Choline Chloride-based Deep Eutectic Solvents Research Articles

Choline chloride-based deep eutectic solvents do not improve the ethanolic extraction of carotenoids from buriti fruit (Mauritia flexuosa L.)

The aim of the present study was to evaluate the effect of choline chloride-based deep eutectic solvents (DESs) as co-solvents for the ethanolic extraction of total carotenoids from buriti fruit (Mauritia flexuosa L.). Choline chloride-based DESs were synthesized by the heating method. The systems were prepared using ethanol and DESs as a co-solvent in concentrations of 0.5–70.0% (w/v). In addition, a control condition was performed using ethanol as the sole solvent. The total carotenoid concentration in the systems was determined by spectrophotometry at 450 nm. The results showed that the ethanol used without co-solvent obtained total carotenoid yields of 10.06 ± 0.03 mg/g for the buriti pulp and 10.43 ± 1.27 mg/g for the buriti peel. In turn, the use of choline chloride-based DESs as co-solvents did not increase the ethanolic extraction yield of carotenoids. However, it was observed that the buriti peel can be a rich source of carotenoids with yields comparable to the fruit. Thus, it is suggested that new green solvents be evaluated to increase the recovery of total carotenoids from buriti fruit using ecofriendly processes.

Prototropic forms of hydroxy derivatives of naphthoic acid within deep eutectic solvents.

Deep eutectic solvents (DESs) are not only recognized as benign and inexpensive alternatives to ionic liquids, they offer a unique solvation milieu due to the varying H-bonding capabilities of their constituents. Proton-transfer involving a probe and its prototropic forms strongly depend on the H-bonding nature of the solubilizing media. The presence of prototropic forms of three probes, 1-hydroxy-2-naphthoic acid (1,2-HNA), 3-hydroxy-2-naphthoic acid (3,2-HNA), and 6-hydroxy-2-naphthoic acid (6,2-HNA) is investigated in two DESs, named ChCl:urea and ChCl:glycerol, constituted of H-bond acceptor choline chloride and different H-bond donors, urea and glycerol, respectively, in a 1 : 2 mole ratio under ambient conditions. While 1,2-HNA and 3,2-HNA exhibit an intramolecular H-bonding ability, 6,2-HNA does not. In contrast to common polar solvents, where the monoanionic emitting form of 1,2-HNA is also supported along with the neutral one, in both the DESs only the neutral emitting form exists. Addition of acid to the two DESs, respectively, fail to generate the monocationic form of the probe. Addition of a base to ChCl:urea results in the generation of the monoanionic form; even a very high strength of the base fails to generate the monoanionic emitting form in ChCl:glycerol. Relatively higher H-bond donating acidity of ChCl:glycerol results in added hydroxyl getting involved in H-bonding with alcohol functionalities of ChCl:glycerol leading to the absence of proton extraction to create the monoanionic form of the probe. Only the monoanionic emitting form of 3,2-HNA is present in ChCl:urea; in ChCl:glycerol, due to its higher H-bond donor acidity, the neutral emitting form is also detected. Addition of high strength of acid to ChCl:urea does result in formation of the neutral emitting form. Addition of an aqueous base results in the formation of the dianionic form of 3,2-HNA in ChCl:urea; however, in ChCl:glycerol, the added base fails to convert the neutral form of this probe to the monoanionic form as efficiently as that in ChCl:urea. The monoanionic (carboxylate) form of 6,2-HNA exits in ChCl:urea, whereas the neutral form is present in ChCl:glycerol due to its higher H-bond donating acidity. Addition of an acid can induce a shift in prototropic equilibrium towards the neutral form of 6,2-HNA in ChCl:urea; no change is observed in the behavior of this probe in ChCl:glycerol as the acid is added. Both the DESs support the dianionic form of 6,2-HNA in the presence of the base; the added base helps extract both -OH and -COOH protons of this probe. The H-bond donor component of the DES is clearly established to play a critical role in the prototropic behavior of the probe.

Choline chloride-based deep eutectic solvents as effective electrolytes for dye-sensitized solar cells

Electrolytes for dye-sensitized solar cells remain a challenge for large-scale production and commercialization, hindering the wide application of solar cells. We have developed two new electrolyte-based deep eutectic solvents using a mixture of choline chloride with urea and with ethylene glycol for dye-sensitized solar cells. The prominent features of the two deep eutectic solvent electrolytes are simple preparation for large-scale production with inexpensive, available, and nontoxic starting materials and biodegradability. The solar cell devices proceeded in a safe manner as the two deep eutectic solvents afforded low-cost technology and comparative conversion efficiency to a popular ionic liquid, namely 1-ethyl-3-methylimidazolium tetracyanoborate. Results showed that devices with choline chloride and urea electrolyte exhibited improved open circuit voltage values (VOC), while the ones with choline chloride and ethylene glycol showed an increase in the short circuit current (Isc). Characterization of the devices by electrochemical impedance spectroscopy helped explain the effects of their molecular structures on the enhancement of either VOC or Isc values. These new solvents expand the electrolyte choices for designing dye-sensitized solar cells, especially for the purpose of using low-cost and eco-friendly materials for massive production.

Self-assembled luminescent cholate gels induced by a europium ion in deep eutectic solvents.

Deep eutectic solvents (DESs) with excellent physicochemical properties similar to ionic liquids and biocompatibility are potential solvent candidates for designing novel lanthanide luminescent soft materials. In this paper, the fabrication and characterization of such luminescent gels in three choline chloride (ChCl)-based DESs through self-assembly of the sodium cholate and europium nitrate are presented. The microstructure and gel-like nature of the obtained eutectogels were explored and confirmed by scanning electron microscopy and rheology measurements. While Fourier transform infrared spectroscopy and small-angle X-ray scattering were used to analyze the gel formation mechanism, which was considered to be synergistically driven by metal coordination, hydrogen bonding and solvophobic interactions. All three eutectogels exhibited good photophysical properties. Among these, the one formed in ChCl/urea DES was found to possess the strongest mechanical strength. While the one formed in ChCl/glycerol DES exhibited the longest luminescence lifetime and quantum efficiency. The obtained results demonstrate the possibility of using DESs to construct lanthanide luminescent soft materials or control their properties through the choice of hydrogen-bond donor molecules.

Toxico-metabolomics study of a deep eutectic solvent comprising choline chloride and urea suggests in vivo toxicity involving oxidative stress and ammonia stress

The in vitro and in vivo studies suggest that choline chloride-based deep eutectic solvents may not be considered as pure, safe mixtures even if they consist of safe compounds.

Physicochemical Characterization of Candlenut (Aleurites moluccana)-derived Biodiesel Purified with Deed Eutectic Solvents.

A high-oil candlenut (Aleurites moluccana)-derived biodiesel was purified using new generation solvents called Deep eutectic solvents (DESs) and physicochemical properties of the purified biodiesel were assessed according to the accepted international standards for biodiesel (ASTM D6751; EN 14214). Binary and ternary choline chloride-based DESs containing glycerol and ethylene glycol as hydrogen bond donors were synthesized. The results of the investigation showed that the quality of DESs-purified biodiesel generally improved compared with the unpurified biodiesel and fulfilled the accepted standard limits for biodiesel except carbon residue and oxidation stability properties. Choline chloride/ethylene glycol (ChCl/Eg, 1:2 molar ratio) having a DES/biodiesel ratio of 1:1 (DES2-11) has enhanced the Fatty Acid Methyl Ester (FAME) content of unpurified biodiesel from 81.89% to 98.13%, and the oxidation stability from 2.36 h to 3.06 h. 1H NMR examination showed the successful synthesis of DESs; GC-MS analysis of candlenut oil and its biodiesel revealed oil and fatty acid methyl ester compositions, respectively. The similarity in FAME compositions between DESs-purified and unpurified biodiesel as revealed through GC-MS examination suggests the selective removal of impurities and the efficiency of DESs in improving the quality of candlenut-derived biodiesel.

CTAB adsorption onto dolomite in the presence of ionic liquid and deep eutectic solvent: Experimental and theoretical studies

Surfactant adsorption onto reservoir rock surfaces would undesirably influence its functionality from standpoint of enhanced oil recovery (EOR). This study investigates the performance of an imidazolium-based ionic liquid (IL) and a choline chloride-based deep eutectic solvent (DES) as additives to inhibit cetyltrimethylammonium bromide (CTAB) adsorption onto dolomite rock surface from experimental and theoretical perspectives. In the experimental part, static adsorption tests were conducted using UV–Vis spectrophotometer to find the adsorption density of the chemicals in both single (e.g. only CTAB) and combination modes (CTAB-IL and CTAB-DES). In addition, Langmuir and Freundlich isotherms were used to fit the experimental data and also to discern the adsorption patterns. In the theoretical part, interaction energies were determined using the XDLVO theory. The experimental results revealed lower adsorption of IL and DES in comparison with CTAB. Moreover, the addition of IL and DES, as potential adsorption inhibitors, effectively reduced CTAB adsorption where almost 73% reduction was observed when 1000 ppm of the IL was added to 2000 ppm of CTAB in seawater. From theoretical investigation, it was found that among different interaction energies, Lewis acid-base interaction was primarily dominant. The consistency between the experimental and theoretical results was further confirmed when the work of adhesion was calculated and compared for different chemicals investigated in this study.

Application of deep eutectic solvents as a green and biodegradable media for extraction of anthocyanin from black carrots

Deep eutectic solvents (DESs) not only could keep a high extraction efficiency, but also could easily be applied to pharmaceutical and food products. This study aimed to set out an eco-friendly technique for the anthocyanin extraction from natural sources. In this study, DESs coupled with ultrasound-assisted extraction (UAE) were considered as an alternative green method to classical applications. The choline chloride-based DESs was prepared with the hydrogen bond donor. The conventional, UAE and DES extraction methods were studied and compared. Citric acid was selected as the most promising hydrogen bond donor for the preparation of DES. The results showed that the biodegradability of all tested DESs was >80% after 28 days. Based on the analyses, it could therefore be assumed that all of the analysed DESs were biodegradable green solvents. The results of FT-IR revealed that pure choline chloride demonstrated several functional groups and many of these functional groups coexisted after DES formation. Thermogravimetric analysis (TGA) showed that all the DESs and their components were degraded in a single stage and the polymeric colour ratio was lower if acid was present in the DES composition. The results indicated that the developed method could be regarded as a sustainable, effective, and green approach for anthocyanin extraction.

Influence of Deep Eutectic Solvents (DESs) on Antioxidant and Antimicrobial Activity of Seed Extracts of Selected Citrus Species

Deep eutectic solvents (DESs), as an alternative to ionic liquids, have greener credentials than ionic liquids and have attracted increasing attention in many applications. Choline chloride-based DESs in combination with different hydrogen bond donors (organic acid, sugars and urea), showed a high extraction efficiency. The aim of this study was to examine the possible effects of choline chloride-based eutectic solvents on the antioxidant and antimicrobial activity of lemon and mandarin orange seed extracts. Lactic acid, glucose, urea and water were used to prepare choline chloride-based Natural Deep Eutectic Solvents (NADESs). Ferric-Reducing Antioxidant Power (FRAP) Assay and 2,2-diphenyl-1-picryl-hydrazyl (DPPH) method were used to determine antioxidant activity. Antibacterial activity was investigated by diffusion method on reference bacterial strains E. coli, E. faecalis, S. aureus, B. subtilis and L. monocytogenes. The analysis revealed a significant reduction potential of the eutectic solvent based on lactic acid as well as significant antioxidant activity of lemon and mandarin seed extracts. In general, mandarin extracts showed better antioxidant capacity. In vitro antibacterial activity assays showed a complete absence of bacterial growth inhibition of the extracts. However, eutectic solvents with lactic acid have shown a significant antimicrobial effect.

Enhancement of curcumin solubility by some choline chloride-based deep eutectic solvents at different temperatures

Curcumin (CUR) is a biologically active substance and a natural antioxidant, but it is almost insoluble in water and has low bioavailability. A possible solution to this barrier could be to use solvents that exhibit low toxicity and are biodegradable. Choline chloride-based deep eutectic solvents (DESs) can be used as a co-solvent to increase the solubility of curcumin. The objectives of this study are to introduce and prepare DESs, to measure the solubility of CUR in water and DESs as well as in water-DES mixtures with different weight fractions. In this perspective, the solubility of CUR is measured in the mixtures of water with some DESs based on choline chloride (ChCl) and in pure solvents at T = 298.15 K to 318.15 K. The measured solubility data were correlated by the activity coefficients models e-NRTL and UNIQUAC. Finally, the apparent thermodynamic functions entropy, enthalpy, and Gibbs free energy were estimated for dissolution process using van't Hoff equation.

Physicochemical Properties of Choline Chloride-Based Deep Eutectic Solvents with Polyols: An Experimental and Theoretical Investigation

Within the framework of green chemistry, solvents occupy a strategic place. To be qualified as a green medium, solvents should meet a few important standards such as availability, nontoxicity, biodegradability, recyclability, flammability, and low price among others. Deep eutectic solvents (DESs) are the type of solvents that can meet these conditions. In this work, we performed experimental and computational studies on the DESs, type III group, which are mixtures of xylitol and sorbitol with choline chloride at eutectic composition. The mentioned DESs were compared with commonly used DESs of sugar alcohols: ethylene glycol and glycerol. Moreover, the key factor for choosing these solvents is that their freezing points are below 293.15 K, and so, they are all liquids at room temperature. With the growing interest in this field, there is an urgent need for a deep understanding on the formation and functioning of these solvents at the molecular level. Besides, complementarity of theoretical and experimental studies can be helpful in further designing novel DESs. Thus, in this work, we report the physicochemical properties of the mentioned DESs, which include density, viscosity, electrical conductivity, molar volume, refractive index, molar refraction, and free molar volume in temperatures ranging from 293.15 to 353.15 K. The reported properties were fitted to appropriate linear or polynomial equations with very satisfactory correlation coefficients (R2). Moreover, the density functional theory (DFT) method and molecular dynamics (MD) simulations have been used to probe DESs at the molecular level. Molecular dynamic simulations confirmed that hydrogen bonds between sorbitol, xylitol, and choline chloride play a fundamental role in the observed properties of these DESs.

Cellulose nanocrystalline hydrogel based on a choline chloride deep eutectic solvent as wearable strain sensor for human motion

Owning to the viscoelastic properties, good biocompatibility and high strain sensitivity, choline chloride-based deep eutectic solvent (DES) hydrogels have been considered to be promising wearable strain sensors for human motion. However, traditional hydrogels are far away from the wearable strain sensor applications caused by their unsatisfied conductivity and weak mechanical properties. Herein, the strategy for functional ionic inorganic/organic interpenetrating (IPN) hydrogels preparation by cyclic freezing/thawing method was successfully developed. Polyvinyl alcohol (PVA) was proposed to dissolve in choline chlorede-based DES as hydrogel matrix for the first time. Encouragingly, the obtained DES/PVA/CNCs/g-C3N4 hydrogel (choline chloride with glucose) exhibits excellent mechanical properties, included excellent tensile strength (≈ 2.55 MPa), high elongation (≈1200 %) and satisfactory tensile modulus (≈3.65 MPa). Interestingly, the thermal diffusivity (the maximum value was 0.675 W/mK) and conductivity (the maximum value was 0.18 mm2/s) of the DES-hydrogels were successfully achieved through adding graphitic-like nitride nanosheet (g-C3N4) and sustainable cellulose nanocrystalline (CNCs). These enhancements were attributed to the synergistic interactions of powerful hydrogen bonding among DES, CNCs, g-C3N4 and PVA chains. More importantly, the as-prepared hydrogels have the potential as a human motion sensor to accurately in-situ detect human activities on the fingers, wrists, elbows and knee joints. Those hydrogel-type strain sensors with flexibility, excellent mechanical properties, self-recovery, good heat transfer, and electrical conductivity have broad application prospects in the fields of intelligent robot, bionic prostheses, and human care areas.

Extraction of phenolic compounds from rosemary using choline chloride – based Deep Eutectic Solvents

Deep eutectic solvents (DES) have been explored as an alternative to hazardous solvents to extract natural bioactive compounds. In this work, choline chloride-based DES (neat and hydrated) were assessed in the extraction of phenolics from rosemary leaves. The DES studied on an initial screening showed a total phenolic content (TPC) up to 220% higher than the control. The solubilities of the main rosemary biocompounds, estimated by COSMO-RS, showed a positive correlation to TPC. Choline chloride:1,2-propanediol (CPH) was selected for further optimization. At the optimal conditions (65 °C, liquid: solid ratio of 40:1 and 50 %wt of water), the antioxidant activity and TPC were 80 mg of Trolox equivalent/g and 78 mg of gallic acid equivalent/g, respectively. The antimicrobial activity of the optimized extract revealed inhibition of 39–51% to all bacteria tested. In summary, an extract with good antioxidant and antimicrobial activities was obtained from rosemary leaves using CPH as solvent.

Desulfurization Performance of Choline Chloride-Based Deep Eutectic Solvents in the Presence of Graphene Oxide

Extractive catalytic oxidative desulfurization (ECODS) is the one of the recent methods used in fuel desulfurization which involved the use of catalyst in the oxidative desulfurization of diesel fuel. This study is aimed to test the effectiveness of synthesized choline chloride (ChCl) based deep eutectic solvent (DES) in fuel desulfurization via ECODS method, with the presence of graphene oxide (GO) as catalyst and hydrogen peroxide (H2O2) as oxidant. In this study, 16 DESs based on choline chloride were synthesized using glycerol (GLY), ethylene glycol (EG), tetraethylene glycol (TEG) and polyethylene glycol (PEG). The characterization of the synthesized DES was carried out via Fourier transform infrared spectroscopy (FTIR) analysis, density, and viscosity determination. According to the screening result, ChCl-PEG (1:4) was found to be the most effective DES for desulfurization using ECODS method, with a removal of up to 47.4% of sulfur containing compounds in model oil in just 10 min per cycle after the optimization of the reaction parameters, and up to 95% desulfurization efficiency could be achieved by six cycles of desulfurization. It is found that the addition of GO as catalyst does not increase the desulfurization performance drastically; hence, future studies for the desulfurization performance of DESs made up from ChCl and PEG and its derivatives can be done simply by using extraction desulfurization (EDS) method instead of ECODS method, for cost reduction purpose and easier regulation of DES waste into environment.

Viscosity of Choline Chloride-Based Deep Eutectic Solvents: Experiments and Modeling

Deep eutectic solvents (DESs) have emerged as promising “green” solvents, but their successful industrial application requires relatively low viscosity. DESs prepared from choline chloride and glyc...

An efficiency strategy for extraction and recovery of ellagic acid from waste chestnut shell and its biological activity evaluation

Chestnut shells in large amounts are significantly underutilized agricultural and forestry waste that can be exploited as a resource for the production of high-valued nature active compounds. In this study, an efficient and green approach was established to extract and recover the highly valued phenolic compound, ellagic acid, from waste chestnut shells with choline chloride-based deep eutectic solvents (DESs). By utilizing optimized ultrasonic-assisted extraction conditions with choline chloride/n-propanol DES, solid–liquid ratio of 40 mg/mL, extraction time of 70 min and extraction power of 200 W, highly efficient extraction value for ellagic acid of 4.64 mg/g was obtained. Meanwhile, ellagic acid was recovered easily with a recovery percentage of 94.9% by anti-solvent precipitation method through the denaturation of DES with water. The purity of ellagic acid in the extracts reached 85.6%, which is more than two times to that via ethanol extraction methods (36.4%). In addition, the recovered ellagic acid exhibited strong antioxidant activity with IC50 (0.309 mg/mL) and significant antibacterial activity with Minimal inhibitory concentration (MIC) (250 mm) and diameter of inhibition zone (DIZ) (17.60 μg/mL). The anti-solvent precipitation method could denature DES, led to higher extraction and recovery efficiency and high-purity ellagic acid simultaneously in one step. The novel method is of great significance to the whole chestnut production process for the utilization of waste chestnut shells. Furthermore, this method can also be used as a green, pollution-free alternative method for the extraction and recovery of phenolic components from natural resources for pharmaceutical and biochemical applications.

Use of green solvents as pre-treatment of dissolving pulp to decrease CS2 consumption from viscose production

Choline chloride-based deep eutectic solvents are widely used in biomass processing. In this work, four different green solvent mixtures were used as pre-treatment of acid sulphite dissolving pulp with the hypothesis of increasing the possibilities to produce viscose fibres and decreasing the use of the harmful and toxic carbon disulphide in the process. The experiments were performed at two different pulp to solvent mass ratios. Pulp quality parameters were also measured to determine the suitability of the pre-treatment: α-cellulose, viscosity, lignin and pentosan content. In addition, X-ray diffraction analysis of pulps at the best solid to liquid ratio was performed to obtain the influence of the crystallinity index. Best results were obtained with the use of lactic acid, with reactivity values close to 94%, giving a reduction of CS2 usage of 15.83%. Furthermore, a linear relationship between the crystallinity index calculated by the XRD and reactivity with a regression factor of 0.87 was found.

Fractional recovery of oleaginous bioactive produced by Rhodotorula mucilaginosa CCT3892 using deep eutectic solvents

The use of four choline chloride-based deep eutectic solvents (DES) in the recovery of oleaginous compounds from Rhodotorula mucilaginosa CCT3892 cells were investigated in this study, focusing on a novelty treatment to recovery mini-compounds intercellular produced by the yeast, as alternative for conventional methods. Regarding DES ability to improve the yeast permeability for an eventual oil-lipids recovery, it was noticed that all solvents were as efficient as a hydrochloride acid treatment, presenting a recovery percentage above 100.0% in relation untreated cells extraction. The best total carotenoid recovery was achieved using DES synthetized with choline chloride an glycerol (ChGy treatment) (0.110 ± 0.005 mg.mL−1). DES promoted a fractional recovery of carotenoids being such process for R. mucilaginosa mentioned for the first time in this paper. Thus, showing potential to be used in the industry once the solvent preserved the antioxidant activity of carotenoids and exhibit moderated cytotoxicity.

Study of deep eutectic solvents (DESs) performance on aromatics (benzene and thiophene) extraction: thermophysical study

Thermophysical properties of some binary mixtures of novel choline chloride-based deep eutectic solvents and two aromatics (benzene and thiophene) were measured to evaluate the nature of solute–solvent interactions at T = (283.15–303.15) K and atmospheric pressure. Choline chloride was selected as hydrogen bond donor and (mono-, di- and tri-) ethylene glycols or (mono-, di- and tri-) ethanolamines were used as hydrogen bond donors. The density (d), speed of sound (u), viscosity (η) and refractive index (nD) data were measured for binary mixtures of benzene or thiophene with the selected DESs at T = (283.15–303.15) K. The apparent molar volume (Vφ), standard partial molar volume (Vφ0 ), partial molar isentropic compression (κφ0 ), excess molar volume (VE), viscosity B-coefficient and molar refraction (RD) values, were obtained for the binary mixtures at dilute region of aromatics. These quantities are used for interpreting of the studied DESs and benzene or thiophene molecular interactions. Also, the scaled particle theory (SPT) was used for calculation of interaction volume (Vint), and cavity volume (Vcav). The obtained results indicate that DESs with amine functional groups interact more effectively with benzene or thiophene rather than ethylene glycolic-based DESs.

Reversible absorption of nitrogen dioxide by choline chloride-based deep eutectic solvents and their aqueous mixtures

The adoption of cost-effective and reusable materials is critical for developing absorption liquids for industrial applications such as scrubbing technology. Here, we demonstrate that the use of deep eutectic solvents (DESs) and their aqueous mixtures is a new strategy for capturing nitrogen dioxide (NO2) because of their high absorption capacity and good reusability. The DESs are composed of a hydrogen bond acceptor (HBA) (i.e., choline chloride (ChCl)) and a hydrogen bond donor (HBD) (i.e., glycerol (Gly) or ethylene glycol (EG)). The results indicate that ChCl-based DESs exhibit excellent NO2 absorption capability, which increases with increasing HBD content, and the highest value reaches 55.1 wt% (NO2/DES) for the ChCl-EG DES at 298 K with a NO2 partial pressure of 101.3 kPa. Moreover, with the introduction of water, the DES aqueous mixtures retain high NO2 solubility while exhibiting a lower viscosity. This improvement in the transport properties largely advances the applicability of the proposed DESs as industrial scrubbing solutions for NO2 elimination. The compiled results provide insights into the factors determining the interaction of NO2 with DESs, where the NO2 solubility is directly affected by the HBD, and inform future material design for improving the NO2 absorption performance.