Complexation de l’aluminium par des hétéropolyanions lacunaires : Récupération par membrane liquide émulsionnée

L'objectif visé par cette étude est la dépollution des eaux à partir de la complexation d’un métal toxique, l’aluminium en solution, par des hétéropolyanions lacunaires (HPA) de type Dawson. Les complexes formés sont récupérés par membrane liquide émulsionnée (MEL).Les résultats de la complex1ation de l’aluminium pars deux hétéropolyanions : (α2P2W17O61)10- et (P2W15Mo2O61)10- se sont avérés très intéressants. Les constantes de stabilité des complexes formés Al3+ (α2P2W17O61)7- et Al<sup3+ (P2W15Mo2O61)7- sont respectivement : β1=6,12.107et β2 =1,28.106. En ce qui concerne la récupération des complexes formés, par (MEL), le rendement d'extraction est de 86% pour Al3+ (α2P2W17O61)7-, pour un temps de contact de 4min, et de 91 % pour Al 3+ (P2W15Mo2O61)7-, pour un temps de contact de 6min.Mots clés : hétéropolyanions; aluminium; complexation; extraction; membrane liquide émulsionné

Extraction du complexe (&#87331P2W17O61Fe)7-, par membrane liquide emulsionnee

Extraction of complex (∝1P2W17O61Fe)7- by liquid surfactantmembrane The extraction of a Dawson-type heteropolyanion (∝1P2W17O61Fe) 7- was carried out by liquid surfactant membrane using (SPAN80) as surfactantand (TIBA) as extractant, internal phase used (NH4)2CO3. The extraction efficiency is 90 %. Then in order to regenerate the membrane, the stripping efficiency was given according to the concentration of the internal phase, the stripping efficiency is 76 % was obtained for (NH4)2CO3 concentration 1 M

Synthèse de HCs5P2W18O62.16H2O et application à l’adsorption de la matière organique: bleu de méthylène

La présente étude porte sur l'adsorption d'un colorant, le bleu de méthylène (BM), par un hétéropolyanion saturé de type Dawson, substitué par le césium HCs5P2W18O62.16H2O. La première partie a trait à la synthèse et à la caractérisation de l'adsorbant. La dernière partie est consacrée à l'étude de l'adsorption et à l'optimisation des paramètres qui la gouvernent ainsi qu'à la régénération de l'adsorbant. Le rendement optimal de l'adsorption est de 88% pour une concentration en BM de 25 mg/L et une masse d’adsorbat de 0.25g. Le rendement de la régénération est de 98% pour une température de 80°C.Mots clés: Adsorption - Bleu de méthylène - Hétéropolyanion - Caractérisation spectroscopique - DawsonThe adsorption of a dye, the deals with methylene blue, by a Dawson type heteropolyanion HCs5P2W18O62.16H2O, substituted by caesium, was investigated. The first part is for the synthesis and characterization of the adsorbent. The experimental parameters affecting the adsorption were then optimized. The regeneration of the adsorbent was finally studied. The optimal yield found was 88% for a MB concentration of 25 mg/L and an adsorbent mass of 0.25g. The yield of the regeneration was 98%, at 80°C.Keywords: Adsorption - Methylene blue - Heteropolyanion - Dawson - Spectroscopic characterizatio

Electrochemical Behavior of α1/α2-[Fe(H2O)P2W17O61]7– Isomers in Solution: Experimental and DFT Studies

The unusual redox behavior displayed by the two isomers of the Wells–Dawson phosphotungstate anion [Fe(H2O)P2W17O61]7– is presented. The electrochemical measurements have been performed in aqueous media at different pH values from 0.5 up to 8.0. The cyclic voltammetry has also been carried out in organic media to get additional experimental data to establish the effect of the protonation on the redox properties of both isomers. At high pH values (pH ≥ 6) or in an organic medium, the reduction of the Fe center is easier in the case of the alpha-1 isomer, whereas for the alpha-2 isomer such reduction takes place at more negative potentials, as expected. In contrast, at lower pH values (pH ≤ 5), an inversion of this trend is observed, and the reduction of the Fe center becomes easier for the alpha-2 isomer compared to the alpha-1. We were able to highlight the influence of the pH and the pKa of the electrolyte on POM-based redox potentials given the pKa of the latter. A complementary theoretical study has also been performed to explain the experimental data obtained. In this sense, the results obtained from the DFT study are in good agreement with the experimental data mentioned above and have provided additional information for the electrochemical behavior of both isomers according to their different molecular orbital energies. We have also shown the influence of protonation state of the iron derivative on the relative reduction potentials of both isomers

183W INADEQUATE 2D NMR Spectroscopy of Hetero Arsenato–Phosphato–Tungstate PV/AsV Substitution in Dawson-Type α-[AsxP2–xW18O62]6– (x = 0–2) and α-[H4AsyP1–yW18O62]7– (y = 0, 1)

International audienceThe Dawson-type arsenato-phosphato-tungstate alpha-[AsPW18O62](6-) has been prepared and unambiguously identified for the first time. A comparative study. including the four other already known compounds, the symmetric alpha-[X2W18O62](6-) and unsymmetric alpha-[H4XW18O62](7-) for X = P-V, As-V, has been performed by spectroscopic W-183 and P-31 NMR. 2-D W-183 INADEQUATE experiments were systematically employed to unequivocally verify structures, assign all resonances, and determine precisely (2)J(W-O-W) scalar couplings. The effects of P/As substitutions, generating unsymmetric structures, on the NMR observables delta(W-183), delta(P-31), (2)J(W-O-W), and (2)J(W-O-P) are discussed in relation to their bond length and bond angle alteration. General trends with respect to NMR parameter variations have been found when filling central cavities with P or As atoms, with less pronounced effects for As than for P. In addition, NMR characterization of three other isomers, i.e., beta-[X2W18O62](6-) and [As2W18O62](6-), were also provided for comparison. The present NMR results could serve as representative reference data for understanding the relationship between structure and NMR observables in polyoxotungstates