Microémulsions inverses de systèmes fluorés : effet des sels et étude conductimétrique

On étudie dans ce travail certaines propriétés des microémulsions inverses obtenues à partir de mélanges ternaires eau/fluorocarbure/tensioactif non-ionique fluoré lorsque l'eau est remplacée par une solution saline. Le mécanisme d'action des sels sur les propriétés des systèmes à base de tensioactifs non-ioniques ainsi que certaines manifestations de leurs effets sont d'abord brièvement rappelés. Les résultats, relatifs à deux systèmes (eau salée/perfluorodécaline/C6F13CH2(EO)4 et eau salée/C8F17CH=CH2/C6F13 CH2(EO)5) concernent d'une part l'effet des sels sur les domaines d'existence de microémulsions inverses et d'autre part l'utilisation de la conductimétrie pour tenter de préciser l'organisation moléculaire à l'intérieur de ces domaines. L'effet des sels est tout-à-fait comparable à celui observé pour des tensioactifs non-ioniques hydrogénés possédant de longues chaînes polyoxyéthylène. On montre qu'il peut être annulé si on utilise des mélanges de sels. Les mesures de conductivité font apparaître, dans le cas du système formulé avec le C6F13CH2(EO)4, une transition structurale à l'intérieur du domaine isotrope

Stopped-flow study of the kinetics and mechanism of nickel (II). Complexation with 8-Hydroxyquinoline in basic aqueous solutions

The complexation of nickel (II) with 8-hydroxyquinoline is studied in basic aqueous solutions buffered with triethanolamine. The pH influence is interpreted quantitatively in terms of a mechanism involving the neutral (LH) and anionic (L-) forms of the ligand in addition to the metallic species Ni2+ and Ni(OH)+ . Due to the large similitude existing between the ionization constant of the ligand on the one hand the hydrolysis constant of the metal on the other hand, the influence of the pH on the kinetics of complexation can originate as well from reaction LH + Ni(OH)* as from reaction L- + Ni2+. It is show that the ambiguity cannot be removed by studying the ionic strength dependence of the reaction rate

Glucose Encapsulation in Catanionic Vesicles and Kinetic Study of the Entrapment/Release Processes in the Sodium Dodecyl Benzene Sulfonate/Cetyltrimethylammonium Tosylate/Water System

International audienc

Absorption du gaz carbonique par les amines en solutions aqueuses : modélisation des cinétiques obtenues par la méthode de l'écoulement bloqué

On développe les équations nécessaires à l'élaboration d’un programme de calculs permettant de simuler les cinétiques de réaction entre le gaz carbonique et les amines obtenues par la méthode de l’écoulement bloqué avec détection du changement d’absorption d'un indicateur de pH. Le traitement s'applique au cas des amines primaires ou secondaires donnant lieu à la formation de carbamates, et permet la prévision de la courbe cinétique dans les unités réelles de transmission optique

Etude ultrasonore de la fixation sur site des ions alcalins de densités de charge variable

International audienc

Micellar extraction: removal of copper(II) by micelle-solubilized complexing agents of varying HLB using ultrafiltration

The hydrophobic core of micellar systems can solubilize hydrophobic extractants in a way similar to the organic solvent in a classical solvent extraction. In this paper it is demonstrated that micellar extraction can be as effective as solvent extraction and shows the same characteristic features (effect of pH, effect of the hydrophilic/lipophilic balance (HLB) of the extractant, extractant concentration, etc.). A series of 6-[(alkylamino)methyl]-2-(hydroxymethyl)pyridines (CnNHMePyr with n = 4, 8, 10, 12, 14, and 16) are used for this purpose in combination with CTAB and C12EO6 micelles. The removal of copper(II) is achieved by ultrafiltration. A simple model is developed on the basis of equilibrium relations to theoretically predict the yield of copper extraction

Copper(II) complexation by micelle-solubilized long-chain complexing agents: Unusually slow reaction rates

We consider in this work the complexation of copper(II) by two different complexing agents [7-4(ethyl-1-methyloctyl)-8-hydroxyquinoline (C-11-HQ) and 6-(hexadecylamino)methyl-2-hydroxymethylpyridine (C16NHMePyr)] in different kinds of micellar surfactant solutions (SDS, C12EO6, CTAB and mixed CTAB/butanol). Stopped-flow kinetic experiments at controlled pH have provided values of the apparent rate constants for complex formation, which are discussed with reference to literature data in homogeneous solutions. They show considerable rate decreases, especially in CTAB micellar systems

Copper(II) complexation by 6-(alkylamino)methyl-2-hydroxymethylpyridines with varying alkyl chain length in aqueous solutions. Kinetics and thermodynamics

Kinetic parameters have been obtained from stopped-flow experiments for the complexation of copper(II) by a series of 6-(alkylamino)methyl-2-hydroxymethylpyridines with alkyl chains varying from C1 to C-14, in aqueous solutions (T = 25-degrees-C, pH 2.0-5.0). The apparent rate constants for complex formation at pH 3.5 were found to be weakly dependent on the alkyl chain length. A kinetic model has been proposed which is in excellent agreement with the experimental data, especially the change of the reciprocal relaxation time (or observed rate constant) with pH. Even in a fairly acidic pH range, the contribution of the unprotonated ligand species cannot be neglected. Equilibrium measurements were carried out in parallel using UV-visible spectrophotometry and potentiometric titrations in order to determine the values of thermodynamic parameters such as ionization and stability constants