial for designing novel and selective methodologies for the processing of biomacromolecules, opening doors for better material research in areas such as biotechnology and biological sciences. Full article
(This article belongs to the Special Issue Alternative Solvents for Green Chemistry)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: An overview on the recent advances in alternative solvents as stabilizers of proteins, enzymes and nucleic acids

Authors: Jéssica Almeida, Ana Margarida Loureiro, Emanuel V. Capela, Mara G. Freire, Ana P. M. Tavares

Abstract: Nowadays, the use of alternative solvents such as ionic liquids (ILs) and deep eutectic solvents (DES) in chemical, biotechnology and biomedical applications has been increasing. For instance, they present high relevance for biomolecules since solubility, structure stability and biological activity of biomolecules can be significantly enhanced rather than most of the traditional solvents. Therefore, this review aims to provide an outlook on the recent efforts and technological developments made on the use of ILs and DES for the stabilization and activation of proteins, enzymes and nucleic acids. The most relevant IL- and DES-based formulations reported for several biomolecules are herein described and the main molecular mechanisms underneath the increased stability promoted by these formulations are addressed, while highlighting their key advantages for the biotechnology and biomedical fields.

Title: Alkaline Iodide Deep Eutectic Solvents as alternative electrolytes for Dye Sensitized Solar Cells

Author: Hugo Cruz and Luis Branco 

Abstract:

Different alkaline deep eutectic solvents (DES) such as LiI:nEG, NaI:nEG and KI:nEG have been tested as electrolytes for dye sensitized solar cells (DSSCs). These DSSCs were prepared using pure DES or alternatively DES combined with different amounts of iodine (I2). The most important parameters such as open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF) and the overall conversion efficiency (η) were evaluated. Some DES seems to be promising candidates for DSSC applications, since they present higher VOC (up to 140 mV), similar FF values but less current density values, when compared with a reference electrolyte in the same experimental conditions. Additionally, electrochemical impedance spectroscopy (EIS) has been performed to elucidate the charge transfer and transport processes that occur in DSSCs. The values of different resistance (W.cm2) phenomena and recombination/relaxation time (s) for each process have been calculated. The best-performance was obtained for DES-based electrolyte, KI:EG (containing 0.5 mol% I2) showing an efficiency of 2.3%. The efficiency of this DES-based electrolyte is comparable to other literature systems but the device stability is higher (only after 7 months the  performance of the device drop to 60%).

Title: Green Chemistry Approach for Fabrication of Polymer Composites

Author: Sabu Thomas

Abstract:

Solvents are inevitable part of industries. They are widely used in manufacturing and processing industries. Despite of numerous controlling measures taken; solvents contaminate our environment to a vast extend. Green and sustainable solvents have been a matter of growing interest within the research community over few years due to the increasing environmental concerns. Solvents are categorized ‘green’ based on their non-volatility and non-flammability. The use of ionic liquids, super critical carbon dioxide and aqueous solvents for the fabrication of polymer composites are discussed in this review. The progress of utilizing solvent free approaches for polymer composite preparation and efforts to produce new biobased solvents are also summarized.

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