Search Results

You are looking at 11 - 20 of 27 items for :

  • Author or Editor: D. Fávaro x
  • Chemistry and Chemical Engineering x
  • Refine by Access: All Content x
Clear All Modify Search
Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Torres, S. Olivares, D. De La Rosa, L. Lima, F. Martínez, C. Munita, and D. Favaro

Abstract  

Adsorption of mercury(II) and methylmercury by two tannin sorbents was investigated using radiotracers. High sorption capacities for mercury are registered for both sorbents at pH 7. ForEucaliptus Saligna Sm sorbent (ETS) the maximum sorption capacity was 1.2±0.2 mmol/g and forLysiloma latisiliqua sorbent (LTS) was 8.5±0.2 mmol/g. Methylmercury adsorption maximum was recorded at pH 4 and in buffered solutions at pH2. This species can be recovered in the presence of mercury(II). Influence of different ions present in water was examined. High recoveries were reported for ETS in tap water samples but a decrease of uptake is observed for seawater.

Restricted access

Abstract  

In the present work, the concentration of the 14 elements Br, Ca, Cl, Co, Cs, Fe, K, Mn, Na, Rb, Sc Se and Zn have been determined by INAA in diets of four different groups: (a) 19 pre-school children, (b) 18 healthy adults, (c) 23 elderly people living in private institutions and (d) 19 patients with chronic renal failure (CRF). The contents of proteins, lipids and carbohydrates were also analysed in the diets. The daily intakes of the elements analysed were compared to the recommended values set by RDA or WHO.

Restricted access

Abstracts  

The Itingussú drainage basin is situated at 22°44′–22°55′ SL and 44°53′–43°55′ WL, in Coroa-Grande district, Sepetiba Bay, southwest of Rio de Janeiro, Brazil. Its total area is less than 10 km2 and includes a waterfall with three drop offs. The study area is located in a granitic pre-Cambrian embasement, discharging in a mangrove forest fringe. This work attempts to investigate the influence of lithology types in the elemental composition of soil of region and sediments of related mangrove. Instrumental neutron activation analysis and subsequent gamma-ray spectrometry were used. This technique enabled the measurement of at least twenty-one chemical elements. The more representative soil samples were enriched with U and Th. Multivariate Statistical Analysis showed that the soil and sediments formed in this area have been influenced by the leucocratic rocks, enriched with LREE and Th. The factorial analysis enables the identification of five factors of influence in the ordination of elements: presence of iron minerals (biotite); presence of allanite; marine influence in the sediment; differentiated kinetic of transport and diagenesis.

Restricted access
Restricted access

Abstract  

The biological standard reference materials Orchard Leaves SRM 1571 and Oyster Tissue SRM 1566a was analysed by instrumental neutron activation analysis (INAA) at the International Centre for Environmental and Nuclear Sciences, Jamaica at (ICEN) and at the Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Brazil. The comparison of the results with those obtained with the more powerful reactor are used to evaluate the possibilities of INAA for the analysis of biological samples at ICENS. The detection limits, the precision and accuracy of the results obtained in both laboratories are compared. The advantages and disadvantages of the different irradiation facilities are discussed. Some results obtained for Jamaican biological samples are also presented.

Restricted access

Abstract  

The present paper describes radiochemical separation procedures developed for the determination of the elements As, Cr, Hg, Sb and Se in biological reference materials. The methods chosen utilize ion exchange, retention on inorganic exchangers and solvent extraction techniques for the isolation of the elements of interest. These procedures are more rapid than previously used methods, such as distillation and precipitation. As to the sample dissolution, the following procedures were tested using radioactive tracers and reference materials: treatment of the materials in teflon bombs with a mixture of HNO3+H2SO4 or HNO3 only in a normal oven, and with HNO3 in a microwave oven using specially designed digestion bombs.

Restricted access

Abstract  

This study presents preliminary results on mercury distribution, released by gold mining activities, in soils from Vila Nova River region, an area located in Serra do Navio, Amapá, in the Brazilian Amazon. The soil samples were separated in two grain sizes, sand (between 2 and 0.063 mm) and silt+clay (<63 μm), and have been analysed by radiochemical neutron activation analysis. The precision and accuracy of the method were verified by means of the reference material analysis GXR-5 (USGS).

Restricted access

Abstract  

Using instrumental neutron activation analysis, the vertical distribution of La, Ce, Nd, Sm, Eu, Tb, Yb and Lu was determined in 3 well dated sedimentary cores collected from Laguna Mar Chiquita, Argentina. Validation of the methodology was done using the Soil 7 (IAEA) reference material. The REE contents vary according to core location and lithological units, depending on the proportion of fluvial terrigenous components in the lake sediments. Lithologies with higher proportion of terrigenous components show higher REE concentrations, suggesting that the dominant REE carrier phase might be a detrital mineral. There is a consistent value of about 1.2 for (La/Yb)N and (LREE/HREE)N ratios for all sediments at the three sites, indicating a slight LREE enrichment in relation to the average shale NASC. Ce/Ce* values are close to 1.0, meaning that Ce behaves similarly to other light REE's.

Restricted access

Summary  

In the last decades considerable attention has been given to technologically enhanced natural occurring radioactive material (TENORM). Within this frame, of particular concern is the phosphate fertilizer industry, located in Cubatão, São Paulo State, Southwest Brazil. This industry is responsible for the production of 69 million tons of phosphogypsum waste, which is stockpiled in the surrounding environment. This waste concentrates radionuclides of the natural series originally present in the phosphate rocks used as raw material. This study aims to evaluate the environmental impact of such activities in the sediments of the estuarine system. Contents of natural radionuclides from thorium and uranium series were measured in sediments from Cubatão estuarine system, using high-resolution gamma-spectrometry. U and Th were determined by instrumental neutron activation analysis (INAA). It was observed that U and Th concentration is higher in the rivers close to the phosphogypsum piles, at least five points were identified as being affected by anthropogenic factors.

Restricted access