Complexation of trivalent cations (Al(III), Cr(III), Fe(III)) with two phosphonic acids in the pH range of fresh waters

Stella Lacour; Véronique Deluchat; Jean-Claude Bollinger; Bernard Serpaud

Complexation of trivalent cations (Al(III), Cr(III), Fe(III)) with two phosphonic acids in the pH range of fresh waters

Stella Lacour ¹ Véronique Deluchat ² Jean-Claude Bollinger ² Bernard Serpaud ²

1 LSEE - Laboratoire des Sciences de l'Eau et de l'Environnement

2 GRESE - Groupement de Recherche Eau, Sol, Environnement

Abstract : The complex formation constants of two phosphonic acids, HEDP and ATMP, with three trivalent metallic cations, Al(III), Cr(III) and Fe(III), have been determined by acid-base titration at 25°C and constant ionic strength (0.1 mol l 1, KNO3), using Martell and Motekaitis' computer programs. Species distribution curves showed that all three cations are in complex form in the pH range of fresh waters (5-9). The study of different cation:ligand ratios proved that both ligands mainly form anionic soluble complexes for systems having an excess of ligand--as protonated and unprotonated forms and especially ternary complexes with HEDP. For higher metal concentrations (excess of cation), weakly soluble species of HEDP and ATMP were formed with Al(III) and Cr(III). Two insoluble complexes with ATMP have been identified by SEM:EDAX as AlH3X(s) and Cr2X(s). Regarding Fe(III) species, Fe(OH)3(s) precipitate seems to predominate in solution.

Keywords : Complexation Phosphonic acids Speciation Trivalent cations

Type de document :

Article dans une revue

Domaine :

Sciences de l'environnement / Ingénierie de l'environnement

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https://hal-unilim.archives-ouvertes.fr/hal-00943981
Contributeur : Véronique Deluchat <>
Soumis le : lundi 10 février 2014 - 01:03:21
Dernière modification le : vendredi 21 juin 2019 - 07:56:04

Complexation of trivalent cations (Al(III), Cr(III), Fe(III)) with two phosphonic acids in the pH range of fresh waters

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Complexation of trivalent cations (Al(III), Cr(III), Fe(III)) with two phosphonic acids in the pH range of fresh waters

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