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Roth E.,CNRS Molecular and Atmospheric Spectrometry Group | Mancier V.,French Atomic Energy Commission | Fabre B.,CNRS Risk Management and Environment Laboratory
Geoderma | Year: 2012

Kinetic and thermodynamic studies are carried out at low initial cadmium concentration on a soil sample extracted from Aspach le Bas in Eastern France. It can be concluded from kinetic experiments that the implied process is of pseudo-second order. Rate constants, relaxation times and activation energy are calculated. The energy value determined in this study (40kJmol -1) shows that the process implies both physisorption and chemisorption.The influence of soil particle size (i.e. of the initial soil and its different fractions: sand, coarse silt, fine silt and clay), organic matter and temperature on the cadmium sorption capacity is also investigated. The Langmuir and the Dubinin-Radushkevich models are chosen to analyze these thermodynamic experiments. The isotherms have revealed that the Cd 2+ sorption is enhanced by increasing temperature and organic matter for all the fraction but the sand (in this last case, no temperature or organic matter have changed Cd 2+ sorption). Thermodynamics parameters ({increment}G, {increment}H and {increment}S) are determined from experimental isotherms fitting following three methods used in the literature. It can be deduced from the different results that adsorption (exo or endothermic according to the fraction). Finally, a mean free energy of adsorption is obtained via Dubinin-Radushkevich model and confirms that the two types of sorption (physical and chemical) act in the whole process. © 2012 Elsevier B.V.

Deon S.,University of Franche Comte | Escoda A.,University of Franche Comte | Fievet P.,University of Franche Comte | Dutournie P.,CNRS Risk Management and Environment Laboratory | Bourseau P.,University of Nantes
Chemical Engineering Journal | Year: 2012

Prediction of ions rejection by nanofiltration membranes is of prime importance for many industrial or environmental applications. For this purpose, many knowledge models were developed in the last decades to understand which phenomena govern the selectivity between various ions. In the present work, the possibility of predicting salts rejection by nanofiltration membranes with a classical transport model has been investigated. The Pore Transport Model (PPTM) used in this study is based on the coupling between the equilibrium partitioning at the membrane-solution interfaces and the extended Nernst-Planck equation to describe transport within the membrane pores. The main difficulty of such a model is the parameters estimation and especially the volume membrane charge (X d) and the dielectric constant inside pores (e{open} p). The membrane charge is usually characterized by streaming potential whereas the difficulty of measuring dielectric constant leads to a numerical adjustment from experimental rejections. In this work, the values of e{open} p and X d are numerically identified from ternary mixtures and the possibility of fully predicting single salts and mixtures rejection is investigated. The identification method is implemented for two membranes and various divalent ions at various concentrations. The agreement between experimental and predicted curves, presented in this paper for many conditions, allows the feeling that the full prediction of ionic separations is not completely unrealistic. © 2012 Elsevier B.V.

Maryandyshev P.,Northern (Arctic) Federal University | Chernov A.,Northern (Arctic) Federal University | Lyubov V.,Northern (Arctic) Federal University | Trouve G.,CNRS Risk Management and Environment Laboratory | And 2 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2015

The thermal degradation of different wood biofuels collected in the Arkhangelsk region (northwest of the Russian Federation) was investigated in order to extract their kinetic parameters. Thermogravimetric analysis was carried out for small samples under inert atmosphere or air. These samples were heated from 20 to 1300 °C under three heating rates of 5, 10 or 20 °C min−1. The mass loss rates were measured during the drying, devolatilization and char combustion processes. Average values of the activation energies were determined using Friedman’s and Ozawa–Flynn–Wall’s methods under inert atmosphere and air. The morphological analysis of raw samples and of the corresponding chars was also performed. Pore development presents an effective impact on char reactivity. These experimental results and the kinetic data obtained in this work should be considered for the simulation of the pyrolysis and combustion processes of different biofuels in industrial devices. © 2015 Akadémiai Kiadó, Budapest, Hungary

Popova E.,Northern (Arctic) Federal University | Chernov A.,Northern (Arctic) Federal University | Maryandyshev P.,Northern (Arctic) Federal University | Brillard A.,CNRS Risk Management and Environment Laboratory | And 4 more authors.
Bioresource Technology | Year: 2016

The thermal degradation of wood biofuels (spruce, pine), of coals from different fields of the Russian Federation and of hydrolysis lignin is investigated using a thermogravimetric analyzer under different heating conditions and under non-oxidative or oxidative atmospheres. The samples are indeed submitted to a linear temperature ramp of 10 K/min or to a temperature ramp of 200 K/min up to a residence temperature between 250 and 450 °C where they are maintained during 4 h (isothermal conditions). The values of the kinetic parameters are determined for these different samples in both thermal conditions, either using the differential isoconversional method or by means of an Extended Independent Parallel Reaction (EIPR) model. The values of the kinetic parameters obtained with this EIPR model for spruce trunk are also compared with that of its main constituents (hemicellulose, cellulose and lignin). © 2016 Elsevier Ltd

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