Sincrotrón ALBA
Héloise Tissot, KTH Royal Institute of Technology, Stockholm (Sweden)
Cuándo
Información de contacto
Inma Hernández
Abstract
Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) is an excellent method for the investigation of the interfacial chemistry. In newly developed NAP-XPS setups, the work pressure in the analysis chamber is raised up to 20 mbar. In those conditions, not only solid/gas interfaces are investigable by NAP-XPS, but also liquid water/solid and vapor/ liquid interfaces. The interaction of liquid water with gases or surfaces plays a major role in many processes in environmental chemistry, in particular at the interface between liquid water and mineral surfaces as clays.
Natural clays are key materials in ecological engineering, from the geological storage of long half-time radioactive waste to CO2 sequestration. With respect to these issues, it is crucial to establish a bridge between the microscopic scale (ionic exchange, ion solvation, ion and matter transport) and the macroscopic scale (swelling, retention capacities). Using NAP-XPS, we monitored the hydration process for different swelling clays containing different type of ions in their interlayer. Indeed, inside the clay interlayer, ions core-level are sensitive to the hydration state (change in binding energy) due to a screening effect of the negatively charged clay layers by water molecules. These results were compared with the behaviour of alkali-halide ions in aqueous solutions.
References:
(1) Tissot, H.; Olivieri, G.; Gallet, J. J.; Bournel, F.; Silly, M. G.; Sirotti, F.; Rochet, F. Cation Depth-Distribution at Alkali Halide Aqueous Solution Surfaces. J. Phys. Chem. C 2015, 119 (17), 9253–9259.
(2) Malikova, N.; Cade, A.; Dubois, E.; Marry, V.; Turq, P.; Breu, J.; Longeville, S. Water Diffusion in a Synthetic Hectorite Clay Studied by Quasi-Elastic Neutron Scattering. J. Phys. Chem. C 2007, 111, 17603–17611.