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- Author or Editor: M. S. Crespi x
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Abstract
A neutron activation analysis method for the determination of uranium in natural fresh waters is described. The method is based on a preconcentration step by precipitation of the metal oxinate on a phenolphtalein bed followed by instrumental neutron activation analysis. Preliminary investigations with239U radiotracer were carried cut to set up the best working conditions and to evaluate the chemical yield. The whole procedure has been applied to the determination of uranium in river water.
Abstract
The adsorption of about 50 ions on molybdenum dibromide, (Mo6Br8)Br4·2H2O, in nitric acid was investigated. The preparation of the adsorber and its characterization is presented and discussed. Adsorption mechanism studies were carried out for some noble metals and chromium. Sorption cannot be ascribed to ion exchange mechanism but to formation of insoluble species, and to settlement of few ions into surface sorption sites or into a limited number of cavities in the cluster crystal structure of the adsorber.
Abstract
The composting process using sugarcane bagasse, animal manure, and urea as source of organic matter, microorganism, and nitrogen, respectively, were evaluated regarding the thermal behavior considering the maturation period: 0 (raw), 15, 22, 30, and 60 days. Thermogravimetric and differential thermal analysis curves were obtained in a synthetic air atmosphere and heating rate of 10 °C min−1 in the range of 30–600 °C. The raw compost showed 80% organic matter, which was reduced up to 58% to 60 days compost. Two main mass losses were verified, corresponding to characteristics exothermic peak in differential thermal analysis curves depending on the maturation period. The variation in organic composition was evaluated by Fourier transform infrared spectroscopy verifying the structures (lignin, cellulose, and hemicelluloses) changes with composting process, and the gas chromatography–mass spectrometry was used to identify substance soluble in hexane.
Abstract
Poly(3-hydroxybutyrate), PHB, has been structurally modified with maleic anhydride, MA, in the presence of triethylamine, TEA. Glass transition, melting, and crystallization temperature, obtained from DSC curves, and thermal degradation temperatures obtained from TG ones, were employed to evaluate the influence of the MA proportion on the modification in the PHB chain. According to the results, most of chain modification reactions are the 80/20 and 90/10 proportions. Observations suggest that most chain modification reactions occur when the ratio of PHB/MA is 80/20 or 90/10. This suggests that modifications of PHB in the presence of MA involve main chain scission.
Abstract
Neutron activation analysis of palladium, iridium, platinum, gold, silver and copper in different matrices was carried out by using inorganic adsorbers such as molybdenum dibromide, zinc ferrocyanide and cadmium metal for their radiochemical separation. The matrices chosen to show the versatility of the method were: high-purity copper and nickel metals, NBS standard reference material SRM 1571 (Orchard leaves), Pultusk meteorite and the U. S. Geological Survey standard rock W-1. The method elaborated is very simple as it involves only a few steps and it has been shown to be accurate and capable of yielding reliable results.
Abstract
Copper, iridium, platinum and gold content was determined in 15 italian chondritic meteorites by destructive neutron activation analysis. The chemical procedure involves few steps: sample dissolution, group separation of noble metals on inorganic adsorbers and gamma-ray spectrometry. Element content and atomic abundances (Si=106 atoms) are presented and discussed. Precision and accuracy of the analytical method are given as well. Copper, platinum and gold content is within the reported ranges for ordinary chondrites, whereas the iridium content is located on the low side of reported values.
Abstract
In the present investigation iron and trace elements were determined by instrumental neutron activation analysis in a number of sea bottom sediment samples, collected in the Ross Sea and close to the Italian Station at Terra Nova Bay in Antarctica. Full listing of results is presented and discussed as well as the evaluation of precision and accuracy. In order to find correlations and similarities among the sediment samples, the analytical data were submitted to statistical treatment. In addition rare earth element patterns were obtained. Typical trends were observed with no evident Eu negative anomaly and a depletion of heavy rare earth elements.
