Polycyclic aromatic hydrocarbons remobilization from contaminated porous media by (bio)surfactants washing.

Biosurfactants, surface-active agents produced by microorganisms, are increasingly studied for their potential use in soil remediation processes because they are more environmentally friendly than their chemically produced homologues. In this work, we report on the use of a crude biosurfactant produced by a bacterial consortium isolated from a PAHs-contaminated soil, compared with other (bio)surfactants (Tween80, Sodium dodecyl sulfate - SDS, rhamnolipids mix), to wash PAHs from a contaminated porous media. Assays were done using columns filled with sand or sand-clay mixtures (95:5) spiked with four model PAHs.

Production of biosurfactant using the endemic bacterial community of a PAHs contaminated soil, and its potential use for PAHs remobilization.

Biosurfactants are surface-active agents produced by microorganisms whose use in soil remediation processes is increasingly discussed as a more environmentally friendly alternative than chemically produced surfactants. In this work, we report the production of a biosurfactant by a bacterial community extracted from a polluted soil, mainly impacted by PAHs, in order to use it in a soil-washing process coupled with bioremediation. Nutrient balance was a critical parameter to optimize the production.

Browning phenomenon of medieval stained glass windows.

In this work, three pieces of historical on-site glass windows dated from the 13th to 16th century and one archeological sample (8th century) showing Mn-rich brown spots at their surface or subsurface have been characterized by optical microscopy and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy. The oxidation state of Mn as well as the Mn environment in the alteration phase have been characterized by X-ray absorption spectroscopy at the Mn K-edge. Results show that the oxidation state of Mn and therefore the nature of the alteration phase varies according to the sample considered and is correlated with the extent of the brown alteration.

Fluorescence detection to determine proteins and humic-like substances fingerprints of exopolymeric substances (EPS) from biological sludges performed by size exclusion chromatography (SEC).

Fingerprints of extracellular polymeric substances (EPS) from activated and anaerobic granular sludges were obtained by size exclusion chromatography coupled to UV (210 and 280 nm) and fluorescence (221/350 nm (protein-like molecules) and 345/443 nm (humic-like substances)) detection. The total area below the peaks obtained with fluorescence detection is linked to the protein or humic-like substances EPS content. The EPS protein fingerprints, usually recorded with UV-280 nm, change dramatically, mainly in the relative size of peaks when they were measured by a florescence detection method.

Site partitioning of Cr3+ in the trichroic alexandrite BeAl2O4:Cr3+ crystal: contribution from x-ray absorption spectroscopy.

X-ray absorption spectroscopy measurements at the Cr K-edge of a trichroic crystal of alexandrite BeAl(2)O(4):Cr(3+) for different orientations of the crystal with respect to the polarization and direction of the x-ray incident beam have been performed. Analysis of the experimental spectra with the help of first-principles calculations of x-ray absorption spectra allowed us to estimate the proportion of chromium Cr(3+) cations among the two different octahedral sites of the alexandrite structure (70% in the C(s) site-30% in the C(i) site). The methodology presented in this work opens up new possibilities in the field of mineralogy for the study of complex minerals containing several sites potentially occupied by several transition elements or for solid solutions.

Contribution of molecular dynamics simulations and ab initio calculations to the interpretation of Mg K-edge experimental XANES in K(2)O-MgO-3SiO(2) glass.

The structural environment of Mg in a K-bearing silicate glass of composition K(2)MgSi(3)O(8) is investigated by x-ray absorption near-edge structure (XANES) spectroscopy at the Mg K-edge. XANES calculations are performed using a plane-wave electronic structure code, and a structural model obtained by classical molecular dynamics coupled to ab initio relaxation. Bond valence theory is used to validate plausible environments within the structural models.

Order and disorder in titanosilicate glass by 17O MAS, off-MAS, and 3Q-QCPMG-MAS solid-state NMR.

An 17O-enriched version of the titanosilicate glass, KTS2 (K(2)O.TiO(2).2SiO(2)), was analyzed by 17O MAS, off-MAS, and 3Q-QCPMG-MAS experiments.

First-principles calculation of 17O and 25Mg NMR shieldings in MgO at finite temperature: rovibrational effect in solids.

The temperature dependence of (17)O and (25)Mg NMR chemical shifts in solid MgO have been calculated using a first-principles approach. Density functional theory, pseudopotentials, a plane-wave basis set, and periodic boundary conditions were used both to describe the motion of the nuclei and to compute the NMR chemical shifts. The chemical shifts were obtained using the gauge-including projector augmented wave method.