Etude expérimentale et modélisation cinétique du transfert des ions métalliques en solution aqueuse dans un milieu poreux sous gradient de concentration

With the progresses of material science and technology, a variety of nanoporous solids have been employed as catalysts or adsorbents in chemical processes for energy production, purification and depollution. These processes involve aqueous solution of metal ions in contact with nanoporous solids. For example, certain heterogeneous catalysts are prepared by contacting an aqueous solution of metal ions on a solid support to form chemically nanoparticles [1,2]. In the field of depollution, adsorbents are used to selectively eliminate metal ions contaminating water [3]. The efficiency of these processes depends on the physical and chemical properties of the nanoporous solids and especially their surfaces. To improve the performance of the processes, a better understanding of the mass transfer of
ionic species in nanopore, comprising the study of the non-ideality of the ionic solution, adsorption and precipitation phenomena on the solid surface under concentration gradient, needs to be performed. The level of knowledge in the field is largely incomplete, although it is of major interest for various industrial applications.
The objective of this thesis is to study experimentally and theoretically the diffusion, adsorption and precipitation of ionic aqueous media in porous solids, taking into account the critical physicochemical phenomena that are:
• The strongly non-ideality of the aqueous phase thermodynamic equilibria, in
particular at high ionic strength and the influence of this non ideality on adsorption and diffusion steps.
• The impact of the physicochemical properties of the surface on adsorption and
diffusion.
• The influence of confinement of molecules on phase equilibria in meso and micro
porous systems.
• The ionic specie diffusion in nanoporous solid.
The scientific problematic being particularly complex, we propose to limit the study to a simple but relevant system in the field of heterogeneous catalyst: the interaction between metal ions and the surface of gamma alumina. The heterogeneous catalyst preparation consists on the deposition of metal nanoparticles on a solid support which forms the active phase of the adsorbent. The adsorbent is brought into contact with an aqueous solution containing the metal precursor. The ionic species are adsorbed on the surface of the solid, according to a thermodynamic equilibrium which depends on the operating conditions (temperature, concentration, pH, ionic strength, physicochemical properties of the surface), before forming nanocrystals by precipitation.
The study will be performed by decoupling as much as possible the different phenomena and by stages of increasing complexity.
• The first part of the study will be carried out at a low concentration in order to avoid the salts precipitation. Under these conditions, the equilibrium behaviour of the fluid phase and the adsorbed phase will be measured and modelled, as well as the
diffusion kinetics in the porous network of the solid.
• In a second time the precipitation phenomena will be undertaken. The main
objective will be to evaluate the impact of pore size (confinement) on the size and
morphology of the metal nanoparticles.
The phD student will be welcomed in the LAGEPP Laboratory. Its thesis program is
proposed as follows:
• Carry out a literature review
• Develop data analysis tools to follow the different ionic species in solution on line
and the precipitated forms on the solid surface out of line
• Study the catalyst impregnation (adsorption, solid deposit and precipitation of
nickel ions) under different conditions of nickel, pH and ionic force in continuous
stirred tank reactor, based on reversed-phase chromatography method
(breakthrough experiments by adding salt or acid).
• Measure and model the fluid phase equilibria.
• Study of salt precipitation by a controlled evaporation of water.
• Begin the modelling of the mass transfer, phase apparition and growing of the solid on the solid surface by phase field method.
The theoretical and experimental methodologies developed during this thesis will be useful for other applications. For example, the results of this work will be used to remove cesium ion efficiently from the aqueous solution [4] employing porous materials. Indeed, this subject has been of great interest after the serious accidents of nuclear power plants in Japan and it will be done in collaboration with T. Yamamoto (Professor of University of Hyogo.) An extension of this work to ion mixtures can be of great interest in the field of heterogeneous catalysts impregnation.
[1] K.-M. Hong, M.-S. Kim and J. G. Chung Chemosphere 54 (2004) 927–934
doi:10.1016/j.chemosphere.2003.08.036
[2] S. Malamis, E. Katsou Journal of Hazardous Materials 252– 253 (2013) 428– 461 doi :
http://dx.doi.org/10.1016/j.jhazmat.2013.03.024
[3] C. Jeon, J-O Kim and Seung-Mok Lee. Korean Journal of Chemical Engineering. 31.
(2014). 1219-1224. Doi: 10.1007/s11814-014-0058-7.
[4] C. Dwivedi, A. Kumar, J.K. Ajish, K.K. Singh, M. Kumar, P.K. Wattal and P.N. Bajaj, RSC Advances 2 (2012) 5557-5564 DOI: 10.1039/c2ra20054f
Profil The candidate will have an initial background in analytical chemistry and a strong interest in multidisciplinary research (On-line analysis, chemical engineering, modelling and simulation)

Contacts
M. Tayakout-Fayolle
Professor, University of Claude Bernard Lyon 1
Tél. +33 (0)4 72 43 18 67
melaz.tayakout-fayolle@univ-lyon1.fr
A. Galfré
Assistant professor, University of Claude Bernard Lyon 1
Tél. +33 (0)4 72 43 18 62
aurelie.galfre@univ-lyon1.fr
Laboratoire d’Automatique, de Génie dEs Procédés et de
génie Pharmaceutique (LAGEPP) UMR5007 – Université
Lyon 1 Bâtiment 308G. 69622 Villeurbanne Cedex France

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