Publications

Abstract Ionic liquids (ILs) are a novel class of chemical compounds with interesting properties that are driving a lot of research in several fields. For ionic liquids to be effectively used as solvents in liquid-liquid extractions, the knowledge of the mutual solubilities between ILs and the second liquid phase is fundamental. Furthermore, while ILs cannot volatilise and lead to air pollution, even the most hydrophobic ones present some miscibility with water posturing secondary aquatic environmental risks. Despite the importance of the ILs and water systems, there are few extensive reports on their phase equilibria. The aim of this work is to discuss and understand the mutual solubilities of water and imidazolium-based ILs. The results indicate that these mutual solubilities are primarily defined by the anion followed by the cation alkyl side chain length. It was also found that the solubility of the studied ILs in water is more dependent on the ILs structural modifications than the solubility of water in those ILs. The substitution of the most acidic hydrogen in the imidazolium cation by a methyl group leads to different behaviours in both rich-phases, where the solubility of water in ILs showed to be more hydrogen bonding dependent. From the solubility results it can be concluded that the hydrophobicity of the anions increases in the order [BF4](-) < [CH3(C2H4O)(2)SO4](-) < [C(CN)(3)](-) < [PF6](-) < [N(SO2CF3)(2)](-) while the hydrophobicity of the cations increases, as expected, with the alkyl chain length increase.

Abstract This letter reports the importance and advantages of the constraints in the Redlich-Peterson isotherm exponent. (C) 2007 Published by Elsevier B.V..

Abstract The standard (p degrees = 0.1 MPa) molar energies of combustion in oxygen, at T= 298.15 K, of two crystalline bis(N,N-diethylthioureas) R(CONHCSNEt2)(2): pyridine-2,6-dicarbonyl-bis(N,N-diethylthiourea), R = pyridyl. abbreviated as (bis-py-DETU). and adipoyl-dicarbonyl-bis(N,N-diethylthiourea), R = (CH2)(4), abbreviated as (bis-ad-DETU). were measured by rotating bomb calorimetry so, the standard molar enthalpies of formation of both compounds, in their crystalline phase, were derived. [GRAPHICS] Furthermore, the energetics of the title compounds were studied by means of density functional theory Calculations at the B3LYP/6-311G(dp) level of theory.

Abstract The standard (p = 0.1 MPa) molar enthalpies of combustion in oxygen of five N-thenoylthiocarbamic-O-n-alkylesters, C4H3SCO-NHCSOR, R = Et (Httee), n-Pr (Httpe), n-Bu (Httbe), n-Pen (Httpene), and n-Hex (Htthe), were measured, at T = 298.15 K, by rotating-bomb calorimetry. The standard molar enthalpies of sublimation of these compounds were determined using Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the title compounds, in their crystalline and gaseous phases, respectively. Furthermore, differential scanning calorimetry was applied in order to measure the temperatures and enthalpies of fusion for all compounds. Entropies of fusion were derived from the experimental results and the odd and even effect was found. [GRAPHICS]

Abstract Batch processes were carried out for the photocatalytic degradation of Acid Red 151 from its aqueous solution using ZnO catalyst at different initial dye concentrations. The process was found to be diffusion controlled for the first 15-20 minutes (before irradiation) with an average diffusion coefficient of 6.759 × 10 -6 cm 2/s. The photocatalytic degradation kinetics was analyzed using the first order, second order and Langmuir-Hinshelwood expressions by linear and non-linear method. The four types of second order kinetic and Langmuir-Hinshelwood kinetic models were also discussed. Non-linear method is a better way to obtain the kinetic parameters. The photocatalytic degradation process was found to follow first order kinetics at lower substrate concentrations and second order kinetics at higher substrate concentrations. © 2007 Science &amp; Technology Network, Inc.

Abstract A new mini-bomb combustion calorimeter designed at the University of Lund was improved, installed and calibrated at the University of Porto. This calorimeter is suitable for high precision combustion calorimetry with samples of mass about (10 to 40) mg. The energy equivalent of the calorimeter, = (1946.45 +/- 0.11) J center dot K-1, was obtained from 15 independent calibration experiments with benzoic acid SRM 39i. Anthracene, succinic acid, acetanilide, and 1,2,4-triazole were used as test compounds, with excellent agreement with the literature values. [GRAPHICS]

Abstract This letter explains the appropriate way to calculate the parameters in pseudo first and second order kinetics, Langmuir and Freundlich isotherm.