RESUMEN
In the present study, highly effective and reusable monodisperse ruthenium-nickel (Ru-Ni) nanomaterials supported on poly(N-vinyl-2-pyrrolidone) (Ru-Ni@PVP) were synthesized (3.51⯱â¯0.38â¯nm) by a facile sodium-hydroxide-assisted reduction method; Ru and Ni reduction in PVP solution was accomplished. The prepared nanocomposites were characterized by TEM, HRTEM, XRD, and XPS and performed as a catalyst for dehydrocoupling of dimethylamine-borane (DMAB). It was found that Ru-Ni nanomaterials are one of the most active catalysts at low concentrations and temperature for dehydrocoupling of DMAB. This catalyst with its turnover frequency of 458.57â¯h-1 exhibits one of the best results among all the catalysts prepared in the literature for dehydrocoupling of DMAB. Significantly low Ea value (36.52⯱â¯3â¯kJâ¯mol-1) was also found for dehydrocoupling of DMAB.
RESUMEN
In real environmental applications, such as heavy metal bioremediation, microorganisms are generally not kept at their optimum growth conditions; therefore, it is imperative to investigate their heavy metal removal performance under diverse environmental conditions. The present study aims to investigate the effects of pH, temperature and growth phases on the removal of Cu(2+) and Cr(6+) by two environmental isolates identified as Ochrobactrum intermedium LBr and Cupriavidus metallidurans CH34. Results showed that cells in logarithmic phase presented better biosorption capacity than cells in stationary phase for both isolates. The Cr(6+) metal was removed more efficiently by live O. intermedium LBr than dead cells; while dead C. metallidurans CH34 biosorbed better than live ones. It was also found that the pH and temperature affected the biosorption capacity. The optimum temperatures were determined to be 37°C and 27°C, and the optimum pH values were 6 and 7 for O. intermedium LBr and C. metallidurans CH34, respectively. Additionally, both microorganisms preferentially adsorbed Cu(2+) in Cu(2+)/Cr(6+) mixtures. The main mechanism of adsorption was determined to be through carboxylic, hydroxyl, and amino functional groups.
Asunto(s)
Biodegradación Ambiental , Cupriavidus/química , Metales Pesados/química , Ochrobactrum/química , Biomasa , Compuestos de Cromo/química , Compuestos de Cromo/toxicidad , Cobre/química , Cobre/toxicidad , Concentración de Iones de Hidrógeno , Metales Pesados/toxicidad , Pruebas de Sensibilidad Microbiana , Temperatura , TermodinámicaRESUMEN
A novel high throughput colorimetric urease activity assay was compared to the Nessler method. The new method employs phenol red to determine the urease activity. This method reduces significantly sample processing time and allows real-time investigations. This method is rapid, sensitive, easy, cost-effective, and does not use any toxic chemical reagents.