Microfibrous TiO2 supported photocatalysts prepared by metal-organic chemical vapor infiltration for indoor air and waste water purification

The photocatalytic degradation of gaseous (toluene) and aqueous (imazapyr, malic acid, orange G) pollutants over TiO2 supported photocatalysts is investigated using a batch reactor. A strong influence of the microstructural characteristics of TiO2 on the decomposition kinetics of the pollutants is found. Well crystallized, porous TiO2-anatase films grown under low pressure at 400–500 8C by MOCVD on glass plates and by MOCVI on glass micro-fibers are the best heterogeneous photocatalysts, showing the highest activity. We demonstrate a good control of these characteristics by choosing the deposition parameters. Achieving conformal coverage (i.e. good infiltration) of glass micro-fibers by the TiO2 thin films has also a strong influence on the photocatalytic activity. A correlation between optimal infiltration, film microstructure and photocatalytic activity is established. Strong similarities between optimal photocatalytic decomposition rate in gas and liquid phase were found with respect to the film microstructure and the photocatalyst mass. The total mineralization of the toluene was prevented because of the deactivation of the photocatalyst surface. However the reactivation of the photocatalyst was achieved by UV irradiation under oxygen stream. This allows a long-term use of the photocatalyst

Synthesis, characterization and photocatalytic activity of TiO2 supported natural palygorskite microfibers

This study deals with the synthesis of TiO2 supported Moroccan palygorskite fibers and their use as photocatalyst for the removal of Orange G pollutant from wastewater. The TiO2-palygorskite nanocomposite synthesis was accomplished according to a colloidal route involving a cationic surfactant as template (hexadecyltrimethylammonium bromide) assuring hence organophilic environment for the formation of TiO2 nanoparticles. The clay minerals samples were characterized before and after functionalization with TiO2. Anatase crystallizes above ca. 450 °C and remarkably remains stable up to 900 °C. In contrast, pure TiO2 xerogel obtained from titanium tetraisopropoxide (TTIP) showed before calcination a nanocrystalline structure of anatase. By increasing the temperature, anatase readily transforms into rutile beyond 600 °C. The remarkable stability at high temperature of anatase particles immobilized onto palygorskite microfibers was due to the hindrance of particles growth by sintering. Homogeneous monodisperse distribution of anatase particles with an average size of 8 nm was found by TEM and XRD onto palygorskite fibers. This anatase particle size remains below the nucleus critical size (ca. 11 nm) required for anatase–rutile transition. The TiO2 supported palygorskite sample annealed in air at 600 °C for 1 h exhibits the highest photocatalytic activity towards the degradation of Orange G compared to nanocomposite samples prepared under different conditions as well as pure TiO2 powders obtained from the xerogel route or commercially available as Degussa P25

Emergence de la notion de service environnemental dans les politiques agricoles en France : l'ébauche d'un changement de paradigme?

Cet article traite des modalités d'importation de la notion de service environnemental dans les politiques agricoles en France. Le travail est basé sur une analyse bibliographique et sur des entretiens semi-directifs réalisés de septembre 2009 à mai 2010 auprès de 62 représentants des institutions du monde agricole en France

Photocatalytic activity of TiO2/stevensite nanocomposites for the removal of Orange G from aqueous solutions

TiO2/stevensite nanocomposite photocatalysts were synthesized by a solvothermal method using TiCl3/HCl as reactants and the stevensite clay mineral extract as support. The prepared photocatalyst samples were then characterized using various techniques such as X-ray diffraction (XRD), Infrared spectroscopy (IR) and Transmission Electron Microscopy (TEM). The Points of Zero Charge (PZC) of the various samples were evaluated by titration of the non-modified and the Ti-modified clay aqueous dispersions, with cationic surfactant solutions. The photocatalytic activity of the resulting nanocomposites samples were evaluated for the removal of Orange G (OG) from aqueous solution as a model dye pollutant. The data indicate that the formation of Na+-stevensite by the TiO2 particles leads to TiO2/stevensite nanocomposites having higher specific surface areas and mesopore volumes, and lower PZC values. Further, the photocatalytic activity was found to be greater for the TiO2/stevensite nanocomposites having the greatest Ti amount, as compared to a pure TiO2 sample, and increased with the increase of the TiO2 amount in the TiO2/stevensite nanocomposites

6 - Émergence tardive des services écosystémiques en France

La notion de service écosystémique a été développée dans la sphère scientifique, avant d’acquérir une légitimité politique. La notion de service écosystémique et l’instrument qui lui est souvent associé, le paiement pour services environnementaux (PSE), rencontrent ensuite un engouement important et sont progressivement incorporés dans les cadres nationaux et internationaux de régulation environnementale où ils font l’objet ..

Synthèse, caractérisations et tests photocatalytiques d’un matériau argileux d’origine naturelle à base de beidellite fonctionnalisée par TiO2

Cette étude porte sur la fonctionnalisation par TiO2 d’une argile marocaine de type beidellite et sur l’évaluation de son activité photocatalytique pour l’élimination d’un colorant anionique : l’orange G (OG), utilisé dans l’industrie textile. Les échantillons argileux ont été caractérisés, avant et après fonctionnalisation, par DRX, MEB et MET couplé à l’analyse EDX, TG-ATD, FTIR, ICP et RMN du solide. La beidellite est aluminifère, dioctaédrique, de formule chimique (Si7,57Al0,43)8 (Al2,75Fe0,73Mg0,38Ti0,14)4 (Na0,37K0,23Mg0,01) avec une CEC, une surface spécifique et un volume poreux total de l’ordre de 48 méq/100 g, 72 m2/g et 0,128 cm3/g respectivement. Les matériaux argileux nanocomposites obtenus sont constitués de nanoparticules de TiO2 (taille moyenne 10 nm) supportées par les feuillets de la beidellite. Leurs surfaces spécifiques sont quasiment du même ordre de grandeur que celle de la beidellite tandis que leurs volumes poreux augmentent pour atteindre 0,226 cm3/g. L’échantillon calciné à 600 ◦C, dans lequel TiO2 est sous forme d’anatase, manifeste une activité photocatalytique remarquable vis-à-vis de l’élimination de l’OG en milieu aqueux

Mineralogical and Physico-Chemical Characterizations of Ferruginous Beidellite-Rich Clay from Agadir Basin (Morocco)

The mechanism of formation of detrital, beidellite-rich clay occurring in the Agadir basin (Morocco) is well documented, but its detailed characterization is incomplete which limits its application. The aim of the present study was to provide further details of the mineralogical and physico-chemical characteristics of this clay. Bulk raw clay and its Na+-saturated, <2 mm fraction were characterized using chemical, structural, and thermal techniques. Measurements of induced streaming potential (e.g. particle charge) and of specific surface area and porous volume are reported. The raw clay contained carbonate and quartz as associated minerals along with phyllosilicates (<2 mm particle size). X-ray diffraction and scanning electron microscopy analyses showed that the <2 mm fraction was dominated by a dioctahedral smectite. Because dehydroxylation of this mineral occurred at 510ºC, and because it re-expanded in ethylene glycol after Li+-saturation followed by heating at 240ºC for 24 h, the mineral was shown to be a beidellite rather than montmorillonite. This assertion was further supported by 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectra showing predominantly negative charges in the tetrahedral sheets due to notable Al-for-Si substitutions. The chemical composition of the <2 mm fraction showed an Fe2O3 content which was ~7.52 wt.% greater than those of other beidellite occurrences but not so much that it would be identified as a nontronite. The absence of stretching and bending absorption bands corresponding to characteristic (Fe2OH) units in mid-infrared spectra and their corresponding fundamental overtones or combination bands in near-infrared spectra supported this notion. The structural formula of the beidellite in the present study was determined to be (Si7.51Al0.49)(Al2.99Fe0.68Mg0.33) (Ca0.03Na0.54Mg0.11)O20(OH)4, having dioctahedral ferruginous characteristics with almost 60% of the negative charge found in tetrahedral sheets. The cation exchange capacity determined from the structural formula was ~108 meq/100 g. The specific surface area and total pore volume were ~82.2 m2/g and 0.136 cm3/g, respectively. Interestingly, a detrital rather than a hydrothermal-alteration origin, as reported for other beidellite occurrences, explains its natural abundance and emphasizes the great interest in it

Cross-border outbreak of listeriosis caused by cold-smoked salmon, revealed by integrated surveillance and whole genome sequencing (WGS), Denmark and France, 2015 to 2017

International audienceIn August 2017, an outbreak of six listeriosis cases in Denmark was traced to cold-smoked salmon, using epidemiological investigations and whole-genome sequencing (WGS) analyses. Exchange of genome sequences allowed identification in France of a food isolate from a salmon-derived product and a human isolate from 2016 within the same cgMLST cluster as the Danish isolates (L2-SL8-ST8-CT771). The salmon product came from a third European Union country. WGS can rapidly link human cases and food isolates across Europe