Contamination of natural groundwater by arsenic (As) is a serious problem that appears in some areas of Northern Central Mexico (NCM). In this research, As was removed from NCM wells groundwater by the electrocoagulation (EC) technique. Laboratory-scale arsenic electroremoval experiments were carried out at continuous flow rates between 0.25 and 1.00 L min−1using current densities of 5, 10, and 20 A m−2. Experiments were performed under galvanostatic conditions during 5 min, at constant temperature and pH. The response surface methodology (RSM) was used for the optimization of the processing variables (flow rate and current density), response modeling, and predictions. The highest arsenic removal efficiency from underground water (99%) was achieved at low flow rates (0.25 L min−1) and high current densities (20 A m−2). The response models developed explained 93.7% variability for As removal efficiency.
The magnetorheological fluids have the ability to modify their viscosity quickly by subjecting it to a magnetic field, a quality that classifies them in the category of intelligent materials. Such fluids include three main components; the base fluid that is generally mineral or synthetic oil, magnetizable particles which are dispersed in the base fluid and the additives or stabilizers that prevent agglomeration and sedimentation of the particles, as well as the degradation induced by the carrier medium. The main challenge of these fluids is to maintain the rheological response to the magnetic field, as well as avoid the chemical and microstructural instability of the magnetoreological fluids. In the present investigation an exhaustive bibliographic review was carried out to understand the main aspects of these types of materials, their properties as well as the main applications in the different branches of industry and medicine. The most recent contributions focused on the chemical stability of magnetic particles through the application of surface coatings are discussed.
Abstract. 1 We have investigated the formation of mesophase carbon microbeads in tar pitch generated by the coal coking in a steelmaking plant. Pitches were obtained at different distillation temperatures (643, 673 and 723 K). The distilled samples were then thermally treated in nitrogen atmosphere either at 723 K for 8 h (T1) for at 703 K for 4 h (T2). A new phase appears, seen in optical microscopy with a polarizing filter. Samples subjected to the T1 thermal treatment were found to form a discontinuous fluid phase distinct from the main phase. Formation of mesophase carbon microbeads is seen also in samples subjected to the T2 treatment, with the particle diameters from 30 to 60 µm. The microbeads can be used as precursors for the synthesis of graphitic materials.
RESUMENLa brea generada a partir de alquitrán de hulla constituye un precursor de bajo coste, de materiales avanzados de carbono de excelentes prestaciones mecánicas debido a su alto rendimiento en carbono con estructura grafítica derivado de su alto grado de aromaticidad. En este artículo se revisan las contribuciones que han dado impulso al desarrollo tecnológico de los materiales avanzados de carbono obtenidos a partir de alquitrán de hulla. Se analiza el efecto de las condiciones experimentales, de cada una de las etapas de síntesis, sobre los parámetros caracterís-ticos de la materia en las diferentes fases de procesamiento que incluyen la coquización del carbón, la destilación del alquitrán, la pirólisis de la brea y la carbonización de la mesofase.Palabras clave: Alquitrán de hulla, Mesofase de brea, Carbonización, Materiales avanzados de carbono. ABSTRACTPitch generated from the coal tar is a low cost precursor of advanced carbon materials with excellent mechanical properties due to its high carbon yield with graphitic structure derived from its high degree of aromaticity. This article reviews the contributions that have given impetus to the technological development of advanced carbon materials derived from coal tar. Analyze the effect of experimental conditions, each of the synthesis steps, on the characteristic parameters of the material in the different processing stages including the coking of coal, tar distillation, pyrolysis of tar and carbonization of mesophase.Keywords: Coal tar, Tar pitch mesophase, Carbonization, Advanced carbon materials. INTRodUCCIóNEl proceso de coquización del carbón es extraordinariamente complejo, en términos bastante simples consiste en la destilación del carbón del que se obtiene el coque como residuo sólido, una mezcla de gases denominado gas coque y una mezcla de hidrocarburos condensados que constituyen el alquitrán.El alquitrán de hulla es el producto de la condensación obtenido por el enfriamiento hasta la temperatura ambiente, del gas desprendido en la destilación destructiva del carbón. Es un líquido negro viscoso más denso que el agua y compuesto principalmente de una mezcla compleja de hidrocarburos aromáticos con anillos condensados. Puede contener compuestos fenólicos, bases nitrogenadas aromáticas y sus alquil derivados e hidrocarburos parafínicos y olefínicos [1].
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