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Metal Leaching (metal + leaching)
Selected AbstractsChemInform Abstract: Tunable Palladium-FibreCats for Aryl Chloride Suzuki Coupling with Minimal Metal Leaching.CHEMINFORM, Issue 11 2009Thomas J. Colacot Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Leaching of copper, chromium, and boron from treated timber during aboveground exposureENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2006Ana I. García-Valcárcel Abstract Field studies were conducted to evaluate leaching of Cu, Cr, and B from timber treated with a Cr, Cu, and B wood preservative and exposed aboveground in Spanish weathering conditions during one year with a total rainfall of approximately 500 mm. The effect of timber orientation (horizontal for decks and vertical for fences) on metal leaching was assessed. Leaching of metals after one year was higher for decks than for fences, with total amounts of metals leached being 226.6 and 87.8 mg/m2 for Cu, 199.5 and 42.4 mg/m2 for Cr, and 110.1 and 32.6 mg/m2 for B from decks and fences, respectively. Leaching rates did not drop constantly with time, because an increase in metal leaching, except for B, was observed at the end of the year after a long dry period. The order of metal emission varied with cumulative rainfall: Leaching of B was higher than Cr initially, but the opposite occurred at the end of the assay. Total emissions of Cu and Cr obtained in a laboratory assay were lower than those for decks and fences under field conditions when expressed per unit surface area (mg/m2), but they were similar to the values obtained for fences when expressed as a percentage of the initial amount. However, the percentage of B leached from wood was higher in laboratory than in field assays for both orientations, with the amount of B leached per unit surface area under laboratory conditions being higher than that leached from fences but lower than that leached from decks. Emission rates extrapolated to one year from laboratory data underestimated metal leaching from decks and overestimated emissions from fences. [source] Chirally Modified Platinum Nanoparticles Stabilized by Dendritic Core-Multishell Architectures for the Asymmetric Hydrogenation of Ethyl PyruvateADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Juliane Keilitz Abstract In this paper we present the asymmetric hydrogenation of ,-keto esters with platinum nanoparticles homogeneously stabilized in dendritic core-multishell architectures. The main focus lies on recycling and metal leaching, because little is reported so far about these aspects. It is shown that the stabilizing polymer allows for the efficient modification of the Pt surface with the chiral alkaloid cinchonidine, thereby inducing enantioselectivity and enhancing the reaction rate in the asymmetric hydrogenation of ethyl pyruvate. After optimization of the reaction conditions 63% ee for (R)-ethyl lactate was obtained. During recycling it was found that this value could even be increased upon ultrafiltration of the catalyst prior to use. Recycling was accomplished for 10,cycles with stable activity and enantioselectivity (,73% ee) in the first eight runs. Aggregation of the initially well dispersed nanoparticles was observed by transmission electron microscope (TEM) analysis, leading to reduced conversion after the 8th cycle, but metal leaching into the product has been observed only in the very first run. [source] Heterogeneously Catalyzed Oxidative Cyanation of Tertiary Amines with Sodium Cyanide/Hydrogen Peroxide using Polymer-Supported Iron(II) Phthalocyanines as CatalystADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2010Sweety Singhal Abstract The first report on heterogeneously catalyzed oxidative cyanation of various tertiary amines to the corresponding ,-amino nitriles with high yields and selectivity by using hydrogen peroxide oxidant in presence of sodium cyanide and Fe(II) phthalocyanine supported on a polymer as catalyst is described. The present method has the added benefits of facile recovery of the catalyst from the reaction mixture and its subsequent use without further activation. Consistent catalytic activity with no metal leaching was observed during this course. [source] Mineralization improvement of phenol aqueous solutions through heterogeneous catalytic ozonationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2003Fernando J Beltrán Abstract To assess the mineralization level achieved, aqueous solutions of phenol have been treated with ozone in the presence of different solid catalysts. Activated carbon was the principal catalyst investigated, although some additional experiments were carried out by utilizing metal oxide-based catalysts (ie Ti, Co and Fe) supported onto alumina. Usage of Co/Al2O3 led to the highest values of phenol byproduct mineralization, nevertheless some metal leaching was experienced in the process. The operating variables studied when using activated carbon as the catalyst were ozone gas concentration, amount of catalyst added and temperature. Regardless of the catalyst type used, two different ozonation kinetic regimes were observed: (I) an initial period, corresponding to the presence of phenol in solution, characterized by small amounts of dissolved ozone and no improvement of the mineralization degree if comparing catalytic and non-catalytic runs; (II) a second period, free of phenol, in which dissolved ozone accumulated in water and the beneficial effects of catalysts on mineralization were noticed. Experimental data also demonstrated the improvement in oxalic acid elimination in the presence of heterogeneous catalysts. Finally, consumption of ozone per mass of carbon removed, reaction factors and Hatta numbers were also calculated. Copyright © 2003 Society of Chemical Industry [source] ChemInform Abstract: Heterogeneously Catalyzed Oxidative Cyanation of Tertiary Amines with Sodium Cyanide/Hydrogen Peroxide Using Polymer-Supported Iron (II) Phthalocyanines as Catalyst.CHEMINFORM, Issue 41 2010Sweety Singhal Abstract The catalyst can be easily recovered and reused for at least five times without any loss of activity and metal leaching. [source] | ||||||||||