title: Extraction of Nb(v) by quaternary ammonium-based solvents: toward organic hexaniobate systems.
abstract: Solvent extraction of Nb(v) from alkaline aqueous media using quaternary ammonium solutions, especially Aliquat® 336 diluted in an aliphatic diluent, was investigated. The hexaniobate ions (HxNb6O19x-8) were extracted into the organic phase with very high yields at room temperature and within a few minutes, affording easy access to organic solutions of hexaniobates. Several parameters were found to influence the extraction of HxNb6O19x-8including the nature and concentration of alkali cations, confirming subtle effects previously described for polyoxoniobates such as ion-pairing with alkali ions. The extraction of HxNb6O19x-8with Aliquat® 336 is also influenced if competing anions are present in the aqueous phase (NO3-, Cl-, C2O42-, SO42-and CO32-) and varies with the pH mainly due to the competitive extraction of hydroxide ions at high pH. The co-extraction of sodium ions with HxNb6O19x-8was observed as well as the co-extraction of water molecules, suggesting a self-association of the extractant. The proposed liquid-liquid extraction generic system paves the way for innovative niobium (and potentially tantalum) hydrometallurgical processes and it may also afford more direct routes for exploring the chemistry of hexaniobates in organic solvents.
authors.affiliation: PSL Research University, Chimie ParisTech - CNRS, Institut de Recherche de Chimie Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France. gauthier.deblonde@alumni.chimie-paristech.fr and Eramet Research, Hydrometallurgy department, F-78193 Trappes, France.
authors.forename: Gauthier J-P
authors.identifier: http://orcid.org/0000-0002-0825-8714
authors.initials: GJ
authors.lastname: Deblonde
authors.affiliation: PSL Research University, Chimie ParisTech - CNRS, Institut de Recherche de Chimie Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France. gauthier.deblonde@alumni.chimie-paristech.fr and University of Lorraine, GeoRessources Lab, UMR CNRS 7359, 2 Rue Doyen Marcel Roubault, TSA 70605, 54518 Vandoeuvre Les Nancy, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Chagnes
authors.affiliation: Eramet Research, Hydrometallurgy department, F-78193 Trappes, France.
authors.forename: Marie-Aude
authors.initials: MA
authors.lastname: Roux
authors.affiliation: Eramet Research, Hydrometallurgy department, F-78193 Trappes, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Weigel
authors.affiliation: PSL Research University, Chimie ParisTech - CNRS, Institut de Recherche de Chimie Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France. gauthier.deblonde@alumni.chimie-paristech.fr.
authors.forename: Gérard
authors.initials: G
authors.lastname: Cote