Formation Of Aqueous Biphasic Systems Research Articles

Complete removal of organophosphate pesticides from wastewaters with sustainable ionic liquid-based aqueous two-phase strategy

Due to extensive food production, organophosphate pesticides (OPs) are widely utilized for crop protection, leading to their presence in the environment. The focus of this study was the design of an efficient aqueous biphasic system (ABS) strategy for OP removal, namely, malathion (MAL), azinphos-methyl (AZM), and chlorpyrifos (CHP) from water. Different ionic liquids (ILs) with symmetrical cations were selected as ABS phase-formers (tetrabutylphosphonium salicylate, tetrabutylammonium salicylate, 1,3-dibutylimidazolium dicyanamide, 1,3-dibutylimidazolium salicylate and 1,3-dibutylimidazolium bromide) with citrate salt as a salting-out agent. Initially, phase diagrams were determined, followed by partition studies revealing that the partition of MAL and CHP aligns with the IL- ABS formation trend, while the AZM partition is governed by specific interactions with ILs. For optimization studies, tetrabutylphosphonium-salicylate i.e. [TBP][Sal]-based ABS was chosen, due to obtained high extraction efficiencies of over 99.3 %. After establishing the effects of pH, temperature, tie-line length, and phase ratio on extraction performance, extraction of OPs from a real wastewater sample further confirmed the effectiveness of the designed method achieving complete removal of each pesticide. Furthermore, recovery of IL was achieved using an antisolvent method to precipitate CHP followed by IL-reuse in three consecutive cycles without efficiency decreased. Finally, it was demonstrated that [TBP][Sal] exhibits low cytotoxic potential, indicating that the presence of low amounts of this IL in aqueous media could be acceptable from ecotoxicological standpoint. This study showcased the exceptional potential of the proposed technology for the efficient and sustainable treatment of wastewater contaminated with OPs, affirming its capability to treat significant wastewater volumes.

Insights into application of aqueous biphasic systems of deep eutectic solvents composed of benzyltrialkylammonium chloride in dye separation

Deep eutectic solvents (DES) are considered the newest entry in the list of green solvents and they are analogues of ionic liquids (ILs), with excellent solvent characteristics better than commonly used organic solvents and ILs. Owing to this, We have prepared DES using benzyltrialkylammonium chloride (BTAAC) including benzyltrimethylammonium chloride (BTMAC), benzyltriethylammonium chloride (BTEAC), and benzyltributylammonium chloride (BTBAC) as hydrogen bond acceptors (HBA) and glycols, like ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG) as hydrogen bond donors (HBD). Aqueous biphasic systems (ABS) were developed using the synthesized DESs and K3PO4, K2HPO4, and K2CO3 at 298.15 K and atmospheric pressure. The phase-forming ability of DES has been evaluated based on the nature of potassium salts, HBA and HBD. In most cases, the influence of salts on ABS formation was found to follow the order: K3PO4 > K2HPO4 > K2CO3, while HBAs follow: BTBAC > BTEAC > BTMAC. The performance of the ABSs was experimentally applied for the extraction of Methyl orange (MO), Eriochrome black T (EBT), and Eosin Y (EY). In most ABS, the extraction order for the studied dyes noticed was: MO < EBT < EY, consistent with their hydrophobic nature. ABS consisting of BTBAC:TEG + K2HPO4 and BTBAC:TEG + K3PO4 was found to lead to the complete extraction of MO, EBT, and EY. The recovery of extracted EY dye was performed by adsorption method using starch-modified chitosan as an adsrobent.

Harnessing the power of natural deep eutectic solvents (choline chloride/sucrose) and polypropylene glycol in the formation of aqueous biphasic systems and the application of these systems in drug extraction.

In recent times, there has been considerable interest in utilizing aqueous biphasic systems (ABSs) containing natural deep eutectic solvents (NADESs) for the extraction of various substances. In this study, we focused on investigating the phase behavior of ABSs composed of poly(propylene) glycol 400 and NADESs (specifically, choline chloride/sucrose with molar ratios of 2 : 1 and 1 : 1). By analyzing the compositions of tie-lines, it was observed that these ABSs, which consist of four components, exhibit characteristics similar to ternary systems. To examine the influence of molar ratios on phase separation, the binodal model was applied to the obtained binodal data. The NRTL and UNIQUAC models were employed to establish correlations for the tie-lines. Moreover, we examined the extraction capabilities of the aforementioned ABSs for three commonly used drugs: diclofenac potassium, acetaminophen, and salicylic acid. To assess the efficiency of extraction, partition coefficients and extraction efficiencies were calculated for each drug. The results revealed that the extraction efficiency of these drugs into the polymer-rich top phase is dependent on their hydrophobicity. Furthermore, we employed the Diamond-Hsu equation, along with its modified version, to establish correlations between the experimental partition coefficients of the drugs and NADES overall concentrations.

Tailored pretreatment of serum samples and biomarker extraction afforded by ionic liquids as constituents of aqueous biphasic systems

Prostate cancer serum biomarkers, such as the U.S. Food and Drug Administration (FDA)-approved prostate specific antigen (PSA), are valuable markers of diagnosis, response to treatment and disease progression. Despite the expected benefits of using PSA to better manage the mortality and morbidity associated to prostate cancer, sample complexity and interference within analysis make its quantification in serum a high-cost and strenuous assignment. Here, we make use of the simple preparation, water-rich environment, and selectivity of aqueous biphasic systems (ABS) to develop alternative serum pretreatment strategies. A set of ammonium- and phosphonium-based ionic liquids (ILs) were used as either main phase-forming agents in IL-salt ABS or as adjuvants in polymer-salt ABS, allowing to explore the IL designer solvent nature and versatile role in ABS formation and performance. Serum pretreatment efficiency was evaluated by the capacity of each ABS to simultaneously deplete high abundance serum proteins (immunoglobulin G, IgG, and human serum albumin, HSA) at the systems’ interphase (thus, generating a three-phase partitioning system – ABS-TPP) and extract PSA to a single ABS phase. Regardless of the ABS typology under appraisal (IL-salt or polymer-salt-IL), the proper design of the IL structure is critical for both the ability to deplete high abundance serum proteins and extract PSA. The results demonstrate that, in addition to the proper choice of the ABS typology, a careful adjustment of the IL hydrophobicity is key to achieve the simultaneous depletion of high-abundance proteins and complete PSA extraction in a single step, creating new approaches for PSA analysis and its application in diagnosis/prognosis.

Hydrodynamics of cholinium chloride-based aqueous biphasic systems (ABS): A key study for their industrial implementation

Aqueous biphasic systems (ABS) have been widely studied for extraction and purification processes. Although they are considered biocompatible, amenable, and sustainable separation platforms, their application on an industrial scale remains impractical without proper scaling and integration into existing processes. To better understand the hydrodynamics of ABS formation, three cholinium chloride ([Ch]Cl)-based ABS composed of polypropylene glycol with a molecular weight of 400 g.mol−1 (PPG-400), tripotassium phosphate (K3PO4), and dipotassium hydrogen-phosphate (K2HPO4) were studied. The hydrodynamics of phase separation of ABS composed of PPG-400/[Ch]Cl, [Ch]Cl/K3PO4 and [Ch]Cl/K2HPO4 was studied by analysing the relationship between the mixing time (Tm) and the phase settling time (Ts), at 25 °C and 50 °C. The results showed that Ts is independent of Tm, which is very long for the polymer/salt systems (Ts > 6 h), while for salt/salt ABS, a very fast phase settling was observed (Ts < 150 s). The hydrodynamics of each salt/salt system was then correlated with the physicochemical properties of the coexisting phases and the nature of the phase-forming compounds. The increase in the salting-out effect of the inorganic salts, and the consequent larger differences between the compositions of the coexisting phases, improved the hydrodynamics of the [Ch]Cl-based ABS. With the increase of the tie-line lengths, the composition of the phases stabilized, resulting also in more stable physicochemical properties in each phase and constant Ts. The correlations obtained in this work allow the definition of the best operating region within the biphasic (liquid-liquid) region of [Ch]Cl/salt-based ABS as being the largest TLLs within the LLE region. The definition of these criteria and region of operation is crucial for the design and industrial implementation of these types of LLE processes using conventional mixer-settler units.

Partition of parthenolide in ternary {block copolymer + biocompatible ionic liquid or natural deep eutectic solvent + water} systems

In this work, aqueous biphasic systems (ABSs) formed by copolymers, ionic liquids (ILs) and natural deep eutectic solvents (NADES) have been demonstrated to be effective separation platforms for the extraction of hydrophobic pharmaceutical ingredients such as parthenolide (PAR). This work addresses the determination of the liquid–liquid equilibrium of ABS composed of choline lactate IL or choline chloride – lactic acid NADES and two different block copolymers Pluronic (PL17R4 and PL10R5), and their influence on the ABS formation and extraction efficiency of PAR. The ability of Pluronics to form ABS is compared to widely used polypropylene glycol polymer (PPG400). Comparing the effect of the ionic liquid and NADES on the ABS formation, it is shown that both salting-our reagents successfully form ABS and do not affect the extraction efficiency of PAR. The main influence on the high parthenolide extraction efficiency (>96%) is governed by the hydrophobic interactions between Pluronic and investigated compound, regardless on the applied salting-out reagent. Due to a high extraction efficiency achieved in PL-rich phase and promissing medical features of PAR, obtained results showed that this phase could be used as biocompatible drug delivery system. Avoiding commercially available organic solvents, elevated temperatures and pressure, the proposed method is greener alternative for PAR extraction.

Use of Tunable Copolymers in Aqueous Biphasic Systems for Extractive Bioconversion Aimed at Continuous Fructooligosaccharide Production

Aqueous biphasic systems (ABSs) based on sodium polyacrylate (NaPA), ethylene oxide/propylene oxide (EO/PO) polymers, and (EO)x-(PO)y-(EO)x triblock copolymers were prepared and applied aiming at continuous fructooligosaccharide (FOS) production and separation. EO/PO hydrophilicity/hydrophobicity balance had a significant effect on ABS formation. To develop an integrated process including the continuous enzymatic (levansucrase) production of FOSs and their purification while improving the production yield by further glucose separation, the potential of these novel polymer-based ABSs as alternative platforms was investigated. They were used for the partitioning of different carbohydrates (FOS, sucrose, d-fructose, and d-glucose) and levansucrase. Results revealed a highly polymer-dependent partition of carbohydrates and a poorly dependent one of the enzymes. Changing EO/PO and copolymers, FOS was purified with high yields (72.94–100.0%). Using polypropylene glycol 400 + NaPA 8000-based ABS, the FOS was precipitated in the interphase and separated from the other components. Pluronic PE-6800 + NaPA 8000 was identified as the best ABS for FOS continuous production and in situ purification, while minimizing levansucrase inhibition by d-glucose. This system allowed selective partition of FOSs and d-glucose toward the top phase and that of levansucrase and its substrates toward the bottom one. COnductor-like Screening MOdel for Real Solvent (COSMO-RS) suggested that ABS formation may have been due to NaPA and polymer/copolymer competition to form hydrogen bonds with water molecules. Moreover, the partition of FOSs and sugar may have been the result of a subtle balance between hydrogen bonding of sugar and polymer/copolymer and electrostatic misfit of solute with NaPA. Finally, two integrated processes were proposed to be applied with real FOS extracts obtained by chemical or enzymatic hydrolysis of inulin or by transfructosylation of concentrated sucrose solutions using bacterial levansucrases.

Greener sample preparation method for direct determination of Cd(II) and Pb(II) in river sediment based on an aqueous biphasic system with functionalized ionic liquids

Although sample preparation, as an unavoidable step of the analytical process should be simple, it is very often identified as a bottleneck. Simplicity of sample preparation based on cost-effective and non-hazardous materials is mandatory for any sustainable and environmental friendly approach. Aqueous biphasic systems (ABS), based on functionalized ionic liquids (FILs) are acceptable alternatives to classical extraction procedures, due to the replacement of organic solvent with diluted aqueous-soluble ionic liquids. In this work, two water soluble FILs based on 2-mercaptobenzothiazolate anion, [mbt]: 1-butyl-3-methylimidazolium [mbt] ([bmim][mbt]) and 1-ethyl-3-methylimidazolium [mbt] ([emim][mbt]), were designed and synthesized in order to selectively extract Cd(II) and Pb(II) from the river sediment. It was found that [mbt]– anion acts as the ligand and forms complexes with Cd(II) and Pb(II) which are responsible for their efficient extraction, while cation is more responsible for the formation of ABS. Partition coefficients of 408 and 180 for Cd(II) and Pb(II), respectively, were obtained using ABS based on [bmim][mbt]. Direct extraction of Cd(II) and Pb(II) from the river sediment has been investigated and obtained optimal conditions are: 60 min direct contact of the aqueous solution of [bmim][mbt] and the sediment sample at 90 °C, followed by formation of ABS upon addition of potassium citrate. Using AGRE and AGREEprep tools greenness of the proposed method for direct extraction of Cd(II) and Pb(II) from the sediment are calculated. Obtained values of 0.69 and 0.71 for Cd(II) and Pb(II) extraction, respectively, showed a high level of the greenness of the proposed method.

Separation of Rare Earths and Transition Metals Using Ionic-Liquid-Based Aqueous Biphasic Systems

An aqueous biphasic system (ABS) based on the ionic liquid (IL) tributyltetradecylphosphonium chloride ([P444,14]Cl) has been developed for the separation of the Sm/Co, Nd/Fe, Eu/Zn, and La/Ni rare-earth element and transition metal pairs. Phase diagrams of the new ABSs based on [P444,14]Cl–CoCl2/SmCl3–H2O were constructed, and these showed that ABS formation was facilitated by higher temperatures (e.g., 50 °C). The effects of salting-out agents (NaCl, LiCl, and HCl) and the amount of IL on metal extractions were investigated for the separation of samarium and cobalt. The graph showing the variation of the distribution ratio of cobalt as a function of the chloride concentrations exhibited a maximum, while the distribution ratios for samarium stayed close to 0 at low chloride concentrations and then gradually increased with increasing chloride concentration. Ferric and zinc ions could be fully transferred to the IL phase without contamination by rare-earth elements at low concentrations of salting-out agents, whereas the maximum in Ni/La selectivity was observed at 8 mol/kg of LiCl in the system. Cobalt was removed from the loaded IL phase by precipitation stripping with Na2CO3, and the quantitative removal of cobalt could be achieved at a Na2CO3 to Co molar ratio of 1.5:1. Infrared spectra confirmed that the precipitate was pure CoCO3 without contamination by the IL. By selecting economic and environmental-friendly ILs, the IL-based ABS can be used for development of sustainable green processes for metal separations.

Insights into the Partitioning of DNA in Aqueous Biphasic System Containing Ammonium-based Ionic Liquid and Phosphate Buffer

Aqueous biphasic system (ABS), as an efficient separation process, can be applied in the extraction and purification of DNA which is an integral part of life science studies. Ammonium-based ionic liquids (ILs) were synthesized, and ABS formation was evaluated with phosphate buffer [K2HPO4-KH2PO4 (1.82:1.00)] as the second phase forming component. The structural influences of the cation of ILs, including alkyl chain length and the effect of functional groups on phase formation, were methodically assessed. The experimental binodal data were correlated with Merchuks’ equation and showed adequate fitting. The constituents of ABS were carefully selected to obtain a biocompatible system with controlled pH to use for the partitioning of biomolecules. The proposed system was applied in model DNA partitioning and resulted in a single step, highly efficient extraction at 298.15 K. The structural variations of the selected ILs influenced the partitioning, and thus, ABS containing benzyltributylammoniumchloride ([BTBA]Cl) IL was found to be efficient among the studied systems. Furthermore, the partition conditions were optimized in terms of the concentrations of IL and buffer using [BTBA]Cl/K2HPO4-KH2PO4 (1.82:1.00)/water system. Finally, the extraction mechanism involved in the partitioning and stability of DNA was investigated through FT-IR and circular dichroism spectra.

Synthesis of Purine-Based Ionic Liquids and Their Applications.

Bio-based ionic liquids (ILs) are being increasingly sought after, as they are more sustainable and eco-friendly. Purines are the most widely distributed, naturally occurring N-heterocycles, but their low water-solubility limits their application. In this work, four purines (theobromine, theophylline, xanthine, and uric acid) were combined with the cation tetrabutylammonium to synthesize bio-based ILs. The physico–chemical properties of the purine-based ILs were characterized, including their melting and decomposition temperatures and water-solubility. The ecotoxicity against the microalgae Raphidocelis subcapitata was also determined. The ILs show good thermal stability (>457 K) and an aqueous solubility enhancement ranging from 53- to 870-fold, in comparison to their respective purine percursors, unlocking new prospects for their application where aqueous solutions are demanded. The ecotoxicity of these ILs seems to be dominated by the cation, and it is similar to chloride-based IL, emphasizing that the use of natural anions does not necessarily translate to more benign ILs. The application of the novel ILs in the formation of aqueous biphasic systems (ABS), and as solubility enhancers, was also evaluated. The ILs were able to form ABS with sodium sulfate and tripotassium citrate salts. The development of thermoresponsive ABS, using sodium sulfate as a salting-out agent, was accomplished, with the ILs having different thermosensitivities. In addition, the purine-based ILs acted as solubility enhancers of ferulic acid in aqueous solution.

Opposite Effects Induced by Cholinium-Based Ionic Liquid Electrolytes in the Formation of Aqueous Biphasic Systems Comprising Polyethylene Glycol and Sodium Polyacrylate.

Cholinium-based ionic liquids ([Ch]-based ILs) were investigated as electrolytes in the formation of aqueous biphasic systems (ABS) composed of polyethylene glycol (PEG) and sodium polyacrylate (NaPA) polymers. Both enhancement and decrease in the liquid-liquid demixing ability induced by electrolytes in PEG-NaPA aqueous biphasic systems were observed. It is shown that the ILs that most extensively partition to the PEG-rich phase tend to act as inorganic salts enhancing the two-phase formation ability, while those that display a more significant partition to the NaPA-rich phase decrease the ABS formation capacity. The gathered results allowed us to confirm the tailoring ability of ILs and to identify, for the first time, opposite effects induced by electrolytes on the PEG-NaPA ABS formation ability. The distribution of the electrolyte ions between the coexisting phases and the polyelectrolyte ion compartmentalization are key factors behind the formation of PEG-NaPA-based ABS.

Amino-acid-based chiral ionic liquids characterization and application in aqueous biphasic systems

By using amino acids as anions, ten chiral ionic liquids (CILs) composed of tetrabutylammonium or cholinium as cations were synthesized by neutralization reactions and further characterized by assessing their optical rotation, thermophysical properties (melting and decomposition temperatures, density, viscosity and refractive index) and ecotoxicity against the marine bacterium Aliivibrio fischeri. The CILs are shown to display, in general, high thermal stability (> 439 K) and low to moderate toxicities (86-217 mg·L−1). It was found that the cation plays an important role in the density and viscosity of the CILs. Additionally, the effect of CILs optical configuration on these properties was evaluated by comparing the tetrabutylammonium D/L-phenylalaninate ([N4444][D/L-Phe]) and cholinium D/L-phenylalaninate ([N1112(OH)][D/L-Phe]) pairs. Finally, the CILs potential to form aqueous biphasic systems with sodium sulfate, citrate buffer and phosphate buffer was assessed and the ternary phase diagrams were determined. These allowed to infer the impact of the CILs’ cation, anion, and salt on the aqueous biphasic system formation. It was shown that the cation has a more pronounced impact on the aqueous biphasic system formation than the anion. Cholinium-based CILs failed to form aqueous biphasic systems with sodium sulfate under the tested conditions, contrary to the more hydrophobic tetrabutylammonium-based CILs. The ability of the tested salt and buffers to induce liquid-liquid demixing shows that citrate buffer and sodium sulfate represent the weakest and the strongest salting-out agents, respectively.

Effect of Ionic Liquid [C4C1im]Br on the Formation of Aqueous Biphasic Systems Composed of PEG and Biodegradable Salts, and on the Partition of L-Tryptophan

In this work, the extractive potential, for biomolecules, of several aqueous biphasic systems (ABS) composed of polyethylene glycol (PEG) with varying molecular weight (400 and 4000) and different biodegradable organic salts, sodium citrate (Na3C6H5O7), sodium tartrate (Na2C4H4O6), and sodium succinate (Na2C4H4O4), were evaluated in the presence of the ionic liquid (IL) 1-butyl-3-methylimidazolium bromide ([C4C1im]Br) as adjuvant. For this purpose, firstly, the binodal curves and the liquid-liquid equilibrium (LLE) data of the studied ABS were determined, at T = 298.15 K, by the addition of 5 wt% IL to investigate its effect on the two-phase formation. The tie-line lengths (TLL) were also addressed. To evaluate the extraction capacity of the studied ABS for biomolecules, the essential amino acid L-tryptophan (Trp) was used as a molecular probe. Thus, the partition coefficients of Trp, KTrp, were determined, at T = 298.15 K, in ABS with and without IL. The effects of salt, PEG molecular weight, and ABS composition on the partition coefficients of Trp were also investigated. It was found that the KTrp values are increased with increasing the salting-out strength of salts, PEG molecular weight, and the ABS composition. Moreover, in the studied ABS, by the addition of 5 wt% [C4C1im]Br into the ABS containing PEG 400, the KTrp values are increased, whereas, the opposite is observed for systems with PEG 4000. Finally, the experimental LLE and partition coefficients data are accurately correlated using the NRTL model.

Construction of a novel reversible aqueous biphasic system for water purification

A novel aqueous biphasic system (ABS) composed of acetonitrile and amine solution (MeCN + TEOA) has been constructed by CO2 (1 atm) gas flush process and applied for water purification. The formation process can be approached by various ways, including gas flush, salt addition and pH regulation. The usage of low cost materials in current system provided a feasible way in terms of large scale industrial applications. In this study, the influence factors of temperature (15 °C, 20 °C, 30 °C) and ratio distribution have been also discussed for the ABS formation, the results indicated that lower temperature is beneficial to current ABS formation. In addition, the tested system has been applied to estimation of the extraction efficiency towards the different metal ions. Nearly 100% metal ions were concentrated into bottom phase. All these attempts broaden the alternative materials of ABS construction and deepen the understanding of the mechanism of ABS formation, and demonstrated a practical model for ions extraction and water purification.

Aqueous biphasic systems comprising copolymers and cholinium-based salts or ionic liquids: Insights on the mechanisms responsible for their creation

Aqueous biphasic systems (ABS) formed by copolymers and ionic liquids (ILs) have demonstrated to be effective separation platforms, but there is still a gap on the complete understanding of the molecular-level mechanisms ruling the two-phase formation for this type of systems. This work addresses the determination of the liquid–liquid equilibrium of ABS composed of cholinium-based salts or cholinium-based ILs and the triblock copolymer Pluronic PE6200 (PL6200). It is demonstrated that PL6200 can form ABS with all investigated cholinium-based salts or ILs, contrarily to most poly(ethylene)glycol polymers, which is due to the presence of hydrophobic propylene oxide (PO) blocks. From the phase diagrams behavior and IL/salt anions properties, it is shown that the formation of ABS with cholinium-based salts is ruled by the anions polar surface and ability to be hydrated, whereas in systems comprising ILs van der Waals interactions between the copolymer and the IL cannot be discarded. The partition of a series of alkaloids in these systems, namely caffeine, nicotine, theophylline, and theobromine, was additionally appraised. It is shown that caffeine, theophylline, and theobromine preferentially migrate to the more hydrophobic PL6200-rich phase, and that their partition depends on the water content in the respective phase, being ruled by the phases’ hydrophobicity. On the other hand, nicotine, with the most prominent hydrophobic character amongst the studied alkaloids, preferentially migrates to the salt- or IL-rich phase, in which interactions occurring between this alkaloid and the IL/salt cannot be discarded. The ABS formed by cholinium dihydrogenphosphate is the most selective system identified to separate nicotine from the remaining alkaloids, giving some insights into their investigation as separation platforms for alkaloids from natural extracts.

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.

Protic ionic liquids as adjuvants to enhance extraction and separation performance of diverse polarity compounds in PEG-salt based aqueous biphasic system

This work addresses use of a set of 2-hydroxypropylammonium based protic ionic liquids (PILs) as adjuvants in the aqueous biphasic system (ABS) composed of polyethylene glycol, with molecular weight 2000 g/mol (PEG 2000) and potassium carbonate. The phase diagrams were determined at 25 °C for ABS without and with the addition of 5 wt% of PIL. Comparative analysis of solubility curves indicates that PILs influence liquid-liquid equilibria of PEG 2000-K2CO3 ABS by heightening the hydrophilicity of a PEG-rich phase in various degrees. The compositions of the phases (tie lines) were determined for the selected ABS mixture composition, 26 wt% of PEG 2000 + 10 wt% of K2CO3, without and with 5 wt% of PILs, that is further used for the separation studies. The distribution of PILs between two phases is mainly dependent on specific PEG-PIL interactions and on the PIL content in ABS mixture. The experimental results are supported by molecular simulations that contributed to a broader picture of underlying effects of PILs as adjuvants on ABS formation. The partition of four dye compounds, Remazol Brilliant Blue R (RBBR), Orange II (OII), Rhodamine B (RB) and Congo Red (CR), as probe molecules with different intrinsic properties, was investigated. Obtained results show that the addition of PILs can improve the extraction of hydrophilic and charged compounds as OII, RBBR and CR in PEG-rich phase. On the other hand, it promotes the extraction of hydrophobic and neutral solutes as RB in salt-rich phase. By the addition of the most hydrophilic 3-chloropropanoate based PIL in the PEG 2000-K2CO3 ABS 12 times higher separation factor for OII and RB was achieved.

Enhanced extraction of astaxanthin using aqueous biphasic systems composed of ionic liquids and potassium phosphate

Shrimp waste containing a substantial amount of valuable nutrients presents a challenge for food industry. In this work, extraction of astaxanthin from shrimp waste via aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and potassiumphosphate (K3PO4) was investigated. The influence of phosphonium- and ammonium-based ILs and temperature on the phase behavior and astaxanthin extraction was evaluated. The hydrogen-bond basicity of each IL studied shows a negative linear correlation with tie-line lengths of ABS and a positive linear correlation with extraction efficiency (EEAst). In general, lower temperature are favourable for astaxanthin extraction. Tributyloctylphosphonium bromide ([P4448]Br) resulted in the strongest ABS formation ability and bonding interactions between the anion and astaxanthin. Compared with organic solvents, [P4448]Br + K3PO4 ABS achieved higher EEAst of 93.08% at 308 K. The chemical properties provide the possibility of prescreening appropriate ILs for ABS formation and predicting the partition of a target molecule.

Understanding the role of the hydrogen bond donor of the deep eutectic solvents in the formation of the aqueous biphasic systems

Deep eutectic solvents (DES) have been proposed as phase-forming compounds of aqueous biphasic systems (ABS). However, due to DES nature and the high water content of the ABS, their nature and behavior remains controversial. To foster the understanding of DES-based ABS, the present work uses the relative hydrophilicity of the hydrogen bond donor (HBD) as a descriptor to clarify its role on ABS formation and phase properties. Dipotassium phosphate (K2HPO4)-based ABS phase diagrams composed of cholinium chloride ([N111(2OH)]Cl), as hydrogen bond acceptor (HBA), and several HBD (alcohols and sugars) were compared in molality units and the saturation solubility point for each binodal curve determined. The results here reported establish the HBD role as function of its relative hydrophilicity: very hydrophilic HBD act only as an adjuvant in the formation of ABS; HBD of intermediate hydrophilicity influence the ABS formation; while the most hydrophobic HBD tend to form organic-aqueous two-phase systems, where the HBA acts as an adjuvant to the system.