Sorption de l'atrazine et du diuron sur charbon actif en poudre en présence de tensioactifs, ions calcium et bichromate. Essai de modélisation

La contamination des eaux naturelles par les micropolluants organiques tels que les herbicides, nécessite le recours à des procédés très performants, en particulier l'adsorption sur charbon actif pour satisfaire aux normes de potabilité sur les eaux distribuées. Si le charbon actif en poudre (CAP) présente une bonne efficacité pour l'élimination des herbicides seuls dans l'eau distillée, la présence dans l'eau d'autres composés organiques et / ou minéraux aura pour conséquence la modification des paramètres de l'équilibre de l'adsorption du système initial et la modification des performances du matériau adsorbant. Cette étude a montré que le CAP utilisé présente une bonne affinité pour les deux herbicides étudiés (atrazine et diuron), dont les capacités d'adsorption, déterminées par le modèle de Langmuir, sont 1,42 et 1,72 mmol.g-1 respectivement. La présence de composés organiques tels que les tensioactifs anionique le dodécylsulfate de sodium (DSS), et cationique le bromure d'hexadécyl triméthyl ammonium (BHTA) provoque une forte diminution de la capacité d'adsorption des deux herbicides par le charbon actif. Le BHTA provoque l'effet le plus marqué, par contre, les ions calcium et bichromate n'ont pas d'influence sur l'adsorption des deux herbicides. Les essais de désorption ont montré que l'introduction des coadsorbats organiques provoque la désorption d'une partie de l'herbicide. Ce phénomène est accentué dans le cas du DSS en présence d'ions calcium. L'application de modèles simples de coadsorption, a permis de mettre en évidence l'existence presque exclusive de sites spécifiques d'adsorption pour chacun des substrats étudiés et une inhibition non compétitive due a une interdépendance possible entre les sites d'adsorption et une altération des interactions de chaque composé à la surface du charbon.Contamination of natural waters by organic micropollutants like pesticides requires the use of powdered activated carbon (PAC) during the flocculation step of water treatment. One of the main factors affecting the efficiency of this process is the presence in natural waters of organic and mineral compounds. The aim of this study was to determine the influence of two surfactants [(i) anionic (sodium dodecyl sulfate : SDS) and (ii) cationic (hexadecyl-trimethyl ammonium bromide : HTAB)], and two mineral ions (calcium and dichromate) upon atrazine and diuron adsorption on powderd activated carbon resulting from Chemviron Filtrasorb-400. The adsorption capacities on PAC of atrazine and diuron alone were determinated according to the Langmuir model for the isothermes (table I). They were estimated to be 1.42 and 1.72 mmol.g-1 respectly at pH 5.5. Coadsorption results pointed out that the herbicide adsorption was inhibited in the presence of surfactants whatever their nature (fig. 1 and 2).This inhibition was most importante with HTAB (45%), according to the zeta surface potential and the streric dimensions of molecules, than with SDS (23%) for atrazine . The same result was noted for diuron with an inhibition respectly of 15% for SDS and 27% for HTBA. Calcium and dichromate ions, each one with one herbicide had no effect. In any case, Langmuir isothermes were drawn and adsortion capacities were calculated with a good correlation (tables II and III). The influence of coadsorbats was always greatest for atrazine than for diuron. All the experiments were performed at pH=5.5, without influence upon the adsorption, even for the dichromate ions. Desorption tests showed that a part of adsorbed pesticides was desorbed with surfactants introduction (fig. 3) : with SDS 12.3% of atrazine and 8% of diuron against respectly 23% and 17% with HTBA. The phenomenon was increased with SDS in presence of calcium ions (fig. 4 and 5) according to the increase of SDS adsorption (table II and III). The use of two simple coadsorption models was reinforced by the calculated values obtained for adsoartion capacities (fig. 6 and 7) which were very closely with the experimental ones. The calculation of constantes given by the models confirmed the existence of specific sites of adsorption for every compound and a non competitive inhibition due to a change in the nature of the interactions between pesticides and activated carbon surface (table III)

Influence de l'ordre d'introduction des solutés (Naphtol-2 et Calcium) sur l'adsorption des tensioactifs sur charbon actif F400

L'effet de l'ordre d'introduction des solutés Naphtol-2 et Calcium (N-2 et Ca) sur l'adsorption de tensioactifs par le charbon actif en poudre (CAP) F400 brut a été étudié en discontinu. Les mélanges étudiés sont: le tensioactif anionique dodécyl-sulfate de sodium (DSS) et le N-2; le DSS, le N-2 et le Ca; le tensioactif cationique bromure de benzyldodécyldiméthylammonium (BBDDA) et le N-2 et enfin le BBDDA et Ca. Les résultats expérimentaux montrent tout d'abord que quel que soit l'ordre d'introduction des solutés N-2 et Ca, les concentrations en DSS à l'équilibre sont sensiblement identiques. Par ailleurs, la cinétique d'adsorption du DSS et du BBDDA croît en présence des ions Ca.Cependant, la cinétique d'adsorption du N-2 en présence du DSS diminue ce qui se traduit par une inhibition de l'adsorption du N-2 par le DSS. Quant à l'adsorption du BBDDA en présence du N-2 pour différents ordres d'introduction, le tracé des isothermes de LANGMUIR montre que la capacité maximale d'adsorption Г∞ du BBDDA ne change pas tandis que la constante de LANGMUIR (K) diminue. Par contre la capacité maximale d'adsorption du N-2 ** varie légèrement et passe de 1,67 à 1,5 mmol/g pour différent ordre d'introduction du BBDDA. On note également que Г∞ du N-2 en présence de concentrations croissantes en BBDDA diminue fortement et passe de 1,67 à 0,8 mmol/g.L'ajout de N-2 après 3 heures de contact du BBDDA /CAP ne provoque pas la désorption de ce dernier. Le même comportement a été observé avec le N-2, alors que l'ajout du DSS au mélange N-2/CAP provoque la désorption de celui ci.The effect of the introduction order of naphtol-2 and calcium (N-2 and ca) on the adsorption of surfactants by raw powdered activated carbon (PAC) F 400 has been studied in a static system, studied mixtures included the anionic surfactant: sodium dodecyl-sulfate (SDS) with N-2 or with N-2 + Ca, and the cationic surfactant beniyldodecyldimethylarnmoniurn bromide (BDDAB) with N-2, or with Ca. The experimental results demonstrate that whatever the order of solute introduction, the SDS concentrations at equilibrium are almost identical. Moreover, the adsorption kinetics of SDS and BDDAB increase in the presence of calcium ions. The adsorption kinetics of N-2 decrease in the presence of SDS, suggesting inhibition of N-2 adsorption by SDS. Concerning the adsorption of BDDAB the presence of N-2, for different introduction orders, plotting of the LANGMIIIR isotherms shows that the maximal BDDAB adsorption capacity Г∞, does not change but the LANGMUIR constant (K) decreases. For naphtol-2, however the maximal adsorption capacity Г∞, does vary slightly, going from l,67 to l.5 mmol/g for different BDDAB introduction orders. In the presence of increasing BDDAB concentrations, the maximum adsorption capacity of N-2 decreases from 1.67 to 0.8 mmol/g.The addition of N-2 after 3 hours of BDDAB/PAC contact does not lead to BDDAB desorption. similar behavior is observed on addition of N-2 after 3 hours of SDS/PAC contact, even though the addition of SDS to a N-2/PAC mixture leads to N-2 desorption

Luxation obturatrice de la hanche: un traumatisme rare en pratique sportive

Les luxations antérieures traumatiques de la hanche sans fracture du cotyle ou de la tête fémorale sont rares. Elles sont souvent secondaires à des accidents de haute énergie cinétique. La prise en charge thérapeutique nécessite un chirurgien vigilant et prévenu du risque de complications. Nous rapportons le cas d'une luxation obturatrice (antéro-inférieure) chez un jeune de 18 ans pratiquant le rolle

Chilling requirements and dormancy evolution in grapevine buds.

Fluctuations in winter chilling availability impact bud dormancy and budburst. The objective of this work was to determine chilling requirements to induce and overcome endodormancy (dormancy controlled by chilling) of buds in different grape cultivars. "Chardonnay", "Merlot" and "Cabernet Sauvignon" shoots were collected in Veranópolis-RS vineyards in 2010, and submitted to a constant 3 °C temperature or daily cycles of 3/15 °C for 12/12h or 18/6h, until reaching 1120 chilling hours (CH, sum of hours with temperature ≤ 7.2 °C). Periodically, part of the samples in each treatment was transferred to 25 °C for budburst evaluation (green tip). Chilling requirements to induce and overcome endodormancy vary among cultivars, reaching a total of 136 CH for "Chardonnay", 298 CH for "Merlot" and 392 CH for "Cabernet Sauvignon". Of these, approximately 39, 53 and 91 CH are required for induction of endodormancy in the three cultivars, respectively. The thermal regimes tested (constant or alternating) do not influence the response pattern of each cultivar to cold, with 15 °C being inert in the CH accumulation process. In addition, time required to start budburst reduces with the increase in CH, at a rate of one day per 62 CH, without significant impacts on budburst uniformity. Index terms: Chilling hours; endodormancy; budburst; Vitis vinifera

Impact of species and antibiotic therapy of enterococcal peritonitis on 30-day mortality in critical care - An analysis of the OUTCOMEREA database

Introduction: Enterococcus species are associated with an increased morbidity in intraabdominal infections (IAI). However, their impact on mortality remains uncertain. Moreover, the influence on outcome of the appropriate or inappropriate status of initial antimicrobial therapy (IAT) is subjected to debate, except in septic shock. The aim of our study was to evaluate whether an IAT that did not cover Enterococcus spp. was associated with 30-day mortality in ICU patients presenting with IAI growing with Enterococcus spp. Material and methods: Retrospective analysis of French database OutcomeRea from 1997 to 2016. We included all patients with IAI with a peritoneal sample growing with Enterococcus. Primary endpoint was 30-day mortality. Results: Of the 1017 patients with IAI, 76 (8%) patients were included. Thirty-day mortality in patients with inadequate IAT against Enterococcus was higher (7/18 (39%) vs 10/58 (17%), p = 0.05); however, the incidence of postoperative complications was similar. Presence of Enterococcus spp. other than E. faecalis alone was associated with a significantly higher mortality, even greater when IAT was inadequate. Main risk factors for having an Enterococcus other than E. faecalis alone were as follows: SAPS score on day 0, ICU-acquired IAI, and antimicrobial therapy within 3 months prior to IAI especially with third-generation cephalosporins. Univariate analysis found a higher hazard ratio of death with an Enterococcus other than E. faecalis alone that had an inadequate IAT (HR = 4.4 [1.3-15.3], p = 0.019) versus an adequate IAT (HR = 3.1 [1.0-10.0], p = 0.053). However, after adjusting for confounders (i.e., SAPS II and septic shock at IAI diagnosis, ICU-acquired peritonitis, and adequacy of IAT for other germs), the impact of the adequacy of IAT was no longer significant in multivariate analysis. Septic shock at diagnosis and ICU-acquired IAI were prognostic factors. Conclusion: An IAT which does not cover Enterococcus is associated with an increased 30-day mortality in ICU patients presenting with an IAI growing with Enterococcus, especially when it is not an E. faecalis alone. It seems reasonable to use an IAT active against Enterococcus in severe postoperative ICU-acquired IAI, especially when a third-generation cephalosporin has been used within 3 months. © 2019 The Author(s)

Pollution reduction and biodegradability index improvement of tannery effluents

Al2 (SO4)3, 18H2O, FeCl3 and Ca (OH)2 were used for the treatment of tannery wastewaters. The influences of pH and coagulant dosages were studied. Conditions were optimised according to the pollutant removal efficiencies, the volume of decanted sludge and the biodegradability index improvement. The results indicate that 6771% of total COD, 76-92% of color and 79-97% of Cr can be removed using the optimum coagulant dosages at the optimum pH range. Al2 (SO4)3, 18H2O and Ca (OH)2 produced better results than FeCl3 in terms of COD, color and Cr removal as well as in terms of biodegradability improvement. Moreover, Al2 (SO4)3, 18H2O and FeCl3 produced the least amount of sludges for a given amounts of COD, color and Cr removed in comparison with Ca (OH)2. Al2 (SO4)3, 18H2O seems to be suitable for yielding high pollutant removals and corresponding low volumes of decanted sludges in addition to improving wastewaters biodegradability index

Optimisation of biodegradation conditions for the treatment of olive mill wastewater

International audienceThe aim of the present paper was to optimise the conditions of aerobic treatment of olive mill wastewater. To do so, the waste was treated following the experimental optimal design methodology studying the set of factors susceptible to influence the treatment (pH, C/N ratio, aeration and temperature). The results of a first series of experiments showed a strong correlation between the reduction in the levels of polyphenols and three of the parameters studied, i.e. the C/N ratio, aeration and temperature. Optimised conditions led to a 94% drop in polyphenols. Then, for a finer study of the conditions, just two parameters were varied, the pH and the C/N ratio. The results showed that the conditions of pH modification (addition of lime or sodium hydroxide) and the C/N ratio (urea or ammonium nitrate) allowed the micro-biological activity to be very significantly improved. This led to polyphenol reductions of 51% and 76%