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International audience; In this paper, we report and discuss the reduction mechanism of pentavalent tantalum salt (TaF5) in a room temperature ionic liquid (RTIL) by coupling two complementary electrochemical techniques: the cyclic voltammetry and the electrochemical quartz crystal microbalance (EQCM). The experiments were performed in the hydrophobic 1-butyl-3-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide ([BMPyr][TFSI]) RTIL used both as a solvent and as an electrolyte. Four different reduction peaks are present in the obtained voltammogram in the range from 0 V (vs Pt-Fc/Fc+) to −3.5 V (vs Pt-Fc/Fc+). The existence of the first reduction peak depends mainly on the nature of the substrate of the working electrode and is therefore not related to the reduction of the tantalum salt. The second reduction peak is ascribed to the direct tantalum salt reduction to its metallic state. During this reduction, free fluoride ions are produced in the electrolyte in the vicinity of the electrode surface. These ions can then react with diffusing TaF5 to form TaF5+x−x complexes and thus the reduction peaks occurring at lower potential are referred to the reduction of such complexes. This hypothesis was confirmed by addition of LiF in the electrolyte.

International audience; The present work deals with the modeling of selenium oxyanion (selenite/selenate) retention in TiO2 rutile porous media. A set of chemical interactions was elaborated from spectroscopic measurements and adsorption experiments in batch and column reactors, and a model of transient transport of the selenium species through laboratory column was developed. The adsorption model considered that both forms of selenium (Se) compete for the same sorption sites, hydroxyl groups, allowing taking into account a competitive adsorption. Stoichiometry and equilibrium constants of adsorption reactions were determined on the basis of spectrometric measurement and adsorption isotherm curve fitting. This approach led to a model of Sips type isotherm including a pH-dependence. It offers an excellent fitting compared to the classical Langmuir equation and provides a unique set of parameters for both oxyanions. IMPACT code and associated modeling method were then used to couple transport and chemical reactions. The obtained numerical results showed a reasonable prediction of the shape and the time location of selenium oxyanions and pH breakthrough curves.

Two kinds of waste biomass (Penicillium oxalicum var. Armeniaca, Tolypocladium sp.) used in fermentation industry were submitted to different treatments and were tested as biosorbents of cadmium, lead and mercury. The study was initially focused on the evaluation of the impact of pH on the sorption of selected metals and continued with the sorption isotherms determination. The sorption capacities for the target metals can be ranked according to Hg ≫ Pb > Cd for P. oxalicum sorbent and Hg ≫ Cd > Pb for Tolypocladium sp. sorbent. P. oxalicum shows greater sorption capacities (based on sorption capacities in molar units) than Tolypocladium sp. Maximum sorption capacity as high as 270 mg Hg g−1 (initial pH 5, equilibrium pH close to 6.2) has been obtained for Penicillium derived biosorbent. The Langmuir isotherm equation fits significantly better experimental data than the Freundlich isotherm equation. FT-IR spectra and elemental analysis of the biosorbents have shown significant changes in their composition according to the treatment.