Microplastic pollution in long-term urban compost amended soils.

International audienc

Valorisation of CO2 with epoxides: Influence of gas/liquid mass transfer on reaction kinetics

International audienc

A long-term field experiment reveals the accumulation of high amounts of microplastics in soils amended with composted waste residues.

International audienc

CO2 valorization using epoxides under mild conditions

International audienceCarbon dioxide is the major greenhouse gas suspected to produce the climatic change. In order to reduce the emissions of CO 2 , several ways have been studied like capture process, geological storage and valorization. Recently one of the most important studies is concentrated on chemical valorization of CO 2. This option offers a great potential to recycle CO 2 and to convert it in different high value products. One alternative consider the reaction between epoxides (products with high energy), with CO 2 to obtain cyclic carbonates. These kind of reaction are biphasic and not spontaneous requiring a catalyst. In order to model the system, the liquid/gas interaction between epoxides and CO 2 should be studied. V. Contreras Moreno et al. / Chemical Engineering Science 170 (2017) 77-90 A calorimeter Reactor (Mettler RC1 M) was used to study gas/liquid equilibrium for several temperatures and pressures conditions. The isothermal method was used to measure CO 2 solubility. The injection of CO 2 is controlled by a gas chamber and a pressure sensor in the reactor. The pressure inside of the reactor is followed with the time to study the absorption and the liquid/gas equilibrium. A stirrer allows to keep the homogeneity in liquid phase and accelerate the mass transfer of the gas. T7.7.274 • The influence of the mass transfer kinetics on the chemical valorisation of CO2 by using ECH and a non-metallic catalyst was studied. • In the absence of a catalyst, the mass transfer of CO2 followed a purely physical profile and the stirring degree and temperature determined the absorption rate. • Under the conditions employed in this work, the reaction between CO2 and ECH was controlled by the reaction kinetics and not by the mass transfer The solubility of CO2 in ECH was studied at different temperatures and partial pressures of CO2; The solubility data and Henry's law constant were estimated by using the pressure data. The gas chamber pressure (PR) and the equilibrium pressure in the reactor (Peq) were used respectively to calculate the total amount of CO2 introduced in the reactor and the amount of CO2 remaining in the gas phase Henry's law constant has been obtained from the slope of the solubility curves between the partial pressure of CO2 (PCO2) and the molar solubility of CO2 increase of the stirring speed improved the absorption rate It is known that increasing agitation of the liquid increases the diffusion of the gas through the liquid film. As a matter of fact, increasing the stirring speed produces a reduction in the thickness of the contact film, which promotes the gas diffusion into the liquid and hence increases the absorption rate. after 300 rpm, the absorption rate was in fact not enhanced because the minimum boundary layer was attained enhancement factor model with the experimental data when the catalyst was introduced into the system at (a) 50°C, (b) 60°C, (c) 70°C, (d) 80°C. under hydrodynamic conditions, the minimum boundary layer was reached when the stirring speed was higher than 300 rpm, regardless of the temperature used during the absorption. This means that at this specific minimum, increasing turbulence did not have any influence on the mass transfer kinetics. Variation of the mass transfer coefficient with the stirring speed at different temperatures. It can be seen that as the stirring speed increased, the mass transfer coefficient increased as well. This behaviour was due to the reduction in film thickness, which increased the transfer through the liquid film. Chemical absorption profiles involving variation of normalised pressure against time at different temperatures and stirring speeds. It was noticed that at 300 rpm, the absorption rate increased as the temperature increased because of the occurrence of the reaction. However when the stirring speed was 500 rpm, a small effect of the temperature on the absoption rate was detected, because no appreciable changes in the pressure drop were observed. This means that the mass transfer kinetics at higher stirring speeds were faster than the kinetics of the chemical reaction.Therefore, even if the diffusion of gas through the liquid film was most important and the kinetic of the reaction was faster at high temperatures, the gas was not entirely consumed by the reaction. Comparison of absorption rate with or without reaction the absorption rates when the chemical reaction occurred in the system were lower than in the case of physical absorption. The pressure profiles at low stirring speeds (100, 200 rpm) presented the most important differences between physical and chemical absorption, because at low agitation, the effective film thickness of transfer was still not reached. Otherwise, when the stirring speeds were higher than 300 rpm, the physical and chemical profiles were closer, indicating the effective reduction of the film transfer. Evaluation of R factor For this study, R ratio took values between 0.1 and 100. Two pseudo-regimes were identified: a pseudo-regime in which the diffusional process interfered in the rate of the process and a pseudo-regime of transition between the kinetic and diffusional regime

AFPP - 22e Conférence du COLUMA - Journées Internationales sur la lutte contre les mauvaises herbes

National audienc

SI-Hex: a new catalogue of instrumental seismicity for metropolitan France

Abstract. – The aim of the SI-Hex project (acronym for « Sismicité Instrumentale de l’Hexagone ») is to provide a cata-logue of seismicity for metropolitan France and the French marine economic zone for the period 1962-2009 by taking into account the contributions of the various seismological networks and observatories from France and its neighbouring coun-tries. The project has been launched jointly by the Bureau Central Sismologique Français (CNRS-University/BCSF) and the Laboratoire de Détection et de Géophysique (CEA-DAM/LDG). One of the main motivations of the project is to pro-vide the end user with the best possible information on location and magnitude of each earthquake. So far, due to the vari-ous procedures in use in the observatories, the different locations and magnitudes of earthquakes located in the SI-Hex zone were presenting large discrepancies. In the 2014 version of the catalogue, 1D localizations of hypocentres performed with a unique computational scheme and covering the whole 1962-2009 period constitute the backbone of the catalogue (SI-Hex solutions). When available, they are replaced by more precise localizations made at LDG or, for recent times, by the regional observatories within: 1) the French Alps, 2) the southernmost Alps and the Mediterranean domain including Corsica, 3) the Pyrenees, and 4) the Armorican massif. Moment magnitudes Mw are systematically reported in the SI-Hex catalogue. They are computed from coda-wave analysis of the LDG records for most Mw>3.4 events, and are converte