Mixtures Of Deep Eutectic Solvents Research Articles

Comparison of Soda, Kraft, and DES Pulp Properties of European Black Poplar

Kraft pulping as the dominant pulping method contributes to several environmental problems. To overcome these problems, environmentally friendly pulping methods have been investigated. In the last years, deep eutectic solvents (DESs) have been identified as up-and-coming reagents in the lignocellulosic material processing and they are characterized as environmentally friendly. This study investigated the use of DES in pulp production from European black poplar chips. The DES mixture was prepared from choline chloride (ChCl) and ethylene glycol (EG). In addition, traditional soda and kraft pulping methods were carried out with poplar chips for comparison with the DES pulps. It was found that pulp production from poplar chips using DES was comparable to the soda and kraft pulps in terms of pulp yield, pulp viscosity, and opacity. The DES pulps easily reached target pulp freeness levels. However, the strength properties and brightness of the DES pulps were lower than those of the soda and kraft pulps. The strength properties of DES pulps can be improved with paper strength enhancers such as starch and micro or nanofibrillated cellulose. Also, the utilization of DES in pulp production may have an important role in cleaner production and it represents a greener alternative to traditional pulp production methods.

Eutectic Thin-Layer Chromatography as a New Possibility for Quantification of Plant Extracts—A Case Study

Deep eutectic solvents (DES), compared to classic ones, have interesting properties, such as the ability to solubilize compounds differing in polarity or increased dissolution of selected chemical compounds. They also offer specific interactions between the mobile and stationary phases. Those features make them promising solvents in chromatographic techniques, including the use in the separation of complicated samples. The first quantitative analysis with eutectic thin-layer chromatography (TLC) is presented in the paper. As a case study, five alkaloids from Chelidonium maius were selected as target compounds. A wide range of terpene-based DESs was investigated to develop the chromatographic system, both pure and after dilution. Moreover, a novel approach was employed to adjust polarity, involving mixing DESs differing in chromatographic properties. This procedure has proved to be effective. The best results were obtained with a 2:1 (wt/wt) mixture of DESs: camphor + phenol and menthol + limonene, with a 20% addition of methanol. The chromatographic system was validated and checked on the real sample, which made it the first applicable and operational quantitative eutectic TLC system.

Solubilities and Transport Properties of CO2, Oxalic Acid, and Formic Acid in Mixed Solvents Composed of Deep Eutectic Solvents, Methanol, and Propylene Carbonate.

Recently, deep eutectic solvents (DES) have been considered as possible electrolytes for the electrochemical reduction of CO2 to value-added products such as formic and oxalic acids. The applicability of pure DES as electrolytes is hindered by high viscosities. Mixtures of DES with organic solvents can be a promising way of designing superior electrolytes by exploiting the advantages of each solvent type. In this study, densities, viscosities, diffusivities, and ionic conductivities of mixed solvents comprising DES (i.e., reline and ethaline), methanol, and propylene carbonate were computed using molecular simulations. To provide a quantitative assessment of the affinity and mass transport of CO2 and oxalic and formic acids in the mixed solvents, the solubilities and self-diffusivities of these solutes were also computed. Our results show that the addition of DES to the organic solvents enhances the solubilities of oxalic and formic acids, while the solubility of CO2 in the ethaline-containing mixtures are in the same order of magnitude with the respective pure organic components. A monotonic increase in the densities and viscosities of the mixed solvents is observed as the mole fraction of DES in the mixture increases, with the exception of the density of ethaline-propylene carbonate which shows the opposite behavior due to the high viscosity of the pure organic component. The self-diffusivities of all species in the mixtures significantly decrease as the mole fraction of DES approaches unity. Similarly, the self-diffusivities of the dissolved CO2 and the oxalic and formic acids also decrease by at least 1 order of magnitude as the composition of the mixture shifts from the pure organic component to pure DES. The computed ionic conductivities of all mixed solvents show a maximum value for mole fractions of DES in the range from 0.2 to 0.6 and decrease as more DES is added to the mixtures. Since for most mixtures studied here no prior experimental measurements exist, our findings can serve as a first data set based on which further investigation of DES-containing electrolyte solutions can be performed for the electrochemical reduction of CO2 to useful chemicals.

Sustainable Drying and Green Deep Eutectic Extraction of Carotenoids from Tomato Pomace.

The extraction of molecules with high added value plays an important role in the recovery of food waste. This work aimed to valorize tomato pomace, a by-product composed of skin and seeds, through extraction of carotenoids, especially lycopene and β-carotene. The tomato pomace was dried using three different methods (freeze-drying, heat drying, and non-thermal air-drying) to reduce its weight, volume, and water activity and to concentrate the carotenoid fraction. These drying approaches were compared considering the extractive potential. Three solvent mixtures were compared, a traditional one (n-hexane:acetone) and two green deep eutectic solvent mixtures (ethyl acetate:ethyl lactate and menthol:lactic acid) in combination with different drying procedures. The extract obtained using ethyl acetate:ethyl lactate with non-thermal air-drying showed the highest contents of lycopene and β-carotene (75.86 and 3950.08 µg/g of dried sample, respectively) compared with the other procedures.

Intermolecular and Intramolecular Friedel‐Crafts Acylation of Carboxylic Acids using Binary Ionic Liquids: An Experimental and Computational Study

AbstractTraditional Friedel‐Crafts acylation with acid halides suffers from waste byproducts such as SO2, HCl, and the hydrolysis of Lewis acid catalyst. Thus, the environmentally benign intermolecular and intramolecular Friedel‐Crafts acylation of arenes with carboxylic acids as acylating agents has been investigated using a mixture of deep eutectic solvent and an ionic liquid as reaction media under microwave irradiation. The Friedel‐Crafts acylations with carboxylic acids as acylating agents are challenging due to the low reactivity of carboxylic acids. In this paper, the desired products were obtained at moderate to good yields under microwave irradiation for a short reaction time. The Friedel‐Crafts cyclization of 4‐phenylbutyric acid is more effective than 3‐phenylpropionoic acid under the present method. The reaction mechanism is proposed by combining experiments with density functional theory calculations, highlighting the critical role of ZnCl2, triflate anion (CF3COO−) in binary ionic liquids, and acidic conditions in accomodating a kinetic accessible pathway making the C−C bond.

Insights on choline chloride-based deep eutectic solvent (reline) + primary alcohol mixtures: a molecular dynamics simulation study.

Deep eutectic solvents (DESs) emerged as green solvents for new generation technologies owing to their high chemical and thermal stability. Addition of restricted amount of organic solvents into the DESs plays a significant role in the improvement of thermodynamic and the transport properties to work as a potential solvent in process industries. In this paper, molecular dynamics (MD) simulations were performed to understand the thermophysical and transport properties of choline chloride-based DES (reline) and primary alcohol (methanol and ethanol) mixture in relation to microscopic structure. Density, radial distribution function, coordination number, average number of H-bond, diffusion coefficient and spatial distribution function was calculated in order to understand the structure and involvement of H-bond network at an atomic level. H-bond and spatial distribution function analyses revealed that the chloride ion prefers to be spatially distributed around hydroxyl group of alcohol and found to be more pronounced upon increase in alcohol concentration. As a consequence, it was observed that the H-bonds between Cl- and urea decreases overall with the loading of alcohol and effect is more pronounced beyond a concentration of 0.4. Self-diffusion values for choline, Cl- and urea were found to be increased significantly upon increase in concentration of alcohol from 0.6 to 0.8. Overall, our simulation points to the interplay and interactions between the chloride ions and the solvents in determining the structural and transport properties of choline chloride-based DES.

Implementation of Artificial Neural Networks in the assessment of CO2 solubility in deep eutectic and ionic liquid solvents – Performance and cost comparison

In order to counteract the economic and environmental issues presented by Ionic Liquids (ILs) for carbon capture in post-combustion processes, Deep eutectic solvents (DESs) are being researched as potential absorbents. These are an emerging class of ILs that have a strong contribution from hydrogen bonding and have shown promising trends in CO 2 absorption in recent times. In this study, three hydrogen bond acceptors (HBA), along with 2-hydroxypropanoic acid (Lactic Acid (LA)) as the hydrogen bond donor (HBD), have been identified and analyzed as CO 2 absorbents. Considering their structural properties, thermodynamic behavior, and experimental conditions as input parameters, a backpropagation neural network (BPNN) has been implemented to analyze and predict the extent of CO 2 solubility within each of the DES mixtures. BPNN successfully predicted trends in the solubility as a function of the alkyl chain length, temperature, and pressure. It was observed that the solubility of CO 2 increased with increasing alkyl chain length and pressure but decreased with increasing values of temperature. DES is found to be more economical than other ionic liquid solvents used for CO 2 absorption.

Impact of deep eutectic solvents and their constituents on the aqueous solubility of phloroglucinol dihydrate

Phlorotannins are highly bioactive phenolic compounds mainly found in brown algae. Phloroglucinol is the basic unit from which phlorotannins polymerize. Deep eutectic solvents (DES) are potentially beneficial for increasing phenolics solubility, therefore good solvent candidates for phlorotannins extraction processes. Solubility measurements were performed for phloroglucinol in pure water and aqueous mixtures of DES or their constituents, i.e., different hydrogen bond donors (HBD) and choline chloride (ChCl). The stable crystal form of the phenolic in equilibrium was phloroglucinol dihydrate within the studied temperature range (293.15–313.15 K) and water weight fractions (≥0.25). The water + ChCl + HBD mixtures yielded higher solubility for phloroglucinol dihydrate than the corresponding water + HBD or water + ChCl mixtures. Solubility predicted with PC-SAFT was in quantitative agreement with the experimental data. The solubility behavior of phloroglucinol dihydrate in the different mixtures was related to the hydrogen bonds formed using molecular dynamics and PC-SAFT.

Separation of cobalt, lithium and nickel from the “black mass” of waste Li-ion batteries by ionic liquids, DESs and organophosphorous-based acids extraction

New methods of metal extraction from the “black mass” (BM) from spent lithium-ion batteries have been presented with ionic liquids (ILs), Deep Eutectic Solvents (DESs) and organophosphorous-based acids. The low-temperature method of extraction of cobalt, nickel, lithium and other metals without pre-leaching of BM with acids have been proposed in comparison with many methods already described in the literature. Extraction has been studied in detail with ILs: methyltrioctylammonium chloride ([N8,8,8,1][Cl], Aliquat 336), trihexyltetradecylphosphonium chloride ([P6,6,6,14][Cl], Cyphos IL 101), trihexyltetradecylphosphonium thiocyanate ([P6,6,6,14][SCN]), benzethonium tricyanomethanide ([Benzet][TCM]), as well as with DESs mixtures and well known organophosphorous-based acids: bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) and di-(2-ethylhexyl) phosphoric acid (D2EHPA). It was shown that fast and efficient extraction, with 90–100 wt% recovery of Co(II), may be obtained using DESs. Well known for the extraction of metal ions from the aqueous phase ILs, binary mixtures of ILs (synergistic effect) and Aqueous Biphasic System (ABS) method with NaCl, {[P4,4,4,14][Cl] + NaCl + Co(II)} have shown very low efficiency in the recovery of metals from BM. The extraction of cobalt (30–58 wt%) and the high extraction efficiency of lithium (41–92 wt%) and nickel (37–52 wt%) was obtained using Cyanex 272 in a mixture with diethyl phosphite. Process factors such as solvent content, extraction additivities, stripping and precipitation methods, temperature, holding time, pH and liquid/solid as well as organic/water ratios were studied. For all extractions, the selectivity and distribution ratios were described. A schematic flow chart for the selective recovery of cobalt(II), lithium(I) and nickel(II) from BM has been proposed. The presented extraction processes can compete with the costly hydrometallurgical methods for recovering metals from secondary waste.

Covalently linked hydrogen bond donors: The other side of molecular frustration in deep eutectic solvents.

In this work, we investigated the effects of a single covalent link between hydrogen bond donor species on the behavior of deep eutectic solvents (DESs) and shed light on the resulting interactions at molecular scale that influence the overall physical nature of the DES system. We have compared sugar-based DES mixtures, 1:2 choline chloride/glucose [DES(g)] and 1:1 choline chloride/trehalose [DES(t)]. Trehalose is a disaccharide composed of two glucose units that are connected by an α-1,4-glycosidic bond, thus making it an ideal candidate for comparison with glucose containing DES(g). The differential scanning calorimetric analysis of these chemically close DES systems revealed significant difference in their phase transition behavior. The DES(g) exhibited a glass transition temperature of -58°C and behaved like a fluid at higher temperatures, whereas DES(t) exhibited marginal phase change behavior at -11°C and no change in the phase behavior at higher temperatures. The simulations revealed that the presence of the glycosidic bond between sugar units in DES(t) hindered free movement of sugar units in trehalose, thus reducing the number of interactions with choline chloride compared to free glucose molecules in DES(g). This was further confirmed using quantum theory of atoms in molecule analysis that involved determination of bond critical points (BCPs) using Laplacian of electron density. The analysis revealed a significantly higher number of BCPs between choline chloride and sugar in DES(g) compared to DES(t). The DES(g) exhibited a higher amount of charge transfer between the choline cation and sugar, and better interaction energy and enthalpy of formation compared to DES(t). This is a result of the ability of free glucose molecules to completely surround choline chloride in DES(g) and form a higher number of interactions. The entropy of formation for DES(t) was slightly higher than that for DES(g), which is a result of fewer interactions between trehalose and choline chloride. In summary, the presence of the glycosidic bond between the sugar units in trehalose limited their movement, thus resulting in fewer interactions with choline chloride. This limited movement in turn diminishes the ability of the hydrogen bond donor to disrupt the molecular packing within the lattice structure of the hydrogen bond acceptor (and vice versa), a crucial factor that lowers the melting point of DES mixtures. This inability to move due to the presence of the glycosidic bond in trehalose significantly influences the physical state of the DES(t) system, making it behave like a semi-solid material, whereas DES(g) behaves like a liquid material at room temperature.

Phase behavior of water-menthol based deep eutectic solvent-dodecane system

In the current work, two menthol-based hydrophobic deep eutectic solvents (DESs) have been synthesized to extract dodecane from water-dodecane emulsion at 298 K and atmospheric pressure. The equilibrium mixture produces two biphasic liquid-liquid equilibrium systems and one triphasic liquid-liquid-liquid equilibrium system. 1H NMR has been used to calculate the molar composition of each phase. For both the lauric and decanoic acid-based DES, the extract phase of biphasic region-1 is rich in DES; whereas the raffinate phase is predominantly water. However, for the biphasic region-2, the extract phase is the dodecane rich phase and raffinate phase is the mixture of DES and dodecane having a dominant composition of DES. In case of triphasic region, i.e. top phase consists of dodecane and the bottom phase is only water. The middle phase becomes an emulsion where DES is the dominant component. The selectivity analysis in the triphasic region proves that both the DESs have high selectivity to extract dodecane from the water-dodecane microemulsion. The experimental mole fractions are correlated with genetic algorithm (GA) promoted NRTL and UNIQUAC models to predict the phase behavior. An average overall root means square deviation (RMSD, %) of 0.174% is observed for the biphasic region and 0.048% for the triphasic employing GA-NRTL model. GA-UNIQUAC predicts an average overall RMSD of 0.340% for biphasic regions and 0.129% for the triphasic region.

Volumetric and compressibility studies on aqueous mixtures of deep eutectic solvents based on choline chloride and carboxylic acids at different temperatures: Experimental, theoretical and computational approach

Deep eutectic solvents (DESs) constitute a new class of green solvents, the studies on which are going at a fast pace. The binary mixtures of DESs with water are attracting a great deal of interest for various industrial applications owing to their unique properties not exhibited by the neat components. Therefore, thermodynamic properties of DESs-water mixtures should be explored to better understand the prevailing intermolecular interactions for enhancing the application arena of such binary mixtures. Herein, the density (ρ) and speed of sound (u) of binary mixtures of DESs (choline chloride: acetic acid; 1: 2; and choline chloride: L-(+)-lactic acid; 1: 2) with water has been measured over whole composition range at different temperatures (T = 298.15 to 313.15 K) and atmospheric pressure. The values of various thermodynamic parameters have been derived and discussed in terms of the varying extent of intermolecular interactions governed by the components of DESs. The negative values of excess molar volumes (VmE) are ascribed to the stronger hydrogen bond interactions and efficient molecular packing in the binary mixtures over repulsive interactions. The VmE values have been analyzed using Prigogine-Flory-Patterson (PFP) theory, which satisfactorily explained the volumetric behaviour of the binary mixtures. Density functional theory (DFT) calculations have been made to support the variation in VmE and the underlying interactions prevailing between the components. Further, isentropic compressibility (ks) and excess isentropic compressibility (ksE) have been evaluated from the speed of sound data. It is expected that such studies will be beneficial from the academic as well as industrial point of view considering the increasing utilization of DESs for various applications.

Density, dynamic viscosity, conductivity and refractive index for mixture D-glucose and deep eutectic solvent (choline chloride + urea) at different temperatures

ABSTRACT To convert carbohydrates into platform compounds, the deep eutectic solvent (DES) based on choline chloride and urea (molar ratio 1:2) was adopted as a green solvent. The physical properties of density, dynamic viscosity, conductivity and refractive index were determined for the mixture of D-glucose and DES including neat reline at a temperature from 293.15 K to 363.15 K at 101.3 kPa. The measured data of density, dynamic viscosity, conductivity and refractive index were correlated, respectively. Meanwhile, the molecular volume, standard molar entropy, lattice energy and free volume were calculated. The spectra of FTIR indicates that the hydrogen bond was changed in the mixture with increasing the content of D-glucose.

Nitroalkene reduction in deep eutectic solvents promoted by BH3NH3.

Deep eutectic solvents (DESs) have gained attention as green and safe as well as economically and environmentally sustainable alternative to the traditional organic solvents. Here, we report the combination of an atom-economic, very convenient and inexpensive reagent, such as BH3NH3, with bio-based eutectic mixtures as biorenewable solvents in the synthesis of nitroalkanes, valuable precursors of amines. A variety of nitrostyrenes and alkyl-substituted nitroalkenes, including α- and β-substituted nitroolefins, were chemoselectively reduced to the nitroalkanes, with an atom economy-oriented, simple and convenient experimental procedure. A reliable and easily reproducible protocol to isolate the product without the use of any organic solvent was established, and the recyclability of the DES mixture was successfully investigated.

Binary mixtures of choline chloride-based deep eutectic solvents as green extractants for the extraction of benzene from n-hexane

A suitable green solvent for extraction of aromatics from aliphatics must possess good solvation and physicochemical properties, a rare occurrence in a single deep eutectic solvent (DES). Mixture of DESs could enable synergy and provide a good candidate extractant. In this study, DESs of glyceline, ethaline, and reline were synthesized and their binary mixtures (glyceline/ethaline, reline/ethaline, and glyceline/reline) produced by blending in various volume proportions. Twelve of such mixed solvents were prepared and their extraction efficiency for separating benzene from n-hexane investigated in a batch equilibrium process. Liquid–liquid equilibria (LLE) data for the pseudo-ternary systems of n-hexane + benzene + mixed DESs were measured at 303 K and 101.3 kPa. The distribution coefficient (D) and selectivity (S) of each pseudo-ternary system were determined to elicit extraction efficiency. The physicochemical properties of the mixed DESs were also measured. The results show that generally the distribution coefficients, selectivities, and physicochemical properties of the mixed DESs lie between the corresponding values for the constituent DES. The best performance was given by the mixed solvent of glyceline and ethaline in the 80:20 volume ratio, respectively, with D = 0.75 and S = 422.485. This assertion was further corroborated by higher percent recovery of benzene obtained from the said mixed DES (57.88%) relative to other mixed DESs (≤ 49.11%) examined in this study. Furthermore, its separation efficiency is superior to sulfolane but lower than glyceline, though there was a 9.4% reduction in its viscosity relative to glyceline.

Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues.

Pretreatment is still the most expensive step in lignocellulosic biorefinery processes. It must be made cost-effective by minimizing chemical requirements as well as power and heat consumption and by using environment-friendly solvents. Deep eutectic solvents (DESs) are key, green, and low-cost solvents in sustainable biorefineries. They are transparent mixtures characterized by low freezing points resulting from at least one hydrogen bond donor and one hydrogen bond acceptor. Although DESs are promising solvents, it is necessary to combine them with an economic heating technology, such as microwave irradiation, for competitive profitability. Microwave irradiation is a promising strategy to shorten the heating time and boost fractionation because it can rapidly attain the appropriate temperature. The aim of this study was to develop a one-step, rapid method for biomass fractionation and lignin extraction using a low-cost and biodegradable solvent. In this study, a microwave-assisted DES pretreatment was conducted for 60 s at 800 W, using three kinds of DESs. The DES mixtures were facilely prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBDs): a monocarboxylic acid (lactic acid), a dicarboxylic acid (oxalic acid), and urea. This pretreatment was used for biomass fractionation and lignin recovery from marine residues (Posidonia leaves and aegagropile), agri-food byproducts (almond shells and olive pomace), forest residues (pinecones), and perennial lignocellulosic grasses (Stipa tenacissima). Further analyses were conducted to determine the yield, purity, and molecular weight distribution of the recovered lignin. In addition, the effect of DESs on the chemical functional groups in the extracted lignin was determined by Fourier-transform infrared (FTIR) spectroscopy. The results indicate that the ChCl-oxalic acid mixture affords the highest lignin purity and the lowest yield. The present study demonstrates that the DES-microwave process is an ultrafast, efficient, and cost-competitive technology for lignocellulosic biomass fractionation.

Cooperative dynamics and speciation in deep eutectic solvent + DMSO mixtures

Dielectric relaxation (DR) spectra within the frequency range of 0.05 ≤ ν/GHz ≤ 89 were measured at T = 308.15 K to reveal structure and dynamics of mixtures of deep eutectic solvents (DESs) with dimethylsulfoxide (DMSO). Studied DESs were reline, glyceline and ethaline, ie. 1:2 molar ratio mixtures of choline chloride (ChCl) and the hydrogen bond donors (HBDs) urea, glycerol and ethylene glycol. The obtained DR spectra were best fit by a superposition of relaxations associated with the reorientation of dipolar DES components and individual DMSO molecules. In contrast to previously studied mixtures of glyceline and reline with water, the analysis of the obtained relaxation amplitudes revealed that the present DES/DMSO systems cannot be simply regarded as mixtures of individual Ch+, Cl−, HBD and DMSO units over the entire mixture range. Instead, a significant amount of ChCl contact ion pairs (CIPs) is formed at moderate DES concentrations. Due to their high dipole moment these CIPs cause pronounced maxima at ChCl:HBD:DMSO ratios of ~1 : 2 : 9 in the static permittivity of the mixtures. Pronounced solute-solvent interactions slow down the rotational motion of solvating DMSO molecules. At infinite dilution the derived total effective solvation numbers, Zt, extrapolate to ~8 − 9 DMSO per ethaline, ~16 per glyceline and ~7 − 8 per reline unit but numbers decrease rapidly with rising DES mole fraction. For the latter two DESs Zt could be split into ChCl and HBD contributions. Finally, careful analysis of the relaxation times provided evidence for pronounced micro-heterogeneity of the studied mixtures.

Deliquescence Behavior of Deep Eutectic Solvents

Deep eutectic solvents (DESs) are formed by a hydrogen bond donor and an acceptor. The hydrogen bond interactions between these two components significantly depress the melting temperature of the mixture. DESs have been used as an alternative for organic solvents in various branches of the chemical industry. Many DESs are very hygroscopic and water is known to change the properties of DESs, but there has neven been a systematic study performed on the deliquesence behavior of DESs. Therefore, this study investigated the thermal and deliquescent behavior of four DESs. The DES mixtures were stored in desiccators at different relative humidities (RH) to investigate the critical RH (RH0) for deliquescence. It was found that, due to the formation of a eutonic mixture, the RH0 to induce deliquescence for a given DES mixture was lower compared to the individual components comprising the DES. The results showed that, even though all investigated DESs had eutectic melting temperatures above room temperature, but due to the low RH0, they were able to appear liquid at room temperature under ambient conditions. The eutonic and eutectic compositions were identified at different compositions for the DESs. The results emphasize that great care must be taken to control the process and storage conditions for DESs.

Paracetamol in aqueous solutions of polymeric-based deep eutectic solvents; solubility, partitioning, volumetric and compressibility studies

Paracetamol (PCM) is a widely used nonprescriptive analgesic and antipyretic agent. However, the low aqueous solubility of this drug is an important issue that mainly affects the extent of oral bioavailability, desirable formulation, and extraction process. Alternatively, deep eutectic solvents (DESs) as new green and sustainable category of solvents can be used to overcome the low solubility of drugs. The purpose of this research was three-fold. First, the solubility of PCM was investigated in the aqueous mixture of DESs containing choline chloride (ChCl) and polyethylene glycol (PEG300 or 600) at 298.15 K, and the partitioning of PCM from aqueous solutions was studied in aqueous two phase system for the second one. Finally, the volumetric and compressibility properties of the PCM in the water + DESs mixtures were studied to evaluate the interactions between the components of the systems. The evaluation results on three different test sets showed that the three measurement processes are very consistent, which demonstrated that the solubility and the partitioning yield of PCM in the presence of ChCl/PEG300 are higher than ChCl/PEG600. Also, according to calculated thermodynamic volumetric and compressibility properties, strong interactions between PCM and DESs are observed and the data is in agreement with measured solubility data.

Measurement and PC-SAFT Modeling of the Solubility of Gallic Acid in Aqueous Mixtures of Deep Eutectic Solvents

Deep eutectic solvents have appeared as potential solvents for improving the extraction of polyphenols from vegetable or fruit matrixes. Since gallic acid is abundant in these sources, it is considered as a typical standard for quantifying their total polyphenol content after extraction with solvents. However, there are no extensive studies on the solubility behavior of gallic acid in different solvents or deep eutectic solvents. Thus, in this work, the solubility of gallic acid is measured in pure water; aqueous solutions of different hydrogen bond donors such as ethylene glycol, levulinic acid, and glycerol; and aqueous mixtures of deep eutectic solvents using choline chloride as the hydrogen bond acceptor and ethylene glycol, levulinic acid, and glycerol as the hydrogen bond donors. All of the measurements were performed at 293.15, 303.15, and 313.15 K and at 101.3 kPa and were validated by comparing the solubility of gallic acid in water from the literature. Results suggest that a 50 wt % aqueous solution of deep eutectic solvent based on ethylene glycol or glycerol improves the gallic acid solubility compared with a 50 wt % aqueous solution of its corresponding hydrogen bond donor. The deep eutectic solvent containing levulinic acid acts as the best aqueous mixture for gallic acid dissolution. Nondissolved gallic acid was measured after equilibrium using powder X-ray diffraction, showing that its structure does not change upon mixing with all of the liquid mixtures. All of the solid–liquid equilibrium results were accurately modeled with perturbed-chain statistical associating fluid theory (PC-SAFT).