Vibrational spectroscopic characterization of the arsenate mineral barahonaite: Implications for the molecular structure

The mineral barahonaite is in all probability a member of the smolianinovite group. The mineral is an arsenate mineral formed as a secondary mineral in the oxidized zone of sulphide deposits. We have studied the barahonaite mineral using a combination of Raman and infrared spectroscopy. The mineral is characterized by a series of Raman bands at 863 cm−1 with low wavenumber shoulders at 802 and 828 cm−1. These bands are assigned to the arsenate and hydrogen arsenate stretching vibrations. The infrared spectrum shows a broad spectral profile. Two Raman bands at 506 and 529 cm−1 are assigned to the triply degenerate arsenate bending vibration (F 2, ν4), and the Raman bands at 325, 360, and 399 cm−1 are attributed to the arsenate ν2 bending vibration. Raman and infrared bands in the 2500–3800 cm−1 spectral range are assigned to water and hydroxyl stretching vibrations. The application of Raman spectroscopy to study the structure of barahonaite is better than infrared spectroscopy, probably because of the much higher spatial resolution.

Determinação in situ de metilmercúrio e mercúrio (II) em sistemas aquáticos nas proximidades de refinarias de petróleo, utilizando a técnica difusão em filmes finos por gradiente de concentração (DGT)

Pós-graduação em Geociências e Meio Ambiente - IGCE

La construcción del bárbaro en la obra de Julio César

El término bárbaro registra una larga historia y, formando antinomias, recorre un largo itinerario. Desde la clásica oposición helenos-bárbaros, pasando por romanos-bárbaros, pasó a contribuir al surgimiento de nuevas antinomias, cristiano-pagano y civilizado-bárbaro. ¿Cómo fueron posibles estas continuas metamorfosis, que comenzaron en la Antigüedad, se continuaron reeditando durante la Edad Media y Moderna y las vemos aparecer aún en nuestros días? Son posibles porque el bárbaro es, por sobre todo, el "otro", tenga éste las características que tenga. En esa historia de invención del "otro" queremos detenernos para considerar el aporte de la cultura romana a esta construcción, basándonos en el De bello Gallico de Julio César

La construcción del bárbaro en la obra de Julio César

El término bárbaro registra una larga historia y, formando antinomias, recorre un largo itinerario. Desde la clásica oposición helenos-bárbaros, pasando por romanos-bárbaros, pasó a contribuir al surgimiento de nuevas antinomias, cristiano-pagano y civilizado-bárbaro. ¿Cómo fueron posibles estas continuas metamorfosis, que comenzaron en la Antigüedad, se continuaron reeditando durante la Edad Media y Moderna y las vemos aparecer aún en nuestros días? Son posibles porque el bárbaro es, por sobre todo, el "otro", tenga éste las características que tenga. En esa historia de invención del "otro" queremos detenernos para considerar el aporte de la cultura romana a esta construcción, basándonos en el De bello Gallico de Julio César

La construcción del bárbaro en la obra de Julio César

El término bárbaro registra una larga historia y, formando antinomias, recorre un largo itinerario. Desde la clásica oposición helenos-bárbaros, pasando por romanos-bárbaros, pasó a contribuir al surgimiento de nuevas antinomias, cristiano-pagano y civilizado-bárbaro. ¿Cómo fueron posibles estas continuas metamorfosis, que comenzaron en la Antigüedad, se continuaron reeditando durante la Edad Media y Moderna y las vemos aparecer aún en nuestros días? Son posibles porque el bárbaro es, por sobre todo, el "otro", tenga éste las características que tenga. En esa historia de invención del "otro" queremos detenernos para considerar el aporte de la cultura romana a esta construcción, basándonos en el De bello Gallico de Julio César

Characterisation of montmorillonites simultaneously modified with an organic dye and an ammonium salt at different dye/salt ratios. Properties of these modified montmorillonites EVA nanocomposites

In this work, a sodium montmorillonite (Na+-Mt) was modified with two molecules simultaneously, an organic dye, methylene blue (MB), and ethyl hexadecyl dimethyl ammonium (EHDDMA). The synthesised organo-montmorillonites (OMt) combining different proportions of the two molecules were thoroughly characterised and mixed with ethylene vinyl acetate copolymer (EVA) in order to check the ability of these OMt as pigments and reinforcing additives. The synthesised OMt combining both surfactants, MB and EHDDMA, present higher interlayer distances than those with only MB, which were employed in previous works as nanopigments. When these OMt were incorporated in the EVA matrix, the obtained clay polymer nanocomposites (CPN) showed a high exfoliation degree of the OMt in the polymer, in such a way that at 80% of the cationic exchange capacity (CEC) of the Mt exchanged with EHDDMA, most of the OMt was exfoliated. Moreover, all the obtained CPN showed an increase in the Young's Moduli compared to the EVA reference, and especially those containing higher amounts of MB. The thermal stability of the CPN also increases with the MB content, compared to other CPN including conventional surfactants. The hiding power and colouring power achieved in the CPN are higher even with a much lower load of MB when EHDDMA is exchanged in the Mt.

Pyrolysis and combustion study of flexible polyurethane foam

The thermal degradation of flexible polyurethane foam has been studied under different conditions by thermogravimetric analysis (TG), thermogravimetric analysis-infrared spectrometry (TG-IR) and thermogravimetric analysis-mass spectrometry (TG-MS). For the kinetic study, dynamic and dynamic+isothermal runs were performed at different heating rates (5, 10 and 20 °C min−1) in three different atmospheres (N2, N2:O2 4:1 and N2:O2 9:1). Two reaction models were obtained, one for the pyrolysis and another for the combustion degradation (N2:O2 4:1 and N2:O2 9:1), simultaneously correlating the experimental data from the dynamic and dynamic+isothermal runs at different heating rates. The pyrolytic model considered consisted of two consecutive reactions with activation energies of 142 and 217.5 kJ mol−1 and reaction orders of 0.805 and 1.246. Nevertheless, to simulate the experimental data from the combustion runs, three consecutive reactions were employed with activation energies of 237.9, 103.5 and 120.1 kJ mol−1, and reaction orders of 2.003, 0.778 and 1.025. From the characterization of the sample employing TG-IR and TG-MS, the results obtained showed that the FPUF, under an inert atmosphere, started the decomposition breaking the urethane bond to produce long chains of ethers which were degraded immediately in the next step. However, under an oxidative atmosphere, at the first step not only the urethane bonds were broken but also some ether polyols started their degradation which finished at the second step producing a char that was degraded at the last stage.

Gasification and pyrolysis of Posidonia oceanica in the presence of dolomite

In the present work, a very detailed study of the reforming of syngas produced in the decomposition of Posidonia oceanica is done. The effect of the presence of different amounts of dolomite is analyzed. Also pyrolysis is studied, in nitrogen atmosphere, and gasification in the presence of air, oxygen and different amounts of steam. A detailed discussion on formation and destruction of tars is done. Furthermore, the effect of the heating rate in the decomposition and the residence time of the evolved gases are discussed. Syngas with ratio H2/CO from 0.3 to ca. 3 can be obtained from this interesting material. Marine species (microalgae) are usually studied with the aim of cultivating them for gas or oil production, but in this paper we draw attention to the possibility of using a natural resource with a very small impact in the ecosystem.

Study of the emissions from pyrolytic and oxidative thermal decomposition of PVC

Polyvinyl chloride (PVC) is one of the plastics most extensively used due to its versatility. The demand of PVC resin in Europe during 2012 reached 5000 ktonnes1. PVC waste management is a big problem because of the high volume generated all over the world and its chlorine content. End-of-life PVC is mainly mixed with municipal solid waste (MSW) and one common disposal option for this is waste-to-energy incineration (WtE). The presence of plastics such as PVC in the fuel mix increases the heating value of the fuel. PVC has two times higher energy content than MSW ‒around 20 MJ/kg vs 10 MJ/kg, respectively. However, the high chlorine content in PVC resin, 57 wt.%, may be a source for the formation of hazardous chlorinated organic pollutants in thermal processes. Chlorine present in the feedstock of WtE plants plays an important role in the formation of (i) chlorine (Cl2) and (ii) hydrochloric gas (HCl), both of them responsible for corrosion, and (iii) chlorinated organic pollutants2. In this work, pyrolytic and oxidative thermal degradation of PVC resin were carried out in a laboratory scale reactor at 500 ºC in order to analyze the influence of the reaction atmosphere on the emissions evolved. Special emphasis was put on the analysis of chlorinated organic pollutants such as polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs) and other related compounds like polychlorobenzenes (PCBzs), polychlorophenols (PCPhs) and polycyclic aromatic hydrocarbons (PAHs). Another objective of this work was to compare the results with those of a previous work3 in which emissions at different temperatures in both pyrolysis and combustion of another PVC resin had been studied; in that case, experiments for PCDD/Fs emissions had been performed only at 850 ºC.

Analysis of pollutants evolved from combustion and pyrolysis of flexible polyurethane foam in a laboratory furnace

Resumen del póster presentado en PIC2015 – the 14th International Congress on Combustion By-Products and Their Health Effects, Umeå, Sweden, 14-17 June 2015.

Emissions of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) from a cement kiln using a continuous monitoring system

Resumen de la comunicación presentada en PIC2015 – the 14th International Congress on Combustion By-Products and Their Health Effects, Umeå, Sweden, 14-17 June 2015.

Emissions of Gases, Polycyclic Aromatic Hydrocarbons and Brominated Pollutants during Thermal Degradation of Waste Printed Circuit Boards

Resumen del póster presentado en Symposium on Renewable Energy and Products from Biomass and Waste, CIUDEN (Cubillos de Sil, León, Spain), 12-13 May 2015

Gasification and Pyrolysis of Posidonia oceanica in the Presence of Dolomite

Resumen del póster presentado en Symposium on Renewable Energy and Products from Biomass and Waste, CIUDEN (Cubillos de Sil, León, Spain), 12-13 May 2015

Uso de Google Calendar para la coordinación entre asignaturas del Grado en Ingeniería Química

Uno de los aspectos peor valorados por los estudiantes de las nuevas titulaciones de grado es la coordinación entre asignaturas del mismo curso en cuanto a la distribución de controles y otro tipo de pruebas objetivas a lo largo del cuatrimestre, que afecta a la carga de trabajo no presencial en determinados momentos. En la guía docente de cada asignatura aparece la información sobre las pruebas a realizar dentro de un cronograma aproximado por semanas, y está disponible antes del comienzo del curso. Sin embargo, esa distribución puede variar ligeramente una vez empezado el curso debido a diversos motivos, y no se dispone de la información para todas las asignaturas del cuatrimestre en un mismo documento, lo que facilitaría su visualización. En este trabajo se propone el uso de la herramienta Google Calendar con el objetivo de tener un mayor control de este aspecto y poder detectar y corregir conflictos que puedan surgir, aplicándolo al Grado en Ingeniería Química.

Formación de equipos de trabajo eficaces a través de la cocina

El presente trabajo se ha desarrollado conjuntamente con alumnos de la asignatura obligatoria “Gestión Integrada y Seguridad Industrial” del Máster de Ingeniería Química y la asignatura optativa de cuarto curso “Gestión Integrada en la Industria Química” del grado de Ingeniería Química. Se ha diseñado una actividad práctica con el fin de aplicar los conceptos teóricos impartidos en estas asignaturas. Con el reto de cocinar un Mug Cake o “bizcocho en taza” se ha logrado poner en práctica varios de los contenidos teóricos de las asignaturas, especialmente el capítulo 7 de la norma ISO 9001:2008, “Realización del producto”; así como otros conceptos de liderazgo y mejora continua. Los alumnos se dividieron en dos equipos formados por el mismo número de miembros y en los que se mantenía el mismo número de alumnos del grado y del máster. Previamente a la realización del taller los alumnos elaboraron una serie de procedimientos, registros y listados de verificación. La experiencia ha resultado altamente fructífera puesto que los alumnos se han enfrentado al reto de aplicar contenidos teóricos a procesos reales, ha mejorado su motivación e interés por la materia y han desarrollado técnicas de trabajo en equipo y organización personal aumentando su productividad.