510 research outputs found
Insights into the nature of eutectic and deep eutectic mixtures
A stricter definition of a deep eutectic solvent (DES) is urgent, so that it may become a sound basis for further developments in this field. This communication aims at contributing to deepening the understanding of eutectic and deep eutectic mixtures concerning their definition, thermodynamic nature and modelling. The glut of literature on DES applications should be followed by a similar effort to address the fundamental questions on their nature. This hopefully would contribute to correct some widespread misconceptions, and help to establish a stringent definition of what a DES is. DES are eutectic mixtures for which the eutectic point temperature should be lower to that of an ideal liquid mixture. To identify and characterize them, their phase diagrams should be known, in order to compare the real temperature depression to that predicted if ideality is assumed, and to define composition ranges for which they are in the liquid state at operating temperatures. It is also shown that hydrogen bonding between the DES components should not be used to define or characterize a DES, since this would describe many ideal mixtures. The future of deep eutectic solvents is quite promising, and we expect that this work will contribute to the efficient design and selection of the best DES for a given application, and to model properties and phase equilibria without which the process design is impractical.This work was developed in the scope of the Project CICECO – Aveiro Institute of
Materials, POCI-01-0145-FEDER-007679 (Ref. FCT UID/CTM/50011/2013) and Associate Laboratory
LSRE-LCM, POCI-01-0145-FEDER-006984 (Ref. FCT UID/EQU/50020/2013), both financed by national
funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership
Agreement. This work is also a result of Project “AIProcMat@N2020 - Advanced Industrial Processes
and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-
FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the
Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). FCT
is also acknowledged for funding the project DeepBinfo:eu-repo/semantics/publishedVersio
Aqueous two-phase systems: Towards novel and more disruptive applications
Aqueous two-phase systems (ATPS) have been mainly proposed as powerful platforms for the separation
and purification of high-value biomolecules. However, after more than seven decades of research, ATPS
are still a major academic curiosity, without their wide acceptance and implementation by industry,
leading to the question whether ATPS should be mainly considered in downstream bioprocessing.
Recently, due to their versatility and expansion of the Biotechnology and Material Science fields, these
systems have been investigated in novel applications, such as in cellular micropatterning and bioprinting,
microencapsulation, to mimic cells conditions, among others. This perspective aims to be a reflection on
the current status of ATPS as separation platforms, while overviewing their applications, strengths and
limitations. Novel applications, advantages and bottlenecks of ATPS are further discussed, indicating
some directions on their use to create innovative industrial processes and commercial products.publishe
Hydrodynamics of cholinium chloride-based aqueous biphasic systems (ABS): a key study for their industrial implementation
Aqueous biphasic systems (ABS) have been widely studied for extraction and purification processes. Although they are considered biocompatible, amenable, and sustainable separation platforms, their application on an industrial scale remains impractical without proper scaling and integration into existing processes. To better understand the hydrodynamics of ABS formation, three cholinium chloride ([Ch]Cl)-based ABS composed of polypropylene glycol with a molecular weight of 400 g.mol−1 (PPG-400), tripotassium phosphate (K3PO4), and dipotassium hydrogen-phosphate (K2HPO4) were studied. The hydrodynamics of phase separation of ABS composed of PPG-400/[Ch]Cl, [Ch]Cl/K3PO4 and [Ch]Cl/K2HPO4 was studied by analysing the relationship between the mixing time (Tm) and the phase settling time (Ts), at 25 °C and 50 °C. The results showed that Ts is independent of Tm, which is very long for the polymer/salt systems (Ts > 6 h), while for salt/salt ABS, a very fast phase settling was observed (Ts < 150 s). The hydrodynamics of each salt/salt system was then correlated with the physicochemical properties of the coexisting phases and the nature of the phase-forming compounds. The increase in the salting-out effect of the inorganic salts, and the consequent larger differences between the compositions of the coexisting phases, improved the hydrodynamics of the [Ch]Cl-based ABS. With the increase of the tie-line lengths, the composition of the phases stabilized, resulting also in more stable physicochemical properties in each phase and constant Ts. The correlations obtained in this work allow the definition of the best operating region within the biphasic (liquid-liquid) region of [Ch]Cl/salt-based ABS as being the largest TLLs within the LLE region. The definition of these criteria and region of operation is crucial for the design and industrial implementation of these types of LLE processes using conventional mixer-settler units.publishe
Ion speciation: A key for the understanding of the solution properties of ionic liquid mixtures
Recently, combinations of two (or more) ionic liquids, known as ionic liquid mixtures, have become
popular and have a broad range of applications. However, the fundamental knowledge on the molecular
interactions that exist in ionic liquid mixtures is far from being understood. In this work, the experimental
measurement of the water activity coefficient and computational modelling using Conductor-like
Screening Model for Real Solvent (COSMO-RS) were carried out to get an insight into the molecular
interactions that are present in ionic liquid mixtures in aqueous solution. The results show that the
combination of two ionic liquids of different basicity in aqueous solution allows fine tuning of the water
activities, covering a wide range of values that could replace several pure fluids. This is an important
feature resulting from the unexpected ion speciation of the ionic liquid mixtures in aqueous solution.We thank the CICECO – Aveiro Institute of Materials, POCI-01-
0145-FEDER-007679 (Ref. FCT UID/CTM/50011/2019) and Associate
Laboratory LSRE-LCM, POCI-01-0145-FEDER-006984 (Ref. FCT UID/
EQU/50020/2019), financed by national funds through the FCT/MEC
and when appropriate co-financed by FEDDER under the PT2020
Partnership Agreement.info:eu-repo/semantics/publishedVersio
Solubilities of Amino Acids in the Presence of Chaotropic Anions
This work addresses the effect of chaotropic anions (thiocyanate and tosylate) on the solubility of glycine, L-leucine, L-phenylalanine, and L-aspartic acid in aqueous solutions at 298.2 K. The salts used were NaSCN, KSCN, NH4SCN, and NaC7H7SO3 (sodium tosylate), with salt concentrations ranging from 0 to 2 molal. The pH of the saturated solutions was registered, and solid-phase studies were also performed. All the thiocyanate salts and sodium tosylate induced a salting-in effect, except in the systems composed of glycine in aqueous sodium tosylate solutions at 0.5 and 1 molal. For L-leucine, L-phenylalanine, and L-aspartic acid the salting effect of anions followed the order tosylate− > SCN− > NO3- > Cl−, in good agreement with the behavior predicted by the Hofmeister series. Differently, the relative solubility of glycine in aqueous nitrate solutions was higher than in those containing thiocyanate, followed by the chloride and, closing the rank, the solutions containing the tosylate anion, suggesting that the solubility change in this case is achieved by a different mechanism.This work was developed within the scope of the project CIMO-Mountain Research
Center, UIDB/00690/2020 and LA/P/0007/2020 and CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the Portuguese Foundation
for Science and Technology (FCT)/MCTES. Mehriban Aliyeva thanks FCT and European Social Fund
(ESF) for her Ph.D. grant (SFRH/BD/139355/2018).info:eu-repo/semantics/publishedVersio
Solid-liquid equilibria for hexafluorophosphate-based ionic liquid quaternary mixtures and their corresponding subsystems
The present work describes an experimental study and the
thermodynamic modeling for the solid−liquid phase diagram of an ionic liquid
quaternary system constituted by hexafluorophosphate ([PF6]−) as the common
anion and by 1-methyl-3-propylimidazolium ([C3mim]+), 1-methyl-1-propylpyrrolidinium
([C3mpyrr]+), 1-methyl-3-propylpyridinium ([C3mpy]+), or 1-methyl-
1-propylpiperidinium ([C3mpip]+) as the cations. The Modified Quasichemical
Model was used to model the liquid solution, and the Compound Energy
Formalism was used for the relevant solid solutions. The liquidus projections of
the four ternary subsystems (1) [C3mim][PF6]−[C3mpip][PF6]−[C3mpyrr]-
[PF6], (2) [C3mpy][PF6]−[C3mpip][PF6]−[C3mpyrr][PF6], (3) [C3mpip]-
[PF6]−[C3mpy][PF6]−[C3mim][PF6], and (4) [C3mpyrr][PF6]−[C3mpy]-
[PF6]−[C3mim][PF6] were predicted using a standard symmetric (for systems 3
and 4) or asymmetric (for systems 1 and 2) interpolation method. In order to test
the accuracy of the thermodynamic model, two isoplethal sections were experimentally measured in each of the four ternary
systems using differential scanning calorimetry. Overall, agreement was very satisfactory, not requiring fitting of any ternary
interaction parameters for the liquid solution model. In each of the four calculated ternary liquidus projections, the region of
composition corresponding to room temperature ionic liquid mixtures was determined. The global minimum of the liquidus
temperature in the complete composition space was calculated to be about −16 °C, with a mole percentage composition of
(33.8% [C3mpyrr][PF6] + 33.9% [C3mpy][PF6] + 32.3% [C3mim][PF6]).The modeling part of this project was supported by the
Natural Sciences and Engineering Research Council of Canada
(Discovery Grant RGPIN 435893-2013). The new DSC
measurements in the four ternary subsystems were supported
by the laboratories CICECOAveiro Institute of Materials,
project POCI-01-0145-FEDER-007679 (ref FCT UID/CTM/
50011/2019), and Associate Laboratory LSRE-LCM (ref FCT
UID/EQU/50020/2019), both financed by national funds
through the FCT/MEC and when appropriate cofinanced by
FEDER under the PT2020 Partnership Agreement, and the
project “AIProcMat@N2020Advanced Industrial Processes
and Materials for a Sustainable Northern Region of Portugal
2020” (ref NORTE-01-0145-FEDER-000006) supported by
Norte Portugal Regional Operational Programme (NORTE
2020), under the Portugal 2020 Partnership Agreement,
through the European Regional Development Fund (ERDF).
Constructive discussions with Dr. Aım̈ en Gheribi, Prof. Youn-
Bae Kang, and Prof. Nick Virgilio were much appreciated.info:eu-repo/semantics/publishedVersio
The one-dimensional XXZ model with long-range interactions
The one-dimensional XXZ model (s=1/2, N sites) with uniform long-range
interactions among the transverse components of the spins is considered. The
Hamiltonian of the model is explicitly given by
where the
are half the Pauli spin matrices. The model is exactly solved by
applying the Jordan-Wigner fermionization, followed by a Gaussian
transformation. In the absence of the long-range interactions (I=0), the model,
which reduces to the isotropic XY model, is known to exhibit a second-order
quantum phase transition driven by the field at zero temperature. It is shown
that in the presence of the long-range interactions (I different from 0) the
nature of the transition is strongly affected. For I>0, which favours the
ordering of the transverse components of the spins, the transition is changed
from second- to first-order, due to the competition between transverse and xy
couplings. On the other hand, for I<0, which induces complete frustration of
the spins, a second-order transition is still present, although the system is
driven out of its usual universality class, and its critical exponents assume
typical mean-field values.Comment: 5 pages, 1 figure, presented at ICM2000, to be published in the
Proceedings (Journal of Magnetism & Magnetic Materials
Sustainable hydrophobic terpene-based eutectic solvents for the extraction and separation of metals
Sustainable hydrophobic eutectic solvents, composed of low-priced and biodegradable terpenes and fatty acids, were used for the extraction and separation of Cu(ii) from other transition metals in mildly acidic solutions. Multiple parameters were evaluated for metal extraction and the hydrophobic eutectic solvent was successfully recovered and reused.This work was part of BATRE-ARES project (ERA-MIN/0001/2015) funded by ADEME and FCT and partly developed in the
scope of the project CICECO – Aveiro Institute of Materials,
POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013).
C. M. S. S. Neves acknowledges FCT for the postdoctoral grant
(SFRH/BPD/109057/2015). M. A. R. Martins acknowledges
financial support from NORTE 2020 (NORTE-01-0145-FEDER-
000006) and DeepBiorefinery (PTDC/AGRTEC/1191/2014) projects.info:eu-repo/semantics/publishedVersio
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