Tools and techniques for solvent selection: green solvent selection guides

Driven by legislation and evolving attitudes towards environmental issues, establishing green solvents for extractions, separations, formulations and reaction chemistry has become an increasingly important area of research. Several general purpose solvent selection guides have now been published with the aim to reduce use of the most hazardous solvents. This review serves the purpose of explaining the role of these guides, highlighting their similarities and differences. How they can be used most effectively to enhance the greenness of chemical processes, particularly in laboratory organic synthesis and the pharmaceutical industry, is addressed in detail

3 bit 90° phase shifter using microfluidic technology

International audienceAddressing systems that require broadband devices for high data rate communication or high resolution radar, we develop the concept of a millimeter phase shifter that combines micro strip or coplanar wave guide and microfluidic facilities. To illustrate this approach we built from a simple analytical equation the main steps of the design of a 3 bits 90° 60GHz broadband (3GHz) pbase shifter. Preliminary results performed by a 3D elech.omagnetic simulator are then presented

New concept of RF functions by microfluidic coupling

International audienceWe present a new concept that combines microfluidic circuits designed inside planar waveguides for advanced ultra-wide band functions. Feasibility of such approach is demonstrated on a broadband variable delay line operating in the microwave region. We also show that this approach is very well fitted for the future THz circuit

Evolution spatiale et temporelle des pesticides dans un réseau de canaux

A liquid-liquid extraction method using pulsed column was performed to quantify at the ng/l level the pesticide pollution effect. Over a period of one year on the Languedoc-Roussillon area, the surface water of a canal network fed by the Rhône river was analysed in order to identify organic pollutants. Among the 110 substances found by this method, 7 are pesticides : lindane, alachlor, metolachlor, methyl parathion, simazine, terbutylazine and atrazine. This study permit to know their concentration evolution as a function of seasons, rain and swelling. A spatial evolution was shown their slow disapearance along the canal, phenomenon explained by their degradation or sedimentation. / Dans le but de quantifier l'effet de pollution des pesticides, une technique d'extraction liquide-liquide par colonne pulsée est mise en oeuvre permettant leur détection à des teneurs allant jusqu'au ng/l. Durant un an, la composition organique des eaux d'un réseau de canaux, situé en région Languedoc-Roussillon et alimenté par l'eau du Rhône, a été étudiée. Cette recherche s'est concrétisée par la détection et la quantification de 110 composés dont 7 pesticides : lindane, alachlor, métolachlor, méthyl parathion, simazine, terbutylazine et atrazine. Cette étude a permis de connaître l'évolution de leur concentration en fonction des saisons, des épisodes pluvieux et des crues. Un suivi spatial a montré leur lente disparition le long du canal, phénomène expliqué par leur dégradation ou leur sédimentation

Modelling the breakthrough of activated carbon filters by pesticides in surface waters with static and recurrent neural networks

International audienceA black-box approach is performed to model the breakthrough of activated carbon filters by pesticides present in surface waters with a recurrent neural network (in input–output form) and, as a baseline, by a feed-forward neural network, which includes time as an input variable.In a first part, isotherm experimental runs are performed in static reactors, using five activated carbons and three pesticides, under different operating conditions. The influence of adsorbent and adsorbate properties on adsorption performance in highlighted for pure and natural waters. The modelling of competitive adsorption isotherms by the equivalent background compound (EBC) model enables to determine the Freundlich parameters of the EBC which is the part of natural organic matter in competition with the pesticide.In a second part, experimental breakthrough curves of pesticide in a surface water are assessed in fixed-beds and modelled using neural network approaches. The selection of data is based on physical and statistical approaches, equilibrium parameters assessed in static reactors being considered as influential variables to take into account the competitive adsorption phenomenon. Static and recurrent neural networks provide both high determination coefficients (R2 > 0.990) and low root mean square modelling errors (RMSE < 0.035 while standard deviation of data is equal to 2.9%) for the prediction of the global breakthrough curves. To model the breakthrough zone (C/C0 < 0.1), the recurrent neural network, with a smaller number of parameters, is however more accurate than the feed-forward one, since the process to be modelled is dynamic

Hydrogen sulfide removal from a biogas mimic by biofiltration under anoxic conditions

International audienceThe biofiltration of hydrogen sulfide present in a biogas mimic under anoxic conditions was performed using expanded schist and cellular concrete waste as packing materials. The impact of various parameters, such as H2S concentrations, Empty Bed Residence Time (EBRT) and molar ratio N/S, on the performances of biofilters was evaluated. At an EBRT of 300 s, expanded schist efficiently treated H2S concentrations up to 1100 ppmv (maximum elimination capacity ECmax = 30.3 g m-3 h-1). At an EBRT of 240 s, cellular concrete waste was an effective material for the treatment of concentrations of H2S up to 900 ppmv (ECmax = 25.2 g m-3 h-1). Whatever the molar ratio N/S selected, sulfate and elemental sulfur were produced in the biofilters. Both materials presented a satisfactory mechanical behavior with low pressure drops. Therefore, this study showed that biofilters could be used to treat moderate concentrations of H2S in biogas under anoxic conditions