Trace elements status in the terrain of an impounded vehicle scrapyard

Journal of Radioanalytical and Nuclear Chemistry - The impact of a scrapyard of impounded vehicles in São Paulo state on topsoil was evaluated for As, Ba, Co, Cr, Cu, Mo, Ni, Pb, V, Zn and...     

NAA and UV Laser Ablation ICP-MS for Platinum Group Elements and Gold Determination in NiS Fire Assay Buttons: A Comparison between Two Methods

NAA and UV laser ablation ICP-MS were used to determine platinum group elements (PGEs) and gold in the geological reference materials UMT-1, WPR-1, WMG-1, GPT-4 and GPt-6, after NiS fire assay. Both methods presented results were good agreement with the recommended values. NAA gave more accurate values for Ir (relative errors between 0 to 9%) and UV-LA-ICP-MS presented better results for Pt (relative errors less than 12%, except for WPR-1). UV-LA-ICP-MS showed better sensitivity than NAA for Pd and Os. On the other hand, NAA showed lower detection limits for Ir and Au. Advantages and disadvantages of each method are discussed.     

Fe-site assignments in Y1Ba2Cu3O7 revisited

A new symmetric Fe³⁺ site (labelled E) (δ=0.28(2) mm/s and Δ=0.15 mm/s) is observed in the R₁Ba₂Cu₃O₇ family of superconductors for R=Y and Eu. The decay and growth of site E are established in two seemingly unrelated experiments, one as a function of room temperature aging for R=Y, and the other as a function of oxygen loading at elevated temperatures and pressures for R=Eu. In each experiment, the results show that site E is genetically related to the well documented chainsites A(Δ=1.9 mm/s), C(Δ=1.1 mm/s) and D(Δ=1.6 mm/s). We propose that site E represents a quasi-octahedral chain-site having pairs of O(1), O(4) and O(5) nearestneighbor oxygen sites. The two remaining doublets, B(Δ≈0.4 mm/s) and B′(Δ=0.78 mm/s) represent Fe³⁺ dopant sites present in the all-important CuO₂ planes, possessing coordination numbers of 6 and 5, respectively.     

The unusual glass forming tendency in the Ge2−2xSn2xSe3 ternary

Homogeneous melt-quenched alloy glasses in the indicated ternary have been prepared over a wide range of composition 0<x<0.72. The molecular structure has been examined by differential scanning calorimetry and Mossbauer spectroscopy. The microscopic origin of the unusual glass forming tendency is traced to the existence of a floppy molecular fragment of zig-zag chains of GeSe₄ tetrahedral units, based on the structure of c-GeSnS₃.     

Potentially toxic elements downward mobility in an impounded vehicle scrapyard

Journal of Radioanalytical and Nuclear Chemistry - In Brazil impounded vehicle scrapyards (IVS) are often overcrowded and may pose a source of potentially toxic elements (PTEs). In this study, PTEs...     

The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion: an investigation of low recoveries

A series of experiments was undertaken to measure the recovery efficiency of platinum, palladium and gold from silicate rocks using a sodium peroxide fusion followed by anion exchange separation of the analytes as chloro complexes. Results obtained by graphite furnace atomic absorption spectrometric analysis of standard solutions prepared in dilute HCl or HCl-acidified sodium peroxide solution showed that recoveries were near quantitative. However, when standard solutions were added to an alkaline sodium peroxide solution, which was then acidified, low results were obtained for platinum and gold (46% and 76% respectively). Low and variable results were also obtained when standard solutions were added to a peridotite sample that had been dissolved by the state procedure, and in the analysis of the South African Bureau of Standards certified reference material, SARM 7. Various experiments were undertaken to investigate these low recoveries, but the reason proposed here is the formation of hydroxychloro compounds in alkaline solution which are not, on acidification with HCl, converted quantitatively to the chloro complex necessary for quantitative anion exchange separation. It is concluded that a sodium peroxide fusion followed by an anion-exchange separation does not appear to form the basis of a successful technique for the determination of platinum, palladium and gold in silicate rocks.     

Characterization of Ni-Containing Goethites by Mössbauer Spectroscopy and Other Techniques

A set of goethite samples from the oxidized level of Vermelho Ni-lateritic deposit was investigated by TEM, XRD, TGA-DTA, FTIR and Mössbauer spectroscopy and compared to a series of synthetic goethite samples, with similar Ni content. Natural Ni-containing goethite presents poor crystallinity and does not incorporate more than about 4 mol% Ni. Natural goethite particles also contain significant amounts of Al and Cr (1.6 and 0.7 mol%, in average, respectively). The wavenumbers of the OH deformation vibration bands -OH (in-plane vibration) and lengthening -OH (out of plane vibration) are coarsely negatively correlated with Ni content. The weight loss during the thermal analysis of synthetic samples shows a good linear relationship with Ni content, pointing to a proton uptake in order to compensate a possible charge imbalance due to a Ni²⁺ for Fe³⁺ substitution. The Mössbauer spectra of Ni-goethite present one sextet whose parameters are in agreement with those usually reported for goethite. The magnitude of the hyperfine field slightly decreases with increasing Ni, while the other parameters remain unchanged. These variations may be explained by Ni incorporation, but also by differences in the crystallinity. The effect of the low Ni concentration in our samples was a weak to medium correlation of the analytical signals with the Ni content in goethite, but when considered together, the results indicate that isomorphic substitution is occurring.