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(T/MF142) Modelling of the sorption of inorganic ions on natural minerals. Fedoroff, Michel1, Duc, Myriam1, Jeanjean, Janine1, Lefevre, Gregory1, Rouchaud, Jean-Claude1, 1 ABSTRACT- Sorption and desorption at solid-liquid interfaces play an important role in the migration of toxic elements in surface and underground waters. Rocks, sediments, soils, mobile particles act as sorbents. Modelling of elements migration in water requires a good knowledge of sorption data. But data alone acquired from laboratory measurements, are not sufficient, since they are valid for a limited range of experimental conditions. Sorption modelling, validated by a good knowledge of sorption processes is required for a good modelling of migration in conditions consistent with natural waters. For that purpose, we have performed acquisition of sorption data, study of sorption mechanisms at the atomic scale and evaluation of sorption models. We have chosen some model elements (Cd(II), Pb(II), Eu(III)) and some sorbents (phosphates, carbonates and oxy-hydroxides). In order to study the sorption mechanisms and determine the sorption sites, a multidisciplinary approach was used : batch experiments with kinetics and isotherms, electron and atomic force microscopy, various spectroscopic methods (inductively coupled plasma emission spectrometry, time-resolved luminescence spectroscopy, X-rays, IR and Raman, photoelectron spectroscopy). The evaluation of sorption models was conducted by comparing the ion exchange model, the surface complexation models (with their different electrostatic interactions models) and the multisite model ("music"). Some systems can be modellized by these models, each one leading to a set of values for the sorption parameters. For other systems, such models cannot be used, since the process is controlled either by diffusion, or by the formation of new solid phases. Sorption may also be partially reversible. We discuss the application of these results to migration in water. Modelling must take into account the non-equilibrium, partly non-reversible and multi-site character of sorption. Key words: ion sorption, toxic elements, migration in water, sorption models |
