Colloid/nanoparticle formation and mobility in the context of deep geological nuclear waste disposal (Project KOLLORADO-2) ; final report (KIT Scientific Reports ; 7645)

To assess the relevance of colloidal influences on radionuclide transport for the long-term safety of a radioactive waste repository, the KOLLORADO-2 project integrates the results of geochemical and hydrogeological studies. The results may serve as a basis for an appraisal of the implications of colloid presence in the vicinity of radioactive waste repositories in different deep geological host-rock formations

Layered metal (II) and silico-phosphonates with ion exchange properties

International audienc

Structural Study of Interlayer Zr Particles in Exchanged and Pillared Beidellite

Zirconia pillared clays (with synthetic beidellite as host material) were prepared by replacing the sodium interlayer cations by zirconium hydroxy polycations, and then heating to stabilize the structure. The pillaring solution was an aqueous solution of zirconyl chloride, but the structure of the polycation which is intercalated remains unknown. From the XRD data. the interlayer spacing was found to be 9 Å in Zr exchanged beidellite and slightly lower (7Å) after calcination. The local environment of zirconium in solid zirconyl chloride and in the pillaring solution was first examined and then in the ion-exchanged and calcined beidellite. The EXAFS results for zirconyl chloride in the solid state and in aqueous solution, showed that the nearest neighbours and the next-nearest-neighbours environments of Zr are identical in solid and in solution. In the Zr-exchanged beidellite, the Zr cations have the same environment as in the pillaring solution. On the opposite. the mean Zr-O and Zr-Zr distances in the calcined sample are shortened with respect to Zr-exchanged beidellite

MgAl Hydrotalcite-derived Mixed Oxides for CO2 Adsorption

SSCI-VIDE+ATARI+VFO:AAUInternational audienceLayered Double Hydroxides (LDHs) and LDH-derived materials are potentially good adsorbents for CO2. Moreover, they are relatively cheap, they are easy to synthesize, they present high sorption capacity, and surface basicity. They have been intensively studied in CO2 capture at high temperature, presenting variable sorption capacities for MgAl LDHs with the same composition, but prepared under different synthesis conditions. The sol-gel synthesis method is an attractive one-step procedure to synthesize LDHs under mild conditions, with low energy consumption and short synthesis time. The present study is based on the synthesis of hydrotalcites (HTs) by sol-gel process for CO2 adsorption. The structural and physico-chemical properties of the as-synthesized and calcined HTs have been deeply characterized. Moreover, the effect of the surface basicity and the CO2 sorption capacity have been investigated.Adsorption calorimetry was applied for determining the concentration (from the adsorption volumetric isotherms), strength and strength distribution (using the differential heat of adsorption as a function of coverage) of the basic sites involved in CO2 adsorption. The hydrotalcite-derived mixed oxides surface basicity was probed by adsorption calorimetry of SO2.Two population of basic sites were identified, at low energy (heat of adsorption below 60 kJ/mol) and high energy (heat of adsorption higher than 150 kJ/mol). The sol-gel method led to the formation of hydrotalcites with similar (sometimes higher) performances than conventional LDHs prepared by time and energy consuming methods (like coprecipitation). The calcined hydrotalcites exhibit CO2 adsorption capacities of around 0.5 mmol/g, a value similar to those reported in the literature for sample generally synthesized by coprecipitation (see figure).A linear correlation between the surface basicity (concentration of low and high energy sites) and the adsorption capacity was found. The possibility to tune the Mg/Al molar ratio is a promising feature to obtain a wide range of LDHs (with various surface basicity) with a higher efficiency in CO2 adsorption.Acknowledgments: This work was supported by Université de Haute Alsace and École Doctorale Physique et Chimie- Physique (ED 182). XRD, NMR, XRF, BET, TGA, were performed on the technical platforms of IS2M

Reinforcement of recycled PP polymers by nanoparticles incorporation

Recycling process seems to be the most efficient way to reduce ecological impacts of used polymers. Nevertheless, the properties of the recycled PP polymer are proved to be insufficient during its reuse, particularly with regard to its thermo-mechanical and rheological behaviors. The incorporation of nanoparticles as fillers into polymer matrix seems to be one of the most successful solutions to upgrade recycled PP polymer. This paper presents an overview on the application of different nanofillers such as clay, calcium carbonate (CaCO3), Silica (SiO2), Zinc Oxide (ZnO), carbon black (CB), carbon nanotubes (CNT), antioxidizers and others into recycled PP matrix. Literature works on the effects of nanofillers on obtained nanocomposites are extensively studied. The first section deals with PP recycling and its impact on thermal, mechanical and rheological properties of the polymer. Then, the second part summarizes recent studies on the effects of nanoparticles incorporation on thermo-mechanical and rheological properties of recycled PP. Finally, recyclability of PP-based nanocomposites is discussed

MgAl Hydrotalcite-derived Mixed Oxides for CO2 Adsorption

SSCI-VIDE+ATARI+VFO:AAUInternational audienceLayered Double Hydroxides (LDHs) and LDH-derived materials are potentially good adsorbents for CO2. Moreover, they are relatively cheap, they are easy to synthesize, they present high sorption capacity, and surface basicity. They have been intensively studied in CO2 capture at high temperature, presenting variable sorption capacities for MgAl LDHs with the same composition, but prepared under different synthesis conditions. The sol-gel synthesis method is an attractive one-step procedure to synthesize LDHs under mild conditions, with low energy consumption and short synthesis time. The present study is based on the synthesis of hydrotalcites (HTs) by sol-gel process for CO2 adsorption. The structural and physico-chemical properties of the as-synthesized and calcined HTs have been deeply characterized. Moreover, the effect of the surface basicity and the CO2 sorption capacity have been investigated.Adsorption calorimetry was applied for determining the concentration (from the adsorption volumetric isotherms), strength and strength distribution (using the differential heat of adsorption as a function of coverage) of the basic sites involved in CO2 adsorption. The hydrotalcite-derived mixed oxides surface basicity was probed by adsorption calorimetry of SO2.Two population of basic sites were identified, at low energy (heat of adsorption below 60 kJ/mol) and high energy (heat of adsorption higher than 150 kJ/mol). The sol-gel method led to the formation of hydrotalcites with similar (sometimes higher) performances than conventional LDHs prepared by time and energy consuming methods (like coprecipitation). The calcined hydrotalcites exhibit CO2 adsorption capacities of around 0.5 mmol/g, a value similar to those reported in the literature for sample generally synthesized by coprecipitation (see figure).A linear correlation between the surface basicity (concentration of low and high energy sites) and the adsorption capacity was found. The possibility to tune the Mg/Al molar ratio is a promising feature to obtain a wide range of LDHs (with various surface basicity) with a higher efficiency in CO2 adsorption.Acknowledgments: This work was supported by Université de Haute Alsace and École Doctorale Physique et Chimie- Physique (ED 182). XRD, NMR, XRF, BET, TGA, were performed on the technical platforms of IS2M

Interaction of titanium with smectite within the scope of a spent fuel repository: a spectroscopic approach

AbstractThe Swedish and Finnish nuclear waste repository design, KBS-3H, foresees horizontal emplacement of copper canisters-bentonite modules surrounded by a titanium shell. The interaction of titanium with bentonite was studied here using a combination of wet chemistry and a spectroscopic approach to evaluate the potential impact of Ti corrosion on the clay. For natural analogue clays with high Ti contents, spectroscopic investigations showed that titanium occurs as crystalline TiO2. In contrast, the Ti in the MX-80 bentonite occurs in the clay structure, presumably in the octahedral sheet. Hydrothermal tests conducted at 200°C using synthetic montmorillonite showed little if any change in the montmorillonite structure at near-neutral and acidic conditions. Under alkaline conditions, limited alteration was observed, including the formation of trioctahedral clay minerals and zeolite. These changes, however, occurred independently of the addition of Ti. In the batch tests conducted at 80°C, Ti did not occur as separate TiO2particles. The comparison of experimental data with spectroscopic simulations provides sound evidence that Ti was incorporated in a neoformed phyllosilicate structure.</jats:p

Functionalisation of natural fibers using ionizing radiations

International audiencePlant products arouse great interest in many fields (construction, automotive, textiles, etc …).However, some of their characteristics as their flammability represent major disadvantagesfor some applications. Research is now being conducted in academia and industry to developeffective methods of functionalizing or modifying the surface of these fibers to improve theirperformance. In this respect, radiation-grafting, based on the use of ionizing radiation(gamma or e-beam), represents an interesting method compared to chemical or enzymaticmethods. This technique makes it possible to generate radicals on the fibers allowing thegrafting of molecules of interest, thus offering a large spectrum of possibilities for themodification of the fibers [1][2]. Two ways for grafting under ionizing conditions can beused (Figure 1), pre irradiation and mutual irradiation. In any case, many factors conditionthe success of grafting reactions. In particular, the structure and the composition of thesubstrate influence the nature of the active species formed, and therefore, the feasibility ofthe grafting reaction. Some techniques, such as Electronic Paramagnetic Resonance (EPR),helps us to better understand these parameters, which will be the subject of this presentation