Ana B. Pereiro

Ionic liquid-based aqueous biphasic system for lipase extraction

A successful process to extract lipolytic enzymes based on an aqueous biphasic system (ABS), which uses both ionic liquids (ILs) and a high charge-density inorganic salt (K2CO3), is proposed in this work. The activity of a model Thermomyces lanuginosuslipase (TlL) in some of the most common hydrophilic ILs, based on the 1-alkyl-3-methylimidazolium cation, combined with chloride, alkylsulfate, alkylsulfonate and acetate, was investigated. Several operating conditions influencing lipase activity and ABS formation were investigated. Parameters such as temperature, pH, deactivation kinetics and water content were evaluated in order to propose a viable extraction process. A deeper analysis in terms of enzyme deactivation kinetics was carried out, and the data were modelled through a series-type deactivation equation. ATR-FTIR studies aimed at identifying the TlL structure in selected ILs have also provided an insight into the enzyme deactivation behaviour.

Inorganic salts in purely ionic liquid media: the development of High Ionicity Ionic Liquids (HIILs).

This work explores the possibility of increasing the ionicity of ionic liquids via the solubilization of inorganic salts in their midst. The resulting purely ionic media-distinct ionic liquid plus inorganic salt mixtures-are liquid in an extensive concentration range and can be aptly denominated High Ionicity Ionic Liquids (HIILs).

HMImPF6 ionic liquid that separates the azeotropic mixture ethanol + heptane

1-Hexyl-3-methylimidazolium hexafluorophosphate (HMImPF6) is suitable for use as the solvent in the petrochemical extraction process for the removal of heptane from its azeotropic mixture with ethanol. The experimental determination of the liquid–liquid equilibrium (LLE) for the ternary system heptane + ethanol + HMImPF6 at 298.15 K was carried out. The solute distribution ratio and the selectivity of the HMImPF6 have been determined from the tie-line data. A comparative study has been made in terms of selectivity and solute distribution data with other ionic liquids. The NRTL equation was verified to accurately correlate the experimental data.

Deep eutectic solvents as extraction media for azeotropic mixtures

The separation of azeotropic mixtures is an “old” engineering problem that cannot be solved by simple distillation processes. One of the current ways to overcome this problem is to use other types of processes, such as extractive/azeotropic distillation or liquid–liquid extraction, where entrainers or extraction solvents are applied. Liquid–liquid extraction processes have been emerging as appealing alternatives because they do not require high amounts of energy, volatile organic compounds or high pressures. In this work, deep eutectic solvents (DES) are tested as extraction solvents in the liquid–liquid separation of azeotropic mixtures. For this study three different DES, all based on choline chloride, were used for the liquid–liquid separation of an azeotropic mixture of heptane + ethanol at 25 °C. The feasibility of DES as extraction solvents was assessed by the determination of their selectivities and distribution coefficients, and compared with the literature. The data obtained show that DES surpass the performance of existing extraction solvents, leading to an increase in efficiency and a reduction in energy consumption of the overall process.

Impact of ionic liquids on extreme microbial biotypes from soil

This work aims at identifying, amongst extreme soil biotypes at locations of high salinity and high hydrocarbon load, microbial strains able to survive short or long-term exposure to the presence of selected ionic liquids. We have evaluated the impact of ionic liquids on the diversity of the soil microbiota to identify which microbial strains have higher survival rates towards ionic liquids, and consequently those which might possibly play a major role in their biotic fate. To the best of our knowledge, this is the first study of this kind. Soils, from a region in Portugal (Aveiro) were sampled and the bacterial and fungal strains able to survive after exposure to high concentrations of selected ionic liquids were isolated and further characterised. We have mainly focused on two types of cations: imidazolium – the most commonly used; and cholinium – generally perceived as benign. The surviving microbial strains were isolated and taxonomically identified, and the ionic liquid degradation was analysed during their cultivation. The continuing exposure of the microbial strains to petroleum hydrocarbons is likely to be the basis for their acquired resistance to some imidazolium salts; also, the higher capacity of fungi – compared to bacteria – to grow, even during their exposure to these liquid salts, became evident in this study.

On the Formation of a Third, Nanostructured Domain in Ionic Liquids

The study of solid-fluid transitions in fluorinated ionic liquids using differential scanning calorimetry, rheology, and molecular modeling techniques is an essential step toward the understanding of their dynamics and the thermodynamics and the development of potential applications. Two fluorinated ionic liquids were studied: 1-hexyl-3-methylimidazolium perfluorobutanesulfonate, HMIm(PFBu)SO3, and tetrabutylammonium perfluorobutanesulfonate, NB4(PFBu)SO3. The experimental calorimetric and rheological data were analyzed taking into account the possible mesoscale structure of the two fluorinated ionic liquids. The simulation results indicate the possible formation of three nanosegregated domains-polar, nonpolar, and fluorous-that may have a profound impact on ionic liquid research. In the case of HMIm (PFBu)SO3 the three types of mesoscopic domains can act as interchangeable jigsaw pieces enabling the formation of multiple types of crystals and inducing the observed calorimetry and rheological trends.

Purification of hexane with effective extraction using ionic liquid as solvent

The separation of hexane and ethanol is valuable but difficult due to the formation of an azeotropic mixture. This work demonstrates the ability of the ionic liquid (IL) 1-butyl-3-methylimidazolium methyl sulfate [BMIM][MeSO4] to act as an extraction solvent in petrochemical processes for the removal of hexane from its mixture with ethanol. Knowledge of the phase behavior of the system is key in order to optimize the separation process. For this reason, the experimental liquid–liquid equilibrium (LLE) for the ternary system hexane + ethanol + [BMIM][MeSO4] is investigated at 298.15 K. The separation sequence of the extraction process is checked by using conventional software for simulation. Experimental data are obtained in a laboratory-scale packed column extraction system for the separation of this azeotropic mixture by using [BMIM][MeSO4]. It is concluded that this IL has the highest extraction efficiency.

A thermophysical and structural characterization of ionic liquids with alkyl and perfluoroalkyl side chains

This work represents an essential step towards the understanding of the dynamics and thermodynamic characteristics of a novel family of ionic liquids, namely fluorinated ionic liquids based on the combination of 1-alkyl-3-methylimidazolium cations with perfluoroalkylsulfonates or perfluoroalkylcarboxylates anions. The so far scarce information about these fluids constitutes a limiting factor for their potential applications. In this work, we provide detailed evidence on the influence of hydrogenated and fluorinated alkyl chain lengths in the final characteristics of the fluorinated ionic liquids. Different properties, namely, melting point, decomposition temperature, density, dynamic viscosity, ionic conductivity and refractive index, were determined and the experimental results were discussed taking into account the influence of the length of the hydrogenated and fluorinated alkyl chains. Molecular dynamic simulations were also performed to study the nanoscale structure of these novel compounds.

Cholinium-based ionic liquids with pharmaceutically active anions

Novel ionic liquids (ILs) containing cholinium as a benign cation combined with anions based on five active pharmaceutical ingredients (APIs), namely, nalidixic acid, niflumic acid, 4-amino-salicylic acid, pyrazinoic acid and picolinic acid, were prepared via a simple and sustainable two-step anion exchange reaction. The solubility of the prepared pharmaceutically active ILs (API-ILs) in both water and simulated biological fluids at 25 °C and 37 °C, as well as the solubility of the parent APIs, were measured. Further, in vitro cytotoxicity levels for both cholinium-based API-ILs and parent APIs were established using two different human cells lines, namely Caco-2 colon carcinoma cells and HepG2 hepatocellular carcinoma cells. Herein, the dual nature of ILs is exploited by combining the cheap, available and essential nutrient cholinium cation with pharmaceutically active anions, upgrading the chemical, physical and biopharmaceutical properties, particularly melting point, aqueous solubility and the potential to penetrate cell membranes of the parent APIs, without impair their cytotoxicity response which prompt opportunities for creating further advances in pharmaceutical challenges.

Aggregation Behavior and Total Miscibility of Fluorinated Ionic Liquids in Water

In this work, novel and nontoxic fluorinated ionic liquids (FILs) that are totally miscible in water and could be used in biological applications, where fluorocarbon compounds present a handicap because their aqueous solubility (water and biological fluids) is in most cases too low, have been investigated. The self-aggregation behavior of perfluorosulfonate-functionalized ionic liquids in aqueous solutions has been characterized using conductometric titration, isothermal titration calorimetry (ITC), surface tension measurements, dynamic light scattering (DLS), viscosity and density measurements, and transmission electron microscopy (TEM). Aggregation and interfacial parameters have been computed by conductimetry, calorimetry, and surface tension measurements in order to study various thermodynamic and surface properties that demonstrate that the aggregation process is entropy-driven and that the aggregation process is less spontaneous than the adsorption process. The novel perfluorosulfonate-functionalized ILs studied in this work show improved surface activity and aggregation behavior, forming distinct self-assembled structures.