RESUMO
RESUMEN El objetivo de la presente investigación fue evaluar la cáscara de la mazorca cacao (Theobroma cacao L.) para su uso en la adsorción de cromo hexavalente en solución acuosa, usando columna de lecho empacado, aplicando el método de superficie de respuesta (MSR), con el fin de determinar los valores óptimos de las variables incidentes en el proceso y, posteriormente, con estos valores, realizar los ensayos de adsorción. Se utilizó un diseño de experimentos compuesto central con puntos estrellas. La biomasa, se lavó, se secó, se disminuyó tamaño y se tamizó; los experimentos, se llevaron a cabo a 25°C, a diferentes tamaños de partícula, de caudal y de cantidad de biomasa, en columnas en sistema en continuo, obteniéndose un porcentaje de remoción de 39,16%, de Cr(VI). Al realizar los experimentos en sistema por lotes, se obtuvo que a tamaño de partícula 0,355mm, se favorece la adsorción. De los ensayos de adsorción en columna, utilizando los parámetros óptimos arrojados obtenidos por el MSR, se obtuvo un porcentaje de remoción de 62,65%, encontrando que los modelos de Yoon-Nelson y Thomas fueron los que ajustaron los datos experimentales de la curva de ruptura, con R2= 0,98. Se concluye que la cáscara de cacao es un buen precursor de bioadsorbentes y que las variables más influyentes en la adsorción de Cr(VI) en sistema por lotes y continuo son el tamaño de partícula y la altura del lecho.
SUMMARY The aim of the present investigation was to evaluate the cocoa shell (Theobroma cacao L.) for its use in the adsorption of hexavalent chromium in aqueous solution using packed bed column, applying the surface response method (SRM) in order to determine the optimum values of the variables involved in the process. The adsorption tests were carried out with these values. Was used a central composite experiment design with star points. The biomass was washed, dried, decreased size and sieved; the experiments were carried out at 25°C, at different particle sizes, flow rate and amount of biomass, in columns in continuous system; obtaining a percentage of removal of 39.16% of C (VI). Was obtained when performing the experiments in batch system that at a size of 0.355mm particle favors the adsorption. From the adsorption tests in the column using the optimum parameters obtained by the MSR, was obtained a removal percentage of 62.65%; finding that the models of Yoon-Nelson and Thomas were those that adjusted the experimental data of the rupture curve, with R2 =0.98. It's concluded that the cocoa shell is a good precursor of bioadsorbents and that the most influential variables in Cr (VI) adsorption in batch and continuous systems are particle size and bed height.
RESUMO
An understanding of the characteristics of occupational lung cancer is important to establish policies that prevent carcinogen exposure and to compensate workers exposed to lung carcinogens. This study analyzed the characteristics of occupational lung cancers in workers who were compensated under the Industrial Accident Compensation Insurance Law between 1994 and 2011. A total of 179 occupational lung cancers were compensated. The main carcinogenic exposure was asbestos, followed by crystalline silica and hexavalent chromium. The mean exposure duration and latency were 19.8 and 23.2 yr. The most common industry was manufacturing, followed by construction and transportation. The most common occupation was maintenance and repair, followed by foundry work, welding, painting, and spinning or weaving. Although asbestos was predominant carcinogen, the proportion of these cases was relatively low compared to other developed countries. Proper surveillance system is needed to monitor occupational lung cancer and improve prevention measures.