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Boutinaud P.,National Graduate School of Chemistry of Clermont Ferrand | Boutinaud P.,CNRS Institute of Chemistry
Inorganic Chemistry | Year: 2013

A model is introduced to predict the energy of metal-to-metal charge-transfer transitions in oxide compounds containing Bi3+ ions and d0 or d10 metals (Mn+). The model takes into account the structural characteristics of the host lattices, the anion relaxation resulting from Bi3+ doping, and the electronegativities and coordination numbers of the Bi3+ and Mn+ ions in the compounds. It is shown, through a critical review of the archival literature, that this model provides new insights on the assignment of the luminescence spectra and the related interpretation of the spectroscopic behaviors. © 2013 American Chemical Society.

Cavalli E.,University of Parma | Boutinaud P.,National Graduate School of Chemistry of Clermont Ferrand | Mahiou R.,French National Center for Scientific Research | Bettinelli M.,University of Verona | Dorenbos P.,Technical University of Delft
Inorganic Chemistry | Year: 2010

Single crystals of CaWO4 and CaMoO4 doped with Tb3+ have been grown by the flux growth method. Their luminescence properties have been investigated in the 10-600 K temperature range under different experimental conditions. In spite of very similar spectra at low temperature upon excitation at 365 nm, the crystals show a very different behavior as the temperature is raised or the excitation wavelength is changed. These differences have been accounted for on the basis of models that take into consideration the position of the energy levels of the rare earth relative to the bandgap of the host material. © 2010 American Chemical Society.

Takache H.,University of Nantes | Pruvost J.,University of Nantes | Cornet J.-F.,National Graduate School of Chemistry of Clermont Ferrand
Biotechnology Progress | Year: 2012

The aim of this study was to establish and validate a model for the photosynthetic growth of Chlamydomonas reinhardtii in photobioreactors (PBRs). The proposed model is based on an energetic analysis of the excitation energy transfer in the photosynthesis apparatus (the Z-scheme for photosynthesis). This approach has already been validated in cyanobacteria (Arthorspira platensis) and is extended here to predict the volumetric biomass productivity for the microalga C. reinhardtii in autotrophic conditions, taking into consideration the two metabolic processes taking place in this eukaryotic microorganism, namely photosynthesis and respiration. The kinetic growth model obtained was then coupled to a radiative transfer model (the two-flux model) to determine the local kinetics, and thereby the volumetric biomass productivity, in a torus PBR. The model was found to predict PBR performances accurately for a broad set of operating conditions, including both light-limited and kinetic growth regimes, with a variance of less than 10% between experimental results and simulations. © 2012 American Institute of Chemical Engineers (AIChE).

Gros F.,National Graduate School of Chemistry of Clermont Ferrand | Baup S.,Joseph Fourier University | Aurousseau M.,LGP2
Hydrometallurgy | Year: 2011

In this study, the cementation of copper ions on iron and zinc as sacrificial metals in a fluidized bed configuration was carried out. A preliminary hydrodynamic study checked the non-segregating behaviour of iron/zinc mixtures during fluidization experiments. The efficiency of the mixtures in copper recovery has been estimated in terms of kinetic and apparent mass transfer coefficients according to operating parameter modifications. The influence of temperature on the kinetics revealed a mass transfer limitation of the reaction, with an activation energy of 19.6 kJ mol-1. Maximum apparent mass transfer (13.6 • 10-5 m s-1) was obtained for a 1.5 pH solution due to the presence of hydrogen bubbles that increase local mass transfer. Acid and sacrificial metal consumptions revealed an over-consumption of zinc compared to iron due to copper catalysed hydrogen evolution. The influence of initial copper concentration in the 50-1000 ppm range shows that kinetic and mass transfer dependence is due to modifications of the copper deposit morphology. © 2010 Elsevier B.V.

Cornet J.-F.,National Graduate School of Chemistry of Clermont Ferrand
Chemical Engineering Science | Year: 2010

This article examines the optimal design and ideal kinetic performances of volumetrically lightened photobioreactors (PBR). From knowledge models developed for several years by the author, simple theoretical rules are established at first to define the optimal functioning of solar and artificially lightened PBR. The constructal approach is then used accordingly, which allows the emergence of the optimal design, or the best lighting structures assembly, in Cartesian and curvilinear geometries, with a privileged treatment for the practical case of the 2D-cylindrical geometry. The obtained results confirm the considerable potential of this approach which is applied here for the first time to the case of the radiant light transfer in participating and reactive media. This enables to define clearly, from a theoretical point of view, the concept of ideal PBR (both for solar or artificial illuminations), which is demonstrated to correspond exactly in most cases to volumetrically lightened PBR, mainly for the solar DiCoFluV (Dilution Contrôlée du Flux en Volume) concept developed in this article. For this last case, the results of the calculations allow to announce maximal biomass productivities as thermodynamic limits, what can contribute to clarify a today confused debate on this point. The work proposed in this article finally establishes guidelines to conceive more efficient large-scale PBR of any desired geometry and criteria like volume (for artificial illumination) or surface (for solar illumination) maximum productivities and internal or external irradiation. © 2009 Elsevier Ltd. All rights reserved.

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