Showing papers on "Solvent published in 2017"
TL;DR: In this article, the authors report efficient and fast filtration of organic solutions through Graphene oxide (GO) laminates containing smooth two-dimensional (2D) capillaries made from large (10 to 20) flakes.
Abstract: Highly laminar graphene oxide flakes (10 to 20 μm in diameter) are fabricated. Reducing flake thickness to 10 nm enables water and organic solvent permeation, enabling the flakes to act as a highly effective organic solvent membrane. Graphene oxide (GO) membranes continue to attract intense interest due to their unique molecular sieving properties combined with fast permeation1,2,3,4,5,6,7,8,9. However, their use is limited to aqueous solutions because GO membranes appear impermeable to organic solvents1, a phenomenon not yet fully understood. Here, we report efficient and fast filtration of organic solutions through GO laminates containing smooth two-dimensional (2D) capillaries made from large (10–20 μm) flakes. Without modification of sieving characteristics, these membranes can be made exceptionally thin, down to ∼10 nm, which translates into fast water and organic solvent permeation. We attribute organic solvent permeation and sieving properties to randomly distributed pinholes interconnected by short graphene channels with a width of 1 nm. With increasing membrane thickness, organic solvent permeation rates decay exponentially but water continues to permeate quickly, in agreement with previous reports1,2,3,4. The potential of ultrathin GO laminates for organic solvent nanofiltration is demonstrated by showing >99.9% rejection of small molecular weight organic dyes dissolved in methanol. Our work significantly expands possibilities for the use of GO membranes in purification and filtration technologies.
487 citations
TL;DR: The emerging optical properties of the degraded solvent present challenges for spectroscopy of nanomaterial dispersions; most notably the possibility of observing solvent photoluminescence in the spectra of 2D materials such as MoS2, highlighting the need for stable solvents and exfoliation processes to minimise the influence of solvent degradation on the properties of liquid-exfoliated 2D material.
Abstract: N-methyl-2-pyrrolidone (NMP) has been shown to be the most effective solvent for liquid phase exfoliation and dispersion of a range of 2D materials including graphene, molybdenum disulphide (MoS2) and black phosphorus. However, NMP is also known to be susceptible to sonochemical degradation during exfoliation. We report that this degradation gives rise to strong visible photoluminescence of NMP. Sonochemical modification is shown to influence exfoliation of layered materials in NMP and the optical absorbance of the solvent in the dispersion. The emerging optical properties of the degraded solvent present challenges for spectroscopy of nanomaterial dispersions; most notably the possibility of observing solvent photoluminescence in the spectra of 2D materials such as MoS2, highlighting the need for stable solvents and exfoliation processes to minimise the influence of solvent degradation on the properties of liquid-exfoliated 2D materials.
263 citations
TL;DR: This review focuses on the ability of different formation methods to cope with the huge variety of lignin types and points out which particle characteristics can be achieved by which method.
Abstract: Lignin is the second most abundant biopolymer after cellulose. It has long been obtained as a by-product of cellulose production in pulp and paper production, but had rather low added-value applications. A changing paper market and the emergence of biorefinery projects should generate vast amounts of lignin with the potential of value addition. Nanomaterials offer unique properties and the preparation of lignin nanoparticles and other nanostructures has therefore gained interest as a promising technique to obtain value-added lignin products. Due to lignin's high structural and chemical heterogeneity, methods must be adapted to these different types. This review focuses on the ability of different formation methods to cope with the huge variety of lignin types and points out which particle characteristics can be achieved by which method. The current research's main focus is on pH and solvent-shifting methods where the latter can yield solid and hollow particles. Solvent shifting also showed the capability to cope with different lignin types and solvents and antisolvents, respectively. However, process conditions have to be adapted to every type of lignin and reduction of solvent demand or the integration in a biorefinery process chain must be focused.
158 citations
TL;DR: In this article, the authors studied the electrochemical interface between rutile IrO2(110) and water to investigate how the inclusion of an explicit solvent influences the stabilities of adsorbed intermediates in the oxygen evolution reaction.
Abstract: We study the electrochemical interface between rutile IrO2(110) and water to investigate how the inclusion of an explicit solvent influences the stabilities of adsorbed intermediates in the oxygen evolution reaction. Solvent is modeled by explicit nondissociated water molecules, and their structure is determined by a global optimization method. We find that the inclusion of an explicit solvent can significantly affect the geometry of adsorbed intermediates, changing from an interaction with the surface to an interaction with the water bilayer. These water structures consist of stacked octagonal sheets in an ordered network. Solvent stabilization is pronounced for adsorbed *OH and *OOH, which are capable of donating hydrogen bonds. We find little to no change in adsorbate binding energy as the number of layers of solvent is increased from 1 to 3, suggesting a single water bilayer is sufficient to describe the system. With either *O or *OH coadsorbates, the energetics of the reaction pathway are relatively ...
156 citations
TL;DR: In this article, the authors demonstrate that control of the competition between hydrogen bonds and halogen bonds, the two most highly studied directional intermolecular interactions, can be exerted by choice of solvent (polarity) to direct the selfassembly of co-crystals.
Abstract: Control of intermolecular interactions is integral to harnessing self-assembly in nature. Here we demonstrate that control of the competition between hydrogen bonds and halogen bonds, the two most highly studied directional intermolecular interactions, can be exerted by choice of solvent (polarity) to direct the self-assembly of co-crystals. Competitive co-crystal formation has been investigated for three pairs of hydrogen bond and halogen bond donors, which can compete for a common acceptor group. These competitions have been examined in seven different solvents. Product formation has been determined and phase purity has been examined by analysis of powder X-ray diffraction patterns. Formation of hydrogen-bonded co-crystals is favoured from less polar solvents and halogen-bonded co-crystals from more polar solvents. The solvent polarity at which the crystal formation switches from hydrogen-bond to halogen-bond dominance depends on the relative strengths of the interactions, but is not a function of the solution-phase interactions alone. The results clearly establish that an appreciation of solvent effects is critical to obtain control of the intermolecular interactions.
150 citations
TL;DR: A class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts is reported, which cannot be explained by traditional electrostatic and steric mechanisms.
Abstract: A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other. Electrostatic stabilization of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute-solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute-solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.
149 citations
TL;DR: A low–molecular weight monomer whose supramolecular polymerization is triggered by the incorporation of water is reported, indicating the presence of water molecules as comonomers is essential to the polymerization process.
Abstract: Although the concept of structural water that is bound inside hydrophobic pockets and helps to stabilize protein structures is well established, water has rarely found a similar role in supramolecular polymers. Water is often used as a solvent for supramolecular polymerization, however without taking the role of a comonomer for the supramolecular polymer structure. We report a low-molecular weight monomer whose supramolecular polymerization is triggered by the incorporation of water. The presence of water molecules as comonomers is essential to the polymerization process. The supramolecular polymeric material exhibits strong adhesion to surfaces, such as glass and paper. It can be used as a water-activated glue, which can be released at higher temperatures and reused many times without losing its performance.
135 citations
TL;DR: Propylene carbonate has been shown to be a green polar aprotic solvent which can be used to replace dichloromethane and DMF in both solution- and solid-phase peptide synthesis.
131 citations
TL;DR: Overall, ultrasound has been established to be a green process for extraction of curcumin with benefits of reduction in time as compared to batch extraction and the operating temperature asCompared to Soxhlet extraction.
123 citations
TL;DR: In this article, the relationship between the structure and solvent effects on the basicity of conjugated N-heterocyclic nitrogen bases in different media: the polar aprotic solvent acetonitrile, the polar protic solvent water and the gas phase.
103 citations
TL;DR: It is shown that the high acidity of the deep eutectic solvents investigated is mainly provided by the organic acid present in the mixture, and that an increase of the alkyl side chain of both the HBA and the HBD species leads to a lower ability of the solvent to donate protons.
TL;DR: In this article, a water-controlled three-component thiourea-catalyzed cascade reaction of unactivated alkynes, 1,3-dihalo-5,5-dimethylhydantoin and water has been developed.
TL;DR: In this paper, the authors show that the interlayer hydrogen bonds can be disrupted by solvents such as DMSO, leading to solvent-induced delamination of 2D metal-organic nanosheets.
Abstract: Trigonal 3-connecting imidazole-annulated triptycene triacid (H3TPA) is a molecular module that is programmed for orthogonal self-assembly. Upon treatment with metal salts such as CoCl2, Mn(NO3)2, Zn(NO3)2 and Cd(NO3)2, highly porous isostructural MOFs are obtained in which the TPA linker undergoes metal–ligand coordination and hydrogen bonding through carboxylate groups and imidazole moieties, respectively. The MOFs are constructed by hydrogen bond-mediated offset stacking of porous (3,3) honeycomb layers formed by the self-assembly of TPA with 3-connecting triangular bimetallic SBUs. We show that the interlayer hydrogen bonds can be disrupted by solvents such as DMSO, leading to solvent-induced delamination of 2D metal–organic nanosheets. The delamination is signaled by turn-on of fluorescence, which is suppressed in the bulk state. Indeed, the extent of exfoliation with different solvents – as reflected from fluorescence quantum yields as well as solvent-induced shifts in emission maxima – can be nicely correlated with Gutmann's solvent DN numbers, which are a measure of the ability of solvents to accept hydrogens in hydrogen bonds. The results demonstrate how the bulk materials with layered structures can be (i) engineered in a ‘bottom-up’ approach by orthogonal self-assembly of an organic linker created by de novo design and (ii) in turn be exfoliated in a ‘top-down’ approach by solvent-induced ultrasonication. As bulk materials, the hydrogen-bonded MOFs lend themselves to selective as well as high adsorption of CO2 under ambient conditions as a result of the nitrogenous environment of pores conferred by the benzimidazole moieties.
TL;DR: In this article, the catalytic valorization of vegetable waste into levulinic acid (LA) over a solid Bronsted acid, Amberlyst 36, in aqueous solution with/without polar aprotic solvent (dimethyl sulfoxide, DMSO).
TL;DR: This method was successfully applied to determine methadone in water and biological samples with an appropriate recovery about 98.4-101.2% and the precision, as the relative standard deviation (RSD) was <6% respectively.
TL;DR: In this article, the authors demonstrate that the solubility of GO and the stability of the as-formed solutions depend not only on the solute and solvent cohesion parameters, as commonly believed, but mostly on the chemical interactions at the GO/solvent interface.
Abstract: One of the main advantages of graphene oxide (GO) over its non-oxidized counterpart is its ability to form stable solutions in water and some organic solvents. At the same time, the nature of GO solutions is not completely understood; the existing data are scarce and controversial. Here, we demonstrate that the solubility of GO, and the stability of the as-formed solutions depend not just on the solute and solvent cohesion parameters, as commonly believed, but mostly on the chemical interactions at the GO/solvent interface. By the DFT and QTAIM calculations, we demonstrate that the solubility of GO is afforded by strong hydrogen bonding established between GO functional groups and solvent molecules. The main functional groups taking part in hydrogen bonding are tertiary alcohols; epoxides play only a minor role. The magnitude of the bond energy values is significantly higher than that for typical hydrogen bonding. The hydrogen bond energy between GO functional groups and solvent molecules decreases in the sequence: water > methanol > ethanol. We support our theoretical results by several experimental observations including solution calorimetry. The enthalpy of GO dissolution in water, methanol and ethanol is −0.1815 ± 0.0010, −0.1550 ± 0.0012 and −0.1040 ± 0.0010 kJ g−1, respectively, in full accordance with the calculated trend. Our findings provide an explanation for the well-known, but poorly understood solvent exchange phenomenon.
TL;DR: The preferential solvation parameters of rosmarinic acid in binary solvent mixtures of ethanol+water and methanol+water were derived from their thermodynamic properties by means of the inverse Kirkwood-Buff integrals method.
TL;DR: In this paper, a deep-eutectic solvent based on choline chloride and lactic acid was used for the leaching of rare earths and other metals from NdFeB magnets.
Abstract: Deep-eutectic solvents (DESs) are used as a promising alternative to aqueous solutions for the recovery of valuable metals from NdFeB magnets. A deep-eutectic solvent based on choline chloride and lactic acid (molar ratio 1 : 2) was used for the leaching of rare earths and other metals from NdFeB magnets. A process for the separation of Fe, B and Co from Nd and Dy in the deep-eutectic solvent was developed by using the ionic liquid tricaprylmethylammonium thiocyanate (Aliquat 336 SCN, [A336][SCN]) diluted in toluene (0.9 M). The extraction parameters were optimized and stripping of B was efficiently carried out by HCl, while EDTA was employed for the recovery of Fe and Co. The separation of Nd and Dy was assessed by using two different types of extractants, a mixture of trialkylphosphine oxides (Cyanex 923) and bis(2-ethylhexyl)phosphoric acid (D2EHPA). Based on the distribution ratios, separation factors and the ease of subsequent stripping, Cyanex 923 was chosen as the most effective extractant. The purified Dy present in the less polar phase was easily recovered by stripping with water, while the Nd present in the deep-eutectic solvent was recovered by precipitation stripping with a stoichiometric amount of oxalic acid. Nd2O3 and Dy2O3 were recovered with a purity of 99.87% and 99.94%, respectively. The feasibility to scale up this separation process was corroborated by a setup of mixer-settlers and highlighted by the possibility to fully recover and reuse the deep-eutectic solvent and the less polar phases employed in the extractions. The new proposed system based on a deep-eutectic solvent combined with traditional organic extraction phases presented higher selectivities and efficiencies than the analogous aqueous system. Extended X-ray absorption fine structure (EXAFS) was employed to elucidate the different mechanisms for extraction of Co and Fe from the deep-eutectic solvent and from an aqueous solution.
TL;DR: In this paper, the effects of different solvents on the morphology and permeation of poly(etherblock-amide) (Pebax-1657) membranes were investigated.
Abstract: In this study, the effects of different solvents on the morphology and permeation of poly(ether-block-amide) (Pebax-1657) membranes were investigated. Pebax membranes were fabricated via a solution casting method with five different solvents, that is, N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMAc), N-methyl-2-pyrrolidone (NMP), formic acid, and a mixture of ethanol (EtOH) with water (H2O). Cross-sectional scanning electron microscopy analysis of the membranes was performed to investigate the morphology of the prepared membranes. X-ray diffraction and Fourier transform infrared analysis were also carried out to characterize the membranes. The interactions of the polymer and various solvents were evaluated with Hansen solubility parameters. Permeation experiments for CO2 and CH4 gases were performed to study the effects of the solvents on the permeation properties of the membranes. The solvent properties, such as the molar volume, boiling point, and solubility parameters, were investigated as were the membranes characteristics, such as the crystallinity, d-spacing, and fractional free volume. The results obtained from the experiments show that the CO2 permeability for the membranes prepared with different solvents followed this order: NMP > DMF > Formic acid > DMAc > H2O/EtOH mixture. With increasing molar volume, the gas permeability increased for all of the membranes, except for DMAc, which showed a lower permeability because of its highly crystalline structure. DMF showed a higher CO2/CH4 ideal selectivity compared to the other membranes and, consequently, could be introduced as the best solvent from all aspects for the Pebax-1657 membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44531.
TL;DR: In this paper, a hydrogen sulfate ionic liquid was used as co-solvent and as homogeneous catalyst in ethanol solvent for 5-ethoxymethylfurfural (5-EMF) conversion.
TL;DR: In this article, a series of MnO x /CeO 2 catalysts were prepared by modulating the solvents (deionized water (DW), anhydrous ethanol (AE), acetic acid (AA), and oxalic acid (OA) solution) with the purpose of improving the low-temperature NH 3 -SCR performance, broadening the operating temperature window, and enhancing the H 2 O+−SO 2 resistance.
TL;DR: Two solvent-induced porous hydrogen-bonded organic frameworks have been obtained, and their synthesis, crystal structures, gas sorption behaviours and fluorescence sensing applications have been systematically investigated to elucidate the solvent effects on the structures and functionalities of HOFs.
TL;DR: The strong intermolecular hydrogen bonds between water molecules may play a key role in disfavoring protonolysis, which occurs extensively in other protic media such as methanol.
Abstract: In contrast to classic methods carried out under inert atmospheres with dry volatile organic solvents and often low temperatures, the addition of highly polar organometallic compounds to non-activated imines and nitriles proceeds quickly, efficiently, and chemoselectively with a broad range of substrates at room temperature and under air with water as the only reaction medium. Secondary amines and tertiary carbinamines are furnished in yields of up to and over 99 %. The significant solvent D/H isotope effect observed for the on-water nucleophilic additions of organolithium compounds to imines suggests that the on-water catalysis arises from proton transfer across the organic-water interface. The strong intermolecular hydrogen bonds between water molecules may play a key role in disfavoring protonolysis, which occurs extensively in other protic media such as methanol. This work lays the foundation for reshaping many fundamental s-block metal-mediated organic transformations in water.
TL;DR: In this paper, the feasibility of replacing hexane, which is traditionally used to extract vegetable oils, with safer solvents, namely, ethanol and isopropanol, in rice bran oil (RBO) extraction was assessed.
TL;DR: In this article, the authors investigated SO2 absorption by deep eutectic solvents (DESs) formed by 1-ethyl-3-methylimidazolium chloride (EmimCl) and ethylene glycol (EG) under different conditions.
Abstract: In this work, we investigated SO2 absorption by deep eutectic solvents (DESs) formed by 1-ethyl-3-methylimidazolium chloride (EmimCl) and ethylene glycol (EG) under different conditions. DESs with different molar ratios of EmimCl and EG (from 2:1 to 1:2) were prepared. The results showed that all the EmimCl-EG solvents were very efficient for SO2 capture. It was demonstrated that the SO2 solubility increased with increasing concentrations of EmimCl in DESs. The effects of temperature and SO2 partial pressure were also investigated. The Emim-EG (2:1) solvent could absorb 1.15 (53 wt %) g SO2/g solvent at 20 °C and 1.0 atm, a much higher capacity than that of other DESs reported to date under the same conditions. Moreover, the SO2 desorption temperature of the solvents could be tuned by changing the composition of the solvents, and all the EmimCl-EG solvents showed excellent reversibility. Nuclear magnetic resonance and Fourier transform infrared spectra showed the interactions of the solvents and SO2.
TL;DR: In this paper, an efficient and selective production of levulinic acid from D-fructose in the presence of polystyrene-based sulphonic acid resin catalyst, Dowex 50× 8-100, at mild reaction conditions of 120°C, over 24h in a 50:50 mixture of water/GVL resulting in 72% yield under optimized reaction conditions.
Abstract: Highly efficient and selective production of levulinic acid has been achieved from D-fructose in the presence of polystyrene-based sulphonic acid resin catalyst, Dowex 50 × 8-100, at mild reaction conditions of 120 °C, over 24 h in a 50:50 mixture of water/GVL resulting in 72 mol% yield under optimized reaction conditions. Optimization of the effect of reaction temperature, time, pressure, catalyst to substrate ratio, fructose concentration and solvent was performed. Various polystyrene-based sulfonic acid resins were also investigated for quantitative production of LA from 5-hydroxymethylfurfural (5-HMF) in pure water. Catalyst recycling was carried out up to 6 cycles. Significant mechanistic information was obtained for the formation of “humins”, which are the primary cause of catalyst fouling, by the identification of soluble by-products and polymerization presursors using Q-Tof mass spectrometry based on accurate masses.
TL;DR: In this article, a new lipid extraction protocol for obtaining a fatty-acids-rich extract from the diatom Phaeodactylum tricornutum was developed, which used deep eutectic solvents and microwaves as pretreatments for environmentally friendly solvent extractions using dimethyl carbonate (DMC) and supercritical CO2 (scCO2).
Abstract: Microalgae are promising alternative sources of several bioactive compounds that are useful for human applications. However, lipids are traditionally extracted with toxic organic solvents (e.g., mixtures of chloroform and methanol or hexane). In this work, we develop a new lipid extraction protocol for obtaining a fatty-acids-rich extract from the diatom Phaeodactylum tricornutum. Deep eutectic solvents (DESs) and microwaves (MWs) were investigated as pretreatments for environmentally friendly solvent extractions using dimethyl carbonate (DMC) and supercritical CO2 (scCO2). Pretreatments with various DESs formed by choline chloride (ChCl) and different hydrogen-bond donors (oxalic acid, levulinic acid, urea, ethylene glycol, and sorbitol) were tested in combination with DMC extraction. DESs formed by ChCl and carboxylic acids gave the best results, increasing both the selectivity and the total fatty acid (TFA) extraction yield of DMC (by 16% and 80%, respectively). DESs combined with MW heating followed b...
TL;DR: The aim of this study was to select alternative solvent to hexane such as ethanol or isopropanol, and, to adjust the oil extraction process by developing an ultrasound assisted method to reach a comparable efficiency but also to enhance the oil quality.
TL;DR: In this article, a biphasic solvent for CO2 capture has recently attracted increasing attention for its high potential in reducing energy penalty of power plant, and a novel blend of N,N, N, N′, NN,N′,N″, N″-pentamethyldiethylenetriamine (PMDETA) and DETA was used to obtain a liquid-liquid phase separation solvent, which maintained a high CO2 absorption capacity and good phase separation at 30-60°C.
TL;DR: A new approach has been adopted for SFE in which the solubility of nonpolar supercritical CO2 can be enhanced by the addition of small amounts of cosolvent, which is elaborated upon in this paper.
Abstract: There has been growing interest in the application of supercritical solvents over the last several years, many of the applications industrial in nature. The purpose of plant material extraction is to obtain large amounts of extract rich in the desired active compounds in a time-sensitive and cost-effective manner. The productivity and profitability of a supercritical fluid extraction (SFE) process largely depends on the selection of process parameters, which are elaborated upon in this paper. Carbon dioxide (CO2) is the most desirable solvent for the supercritical extraction of natural products. Its near-ambient critical temperature makes it suitable for the extraction of thermolabile components without degradation. A new approach has been adopted for SFE in which the solubility of nonpolar supercritical CO2 can be enhanced by the addition of small amounts of cosolvent.