Ionic Liquid-based Aqueous Biphasic Systems Research Articles

Green Extraction Strategy Using Bio-Based Aqueous Biphasic Systems for Polyphenol Valorization from Grape By-Product.

Polyphenols are natural compounds with enhanced antioxidant properties. They are present in relatively high concentrations in fruit/vegetable by-products. Therefore, there is a need for the development of efficient and cost-effective methods for the separation and purification of these valuable compounds. Traditional extraction with organic solvents needs to be switched to novel methods that are more efficient, with reduced extraction times and low consumption of organic solvents. Aiming at developing sustainable processes for the separation and purification of phenolic compounds, we used three model compounds, namely resveratrol, quercetin, and gallic acid, to investigate ionic liquid-based aqueous biphasic systems (IL-ABSs) formed by cholinium-based IL in combination with polypropylene glycol with a molecular mass of 400 g/mol (PPG400). The ABS composition in the two-phase region was selected according to a previously determined phase diagram. Extraction studies indicated the preferential partition of resveratrol and quercetin toward the hydrophobic PPG-rich phase that is mainly dominated by its hydrophobic nature and the strong salting-out effect of ILs. On the other hand, due to its considerably hydrophilic nature, gallic acid preferentially migrates toward the IL phase. The achieved results from grape stem extract demonstrated high extraction efficiencies of cholinium dihydrogen phosphate (~99% for resveratrol for the PPG phase and 78% for gallic acid for the IL phase), with considerable selectivity, demonstrating promising outcomes for potential applications.

Recycling of metals from LiFePO4 battery cathode material by using ionic liquid based-aqueous biphasic systems.

Lithium-ion batteries are essential for electric vehicles and energy storage devices. With the increasing demand for their production and the concomitant surge in waste generation, the need for an efficient and environmentally friendly recycling process has become imperative. This work presents a new approach for recycling of metals from the LiFePO4 (LFP) cathode material. The cathode material was first leached by a HCl solution without an oxidizing agent. Subsequently, an ionic-liquid-based aqueous biphasic system (IL-based ABS) was used for the separation of lithium and iron from leachate solutions, followed by a precipitation process. The influence of the acid concentration, solid-to-liquid ratio and leaching time on the leaching yield was investigated. UV-vis absorption spectra revealed the presence of mixed-valent iron in the leachate, with 83 ± 1% Fe(ii) and 17 ± 1% Fe(iii). The ABS systems comprised tributyltetradecylphosphonium chloride [P44414]Cl and a salting-out agent (HCl or NaCl). The extraction percentage of iron reached 90% and less than 1% of lithium was extracted under the studied optimal conditions. Further enhancement of iron extraction, reaching 98%, was achieved via a two-stage cross-current extraction process. Iron was precipitated from the loaded IL phase with an efficiency of 97% as Fe(OH)2 and Fe(OH)3, using an aqueous ammonia solution. Lithium was precipitated as Li3PO4 with a lithium purity of 99.5% by adding K3PO4 solution. The ionic liquid used in the process was efficiently regenerated and used in four extraction cycles with no activity decline, with an extraction percentage of 90% of iron in each cycle.

Continuous plug flow extraction of L-tryptophan using ionic liquid-based aqueous biphasic systems in small channels

A double process intensification of the conventional solvent extraction was accomplished by employing two strategies. Firstly, by utilizing continuous small channels and secondly by replacing organic solvents with novel ionic liquid based aqueous biphasic systems (IL-ABS). The flow extraction of the amino acid L-tryptophan was investigated in small channels with internal diameters of 0.5 and 0.8 mm and three different IL-ABS. The partition coefficients for two different L-tryptophan concentrations (0.325 and 0.5 wt%) were measured for IL-ABS compositions 18, 20 and 22 wt% K3PO4 and C4mimCl. Increasing the weight composition of the conventional salt and the ionic liquid increased the partition of the amino acid for the top ionic liquid rich phase. The continuous extractions were carried out in the plug flow regime. Correlations were proposed for the plug length and the film thickness as functions of the capillary number. It was found that the extraction efficiency with the 20 wt% ABS reached 95 % in under 15 s in the 0.5 mm channel and in about 40 s in the 0.8 mm channel. When comparing the IL-ABS, the 22 wt% reached 96 % extraction efficiency in 14 s compared to the 70 s of the 20 wt% in the 0.8 mm channel. The overall mass transfer coefficients varied between 0.05 and 0.2 s−1 for all cases studied, which were significantly higher than those in conventional solvent extraction systems.

Efficiently Removing Heavy Metals from High-Salinity Wastewater via Ionic Liquid-Based Aqueous Biphasic Systems.

For the separation of metal ions, ionic liquid-based aqueous biphasic systems (IL-ABSs) offer a promising alternative to solvent extraction. However, the incorporation of an extensive quantity of inorganic salts restricts their practical application. Because heavy metal wastewater often contains high concentrations of inorganic salts, it offers good prospects for the application of IL-ABSs in the separation of heavy metals. In this work, an IL-ABS was formed by tributyltetradecylphosphonium chloride ([P44414]Cl), and simulated high-salinity wastewater (NaCl and Na2SO4 as the main inorganic salts) was used for the separation of heavy metals. The phase diagram results indicated that the formation of a two-phase system required a relatively high salt concentration. The extraction process followed the mechanism of anion exchange; thus, heavy metals such as zinc and cadmium that formed complexes with chloride ions could be effectively extracted (extraction rate >99.5%) with a very fast rate (extraction time <1 min) at a wide pH range (pH = 2-7). After extraction, the metals could be stripped well (stripping rate >99.5%) after contact with the NaOH solution. This research provided a new approach for treating heavy metals in high-salinity effluents, which has the advantages of IL-ABS and avoids the disadvantages of adding large amounts of inorganic salts at the same time.

Combined Use of Ionic Liquid-Based Aqueous Biphasic Systems and Microfluidic Devices for the Detection of Prostate-Specific Antigen.

Prostate cancer (PCa) is one of the cancer types that most affects males worldwide and is among the highest contributors to cancer mortality rates. Therefore, there is an urgent need to find strategies to improve the diagnosis of PCa. Microtechnologies have been gaining ground in biomedical devices, with microfluidics and lab-on-chip systems potentially revolutionizing medical diagnostics. In this paper, it is shown that prostate-specific antigen (PSA) can be detected through an immunoassay performed in a microbead-based microfluidic device after being extracted and purified from a serum sample through an aqueous biphasic system (ABS). Given their well-established status as ABS components for successful bioseparations, ionic liquids (ILs) and polymers were used in combination with buffered salts. Using both IL-based and polymer-based ABS, it was demonstrated that it is possible to detect PSA in non-physiological environments. It was concluded that the ABS that performed better in extracting the PSA from serum were those composed of tetrabutylammonium chloride ([N4444]Cl) and tetrabutylphosphonium bromide ([P4444]Br), both combined with phosphate buffer, and constituted by polyethylene glycol with a molecular weight of 1000 g/mol (PEG1000) with citrate buffer. In comparison with the assay with PSA prepared in phosphate-buffered saline (PBS) or human serum in which no ABS-mediated extraction was applied, assays attained lower limits of detection after IL-based ABS-mediated extraction. These results reinforce the potential of this method in future point-of-care (PoC) measurements.

Ionic liquid-based aqueous biphasic systems as one-step clean-up, microextraction and preconcentration platforms for the improved determination of salivary biomarkers

Ionic liquid-based aqueous biphasic systems succeed in one-step clean-up, microextraction, and preconcentration strategies for biomarkers in saliva. These novel platforms improve the saliva bioanalysis in terms of simplicity and greenness.

Temperature-Responsive Deep Eutectic Solvents for Highly Selective Separation of 5-Hydroxymethylfurfural from Reaction Mixture

5-Hydroxymethylfurfural (HMF) is a key biobased platform compound for the production of high-value chemicals and fuels. However, separation and purification of HMF is currently the bottleneck for HMF production. In this work, a novel class of temperature-responsive deep eutectic solvent (DES)–water systems have been explored to selectively separate HMF from reaction mixtures. The fructose dehydration reaction was conducted in homogeneous DES–H2O systems, and then, the produced HMF was migrated to the DES-rich phase while the unreacted fructose was retained in the H2O-rich phase upon cooling. Thus, selective separation of HMF was realized. It was found that water–water and DES–DES interactions predominate over DES–water interactions during cooling, thus resulting in upper critical solution temperature phase separation. Under optimal conditions, the partition coefficient and separation factor of HMF could reach up to 78 and 609, respectively, which is about 5 and 13 times those reported in ionic liquid-based aqueous biphasic systems. Furthermore, HMF could be removed from the DES-rich phase, giving a high recovery efficiency of 69%, which is much higher than the best value reported in the literature. At the same time, DES was regenerated and reused in the next process, and no obvious decrease in partition coefficient of HMF was observed after six cycles.

Extraction and separation of flavonoids and iridoids from Eucommia ulmoides leaves using choline tryptophan ionic liquid-based aqueous biphasic systems

The choline tryptophan ionic liquid (IL)-based aqueous biphasic system (ABS) was designed and applied to extract and separate flavonoids and iridoids from Eucommia ulmoides leaves. This ABS possessed a unique viscous layer enriching iridoids that can be directly removed at the interface between the IL-rich and salt-rich phases. The extraction yield of total flavonoids was optimized by RSM to obtain a predicted maximum of 2.91% at the IL concentration of 36.73%, liquid to solid ratio of 38, extraction temperature of 44 °C and extraction time of 105 min. The determined extraction yield of total flavonoids is 2.78% ± 0.12% under revised optimization conditions. The distribution coefficient K and extraction rate E of total flavonoids in the IL-rich phase reach the maximum of 129% and 98.53% at the K 3 PO 4 content of 26% in the ILABS, respectively. The HPLC analysis shows a high content of rutin in the flavonoids precipitate induced by water as an anti-solvent. Aucubin content reaches 15.19% in the intermediate viscous layer enriching iridoids. Hence, the designed process has the potential to be applied to the separation and enrichment of rutin and aucubin from other industrial crops. • [Ch][Try] based ILABS integrate extraction and separation of flavonoids and iridoids from EULs. • The iridoids enriched in the interface can be directly recovered. • Flavonoids with higher rutin content were obtained by precipitation with water as antisolvent.

Flow patterns of ionic liquid based aqueous biphasic systems in small channels

Ionic liquid based aqueous biphasic systems (IL-ABS) were formed by the addition in water of a hydrophilic ionic liquid (1-Butyl-3-methylimidazolium Chloride, C4mimCl) and a kosmotropic salt (tripotassium phosphate, K3PO4). The flow patterns of IL-ABS were studied in capillary channels with 0.2, 0.5 and 0.8 mm internal diameter; this is the first time such two-phase flows have been investigated. Three weight concentrations of the ionic liquid and the salt (18, 20 and 22 wt%) were chosen within the biphasic region. The main flow patterns included plug, dispersed and parallel flow. It was found that both channel diameter and weight concentrations would affect the flow patterns observed. Finally, a generalized flow pattern map was plotted using a combination of capillary and Reynolds numbers, where the transition boundaries of plug flow collapsed for all ionic liquid and salt concentrations studied.

Purified Saponins in Momordica charantia Treated with High Hydrostatic Pressure and Ionic Liquid-Based Aqueous Biphasic Systems.

Momordica charantia L. (Cucurbitaceae) is rich in saponins, which have multiple biological effects. In this study, the total saponins of M. charantia were extracted by high hydrostatic pressure (HHP) technology. The optimal extraction process was determined (ethanol concentration 68%, pressure-holding time 8 min, ratio of material to solvent 1:35 and pressure 510 MPa), and the extraction amount of saponins reached 127.890 mg/g. On this basis, an ionic liquid-based aqueous biphasic system was constructed to purify the total saponins. Under the optimized conditions, the purity of M. charantia saponins was 76.06%. Liquid chromatography–mass spectrometry (LC/MS) was used to characterize the saponins in the purified extract of M. charantia. It was found that there were four kinds of saponins in the extract of M. charantia: kuguaglycoside A, momordicoside L, kuguacin B and kuguacin J, providing a basis for the study of the biological activity of saponins.

Modelling study on phase equilibria behavior of ionic liquid-based aqueous biphasic systems

The ability to predict the phase equilibria behavior is of crucial relevance in the early design stage of biphasic liquid-liquid systems. Ionic liquid-based aqueous biphasic systems (IL-ABS) have demonstrated superior performance in many applications such as the recovery of bio-products and the recycling of hydrophilic ILs from aqueous solutions. In order to better utilize these novel biphasic liquid-liquid systems, modelling studies on phase equilibria behavior are carried out in this work. First, the IL database developed in our previous work is extended to these unconventional biphasic systems. In total, 17,449 experimental binodal data points covering 171 IL-ABS at different temperatures (278.15 K-343.15 K) are collected. Then, all involved IL-ABS are correlated using a popular three-parameter mathematical description and the optimal parameters of each IL-ABS are obtained. Afterwards, we try to build a linear group contribution (GC) model to predict the phase equilibria behavior of IL-ABS, but it fails due to the high complexity of these biphasic systems. For this reason, we finally turn to applying a well-known machine learning algorithm, i.e., artificial neural network (ANN), to build a nonlinear GC model for such a purpose. This model gives a mean absolute error (MAE) of 0.0175 and squared correlation coefficient (R2) of 0.9316 for the 13,789 training data points, and for the 3,660 test data points they are 0.0177 and 0.9195, respectively. The results indicate that the proposed nonlinear ANN-GC model, to some extent, is capable to predict the phase equilibria behavior of IL-ABS. Besides the efforts of building GC models, we also discuss some main issues that govern the phase equilibria behavior of IL- ABS, which could be a guidance in the design of IL-ABS.

Valorization of Expired Energy Drinks by Designed and Integrated Ionic Liquid-Based Aqueous Biphasic Systems

Expired energy drinks are rich in bioactive added-value compounds that can be recovered and reused in order to valorize food waste within a circular economy perspective. However, to accomplish such...

Further insight into the influence of functionalization and positional isomerism of pyridinium ionic liquids on the aqueous two-phase system equilibria

Despite a large collection of publications dealing with the characterization of ionic liquid-based aqueous biphasic systems (IL-ABS), a gap still exists regarding the impact of functionalized alkyl side branches and IL positional isomers on phase equilibria. Therefore, this work addresses the investigation of the ability of different methyl substituted pyridinium based ILs on the formation of ABSs with K3PO4. We evaluated the impact of (i) functional groups (hydroxyl or ether) embed in side alkyl chains of pyridinium cations, (ii) positional isomerism of methyl group (ortho, meta and para) and (iii) the IL cation core. Ternary phase diagrams of the ABSs formed by these ILs and K3PO4 and the appropriate tie lines were determined and presented. It is shown that the presence of functionalized alkyl chain largely affects the salting-in behavior of ILs (ILs with the oxygen groups are more difficult to form ABS) while more subtle differences were observed among positional isomers. Based on the obtained results it is concluded that change of biphasic area of ABS is the manifestation of the altered affinity of ILs for water as a consequence of cation structure. Moreover, aiming at gathering a broader picture of the relationship between ILs structure and ABS properties, molecular simulations were performed, and it was showed that the obtained results are consistent with the experimental results.

One step selective partition of ε-polylysine present in broth cultures in ionic liquid-based aqueous biphasic systems

ABSTRACT Four different ionic liquids were synthesized, characterized and used with polypropylene glycol for the formation of aqueous biphasic systems and were used to selectively separate ε-PL from culture broth. It was observed that the partition of ε-PL to the IL-rich phase was achieved, and with pure ε-PL, the extraction efficiency was found to be 99.92% while with culture broth, it was 93.42% for the ABS formed with 2-hydroxyethylammonium formate. Preservation of the chemical and structural stability of ε-PL in the ABSs indicated the potential of such systems as remarkable platform for the selective separation of ε-PL from the culture broth.

Structural effects of choline amino acid ionic liquids on the extraction of bovine serum albumin by green and biocompatible aqueous biphasic systems composed of polypropylene glycol400 and choline amino acid ionic liquids

Ionic liquid-based aqueous biphasic systems (IL-based ABSs) are considered as promising extraction and purification routes. For designing an efficient process of protein extraction, it is necessary to complete information about phase diagrams including binodal and tie-lines for new ABSs. In this respect, here, binodal curves and tie-lines for ternary aqueous solutions composed of polypropylene glycol 400 and some of choline amino acid ionic liquids, [Ch][AA]-ILs, including choline L-histidine, choline L-arginine, choline L-proline, and choline L-valine as a green and biocompatible entrainers have been determined at T = 298.15 under atmospheric pressure (≈85 kPa). The results indicated that the binodals of these ABSs affected strongly by the ILs structures; so that, biphasic region is increased by decreasing of hydrophobicity of IL anion from valine to arginine. The effective exclude volume theory (EEV) and Setschenow equation have been utilized for addressing phase formation capability in these systems. Phase formation ability in these ABSs followed in the order: choline L-arginine > choline L-histidine > choline L-proline > choline L-valine which is parallel with an increasing hydrophilicity of amino acid exists in each of IL structures. Moreover, osmotic virial equation was used for modeling of tie-lines in the studied ABSs. Finally, the performance of these ABSs for separation of biomolecules was evaluated by studying the partition behavior of bovine serum albumin, BSA, via measuring of partition coefficient and extraction efficiency. The obtained results from BSA partitioning in these ABSs indicated that BSA is migrated preferentially to the [Ch][AA]-ILs-rich bottom phase and this migration is increased by increasing hydrophilicity of amino acid exists in IL structure, i.e. choline L-arginine > choline L-histidine > choline L-proline > choline L-valine. Also, it was found that the salting-out effect and π-π interactions between BSA and [Ch][AA]-ILs have important role in BSA partitioning as well as hydrophilicity/hydrophobicity interactions.

Efficient extraction of gold(I) from alkaline aurocyanide solution using green ionic liquid-based aqueous biphasic systems

Abstract Ionic liquid-based aqueous biphasic extraction is an environmentally benign technology for separation of various substances. In this study, aqueous biphasic systems (ABSs) consisting of 1-alkyl-3-methylimidazolium bromide ionic liquids (ILs) (alkyl = butyl, hexyl, and octyl) and phosphate-based salts were studied for extraction of gold(I) from alkaline aurocyanide solutions for the first time. The results indicated that gold(I) preferentially migrated into the IL-rich phase, achieving remarkable extraction efficiency up to 99.9%. The extraction mechanism of gold(I) was evaluated based on characterization by FT-IR spectroscopy, X-ray photoelectron spectroscopy. The results revealed the electrostatic interaction between gold(I) cyanide complex and IL was the main driving force for gold(I) partition. The migration of gold(I) into IL-rich phase was associated with an extraction mechanism by ion pair formation of [Cnmim+]•[Au(CN)2−]. Furthermore, the microscopic structure of the IL-rich solution was also determined by transmission electron microscopy. It was found that the presence of [Au(CN)2−] anion induced the aggregation of ionic liquids. Finally, the gold present in IL-rich phase was successfully recovered by direct electrodeposition on a copper cathode. The proposed extraction strategy using IL-based ABSs is envisaged as potential platform for the green partition of gold(I) from alkaline aurocyanide solution.

Analysis of acetylcholinesterase inhibitors by extraction in choline saccharinate aqueous biphasic systems

Ionic liquid-based aqueous biphasic systems (IL-ABS) formed by ILs composed of ions of low toxicity, choline ([Chol]+) coupled with saccharinate ([Sac]−) and acesulfamate ([Ace]−), and inorganic salts with distinct water-structuring properties were employed for simultaneous extraction and concentration of acetylcholinesterase (AChE) inhibitors – galantamine (gal), N-desmethyl galantamine (des) and ungiminorine (ung). Comprehensive experiments aimed to assess the influence of salt and IL type and concentration, as well as the pH and temperature on the phase-forming ability and distribution of the target alkaloids between the two phases formed reveled that the IL anion and pH are the most important factors. At the optimal conditions found a quantitative recovery into the IL-rich phase of gal, des and ung was achieved in a single extractive step. These results were further used as a platform for the development of a simple and safer sample pretreatment method for analysis of the three analytes, followed by RP-HPLC/UV detection. The method showed satisfactory analytical performance, the latter allowing quantitative determination of these AChE inhibitors in pharmaceutical dosage form and in human urine.

Lipase production and purification by self-buffering ionic liquid-based aqueous biphasic systems

Abstract In this work, a group of Good’s buffer ionic liquids (GB-ILs) comprised of tetrabutylammonium, tetrabutylphosphonium and cholinium cations paired with Good’s buffer (GB) anions (MOPSO, BES and TAPSO) was studied. Their distinctive capability to induce the formation of aqueous biphasic systems (ABS) with the salts K 3 PO 4 , K 2 CO 3 , and (NH 4 ) 2 SO 4, and the polymers poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and PEG-PPG copolymers was demonstrated. Their application as purification tools to recover a lipase produced via submerged fermentation by Burkholderia cepacia ST8 was investigated. The lipase was preferentially partitioned towards the GB-IL-rich phase in both the GB-IL + salt and polymer + GB-IL purification systems. Molecular docking studies were performed aiming at to understand the possible interactions between the GB-IL ions and the lipase residues. Furthermore, the selected GB-IL-based ABS was investigated as part of an integrated process developed to successfully recover and purify an extracellular B. cepacia ST8 lipase from the fermentation broth, in which a purification factor of 22.4 ± 0.7 and a recovery yield of (94.0 ± 0.2) % were achieved.

A novel combined process for extracting, separating and recovering flavonoids from flos sophorae immaturus

Abstract The hydrotropic characteristic of ionic liquids can be used to recover bio-molecules from aqueous media and ionic liquid based-aqueous biphasic systems have been extensively applied to the separation and purification of value-added compounds. According to the hydrotropy effect and the phase separation ability, n-1,3-dibutylimidazolium propionate was chosen from several imidazolium carboxylate ionic liquids to carry out the novel combined process integrating extracting, separating and recovering flavonoids from flos sophorae immaturus with the aid of aqueous biphasic systems. The optimum separation conditions derived from the response surface analysis were potassium citrate concentration 26.12%, pH 9.83 and temperature 41.89 °C, with the predicted extraction efficiency 100.27% and measured one 99.68%. The flavonoids in the ionic liquid-rich phase were precipitated out and recovered by the dilution of using pure water as an anti-solvent and the cooling of refrigerator, producing the maximum recovery rate 82% or so and establishing the appropriate dilution ratio 5 in the involved recovery systems. The extracts presented good scavenging activity, namely, 62% on the 2, 2-diphenyl-1-picrylhydrazyl radical and 85% on the hydroxyl radical from the well-known Fenton reaction when the sample concentration was approximately 0.125 mg/mL, elucidating the combined process efficient and feasible.

Phase behavior of aqueous biphasic systems composed of novel choline amino acid ionic liquids and salts

Phase diagrams of a series of ionic liquid-based aqueous biphasic systems (ILABS) composed of novel choline amino acid ionic liquids and inorganic salts were measured experimentally at T=(288.15, 298.15 and 308.15) K. Ionic liquids, salts, and temperature influenced the phase separation ability of the studied ILABS. Several parameters of the Merchuk equation were estimated by fitting the binodal curve data. Liquid-liquid equilibria of the investigated ILABS were determined by a gravimetrical method, including the tie-line lengths and slope of the tie-lines. Critical points of the corresponding ILABS were obtained by a mathematical calculation different from the conventional extrapolation. In the case of the phenylalanine+K3PO4+H2O system at 298.15K, the gravimetrical method and the mathematical calculation were validated by the tie-lines determined experimentally and the critical point derived from the extrapolation.