ResumenSe estudió la cinética de la desinfección fotocatalítica de agua (DFA) con E. coli usando dos ecuaciones cinéticas tipo Langmuir-Hinshelwood de tres parámetros: la constante cinética, la constante de interacción bacteria-fotocatalizador y el coeficiente de inhibición. Se analizó el efecto de la concentración de TiO 2 y la potencia de irradiación sobre los parámetros cinéticos. En los intervalos estudiados, la constante cinética incrementa con el aumento de la concentración del fotocatalizador y de la potencia de irradiación, mientras que, la constante de interacción bacteriafotocatalizador disminuye. Además, el coeficiente de inhibición no presenta dependencia de estas variables. Se usaron medios selectivos para seguir la concentración de bacterias con el fin de evaluar el efecto de la DFA sobre la bacteria y los daños sucesivos que ocurren en ésta hasta llegar a un umbral límite de daño. El modelo cinético utilizado permite la predicción de valores aproximados de las poblaciones bacterianas lastimadas y no lastimadas. Palabras clave: inactivación de bacterias, fotodesinfección, parámetros cinéticos, bacterias lastimadas Kinetics of the Photocatalytic Disinfection of Water contaminated with E. coli. Effect of the Photocatalyst Concentration and of the Irradiation Power AbstractThe photocatalytic water disinfection (PWD) kinetics with E. coli was studied, using two Langmuir-Hinshelwood type kinetic equations involving three parameters: the kinetic constant, the interaction bacteria-photocatalyst constant, and the inhibition coefficient. The TiO 2 concentration and the irradiation power were modified, and their effects on the inactivation kinetics were analyzed. It was found that the kinetic constant increased with the increase of the catalyst concentration and the irradiation power, while the constant related to the interaction bacteria-photocatalyst decreased. In addition, it was found that the inhibition coefficient does not depend on these variables. Furthermore, the bacteria concentration was followed using selective media to assess the effect of the PWD process on the bacteria, and its subsequent attacks to reach a threshold limit of damage. It was observed that the kinetic model predicts approximate values of the undamaged and injured bacteria population.
Ultrathin and nanometric materials (minerals and amorphous phases) are detected in transitory deposits of potential hazardous elements (PHEs), especially in acidic coal mine drainages. The main goal of this work was to evaluate the occurrence of PHEs in nanoparticles (NPs) in evaporative structures in coal mining areas with high concentrations of PHEs. The precipitates were sampled in several coal mining areas in Colombia, with the purpose of evaluating the geochemical and environmental structures. In the present work, to better diagnose areas affected by coal mining, an innovative analytical procedure is proposed to define the association between PHEs in mine drainage sediments. The procedure includes the analytical study with X-Ray Diffraction (XRD) and advanced electron microscopy, before and after a series of sequential extractions to separate amorphous, magnetic, and crystalline compounds. Of the three main types of precipitates identified, the yellowish precipitates had the highest amounts of PHEs while the white precipitates had only small amounts of PHEs and the greenish precipitates contained TiO2 nanoparticles. The results from this study will be usable for more than fifty countries that have coal mine drainages.
MSC :65c20, 61.82.Fk, ResumenEn este artículo se presenta el efecto de las sales inorgánicas MgSO4, NaCl y CaCO3 en la desinfección fotocatalítica del agua. Se usó TiO2-P25 como fotocatalizador y E. Coli como microorganismo contaminante. Las pruebas de desinfección se realizaron mediante la iluminación controlada de reactores batch cargados con agua contaminada, sales y TiO2. Los resultados de estas pruebas fueron usados para determinar los parámetros cinéticos de un modelo tipo Langmuir-Hinshelwood. Se encontró que las sales tienen una fuerte influencia sobre la inactivación fotocatalítica de E. Coli, y que cada sal y su concentración afectan la desinfección de forma diferente y en el siguiente orden: NaCl>CaCO3>>MgSO4. Adicionalmente, el valor de los parámetros calculados fue diferente para cada sal, evidenciando que las sales afectan el
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