Hydrophobic Solvents Research Articles

Separation of furfuryl alcohol from water using hydrophobic deep eutectic solvents

Furfuryl alcohol (FA) is an important organic chemical feedstock that must be separated from water to upgrade it into high-value-added products. Since FA forms an azeotrope with water, liquid-liquid extraction is a suitable option for separating both compounds. This work evaluates the separation of FA from water using hydrophobic deep eutectic solvents (DES). Three DES were prepared using menthol, thymol, and octanoic acid by combining them in molar ratio as follows: thymol + octanoic acid (1:2), menthol + octanoic acid (1:2), and thymol + menthol (1:1). Experimental liquid-liquid equilibria (LLE) of ternary systems water + FA + DES measured at 313.15 K and 101.13 kPa were used to determine the distribution coefficient and selectivity values for FA when using each DES. The experimental results were compared with molecular dynamics (MD) using Martini 3 force field and modeled using Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) without any adjustable binary parameters. According to the results, selectivities and distribution coefficients using hydrophobic DES have comparable values to traditional volatile organic compounds (VOCs) used to separate FA from water. In general, DES shows better distribution coefficients compared with typical organic solvents. According to the results, a good alternative would be menthol + octanoic acid (1:2) or thymol + menthol (1:1) to replace typical VOCs. MD and PC-SAFT provide accurate estimations for ternary LLE in the range of examined thermodynamic conditions, which confirms the predictive consistency of both approaches. Microscopic properties computed with MD simulations evidence a surface activity or absolute adsorption of FA in the interfacial region, which is correlated with favorable distribution coefficients and selectivities.

A two-step green liquid-liquid extraction strategy for selective lithium recovery and application to seawater

Efficiently harvesting lithium from seawater remains a challenge due to the extremely dilute concentration of lithium ions (Li+) and the existence of many foreign metal ions that are far more abundant. Here, a hydrophobic deep eutectic solvent (HDES)-based two-step liquid-liquid extraction (LLE) strategy is developed for the first time that realizes the separation of dilute Li+ (<1 mg/L) from solutions with a high concentration of sodium, potassium, magnesium and calcium ions. This strategy contains the removal of divalent cations and selective recovery of Li+, which minimizes the influence of coexisting metal ions. In the first LLE step, the unwanted divalent cations are removed with a negligible loss of Li+ by the bis(2-ethylhexyl)phosphate/kerosene (DEHPA/KERO) system. Then, the DEHPA/HDES system can selectively extract Li+ from monovalent cations. All solvents used are readily available and low cost with methyltrioctylammonium chloride and decanoic acid at a 1:2 mol ratio (N8881Cl/2DecA) as the main extractant. Extraction equilibrium is reached within 10 s. The single extraction efficiency of Li+ is 66.4%, and the separation coefficient of lithium and sodium (βLi/Na) reaches 11.6 at the optimized extraction conditions. Finally, the proposed two-step LLE strategy is applied to the simulated seawater. The extraction performance of N8881Cl/2DecA-DEHPA was not significantly weakened after being reused ten times.

Preparation of a hydrophobic deep eutectic solvent and its application in the detection of quinolone residues in cattle urine.

Enrichment for the detection of quinolone residues is usually cumbersome and requires large amounts of toxic organic reagents. Therefore, this study synthesized a low-toxicity hydrophobic deep eutectic solvent (DES) with DL-menthol and p-cresol, which was then characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermal analysis. A simple and rapid vortex-assisted liquid-liquid microextraction method was developed based on this DES for the extraction of eight quinolones from cattle urine. The optimal extraction conditions were screened by examining the DES volume, extraction temperature, vortex time, and salt concentration. Under the optimal conditions, the linear ranges of the eight quinolones were 1 ~ 100μg/L with good linearity (r2 was 0.998 ~ 0.999), and the limits of detection and quantification were 0.08 ~ 0.30μg/L and 0.27 ~ 0.98μg/L, respectively. The average extraction recoveries of spiked cattle urine samples were 70.13 ~ 98.50% with relative standard deviations below 13.97%. This method can provide a reference for the pre-treatment of quinolone residue detection.

Improvements in the Modeling and Kinetics Processes of the Enzymatic Synthesis of Pentyl Acetate

In this work, the enzymatic synthesis of pentyl acetate obtained from acetic acid and pentan-1-ol using the commercial immobilized lipase Lipozyme®435 was studied. Specifically, the effects of several variables of the process on the kinetics were shown, such as the initial concentration of the acetic acid, the alcohol/acid molar ratio, and the possible reuse of the enzyme, while other variables, such as temperature, agitation, and the enzyme/acid ratio were held constant. The kinetics were determined by assessing the acetic acid concentration throughout the reactive process. Experimental data were correlated with the rate equation consisting of a modified version of the Bi–Bi Ping-Pong mechanism. The results showed that when no hydrophobic solvents were used with the reagents in stoichiometric proportion, a high molar fraction of acetic acid (x0,acid ≈ 0.50) caused the loss of enzymatic activity, achieving a conversion of only 5%. However, when there was an excess of pentan-1-ol, the reaction occurred successfully. Under optimal conditions (solvent-free conditions, x0,alcohol/x0,acid = 2, and x0,acid = 0.33), it was found that the enzyme could be reused up to 10 times without a loss of activity, reaching conversions higher than 80% after 8 h. Therefore, those conditions are advantageous in terms of productivity.

Density functional theory investigation of interactions between phenolic compounds and water or hydrophobic deep eutectic solvent

Density functional theory investigation of interactions between phenolic compounds and water or hydrophobic deep eutectic solvent

How hydrogen bond donor acceptor ratio and water content impact heterogeneity in microstructure and dynamics of N,N-diisooctylacetamide and decanol based hydrophobic deep eutectic solvent

Recently hydrophobic deep eutectic solvents (HDESs) have emerged as a potential green alternative media for the extraction of compounds from aqueous environment, and their increased importance as water immiscible solvent has attracted researchers to gain more insights into this domain. The present study employs atomistic molecular dynamics simulations to elucidate the microscopic structural organization, dynamics, and crucial interactions in N,N-diisooctylacetamide (DOA) plus decanol (DEO) based HDES at different mole ratios of the hydrogen bond donor (HBD) and acceptor (HBA). The analysis of simulated X-ray and neutron scattering structure functions reveals a nanoscale heterogeneous structural organization in the HDES at all compositions. The genesis for this heterogeneity can be derived from the polarity alternation peaks of partial structure functions in the low-q region. Polarity ordering in DOA:DEO (1:2) HDES is observed at longer length-scales in comparison to that in DOA:DEO (1:1) and DOA:DEO (2:1) HDESs. Moreover, the liquid morphologies are portrayed by nano-polar domains ingrained into the apolar environment depicting polar and apolar self-segregation. The analysis of angle-resolved radial distribution functions suggests that the microstructures of these HDESs are dominated by a strong DEO-DEO and DEO-DOA hydrogen bonding interactions. Slower decay of the hydrogen bond autocorrelation function corresponding to DOA-DEO suggests stronger hydrogen bonding in DOA-DEO than DEO-DEO. The translational mobility of both the components decreases as the DOA concentration increases. The DEO molecules exhibit faster diffusion in bulk HDES than the DOA molecules. A small water content in the HDES leads to slightly enhanced segregation of polar and apolar environments in the HDESs. We observe that water molecules interfere with the hydrogen bonding network of DOA and DEO by establishing hydrogen bond with them, thereby reducing the strength of DEO-DEO and DOA-DEO hydrogen bond interactions. The hydration also causes slightly faster hydrogen bond relaxation dynamics, indicating the weakening of hydrogen bond interactions between the constituent species of the HDESs.

Revolutionizing Drug Removal: Green Magnetic Nanoparticles Functionalized with Hydrophobic Deep Eutectic Solvents for Anti-Inflammatory Drug Adsorption

Non-steroidal anti-inflammatory medications are popular pharmaceutical and personal products due to their anti-inflammatory properties and ease of availability. However, the complex structure of these pollutants and their existence at low concentration makes them difficult to trace, posing a major challenge in their removal from aquatic environments. Therefore, the disposal and treatment of these emerging compounds have become a key concern in water treatment. In this study, new hydrophobic deep eutectic solvents (HDES) were successfully prepared using a cheap and simple component consist of decanoic acid and 2-pentanol as the hydrogen bond acceptor and hydrogen bond donor, respectively. The prepared HDES was functionalized onto magnetic nanoparticles, namely Fe3O4@HDES, as an efficient adsorbent for diclofenac and ibuprofen. Based on the findings of the cytocompatibility study, HDES offers new possibilities for safe distribution and application. The optimum adsorption conditions, including solution pH, adsorbent amount, and sample volume, were determined using the Taguchi experimental design. The One-Variable-at-a-Time (OVAT) method was used to determine the other parameters, such as the types of adsorbents, contact time, initial concentration, and initial temperature. Analysis of Variance (ANOVA) revealed that the solution pH played the most significant role in the adsorption of both diclofenac and ibuprofen, followed by the adsorbent amount and sample volume. The characterization involved several tools, including Fourier transform-infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET) analysis. Both diclofenac and ibuprofen adsorption followed chemisorption, and the process was feasible, spontaneous, and exothermic. Molecular docking also supported the choice of HDES as a functionalized agent by suggesting a schematic diagram of the energetically advantageous adsorption mechanism, which was in good accord with the experimental findings. The interaction between the adsorbent and adsorbates via hydrophobic interaction and hydrogen bonding was found to be accountable for adsorption. The results indicated that green synthesized Fe3O4@HDES offers a possible sustainable and green benefit through the adsorption of diclofenac and ibuprofen from contaminated water as an adsorbent.

A theoretical study of low concentration per- and polyfluoroalkyl substances (PFAS) remediation from wastewater by novel hydrophobic deep eutectic solvents (HDES) extraction agents

In this study, we focus on hydrophobic deep eutectic solvents (HDES) and investigate their potential for per- and polyfluoroalkyl substances (PFAS) remediation from wastewater through a nanoscopic approach using quantum chemistry and classical molecular dynamics simulations. Specifically, we study the properties of two selected widely used long-chain PFAS, Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), solutions in H2O with a novel HDES obtained by 1:1 M mixing ratio of cineole (CIN) and linoleic acid (LNA). Our results show that the strong affinity of PFAS substances for CIN and LNA molecules forming the HDES is accompanied by a disruption of interactions between PFAS and H2O molecules, confirming the HDES capability for PFAS removal from aqueous environments. The liquid structures are characterized by strong hydrogen bonding in the PFAS hydroxyl groups with the O atoms in CIN and the carbonyl groups in LNA. Our study provides a molecular-level understanding of the PFAS extraction mechanism and suggests that the use of HDES solvents with low toxicity as extraction agents for PFAS remediation from wastewater could be a proper solution to design novel PFAS treatment materials suitable for liquid extraction.

Cineole – Decanoic acid hydrophobic natural Deep eutectic solvent for toluene absorption

The hydrophobic deep eutectic solvent formed by the equimolar combination of natural compounds cineole and decanoic acid is studied as an archetypical compound for aromatics (toluene) solubilization/extraction purposes. The physicochemical properties of toluene solutions in the solvents are studied as a function of composition and temperature. The nature of intermolecular forces between toluene and solvent molecules is analyzed using a minimal clusters approach through quantum chemistry methods. Classical molecular dynamics simulation on toluene solution allowed us to infer nanoscopic behavior and structuring of the toluene mixtures using static and dynamic approaches. Likewise, the possible biological effects of the considered solvent are studied considering its effect on lipid bilayers as a model of plasma membranes using coarse-grained molecular dynamics methods. The reported results provide a multiscale combined experimental and computational characterization of hydrophobic Deep Eutectics as suitable solvents for aromatic hydrocarbons.

PVT behaviour of hydrophilic and hydrophobic eutectic solvents

Among the basic principles of green chemistry is the search for less harmful alternative solvents than conventional solvents. Knowing the thermophysical properties of fluids under different pressure and temperature conditions is essential to propose them. Herein, we present data on the densities at several pressures (from 0.1 to 65 MPa) and temperatures (from 283.15 to 338.15 K) of two deep eutectic solvents with hydrophilic characteristics (choline chloride + ethylene glycol or glycerol) and two eutectic solvents with hydrophobic characteristics (camphor + thymol or menthol). We used the Tait equation of state to correlate and calculate derived properties. Moreover, we modelled the mixtures with the PC-SAFT equation of state. The results showed that the hydrophilic solvents were more compact than the hydrophobic ones. The former exhibited an abnormal thermal behaviour of the isobaric thermal expansibility. The deviations in the correlation of densities with the thermodynamic model were between 0.5 and 3%. They were lower for the mixtures with weaker interactions.

Multicriteria design of novel natural hydrophobic deep eutectic solvents for the extraction of perfluoroalkyl acids using COSMO-RS

In this study, a molecular modeling approach was used to identify the most effective natural hydrophobic deep eutectic solvents (HDESs) for extracting the emerging pollutants, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) from synthetic wastewater. The use of HDESs for this purpose has not been reported in the literature, making this a pioneering contribution to the field. First, an extensive literature search was conducted to generate a list of 74 non-ionic HDES constituents. In the second step, a systematic screening of natural components was conducted to identify 55 new compounds that can be used for the synthesis of HDESs. The Conductor-like Screening Model for Real Solvents (COSMO-RS) was then used to screen the 129 potential HDES constituents based on three key performance indicators: distribution ratio, selectivity, and performance index at infinite dilution compared to the predicted performance of toluene as a benchmark, as the use of molecular solvents or DESs for this purpose has never been reported in the literature. The top 20 HDES constituents with the highest extraction performance were predominantly from the terpene and terpenoid families. The median lethal dose was also used to analyze toxicity. A multicriteria evaluation approach was adopted to evaluate several properties important to liquid–liquid extraction (LLE) processes, including the extraction performance, density, vapor pressure, water solubility, and leachability of DESs. Three HDESs, namely, trioctylphosphine oxide: 2-methylbenzothiazole (1:9), trioctylphosphine oxide: menthyl acetate (1:4), and 1,8-cineole: menthyl acetate (2.5:1), showed promising results. This study provides molecular insights on extracting PFOA/PFOS from wastewater using HDESs and emphasizes the need to evaluate LLE units using multicriteria. In addition, the results may serve as a starting point for further research, including the synthesis and characterization of novel HDES constituents and the development of optimized HDESs for the extraction of PFOA/PFOS from wastewater.

Multiple-Stimuli-Responsive Surfactant-Free Microemulsions Based on Hydrophobic Deep Eutectic Solvents.

Hydrophobic deep eutectic solvents (HDESs) have been applied to colloidal systems such as microemulsions, despite the development of stimulus-responsive HDESs still being in a preliminary stage. Here, menthol and indole were hydrogen bonded to form CO2-responsiveness HDES. A surfactant-free microemulsion constituted of HDES (menthol-indole) as the hydrophobic phase, water as the hydrophilic phase, and ethanol as the double solvent was demonstrated to be CO2- and temperature-responsive. Dynamic light scattering (DLS) proved the single-phase region of the phase diagram, while conductivity and polarity probing techniques confirmed the kind of microemulsion. The ternary phase diagram and DLS methods were used to investigate the responsiveness of CO2 and effect temperature on the microemulsion drop size and behavior of the phase of the HDES/water/ethanol microemulsion. The findings revealed that when temperature increased, the homogeneous phase region increased. The droplet size in the homogeneous phase region of the associated microemulsion may be reversibly and accurately adjusted by adjusting the temperature. Surprisingly, a slight temperature change can cause a significant phase inversion. Furthermore, in the system, there was no demulsification in time for the CO2/N2 responsiveness process but rather the production of a homogeneous and pellucid aqueous solution.

Understanding molecular interaction between thermally modified β-lactoglobulin and curcumin by multi-spectroscopic techniques and molecular dynamics simulation

This study elucidated the binding of curcumin (CUR) onto preliminary thermally modified β-lactoglobulin (β-LG). β-LG at pH 8.1 was heated at 75 °C, 80 °C and 85 °C for 10 min to construct denatured proteins (β-LG75, β-LG80, β-LG85). Steady and time-resolved fluorescence studies uncovered that CUR quenched proteins in simultaneous static and dynamic mode. Pre-heating β-LG improved its binding with CUR and the strongest affinity occurred in β-LG80. Fluorescence resonance energy transfer (FRET) analysis indicated that binding distance between CUR and β-LG80 was the smallest and energy transfer was the most efficient. β-LG80 had the highest surface hydrophobicity. Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimeter (DSC) confirmed that CUR transferred from crystal to amorphous state after association with protein and revealed the contribution of hydrogen bonds. Combination of β-LG80 with CUR retained the antioxidant capacity of each component. Molecular dynamics simulation demonstrated enhanced hydrophobic solvent accessible surface area of β-LG80 compared with native protein. Data obtained from this study may provide useful information for comprehensively understanding the ability of β-lactoglobulin to bind hydrophobic substances under different environmental conditions like high temperature and alkaline medium.

COSMO-RS predictive screening of type 5 hydrophobic deep eutectic solvents for selective platform chemicals absorption

Platform chemicals are crucial to the development of designer chemicals in industry; however, the utilization of these chemicals is limited from requiring separation from an aqueous phase. Type 5 hydrophobic deep eutectic solvents (HDES) have recently proven their ability to extract various low concentration solutes from aqueous solution. However, identifying a suitable HDES experimentally is a daunting task due to the large number of hydrogen bond donors (HBD), hydrogen bond acceptors (HBA), and their mixing ratio, with the HDES being ever increasing. In this study, Conductor-like Screening MOdel for Real Solvents (COSMO-RS) was utilized for over one hundred HDES and their relative solubilization ability for sorbitol, 5-hydroxymethyl furfural, and levulinic acid. Moreover, energetic mechanisms of solubilization were analyzed through the prediction of sigma profiles, sigma potentials, activity coefficients, and excess enthalpy of absorption. COSMO-RS results show that HBAs with tetra alkyl chains and amino acid-based HBDs are suitable HDES components for absorbing sorbitol, 5-hydroxymethyl furfural, and levulinic acid through a combination of van der Waals and hydrogen bonding interactions. These interactions are quantitatively examined through calculated excess enthalpy predictions, for example tetrabutylammonium bromide and arginine with a compositional ratio of 8:1, respectively, had an excess enthalpy of mixing with HMF of −7.9 kcal/mol despite the steric hindrance factor valuing ∼ 4.0 kcal/mol.

Magnetic nanofluid based on hydrophobic deep eutectic solvent for efficient and rapid enrichment and subsequent determination of cinnamic acid in juice samples: Vortex-assisted liquid-phase microextraction

A quick, environmentally friendly and easy approach for the determination of cinnamic acid in juice samples based on the creation and usage of a novel magnetic nanofluid (mixture of hydrophobic deep eutectic solvent and magnetic nanoparticles) has been reported. Response surface methodology was applied to justify the contribution of the efficient factors including pH, nanofluid volume, ionic strength and vortex time. Cinnamic acid concentrations were monitored and quantified based on their HPLC peak representing linear correlations under the best operational circumstances showing linearity between 3 and 550 ng mL−1. The LOD, LOQ, and enrichment factor for cinnamic acid were 0.8 ng mL−1, 2.7 ng mL−1 and 57.2, respectively. The proposed method was used for enrichment and subsequent determination of cinnamic acid from juice samples which suggests a potential alternative approach for cinnamic acid analysis in complicated food samples.

New Class of Tunable Choline Bromide-Based Hydrophobic Deep Eutectic Solvents for the Extraction of Bioactive Compounds of Varying Polarity from a Plant Matrix.

Deep eutectic solvents (DESs) are a class of sustainable solvents that have found numerous applications in different fields. One of their main attributes is the possibility of easily modifying their physicochemical properties by varying the type of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) that comprise them. Choline chloride ([Ch+][Cl-])-based hydrophilic DESs were among the first studied and the most used because of their capacity to easily create a hydrogen bonding network that lies in its unique chemical structure, characterized by a hydroxyl substituent within the ammonium headgroup. In this study, a new class of hydrophobic [Ch+][Br-]-modified salts were synthesized to produce HBAs with similar properties to choline for the preparation of hydrophobic DESs. Six different [Ch+][Br-]-based HDESs were prepared and characterized in terms of hydrophobicity, viscosity, and solvation properties (hydrogen bonding, dispersion, dipolarity/polarizability, n-π, and π-π interactions). They were employed as solvents in a microextraction method for the determination of phytochemicals in Cannabis sativa L. plant. The extraction performance of the [Ch+][Br-]-based HDESs was compared to eutectic mixtures based on conventional hydrophobic HBAs, and the results revealed that the unique properties of [Ch+][Br-]-modified salts allowed for the extraction of both hydrophilic (i.e., flavonoids) and hydrophobic compounds (i.e., cannabinoids).

Green solvents for the selective extraction of bioactive compounds from by-products of the coffee production chain

Approximately 15–20 million tonnes of by-products were generated globally in the coffee production chain during the 2020/21 season. The current uses for these by-products are inadequate or contribute to environmental degradation. This work reports the screening of hydrophilic and hydrophobic solvents, including deep eutectic solvents (DES), for their ability to extract the valuable metabolites caffeine and chlorogenic acid (markers in commercial extraction) from four coffee-related by-products. Water was the best solvent for recovering caffeine and chlorogenic acid from defective green coffee beans, while all hydrophilic DES surpassed water in the extraction of chlorogenic acid from coffee pulp. For the two remaining by-products, at least one DES was as good or better at extracting the caffeine or chlorogenic acid compared to water. The array of hydrophobic solvents tested here showed different selectivities, allowing the annotation of 12 compounds that have not been previously reported in coffee by-products. These results demonstrate the ability to obtain a new and controllable range of extracts from coffee by-products using green and functional solvents.

Green hydrophobic deep eutectic solvents as low-viscosity and efficient lubricants

Development of novel green lubricants that meet low viscosity and effective anti-wear requirements is a tireless pursuit to improve fuel economy and reduce exhaust emissions, as well as enhance reliability. Herein a series of hydrophobic deep eutectic solvents (HDESs) with ultra-low viscosity were successfully synthesized by combining eco-friendly economical DL-menthol (DL) with fatty acids of various alkyl chain lengths. According to quantum chemistry method, weak hydrogen bond interaction between DL and fatty acid was calculated. The as-prepared DL-based HDESs lubricants present prominent physicochemical properties and lubrication functions. Thereinto, DL+Dodecanoic acid HDES with a low viscosity of 8.73 mm2/s (40 °C) achieves a 23.05 % reduction in friction and a 44.22 % reduction in wear compared to the PEG 200 base oil at 491N. According to experimental characterizations and first-principles calculations to reveal their anti-wear mechanism, the excellent wetting and ultra-low viscosity of the HDESs fluid facilitates rapid physisorption and chemisorption. Meanwhile, the absorbed film contributes to the formation of the long alkyl chains flow layer and the tribo-chemical film composed of hydrocarbon (CxHy), oxy hydrocarbon (CxHyOz) fragments and iron oxide/hydroxide-rich layer, which endows HDESs with excellent lubrication properties. This founding furnishes a new strategy to design green low-viscosity and high-performance anti-wear HDESs lubricants in sustainable lubrication applications.

Chiral separation by capillary electrokinetic chromatography with hydrophobic deep eutectic solvents as pseudo-stationary phases

This study demonstrated for the first time that hydrophobic deep eutectic solvents (HDESs) can be used in capillary electrophoresis (CE) for chiral separations. We found that the an HDES methyltrioctylammonium chloride:octanoic acid (N8881Cl:OctA) can exist in the form of nano-sized microdroplets in CE background electrolyte solutions, and show hydrophobic effects as a new type of pseudo-stationary phase (PSP) during CE separation. When used in combination with various cyclodextrin (CD)-type chiral selectors, the presence of N8881Cl:OctA significantly improved the enantioresolutions of several model drugs. Moreover, the migration time of the enantiomers can also be reduced when an anionic CD (e.g., carboxymethyl-β-cyclodextrin (CM-β-CD)) was used. Critical factors influencing the chiral separations were systematically investigated including the HDES concentration, hydrogen-bond acceptor (HBA)/hydrogen-bond donor (HBD) ratio, CD concentration, buffer pH, and applied voltage, etc. An insight into chiral recognition mechanism with HDES is provided for reference. A comparison of the chiral CE performance of HDESs with traditional surfactants was also performed to demonstrate their superiority as a new type of PSP.

Lipid extraction from fresh Nannochloropsis oceanica using semi-hydrophobic eutectic solvents

Conventional lipid extraction from microalgae involves energy-intensive pretreatments and the use of non-renewable organic solvents. Eutectic solvents (ES), a new class of designer solvents, hold the potential to improve lipid extraction. Hydrophilic ES have been reported to impair the cell wall of microalgae, bypassing the need for pretreatments. However, other hydrophobic solvents were still required as extraction medium. Recently, ES imidazole and hexanoic acid was discovered to exhibit tuneable hydrophobicity, i.e., dissolving both water and lipids depending on their molar composition. In this work, we evaluated the feasibility of imidazole/hexanoic ES as a single solvent for lipid extraction from intact wet and dried microalga Nannochloropsis oceanica. Single-factor multilevel design of experiments is used to evaluate the yield under different conditions (ES composition, temperature, time, solvent/biomass ratio, and water content). Interestingly, the extractions from wet algae paste were higher than dried biomass, reaching a comparable yield to the traditional chloroform/methanol method. From wet biomass, >80 % lipids were extracted by the imidazole/hexanoic acid ES (15:85 mol/mol) at 50 °C within 2 h. Whereas, the extraction yield of dry biomass was lower, reaching only 65 % even after 12 h under the same condition. Supplementation of water during the dry extraction resulted in the same yield as the wet extraction. This research demonstrated that ES can be used to replace non-renewable organic solvents without the need of using mechanical disruption and can be applied directly on wet biomass.