Electrochemical and surface analytical characterization study of the inhibition effect of boiled red onion extract on tin corrosion in 0.2 M Maleic acid medium.

The inhibition efficiency of boiled red onion skin extracts (BROE) against tin corrosion in 0.2 M Maleic acid has been studied using electrochemical and surface analytical methods. The electrochemical polarization curves displayed the active/passive transition of the anodic behavior of the tin electrode. The electrochemical impedance measurements demonstrated the effect of increasing BORE concentration on the inhibition efficiency (η %) (to a ηmax = 94% at 300 mg/L of BORE). The inhibition mechanism is attributed to the formation of adsorbed protective layers, on the metal surface, that fit the Langmuir adsorption isotherm model. Increasing the temperature hindered the η values

Synchronization of the astronomical time scales in the Early Toarcian: a link between anoxia, carbon-cycle perturbation, mass extinction and volcanism

International audienceThe Late Pliensbachian–Early Toarcian is a pivotal time in the Mesozoic era, marked by pronounced carbon-isotope excursions, biotic crises and major climatic and oceanographic changes. Here we present new high-resolution carbon-isotope and magnetic-susceptibility measurements from an expanded hemipelagic Late Pliensbachian–Early Toarcian section from the Middle Atlas Basin (Morocco). Our new astronomical calibration allows the construction of an orbital time scale based on the 100-kyr eccentricity cycle. The Early Toarcian Polymorphum Zone contains 10 to 10.5 repetitions of the 100-kyr eccentricity both in the carbon-isotope and the magnetic-susceptibility data, leading to an average duration of 1.00±0.081.00±0.08 myr. We also show that the Late Pliensbachian–Early Toarcian global carbon-cycle perturbation has an average duration of 0.24±0.020.24±0.02 myr. These durations are comparable to previous astrochronological time scales provided for this time interval in the most complete sections of the Tethyan area, and longer than what has been provided in condensed sections. Anchoring this framework on published radiometric ages and astrochronological time scales, we estimate that the carbon-cycle perturbation of the Late Pliensbachian–Early Toarcian corresponds with the early phase of the Karoo and Chonke Aike large igneous provinces. Likewise, our new age constraints confirm that the Toarcian oceanic anoxic event is synchronous to the main phase of the Ferrar volcanic activity. Thus, these successive and short phases of the volcanic activity may have been at the origin of the successive phases of the mass extinctions observed in marine biotas in the Pliensbachian and Toarcian times

Corrosion behaviour of steel rebar: effect of simulated concrete pore solution and chloride ions

In this work, we investigate the corrosion behavior of steel rebar (SR) in four simulated concrete pore solutions (CPS): NaOH+KOH (CPS1), Na2CO3 (CPS2), NaOH (CPS3) and Ca(OH)2 (CPS4) medium.  Effect of addition of Cl- anions as pollutant on pitting and uniform corrosion of SR is investigated by using potentiodynamic polarization (PDP) technic. The result obtained show that uniform and pitting corrosion of SR are strongly influenced by the nature of simulated CPS. In unpolluted CPS’s, only uniform corrosion of SR is observed in all cases. SR has excellent corrosion resistance in CPS4 compared to the other simulated CPS. In the polluted CPS’s by Cl- anions, we observe an accelerated uniform corrosion especially in CPS1, CPS3 and CPS4 mediums. The sensitivity to localized corrosion of SR varies from one simulated environment to another. It has the best resistance to pitting corrosion in polluted CPS3 medium. In CPS1 (pH = 13) and CPS2 (pH = 11.6) polluted by 3% NaCl, the tendency to pitting corrosion is the same. The localized attack is more pronounced in polluted CPS4 (pH=12.7). These results demonstrate that there are no limit values of the pH and the content of Cl- ions for the initiation of pitting and / or uniform corrosion. Therefore, it is the chemical composition of the simulated medium which imposes the pH value and the Cl- content for systematic corrosion study of the SR in the simulated CPS

Studies on the adsorption of heptamolybdate ions on AISI 304 stainless steel from acidic HCl solution for corrosion inhibition

Surface interaction of heptamolybdate ions Mo7O24 6- on ASI 304 stainless steel (SS) greatly reduces the corrosion rate of the material in acid environments, providing an environmentally-friendly inhibitor system. Corrosion inhibition properties have been studied in naturally aerated 0.5 M HCl solution from weight loss measurements. The influences of inhibitor concentration and solution temperature were investigated. The percentage inhibition efficiency, SW(%), increased for increasing concentrations of the ionic inhibitor species. Conversely, the increase of temperature decreased the inhibition efficiency. That is, the corrosion rate, vcor, was faster at higher temperature whereas it was slower for increasing inhibitor concentrations. The adsorption of the inhibitor ions onto the SS surface was found to follow the Langmuir adsorption isotherm. The values of the standard adsorption free energy, 0 ads G , are consistent with a spontaneous physisorption mechanism of the inhibitor ions on the surface of the steel

Inhibitory action of non toxic compounds on the corrosion behaviour of 316 austenitic stainless steel in hydrochloric acid solution: comparison of chitosan and cyclodextrin

The inhibitory action of two non toxic organic compounds, chitosan and hydroxypropyl-beta-cyclodextrin (HP-β-CD), against the corrosion of 316 austenitic stainless steel in acidic chloride solutions was studied. Weight loss and electrochemical tests show that the inhibitory action increases with concentration of the organics, though the effect is greater with chitosan than with HP-β-CD for a given concentration. These compounds act as anodic inhibitors (by forming an adsorbing film on the metal surface and blocking the active corrosion sites), whereas the cathodic half-reaction is not significantly affected. The highest inhibition efficiency attained in 0.1 M HCl solution was 76% by using chitosan

Inhibition of the pitting corrosion of 304 stainless steel in 0.5 M hydrochloric acid solution by heptamolybdate ions

The corrosion inhibition effect of heptamolybdate ions on 304 stainless steel in 0.5 M hydrochloric acid solution at 298 K was investigated using gravimetric, electrochemical and optical microscopy methods. Increasing inhibitor concentration led to significant reduction in the corrosion rate of stainless steel, withinhibitor efficiency values above 90%. The adsorption of the inhibitor onto the steel surface is described using the Langmuir adsorption isotherm. The value of the free energy of adsorption determined at 298 K (ΔG° = -31.1 kJ mol-1) characterizes the adsorption process of heptamolybdate ions on the surface of the metal

Etude de la biodégradation des polluants industriels –cas des colorants azoïques

Les colorants sont parmi les effluents industriels les plus rejetés dans l’environnement vu leur grande utilisation dans plusieurs domaines notamment le textile, cosmétique et l’agroalimentaire. Les colorants azoïques constituent la plus grande classe des colorants synthétiques utilisés commercialement. Afin de limiter l’action de ses polluants organiques de façon écologique et durable, des procédés biologiques, tel que la bioremédiation, sont largement utilisés. Cette technique consiste à la dépollution et la décontamination des milieux pollués sous l’action des microorganismes vivants, ces micro-organismes jouent un rôle majeur dans la dégradation des matières organiques et une simple adaptation à une molécule polluante peut conduire à sa biodégradation ou sa biotransformation.L’objectif de notre travail est d'évaluer la dégradation des colorants synthétiques par de nouvelles souches bactériennes isolées du sol d’arganeraie en utilisant le Rouge de Méthyle comme colorant azoïque modèle. Les résultats obtenus ont montré que la bactérie isolée présente une grande capacité de décoloration de plus de 100 ppm du rouge de méthyle dans moins de 24h d'incubation. Plusieurs paramètres tels que le pH, la température et la concentration initiale du colorant ont été optimisés pour développer un processus de décoloration complet.La forte capacité de décoloration du Rouge de Méthyle (RM) et les faibles besoins en nutriments de cette bactérie la rendent très utile dans le traitement biologique des effluents industriels contenant des colorants azoïques. Le test de phytotoxicité avec des graines de poivron (Capsicum annuum), très cultivées dans la région de Souss Massa, a révélé que la décoloration du rouge de méthyle produit des métabolites non toxiques

Les séries du Dogger moyen du Haut Adas au Nord d'Errachidia (Maroc) : lithostratigraphie et sédimentologie d'une nouvelle formation : la formation Tazigzaout

The Middle Dogger series of the High Atlas at north Errachidia (Morocco) : lithostratigraphy and sedimentology of a new Tazigzaout formation. The stratigraphie and sedimentological study of Middle Dogger facies of the Moroccan High Atlas of north Errachidia allows to propose the Tazigzaout serie like a new forma tion. Its equivalents at the Central High Atlas are Bin el Ouidane 2 and 3, Ait Abdi 2 and Assoul 1 formations. Following this discovery a review of locally and regionally correlations linked to the basin geodynamic evolution became a necessity. At the northern basin field of our studied area, the Tazigzaout formation, assigned to Bajocian-Bathonian pp., is very well marked and make up the Tazigzaout syn-cline which fits in the large syncline of jebel Boukendl with the upper terms of the underlain Agoudim formation. Each one of these two formations shows an upward-shallowing evolution and capped by patch reef carbonate bars. Their equivalents in the southern platform area are very delicate to determine. However, on the basis of sedimentological and palaontological data we have distinguished these two formations and gradually established the facies correlations between different studied outcroup sections.L'étude stratigraphique et sédimentologique des faciès du Dogger moyen du Haut Atlas marocain au Nord d'Errachidia permet d'individualiser une nouvelle formation nommée formation Tazigzaout. Ses équivalents, dans le Haut Atlas central, sont les formations Bin el Ouidane 2 et 3, Ait Abdi 2 et Assoul 1. Une révision des corrélations stratigraphiques (locales et régionales) en relation avec l'évolution géodynamique du bassin s'avérait nécessaire. Dans le domaine distal septentrional de notre zone d'étude, la formation Tazigzaout attribuée au Bajocien-Bathonien pp., est bien individualisée et empli le synclinal de Tazigzaout formant l'axe du grand synclinal perché du jebel Boukendil formé par les termes sommitaux de la formation Agoudim sous-jacente. Chacune de ces deux formations montre une évolution de type "shallowing-upward" et apparaît coiffée par des barres carbonatées à monticules bioconstruits. Leurs équivalents latéraux en domaine de plate-forme sud sont très délicats à déterminer. Toutefois, sur la base de données sédimentologiques et paléontologiques nous avons pu distinguer ces deux formations et établir de proche en proche des corrélations entre les faciès qui les composent.Ait Addi A. Les séries du Dogger moyen du Haut Adas au Nord d'Errachidia (Maroc) : lithostratigraphie et sédimentologie d'une nouvelle formation : la formation Tazigzaout. In: Géologie Méditerranéenne. Tome 27, numéro 1-2, 2000. pp. 57-69

Les bioconstructions du Bajocien-Bathonien pp. du Haut-Atlas marocain (Nord d'Errachidia-Boudenib) : sédimentogenèse et contexte paléogéographique

The Bajocian-Bathonian pp. buildups of Moroccan High Atlas (North of Errachidia-Boudenib) : sediment genesis and palaeo-geography context. The Bajocian-Bathonian pp. buildups of Moroccan High Atlas (North of Errachidia-Boudenib) are mainly maked up by corals that are associated to some species of sponge, alguae, and bryozoan and also with abandant of neritic macrofauna (mollusks, echinoids, brachiopods...). The immaturity and fragility of these buildups reveal the absence of a precocious cementing and relatively unfavorable ecological conditions for a better proliferation of builder maker organisme. These buildups indicated the installation, on the studied area, of shalow-water deposits during the middle, and upper Bajocian, and Bathonian pp. These occasional buildups are enhanced by rise of water-level which's resulting from a filled avai¬ lable space ; and by lull tectonic phases.Les bioconstructions d'âge bajocien-bathonien pp. du Haut-Atlas marocain (Nord d'Errachidia-Boudenib), sont principalement constituées par des madréporaires associés à quelques éponges, algues et bryozoaires et à une macrofaune néritique très abondante (mollusques, échinodermes, brachiopodes...). L'immaturité et la fragilité de ces bioconstructions révèle l'absence de cimentation précoce et des conditions écologiques relativement défavorables pour une plus grande prolifération des organismes constructeurs. L'édification de ces bioconstructions marque l'installation de plate-formes carbonatées sur toute la zone étudiée pendant le Bajocien moyen et supérieur et au Bathonien ? Ces épisodes bioconstruits sont rehaussés par la montée des eaux consécutive au comblement de l'espace disponible et par des phases d'accalmie tectonique.Ait Addi A., El Hanbali M., Bobier Claude. Les bioconstructions du Bajocien-Bathonien pp. du Haut-Atlas marocain (Nord d'Errachidia-Boudenib) : sédimentogenèse et contexte paléogéographique. In: Géologie Méditerranéenne. Tome 25, numéro 1, 1998. pp. 43-54