Kinetic Modeling of VOC Photocatalytic Degradation Using a Process at Different Reactor Configurations and Scales

International audienceThis work investigated the performance of isovaleraldehyde (3-methylbutanal) removal from gas streams in photocatalytic reactors at room temperature. The feasibility of pollutant removal using the up-scaled reactor was systematically assessed by monitoring the removal efficiency at different operational parameters, such as geometries of reactor, air flow rate and inlet concentration. A proposal modeling for scaling up the photocatalytic reactors is described and detailed in this present study. In this context, the photocatalytic degradation of isovaleraldehyde (Isoval) in gas phase is studied. In fact, the removal rate has been compared at different continuous flow reactors: a photocatalytic tangential reactor (PTR), planar reactor and P5000 pilot. The effects of the inlet concentration, flow rate, geometries and size of reactors on the removal efficiency are also studied. A kinetic model taking into account the mass transfer step is developed. The modeling is done by introducing an equivalent intermediate (EI) formed by the photo-oxidation of Isoval. This new approach has substantially improved the agreement between modeling and experiments with a satisfactory overall description of the mineralization from lab to pilot scales

Study of synergetic effect by surface discharge plasma/TiO2 combination for indoor air treatment: sequential and continuous configurations at pilot scale

International audienceThis work investigated the performance of butyraldehyde decomposition with the help of dielectric barrier discharge (DBD) plasma coupled with photocatalysis (TiO2+UV) at room temperature. Effects of flow rate and initial butyraldehyde concentration on the decomposition and the distribution of byproducts were examined and discussed. The combination of these two technologies led to an enhancement of butyraldehyde abatement compared to the separate systems at pilot scale from 5 to 10 m3.h−1 of flowrate. The synergy factor due to combination processes ranged from 1.13 to 1.27. In the same way, CO2 selectivity was significantly improved when compared to the DBD plasma alone. In this research, DBD plasma system and an immobilized TiO2 photocatalysis system is sequentially combined to oxidize the target pollutant. Indeed, different ways to combine sequentially DBD plasma with photocatalytic materials are listed. Results at pilot scale showed that when photocatalyst is placed in the post discharge, the performance of sequential coupling plasma–photocatalyst process is improved in term of decomposition, by-products formation and energy yiel

Le statut des femmes kabyles autochtones de l'Algérie

Ce mémoire interroge les processus par lesquels s'opère une discrimination à l'égard des femmes kabyles. Pour ce faire, nous nous sommes située dans le paradoxe des pratiques constitutives du droit coutumier et du droit formel: d'une part le droit coutumier kabyle invoque une imposition et une incorporation des pratiques culturelles du code de l'honneur et de la parenté qui se manifestent par des valeurs collectives et par des limites symboliques et corporelles, et cela sur le plan familial, comme dans la répression de la circulation, dans l'imposition du conjoint et dans le déshéritement. Ceci trouve une justification par le pouvoir masculin dans l'honneur qui ne doit aucunement être bafoué et aussi dans la nécessité de perpétuer la lignée. Les femmes intériorisent les valeurs et notamment les limites qui leur ont été incorporées. Cette intériorisation de limites et l'enracinement des pratiques dans leurs mémoires font souvent d'elles les reproductrices de l'ordre social. D'autre part, le droit formel contient des pratiques qui portent atteinte aux femmes dans leur vie familiale et identitaire. Le Code de la famille, en effet enlève aux femmes kabyles leur droit au logement lors d'un divorce. De même que sur le plan identitaire, les nationalistes algériens qui détiennent le pouvoir ont imposé la politique d'arabisation qui a généré une exclusion de la culture autochtone et notamment une régression scolaire des étudiants kabyles, car ces derniers sont affectés arbitrairement vers la filière de la littérature arabe. L'enjeu est de reproduire la culture arabo-islamique par les Kabyles eux-mêmes. Ajoutant à cela la pénétration de la culture arabo-islamique dans les foyers n'a fait qu'aviver la culture arabo-islamique au détriment de la culture kabyle, en aliénant les femmes kabyles. À l'aide de l'analyse documentaire qui repose sur un corpus (la Charte, la Constitution, et le Code de la famiIle) et de l'analyse de contenu des entrevues de 20 femmes qui ont vécu sous les deux systèmes de droits, nous tentons d'esquisser l'ensemble des réponses à notre question de recherche. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Pouvoir coutumier, Pouvoir formel, Femme kabyle, Reproduction sociale, Stratégies matrimoniales, Stratégies de reproduction, Arbitraire culturel, Capital culturel, \ud Honneur, Parenté

Monometal and competitive sorption of heavy metals in mine soils: Influence of mine soil characteristics

pas de DOI / http://www.researchgate.net/publication/236158313International audienceThe environmental and health effects of the contamination of soils by heavy metals depend on the ability of the soils to immobilize these contaminants. This study was conducted to assess the monometallic and competitive sorption of lead, copper, zinc and cadmiumin surface samples of four soils from eastern Algeria. Sorption isotherms were characterized using Freundlich and Langmuir equations. Retention selectivity sequences indicate that, inmost of the soils, Pb is the preferred retainedmetal, followed by Cu. The last metals in these sequences are Cd and Zn.All soils showed greater sorption capacity. On the basis of distribution coefficient values for the metal concentration of 100 mg. l-1 (Kd100) for each soil and trace element, the two most common adsorption sequences found were Pb>>Cu>Cd>Zn and Pb>>Cu>Zn>Cd. Competition significantly reduced metal Kd, especially that of Cd

Modélisation et optimisation de la photodégradation du 4-méthylphénol dans un réacteur à recirculation en présence d’UV/ZnO

L’étude de la photodégradation du 4-méthylphénol a été menée sur un pilote à recirculation. Cette molécule a été prise comme composé modèle pour le traitement des effluents de l’industrie avicole. Ce travail a consisté en l’optimisation et la modélisation de l’élimination du 4-méthylphénol par photocatalyse en présence de ZnO. L’utilisation des plans d’expériences, et en particulier de la méthodologie de surface de réponse (RSM) et un plan central composite (CCD), a permis la détermination de l’influence des effets simultanés et de l’interaction des paramètres opératoires sur le rendement de la photodégradation. Les paramètres étudiés sont la concentration initiale en 4-méthylphénol, la concentration en catalyseur et le débit de recirculation de la solution.Les résultats montrent que l’application de la RSM permet de décrire d’une manière correcte l’influence de ces trois paramètres expérimentaux sur l’efficacité du traitement. Les valeurs optimales des paramètres donnant un rendement maximal (100 %) ont pu être déterminées. Les modèles de second ordre obtenus, pour le rendement de dégradation et pour l’abattement de DCO, ont été validés en utilisant différentes approches statistiques. L’utilisation de la méthode ANOVA a montré que les modèles sont hautement significatifs et en bonne adéquation avec les résultats expérimentaux.The study of the photodegradation of 4-methylphenol was carried out in a recirculating pilot plant. This compound is present in the liquid processing waste of the poultry industry. This work consisted of the optimization and the modelling of the elimination of 4-methylphenol by photocatalysis in the presence of ZnO. The use of a design of experiments (DOE) approach, and in particular the response surface methodology (RSM) and a central composite design (CCD), allowed the determination of the influence of the simultaneous effects and the interaction of the operational parameters on the degree of photodegradation. The studied parameters were the initial concentration of 4-methylphenol, the catalyst concentration and the solution recirculation flow. The RSM application made it possible to describe the influence of these three experimental parameters on the effectiveness of the treatment. The optimal parameter values leading to maximum efficiency (100%) were determined. The second-order models obtained for the degradation output and the reduction of COD were validated using various statistical approaches. The use of an ANOVA method showed that the models were highly significant and in good agreement with the experimental results

Use of DBD plasma, photocatalysis, and combined DBD plasma/photocatalysis in a continuous annular reactor for isovaleraldehyde elimination - Synergetic effect and byproducts identification

International audienceRemoval of isovaleraldehyde from air was investigated experimentally by three processes: dielectric barrier discharge (DBD) plasma, photocatalysis and a DBD plasma/photocatalysis combination. The latter led to a synergetic effect. Many operating parameters were investigated in this study such as the specific energy of discharge, the inlet concentration of isovaleraldehyde and the relative humidity. The UV light generated by the DBD plasma reactor did not activate the photocatalytic medium. Thus, its contribution to the removal of isovaleraldehyde by photocatalysis could be ignored. On the other hand, the use of external UV light significantly improved the removal efficiency. Using a photocatalytic reactor in the presence of water vapor, in small amounts, had a promoting effect on the degradation due to the formation of OHradical dot radicals. The same phenomenon has been observed in other processes for small amounts of water in air. The identified and analyzed byproducts were classified into four groups: intermediate products (propionic acid, acetic acid and acetone), carbon monoxide, carbon dioxide and ozone. The carbon balance on carbon products was achieved at about 90%

Macrolide antibiotics removal using a circulating TiO2-coated paper photoreactor: parametric study and hydrodynamic flow characterization

International audienceThe present work investigates the photocatalytic degradation efficiency of biorecalcitrant macrolide antibiotics in a circulating tubular photoreactor. As target pollutants, spiramycin (SPM) and tylosin (TYL) were considered in this study. The photoreactor leads to the use of an immobilized titanium dioxide on non-woven paper under artificial UV-lamp irradiation. Maximum removal efficiency was achieved at the optimum conditions of natural pH, low pollutant concentration and a 0.35 L min(-1) flow rate. A Langmuir-Hinshelwood model was used to fit experimental results and the model constants were determined. Moreover, the total organic carbon analysis reveals that SPM and TYL mineralization is not complete. In addition, the study of the residence time distribution allowed us to investigate the flow regime of the reactor. Electrical energy consumption for photocatalytic degradation of macrolides using circulating TiO2-coated paper photoreactor was lower compared with some reported photoreactors used for the elimination of pharmaceutic compounds. A repetitive reuse of the immobilized catalyst was also studied in order to check its photoactivity performanc

Removal of trimethylamine and isovaleric acid from gas streams in a continuous flow surface discharge plasma reactor

International audienceThe removal of isovaleric acid (IVA) and trimethylamine (TMA) using nonthermal plasma (NTP) in a continuous surface discharge reactor is investigated. The influence of the energy density shows that its increment is accompanied by the increase of the removal rate. At flowrate equal to 2 m3 h−1, when energy density extends three times, the removal rates of IVA and TMA are increased from 5 to 15 mmol m−2 h−1 and from 4 to 11 mmol m−2 h−1, respectively. The impact of relative humidity (RH) is also studied. An increase in % RH (up to 20%) leads to a decrease of the removal rate. Additionally, the formation of by-products in the surface discharge reactor and the plausible reaction mechanism of the two VOC were also detected and discussed. Moreover, a kinetic model taking into account the mass transfer step is developed in order to represent the experimental results. The model shows a good agreement with experimental results

Modeling and simulation of VOCs removal by nonthermal plasma discharge with photocatalysis in a continuous reactor: Synergetic effect and mass transfer

International audienceThis paper deals with photocatalysis (TiO2 + UV), nonthermal plasma (NTP) and their combinations. These processes have been widely studied for isovaleraldehyde (Isoval) treatment. Isoval removal, selectivity of CO2 and CO, and ozone formation are investigated in order to evaluate the performance of the combined process. The results show that the performance of the process has enhanced and a synergetic effect is observed. On the other hand, this work aims at investigating kinetic modeling of combined process with taking into account the mass transfer step. The model is based on mass balances in three types of region: bulk region, discharge zone and solid phase which contains the photocatalyst. The oxidation in discharge and solid phases is described in two stages. Firstly, the removal of Isoval gives an equivalent intermediate (EI). Secondly, EI is oxidized into carbon dioxide (CO2) and carbon monoxide (CO). This simplified approach of removal allows for an agreement between modeling and empirical data in terms of degradation and mineralization. It also allows for the simulation of NTP and photocatalytic kinetics without knowing the plausible pathway. Moreover, the synergetic effect can be represented correctly by increasing mass transfer constant

Photocatalytic degradation of indole–4-methylphenol mixture in an aqueous solution: optimization and statistical analysis

International audienceThe photocatalytic degradation of indole and 4-methylphenol mixture, using ZnO, was studied. The optimal conditions for the degradation were determined using response surface methodology. We showed that in, our experimental domain, the quasi-complete degradation of the mixture’s organic constituents is possible. Moreover, we note that the effects of the entire variables are not linear. Indeed, the optimum removal conditions were determined. Thus, the optimal conditions for indole degradation were 1.5 mg/L catalyst concentration, 2.5 L/min airflow, and 7.16 pH. For 4-methylphenol, they were 1.37 mg/L of catalyst concentration, 2.38 L/min airflow, and 6.96 pH. Under optimized conditions, the complete photocatalytic degradation was obtained at 30 μL/L 4-methylphenol and 10 mg/L indole concentration. Similarly, the optimized correlation coefficients R2 and for a quadratic model was satisfactorily evaluated as 99.5 and 99.1%, respectively with indole and 99.7 and 99.4%, respectively, with 4-methylphenol. Our results reveal that the tested ZnO photocatalyst can be employed as a powerful tool for the pollutant degradation in wastewater