Modified TiO2-based Photocatalytic Films and Powders produced by Aqueous and Non-Aqueous Sol-Gel Processes for Water Purification

Doctoral thesis (2013)

Summary Two major research goals have been proposed for this thesis. The first goal concerns the development of photocatalysts in the shape of thin films coated on glass substrates which includes (i) the ... [more ▼]

Summary Two major research goals have been proposed for this thesis. The first goal concerns the development of photocatalysts in the shape of thin films coated on glass substrates which includes (i) the development of a sol-gel chemistry suitable for the production of stable colloidal suspensions of TiO2 particles, (ii) the optimization of the deposition method and (iii) the development of an experimental device to measure the photocatalytic activity of the films. The second objective is the development of innovative non-aqueous and aqueous sol-gel routes, including the development of new methods for the introduction of dopants as well as the photocatalytic testing of the resulting materials. Two original non-aqueous sol-gel processes involving respectively, an in situ production of water and the controlled addition of a small amount of water, have been developed to produce a series of stable colloidal suspensions of TiO2 particles (sols). From those sols, transparent, adherent, homogeneous thin films have been produced using an optimized dip-coating deposition method and have been proven to be photocatalytically active for the degradation of an organic pollutant in aqueous solution. The photocatalytic activity of the films has been improved through an increase of their roughness thanks to the addition of an organic additive into the sol, leading to an increased active surface involved into the photocatalytic reaction. A mathematical model allowing the rigorous evaluation of the kinetic parameters of the photocatalytic reaction taking into account the influence of the variation of the volume inside the batch photoreactor has been developed. The equations have been established in the case of a photocatalytic powder homogeneously dispersed in the pollutant solution, and in the case of a photocatalytic thin film placed at the bottom of the reactor. The particular case of a first order reaction has been treated and the error on the reaction rate constant induced by neglecting the volume variation has been quantified. An environmentally-friendly aqueous sol-gel process for producing undoped and Cu2+, Ni2+, Zn2+, Pb2+, Fe3+, Cr3+, La3+ or Eu3+ single-doped as well as La3+- Fe3+ and Eu3+- Fe3+ co-doped TiO2 bulk photocatalysts composed of nanocrystallites of anatase and exhibiting a remarkably high photocatalytic activity without requiring any calcination step has been developed. Different effects of the metal ion dopant on the photocatalytic activity have been observed and discussed according to the dopant nature and content. A kinetic study of the photocatalytic degradation of a model pollutant (4-nitrophenol) in aqueous solution under UV-Visible light (330 nm < λ < 800 nm) has been performed over a promising TiO2-Zn2+ doped catalyst. Statistical validations have confirmed the suitability of the phenomenological reaction rate model developed to represent the 4-nitrophenol photocatalytic degradation over time. [less ▲]

À la limite de l’orthodoxie, aux confins de l’imperium christianum

Conference (2013, April 26)

Echanges transfrontaliers et déplacements de la population rwandaise pendant la Deuxième Guerre mondiale

Conference (2013, April 25)

Nourishing the body, crafting the self, facing the other. Subjectivities and encounters through Moroccan food in Italy

Scientific conference (2013, April 25)

Each individual is composed of material objects and practices that witness one’s personal life history and everyday life and which shape one’s same subjectivity (Julien and Rosselin 2009). Subjectivity ... [more ▼]

Each individual is composed of material objects and practices that witness one’s personal life history and everyday life and which shape one’s same subjectivity (Julien and Rosselin 2009). Subjectivity that is fulfilled through material culture, the performing of which turns out to be a technology of the self (Martin, Gutman, Hutton 1988). Considering the subject as the result of praxeological activities and of the incorporation of objects belonging to one’s meaningful universe of reference and action, my paper aims at exploring the construction of the self of Moroccan female migrants through their body techniques exerted while cooking. Specific gestures are performed to adhere to a cultural heritage which needs to be preserved while living abroad. An essentialized bodily tradition, relying on a set of specific objects, becomes the place where, on the one hand, the members of a community share knowledge. On the other hand, such tradition lets an encounter with otherness take place. As a matter of fact, in the context considered, food is a frequent object of intercultural policies and practices, giving migrants a controlled opportunity to express themselves while producing material culture. A locally held Arabic cooking class, for example, provides the occasion to perform cultural differences (or similarities) by means of corporeal languages. My presentation will consider the body both in its private and public dimensions, since constantly intertwined. Through images and videos I will show what such embodied material knowledge consists of and in which ways it is the object of social dynamics and interactions. [less ▲]

Ecriture: marqueurs de la représentation. Le cas de l'Egypte ancienne. 1. La naissance de l'écriture

Scientific conference (2013, April 25)

Les allergies alimentaires : point de vue du biologiste

Conference (2013, April 25)

Quelle place pour la viande rouge dans nos assiettes ?

Conference given outside the academic context (2013)

Le montage comme réponse moderne à la crise du sens

Scientific conference (2013, April 24)

Notre idée est ici de repartir de la conjoncture moderne pour étudier sous un angle renouvelé le problème du montage (à partir des textes de Kracauer, notamment) – problème qui nous semble déboucher sur ... [more ▼]

Notre idée est ici de repartir de la conjoncture moderne pour étudier sous un angle renouvelé le problème du montage (à partir des textes de Kracauer, notamment) – problème qui nous semble déboucher sur des enjeux politiques et esthétiques toujours actuels (que l’on tentera d’éclairer au fur et à mesure de l’exposé à travers quelques cas précis). Le débat autour du montage semble atteindre son maximum de vivacité dans les années 1920 (aussi bien dans les milieux intellectuels que dans les milieux artistiques). À cette époque, suite aux transformations amenées par l’essor de la société industrielle (sur le plan axiologique, sociologique ou technologique), suite à la première Guerre mondiale surtout et au déchaînement de la violence sur les individus, l’homme moderne se dépeint fréquemment sur le mode de celui qui, ayant perdu l’essentiel de ses repères, et déstabilisé dans ses croyances, se voit contraint à errer dans un monde désenchanté qu’il ne reconnaît plus. Or, ces mêmes années sont aussi celles qui voient se développer toutes sortes d’avant-gardes artistiques pour lesquelles l’opération du montage constitue un outil primordial. [less ▲]

Time variyng groundwater flux measurement using a single well tracer technique

Poster (2013, April 24)

Contaminant mass discharge measurements are often performed at given times or integrated over a certain period of time, using active or passive sampling techniques. One problem arising is that such ... [more ▼]

Contaminant mass discharge measurements are often performed at given times or integrated over a certain period of time, using active or passive sampling techniques. One problem arising is that such measurements may not be representative of the temporal dynamics of the mass discharge variations. These variations can be caused by fluctuations in contaminant concentrations or, more frequently, by changes in the groundwater fluxes. Pollutant mass fluxes are typically estimated through a combination of solute concentrations and groundwater fluxes measured across a control plane made of several multi-level wells. Accurate measurements of local transient Darcy fluxes have been recognized as the weakest points in most of the developed techniques for groundwater contaminant mass flux measurements. The main objective here is to extend the FVPDM technique for temporal monitoring of groundwater fluxes and to demonstrate its ability to be used in combination with passive sampling devices for measurement of contaminant mass fluxes in groundwater. The Finite Volume Point Dilution Method (FVPDM) is a single well tracer technique for the measurement of local groundwater fluxes based on the continuous injection of tracer at very low injection rate (Brouyère et al. 2008). These developments are based on the application of the adapted technique on a case study in a fractured granitic aquifer in Ploemeur (France). This application investigates transient groundwater fluxes that are controlled by pumping in a well nearby the tested piezometers. Long monitoring time series have been recorded under these controlled conditions of transient groundwater flow. Results show the high sensivity of the FVPDM technique to small variations in groundwater flow velocities and its aptitude for long term monitoring of groundwater fluxes. The comparison between the results of FVPDM and classical point dilution tests performed in same conditions shows close correlation. Interpretation of FVPDM tests in transient conditions have been developed together with an evaluation of the uncertainties that can happen if the frequency of the groundwater flow variations is high. The tests carried on the Ploemeur site also illustrate the first ever application of the FVPDM technique between a double-packer system used for the investigation of a defined layer of an aquifer. This innovative application of the FVPDM using packers opens concrete perspectives for investigation of vertical heterogeneities of groundwater fluxes across a well. [less ▲]

Overview of technologies for mineral/metal recuperation – challenges and technological gaps

Conference given outside the academic context (2013)