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International audienc
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Our aim was to assess the feasibility of using solar energy for the thermal regeneration of spent activated carbons (ACs). The context was water treatment, for which ACs are commonly used. The target pollutant was perchloroethylene (PCE).... more
Our aim was to assess the feasibility of using solar energy for the thermal regeneration of spent activated carbons (ACs). The context was water treatment, for which ACs are commonly used. The target pollutant was perchloroethylene (PCE). Preliminary experiments were performed to select the best-suited adsorbent among five ACs (Aquacarb, surface area Brunauer–Emmett–Teller, 1100 m2 g–1; micropores areas, 870 m2 g–1). Water properties influence adsorption capacity; this is lower with natural water (groundwater) than with ultrapure water. The competition between natural organic matter (found in groundwater but not in ultrapure water) and the target pollutant accounts for this difference. Groundwater was used in regeneration tests so as to approximate to field conditions. Operating conditions for regeneration were determined: the working temperature ranged between 130 and 400 °C, and the treatment time was set so as to prevent any kinetic limitation. Four regeneration cycles showed the same decrease in adsor...
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In the field of advanced oxidization processes based on solar radiation, heterogeneous solar catalysis involves exciting a photocatalyst with UV rays and one of the major problems encountered is optimizing the use of the sunlight. The... more
In the field of advanced oxidization processes based on solar radiation, heterogeneous solar catalysis involves exciting a photocatalyst with UV rays and one of the major problems encountered is optimizing the use of the sunlight. The work presented here aimed to use an efficient material able to provide a high active specific surface expressed in square meter per unit volume
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Abstract Activated-Carbon/Titania composites (AC/TiO2) is a relevant option to gather the dual adsorption/photodegradation property within a single material. This work aimed to investigate the composition influence on the adsorption and... more
Abstract Activated-Carbon/Titania composites (AC/TiO2) is a relevant option to gather the dual adsorption/photodegradation property within a single material. This work aimed to investigate the composition influence on the adsorption and photodegradation properties of AC/TiO2 composites against caffeine. TiO2 grafted AC powders covering the whole composition scale were synthesized by a one-step mechanical milling process. This original simple elaboration route led to the obtention of powders which particles size and composition were homogeneous and well controlled. When the adsorbent mass ratio varied in the range 0.01−0.75, the adsorption properties, i.e. apparent kinetic and maximum adsorption capacity of the composites increased respectively by 1 and 2-log. At the opposite, the photo-oxidation rate decreased significantly when the adsorbent ratio increased. The simple elaboration route explored produces flexible AC/TiO2 composites with adjustable properties that can easily be managed to meet the requirements of different target applications.
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Abstract An aerosol-assisted plasma process was used to deposit, at low temperature and atmospheric pressure, photocatalytic hydrocarbon polymer/TiO2 nanoparticles nanocomposite coatings onto both flat glass slides and open-cell... more
Abstract An aerosol-assisted plasma process was used to deposit, at low temperature and atmospheric pressure, photocatalytic hydrocarbon polymer/TiO2 nanoparticles nanocomposite coatings onto both flat glass slides and open-cell polyurethane foams. Various characterization techniques were used to demonstrate the potential of the developed process for the controlled deposition of TiO2-based coatings on the different supporting substrates, with special attention to the foams due to their complex three-dimensional porous structure. The photocatalytic activity of the plasma-coated materials was evaluated by the decomposition of methyl orange in aqueous solution under UV irradiation, using a purposely designed recirculating batch photoreactor. The comparative study revealed that greater photocatalytic activity can be achieved with the open-cell foams, pointing to the beneficial properties of macroporous photocatalyst supports in comparison with conventional flat ones. The prepared photocatalytic materials presented remarkable reusability and maintained good activity after prolonged operation (40 h) corresponding to 20 consecutive reaction runs. Results on the evolution of the photocatalytic performance of the plasma-coated samples over multiple runs were correlated with those obtained from the detailed characterization of their surface chemical composition, morphology and wettability as a function of the operation time in photocatalytic water treatment.
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Schematic representation of core–shell intrinsic defects in Zn1−xCaxO nanoparticles observed by EPR spectroscopy.
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Wastewater tertiary treatment by advanced oxidation processes is thought to produce a treated effluent with lower toxicity than the initial influent. Here we performed tertiary treatment of a secondary effluent collected from a Waste... more
Wastewater tertiary treatment by advanced oxidation processes is thought to produce a treated effluent with lower toxicity than the initial influent. Here we performed tertiary treatment of a secondary effluent collected from a Waste Water Treatment Plant via homogeneous (solar/HSO5(-)/Fe(2+)) and heterogeneous (solar/TiO2) solar advanced oxidation aiming at the assessment of their effectiveness in terms of contaminants' and toxicity abatement in a plain solar reactor. A total of 53 organic contaminants were qualitatively identified by liquid chromatography coupled to high-resolution mass spectrometry after solid phase extraction. Solar advanced oxidation totally or partially removed the major part of contaminants detected within 4.5 h. Standard toxicity tests were performed using Vibrio fischeri, Daphnia magna, Pseudokirchneriella subcapitata and Brachionus calyciflorus organisms to evaluate acute and chronic toxicity in the secondary or tertiary effluents, and the EC50% was ca...
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Les materiaux granulaires presentent des proprietes singulieres liees a la fois aux proprietes physiques et morphologiques des grains et a la texture et la constitution de l'empilement. Dans ce travail, les proprietes de transferts... more
Les materiaux granulaires presentent des proprietes singulieres liees a la fois aux proprietes physiques et morphologiques des grains et a la texture et la constitution de l'empilement. Dans ce travail, les proprietes de transferts radiatifs, electriques et mecaniques et les mecanismes de densification d'empilements granulaires constitues de particules polymeres ont ete abordes. L'originalite reside a la fois, dans l'approche de materiaux denses, confines dans un espace restreint, soumis aux conditions de densification engendrant des modifications de la texture, de la structure et des proprietes physiques de l'empilement et dans l'utilisation du polypyrrole, polymere conducteur, conferant des proprietes de transferts aux materiaux divises intrinsequement isolant en preservant les proprietes mecaniques des grains. Cette etude a necessite la mise en place d'une cellule de mesure de la resistance et de la deformation des empilements et l'utilisation de techniques de caracterisation spectrales et d'observation (spectrophotometres, MEB, AFM). Une etude de caracterisation des proprietes physiques des empilements de grains recouverts ou pas de polypyrrole a permis de mettre en evidence et d'optimiser des conditions de synthese (temps, temperature, concentrations,. . . ) et de densification (vitesse, contrainte,. . . ) des empilements sur les proprietes de transferts des empilements. L'etude des proprietes de transferts electriques et du processus de densification, traite a la fois dans le cas de particules individuelles et d'empilements, ont permis de mettre en evidence, a l'aide de modele numerique et theorique, les comportements caracteristiques des empilements polymeres et les correlations entre les proprietes electriques et mecaniques liees aux distributions des contacts au sein des empilements. La finalite de ces travaux reside dans l'etude des proprietes radiatives, structurales et electriques d'empilements densifies constitues de particules de nature (polymere, verre,. . . ) de taille et de morphologie differents (fibres, grains, particules,. . . ) recouvertes ou non de polypyrrole et de leurs melanges. Ce travail a permis de mettre en evidence les correlations et similitudes existantes entre les proprietes de transferts et les proprietes mecaniques et texturelles des empilements liees a la distribution des contacts et des contraintes au sein de l'empilement et aux proprietes physiques des particules.
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The concept of a hybrid process resulting of the association from the photocatalytic and the adsorption principles opens various opportunities for the design of efficient detoxification processes. One option particularly attractive in the... more
The concept of a hybrid process resulting of the association from the photocatalytic and the adsorption principles opens various opportunities for the design of efficient detoxification processes. One option particularly attractive in the case of solar applications consists in developing a storage function thanks to the adsorbent and its adsorption capacities. As for any solar process, such a property is essential for the design of efficient photocatalytic water treatment. Before optimization of a hybrid process, preliminary studies necessary were carried out in a close fluid loop connecting a photocatalytic reactor based on supported TiO2 and a separate cell filled with a commercial activated carbon. With the 2-4 dichlorophenol selected as a model pollutant molecule, a series of successive cycles corresponding to dark adsorption followed by photocatalysis under UV irradiation was performed. The initial results are promising and indicate that the activated carbon is regenerated reproducibly thanks to photocatalysis. The coupling phenomenon has been explored numerically with mass balances applied to the liquid and the adsorbed phase.
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Sunlight irradiating the surface of the Earth represents a maximum input available for a solar catalytic process of 50WUVm−2. We propose using high-porosity, metallic, reticulated foams as the support medium for the photocatalyst in order... more
Sunlight irradiating the surface of the Earth represents a maximum input available for a solar catalytic process of 50WUVm−2. We propose using high-porosity, metallic, reticulated foams as the support medium for the photocatalyst in order to improve the apparent quantum yield. The layer of TiO2 was applied by dip-coating. The measurement of the degradation kinetics was carried out on a model target molecule, 2,4 dichlorophenol, at an initial concentration of 10mgl−1. The aim was to assess the efficiency of the foams as a photocatalytic media compared to that of a suspension of catalytic powder (Degussa P25) and the flat 2D support (Ahlstrom cellulose media). The apparent quantum yield of the foam scaffold carrying the TiO2 was high, showing that, as with the powder suspension, foam makes good use of the UV rays to break down molecules. It is noteworthy that the apparent quantum yield of the foam tended towards that observed for suspensions which form the ideal support thanks to their optimal ability to harness the light.
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Modeling the mineralization of an organic pollutant was studied using a slurry of TiO2 powder. 2-4 dichlorophenol was chosen as the target molecule. In a first stage, a study was carried out, on the basis of a semi-empirical approach in... more
Modeling the mineralization of an organic pollutant was studied using a slurry of TiO2 powder. 2-4 dichlorophenol was chosen as the target molecule. In a first stage, a study was carried out, on the basis of a semi-empirical approach in order to define the optimal concentration of the catalyst. In a second stage, a series of photocatalytic mineralization was performed with a laboratory set-up using an artificial UV source. The parameters involved in the kinetics of mineralization were identified by a comparison of results obtained by simulations and experiments at constant but different levels of irradiation. In a third stage, the robustness and suitability of the model were tested with experiments carried out with an experimental solar set-up with different dimensions. No supplementary adjustment of parameters was needed to simulate the experiments performed under unsteady irradiation. Finally, the model is used to illustrate the great variation in treatment capability of a solar p...
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ABSTRACT The photocatalytic oxidation of atrazine was studied. The time-dependent concentration profiles were measured under different experimental working conditions in a laboratory plant. All experiments were carried out using... more
ABSTRACT The photocatalytic oxidation of atrazine was studied. The time-dependent concentration profiles were measured under different experimental working conditions in a laboratory plant. All experiments were carried out using immobilized TiO2 and a reactor design adapted to solar application. Not only influence on the rate of degradation of the initial pollutant concentration and UV irradiation but also that on mass fluid flow was studied. Whatever the conditions, profiles were successfully modeled thanks to a coupling that involves mass transfer limitation between the fluid and the photocatalytic media and the degradation reaction happening for the adsorbed pollutant. The mathematical model suggested can readily be applied to reactor design and scale-up.
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This paper presents for the first time the integration of a biosensor for the on-line, real-time monitoring of a photocatalytic degradation process. Paracetamol was used as a model molecule due to its wide use and occurrence in... more
This paper presents for the first time the integration of a biosensor for the on-line, real-time monitoring of a photocatalytic degradation process. Paracetamol was used as a model molecule due to its wide use and occurrence in environmental waters. The biosensor was developed based on tyrosinase immobilization in a polyvinylalcohol photocrosslinkable polymer. It was inserted in a computer-controlled flow system installed besides a photocatalytic reactor including titanium dioxide (TiO2) as photocatalyst. It was shown that the biosensor was able to accurately monitor the paracetamol degradation with time. Compared with conventional HPLC analysis, the described device provides a real-time information on the reaction advancement, allowing a better control of the photodegradation process.
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ABSTRACT We use specific surface area as a metric to assess the performances of photocatalytic media, where specific surface area is calculated as irradiated catalytic surface developed per unit of photoreactor volume. The photocatalytic... more
ABSTRACT We use specific surface area as a metric to assess the performances of photocatalytic media, where specific surface area is calculated as irradiated catalytic surface developed per unit of photoreactor volume. The photocatalytic media compared were selected to cover a wide range of specific surface areas from within a panel of various formats proposed in the literature, i.e. powder suspensions (nanometer-scale and micrometer-scale), 2D media (tissue, glass rods), macroporous media including reticular foams and bulk solids including fiber stacks. The overarching approach, where we define the configurations that deliver the best photocatalytic performances possible, is split into a two-stage phases. Stage 1 aims to correlate the media's structural properties to its transmittance. Stage 2 aims to study and rank the media in terms of their photocatalytic performances. This two-stage process, based on a panel of media, make it possible to define the configurations of photocatalytic media that make the best use of all available incident light in a given photoreactor geometry, and to adapt the media format to in-use constraints (depth, volume, light flux density). Ranked into ascending order of increasingly active specific surface area (expressed in m(2) m(-3)), the results read as follows: cellulosic tissue < metallic fibers < reticulated foams < powder suspensions.