Mode de desactivation des zeolithes : caracterisation des zeolithes cokees par adsorption de diverses molecules

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Elimination de composés organiques volatils (COV) chlorés sur zéolithes par couplage adsorption-oxydation catalytique

Au cours de ce travail nous avons étudié l adsorption du tétrachloroéthylène (PCE) sur des zéolithes faujasites, en conditions statique et dynamique, en présence et en absence de vapeur d eau, ainsi que l oxydation catalytique du PCE sur des catalyseurs à base de zéolithes faujasites dopées ou non avec du platine dans l objectif de réaliser le couplage adsorption/oxydation catalytique pour l élimination du tétrachloroéthylène. Nous avons également étudié l adsorption et l oxydation seules et en couplage d une autre molécule de COV, la butan-2-one.This study is focused on tetrachloroethylene (PCE) adsorption over faujasite type zeolites, in static and dynamic conditions, in dry and humid environment. In addition, catalytic oxidation of PCE over zeolite FAU based catalyst exchanged or not with platinum was studied. Lastly, PCE removal was carried out over dual functional adsorbent/catalyst system. The elimination of methylethylketone (MEK) was also performed by single adsorption and oxidation, and using adsorbent/catalyst media.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Hierarchical zeolites as adsorbents for mesosulfuron-methyl removal in aqueous phase

International audienceDesilication and soft acid leaching lead to hierarchical zeolites with low debris.•Hierarchical zeolites are promising adsorbents for bulky pesticides in water.•Mesosulfuron-methyl (MM) is chemisorbed on zeolite Brønsted acid sites.•The zeolite mesoporosity enhances significantly MM diffusion behavior and capacity.•MM abatement rate is up to 80% in water for hierarchical large pore H-MOR zeolite

Ajustement de l'hydrophobicité de silices mésoporeuses organisées pour l'adsorption sélective de polluants organiques en présence d'eau

Les charbons actifs et les zéolithes microporeuses hydrophobes sont généralement utilisés pour l'élimination par adsorption des polluants organiques des effluents industriels. Grâce à leur très grande surface spécifique et à un volume poreux élevé, les silices mésoporeuses organisées ont des capacités de stockage plus importantes que leurs analogues microporeux. De plus, ces solides présentent une faible interaction eau-adsorbant aux faibles valeurs de P/P0 vis-à-vis de l eau ce qui leur confère un caractère hydrophobe. Cependant, la présence de groupements silanols dans les canaux limite fortement l'adsorption des molécules organiques en présence d'eau. Afin d'accroître fortement l'hydrophobicité des silices mésoporeuses, différentes modifications au cours de la synthèse (incorporation de groupements phényles) ou post-synthèse (greffage de groupements triméthylsilyles, aminopropyles et propyle sulfoniques) ont été envisagées. Le greffage de groupements triméthylsilyles et l'incorporation de groupements phényles permettent donc d'augmenter considérablement l'hydrophobicité des solides en réduisant le nombre de groupements silanols. Dans le cas de l'adsorption en phase gaz, l'hydrophobicité s'est révélée être un facteur clef positif. L'adsorption de polluants organiques apolaire en phase aqueuse nécessite également une silice hydrophobe. Pour des molécules polaires, le greffage de groupements polaires adaptés (amino ou sulfonique) à la forme chimique du polluant a un rôle déterminant sur son adsorption.Activated carbons and hydrophobic microporous zeolites are usually used for the removal of organic pollutants in wastewater. An extended BET surface and a relevant pore volume both confer high sorption capacities to organised silica materials. Moreover, these solids exhibite a low water-adsorbent interaction at low P/P0 giving them an hydrophobic character. However, the presence of silanol groups limits the adsorption of organic molecules in aqueous phase. In order to significantly increase the mesoporous silica hydrophobicity, various modifications during synthesis (phenyl groups incorporation) or post-synthesis (grafting of trimethylsilyl, aminopropyl and mecaptopropyl groups) were considered. The grafting of trimethylsilyl groups and phenyl groups incorporation can therefore considerably reduce the hydrophilicity of these solids by reducing the number of silanol groups. In the case of gas adsorption, hydrophobicity proved to be a positive key factor. In aqueous phase, the non-polar organic pollutants adsorption also requires hydrophobic silica. For polar molecules, the grafting of polar groups (amino or sulfonic) increases the pollutant adsorption capacities.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Caractérisation et ajustement de l'hydrophobicité de divers solides poreux (application à l'élimination de polluants organiques)

Les solides poreux hydrophobes ont un vaste champ d'application potentiel dans les procédés de dépollution de l'air et des eaux résiduelles. Elles constituent donc une alternative intéressante aux charbons actifs pour l'élimination sélective des polluants organiques, car elles sont facilement régénérables à haute température. Leurs propriétés adsorbantes sont en grande partie liées à leurs indices d'hydrophobicité HI. Différents paramètres influent sur l'indice d'hydrophobicité. Dans le cas des zéolithes, ce sont la structure poreuse, l'acidité des échantillons (rapport Si/Al de charpente), la taille des cristallites, la présence de défauts (nids silanols) ou d'EFAl. Dans le cas des silices mésoporeuses, ce sont le volume poreux, le taux de greffage et la concentration en silanols. L'élimination du phénol est favorisée sur les zéolithes très hydrophobes, celle du chlorobenzène sur les zéolithes peu hydrophobes ; les silices mésoporeuses hydrophobes adsorbent bien le chlorobenzèneHydrophobic silica and zeolites found numerous applications in separation technologies. They are going to replace activated carbon because of their interesting regeneration properties. Their adsorptive properties are linked to their Hydrophobicity index defined by Weitkamp. Many parameters play a key role in the values of Hydrophobicity indexes. In the case of zeolites, parameters such as the partial pressure of sorbates, their acidity, their crystallite sizes, the presence of structural defects and EFAl species in the structure... determine the strength of the hydrophobic character. In the case of mesoporous silica, the silylation level is the main parameter determining the hydrophobic character. Phenol removal in aqueous solutions is efficient on hydrophobic zeolites and silylated silica. Chlorobenzene removal is efficient on the most acidic supports. This removal is improved on silylated mesoporous silicas.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Dripping to jetting transitions observed from supercritical fluid in liquid microcoflows

Dripping to jetting transition from liquid-liquid to liquid-gas systems has been widely studied in microfluidics. Recent developments have permitted the use of supercritical fluids at high pressure and various temperatures in microfluidic systems to develop sustainable processes. In this article, we use this strategy to demonstrate the possibility to generate stable droplets and reversible dripping to jetting transitions at microscale from supercritical carbon dioxide-liquid water microcoflows

Tuning the hydrophobicity of mesoporous silica materials for the adsorption of organic pollutant in aqueous solution.

International audienceThe ability of various as-prepared and organically modified MCM-41 and HMS mesoporous silica materials to behave as efficient adsorbents for organic pollutants in aqueous solution was investigated by using different surface functionalization procedures, so as to adjust their hydrophilic/hydrophobic balance. The hydrophilic and organophilic properties of the parent silica materials and their corresponding surface functionalized counterparts were studied by using water and toluene adsorption isotherms. Their quantification was determined by the hydrophobic static index value (HI(static)), as well as by the silanol and organic group densities after the functionalization step. A clear correlation could be found between the HI(static) values and either the superficial silanol density, or the amount of organic moieties grafted or incorporated to the silica materials. For the highly organically functionalized samples, the residual superficial silanol groups (<50%) are sufficiently isolated from each other so as to prevent the water capillary condensation within the pores, thereby leading to an increased hydrophobic character of the resulting mesoporous silica. Those hydrophobic samples, for which the water liquid meniscus formation within the mesopores was minimized or avoided, exhibited a storage capacity for an organic pollutant (N,N-diethyl-m-toluamide, DEET) in aqueous solution more than 20 times higher than that of the corresponding unmodified sample, independently of the silica nature (MCM-41 or HMS). For all calcined and silylated samples, the DEET maximum adsorption capacities determined by the Langmuir model could be correlated with the silica surface coverage by trimethylsilyl groups and thus with the remaining silanol amount

Microfluidic Supercritical Antisolvent Continuous Processing of Poly(3-hexylthiophene) Nanoparticles

Organic electronic devices are promising alternatives to conventional inorganic technologies. Ink-based processes can easily be used to obtain active films, e.g. by spray-drying or roll-to-roll techniques. But their industrial development might be limited by the use of chlorinated solvents. An alternative consists in using solvent-dispersed NPs of organic semi-conductor. Previous work have demonstrated that it was possible to obtain organic semi-conducting dispersions of P3HT and/or [6,6]-Phenyl C61-Butyric acid Methyl ester (PCBM) NPs using an antisolvent approach. For organic photovoltaic devices, the nano-morphology has to be controlled in order to have donor and acceptor domains size in the range of the exciton diffusion length (10 nm). However, conventional synthesis approaches are based on slow solvent / antisolvent mixing process, whereas strong mixing is required to access small sizes and narrow size distributions. Admittedly, micromixing has a significant effect over particles size and size distribution since homogeneous concentration distribution and high degree of supersaturation can only be reached by intense micromixing. This can be achieved by performing antisolvent processes at microscale using microfluidic devices and/or by using supercritical fluids as antisolvents.By coupling both, we will present in here the first demonstration of a supercritical antisolvent process performed within a microsystem, so called µSAS. The µSAS process was applied to the processing of P3HT NPs as small as 36 ± 8 nm. The designed set-up includes a spraying nozzle at the outlet of the back pressure regulator allowing depositing P3HT NPs films onto a substrate. The µSAS process benefits from both the advantages of supercritical antisolvent approaches and microscale processes (fast mixing, high supersaturation, etc.) and can be successfully used to synthesize semi-conducting polymeric NPs, which size are compatible with the diffusion-length of excitons in active layer of photovoltaic devices