Acid Mine Drainage Precipitates from Mining Effluents as Adsorbents of Organic Pollutants for Water Treatment

Acid mine drainage (AMD) is one of the main environmental problems associated with mining activity, whether the mine is operational or abandoned. In this work, several precipitates from this mine drainage generated by the oxidation of sulfide minerals, when exposed to weathering, were used as adsorbents. Such AMD precipitates from abandoned Portuguese mines (AGO, AGO-1, CF, and V9) were compared with two raw materials from Morocco (ClayMA and pyrophyllite) in terms of their efficiency in wastewater treatment. Different analytical techniques, such as XRD diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N2 adsorption isotherms, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) were used to characterize these natural materials. The adsorption properties were studied by optimizing different experimental factors, such as type of adsorbent, adsorbent mass, and dye concentration by the Box–Behnken Design model, using methylene blue (MB) and crystal violet (CV) compounds as organic pollutants. The obtained kinetic data were examined using the pseudo-first and pseudo-second order equations, and the equilibrium adsorption data were studied using the Freundlich and Langmuir models. The adsorption behavior of the different adsorbents was perfectly fitted by the pseudo-second order kinetic model and the Langmuir isotherm. The most efficient adsorbent for both dyes was AGO-1 due to the presence of the cellulose molecules, with qm equal to 40.5 and 16.0 mg/g for CV and MB, respectively. This study confirms the possibility of employing AMD precipitates to adsorb organic pollutants in water, providing valuable information for developing future affordable solutions to reduce the wastes associated with mining activity

Saccharomyces cerevisiae oxidative response evaluation by cyclic voltammetry and gas chromatography−mass spectrometry

This study is focused on the evaluation of the impact of Saccharomyces cerevisiae metabolism in the profile of compounds with antioxidant capacity in a synthetic wine during fermentation. A bioanalytical pipeline, which allows for biological systems fingerprinting and sample classification by combining electrochemical features with biochemical background, is proposed. To achieve this objective, alcoholic fermentations of a minimal medium supplemented with phenolic acids were evaluated daily during 11 days, for electrochemical profile, phenolic acids, and the volatile fermentation fraction, using cyclic voltametry, high-performance liquid chromatography-diode array detection, and headspace/solid-phase microextraction/gas chromatography-mass spectrometry (target and nontarget approaches), respectively. It was found that acetic acid, 2-phenylethanol, and isoamyl acetate are compounds with a significative contribution for samples metabolic variability, and the electrochemical features demonstrated redox-potential changes throughout the alcoholic fermentations, showing at the end a similar pattern to normal wines. Moreover, S. cerevisiae had the capacity of producing chlorogenic acid in the supplemented medium fermentation from simple precursors present in the minimal medium.C.C.C. (SFRH/BD/46737/2008) gratefully acknowledges the Fundacao para a Ciencia e Tecnologia (FCT) for her Doctoral grant. This research was funded by the projects: "Open-Microbio (PTDC/BIO/69310/2006)-Framework for Computational Simulation of Cellular Communities during BioProcess Engineering" (FCT), "A Metrica do Vinho: Elucidar o Padrao Molecular Volatile Responsavel pelo aroma "Tipo-Vinho" Fundamental para a Definicao da Qualidade" (PTDC/AGR-ALI/121062/2010), and partially supported by CBMA, IBB, and ESB/UCP plurianual funds through the POS-Conheci-mento Program that includes FEDER funds

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Evaluating Cubic Plus Association Equation of State Predictive Capacities: A Study on the Transferability of the Hydroxyl Group Associative Parameters

To create a predictive method for an associative equation of state, the parameters of a specific associative group should be transferrable among molecules. The hydroxyl group, one of the most common associative groups, is a good starting point for this development. On the basis of a previous study where a modified version of the Cubic Plus Association (CPA) EoS was shown to present accurate results for alkanols with almost constant association parameters, this work addresses branched, secondary alcohols, 1,ω-alkanediols, and glycerol to evaluate how CPA can handle steric hindrances and the presence of more than one hydroxyl group. The pure component properties studied here are vapor pressure, saturated liquid density, saturated liquid isobaric heat capacity, and heat of vaporization. Some VLE, LLE, and GLE of binary systems are also analyzed, showing how the modifications affect the description of binary/multicomponent systems. Some systems containing petroleum fluids are also analyzed

Effect of a pH Gradient on the Protonation States of Cytochrome <i>c</i> Oxidase: A Continuum Electrostatics Study

Cytochrome <i>c</i> oxidase (C<i>c</i>O) couples the reduction of dioxygen to water with transmembrane proton pumping, which leads to the generation of an electrochemical gradient. In this study we analyze how one of the components of the electrochemical gradient, the difference in pH across the membrane, or ΔpH, influences the protonation states of residues in C<i>c</i>O. We modified our continuum electrostatics/Monte Carlo (CE/MC) method in order to include the ΔpH and applied it to the study of C<i>c</i>O, in what is, to our best knowledge, the first CE/MC study of C<i>c</i>O in the presence of a pH gradient. The inclusion of a transmembrane pH gradient allows for the identification of residues whose titration behavior depends on the pH on both sides of the membrane. Among the several residues with unusual titration profiles, three are well-known key residues in the proton transfer process of C<i>c</i>O: E286_I, Y288_I, and K362_I. All three residues have been previously identified as being critical for the catalytic or proton pumping functions of C<i>c</i>O. Our results suggest that when the pH gradient increases, these residues may be part of a regulatory mechanism to stem the proton flow

High-Pressure Biodiesel Density: Experimental Measurements, Correlation, and Cubic-Plus-Association Equation of State (CPA EoS) Modeling

Density is one of the most important biodiesel properties, because engine injection systems (pumps and injectors) must deliver an amount of fuel precisely adjusted to provide a proper combustion while minimizing greenhouse gas emissions. The pressure influence in fuel density has become particularly important with the increased use of modern common rail systems, where pressures can reach 250 MPa. Nevertheless, besides its importance, little attention has been given to high-pressure biodiesel densities. In fact, there are almost no reports in the literature about experimental high-pressure biodiesel density data. To overcome this lack of information, in this work, new experimental measurements, from 283 to 333 K and from atmospheric pressure to 45 MPa, were performed for methyl laurate, methyl myristate, and methyl oleate, for methyl biodiesels from palm, soybean, and rapeseed oils, and for three binary and one ternary mixture of these oils. Following previous works, where the cubic-plus-association equation of state (CPA EoS) was shown to be the most appropriate model to be applied to biodiesel production and purification processes, the new high-pressure experimental data reported here were also successfully predicted with the CPA EoS, with a maximum deviation of 2.5%. A discussion about the most appropriate CPA pure compound parameters for fatty acid methyl esters is also presented