Action du sulfite de sodium sur la concentration en composés organohalogénés et sur l'activité mutagène de solutions chlorées de substances humiques

Cette étude a eu pour but de déterminer l'effet d'un traitement par le sulfite de sodium sur la concentration en composés organohalogénés totaux (TOX) et sur l'activité mutagène de solutions chlorées de substances humiques d'origine aquatique (SHA), après avoir cherché à préciser l'influence du pH et du temps sur la concentration en TOX.Les résultats obtenus à partir d'échantillons chlorés de SHA en absence de chlore résiduel ont permis de mettre en évidence une diminution de la concentration en composés organohalogénés totaux, soit par stockage en milieu neutre ou basique, soit par addition de sulfite de sodium. L'intensité de cette réduction de la concentration en TOX augmente avec le pH, le temps de réaction et la dose de sulfite de sodium introduite.Les résultats obtenus à partir d'échantillons contenant du chlore libre indiquent que seule une déchloration totale avec un excès de sulfite de sodium peut conduire, en milieu neutre, à une diminution de l'activité mutagène et de la concentration en TOX des solutions diluées de SHA. La comparaison des pourcentages d'abattement obtenus sur le paramètre TOX et sur l'activité mutagène indique que la diminution de la génotoxicité par déchloration totale est due à l'action du sulfite sur des composés mutagènes non chlorés ou sur des composés chlorés fortement mutagènes et ne représentant qu'une très faible fraction du TOX.If is a well known tact that mimerous organohalogenated compounds are formed during the chlorination (preoxidation or final disinfection) of drinking water. Some of these compounds have been shown to be mutagenic. Recent studies have suggested that a treatment with oxygenated derivatives of SIV (SO2, NaHSO3 and Na2SO3) could reduce the genotoxicity of chlorinated drinking water.The general aim of Ibis study was to determine the effect of dechlorination treatments on the mutagenic activity of chlorinated drinking water. The following experiments were carried out in order to point out the effect of a treatment with sodium sulfite on the concentration of total organohalogenated compounds (TOX) and on the mutagenic activity of chlorinated dilute solutions of Aquatic Humic Substances (AHS).At first, the affects of pH, sodium sulfite dose and contact time on TOX concentration were investigated. Then, the importance of the dechlorination rate (partial or complete) on TOX concentration and also on the mutagenic activity could be studied.ExperimentalAquatic Humic Substances (natural mixture of fulvic and humic acids) were dissolved in phosphate-buffered ultra-pure water at 5 and 15 mg l-1 concentrations (pH 6.1 and 6.9 respectively). Stock solutions of chlorine were prepared in the laboratory and titrated by iodometry. Chlorination and dechlorination treatments were carried out in headspace-free baffles, at 20± 1 °C in the dark. Residual chlorine was determined by spectrophotometric measurements at 510 nm, following the calorimetric method using N,N-diethylphenylene-1,4-diamine (DPD). To avoid the slow oxidation of Slv into Svl by dissolved oxygen, the sodium sulfite solutions were prepared freshly before use. TOX concentrations were measured using a DOHRMAN DX-20 TOX analyser equipped with a MC-1 microcoulometric cell and with an AD-2 adsorption module. Before analysis, the residual chlorine was neutralized with sodium thiosulfate and samples were acidified to pH 1.4.The mutagenic activity was determined using acetone-dichloromethane extracts (AMBERLITE XAD-8 and XAD-2 resins) of the aqueous samples of chlorinated and dechlorinated solutions of AHS, acidified to pH 2.0 before extraction. The mutagenicity tests were carried out on TA 98 and TA 100 tester strains, following the method described by MARON and AMES (1983).Results-Effect of pH, addition of sodium sulfite and storage time on the TOX concentrationThe experiments carried out with dilute solutions of AHS ([AHS] = 5 mg 1-1; DOC = 2.5 mg Cl-1; pH = 6.1) showed a linear relationship between TOX production and chlorine consumption in the range 0-2.0 mg Cl2 l-1 (fig. 2).15 % of the chlorine demand was incorporated as organic chlorine in molecules.Experiments performed on solutions containing no residual free chlorine showed that organohatogenated compounds could be partially destroyed upon storage at neutral or basic pH (table 1). Reductions in TOX concentrations of 10 % at pH 6.1-8.5 in 24 hours and of 20 % at pH 11.5 in 2 hours were observed. This was enhanced by increasing the storage time.The addition of sodium sulfite (100 µmol l-1) in solutions containing no residual free chlorine significantly reduced the TOX concentration (10 % in 2 hours at pH 6.1-8.5; table 1). This reduction was enhanced by increasing sulfite dose and storage time and by increasing pH (30 % in 2 hours at pH 11.5). Furthermore, at a given pH value and for a reaction time of 2 hours, the decrease in TOX concentration was larger in presence of sulfite.- Effect of a dechlorination treatment on the TOX concentrationAs shown in figure 3, a dechlorination treatment (reduction of the residual free chlorine concentration) with sodium sulfite could significantly reduce the TOX concentration of the dilute solutions of AHS at pH 6.1 only if an excess of the dechlorinating agent was added. This effect was enhanced by increasing the excess of sulfite but nevertheless seemed to be limited (less than 15 % of reduction for the highest doses used; table 2).The free chlorine residuals measured after a 2 hours partial dechlorination confirmed the stoichiometric factor of 1 mole/mole for the reaction between chlorine and sodium sulfite.- Effect of a dechlorination treatment on the mutagenic activity and on the TOX concentrationThe dechlorination treatments were carried out on chlorinated dilute solutions of AHS ([AHS] = 15 mg l-1; DOC 7.5 mg C l-1; pH = 6.9). The TOX concentrations were measured on aqueous solutions and mutagenicity tests were performed on the corresponding acetone-dichloromethane extracts following a solvent exchange (dimethylsulfoxide). The results obtained showed again that only a total dechlorination treatment could reduce the TOX concentration of the aqueous chlorinated solutions and was able to destroy a significant part of the mutagenic activity of the extracts (table 3 and fig. 4).Although the effect of sulfite on TOX concentration seemed limited (less than 7 % reduction for the highest sulfite dose tested), the reduction in the genotoxicity was more important when the excess of sulfite was increased. No correlation between the TOX concentration and the mutagenic activity could be established. The mutagenic compounds destroyed by sodium sulfite do not appear to be organohalogenated ones. If they are, they are present at trace levels and thus are extremely patent and account for a very little part of the TOX concentration

Recent approaches in designing bioadhesive materials inspired by mussel adhesive protein

Marine mussels secret protein-based adhesives, which enable them to anchor to various surfaces in a saline, intertidal zone. Mussel foot proteins (Mfps) contain a large abundance of a unique, catecholic amino acid, Dopa, in their protein sequences. Catechol offers robust and durable adhe-sion to various substrate surfaces and contributes to the curing of the adhesive plaques. In this article, we review the unique features and the key functionalities of Mfps, catechol chemistry, and strategies for preparing catechol-functionalized poly- mers. Specifically, we reviewed recent findings on the contributions of various features of Mfps on interfacial binding, which include coacervate formation, surface drying properties, control of the oxidation state of catechol, among other features. We also summarized recent developments in designing advanced biomimetic materials including coacervate-forming adhesives, mechanically improved nano- and micro-composite adhesive hydrogels, as well as smart and self-healing materials. Finally, we review the applications of catechol-functionalized materials for the use as biomedical adhesives, therapeutic applications, and antifouling coatings

Action du sulfite de sodium sur l'activite mutagene de solutions de substances humiques et d'eaux de surfaces chlorees. Application a la dechloration des eaux potables

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 80700 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Development of a multiplex method based on surface plasmon resonance imaging (SPRi) for pathogenic bacteria detection in food samples

La présence de micro-organismes pathogènes dans les produits alimentaires représente un risque important de santé publique. La réglementation régit leur contrôle en imposant, dans la majorité des cas, la recherche d’une faible quantité de ces bactéries. Les méthodes de détection de référence sont simples à mettre en œuvre mais chronophages et nécessitent un temps d’analyse de plusieurs jours. Aussi, un des enjeux majeurs dans le domaine du contrôle alimentaire, est la mise au point de méthodes sensibles et rapides pour la détection d’un ou plusieurs pathogènes dans des matrices alimentaires. Ces nouvelles technologies ont pour but de réduire le nombre de toxi-infections alimentaires tout en augmentant la durée de commercialisation des produits et en limitant les impacts économiques négatifs pour les industries (longues périodes de stockage, rappels de lot, etc.).Dans ce contexte, nous nous sommes intéressés à la mise au point d’une méthode alternative aux méthodes de références, basée sur un biocapteur présentant une transduction de type résonance des plasmons de surface (SPR). Cette technologie présente de multiples avantages : simplicité de mise en œuvre, analyse en temps réel, absence de marquage, etc. Des preuves de concept de son utilisation, pour la détection de bactéries pathogènes ont été présentées dans la littérature, utilisant principalement des récepteurs de type anticorps.Au cours des travaux présentés dans cette thèse nous nous sommes intéressés à la détection de bactéries pathogènes alimentaires majeures en termes de prévalence ou de gravité de l’infection, qu’elles soient Gram positif ou Gram négatif. La production d’anticorps performants a également été optimisée pour obtenir des anticorps polyclonaux sensibles et spécifiques de plusieurs genres bactériens. Les cinétiques de croissance bactérienne ont été analysées par SPR afin d’identifier les principaux phénomènes impactant la détection. Des techniques en haute résolution ont permis une meilleure compréhension des événements se produisant à la surface du biocapteur. Ces études ont menés à l’obtention d’un système permettant la détection multiplexe d’un faible inoculum de bactéries pathogènes dans des matrices alimentaires (salade et poudre de lait infantile) en moins de 24h.The presence of pathogenic micro-organisms in foodstuff is a major concern for health safety. Regulations impose, in most cases, the research of low levels of these bacteria. Although reference methods are simple, they are time-consuming and can require several days before obtaining results. This is why one of the major challenges in food hygiene science is the development of sensitive and rapid methods, for the detection of one or more pathogens. These new technologies aim to decrease the occurrence of foodborne infections, while improving both the shelf life of food products and industrial production costs (long storage times, recalls …).In this context, the development of an alternative method has been carried out in this work, using a biosensor with a transduction based on surface plasmon resonance (SPR). Such optical technology offers multiple benefits: ease-of-use, real-time analysis, label-free process… Proofs of concept for the use of this technology in basic conditions, for the detection of model bacteria, have been described in the literature, mostly using antibodies as receptors, but the full operation in "real" conditions encountered in industrial facilities still has to be tested and optimizedThis manuscript thus describes the detection of foodborne pathogenic bacteria playing a major role in terms of prevalence and/or severity of the caused infection, whether Gram positive or negative. The production of efficient antibodies was optimized, resulting in polyclonal antibodies sensitive and specific for multiple bacterial genera. Dynamics of bacterial growths were analysed by SPR in an effort to identify the main factors having an impact on the detection. High resolution SPR was used for a better understanding of reactions occurring at the surface of the biosensor. These studies lead to the development of a system capable of multiplex detection of low bacterial inoculum in food samples (lettuce and powdered infant formula) within less than 24 hours

Activated carbon technoligies - examples from France.

internationa

Interprétation critique des isothermes de physisorption d'azote de trois charbons actifs utilisés dans l'industrie du traitement des eaux

nationa

Contribution to the textural characterisation of Filtrasorb 400 and other commercial activated carbons commonly used for water treatment

Morlay, Catherine Joly, Jean-PierreThe textural characteristics of three commercial activated carbons, Filtrasorb 400 (F400), Industrial React High Affinity and Picabiol, commonly used in water treatment, are reinvestigated. Nitrogen physisorption isotherms are determined in the range P/P (0) = [4 x 10(-7)-0.998] and processed using BET, alpha(S) (Sing), Dubinin-Radushkevich and Density Functional Theory methods. In addition, fractal dimensions are determined by the Frenkel-Halsey-Hill procedure. Since F400 is often considered as a reference material in studies on the adsorption of solutes in aqueous solutions, a review of the textural characteristics of this carbon is carried out. The results obtained in this work using the different methods are consistent and a critical crossed comparison of these results allows discussing the limitations of the methods used. In particular, the impact of the P/P (0) range considered on S (BET) value is examined. In addition, the accuracy of the BET specific surface area is assessed in the light of information from recent literature