Traitement de composés organiques volatils par lavage chimique compact: recyclage de la solution de lavage par oxydation avancée O3/H2O2

National audienceThis study focuses on Volatile Organic Compounds (VOC) treatment in a compact chemical scrubber composed of a structured packing operating at co-current and high gas superficial velocity (> 10 m.s-1). The scrubbing liquid is composed of ozone and hydrogen peroxide to generate very reactive hydroxyl radicals. Results demonstrate a high mineralisation rate of the transferred VOC, even with low oxidant concentrations. Therefore, the scrubbing liquid can be recycled and recirculated at the top of the scrubber without efficiency drop over time. Neutral VOC removal efficiency increases with their solubility in water, from 14% for dimethyldisulfide to 86% for butanol using a mass flow rates ratio (L/G) of 2.5 and residence time of 20 ms. For trimethylamine, a basic VOC, the increased apparent solubility at pH = 8 leads to a high removal efficiency of 80%. Major by-products were identified and quantified. An absence of stripping in the treated gas emphasizes their innocuity.Cette étude porte sur le traitement de Composés Organiques Volatils (COV) dans un laveur chimique compact composé d’un garnissage structuré fonctionnant à co-courant et à vitesse superficielle du gaz élevée (> 10 m.s-1). La solution aqueuse de lavage se compose d’un mélange d’ozone et de peroxyde d’hydrogène afin de générer des radicaux hydroxyles très réactifs. Les résultats démontrent une minéralisation poussée des COV transférés même avec des concentrations en oxydants modestes. La solution de lavage peut donc être régénérée et réinjectée en tête du laveur sans diminution d’efficacité au cours du temps. L’abattement en phase gazeuse des COV neutres, observés pour un rapport des débits massiques L/G de 2,5, augmente avec leur solubilité en phase aqueuse, démarrant à 14% pour le dimethyldisulfide jusqu’à 86% pour le butanol en 20 ms de temps de contact. Pour la triméthylamine, composé basique, l’augmentation de la solubilité apparente à pH 8 permet d’atteindre un abattement élevé de 80%. Les sous-produits majoritaires ont été identifiés et quantifiés. L’absence de stripping dans le gaz traité met en évidence leur innocuité

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Volatile organic compounds absorption in packed column: theoretical assessment of water, DEHA and PDMS 50 as absorbents

International audienceA fixed volume packed column was simulated for the absorption at counter-current of four more or less hydrophobic volatile organic compounds (VOCs) in water and in two heavy organic solvents (PDMS 50, a silicone oil) and DEHA (Bis(2-ethylhexyl) adipate). Reliable values of the mass-transfer coefficients were deduced allowing to calculate the VOCs removal efficiency. Disappointing performances in heavy solvents, lower than 60% for isopropanol and acetone, were computed in a 3 m height column and using mild conditions (atmospheric pressure and a liquid-to-gas mass flow rate ratio around 2). However, toluene removal efficiencies higher than 90% were simulated. (C) 2017 The Korean Society of Industrial and Engineering Chemistry

Intensification of volatile organic compound absorption in a compact wet scrubber at co-current flow

International audienceThree volatile organic compounds (VOC) with no acidic or basic function (butanol, butyraldehyde, methylethylketone), encountered at low concentrations in odorous effluents, were absorbed in water in a compact wet scrubber. This gas-liquid contactor consisted of a wire mesh packing structure where the gas phase flows at high velocity (>12 m s(-1)). A very turbulent two-phase downward flow could be observed in the scrubber with dispersed fine droplets (around 10 μm). For compounds showing a good affinity for water, such as butanol, removal efficiencies up to 90% were measured for a short contactor length of 32 cm leading to a gas residence time of 20 ms. However, the removal efficiency of butyraldehyde, which is poorly soluble in water, ranged between 10 and 30%. Mass-transfer modeling was achieved and underlined that working with several small scrubbers in series, fed with an unloaded solution, is effective to improve the removal efficiency. The influences of the VOC/solvent affinity, the contactor length, and the mass-transfer and hydrodynamic parameters on the removal efficiency were evaluated through a sensitivity analysis

Assessment of a Stirred-Cell Reactor Operated Semicontinuously for the Kinetic Study of Fast Direct Ozonation Reactions by Reactive Absorption

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Determination by reactive absorption of the rate constant of the ozone reaction with the hydroperoxide anion

International audienceThe reaction rate constant between the hydroperoxide anion (HO2−) and molecular ozone was evaluated from the reactive absorption method in the range of temperature from 20 to 35 °C. This reaction is crucial in the initiation step of the ozone decomposition, especially using the peroxone process which combines ozone and hydrogen peroxide in solution. A stirred-cell operated semi-continuously was used for this purpose. A high initial concentration of tert-butanol (0.05 mol L−1) was applied to efficiently scavenge all radicals and to avoid any parasite reaction. Based on the dissolved H2O2 concentration decreasing and the outlet ozone concentration time-course, the stoichiometry of the initiation reaction was determined, with one mol of H2O2 consumed per mol of ozone transferred. The chemical conditions were thoroughly selected to reach a fast pseudo-first order absorption regime. The reaction rate constant increased from 1.91 × 106–2.40 × 106 L mol−1 s−1 at 20 °C to 5.68 × 106–7.31 × 106 L mol−1 s−1 at 35 °C

Volatile organic compounds treatment by compact chemical scrubbing:scrubbing solution recycling by advanced oxidation O3/H2O2.

International audienceThis study focuses on Volatile Org. Compds. (VOC) treatment in a compact chem. scrubber composed of a structured packing operating at co-current and high gas superficial velocity (\textgreater 10 m.s-1). The scrubbing liq. is composed of ozone and hydrogen peroxide to generate very reactive hydroxyl radicals. Results demonstrate a high mineralization rate of the transferred VOC, even with low oxidant concns. Therefore, the scrubbing liq. can be recycled and recirculated at the top of the scrubber without efficiency drop over time. Neutral VOC removal efficiency increases with their soly. in water, from 14% for dimethyldisulfide to 86% for butanol using a mass flow rates ratio (L/G) of 2.5 and residence time of 20 ms. For trimethylamine, a basic VOC, the increased apparent soly. at pH = 8 leads to a high removal efficiency of 80%. Major byproducts were identified and quantified. An absence of stripping in the treated gas emphasizes their innocuity. [on SciFinder(R)

Assessment of an hybrid process coupling ozonation and anodic oxidation in a monophasic configuration

International audienceThis prospective study assessed a hybrid process that combines ozonation with anodic oxidation (AO/O3) with two boron-doped diamond (BDD) electrodes to treat a model aqueous solution containing 30 ppm of alachlor at pH 5 in a phosphate buffer. An innovative monophasic configuration, operated batch-wise, in which an ozone-stock solution was injected at t0 in the electrochemical reactor, was proposed in order to avoid introduction of ozone-enriched gas bubbles. The alachlor parent molecule was almost entirely degraded within around 150 min of reaction time by anodic oxidation alone, whatever the applied current intensity (200, 500 and 800 mA). The mineralization efficiency varied from 50 % at 200 mA to 80 % at 800 mA after 120 min. The results emphasized that the anodic oxidation was a diffusion-controlled process. Addition of ozone at a low ozone dose of 1.9–2.3 mol of ozone per mol of alachlor allowed to decrease the ozone half-life time 2.7 times with the hybrid process compared to ozonation alone. This faster ozone consumption was concomitant with an enhanced alachlor degradation rate, with a corresponding half-life time around two-times lower. However, owing to the low ozone dose applied and the short ozone lifetime in solution (around 25–30 min), similar mineralization efficiencies were noticed for both AO/O3 and AO processes. Thus, the application of pulse ozone-stock solution re-injections every 20 min to prolong the ozone exposure was assessed to overcome this limitation. However, the effect on the mineralization rate remained small, even if it allows to enhance even more the alachlor parent molecule degradation rate. The low influence of the hybrid process on the mineralization rate was attributed to the production of aliphatic fatty acids by-products that are poorly reactive with hydroxyl radicals, and whose the degradation by AO is the rate limiting step

Intensification of the O3/H2O2 advanced oxidation process using a continuous tubular reactor filled with static mixers Proof of concept

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