Algunos aspectos cinéticos de las reacciones de sólidos con cloro

The present paper describes detailed kinetics investigations on some selected chlorine-solid reactions through thermogravimetric measurements. The solids studied in this article include chemical pure oxides and sulfides as well as their natural bearing materials. The chlorinating agents employed are gaseous mixtures of Cl2+N2 (chlorination), Cl2+O2 (oxychlorination), and Cl2+CO (carbochlorination). Results are presented as effects of various parameters on the reaction rate of these solids with these chlorinating agents. It was observed that the reactivity of these solids towards different chlorinating agents varied widely. Sulfides could be chlorinated at room temperature, while carbochlorination of chromium (III) oxide was possible only above 500 °C. The variation of the chlorination rate of these complex materials with respect to gas velocity, composition and temperature enabled us to focus some light on the plausible reaction mechanisms and stoichiometries. The obtained results were used for selective removal of iron from chromite concentrates, extraction of valuable metals from sulfide materials, purification of MgO samples, etc.Este trabajo describe detalladas investigaciones cinéticas en algunas reacciones seleccionadas de cloro-sólido a través de medidas termogravimétricas. Los sólidos estudiados en este artículo incluyen óxidos químicos puros y sulfuros, así como sus materiales naturales de soporte. Los agentes de cloración empleados son mezclas de gases de Cl2+N2 (cloración), Cl2+O2 (oxicloración) y Cl2+CO (carbocloración). Los resultados se presentan como efecto de varios parámetros en el porcentaje de reacción de estos sólidos con los agentes de cloración. Se ha observado que la reactividad de estos sólidos a través de diferentes agentes de cloración varía ampliamente. Los sulfuros se pudieron clorar a temperatura ambiente mientras que la carbocloración del óxido de cromo (III) sólo fue posible por encima de los 500 °C. La variación del porcentaje de cloración de estos materiales complejos con respecto a la velocidad del gas, composición y temperatura permitió arrojar alguna luz en los posibles mecanismos de reacción y estequiometrías. Los resultados obtenidos se han usado para la eliminación selectiva del hierro de concentrados de cromo, extracción de metales valiosos de materiales sulfhídricos, purificación de muestras de MgO, etc.Peer reviewe

XPS study on calcining mixtures of brucite with titania

Universidad Autonoma de Nuevo Leon PAICYT-UANL [IT1382-20]; (Juan de la Cierva-Formacion program) [FJC2019-041139I, MCIN/AEI/10.13039/501100011033]; (Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación

Justice, culture and the political determinants of indigenous Australian health

Indigenous Australian health is distinguished by a median age of death in the order of 20 years less than that of the non-indigenous population (Australian Bureau of Statistics, 2009). This makes Australia unique among comparable post-colonial societies in failing to make substantive reductions to the indigenous/non-indigenous health differential. Relatively poor indigenous housing, educational attainment, labour market participation and access to traditional resources for economic purposes contribute to the differen- tial. These contributing variables have an inherently political character which is integral to examining the just distribution of public authority, the purpose of political activity, equal political participation and cultural responsiveness in the provision of health ser- vices as important theoretical considerations in reducing cross-cultural inequities in the burden of disease

Development of an Ultra-Low Carbon MgO Refractory Doped with α-Al2O3 Nanoparticles for the Steelmaking Industry: A Microstructural and Thermo-Mechanical Study

The effect of α-Al2O3 nanoparticles (up to 5 wt.%) on the physical, mechanical, and thermal properties, as well as on the microstructural evolution of a dense magnesia refractory is studied. Sintering temperatures at 1300, 1500, and 1600 °C are used. The physical properties of interest were bulk density and apparent porosity, which were evaluated by the Archimedes method. Thermal properties were examined by differential scanning calorimetry. The mechanical behavior was studied by cold crushing strength and microhardness tests. Finally, the microstructure and mineralogical qualitative characteristics were studied by scanning electron microscopy and X-ray diffraction, respectively. Increasing the sintering temperature resulted in improved density and reduced apparent porosity. However, as the α-Al2O3 nanoparticle content increased, the density and microhardness decreased. Microstructural observations showed that the presence of α-Al2O3 nanoparticles in the magnesia matrix induced the magnesium-aluminate spinel formation (MgAl2O4), which improved the mechanical resistance most significantly at 1500 °C