Hierarchical classification and matching of mid-infrared spectra of paint samples for forensic applications.

A novel fast and automatic methodology for the hierarchical classification and similarity matching of mid-infrared spectra of paint samples based on the principles of Soft Independent Modelling of Class Analogy (SIMCA) and on the definition and properties of the Mahalanobis distance is here proposed. This approach was tested in a so-called market study (i.e., targeting products largely accessible to the general public and conceived for a considerably wide range of usages) conducted across the surroundings of the city of Lille, in France, and has permitted not only to successfully achieve the chemical characterisation of most of the analysed samples but also to discover specific commonality patterns among specimens sharing the same chemical features.

The five-analyzer point-to-point scanning crystal spectrometer at ESRF ID26.

X-ray emission spectroscopy in a point-to-point focusing geometry using instruments that employ more than one analyzer crystal poses challenges with respect to mechanical design and performance. This work discusses various options for positioning the components and provides the formulas for calculating their relative placement. Ray-tracing calculations were used to determine the geometrical contributions to the energy broadening including the source volume as given by the beam footprint on the sample. The alignment of the instrument is described and examples are given for the performance.

TEXS: in-vacuum tender X-ray emission spectrometer with 11 Johansson crystal analyzers.

The design and first results of a large-solid-angle X-ray emission spectrometer that is optimized for energies between 1.5 keV and 5.5 keV are presented. The spectrometer is based on an array of 11 cylindrically bent Johansson crystal analyzers arranged in a non-dispersive Rowland circle geometry. The smallest achievable energy bandwidth is smaller than the core hole lifetime broadening of the absorption edges in this energy range. Energy scanning is achieved using an innovative design, maintaining the Rowland circle conditions for all crystals with only four motor motions. The entire spectrometer is encased in a high-vacuum chamber that allocates a liquid helium cryostat and provides sufficient space for in situ cells and operando catalysis reactors.

Double metal cyanides as heterogeneous Lewis acid catalysts for nitrile synthesis via acid-nitrile exchange reactions.

A series of transition metal-based double metal cyanides (DMCs) were studied as catalysts for the synthesis of nitriles via acid-nitrile exchange reaction. The best nitrile yields were obtained with Co3[Co(CN6)]2 DMC, which proved to be a versatile, stable, reusable and highly active catalyst, exhibiting an activity comparable to that of homogeneous Lewis acid catalysts.

A contribution to improve the calculation of the acid generating potential of mining wastes.

Mine wastes from sulfide-bearing ore extraction and processing are often stored at the surface of mine sites and could generate mine drainage. Prediction tests are completed to predict the water quality associated with the deposition of mining wastes. Static tests can quickly assess the acid-generating potential (AP) and the neutralization potential (NP). Whereas some studies recommend to take into account a mineral reactivity factor for the NP determination, the reactivity rates of acidifying minerals are not considered in the AP calculation. The aim of this study is to bring contribution to the improvement of the static test determination by adding kinetic factors in the AP determination. Eight sulfides (pyrite, Ni-pyrite, pyrrhotite, Ni-pyrrhotite, chalcopyrite, galena, sphalerite, arsenopyrite) and a sulfosalt (gersdorffite) were separately submitted to kinetic tests in modified weathering cells. This test was selected for its rapidity of results and for the low amount of material used, as it is somewhat difficult to obtain pure minerals samples. Five synthetic tailings were composed by mixing pure sulfides in various proportions and submitted to the same kinetic tests. The oxidation rates of synthetic tailings were compared with the weighted combined oxidation rates of individual pure sulfides. The oxidation rates of the synthetic tailings calculated from those of pure sulfides are within the same order of magnitude than those obtained through the kinetic experiments. The AP of synthetic tailings were calculated according to standard equations of the literature and compared with the new method.

Geochemical investigation of the galvanic effects during oxidation of pyrite and base-metals sulfides.

Predicting the water quality at mine sites is of significant importance for developing mines with respect for the environment. Acid mine drainage (AMD) occurs when sulfides are in contact with oxygen and water, and several parameters and mechanisms influence final drainage quality. Galvanic interactions influence the reactivity of sulfide minerals, which act as semi-conductors. These galvanic interactions have been insufficiently studied in the context of AMD generation. In this study, the influence of pyrite on the reactivity of sphalerite and chalcopyrite was investigated. Five blends, comprised of free grains of quartz/pyrite, quartz/chalcopyrite, quartz/sphalerite, quartz/pyrite/chalcopyrite, and quartz/pyrite/sphalerite, were subjected to geochemical testing. Five weathering cells were monitored over a 200-day period during which they were leached twice weekly. Leachates were analyzed for pH, Eh, electrical conductivity, and sulfate and metal concentrations. The results of these analyses showed that galvanic interactions occurred between free sulfide grains. Pyrite was galvanically protected over the full testing period in the quartz/pyrite/chalcopyrite blend, and partially protected in the quartz/pyrite/sphalerite blend. Moreover, the release of Cu from chalcopyrite and Zn, Mn, and Cd from sphalerite was accelerated in the presence of pyrite. This work provides a better understanding of the influence of pyrite on chalcopyrite and sphalerite reactivity by highlighting the galvanic effects. In the future, to improve the reliability of AMD prediction tests, galvanic interactions should be considered in both the prediction of the acid generation potential and the estimation of metal and metalloid release rates.