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Etude de l'adsorption critique par réflectivité de neutrons. Application à la compréhension de mécanismes environnementaux

Abstract : This study is within the scope of fundamental knowledge transfer to a field case-study, i.e. the understanding of the adsorption properties of binary mixtures against a wall in the case of soil pollution by liquid hydrocarbons. From the theoretical study of critical adsorption, which has been well described in the literature, we carried out experiments on model systems by using neutron techniques. Neutron reflectivity was then applied to the liquid-vapeur interface of three different binary mixtures: perfluorohexane-hexane, deuterated methanol-cyclohexane and methanol-deuterated cyclohexane. The experimental data were analysed according to the theoretical prediction of Fisher and De Gennes, along with Liu and Fisher that suggested a power law decrease of the concentration profile (with an exponent equal to 0.52) followed by an exponential function. The characteristic exponent and the amplitude ratios for the methanol-cyclohexane mixtures were found fitted well with theoretical values for the three systems. Only the perfluorohexane-hexane mixture exibited a particular behavior in the adsorption process that affected the power law amplitude value. This step allowed us to study non critical adsorption and to apply neutrons techniques, e.g reflectivity and small angles neutrons scattering, to a water-2,5 dimethylpyridine mixture against silica, wich is a model system for soils polluted by water/hydrocabon mixtures. These experiments highlighted new experimental dificulties, which were not fully solved over this study, together with some problems in the analysis that would require specific modelling. Nevertheless, this study shows the capabilities of neutrons techniques to investigate some environmental mechanisms. Moreover, some of the results reported here can be used as a basis for future experiments.
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https://tel.archives-ouvertes.fr/tel-00001286
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Submitted on : Wednesday, March 27, 2002 - 10:34:17 AM
Last modification on : Monday, February 10, 2020 - 6:12:21 PM
Long-term archiving on: : Friday, April 2, 2010 - 6:14:48 PM

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  • HAL Id : tel-00001286, version 1

Citation

Jacques Jestin. Etude de l'adsorption critique par réflectivité de neutrons. Application à la compréhension de mécanismes environnementaux. Dynamique des Fluides [physics.flu-dyn]. Université de Bretagne occidentale - Brest, 2001. Français. ⟨tel-00001286⟩

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