Road tunnels have been a successful means of avoiding congestion in the city of Guanajuato.They are also used by pedestrians to reduce travel time and distance. However, exposure to elevated levels of carbon monoxide (CO) and particulate matter such as PM2.5 and PM10 from vehicle emissions, as well as the resuspension of particulate matter are risk factors for health. In the city of Guanajuato, the CO, PM2.5 and PM10 concentrations, wind speed and number of vehicles in three of the more polluted and most frequently used tunnels by pedestrians was monitored. To monitor the CO concentration, non-dispersive infrared radiation was used. The PM2.5 and PM10 concentrations were evaluated using a handheld analyzer with a high precision laser sensor (Aerocet-831). The mineralogy, chemical composition, and morphology of particulate matter were analyzed by XRD, XRF and SEM-EDS, respectively. The average CO concentration does not exceed 50 ppm for an exposure time of 30 minutes as recommended by the World Health Organization, however the average concentrations for PM10 in the three tunnels are above the permissible limit of 50 µg m -3 24-hour average for the air quality inside the tunnels. The high emission factors suggest the necessity of the implementation of a ventilation system inside the tunnels. The chemical composition of particulate matter corresponds to the mineral dust present.
Alumina and alumina-zirconia mixed oxides were compared as supports to prepare nickel catalysts. The oxides were prepared by the sol-gel method using aluminum tri-sec-butoxide and zirconium (IV) propoxide as precursors, and its physicochemical properties were determined by BET, TGA, DTA, XRD, SEM and TEM. The catalysts of nickel were obtained by the impregnation of the supports with nickel nitrate (10 wt%) and were heat-treated at 700 • C. The specific area of the supports and catalysts decreased with the increase in the zirconia content in agreement with the crystalline phase formed. TEM micrographs of nickel catalysts revealed particles in the size range of 10-30 nm. The Ni/Al 2 O 3 -ZrO 2 catalysts were tested in the steam reforming reaction of ethanol (SRE) at 500 • C, and the obtained results suggest that the differences in catalytic activities depended on the content of ZrO 2 . The selectivity towards H 2 was ∼56% for the named catalyst Ni-Al-0.25Zr.
En muchos países del mundo, incluido México, la presencia de elementos tóxicos, como el arsénico y flúor por encima de los niveles máximos permitidos en el agua potable (0.01 mg/L y 1.5 mg/L), respectivamente está generando problemas a la salud, como el cáncer y la fluorosis esquelética, respectivamente. El objetivo de este trabajo fue determinar la cinética del proceso de adsorción del fluoruro y arsénico en soluciones sintéticas, utilizando gamma alúmina (γ-Al2O3) para establecer si el proceso se desarrolla espontáneamente. Se sintetizó γ-Al2O3 nano-fibrilar, con alta área superficial (352 m2/g), por precipitación homogénea, y se secó por espray. El nanomaterial adsorbente obtenido se usó para eliminar el fluoruro y el arsénico total de soluciones sintéticas. La morfología de la nano-fibra de γ-Al2O3 mesoporosa se analizó usando microscopía electrónica de transmisión y de barrido. El área superficial se determinó por adsorción-desorción a pH 7 de nitrógeno. Las isotermas de adsorción del proceso de remoción coincidieron con el modelo de Langmuir para ambos elementos. La γ-Al2O3 eliminó hasta 96 % de iones flúor y 92 % de arsénico total a pH 5, mientras que a pH 7 se alcanzó una remoción del 90 % y 94.2 % de fluoruro y arsénico, respectivamente. La cinética de remoción siguió el modelo de seudo-segundo orden, y el parámetro de equilibrio adimensional y la energía libre estándar de Gibbs confirmaron que el proceso se desarrolló espontáneamente. La gamma alúmina nano-fibrilar permitió la remoción natural y espontánea de arsénico y fluoruro presente en las soluciones utilizadas en este estudio.
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