characterization of (poly)molybdate and (poly)tungstate ions sorbed onto iron (hydr)oxides by ATR-FTIR spectroscopy

The sorption of (poly)molybdate and (poly)tungstate ions onto four iron (hydr)oxides, hematite (α-Fe2O3), goethite (α-FeOOH), akaganeite (β-FeOOH) and lepidocrocite (γ-FeOOH), was followed by in situ attenuated total reflection infrared spectroscopy. The different behaviors of the ionic species and the surface reactivity of these various solids have been investigated and different inner-sphere complexes have been found. On lepidocrocite and goethite a monodentate structure is preferred, while a polymerization of molybdate and tungstate species has been observed onto hematite surface. Both ions have a different behavior on akaganeite: molybdate ions polymerize while tungstate species seems to have the same monodentate structure than those found on goethite

Institutiones ac meditationes in graecam linguam, N. Clenardo authore, cum scholiis et praxi P. Antesignani Rapistagnensis. Operi praefixi sunt indices copiosissimi duo, rerum unus, verborum alter, ex quibus facile quivis perspiciet quantum adjumenti ad intelligendos optimos quosque graecos authores oratione, ac stylo, dialectisve quantumvis dissimiles liber hic sedulis ejus lectoribus sit allaturus : maxime vero novitiis, ut themata in verbis omnibus anomalis ac vocabulis aliis subobscuris sine magno labore aut longa disquisitione possint invenire. Sed et in eorundem gratiam libellus ad operis calcem annexus est, in quo plenissime tota hujus argumenti difficultas exorbetur. Editio postrema.

GLN-2783Bakelants-Hoven, Clénard, n° 248Cat. BN Hung., C836CDM, p. 9

Adsorption Behavior of Arabinogalactan-Proteins (AGPs) from Acacia senegal Gum at a Solid–Liquid Interface

International audienceAdsorption of five different hyperbranched arabinogalactan-protein (AGP) fractions from Acacia senegal gum was thoroughly studied at the solid-liquid interface using a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR), and atomic force microscopy (AFM). The impact of the protein/sugar ratio, molecular weight, and aggregation state on the adsorption capacity was investigated by studying AGP fractions with different structural and biochemical features. Adsorption on a solid surface would be primarily driven by the protein moiety of the AGPs through hydrophobic forces and electrostatic interactions. Increasing ionic strength allows the decrease in electrostatic repulsions and, therefore, the formation of high-coverage films with aggregates on the surface. However, the maximum adsorption capacity was not reached by fractions with a higher protein content but by a fraction that contains an average protein quantity and presents a high content of high-molecular-weight AGPs. The results of this thorough study highlighted that the AGP surface adsorption process would depend not only on the protein moiety and high-molecular-weight AGP content but also on other parameters such as the structural accessibility of proteins, the molecular weight distribution, and the AGP flexibility, allowing structural rearrangements on the surface and spreading to form a viscoelastic fil

Adsorption of Hyperbranched Arabinogalactan-Proteins from Plant Exudate at the Solid–Liquid Interface

Adsorption of hyperbranched arabinogalactan-proteins (AGPs) from two plant exudates, A. senegal and A. seyal, was thoroughly studied at the solid−liquid interface using quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR), and atomic force microscopy (AFM). Isotherms of the adsorption reveal that 3.3 fold more AGPs from A. seyal (500 ppm) are needed to cover the gold surface compared to A. senegal (150 ppm). The pH and salt concentration of the environment greatly affected the adsorption behavior of both gums, with the surface density ranging from 0.92 to 3.83 mg m−2 using SPR (i.e., “dry” mass) and from 1.16 to 19.07 mg m−2 using QCM-D (wet mass). Surprisingly, the mass adsorbed was the highest in conditions of strong electrostatic repulsions between the gold substrate and AGPs, i.e., pH 7.0, highlighting the contribution of other interactions involved in the adsorption process. Structural changes of AGPs induced by pH would result in swelling of the polysaccharide blocks and conformational changes of the polypeptide backbone, therefore increasing the protein accessibility and hydrophobic interactions and/or hydrogen bonds with the gold substrate

Adsorption of arabinogalactan-proteins from Acacia gums (senegal and seyal) and its molecular fractions onto latex particles

International audienceAdsorption of Acacia gums (GA) (A. senegal and A. seyal) and A. senegal molecular fractions, made ofarabinogalactan-proteins (AGPs) with different molecular weights, onto latex particles, with different sizes andsurface charges, was studied using molecular (fluorescence and nanoIR spectroscopies, microscopies includingAtomic Force Microscopy) and mesoscopic (Dynamic Light Scattering, zeta potential, Asymmetrical flow field-flow fractionation) methods. Adsorption of GA onto latex particles revealed a complex mechanism of adsorp-tion where the highest adsorption was observed when A. senegal and latex particles were negatively charged. Theinvert was observed for A. seyal where the maximum of adsorption was observed when gum and latex wereoppositely charged. The duality of positive and negative charges on GA macromolecules together with confor-mational changes certainly explain the complex mechanism of adsorption. A mechanism where either the proteinmoiety either the sugars blocks adsorb is to be preferred. This mechanism seems to produce differences ofbehaviour due to viscoelastic properties of adsorbed layers, and differences of hydration due to differences ofpolarity of AGPs. The consequence of electrostatics in the adsorption process is a water release from the adsorbedlayers and important gain in entropy. A fair agreement was found between protein content and adsorbed layerthickness of GA, with the formation of partial coverage, monolayer and multilayer films depending on GAconcentration. Structural changes induced by GA adsorption onto latex particles was probed using fluorescenceand nanoIR spectroscopies without giving clear evidence of conformational changes induced after GA adsorption.The results of this study highlighted that GA surface adsorption process depend not only on the protein moietyand electrostatic interactions but also on other parameters related to AGP hydration status. The protein structuralaccessibility, the molecular weight distribution, the AGPs intrinsic viscoelastic properties allowing structuralrearrangements on the surface and spreading in order to form a viscoelastic film onto latex particles should alsoplay a pivotal role in the adsorption process

Production of added-value materials from a hazardous waste in the aluminium tertiary industry: Synergistic effect between hydrotalcites and glasses

© 2015 Elsevier Ltd. All rights reserved. The powdered solids trapped in filter sleeves in the aluminium tertiary industry are currently disposed of in secure landfills as a result of environmental considerations. Their classification as a hazardous waste is due to their high aluminium content as metallic aluminium or in compounds such as aluminium nitride. These compounds can react with a very low moisture content to release toxic or hazardous gases such as hydrogen and ammonia. This paper presents a low-cost process for the full recovery of this hazardous waste in three steps leading to the production of two different added-value materials. In the first step, mild acid hydrolysis of the waste is carried out to obtain a concentrated aluminium solution and an inert cake. The following steps consist of hydrotalcite synthesis with the resulting solution, and the production of transparent glasses in the CaO-Al2O3-SiO2 system with the cake. Characterisation of the products obtained indicates that the hydrotalcites can adsorb anionic pollutants (molybdates) in a simple way, while the glasses afford improved optical properties in comparison with those prepared by direct vitrification of the waste.The authors thank Metalquex SL (Zaragoza, Spain) for supplying the wastes and CSIC for its financial support (P.I.E 201260E115). We also gratefully acknowledge the assistance provided by Dr. Blanca Casal for helpful discussion during this research. R. Sánchez-Hernández thanks MINECO for grant BES-2013-066269.Peer Reviewe

Production of added-value materials from a hazardous waste in the aluminium tertiary industry: Synergistic effect between hydrotalcites and glasses

The powdered solids trapped in filter sleeves in the aluminium tertiary industry are currently disposed of in secure landfills as a result of environmental considerations. Their classification as a hazardous waste is due to their high aluminium content as metallic aluminium or in compounds such as aluminium nitride. These compounds can react with a very low moisture content to release toxic or hazardous gases such as hydrogen and ammonia. This paper presents a low-cost process for the full recovery of this hazardous waste in three steps leading to the production of two different added-value materials. In the first step, mild acid hydrolysis of the waste is carried out to obtain a concentrated aluminium solution and an inert cake. The following steps consist of hydrotalcite synthesis with the resulting solution, and the production of transparent glasses in the CaO–Al2O3–SiO2 system with the cake. Characterisation of the products obtained indicates that the hydrotalcites can adsorb anionic pollutants (molybdates) in a simple way, while the glasses afford improved optical properties in comparison with those prepared by direct vitrification of the waste.The authors thank Metalquex SL (Zaragoza, Spain) for supplying the wastes and CSIC for its financial support (P.I.E 201260E115). We also gratefully acknowledge the assistance provided by Dr. Blanca Casal for helpful discussion during this research. R. Sánchez-Hernández thanks MINECO for grant BES-2013-066269