Washcoated Pd/Al2O3 monoliths for the liquid phase hydrodechlorination of dioxins

The catalytic activity and durability of 2 wt.% Pd/Al2O3 in powder and washcoated on cordierite monoliths were examined for the liquid phase hydrodechlorination (LPHDC) of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs), also known as dioxins. NaOH was employed as a neutralizing agent, and 2-propanol was used as a hydrogen donor and a solvent. Fresh and spent powder and monolith samples were characterized by elemental analysis, surface area, hydrogen chemisorption, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), and transmission electron microscopy/energy dispersive X-ray spectroscopy (TEM/EDX). Three reactor configurations were compared including the slurry and monolith batch reactors as well as the bubble loop column resulting in 100, 70, and 72% sample toxicity reduction, respectively, after 5 h of reaction. However, the slurry and monolith batch reactors lead to catalyst sample loss via a filtration process (slurry) and washcoat erosion (monolith batch), as well as rapid deactivation of the powder catalyst samples. The monolith employed in the bubble loop column remained stable and active after four reaction runs. Three preemptive regeneration methods were evaluated on spent monolith catalyst including 2-propanol washing, oxidation/reduction, and reduction. All three procedures reactivated the spent catalyst samples, but the combustion methods proved to be more efficient at eliminating the more stable poisons.

NaOH and KOH for preparing activated carbons used in energy and environmental applications

Alkaline hydroxides, especially sodium and potassium hydroxides, are multi-million-ton per annum commodities and strong chemical bases that have large scale applications. Some of them are related with their consequent ability to degrade most materials, depending on the temperature used. As an example, these chemicals are involved in the manufacture of pulp and paper, textiles, biodiesels, soaps and detergents, acid gases removal (e.g., SO2) and others, as well as in many organic synthesis processes. Sodium and potassium hydroxides are strong and corrosive bases, but they are also very stable chemicals that can melt without decomposition, NaOH at 318ºC, and KOH at 360ºC. Hence, they can react with most materials, even with relatively inert ones such as carbon materials. Thus, at temperatures higher than 360ºC these melted hydroxides easily react with most types of carbon-containing raw materials (coals, lignocellulosic materials, pitches, etc.), as well as with most pure carbon materials (carbon fibers, carbon nanofibers and carbon nanotubes). This reaction occurs via a solid-liquid redox reaction in which both hydroxides (NaOH or KOH) are converted to the following main products: hydrogen, alkaline metals and alkaline carbonates, as a result of the carbon precursor oxidation. By controlling this reaction, and after a suitable washing process, good quality activated carbons (ACs), a classical type of porous materials, can be prepared. Such carbon activation by hydroxides, known since long time ago, continues to be under research due to the unique properties of the resulting activated carbons. They have promising high porosity developments and interesting pore size distributions. These two properties are important for new applications such as gas storage (e.g., natural gas or hydrogen), capture, storage and transport of carbon dioxide, electricity storage demands (EDLC-supercapacitors-) or pollution control. Because these applications require new and superior quality activated carbons, there is no doubt that among the different existing activating processes, the one based on the chemical reaction between the carbon precursor and the alkaline hydroxide (NaOH or KOH) gives the best activation results. The present article covers different aspects of the activation by hydroxides, including the characteristics of the resulting activated carbons and their performance in some environment-related applications. The following topics are discussed: i) variables of the preparation method, such as the nature of the hydroxide, the type of carbon precursor, the hydroxide/carbon precursor ratio, the mixing procedure of carbon precursor and hydroxide (impregnation of the precursor with a hydroxide solution or mixing both, hydroxide and carbon precursor, as solids), or the temperature and time of the reaction are discussed, analyzing their effect on the resulting porosity; ii) analysis of the main reactions occurring during the activation process, iii) comparative analysis of the porosity development obtained from different activation processes (e.g., CO2, steam, phosphoric acid and hydroxides activation); and iv) performance of the prepared activated carbon materials on a few applications, such as VOC removal, electricity and gas storages.

Thermogravimetric study of the decomposition of printed circuit boards from mobile phones

Thermal decomposition of printed circuits boards (PCB) is studied, using thermogravimetric analysis to compare the thermal behavior of PCB of mobile phones before and after the removal of the metallic fraction by acid washing. Several dynamic and dynamic + isothermal runs have been carried out at different heating rates (5, 10 and 20 K min−1), from room temperature to more than 1100 K. Also runs in the presence and in the absence of oxygen were performed (combustion and pyrolysis runs). Moreover, TG–MS experiments were performed (both in inert and oxidizing atmosphere) in order to better understand the thermal decomposition of these wastes and identify some compounds emitted during the controlled heating of these materials. Different reaction models are proposed, one for pyrolysis and one for combustion of the two kinds of wastes studied, which proved to simulate appropriately the experimental results at all the heating rates simultaneously.

Water reduction in waste-activated sludge by resettling and filtration in batch. Phase (1): pilot-scale experiments to optimize performance

This article describes an effective procedure for reducing the water content of excess sludge production from a wastewater treatment plant by increasing its concentration and, as a consequence, minimizing the volume of sludge to be managed. It consists of a pre-dewatering sludge process, which is used as a preliminary step or alternative to the thickening. It is made up of two discontinuous sequential stages: the first is resettling and the second, filtration through a porous medium. The process is strictly physical, without any chemical additives or electromechanical equipment intervening. The experiment was carried out in a pilot-scale system, consisting of a column of sedimentation that incorporates a filter medium. Different sludge heights were tested over the filter to verify the influence of hydrostatic pressure on the various final concentrations of each stage. The results show that the initial sludge concentration may increase by more than 570% by the end of the process with the final volume of sludge being reduced in similar proportions and hydrostatic pressure having a limited effect on this final concentration. Moreover, the value of the hydrostatic pressure at which critical specific cake resistance is reached is established.

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.

Conhecimento e adesão da prática de higienização das mãos dos profissionais da saúde: revisão de literatura

O presente estudo objetiva conhecer a produção científica da saúde acerca da higienização das mãos realizada pelos profissionais e relacionar o conhecimento e adesão do profissional a essa prática. Trata-se de uma revisão bibliográfica sistemática, realizado na Biblioteca Virtual de Saúde (BVS), nas bases de dados LILACS e SCIELO, com os descritores: pessoal de saúde, lavagem de mãos e adesão. Selecionou-se 13 artigos no período de 2002 a 2012, que foram analisados em categorias. Os critérios de inclusão para a seleção dos artigos foram: artigos publicados em português e estar disponível em texto completo. Os resultados da pesquisa evidenciaram que a grande maioria dos profissionais tem embasamento teórico e prático sobre higienização das mãos. Porém, no campo de trabalho temos resultados contrários, não há adesão esperada nem a técnica correta da lavagem das mãos. Por diversos motivos ainda não realizam por completo essa tarefa. Concluindo assim que as ações de educação que tem função de orientar e motivar esses profissionais devem ser discutidas e implementadas, a fim de sanar todas as dúvidas que ainda existem sobre a técnica de higienização das mãos.