Molecular Fractionation of Ancient Organic Compounds in Deeply Buried Halite Crystals.

The molecular fractionation of organic compounds through adsorption in minerals has wide implications, including tracing the origins of life, carbon sequestration, and climate change. Here we present the first in situ examination of molecular fractionation within individual crystals via optical-photothermal infrared (O-PTIR) spectroscopy. Our study focuses on a unique inclusion trail within deeply buried halite crystals, characterized by a distinctive orange-to-blue fluorescence gradient, providing primary evidence of molecular variation in ancient carbon-based fluids within the inclusion trail.

Identification and composition of carbonate minerals of the calcite structure by Raman and infrared spectroscopies using portable devices.

A portable Raman device with a 532 nm excitation laser and a portable infrared spectrometer with ATR (Attenuated Total Reflection) mode were used to analyse the spectral features associated with the identification and compositional variation of Ca-Mg-Fe-Mn natural carbonate minerals with a calcite structure (calcite, ankerite, dolomite, siderite, rhodochrosite, and magnesite). A systematic study of the variations of the peak positions with various compositional ratios was carried out. Most of the band positions were shifted to lower wavenumbers with increasing ionic radius or atomic mass of the divalent cations but the band of the translational lattice (T) mode in Raman and the symmetric bending (ν) band in the mid-infrared were the most sensitive.

Adsorption mechanisms of fatty acids on fluorite unraveled by infrared spectroscopy and first-principles calculations.

Hypothesis: The adsorption mechanisms of fatty acids on minerals are largely debated from years, and their understanding is now required to improve flotation processing in the critical context of raw materials. Three wavenumbers have been observed in the literature for the asymmetric stretching vibration of COO after the adsorption of fatty acids on mineral surfaces. They have been interpreted as different adsorbed forms, such as a precipitate formation, an adsorption of sole or bridged carboxylates, an anion exchange, or adsorbed modes, such as monodentate or bidentate configurations.

Synergistic adsorptions of NaCO and NaSiO on calcium minerals revealed by spectroscopic and molecular dynamics studies.

The synergistic effects between sodium silicate (NaSiO) and sodium carbonate (NaCO) adsorbed on mineral surfaces are not yet understood, making it impossible to finely tune their respective amounts in various industrial processes. In order to unravel this phenomenon, diffuse reflectance infrared Fourier transform and X-ray photoelectron spectroscopies were combined with molecular dynamics to investigate the adsorption of NaSiO onto bare and carbonated fluorite (CaF), an archetypal calcium mineral. Both experimental and theoretical results proved that NaCO adsorbs onto CaF with a high affinity and forms a layer of NaCO on the surface.

FTIR spectroscopy of woods: A new approach to study the weathering of the carving face of a sculpture.

Fourier transform infrared spectroscopy (FTIR), a useful method to study woods, has been applied in order to measure an eventual gradient of water absorbed (more precisely, hydroxyl groups, OH) between the surface and the inner part of an ancient and a modern wooden sculptures. The methodology adopted has consisted in comparing FTIR bands within two spectral ranges, one corresponding to the OH content in the wood (around 3400cm(-1)) and the other to the lignin molecules (aromatic CC, around 1610cm(-1)). The ratio between the intensities of the peaks leads to a self-normalization of the measurements which avoids the effects of some experimental parameters (such as sample preparation).

A 'dry' condensation origin for circumstellar carbonates.

The signature of carbonate minerals has long been suspected in the mid-infrared spectra of various astrophysical environments such as protostars. Abiogenic carbonates are considered as indicators of aqueous mineral alteration in the presence of CO2-rich liquid water. The recent claimed detection of calcite associated with amorphous silicates in two planetary nebulae and protostars devoid of planetary bodies questions the relevance of this indicator; but in the absence of an alternative mode of formation under circumstellar conditions, this detection remains controversial.

Infrared spectroscopy of OD vibrators in minerals at natural dilution: hydroxyl groups in talc and kaolinite, and structural water in beryl and emerald.

An infrared (IR) study of natural deuteration is conducted on minerals containing hydroxyl groups (talc and kaolinite) and channel-water-bearing minerals (beryl and emerald). In talc, the OD valence vibration is located at 2710 cm(-1), corresponding to OD groups surrounded by 3 Mg atoms. In kaolinite, the OD valence vibrations are located at 2671 cm(-1) (inner OD group), 2712, 2706, and 2700 cm(-1) (three inner-surface OD groups).

Use of treated bark for the removal of lipids from water.

Raw, biologically treated bark and bark impregnated with transition metal ions were used to retain the lipids from synthetic emulsions. Several experimental parameters affecting the lipid removal efficiency (RE) were studied (initial concentration of lipids, temperature, time, pH, carboxylic acid chain length, etc.).

Study of tropaeolin degradation by iron--proposition of a reaction mechanism.

The degradation of tropaeolin by iron was studied under oxidizing and inert atmospheres. The products were identified by various chromatographic and spectroscopic methods. Under inert atmosphere, the proposed model of mechanism is based on the adsorption of tropaeolin by the sulfonate function on the solid iron, followed by a reduction of the [bond]Nz[double bond]N[bond] bond with formation of 1-amino-2-naphthol and sulfanilic acid.