Ana Rodríguez

Mixing properties of (methanol, ethanol, or 1-propanol) with (n-pentane, n-hexane, n-heptane and n-octane) at 298.15 K

In this work, we present experimental values of the density, refractive index, speed of sound, and dynamic viscosity of the binary mixtures (methanol, ethanol or 1-propanol) with (n-pentane, n-hexane, n-heptane, and n-octane) at 298.15 K and atmospheric pressure, as a function of the molar fraction. From the experimental values, the corresponding excess and deviation values were computed (excess molar volumes, changes of refractive index on mixing, changes of isentropic compressibility and dynamic viscosity deviations), variable-degree polynomials being fitted to the results. Different methods were applied in order to estimate values of these physical properties, in good agreement with experiment. The binodal tie lines for each methanol + alkane binary mixture at different temperatures were determined by the measurement of physical properties and application of the corresponding fitting polynomials. UNIFAC-Dortmund group contribution method was applied to predict these liquid-liquid equilibria.

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.

Binary mixture properties of diethyl ether with alcohols and alkanes from 288.15 K to 298.15 K

Abstract Density, refractive index and speed of sound of the binary mixtures (diethyl ether+methanol, or ethanol, or n-hexane, or n-heptane) from 288.15 K to 298.15 K and atmospheric pressure, have been measured over the whole composition range. Excess molar volumes, changes of refractive index on mixing and excess isentropic compressibilities for the binary systems were calculated and fitted to Redlich–Kisters equation to estimate the fitting parameters and the root mean square deviations between calculated and experimental data. Values of density and refractive index were evaluated and compared by different methods. Excess partial molar volumes and those corresponding to the infinite dilution condition are also calculated.

On the double role of surfactants as microalga cell lysis agents and antioxidants extractants

An integrated process based on the concomitant role of non-ionic surfactants as cell disrupters and organic extractants of intracellular antioxidants is proposed for the first time in this work. The lytic effect of two common families of surfactants on the cell walls of the microalga Tetraselmis suecica has been initially evaluated. The antioxidant extraction based on aqueous two-phase systems (ATPS) was proposed using different potential salting out agents such as sodium inorganic and organic salts in aqueous solutions of the selected surfactants. The extraction efficiency was ascertained for the most representative biomolecules previously detected in this microalga: α-tocopherol, β-carotene and gallic acid. The viability of the process was checked in real lyophilized microalga samples, yielding higher antioxidant activity than that provided by an ultrasound-based conventional method.

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.

On the hunt for truly biocompatible ionic liquids for lipase-catalyzed reactions

One of the challenges in the field of biocatalysis is the search for efficient reaction media avoiding enzyme deactivation. This work shows for the first time that water + hydrophilic ionic liquids mixtures enhance (up to 50%) the enzymatic activity of lipases, opening new opportunities for enzyme extraction and biocatalysis.

Novel physico-biological treatment for the remediation of textile dyes-containing industrial effluents

In this work, a novel remediation strategy consisting of a sequential biological and physical process is proposed to remove dyes from a textile polluted effluent. The decolorization ability of Anoxybacillus flavithermus in an aqueous effluent containing two representative textile finishing dyes (Reactive Black 5 and Acid Black 48, as di-azo and antraquinone class, respectively) was proved. The decolorization efficiency for a mixture of both dyes reached almost 60% in less than 12h, which points out the suitability of the selected microorganism. In a sequential stage, an aqueous biphasic system consisting of non-ionic surfactants and a potassium-based organic salt, acting as the salting out agent, was investigated. The phase segregation potential of the selected salts was evaluated in the light of different thermodynamic models, and remediation levels higher than 99% were reached.

Thermodynamic behaviour of mixtures containing methyl acetate, methanol, and 1-butanol at 298.15 K: application of the ERAS model

Abstract Excess molar volumes, and changes of refractive indices, of the ternary mixture methyl acetate+methanol+1-butanol, and the binary mixtures methyl acetate+1-butanol, and methanol+1-butanol have been evaluated from density, and refractive indices measurements at 298.15 K, and 1 atm. These derived properties of binary, and ternary mixtures were fitted to Redlich–Kister, and Cibulka type equations, respectively. The ERAS model interaction parameters of the binary systems contained in the ternary mixture were computed, the obtained results showing good accuracy. The high polar/associative behaviour of the mixtures should be the cause of high deviations in ternary excess prediction. The obtained results suggest the convenience of extending the model to multicomponent polar/associative mixtures in order to take into account all binary polar effects, and higher order polar effects in the mixtures.

Structural–functional evaluation of ionic liquid libraries for the design of co-solvents in lipase-catalysed reactions

Using ionic liquids as co-solvents may improve reaction media in enzyme-based biotechnological processes. To establish new conditions, large libraries need to be screened for bio-compatibility and protein stabilisation. Using a lipase model, we herein describe a combination of methods leading to an expedited evaluation of 61 different solvent compositions.

Ionic liquids improve the anticorrosion performance of Zn-rich coatings

In this work, the suitability of the ionic liquid 1-ethyl-3-methyl imidazolium ethylsulfate (C2C1imC2SO4) for improving the anticorrosive behaviour of zinc rich paints (ZRP) has been demonstrated. The electrochemical performance of the coating has been evaluated by means of electrochemical impedance spectroscopy. These data allowed validating the use of the ionic liquid to measure the water diffusivity during inward and outward processes. The ionic liquid seems to play a positive role in the cathodic protection provided by the ZRP, as concluded from the current density and open circuit potential values. The observed improvement of the cathodic protection was attributed to the ionic liquid, whose presence was confirmed through surface characterization techniques such as FTIR, SEM, EDX and XRF.