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- Author or Editor: A. Rodriguez S x
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Abstract
Se in Ni and Co concentration in concentrates obtained from the nickel industry has to be determined for quality control requirements in their commercialization. Analysis of Se at minor and trace levels is relatively complicated and destructive procedures are frequently required. In this work the determination of Se by epithemal neutron activation analysis (ENAA) in 17 samples from Cuban nickel industry was investigated. Application of ENAA allowed nondestructive determination of Se concentration down to ppm level in spite of the presence of high Co, Fe, Ni and Cr contents in the samples. For attenuation of the thermal neutron flux a Cd filter was utilized.
Abstract
In this work the determination of elemental composition of MIBI, MAG-3 and sodium phytate by INAA was investigated. Analytical information about the concentration and/or detection limits of some toxic elements (Hg, Cd, As, Se, Sb) and other trace element of interest (Fe, Cr, Co, Zn, Br) was obtained.
Abstract
A dredged sludge was studied to investigate the influence of ageing and of pretreatment on its drying rate, water sorption/retention, thermal mass loss, XRD and microstructure (SEM).
Ageing caused change in particle thickness and specific surface, a gradual aggregation to form units of the size 10–50 μm, formation of macropores of similar size, unhomogeneity and fissures between aggregates and “super-aggregates”. Macropores were detectable by the initial drying rate especially at 45°C. They indicated a tendency of collapsing at a lower drying rate at 30°C. This is consistent with SEM observations. With ageing the aggregates were more compact and less sensitive to drying.
The aggregated system indicated a higher initial drying rate (higher permeability), whereas stirring induced a lower drying rate, favouring the formation of compact laminar structure.
XRD peak intensity was lowered with ageing due to decrease in crystallinity (stacking faults and/or decrease in crystallite size). The content of amorphous material was lowered as well, reducing water sorption/desorption, which indicated that the specific surface is lower.
From the suitable microstructure induced by ageing some new phases may form (feldspar, zeolites), preferably in the coarser fraction of the sludge. This is disturbed by stirring which operation expels also carbonates from the particle edges and this may reduce the structural strength of the sludge. In aged bentonite suspension a similar tendency was observed of formation of specific microstructures capable of phase transformation, e.g. to feldspar.
Abstract
Thirty elements were determined by INAA in Cuban soil samples collected in 17 zones from western regions of Cuba, which were affected by neuropathy epidemic in 1992. The presence of toxic elements was evaluated to provide data for the analysis of possible paths of intoxication through local agriculture product consumption. The results obtained for As, Th and U are compared with similar data reported on literature.
Summary
Neutron activation analysis has been used to study uranium incorporation in poultry bones as function of chow doped with: (a) uranium (20 ppm); (b) U-doped food (20 ppm) plus phytase (120 ppm) and (c) U-doped food (20 ppm) plus phytase (180 ppm). To investigate this situation experiments involving several groups of Cobb broilers was performed. Two animals per group were sacrificed weekly up to their adultness and uranium concentration in the tibia was measured. It was observed that the concentration of uranium (µg U/g bone) is decreasing all along the animal life spanning period of 14-42 days. This behavior suggests that the skeleton mass is growing faster than the corresponding accumulation of uranium. The administration of phytase seems not to alter this scenario.
Abstract
A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (40K, 234U, 238U, and 239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (137Cs, 210Pb(210Po), 226Ra, 228Ra, 228Th, 230Th, 232Th, 235U, and 241Am). Results for less frequently reported radionuclides (90Sr, 129I, 238Pu, 239Pu, and 240Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.