Détermination potentiométrique des constantes de stabilité des complexes de l’acide (D-L) isocitrique avec le magnésium (II), le manganèse (II) et le cobalt (II)

La formation de complexes entre l’acide (DL) isocitrique (H4A) et Mg (II), Mn (II) et Co (II) a été étudiée par potentiométrie, à différents pH. On a déterminé les constantes de stabilité des différentes espèces et on a tracé les courbes de distribution correspondantes en fonction du pH et de la concentration. A pH 7, en présence de Mg (II) ou de Mn (II), MHA est la seule espèce présente en quantité significative; en présence de Co (II), on observe en plus M(HA)2 et MA. A pH plus élevé, pour les trois métaux, on observe une espèce MA(OH) en plus de MA. Ces résultats sont discutés en relation avec la détermination du substrat de l’isocitrate déshydrogénase de cœur de porc, dépendante du NAD

Potentiometric studies on interactions of α-L-glutamic acid oligomers with Cu(II) in aqueous solutions

International audienc

The Use of Eucalyptus Barks for the Adsorption of Heavy Metal Ions and Dyes

Eucalyptus barks harvested in Lebanon were used for the adsorption of pollutants such as heavy metal ions and dyes. Washing with water or pretreatment with formaldehyde was performed on the bark powder. The adsorption capacity of this material towards Cu II , Cr III , Cd II and Ni II was evaluated in a batch process for various parameters. The results obtained showed that the retention capacity increased with contact time, pH and initial metal ion concentration but decreased with temperature. The adsorption capacities were 2.61, 0.71, 2.24 and 0.75 mmol/g adsorbent for Cu II , Cr III , Cd II and Ni II , respectively. Eucalyptus barks are also very efficient for the adsorption of dyes (Acid Blue 25, Erichrome Blue Black B and Calmagite) because of interaction between the hydroxy and amino groups of the dyes and the phenolic moities of bark. This adsorption was modified when metal ions had already been adsorbed on to the barks as a result of the formation of a 1:1 complex between the dye and the metal ion. Desorption was achieved by treating with the sodium salt of ethylenediamine-tetraacetic acid (EDTA) for metal ions and by heating at 75°C in aqueous medium for dyes. After desorption, the recycling of the support was tested for potential use as a means of concentrating pollutants

Conformational study of aminocalixarenes

Chiral calix[4]arenes bearing (R) - (+) or S - (-) (methoxymethyl)-pyrrolidin groups (MMP) on the upper ring are synthesized. The conformation is studied by 2D 1H NMR and by High Temperature Annealed Molecular Dynamics Simulations. A new conformation due to the hydrogen bond between the OH phenolic group and the oxygen atom of the methoxy group is found. These calixarenes exhibit circular dichroism with split Cotton effects as a result of exciton chirality induction. The optical activity is in agreement with the conformation studied by MD simulations which indicate that the MMP groups are twisted forming, with the aromatic nucleus, the beginning of an helix

Photominéralisation de l'uracile et des 5-halogeno-uraciles sur le dioxyde de titane. Effet du pH et de quelques anions sur la photodégradation de l'uracile

In oxygenated aqueous solutions, the photocatalytic degradation of uracil and its halogenated homologous is achieved on irradiated titanium dioxide. The kinetics of disappearance and mineralisation in carbon dioxide, ammonium, and nitrate ions are established. In presence of chloride, carbonate, sulphate and nitrate ions, photodisappearance of uracil is inhibited. This can be due to a partial blockage of catalyst active sites by these ions or their reaction with the oxidizing radicals such as HO$_3^0$ or OH$^0$. It is reported that, at pH lower than 6, disappearance kinetics of this pollutant is reduced

Analytical investigations of water sediment exchanges contribution of the HSF-SIMS technique

BIA

Place de la technique HSF-SIMS dans l'étude des échanges eau-sédiment

BIASpas resum