Formation Of Aqueous Biphasic Systems Research Articles

Synthesis and characterization of analogues of glycine-betaine ionic liquids and their use in the formation of aqueous biphasic systems

A series of novel analogues of glycine-betaine ionic liquids (AGB-ILs), viz. 1-(4-ethoxy-4-oxobutyl)-1-methylpyrrolidin-1-ium, N,N,N-tri(n-butyl)(4-ethoxy-4-oxobutyl)-1-phosphonium and N,N,N-trialkyl(4-ethoxy-4-oxobutyl)-1-aminium cations with ethyl, n-propyl and n-butyl alkyl chains, combined with the bromide anion, have been synthesized and characterized. Their synthesis and characterization by spectroscopic methods and elemental analysis is here reported. These ILs were further characterized in what concerns their thermal properties and ecotoxicity against Allvibrio fischeri, and compared with the commercial tetra(n-butyl)ammonium and tetra(n-butyl)phosphonium bromide. The novel AGB-ILs described in this work have low melting points, below 100 °C, display high degradation temperatures (180–310 °C), and low toxicity as shown by being harmless or practically harmless towards the marine bacteria Allvibrio fischeri. Finally, the ability of the synthesized AGB-ILs to form aqueous biphasic systems with potassium citrate/citric acid (at pH 7) was evaluated, and the respective ternary phase diagrams were determined. It is shown that the increase of the cation alkyl chain length facilitates the creation of ABS, and that phosphonium-based ILs present a slightly better separation performance in presence of aqueous solutions of the citrate-based salt.

Chasing Aqueous Biphasic Systems from Simple Salts by Exploring the LiTFSI/LiCl/H2O Phase Diagram.

Aqueous biphasic systems (ABSs), in which two aqueous phases with different compositions coexist as separate liquids, were first reported more than a century ago with polymer solutions. Recent observations of ABS forming from concentrated mixtures of inorganic salts and ionic liquids raise the fundamental question of how “different” the components of such mixtures should be for a liquid–liquid phase separation to occur. Here we show that even two monovalent salts sharing a common cation (lithium) but with different anions, namely, LiCl and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), may result in the formation of ABSs over a wide range of compositions at room temperature. Using a combination of experimental techniques and molecular simulations, we analyze the coexistence diagram and the mechanism driving the phase separation, arising from the different anion sizes. The understanding and control of ABS may provide new avenues for aqueous-based battery systems.

Formation of Aqueous Biphasic Systems with an Ionic Liquid Induced by Metallic Salts: Nanoscopic Views from Molecular Dynamics Simulations.

The formation of aqueous biphasic systems (ABSs) based on aqueous ionic liquid (IL)/salt mixtures has been investigated via molecular dynamics simulations (with IL butyl-methyl-imidazolium triflate; salts NaCl, CsCl, SrCl2, and EuCl3). The analysis of ion distributions, solvation, and mutual interactions during the dynamics reveals the heterogeneity of all solutions due to ion segregation into mutually exclusive IL and salt domains, even in monophasic solutions ("ionic sociology"). Ion segregation and ABS formation are found to increase with (i) the salt content and (ii) the IL content, (iii) in the order Na+ < Sr2+ < Eu3+, and (iv) when the IL ion "polarity" is diminished, following experimental trends. The structuration of the solution is rationalized as a synergistic water transfer from the best donating ion pair (first hydration shell of hydrophobic moieties of IL ions) to the best accepting pair (M n+ and Cl- ions, beyond their first shell). In ABSs, the IL- and salt-containing phases are linked by a well-defined "interface" that decreases in width when MCl n becomes more hydrophilic and/or more concentrated. In the IL-rich phase of ABSs, the hydration of IL ions and their mutual interactions are shown to be similar to those displayed at aqueous interfaces.

Odd-even effect on the formation of aqueous biphasic systems formed by 1-alkyl-3-methylimidazolium chloride ionic liquids and salts.

This work provides a comprehensive evaluation of the effect of the cation alkyl side chain length of the 1-alkyl-3-methylimidazolium chloride series ([C n C1im]Cl, n = 2-14) of ionic liquids (ILs) on their capability to form aqueous biphasic systems (ABSs) with salts and self-aggregation derived properties. The liquid-liquid phase behavior of ternary systems composed of [C n C1im]Cl, water, and K3PO4 or K2CO3 and the respective Setschenow salting-out coefficients (ks ), a quantitative measure of the two-phase formation ability, were determined. An odd-even effect in the ks values along the number of methylene groups of the longest IL cation alkyl side chain was identified for the ABS formed by K2CO3, a weaker salting-out agent where the phenomenon is clearly identified. In general, cations with even alkyl side chains, being likely to display higher molar volumes, are more easily salted-out and thus more prone to undergo phase separation. The odd-even effect in the ks values is, however, more significant in ILs up to n = 6, where the nanostructuration/nanosegregation of ILs plays a less relevant role. Still, with the [C n C1im]Cl (n = 7-14) series of ILs, an odd-even effect was also identified in the ILs' ionization degree, molar conductivity, and conductivity at infinite dilution. In summary, it is shown here that the ILs' odd-even effect occurs in IL aqueous solutions and not just in neat ILs, an already well-established phenomenon occurring in a series of ILs' properties described as a result of the orientation of the terminal methyl groups to the imidazolium ring cation and consequent effect in the ILs' cohesive energy.

Thermodynamics investigation of phase behavior of deep eutectic solvents-polymer aqueous biphasic systems

Phase behavior including vapor-liquid and liquid-liquid equilibria of aqueous solutions of three deep eutectic solvents (DES), prepared by mixing of choline chloride as HBA, and urea, ethylene glycol and glycerol as HBD at a molar ratio of 1:2 (ChCl:2HBD), were investigated in the absence and presence of water soluble polymers polypropylene glycol400 (PPG400), polyethylene glycol400 (PEG400) and polyethylene glycol10000 (PEG10000) at different temperatures. Among all the DES/Polymer/H2O systems investigated in this work, only in the case of DES/PPG/H2O systems the aqueous biphasic system (ABS) is formed. Evidently, the ABS formation appeared to be controlled by the competition between the preferential hydration and hydrogen bonding interaction depending on the polymer and DES structures. Furthermore the LLE results for DES/PPG/H2O systems showed that the capability of DES for soluting-out of PPG in the aqueous solutions followed the order glyceline > ethaline > reline. In order to gain further insight regarding the DES properties which govern the preferential hydration in DES/PPG/H2O solutions, the ability of each DES component (hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD)) to form ABS with PPG was also evaluated. The results revealed that choline chloride as HBA and only glycerol as HBD could solute-out of PPG and undergo phase separation in the aqueous solutions. The equal water activity lines obtained from the isopiestic measurements for different DES/Polymer/H2O systems indicated a relationship between the vapor-liquid equiliria and liquid-liquid equiliria behavior of these systems. Finally, the effect of temperature, the polymer and DES structures on the equal water activity lines and also the binodal curve of the systems were also investigated and the results were discussed on the basis of the hydrogen bond interactions in these systems.

The capability of tetra alkyl ammonium bromides for aqueous biphasic systems formation with both polymers and electrolytes in aqueous solutions

It was found that the tetra alkyl ammonium halides can solute-out the water soluble polymers and solute out by electrolyte in aqueous solutions and form the aqueous biphasic systems (ABS). To investigate these new kinds of ABS, vapor – liquid equilibria (VLE), vapor – liquid - liquid equilibria (VLLE) and liquid – liquid equilibria (LLE) measurements were carried out for ternary systems containing tetra alkyl ammonium bromides (TAAB): tetra methyl ammonium bromide (TMAB), tetra ethyl ammonium bromide (TEAB), tetra propyl ammonium bromide (TPAB) and tetra butyl ammonium bromide (TBAB); electrolytes: NaCl, NaNO3, Na2CO3 and Na3Cit; and polymers: polypropylene glycol400 (PPG400) and polyethylene glycol400 (PEG400) at different temperatures. It was found that in these systems the soluting-out effect and then the tendency to ABS formation increases by increasing the difference between the hydrophilicity of two components. In the case of TAAB + polymer aqueous systems, the polymer is solute out by the more hydrophilic component TAAB and therefore ABS are formed for aqueous solutions containing PPG (which is more hydrophobic than PEG) and TMAB/TEMB (which are more hydrophilic than TPAB and TBAB). In these types of ABS, the soluting-out effects increase with an increase in temperature. On the other hand, in the case of TAAB + salt aqueous systems, the TAAB is solute out by salt which is the more hydrophilic than TAAB and therefore aqueous solutions containing (TBAB + NaNO3, Na2CO3 and Na3Cit), (TPAB and TEAB + Na2CO3 and Na3Cit) and (TMAB + Na2CO3) are undergoing phase separation and their soluting-out effects increase with decreasing temperature. The isopiestic measurements of the investigated systems show that the constant water activity lines of aqueous PPG + TAAB systems show the positive and the negative deviation from the semi-ideal behavior respectively in biphasic and monophasic area, but those of aqueous salt + TAAB systems show the negative deviation in both biphasic and monophasic area. However, the constant water activity lines of the systems with soluting-in effect, show the positive deviation from the semi-ideal behavior.

Evaluation of anion chain length impact on aqueous two phase systems formed by carboxylate anion functionalized ionic liquids

Abstract Aqueous biphasic systems (ABS) based on ionic liquids (ILs) are considered as promising separation and extraction media for replacing conventional extraction systems consisting of volatile organic solvents. In the present work, set of ILs consisting of tetrabutylammonium cation and carboxylate anions were synthesised and studied for their ability to form ABS in presence of strong salting-out agent K3PO4 at 298.15 K and atmospheric pressure. The influence of alkyl chain length of ILs’ anions on the phase splitting ability has been systematically investigated. Experimentally determined binodal curve data has been fitted to Merchuk’s equation and corresponding fitting parameters have also been determined. Further, selected ternary systems have been analysed for their extraction efficiencies for an amino acid, Tryptophan. Solvatochromic parameters of aqueous solutions of ILs have been determined to further scrutinize their influence on extraction efficiencies of studied ABS. The results indicated that phase behaviour and extraction efficiencies are governed by multiple factors prevailing at microscopic level like hydrophobicity, hydrogen bond accepting ability etc. The combination of suitable cation and anion entities of ILs, in turn, decides the dominant physical phenomenon and consequent phase behaviour and extraction aptitudes. In addition, this work addresses the effect of temperature on ABS formation and temperature dependence similar to that of ABS consisting of polymers and inorganic salts have been observed. This work gives insights into multifaceted effects of longer alkyl chains of IL’s anion on phase behaviour and extraction aptitudes of IL based ABS.

Hydrogen bond basicity of ionic liquids and molar entropy of hydration of salts as major descriptors in the formation of aqueous biphasic systems.

Aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and conventional salts have been largely investigated and successfully used in separation processes, for which the determination of the corresponding ternary phase diagrams is a prerequisite. However, due the large number of ILs that can be prepared and their high structural versatility, it is impossible to experimentally cover and characterize all possible combinations of ILs and salts that may form ABS. The development of tools for the prediction and design of IL-based ABS is thus a crucial requirement. Based on a large compilation of experimental data, a correlation describing the formation of IL-based ABS is shown here, based on the hydrogen-bonding interaction energies of ILs (EHB) obtained by the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) and the molar entropy of hydration of the salt ions. The ability of the proposed model to predict the formation of novel IL-based ABS is further ascertained.

Vapor Pressure Osmometry, Volumetry, and Compressibility Properties for Solutions of Several Imidazolium Based Ionic Liquids in (Glycine + Water) Solutions

In this study, the effect of glycine on the thermodynamic properties of aqueous solutions containing ionic liquids 1-butyl-3-methylimidazolium chloride, [C4mim]Cl, 1-hexyl-3-methylimidazolium chloride, [C6mim]Cl, 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [C4mim][CF3SO3], has been studied. For this purpose, first with help of the vapor pressure osmometery (VPO) method the water activity measurements have been performed on the ternary aqueous systems of (glycine + [C4mim]Cl, [C6mim]Cl, and [C4mim][CF3SO3]) at T = 308.15 K. The influence of the IL nature on the vapor–liquid equilibria behavior of the investigated systems has been studied. The VPO measurements of these solutions show that due to the unfavorable IL-glycine interactions, the negative deviations from the semi-ideal state and in conclude the soluting-out effects have been observed in these solutions. The soluting-out phenomena appears by aqueous biphasic system formation in the case of aqueous [C4mim][CF3SO3] + glycine system and pr...

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.

Simultaneous extraction of pesticides of different polarity applying aqueous biphasic systems based on ionic liquids

In this paper we report a simultaneous one-step extraction of five pesticides (acetamiprid, imidaclopride, simazine, linuron and tebufenozide) of different polarity using aqueous biphasic system based on 1-butyl-3(methyl or ethyl) substituted imidazolium or pyrrolidinium ionic liquids with bromide or dicyanamide anion and potassium carbonate as a salting-out agent. Experimentally data obtained for the ternary system {ionic liquid+K2CO3+H2O} were fitted and correlated by Merchuk equation with satisfactory high correlation factor. The effect of the cation alkyl chain length and the variation of anions of the ionic liquid on the aqueous biphasic system formation and the efficiency of pesticide extraction were investigated. Complete extraction of all studied pesticides was obtained applying aqueous biphasic system based on 1-butyl-3-ethyl imidazolium dicyanamide. It was shown that simultaneous extraction of the different polarity pesticides is achieved in a single-step procedure applying properly tailored ionic liquids in the aqueous biphasic system formulation. In order to explain excellent extraction of the polar pesticides in the studied aqueous biphasic systems, molecular dynamics was applied and the binding energies and non-covalent interactions were calculated. It was found that 1-butyl-3-ethyl imidazolium dicyanamide achieves the strongest interactions with the polar pesticides (acetamiprid and imidaclopride) leading to the highest partition coefficients. It was shown that combination of experimental and computational approach can be successfully applied for the selection and design of suitable ionic liquids for efficient extraction of various polarity pesticides using simple aqueous biphasic ionic liquid based systems.

Thermodynamic investigations of fullerene-polyglycerol nanostructure in aqueous solutions

In this work, for the first time, various thermodynamic investigations were performed on the aqueous solutions of fullerene-polyglycerol nanostructure (FPG). The precise vapor pressure osmometry method was used to determine water activities and vapor pressures of binary FPG aqueous solutions at T = 308.15 K. Volumetric and compressibility behavior of FPG aqueous solutions were studied by precise measuring of density and sound velocity data at different temperatures. Different infinite dilution apparent specific properties of FPG in water were obtained. The potential of a ternary system composed of FPG, salt and water, for the formation of aqueous biphasic systems (ABS) was evaluated. It was found that, FPG – sodium citrate aqueous system can form ABS above critical concentrations, so the binodal curves at different temperatures were determined. This work can be the starting point for the production of nanomaterial – based ABS which may open a new window towards more advantageous and efficient separation processes.

Evaluation of the Capability of Ionic Liquid-Amino Acid Aqueous Systems for the Formation of Aqueous Biphasic Systems and Their Applications in Extraction.

To obtain further experimental evidence for a better understanding of the molecular mechanisms responsible for the soluting-out effect phenomena in ternary systems composed of an ionic liquid (IL), amino acid, and water, systematic studies on the vapor-liquid, liquid-liquid, and solid-liquid equilibrium behavior of aqueous solutions of several ILs were carried out in the presence of a range of amino acids. Water activities for binary and ternary aqueous solutions containing 1-butyl-3-methylimidazolium chloride, [C4mim]Cl, 1-hexyl-3-methylimidazolium chloride, [C6mim]Cl, 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [C4mim][CF3SO3], l-Ser, Gly, Ala, and l-Pro were measured using both vapor pressure osmometry and isopiestic methods. All of the ternary IL + amino acid + water systems show negative deviations from semi-ideal behavior and therefore soluting-out effects have been observed in these systems. In the case of the [C4mim][CF3SO3] + amino acids aqueous systems, the IL is soluted-out by the amino acids and the soluting-out effect appears by aqueous biphasic system formation. For these systems, the phase diagram and partition coefficient of caffeine were measured at 298.15 K. However, for the [C4mim]Cl and [C6mim]Cl containing systems, the amino acids are soluted-out by the ILs and the soluting-out effect appears by precipitation of the amino acids from the solution, and the solubilities of the amino acids in the aqueous solutions decrease in the presence of [C4mim]Cl and [C6mim]Cl.

Aqueous biphasic system formation using 1-alkyl-3-ethylimidazolium bromide ionic liquids as new extractants

In this work three 1-alkyl-3-ethylimidazolium bromide ionic liquids (alkyl=ethyl, hexyl and octyl) were synthesized applying both, conventional and microwave assisted synthetic paths. The phase diagrams for aqueous solutions of 1-alkyl-3-ethylimidazolium bromide ionic liquids as novel extractants combined with phosphate-based salts are reported and discussed in terms of aqueous biphasic system (ABS) formation. Merchuk equation was applied in order to correlate the experimental binodal data. The liquid⿿liquid equilibrium data (tie-line compositions and tie-line length) were also experimentally determined by a gravimetric method. The influence of the alkyl chain length on ABS formation ability was investigated. It was found that ability to form ABS increases with the increase of the alkyl chain length on the imidazolium cation. Also, it was found that ionic liquids with ethyl group in the N-3 position better form ABS compared to those with methyl substituent. This was discussed in terms of increasing ionic liquid hydrophobicity and poor affinity for water. In order to better understand the impact of the alkyl side chain of the imidazolium ion and the efficiency of ABS formation, computer simulations were performed using investigated ionic liquids with the ethyl group in the position N-3 of the cation and different alkyl substituents in the position N-1. Also, extraction of selected organic dyes was performed to demonstrate application of studied ionic liquids as novel extractants.

Investigation of carbohydrates as non-charged, non-toxic and renewable soluting-out agent for polymer based aqueous biphasic systems implementation

Abstract In order to obtain new insights into the molecular-level mechanisms behind the polymer based aqueous biphasic systems (ABS) formation, phase equilibria including both liquid–liquid and vapor–liquid equilibria of different aqueous polymer–carbohydrate systems was deeply scrutinized in this work. For this purpose, the relative ability of a large range of mono-, di- and trisaccharides, as well as polyols to form ABS with different water soluble polymers PPG400, PPG725, PEG400, PEG4000 and PEG10000 was investigated at different temperatures. It was found that, the ABS formation seems to be controlled by the interplay of the relative strength of the carbohydrate–water, polymer–water and carbohydrate–polymer interactions. In the case of aqueous PPG + carbohydrates systems, because of the unfavorable PPG-carbohydrate interactions, the solutes exclude themselves from the vicinity of each other and therefore ABS are entropically formed when PPG and carbohydrate are mixed above a given concentration in an aqueous media. These systems show the negative deviation from the semi-ideal behavior. By increasing temperature and PPG molecular weight (PPG-water interactions become weaker) and increasing hydrophilicity of the carbohydrate (stronger carbohydrate–water interactions) the immiscibility region increases. However, in the case of PEG + carbohydrate aqueous systems which not capable of inducing phase separation, because of the favorable PEG-carbohydrate interactions, the interaction of each solute with water molecules becomes weaker in the presence of the other solute. Therefore the vapor–liquid equilibria behavior of these systems shows the positive deviations from the semi-ideal behavior. By increasing the PEG molar mass as well as the hydrophobicity of carbohydrate, the carbohydrate-PEG interaction increases and then the positive deviations from the semi-ideal behavior increase.

Are Aqueous Biphasic Systems Composed of Deep Eutectic Solvents Ternary or Quaternary Systems?

Deep eutectic solvents (DES) have emerged in the past few years as a new class of solvents with promising applications in several fields. In the present work, the application of DES (formed by binary mixtures of cholinium chloride and carboxylic acids or urea) as phase-forming components of aqueous biphasic systems (ABS) is investigated. The mechanisms associated with the phases demixing of ABS composed of DES, as well as the DES stability in aqueous solutions, are investigated to address the critical question whether DES-based ABS are in fact ternary or quaternary mixtures. It is shown that the DES integrity is destroyed in ABS by the disruption of the hydrogen-bonding interactions of the complex (a result of the isolated components preferential solvation by water), and as confirmed by a nonstoichiometric partition of the DES components between the coexisting phases. As a result, there are no “real” DES-based ABS; instead, there is the formation of ABS composed of four components, where the carboxylic ac...

A critical assessment of the mechanisms governing the formation of aqueous biphasic systems composed of protic ionic liquids and polyethylene glycol

An extensive study on the formation of aqueous biphasic systems (ABS) using aqueous solutions of protic ionic liquids (PILs) and polyethylene glycol (PEG) was performed in order to understand the mechanisms underlying the phase separation. Aqueous solutions of PEG polymers with different molecular weights (600, 1000, 2000, and 3400 g mol-1) and several N-alkyl-, dialkyl-, and trialkyl-ammonium salts of acetate, propanoate, butanoate, hexanoate and octanoate were prepared and their ability to form ABS at several temperatures assessed. The ternary liquid-liquid phase diagrams were determined at several temperatures, as well as binary PIL (or salt)-PEG-1000 and salt-water solubility data to better clarify the mechanisms responsible for the phase separation. All data gathered indicate that the formation of PEG-PIL-based ABS is mainly governed by the PIL-PEG mutual interactions, where PILs with a higher solubility in the polymer exhibit a lower aptitude to form ABS displaying thus a smaller biphasic region, for which a direct correlation was identified. The effects of the molecular weight and temperature of the polymer were also addressed. The increase of the PEG hydrophobicity or molecular weight favours the phase separation, whereas the effect of temperature was found to be more complex and dependent on the nature of the PIL, with an increase or decrease of the biphasic regime with an increase in temperature.

Aqueous biphasic systems composed of ionic liquids and polypropylene glycol: insights into their liquid-liquid demixing mechanisms.

Novel ternary phase diagrams of aqueous biphasic systems (ABSs) composed of polypropylene glycol with an average molecular weight of 400 g mol(-1) (PPG-400) and a vast number of ionic liquids (ILs) were determined. The large array of selected ILs allowed us to evaluate their tuneable structural features, namely the effect of the anion nature, cation core and cation alkyl side chain length on the phase behaviour. Additional evidence on the molecular-level mechanisms which rule the phase splitting was obtained by (1)H NMR (Nuclear Magnetic Resonance) spectroscopy and by COSMO-RS (Conductor-like Screening Model for Real Solvents). Some systems, for which the IL-PPG-400 pairs are completely miscible, revealed to be of type "0". All data collected suggest that the formation of PPG-IL-based ABSs is controlled by the interactions established between the IL and PPG, contrarily to previous reports where a "salting-out" phenomenon exerted by the IL over the polymer in aqueous media was proposed as the dominant effect in ABS formation. The influence of temperature on the liquid-liquid demixing was also evaluated. In general, an increase in temperature favours the formation of an ABS in agreement with the lower critical solution temperature (LCST) phase behaviour usually observed in polymer-IL binary mixtures. Partition results of a dye (chloroanilic acid, in its neutral form) further confirm the possibility of tailoring the phases' polarities of IL-PPG-based ABSs.

Effect of Cations in Ionic Liquids on the Extraction Characteristics of 1,3-Propanediol by Ionic Liquid-based Aqueous Biphasic Systems

Separation of 1,3-propanediol (1,3-PDO) from fermentation broths becomes a bottleneck in biological production due to its high hydrophilicity and low concentration. Aqueous biphasic systems (ABS) composed of piperidinium-based ionic liquids (ILs) and K2HPO4 could be an alternative to extract 1,3-propanediol from fermentation broths. In this study, the ability of piperidinium-based ILs to form ABS with aqueous K2HPO4 solution was investigated. Binodal curves and tie-lines and tie-line length were evaluated by three parameter equation and mass balances for each components in top and bottom phases. The piperidinium-based ILs was effective on promoting ABS formation in the presence of K2HPO4 and the forming ability of ABS increased with alkyl chain length of cations in ILs. The volume ratio to top and bottom phase decreased with K2HPO4 concentration and alkyl chain length of cations in ILs. However, above 20 wt % of K2HPO4, the partitioning of water into top phase is dominant, resulting in low phase volume ratio. The extraction efficiency of 1,3-PDO reached up to 95%. It is expected that piperidinium IL-based ABS is a prospective extraction media for the separation and concentration of 1,3-PDO.

Controlling the Formation of Ionic-Liquid-based Aqueous Biphasic Systems by Changing the Hydrogen-Bonding Ability of Polyethylene Glycol End Groups.

The formation of aqueous biphasic systems (ABS) when mixing aqueous solutions of polyethylene glycol (PEG) and an ionic liquid (IL) can be controlled by modifying the hydrogen-bond-donating/-accepting ability of the polymer end groups. It is shown that the miscibility/immiscibility in these systems stems from both the solvation of the ether groups in the oxygen chain and the ability of the PEG terminal groups to preferably hydrogen bond with water or the anion of the salt. The removal of even one hydrogen bond in PEG can noticeably affect the phase behavior, especially in the region of the phase diagram in which all the ethylene oxide (EO) units of the polymeric chain are completely solvated. In this region, removing or weakening the hydrogen-bond-donating ability of PEG results in greater immiscibility, and thus, in a higher ability to form ABS, as a result of the much weaker interactions between the IL anion and the PEG end groups.