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Chitosan (CS) hydrogel beads and hybrid beads made of a blending of CS hydrogels and Multilayer Graphene Oxide (MGO) were synthesized. The hybrid beads were prepared by gelation in NaOH solution of a 1 wt% CS acid solution with addition of MGO at either 1.5 wt% or 3 wt% loading rates. Prepared beads were characterized by infrared spectroscopy, thermogravimetric analysis (TGA), scanning electron cryo-microscopy and Brunauer--Emmett--Teller (BET) specific surface area measurements. Zn2+ and Metoprolol (MTP) adsorption kinetics and isotherms were studied on the pristine and hybrid CS hydrogel beads. The adsorption kinetics of Zn2+ and MTP in hybrid beads is limited by the diffusion to the MGO sites depending on their accessibility. While pure CS is not efficient for the MTP adsorption, the Langmuir-type isotherms of the 3wt% MGO hydrogel beads (dose: 5 mg/100 mL) show 163 mg⋅g-1 maximum adsorption uptake. The MTP adsorption kinetics and isotherm suggest a MTP trapping on the MGO anionic sites (carboxylate groups) by electrostatic interactions. The Zn2+ adsorption capacities are the highest for the 3 wt% MGO hydrogel beads (236 mg⋅g-1), and only of 40 mg⋅g-1 for the pure CS beads. The presence of Zn2+ adsorption sites in the hybrid bead, such as MGO carboxylate groups giving electrostatic interactions, and CS amine groups leading to complexation, provides synergic adsorption effects. The competitive adsorption of Zn2+ with respect to MTP in equimolar mixture was observed on hybrid beads (dose: 200 mg/100 mL) at 2 mmol⋅L-1 initial total concentration. At pollutant initial total concentration lower than 1.5 mmol⋅L-1, no competition occurs. The regeneration at pH 4 of the hybrid beads toward MTP or Zn2+ adsorption was found to be 35-40% of the initial adsorption uptake for five adsorption/regeneration cycles. [ABSTRACT FROM AUTHOR]

Abstract: Stone substitution is a conventional operation during heritage buildings’ restoration, but becomes problematic for architects and restorers when the quarry is mined out. The compatibility of the substitution stones with the original ones has been for long mainly based on the aesthetical aspect, this resulting too often in a patchwork of original and substitution stones with different patina after several years because of differences of properties. In this study, the objective is to show how substitution stones can be selected by combining aesthetic criteria and stones properties that are relevant for analyzing their compatibility. A couple of French limestones with their potential substitution stones were selected for the study. Our results showed that potential substitution stones selected on their aesthetic criteria require to be rejected because of their differences of physical properties. On the other hand, our results showed also the possibility to select substitution stones with satisfactory aesthetic aspect and properties that enable to expect a satisfactory compatibility with the original stone. [Copyright &y& Elsevier]

Abstract: The mineralogy of the Latosols of the Brazilian Central Plateau remains under discussion in the absence of a clear relationship with their age according to their geomorphic location. The aim of this study was thus to clarify the origin of the kaolinite and gibbsite content variation by studying a regional toposequence and using data from the literature. Chemical composition and soil color were used to discuss mineralogy. The mineralogy of the clay fraction was also investigated using X-ray diagrams. Our results showed that the large variation of kaolinite and gibbsite content can be explained by taking into account both their local and regional location, the variation of the hematite and goethite content remaining limited. The model that is proposed to explain such variation combines a regional component, which is mainly associated to the age of the geomorphic surface and a local component which is mainly associated to the hydraulic conditions along the toposequence. [Copyright &y& Elsevier]

The article addresses the structural effects of solutions of lead nitrate on a suspended or compacted bentonite. A permeability increase is observed on compacted clay. Investigating the composition of output solution, using X-Rays Diffusion at Small Angles and Scanning Electron Microscopy, this permeability increase is explained from structural variations at nanometric (reduction of particle size) and micrometric scales (microfissuration of aggregates). To cite this article: N. Jozja et al., C. R. Geoscience 335 (2003). [Copyright &y& Elsevier]